A straw wet anaerobic fermentation + aerobic fermentation combined treatment device and method

Abstract

A straw wet anaerobic fermentation + aerobic fermentation combined treatment device and method, belonging to the technical field of using straw anaerobic fermentation to produce biogas. The biogas liquid transported from the outside enters the biogas liquid storage tank for temporary storage, enters the hydrolysis tank through a pump, and the straw enters the straw crusher through a loading tool. The crushed straw enters the hydrolysis tank through a belt conveyor. The straw and the biogas liquid tank are fully hydrolyzed and acidified, and hydrolytic enzymes are added at the same time. After hydrolysis and acidification, aerobic fermentation products are separated by a type I solid-liquid separator. The separated solid enters a pipeline pulping machine, and all the slurry enters a type II solid-liquid separator. After solid-liquid separation, the solid part, i.e., cellulose and hemicellulose, enter the aerobic fermentation organic fertilizer production workshop, and the liquid part enters the temporary storage tank and enters the anaerobic fermentation tank through a pump. The produced biogas is used externally, and the produced biogas liquid is refluxed. This application can consume a large amount of biogas liquid, without biogas liquid discharge, and the hydraulic retention time of straw anaerobic fermentation is shortened from 48 days to about 22 days.

Description

Technical Field

[0001] The present invention relates to the technical field of biogas production by anaerobic fermentation of straw, which is used to consume biogas slurry (or livestock and poultry manure) without generating biogas slurry, and at the same time avoid the difficult-to-decompose cellulose from entering the anaerobic fermentation process, and the cellulose is used for aerobic composting. Specifically, it is a straw wet anaerobic fermentation + aerobic fermentation combined treatment device and method. Background Art

[0002] Whether it is rice straw and energy crops in the south or corn straw and wheat straw in the north, my country has a large output and is agricultural waste. It has had a great adverse impact on the environment and is difficult to utilize as a resource. It is necessary to develop and fill the gap in straw resource utilization technology. Using straw as a raw material to produce biogas using anaerobic fermentation technology is a good development direction, but the bottleneck restricting the development of technology is that the cellulose in the straw is difficult and time-consuming to decompose. At the same time, wet anaerobic fermentation technology has a high gas production rate, but the bottleneck restricting the development of technology is that it will produce a large amount of biogas (liquid with high ammonium nitrogen content and high COD content) that cannot be treated.

[0003] Therefore, solving the problem of straw anaerobic fermentation technology and reducing the production of biogas has become an important research direction. The current research approaches are mainly concentrated on the following three points: (1) Straw dry anaerobic fermentation technology. (2) Increasing the hydraulic retention time of anaerobic fermentation. (3) Facultative aerobic hydrolysis technology. The rumen of a bionic cow is used to pretreat the straw, hydrolyze and ferment cellulose and hemicellulose into volatile fatty acids. In this process, biological enzymes and facultative bacteria play an important role. The main function of this technology is to improve the cellulose decomposition capacity and increase the biogas production of the anaerobic fermentation process.

[0004] In the technology of producing biogas by anaerobic fermentation of straw, how to make full use of resources, shorten the fermentation time, achieve stable gas production, and not produce biogas slurry has become a bottleneck in the development of biogas projects. Summary of the invention

[0005] The present invention relies on efficient straw pulping equipment and slurry separation equipment to develop a technology that separates cellulose and hemicellulose from straw that are not easily decomposed by anaerobic fermentation for aerobic composting, and anaerobic fermentation of the remaining organic matter to produce biogas. The raw materials used in the present invention are straw and biogas slurry, and the products are biogas and organic fertilizer, realizing the comprehensive utilization of agricultural waste. This invention can consume a large amount of biogas slurry, and the project itself no longer produces biogas slurry discharge. This invention can also shorten the hydraulic retention time of straw anaerobic fermentation from 48 days to about 22 days, reducing the investment in the anaerobic fermentation part of projects of the same scale by nearly 50%.

[0006] The purpose of the present invention is to solve the problem through the following solutions:

[0007] The straw wet anaerobic fermentation + aerobic fermentation combined treatment device is characterized in that: the biogas slurry storage tank (1) is connected to the hydrolysis tank (4) via a water inlet pump and a water inlet valve; the loading tool (2) is used to load straw to the straw crusher (3); the straw crusher (3) is connected to the hydrolysis tank (4) via a belt for conveying straw powder; the hydrolysis tank (4) is connected to the I-type solid-liquid separator (5); the liquid outlet of the I-type solid-liquid separator (5) is connected to the hydrolysis tank (4); The solid outlet of the solid-liquid separator (5) is connected to the pipeline pulping machine (6), the pipeline pulping machine (6) is connected to the II solid-liquid separator (7), the solid outlet of the II solid-liquid separator (7) is connected to the aerobic fermentation organic fertilizer production workshop (10), the liquid outlet of the II solid-liquid separator (7) is connected to the temporary storage tank (8), the temporary storage tank (8) is connected to the anaerobic fermentation tank (9) via a valve and a pump, and the bottom of the anaerobic fermentation tank (9) is connected to the hydrolysis tank (4) via a valve;

[0008] The hydrolysis tank (4) is provided with a stirring device inside, and the upper part is connected with a pipeline for dripping cellulose hemicellulose hydrolyzing enzyme, and the pipeline of cellulose hemicellulose hydrolyzing enzyme is provided with a pipeline pump and a flow meter; the hydrolysis tank (4) is provided with a heating device, and an aeration device is provided at the bottom of the hydrolysis tank (4).

[0009] The anaerobic fermentation tank (9) is provided with detection instruments such as a temperature transmitter, a pressure transmitter, a level meter, a material level meter, etc., a gas storage cabinet is provided on the top, and a positive and negative pressure protector is provided on the top.

[0010] The biogas slurry storage tank (1) is connected to the temporary storage tank (8) via a valve, so as to adjust the solid content in the temporary storage tank (8).

[0011] Each of the valves and pumps described above may be connected to a controller, and the controller is used to control the opening and closing of the corresponding valves and pumps.

[0012] The method for combined treatment of wet anaerobic fermentation and aerobic fermentation of straw using the above-mentioned device is characterized by comprising the following steps:

[0013] The biogas liquid transported from outside enters the biogas liquid storage tank (1) for temporary storage, and enters the hydrolysis tank (4) through a pump. The straw enters the straw crusher (3) through a loading tool (2). The crushed straw enters the hydrolysis tank (4) through a belt conveyor. The straw and the biogas liquid tank are fully hydrolyzed and acidified, and hydrolytic enzymes are added at the same time. After hydrolysis and acidification, aerobic fermentation products are separated by a type I solid-liquid separator (5). The separated solid enters a pipeline pulping machine (6), and all the pulp enters a type II solid-liquid separator (7). After solid-liquid separation, the solid part, i.e., cellulose and hemicellulose, enters the aerobic fermentation organic fertilizer production workshop (10), and the liquid part enters the temporary storage tank (8), and enters the anaerobic fermentation tank (9) through a pump. The produced biogas is used externally, and the produced biogas liquid is refluxed;

[0014] The specific processes include:

[0015] (1) Straw crushing and feeding

[0016] According to the designed feed volume and hydraulic retention time of the hydrolysis tank, the straw crushing and feeding time are controlled by weighing; the straw is fed in batches, and the feeding starts when the hydrolysis tank reaches the low level, and stops when the feeding weight or the high level of the hydrolysis tank is reached;

[0017] The particle size of straw crushing is required to be 5-10cm, and basic parameters (solid content, etc.) of each batch of straw are tested;

[0018] (2) Biogas slurry feed

[0019] The biogas slurry feeding time is determined according to the designed water inflow of the hydrolysis tank and the low level height, and the opening and closing of the water inlet pump and the water inlet valve are controlled by the process controller. After the system is started, the water inlet pump and the water inlet valve are started to inject the biogas slurry into the hydrolysis tank. When the preset time or material level is reached, the water inlet pump and the water inlet valve are automatically closed, and the water inlet is finished;

[0020] (3) Hydrolysis and acidification

[0021] After all the feeding is completed, cellulose and hemicellulose hydrolases are added. The amount of hydrolases added is controlled by a pipeline pump and a flow meter. The amount of hydrolases added is 5-25 FPU / g substrate. The stirring device is turned on to immerse the straw completely in the biogas slurry. The hydrolysis process is an anoxic reaction. When the straw is soaked and the water rises, aeration is started and the hydrolysis tank is heated at the same time. The hydraulic retention time is 36-72h. The temperature is controlled at 35-37℃.

