DE102014212827A1 - Method and device for mechanical ammonia stripping in a biogas plant - "Mechanical stripping" - Google Patents

Abstract

The invention relates to a method for expelling (stripping) ammonia and carbon dioxide from a mashed solids-containing fermentation substrate (GS) and / or a solid-containing digestate (GR) having a predeterminable dry matter content (ΔTS), characterized by mechanical forced-milling of the milled solid-containing fermentation substrate (US Pat. GS) and / or the solids-containing digestate (GR) within a Strippbehälters (100) for compulsory mechanical disruption of the solids of the mashed solids-containing fermentation substrate (GS) and / or bemaischten solids-containing digestate (GR), wherein in addition to the actively outgassing ammonia and carbon dioxide bound Inactive ammonia and carbon dioxide are activated and expelled by mechanical forced grinding.

Description

The invention relates to a method and a device for expelling (stripping) ammonia and carbon dioxide from a mashed solids-containing fermentation substrate (GS) and / or a solids-containing digestate (GR) within a fermentation zone.

Biogas or digester gas is a gas mixture of mainly methane (about 50-70%) and carbon dioxide (about 30-50%) with small amounts of hydrogen sulfide, nitrogen, hydrogen, ammonia and carbon monoxide. It is produced during biodegradation processes. As a high-quality and CO2-neutral energy source, it is used as an ecologically and economically sensible source of energy.

It is known to use fermenters as the central component of a fermentation section as reactors. In this biomass is continuously introduced as a fermentation substrate, which was previously stored and pretreated.

Under exclusion of oxygen, the fermentation substrate is converted into biogas and residues using a variety of bacterial strains in a multi-stage anaerobic digestion process.

The biogas is discharged, purified and e.g. converted into energy in an internal combustion engine. The residues, usually referred to as fermentation residue, must be discharged from the fermenter and serve as a fertilizer due to their high-quality inorganics for agriculture.

The composition of the biomass substrates used (fermentation substrates) varies depending on availability, price and must also meet certain legal requirements.

Under these conditions, the use of biomass as a fermentation substrate, which has already been digested by an animal, i. the use of animal excrement, possible.

However, such substances contain a high proportion of nitrogen, which is present as ammonia, in bound form. Bound ammonia is present in the fermentation process as the salt of the carboxylic acid in dissolved form. This salt of the carboxylic acid decomposes from a temperature greater than 54 ° C depending on the pH and depending on the pressure in its gaseous components ammonia and carbon dioxide.

For the transition from the aqueous solution into the gas phase, moreover, the size of the interface between the liquid phase and the gaseous phase of the fermentation substrate and / or digestate is decisive. As the interface increases, the rate of transition from the aqueous solution to the gas phase increases.

The processes available on the market for stripping the gases ammonia and carbon dioxide are based on physical processes such as heating, raising the pH, lowering the pressure and increasing the interface by injecting an additional gas into aqueous solutions. The latter also increases the interface.

For the pH increase, for example, lye should be added, which would have a negative impact on the fermentation process.

The blowing in of an additional gas for stripping adversely contaminates the gas mixture of ammonia and carbon dioxide to be stripped.

A method for stripping an organic waste product in the liquid phase is known. By way of example, the publication DE 103 54 063 A1 called, which describes a method which causes using the organic waste product in the liquid phase, for example liquid manure with heating of the liquid and by lowering the atmospheric pressure surrounding the liquid, an escape (stripping) of ammonia and carbon dioxide.

A well-known and widespread biogas process is the wet fermentation in a fermenter. A process fluid is metered into a biomass starting substrate with a mostly high dry matter content, whereby a fermentation substrate is obtained which releases biogas in a fermenter.

As a fermentation substrate, the starting product is referred to, which is used in the production of biogas in fermentation lines mostly for the fermenter located in the fermentation.

Within the process of wet fermentation of biomass in a fermenter, the biomass after dosing of the process liquid at the beginning of the fermentation section is thus present as a bemaischtes with a process liquid solids-containing fermentation substrate, which is fermented in the fermenter by enzymatic conversion of organic substances. This biomass is referred to below as bemaischtes solids-containing fermentation substrate.

