To ensure the pulverizing system of newly built thermal power units can meet the requirements for power generation capacity and peak-shaving capability and the fineness of the pulverized coal for combustion

this article investigates the practical grinding output and theoretical calculated grinding output of medium speed mills

on the basis of performance evaluation results of the medium speed mills in operation. The results show that

the output of current most medium speed mills can not meet the design requirements

and the fineness and size uniformity indexes of the pulverized coal can not meet the design requirements in some cases either

which indicates that only using the commonly used theoretical calculation method for coal mill selection has certain risks. It suggests that the mill type of a power unit can be selected according to the field test results of grinding design coal and check coal using the same type of coal mill. In addition

it is also necessary to consider the requirements of load capacity and peakshaving capacity of the unit to avoid the difference between peak-shaving capacity and load-regulation capacity caused by too large or too small scale selection of the coal mill type. This study provides a reference for selection of the medium speed mill for large-scale pulverized coal boilers and for fuel structure optimizations of the coalfired units in operation.