Although the total amount of biomass energy resources in China is huge, the energy density is low, widely distributed, and difficult to collect and utilize. China’s social production activities each year produce a large amount of industrial and agricultural wastes. Especially in the vast rural areas of China, most farmers still use firewood and straw as their main living fuels. Frequent open burning of straws not only affects the improvement of living conditions, but also causes serious damage to vegetation and worsens the rural ecological environment.
Modern biomass energy technology provides great development space for China’s industry and agriculture. Using modern technology, biomass energy can be converted into solid, liquid and gaseous biomass fuels, significantly improving energy utilization and working environment, and greatly improving utilization Efficiency is conducive to the improvement of people's living standards.
1. Biogas technology
China has a long history of biogas development. Household biogas digesters (6-10m³) with Chinese characteristics have now grown to 465×104, with an annual biogas output of about 15×108m³. Moreover, in recent years, the Chinese government has given strong and continuous support and investment in rural biogas construction. Large and medium-sized biogas projects with anaerobic digestion as the core technology and waste resource utilization have become the treatment and utilization of livestock manure and crops. One of the most effective methods for straw and industrial organic wastewater.
As of the end of 2008, 39,800 biogas projects of various types have been built nationwide, and 30.49 million rural households have used rural biogas, producing 11.39 billion cubic meters of biogas each year; 164,000 biogas digesters for domestic sewage purification have been built across the country for special treatment. Public toilets, hospitals and other public places and other domestic sewage have a total pool capacity of 7.85 million cubic meters. At the same time, various regions have also integrated solar energy, biogas technology, and the industrial structure of planting and breeding industries in accordance with local conditions, and have practically explored a series of "quaternary bodies" in the north, "pig biogas" in the south, and northwest "quaternary bodies" suitable for popularization and application in rural areas in China. The "non-supporting" energy ecological model has become a characteristic of China's biomass energy utilization.
In terms of the development of biomass gasification technology, China's in-depth research on the gasification technology of agricultural and forestry waste and other resources began in the late 1970s and early 1980s. As of the end of 2006, the number of straw gasification stations in China's biomass gasification centralized gas supply system was 539, and the annual production of material gas was 1.5×108m³; the rice husk gasification power generation system with an annual power generation of 160kW·h has entered the industrialization stage .
2. Direct combustion technology
Farmers in most rural areas of China still use traditional stoves for cooking and heating, and their living fuel mainly comes from crop stalks and firewood. By improving the existing cooking stoves in rural areas, not only has the combustion efficiency of traditional stoves increased (about 20%), but also reduced indoor air pollution and improved the rural living environment. By the end of 2008, China’s rural areas had promoted a total of 146 million firewood-saving and coal-saving stoves, 33.42 million high-efficiency low-emission energy-saving stoves, and 20.5 million kang shops. The new stoves have increased thermal efficiency by more than 10% and alleviated the shortage of firewood in some areas. Tense situation. In areas where firewood-saving stoves have been popularized, the problem of fuel shortage has basically been solved, thereby greatly reducing the phenomenon of cutting trees and shoveling uphills, protecting forests and vegetation, restoring the virtuous cycle of natural ecology, and greatly alleviating rural areas. The energy shortage situation has improved the environmental conditions of rural residents’ daily lives.
3. Gasification technology
Centralized gas supply for crop straw gasification is a technology developed in China in the 1990s. At present, a variety of fixed-bed and fluidized-bed gasifiers have been developed to produce gas using straw, wood chips, rice husks, and branches as raw materials. In 2006, more than 800 units were used for drying wood and agricultural and sideline products, and there were nearly 600 centralized gas supply systems for the gasification of straw at the village and town level, and the annual production of biomass gas was 20 million cubic meters. By the end of 2008, the number of gas supply stations in China's crop straw gasification centralized gas supply system had reached 856, producing 312 million cubic meters of material gas annually. In addition, the production of biogas through anaerobic fermentation using crop straws as raw materials has also begun experimental demonstrations and extensions in some rural areas of China in the past two years. At present, nearly 200,000 farmers are using this technology. In 2009, the Ministry of Agriculture was organizing relevant scientific research units and enterprises to carry out 16 straw biogas demonstration projects in 12 provinces (regions).
