NL2021457B1 - Method and device for biological drying - Google Patents

Abstract

In a method and apparatus for the biological drying of an organic residual material, the residual material is fed into a reactor space (100) and subjected to a microbial degradation process. The residual material is passed through the reactor space in a first direction while at the same time a forced air flow is passed through the reactor space in a second direction opposite to the first direction. The forced air flow is thereby partly, in particular largely, captured between an air inlet (20) of the reactor space and a product inlet (105) of the reactor space and discharged from the reactor space via a vapor outlet (22). As a result, moisture is extracted from the residual material and the residual material can be removed in an at least partially dried form from a product outlet (110) of the reactor space.

Description

The present invention relates to a method for the biological drying of an organic residual material, wherein: the residual material is fed into a reactor space; the residual is subjected to a microbial degradation process; water is extracted from the residual material; and the residual material is removed from the reactor space in an at least partially dried form at a product outlet.

The invention also relates to a device for the biological drying of an organic starting mass comprising a process reactor with a reactor space and with a product inlet for receiving the starting material at or near a top of the reactor space, which reactor space at a bottom side remote from the product inlet. opens into a product outlet where at least partially dried organic mass is removable.

As regards the starting material used, this is a biodegradable organic mass, which remains as a residual from a waste stream from an industrial or agricultural production process. The substances will often be waste or animal fertilizers, but need not necessarily be of biological origin. These substances have a high moisture content, which means that the substances are usually also biologically unstable and infectious (rot, germs). In such a case, an important mass reduction of the residual substance and a biological stabilization can be achieved by (biological) drying.

The present invention particularly relates to a method and device for biological drying of starting material, hereinafter also referred to briefly as biodrying. Specifically, this may in particular concern the processing of:

Dehydrated pig manure (raw or fermented)

Dewatered sewage sludge, industrial or communal (raw or fermented)

Dehydrated digestate from other (liquid) fermentation

Biodegradable organic waste from the chemical industry Slaughter by-products and waste

In addition, liquid biological waste can be dried as an additive in combination with other material.

-2 Traditionally, industrial biodrying takes place in the form of composting in large centralized installations (installations). Small plants for industry have not been developed. The development of decentralized plants for biological drying has hitherto been limited to agricultural applications in intensive livestock farming. This mainly concerns the composting of animal manure in a rotating drum. The drum is used for aeration, homogenization and internal transport of the material to be processed. The water vapor released during the process is discharged by blowing with a lot of air. However, these systems require porosity (structure) in the starting material for adequate oxygenation. This system can therefore only be used for certain types of manure, such as poultry manure and cow manure.

The object of the present invention is inter alia to provide a method and device for biological drying which are more widely applicable, are energy-efficient and, in addition to being suitable for a centralized large-scale application, are also particularly suitable for relatively small-scale decentralized applications.

In order to achieve the intended object, a method of the type described in the opening paragraph according to the invention has the feature that during the process the residual material is displaced in a first direction through the reactor space, which simultaneously forces a forced air flow in a second direction opposite to the first direction. direction through the reactor space, and that the air flow between an air inlet and a product inlet is partially exhausted from the reactor space. According to the invention, a device of the type described above has the feature that the reactor space on the bottom side comprises an air inlet, that the reactor space is provided with fan means for maintaining and directing a forced air flow to the air inlet and that the reactor space between the air inlet and the product inlet includes evacuation means for capturing and evacuating a portion of the air stream through a vapor outlet.

The invention concerns a microbial conversion process under the influence of micro-organisms. These microorganisms can only absorb dissolved substrate (monomers) through their cell wall. To this end, solid (polymerized) substrate must first be hydrolysed, i.e. it is broken down under the influence of water. The hydrolysis takes place enzymatically and / or thermally. If oxygen is sufficiently present,

-3the dissolved substrate used by the biomass for growth and metabolism. These two processes, ie growth and metabolism, go hand in hand. The amount of biomass increases due to growth with simultaneous and proportional production of heat. Eventually, part of the organic starting material is biologically converted (burned) into carbon dioxide and water.

In a conventional composting process, the initial amount of dissolved substrate is consumed after a few days and the process enters an equilibrium phase. From that moment on, hydrolysis is the rate determining factor of conversion and heat production; what is hydrolysed is immediately consumed. The temperature is an important factor in the hydrolysis rate and thus in the conversion rate of the biomass.

