[Objective

]

In order to further promote the coupling of coal-fired power units with biomass fuel and advance the development of low-carbon transformation technology in coal-fired thermal power units

this paper investigates the adaptability of directly using a medium speed coal mill to grind biomass pellet fuel without any equipment modification

which is one of the key processes in directly fired biomass fuel coupling technology with coal-fired thermal power units. [Methods

]

Firstly

an industrial trial grinding test of pure biomass pellet fuel was conducted on a medium-speed coal mill(model MP212B

in commercial operation) of a coal-fired boiler unit. Then

the characteristics of the medium speed coal mill in grinding the biomass pellet fuel were studied usin

g the standard method specified in the current national standard

and the results were compared with the experimental data. Finally

based on the results of the experiments and theoretical analysis

further technical improvement measures were proposed to enhance the adaptability of medium speed mills to biomass pellet fuel. [Results

]

The MP212B model mill test results showed that the mill could achieve a maximum biomass fuel output capacity of 25 t/h

which was about 0.6 times the output capacity for coal grinding. The air-to-fuel ratio was maintained between 3.0 and 5.0. The loading force of grinding rollers was controlled at 7.5 MPa

which was much higher than that for coal grinding. The fineness of the biomass powder R

500

in mill outlet was lower than 40%

and it was decreasing with the increase in separator speed. Compare with the experimental results

the theoretical calculations and analysis results of medium speed mill to biomass pellet fuel were significantly inconsistent. Therefore

in the fundamental theoretical level

an improved algorithm was proposed

which was replacing the current method's Hardgrove grindability index correction factor with a method based on internal mill circulation rate and bulk density for correction. Using the improved algorithm

the corrected calculation results were basically consistent with the experimental results. [Conclusion

]

The research findings further enrich the experimental data and theoretical basis of direct-fired biomass coupling technology with coal-fired power units

and have reference significance for accelerating the development of biomass coupled power generation technology of coal-fired power units.