EP0426783A1

EP0426783A1 - Process for manufacturing pelletized materials for use in chemical reactions in industry or agriculture

Info

Publication number: EP0426783A1
Application number: EP90905194A
Authority: EP
Inventors: Zbigniew Dr. Boguslawski
Original assignee: AQUAMOT AG
Current assignee: AQUAMOT AG
Priority date: 1989-03-23
Filing date: 1990-03-21
Publication date: 1991-05-15
Also published as: WO1990011264A2; WO1990011264A3; CH680586A5; CA2029887A1

Abstract

Dans le procédé décrit, des composés alcalins pulvérulents sont pelletisés avec des hydroxides de substances présentant des produits de solubilité différant considérablement. Dans une première phase, une faible quantité d'eau de pelletisation est ajoutée pour former des germes d'une granulométrie comprise entre 0,05 et 0,15 mm, qui se combinent pour former des pellets lors de l'adjonction d'une quantité supplémentaire d'eau de pelletisation. La quantité d'eau de pelletisation ajoutée au matériau dans cette première phase doit suffire à son hydratation mais ne doit pas être notablement plus importante. Après le commencement de la formation des germes, on n'ajoute plus d'eau jusqu'à ce que la matière première soit complètement hydratée et ce n'est qu'après que l'on ajoute la quantité d'eau de pelletisation nécessaire à la poursuite de la formation des germes. Pour fabriquer des pellets destinés à éliminer des impuretés azotées, conjointement avec des impuretés phosphorées et éventuellement des métaux lourds, les substances actives utilisées sont des phosphates d'hydrogène ou des phosphates d'un cation des deuxièmes groupes principal et auxiliaire du système périodique.In the process described, powdery alkaline compounds are pelletized with hydroxides of substances having considerably different solubility products. In a first phase, a small amount of pelletizing water is added to form seeds with a particle size between 0.05 and 0.15 mm, which combine to form pellets when adding a quantity additional pelletizing water. The amount of pelletizing water added to the material in this first phase must be sufficient for its hydration but must not be significantly greater. After the germination has started, no more water is added until the raw material is completely hydrated and it is only after adding the amount of pelletizing water necessary to further germ formation. To manufacture pellets intended to remove nitrogenous impurities, together with phosphorus impurities and possibly heavy metals, the active substances used are hydrogen phosphates or phosphates of a cation of the second main and auxiliary group of the periodic system.

Description

Process for the production of pelleted

Feedstocks for use in chemical

Implementation processes in industry or agriculture

The invention relates to a process for the production of pelletized feedstocks for use in chemical conversion processes d industry ^• or agriculture, for example in the cleaning of municipal, industrial and private ^• wastewater, in fertilization or deacidification used for agricultural or forestry purposes or the like.

One of the main problems in the chemical reaction process is to control the reaction rate and in particular to regulate the amount of reagents used. This applies in particular to reaction processes in which water-soluble materials are used as reagents, the reaction material is still in an aqueous solution and one longer contact time between the reagent and the solution is unavoidable. This is the case, for example, in the deacidification of soils in agriculture and forestry and in a large number of chemical conversion processes in industry, for example in wastewater treatment. For example, the materials that are spread to improve the soil are permanently exposed to the effects of soil moisture, which is particularly the case during rainy periods leads to an excessive dissolution of the soil improvement with the consequence that on the one hand the materials used to improve the soil due to their oversupply themselves damage the gusts - z -

cause and there is a risk that these materials are introduced into the groundwater. The same applies to the use of chemical conversion processes, for example in the wastewater treatment process, in which the reagents have to be used in a large excess on the one hand and on the other hand for a longer period of time in order to adequately convert the pollutants, which also leads to the risk of excessive absorption of the reagent material with the resulting Wastewater disposal risks are justified.

In this sense, the cleaning of acidic wastewater in particular continues to be an unsatisfactorily solved problem, whereby acidic wastewater is to be understood as any kind of wastewater with a low pH value, of which the condensates accumulating in the chimneys of household heating and industrial plants have gained special importance from flue gases, because on the one hand they have an extraordinarily low pH value and - as recent studies have shown - they also carry considerable proportions of heavy metals, which are caused by the condensate when it drips off. Drainage in the chimney from the chimney lining is recorded as abrasion or release. The neutralization of such wastewater represents a considerable environmental problem; its discharge into the public receiving water leads to considerable damage to the biological cleaning plants and, as a result, to environmental damage. To avoid such damage, it is therefore increasingly necessary to develop chemical wastewater treatment processes that supplement or as an alternative to the biological cleaning processes in which the clarifying effects are achieved by bacterial, enzymatically catalyzed. _ i -

due to metabolic reactions, cleaning by chemical or physico-chemical reactions.

Biological processes are limited to one another by the fact that only substances that fit into the metabolism of the bacteria are recorded and absorbed and implemented in the biological system (aeration tank, trickling filter) within the retention time, i.e. be dismantled. With the increasingly complex composition of municipal and above all industrial wastewater, the biologically undetectable residual loads from the biological treatment processes will increase. For this reason too, the chemical processes of wastewater treatment are of particular importance in the future protection of the aquatic part of our ecosystem.

E _SS known for the neutralization of acid wastewater use so-called neutralization boxes, which are filled with a basic feed and into which the acidic solution drips, reacting with the reaction material during the more or less long residence time. The main disadvantage of the known methods is, on the one hand, the high material consumption caused by complete saturation of the condensates and, moreover, in particular the fact that, on the one hand, high proportions of the neutralization material dissolve during the dwell time of the wastewater and thus lead to an excessive load and that in particular removal of the heavy metals contained in the wastewater is not possible. It is an object of the invention to provide a method which enables the production of feedstocks for use in chemical conversion processes with consumption regulated in a metered manner as a function of the desired conversion rate.

This object is achieved by the method given in claim 1.

Through the use of feed materials with an extremely different solubility product on the one hand and their pelletization in a specific granulation, to be referred to as "micro-coated build-up agglomeration", through the formation of initially pelletizing germs and their connection, a feed material is achieved which, upon contact with the Solution containing reactive substances is implemented in a targeted manner and in a quasi-buffered manner in such a way that the more easily soluble materials are protected from premature release and thus excessive accumulation in the solution by the more difficult to poorly soluble materials. The formation of pellets ensures that the solution containing the reaction substances has a large contact area and thus the direct contact of the reaction substance which is usually only present in a large dilution in the solution with the reagent and thus its implementation is ensured. It is thus in this sense - using the example of the deacidification of wastewater - even with a simple flow of the wastewater through a bed of pellets produced in the manner according to the invention, that the wastewater on the one hand at all times the amount required for neutralization - s -

Reaction material is available, but it is achieved by the special in particular in the outer layers of the germs and the pellets materials with extremely low solubility product targeted buffering, which excessive dissolution and thus i i same way as the acidification prevents environmentally harmful excessive neutralization (slow-release effect). Another essential Before part of the invention is also to be seen in that, simultaneously with the New sewage treatment tralization a complete elimination of the heavy metals can be obtained, consisting in the gradual transition of the Abwas _S ers from the acidic phase to the basic phase the solution precipitate into such particle sizes that they are initially physically bound to the surface of the pellets and can be collected in a special filter layer when washed out of the pellet bed.

In order to achieve this effect, in addition to the choice of the input materials, the structure mentioned of germs and matrix material of different solubility products is of crucial importance, the achievement of which is the metered addition of the pelletizing water during their production. The build-up granulation is based on the fact that, in view of the greatly reduced supply of pelletizing water in the nucleation phase, the surfaces of the more easily soluble mineral particles begin to dissolve, which thus preferably agglomerate with the binding of only small amounts of the less soluble material during dissolving of the surfaces of the particles of the less soluble material takes place at a much later time, so that after the end of the pelleting process, this material is predominantly in de outer layers including germs and residual amounts of non-pre-germinated material with greater solubility product.

As an example of the particularly advantageous use of the pellet materials produced by the process according to the invention, even agricultural, agricultural and forestry soil neutralization can be mentioned with pellets of 40 to 65, preferably 45 to 55% by weight of dolomite, 10 to 25, preferably 15, 20% by weight calcium carbonate, 2.5 to 7.5, preferably 4 5% by weight disodium monohydrogen phosphate, 2.5 and 7.7, preferably 4% by weight calcium hydrogen phosphate, 10 up to 15, preferably 6.5 to 7% by weight calcium hydroxide, 2.5 to 7.5, preferably 4.5 to 5.0% by weight bentonite, 1 to 5.0, preferably 2.5 3.0% by weight feldspar, 1.5 to 5.0, preferably 2.5 to 3.0% by weight potassium silicate, and 1.5 to 5.0, preferably 3.5% by weight magnesium oxide. In this case, the pelleting is advantageously polidisperse, that is to say with widely differing sizes, with a proportion of small-grained material which is inversely proportional to the pH of the soil treating z. By increasing the small-grained fraction at a lower pH value and vice versa, in conjunction with the targeted selection of the materials used according to their solubility products, the time and speed of action, i.e. the time within which a soil with a pH of For example, 2 given the weather conditions to a pH between 6 and brought and then maintained at this value. In this sense, the pelleting of dolomite (calcium magnesium carbonate) with a solubility product of 2.6 x 10 ~ ^β for magnesium carbonate and 4.7 10 ~ * for calcium carbonate can buffer that in the nucleation phase instead of calcium hydroxide (solubility product 3.9 x 10 "*) magnesium hydroxide (1.5 x 10 ~ ¹² ), aluminum hydroxide (1.9 x 10" ³¹ ) or iron hydroxide (5.0 x 10 ^-3 ") as a binder uses and thereby specifically causes a more or less strong buffering of the active material, through which the dissolution of the material is delayed accordingly.

Further active substances can be added to the feed material, for example active bentonite and or sodium sulfate decahydrate for regulating the water balance in the soil, of which active bentonite is capable of storing water in an amount of 30 times its weight, while this sodium sulfate decahydrate congruently splits off its crystal water at a temperature of over 30 ° C. In a corresponding manner, an active substance can be added to the pellets, through which the plant absorbs the ozone which is absorbed by the leaves due to the sun's rays and which has a detrimental effect on the plant organ. This can either be a buffer agent imparting a weakly alkaline reaction - pH> 7 - to the plant juices or an agrotechnologically justifiable catalyst, for example manganese sulfa (MnSO- *), which causes the decomposition of the ozone, the rate of decomposition increasing with increasing alkalinity of the solution (plant juice ) decreases.

In a further embodiment, as active substances for the production of pellets for the removal of nitrogen impurities and in connection therewith phosphorus impurities and possibly heavy metals as use or. Active substances Hydrogen-Phos - O -

phosphate salts of a cation of the 2nd main and subgroups of the periodic table (MeHPO), in particular magnesium hydrogen phosphate (MgHPO.), and / or phosphate salts, in particular the orthophosphate salts , a cation of the 2nd main and subgroups of the periodic table, in particular tri-magnesium-di-phosphate, the phosphate salt, in particular the orthophosphate forming one of the active substances, being synthesized in the first pelletizing stage in such a way that initially a partial amount of metal oxide is reacted with a sufficient amount of phosphoric acid for the reaction and then further magnesium oxide is added, whereupon after complete reaction the pelleting takes place using the magnesium hydroxide formed in the second reaction stage as a binder in conjunction with the excess water of reaction formed in the first reaction stage . It is thus possible in a particularly simple manner to control the use of pellet water i in the first pelletization stage, provided that when the magnesium oxide is reacted with the phosphoric acid, an excess amount of reaction water is released, which is used to hydrate the magnesium oxide which is subsequently added to hydrate it is sufficient and also gives the metered small amount of water that is needed to form the germ from preferably the more soluble active materials, while the less soluble materials only take part in the agglomeration at a later point in time and in a mixture with later agglomerating, more easily soluble parts, on the one hand the more soluble Enclose germs and, on the other hand, connect the germs formed as matrix material in the second stage of pelleting. The process of the invention can furthermore be used with great advantage in the production of pellets for the neutralization of acids with, if appropriate, simultaneous removal of heavy metals. In this case, the pelleting is expediently carried out in such a way that initially nuclei are formed with a nucleus essentially consisting of bases from the second main group of the periodic system, in particular magnesium hydroxide, and a coating of iron III hydroxide and the nuclei subsequently in pelletized in a matrix, pellets with different composition, ie in particular pellets with a different magnesium hydroxide / iron III hydroxide ratio can be formed, of which the pellets containing a high proportion of magnesium hydroxide of the (rapid ) Neutralization of the acids dissolved in the treated liquid and the pellets containing a higher proportion of iron-III-hydroxide serve the stronger inclusion (encapsulation) of magnesium hydroxide with the effect that in the neutralization phase with the aim of separating the heavy metals to a value above elevated pH to the more environmentally friendly value of about 7, 5 to reduce. The weakly acidic effect of the iron hydroxide is based on the fact that the iron hydroxide is in the form of a trivalent hydrated iron ion, which is derived from this - - For gradually converting i Fe (H3Jθ) s: (OH) _* ι.- with continuous elimination of hydrogen ions. In addition to this advantageous effect of pH regulation, there are further advantages with the pellets produced in this way that heavy metals contained in the solution precipitate out in the phase of the increased pH (> 9) and the precipitate a in colloidal form present iron hydroxide is adsorbed. The invention is explained below using a few examples:

Example 1:

15 kg dolomite 18/23, 5 kg calcium carbonate, 0.5 kg disodium monohydrogen phosphate and calcium hydrogen phosphate, 2.5 kg calcium hydroxide, 1.5 kg feldspar, 1.0 kg potassium are added to the pellet mixer silicate, 3.0 kg active bentonite and 1 kg manganese sulfate.

The mixture is homogenized intensively. Now 2.5 kg of water, 2.5 kg of magnesium oxide and 5.0 kg of white lime are added "and mixed intensively. After the exothermic reaction of the lime quenching has ended, the mixture is pelleted with the addition of 4.5 kg of pelletizing water until the germination stage, whereupon the final pelleting with the addition of a further 0.5 to 0.6 kg of water until the desired micro-coated germ-based pellet with a grain size of between 3 and 6 mm is formed, they contain water in an amount of approximately 2.0 to 2.2 kg, have a deactivating effect Ozone solutions show a pH in water of about 11.6, in acidic water - starting value 3.8 - a buffered value of 7.35.

Example 2;

100 kg of magnesium oxide with a purity of more than 98 and a calcium ion content of less than 0.5% by weight are mixed together - // -

10 kg of iron oxide - purity also over 98% - weighed into the pelleting mix. After intensive mixing - about 10 minutes - 48.4 k de-ionized (softened, distilled) water are added, which is sufficient to convert the oxides into hydroxides. An excess of about 0.5 to% by weight should not be exceeded. The reaction is carried out with intensive cooling to remove the heat of reaction such that a reaction temperature of 35 ° C is not exceeded. After the intensive reaction phase has ended, the mixture is ripened for about 30 and 120 minutes for the purpose of ripening.

Further pelletizing water is then added to the cooled reaction mass in three steps with constant pelleting, and initially an amount of about 2.75 kg, then after a time of about 1 minute another 1.35 kg. After a pelleting time of a further 10 minutes, pelletizing nuclei have formed which, after the addition of a further 1.35 k of pelleting water, are finally pelleted to pellets of a size between 3 mm and 6 m. The moist pellets are powdered with about 2.5 kg of magnesium oxide and air-dried for 12 hours.

Example 3:

100 kg of iron oxide with 10 kg of magnesium oxide are added with vo

34.0 kg of hydrating water and - in three batches - 2.0 + 0.95 + 0.95 k

Pelletizing water processed into pellets, which are suitable for pH adjustment. The production takes place in the same, shown in example

Way, taking into account the conditions there.

Claims

- fl patent claims

1. Process for the production of pelleted feedstocks for use in chemical conversion processes in industry or agriculture, for example in the purification or neutralization of municipal, industrial and private waste water, in the fertilization or deacidification land or. soils used for forestry or the like, characterized in that powder-form alkaline compounds with hydroxides of substances with widely differing solubility products are pelleted in such a way that initially in a first stage by adding a small amount of pelleting water, germs of a size between 0.05 and 0.15 mm and then the germs formed are combined into pellets by adding further pelletizing water

2. The method according to claim 1, characterized in that the feed in the first stage is sufficient for its hydration and this does not significantly exceed the amount of pelletizing water and after the onset of nucleation the further addition of water until complete hydration of the feedstocks and only then is the pelletizing water required to continue nucleation added. -73-

3. The method according to claim 1 or 2, characterized in that z production of pellets for the removal of nitrogen impurities and in connection with this, phosphorus impurities and, where appropriate, heavy metals as a use or. Active substances hydrogen phosphate salts of a cation of the 2nd main and subgroups of the periodic table (MeHPO *), especially magnesium hydrogen phosphate (MgHPO and / or phosphate salts, especially the orthophosphate salts a cation of the 2nd main and subgroups of the periodic system, in particular tri-magnesium di-phosphate.

4. The method according to claim 3, characterized in that the phosphate salt, in particular that form one of the active substances, orthophosphate is synthesized in the first pelletizing stage in such a way that d a portion of metal oxide is first reacted together with an amount of phosphoric acid which is sufficient for the reaction and thereafter further magnium oxide is added, whereupon after complete reaction the pelleting is carried out using the magnesium hydroxide formed in the second reaction stage as a binder in conjunction with the excess water of reaction formed in the first reaction stage.