The present invention is based on a counterflow of air through a moving biomass. As a result, different zones develop in the biomass, whereby at an output mainly a conversion of organic matter into carbon dioxide and water takes place, producing heat, and at an input of the reactor a zone in the biomass mainly through hydrolysis of larger organic molecules (polymers). is characterized as a preliminary phase for the later conversion.

By forcing the airflow through the mass in the opposite direction, the generated heat is dissipated and directed upstream into the biomass where the hydrolysis takes place. This leads to a significant increase in temperature of this process and thus to a significant increase in the rate of hydrolysis. A second aspect of hydrolysis at a higher temperature is that more difficult degradable substrates will also be hydrolysed. In addition to an increase in the hydrolysis rate, more energy will thus also become available in the later conversion phase. All in all, a particularly rapid and efficient hydrolysis can thus be achieved without the need for an external heat source. A balance between heat production (conversion) and heat dissipation (amount of air blown) determines the temperature.

At the same time, this warm airflow will be at least substantially saturated with water vapor produced in the conversion zone and will be extracted from the biomass. Between the air inlet and the product inlet, this warm air flow (sideways) is partly, in the

-4 in particular largely, exhausted via a vapor outlet provided for this purpose, and thereby separated from the biomass. This extraction of moisture leads to the intended drying of the starting material and thus to an important mass reduction thereof. A remaining part of the supplied air flows through the hydrolysis zone and there ensures adequate aeration of the biomass. The material fed in the front of the reactor will heat up quickly by condensation of this hot saturated air and then heat up further by biological activation with limited air cooling.

Translated to conventional composting, the present invention provides thermally enhanced hydrolysis as a pre-treatment with a higher energy yield as a result, with equal reactor volume and equal reaction time, and thus higher capacity per cubic meter of reactor volume. Due to the vertical arrangement of the conversion reactor, the device according to the invention also requires a relatively small surface area in terms of space and smart use is made of the sagging of the biomass under the influence of gravity. The steady flow of product through the reactor space therefore requires only an inlet and an outlet. It is preferably performed step by step.

The hot air, saturated with water vapor, which is let out laterally, ensures the actual dewatering and thus drying of the reactor mass. Outside the reactor space, the air can be dried relatively simply by condensing the water vapor. The heat released during this process can be used for preheating the air that is fed into the reactor. It has been found in practice that already a small part of the total air flow is sufficient to supply the hydrolysis zone with sufficient oxygen and to establish the intended ambient temperature therein. A special embodiment of the method according to the invention therefore has the feature that the air flow between the air inlet and the product inlet is for the most part, namely about 70% -90%, in particular around 80%. Like the branch airflow, the continuous airflow is warm and saturated with water vapor, which was taken up from the conversion zone. Condensation will therefore take place in the cooler hydrolysis zone and the heat of condensation released thereby will make an additional contribution to the intended relatively high ambient temperature in the hydrolysis zone.

-5 The optimal position of this branch depends somewhat on the starting material, but in most cases it is approximately halfway. A special embodiment of the device according to the invention is therefore characterized in that the evacuation means are provided approximately halfway between the reactor space between the air inlet and the product inlet. The branch of the air flow realized therewith creates a separation between the conversion zone, which is cooled by a still complete air flow, on the one hand, and the hydrolysis zone, which is at a considerably higher temperature due to a considerably reduced air flow, on the other hand. A special embodiment of the device according to the invention is therefore characterized in that the reactor space comprises a hydrolysis zone, in which hydrolysis of the starting mass takes place at a relatively high temperature during operation, as well as a conversion zone, in which organic matter becomes microbial molecular at a lower temperature during operation. demolished, whereby the evacuation means are provided between the hydrolysis zone and the conversion zone.

With a view to adequate aeration of the reactor space, a further special embodiment of the device according to the invention has the feature that, downstream of the air inlet, a lamellar system is provided which is capable and arranged from an air chamber of the air flow at the bottom of the reactor space over the reactor space. spreading. Air holes can be provided under the slats to ensure the air supply. The material, on the other hand, slides over the slats, while the air is introduced into the material via an initial downward trajectory. In this way it is prevented that material can enter the air chamber, while nevertheless the air flow can enter the reactor space, with the material therein.

In view of a minimal ecological footprint, it is preferable that the process absorbs as little fresh air as possible, while also an amount of exhausted air is preferably low. In view of this, a preferred embodiment of the method according to the invention is characterized in that the air flow, after having left the reactor space, is returned to the reactor space in an at least substantially closed system, at least for the most part. To this end, a special embodiment of the device according to the invention has the feature that the vapor outlet is coupled in an at least substantially closed circuit to an inlet of the fan means. In a further embodiment, the device according to the invention is characterized in that near the top of the reactor space

-A defined air outlet is provided to which a residual of the air flow is at least largely received and that the air outlet is coupled in an at least substantially closed circuit to an inlet of the fan means.