At the end of the process, a so-called fermentation residue is produced which represents largely outgassed biomass. This digestate is the outgassed solids-containing fermentation substrate and is therefore referred to as digestate, since it is the remainder at the end of the fermentation section accrues. The fermentation residue is thus the residue (the end product), which remains after fermentation of biomass in a fermentation section. Because of its high content of nutrients, it is used as agricultural fertilizer, the existing disadvantages are known.

There are various methods that also allow use of the digestate, for example, in the document DE 10 2009 024 536 A1 respectively DE 10 2010 033 A1 are described.

The fermentation substrate within the fermentation process is comparatively no liquid but also no solid. The dry matter content is 5% to 15%.

Ammonia-containing fermentation substrate causes the following problems in the biogas fermentation process in the fermenter (s) and in the subsequent use of the digestate and the biogas released during wet fermentation.

There is a chemical equilibrium between the ammonia (NH ₃ ) and the dissolved form of ammonium (NH ₄ ). An increasing pH, ie an increasing OH concentration, leads to a shift in the equilibrium in favor of the ammonia concentration in the fermentation substrate. The supply of ammonia-containing fermentation substrates leads to an increase in the pH value and thus to a shift in the equilibrium in favor of the ammonia concentration

While ammonia serves as the nitrogen source for most bacteria, ammonia can inhibit the bacteria even in small quantities. In addition, the equilibrium shifts with increasing temperature in favor of the ammonia. As a result, the inhibitory effect increases with increasing temperature, which can have a problematic effect especially in thermophilically operated fermentation sections.

The ammonia-containing fermentation substrate acts toxic from a certain ammonia concentration depending on the pH and the temperature of the fermentation substrate and thus inhibiting the fermentation process and the involved biology (bacterial strains and / or enzymes), d. H. toxic or inhibiting the microbiological processes in the fermenter.

As a result, for example, ammonia-containing animal faeces are currently only used in a limited amount for biogas fermentation.

Especially this amount of ammonia-containing animal feces is relatively high in Germany, so that a quantitative increase in the use of a biogas plant is desirable.

In addition, in the digestate still a high proportion of ammonia is present, so that when applied to agricultural land to gaseous losses of ammonia and the nitrogen-containing fertilizer does not fully unfold its effect on the target area.

Finally, the ammonia present in the biogas pollutes the combustion chambers of the engines used to generate electricity. There is a deterioration in the efficiency and it leads to the combustion of biogas to uncontrolled combustion, which is noticeable by the so-called knocking and lower exhaust emissions. It also leads to acidification of the engine oil with the result of reduced oil life.

For these reasons, it is desirable to remove ammonia as far as possible and as early as possible from the biogas process, ie from the biomass, thus from the fermentation substrate and thus from the digestate or at least reduce, collect and prepare such that a later use of the Biogas and / or the digestate without the disadvantages mentioned is possible.

By removing the ammonia beyond the known extent, it is to be achieved that, in particular, the biogas fermentation process and the combustion chambers coming into contact with the biogas of the engines used for power generation are no longer adversely affected.

The object of the invention is therefore to provide a method and a device or a system with a device which ensures that a high proportion of ammonia is removed from the biogas process as early and efficiently as possible. In particular, it is to be achieved that, as fermentation substrate (as starting product), ammonia-containing animal fecal matter can be used in larger quantities, since the method and the device are intended to remove a higher ammonia content than hitherto without the disadvantages described. Furthermore, it should still be achieved that the digestate of the biogas plant (as the end product) has a lower ammonia content than previously.

The publication DE 10 2008 024 388 B4 discloses a method for grinding a biomass regrind present as a starting product (fermentation substrate). The document describes that the fermentation substrate of a grinding chamber of an impact mill with is fed to a closed screen basket, wherein the fermentation substrate is metered within a forced-wet grinding a process liquid and ground simultaneously with the fermentation substrate, and then sieved and discharged on reaching a predetermined by the sieves of the screen basket particle size through the screen basket and discharged. The structure of the impact mill will be explained in detail. The description of the impact mill is hereby incorporated by reference. The structure and mode of action of the publication DE 10 2008 024 388 B4 described impact mill is to be regarded as part of this patent application. It is explained there, for example, that as the process liquid either water or recirculate from the fermentation process and also a biochemically acting additive is added. In the impact mill, a fermentation substrate (referred to therein as a product substrate) is prepared by forced wet grinding with the addition of a process liquid.

