EP3947321A1

EP3947321A1 - Fertiliser pellets consisting of secondary phosphate and depleted of heavy metals, and method for the production thereof

Info

Publication number: EP3947321A1
Application number: EP19835293.2A
Authority: EP
Inventors: Frank Thoralf Hager; Matthias Hoger
Original assignee: Pontes Pabuli GmbH
Current assignee: Pontes Pabuli GmbH
Priority date: 2019-03-26
Filing date: 2019-12-20
Publication date: 2022-02-09
Also published as: WO2020192958A1; DE112019007082A5

Abstract

Agricultural exploitation depletes the soil of mineral raw materials, such as phosphorous compounds, which must be replaced by subsequent supply of mineral fertilisers. The material and energetic use of biomass, for example from domestic wastes or sewage sludge, is associated with a withdrawal of nutrients and considerable amounts of organic matter from the natural substance cycles. Obtaining soil fertility by the use of artificial mineral fertilisers from fossil resources should be viewed critically from an ecological standpoint, firstly because of environmentally damaging extraction and secondly because of the introduction of heavy metals into the soils by mineral fertilisers. Phosphorus is a limited raw material, and the efficient use thereof for a fertile soil is of great importance against the background of a growing world population. From a sustainability standpoint, the closing of natural nutrient cycles is becoming increasingly important and also provides a local source of raw materials which has so far been used only to a limited extent.

Description

Heavy-metal-depleted fertilizer granules made from secondary phosphate and processes for their production

State of the art:

Agricultural use removes mineral raw materials from the soil, such as compounds containing phosphorus, which have to be compensated for by adding mineral fertilizers. The material and energetic use of biomass, such as from household waste or sewage sludge, is associated with a withdrawal of nutrients and considerable amounts of organic matter from the natural material cycles. The preservation of the fertility of the soil through the use of artificial mineral fertilizers from fossil resources is to be assessed critically from an ecological point of view, on the one hand because of the environmentally destructive degradation and on the other hand because of the heavy metal input into the soil through mineral fertilizers. Phosphorus is a limited raw material and its efficient use for fertile soil in the context of a growing world population is of great importance. From the point of view of sustainability, the closure of natural nutrient cycles is becoming more and more important and also offers a local source of raw materials that has so far only been used to a limited extent.

Organic residues, such as sewage sludge, digestate or liquid manure, are in principle a cost-effective and sustainable alternative to mineral fertilizers and thus to close the nutrient cycle. Some of these organic residues are still applied directly to fields. For some time now, however, the acceptance of this recycling method has been decreasing progressively, since direct application leads to undesirable odor nuisance and the associated cycles are suspected of leading to an undesired concentration of certain pollutants, such as perfluorinated surfactants (PFT) and various heavy metals. Sewage sludge that has not been subjected to any hygienic treatment can also contain a large number of epidemic and phytosanitary pathogens such as bacteria, viruses, parasites and worm eggs. If the organic residues are to be recycled in agriculture, there is a fundamental risk that pathogens can reach humans and animals via food and feed and thus endanger them.

The thermal recycling of these organic residues is currently gaining in importance. Ashes from thermal recycling and / or incineration of organic residues are suitable sources of raw materials due to the high content of nutrients such as phosphorus (P). However, the heavy metals are also concentrated. Because of the bad

Plant availability of the phosphorus (P) contained in the ashes and the pollutant content, direct use of the ashes as fertilizer is hardly possible. Therefore, such ashes are currently mostly dumped or used in landscaping and are therefore no longer available as a source of raw materials for the material cycle.

In the prior art, different processes for the material utilization of phosphorus-containing ashes, for example from sewage sludge, are known. The known processes are based on the raw material ash, whereby the P content in the ash should be as high as possible. The processes differ with regard to the P deposition (acid and precipitant), the

Recycling product and the type of heavy metal separation. The processes for obtaining phosphate from sewage sludge ash can generally be subdivided into thermochemical, thermoelectric and wet-chemical approaches. In the wet chemical process, numerous different concepts are pursued, with a general distinction between processes in which the acid is only mixed with the ash and fertilizer is made from it, and processes in which phosphorus is extracted from the ash and thus brought into the liquid phase becomes.

The wet chemical processes, in which basically only ash is mixed with acid, in particular earth-moist, in order to produce fertilizer from it, are economical. The largely insoluble phosphate from phosphate-containing ashes is digested using mineral acid. Such a method is known from DE 10 2010 034 042 B4, for example. The process produces a phosphate or multi-nutrient fertilizer by mixing ashes from sewage sludge mono-incineration with mineral acid with the addition of potassium and / or a nitrogen carrier. The mineral acid breaks down the poorly soluble phosphate compounds in the sewage sludge ash. The desired conversion reactions and granulation take place largely simultaneously. Mixing, reaction and granulation take place in a mixing apparatus. Ploughshare mixers with a set of knives, a continuously operating continuous mixer or a twin-shaft paddle mixer are proposed for this purpose. With this type of wet chemical process, as described, for example, in DE 10 2010 034 042, the resulting nutrient composition can be adapted to the needs of the soil and plants.

^■ This type methods, such as for example from DE 10 2010 034 042 B4 known that heavy metals from the ash can not be separated, but get completely into the fertilizer and thus into the nutrient cycle. There is currently no legal clarity as to whether this is why such procedures are even allowed and, if so, with what conditions or restrictions. In any case, these processes do not meet high sustainability requirements, where a discharge of pollutants in recycling processes is required.

^■ In addition, these processes have considerable procedural problems in the technical implementation, since when the phosphate-containing ashes are mixed with the mineral acid, spontaneous and sometimes very exothermic reactions take place, which significantly disrupt the simultaneous granulation. In addition, the mixture of ash with acid is often particularly sticky, which makes stable process management significantly more difficult and often leads to process disruptions due to adherence and clogging of system parts. Another problem is that mineral acids are very corrosive and with this process management many parts of the system, for example the granulating unit, drying unit or connecting sections, come into contact with them and are damaged accordingly.

From DE 10 2016 116 633 A1 a method is known in which a suspension of at least one phosphate-containing secondary raw material and at least one mineral acid is first produced, then the poorly soluble phosphates of the phosphate-containing secondary raw material are at least partially dissolved in the suspension produced and / or in a water- and / or neutral ammonium citrate-soluble phosphate phase are converted and finally this suspension is fed to a granulation, the fertilizer granules being formed and the P205 content contained in the fertilizer granules being more than 75% neutral ammonium citrate-soluble. As a procedural advantage, this document describes the fact that by generating a raw material dispersion, the reaction, which sometimes occurs spontaneously and violently when the phosphate-containing secondary raw materials and the mineral acid are brought together, should be manageable, controllable and controllable by the process. The suspensions produced in this process have a significantly higher proportion of water than in comparison to processes in which the phosphate-containing ones Secondary raw materials and diluted or undiluted mineral acid are mixed directly, quasi-moist, and optionally granulated (for example as described in DE 10 2010 034 042 B4). This higher proportion of water is intended to act as a buffer. In this process, the suspension produced in this way is fed to a granulation, whereby the fertilizer granules are formed.

^{■ The} disadvantage of this process management is that the high proportion of water in the suspension must ultimately be separated off during or after the granulation. In this process, this can only be done thermally by drying, which, however, is particularly energy-intensive and therefore expensive. In order to provide a particularly cost-effective method, the method according to document DE 10 2016 116 633 A1 does not include any stage of separation of pollutants, in particular heavy metals. As already stated above, the legal approval is therefore in question and the process does not meet the requirements for sustainable recycling processes with pollutant separation.

With other wet chemical processes, such as BioCon, SEPHOS, SESALPhos, Tetraphos, PASCH or Leachphos processes, the heavy metals can be at least partially separated, but considerable process residues are created. All these processes have in common that by mixing the sewage sludge ash with mineral acid, depending on the type and concentration of the mineral acid and depending on the process management, a large part of the phosphate in the ash is dissolved, but a considerable proportion of undissolved components remains. Subsequently, in this process, the phosphate-containing solution is very expensive and processed further through very complex precipitation or extraction processes. In contrast, it is advantageous in this process that the phosphate-containing solution obtained is at least partially freed from heavy metals and these heavy metals are discharged from the process.

^{■ The} disadvantage of this process is that considerable amounts of waste are generated (the undissolved components are process residues that have to be disposed of at great expense, although they also contain nutrient components. In addition to the considerable costs arising from this, the formation of the large waste streams that lead to are to be deposited, also the fundamental question of the sustainability and usefulness of such processes. At least the amount of waste is not reduced by such processes as required.

^{■ The} cost driver in these processes continues to be the considerable use of additional chemicals. Often, products are then created that cannot be used directly as fertilizer, for example, but instead have to be processed again. As a result, economic viability is not given under current market conditions.

From EP 3 037 396 A1 a method for the production of a phosphate-containing fertilizer from an ash or a char residue of a sludge from a waste water treatment or waste fermentation is known. Here, an ash or the charring residue is mixed with a mineral acid and the resulting suspension is incubated in a first vessel, then moist solids are separated from the suspension and the separated solids are replaced by further ash or further charring residue, the further ash is mixed or the further charring residue with the mineral acid remaining in the first vessel and incubation of the resulting suspension in the first vessel. The separated solid is transferred to a second vessel and mixed there with a pH-neutral, basic or buffered aqueous liquid, then part of the liquid resulting from the mixing is separated from the second vessel, the heavy metal ions contained in it are separated from it and this liquid is transferred the second vessel returned. To separate the heavy metal ions, ion exchangers, activated carbon, Bacteria, fungi, algae, a biomass from bacteria, fungi or algae, the use of precipitants and / or a nanofilter and / or electrolytically proposed.

In EP 3 037 396 A1, a moist solid is separated off in process step 2, the solution remaining in vessel 1. New ash is added to the remaining liquid in vessel 1. Accordingly, no further acid is added as a reactant in the subsequent batch. This reduces the acid strength from batch to batch and thus the dissolving or conversion potential of the acid compared to the phosphate.

^The disadvantage of this process is that the phosphate solubility of the ash is increased sufficiently in the first batch at best; with each subsequent batch, the solubility decreases until there is ultimately no change compared to the initial ash. This means that a suitable supply of nutrients for the plants cannot be given within one growth period.

^■ The proposed options for separating heavy metals are either expensive due to a high proportion of consumables (e.g. ion exchangers, precipitants), require a long reaction time (bacteria, fungi, algae, fungi or algae), are technically questionable in their function (e.g. heavy metal separation from solution activated carbon) or technically hardly or only with great effort (nanofiltration). A practicable and cost-effective way to separate the heavy metals from the incineration ash is not shown.

In addition to the recycling of phosphate-containing ashes, the recycling of ammonium-sulphate-containing solutions is also an economic problem. In principle, ammonium sulphate-containing solutions, such as those obtained in considerable quantities in waste gas scrubbers and especially in biogas plants, are untreated or conditioned and very suitable as fertilizers apply accordingly.

^{■ The} disadvantage of the previous use of these solutions is often that concentration is expensive and only a concentration of 40% (maximum solubility) can be achieved even through concentration.

^■ The application of these (concentrated) liquids to the fields is logistically complex and expensive. The limitation of the application to only certain periods of time makes expensive storage or other recovery necessary.

Furthermore, the prior art describes pedosphere-improving granules, which, however, often have a disadvantageous effect. Many of these known structures have a positive effect on plant growth, but this is associated with negative effects on microorganisms and microorganisms. It has been observed several times that granules of the prior art, for example, reduce the number of earthworms and that fewer nitrogen-assimilating microorganisms continue to occur in the soil. While in the past the reduction of such soil organisms was considered to be of little relevance, today we know that the organisms mentioned are central to the quality of soils. In particular, soils that are exposed to strongly changing weather conditions, such as high temperatures or heavy rain, require a healthy biomass, such as B. insects, nematodes or annelids, in order to ensure high yields in plants even under highly fluctuating weather conditions.

In summary, no sustainable, technologically easy to implement and economical phosphate recovery processes that use granules are known from the prior art be able to generate an exact plant and soil-specific nutrient supply, whereby the nutrients contained are also optimally available to the plants.

The invention is therefore based on the object of providing new, improved and heavy metal-depleted granules which optimize the pedosphere with regard to soil flora and fauna. The soil flora mainly includes plant or non-animal organisms, such as Bacteria, ray fungi, fungi, algae and lichens. The soil fauna is composed of animal protozoa and multicellular organisms, which are differentiated according to their size into microfauna (<0.2 mm; e.g. ciliates, flagellates, amoebas, small roundworms), mesofauna (<2 mm; e.g. springtails, rotifers , Mites), macrofauna (> 2 mm; e.g. bristle worms, woodlice, insects) and megafauna (> 20 mm; e.g. vertebrates such as voles, shrews, moles). The optimization primarily affects the improved plant growth as well as the growth of bacteria, flagellates, nematodes, annelids or insects and others.

The present invention is also based on the object of providing an economical, ecological, flexible, simple and technically feasible method for the production of soil- and / or plant-specific, heavy metal-depleted fertilizers with exactly adjustable nutrient composition in granulate form. The method according to the invention is intended to enable a wide variety of inorganic secondary phosphates to be processed efficiently and inexpensively, with soil- and plant-specific fertilizer compositions also being provided in a targeted manner, with a large part of the phosphate in the resulting fertilizer granules being in a form readily available to plants and at least part of the heavy metals being separated off is. In addition, in the process according to the invention, solutions containing ammonium sulfate should be inexpensive and technologically easy to integrate and use as a further nutrient. In addition, a fertilizer is to be provided that can be used and / or used as a pedophore improver in agriculture, forestry or horticulture.

Description of the invention:

The object is achieved by the features of the independent claims. Advantageous embodiments of the invention are described in the dependent claims. According to the invention, a heavy metal-depleted, pedoshare-improving granulate is provided that is produced using a method that comprises the following steps:

a) Production of a raw material suspension comprising at least one inorganic secondary phosphate (1) and at least one reactant (2), the proportion of liquid phase in the raw material suspension being greater than 45%,

b) maintaining an incubation time between inorganic secondary phosphate (1) and reactant (2) between 1 and 300 minutes,

c) Carrying out an electrochemical heavy metal depletion directly in the raw material suspension (3) produced and discharging at least some of the separated pollutants (4), wherein the electrochemical heavy metal depletion can begin with or during the production of the raw material suspension or thereafter, with the electrochemical heavy metal depletion at least simultaneously can run with or at times in parallel during the incubation period and / or beyond the incubation period, d) Granulation and / or extrusion of the heavy metal-depleted raw material dispersion (5), it being possible for at least one drying and / or fractionation to follow and

e) Continuous and / or batchwise repetition of process steps a) to d).

In step a) a raw material suspension is produced from at least one inorganic secondary phosphate (1) and at least one reactant. In this raw material suspension, the phosphate is converted from the inorganic secondary phosphate, which is insufficiently soluble in the inorganic secondary phosphate, that is to say is insufficiently available to plants. The conversion of the phosphate takes place by reaction with a reaction agent with the aim of considerably improving the solubility and thus the availability of this phosphate to plants. In this context, a reactant is to be understood as a substance, such as acid or alkali, which on the one hand dissolves at least part of the phosphate supplied by the inorganic secondary phosphate and / or reacts with it. Reactants are for example

According to the invention, this reaction between the inorganic secondary phosphate and the reactant takes place in a raw material suspension. The reaction that takes place in a raw material suspension can be controlled and monitored. The liquid phase required to form the raw material suspension results either from the fact that the reaction agent is a solution or suspension or is added specifically in addition to the inorganic secondary phosphate and reactant, for example in the form of water. According to the invention, the proportion of the liquid phase and the composition of the suspension are essential control variables for the desired reaction between inorganic secondary phosphate and reactant, and the resulting solubility of the converted phosphate as a reaction product can thus be adjusted.