Both partial air flows through the system can thus be captured. In that case, a net air consumption of the system mainly comprises an amount of oxygen consumed by the aerobic degradation processes within the reactor. This relatively low oxygen requirement can easily be supplemented by outside air or, if desired, otherwise from the outside. This also means that the waste gas flow from the system to the environment is minimal and any waste gas flow can be easily controlled and, if necessary, cleaned by means of a small-scale installation.

The air from the reactor will usually contain a high concentration of ammonia, which can be up to several thousand ppm from proteins involved in the degradation process and other nitrogenous compounds. In order not to allow this ammonia to dissolve in condensate, which could otherwise cause a discharge or discharge problem, a further embodiment of the method according to the invention is characterized in that the air flow, after leaving the reactor space, is cleaned, in particular the ammonia is removed before passing it over a condenser. To this end, a special embodiment of the device according to the invention has the feature that the vapor outlet is coupled via an ammonia scrubber to a condensation device which is capable and adapted to extract moisture from an air stream. In a further embodiment, the device according to the invention is characterized in that the air outlet is also coupled via an ammonium scrubber to a condensation device, whether or not shared with the vapor outlet, which is capable and adapted to extract moisture from an air stream.

For optimal processing it is important that the material that is left in the reactor has sufficient structure and is well aerated to allow oxygen to flow through the forced air flow and to remove water vapor. Particularly for those cases where the starting material does not naturally have this, a further special embodiment of the process according to the invention is characterized in that the dry, at least dried, substance is mixed with fresh residual material before the residual material is fed to the reactor space. Has a special embodiment of the device according to the invention

This is characterized in that feed means are coupled to an outlet of a mixing device, which mixing device comprises a first inlet for the starting mass and a second inlet for dry, at least partially dried mass.

Thus, by intensively mixing the fresh material with dried material, a homogeneous and free-flowing mass can be obtained with an adequate dry matter content, which after mixing can typically be of the order of about 40-50%. This mixing step leads to a solids circulation flow over the reactor and has several beneficial effects.

Grains are broken and are therefore well mineralized into optimal starting material for the microbial degradation process and any inhomogeneities in the flow of air and / or solid matter through the reactor are therefore temporary and / or varying in location. This ensures a constant quality of the product flow.

In a preferred embodiment, the method according to the invention is characterized in that dried residual material is removed from the product outlet for this purpose and is mixed as fresh material with fresh residual material before the residual material is fed to the reactor space. To this end, a preferred embodiment of the device according to the invention is characterized in that the second inlet of the mixing device is coupled to the product outlet of the reactor. Thus, part of the dried product is used as an additive to the processing mass to give it optimum composition and consistency.

In addition to the above-described advantages, this back-mixing (back-mixing) of the reactor product also has the advantage that it is inoculated with microbial biomass. This vaccination ensures rapid biological activation. Moreover, the microbial housekeeping in the reactor can thereby specialize and in particular attune to higher reaction temperatures, especially where the hydrolysis step is concerned. A further particular embodiment of the method according to the invention is therefore characterized in that the process is carried out at a temperature approaching an upper limit of the microbial degradation process. The microbial household then develops into a hyper-thermophilic. In practice, the efficiency gain that is achievable thereby appears to more than outweigh the amount of dry or dried product that may be required for the desired back-mixing. A particularly favorable embodiment of the method according to the

In this connection, the invention is characterized in that dry, at least dried, material is mixed with fresh residual material in a ratio of about 1: 2 to 1: 4.

The input material should preferably be free of coarser solids because they can cause blockages in further processing and internal transport and, by the way, are less susceptible to microbial degradation. In order to avoid this, a further special embodiment of the process according to the invention therefore has the feature that the residual material is ground before feeding it to the reactor space. To this end, a special embodiment of the device according to the invention has the feature that a grinding device is provided, an outlet of which is coupled to the product inlet of the reactor and with an inlet that receives output mass from a buffer storage. The buffer storage serves to ensure that the feed to the reactor runs smoothly and to make it less or not dependent on variations in an external supply.

An input of too cold air into the conversion zone can lead to a stagnation of the conversion process and should therefore preferably be avoided. It is therefore preferable to impose a defined air temperature on the airflow before the air is introduced into the reactor. The heat produced during the conversion can advantageously be used for this. To this end, a special embodiment of the method according to the invention is characterized in that the air flow is preheated with heat that was extracted from the residual material before the air flow is led into the reactor space. Not only does this provide more complete control of the entire process, it also leads to a faster and more efficient system start-up.