To solve the problem, the following method for expelling (stripping) of bound ammonia and carbon dioxide from a mashed solids-containing fermentation substrate and / or a solid-containing digestate is provided. Fermentation substrate and digestate have a predeterminable dry matter content and thus a high proportion of liquid phase.

According to the invention, a method is provided for expelling (stripping) ammonia and carbon dioxide from a mashed solids-containing fermentation substrate and / or a solid-containing digestate having a predefinable dry matter content, which is characterized in that a mechanical compulsory milling of the mashed solids-containing fermentation substrate and / or the solids-containing digestate within a Strippbehälters for compulsory mechanical disruption of the solids of the mashed solids-containing fermentation substrate and / or solidified digestate is carried out, in addition to the actively outgassing ammonia and carbon dioxide, the solid-bonded inactive ammonia and carbon dioxide are activated and expelled by the mechanical forced grinding.

In a preferred embodiment of the invention, it is provided that an impact effect is exerted on the cell walls during the mechanical compulsory milling an impacting the cell walls of bemaischten solids-containing fermentation substrate and / or the solid-containing digestate, whereby the cell walls are broken and the particle size of the solid is reduced and homogenized, which in addition to the actively outgassing ammonia and carbon dioxide bound inactive ammonia and carbon dioxide are mechanically activated and released. This process of activation and release of bound ammonia and carbon dioxide takes place as a function of the temperature of the solid f; (T) and / or the pressure f; (P) of the solid instead, as will be discussed.

An effect has been found which consists in activating and releasing the ammonia and carbon dioxide activated by the digestion of the solid of the mashed fermentation substrate and / or the digestate by a partial impact effect, the partial impact effect in the stripping vessel being between a mechanical grinding - And crushing tool and a grinding chamber is generated. It was inventively recognized that the particle size of the solid is reduced and homogenized by the forced wet grinding /, and further contained in the solid - previously inactive / er - ammonia and carbon dioxide mechanically activated as a function of temperature and pressure and as a function of pH and be released. In addition, the interface is increased.

This is a significant advantage of the method, namely, that the mechanical forced milling, in particular the impact effect further open up the cell walls of the solids-containing fermentation substrate and / or digestate and increases the interface, so that a larger proportion of ammonia and carbon dioxide from the fermentation substrate and / or digestate are stripped can.

It is advantageous in a preferred embodiment of the invention if the pH f; (pH) of the mashed solids-containing fermentation substrate and / or the digestate is determined, and the temperature of the fermentation substrate f; (T) and / or the pressure f; (p) the fermentation substrate during the mechanical compulsory milling as a function of the pH f; (pH) is selected and set.

It has also been found that the partial impact effect alone already leads to a partial increase in temperature and to a partial pressure increase in the impact area, where the mechanical grinding and comminution tools strike the solid. The occurring mechanical impact occurs within the stripping container.

The method is characterized in that the ammonia and carbon dioxide contained by the digestion of the solid is already activated and released by a partial impact, wherein the digestion process by the partial impact on the solids in the stripping begins and by the further digestion of the solids between the mechanical grinding and crushing tool and the grinding chamber is completed under partial pressure and temperature increase is perfected.

The method is characterized by parameters that are generated by the partial impact effect. Within the process, the partial impact effect leads to a partial increase in temperature T _partially and to a partial pressure increase p _{partially to} the solid particles in the region of the impact effect a) upon impact of the mechanical grinding and comminution tool on the solids and b) between the mechanical Grinding and comminution tool and the grinding chamber passing solids within the stripping, as will be explained in more detail below.

This temperature and pressure increase leads advantageously to the fact that the cell walls of the solid-containing fermentation substrate and / or digestate are completely digested or broken.

By grinding, there is an increase in the mass transfer surfaces in the fermentation substrate and / or digestate. It is the interface between the liquid and gaseous phase of the fermentation substrate and / or the digestate extremely increased. This favors the decomposition of the dissolved ammonium carbonate into ammonia and carbon dioxide and the transition to the gas phase. Likewise, the pressure drop after the partial pressure increase favors the transition to the gas phase. In particular, the increase in the interface between liquid and gaseous phase allows the ammonia stripped from mashed fermentation substrates with TS levels up to 15%.

In addition, it is advantageous to homogenize the fermentation substrate and / or digestate. Homogenization and mechanical digestion lead to increased biogas yield in the following fermentation. The stripping and removal of ammonia inhibits the negative effects of inhibiting ammonia.

Furthermore, it is provided that the admixed solids-containing fermentation substrate and / or the digestate in the stripping container is additionally metered into an additive and a process liquid, in particular water and / or recirculate from the fermentation process.

Advantageously, the dry matter content of the fermentation substrate and / or digestate can thereby be influenced and controlled, which in turn can influence the impact effect within the mechanical compulsory milling, so that as a result the stripping, i. the activation and release of the solid ammonia fraction and the carbon dioxide fraction is indirectly influenced in favor of a high activation rate.

In this case, biochemical ingredients can be dosed to the water, wherein the biochemical ingredients are, for example, anaerobic bacterial strains and / or enzymes.

This has the advantage that the biochemical constituents present in the recirculate and / or in the water biochemically support the compulsory mechanical disruption process, so that the biochemical effects and the compulsory mechanical effects taken alone and in combination to a better activation of solid-bound inactive Ammonia and carbon dioxide within the compulsory milling and accelerate the process.

The essential part of the activation and expulsion of the solid-state inactive ammonia and carbon dioxide is based on the positive mechanical effects.

It is also envisaged that all ammonia and carbon dioxide activated and released by the process will be collected and recombined.

In a preferred embodiment, it is provided that the mashed solids-containing fermentation substrate and / or the digestate before the stripping and / or in the stripping is heated to a predetermined temperature, in particular to a temperature between 54 ° C and 75 ° C.

In addition, in a further embodiment, it is provided that the mechanical forced grinding in the stripping container is carried out under reduced pressure, wherein the predefinable negative pressure in the prescribable negative pressure region in the stripping container is set to 150 mbar relative to the ambient pressure.

The mashed solids-containing fermentation substrate has in a preferred embodiment of the invention to a predetermined dry matter content up to 15% dry matter.

In a preferred embodiment of the invention, the digestate has a predefinable dry matter content of up to 8% dry matter.

It will be appreciated that within the process both fermentation substrate or digestate may be stripped alone or in combination.

In the following description will be explained in more detail to what extent fermentation substrate and digestate stripped alone or in combination within the procedure.

In a preferred embodiment, the method according to the invention is suitable for stripping the fermentation substrate in the container, in which also the forced wet grinding of the fermentation substrate takes place.

However, there is also the possibility of stripping the fermentation substrate and digestate in the container in which hitherto only forced wet grinding of the fermentation substrate has taken place.

Finally, it is possible to strip only the fermentation residue in the container in which so far the forced wet grinding of the fermentation substrate has taken place.

In summary, a significant advantage of the method is that a solids-containing starting material, in particular fermentation substrate as a function of temperature, pressure and the pH is mechanically digested /, whereby by mechanical digestion of the starting substrate (fermentation substrate) over the previous methods, a higher proportion of Ammonia and carbon dioxide is strippable. So far not digested digestate or not completely digested digestate can be subjected to the same digestion process advantageously together with the fermentation substrate or alone.

To carry out the method according to the invention an impact mill is used, the structure already in the document DE 10 2008 024 388 B4 is explained. With the impact mill, the mechanical forced grinding of the mashed solids-containing fermentation substrate and / or the digestate is carried out. The impact mill is part of a plant for expelling (stripping) of active and bound ammonia and carbon dioxide from the fermentation substrate and / or the digestate with a predeterminable dry matter content, wherein it is provided that the impact mill is also the stripping.

Experiments have shown that the impact mill according to the patent DE 10 2008 024 388 B4 is very well suited to carry out the mechanical forced grinding of the heated solids-containing fermentation substrate and / or digestate under atmospheric pressure and under reduced pressure.

The impact mill thus represents as a device within a plant for Zwangsnassvermahlung the fermentation substrate and / or the digestate according to the invention simultaneously the stripping, is stripped in the ammonia and carbon dioxide under mechanical forced grinding of the fermentation substrate and / or digestate, as will be explained in more detail in an embodiment ,

The impact mill is characterized essentially by the fact that a grinding chamber is arranged with a closed screen basket. It comprises at least one starting product feed.

The impact mill comprises the grinding chamber, in particular the screen basket and rotating grinding / crushing tools and a feed for the metering of the process liquid, which means impact strength on the grinding / crushing tools and in particular on the grate of the grinding chamber a continuously emerging from the basket solids aufgeschlossenes end product with particles homogeneous size can be generated.

