Process for preparing biogas by resource utilization of potato starch wastewater and waste residues

Abstract

The invention relates to the technical field of potato starch wastewater and waste residue treatment, in particular to a process for preparing biogas through resource utilization of potato starch wastewater and waste residues. Comprising the following steps: collecting potato starch waste residues and wastewater, crushing the potato starch waste residues, mixing the crushed potato starch waste residues with the wastewater, adjusting the solid content to 8-12% to obtain a mixed liquid, carrying out heat treatment on the mixed liquid, cooling, adding a compound enzyme preparation, and adding a nitrogen material to adjust the carbon-nitrogen ratio to obtain a pretreated raw material; adding the pretreated raw materials into an acidogenic phase reactor for hydrolysis and acidification, then pumping the pretreated raw materials into a methanogenic phase reactor to produce methane, and collecting and purifying biogas generated at the top of the methanogenic reactor by a gas collecting cover and storing the biogas in a gas storage cabinet. The biogas prepared by the biogas preparation process is high in yield, the content of methane in unpurified biogas is high, and subsequent purification is convenient.

Description

Technical Field

[0001] This application relates to the field of potato starch wastewater and waste residue treatment technology, specifically to a process for resource utilization of potato starch wastewater and waste residue to prepare biogas. Background Technology

[0002] Potato starch processing generates large amounts of high-concentration organic wastewater and solid waste residue, which are characterized by high chemical oxygen demand (COD), strong acidity, and easy biodegradation. Improper treatment can cause serious environmental pollution. Traditional treatment methods, such as aerobic biological treatment, are energy-intensive and cannot achieve resource recovery. Anaerobic digestion technology can convert such organic waste into biogas, achieving energy recovery and representing a more sustainable treatment approach. However, conventional single-phase anaerobic digestion processes have significant limitations due to the characteristics of potato starch wastewater and residue. First, the complex organic matter in the raw materials hydrolyzes slowly, limiting overall gas production efficiency. Second, this waste is prone to rapid hydrolysis and acidification during digestion, leading to a large accumulation of volatile fatty acids in the reactor, causing a rapid drop in the system pH, severely inhibiting or even poisoning the activity of methanogens, resulting in process instability and even rancidity. Therefore, developing an integrated process that can deeply enhance hydrolysis and mitigate the risk of acid inhibition is of great significance for the efficient and stable energy utilization of potato starch wastewater and residue. Summary of the Invention

[0003] To address the aforementioned issues, the purpose of this application is to provide a process for the resource utilization of potato starch wastewater and residue to produce biogas. This process yields high biogas production, and the unpurified biogas has a high methane content, making subsequent purification convenient.

[0004] To achieve the above objectives, this application provides a process for the resource utilization of potato starch wastewater and waste residue to produce biogas, comprising the following steps: S1. Collect potato starch waste residue and wastewater, crush the potato starch waste residue, mix it with the wastewater, adjust the solid content to 8-12%, obtain a mixed liquid, heat treat the mixed liquid, add compound enzyme preparation after cooling, and then add nitrogen to adjust the carbon-nitrogen ratio to obtain pretreated raw materials. In the above process, crushing potato starch waste can increase the specific surface area, which is beneficial for subsequent hydrolysis. Heat treatment can effectively destroy the cellulose structure, dissolve more organic matter, and improve the subsequent hydrolysis rate. Adding compound enzyme preparations can specifically improve the hydrolysis efficiency of waste residue. Amylase quickly opens the starch coating, and cellulase attacks the fiber structure, improving the hydrolysis efficiency of the substrate and increasing biogas production.

[0005] S2. The pretreated raw materials are added to the acid-producing phase reactor for hydrolysis and acidification, and then pumped to the methanogenic phase reactor to produce methane. The biogas produced at the top of the methanogenic reactor is collected by a gas collection hood, purified, and stored in a gas storage tank.

[0006] In the above process, the acid-producing phase and the methanogenic phase are separated, and the hydrolytic acidifying bacteria and methanogenic bacteria are placed in two independent reactors to create the most suitable growth environment for each of them. Under optimal conditions, the acid-producing phase can more quickly and thoroughly convert complex organic matter into volatile fatty acids; while the methanogenic phase can efficiently and specifically convert volatile fatty acids into methane, thereby improving biogas yield and biogas purity.

