Multi-source waste comprehensive utilization system with anaerobic digestion coupled with pyrolysis gasification

Abstract

The invention relates to the technical field of waste recycling and comprehensive utilization, in particular to a multi-source waste comprehensive utilization system with anaerobic digestion coupled with pyrolysis gasification. According to the method, high-water-content sludge is added into an anaerobic digestion tank for collaborative anaerobic digestion; in the anaerobic digestion sludge conditioning stage, waste with ultralow water content is added and plays a role of a framework supporting material; in the dehydration stage, wastes with medium water content are added; in the drying stage, waste with low water content is added; before the pyrolysis gasification stage, the waste with ultralow water content and the dried sludge are mixed and granulated. According to the method disclosed by the invention, anaerobic digestion and pyrolysis gasification are coupled, so that comprehensive utilization of wastes with high water content, medium water content, low water content and ultralow water content is realized, emission reduction and utilization of CO2 are realized, meanwhile, the heat value of combustible gas generated by pyrolysis gasification is also improved, the energy output of the system is increased, and the energy consumption of the system is reduced. And saving and comprehensive utilization of resources are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of waste resource recovery and comprehensive utilization, and in particular to a multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification. Background Art

[0002] In recent years, under the policy background of the country's continuous promotion of the construction of "zero-waste cities", the construction of "Beautiful China", and the construction of a waste recycling system, the solid waste treatment and utilization industry has developed rapidly. However, there is currently no systematic method on the market that can achieve the treatment and utilization of organic solid waste from different sources and with different characteristics. Anaerobic digestion and pyrolysis gasification are two typical organic solid waste treatment processes, but due to the different scope of application of the two processes for treating organic solid waste, they are often constructed and operated independently. The anaerobic digestion process can produce biogas. There are two main types of biogas utilization in existing anaerobic digestion projects. One is to directly burn biogas to produce heat or electricity, and the other is to separate and purify biogas and sell it as natural gas. For the technology of directly burning biogas to generate heat or electricity, since biogas contains only about 60% CH4 and the other 40% is non-combustible gases such as CO2, the calorific value is relatively low, which limits the possibility of higher quality utilization; for the technology of selling natural gas after biogas separation and purification, since the CO2 content in biogas is usually around 40%, a large amount of CH4 is collected after biogas separation and purification, and a large amount of CO2 is also produced, but this part of CO2 is often not utilized and enters the atmosphere, exacerbating the greenhouse effect.

[0003] Pyrolysis gasification technology usually uses steam as a gasification agent, but a large amount of energy is required in the steam generation process, resulting in high energy consumption. In fact, CO2 is a good gasification agent. Replacing steam with an appropriate proportion of CO2 can reduce steam consumption and operating energy consumption on the one hand, and on the other hand, the introduced CO2 can react with carbon to increase the proportion of combustible gas in the pyrolysis gas and improve the calorific value of the pyrolysis gas. At the same time, it can realize the reuse of CO2 and reduce greenhouse gas emissions.

[0004] Therefore, if anaerobic digestion and pyrolysis gasification technologies can be coupled and used, it will be possible to achieve high-value utilization of multi-source waste in one system, and greatly improve energy and resource utilization, ultimately achieving the effect of "1+1>2". Summary of the invention

[0005] The purpose of the present invention is to provide a multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification, so as to achieve the coordinated treatment and disposal of multi-source wastes, while increasing energy output and improving energy and resource utilization.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification, comprising an anaerobic digestion tank and a pyrolysis and gasification furnace, wherein the biogas generated in the anaerobic digestion tank is separated and purified to obtain CH4 and CO2, and the CO2 enters the pyrolysis and gasification furnace at the rear end as a gasifying agent; the digested sludge generated in the anaerobic digestion tank is conditioned, dehydrated and dried, and then enters the pyrolysis and gasification furnace, and pyrolysis and gasification reaction is carried out with steam and CO2 as gasifying agents; high-water content waste is added to the anaerobic digestion tank for coordinated anaerobic digestion ; In the conditioning stage, waste with ultra-low moisture content is added as an organic conditioning agent, and the waste with ultra-low moisture content is mixed with the digested sludge after digestion to play the role of skeleton supporting material; in the dehydration stage, waste with medium moisture content is added, and the waste with medium moisture content and the conditioned sludge enter the dehydrator together for dehydration; in the drying stage, waste with low moisture content is used, and the waste with low moisture content and the dehydrated sludge enter the dryer together for further drying; before the pyrolysis gasification stage, waste with ultra-low moisture content is mixed with the dried sludge for granulation.

