CN1769220A - Biogas production technology using kitchen waste, straw, livestock and poultry manure and activated sludge as raw materials - Google Patents

Abstract

The invention discloses a technique for producing methane with kitchen residue, straw fecal and active sludge as raw material, and relates to the key technique of methane production and a high solid methane fermentation reactor. It is characterized in: rigid anaerobic environment, adequate and good inoculum, necessary fermentation temperature, proper acid-base scale, proper fermentation concentration and carbon-hydrogen ration; the breeding speed safeguard of zymogeneous bacteria in fermentate; the killing of toxic and harmful bacterium; and the high solid reactor of stable operation. The invention is characterized in that it has significant academic meaning and practical meaning for producing methane with low investment, high stability and clean production.

Description

Biogas production technology using kitchen waste, straw, livestock and poultry manure and activated sludge as raw materials

technical field

Biogas production technology that uses organic waste such as kitchen waste, straw, livestock and poultry manure, and activated sludge as fermentation raw materials, involving key technologies for biogas production and high-solids biogas fermentation reactor technology.

Background technique

How to produce biogas safely, economically and stably has always been a worldwide problem. Straw is considered as an important raw material for biogas fermentation. In order to solve the technical problems of straw fermentation, the state has arranged a series of research topics on the application of basic and applied technologies. The main goals are: whether straw can produce gas, how much biogas can be produced, how to use straw and manure together, and how to pretreat , Straw discharge method and discharge machine research and so on. The "four-in-one" high-efficiency planting and breeding development model developed in northern my country, that is, solar greenhouses, biogas digesters, pigsty, toilets and the "trinity" model of pigsty, biogas digesters, and orchards developed in the south, was once considered to be suitable for our country. An effective model for national conditions.

However, the traditional wet technology of biogas fermentation occupies a large area, produces a large amount of secondary garbage and wastewater, and the investment cost and operation cost of wastewater treatment are high; in addition, to improve the cycle rate of anaerobic fermentation of garbage, anaerobic A series of disadvantages such as high fermentation energy consumption and high cost of processing dry matter due to the living temperature environment of fermentation bacteria limit the scope and area of its adaptation.

At present, there are researches on the fermentation of dry biogas both at home and abroad. Dry anaerobic digestion of solid organic waste has been well developed in practical applications in Europe and America. In terms of anaerobic digestion process, it can be divided into one-phase treatment and two-phase treatment according to the number of reaction stages. The one-phase treatment process is simple, and can effectively treat organic solid waste with a total solid content of 20% to 40%. Due to the high viscosity of the substrate, the substrate generally moves by plug flow in the reactor. Now there are many effective processes that can be applied on a large scale, such as the Dranco process in Belgium, the Kompogas process in Switzerland, and the Valorga process in France. In China, a dry-type two-phase high-temperature and medium-temperature anaerobic fermentation technology-dehydration technology has also been developed, which is used for high-solids fermentation of biogas.

In terms of large-scale application of biogas, Henan Nanyang Alcohol Factory established a biogas production system using distiller's grain wastewater many years ago, using multiple large-scale anaerobic reaction tanks to produce biogas, and the biogas was incorporated into the urban natural gas pipeline network, which has achieved good results The application effect and accumulated experience in the application of urbanization biogas. Using straw and kitchen waste as raw materials, there is no complete and systematic research on the large-scale production of biogas with high solids for the energy supply of small town residents. There are still some studies on the development of biogas energy for organic materials such as straw and kitchen waste. Many aspects require research and development.

Contents of the invention

The purpose of the present invention is to propose a biogas production technology using organic waste such as kitchen waste, straw, livestock and poultry manure and activated sludge as fermentation raw materials. The representative solid organic waste in cities and towns is used as the main raw material for biogas production, providing urbanization biogas production elements and large-scale production process, establishing urbanization biogas demonstration projects, and overcoming the problems existing in traditional wet biogas fermentation technology.

Main object of the present invention is:

(1) Strict anaerobic environment, sufficient and excellent inoculum, necessary fermentation temperature, suitable pH, suitable fermentation concentration and carbon-hydrogen ratio;

(2) Guarantee of the propagation speed of the fermented bacteria in the fermented product;

(3) Killing of toxic and harmful microorganisms;

(4) High solids biogas reactor with stable operation.