[0022] (4) Loading

[0023] After the hydrolysis, acidification and aerobic fermentation processes are completed, there will still be free water in the hydrolysis tank. The materials in the hydrolysis tank are subjected to the first solid-liquid separation. The high-solid content materials enter the pipeline pulping machine for pulping. The pulped materials enter the second solid-liquid separation to separate the cellulose and hemicellulose that are difficult to anaerobically ferment. The remaining slurry is pumped to the temporary storage tank and then pumped into the anaerobic fermentation tank.

[0024] Generally, the solid content of the slurry entering the buffer tank is 12.5%.

[0025] (5) Anaerobic fermentation

[0026] The CSTR anaerobic fermentation process is used, and the solid content in the fermentation tank is 7.83%. The material is continuously fed for several hours every day, and the material is heated by regular external circulation stirring to maintain the temperature in the fermentation tank at 35-38°C. Anaerobic fermentation is carried out; the biogas produced by anaerobic fermentation is treated according to the project requirements; the biogas produced by anaerobic fermentation does not produce NH4 +Enriched, so all can be reused;

[0027] (6) Organic fertilizer

[0028] The straw fiber and hemicellulose fraction after solid-liquid separation in step (4) has a solid content of 30-35% and is directly used for aerobic composting.

[0029] Compared with other straw and biogas slurry treatment technologies, the present invention has the following advantages:

[0030] (1) Compared with other straw treatment technologies, such as incineration power generation, it requires less investment and is energy-saving and environmentally friendly.

[0031] (2) Compared with other biogas slurry treatment technologies, such as ammonium nitrogen removal, membrane treatment, flocculation solid-liquid separation, and evaporation treatment, it has small investment, low operating cost, and is energy-saving and environmentally friendly.

[0032] (3) Compared with other anaerobic fermentation technologies, such as whole straw dry anaerobic and whole straw wet anaerobic, it has small investment, low operating cost, no environmental pollution and high efficiency.

[0033] The whole straw dry anaerobic fermentation technology (solid content 25% to 30%) is still in the development stage due to the poor fluidity of straw and the difficulty in decomposing cellulose. There is no mature and stable technology yet, but it has already shown the characteristics of high input and low output.

[0034] Since straw contains a large amount of cellulose, anaerobic decomposition takes a long time. This technology directly separates the cellulose for aerobic composting. In this way, the anaerobic fermentation time is shortened from about 45 days to about 20 days. For the same raw material processing volume, the facilities and equipment and construction land are reduced by half. At the same time, the initial investment is also reduced by half, and the operating costs are greatly reduced.

[0035] This technology has almost no impact on the amount of biogas and organic fertilizer produced, and improves the rate of return while reducing investment and operating costs.

[0036] The wet anaerobic fermentation technology currently used is difficult to promote because it produces a large amount of biogas slurry that cannot be treated. One of the raw materials used in this technology is biogas slurry. This not only can treat biogas slurry, but also the biogas slurry produced by this project can be fully reused. Not only will it not pollute the environment due to storage, but it will also greatly reduce the difficulty of promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a process flow chart of a straw wet anaerobic fermentation + aerobic fermentation combined treatment technology.

[0038] Figure 2 This is a material balance diagram of the straw wet anaerobic fermentation + aerobic fermentation combined treatment technology of the present invention.

[0039] In the figure: 1 biogas slurry storage tank, 2 loading tool, 3 straw crusher, 4 hydrolysis tank, 5 type I solid-liquid separator, 6 pipeline pulping machine, 7 type II solid-liquid separator, 8 temporary storage tank, 9 anaerobic fermentation tank, 10 organic fertilizer production workshop. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0041] Example 1

[0042] (1) First, the straw (a straw storage tank is provided in the field) is fed into the straw crusher 3 for kneading by the straw loading tool 2 and then fed into the hydrolysis tank 4 by a belt.

[0043] (2) The biogas slurry from outside the site is transported to the biogas slurry storage tank 1 and then pumped into the hydrolysis tank 4 for hydrolysis and acidification treatment.