In a preferred embodiment of the invention, the supply of the process liquid is subdivided into nozzle regions, wherein it is provided in particular that the metered addition of the process liquid takes place via a first nozzle region into the interior of the impact mill and via a second nozzle region from the outside to the grinding chamber.

In a preferred embodiment of the invention, the impact mill on grinding / crushing tools, which are rotating about an axis of the screen basket arranged static impact hammers or beaters, which it in the impact area and between impact hammers or impact beaters and grinding chamber to the partial impact effect with the above-mentioned pressure and temperature increase comes with the described effects.

It is envisaged that to set the desired particle size of the product substrate to be produced, the peripheral speed, the number of impact hammers or impact beaters and the flow rate of the starting product are variable.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The invention will be explained below in embodiments with reference to the accompanying drawings. It shows:

1 a plant configuration (facility) for mechanically assisted ammonia stripping in a biogas plant - "mechanical stripping".

1 shows a plant A (a plant configuration) for mechanically assisted ammonia stripping within a biogas plant.

In a first embodiment variant, the mechanically assisted ammonia stripping of a fermentation substrate is explained. The mechanically assisted ammonia stripping of a fermentation substrate in combination with a digestate is explained later in an alternative embodiment.

The plant A initially comprises a reactor R in which the fermentation substrate GS is located.

Within a biogas plant, this reactor R is generally a fermenter in which at least the mashing of the solids-containing biomass used has already taken place. The fresh biomass to be fermented is already mixed with the process liquid.

The reactor R may, for example, also generally be a storage container in that a mashing of the biomass with the process liquid has already taken place so that the mashed solids-containing fermentation substrate is not introduced into the fermenter until after the mechanically assisted ammonia stripping.

The mashed, solids-containing fermentation substrate GS held in the reactor R has a predeterminable dry matter content ΔTS of up to 15%.

The fermentation substrate GS is, for example via a first pump unit P1 (entry pump unit) via a fermentation substrate line GS-L1 (solid line) via a first heat exchanger WT1 to an impact mill 100 led, which serves the mechanical forced grinding of solid-containing fermentation substrate GR and at the same time as a stripping.

Before entering the fermentation substrate GS in the impact mill 100 the solids-containing fermentation substrate GS is heated. The solids-containing fermentation substrate GS is heated to a temperature between 54 ° C and 75 ° C in a predeterminable temperature range .DELTA.T.

The process is also feasible without heating, but the strippable portion of the ammonia and carbon dioxide is lower, since the expulsible amount is also a function of the temperature f; (T) is.

Irrespective of the temperature, activation of the otherwise inactive ammonia and carbon dioxide takes place as a result of mechanical forced-grinding.

At the same time provided as a stripping container impact mill 100 is for example an extraction system 200 connected. The connection between the impact mill 100 and the exhaust system 200 is made by a gas line BL-1 (dot-dash line).

To the exhaust system 200 heard a blower 210 (Compressor), which ammonia- and carbon dioxide-containing gas from the impact mill 100 sucks. That in the impact mill 100 Resulting gas is referred to below as "residual biogas".

On the reactor R, a gas line M-L1 is arranged, through which the main stream of the biogas produced in the reactor R is withdrawn from the reactor R, which is referred to as "biogas main stream".

In Appendix A thus falls a methane-containing Biogas main stream in the reactor R and a methane-containing biogas residual stream in the impact mill 100 , wherein in each case ammonia and carbonic acid are present in the gaseous state.

The biogas gas main stream and the residual biogas flow together form the resulting biogas stream of the biogas plant.

The exhaust fan 210 the suction system 100 generated in the impact mill 100 a negative pressure p _u in a predeterminable negative pressure range Δp _u to 150 mbar.

After the addition of the solids-containing fermentation substrate GS into the impact mill 100 is the mechanical forced wet grinding of the preferably heated solids-containing fermentation substrate GS within the negative pressure impact mill 100 carried out, which leads to the compulsory mechanical disruption of the solids of the solids-containing fermentation substrate and to the activation and expulsion of the previously solid-bonded inactive ammonia and carbon dioxide, so that within the impact mill 100 the residual biogas is produced.

The process is temperature- and pressure-dependent as well as pH dependent and depending on the mechanical forces acting on the solids.