The inorganic secondary phosphate contains heavy metals. In addition to the reaction between the reactant and phosphate, the reactant should also at least partially dissolve the heavy metals present in the inorganic secondary phosphate. For example, the type and concentration of the reactant and the amount of liquid phase can be used to set the rate of dissolution and the proportion of heavy metals dissolved.

Step b) calls for an incubation time, which means that the reaction agent is allowed to act on the inorganic secondary phosphate. Targeted setting of this reaction time influences the progress and scope of the reaction. On the one hand, this enables the proportion of dissolved heavy metals to be controlled. On the other hand, the solubility of the resulting phosphate after the conversion can also be adjusted via the reaction time.

Step c) describes the electrochemical heavy metal depletion according to the invention directly in the raw material suspension produced. Electrochemical heavy metal depletion is defined as the chemical separation reactions taking place with the participation of electrons that flow through an external conductor circuit. The electrodes are the active components in the electrochemical reaction, on the surfaces of which the heavy metals attach or adhere. This means that the heavy metals dissolved in the previous steps by the reactant and thus present dissolved in the suspension are deposited on the electrode or adhere to it through an electrochemical process. Following this electrochemical process, the electrode with the heavy metal-containing adhesions is spatially separated from the suspension. This removes the heavy metals adhering to the electrode from the suspension. The heavy metal-containing adhesions on the electrode are detached and a heavy metal-containing portion is discharged from the raw material suspension. This electrochemical reaction assumes that the heavy metals are at least partially dissolved. With the formation of the raw material suspension according to step a), inorganic secondary phosphate are combined with the heavy metals and reactants contained therein, as a result of which the reaction according to the invention begins between the two components. Through this reaction, the heavy metals contained in the inorganic secondary phosphate are at least partially dissolved. The reactant thus has the additional function of at least partially dissolving heavy metals from the inorganic secondary phosphate.

Starting from this reaction point of bringing together the inorganic secondary phosphate and the reactant, the heavy metals are dissolved out of the inorganic secondary phosphate, which takes place as a function of the reaction kinetics. In this way, the electrochemical heavy metal depletion can in principle begin with or during the production of the raw material suspension or afterwards, since then proportionally dissolved heavy metals are already present. In this case, the electrochemical depletion process takes place parallel to the incubation time according to step b). Since the electrochemical reaction is also time-dependent, the incubation time can advantageously be used, which shortens the overall time of the process. The electrochemical reaction can also take place beyond the incubation period. This is advantageous, for example, in that, at the end of the incubation period from step b), dissolved heavy metal components are given time to adhere to the electrode. In principle, the electrochemical reaction according to step c) can also take place after the incubation time according to step b), for example in a separate vessel or in a separate flow-through circuit.

After the electrochemical depletion, granulation or extrusion takes place in step d) with the aim of forming heavy-metal-depleted, pedosphere-improving granules. The type of granulation or extrusion depends on the technical requirements and, in particular, on the consistency and processing properties of the heavy metal-depleted raw material dispersion. Pumpable and sprayable heavy metal-depleted raw material dispersions can be processed, for example, by spray granulation. If, on the other hand, part of the liquid phase of the heavy metal-depleted raw material dispersion is mechanically separated off, the earth-moist, heavy-metal-depleted raw material dispersion thus formed can, for example, be processed by means of a granulating plate or an extruder.

The granules or extrudates formed by granulation and extrusion are often unsuitable for storage or direct use. Subsequent drying, for example, usually increases strength and storage stability. Defined grain fractions are often required for the application, which is achieved through appropriate fractionation.

Steps a) to d) can be implemented in batches and / or continuous processes, it being possible for buffer containers to be used between the process steps. To implement all or individual process steps, a single unit and / or, in particular to map larger production quantities, several identical or similar units can be used. Several units in one or more process steps can be connected in parallel and / or alternately.

In the production of the heavy metal-depleted fertilizer granulates according to the invention, the process steps are carried out batchwise and / or continuously, for example, continuously until the desired production amount is reached, i.e. steps a) to d) are repeated correspondingly often.

In the further description, the individual steps listed, their configuration and preferred embodiments are described in more detail and illustrated in addition and in more detail. The method according to the invention provides an economical, ecological, flexible, simple and technically feasible method for the production of soil- and / or plant-specific, heavy metal-depleted fertilizers with precisely adjustable nutrient composition in granular form, which has numerous technological advantages over the prior art, such as:

^■ With the inventive method it is possible to unlock the bad plant available phosphate in inorganic phosphate secondary and make optimal plant available. The process design according to the invention solves the existing technical problems of the process in which ash is mixed with acid in a quasi-earth-moist manner in order to produce fertilizers therefrom, as are known, for example, from the publication DE 10 2010 034 042 B4. In these processes, the reaction between inorganic secondary phosphate and mineral acid (here reactant) can hardly be monitored and controlled. This means that the solubility and plant availability cannot be precisely adjusted. In addition, the reaction superimposes the granulation process when the reaction is carried out, which is therefore hardly controllable. Such processes are technically hardly controllable. The resulting inferior product quality also fluctuates greatly. The reaction in the raw material suspension makes the reaction controllable and controllable.

^■ The advantage of carrying out the reaction in a suspension of raw materials, although of methods, such as DE 10 2016 116 633 Al is known. However, in this process, the entire raw material suspension is directly granulated with the correspondingly high proportion of liquid phase. During granulation, this liquid phase is thermally separated in an energy-intensive manner. In a preferred embodiment, the method according to the invention offers the possibility of separating a large part of the liquid phase mechanically (solid / liquid separation). Much less energy is required for mechanical separation, which means significantly lower process costs. In addition, technologically simple granulation technologies such as granulation plates can then be used, which is otherwise not possible.

These methods, such as DE 10 2016 116 633 A1, for example, also do not offer any possibility of separating heavy metals. This results in a digested, phosphate-containing fertilizer, but it still contains all of the heavy metals, in particular with the inorganic secondary phosphate. The phosphate-containing fertilizer product produced in the process according to the invention differs fundamentally therefrom, since environmentally harmful heavy metals are depleted.

^■ With the known wet chemical processes, such as BioCon, SEPHOS, SESALPhos, Tetraphos, PASCH or Leachphos processes, which dissolve the phosphate from the inorganic secondary phosphate by means of mineral acid (reactants) and separate this phosphate-containing solution from the undissolved portion and process it further, The process according to the invention produces significantly less waste, namely only the separated heavy metals. In addition, the method according to the invention does not separate the dissolved phosphate from the undissolved portion, but instead transfers all of the constituents of the inorganic secondary phosphate into a fertilizer that has been depleted of heavy metals. Other phosphate-containing products such as phosphoric acid or calcium phosphate result from the other processes. Compared to processes such as from EP 3 037 396 ^{A1, the} process according to the invention results in a very well digested and therefore specifically plant-available phosphate fertilizer. In the case of the method such as from EP 3 037 396 A1, the phosphate from the inorganic secondary phosphate is broken down significantly less strongly by the process management and is thus made less readily and less specifically available to plants. Although the method offers heavy metal depletion, the methods proposed there are not as practicable and not as cost-effective as in the method according to the invention with electrochemical heavy metal separation.

^■ Some methods of the prior art indicate that the phosphate is increased by the method, the solubility. In most cases, it remains unclear by how much which solubility increases.

o There are a number of different methods for determining the solubility of phosphate, which differ in the dissolution procedure and the dissolution medium (water, citric acid, neutral ammonium citrate, etc.). Correspondingly, different information on solubility results from the process.

o The solubilities of the various dissolution processes cannot be converted into one another in a generally valid way, for example with an approximately fixed factor. Nor does a trend have to be concurrent. Depending on the type of phosphate (phase composition) and the matrix, there are considerable differences in solubility with one dissolving medium and with different dissolving media, which vary considerably in tendency and relationship. For example, inferring that the solubility in water is neutral in terms of ammonium citrate solubility is not permitted.

If a defined solubility of the phosphate in the end product is specified in the process, this does not (automatically) define the conclusion that the solubility of the phosphate from the inorganic secondary phosphate is increased.

o If further phosphate nutrients can be added in the process (as is usually provided), which may already be very soluble themselves, this automatically increases the percentage solubility in the end product compared to the ash. If the information in the prior art does not clearly relate to the phosphate, which comes from the inorganic secondary raw material, no conclusion can be drawn about an improvement in solubility.

In the process according to the invention, a significant improvement in the solubility of the phosphate is achieved from the inorganic secondary phosphate. This increase in the neutral ammonium citrate solubility based on the phosphate from the inorganic secondary phosphate alone is at least 20%, and a neutral ammonium citrate solubility of greater than 60% based on the phosphate content from the inorganic secondary phosphate is achieved.

Compared to the prior art, the method according to the invention provides new, improved and heavy metal-depleted fertilizer granulates which optimize the pedosphere in terms of soil flora and fauna and are sustainable and environmentally friendly due to the heavy metal reduction.

In a further aspect, the invention relates to a process for the production of these heavy metal-depleted, pedosphere-improving granulates, which comprises the process steps mentioned. In a further aspect of the invention, a precipitation and / or crystallization product from an ammonium- and sulfate-containing starting solution is provided, which is produced using a method which comprises the following steps:

^■ Supply of at least one alkali or alkaline earth compound as a precipitation reagent for at least partial precipitation and / or crystallization of sulfate from the ammonium and sulfate-containing starting solution,

^■ previous, joint or subsequent supply of at least one P compound as a precipitation reagent for at least partial precipitation and / or crystallization of ammonium from the ammonium and sulfate-containing starting solution as at least one N / P compound and setting the pFI value between from 6 to 11 and

^■ Separate or joint separation of the precipitates and / or crystallization products formed,

wherein the generated precipitation and / or crystallization products can be used in the process for the preparation of the heavy metal-depleted, pedophore-improving granules and / or used separately therefrom.

In a further aspect, the invention relates to a method for the preparation of this precipitation and / or crystallization product, which comprises the process steps mentioned.

In a further aspect, the invention relates to a combined method for the production of a precipitation and / or crystallization product according to the above-mentioned process steps with the method for the production of heavy metal-depleted, pedophore-improving granules according to the above-mentioned process steps.

All percentages (%) in the context of the invention relate to percent by weight (% by weight, i.e.% w / w), unless stated otherwise.

A particular advantage of the proposed granules and the proposed method is that the neutral ammonium citrate solubility of the phosphate supplied with the inorganic secondary phosphate is increased by reaction with the at least one reactant and the P205 content from the inorganic secondary phosphate in the fertilizer granules is more than 60% neutral ammonium citrate soluble is. In the context of the invention, the term "P205 portion" preferably describes the portion of P205 in the fertilizer granulate. The total amount of phosphorus (P) and heavy metals such as lead, cadmium, nickel are determined by means of inductively coupled plasma atomic emission spectrometry (ICP- OES) in accordance with DIN EN ISO 11885: 2009. For this purpose, the sample to be determined is first digested with an aqua regia digestion in accordance with DIN EN 13346: 2001-04. Different methods, in particular different extraction methods, are known for determining the soluble phosphate content. For this purpose, the availability of fertilizers is examined in the laboratory with different solvents and marked accordingly. The most important solvents used are water, ammonium citrate, citric acid, formic acid and mineral acids. The EU fertilizer regulation also standardizes various methods for determining the phosphate solubility of fertilizers to Different methods can be used for the origin and nature of the P fertilizer to be tested. To characterize the solubility of the phosphate, the following three extraction methods are used in the context of the present invention: The extraction of the water-soluble phosphorus (P) takes place in accordance with DIN EN15958: 2011. The phosphorus (P), which is soluble in neutral ammonium citrate, is extracted in accordance with DIN EN15957: 2011. The The 2% citric acid soluble phosphorus (P) is extracted in accordance with DIN EN15920: 2011. The phosphate content (P) is then determined by means of inductively coupled plasma atomic emission spectrometry (ICP-OES) in accordance with DIN EN ISO 11885: 2009.

Particularly with high proportions of water- and ammonium citrate-soluble phosphate, it is guaranteed that a large part of the fertilizer phosphate is actually available to the plant in the short and medium term. The phosphorus content, which is soluble in neutral ammonium citrate, can be used as an indication of the medium-term availability of fertilizer phosphorus to plants, i.e. H. over the period of about one crop rotation. The immediately available P component of a fertilizer is described by its solubility in water. The higher the water-soluble P component, the faster or easier the availability of the fertilizer phosphorus for the plant. Stronger solvents such as citric or formic acid also dissolve P components that are only available to plants over the long term or only under certain site conditions such as low pH values. Planting and vegetation experiments have shown that there is above all a good correlation between the neutral ammonium citrate-soluble phosphate content and the growth of the plants. High water solubility makes phosphate available very quickly in large quantities, which the plant may not be able to absorb completely in the same time sequence as it grows, so it remains unused and is possibly washed out. According to current scientific opinion, for reasons of resource protection, preference should be given to using P-fertilizers that have a particularly high phosphate content that is soluble in neutral ammonium citrate. In this respect, the present invention fulfills the requirement for high neutral ammonium citrate-soluble phosphate proportions by using the proposed method fertilizer granulates with a particularly high neutral ammonium citrate-soluble P205 proportion of greater than 60%, preferably greater than 70%, particularly preferably greater than 80% of the total P205 proportion are provided in the fertilizer granulate.

For the purposes of the invention, fertilizers are substances or mixtures of substances that supplement or adjust the nutrient supply for the cultivated plants, in particular crops, in agriculture, forestry and horticulture, and they can optionally be combined with other materials and / or functionalized. Both single nutrient fertilizers such as phosphate fertilizers and complex fertilizers are understood as fertilizers. Fertilizers in granular form, i.e. Fertilizer granulate is a pile typically in an approximately spherical shape and sufficient inherent strength with an average granulate size of 0.5-10 mm, preferably 1-7 mm, very particularly preferably 2-5 mm.

In the context of the invention, inorganic secondary phosphate refers to those substances that arise during the processing, preparation or manufacture of something (residue) and have a phosphorus content greater than 5% P205 and a TOC content (TOC = total organic carbon) of less than 3 % exhibit. Examples of inorganic secondary phosphates are ash and / or slag from the mono- or co-incineration of sewage sludge, ash and / or slag from the incineration or co-incineration of animal excrement, animal meal, animal remains and carcasses or ashes / slag from the incineration of liquid manure and digestate as Single substance or mixtures thereof.

A TOC content (TOC = total organic carbon) of more than 3% as in sewage sludge, animal excrement, animal meal, animal remains and animal bodies, manure and fermentation residues is not by definition for an inorganic secondary phosphate, since the organic fraction in the process according to the invention is in the process to be produced Fertilizer is transferred. In the case of inorganic fertilizers, as is characteristic of typical conventional fertilizers, an organic proportion of less than 3%, often less than 1 % required. The inorganic secondary phosphate should initially make it possible in principle to produce such inorganic fertilizers.

Organic residues, such as sewage sludge in particular, or liquid manure or digestate with a typical organic content of 40-90% (TS), are expressly excluded from the definition of inorganic secondary phosphate. The phosphate present in these substances is in a different, more readily plant-available bond form than, for example, in cremation ashes. Sewage sludge has been used for fertilization for decades, as the phosphates are sufficiently available to plants there. The digestion (reaction with the reactant) required according to the invention to increase the phosphate solubility is not required for these substances.

The thermal utilization of sewage sludge, but also meat and bone meal and other organic residues is now mostly done in fluidized bed systems. As a result of this type of incineration, a high proportion of sand from the fluidized bed often ends up in the ash or slag. Sand is to be understood here in the sense of a particle size grain, as a rule consists of very SiO2-rich compounds up to quartz. The SiO2 content in such ashes from a fluidized bed can be well over 20%, sometimes over 30%. On the one hand, this proportion of sand reduces the proportion of phosphate due to the dilution effect and can also lead to technical problems with abrasion. With alternative combustion technologies such as so-called dust firing, such a fluidized bed does not exist and consequently an ash or slag with a significantly reduced proportion of sand results. Ash or slag with an SiO 2 content of less than 20%, particularly preferably less than 15%, is preferred.

