Key technologies for distributed utilization of biomass

At present, there are a variety of biomass energy distributed utilization technologies that have basically matured and are most likely to be marketed, including biogas, biomass molding, biomass gasification, biomass heating and thermal utilization, etc., and the current status of development of related core technologies.

3.1 Large and medium-sized biogas technology

The organic waste handled by the biogas project is relatively wide, such as: livestock and poultry fee, silage, expired residual grain, food residue, domestic organic waste, waste from animal slaughtering, waste from agricultural and sideline product processing, etc., or a mixture of the above several kinds of organic waste. Because of the rapid development of animal husbandry in China in the past 10 years, the total amount of livestock and poultry poop emission far exceeds the carrying capacity of the environment, and the government hopes to basically solve the pollution problem of livestock and poultry farms in the key areas to the surrounding environment through the implementation of biogas engineering construction projects, so the shibuya gas project will play a multi-functional role (production of energy, comprehensive utilization, and environmental protection, etc.), and it has a broad prospect of application.

Large and medium-sized gas project has been very mature, is the main way of biomass energy distributed utilization, but also the current industrial development of one of the best biomass energy utilization direction. However, China's traditional biogas utilization method is based on domestic gas pool, small scale, low efficiency; face of large and medium-sized road gas project compared with foreign technology there is still a big gap between the level of equipment technology and manufacturing technology is not high, such as the international CSTR process of gas production can reach up to 15m3-m-3-d-1, the rate of thermoelectric system up to 90%, and to find the domestic gas production rate of 0.8-5.0m3-m-3-d-1, power generation efficiency is only 35%. d-1, power generation efficiency is only 35%. At present, China has built large and medium-sized livestock and poultry pollution biogas project in the process design stage did not consider the full use of resources, most do not use combined heat and power supply, room temperature fermentation or external heat source near the medium-temperature hair alcohol process in the winter can not maintain a stable production of gas, the net energy output rate is very low.

3.2 Biomass molding technology

There are two main types of molding technology: one is the pellet fuel molding machine, different specifications of the ring mold machine is the mainstream pellet fuel molding machine; the other is the rod or block molding machine, rod or block molding fuel is mainly used in farms, raw material is crop residue, the vast majority of large pitch, large diameter extruder, there is also a hydraulically driven piston press molding machine. At present, biomass forming fuel from raw material collection, drying, crushing, packaging, sales links all realize the production line production, automation, scale and commercialization are very high, the production scale of a single machine is mostly in the 2 tons per hour or more.

China's production of molded fuel to crop straw as the main raw material, straw molding characteristics, combustion characteristics and forestry residues are very different, can not copy the foreign technology and equipment, currently in the biomass stamping briquette technology and equipment, extrusion briquette technology and equipment, baked charcoal technology and equipment and so on, there is a clear progress, but China's biomass molding machine is still widespread in the high energy consumption, wear and tear, and the use of short life and other issues need to further strengthen the technical research and development to improve the energy use efficiency. However, China's biomass molding machines still generally have the problems of high energy consumption, serious wear and tear, short service life, etc. It is necessary to further strengthen the technical research and development to improve the energy utilization efficiency. In addition, straw-fueled boiler combustion application technology is still immature, but also the lack of core technology and equipment, there is no technically mature boiler product manufacturers, boiler combustion is prone to slagging, coking, corrosion and fly ash is serious and other problems, operation and maintenance is not easy. Therefore, to improve the adaptability of the boiler to the sticky straw molding fuel is one of the key technologies to promote biomass molding fuel on a large scale.

3.3 Biomass gasification technology

The main advantage of biomass gasification is to convert biomass low-grade fuels that are difficult to burn into gas, to achieve clean and efficient title burning, which is an effective way of biomass distributed utilization. China's small-scale biomass gasification and utilization technology has reached the international advanced level, especially in the gasification of power generation and biogas alternative industrial fuel. But in general, the current gasification equipment for fuel adaptability is poor, on the raw material moisture, ash or calorific value of the changes in the more sensitive; gasification power generation also exists in low efficiency, poor qualitative and gas purification system of the big residual and so on, the need to improve the efficiency of biomass gasification and its automation and control level; biomass gas combustion exists in the gas and conventional combustion equipment (eg, boilers, kilns, etc.) to match the immaturity of technology, etc. The problem of biomass gas combustion and conventional combustion equipment (such as boilers, kilns, etc.) match immature technology and other issues, there is an urgent need to solve the biomass gas efficient combustion, gasification system and industrial boilers / kilns coupled with key technologies. Therefore, the development of new biomass gasification technology and equipment, improve and enhance the gas utilization efficiency, build demonstration projects, and form commercial solutions for distributed biomass gasification utilization is the main direction of biomass gasification technology development.

3.4 Biomass pyrolysis technology

 
Biomass pyrolysis technology can convert low-grade biomass into high-grade charcoal, fuel oil, etc., which is one of the main ways to utilize biomass in a high-value way. China's biomass pyrolysis technology research earlier, but the industrialization progress is slow, mainly because the research is dominated by a single technology, lack of systematic, compared with Europe and the United States and other countries there is still a big gap. In particular, there are obvious gaps in the research and development of high-efficiency reactors, optimization of process parameters, refining of liquefied products, and the impact of biofuel on engine performance. At the same time, pyrolysis technology also exists the following problems: the cost of bio-oil is usually higher than that of mineral oil, bio-oil is incompatible with traditional liquid fuels, and special fuel treatment equipment is needed; bio-oil is a highly oxygenated hydrocarbon, unstable in physical and chemical properties, and long time storage will lead to phase separation, precipitation and other phenomena, and corrosion; due to the unstable physical and chemical properties, bio-oil can't be used for existing power equipments, it must be processed through the process of refining. used in existing power equipment, it must be modified and refined before use; these are the bottlenecks that hinder the scale utilization of biomass pyrolysis. In view of the above gaps and problems, future research focuses on how to improve the yield of liquefied products, seek for efficient refining technology, improve the quality of bio-oil, reduce the operating cost, and realize the comprehensive utilization and industrial production of the products.