The invention will be explained in more detail below with reference to an exemplary embodiment and an accompanying drawing. In the drawing shows:

Figure 1 shows a schematic representation of a solid handling in an exemplary embodiment of a method and device according to the invention;

Figure 2 shows a schematic representation of an air treatment in the exemplary embodiment of figure 1;

Figure 3 shows a schematic representation of a microbial cycle in the process and the device according to the invention;

Figure 4 shows a schematic zone distribution in a reactor space in the process and the device according to the invention;

Figure 5 in perspective, an exemplary embodiment of a device according to the invention, applied in the exemplary embodiment of Figures 1 and 2;

Figure 6 shows a first cross section of the device of figure 5;

Figure 6B is an enlargement of a circle area B in Figure 5;

Figure 7 is a second cross section, transverse to the section of Figure 6, of the device of Figure 5; and

Figure 7B is an enlargement of a circle area B in Figure 7.

Incidentally, it should be noted that the figures are purely schematic and not always drawn on (the same) scale. In particular, some dimensions may be exaggerated to a greater or lesser extent for the sake of clarity. Corresponding parts are designated with the same reference numerals in the figures.

An exemplary embodiment of a system in which an embodiment device according to the invention has been applied is schematically shown in Figures 1 and 2. The device according to the invention here comprises a conversion reactor 100 with a solid-state system coupled thereto, which is shown in Figure 1 to the left of the reactor. 10 is shown schematically, as well as an air treatment system, which is schematically shown in figure 2 on the right side of the reactor 10. These systems will be described in more detail below.

To illustrate the biological activity of the reactor 100, the aerobic biological conversion process induced in the reactor 100 is shown schematically in Figures 3 and 4. In the process diagram of Figure 3, the rectangles represent quantities, the circles process and the arrows represent material flows. Wet substrate material 50 is fed into the reactor. This mainly concerns organically polymerized substrate. Microorganisms can only absorb released substrate (monomer) through the cell wall. To this end, solid polymerized substrate must first be hydrolysed, i.e. broken down under the influence of water. This hydrolysis takes place enzymatically and / or thermally in a first part 52 of the reactor. If sufficient oxygen is present, the dissolved substrate is used by the biomass for growth and metabolism 54. The amount of biomass increases by growth while simultaneously producing proportional heat. The organic

-10 fraction is (biologically) burned to carbon dioxide and water. The organic nitrogen becomes ammonia.

From the moment the initial amount of substrate dissolved via hydrolysis is consumed, the process enters an equilibrium phase: what is hydrolysed is immediately consumed. Hydrolysis is now the rate determining factor of conversion and heat production. Temperature is an important factor in the rate of hydrolysis and thus in the rate of conversion of the decaying mass. The balance of heat production (conversion) and heat dissipation (amount of air blown) determines the temperature. This is influenced midway through the reactor by here discharging part of the blown-in airflow between a conversion zone and the hydrolysis zone 52. As a result, the hydrolysis zone 52 experiences less cooling and the (hydrolysis) temperature can be raised to a maximum acceptable for the micro-organisms. Here, a hyper-thermophilic micro-culture can thus develop / specialize. With the released air, moisture is also removed from the reactor and drying of the material 56 is thereby effected.

Due to the counterflow principle, different temperature zones are created in the reactor, which are shown schematically in Figure 4. Two specific temperature zones are defined by the air separation approximately halfway down the reactor: a hydrolysis zone 52 and a conversion zone 54. A number of other zones that can be distinguished as such are also indicated in the diagram. In practice, all zones are not sharply delineated, but gradually merge. The following is a brief description of each of the successive zones in the reactor.

HEATING ZONE 50

The material fed into the top of the reactor will heat up quickly due to condensation of the hot saturated air. This creates a heating zone 50 at the top of the reactor.

HYDROLYSIS ZONE 52

In the hydrolysis zone 52, a high temperature prevails for a high hydrolysis rate. This high temperature is achieved because the air from the (next underlying) conversion zone 54 is already at a high temperature and due to a limited, relatively small air flow (20%) through the hydrolysis zone. The latter does provide sufficient

-11 oxygen but offers only a low cooling capacity. As a result of condensation, additional (condensation) heat can even develop in the hydrolysis zone 52. The target temperature is the maximum achievable for the microbial conversion, which is of the order of about 80-82 ° C. This is controlled by the control valve 26, which determines the pressure drop and thus the air flow over this zone 52.