4. Solid molding technology
A few days ago, the biomass solid briquettes developed by China come in pellets, blocks and rods. They are mainly used for civil cooking and heating, commercial catering and bathing, industrial boilers and power generation. Biomass solid molding equipment is generally divided into screw extrusion type, piston stamping type and ring die rolling type. The Institute of Chemical Industry of Forest Products of the Chinese Academy of Forestry has been researching and developing the molding technology of forest biomass raw materials and agricultural wastes since the 1980s. Southeast University, Guangzhou Energy Research Institute of Chinese Academy of Sciences, Hunan Agricultural University, Renewable Energy and Environment Research Institute of Chinese Academy of Agricultural Machinery have also conducted some characteristic research. Some Chinese manufacturers of pellet feed have also begun to produce biomass compact fuels based on the original equipment. A prominent problem in the actual use of China's biomass solid molding fuel equipment in processing and production is the short service life of the key components of extrusion molding and the high cost of molding fuel. This is also the biggest obstacle to the development of biomass solid molding technology. Since 2000, due to the close cooperation of industry, university and research, the biomass solid molding technology has developed significantly, and the production and application of molding equipment has initially formed a certain scale. As of the end of 2008, there were 102 demonstration projects in operation across the country, and biomass solid briquettes in Beijing, Henan, and Jiangsu have begun to market and commercialize, and have achieved success.
5. Biological liquid fuel
The main raw materials for the production of bio-fuel ethanol in China are corn and wheat and other food crops. Starting from June 30, 2002, the National Development and Reform Commission has respectively supported Zhengzhou, Luoyang and Nanyang in Henan Province and Harbin and Zhao in Heilongjiang Province. Five cities including Dongshi have carried out pilot work on the use of ethanol gasoline for vehicles using aged grains, and have respectively built fuel ethanol production plants using aged grains as raw materials, with a total output of 10,204 tons per year. China's fuel ethanol process production technology is more advanced in the corn "semi-dry" production process of COFCO Biochemical Energy (Zhaodong) Co., Ltd. (with a production capacity of 10×104t/a). COFCO Zhaodong’s third phase ethanol plant all adopts the "semi-dry pulverization process", completely abandoning the "wet" or "modified wet" soaking process, the process is further simplified, and the water consumption is reduced. At the same time, the "semi-dry method" overcomes the shortcomings of the difficulty of oil extraction in the "dry method", and the corn oil yield is close to that of the "improved wet method", which is more technically and economically reasonable. The technology of this device has reached China's leading and internationally advanced level, achieving cleaner production. At the end of 2005, ethanol for vehicles was basically substituted for gasoline in parts of 9 provinces, with an annual production of about 1.5 million tons of ethanol fuel. However, due to the constraints of grain production, the Chinese government has emphasized the principle of “not competing for food or land with food” to develop and utilize biofuels, and clearly proposed to expand the production of non-food bioethanol and biodiesel fuels. Organize scientific research units and experts to carry out projects for the production of bio-fuel ethanol from sweet sorghum stalks, potatoes (cassava, sweet potato), sugarcane and crop straws, as well as the use of rapeseed oil, cottonseed oil, ebony oil, wood oil, tea oil and sewage Projects for the small-scale production of biodiesel from raw materials such as oil, and establishment of bio-liquid fuel production and processing bases in some provinces (regions) have initially met the conditions for commercial development.
Potato raw materials have been recognized as a raw material for ethanol production with great development potential because of its good processing performance and the advantages of not competing with grain for land. The DDGS of cassava has low nutritional value and is usually used for biogas or fertilizer, with low added value. In 2005, the planting area of cassava in China was about 60×104hm², with a total output of 1100×104t. In the five provinces of Guangxi, Guangdong, Hainan, Fujian and Yunnan suitable for the growth of cassava, there are about 2×108 mu of unused land such as waste grassland, bare land, reserve suitable for forestry, agriculture, barren hills and wasteland, etc. If development 1/ 5. The available planting area is at least 4000×104 mu. Calculated on the basis of 2t per mu, 8000×104t cassava can be harvested every year. Under the condition of ensuring the current production level of cassava starch, it can produce about 1000×104t fuel ethanol.
In December 2007, Guangxi COFCO Biomass Energy Co., Ltd. had an annual production capacity of 20×104t/a cassava fuel ethanol demonstration production device. The first commissioning and trial run were successful, and the production technical indicators of potato fuel ethanol were at the world's leading level. However, the tapioca starch processing technology consumes a lot of water, and the later sewage treatment is more difficult.
