This paper briefly expounds several forms of biomass power generation, analyzes and discusses the advantages of mixing burning of boiler straw in power plant, and on this basis, discusses how to mix burning of large proportion of straw in biomass power plant.

Key words: biomass power generation; biomass fuel; straw burning

Biomass power generation is a kind of renewable energy power generation, which uses the biomass energy of biomass to generate electricity. Biomass power generation is a clean and renewable energy source. Under the pressure of environmental protection in China, vigorously promoting biomass power generation and using biomass fuels such as crop straw instead of fossil fuels such as coal to generate electricity is an important way to save energy and reduce emissions in thermal power plants, and also an important way to solve energy shortage in the future. 1.

1 several forms of biomass power generation

Biomass power generation mainly consists of direct fired power generation, gasification power generation and mixed burning and hybrid power generation.

Biomass direct-fired power generation is the direct combustion of biomass in boilers, producing steam to drive steam turbines and generators to generate electricity. The key technologies of biomass direct combustion power generation include biomass raw material pretreatment, boiler anti-corrosion, boiler raw material applicability and fuel efficiency, steam turbine efficiency and other technologies.

The technology of biomass gasification power generation refers to the conversion of biomass into gas fuel in the gasifier, which is purified and then directly burned into a gas engine or directly into a fuel cell for power generation. One of the key technologies of gasification power generation is gas purification. The gasified gas contains certain impurities, including ash, coke and tar. The impurities need to be removed by purification system to ensure the normal operation of power generation equipment.

Biomass mixed burning power generation means mixing biomass fuel with coal to generate electricity. There are two main types of mixed combustion. One is that biomass is directly mixed with coal and put into combustion, which requires higher fuel treatment and combustion equipment, not all coal-fired power plants can use; the other is that biomass gasification produces gas and coal mixed combustion, which combusts in the mixed combustion system and produces steam which is fed into the steam turbine generator set.

Direct combustion power generation technology is to burn straw after burning, and a special straw burning boiler is needed. Gasification power generation technology is to convert solid biomass energy into gas fuel by chemical methods for power generation. Mixed-combustion power generation technology is mainly used in combustion power plants, which can effectively improve the combustion efficiency of coal, and has a good effect of energy saving and emission reduction.

2 advantages of mixing straw burning in Power Plant Boilers

China is a large agricultural country with abundant biomass resources. Various crops produce more than 600 million tons of straw annually, of which about 400 million tons can be used as energy. It has the advantages of wide sources, low pollution, renewable and zero emission of CO2.

Compared with fossil fuels, straw is a kind of green renewable energy with the largest scale of development and utilization. Straw is a low-carbon fuel with higher volatile components and lower sulfur and ash content than coal. Therefore, burning straw in power plant boilers can effectively reduce greenhouse gas, SO2 and other emissions, resulting in air pollution. Straw incineration is an important aspect of air pollution. Rational utilization of straw as biomass fuel can effectively control environmental pollution and reduce environmental pressure. On the other hand, it can also increase farmers'income to a certain extent and solve the problem of straw. Combustion of straw in power plant boiler can improve the ignition performance of coal and make coal get better burnout characteristics, and biomass fuel can replace part of coal. The price of biomass fuel is lower than coal price, which can produce certain direct economic benefits. Ash is very few, which can lighten the abrasion of boiler equipment to a certain extent.

3 biomass power plant straw burning control

Compared with fossil fuels, straw has higher volatile components, sulphur content and ash content than coal.

The alkali metal content in straw is high and ash melting point is low. As far as its combustion characteristics are concerned, straw is easy to be coked. If straw is used only as fuel, corrosion and sintering will occur in the actual operation of the boiler, which will seriously affect the reliability, safety of the equipment and the economy of the power plant. This has already been considered as follows A large number of foreign experience has been proved. Mixed combustion of straw and coal can adapt to the diversity of straw without much modification of existing equipment in power plant. From the technical point of view, the main way out for power generation with straw combustion is to adopt the mixture combustion of straw and coal by primary or compression molding. As long as the problem of measuring and supervising the amount of straw mixed combustion in power plant is solved, it can be obtained. Better environmental protection and economic benefits.

Correlation studies showed that the combustion characteristics of straw were generally good. Straw combustion is mainly concentrated in the early stage of combustion, while coal combustion is mainly concentrated in the late combustion stage. Blending straw can improve the ignition performance of coal and obtain better burnout characteristics. Experiments on different proportions of blended briquette straw combustion show that no coking occurs when the straw burns at 1050 C. As long as the amount of burned straw does not exceed 20%, the combustion characteristics of blended fuel are comparatively close to the combustion characteristics of coal. The combustion characteristics of blended 10%~20% blended with anthracite are similar to that of bituminous coal. Pollutant emissions can be controlled within the required range by blending 10%~20% shaped straw mixed fuel. In the current circulating fluidized bed boiler equipment, it is technically entirely feasible to mix 10%~20% briquette straw directly into coal without modification.