The hydrolysis zone 52 requires an additional volume where the conversion is limited (about 20% of the conversion zone). However, the hydrolysis rate is exponential with temperature, so that the condition for more than proportionally accelerated conversion (in the conversion zone) is realized here. On balance, the effect is clearly positive. In addition, with the same bed height and capacity, this solution costs little electrical energy, because the airflow here is only about one fifth of the total and the required pressure drop is correspondingly lower. Because the oxygen content after the hydrolysis zone 52 will be very low (expected to be well below 10%), it is possible to preferentially blow this air and keep the total air consumption extremely low.

CONVERSION ZONE 54

The material enters the conversion zone 54 with a high concentration of dissolved substrate. Here the aeration is high so that heat is dissipated, causing the temperature to drop. This forms an ideal climate for an (explosive) growth and activity of biomass that is accompanied by a corresponding heat development.

BALANCING ZONE 56

As the fuel for conversion runs out, the system becomes in a condition where the hydrolysis and conversion are in equilibrium. This equilibrium zone 56 is kept small by size of the reactor because it is less efficient.

COOLING ZONE 58

In a cooling zone 58 at a product outlet of the reactor, the material is cooled by the supply of colder air and by swelling.

An input buffer 10 is provided to ensure that a wet / moist product feed to the reactor proceeds smoothly and continuously and does not depend on variations in

-12 a local or external supply, for example from dewatering presses. The input material for the reactor 100 must be free of coarser solids, as they may otherwise cause blockages in the reactor lockout and in transport systems. In view of this, a pretreatment 12 is provided. If there is a risk of coarse parts, larger than typically of the order of three centimeters, the entire material flow can be reduced by a grinder provided therein that reduces larger parts to below this size. It can also screen for coarse, non-processable materials, such as stoneware and metals.

If the input material has little or no structure, the aeration may therefore be too low for biological activation and / or removal of water vapor. This is remedied with a blender 14 capable of mixing the fresh material with dry or dried material. By carrying out this mixing intensively, a homogeneous and free-flowing mass can be obtained. The required dry matter, after mixing, will be about 40-50%. In this case, a so-called back-mixing (back-mixing) is used in this connection by taking a part, for example of the order of 15%, of the dried material from the outlet 110 of the reactor 100 and transfer it to the mixer 14. feed. The mixer 14 is an important component of the entire system. This serves to make the feed for the reactor 100 homogeneous and aerable. A reliable method of mixing has been found to be batch mixing, the two streams to be mixed being loaded by weight. This mixing (backmixing) makes the structured material aeration and introduces active biomass into the material (grafting). Thus, there is a solid recirculation flow over the reactor. This has positive effects:

Grains are broken and are therefore well mineralized (comparable to conversion to composting)

Inhomogeneities in the flow (air and / or solid matter) in the reactor are therefore temporary and / or change of place. This ensures a constant quality of the product.

The input stream is inoculated with product which allows the biomass in the reactor to specialize (matching to the high temperature)

The inoculation ensures rapid biological activation; and

There is a specialization of the types of micro-organisms (hyper-thermophilia).

-13 Depending on the dry matter of the input stream, the backmix flow is approximately double the feed flow in kilograms. After an (average) residence time, the material has thus typically been round five times.

In the exemplary embodiment of Fig. 5-7, the reactor feed 105 is at a height of approximately six to seven meters. The mixed material is brought up by a conveyor system (not shown in more detail) that does not affect the structure. The biomass to be dried, mixed with a proportion of dried end product, is fed into the top of the reactor 100 and finished flat by a rotating rake so that the air flow is homogeneous.

At the bottom and in front of an outlet 110 of the reactor 100 there is a discharge system which ensures an even subsidence of the reactor contents. The dried material is discharged from the reactor by a number of parallel metering sluices 111..113, see also figure 7. This allows the transmission of solid matter to the conveyor screws 114 to be controlled. Locks 111..113 cover the full width of the reactor. In the reactor shown, with a diameter of approximately three by three meters, three frequency-controlled rotary valves 111..113 are thus provided. The material runs through a steep funnel shape to the relevant lock. The rotary valves 111..113 periodically change direction of rotation so that preferred flow along the hopper sides is canceled. By means of an inspection provided for this! uiken 115, this process can be controlled and any obstacles in the discharge of material can be remedied.

