Development prospect of domestic biomass power generation technology and equipment

In fact, the core of biomass power generation technology is the choice of circulating gasifier. The gasifier uses diesel ignition equipment, so that the temperature in the gasifier is always maintained at about 800 ° C, and the furnace is in an internal environment of approximately hypoxia, which is more conducive to the adequate pyrolysis of biomass fuel, and then the biomass mixture of hydrogen, carbon dioxide and carbon monoxide is produced. Only when the mixture stays fully and completely in the furnace body can it ensure efficient gasification yield and combustion efficiency.

5.2 Mixture cooling system

The core equipment of the gas cooling system [10] is the high-pressure heat exchanger, whose function is to reduce the high temperature (about 650℃ above) gas generated by the gasifier to the medium temperature or low temperature, where the moderate and low temperature refers to less than 400℃. Because of the special working nature of the high pressure heat exchanger, the heat transfer oil that needs to be selected should be selected at 500 ° C or above, so as to ensure high efficiency conversion and ensure production safety. This heat transfer oil in the country is basically customized, according to the specific situation to choose. Heat transfer oil in the high pressure heat exchanger is placed behind the biomass gasifier, the heat transfer oil through the circulating oil pump to the heat collection equipment, the heat transfer equipment under high pressure through the transfer of heat transfer oil, the heat collection and then the heat transfer oil through the return pump re-injection collector heat, through such equipment circulation to achieve the purpose of temperature control.

5.3 mixture pressure conveying equipment

After experiencing the cooling system, the mixed biomass gas is basically in the middle temperature (300~500 ° C), so for the safety of the pressurized equipment, the equipment used for pressurized hot air should be able to meet the temperature of at least 500 ° C. When the mixture enters the furnace from the outside, the air pressure and gas amount will change due to the different position and quantity of the air intake. Therefore, it is necessary to depressor or boost the pressure to the standard degree before the mixture enters the furnace body, so that it is not affected. When the air pressure reaches stability, the mixture is sent to the tube body, and the tube body will finally equalize the gas and then send it to the furnace through the branch line for reaction. In the actual design of the pipeline, the gas backsuction and backflow caused by unstable air pressure and uneven heat should be considered, and the corresponding anti-backsuction and backflow valves should be set.

5.4 Coupling burner

The biomass gas burned in the coupling burner basically does not contain ash and volatiles, so the rotary convection device assembled in the front or back section of the furnace in the burner can continue to use the hot steam as a secondary energy source. The selection and installation of coupled burners requires a more scientific design based on factors such as the amount of biomass gas produced and the change in the combustion zone of the furnace. In China, if the coupling rate of biomass gas is less than 5% of the pulverized coal boiler [11], it can basically ensure that there is no need to treat the water wall of the boiler.

6 Development prospects of biomass power generation in China

(1) China's biomass power generation industry is extremely affected by government support, and has a particularly obvious embedment in the current industrial chain. China's agricultural production mode and current situation is very different from that of developed countries. Developed countries' agricultural economy, which is mainly based on farms, has a complete upstream and downstream system. Whether it is from transportation to recycling or to sales, each link and each chain has a clear division of labor and accurate positioning. Looking at China's agricultural model and policy conditions, this leads to the collection and transportation of biomass raw materials will inevitably be limited by local governments and farmers, resulting in the contradiction of raw material supply. In addition, incomplete acquisition channels, transportation and other industries will also restrict the normal operation of power plants.

(2) For the current power plant, the installed capacity of the equipment is basically 200 ~ 600MW, but for large thermal power generation units, it is mainly more than 600MW. Therefore, the characteristics of the equipment make the coupling rate of biomass power generation in China less than 10%. This shows that if China's biomass power generation industry wants to develop rapidly and on a large scale, it must use small boilers and do not need to carry out a comprehensive modification of the original coal-fired boilers. In fact, the uneven distribution of agricultural resources under the smallholder economy and the difference in production methods are bound to be the most fatal bottleneck among the many adverse effects on biomass power generation in China. From the perspective of the operation of domestic biomass power generation enterprises, the source and quality of raw materials are unstable, which is the main reason for the poor economic benefits of enterprises, and even the operating losses of power plants and power stations.