[0044] (3) The hydrolyzed and acidified material is subjected to the first solid-liquid separation by a type I solid-liquid separator 5.

[0045] (4) Then it enters the pipeline pulping machine 6 to be prepared into slurry. The slurry after pulping enters the second solid-liquid separation, and the cellulose that is difficult to anaerobically ferment is separated and sent to the organic fertilizer workshop. The remaining slurry (solid content 12.5%) is pumped to the temporary storage tank and then pumped into the anaerobic fermentation tank.

[0046] (5) The slurry is subjected to a second solid-liquid separation by a type II solid-liquid separator 7, and the liquid portion enters a temporary storage tank 8 and is pumped and distributed to an anaerobic fermentation tank.

[0047] (6) The slurry is fermented in an anaerobic fermentation tank for 22 days at a fermentation temperature of 35-38°C. The solid content of the material in the fermentation tank is 7.83%. The generated biogas is sent out for purification and decarbonization to produce biogas or for desulfurization and purification to generate electricity. All the biogas liquid is returned to the hydrolysis tank 4 for reuse. The solid content of the straw fiber part after the solid-liquid separation of the organic fertilizer is 30-35%, which is directly used for aerobic composting.

[0048] (7) The cellulose that is difficult to ferment anaerobically is separated after the second solid-liquid separation and is aerobically composted to produce bio-organic fertilizer for export.

[0049] Example 2

[0050] Material balance is introduced with case studies of projects using silage corn straw (TS45%) and biogas slurry (TS5%) as raw materials.

[0051] (1) Raw materials: 120 tons of corn stalks (TS45%) processed per day, 360 tons of biogas slurry (TS5%) consumed per day, 480 tons of total materials per day. The biogas slurry storage tank 1 is insulated at a temperature of about 20°C.

[0052] (2) The hydraulic retention time of the hydrolysis tank is 24 hours, and the TS is 15%.

[0053] (3) After the second solid-liquid separation of the hydrolyzed and acidified materials, the cellulose part used for composting is about 177.91 tons per day (including the solid-liquid separation part after anaerobic fermentation), TS30%, and the part used for anaerobic fermentation is about 360 tons per day, TS10%.

[0054] (4) Anaerobic fermentation produces 10,500 cubic meters of biogas and about 289.25 tons of biogas slurry per day (70.75 tons of biogas slurry is consumed per day), with a TS2%.

[0055] (5) 90.6 tons of organic fertilizer are produced every day.

Claims

1. A straw wet anaerobic fermentation + aerobic fermentation combined treatment device, characterized in that: The biogas slurry storage tank (1) is connected to the hydrolysis tank (4) via a water inlet pump and a water inlet valve; the loading tool (2) is used to load straw into the straw crusher (3); the straw crusher (3) is connected to the hydrolysis tank (4) via a belt for conveying straw powder; the hydrolysis tank (4) is connected to a type I solid-liquid separator (5); the liquid outlet of the type I solid-liquid separator (5) is connected to the hydrolysis tank (4); the solid outlet of the type I solid-liquid separator (5) is connected to a pipeline pulping machine (6); the pipeline pulping machine (6) is connected to a type II solid-liquid separator (7); the solid outlet of the type II solid-liquid separator (7) is connected to an aerobic fermentation organic fertilizer production workshop (10); the liquid outlet of the type II solid-liquid separator (7) is connected to a temporary storage tank (8); the temporary storage tank (8) is connected to an anaerobic fermentation tank (9) via a valve and a pump; the bottom of the anaerobic fermentation tank (9) is connected to the hydrolysis tank (4) via a valve; The hydrolysis tank (4) is provided with a stirring device inside, and a pipeline for dripping cellulose hemicellulose hydrolyzing enzyme is connected to the upper part, and the pipeline of cellulose hemicellulose hydrolyzing enzyme is provided with a pipeline pump and a flow meter; the hydrolysis tank (4) is provided with a heating device, and an aeration device is provided at the bottom of the hydrolysis tank (4); The anaerobic fermentation tank (9) is provided with a temperature transmitter, a pressure transmitter, a level meter, a material level meter, a gas storage cabinet on the top, and a positive and negative pressure protector on the top; The biogas slurry storage tank (1) is connected to the temporary storage tank (8) via a valve, so as to adjust the solid content in the temporary storage tank (8).