The process is also feasible with only a slight suction vacuum, but the strippable portion of the ammonia and carbon dioxide is higher at greater negative pressure because the expulsible amount is also a function of the pressure f; (p) is.

The stripping supported by the mechanical forced wet grinding according to the invention also takes place without generating a high underpressure and without increasing the temperature in the ambient air inside the impact mill 100 instead, because the effect according to the invention is already caused solely by the mechanical forced wet grinding. The mechanical forced grinding causes the activation of the otherwise inactive ammonia and carbon dioxide.

Due to the mechanical energy input in the impact area during compulsory milling, in which the solids are exposed to the impact mill in the grinding chamber 100 applied pressure and temperature are subject to an increased partial pressure and temperature difference, it comes to previous methods - in which no mechanical or thermomechanical forced milling takes place - to increased release of ammonia and carbon dioxide in Biogasreststrom.

In addition, as explained, there is the possibility that the impact mill 100 in total, in a predeterminable negative pressure, that is to say a total negative pressure p _u acting on the fermentation substrate GS in the impact mill 100 can be driven, so that acting on the solids partial overpressure p _partially in the forced wet grinding combinatorial with the negative pressure p _u in the impact mill 100 effect that a high proportion of inactive ammonia and carbon dioxide is activated, so that more ammonia and carbon dioxide can be stripped compared to conventional methods.

Even without negative pressure in the impact mill 100 There is an increase in strippbarem ammonia and carbon dioxide, since the acting on the solids partial overpressure p _partially in the forced wet grinding to a digestion of solids and a release of ammonia and carbon dioxide leads that can not be achieved without forced wet grinding.

The one in the impact mill 100 generated negative pressure p _u promotes advantageously in addition to the corresponding increase in temperature additionally the transition of the compounds to be stripped ammonia and carbon dioxide from the solid into the gas phase.

In addition to the increase in temperature due to the preheating of the fermentation substrate GS via the first heat exchanger WT1, the mentioned partial temperature increase T _{partially occurs} a) in the contact area of the grinding / crushing tools of the impact crusher impinging on the solids 100 and b) in the area of contact of the solids which, during the forced wet grinding, fall between the mechanical grinding and comminution tool and the grinding chamber. This elevated temperature T _partially lies in the contact regions even above the preheating temperature of the fermentation substrate GS in the intended temperature range .DELTA.T to 75.degree. As a result of this effect, increasing the temperature in the contact region beyond the preheating temperature advantageously results in an increased release of ammonia and carbon dioxide in the residual biogas stream.

In the impact mill 100 is created by the described boundary conditions and the mechanical energy input a special process situation, by the combination of vacuum, preheating the heat exchanger and the partial pressure and temperature increase in the contact area of the solids with the grinding / crushing tools and the grinding chamber in the impact mill 100 and the increase in the interfaces between liquid and gaseous phase is characterized.

The exhaust fan 210 (Compressor), which ammonia- and carbon dioxide-containing gas from the impact mill 100 sucks, is connected in a preferred embodiment of the invention with a treatment plant, not shown. In designated treatment plant the ammonia is removed from the gas stream by known methods for further processing. The remaining residual biogas stream is fed to the main stream and purified.

As in 1 is apparent, the fermentation substrate GS via the impact mill 100 circulated back to the reactor R. On the output side, a second pump unit P2 (discharge pump unit) is arranged, which leads the fermentation substrate GS via a second heat exchanger WT2.

In the second heat exchanger WT2, the fermentation substrate GS is cooled, as otherwise undesired heating of the fermentation substrate GS in the reactor R occurs. The return takes place via the second fermentation substrate line GS-L2 (continuous line). The waste heat of the second heat exchanger WT2 can be used meaningfully within the process.

Due to the fact that the fermentation substrate GS is correspondingly circulated, ammonia and carbon dioxide are advantageously removed from the reactor R and at the same time the fermentation substrate is comminuted and homogenized. This reduces the ammonia inhibiting the involved biology within reactor R, i. The process of the microbiological bacteria in the fermenter, which are used for biogas fermentation, is positively influenced, whereby the operator of a biogas plant by reducing the ammonia can use a higher proportion of ammonia-containing raw materials.