The phosphorus compounds contained in the inorganic secondary phosphate are referred to here as phosphate, even if in their entirety this should not or not completely correspond to the type of binding of the phosphorus in individual cases.

In the context of the present invention, a reactant is to be understood as meaning a substance or a mixture which on the one hand dissolves at least part of the phosphate supplied by the inorganic secondary phosphate and / or reacts with it and on the other hand at least some of the heavy metals from the inorganic Dissolves secondary phosphate. Reactants are, for example, organic or inorganic acids or acid mixtures or bases or mixtures of different bases, in each case in undiluted or diluted form.

In the context of the present invention, the sum of the liquid substances in a coherent system is defined as the liquid phase (also liquid phase). The raw material suspension consists of a solid and a liquid phase. In the context of the present invention, the solid phase is the sum of the undissolved substances. The liquid phase in a system, for example in a raw material suspension, can be formed from different liquid components. For example, liquid components can be supplied at least partially in the form of moisture, partially in a suspension or as a liquid via various substances or, for example, as water or at least partially in the reactant, for example liquid, in particular, dilute acids.

The term "moisture" corresponds in the sense of the invention to the physically bound water that adheres to the substance or mixture of substances. The term "moisture" is also used synonymously with the term "moisture content". The moisture or the moisture content is gravimetric in the context of the present invention determined according to DIN 52183. In the gravimetric moisture determination, also known as the Darr method, the sample is first weighed and then dried to constant weight in a drying oven at 105 ° C. The free water contained in the sample escapes in context corresponds to the present invention of the moisture or the moisture content. Since the liquid phase can also contain dissolved components that remain as solids during drying, the percentage of the liquid phase is usually significantly higher than the moisture.

The term "earth-moist" defines a consistency. In concrete technology, a concrete with a stiff consistency with a water-cement value <0.40 is generally referred to as earth-moist concrete. In analogy to this definition, an earth-moist raw material mixture is a consistency range of the raw material mixture comparable to a consistency On the one hand, the consistency range according to the invention is limited by a relatively dry mixture, but with more than 5% moisture (based on the raw material mixture), which cannot be shaped by hand, i.e. does not yet disintegrate like powder On the other hand, the range is limited by the fact that the raw material mixture can be balled and shaped in the hand (comparable to a snowball) and does not dissolve without the application of force (such as vibration).

An earth-moist mixture can be clearly distinguished from a suspension. A suspension (Latin suspendere, hang up ',' to let in suspension ') is a heterogeneous mixture of substances made up of a liquid and finely distributed solids (particles), whereby the particles in the liquid are at least partially and at least temporarily in suspension, even if a weaning behavior can set in. The solids are "suspended" in the liquid phase. The liquid referred to as moisture in the earth-moist and / or easily plastically malleable mixture, on the other hand, is physically bound or adhered to the solid or is largely in the form of so-called pore water. Earth-moisture and / or plastic Easily formable mixtures have a significantly lower proportion of liquid phase than suspensions. An earth-moist mixture can also be referred to as a dispersion. According to the definition here, dispersions contain at least one solid and at least one liquid phase. A suspension or an earth-moist mixture also apply here accordingly as a dispersion.

Generation of the raw material suspension and phosphate reaction

The raw material suspension in the proposed method is produced from at least one inorganic secondary phosphate and at least one reactant, the proportion of liquid phase being greater than 45% and the incubation time between inorganic secondary phosphate and reactant being between 1 and 300 minutes.

The raw material suspension that is used in the context of the proposed method has a significantly higher proportion of liquid phase than in comparison to conventional methods known from the prior art. It is known in the prior art that the phosphate ashes are mixed with mineral acid directly and moistly and at the same time granulated. The production of a raw material suspension with a significantly higher proportion of liquid phase, which is provided in the context of the proposed invention, therefore has considerable technical advantages. For example, when the phosphate-containing secondary raw materials are mixed with the mineral acid, the reactions, which often take place spontaneously and are sometimes very exothermic, can be monitored and controlled. The higher proportion of the liquid phase according to the invention advantageously acts as a reaction buffer. A raw material suspension with a significantly higher proportion of the liquid phase is also significantly less sticky. A stable process management is thus made much easier and the adhesion and clogging of system parts can be effectively reduced. For this reason, the raw material suspension produced contains a proportion of liquid phase of preferably greater than 45%. In raw material suspensions in the substance system according to the invention, reactions can occur depending on the type of composition and the chemical-physical parameters of the raw material suspension (such as pH value or temperature), which lead to an increase in viscosity, for example through a type of gelation. This is undesirable because it impairs the processability (such as stirring, pumping, etc.). This can be prevented or reduced by adding suitable additives such as dispersants. This can also be prevented or reduced by using a higher proportion of the liquid phase. For this reason, in a preferred embodiment, the proportion of liquid phase in the raw material suspension is set to greater than 60%.

In a preferred embodiment of the invention, after the incubation time provided according to the invention, the raw material suspension preferably contains an undissolved solid phase, which is preferably also referred to as the undissolved solids content, of less than 40%. The undissolved solid phase is to be understood as the total solids content in the raw material suspension, i.e. also any solid that may have formed through, for example, precipitation or crystallization in the raw material suspension. A particularly good and simple homogenization of the raw material suspension produced is possible in this solids content range. In a particularly preferred embodiment of the invention, the raw material suspension contains an undissolved solids content (solid phase) of less than 30% after the incubation time provided according to the invention. Under such conditions, the rate of dissolution is relatively high, as a result of which the necessary reaction time can advantageously be shortened.

The production of the raw material suspension can also advantageously solve the corrosion problems. The reaction between the inorganic secondary phosphate and the reactant can preferably take place in an acid-proof stirred tank with an acid-proof stirrer, after this reaction the majority of the free acid or alkali is used up and is therefore less harmful to the following system parts.

In addition, the pH of the raw material suspension produced can also be increased further if necessary after the reaction. However, it is advantageously ensured that the heavy metals from the inorganic secondary phosphate which are also at least partially dissolved by the dissolution reaction remain largely dissolved in the raw material suspension. In a preferred embodiment, the pH should not exceed 3, very particularly preferably 2. At higher pH values, the heavy metals typically begin to precipitate, for example as hydroxides. In a likewise preferred embodiment, a complexing agent (for example citric acid) is added to the raw material suspension. The addition of the complexing agent shifts the pH value precipitation of the heavy metals to higher pH values. In this way, in this preferred embodiment, the pH can be adjusted to up to 5, particularly preferably up to 4. In this way, for example, a further neutralization of the raw material suspension is achieved.

To set the preferred proportion of liquid phase, one or more liquid components can be added to the raw material suspension, for example water and / or liquid nutrient-containing solutions. Nutrient-containing solutions preferably contain nutrients and / or trace substances that are contained in the proposed fertilizer granules. In a preferred embodiment, a solution containing at least ammonium and sulfate is added.

The phosphate contained in the inorganic secondary phosphate is made available to plants as a nutrient in the method according to the invention. A high phosphate nutrient content in the inorganic secondary phosphate is therefore particularly advantageous for the nutrient content of the fertilizers produced and increases the economic efficiency of the process. That in the inorganic Phosphate contained in secondary phosphate is used advantageously as a nutrient component in the fertilizer produced. High phosphate contents, especially in the case of inorganic secondary phosphate, are accordingly desirable here. Inorganic secondary phosphates with greater than 10% P205, particularly preferably greater than 13% P205 and very particularly preferably greater than 16% P205, are therefore preferred. In other words, P205 proportions of greater than 10% are preferred, particularly preferably greater than 13% and very particularly preferably greater than 16%. Therefore, preference is given to ashes and / or slag from the individual or combined thermal utilization (incineration) of sewage sludge, animal excrement, animal meal, animal remains and / or animal carcasses as individual substances or mixtures thereof as inorganic secondary phosphates with the typical P205 contents of over 10 % and above. In addition, the inorganic secondary phosphate can contain other components. It is advantageous if further nutrient components are included, such as N, K, Mg or other trace nutrients.

In the proposed method, the inorganic secondary phosphate (s) reacts with at least one reactant. The solubility of the phosphate contained in the inorganic secondary phosphate is advantageously increased. Since there is also a heavy metal depletion, it is preferred in the context of the invention that the reactant is set up to also dissolve a portion of the heavy metals contained - preferably as high as possible.

The phosphate fraction present in the inorganic secondary phosphate typically has a relatively low solubility. Accordingly, substances such as sewage sludge ash are only suitable to a limited extent as fertilizers. Typically, these inorganic secondary phosphates show a water solubility of less than 30% and a neutral

Ammonium citrate solubility of less than 50%, preferably based in each case on the total phosphate content in the inorganic secondary phosphate. For a meaningful use as a fertilizer, it is preferred in the context of the invention that this insufficiently soluble phosphate is converted into a more soluble and therefore more readily available to plants. According to the invention, the conversion takes place by at least partial reaction of the inorganic secondary phosphate with at least one reactant. The reactant is preferably set up to dissolve at least part of the phosphate contained in the inorganic secondary phosphate and / or to react with this in such a way or to convert the phosphate by reaction so that a phosphate that is more neutral-ammonium citrate-soluble is formed. In the subsequent process, for example by precipitation, recrystallization or drying, the phosphate, which is preferably dissolved by the reactant, advantageously forms a more neutral-ammonium citrate-soluble phosphate than in the inorganic secondary phosphate. The term "better neutral ammonium citrate solubility" in the context of the invention preferably means that the neutral ammonium citrate solubility of the phosphate in the inorganic secondary phosphate is higher after the reaction with the reactant. An increase in the neutral ammonium citrate solubility of greater than 20% is preferred, especially an increase of greater than 50% is preferred. A corresponding calculation example can look like this: the neutral ammonium citrate solubility of the phosphate content from the untreated secondary phosphate from 50% is increased by 20% to 60% due to the reaction with the reactant In particular, the proposed method differs from the state of the art in that the phosphate at least partially reacts and the solubility is increased.

For example, the type and concentration of the reactant, the conduct of the reaction and the reaction time can influence the resulting neutral ammonium citrate solubility of the inorganic secondary phosphate. The phosphate content from the inorganic secondary phosphate is then preferably present in the heavy metal-depleted phosphate produced Fertilizer granules have a neutral ammonium citrate solubility of greater than 60%, preferably greater than 70%, particularly preferably greater than 80%. The preferred reaction or conversion of the phosphate and the preferred resulting neutral ammonium citrate solubility from the inorganic secondary phosphate advantageously result in a better availability of phosphate in plants and thus an improved fertilizing effect.

For the purposes of the invention, it is preferred that the solubility of the phosphate from the inorganic secondary phosphate is increased by the reaction between the inorganic secondary phosphate and the reactant. As shown, the solubility of phosphate in fertilizers is determined using different methods. The P solubility is preferably determined by the type of P bond and the solution medium. The way in which the reaction is carried out in process step a) can influence the binding of the P, that is to say the phosphate phases that form. This can be done, for example, by the type and concentration of the reagent, the reaction time and / or the process temperature.

In a preferred embodiment of the invention, the reaction is preferably controlled so that the phosphate content from the inorganic secondary phosphate then has a neutral ammonium citrate solubility of greater than 60% and a water solubility of less than 40% in the fertilizer granules produced. By setting the solubilities in this form, the effect is that the phosphate is actually sufficiently readily available to the plants in the field for about one growth period, but is not washed out during this time. Leaching can typically take place if there is very good water solubility, i.e. significantly higher, i.e. provided here. In a particularly preferred embodiment of the invention, a neutral ammonium citrate solubility of greater than 80% and a water solubility of less than 30% is set for the phosphate content from the inorganic secondary phosphate in the fertilizer granules produced. Surprisingly, it has been shown that winter rye in particular experiences a particularly favorable P supply over a growth period. In another particularly preferred embodiment of the invention, a neutral ammonium citrate solubility of greater than 90% and a water solubility of less than 15% is set for the phosphate fraction from the inorganic secondary phosphate in the fertilizer granules produced. This ratio is particularly favorable for wheat plants.

The type and concentration of the reactant, the way the reaction is carried out and the reaction time can also influence the type and proportion of dissolved heavy metals. For example, a higher acid strength preferably results in a higher proportion of dissolved heavy metals. A higher proportion of dissolved heavy metals is preferred in this process step, since to a large extent only the proportions that are present in dissolved form can be proportionally separated off in the heavy metal depletion process.

In a preferred embodiment of the invention, sufficient acid is therefore added to the raw material suspension so that a pH value of less than 1 is established during the incubation time. As a result, a significant proportion of heavy metals is already dissolved. In a particularly preferred embodiment of the invention, enough acid is added to the raw material suspension that a pH value of less than 0.5 is established during the incubation time. In particular, the heavy metals arsenic and lead are almost completely dissolved. If the pH value is further reduced to less than 0.2 during the incubation time, as in a particularly preferred embodiment of the invention, other heavy metals also dissolve to a greater extent.

In a preferred embodiment of the invention, at least one reactant is used which contains at least one of the elements nitrogen (N), sulfur (S), potassium (K) and / or phosphorus (P) includes, for example, phosphorous acid (H3P03), phosphoric acid (H3P04), nitric acid (HN03), sulfuric acid (H2S04), sulphurous acid (H2S03) and / or potassium hydroxide (KOH). By using such reactants, additional nutrient components such as nitrogen, sulfur, potassium and / or phosphorus are introduced into the granulate. By means of a suitable reaction sequence, the nutrient binding form of the nutrients contained in the reactant, for example nitrogen and / or sulfur, can preferably be converted into a form suitable for the fertilizer.

In a particularly preferred embodiment of the invention, the reactant is a dilute or undiluted phosphoric acid and / or a phosphorous acid or at least a dilute or undiluted acid mixture with a proportion of phosphoric acid and / or phosphorous acid contained. The advantage here is that the phosphorus content in the raw material suspension and thus in the fertilizer produced from it is increased by the reaction agent. In this way, the reactant advantageously not only provides a valuable nutrient component, but also favors the production of phosphate fertilizers in particular. For example, fertilizer granules with a total P205 content of greater than 35%, particularly preferably greater than 40% and a phosphate content of which is neutral ammonium citrate soluble of greater than 80%, particularly preferably greater than 90%, can be produced. For the purposes of the invention, it is particularly preferred that the total content of P205 is greater than 35%, particularly preferably greater than 40%.

The components of the raw material suspension can be brought together in any order. For the purposes of the invention, it is necessary that the reactant reacts sufficiently with at least part of the phosphate supplied by the inorganic secondary phosphate. The term "react adequately" in the context of the invention means that the desired improvement in the neutral ammonium citrate solubility of the phosphate is achieved. In addition, at least some of the heavy metals are preferably dissolved. An incubation period in the sense of allowing the reaction agent to act is accordingly The incubation takes place over a period of time in the range from 1 to 300 minutes, preferably in the range from 5 to 100 minutes and particularly preferably in the range from 10 to 60 minutes, due to the order in which the components are brought together, the time sequence and the incubation time can, for example, have an influence on the reaction taking place and thus also on the proportion of dissolved heavy metals and the neutral ammonium citrate solubility of the phosphate in the fertilizer granules produced.

It was surprisingly found that a relatively short residence time is sufficient to increase the ammonium citrate solubility. In a preferred embodiment of the invention, the incubation time is therefore set between 10 and 60 minutes, in particular to increase the ammonium citrate solubility. In a particularly preferred embodiment of the invention, the incubation time is set to 10 to 30 minutes. High ammonium citrate solubilities can also be achieved here; the shorter incubation time advantageously allows the dimensions of the reaction vessels to be reduced so that process costs can be reduced accordingly.