2. A straw wet anaerobic fermentation + aerobic fermentation combined treatment device according to claim 1, characterized in that: Each valve and pump is connected to a controller, and the controller is used to control the opening and closing of the corresponding valve and pump.

3. A method for combining wet anaerobic fermentation and aerobic fermentation of straw using the device according to claim 1 or 2, characterized in that: The following steps are involved: The biogas liquid transported from outside enters the biogas liquid storage tank (1) for temporary storage, and enters the hydrolysis tank (4) through a pump. The straw enters the straw crusher (3) through a loading tool (2). The crushed straw enters the hydrolysis tank (4) through a belt conveyor. The straw and the biogas liquid tank are fully hydrolyzed and acidified, and hydrolytic enzymes are added at the same time. After hydrolysis and acidification, aerobic fermentation products are separated by a type I solid-liquid separator (5). The separated solid enters the pipeline pulping machine (6), and all the pulp enters the type II solid-liquid separator (7). After solid-liquid separation, the solid part, i.e., cellulose and hemicellulose, enters the aerobic fermentation organic fertilizer production workshop (10), and the liquid part enters the temporary storage tank (8) and enters the anaerobic fermentation tank (9) through a pump. The produced biogas is used externally, and the produced biogas liquid is refluxed.

4. The method according to claim 3, characterized in that The specific processes include: (1) Straw crushing and feeding According to the designed feed volume and hydraulic retention time of the hydrolysis tank, the straw crushing and feeding time are controlled by weighing; the straw is fed in batches, and the feeding starts when the hydrolysis tank reaches the low level, and stops when the feeding weight or the high level of the hydrolysis tank is reached; The particle size of straw crushing should be 5 to 10 cm; (2) Biogas slurry feed The biogas slurry feeding time is determined according to the designed water inflow of the hydrolysis tank and the low level height, and the opening and closing of the water inlet pump and the water inlet valve are controlled by the process controller. After the system is started, the water inlet pump and the water inlet valve are started to inject the biogas slurry into the hydrolysis tank. When the preset time or material level is reached, the water inlet pump and the water inlet valve are automatically closed, and the water inlet is finished; (3) Hydrolysis and acidification After all the feeding is completed, cellulose and hemicellulose hydrolases are added. The amount of hydrolases added is controlled by a pipeline pump and a flow meter. The stirring device is turned on to immerse the straw completely in the biogas slurry. The hydrolysis process is an anoxic reaction. When the straw is soaked and the water rises, aeration is started and the hydrolysis tank is heated at the same time. The hydraulic retention time is 36-72h. The temperature is controlled at 35-37℃. (4) Loading After the hydrolysis, acidification and aerobic fermentation processes are completed, there will still be free water in the hydrolysis tank. The materials in the hydrolysis tank are subjected to the first solid-liquid separation. The high-solid content materials enter the pipeline pulping machine for pulping. The pulped materials enter the second solid-liquid separation to separate the cellulose and hemicellulose that are difficult to anaerobically ferment. The remaining slurry is pumped to the temporary storage tank and then pumped into the anaerobic fermentation tank. (5) Anaerobic fermentation The CSTR anaerobic fermentation process is adopted, and the solid content in the fermentation tank is 7.83%. The material is continuously fed for several hours every day, and the material is heated while the tank is periodically cycled and stirred for anaerobic fermentation. The biogas produced by anaerobic fermentation is treated according to the project requirements. The biogas produced by anaerobic fermentation will not produce NH3+NH4 + Enriched, so all can be reused; (6) Organic fertilizer The straw fiber and hemicellulose fraction after solid-liquid separation in step (4) has a solid content of 30-35% and is directly used for aerobic composting.

5. The method according to claim 4, characterized in that The amount of hydrolase added in step (3) is 5-25 FPU / g substrate.

6. The method according to claim 4, characterized in that The solid content of the slurry entering the buffer tank in step (4) is 12.5%.

7. The method according to claim 4, characterized in that Step (5) maintaining the temperature in the fermentation tank at 35-38°C.

Images