[0007] Furthermore, the water content of the high-moisture content waste is greater than or equal to 90%, including but not limited to concentrated sludge from sewage treatment plants, kitchen waste squeezed liquid, restaurant kitchen waste liquid, food factory waste liquid and livestock and poultry manure wastewater.

[0008] Furthermore, the medium-moisture waste has a moisture content greater than or equal to 60% and less than 90%, including but not limited to dehydrated sludge, distiller's grains, medicinal residues, and livestock and poultry manure solids.

[0009] Furthermore, the water content of the low-moisture waste is greater than or equal to 30% and less than 60%, including but not limited to dried sludge and garden waste.

[0010] Furthermore, the ultra-low moisture content waste has a moisture content of less than 30%, including but not limited to sawdust, crop straw, rice husk and waste activated carbon.

[0011] Furthermore, in the conditioning stage, the amount of ultra-low moisture content waste added does not exceed 15% of the absolute dry weight of the digested sludge.

[0012] Furthermore, in the dehydration stage, the moisture content of the sludge after dehydration is reduced to below 60%; in the drying stage, the moisture content of the sludge after drying is reduced to below 20%.

[0013] Furthermore, in the pyrolysis and gasification stage, CO2 separated and purified from steam and biogas is used as a gasifying agent in a volume ratio of 8:2, and combustible gas is generated after pyrolysis and gasification. The combustible gas enters the energy utilization system after purification.

[0014] Furthermore, the slag produced after the pyrolysis and gasification is transported out for use as building materials, the generated combustible gas and CH4 separated and purified from the biogas are burned in a gas turbine for power generation, the generated electricity is used for self-use and / or connected to the grid, the exhaust gas after combustion is passed through a waste heat boiler to generate steam for waste heat utilization, and the steam is used to heat the anaerobic digester, provide a gasifying agent and provide a heat source for the drying stage.

[0015] Beneficial effects of the present invention:

[0016] 1. While treating high-water content waste in the anaerobic digester, it can also increase biogas production and energy output; in the conditioning stage, using ultra-low water content materials as organic conditioning agents can also open the digested sludge dehydration channel, reduce the amount of conditioning agents, and increase the calorific value, which is conducive to improving the output and calorific value of the pyrolysis gasification combustible gas at the back end and increasing energy output;

[0017] 2. The system of the present invention can make full use of the CO2 in the biogas produced by anaerobic digestion, realize the capture and reuse of CO2, reduce greenhouse gas emissions, reduce the steam digestion amount in the pyrolysis and gasification process, and increase the output of combustible gas and the calorific value of pyrolysis gas. The system of the present invention shares a set of energy utilization system, which can reduce the investment in equipment, save floor space, and realize the comprehensive regulation of energy demand distribution, which is conducive to energy conservation and comprehensive utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0020] like Figure 1 As shown, concentrated sludge and other high-water content wastes from the sewage treatment plant are mixed and transported to the digestion system. An anaerobic digestion tank is provided in the digestion system. The high-water content wastes are mixed and added to the anaerobic digestion tank for coordinated anaerobic digestion. The generated biogas is separated and purified to obtain CH4 and CO2. CO2 is used as a gasifying agent and enters the pyrolysis gasification furnace at the rear end.

[0021] The digested sludge after anaerobic digestion enters the dehydration and drying system, which includes a conditioning tank, a dehydrator and a dryer. The digested sludge after anaerobic digestion first enters the conditioning tank for conditioning. At the same time, ultra-low moisture content waste is added to the conditioning tank as an organic conditioning agent for conditioning; medium moisture content waste is added to the conditioned sludge, and then it enters the dehydrator for dehydration. After dehydration, the moisture content is reduced to below 60%; after the dehydrated sludge is added with low moisture content waste, it enters the dryer and is dried to a moisture content of less than 20%.