The incubation time to achieve the desired solubilities also depends, for example, on the type of reagent used. Thus, strong acids such as concentrated mineral acids or strong bases such as concentrated NaOH typically result in an accelerated reaction and a shorter incubation time is required. If, however, weaker acids, such as organic acids such as citric or oxalic acid, If used, a longer incubation period is required. In a preferred embodiment of the invention, the incubation time is set in a range between 30 and 300 minutes.

Surprisingly, longer reaction times are necessary to increase the water solubility. Therefore, in another preferred embodiment of the invention, the incubation time is set between 60 and 300 minutes.

A higher process temperature preferably increases the reaction rate between the inorganic secondary phosphate and the reactant and thus shortens the incubation time required. In a preferred embodiment of the invention, the process temperature during the incubation of the inorganic secondary phosphate and the reactant is therefore set above 30.degree. C., particularly preferably above 40.degree. C. and very particularly preferably above 50.degree.

The envisaged separation of the reaction for at least a partial conversion of phosphate from the inorganic secondary phosphate from the granulation preferably solves the technical problem that the exothermic, sometimes spontaneous and violent reaction greatly hinders the granulation process. The separation of the reaction from the granulation provided according to the invention is preferably to be understood in the technical sense in such a way that by far the largest proportion of the reaction takes place during the preparation of the raw material suspension and the subsequent incubation period. However, it can also be preferred that the reaction continues after the incubation period, but then with a significantly reduced intensity. By adhering to the incubation time provided according to the invention, the still existing intensity of the possible progress of the reaction is no longer a hindrance to the granulation process. In a preferred embodiment of the invention, the process is preferably controlled such that more than 80% of the increase in neutral ammonium citrate solubility of the inorganic secondary phosphate achieved over the entire process is achieved by the end of the incubation period. In other words, if the reaction were to be stopped by rapid drying after the incubation period, the phosphate from the inorganic secondary phosphate treated with the reactant shows this reaction product that has been stopped in this way already at least 80% of the neutral ammonium citrate solubility of a reaction product which is not stopped, but the entire process runs through until the final fertilizer granulate.

Electrochemical heavy metal depletion

In particular, in the inorganic secondary phosphate added to the raw material suspension, different heavy metals are typically present in different concentrations. These heavy metals are at least partially dissolved by the reaction between the inorganic secondary phosphate and the reactant. The type and amount of dissolved heavy metals depends on the dissolution parameters used as described above. For reasons of sustainability, for example, it is advisable to discharge these heavy metals at least partially from the process and thus separate them from the fertilizers produced.

According to the invention, the heavy metals are at least partially separated off directly from the raw material suspension produced. The advantage over processes in which part of the liquid phase is first separated from the raw material suspension, which is then cleaned of heavy metals in a second step, is, for example, that direct cleaning from the raw material suspension is technically less complex and therefore more cost-effective.

If the heavy metals are to be separated, at least in part, directly from the raw material suspension produced, the difficulty arises that precipitation as hydroxides or sulfides alone is not effective is possible. Through the sole precipitation of the dissolved heavy metals, these pass from the liquid phase to the solid phase of the suspension and are thus still present in the suspension. It is true that the entire solid phase could now be separated off and discharged from the process, but in the method according to the invention the solid phase should be converted into the fertilizer granulate.

Surprisingly, it has now been found that heavy metal depletion can take place directly from the raw material suspension produced by electrochemical separation processes. According to the invention, an electrochemical heavy metal depletion (electrochemical separation process) of the raw material suspension produced takes place accordingly. This means that at least some of the heavy metals present in the raw material suspension are separated directly from the raw material suspension by an electrochemical cleaning process.

An electrochemical heavy metal depletion is defined by the fact that the chemical separation reactions take place with the participation of electrons that flow through an external conductor circuit. A reaction partner in this electrochemical reaction is always an electrode that either accepts or releases electrons. This means that by supplying electrical energy, this chemical material conversion is carried out for the depletion of heavy metals.

For the purposes of the invention, electrochemical separation processes are to be understood as meaning all these processes which essentially cause the chemical and / or physical processes required for the cleaning operation through the action of an electrical current that is introduced into the raw material suspension to be treated via appropriately adapted electrodes. In contrast to the external electrical conductor circuit, the current is transported within an electrochemical reactor by ions in a mostly liquid electrolyte. The raw material suspension with the dissolved components can be viewed here as an electrolyte.

The electrodes are basically the active components in such an electrochemical process. The electrochemical reactions take place on their surfaces. In principle, they act as an electrocatalyst. They can simply consist of the catalytically active metal (full electrodes) or have a more complex structure, if z. B. acts as a substrate as a carrier of the usually expensive electrocatalyst. Materials for the electrodes are, for example, metals and their alloys, carbon or graphite, electrically conductive polymers, metal oxides with a high electronic conductivity and semiconductors. Electrodes conduct the electric current and the charge carriers are electrons. They are also known as first class leaders. Depending on which electrochemical process takes place on the electrode, they are called anodes or cathodes. At the anode, electrons from the electrolyte enter the electrode. The anode absorbs electrons from the reactant (Red) present in the electrolyte. An electrochemical oxidation reaction takes place and the oxidized species (Ox) is formed. The oxidation level of the reacting substance is increased. At the cathode, electrons leave the electrode and enter the electrolyte. The oxidized substance (Ox) takes up the electrons. A reduction reaction takes place and reduced species (Red) are formed. The oxidation level of the reacting substance is lowered.

The electrodes are the active components in the electrochemical reaction. The electrochemical reactions take place on their surfaces and therefore the type and properties of the electrodes are selected according to the desired electrode reactions and the type of electrolyte. The electrodes can have a wide variety of designs. For example, plate electrodes, porous electrodes, electrodes in the form of a network or so-called three-dimensional (3D) electrodes, which have a very large surface and from which to treating liquid are flowed through. Fills or porous bodies made of carbon or suitable metals can be used as 3D electrodes.

The device of the heavy metal depletion according to the invention can be designed, for example, as a fixed or fluidized bed cell. Also possible as basic reactor types are, for example, stationary stirred kettles, continuous stirred kettles, flow reactors or stirred kettle cascades. The arrangement of the electrodes in relation to one another and any separators to be introduced for separating the reaction spaces are an important factor influencing the deposition process. In a preferred embodiment, the separation system corresponds to a parallel plate reactor which is optionally equipped with separators (such as, for example, ion exchange membrane or ceramic diaphragm) for separating the reaction spaces and for preventing undesired side reactions. In another preferred embodiment, the device for the electrochemical deposition largely corresponds to a reactor with a fixed bed cathode. This embodiment offers the advantage of accommodating a large electrode area in a small space. For example, a so-called plug flow reactor can be used as the basic reactor type for continuous operation. This is ideally characterized by a uniform residence time (through-flow pipe), the conversion achieved depending on the length of the reaction space and there is no significant mixing along the flow path. Alternatively, for example, a cascade of homogeneously mixed stirred kettles can also be used as a reactor design, with conversion and residence time behavior converging for multi-stage cascades.

In a preferred embodiment, a so-called electrochemical metal deposition (galvanic deposition process) is used as the electrochemical process. The dissolved metal ions, such as heavy metal ions, are removed from raw material suspensions containing heavy metals by first converting them and depositing them on the cathode as metal and metal oxide, for example. The electrolysis bath is the raw material suspension in which the heavy metals to be deposited are at least partially dissolved. Electrodes, which are connected to an external voltage source, are immersed in the electrolysis bath. When a direct current voltage is applied, one electrode becomes the cathode and the other becomes the anode. The reaction parameters are set in such a way that the heavy metal cation is reduced at the cathode and is at least partially deposited thereon as metal or metal oxide, for example. The processes taking place on the anode depend in principle on its nature. A distinction is made between soluble and insoluble or active anodes. In the case of soluble anodes, the metal of the anode can release electrons and go into solution as a positively charged ion. In a particularly preferred embodiment, an insoluble anode is used, with another oxidation process taking place to maintain the electrical circuit, for example by oxidizing the solvent, for example water, or the anions in solution. Targeted setting of the electrochemical parameters such as the potential ranges for deposition (thermodynamic driving force), the achievable current densities (as an essential measure for, for example, the reaction speeds) and the selection of suitable electrodes for the deposition can influence the degree of deposition and the type of deposited elements be taken. By being deposited on the cathode, the heavy metals can be at least partially separated from the raw material suspension, for example by diverting the raw material suspension from the electrochemical reaction device or removing the cathodes after the at least partial deposition of the heavy metals on the cathode. The departed Heavy metals can then be removed from the cathode, for example by flushing solutions or mechanical separation. A new cleaning process can then take place.

In a particularly preferred embodiment, at least one complexing agent, for example citric acid, is added to the raw material suspension before or during the electrochemical heavy metal depletion. The complexing agent serves, for example, to ensure that when the pH value increases, the dissolved heavy metals only precipitate at a higher pH value, that is to say that the precipitation range is shifted. As a result, the pH range of the raw material solution can be raised, for example preferably in the range 2 to 7, and a higher proportion of heavy metals is dissolved than without a complexing agent. Raising the pH value range can promote electrochemical heavy metal depletion. For example, by increasing the pH from a very acidic range, for example in the range less than 2, it is possible to prevent the most formed metal from dissolving again. In a very particularly preferred embodiment, the pH is set in the range 2 to 4. In this range, the dissolution of most metals can be prevented, but fewer means are required to raise the pH.

The electrochemical heavy metal depletion according to the invention takes place from the raw material suspension produced and can begin directly with or during the production of the raw material suspension or thereafter. In a preferred embodiment, the electrochemical heavy metal depletion begins with the production of the raw material suspension or afterwards and runs at least temporarily in parallel during the incubation period and can go beyond the incubation period. The advantage of this embodiment is that the electrochemical heavy metal depletion requires a sufficient reaction time and in this embodiment this reaction time for the electrochemical heavy metal depletion and the incubation time are at least temporarily coupled, which reduces the overall process time. In another preferred embodiment, an incubation time is first awaited for the reaction between the inorganic secondary phosphate and the reagent and then the electrochemical heavy metal depletion is carried out. The reaction between the inorganic secondary phosphate and the reactant can also continue during the heavy metal depletion.

The electrochemical heavy metal depletion according to the invention can be carried out either continuously and / or discontinuously and can be in one or more stages.

The type and amount of the separated heavy metals result from the set process parameters of the electrochemical heavy metal depletion. In the case of inorganic secondary phosphates, arsenic, cadmium, lead and / or nickel, for example, should often be deposited, the amount to be deposited depending on the concentration of the contamination. In a preferred embodiment, therefore, at least 20% arsenic, cadmium, lead and / or nickel, based on the initial concentration in the inorganic secondary phosphate, are deposited from the raw material suspension. In the technical sense, this can be done relatively easily and therefore inexpensively. In another preferred embodiment, at least 40% arsenic, cadmium, lead and / or nickel based on the initial concentration are separated off. The advantage of this embodiment is that, for example, inorganic secondary phosphates with a higher heavy metal concentration can be used.

In a preferred embodiment, in addition to the at least partial separation of heavy metals according to the invention, the electrochemical separation process also depletes other pollutants. For example, organic pollutants can be caused by a suitable Process management by electrochemical reactions, for example, are broken down into at least less harmful substances.

The electrochemical separation process can also be used for disinfection. This is advantageous, for example, if, for example, organic structural substances are added as a further component, for which disinfection is necessary.

The electrochemical heavy metal depletion according to the invention results in a heavy metal depleted raw material suspension according to the invention.

Possibility of solid / liquid separation of part of the liquid phase

In a preferred embodiment of the method according to the invention, part of the liquid phase is separated from the heavy metal-depleted raw material suspension by solid / liquid separation prior to granulation or extrusion. The liquid phase separated by the solid / liquid separation is also referred to below as (separated) process water. The advantage of this embodiment is that the reaction between inorganic secondary phosphate and reactant can initially take place in a raw material suspension with a higher liquid phase content with the advantages described above, but this high liquid phase content is separated mechanically with significantly less energy and not thermally by drying. In addition, it can basically be achieved that simple and inexpensive granulation and extrusion technologies such as granulating plates or intensive mixers can be used. The amount of liquid phase to be separated in this preferred embodiment is selected according to the requirements of the subsequent granulation / extrusion. For example, the type of granulation or extrusion required determines the proportion of liquid phase to be separated.

In contrast to WO2019 / 149405A1, in the method according to the invention, the electrochemical heavy metal depletion according to the invention already took place directly from the suspension before this suspension is subjected to a solid / liquid separation in this preferred embodiment. In WO2019 / 149405A1 there is first a solid / liquid separation of the suspension produced. The heavy metals can only then be removed in different ways in the separated process water. The electrochemical separation of heavy metals by means of electrodes according to the invention is not described here. The advantage of the electrochemical separation of heavy metals by means of electrodes, however, is that costly consumables (precipitants, reagents, etc.) are not required.

In a preferred embodiment, at least some of the dissolved components are precipitated and / or crystallized out of the liquid phase before the solid / liquid separation. This has the advantage that the process water separated by the solid / liquid separation has fewer dissolved components. This is advantageous when the process water is returned to the freezing of the raw material suspension, since this results in lower cycle concentrations of these components. This also prevents the risk of encrustation of system parts and / or pipes. Such at least partial precipitation and / or crystallization can be increased, for example, by increasing the pFI value, as a result of which dissolved components precipitate, for example, as flydroxides. However, this can also be done, for example, by adding further components which, in reaction with dissolved components, form solid reaction products.

In a particularly preferred embodiment of the invention, so much liquid phase is separated off with the solid / liquid separation that the separated moist solid can be referred to as earth-moist or an earth-moist mixture. An earth-moist mixture is not a suspension according to Definition here (since the solid components in the liquid phase are not finely distributed, at least temporarily, in suspension), but can also be referred to as dispersion or raw material dispersion, since at least one solid and at least one liquid phase are still present. In this preferred embodiment of the invention, the humidity is at least 5% to less than 40%. In other words, it is preferred in the context of the invention that the humidity is in a range between 5 and 40%. Since the non-separated liquid phase can also contain dissolved components which remain as a solid during drying, the percentage of the non-separated liquid phase in this preferred earth-moist mixture is in a range between 10 and 70%. The advantage of such a proportion of moisture or non-separated liquid phase is that an earth-moist mixture can be granulated or extruded directly and a relatively little liquid phase, for example in particular water, has to be evaporated to produce the particularly dry, heavy metal-depleted fertilizer granulate. This saves considerable energy costs.

In a particularly preferred embodiment, the humidity is 10% to less than 30%. In other words, it is preferred in the context of the invention that the humidity is in a range between 5 and 30%. The advantage of this embodiment of the invention is that an earth-moist mixture with this moisture content can typically be granulated directly by means of a granulating plate.

The partial separation of the liquid phase in the context of the present invention can be carried out continuously and / or discontinuously in one or more steps, for example by filtration or centrifugation. Filtration can be carried out discontinuously, for example by means of autopress, pressure suction filters, agitated pressure suction filters, suction suction filters, plate filters, (pressure) leaf filters, bag filters, candle filters, bag filters, sheet filters, filter presses, e.g. Frame filter presses, chamber filter presses, membrane filter presses; Plate filters and / or bulk filters or continuously, for example by means of crossflow filtration, shear gap filters, tubular rotor filters, belt filters, rotary pressure filters, drum filters, rotary vacuum filters, disc pressure filters and / or sliding belt presses, without being limited to them. The centrifugation can be carried out continuously by, for example, sieve centrifuges, screw sieve centrifuges, impact ring centrifuges, sliding centrifuges, pusher centrifuges, vibrating centrifuges, tumbling centrifuges and / or solid bowl centrifuges, or discontinuously, for example by pendulum centrifuges, horizontal peeling centrifuges, inverted peeler centrifuges and / or bag centrifuges, pusher centrifuges. In the context of the invention, it is preferred that the solid-liquid separation is carried out by means of filter presses, centrifuges or vacuum belt filters.

In a preferred embodiment, the liquid phase is partially separated off with a filter press, for example a membrane filter press, in combination with mechanical pressing with dry bals of the filter cake produced. When the filter cake is blown dry (or blown out), a gas is preferably fed to the pressing device, which is controlled in such a way that this gas flows through the filter cake (via the pore structure) and thereby carries along adhering liquid components and thus drives them out of the filter cake. The gas can in this case preferably be compressed air generated from the ambient air, wherein this compressed air can also be supplied heated. The heating also produces a drying effect. The advantage of this embodiment is that it allows lower residual moisture to be achieved. Surprisingly, it was found that the mechanical drainability is limited solely by negative pressure, pressing pressure and / or centrifugal forces. In particular in the case of raw material suspension made from phosphate-containing ash as inorganic secondary phosphate in combination with mineral acid, only residual moisture levels of more than 35% can typically be achieved, depending on the separation technology. Flatter pressures or forces do not cause any further separation, since those still contained Liquid is apparently very strongly physically bound in the pores and / or on the surface. Surprisingly, it has now been found that a further portion of the liquid phase can be separated off by blowing dry and thus residual moisture of less than 35% can be achieved in a technologically comparatively simple manner.

Before or during the partial separation of the liquid phase, the heavy metal-depleted raw material suspension can be conditioned, for example to improve or simplify filtration or sedimentation. For example, flocculants or agents for adjusting the viscosity can be added.

In the case of partial separation of the liquid phase, it is preferably not absolutely necessary that all solid constituents are completely separated off from the separated liquid phase. In particular, very fine solid particles, which in the context of the invention are preferably referred to as suspended particles, can preferably remain in the separated phase. This simplifies the separation process, for example in the case of filtration or centrifugation, since in particular the complete separation of fine particles in a solid-liquid separation with a high solids load is very expensive. However, if too high a proportion of undissolved solids gets into the separated liquid phase, this is also undesirable. It is therefore preferred that a solids content of less than 10%, particularly preferably less than 5% and very particularly preferably less than 2% is set in the separated liquid phase.

The separated liquid phase (separated process water) can be discharged from the process and, for example, disposed of as waste water or fed to another use, or it can be returned and / or used in the process according to the invention itself.

In a preferred embodiment, at least part of the separated process water is fed to the production of the raw material suspension. This recirculated, separated process water can preferably completely or partially replace an adequate portion of the otherwise necessary liquid phase, in particular of added water. The advantage here is, on the one hand, that the process water can be used again directly in the process and accordingly does not have to be disposed of. On the other hand, the separated process water can still contain a proportion of the dissolved nutrient components, for example phosphate, which are thus returned to the process. In a particularly preferred embodiment, at least part of the reactant for the production of the raw material suspension is fed to this separated process water after the separation by the solid / liquid separation and before the production of the raw material suspension. This can be advantageous, for example, if the separated process water contains such a proportion of dissolved components that may already partially precipitate or crystallize out during the return process and cause technical difficulties, for example due to deposits. By supplying at least part of the reaction agent, particularly preferably acids, precipitation or crystallization can at least be reduced.

In another, likewise preferred embodiment, at least part of the separated process water is fed to the granulation for conditioning the raw material dispersion and / or for forming the granules, for example by spraying onto the raw material dispersion on the granulating plate. Feeding of further components to the raw material suspension

For the purposes of the invention, it is preferred that further components can be added to the raw material suspension and / or the raw material dispersion. Targeted setting of the type and composition of the raw material suspension / dispersion as well as the type and intensity of mixing can advantageously influence the ongoing reaction and thus the neutral ammonium citrate solubility of the phosphate, but also other fertilizer properties.

Further components can be added to the raw material suspension / dispersion before, during or after the incubation period, before during or after the heavy metal depletion and / or before or during the granulation or extrusion. Further components here are generally those substances that can improve the process control and / or the properties of the fertilizer granulates, for example nutrient-containing components, dispersants and defoamers, structural substances, pH adjustment agents, urease inhibitors, ammonium stabilizers, humic acid, organic Acids and / or water.

Thus, in a preferred embodiment of the invention, at least one or more nutrient-containing component (s) are added as further components. For the purposes of the invention, nutrient-containing components are preferably substances that supply or supplement the nutrient supply for the cultivated plants in order to control or support the growth and development of the plants. The nutrient-containing components include nitrogen (N), phosphate (P), potassium (K), magnesium (Mg), sulfur (S), essential trace elements individually or in combination. For example, through the possibility of adding nutrient-containing components, the nutrient composition in the fertilizer granulate can be adapted particularly precisely to the needs of the soil and / or plants. In addition, the typical fluctuation range of the composition of the inorganic secondary phosphate can be compensated for in order to ensure a uniform fertilizer quality.

In a particularly preferred embodiment of the invention, additional phosphate carriers, for example ammonium phosphate, potassium phosphate, crystallization products from phosphorus elimination, such as struvite, brushite or hydroxylapatite-like Ca-P phase, are added in such an amount that a fertilizer granulate with a total P205 Content of greater than 35%, particularly preferably greater than 40% and a neutral ammonium citrate-soluble phosphate fraction thereof of greater than 80%, particularly preferably greater than 90%. In another preferred embodiment of the invention, crystallization products from phosphorus elimination, such as struvite, brushite or hydroxylapatite-like Ca-P phase, are added in a range from 1 to 70%, based on the finished pedosphere-improving granules, so that nutrient granules with a Total P205 content of more than 15%, a neutral ammonium citrate-soluble phosphate content of more than 60% thereof and a water solubility of less than 30%, also based on the total P205 content. In a very special embodiment of the invention, crystallization products from phosphorus elimination in the range of 10 to 40%, based on the finished pedosphere-improving granules, are added, nutrient granules with a total P205 content of greater than 15%, with a neutral ammonium citrate-soluble phosphate content thereof , based on total P205, of greater than 85% and a water-soluble phosphate content, based on total P205), of less than 20%, based on the composition of the nutrient granules.

One or more structural substance (s) can be used as further components, for example peat, humus, pyrolysis substrates from biomass, biochar from hydrothermal sources Carbonization (HTC), but also sewage sludge, digestate, liquid manure, animal excrement, animal and / or fish meal. The term "digestate" describes in the context of the invention the liquid and / or solid residue that remains during the fermentation of biomass. In the context of the invention, the term "liquid manure" preferably describes a mixture of manure and urine from farm animals in combination with Litter with changing water content. Depending on the type and concentration of this or these structural substance (s), the fertilizing effect can be adjusted and / or a soil-improving effect can be achieved when using the fertilizer granules. The fertilizing effect is preferably influenced by the fact that the structural properties of the fertilizer granulate produced and thus its properties, such as the porosity, size of the pores, strength and / or solubility, can be adjusted by adding the structural substance. In this way, for example, the nutrient release can be specifically adapted to the plant growth and the time-dependent nutrient requirement of the plant. Targeted soil improvement can also be achieved by adding a structural substance to the fertilizer granulate if the structural substance is used, for example, to form humus, to improve the soil structure and / or to improve the air and / or water balance of the soil when using the Fertilizers in agriculture leads. This can, for example, promote root growth, activate soil life and / or stimulate plant vitality against stressful situations.

In one embodiment of the invention, it is preferred that a total of between 5 to 50% structure substance based on the finished pedosphere-improving granulate is added, since it was surprisingly found that in this concentration range, in particular, the formation of humus is very strongly promoted and therefore particularly good soil and soil Structural improvement is effected. It is very particularly preferred that the granules formed have a carbon content of greater than 5 to 25%, since it was unexpectedly found that in this area of the carbon content, in addition to the formation of humus, the air and water balance of the soil in particular is particularly favorable for the growth of for example winter barley and corn can be adjusted.

The fertilizing effect is preferably influenced by the fact that the structural properties of the generated pedosphere-improving granulate and thus its properties, such as the porosity, size of the pores, strength or solubility, are set by adding the structural substance. In this way, for example, the nutrient release can be specifically adapted to the plant growth and the time-dependent nutrient requirement of the plant. Therefore, in another preferred embodiment of the invention, between 0.1% to 5% structural substance is added. As a result of this relatively low concentration, a particularly large number of nutrient components can be integrated in the fertilizer, whereby the fertilizing effect of the granules in this exemplary embodiment is fundamentally reinforced. Surprisingly, however, it has now been found that it is precisely the proportion of structural substance in this area that leads to a pore structure which greatly enhances the solubility of these nutrient components. This means that the nutrients are much more readily available to the plants. A proportion of structural substance of 1-3.0% is particularly preferred, since it is precisely in this area that there is good porosity for good solubility and, in addition, there is a particularly good distribution of small pores in the basic structure in this concentration range, from which advantageously a particularly high strength results.

If residual materials, such as sewage sludge in particular, are to be used as structural materials, there is a fundamental risk of contamination and the risk of spreading pathogens and thus the possibility that pathogens can reach humans and animals via food and feed and thus endanger them. Therefore, when using one or more residual materials as structural material, in a preferred embodiment of the invention, a sanitation step is used Interruption of infection cycles by killing pathogens, bacteria etc. integrated into the proposed method. Methods such as adding chemical or bacteria-killing agents, hygienizing through an extreme pH shift, for example by adding quick lime or hydrated lime, or thermal treatment are available for sanitation. Such a process step for sanitizing the critical residue (s) can be carried out at a suitable point in the process. Such a sanitization of the residues can take place before the addition of the residues as structural material to the raw material suspension / dispersion. In this way, for example, a residual material, such as sewage sludge, can first be mixed separately with quicklime and the mixture can be added to the raw material suspension / dispersion after a sufficiently long exposure time. In a particularly preferred embodiment of the invention, after the critical residue has been added as a structural substance to the raw material suspension / dispersion, the sanitization takes place by a thermal treatment of at least 10 minutes, preferably longer than 20 minutes and above 60 ° C, particularly preferably above 75 ° C. This temperature action advantageously largely kills the pathogens. In this embodiment of the invention, the thermal treatment of the critical residues can take place, for example, in process step a) and / or d), for example by heating the raw material suspension / dispersion or heating itself up through exothermic reactions.

In a preferred embodiment of the invention, humic acid and / or fulvic acid and / or salts thereof (humates, fulvates) are added. These substances advantageously have growth-promoting properties. This significantly increases the nutrient absorption capacity of the roots and thus stimulates growth. Their addition promotes plant growth and cell formation. They stimulate the cell membranes as well as the metabolic activities and thereby increase the germination rate. Important plant enzymes are also particularly well stimulated. The strong root formation supports the nutrient absorption capacity. The plants strengthened in this way are significantly less susceptible to disease. The addition of these substances can increase the plants' P uptake, as it blocks the P adsorption in the soil and, by complexing Ca, Al, Fe, prevents P from precipitating into poorly soluble compounds. Surprisingly, it was found that adding these substances in a range of 0.1-25% (based on the finished pedosphere-improving granulate) results in a significant increase in the phosphate available to plants in the soil and thus an increased P uptake by the plants. It is particularly preferred to add these substances in a proportion between 0.1 to 10% (based on the finished pedosphere-improving granulate), since a considerable increase in the fertilizing effect is achieved even in this quantity range and consequently the necessary amount of fertilizer is reduced by up to 40% can be. The addition of these substances in a quantity range of 0.1-5% (based on the finished pedosphere-improving granulate) is very special, since in this area a particularly favorable economic relationship between the costs of these substances and the resulting improved properties results.

In a further preferred embodiment of the invention, organic acids are added in solid and / or liquid form. Organic acids are, for example, ascorbic acid, acetic acid, formic acid, gluconic acid, malic acid, succinic acid, oxalic acid, tartaric acid and citric acid. Organic acids play an essential role in the absorption of phosphate by plants from the soil. In particular, the presence of organic acids on the roots means that the plants can absorb sufficient phosphate, whereby microorganisms typically form these organic acids in the ecosystem. Surprisingly, it has now been found that the phosphate uptake of the plants is increased if it is already proportionately in the fertilizer granules supplied

TI one or more organic acids are preferably integrated in total in a range from 0.1 to 30% (based on the finished pedosphere-improving granules). It is presumed that these, along with the organic acids that are fed in, preferably take on a comparable function in the root area of the plant without these organic acids first having to be generated by microorganisms. Citric acid, oxalic acid and / or tartaric acid are preferably used individually or in combination, since these organic acids are relatively inexpensive and available in sufficient quantities. The use of citric acid, oxalic acid and tartaric acid individually or in combination in a quantity range 0.1% to 10% (based on the finished pedosphere-improving granules) is particularly preferred, since the absorption-improving effect of these acids is particularly favorable in relation to the raw material costs. The listed proportions of organic acids in the fertilizer granulate can either be added as an additional component and / or, if organic acids are used as reactants, after the reaction (at least proportionally further in this quantity range) and thus transferred to the fertilizer granulate.

Defoaming agents and dispersants can also be added as additional components. Defoaming agents are advantageous, for example, when a strong gas-forming reaction sets in or a foam forms when individual substances are brought together, for example when producing the basic dispersion. The viscosity can, for example, be adjusted by the dispersant.

Agents for adjusting the pH value, such as alkalis, hydroxides, basic salts, ammonia or quick lime, can also be added as further components. In a preferred embodiment, the pH of the heavy metal-depleted raw material suspension / dispersion is set in the range between 4 and 11 after the heavy metal separation or the earth-moist mixture before or during the granulation or extrusion. In this way, for example, remaining acid residues, for example when using acids, can be neutralized. In a particularly preferred embodiment, the pH of the heavy metal-depleted raw material suspension / dispersion or the earth-moist mixture is set in the range between 6 to 8 before or during the granulation or extrusion. This results in fertilizers that are depleted of heavy metals and whose pH value is largely neutral.

The substances used, such as inorganic secondary phosphate and other components, can be added individually or in combination or the entire raw material suspension / dispersion can be ground. This is advantageous, for example, if the existing particle or aggregate size of individual or several starting materials is not sufficiently fine enough to achieve sufficient homogeneity, for example, or this can lead to process-related difficulties, for example clogging of nozzles. This can advantageously be improved by reducing the particle or aggregate size. The solubility of substances or the compounds they contain can also be improved, for example the solubility of phosphate-containing ashes or slags. It may also be necessary to grind the raw material suspension / dispersion if agglomerates, aggregates or precipitation products form due to a reaction within the raw material suspension / dispersion, which interfere with the further process sequence, for example conveying or pumping or atomizing. Depending on the type of material to be ground and the desired grain size and grain size distribution, different dry or wet grinding technologies with or without grinding aids can be used. The aggregates used for dry or wet milling can be, for example, ball mills, pin mills, jet mills, bead mills, agitator ball mills, high-performance dispersers and / or high-pressure homogenizers. The order in which the further components are added can be carried out depending on the requirements of the process management and / or the possibly desired reaction sequence. All other components can be added together or sequentially at one point in the process, for example after the incubation period before the heavy metal depletion. The other components can also be added at various points in the process.

The addition can be added to the dispersion already produced from at least one inorganic secondary raw material and at least one reactant and / or also during the production of this dispersion. It is also preferred that all or some of the further components are initially taken and only for this purpose the dispersion of at least one inorganic secondary phosphate and at least one reactant or the components for forming this dispersion is added.

In a preferred embodiment of the invention, all or some of the further components are added after the heavy metal depletion. This has the advantage that, on the one hand, the other components initially do not affect the reaction between the inorganic secondary phosphate and the reactant. On the other hand, these additional components also do not influence the heavy metal depletion and simplify the heavy metal depletion. In this embodiment, further components can be added when the raw material suspension / dispersion is transferred from the heavy metal depletion facility to a mixer. The mixing device can be, for example, a mixing container with agitator, roller mixer, which is preferably also referred to as a falling, drum or rotary mixer, shear mixer, compulsory mixer, ploughshare mixer, planetary mixer, Z mixer, Sigma mixer, fluid mixer or intensive mixer. The selection of the suitable mixer depends in particular on the flowability and the cohesive forces of the material to be mixed.

In a preferred embodiment, the raw material suspension according to the invention is first produced, the electrochemical heavy metal depletion and then a solid / liquid separation carried out. The moist solid separated in the solid / liquid separation is then placed in a mill-drying unit. The desired composition, in particular the nutrient composition of the raw material dispersion, is set by adding further components to the moist solid after the solid / liquid separation and / or in the mill-drying unit. In the mill-drying unit, the moist solid is ground together with the other components and at the same time the moisture is reduced to such an extent that the resulting mixture has a residual moisture that is suitable for the subsequent granulation process. The advantage of this embodiment is that on the one hand the filter cake is deagglomerated by the grinding. On the other hand, further components can be added, which are granular or lumpy, whereby these are converted into a powder form by the grinding, which considerably improves the granulation properties and enables the use of such substances in the first place. In addition, the moist solids and the other components are intensively homogenized by the joint grinding and the residual moisture of the mixture can be precisely adjusted through the partial drying of the residual moisture contained. This possibility of intermediate drying simplifies process management and increases process stability.

Granulation / extrusion of the heavy metal-depleted raw material suspension Z-dispersion

According to the invention, the heavy metal-depleted raw material suspension / dispersion is converted into a heavy-metal-depleted fertilizer granulate by granulation or extrusion. The granulation or extrusion can preferably take place during the admixing of further components and / or afterwards, for example in the same mixer or in a separate granulating or extrusion unit, which is formed for example by pelletizing or granulating plates, granulating drums, fluidized bed granulators, spray granulators or extruders .

For the purposes of the invention, it is preferred that the proportion of the liquid phase or the moisture content of the heavy metal-depleted raw material suspension / dispersion has a significant influence on the reactions taking place, the type of granulation, the product quality and / or the economic viability of the process. The total proportion of the liquid phase or the moisture before the granulation and / or extrusion can be, for example, via the process control of the preceding steps, optionally a partial separation of the liquid phase by a solid / liquid separation and the type and amount of the liquid, moist or dry components. If necessary, partial drying can also take place before granulation, for example in order to adjust the total proportion of the liquid phase before granulation and / or extrusion.

In a preferred embodiment of the invention, the raw material dispersion is or will be adjusted before the granulation / extrusion so that it contains a moisture content of less than 30%, preferably less than 25% and particularly preferably less than 20% and thus corresponds to an earth-moist mixture. The preferably earth-moist mixture can preferably be granulated and / or extruded directly. In addition, relatively inexpensive granulation and / or extrusion processes or technologies, such as roller mixers, shear mixers, ploughshare mixers, planetary mixing kneaders, intensive mixers and / or extrusion processes, can be used. The tendency to stick required for granulation can preferably also be adjusted by different substances, such as binders. These can, for example, also be added. The advantage of this preferred embodiment of the invention is that a good roundness of the granules is achieved in the preferred granule size range and the granulation technology and the process costs can be used inexpensively.

For example, in a particularly preferred embodiment of the invention, after the heavy metal depletion, part of the liquid phase is separated by a solid-liquid separation, the heavy metal depleted raw material dispersion thus reduced in the liquid phase portion is then optionally further components in an intensive mixer, for example an intensive mixer type R Fa. Eirich, where the liquid phase content is preferably set and, if necessary, binder added so that the intensive mechanical mixing results in green granules with a desired grain size, preferably in a range from 1 to 10 mm, particularly preferably from 2 to 5 mm . It is preferred within the meaning of the invention that green granules comprise at least all components of the fertilizer granules, the green granules preferably having a liquid phase portion, which is also referred to as "moisture" in the context of the invention, this liquid phase portion preferably being able to be removed by drying.

In another particularly preferred embodiment of the invention, the granulation takes place on a pelletizing or granulating plate. For this purpose, after the heavy metal depletion, part of the liquid phase is separated by a solid-liquid separation, the heavy metal depleted raw material dispersion reduced in the liquid phase portion is then fed to a pelletizing or granulating plate with additional components if necessary. For the purposes of the invention, it is preferred that a liquid component, preferably in combination with a binder contained therein or separately supplied, is sprayed onto the raw material dispersion on the granulating plate. In a preferred form of the invention the liquid component is water. The supplied raw material dispersion is adjusted in terms of moisture content or the proportion of the liquid phase in advance so that the green granules that are formed during and / or after the granulation are advantageously formed by adding the liquid component and the rotating movement of the pelletizing or granulating plate the fertilizer granules can be dried. The advantage of this embodiment of the invention is that the granulation and the necessary technology are particularly inexpensive. In addition, this simple granulation technology is less susceptible to repair.

In another likewise preferred embodiment of the invention, the raw material suspension / dispersion is or will be adjusted before the granulation in such a way that the proportion of the liquid phase is greater than 25%, preferably greater than 35%. In a particularly preferred embodiment of the invention, the granulation of the pollutant-depleted raw material suspension takes place in a fluidized bed or spouted bed reactor, particularly preferably by spray granulation or spray agglomeration. Apparatuses of this type are known to the person skilled in the art and are offered, for example, by Glatt with the AGT or GF series. For this purpose, the pollutant-depleted raw material suspension including any additional components is fed to a fluidized bed reactor. The additional components can be, for example, nutrient-containing components, dispersants and defoamers, agents for adjusting the pFI value and / or water, which can be added individually or in combination beforehand. In a particularly preferred embodiment of the invention, the feed takes place by spraying, for example by spraying through nozzles. For this purpose it is preferred within the meaning of the invention that the raw material suspension is pumpable and sprayable. This can preferably be achieved in that, for example, the proportion of liquid phase is sufficiently high, for example in that correspondingly necessary amounts of preferably water are supplied. Flea quantities of the liquid phase favor the stability and the pumpability of the raw material suspension and thus simplify the technical operation. These positive effects are due in particular to a lower tendency towards precipitation, crystallization and / or gel formation, without being limited thereto. However, since the fertilizer granules to be produced should have a low proportion of liquid phase or a moisture content that is preferably less than 5%, particularly preferably less than 2%, it is preferred in the context of the invention that the liquid phase, for example during granulation in this embodiment is removed. It is therefore particularly preferred to adjust the liquid phase in the raw material suspension in the fleas, so that 40-70% fertilizer granules form from the pollutant-depleted raw material suspension, very particularly preferably 45-60%. A formation of 40-70% fertilizer granulate from the raw material suspension corresponds in the context of the present invention to a solids content in a range from 40 to 70% or between 40 and 70%. With such a proportion of the liquid phase, a pollutant-depleted raw material suspension can advantageously be made sufficiently stable and pumpable, whereby the energetic expenditure for the separation of the liquid phase is to be assessed as acceptable, especially in comparison to conventional methods known from the prior art. The raw material suspension can be frozen in a stirred tank or mixer. The advantage of this preferred embodiment for granulation is that the granulate size can be adjusted particularly well, the granulates are very homogeneous and a particularly round and compact granulate shape is achieved. The granules obtained are particularly easy to handle and particularly easy to apply to fields, for example with spreading devices. The compactness of the granules results in little dust and abrasion, which is also advantageous for spreading using, for example, spreading devices. Drying / fractionation of the heavy metal-depleted fertilizer granules produced

It is preferred in the context of the invention that the pollutant-depleted fertilizer granules have a low level of moisture, i.e. physically bound water. In particular, it is preferred that a humidity is in a range of less than 5%, preferably less than 2%. Depending on the type of granulation, such a moisture range can already be achieved during the granulation, in particular during the spray agglomeration or granulation in which the granulation and / or drying take place largely simultaneously.

For the purposes of the invention, it can be preferred that the generated granules depleted of harmful substances are dried or at least additionally post-dried after the granulation and / or extrusion. Various drying technologies are available for this, such as contact dryers, in which the thermal energy required for drying is preferably supplied through contact with meat surfaces, convective dryers, in which the thermal energy required for drying is preferably supplied through contact with industrial gas, or radiation dryers, in which the thermal energy required for drying is preferably supplied by radiation with a defined frequency. The existing liquid phase, for example the water, is separated off to the required extent by the drying. The drying also preferably results in an increase in the strength of the granules, for example in that binding phases form as a result of the drying or, for example, in that a binder develops its binding effect as a result.

In an advantageous embodiment of the invention, the drying takes place through the inherent heat of the granulates produced or is at least supported by it. The granules receive their own heat preferably through heating. For example, the granules can be heated by the granulation and / or extrusion process or by chemical reaction as a result of the process. If the granules are heated by the granulation and / or extrusion process, it is preferred in the context of the invention that the heating takes place by introducing mechanical energy, the mechanical energy preferably being converted into thermal energy. For example, the reaction between CaO and acid and / or water or the reaction between sulfuric acid and water, especially during dilution, provide exothermic energy, which can preferably be used to heat the raw material dispersion and / or the shaped granules.

If crystallization products from phosphorus elimination, such as struvite, brushite and / or hydroxylapatite-like Ca-P phase, are added to the raw material suspension / dispersion and are consequently contained in the granulate or green granulate produced, it is preferred in the context of the invention that the drying is carried out in one preferred embodiment of the invention takes place above 100 ° C based on the material temperature during drying. These crystallization products preferably contain a large proportion of chemically bound water, which is preferably not "moisture" within the meaning of the invention, but rather water that is bound in the crystal structure. In the range above 100 ° C., this chemically bound water becomes By separating the water from the granules, the percentage of the remaining components is advantageously increased. For example, the concentration of nutrients in the granules can be increased that were previously diluted by the chemically bound water. In a particularly preferred embodiment According to the invention, drying takes place when crystallization products from phosphorus elimination are contained in a range of 100-140 ° C. based on the material temperature during drying. It is therefore very particularly preferred in the context of the invention that drying is carried out in a temperature range between chen 100 and 140 ° C takes place. Above 140 ° C there is a risk that nitrogen will increasingly be split off. This is associated with an undesirable loss of nitrogen from the granulate. In addition, the exhaust air has to be cleaned in a correspondingly more complex manner. By limiting to a temperature of max. 140 ° C. in this preferred embodiment of the invention, these disadvantages can largely be avoided. In a very special embodiment of the invention, drying takes place in a temperature range between 120.degree. C. and 140.degree.

For the purposes of the invention, it is preferred that the pollutant-depleted fertilizer granules can be produced with as precise a shape as possible. A size of the granules that is as uniform as possible advantageously ensures defined, uniform disintegration properties, which is necessary for a targeted supply of nutrients. Since the presence of oversized and undersized grains can impair the machine application of the fertilizer, it is preferred in the context of the invention that oversized and undersized grains are separated from the good grain and, if necessary, from the production process, in particular before or during the mixing and / or Granulation process, if necessary with previous processing and / or grinding, can be recycled. In the context of the invention, the term "good grain" preferably describes a granulate in a desired size range for the granulate grains. In the context of the invention, a good grain in the range 1 to 10 mm, particularly preferably 2-5 mm. In this size range, granulates can typically The terms "oversize grain" and "undersize grain" in the context of the invention preferably describe those granules which - preferably significantly - have larger or smaller diameters than the good grain.

In addition, it is preferred in the context of the invention that the heavy metal-depleted granulate has a good bond within the granulate in order to avoid dust losses when applying the fertilizer even after prolonged storage. The strength of the granules can be adjusted, for example, via the process control. For example, the drying speed has an influence on the porosity and compactness and thus on the strength of the granules and can be influenced by this. The strength can also be influenced, for example, by the type and fineness of the raw material components or increased by adding binding agents.

The heavy-metal-depleted fertilizer granulates produced according to the invention can receive one or more coatings for functionalization (e.g. reducing the tendency to clump, increasing strength), for protection (e.g. against moisture) and / or for controlled release of nutrients (influencing solubility by the coating). Numerous methods and technologies for coating are known to the person skilled in the art, all methods and technologies which produce a desired coating with the desired functionality being suitable here.

To form the heavy metal-depleted fertilizer granules according to the invention, the process steps of the method according to the invention are carried out as described. The individual process steps can be designed as batch and / or continuous processes, with buffer containers being able to be used between the process steps. To implement all or individual process steps, a single unit and / or, in particular to map larger production quantities, several identical or similar units can be used. Several units in one or more process steps can be connected in parallel and / or alternately. In the production of the heavy metal-depleted fertilizer granulates according to the invention, the process steps run in batches and / or continuously, for example, until the desired production amount is reached. Generation and use of N / P connections

In a preferred embodiment, at least one N / P compound from an upstream precipitation and / or crystallization process is added to the process according to the invention for the production of heavy metal-depleted fertilizer granules as a further component of the raw material mixture, the heavy metal-depleted raw material mixture and / or the moist solid.

The starting material for this precipitation process is at least one nitrogen and sulfur-containing, particularly preferably an ammonium and sulfate-containing starting solution or starting suspension. Such solutions or suspensions occur, for example, in washers for exhaust gas purification or in the production of biogas. The concentration of nitrogen or ammonium and sulfur or sulfate can be any. In addition to nitrogen or ammonium and sulfur or sulfate, further components can be present in dissolved form.

The use of such nitrogen- and sulfur-containing solutions or suspensions in the process according to the invention for producing fertilizers with a low level of heavy metals is basically possible without pretreatment. For this purpose, these solutions or suspensions can, for example, be used in the production of the raw material suspension according to the invention and, for example, replace water otherwise supplied in an adequate amount. However, the useful use, i.e. the possible amount added, of such untreated solutions and suspensions is limited. If more nutrients such as N and S are to be used from such solutions / suspensions, for example as an inexpensive source of nutrients, such a nitrogen and sulfur-containing solution or suspension could e.g. be concentrated by (partially) thermal drying. However, thermal drying is energy-intensive and therefore expensive.

The method proposed here for at least partial separation of the nutrients from the solution / suspension offers a possibility of using the nutrients of such nitrogen- and sulfur-containing solutions or suspensions to a greater extent more economically. The proposed precipitation or crystallization and subsequent separation can be used, for example, as an upstream or supplementary process step, and the illustrated subsequent use of these nutrients / precipitation products for the production of the fertilizer granules can be advantageous.

The nitrogen or the ammonium should be at least partially precipitated or crystallized from the at least one nitrogen- and sulfur-containing solution / suspension as at least one nitrogen-phosphate-containing compound. Numerous phases can be considered as nitrogen-phosphate-containing compounds, some of which are also completely miscible in the crystallographic sense. For example, N-phosphates (such as (NH4) 2HP04, NH4H2P04), Mg-N-phosphates (such as MgNH4P04 * 6 H20 (struvite), MgHP04 * 3 H20, Mg3 (NH4) 2 (HP04) are preferred for the purposes of the invention. 4 * 8 H20, Mg (NH4) 2 (HP04) 2 * 4 H20), KN phosphates.

For this purpose, in a particular embodiment, at least one solution / suspension containing ammonium and sulfate is supplied with at least one P compound as a precipitation reagent, for example phosphoric acid or a phosphorus salt. If Mg-N-phosphates are to be precipitated or crystallized, at least one Mg compound is added as a precipitation reagent such as MgO, Mg (OH) 2 or Mg salts or is present in the solution / suspension in sufficient quantity. If K-N-phosphates are to be formed, at least one K compound, for example KOH or K salts, is added as a precipitation reagent or is present in the solution / suspension in sufficient quantity. The amount of P added and, in the particular embodiments, K and / or Mg in the ammonium- and sulfate-containing solution is adjusted so that the desired type and amount of the precipitation and / or crystallization products can be formed stoichiometrically (adjustment of the stoichiometry). The setting of the stoichiometry can also take place superstoichiometrically, that is to say a larger amount of one or more components is added than would be stoichiometrically required to form the target phase. In this way, for example, the reaction and / or dissolution equilibrium can be shifted in favor of a preferred phase. For example, a lower concentration of dissolved nitrogen or ammonia can be achieved. The required P, Mg and K compounds can be added separately or together.