In recent years, China's sugarcane output has been around 8,500×104t/a, and the production of alcohol (edible alcohol) from molasses by-product of sucrose is about 50×104t/a. The application of pure sugarcane juice fermentation technology to produce energy ethanol is still in the pilot stage. At present, 1.2×1104 acres of "double high and one high quality sugarcane industrialization demonstration zone" has been built in Suixi, Guangdong. The area of radiant raw material sugarcane area has reached 1.5×104hm², and 3 energy sugarcane varieties have been transferred to Fujian and Guangdong with compensation through agreement. Leading enterprises in the production of sucrose and alcohol.
The project of using sweet sorghum as raw material to produce fuel ethanol has attracted the attention of relevant Chinese energy companies earlier. Some scientific research institutes have successively carried out research on sweet sorghum varieties and selected a number of varieties suitable for different regions and used for different purposes. , Good varieties with high sugar and high yield. The Beijing Institute of Green Energy Plant has done a lot of work in the research and development of sweet sorghum, and has successively cultivated "Tiansi No. 1", "Lvneng No. 2", "Lvneng No. 3", "Lvneng No. 4", Excellent varieties and hybrids such as "Lvneng No. 5", sweet sorghum varieties cultivated in recent years, such as "BJ-190", "BJ-238", "BJ-281", "BJ-248", etc., are in the national sweet sorghum varieties Both the regional trials and the international regional trials of sweet sorghum varieties rank in the top, and the product quality level is significantly better than that of foreign varieties, and some varieties have been promoted to Africa and the Americas. In 2006, COFCO cooperated with relevant Chinese scientific research institutions to establish a pilot plant for ethanol production from sweet sorghum in Inner Mongolia, and achieved initial results, and completed Hebei Hengshui with sweet sorghum and sweet potatoes as raw materials for an annual output of 20×104t/ a Preliminary preparations for fuel ethanol production equipment. As China's largest energy company, PetroChina actively promotes the research and development of sweet sorghum production technology for fuel ethanol production. It plans to build a project in Binzhou, Shandong Province that uses sweet sorghum and sweet potatoes as raw materials and has an annual output of 10×104t/a fuel ethanol production equipment.
The available lignocellulose in China is about 7×108t per year, so China has a greater advantage in the development of cellulosic ethanol. These abundant and cheap natural resources mainly come from agricultural and forestry wastes, industrial wastes and urban wastes. Cellulosic ethanol is the inevitable direction of the future development of fuel ethanol industry. So far, China has built and is building a number of cellulosic ethanol pilot production lines. Henan Tianguan Group has built a 300t/a cellulosic ethanol experimental device; COFCO built a 500t/a cellulosic ethanol pilot plant with corn straw as raw material in Zhaodong, Heilongjiang in 2006, and produced cellulosic ethanol Products; Jilin Fuel Ethanol Company plans to build a 4000t/a corn stalk demonstration plant for producing cellulosic fuel ethanol.
At present, China has successfully used rapeseed oil, soybean oil, rice bran oil, bare bark oil, industrial lard, tallow, and wild plant jatropha oil as raw materials, and produced biodiesel after pre-esterification with methanol and then esterification. Not only can it be used directly as an alternative fuel, but also as an additive for diesel fuel clean combustion.
In June 2001, Sichuan Gushan Grease Chemical Co., Ltd. invested more than 18 million yuan to build the first phase of the project, with an annual output of 1.2×104t/a biodiesel and glycerin. The company uses leftovers produced in the refining process of vegetable oils and edible recovered oil as raw materials. After acidification and impurity removal, continuous dehydration, esterification, recovery of methanol, standing, separation of the lower layer, recovery of glycerin, continuous distillation, production of biodiesel, its technology Simple, reliable, fast esterification speed, the reaction can be completed within 6 hours, the acid value can be reduced to below 1 mgKOH/g, the fatty acid conversion rate is as high as 93%, the finished product yield is high, the methanol consumption is low, the production cost is low, and it is suitable for large-scale production. Large-scale industrial production. Due to the shortage of products on the market, the company began to expand in January 2002 and officially put into operation on April 13, 2002, with an annual production of 3×104t/a biodiesel.
The private company Hainan Zhenghe Bio-Energy Co., Ltd. built a biodiesel pilot plant with an annual output of nearly 1×104t/a in September 2001. The company mainly uses waste oil from the catering industry and refined vegetable oil as raw materials, and then passes through methanol pre-esterification. Esterification produces biodiesel. The oil has been tested by the Sinopec Research Institute of Petroleum and Chemical Industry and the Environmental Science Research Institute, and the main indicators have reached the requirements of the US biodiesel standards.