[0022] The dried sludge solids enter the pyrolysis gasification system. Before entering the pyrolysis gasification furnace, the dried sludge is mixed with ultra-low moisture content waste for granulation, and then added to the pyrolysis gasification furnace for final pyrolysis. The pyrolysis gasification reaction is carried out with steam and CO2 as gasification agents. The slag produced after pyrolysis gasification is transported out for use as building materials.

[0023] The combustible gas produced by the pyrolysis gasifier and the CH4 separated and purified from the biogas enter the energy utilization system, where they are burned by a gas turbine to generate electricity. The exhaust gas after combustion is passed through a waste heat boiler to generate steam for waste heat utilization. The steam is used to heat the anaerobic digester, provide gasification agent, and provide heat source for the dryer.

[0024] The principle of the present invention is:

[0025] The method of the present invention adds high-water content wastes into an anaerobic digestion tank, wherein the water content of the high-water content wastes is greater than or equal to 90%, and includes concentrated sludge from a sewage treatment plant, kitchen waste squeezed liquid, restaurant kitchen waste liquid, food factory waste liquid, livestock and poultry manure wastewater, etc. By adding different types of high-water content wastes into the anaerobic digestion tank, the effect of coordinated anaerobic digestion is achieved, and while the high-water content wastes are treated, the biogas production and energy output can also be increased.

[0026] The sludge after anaerobic digestion is conditioned in the conditioning tank, and ultra-low moisture content waste is added during the process. Since the water content of the digested sludge after anaerobic digestion is relatively high, the use of ultra-low moisture content waste can reduce the water content of the digested sludge, and can also play the role of skeleton support, which is helpful for the subsequent sludge dehydration process; the water content of the ultra-low moisture content waste is less than 30%, including sawdust, crop straw, rice husk and waste activated carbon; medium moisture content waste is added before sludge dehydration, and the moisture content of the mixture is reduced to below 60% after dehydration by a dehydrator. The moisture content of the medium moisture content waste is greater than or equal to 60% and less than 90%, including dehydrated sludge, wine dregs, medicine residues and livestock and poultry manure solids; the wastewater generated during the sludge dehydration process enters the sewage treatment system for treatment.

[0027] The dehydrated sludge enters the dryer for drying. During the drying process, it is compounded with low-moisture content waste. The moisture content of the low-moisture content waste is greater than or equal to 30% and less than 60%, including dried sludge and garden waste. The low moisture content is not much different from the moisture content of the dehydrated sludge, which can realize the comprehensive utilization of low-moisture content waste.

[0028] After drying, the moisture content of the sludge solids drops below 20%, and then it is compounded and granulated with ultra-low moisture content waste to achieve further comprehensive utilization of the ultra-low moisture content waste.

[0029] The granulated sludge is pyrolyzed and gasified in a pyrolysis gasifier, and combustible gas is generated in the process. The gasifying agent is a combined gas of steam and carbon dioxide. Carbon dioxide can generate CO in the process of gasification, which increases the amount of combustible gas and the calorific value of the pyrolysis gas and increases the energy output. The generated combustible gas and the methane purified by anaerobic digestion can be used for power generation in the plant, for use in the plant area or for grid connection. The tail gas after combustion can enter the waste heat boiler for comprehensive utilization. The steam generated by the waste heat boiler can be used for heating the anaerobic digester, the gasifying agent of the pyrolysis gasifier and for providing heat for the dryer. In addition, the carbon dioxide used as the gasifying agent comes from the purified separation of the biogas generated in the anaerobic digester.

[0030] Example 1

[0031] The moisture content of the sludge after anaerobic digestion is 95%. Sawdust with a moisture content of 5% is added in the conditioning stage, and the added amount is 5% of the absolute dry amount of the sludge. After further flocculation and conditioning, it enters the plate and frame dehydrator for filter pressing and dehydration. After dehydration, the average moisture content of the mud cake is about 56%.

[0032] Example 2

[0033] After drying, the sludge has a moisture content of 15%. It enters the pyrolysis gasification furnace for pyrolysis and gasification reaction. Saturated steam and CO2 are used as gasifying agents. The saturated steam parameter is 0.3MPa. The amount is 48kg of saturated steam per ton of sludge gasified. CO2 is added at a volume ratio of 2:8 to saturated steam. The average gas production per ton of sludge gasified (based on a moisture content of 80%) is 365m 3 The average calorific value of pyrolysis gas is 780kcal / m 3 .

