A Study Of Drying Kinetics Of A Coking Coal On Fluidizedbed Dryer And Microwave Dryer

Coking coal drying was an effective measures to improve our coking coal utilization and conversion efficiency. Fluidized bed drying technology had been widely applied in the field of coal drying, as its simple structure, easy to operate, rapid heat and mass transfer rates, highly thermal efficiency. As a new efficient and environmentally friendly drying technology, microwave drying had many advantages, such as selective heating, rapid heating rates, uniform heating amd highly thermal efficiency, was gradually accepted by the industry of coal drying. Therefore, this study will research kinetics of fluidized bed and microwave drying of Henan Pingdingshan coking coal. This study could provide theoretical support and basic data for the development of drying technology of coking coal and metallurgic coal. It also could provide an effective way for solving the problem of high moisture of coking coal in our country.Firstly, the basic parameters of Henan Pingdingshan coking coal were investigated. It was fould that Henan Pingdingshan coking coal was a high-quality metallurgic coal with low ash, low sulfur and medium volatile content. Its ARD(apparent relative density) was 0.754g/cm3 and its TRD(true relative density) was 1.334 g/cm3. Coal's Harrington grindability index was 104.06. Most particle sizes of coal was larger than 3.3mm, which accounting for 56.86%. It was found that coking coal had the same structure as the common porous media, and its pore was small.A lab scale fluidized bed drying system was built for study the kinetics of fluidized bed drying of Henan Pingdingshan coking coal. The drying rate was shown to increase with increasing drying temperature, initial moisture content and gas flow rate, and decreasing particle size and bed height. All models except Wang and Singh model could well describe kinetics of fluidized bed drying of Henan Pingdingshan coking coal. But the Page model MR = exp(-ktn) was the best model to represent the fluidized bed drying behavior of Henan Pingdingshan coking coal coking coal.A microwave reactor was used to carried out the Henan Pingdingshan coking coal experiment. The drying rate was shown to increase with increasing coal particle size, microwave power and initial moisture content while particle size less than 1mm. The drying rate was shown to decrease with increasing coal particle size and microwave power,but the initial moisture content had no significant effect on the drying time. The Diffusion approach model MR = aexp(-kt)+(1-a)exp(-kbt) was the best model to represent the microwave drying behavior of Henan Pingdingshan coking coal.The changes of chemical structure of Henan Pingdingshan coking coal during fluidized bed and microwave drying were investigated using FTIR technique. It has been found that mild oxidation of coking coal will occur during fluidized bed drying. And the oxidation mainly occurred in naphthenic carbon and aliphatic carbon. The oxidation would increase with increasing temperature. However, the other organic functional groups of coking coal had no significant changes during fluidized bed drying. The organic functional groups of coking coal had no significant changes during microwave drying. But the absorption peak of sulfur functional groups of Henan Pingdingshan coking coal reduced during microwave drying. Microwave drying had some effect to desulfurization of coking coal.