Research on coupled biomass direct combustion power generation technology of coal-fired units

10 yuan /MWh(including tax), particle combustion led to an increase in tax-included on-grid electricity price of 11.41 yuan /MWh(including tax), and the tax-included on-grid electricity price of the two schemes was about 0.32 yuan /kWh.

According to the benchmark price of coal 364.4 yuan /MWh(including tax), the carbon tax subsidy of bulk material scheme reaches 80 yuan /t, and the carbon tax subsidy of particle scheme needs to reach 93.5 yuan /t to maintain the internal rate of return of capital.

Due to the high cost of biomass fuel and low calorific value, the biomass direct combustion coupling will lead to an increase in on-grid electricity price, and the cost of the power plant will increase, and it is recommended that the construction unit actively strive for electricity price subsidies, electricity subsidies or carbon tax subsidies.

4 Advantages of biomass direct combustion coupling scheme

The carbon emission reduction effect of the 10% biomass direct-burning coupling scheme is equivalent to that of the pure biomass burning scheme, and its index analysis is carried out below.

1) Unit efficiency

The power generation of the 35MW pure biomass burning unit is equivalent to that of the 350MW coal-fired unit with 10% biomass burning, as shown in Figure 4. The unit efficiency of the 35MW pure biomass burning unit, 350MW coal-fired unit and 350MW coal-fired unit with 10% biomass burning bulk material with high temperature and high pressure parameters is compared. Unit efficiency corresponding to 10% biomass blending is the unit efficiency when the biomass part is considered independently, that is, the boiler efficiency corresponding to coal burning is assumed to remain unchanged, and the reduction of boiler efficiency after mixing 10% biomass bulk is fully reflected in the boiler efficiency corresponding to biomass bulk. It can be seen that the efficiency of the biomass direct-combustion coupling unit is significantly better than that of the high-temperature and high-pressure pure combustion biomass unit.

2) Initial investment

The initial investment of the 35MW pure burning biomass unit is about 350 million yuan, the initial investment of the direct-burning coupled 10% biomass bulk coupling program of the 350MW unit is about 66 million yuan, and the initial investment of the particle coupling program is about 42 million yuan. The investment of coal-fired coupled biomass direct combustion power generation scheme is significantly lower than that of pure combustion units.

3) Feed-in tariff

The on-grid price of pure combustion biomass unit is 0.75 yuan /kWh, and the on-grid price of 10% direct combustion coupling unit is about 0.32 yuan /kWh.

It can be seen that under the premise of the same carbon emission reduction effect, the biomass direct-combustion coupling scheme has obvious advantages compared with the pure combustion biomass unit in unit efficiency, initial investment, on-grid electricity price and other aspects.

If the use of flue gas post-decarbonization technology to achieve carbon emission reduction of coal-fired units, not only will increase the initial investment, but also will increase the operating cost, the same 350MW coal-fired unit 10% of the flue gas post-decarbonization as an example, the initial investment of about 150 million yuan, the operating cost will cause the on-grid electricity price increase of about 0.12 yuan /kWh. Compared with the flue gas post-decarbonization scheme, the economic benefits of biomass direct-combustion coupling power generation scheme are also very significant.

Therefore, the coupled biomass direct combustion power generation technology is currently a more suitable carbon emission reduction technology route and biomass energy utilization mode for coal-fired units.