[0007] Furthermore, the pulverization is carried out to a particle size ≤10mm.

[0008] Furthermore, the mixture consists of potato starch waste residue and wastewater mixed at a mass ratio of 1-2:10-15.

[0009] Furthermore, the heat treatment is performed by heating to 60-70°C and holding for 30-60 minutes.

[0010] Furthermore, the compound enzyme preparation is composed of α-amylase and cellulase, with the mass ratio of α-amylase to cellulase being 1:3-4.

[0011] Furthermore, the addition of nitrogen feed to adjust the carbon-nitrogen ratio involves adding livestock and poultry manure or urea to adjust the carbon-nitrogen ratio to 20-30:1.

[0012] Furthermore, the hydrolysis and acidification are carried out under the following conditions: temperature 30-35℃, pH value adjusted to 5.5-6.0, stirring speed 20-30 rpm, and reaction time 1.5-2.5 days.

[0013] Furthermore, the methanogenic reactor is an internal circulation reactor, and 40-45% of the reactor volume is inoculated with granular sludge or flocculent anaerobic sludge.

[0014] Furthermore, the methane production process is carried out under the following conditions: temperature 30-35℃, pH value adjusted to 6.8-7.4, and reaction time 15-20 days.

[0015] In summary, this application has the following beneficial effects: This application transforms waste into energy and resources through a series of meticulously designed steps, each contributing unique and crucial value. Crushed potato residue is mixed with wastewater, and after heat treatment and compound enzyme hydrolysis, a pre-digested meal is prepared for microorganisms, enabling faster and more thorough initiation of subsequent anaerobic fermentation. The acid-producing phase confines the acidification process, which could easily damage the system, within a dedicated reactor, transforming it into a controllable and beneficial production step. Optimized environment promotes efficient production of substrates most readily available to methanogens by acid-producing bacteria, laying the foundation for high methanogenesis rates. The acid-producing and methanogenesis phases are linked, allowing methanogens to operate in an optimal, substrate-rich environment, resulting in high methane yields and high biogas purity. Detailed Implementation

[0016] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this invention.

[0017] The α-amylase involved in the specific embodiments of this application was purchased from Xiasheng Biotechnology Development Co., Ltd., catalog number: Xiasheng FDG-2231, with 10,000 enzyme activities; the cellulase was purchased from Xiasheng Biotechnology Development Co., Ltd., catalog number: Xiasheng FDG-2225, with 11,000 enzyme activities.

[0018] Example 1 A process for resource-based utilization of potato starch wastewater and waste residue to produce biogas includes the following steps: S1. Collect potato starch waste residue and wastewater. Crush the potato starch waste residue to a particle size of 5mm using a crusher. Then mix it with wastewater at a mass ratio of 1:10, adjust the solid content to 8%, and the total weight to 1 ton to obtain a mixed liquid. Then heat it to 60℃ and hold for 40 minutes. Cool it down to 30℃ and add 0.2% of the total mass of the mixed liquid with a compound enzyme preparation (α-amylase:cellulase mass ratio of 1:3). Then adjust the pH value to 5 and treat for 2 hours. After that, add urea to adjust the carbon-nitrogen ratio to 20:1 to obtain the pretreated raw material. S2. The pretreated raw materials are added to a fully mixed reactor for hydrolysis and acidification (temperature 30℃, pH 5.5, stirring speed 25 rpm, reaction time 2 days). Then, they are pumped to an internal circulation reactor (inoculated with 40% of the reactor volume of flocculent anaerobic sludge) to produce methane (temperature 30℃, pH adjusted to 6.8, reaction time 20 days). The biogas produced at the top of the reactor is collected by a gas collection hood. The biogas is purified by dehydration, desulfurization, and decarbonization, compressed, and stored in a gas storage tank.

