Qingru Chen

Separation characteristics for fine coal of the magnetically fluidized bed

Dry beneficiation technology with an air dense medium fluidized bed is briefly introduced. Systems for the dry separation of fine coal consisting of a magnetically fluidized bed (MFB) as separation medium are described. The magnetic stabilization produces homogeneity and stability of the fluidized bed and thus enhances the separation efficiency by preventing remixing of the feedstock to be separated. Experiments have been conducted in a 100-mm inner diameter cylinder and results show that a uniform and stable MFB can be formed and fine coal (<6 mm size) can be separated efficiently.

Magnetically stabilized fluidized beds for fine coal separation

Abstract Based on a prior study on air-fluidized dense media for 6–50-mm coal preparation, this paper presents results on magnetically stabilized fluidized bed (MSFB) on fine 1–6-mm coal preparation. Magnetic stabilization improves separation by lowering the lower size limit of separation and by preventing back mixing of the separated solids. This work addresses the fluidization media characteristics, the experimental system and separation results.

Progress in Dry Coal Cleaning Using Air-Dense Medium Fluidized Beds

A commercial dry coal cleaning plant (50 2 6 mm feed) using an air-dense medium fluidized bed has been established in China. It is an important clean coal technology (CCT) due to insufficient water resources in China and abroad. This article studies the fluidization performance and bed density homogeneity of a vibrated fluidized bed and a double-density fluidized bed. The experimental results obtained with a 2000 mm 2 80 mm 2 200 mm model apparatus showed that the vibrated fluidized bed can efficiently separate <6 mm fine coal with an E p value of 0.07 and a lower separation limit of 0.5 mm. A double-density fluidized bed was formed by specially designing the bed structure with a pyramidal part. It can produce three products in a fluidized cascade at aseparation density of 1.49 g/cm 3 with an E p value of 0.06 and a separation density of 1.85 g/cm 3 with an E p value of 0.07.

Fine coal (6-1 mm) separation in magnetically stabilized fluidized beds

Abstract Air-dense medium fluidized beds for separating 50–6 mm coal have been used successfully in commercial applications in China. In this study, the authors studied magnetically stabilized fluidized beds for separating fine coal (6–1 mm). The magnetic stabilization enhances the separation by preventing back mixing of the feed solids. This paper discusses the principle of coal separation in magnetically stabilized fluidized beds, the experimental system, and the separation results.

Fundamentals of a Magnetically Stabilized Fluidized Bed for Coal Separation

The performance of a magnetically stabilized fluidized bed is strongly affected by the properties of the air-fluidized dense medium, especially for the dry fine coal separation. The successful design and operation of a magnetically stabilized fluidized bed system for dry coal separation depend on the ability to accurately predict the fundamental properties of the fluidized bed, particularly the fluidized beds rheological properties and density. These properties are controlled and modified by magnetic field intensity and medium composition. The composition variables include medium density, magnetite particle size distribution, particle shape, and level of contamination. Some of these fundamentals of a magnetically stabilized fluidized bed for dry coal separation are described in this paper.

Separation lower limit in a magnetically gas–solid two-phase fluidized bed

Abstract The magnetically stabilized fluidized bed has the characteristics of a dispersion gas–solid two-phase flow. The essential condition by which the feedstock was separated by bed density was determined through studying the composition and action of dense medium (gas–solid fluidized bed) on feedstock. The forces exerted on a separated feed with sizes close to the lower limit of separation were analyzed. The correlative formula of the lower limit of separation was obtained theoretically. Experimental results in a 100-mm magnetically fluidized bed model show that the coal can be separated efficiently under a good fluidization state with Ep values of 0.05–0.08. The lower limit of separation is about 0.5 mm.

Formation of Double-Density Fluidized Bed and Application in Dry Coal Beneficiation

Currently utilized separators with air-dense medium fluidized bed can only produce two products with single-separating density. Two separators must be employed in series to generate three products, which leads to the complication of the technical system and on increase in construction investment and operation costs. Moreover, they are difficult to operate continuously owing to the problems of preparation and recovery of dense media. The double-density fluidized bed forms two separating areas with different densities in a fluidized cascade. In each separation area, the bed density is uniform and meets the needs for three-product separation of coal. Therefore, the coal can be separated into three products according to density. In this paper, the fluidized behavior of binary dense media was experimentally studied in different bed structure. The segregation and mixing process of binary dense media was analyzed. By use of the proper operation conditions and the specially designed bed structures, a double-density fluidized bed was formed for three-product separation of coal.

Fine Particle Behavior in Air Fluidized Bed Dense Medium Dry Separator

The technique of applying fluidized solid magnetic powder as the dense medium to separate coal was applied in a pilot-scale dry separation plant and commercial coal mill in China recently. The nature of density distribution of the air fluidized bed dense medium is an important factor that influences the performance of the separator. However, during coal processing, fine coal particles would mix with dense medium of magnetite powder and accumulate in the bed. Its behavior will affect the density of the bed. The density distribution with fine coal particles was studied in a laboratory experimental system and in the pilot-scale air fluidized bed dense medium dry separator. The functional relation between density of air fluidized bed dense medium and fine coal particle content was fitted, applying the principle of least-squares method with damping factors, and a mathematical model was obtained. After analyzing the trial testing data, the mechanism of density distribution of the bed was studied and explained.