Luo Zhenfu

Dry beneficiation technology of coal with an air dense-medium fluidized bed

Abstract Dry beneficiation technology of coal with an air dense-medium fluidized bed commenced application lately in China. This paper analyzes the characteristics of gas-solids fluidized beds and basic principles of coal separation, and describes systems for coal dry beneficiation (including raw coal pre-treatment, coal separation, medium solids recovery, air supply and dust removing). Experiments on a 50MTPH air dense-medium fluidized bed system for the dry beneficiation of coal shows that a uniform and stable fluidized bed can be formed with magnetite powder or a mixture of magnetite powder and fine coal as medium solids. The separation performances of the separator were investigated and assessed in detailed. The results indicate that 50×6 mm coal can be separated effectively with an E P value of 0.05. The performance results of this technology are satisfactory.

Effect of fine coal accumulation on dense phase fluidized bed performance

System for the dry separation of 50×6-mm coal is described. It consists of an air dense-medium fluidized bed as the separation medium (using 0.15×0.30-mm magnetite powder as the main medium solid). The bed density stability is a key operational parameter during separation, as the feed coal is separated according to the bed density. In separating process, the fine coal (<1 mm) will continuously accumulate in the fluidized bed, thus inevitably resulting in the fluctuation of bed density. The distribution of fine coal in an air dense-medium fluidized bed was studied. We learn from the study that fine coal can mix with magnetite powder and distribute uniformly in the fluidized bed. Experiment results in the pilot system show that a mixture of magnetite powder and fine coal can also be used as medium solid, and the 50×6-mm coal can be separated efficiently with an Ep value of about 0.05 under 8.8 cm/s gas velocity. The stability of bed density can be maintained through split-flow of used medium solids and complement of fresh medium solids (magnetite powder) in continuous coal separation.

Establishment and Evaluation of a United Dry Coal Beneficiation System

A united dry coal beneficiation system combining the FGX separator with the air-dense medium fluidized bed separator was firstly established basing on careful considerations for the recent situation of dry coal preparation at home and abroad. The main equipment and the process flow of the United System are described in detail. The separation performance of the United System was accessed by separating run-of-mine coal from an open-pit mine in the Wuhai Region. The results showed that the E p value of the roughing stage and the cleaning stage of the United System were 0.13 g/cm3 and 0.055 g/cm3, respectively. Finally, the United System reduced the ash content of the feed coal by 24.87% and increased the calorific value by 10.32 MJ/kg. This result evidenced that the United System had excellent separation ability.

Fine coal and three product dry beneficiation with vibration and double-density fluidized beds

The fluidizing performance and density uniform stability of vibration fluidized beds were analyzed. The experimental results in 2000 mm×80 mm×200 mm model apparatus show that the vibration fluidized bed can efficiently separate fine coal of size 6–0.5 mm, the beneficiation lower limit is 0.5 mm, the Ep value is 0.07. A double-density fluidized bed was formed by which the bed structure was specially designed with a pyramidal part. It can efficiently turn out three products according to densities in a fluidized cascade. The suitable range of gas flow rate is 4.4–4.6 m3/h. In the lighter area, the separation density is around 1.49 g/cm3, and Ep value is 0.06. In the denser area, the separation density is about 1.85 g/cm3, and Ep value is 0.07.