Technical scheme of the present invention:

Two parallel high-solids biogas reactors are used, and the anaerobic digestion sludge of urban domestic sewage treatment plants is used as the seed sludge. In the reactor, the raw food waste, straw, livestock and poultry manure, activated sludge and seed sludge are mixed. , the mass ratio of kitchen waste, straw, livestock and poultry manure and activated sludge is 1:1:1:1, and the amount of seed mud is 25% of the raw material. The region adopts medium and high temperature anaerobic fermentation at 33-55°C, maintains the pH value at 7.0, and controls the humidity at 90%-100%. The content of organic acids, CH ₄ and CO ₂ is detected every day. When the content of CH ₄ in the generated biogas is stable at 50% %-70%, when the _CO2 content is 30%-50%, the reactor reaches the normal operation state.

Beneficial effects of the present invention:

(1) It can directly process solid fermentable organic matter such as crop straw and municipal waste, saving more than 50% of the pretreatment cost compared with traditional wet methods;

(2) Fermentation is not affected by interfering substances such as plastics, wood blocks, sand, etc., and it is not necessary to spend manpower and equipment to detect them before fermentation;

(3) The quality of biogas is high (the sulfur content is lower than that of wet biogas, at 50-300ppm, it can be directly used by biogas engines without gas washing), and the gas output rate of fermentation products is high (25%-35%);

(4) Common construction machinery such as loaders can be used for feeding and discharging, with high equipment efficiency and strong versatility;

(5) Compared with the wet method, the water consumption is reduced by more than 80%, and there is almost no sewage discharge;

(6) The fermentation residue has no wet fermentation biogas slurry, no dehydration treatment, and the fermentation residue can be used as garden fertilizer or crop fertilizer after simple sieving and short-term composting, so storage and post-processing costs are low, and the value high.

(7) The initial investment, operating cost and environmental cost of the high-solids biogas fermentation process are far lower than those of the wet technology (reduced by more than 30%-40%).

The invention has important academic significance and practical value for realizing low investment, low operation cost, high stability and clean production of biogas production. Compared with the wet biogas fermentation technology, the high-solids biogas fermentation technology increases the production scale of biogas and reduces the investment in infrastructure construction; it can consume a large amount of raw materials that are difficult to use in the wet method, such as crop straw and urban kitchen waste, and ferment The heat required for the process is reduced by more than 50%. About 150 cubic meters of biogas containing more than 60% methane can be produced per ton of crop straw or urban kitchen waste during the fermentation period of about 40 days, and a large amount of high-quality green manure can be produced.

Urbanization is the trend of social and economic development in our country. Cities and their surrounding agricultural production areas produce a large amount of domestic and agricultural wastes every year, such as kitchen waste, straw, manure and organic sludge. These wastes are concentrated and fermented to produce biogas, which is used in the daily life of urban residents, reducing the demand for non-renewable coal or natural gas; biogas residues become efficient green agricultural fertilizers, which are beneficial to the growth of crops after returning to the field; crop straws are reused The production of biogas forms a virtuous circle and helps solve the problem of disposal of straw and organic domestic waste of urban residents. At the same time, energy—biogas and high-efficiency agricultural fertilizers are obtained, which is an ecological process.

Description of drawings

Fig. 1 Small town waste disposal and biogas production system.

Fig. 2 Biogas production cycle mode.

Detailed ways

(1) Design two parallel high-solids biogas reactors (2-400m ³ ), use the anaerobic digestion sludge of urban domestic sewage treatment plants as the seed sludge, and feed raw kitchen waste, straw, livestock and poultry into the reactors Manure, activated sludge and seed sludge are mixed, the mass ratio of kitchen waste, straw, livestock and poultry manure and activated sludge is 1:1:1:1, and the amount of seed sludge is 25% of the raw material. Anaerobic fermentation at 33-37°C, medium-high temperature anaerobic fermentation at 33-55°C in the southern region, pH value maintained at 7.0, humidity controlled at 90%-100%, organic acid, _CH4 and _CO2 content in organic matter detected every day , when the content of _CH4 in the generated biogas is stable at 50%-70%, and the content of _CO2 is 30%-50%, the reactor reaches the normal operation state.

During normal operation, the mass ratio of kitchen waste, straw, livestock and poultry manure and activated sludge is 1:1:1:1, and each raw material can fluctuate by 20% to 30%. The moisture content requirement of raw materials: kitchen waste The moisture content of the material is 80%-90%; the moisture content of the stored soaked rice straw is 80%-85%; the moisture content of livestock and poultry manure is 80%-90%; the moisture content of the activated sludge of the sewage treatment plant 75%-80%, the residence time of the material in the reactor is 40-45 days.

Feed once every 2 days, use kitchen waste, straw, livestock and poultry manure and activated sludge from sewage treatment plant as raw materials, mix evenly according to the ratio, and the amount of each feed accounts for 2.5% of the total amount in the reactor. The feeder port is sent to the high solids biogas reactor.

The reaction materials in the high solids biogas reactor are partially mixed evenly by the automatic stirring device in the reactor, and the materials are discharged once every 2 days, and the amount of slag discharged is 2.5% of the total amount of materials in the high solids biogas reactor.

(2) The gas production intensity of raw materials is 0.2-0.4m ³ (biogas)/m ³ (reactor)/day.

(3) The influence of impurities on the reaction: Fermentation is not affected by interfering substances such as plastics, wood, sand, etc., and it is not necessary to spend manpower and equipment to detect them before fermentation.

(4) When the reactor is just started or the reaction conditions are not good (such as the gas production rate decreases, acid accumulation leads to a drop in pH), it is necessary to add an obligate bacterial agent to the reactor—a kind of bacteria containing methanogens and Composite bacterial agents such as acid bacteria, the dosage is 1%-10% of the feed amount. The composite bacterial agent is the "Beijiaqing" obligate bacterial agent researched and developed by Jiangsu Boda Environmental Protection Co., Ltd.

Claims (5)

1. A biogas production technology using kitchen waste, straw, livestock and poultry manure and activated sludge as fermentation raw materials, which is characterized in that two parallel high-solids biogas reactors are used for anaerobic digestion in urban domestic sewage treatment plants Sludge is used as seed sludge. Raw food waste, straw, livestock and poultry manure, activated sludge and seed sludge are mixed in the reactor. The mass ratio of kitchen waste, straw, livestock and poultry manure and activated sludge is 1: 1:1:1, the amount of seed mud is 25% of the raw material, the northern region adopts anaerobic fermentation at medium temperature 33-37°C, and the southern region adopts medium-high temperature anaerobic fermentation at 33-55°C, the pH value is maintained at 7.0, and the humidity is controlled at 90%-100%, detect the content of organic acid, _CH4 and _CO2 every day, when the content of _CH4 in the generated biogas is stable at 50%-70%, and the content of _CO2 is 30%-50%, the reactor is in normal operation state; During normal operation, the mass ratio of kitchen waste, straw, livestock and poultry manure and activated sludge is 1:1:1:1, and each raw material can fluctuate by 20% to 30%. The moisture content requirement of raw materials: kitchen waste The moisture content of rice straw is 80%-90%; the moisture content of stored rice straw is 80%-85%; the moisture content of livestock and poultry manure is 80%-90%; the moisture content of activated sludge in sewage treatment plants is 75% %-80%, the residence time of the material in the reactor is 40-45 days; Feed once every 2 days, use kitchen waste, straw, livestock and poultry manure and activated sludge from sewage treatment plant as raw materials, mix evenly according to the ratio, and the amount of each feed accounts for 2.5% of the total amount in the reactor. The feeder port is transported to the high solids biogas reactor; The reaction materials in the high solids biogas reactor are partially mixed evenly by the automatic stirring device in the reactor, and the materials are discharged once every 2 days, and the amount of slag discharged is 2.5% of the total amount of materials in the high solids biogas reactor. 2. The biogas production technology according to claim 1, characterized in that the volume of the high solids biogas reactor is 2-400m ³ . 3. The biogas production technology according to claim 1, characterized in that the gas production intensity of raw materials is 0.2-0.4m ³ biogas/m ³ reactor/day. 4. The biogas production technology according to claim 1, characterized in that when the reactor is just started, or when the gas production rate decreases or the acid accumulation pH drops and the reaction conditions are not good, it is necessary to add obligate bacteria to the reactor ——Composite bacterial agent containing acid-producing bacteria and methanogenic bacteria, the dosage is 1%-10% of the feed amount, and the compound bacterial agent is "Beijiaqing" developed by Jiangsu Boda Environmental Protection Co., Ltd. Bacteria. 5. The biogas production technology according to claim 1, characterized in that the fermentation is not affected by interfering substances such as plastics, wood or sand, and it is not necessary to spend manpower and equipment to detect them before fermentation.