Method for the preparation of an organic starting substrate

Abstract

The invention relates to a process for the preparation of an organic starting substrate (AS), in particular for the preparation of raw manure or digestate, comprising the steps of: providing the organic starting substrate (AS), clarifying the provided organic starting substrate (AS) in a first clarification stage to form a first solid phase (FE1) and a first clarified liquid phase (FL1) by means of a first separation device (18) and clarifying the first clarified liquid phase (FL1) in a second clarification stage to form a second solid phase (FE2) and a second clarified liquid phase (FL2) by means of a second separation device (32).

Description

The invention relates to a method for processing an organic starting substrate, comprising the steps of: providing the organic starting substrate, clarifying the provided organic starting substrate in a first clarification stage to form a first solid phase and a first clarified liquid phase by means of a first separation device, and clarifying the first clarified liquid phase in a second clarification stage to form a second solid phase and a second clarified liquid phase by means of a second separation device. Furthermore, the invention relates to a processing plant for processing an organic starting substrate, comprising a first separation device by means of which a provided organic starting substrate can be clarified in a first clarification stage by forming a first solid phase and a first clarified liquid phase, and a second separation device by means of which the first clarified liquid phase can be clarified in a second clarification stage by forming a second solid phase and a second clarified liquid phase. When raw slurry and / or digestate are separated using a centrifuge, a solid phase and a clarified liquid phase are produced. To simplify the disposal of the clarified liquid phase, the amount of suspended solids or fine particles it contains must be minimized. In this context, the publication EP 2 823 030 B1 proposes a two-stage process in which raw slurry is first clarified in a first stage, producing a first solid phase and a first clarified liquid phase. After the addition of a flocculant and / or a flocculant aid, the first clarified liquid phase is further clarified in a second stage, producing a second solid phase and a second clarified liquid phase. Due to the addition of the flocculant aid, the second solid phase contains a polymer component. This polymer component can restrict the free transport of the solid for environmental reasons. Furthermore, flocculants and flocculant aids are comparatively expensive. The object underlying the invention is to reduce or avoid the use of flocculants and flocculant aids in the processing of organic substrates, such as raw manure or digestate, and preferably at the same time to improve the quality of the liquid phase. The problem is solved by a process of the type mentioned above, wherein the second clarified liquid phase is clarified in a third clarification stage by means of a third separation device, forming a third solid phase and a third clarified liquid phase. Clarifying the second clarified liquid phase in the third clarification stage allows for a significant reduction or even the elimination of the addition of flocculants and flocculant aids before or during the second clarification stage. Flocculants, such as iron(III) chloride (FeCl3), aluminum chloride (AlCl3), aluminum sulfate (Al2(SO4)3), or polyaluminum chloride (PAC), are substances that destabilize colloidally dissolved components with negative surface charges, causing them to agglomerate into larger flocs. This promotes the growth of microflocs into easily separable macroflocs. Flocculant aids, such as anionic or cationic polymers, for example, polyacrylamides, are substances that improve the shear strength of a coagulate. This improved shear strength allows the coagulate to withstand higher centrifugal forces and be more easily separated during the clarification process.These resources are no longer needed, or only in significantly reduced quantities, due to the third treatment stage. This results in considerably lower material costs. Since flocculants are typically water-based polymers, the need for fresh water for polymer treatment is also reduced. The reduced or eliminated addition of flocculants and flocculant aids also results in a significantly lower environmental impact, ensuring compliance with any environmental regulations governing the disposal of the solids after clarification. The organic starting substrate is preferably stored in a first storage tank before clarification in the first clarification stage. The first clarified liquid phase is preferably temporarily stored in a second storage tank before clarification in the second clarification stage. The organic feedstock can be raw manure or digestate. Alternatively, the organic feedstock can consist of raw manure or digestate. Other organic waste can also be used as the organic feedstock. The process can be used, for example, in biogas plants and wastewater treatment plants. In a preferred embodiment of the process according to the invention, the first separation device, with which the organic starting substrate is clarified in the first clarification stage, is designed as a centrifuge. Alternatively or additionally, the second separation device, with which the first clarified liquid phase is clarified in the second clarification stage, is designed as a centrifuge. The centrifuge used to clarify the organic starting substrate in the first clarification stage is preferably a solid-bowl screw centrifuge. Alternatively, the clarification of the organic starting substrate in the first clarification stage can be carried out by a screw press. The centrifuge used to clarify the first clarified liquid phase in the second clarification stage is preferably a solid-bowl screw centrifuge. In another preferred embodiment of the method according to the invention, the third separation device, with which the second clarified liquid phase is clarified in the third clarification stage, is designed as a centrifugal separator. The centrifugal separator can be a nozzle separator. Alternatively, a chamber separator or a self-emptying disc separator can be used as the centrifugal separator. The process according to the invention is further advantageously developed by not adding any flocculant and / or flocculant to the first clarified liquid phase between the first and second clarification stages. Preferably, no pH-modifying agent is added to the first clarified liquid phase between the first and second clarification stages. Alternatively, less than 5 kg per ton of flocculant can be added to the first clarified liquid phase between the first and second clarification stages. Alternatively, less than 8 l per m³ / h of flocculant can be added to the first clarified liquid phase between the first and second clarification stages. No flocculant or flocculant is added to the second clarified liquid phase between the second and third clarification stages.No pH-modifying agent is added to the second clarified liquid phase between the second and third clarification stages. Alternatively, a small amount of flocculant or flocculant may be added to the second clarified liquid phase between the second and third clarification stages. Furthermore, a process according to the invention is preferred in which the third solid phase formed in the third clarification stage is partially or completely returned to the first clarification stage. The third solid phase is thus partially or completely recirculated. By returning the third solid phase to the first clarification stage, concentration can lead to an accumulation of small particles, which can then be separated by the first separation device in the first clarification stage or by the second separation device in the second separation stage. The partial or complete return of the third solid phase to the first clarification stage can be continuous or batchwise. The third solid phase can be pre-mixed with the organic feedstock or fed to the first clarification stage separately from the organic feedstock.The third solid phase can, for example, have a solids content between 2 percent and 4 percent. The organic starting substrate can, for example, have a solids content of approximately 4 percent. In a further preferred embodiment of the process according to the invention, the third solid phase formed in the third clarification stage is partially or completely removed from the processing plant comprising the first, second, and third separation devices. The partial or complete removal of the third solid phase from the processing plant can be carried out continuously or discontinuously. Furthermore, a method according to the invention is preferred in which a control device, depending on one or more properties of the third solid phase and / or one or more properties of the third liquid phase, selectively causes the third solid phase to be returned to the first clarification stage or to be discharged from the treatment plant. The method can include monitoring, in particular continuous monitoring, of one or more properties of the third solid phase and / or monitoring, in particular continuous monitoring, of one or more properties of the third liquid phase. A property of the third solid phase can, for example, relate to the solids content of the third solid phase. A property of the third liquid phase can, for example, relate to the solids content or the fine particle loading of the third liquid phase.The third solid phase can, for example, be returned to the first treatment stage if one or more limit values ​​for one or more monitored properties fall below the threshold, and be discharged from the treatment plant if one or more limit values ​​for one or more monitored properties are exceeded. Due to recirculation, fine particles can accumulate in the process until they affect the quality of the third liquid phase. From that point on, the solids discharge from the separator is removed until the initial conditions are restored. In a further preferred embodiment of the process according to the invention, the provided organic starting substrate has a solids content in the range of 3 to 6 percent, preferably between 4 and 5 percent. Alternatively or additionally, the first solids phase formed in the first clarification stage has a solids content in the range of 15 to 35 percent, preferably between 18 and 32 percent. Alternatively or additionally, the second solids phase formed in the second clarification stage has a solids content in the range of 15 to 26 percent, preferably between 18 and 23 percent. Alternatively or additionally, the third solids phase formed in the third clarification stage has a solids content in the range of 1.5 to 5.5 percent, preferably between 2 and 5 percent. The problem underlying the invention is further solved by a processing plant of the type mentioned above, wherein the processing plant according to the invention comprises a third separation device by means of which the second clarified liquid phase can be clarified in a third clarification stage to form a third solid phase and a third clarified liquid phase. The processing plant is preferably configured to process the organic starting substrate by means of a process according to one of the embodiments described above. With regard to the advantages and modifications of the processing plant according to the invention, reference is therefore made to the advantages and modifications of the process according to the invention. Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying drawings. Figure 1 shows a schematic representation of a processing plant according to the invention; Figure 2 shows a schematic representation of another processing plant according to the invention; and Figure 3 shows a schematic representation of another processing plant according to the invention. Figure 1 shows a processing plant 10 for processing an organic feedstock AS. The feedstock AS can be, for example, raw slurry. The raw slurry can, for example, have a COD value of around 40,000. The organic feedstock AS has, for example, a solids content in the range of 3 to 6 percent. The feedstock AS is initially collected in a first storage tank 12. In order to obtain the most uniform viscosity possible and to avoid settling of solids as far as possible, the first storage tank 12 has an agitator 14. The starting substrate AS is pumped from the storage tank 12 into a first separation device 18 of a first clarification stage by means of a feed pump 16. The first separation device 18 clarifies the organic starting substrate AS, forming a first solid phase FE1 and a first clarified liquid phase FL1. The first separation device 18, used to clarify the organic starting substrate AS in the first clarification stage, is designed as a centrifuge. The centrifuge used to clarify the organic starting substrate AS in the first clarification stage is a solid-wall screw centrifuge. The first solid phase FE1 is conveyed here, for example, via a screw conveyor 20 into a collection container 22. The first solid phase FE1 has, for example, a solids content in the range of 15 to 35 percent. The first clarified liquid phase FL1 is conveyed via a pump 24 into a second storage tank 26 and collected there. The second storage tank 26 preferably has an agitator 28 to achieve the most uniform viscosity possible of the collected first clarified liquid phase FL1. From the second storage tank 26, the first clarified liquid phase FL1 is pumped by means of a transfer pump 30 into a second separation device 32 of a second clarification stage. No flocculant or flocculant is added to the first clarified liquid phase FL1 between the first and second clarification stages. Furthermore, no pH adjuster is added to the first clarified liquid phase FL1 between the first and second clarification stages. The first clarified liquid phase FL1 is further clarified by the second separation device 32, forming a second solid phase FE2 and a second clarified liquid phase FL2. The second separation device 32, which clarifies the first clarified liquid phase FL1 in the second clarification stage, is designed as a centrifuge. The centrifuge used to clarify the first clarified liquid phase FL1 in the second clarification stage is a solid-wall screw centrifuge. The second solid phase FE2 is conveyed here, for example, via a screw conveyor 34 into a collection container 36. The second solid phase FE2 has, for example, a solids content in the range of 15 to 26 percent. The second clarified liquid phase, FL2, is pumped via pump 38 to a third separation device 40 of a third clarification stage. No flocculant or flocculant is added to the second clarified liquid phase, FL2, between the second and third clarification stages. Furthermore, no pH adjuster is added to the second clarified liquid phase, FL2, between the second and third clarification stages. The third separation device 40 clarifies the second clarified liquid phase FL2, forming a third solid phase FE3 and a third clarified liquid phase FL3. The third separation device 40, which clarifies the second clarified liquid phase FL2, is designed as a centrifugal separator. The centrifugal separator is a nozzle separator. The third solid phase FE3 and the third liquid phase FL3 formed in the third treatment stage are discharged from the treatment plant 10, which comprises the first, second, and third separation devices 18, 32, and 40. The discharge of the third solid phase FE3 and the third liquid phase FL3 is continuous. The third solid phase FE3 formed in the third treatment stage, for example, has a solids content in the range of 1.5 to 5.5 percent. The third clarified liquid phase, FL3, exhibits excellent properties for a biological treatment stage or reverse osmosis. For example, FL3 can be applied by irrigation or via trailing hoses, ensuring that the nitrogen dissolved in the liquid is delivered directly to plant roots with minimal nitrogen loss. In the treatment plant 10 shown in Fig. 2, the third solid phase FE3 formed in the third treatment stage is returned to the first treatment stage via the storage tank 12. The third solid phase FE3 is thus recirculated. Due to the return of the third solid phase FE3 to the first treatment stage, small particles can accumulate due to concentration. These particles can then be separated by the first separation device 18 in the first treatment stage or by the second separation device 32 in the second separation stage. The return of the third solid phase FE3 to the first treatment stage is continuous. In the illustrated embodiment, the third solid phase FE3 is mixed with the organic starting substrate AS in the storage container 12. The third solid phase FE3 can, for example, have a solids content of between 2 and 4 percent. The organic starting substrate AS can, for example, have a solids content of approximately 4 percent. In one embodiment, the processing plant 10 can also include a control device which, depending on one or more properties of the third solid phase FE3 and / or one or more properties of the third liquid phase FL3, selectively causes the third solid phase FE3 to be returned to the first treatment stage or to be discharged from the processing plant 10. In this case, the one or more properties of the third solid phase FE3 and / or the one or more properties of the third liquid phase FL3 can be continuously monitored, for example, by sensors.The third solid phase FE3 can, for example, be returned to the first treatment stage if one or more limit values ​​of one or more monitored properties are not exceeded, and be discharged from the treatment plant 10 if one or more limit values ​​of one or more monitored properties are not exceeded. In the processing plant 10 shown in Fig. 3, the clarification of the starting substrate AS in a first clarification stage is followed by preconditioning of the first clarified liquid phase FL1. Preconditioning is achieved by adding a small amount of a flocculant FM from the storage tank 42 using a pump 44. For further optimization, a small amount of a flocculant aid FHM can also be added from the storage tank 46 using a pump 48. Flocculants FM, such as iron(III) chloride (FeCl3), aluminum chloride (AlCl3), aluminum sulfate (Al2(SO4)3), or polyaluminum chloride (PAC), are agents that destabilize colloidally dissolved components with negative surface charges in such a way that they can agglomerate into larger flocs, thus promoting the growth of microflocs into easily separable macroflocs.Flocculants, such as anionic or cationic polymers, for example polyacrylamides, are agents that improve the shear strength of a coagulate. This improved shear strength allows the coagulate to withstand higher centrifugal forces and be more easily separated during clarification. Between the first and second clarification stages, less than 5 kg per ton of flocculants and less than 8 l per m3 / h of flocculant aids are added to the first clarified liquid phase FL1. Reference sign 10 Processing plant 12 Storage tank 14 Agitator 16 Feed pump 18 Separation device 20 Screw conveyor 22 Collection tank 24 Pump 26 Storage tank 28 Agitator 30 Feed pump 32 Separation device 34 Screw conveyor 36 Collection tank 38 Pump 40 Separation device 42 Storage tank 44 Pump 46 Storage tank 48 Pump AS Starting substrate FE1, FE2, FE3 Solid phases FL1, FL2, FL3 Liquid phases FHM Flocculant FM Flocculant QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature EP 2 823 030 B1

[0004]

Claims

A process for the preparation of an organic feedstock (AS), in particular for the preparation of raw manure or digestate, comprising the steps of: - providing the organic feedstock (AS); - clarifying the provided organic feedstock (AS) in a first clarification stage to form a first solid phase (FE1) and a first clarified liquid phase (FL1) by means of a first separation device (18); and - clarifying the first clarified liquid phase (FL1) in a second clarification stage to form a second solid phase (FE2) and a second clarified liquid phase (FL2) by means of a second separation device (32), characterized by the step of: - clarifying the second clarified liquid phase (FL2) in a third clarification stage to form a third solid phase (FE3) and a third clarified liquid phase (FL3) by means of a third separation device (40). The method according to claim 1, characterized in that: - the first separation device (18) with which the organic starting substrate (AS) is clarified in the first clarification stage is designed as a centrifuge; and / or - the second separation device (32) with which the first clarified liquid phase (FL1) is clarified in the second clarification stage is designed as a centrifuge. Method according to one of claims 1 or 2, characterized in that the third separation device (40), with which the second clarified liquid phase (FL2) is clarified in the third clarification stage, is designed as a centrifugal separator. Method according to one of the preceding claims, characterized in that no flocculant (FM) and / or no flocculant aid is added to the first clarified liquid phase (FL1) between the first clarification stage and the second clarification stage. Method according to one of the preceding claims, characterized in that the third solid phase (FE3) formed in the third clarification stage is partially or completely returned to the first clarification stage. Method according to one of the preceding claims, characterized in that the third solid phase (FE3) formed in the third clarification stage is partially or completely removed from the processing plant (10) comprising the first, second and third separation device (18, 32, 40). Method according to claims 5 and 6, characterized in that a control device, depending on one or more properties of the third solid phase (FE3) and / or one or more properties of the third liquid phase (FL3), selectively causes the third solid phase (FE3) to be returned to the first clarification stage or to be discharged from the treatment plant (10). A method according to any of the preceding claims, characterized in that: - the provided organic starting substrate (AS) has a solids content in the range of 3 to 6 percent, preferably between 4 and 5 percent; and / or - the first solids phase (FE1) formed in the first clarification stage has a solids content in the range of 15 to 35 percent, preferably between 18 and 32 percent; and / or - the second solids phase (FE2) formed in the second clarification stage has a solids content in the range of 15 to 26 percent, preferably between 18 and 23 percent; and / or - the third solids phase (FE3) formed in the third clarification stage has a solids content in the range of 1.5 to 5.5 percent, preferably between 2 and 5 percent. A processing plant (10) for processing an organic starting substrate (AS), in particular by means of a method according to one of the preceding claims, comprising: a first separation device (18) by means of which a provided organic starting substrate (AS) can be clarified in a first clarification stage to form a first solid phase (FE1) and a first clarified liquid phase (FL1); and a second separation device (32) by means of which the first clarified liquid phase (FL1) can be clarified in a second clarification stage to form a second solid phase (FE2) and a second clarified liquid phase (FL2); characterized by a third separation device (40) by means of which the second clarified liquid phase (FL2) can be clarified in a third clarification stage to form a third solid phase (FE3) and a third clarified liquid phase (FL3).

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