Two technical directions of transformation and transformation of coal power units

Biomass fuel market

A prerequisite for the realization of biomass mixed combustion power generation of large coal power units is that there must be sufficient and relatively stable biomass fuel supply. China is a big agricultural country with abundant resources of crop straw and agricultural product processing residues. Although the natural forestry resources are relatively few, there are many fruit trees, artificial afforestation and fuelwood forests. It is estimated that China's existing crop straw and agricultural product processing residual resources and forest fruit wood processing industry residual resources are equivalent to about 1 billion tons of standard coal/year, and these biomass resources provide a guarantee of biomass fuel sources for coal power unit mixed combustion. However, having biomass resources does not mean having a market for biomass fuels. The above resources are distributed in the vast rural fields, mountain forest and urban green space, it is not easy to establish its collection, transportation, processing, storage and logistics system. Due to the characteristics of biomass fuel resource dispersion and different forms, the production supply chain of biomass fuel has not yet formed in China. In particular, because biomass is a fuel with low energy density, irregular shape and high water content in the initial state, its collection, transportation and fuel treatment are difficult. Therefore, the production, collection, treatment, transportation and storage of biomass fuel, as well as the combustion process and the impact on combustion equipment are different from coal. Therefore, the end use of biomass fuel costs (in terms of heat) must be higher than fossil fuels. In order to develop coal and biomass coupled mixed combustion power generation, the formation of biomass fuel market, so for the development of biomass fuel market, the state needs to support food production, agricultural machinery sales, fresh agricultural products transportation, the introduction of consistent appropriate financial subsidies and tax incentives. At the same time, in the establishment of biomass pellet fuel supply and demand market, China should also implement the policy of two markets double cycle, in the domestic cycle at the same time, learn from the advanced experience of foreign countries, rational use of foreign resources, international cooperation, a certain degree of external cycle, in order to meet the needs of China's coal power low-carbon development.

It is mainly used in large and efficient coal-fired power plants

The biomass coupled mixed combustion transformation should be mainly used in large and efficient coal-fired power plants. For the pulverized coal furnace of a large coal-fired power plant, due to the large boiler capacity, the biomass fuel heat output is low, even if the use of a small biomass blending ratio (according to the fuel heat), its annual consumption of biomass fuel is quite considerable. Taking a 660MW ultra-supercritical unit boiler as an example, its power supply coal consumption is about 290g (standard coal) /kWh, if 10% biomass combustion ratio to achieve mixed-combustion power generation, biomass fuel application base heat value of 14.7MJ/kg (grass and woody mixed fuel), the annual operation of 4500 hours, The annual electricity supply (about 300 billion KWH) requires about 172,000 tons of biomass fuel. Because the 660MW ultra-supercritical unit has high power supply efficiency and low coal consumption for power supply, if this fuel amount is used for existing small biomass generators, its power supply is only about half, which shows the energy efficiency superiority of large high-efficiency coal power units with mixed biomass power generation. At present, China has a total of 29.52 million kilowatts of installed capacity of small biomass fuel power generation, and the newly added biomass installed capacity will be 2.43 million kilowatts in 2020, with a growth rate of 22.6%. Because of the low efficiency and high coal consumption of small units, the biomass fuel power generation of small units is compared with the mixed combustion power generation of large advanced and efficient coal-fired units. Priority should be given to the development of large coal-fired units and biomass mixed combustion power generation.

For the biomass co-burning of large coal-fired power plants, such a large amount of biomass fuel cannot be directly transported to compact and highly automated coal-fired power plants in the form of bulk materials, and must be pre-pressed into granular fuel at the source of biomass raw materials and then supplied to the power plant. The density of biomass pellet fuel can reach close to thermal coal (1.1g/cm3 or more), the shape is regular, so it is easy to transport, and the storage, transportation and grinding into powder in the power plant (for the pulverized coal boiler) will be all mechanized and automated operation. Depending on the way biomass and pulverized coal are mixed and the burner is different, the biomass particles to the plant are ground into fine powder, and the average particle size can be from about 0.1 mm fine particles to more than 10 mm coarse particles. In developed countries, solid biomass molding fuel manufacturing and use, has more than 30 years of development history, the main characteristics of biomass pellet fuel are: