Method for regulating and controlling anaerobic fermentation grading through intermediate product feedback

Abstract

The invention provides a method for regulating and controlling anaerobic fermentation grading through intermediate product feedback, in the method, the stage number of hydrolysis stages is divided according to the hydrolysis characteristic of a fermentation material, the stage number of acid production stages is divided according to the acid production characteristic of a hydrolysate, a methane production stage is set as a first-stage methane production reactor, and a second-stage methane production reactor is set as a second-stage methane production reactor; grading nodes of all stages of anaerobic fermentation are provided, efficient and stable operation of multi-stage anaerobic fermentation can be achieved, and the method is simple and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of microbial fermentation technology and relates to a method for regulating anaerobic fermentation fractionation through intermediate product feedback. Background Technology

[0002] Anaerobic fermentation refers to the process by which organic matter such as human and animal manure, straw, and weeds are decomposed and metabolized by a series of microorganisms with different functions under certain moisture, temperature and anaerobic conditions to form a combustible mixture of gases such as methane and carbon dioxide. It is the core technology of biogas engineering.

[0003] Traditional anaerobic fermentation technology typically employs a single-stage fermentation process. The entire biotransformation process, from feed to discharge, occurs within a single closed reactor. Each fermentation stage occurs simultaneously, with microorganisms from each stage coexisting in a relatively disordered, "chaotic" state. The key functional microorganisms at each stage cannot operate under their optimal growth conditions, thus hindering the full realization of their potential activity. Furthermore, the fermentation system exists in a delicate balance; disruption of this balance at any stage can lead to the failure of the entire system.

[0004] Currently, the development trend of anaerobic fermentation technology, both domestically and internationally, is from single-stage to multi-stage. Industrial applications have been achieved, including two-phase fermentation (hydrogen-producing and methanogenic phases) and two-stage fermentation (first-stage dry fermentation and second-stage wet fermentation). The most classic biotransformation process theory of anaerobic fermentation, both domestically and internationally, is the "three-stage" theory. (See attached...) Figure 1 As shown, the hydrolysis and fermentation stage is mainly carried out by microorganisms that secrete various hydrolytic enzymes, degrading various biomolecules into small biomolecules such as monosaccharides. Microorganisms at this stage typically possess a certain degree of acid and oxygen tolerance. The hydrogen- and acetic acid-producing stage is mainly carried out by acid-producing bacteria, which gradually convert soluble small molecules such as glucose into acetic acid. Microorganisms at this stage typically have good acid tolerance. The methanogenesis stage is mainly carried out by methanogens, which convert the acetic acid produced in the acidogenesis stage into methane and carbon dioxide. Microorganisms at this stage typically require a neutral pH and are strictly anaerobic. Microorganisms at different stages progressively convert organic matter into biogas.

[0005] Multi-stage fermentation technology can divide the fermentation process into stages such as hydrolysis, acid production, and methanogenesis, and each stage can be controlled to have its own optimized microbial community and optimal fermentation conditions, resulting in higher fermentation efficiency and stability compared to single-stage fermentation. However, how to design the stages of multi-stage anaerobic fermentation to achieve efficient operation remains an unsolved problem. Summary of the Invention

[0006] The purpose of this invention is to provide a method for controlling the anaerobic fermentation grading through intermediate product feedback, so as to solve the technical problem that existing multi-stage anaerobic fermentation cannot effectively grade the anaerobic products.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: Based on the multi-stage anaerobic fermentation process, which includes hydrolysis, acid production, and methanogenesis stages, this application provides a method for controlling the anaerobic fermentation stage through intermediate product feedback. The method includes: Hydrolysis stage: Based on the hydrolysis characteristics of the fermentation material, it is divided into a single-stage hydrolysis reactor or a two-stage hydrolysis reactor; the hydraulic residence time of the single-stage hydrolysis reactor or the two-stage hydrolysis reactor is determined based on the content of monomolecular organic matter in the hydrolysis products. Acid production stage: Based on the acid production characteristics of the hydrolysis products, it is divided into a primary acid production reactor or a secondary acid production reactor; the hydraulic retention time of the primary acid production reactor or the secondary acid production reactor is determined based on the acetic acid content; Methanogenesis stage: The reactor is set as a single-stage methanogenesis reactor, and the hydraulic residence time of the reactor is determined based on the conversion rate of acetic acid.

[0008] The present invention has the following beneficial effects: In this application, the number of hydrolysis stages is divided according to the hydrolysis characteristics of the fermentation material, the number of acid production stages is divided according to the acid production characteristics of the hydrolysis products, and the methanogenesis stage is set as a first-stage methanogenesis reactor, providing a classification node for each stage of anaerobic fermentation, which can realize the efficient and stable operation of multi-stage anaerobic fermentation, and the method is simple and easy to implement. Attached Figure Description

[0009] Figure 1 This is a theoretical diagram of the three stages of the biotransformation process in anaerobic fermentation at the present stage. Detailed Implementation

[0010] The multi-stage anaerobic fermentation in this application refers to fermentation that includes attached... Figure 1 The anaerobic fermentation process includes a hydrolysis stage, an acid-producing stage, and a methanogenic stage. Based on this multi-stage anaerobic fermentation, this application provides a method for controlling the anaerobic fermentation stage through intermediate product feedback, the method comprising: Hydrolysis stage: Based on the hydrolysis characteristics of the fermentation material, it is divided into a single-stage hydrolysis reactor or a two-stage hydrolysis reactor; the hydraulic residence time of the single-stage or two-stage hydrolysis reactor is determined based on the content of monomolecular organic matter in the hydrolysis products.

[0011] Specifically, starches, lipids, and proteins generally hydrolyze faster, while cellulose hydrolyzes slower. The raw materials for anaerobic fermentation are typically kitchen waste, livestock and poultry manure, and straw. Kitchen waste mainly consists of food scraps and is easily hydrolyzed. Livestock and poultry manure includes chicken manure, pig manure, and cow manure. Chicken and pig manure are easily hydrolyzed because they do not contain cellulose, while cow manure is slightly less hydrolyzable due to its higher cellulose content. Straw also contains a large amount of lignocellulose, which is difficult to hydrolyze. Therefore, when the fermentation material is easily hydrolyzable materials such as kitchen waste, chicken manure, or pig manure, the hydrolysis reactor is a primary hydrolysis reactor. When the fermentation material is difficult-to-hydrolyze materials such as straw, or a mixture of easily and difficult-to-hydrolyze materials, the hydrolysis reactor is a secondary hydrolysis reactor.

[0012] After hydrolysis, fermentation materials produce single-molecule organic compounds such as glucose, amino acids, or fatty acids. In this application, the hydraulic residence time of a single-stage or two-stage hydrolysis reactor is determined by the content of these single-molecule organic compounds. Specifically, when the content of the produced single-molecule organic compounds is 60-65% of the theoretical content, the hydrolysis time is the hydraulic residence time of either the single-stage or two-stage hydrolysis reactor.

[0013] Acid production stage: Based on the acid production characteristics of the hydrolysis products, it is divided into a primary acid production reactor or a secondary acid production reactor; the hydraulic residence time of the primary acid production reactor or the secondary acid production reactor is determined based on the acetic acid content.

[0014] Specifically, after the hydrolysis stage, the fermentation material forms small-molecule hydrolysis products such as reducing sugars, amino acids, fatty acids, or oils. Among these hydrolysis products, the difficulty of converting reducing sugars, amino acids, and fatty acids / oils into acetic acid increases sequentially, thus prolonging the acid-producing stage. Based on this, the acid-producing reactor can be classified as a primary or secondary acid-producing reactor by detecting the content of reducing sugars, amino acids, fatty acids, and oils in the hydrolysis products. That is, when the content of reducing sugars or amino acids in the hydrolysis products is greater than the content of fatty acids or oils, the acid-producing reactor is a primary acid-producing reactor; when the content of fatty acids or oils in the hydrolysis products is greater than the content of reducing sugars or amino acids, the acid-producing reactor is a secondary acid-producing reactor.

[0015] In this application, the hydraulic residence time of the primary or secondary acid-producing reactor is determined based on the acetic acid content. Specifically, the acetic acid content is measured, and the time it takes for the acetic acid content to reach equilibrium is defined as the hydraulic residence time of the primary or secondary acid-producing reactor.

[0016] Methanogenesis stage: Set as primary methanogenesis, the hydraulic residence time of the methanogenesis reactor is determined based on the conversion rate of acetic acid.

[0017] Specifically, compared to the hydrolysis and acidification stages, the methanogenesis reaction is slower, and the hydraulic residence time is relatively longer. Therefore, in this application, the methanogenesis reactor is set as a single-stage methanogenesis reactor. Furthermore, in this application, the hydraulic residence time of the methanogenesis reactor is determined based on the conversion rate of acetic acid. Specifically, the conversion rate of acetic acid is measured, and when the conversion rate reaches 92-96%, the acetic acid conversion time is taken as the hydraulic residence time of the methanogenesis reactor.

[0018] In this application, based on the composition and biodegradation characteristics of the fermentation materials, multi-stage anaerobic fermentation is typically set to 3-5 stages, with each stage of reactor interconnected. Continuous anaerobic fermentation is carried out according to the hydraulic retention time determined when each stage of reactor reacts independently. Furthermore, during continuous fermentation, each stage of reactor contains acclimatized, optimized microbial communities adapted to each stage and with optimal fermentation conditions.

[0019] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0020] Example 1 This application provides a method for controlling the anaerobic fermentation stage through intermediate product feedback, the method comprising: Hydrolysis Stage: Kitchen waste was used as the fermentation material. Since the components of kitchen waste are generally easily hydrolyzed, the hydrolysis reactor was set as a single-stage hydrolysis reactor. Kitchen waste and hydrolytic microorganisms were added to the single-stage hydrolysis reactor for fermentation. Theoretical calculations showed that the theoretical content of reducing sugars in kitchen waste was 100 g / L. After two days of hydrolysis, the reducing sugar content in the kitchen waste was measured at 60 g / L, reaching 60% of the theoretical content. Based on this, the hydraulic retention time of the single-stage hydrolysis reactor was set to 2 days.

[0021] Acidification Stage: The material from the primary hydrolysis reactor is transferred to the acidification reactor. Due to the easily acidified nature of kitchen waste, the acidification reactor is designated as a primary acidification reactor. Acid-producing microorganisms and the hydrolyzed material are simultaneously added to the primary acidification reactor for fermentation. Acetic acid content is monitored during fermentation to determine if an equilibrium state has been reached. After 4 days of fermentation, the acetic acid content was found to have reached equilibrium. Based on this, the hydraulic retention time of the primary acidification reactor is set to 4 days.

[0022] Methanogenesis Stage: The methanogenic reactor was designated as a primary methanogenic reactor. The material from the primary acidogenic reactor was transferred to the primary methanogenic reactor, and acclimatized methanogenic bacteria were added to initiate anaerobic methanogenesis. The initial acetic acid content was measured at 10 g / L. Acetic acid content was monitored during fermentation to determine if the degradation rate reached 95%. After 7 days of fermentation, the acetic acid content was found to be as low as 500 mg / L, indicating a 95% degradation rate. Based on this, the hydraulic retention time of the primary methanogenic reactor was set at 7 days.

[0023] Finally, the volume ratio of each reactor was calculated according to their respective hydraulic retention times, and the first-stage hydrolysis reactor, the first-stage acid-producing reactor, and the first-stage methanogenic reactor were connected in sequence for continuous fermentation, and the fermentation system gradually stabilized.

[0024] Example 2 This application provides a method for controlling the anaerobic fermentation stage through intermediate product feedback, the method comprising: Hydrolysis Stage: Organic household waste and straw were used as fermentation materials. Since the food waste portion of the organic household waste is easily hydrolyzed, while straw is difficult to hydrolyze, the hydrolysis reactor was designed as a two-stage reactor. The mixture of organic household waste and straw, along with hydrolytic microorganisms, was added to the first-stage hydrolysis reactor for fermentation. The easily hydrolyzable components of the organic household waste were hydrolyzed in the first-stage reactor, while most of the straw was not fully hydrolyzed. The material from the first-stage reactor then flowed into the second-stage reactor for further hydrolysis. Theoretical calculations showed that the theoretical content of reducing sugars in the organic household waste was 50 g / L. After two days of hydrolysis, the reducing sugar content in the first-stage reactor was measured at 30 g / L, reaching 60% of the theoretical content of organic household waste. Based on this, the hydraulic retention time in the first-stage hydrolysis reactor was set to 2 days. Theoretical calculations showed that the theoretical content of reducing sugars in the straw was 100 g / L. After 6 days of hydrolysis, the reducing sugar content in the second-stage hydrolysis reactor increased to 90 g / L, reaching 60% of the theoretical content of the total raw materials. Based on this, the hydraulic residence time of the second-stage hydrolysis reactor was set to 4 days, and the total hydraulic residence time of the hydrolysis stage was set to 6 days.

[0025] Acidification Stage: The material from the second-stage hydrolysis reactor is transferred to the acidification reactor. The hydrolysis products of organic household waste and straw have a complex composition, mainly including small molecules such as fatty acids, amino acids, and monosaccharides. Monosaccharides and amino acids are relatively easy to convert into acetic acid, but the conversion rate of fatty acids and residual lignocellulose from the hydrolysis stage to acetic acid is relatively slow. Therefore, a two-stage acidification reactor is considered. Acid-producing microorganisms and the hydrolyzed material are simultaneously added to the first-stage acidification reactor for fermentation. Acetic acid content is monitored during fermentation. When the acetic acid content reaches a temporary equilibrium state after 2 days of fermentation, the hydraulic retention time of the first-stage acidification reactor is set to 2 days. The material from the first-stage acidification reactor continues to ferment in the second-stage acidification reactor. After another 2 days of fermentation, the acetic acid content reaches an equilibrium state. Based on this, the hydraulic retention time of the second-stage acidification reactor is set to 2 days, for a total hydraulic retention time of 4 days for the acidification stage.

[0026] Methanogenesis Stage: The methanogenic reactor was designated as the primary methanogenic reactor. The material from the secondary acidogenic reactor was transferred to the primary methanogenic reactor, and acclimatized methanogenic bacteria were added to initiate anaerobic methanogenesis. The initial acetic acid content was measured at 10 g / L. Acetic acid content was monitored during fermentation to determine if the degradation rate reached 95%. After 7 days of fermentation, the acetic acid content was found to be as low as 500 mg / L, indicating a 95% degradation rate. Based on this, the hydraulic retention time of the primary methanogenic reactor was set at 7 days.

[0027] Finally, the volume ratio of each reactor was calculated according to their respective hydraulic retention times, and the first-stage hydrolysis reactor, the first-stage acid-producing reactor, and the first-stage methanogenic reactor were connected in sequence for continuous fermentation, and the fermentation system gradually stabilized.

[0028] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for controlling anaerobic fermentation fractionation through intermediate product feedback, characterized in that, The anaerobic fermentation includes a hydrolysis stage, an acid production stage, and a methanogenesis stage, and the method includes: Hydrolysis stage: Based on the hydrolysis characteristics of the fermentation material, it is divided into a single-stage hydrolysis reactor or a two-stage hydrolysis reactor; the hydraulic residence time of the single-stage hydrolysis reactor or the two-stage hydrolysis reactor is determined based on the content of monomolecular organic matter in the hydrolysis products. Acid production stage: Based on the acid production characteristics of the hydrolysis products, it is divided into a primary acid production reactor or a secondary acid production reactor; the hydraulic retention time of the primary acid production reactor or the secondary acid production reactor is determined based on the acetic acid content; Methanogenesis stage: The reactor is set as a single-stage methanogenesis reactor, and the hydraulic residence time of the reactor is determined based on the conversion rate of acetic acid.

2. The method for controlling anaerobic fermentation fractionation through intermediate product feedback according to claim 1, characterized in that, The classification of the fermentation material into a single-stage or two-stage hydrolysis reactor includes: If the fermentation material is easily hydrolyzed, then the hydrolysis reactor is a primary hydrolysis reactor; the easily hydrolyzed material includes kitchen waste, chicken manure, or pig manure; If the fermentation material is a difficult-to-hydrolyze material or a mixture of easily hydrolyzable and difficult-to-hydrolyze materials, then the hydrolysis reactor is a two-stage hydrolysis reactor; the difficult-to-hydrolyze material includes cow dung or straw.

3. The method for controlling anaerobic fermentation fractionation through intermediate product feedback according to claim 1, characterized in that, The hydraulic residence time of a single-stage or two-stage hydrolysis reactor is determined based on the content of monomolecular organic matter in the hydrolysis products. When the content of monomolecular organic matter in the hydrolysis products is 60-65% of the theoretical content, the hydrolysis time is the hydraulic residence time of the single-stage or two-stage hydrolysis reactor.

4. The method for controlling anaerobic fermentation fractionation through intermediate product feedback according to claim 1, characterized in that, Based on the acid-producing characteristics of the hydrolysis products, the reactors are classified into primary acid-producing reactors or secondary acid-producing reactors, including: If the content of reducing sugars or amino acids in the hydrolysis products is greater than the content of fatty acids or oils, then the acid-producing reactor is a first-stage acid-producing reactor. When the content of fatty acids or oils in the hydrolysis products is greater than the content of reducing sugars or amino acids, the acid-producing reactor is a secondary acid-producing reactor.

5. The method for controlling anaerobic fermentation fractionation through intermediate product feedback according to claim 1, characterized in that, The hydraulic residence time of a primary or secondary acid-producing reactor is determined based on the acetic acid content. This includes the time it takes for the acetic acid content to reach equilibrium.

6. The method for controlling anaerobic fermentation fractionation through intermediate product feedback according to claim 1, characterized in that, The hydraulic residence time of the methanogenic reactor is determined based on the conversion rate of acetic acid, including when the conversion rate of acetic acid reaches 92-96%, the acetic acid conversion time is the hydraulic residence time of the methanogenic reactor.

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