Furthermore, the pH of the ammonium- and sulfate-containing solution is adjusted so that precipitation and / or crystallization of the desired phases can take place to the desired extent. This area is often referred to as the precipitation area. If, in a preferred embodiment, Mg-N-phosphates are to be precipitated quantitatively and / or crystallized out, the pH is set in the range from 6 to 11, particularly preferably 8 to 10. The pH adjustment of the precipitation conditions can take place before, with or after the adjustment of the stoichiometry. In addition to adjusting the pH, the ammonium and sulfate-containing solution / suspension can also be conditioned before and / or during the precipitation and / or crystallization process. For example, complexing agents, precipitants or dispersants can be added.

According to the invention, the sulfur or the sulfate should likewise be at least partially precipitated or crystallized from this at least one nitrogen- and sulfur-containing solution / suspension as at least one sulfate-containing compound. Suitable sulfur-containing compounds are, for example, alkali and / or alkaline earth sulfates, with alkalis or alkaline earths being added as the precipitation reagent.

In a preferred embodiment, the sulfate is precipitated or crystallized out at least partially as calcium sulfates from the at least one nitrogen- and sulfur-containing solution / suspension. For this purpose, in a particular embodiment, at least one Ca compound is added as a precipitation reagent, for example as Ca (OH) or CaO, to at least one solution containing ammonium and sulphate. The amount of Ca added is adjusted so that the desired type and amount of Ca sulfate can form stoichiometrically. Here, too, the stoichiometry can be set superstoichiometrically, that is to say a larger amount of one or more components is added than would be stoichiometrically required to form the target phase. For example, a lower concentration of dissolved calcium or sulfate can be achieved here.

The separation according to the invention of sulfate from nitrogen- and sulfur-containing solutions / suspensions can take place before, simultaneously with or after the separation according to the invention of the nitrogen or ammonium. This was based, for example, on the type and conditioning of the nitrogen- and sulfur-containing solution / suspension or the type and amount of the desired reaction products. For example, if the precipitation and / or crystallization conditions, such as the pH range required for the separation of the nitrogen or ammonium on the one hand, differ from the suitable conditions for the separation of the sulfate, separate precipitation is advisable, for example. In this case, suitable conditions are first set in the solution / suspension for the precipitation and / or crystallization of nitrogen or ammonium and then for sulfate or vice versa, with the precipitates and / or crystallization products formed being able to be separated off in between. This preferred embodiment can therefore also be advantageous if two separate precipitation and / or crystallization products are to result. In a preferred embodiment, the sulfate is first separated from the nitrogen- and sulfur-containing solution / suspension as described and only then is the nitrogen or ammonium separated from the solution. This is particularly advantageous when the nitrogen and sulfur-containing solution is acidic. Ca sulfates can already be precipitated and / or crystallized out in the sometimes very acidic range (pH value less than 3).

In another, likewise preferred embodiment, the sulfate is largely precipitated and / or crystallized out together with the N / P phase.

A sufficient reaction time is required for the separate or joint precipitation and / or crystallization reactions. This reaction is typically in the range between 1 and 300 minutes. A reaction time between 5 and 100 minutes is preferred, since experience has shown that a quantitative reaction takes place on a sufficient technical scale, a longer residence time increases the proportion of precipitation product somewhat, but also makes it necessary to dimension the equipment. In a particularly preferred embodiment, the reaction time is set in the range between 5 to 30 minutes, since sufficient quantitative precipitation and / or crystallization still takes place here, but the equipment can be made particularly small.

The precipitation and / or crystallization products can be separated between individual precipitation and / or crystallization stages and discharged from the solution / suspension in order to obtain, for example, qualitatively separated precipitation and / or crystallization products. Separation and discharge can also take place during the precipitation and / or crystallization reaction in order, for example, to shift the solution equilibria in a preferred direction.

The extent of the desired precipitation of the dissolved nitrogen and sulfur compounds and the type of precipitation products depend on the technical requirements of the process and the desired quality of the precipitation and / or crystallization compounds, and precipitation and / or crystallization does not have to be complete. According to the invention, however, at least 60% of the dissolved nitrogen and sulfate content should be precipitated and / or crystallized out of the solution / suspension. Precipitation and / or crystallization of the dissolved nitrogen and sulfate of more than 90% is preferred, since the process is then particularly economical.

In a preferred embodiment, the nitrogen and / or sulfur content is precipitated and / or crystallized out of the solution / suspension at least to such an extent that only such a low concentration of nitrogen and sulfur remains in the solution / suspension that after separation of the Solution of the precipitation and / or crystallization products, this solution can be used, for example, as service water. For this purpose, in this preferred embodiment, precipitation and / or crystallization is set to such an extent that a concentration of nitrogen still present in dissolved form of less than 1 g / l and of dissolved sulfur present in less than 10 g / l. If the solution is then to be discharged as waste water, for example, much lower concentrations must often be achieved. For this reason, in a very special embodiment, the concentration of nitrogen still present in dissolved form is set to less than 100 mg / l and of sulfur present in dissolved form is set to less than 1 g / l.

If, for example, the limit values for subsequent use and / or discharge are not reached by the precipitation and / or crystallization alone, at least one additional separation stage for at least dissolved nitrogen or ammonium and dissolved sulfur or sulfate can be performed after the precipitation and / or crystallization or other undesirable substances. In a preferred embodiment, the solution / suspension is brought into connection with an adsorbent and / or absorbent. For example, such a means as a powder or Granules are mixed into the solution / suspension or the solution can be passed over or through a bed with such means. As a result, part of the dissolved nitrogen / ammonia or sulfur / sulfate is at least partially bound to or in the adsorbent and / or absorbent and is thus removed from the solution. The solution and the adsorbent and / or absorbent are then separated. It can be advantageous for the solution / suspension to be conditioned before or during contact with the adsorbent and / or absorbent. For example, reducing or oxidizing substances can be added to change the nature of the dissolved elements or compounds, or a suitable pH value can be set.

This combined or separate precipitation and / or crystallization process of sulfate and nitrogen or ammonium from the nitrogen and sulfur-containing starting solution / suspension results in precipitation and / or crystallization products which can differ depending on the composition of the starting solution / suspension and the process management.

In a preferred embodiment, sulfate-containing and N- / P-containing precipitation and / or crystallization processes that are present separately from one another result. In this embodiment, the sulfate phase was precipitated or crystallized out separately from the N / P phase. Separate is to be understood here in the technical sense. In the case of precipitation and crystallization processes, foreign components can also be precipitated or crystallized out. Separate is to be understood here when the other precipitation and / or crystallization product contains only a proportion of less than 10% based on the concentration ratios in the starting solution.

In another embodiment which is also preferred, the at least one sulfate phase produced and the at least one N / P phase produced are mixed together in an end product. This results when sulfate and nitrogen or ammonium are largely precipitated simultaneously or the precipitation and / or crystallization products are not separated off between separate precipitation and / or crystallization steps.

In a particularly preferred embodiment, such a starting solution is used and the process is controlled in such a way that a mixture with 2 to 8% N, 5 to 15% P and 5 to 10% each of Mg, S and Ca results from the process (analytically determined on a mixture sample dried at 80 ° C). The P is present as a phosphate and, in a preferred embodiment, is more than 80% neutral ammonium citrate soluble.

In another particularly preferred embodiment, such a starting solution is used and the process is controlled in such a way that a mixture with 2 to 8% N and 5 to 15% P, Mg, S and Ca results from the process (analytically determined on one at 80 ° C dried mixture sample). The P is present as a phosphate and in a preferred embodiment is more than 80% neutral ammonium citrate soluble. The precipitation process according to the invention can be carried out either continuously and / or discontinuously and can be in one or more stages.

These resulting precipitation and / or crystallization products can be conditioned further. For example, drying and / or granulation can take place. Further components can also be added, for example for nutrient enrichment. Granulates can be coated to make them more abrasion-resistant or hygroscopic, for example.

In a preferred embodiment, these resulting precipitation and / or crystallization products are at least proportionate to the process according to the invention for the production of heavy metal-depleted fertilizer granules as a further component of the raw material mixture, the heavy-metal-depleted raw material mixture and / or the moist solid admitted. The process for generating the precipitation and / or crystallization products can be temporally, spatially and technically separate from the process for the production of heavy metal-depleted fertilizer granulates, for example in two separately operating plants.

In a particularly preferred embodiment, the process for producing the precipitation and / or crystallization products is procedurally and / or process-technically coupled with the process for the production of fertilizer granules that have been depleted of heavy metals.

In another embodiment, which is also preferred, the precipitation and / or crystallization products produced are at least partially fed to another utilization, for example (conventional) fertilizer production or direct use as fertilizer. Here, the process for generating the precipitation and / or crystallization products is temporally, spatially and technically separate from the process for the production of heavy metal-depleted fertilizer granules, for example in two separate plants.

FIG. 1 describes the basic embodiment of the method according to the invention for producing fertilizers from inorganic secondary phosphate. In the basic embodiment, however, heavy metals are already depleted according to the invention and thus a heavy metal-depleted fertilizer granulate 7 is produced.

To this end, a raw material suspension 3 is first produced from at least one inorganic secondary phosphate 1 and at least one reactant 2. According to the invention, the raw material suspension produced has a liquid phase content of greater than 45%. This high proportion of liquid phase set in this way basically serves as a buffer for the ongoing reaction between the inorganic secondary phosphate and the reactant, which often takes place spontaneously and in some cases very exothermically and is thus controllable and controllable and the stickiness of the mixture is also greatly reduced.

For a sufficient reaction between the at least one reactant 2 and the at least one inorganic secondary phosphate 1, an incubation time is awaited, wherein the raw material suspension can be mixed further. According to the invention, the reactant 2 should react with at least parts of the phosphate introduced by the inorganic secondary phosphate 1 in order to thereby increase the solubility and availability of this phosphate to plants. Only after the reaction between the inorganic secondary phosphate and the reactant has largely taken place is further processing up to the granulate. The reaction of the

According to the invention, phosphate conversion is thus separated from the granulation process.

According to the invention, heavy metals are then depleted from the raw material suspension produced in this way and discharged from the process of producing fertilizer granules as a separated pollutant 4. In a preferred embodiment, this takes place by means of one or more electrochemical processes.

The inventive heavy metal-depleted raw material suspension 5 is formed by the depletion of heavy metals according to the invention. Then the

Granulation / extrusion of the heavy metal-depleted raw material suspension 5, whereby the heavy-metal-depleted fertilizer granules 7 are formed.

The raw material suspension can also contain further components 6 (for example nutrient-containing components, dispersants and defoaming agents, structural substances, agents for pH adjustment, Urease inhibitors, ammonium stabilizers) can be added either during the production of the raw material suspension itself, after the incubation period, after the heavy metal depletion and / or during granulation / extrusion.

This granulation / extrusion process step results in soil- and plant-specific fertilizer granules 7 with a set and constant nutrient composition, with inorganic secondary phosphate (such as sewage sludge ash) being used as at least one source of nutrients, the phosphate contained therein being made more readily available to plants through the action of the reactant and the Heavy metals contained in the inorganic secondary phosphate were at least partially separated.

The granulate / extrudate produced can be dried and fractionated. The granulates / extrudates produced can also be coated with one or more coatings of the further components 6 before, during, between or after drying and / or fractionation.

FIG. 2 likewise describes the basic embodiment of the method according to the invention. The difference to the embodiment according to FIG. 1 is that the electrochemical heavy metal depletion takes place at least temporarily parallel to the incubation time. After the preparation of the raw material suspension according to the invention, the incubation time between the inorganic secondary phosphate and the reagent begins. In this embodiment, the electrochemical heavy metal depletion takes place at a time or offset. The electrochemical heavy metal depletion can be ended before, with or after the incubation period.

After the electrochemical heavy metal depletion, FIG. 2 corresponds to the description of FIG. 1.

FIG. 3 shows a preferred embodiment of the method in which, after the heavy metal depletion, part of the process water is separated from the raw material suspension. The advantage of a partial (mechanical) separation of process water is that it is considerably less costly and energy-intensive than thermal separation, for example by evaporation. In this embodiment, a raw material suspension is initially produced analogously to FIG. 1, the necessary incubation time is observed and the electrochemical heavy metal depletion according to the invention is carried out. Analogously to FIG. 2, the electrochemical heavy metal depletion can also take place at least temporarily in parallel with the incubation period.

Part of the process water is separated by solid / liquid separation after heavy metal depletion and before granulation / extrusion. The separated process water 9, which has already been depleted of heavy metals, can, for example, be discharged from the process and / or supplied before granulation for conditioning the raw material suspension or for granulation to shape the granules. A preferred embodiment is that at least a portion of this separated process water is returned to the production of the raw material suspension. The moist solid 8 resulting from the solid / liquid separation is fed to granulation / extrusion.

The raw material suspension / dispersion can also contain additional components 6 (for example nutrient-containing components, dispersants and defoaming agents, structural substances, agents for pH adjustment, urease inhibitors, ammonium stabilizers) either during manufacture to the raw material suspension / dispersion itself, after the incubation period, after heavy metal depletion and / or during granulation / extrusion.

At least part of the reactant 2 can be added to the separated and heavy metal-depleted process water 9 for the next filling of the raw material suspension. This proportion of reactant 2 then arrives with the heavy metal-depleted process water 9 to freeze the raw material suspension.

Analogous to the basic design according to FIGS. 1 and 2, the granulation / extrusion process step results in soil and plant-specific fertilizer granulates 7 with a set and constant nutrient composition, with inorganic secondary phosphate (such as sewage sludge ash) being used as at least one source of nutrients, with the phosphate contained therein acting through of the reagent was made more readily available to plants and the heavy metals contained in the inorganic secondary phosphate were at least partially separated. The granulate / extrudate produced can be dried and fractionated. The granulates / extrudates produced can also be coated with one or more coatings of the further components 6 before, during, between or after drying and / or fractionation.

FIG. 4 shows the basic design for generating and using N / P compounds from nitrogen and sulfur-containing solution / suspension 12.

The nitrogen- and sulfur-containing solution / suspension 12 is supplied with precipitation reagents 10, 11 for the precipitation or crystallization of the N / P compounds. A reagent 10 is at least one P compound for the formation of one or more N-phosphates. Another reagent 11 serves as a reactant for the precipitation or crystallization of sulfate, for example an alkali or alkaline earth compound. The addition of reagents 10 and 11 can take place simultaneously or staggered in time, also one after the other in stages with intermediate separation of the precipitation and crystallization products.

In addition, additional precipitation reagents 13 can be added to form specific precipitation or crystallization phases, such as, for example, Mg, K compounds. The solution / suspension 12 can also be conditioned by additional precipitation reagents 13 or the pFI value can be adjusted.

The precipitation or crystallization reaction can take place in the same vessel as for supplying reagent 10 and / or 11 and / or in a separate vessel. An incubation period is awaited before the precipitation or crystallization reaction takes place.

As a result of the reaction of the solution / suspension 12 with the precipitation reagents 10, 11, N- (14) and sulfate compounds (15) precipitate and are separated from the solution / suspension. Depending on how the process is conducted, they are available separately or together. These N- (14) and sulfate compounds (15) are present separately, for example, when the N- (14) or the sulfate compounds (15) are initially precipitated or crystallized by adding a suitable precipitation reagent and separated from the solution / suspension the other component remains largely in solution and then the other compound is precipitated or crystallized out. These N and sulfate compounds (14/15) are present together, for example, the precipitation or crystallization takes place simultaneously or the precipitated or crystallized compounds are not separated off separately. They can be present together in the form of a mixture of particles of different types and / or one type is coated or combined with one or more other types and / or crystallographic mixed phases are formed.