Beneath each rotary valve 111..113 is coaxially a conveyor screw 114 which brings the discharged material to one side of the reactor 100. There is a transverse screw 116 which collects the material from three locks 111..113 and brings it to a product outlet 110 outside the reactor. The dosing valves 111..113 are controlled on throughput. Under these locks, the material is conveyed with the conveyor screws 114 and cross screw 116 through the product outlet 110 to the mixer 14 and a product buffer 16. Since there is reasonable air pressure at the bottom of the reactor, an airtight seal is preferably present, or the pressure is temporarily removed during shutdown. The feeding and exclusion take place periodically, for example every hour for five minutes. The entire solid system is thus run periodically, typically five minutes per hour. The board of the

Reactor 100 and of the input buffer 10 are used as control parameters in an automation not shown in more detail.

The space under the hoppers forms an air chamber 125 to which a blower is connected via an air inlet. The blower provides a continuous forced air flow through the reactor, against the material flow, for the drying process. Slats 120 are arranged in the hopper walls. The fins 120 run the full width of the hoppers and are designed in number and discharge height such that the air velocity at the entry of the material is limited to approximately five times the average vertical air velocity in the reactor. The air will push the material slightly behind the slats and keep it moving so that bridging or blockage is prevented. Hidden beneath the fins are slots that open towards the reactor space for a free air supply to the reactor space. The material slides over the slats 120 but the air flows into the material through an initial downward trajectory. This prevents material from penetrating to the air chamber 125. The air is thus blown into the material stream at the bottom of the reactor 100 with only a slight pressure drop over the lamellae system.

The blown air is withdrawn from the reactor at two heights. About halfway up, about 80% of the air is captured via evacuation means 130 provided for that purpose and exhausted via a vapor outlet 22 with a control valve 26. The height of this air branch 22 depends on the input material to be processed.

The evacuation means comprise a system of elongated troughs 130 arranged transversely of a flow direction of the air flow over at least a full width in the reactor space. The troughs 130 are opposed to the air flow to trap air therein and to pass them via pipelines 135 to the vapor outlet 22. The troughs 130 in this example comprise a number of parallel wedged plates arranged across the width of the reactor. The tip of the wedge points to the top of the reactor. The material sinks around the wedge. Under the wedge there is an air space which contacts a pipe 135 connected through the reactor wall. The pipes 135, which can sit on either side of the wedges, pass into a collection channel 22 that runs to the control valve 26. The number of wedges, the angle and the open width of the wedge shape have been adjusted for the best compromise between air resistance and good flow of the sagging material.

-15 The remaining approximately 20% of the air flows further upwards to the top of the reactor under a very low pressure drop. This air is also captured via an air outlet 24 provided there. The percentages of the air quantity mentioned are based on dry air. Solid and air thus pass through the reactor 100 in counter-current.

The biological process in the reactor requires aeration for the supply of sufficient oxygen and for the removal of water vapor. This is provided by the air system schematically shown in Figure 2. This ensures that the incoming and outgoing air conditions (temperature, relative humidity, oxygen content) and the air flow rate for the process are optimal and that as little fresh air as possible is consumed. As a result, the waste gas flow is also kept small and waste gas cleaning can be kept small and well manageable in order to meet environmental requirements for the emission of ammonia and odor.

Normally, the oxygen supply necessary to keep the microbial processes in the reactor going is not an issue. The amount of air required for the effective removal of water vapor is of the order of ten times higher than the amount of air required for the supply of oxygen for the biomass. The air requirements for oxygen and water discharge are therefore decoupled from each other, so that fresh air consumption and exhaust gas emissions can be minimized. This decoupling is made possible by cooling the air back from the reactor 100 by means of a primary condenser 31. This allows the cooled and dried air to be returned to the reactor 100 and to take up water vapor again as the temperature rises. The moisture extracted from the air (condensate), indicated in the figure as H ₂ 0, can be discharged or used as process water.

The air from the reactor can have a high concentration of ammonia, up to several thousand ppm's. In order not to dissolve this ammonia in the condensate H ₂ O and to avoid a discharge or discharge problem, the ammonia (and also amines) is removed from the air with an acid washer 32 with a very high efficiency before the primary condenser 31. The acid washer 32 produces a nearly saturated solution of ammonium sulfate, which is recoverable from the process as a recognized fertilizer. The condensate H ₂ 0 may still contain volatile organic components (VOCs), but these are otherwise harmless in the discharge.