Furthermore, the proportion of ammonia in the resulting biogas stream, the biogas plant lower, so that there is less contamination of the combustion chambers of the motors used for power generation and to increase the efficiency. The uncontrolled knocking caused by a high ammonia content in the biogas is avoided or reduced during combustion. It results in better emissions and the acidification of the engine oil decreases, so that longer oil life can be achieved. Overall, a higher efficiency is achieved by the measures mentioned in the power generation within the biogas plant.

The process can be further positively influenced.

By adding a process liquid, it is initially possible within the impact mill to be able to change the dry substance content ΔTS of the mashed solids-containing fermentation substrate GS in the reactor R by adding further process liquid.

On the one hand, it is possible to add process water via a first process liquid line L1. The process water may contain biochemical ingredients e.g. anaerobic bacterial strains and / or enzymes.

On the other hand, it is possible to add recirculate from reactor R via a second process liquid line L2.

In an alternative embodiment of the method or the system A is proposed not only fermentation substrate GS on the impact mill 100 but also to strip digestate GR. This procedure is appropriate if the plant A has overcapacities, so that accumulating digestate, which has been treated by the method described and / or untreated digestate for activating bound ammonia and carbon dioxide can be stripped.

The digestate GR is usually present in a downstream container. Digestate GR is compared to the actively outgassing fermentation substrate GS a largely gassed substrate residue.

Due to the degradation of organic acids in methane within the biogas process, the process is becoming increasingly basic and in the digestate GR a more basic environment prevails than in the fermentation substrate GS. As a result of the dependence on the pH, ammonia continues to be present at comparable temperature or pressure conditions in a basic medium. This dependence in connection with the described forced wet grinding is used to strip even in the digestate GR ammonia.

The procedure is as follows. According to 1 becomes the impact crusher 100 upstream of the first heat exchanger WT on the suction side of the first pump unit P1 (feed pump unit), digestate GR is added via a fermentation residue feed line GR-L1.

In a first embodiment, the non-preheated or alternatively preheated fermentation residue GR in combination with the fermentation substrate GS in the impact mill 100 mechanically forcibly ground and preferably stripped under reduced pressure conditions and circulated in the reactor R, as explained above. As mentioned, the heating of the digestate GR and the negative pressure in the impact mill 100 advantageous and increases the activatable proportion of ammonia and carbon dioxide, but not mandatory.

In a second embodiment, only the non-preheated or alternatively preheated digestate GR in the impact mill 100 mechanically forcibly ground and stripped under the alternative pressure conditions already described, but not circulated, since the fermentation residue is no longer actively ausgasendes substrate after compulsory milling, so that no movement of the digestate is provided in the reactor R.

In this second embodiment, the digestate GR is transported back to the fermentation residue container, not shown, via the fermentation residue recycling line GR-L2 shown. It is understood that the mechanical compulsory milling of the digestate GR, insofar as the starting product has already been forcibly mechanically ground within the biogas plant as fermentation substrate GS, has no further comminuting effect more, however, it has been found that it by the more basic environment at the end of the fermentation process an activation of the outgassing of the ammonia and carbon dioxide and by the further compulsory milling to a further homogenization of the digestate GR.

The advantage is in particular that the digestate GR can be reduced in terms of its ammonia content. In addition, the reduction of the ammonia content in the fermentation residue GR can essentially be achieved with the described plant technology, which is also used for a reduction of the ammonia content in the fermentation substrate GS. This results in a very good utilization of existing plant technology. In addition, due to the reduction of the ammonia in the fermentation residue GR, lower ammonia losses occur during the application of the digestate to agricultural land.

LIST OF REFERENCE NUMBERS

 A

investment

 R

reactor

 GS

fermentation substrate

 GS-L1

Fermentation substrate line

GS-L2

 Fermentation substrate line

GR

 digestate

 GR-L1

Gärrestzuführungsleitung

 ATS

Dry matter content

.DELTA.T

 temperature range

Δp _U

Under pressure range

p _U

vacuum

p _partially

 partial pressure in the contact area

T _partial

 partial temperature in the contact area

 P1

first pump unit

 P2

second pump unit

WT1

 first heat exchanger

WT

second heat exchanger

100

impact crusher

200

Absaugungsanlage

210

Absaugungsgebläse

BL-1

Gas line of the biogas residual stream

M-L1

Gas pipeline of Biogas mainstream

L1

first process fluid line

L2

second process fluid line

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10354063 A1 [0013]
• DE 102009024536 A1 [0018]
• DE 102010033 A1 [0018]
• DE 102008024388 B4 [0031, 0031, 0060, 0061]

Claims (12)

Process for the mechanical expulsion (stripping) of ammonia and carbon dioxide from a mashed solids-containing fermentation substrate (GS) and / or a solid-containing digestate (GR) having a predeterminable dry matter content (ΔTS), characterized by mechanical forced-milling of the mashed solids-containing fermentation substrate (GS) and / or the solid-containing digestate (GR) within a stripping container ( 100 ) for compulsory mechanical disruption of the solids of the mashed solids-containing fermentation substrate (GS) and / or solidified digestate (GR), wherein in addition to the actively outgassing ammonia and carbon dioxide, the bound inactive ammonia and carbon dioxide are activated and expelled by the mechanical forced milling. A method according to claim 1, characterized in that during the mechanical forced grinding an impact effect under disruption of the cell walls of the mashed solids-containing fermentation substrate (GS) and / or the solid-containing digestate (GR) is exerted on the cell walls, whereby the cell walls are broken and the particle size of the Solid is reduced and homogenized, whereby bound inactive ammonia and carbon dioxide mechanically as a function of the temperature of the solid ((f; (T)), the pH and / or the pressure (f; (p)) of the solid (GS; GR) are activated and released. Method according to claim 1, characterized in that the ammonia and carbon dioxide activated by the digestion of the solid of the admixed solids-containing fermentation substrate (GS) and / or the solid-containing digestate (GR) are activated and released by a partial impact effect, the partial impact effect in the stripping vessel ( 100 ) between a mechanical grinding and crushing tool ( 106 ) and a grinding chamber ( 114 ) is produced. A method according to claim 2, characterized in that the pH (f; (pH)) of the mashed solids-containing fermentation substrate (GS) and / or the solid-containing digestate (GR) is determined, the temperature of the solid ((f; (T )) and / or the pressure (f; (p)) of the solid (GS; GR) during mechanical forced-grinding as a function of the pH (f; (pH)) is selected and set. A method according to claim 3, characterized in that the partial impact effect to a partial increase in temperature (T _partial ) and a partial increase in pressure (p _partial ) of the solid particles in the area of the impact effect, a) upon impact of the mechanical grinding and crushing tools on the solids , and b) through the solids between the mechanical grinding and comminution tool and the grinding chamber inside the stripping container ( 100 ) leads. A method according to claim 1, characterized in that the mashed solids-containing fermentation substrate (GS) and / or the solid-containing digestate (GR) in Strippbehälter ( 100 ) is a process liquid, in particular recirculated from the fermentation process to be dosed /. A method according to claim 6, characterized in that recirculated biochemical ingredients are metered, wherein the biochemical ingredients are anaerobic bacterial strains and / or enzymes. A method according to claim 1, characterized in that the activated and released ammonia and carbon dioxide is collected and recombined. A method according to claim 2, characterized in that the bemaischte solids-containing fermentation substrate (GS) and / or the solids-containing digestate (GR) before the stripping container ( 100 ) and / or in the stripping container ( 100 ) is heated to a predetermined temperature (T), in particular to a temperature between 54 ° C and 75 ° C. A method according to claim 2, characterized in that the mechanical compulsory milling in the stripping container ( 100 ) is carried out under reduced pressure (p _U ), wherein the predefinable negative pressure (p _U ) in the predeterminable negative pressure range (Δp _U ) in the stripping container ( 100 ) is set to the ambient pressure of up to 150 mbar. A method according to claim 1, characterized in that bemaischtes solids-containing fermentation substrate (GS) having a predetermined dry matter content (ΔTS) of up to 15% dry matter and / or solids-containing digestate (GR) with a predetermined dry matter content (ΔTS) of up to 8% Dry substance is used. Use of an impact mill for performing a mechanical forced grinding of a mashed solids-containing fermentation substrate (GS) and / or digestate (GR) within the method according to at least one of claims 1 to 11, wherein the impact mill as part of a plant for stripping (bound) of ammonia and ammonia Carbon dioxide from the mashed solids-containing fermentation substrate (GS) and / or the solids-containing digestate (GR) with a predefinable dry matter content (ΔTS) at the same time the stripping container ( 100 ).

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