The N- (14) and sulfate compounds (15) obtained in this way can be used directly as fertilizers or further processed or as a further component (nutrient component) in the method according to the invention for producing fertilizers from inorganic secondary phosphate, for example according to FIGS. 1 to 3.

FIG. 5 shows the basic structure of the electrochemical heavy metal depletion according to the invention (also to be referred to as an electrochemical reactor). There are two electrodes in a vessel that are connected to a voltage source.

The raw material suspension is introduced into the vessel with the electrodes or produced therein. The raw material dispersion consists of at least one inorganic secondary phosphate and at least one reactant. The reactant reacts at least in part with the inorganic secondary phosphate, proportions of the inorganic secondary phosphate, including the heavy metals contained therein, being dissolved and the remainder being present as undissolved (solid particles). This raw material suspension of at least one liquid and one solid phase can also be referred to as an electrolyte solution.

When a direct current voltage is applied, one electrode becomes the cathode and the other becomes the anode. By setting suitable reaction parameters, heavy metal cations are at least partially reduced and, for example, deposited as metal or metal oxide at least partially on the cathode (adhesions on the cathode).

Embodiment 1:

A raw material suspension of 80 g water, 32 g sulfuric acid (96%) and 40 g sewage sludge ash (P205 content 17.6%, of which neutral ammonium citrate-soluble 40% and <1% water-soluble; heavy metal contents of 1.51 mg / kg for Cd, 14 mg / kg As, 613 mg / kg Cu) and an incubation time of 25 minutes was observed.

After the incubation period, the raw material suspension produced in this way is fed to an electrochemical heavy metal depletion facility. The device for electrochemical heavy metal depletion corresponds to FIG. 5. The raw material suspension is accordingly transferred into a 250 ml glass vessel in which two carbon electrodes (5 × 8 cm) are located approximately 4 cm apart. The raw material suspension is continuously stirred. A current of 2.0 A is applied to the electrodes, one electrode becoming the anode and one electrode becoming the cathode.

The reaction time is 60 minutes. The current is then switched off and the electrodes are removed from the suspension. A deposit / film has accumulated on the cathode, which contains heavy metals, among other things, and which can be removed in dilute nitric acid (3%).

By separating the cathode with the heavy metal-containing coating / adhesion from the raw material suspension, at least some of the heavy metals present in the raw material suspension are separated from the raw material suspension. The regeneration of the cathode with dilute nitric acid creates a waste solution containing heavy metals, which can be disposed of or recycled. In addition, the cathode can then be reused. The following table shows an example of the amount of heavy metals in the raw material suspension before and after the electrochemical separation and indicates the degree of separation in percent for some heavy metals.

The raw material suspension thus depleted of heavy metals can be converted into fertilizer granules in subsequent steps. Embodiments 3 and 4 show two variants of this.

Embodiment 2:

Analogously to embodiment 1, a larger amount of suspension with the same composition is produced as follows: 8 kg of water; 3.2 kg sulfuric acid (96%) and 4.0 kg sewage sludge ash (P205 content 18.3%, of which neutral ammonium citrate soluble 40% and <1% water soluble; heavy metal content of 1.51 mg / kg for Cd, 14 mg / kg As, 613 mg / kg Cu) The incubation time is again 25 minutes.

The electrochemical heavy metal separation then takes place in a manner analogous to that in embodiment 1. The test setup was adapted to the larger amount of suspension by upscaling so that the test parameters for the electrochemical reaction were identical to those in embodiment 1. The reaction time was again 60 minutes. After the reaction time, the heavy metal-depleted raw material suspension is pumped into a storage container and initially stirred there. The following table shows an example of the removal rate for the amount of heavy metals from the raw material suspension achieved by the electrochemical depletion using selected heavy metals.

The heavy metal-depleted suspension is then processed further. To this end, 3.4 kg of KCl are added with stirring and this mixture is further homogenized. This raw material dispersion is then fed to a continuous fluidized bed system for spray granulation. The spray granulation is controlled in such a way that an average granulate size of 3.5 mm results. After the spray granulation, granules smaller than 2 mm and granules larger than 5 mm are separated by sieving and fed to the spray granulation process as core material, the granules larger than 5 mm being ground beforehand. A core material in the form of a fluidized bed, onto which the raw material dispersion is sprayed, is required for spray granulation. In the starting phase, the core material of the species is preferably introduced; in the continuous process, the core material results from the recycling of the separated granulate fractions.

This procedure is repeated continuously. For a continuous process, buffer tanks are installed in the process steps of heavy metal separation and granulation in order to ensure the chronological sequence of the continuous and discontinuous process steps running in parallel.

The heavy metal-depleted granulate produced has a round and compact granulate shape in the range 2-5 mm after the above-described equilibrium cycles have been set, a total P205 content of 7%, 92% of which is ammonium citrate-soluble and 38% is water-soluble, a total K20 content of 21 % and an S content of approx. 10%.

Embodiment 3:

Analogous to embodiment 2, a raw material suspension is produced. Unlike in exemplary embodiment 2, however, the electrochemical heavy metal separation then already takes place during the incubation period with a reaction time of 90 minutes. For this purpose, the raw material suspension produced is transferred to a separate electrochemical reactor according to the basic principle of FIG. Alternatively, the raw material can also be produced directly in this reactor.

The following table shows an example of the separation rate achieved for the amount of heavy metals from the raw material suspension for selected heavy metals.

A large part of the liquid phase is separated from the undissolved solid by means of a chamber filter press in such a way that an earth-moist solid mixture with a liquid phase content of 32% is formed.

The separated solution (liquid phase), which also contains nutrients, is returned to the process of raw material dispersion production for the next batch and replaces the above-mentioned water content in the formulation of the raw material dispersion in an equivalent amount. With continuously Continuous process management creates an equilibrium cycle of the dissolved substances in this sub-cycle. Accordingly, after this equilibrium has been established, the added amount of phosphate will pass through the sewage sludge ash to granulation and thus, as desired, into the granulate.

A major advantage over embodiment 2 is that part of the liquid phase is separated mechanically from the raw material dispersion. This means that significantly less water has to be evaporated, which saves considerable energy costs and makes the process much more economical.

The earth-moist solid mixture resulting from the solid-liquid separation is transferred to an intensive mixer (from Eirich R16W) and mixed intensively there. 3.4 kg of KCl are added as a fine powder and everything is mixed intensively. The ratio of solid to liquid phase is set in the intensive mixer by adding water or a powder (e.g. sewage sludge ash) so that green granules of the desired size are formed during intensive mixing. The green granules formed are then dried at 110 ° C. and fractionated into 2-5 mm. The fraction smaller than 2 mm and the fraction larger than 5 mm are returned to the subsequent granulation batches after previous grinding.

The heavy metal-depleted granulate produced has a round and compact granulate shape in the range of 2-5 mm after setting the above-described equilibrium cycles, a total P205 content of 7%, of which 90% is ammonium citrate-soluble and 28% is water-soluble and a total K20 content of 21 % and an S content of approx. 10%.

Claims

1. Heavy-metal-depleted fertilizer granulate (7) can be produced using a process comprising the steps:

a) production of a raw material suspension (3) comprising at least one inorganic secondary phosphate (1) and at least one reactant (2), the proportion of liquid phase in the raw material suspension being greater than 45%,

c) Carrying out an electrochemical heavy metal depletion directly in the raw material suspension (3) produced and discharging at least some of the separated pollutants (4), wherein the electrochemical heavy metal depletion can begin with or during the production of the raw material suspension (3) or thereafter, with the electrochemical Heavy metal depletion can take place at least simultaneously with or temporarily in parallel during the incubation period and / or beyond the incubation period,

d) granulation and / or extrusion of the heavy metal-depleted raw material dispersion (5), which can be followed by at least one drying and / or fractionation, and

e) Continuous and / or batchwise repetition of process steps a) to d).

2. A method for producing a heavy metal depleted fertilizer granulate (7) comprising the following steps:

d) Granulation and / or extrusion of the heavy metal-depleted raw material dispersion (5), it being possible for at least one drying and / or fractionation to follow and

e) Continuous and / or batchwise repetition of process steps a) to d).

3. Heavy metal depleted fertilizer granules (7) according to claim 1 or method according to claim 2, characterized in that in an upstream precipitation and / or Crystallization process from at least one ammonium- and sulfate-containing starting solution (12), at least one mixture of and / or separately present sulfate-containing and N- / P-containing precipitation and / or crystallization products are formed, which are the raw material dispersion (3), the raw material dispersion (5 ) and / or the earth-moist mixture (8) before and / or during the granulation or extrusion at least partially.

4. Heavy metal depleted fertilizer granulate (7) according to claim 1 or 3 or the method according to claim 2 to 3, characterized in that part of the liquid phase of the heavy metal depleted raw material suspension (5) after the heavy metal depletion and before the granulation and / or extrusion as heavy metal-reduced process water (10) is separated, wherein

^■ first, a semi-dry composition (8) with a moisture content of 5 to 40% results, and

^■ on the other hand a liquid phase separated in the form of a schwermetallabgereicherten process water (10), wherein the separated schwermetallabgereicherte process water (10) is either fed back to generate the raw material dispersion (3) and / or for conditioning the schwermetallabgereicherten raw material dispersion (5) before granulation or granulation used to form the granules and / or removed from the process,

wherein at least some of the dissolved components can be precipitated and / or crystallized out of the liquid phase of the heavy metal-depleted raw material suspension (5) before the separation.

5. Heavy metal depleted fertilizer granulate (7) according to claim 1 or 3 or the method according to claim 2 to 3, characterized in that the heavy metal depleted raw material dispersion (5) has a solids content of 40 to 70% and granulation of the polluted raw material dispersion (5) by spray granulation or Spray agglomeration takes place.

6. Heavy metal depleted fertilizer granulate (7) according to claim 1, 3 to 5 or the method according to claim 2 to 5, characterized in that the pH value of the heavy metal depleted raw material dispersion (5) or the earth-moist mixture (8) is in the range from 4 to 11 .

7. Heavy metal depleted fertilizer granulate (7) according to claim 1, 3 to 6 or the method according to claim 2 to 6, characterized in that after the granulation and / or drying a fractionation of the heavy metal depleted fertilizer granulate (7) follows, wherein a coarse fraction and / or a fine fraction is ground up and can be fed at least partially to the raw material dispersion (3), the heavy metal-depleted raw material dispersion (5) and / or the earth-moist mixture (8) before and / or during granulation or extrusion and / or drying.

8. Heavy metal depleted fertilizer granulate (7) according to claim 1, 3 to 7 or the method according to claim 2 to 7, characterized in that a total of 1 to 70% crystallization products from phosphorus elimination and / or other components of the raw material dispersion (3), the heavy metal depleted raw material dispersion (5) and / or can be fed to the earth-moist mixture (8), wherein drying after granulation and / or extrusion can take place above 100 ° C. based on the material temperature during drying.

9. Device for the production of heavy metal depleted fertilizer granules (7) according to one of the preceding claims 1 or 3 to 8, comprising

^{■ At} least one first mixing container for supplying and / or mixing at least the inorganic secondary phosphate (1) and the reagent (2), whereby a raw material dispersion (3) is obtained, either the first mixing container being used for the incubation period and / or further containers being available into which the raw material dispersion (3) is transferred and mixed for the incubation period,

^At least one device for electrochemical heavy metal depletion, such a device being integrated or separated from the first mixing container and / or the mixing container while waiting for the incubation period, the raw material suspension (3) formed therein or feedable therein and the heavy metal-depleted raw material suspension (5 ) can be removed therefrom and the heavy metals can be discharged at least in part,

^■ at least one granulating and / or extrusion unit for granulating and / or extruding the heavy metal-depleted raw material dispersion (5) or the earth-moist mixture (8), with at least one feed unit from the heavy-metal depletion for transferring the heavy-metal-depleted raw material dispersion (5) or the earth-moist mixture (8) ) is present in the granulating and / or extrusion unit and a mixing unit for mixing or homogenizing the heavy metal-depleted raw material dispersion (5) or the earth-moist mixture (8) can be integrated or upstream,

^■ at least one feed unit, via the further components (6) of the production of the raw material dispersion (3) and / or subsequently before and / or for the electrochemical heavy metal depletion and / or the heavy metal depleted raw material dispersion (5) or the earth-moist mixture (8) before and / or can be fed in during the granulation or extrusion, it being possible for additional mixing units to be present for mixing and / or homogenization.

10. The device according to claim 9, characterized in that

^■ at least one separation unit for separating at least part of the liquid phase from the heavy metal-depleted raw material dispersion (5) and

^■ at least one return unit for the separated heavy metal-depleted process water (10) to the mixing tank for producing a raw material dispersion (3) and / or to the granulating and / or extruding unit

available.

11. Device according to one or more of claims 9 or 10, characterized in that a device for the precipitation and / or crystallization of a mixture from and / or separately present sulphate-containing and N- / P-containing precipitation and / or crystallization product from at least one ammonium and sulphate-containing starting solution consisting of

^■ at least one mixing container for supplying and / or mixing at least ammonium- and sulfate-containing starting solution (12) and at least the precipitation reagent (10) and (11), either this mixing container being used for the incubation time for the precipitation and / or crystallization reaction and / or there are further containers in which this mixture is transferred and mixed for the incubation period,

^■ at least one device for separating the precipitation and or

Crystallization products

^{■ At} least one feed unit via which further precipitation reagent (13) of the ammonium- and sulfate-containing starting solution (12) can be fed before and / or during the precipitation and / or crystallization reaction, additional mixing units for mixing and / or homogenization being available.

12. The device according to claim 9 or 10 or 11, characterized in that the granulating and / or extruding unit is an intensive mixer, a granulating plate or a fluidized bed or spouted bed reactor.

13. Coated or uncoated heavy metal-depleted fertilizer granulate (7), characterized in that the heavy metal-depleted fertilizer granulate (7) comprises at least one inorganic secondary phosphate (1), as well as a greater than 60% neutral ammonium citrate-soluble P205 content based on the total phosphate content in the heavy metal granulate enriched with 7.

14. Coated or uncoated heavy metal-depleted fertilizer granulate (7) according to claim 17, characterized in that the heavy metal-depleted fertilizer granulate (7) comprises at least one inorganic secondary phosphate (1), as well as a more than 60% neutral ammonium citrate-soluble P205 content based on the total phosphate granulate content in the heavy metal waste 7), the P205 portion of the phosphate portion from the inorganic secondary phosphate (1) having a water solubility of less than 40%.

15. Coated or uncoated heavy metal depleted fertilizer granules (7) according to claim 13 or 14, characterized in that the heavy metal depleted fertilizer granules (7) in total 0.1 to 25% humic acid, fulvic acid, their salts (humates, fulvates) and / or in total 0 , 1 to 30% organic acid and / or in total 0.1 to 50% structural substances and / or one or more crystallization products from the phosphorus elimination in the concentration range between 1 to 70%.

16. Use of the heavy metal-depleted fertilizer granules (7) according to one or more of claims 13 to 15 for the supply of nutrients in agriculture, forestry and / or horticulture, characterized in that the heavy-metal-depleted fertilizer granules (7) comprise at least one inorganic secondary phosphate (1), as well as a more than 60% neutral ammonium citrate-soluble P205 content.

17. A method for at least partial separation of ammonium and sulfate from at least one ammonium- and sulfate-containing starting solution comprising the following steps:

^■ Separate or joint separation of the precipitates and / or crystallization products formed.

18. Precipitation and / or crystallization product from the at least partial separation of ammonium and sulfate from at least one ammonium- and sulfate-containing starting solution, comprising the following steps:

^■ Separate separation of the precipitates and / or crystallization products formed, with the precipitation and / or crystallization products 2 to 8% N, 5 to 15% P and 5 to 10% each of Mg, S and Ca (analytically determined on one at 80 ° C dried mixture sample) and where the P as phosphate can be more than 80% neutral ammonium citrate soluble.