-16 From air outlet 24 at the top of the reactor 100, the remainder of the airflow comes at a higher temperature and a substantially lower oxygen content than the air from the branch 22. This flow is most favorable to pass out of the system as displacement air from the necessary fresh air. For this purpose, a separate acid wash 33 and a secondary condenser 34 are provided. This acid washer 33 can be fully integrated with the primary acid washer 31 without additional pumps or measuring and control components. The airflow passing through the branch takes care of most of the drying capacity. The primary condenser 31 should therefore have a higher capacity than secondary condenser 34. The same applies to the acid scrubbers 31,33.

The air that is ultimately emitted is deodorized to at least below a local license value. For this purpose, an air filter 38 is provided that blows off the air from any harmful components, for example on the basis of oxidative washing or biofiltration. Fresh air can simply be outside air, but it is advantageous to draw in an odor-containing air for this purpose, for instance from the storage buffer 10 of input material and / or from the product buffer 16, in order to keep the air flow to a provided odor treatment small. It is also possible to bring oxygen enriched air into the system. At 40% oxygen, the air flow to be treated in the odor removal can be more than halved. The fresh air can be introduced via a control valve 30 and mixed with the recirculating air flow. Optionally, the air can be preheated with the heat from secondary condenser 33 via a heat exchanger 36 provided for this purpose before leaving the air in the reactor. This achieves a part of thermal drying, which improves the final dry matter.

The method and device described here lend themselves, in addition to other organic residual material flows, in particular also for the processing of animal manure. The ratio [organic matter content / water content] and the absolute water content of the starting material largely determine the final dry matter to be achieved. In general, the following limits can be observed:

Input material composition manure wet manure dry Dry matter [%] 20 35 Organic matter [% of dry matter) > 70 > 35 Final dry matter to be achieved [%] 55 70 Mass reduction [kg wet in / kg dry out] ca 5 2.5

-17 Implementation example:

Assuming a throughput of the order of one ton per hour of an organic matter with 25% dry matter (with 70% organic matter, 50 g organic nitrogen / kg dry matter) and a final dry matter of 60%, a practical exemplary embodiment is feasible on the basis of, for example, a parallel arrangement of a number of the reactors shown, with typically a jointly occupied ground area of the order of 10 square meters at a height of the order of meters. This gives the following key figures for the total installation:

- End product 240 kg / h Organic matter conversion 110 kg / h Mass reduction (mass wet in / mass dried out) 4.2 - Calorific value of input material a product 1.4 a 4.3 MJ / kg Backmixing 1900 kg / h Average residence time in reactor 14 day Air flow blower 2100 m3 / h Electricity consumption blower 10 kWe Other electricity consumption approx. 10 kWe Fresh air supply 650 m3 / h Fumigation 780 m3 / h Condensate 670 kg / h Cooling capacity (can be reused at approx. 65 ° C) 520 kW Sulfuric acid (96%) consumption 15 (8) kg / h (liter / h) Ammonium sulfate production (40%) 50 (40) kg / h (liter / h)

All in all, the invention thus offers a particularly efficient biological drying of residual material of various nature, which can be used as starting material. The integrated hydrolysis offers an unparalleled conversion rate and degradation potential of organic matter, which allows the biological drying of more substances, usually experienced as troublesome, for example material with a low dry matter content and / or material that has been fermented and has little structure. .

The air exiting the hydrolysis zone contains very little oxygen. This allows the process to function with an extremely low consumption of fresh air and the waste gas flow is correspondingly small. Furthermore, the system is suitable for continuous operation, in countercurrent, and the process is completely closed. This also makes it easy to control and automate the process. As a result, the layout can be implemented centrally, but also locally, with a minimum of personnel. The biological drying is preferably controlled in such a way that the temperature is close to the upper limit that the micro-organisms can generate. Hereby

-18 there is relatively little air purging and the energy consumption to keep the airflow going will be correspondingly low. Heat becomes attractive and easy to recover, in addition to the potential extraction of other valuable raw materials. Due to a vertical arrangement and the compact bed in the reactor, the required floor space is small compared to belt dryers and sun drying. The reactor is also suitable for outdoor installation. To this end, all structural parts of the reactor are preferably manufactured as much as possible from stainless steel or preserved steel.

Although the invention has been further elucidated above on the basis of only a single exemplary embodiment, it will be clear that the invention is by no means limited thereto. On the contrary, many variations and manifestations are still possible for an average skilled person within the scope of the invention.

Claims (24)

Conclusions: A method for the biological drying of an organic residual substance, wherein the residual substance is fed into a reactor space; the residual is subjected to a microbial degradation process; water is extracted from the residual material; and the residual material is withdrawn in an at least partially dried form from a product outlet of the reactor space, characterized in that the residual material is displaced in a first direction through the reactor space during the process, which simultaneously forces a flow of air in an opposite direction to the first direction is passed through the reactor space in the second direction, and that the forced air flow between an air inlet of the reactor space and a product inlet of the reactor space is partly, in particular largely, exhausted from the reactor space. Method according to claim 1, characterized in that the air flow between the air inlet and the product inlet is about 70% -90%, in particular about 80%, exhausted. Method according to one or more of the preceding claims, characterized in that the air flow, after having left the reactor space, is returned to the reactor space in an at least substantially closed system. Method according to one or more of the preceding claims, characterized in that the air flow, after leaving the reactor space, is cleaned, in particular it is stripped of ammonia before it is passed over a condenser. Process according to one or more of the preceding claims, characterized in that dry, at least dried, material is mixed with fresh residual material before feeding the residual material to the reactor space. Process according to claim 5, characterized in that dried residual material is removed at the product outlet and is mixed as fresh material with fresh residual material before feeding the residual material to the reactor space. Method according to claim 5 or 6, characterized in that the dry, at least dried, substance is mixed with fresh residual material to form a homogeneous free-flowing mass containing 40-50% solids. Method according to claim 5, 6 or 7, characterized in that dry, at least dried, substance is mixed in a ratio of approximately 1: 2 to 1: 4 with fresh residual material. Process according to one or more of the preceding claims, characterized in that the residual material is ground before feeding it to the reactor space. Process according to one or more of the preceding claims, characterized in that the residual material is moved stepwise through the reactor space. Process according to one or more of the preceding claims, characterized in that the air flow is preheated with heat extracted from the residual material before the air flow is led into the reactor space. Method according to one or more of the preceding claims, characterized in that the drying is carried out at a temperature approaching an upper limit of the microbial degradation process. 13. Apparatus for biological drying of an organic starting mass comprising a process reactor with a reactor space and with a product inlet for receiving the starting material at or near a top of the reactor space, which reactor space at a bottom side remote from the product inlet opens into a product outlet where at least partially dried organic mass is removable, characterized in that the reactor space at the bottom side comprises an air inlet, that the reactor space is provided with fan means for maintaining and directing a forced air flow to the air inlet and that the reactor space between the air inlet and the product inlet evacuation means for capturing and evacuating a portion of the air stream through a vapor outlet. 14. Device as claimed in claim 13, characterized in that, downstream of the air inlet, a lamella system is provided which is capable and arranged to distribute the air flow from the bottom of the reactor space over the reactor space from an air chamber. Device according to claim 13 or 14, characterized in that the reactor space comprises a hydrolysis zone, in which hydrolysis of the starting mass takes place at a relatively high temperature during operation, and a conversion zone, in which the starting mass is microbially degraded at a lower temperature during operation, and that the evacuation means are provided between the hydrolysis zone and the conversion zone. 16. Device according to claim 13, 14 or 15, characterized in that the evacuation means are provided approximately halfway between the reactor space between the air inlet and the product inlet. Device according to one or more of claims 13 to 16, characterized in that the evacuation means comprise a system of elongated troughs arranged transversely of a flow direction of the air flow over at least a full width in the reactor space, which are arranged against the open the air stream and lead it to the vapor outlet. Device according to one or more of claims 13 to 17, characterized in that the vapor outlet is coupled via an ammonia scrubber to a condensing device capable of extracting moisture from an air stream. Device according to one or more of claims 13 to 18, characterized in that the vapor outlet is coupled in an at least substantially closed circuit to an inlet of the fan means. Device according to one or more of Claims 13 to 19, characterized in that a defined air outlet is provided near the top of the reactor space, to which a remnant of the air flow is at least largely received and in that the air outlet is at least substantially closed circuit is coupled to an inlet of the fan means. 21. Device as claimed in claim 20, characterized in that air outlet is coupled via an ammonium scrubber to a condensing device which is capable and adapted to extract moisture from an air stream. 5 Device according to one or more of claims 13 to 21, characterized in that feed means are coupled to an outlet of a mixing device, which mixing device comprises a first inlet for the starting mass and a second inlet for dry, at least partially dried mass . 10 An apparatus according to claim 22, characterized in that the second inlet of the mixing device is coupled to the product outlet of the reactor. 24. Device as claimed in one or more of the claims 13 to 23, characterized in that a grinding device is provided, of which a blow-out is coupled to the product inlet of the 15 reactor and with an inlet that receives output mass from a buffer storage.