[0019] Example 2 A process for resource-based utilization of potato starch wastewater and waste residue to produce biogas includes the following steps: S1. Collect potato starch waste residue and wastewater. Crush the potato starch waste residue to a particle size of 5mm using a crusher. Then mix it with wastewater at a mass ratio of 1:12, adjust the solid content to 10%, and the total weight to 1 ton to obtain a mixed liquid. Then heat it to 65℃ and hold for 40 minutes. Cool it down to 33℃ and add 0.5% of the total mass of the mixed liquid with a compound enzyme preparation (α-amylase:cellulase mass ratio of 1:3). Then adjust the pH value to 5.5 and treat for 2.5 hours. After that, add urea to adjust the carbon-nitrogen ratio to 25:1 to obtain the pretreated raw material. S2. The pretreated raw materials are added to a fully mixed reactor for hydrolysis and acidification (temperature 33℃, pH 6.0, stirring speed 25 rpm, reaction time 2 days). Then, they are pumped to an internal circulation reactor (inoculated with 40% of the reactor volume of flocculent anaerobic sludge) to produce methane (temperature 33℃, pH adjusted to 7, reaction time 20 days). The biogas produced at the top of the reactor is collected by a gas collection hood. The biogas is purified by dehydration, desulfurization, and decarbonization, compressed, and stored in a gas storage tank.

[0020] Example 3 A process for resource-based utilization of potato starch wastewater and waste residue to produce biogas includes the following steps: S1. Collect potato starch waste residue and wastewater. Crush the potato starch waste residue to a particle size of 5mm using a crusher. Then mix it with wastewater at a mass ratio of 1:15, adjust the solid content to 12%, and the total weight to 1 ton to obtain a mixed liquid. Then heat it to 70℃ and hold for 40 minutes. Cool it down to 35℃ and add 0.8% of the total mass of the mixed liquid with a compound enzyme preparation (α-amylase:cellulase mass ratio of 1:4). Then adjust the pH value to 5.5 and treat for 3 hours. After that, add urea to adjust the carbon-nitrogen ratio to 30:1 to obtain the pretreated raw material. S2. The pretreated raw materials are added to a fully mixed reactor for hydrolysis and acidification (temperature 35℃, pH 6.0, stirring speed 25 rpm, reaction time 2 days). Then, they are pumped to an internal circulation reactor (inoculated with 40% of the reactor volume of flocculent anaerobic sludge) to produce methane (temperature 35℃, pH adjusted to 7.4, reaction time 20 days). The biogas produced at the top of the reactor is collected by a gas collection hood. The biogas is purified by dehydration, desulfurization, and decarbonization, compressed, and stored in a gas storage tank.

[0021] Compare with Example 1 The difference between this comparative example and Example 3 is that the mass ratio of α-amylase to cellulase is 1:5. This comparative example describes a process for resource-based utilization of potato starch wastewater and waste residue to produce biogas, which includes the following steps: S1. Collect potato starch waste residue and wastewater. Crush the potato starch waste residue to a particle size of 5mm using a crusher. Then mix it with wastewater at a mass ratio of 1:15, adjust the solid content to 12%, and the total weight to 1 ton to obtain a mixed liquid. Then heat it to 70℃ and hold for 40 minutes. Cool it down to 35℃ and add 0.8% of the total mass of the mixed liquid with a compound enzyme preparation (α-amylase:cellulase mass ratio of 1:5). Then adjust the pH value to 5.5 and treat for 3 hours. After that, add urea to adjust the carbon-nitrogen ratio to 30:1 to obtain the pretreated raw material. S2. The pretreated raw materials are added to a fully mixed reactor for hydrolysis and acidification (temperature 35℃, pH 6.0, stirring speed 25 rpm, reaction time 2 days). Then, they are pumped to an internal circulation reactor (inoculated with 40% of the reactor volume of flocculent anaerobic sludge) to produce methane (temperature 35℃, pH adjusted to 7.4, reaction time 20 days). The biogas produced at the top of the reactor is collected by a gas collection hood. The biogas is purified by dehydration, desulfurization, and decarbonization, compressed, and stored in a gas storage tank.

