The concept and characteristics of biomass power generation

The concept and characteristics of biomass power generation

Biomass power generation originated in the 1970s. At that time, after the global oil crisis broke out, Denmark began to actively develop clean renewable energy and vigorously promote power generation from biomass such as straw. Since 1990, biomass power generation has begun to develop rapidly in many European and American countries.

Biomass power generation is a kind of power generation that uses the biomass energy of biomass and is a kind of renewable energy power generation, including direct combustion of agricultural and forestry waste for power generation, agricultural and forestry waste gasification for power generation, waste incineration for power generation, landfill gas for power generation, and biogas power generation.

Among them, the principle of direct combustion power generation is that biomass and excess air are burned in a boiler, and the generated hot flue gas exchanges heat with the heat exchange components of the boiler, and the generated high-temperature and high-pressure steam expands in the steam turbine to perform work to generate electricity.

The principle of gasification power generation is to gasify biomass raw materials in a gasifier to generate combustible gas, which is purified and supplied to an internal combustion engine or small gas turbine to drive a generator to generate electricity.

Biomass power generation has the following characteristics:

(1) Biomass fuel has higher moisture content and lower ash content. Although the ash content is not much, its high content of alkali metals and alkaline earth metals has a tendency to cause slagging, ash accumulation and corresponding corrosion on the heated surface during the combustion process.

(2) The carbon content of biomass fuel is much lower than that of coal. It is a low-carbon fuel, and most of the biomass is low-nitrogen and low-sulfur fuel. The high calorific value of biomass drying base is generally 18~21 MJ/kg, which is much lower than that of coal. The energy density is also much lower than that of coal, about one-tenth that of coal.

(3) The capacity of the biomass direct combustion generator set is relatively large. Currently, the units under construction or planned to be built have reached the level of 25MW units with a single unit capacity abroad, and a unit with a unit capacity of 50MW has been built in Guangdong, my country. It has higher thermal efficiency and is less affected by the environment (biomass fuel can be used wider and processing requirements are lower). It is convenient to be constructed as a public power point alone, and is convenient for large-scale promotion.

(4) The capacity of biomass gasification generator set is small. Generally, it is only a few tenths to a few MW, and the largest is only 4MW at present. It is a reciprocating internal combustion engine unit, and it is in the stage of just construction and trial production.

(5) Biomass gasification generator sets have stricter fuel requirements. It is generally required to use granular biomass fuels such as rice husks and wood chips, and the gas purification requirements are high (except tar and other sundries). Therefore, it is mostly built around wood processing plants, rice mills, etc., and should be used as a self-provided power plant for such plants, which is not convenient for large-scale and large-scale promotion. At the same time, straw gasification has a low calorific value, and it still needs to be further improved in terms of stable operation, tar elimination, and gas purification.

(6) The capacity of biomass biogas generator set is small. Although it is vigorously promoted in rural households to make rural households self-sufficient in electricity consumption and solve the role of manure and garbage, it is not suitable for the construction of public power sources. At the same time, the gas production rate of anaerobic digestion is low and unstable, the automation level of system operation and management is low, the development of industrialization is slow, and it is not convenient for large-scale marketization.

The concept and characteristics of biomass power generation
Flow chart of biomass gasification power plant

Read more: Development status of China’s biomass power generation industry