Simulation study of the energy-size reduction of MPS vertical spindle pulverizer

As an important pulverizing equipment, the vertical spindle pulverizer (VSP) is widely used in power plants to produce fines for combustion. But high temperature and pressure in VSP limit the study of grinding process. Herein, a laboratory roller mill, with the addition of a power recorder, has been designed for the simulated study. Parameters of loading force, table revolution rate and fractional filling in this device can be adjusted. Grinding tests for different combinations of these three parameters are conducted. Confidence analyses of the experimental data illustrate the reliability of results, with a 90% confidence limit being 5% of the mean measured value. Breakage characteristics of the top size show the first-order law and the initial samples of narrow size fraction are all broken and disappear with less than 20 s. Both the loading force and table revolution rate have a positive effect on t10 and the tests for condition of lower fractional fillings also generate the high value of t10. For the analyses of energy-size reduction, t10 and specific energy are conducted as the response results. The mathematical relationship between t10 and specific energy of the grinding test with fixed parameters can be described well by the classical energy-size reduction breakage model, t10=A(1-e-b·Ecs),with the R2 > 0.97. Due to the difference of values of t10 generated at the unit specific energy for the conditions of different parameter combinations, this model only can simulate the grinding process with changes of loading forces or fractional fillings. 10 Sets of additional experimental data demonstrate this conclusion. Reasons of this phenomenon are discussed.