5. The method according to claim 1 or 2, characterized in that z production of pellets for the removal of acids and heavy metal from acidic waste water as a feed micro-coated germ cell pellet aggregates with a matrix of magnesium hydroxide and egg micro-coating of Fe (OH) ^ find use . ^"" '7

6. The method according to claim 5, characterized in that for the production of pellets for adjusting the pH in the cleaned wastewater and the inclusion of the precipitated heavy metal hydroxide as a starting material, hydroxide (Fe (OH) a) in conjunction with magnesium hydroxide as a binder Is used.

7. The method according to claim 1 or 2, characterized in that for the production of pellets for gardening, agriculture or forestry soil neutralization as a use or. Active substances dolomite between 40 and 65, preferably 45-55% by weight,

Calcium carbonate between 10 and 25, preferably 15-20% by weight, disodium monohydrogen phosphate between 2.5 and 7.5, preferably 45% by weight, calcium hydrogen phosphate between 2.5 and 7.7 , preferably 4% by weight,

Calcium hydroxide between 10 and 15, preferably 6.5 to 7% by weight, bentonite between 2.5 and 7.5, preferably 4.5 - 5.0% by weight, feldspar between 1.5 and 5, 0, preferably 2.5-3.0% by weight, potassium silicate between 1.5 and 5.0, preferably 2.5-3.0% by weight, magnesium oxide between 1.5 and 5.0, preferably 3 , 5% by weight, the rest of the pelletizing water is used.

8. The method according to claim 7, characterized in that as Bentoni which has a water-storing function, by multilayer

Construction of pellet-protected active bentonite and / or sodium sulfate deca _ttr

- / -

hydrate (N ^ O * x 10 H2O) is used.

9. The method according to claim 7 or 8, characterized in that substances with low solubility product are added to the feedstock, which cause the decomposition of the ozone dissolved in the vegetable juice under weakly alkaline buffered conditions.

10. The method according to any one of claims 7 to 9, characterized in that the calcium content of the active ingredients is less than 0.5 wt .-%, based on the dry mass.

11. The method according to any one of claims 1 to 10, characterized in that the feed manganese-II salts in an amount between 0.05 and 0.25 wt .-% is added as a catalytically active substance.

12. The method according to any one of claims 1 to 11, characterized in that feedstocks with a solubility product differing by at least about three powers of ten are used to produce the pellets.

13. The method according to claim 12, characterized in that as the materials with low solubility zinc, magnesium, aluminum, aluminum, manganese-II or iron-III hydroxide, and zinc, tin, manganese-II or iron III sulfide and zinc or calcium carbonate can be used individually or in a mixture with one another.

14. The method according to claim 5 and 13, characterized in that the mass of the zinc, magnesium and iron hydroxides in a quantity ratio dependent on the acid content of the wastewater from 3.0 - 8.0 wt. Mg (0H) _a , 3.0-8.5% by weight of Zn (0H) ₃ and furthermore 3.0-17.5% by weight of Fe (0H) ₃ .

15. The method according to claim 13, characterized in that the calcium content of the active ingredients is less than 0,

% By weight, based on the dry mass.

16. The method according to any one of claims 1 to 15, characterized in that the feed materials are pelletized as a function of their solubility products in the course of a build-up agglomeration in the pellet in such a way that predominantly high proportions of the material having a relatively high solubility product and small amounts of materia with a lower solubility product are contained, while the outer layers enclosing a multiplicity of germs are predominantly formed from materia of a low solubility product.

17. The method according to any one of claims 1 to 16, that the pelleting takes place in particular in the hydration phase which proceeds under a strongly exothermic reaction with constant cooling to room temperature.

18. The method according to any one of claims 1 to 17, characterized in that the feed contains 0.5 wt .-% to 3.0 wt .-% kaolin, based on the dry mass as a binder and the finished raw pellets 2 bi 264 _ _t j

3 hours of thermal treatment at 280 "C to 350 ^* C and then gently cooled down to room temperature.

19. The method according to claim 18, characterized in that the the treated active pellets have a porosity of the bed 0.05 to 0, with a specific surface area of 18-65 π / g and a bulk density between 1.1 and 1.25.

20. The method according to any one of claims 1 to 19, characterized in that the active pellets in the inner layers as active ingredients contain carbona and / or hydrogen carbonates, for example Na = C0 ₃ , KzCOa, alone or as a mixture, which form soluble salts with acids.