Study on Electrostatic Preparation High-Ash Coal from China Using Roll-Type Electrostatic Separator and the Combustion Characteristics of the Cleaned Coal

The dry roll-type electrostatic coal beneficiation technology under high voltage is used to study the beneficiation of low-grade and high-ash coal in Inner Mongolia, northern China. The optimal coal beneficiation conditions are determined by adjusting three parameters: the electrode voltage, the distance between the electrode and the drum, and the angle θ of the electrode. The best quality clean coal is obtained under the condition of voltage of 30 kV, angle θ of 75°, and electrode distance of 7 cm. Moreover, after separation, the quality of clean coal accounted for 48.41% of the raw coal mass, while the ash ratio decreased from 38.6% of the raw coal to 18.71% of the clean coal, which significantly improves the coal usability. Finally, through the methods of combustion characteristics analysis, infrared spectrum analysis, and combustion exhaust gas analysis of raw and clean coal, it is proven that the roll-type electrostatic separation technology has a high coal beneficiation effect on the high-ash, low-grade coal in Inner Mongolia.

Selective Crushing of Run-of-Mine as an Important Part of the Hard Coal Beneficiation Process

To obtain commercial product of required quantitative and qualitative parameters, hard coal must be subjected to a number of processing operations. Preliminary stone removal from run-of-mine is one of them. Methods of such removal, including the method of selective crushing are described. Design solutions for a KOMAG-type device for dry stone removal of run-of-mine are presented. The results of laboratory tests for selective crushing susceptibility of steam coal and coke are presented, and a comparative analysis of the tested types of coal is made. Possibilities of increasing the production of commercial products by using a Bradford drum crusher is analyzed from the economical point of view.

Modelling of Hard Coal Beneficiation Process Utilising Negative Pressure Pneumatic Separator

The dry separation methods for coal beneficiation have been regaining attention in the past decades. A number of improved or newly designed devices have been developed—one of them is a negative pressure pneumatic separator (NPPS). The said method of separation is based on the differences in the physical properties between coal and gangue minerals, such as the grain density, size, and shape. The aim of the hereby presented work was to develop working models describing the operation of the NPPS. To validate the models, the calculation results were compared with experimental results of the tests carried out in the previous study on the topic. Based on the findings it can be inferred that the models accurately predict the separation results, i.e., the majority of results are within the range of estimated measurement uncertainties. Consequently, the models allow one to optimise the process to obtain the products with desirable properties.