Research progress of biomass conversion and utilization technology

Biomass layer burning technology has been widely used in the development and utilization of agricultural and forestry wastes. The Benson boiler funded by ELSAM Company in Denmark can not only make straw, wood chips and other materials fully burn on the grate, but also set fiber filters in the furnace and pipes to reduce the corrosion and wear of harmful substances in the flue gas to the equipment. After practical operation, it is proved that the improved biomass boiler runs stably and has good social and economic benefits. According to the burning mechanism of bagasse, Zhai Xuemin developed a kind of bagasse boiler with a closed furnace structure, with the combustion chamber and radiant heating surface arranged separately, which is beneficial to both timely ignition and stable combustion of bagasse. Because bagasse is representative in biomass fuel, the furnace type has certain applicability to bark, rice husk and other biomass fuels.

He Yuheng has developed and designed a layer fired boiler with a novel structure that can burn waste materials such as wood chips, wood flour and bark. The boiler can ensure the full combustion of wood chips and wood powder; Can prevent wood powder deflagration; The boiler is negative pressure combustion, which ensures that the wood powder does not breathe fire outside the furnace when burning, and provides valuable experience for the development and design of boilers for burning wood chips, wood powder and other forestry wastes.

2.1.2.2 Municipal solid waste incineration technology

With the development of urban construction and social progress, the output of municipal solid waste shows an increasing trend year by year. Therefore, it is necessary to develop new waste incineration treatment technology. Since the last century, in addition to Shanghai Pudong Yuqiao, many cities in China such as Beijing, Guangzhou, Xiamen, etc. are carrying out the construction of thousand-ton waste incineration plants, waste incineration can not only reduce environmental pollution, but also save a lot of land resources. Therefore, this technology has become a mainstream technology for domestic waste treatment in large cities. However, the waste incineration technology needs to be continuously improved and perfected in terms of tail gas treatment, secondary pollution and incinerator combustion efficiency in combination with China's basic national conditions. Due to the shortcomings of incineration technology, continuous research and exploration at home and abroad have developed the process of using anaerobic digestion technology to treat urban domestic waste. Compared with traditional incineration technology, the process has great advantages in treatment efficiency, treatment cost, resource recycling and other aspects. At present, this process has been widely used in urban waste treatment.

2.1.3 Compact forming technology

Sawdust, rice husks, branches, straw and other agricultural and forestry wastes with a certain granularity after drying under a certain pressure, can be continuously extruded into a variety of solid forming fuels such as rod, granular, block and other processing technology called biomass dense molding technology. Using the special adhesive action of lignin, or adding certain additives or binder to make it bond together to become a molding fuel, biomass raw materials through extrusion molding, the volume will be reduced, the density will be significantly larger, the moisture content will be reduced, convenient storage and transportation. This technology is widely used in high efficiency combustion furnace, biomass gasifier and small boiler.

According to the difference of process characteristics, the biomass dense forming process is divided into cold pressing dense forming, hot pressing dense forming and carbonizing dense forming, and each process has its own characteristics and application range. In recent years, domestic and foreign scientific research institutions in the biomass molding theory, biomass utilization devices, molding fuel combustion technology and other aspects of research, breakthrough progress has been made, the development and production of a variety of biomass dense molding machines with different functions and applications. In addition, there are single-head and multi-head screw extrusion rod compact forming machines, which have been put into actual production in small batches, and have achieved certain social and economic double benefits. Due to the influence of various factors, there are also problems of one kind or another in the forming machine, forming raw materials and supporting equipment, and it cannot be expected to be fully applied in the short term. In the future, we should focus on the practicability of equipment, reduce energy consumption, reduce wear, the applicability of raw materials, and serialization, so as to provide the necessary technical reserves for large-scale development and better use of biomass energy.

2.2 Biochemical transformation technology

2.2.1 Anaerobic digestion to produce biogas

Biogas fermentation is a (microbiological) process. Organic matter contained in crop straw, human and livestock manure and industrial and agricultural wastewater can be used as raw materials for biogas fermentation, and organic matter can be converted into biogas through the action of microorganisms under suitable conditions and anaerobic environment. The process is mainly divided into three stages: liquefaction, acid production and methane production.