[0022] Compare with Example 2 The difference between this comparative example and Example 3 is that this comparative example provides a process for resource utilization of potato starch wastewater and waste residue to produce biogas, which includes the following steps: S1. Collect potato starch waste residue and wastewater. Crush the potato starch waste residue to a particle size of 5mm using a crusher. Then mix it with wastewater at a mass ratio of 1:15, adjust the solid content to 12%, and the total weight to 1 ton to obtain a mixed liquid. Then heat it to 70℃ and hold for 40 minutes. Cool it down to 35℃ and add 0.8% of the total mass of the mixed liquid with a compound enzyme preparation (α-amylase:cellulase mass ratio of 1:4). Then adjust the pH value to 5.5 and treat for 3 hours. After that, add urea to adjust the carbon-nitrogen ratio to 30:1 to obtain the pretreated raw material. S2. Add the pretreated raw materials to the internal circulation reactor (inoculate 40% of the reactor volume with flocculent anaerobic sludge) to produce methane (temperature 35℃, pH value adjusted to 7.4, reaction time 20 days). The biogas produced at the top of the reactor is collected by a gas collection hood. The biogas is purified by dehydration, desulfurization, and decarbonization, compressed, and stored in a gas storage tank.

[0023] Performance testing Functional tests were performed on the preparation processes of Examples 1-3 and Comparative Examples 1-2.

[0024] Unpurified biogas purity test: Use a portable infrared biogas analyzer to detect the methane content in biogas and calculate the methane purity; Biogas production testing: The biogas content produced per ton of substrate was measured using a turbine flow meter for the preparation processes of Examples 1-3 and Control Examples 1-2. The test results are shown in Table 1. Table 1

[0025] As shown in Table 1, the biogas produced by the process of this application embodiment has a high methane content and a high biogas yield when it is not purified. The difference between Comparative Example 1 and Example 3 is that the mass ratio of α-amylase to cellulase is 1:5. The results show that the biogas yield is lower than that of Example 3, and the methane content in the unpurified biogas is lower than that of Example 3. Compared with Example 3, Comparative Example 2 only used one reactor, and the test results show that the methane purity and biogas yield are relatively low.

[0026] The above description is merely an example and illustration of the concept of this application. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined in the claims, they should all fall within the protection scope of this application.

Claims

1. A process for resource-based utilization of potato starch wastewater and waste residue to produce biogas, characterized in that, Includes the following steps: S1. Collect potato starch waste residue and wastewater, crush the potato starch waste residue, mix it with the wastewater, adjust the solid content to 8-12%, obtain a mixed liquid, heat treat the mixed liquid, add compound enzyme preparation after cooling, and then add nitrogen to adjust the carbon-nitrogen ratio to obtain pretreated raw materials. S2. The pretreated raw materials are added to the acid-producing phase reactor for hydrolysis and acidification, and then pumped to the methanogenic phase reactor to produce methane. The biogas produced at the top of the methanogenic reactor is collected by a gas collection hood, purified, and stored in a gas storage tank.

2. The process for preparing biogas from potato starch wastewater and residue according to claim 1, characterized in that, The pulverization process involves pulverizing particles to a size ≤10mm.

3. The process for preparing biogas from potato starch wastewater and residue according to claim 1, characterized in that, The mixture is made by mixing potato starch waste residue and wastewater at a mass ratio of 1-2:10-15.

4. The process for preparing biogas from potato starch wastewater and residue according to claim 1, characterized in that, The heat treatment is performed by heating to 60-70°C and holding for 30-60 minutes.

5. The process for preparing biogas from potato starch wastewater and residue according to claim 1, characterized in that, The compound enzyme preparation consists of α-amylase and cellulase, with a mass ratio of α-amylase to cellulase of 1:3-4.

6. The process for preparing biogas from potato starch wastewater and residue according to claim 1, characterized in that, The addition of nitrogen feed adjusts the carbon-nitrogen ratio, and the addition of livestock and poultry manure or urea adjusts the carbon-nitrogen ratio to 20-30:

1.

7. The process for preparing biogas from potato starch wastewater and residue according to claim 1, characterized in that, The hydrolysis and acidification are performed under the following conditions: temperature 30-35℃, pH adjusted to 5.5-6.0, stirring speed 20-30 rpm, and reaction time 1.5-2.5 days.

8. The process for preparing biogas from potato starch wastewater and residue according to claim 1, characterized in that, The methanogenic reactor is an internal circulation reactor, and is inoculated with 40-45% of the reactor volume with granular sludge or flocculent anaerobic sludge.

9. The process for preparing biogas from potato starch wastewater and residue according to claim 1, characterized in that, The methane production process involves a reaction temperature of 30-35°C, a pH value adjusted to 6.8-7.4, and a reaction time of 15-20 days.

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