[0034] Comparative Example 1

[0035] The moisture content of the sludge after anaerobic digestion was 95%. No sawdust was added in the conditioning stage. The other operations were the same as those in Example 1. After conditioning, the sludge entered the plate and frame dehydrator for filter pressing and dehydration. After dehydration, the average moisture content of the mud cake was about 62%.

[0036] Comparative Example 2

[0037] After drying, the sludge has a moisture content of 15%. It enters the pyrolysis gasification furnace for pyrolysis and gasification reaction. Saturated steam is used as the gasification agent. The saturated steam parameter is 0.3MPa. The amount is based on 60kg of gasification agent for each ton of sludge gasified. The average gas production per ton of sludge gasified (based on a moisture content of 80%) is 328m 3 The average calorific value of pyrolysis gas is 671kcal / m 3 .

[0038] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A multi-source waste comprehensive utilization system combining anaerobic digestion and pyrolysis and gasification, characterized in that: It includes an anaerobic digester and a pyrolysis gasifier. The biogas generated in the anaerobic digester is separated and purified to obtain CH4 and CO2, and the CO2 is used as a gasifying agent to enter the pyrolysis gasifier at the rear end; the digested sludge generated in the anaerobic digester is conditioned, dehydrated, and dried, and then enters the pyrolysis gasifier, and pyrolysis and gasification reaction is carried out with steam and CO2 as gasifying agents; high-water content waste is added to the anaerobic digester for coordinated anaerobic digestion; in the conditioning stage, ultra-low water content waste is added as an organic conditioning agent, and the ultra-low water content waste is mixed with the digested sludge after digestion to play the role of skeleton support material; In the dehydration stage, waste with medium moisture content is added, and the waste with medium moisture content and the conditioned sludge enter the dehydrator together for dehydration; in the drying stage, waste with low moisture content is used, and the waste with low moisture content and the dehydrated sludge enter the dryer together for further drying; before the pyrolysis gasification stage, waste with ultra-low moisture content is mixed with the dried sludge for granulation.

2. The multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification according to claim 1 is characterized by: The water content of the high-moisture content waste is greater than or equal to 90%, including but not limited to concentrated sludge from sewage treatment plants, kitchen waste squeezed liquid, restaurant kitchen waste liquid, food factory waste liquid and livestock and poultry manure wastewater.

3. The multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification according to claim 1 is characterized by: The medium-water-content waste has a water content of greater than or equal to 60% and less than 90%, including but not limited to dehydrated sludge, distiller's grains, medicinal residues and livestock and poultry manure solids.

4. The multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification according to claim 1 is characterized by: The low-moisture waste has a moisture content greater than or equal to 30% and less than 60%, including but not limited to dried sludge and garden waste.

5. The multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification according to claim 1 is characterized by: The ultra-low moisture content waste has a moisture content of less than 30%, including but not limited to sawdust, crop straw, rice husk and waste activated carbon.

6. The multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification according to claim 1 is characterized by: In the conditioning stage, the amount of waste with ultra-low moisture content added does not exceed 15% of the absolute dry weight of the digested sludge.

7. The multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification according to claim 1 is characterized by: In the dehydration stage, the moisture content of the sludge after dehydration is reduced to below 60%; in the drying stage, the moisture content of the sludge after drying is reduced to below 20%.

8. The multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification according to claim 1 is characterized by: In the pyrolysis and gasification stage, CO2 separated and purified from steam and biogas is used as a gasifying agent in a volume ratio of 8:

2. Combustible gas is generated after pyrolysis and gasification, and the combustible gas enters the energy utilization system after purification.

9. The multi-source waste comprehensive utilization system of anaerobic digestion coupled with pyrolysis and gasification according to claim 8, characterized in that: The slag produced after the pyrolysis and gasification is transported out for use as building materials, the generated combustible gas and the CH4 separated and purified from the biogas are fed into the gas turbine for combustion and power generation, the generated electricity is used for self-use and / or grid-connected, the exhaust gas after combustion is passed through the waste heat boiler to generate steam for waste heat utilization, and the steam is used to heat the anaerobic digester, provide gasification agent and provide heat source for the drying stage.

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