振动筛外文资料及翻译(共11页).doc
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1、精选优质文档-倾情为你奉上2012 届华北科技学院本 科 毕 业 设 计 外 文 翻 译翻 译 题 目：Hydrocyclone in the coal cleaning applications姓 名： 丁清珍 学 号： 5 专业班级： 矿物B081 院 部： 环境工程学院 指导教师： 张秀梅 2012年 6月20日Hydrocyclone in the coal cleaning applicationsTABLE 7-14. Effect of Geometry and Concentration of Feed Solids on throughput for a 1/6-in, di
2、am hydro cyclone cleaning 1/4-inVarying the distance between the bottom of the vortex finder and the hydro cyclone cone bottom. For example, the washed coal ash can be reduced by decreasing the diameter of the vortex finder, decreasing the length of the vortex finder, or increasing the diameter of t
3、he underflow orifice. Increasing feed-Solids content increases the specific gravity of separation and, therefore, washed coal yield and ash, which indicates the importance of maintaining a constant feed-solids content to preserve washed coal quality.Capacity is influenced by cyclone geometry, i.e.,
4、the sizes of the overflow, underflow, and inlet openings, and by feed-solids content. The effects of these parameters is given in Table 7- 14.Increasing inlet pressure is a simple method of increasing capacity without changing hydro cyclone geometry, and washed yield and ash are not significantly af
5、fected. However, the penalty is increased pumping cost, and degradation of the coal. Flow sheetsSoon after the hydro cyclone was developed, it became evident that performance was inferior to nearly all other cleaning devices. Consequently, in an effort to improve performance, three two stage circuit
6、s, shown in Fig. 764, were developed. In the earliest two-stage circuit, called two-stage relearn or TSR, the refuse from a primary hydro cyclone is simply relearned in a secondary hydro cyclone, The overflows from the two hydro cyclones are recombined as the washed coal product, and the underflows
7、from the secondary hydro clone contains the final refuse. In more recent installations, one of the products from the secondary hydro cyclone is recirculated to the feed of the primary hydro cyclone. In the two-stage overflow recirculation circuit, TSOR, the primary or first-stage hydro cyclone is ad
8、justed to produce an acceptable clean coal and the secondary hydro cyclone is adjusted to produce a refuse essentially free of misplaced coal. The overflow from the secondary hydro cyclone, which contains the misplaced coal in the underflows of the primary hydro cyclone, is returned to the feed of t
9、he primary hydro cyclone for reprocessing. In the two-stage underflow recirculation circuit, TSUR, and the overflow is relearned in the secondary hydro cyclone. The underflow from the secondary hydro clone is recalculated to the feed of the primary hydro cyclone. The overflow from the secondary hydr
10、o cyclone contains the washed coal.Each of these circuits has advantages that depend upon the size and specific gravity compositions of the feed, as well as the required washed coal quality. The TSOR circuit is more effective in recovering washed coal whereas the TSUR circuit is more effective in re
11、jecting heavy impurity. The TSR circuit is most effective when the specific gravity of separation of the two hydro cyclones is similar. Conversely, the performance of TSOR and TSUR is improved by diverging the specific gravity of separation of the two cyclones. At the present time, the TSOR is the m
12、ost common circuit. A variation of the TSR circuit has been proposed whereby underflow from the primary cyclone is relearned on a concentrating table rather than a secondary hydro cyclone.Some plants using jigs to clean the coarse coal utilize hydro cyclones to improve performance on the finer sizes
13、. One method is to relearn the underflow of the washed coal screen, commonly the 1/4-in.material, with hydro cyclones. Another method is to screen the raw coal at about this size and clean the undersize with hydro cyclones.Hydro cyclones have been used ahead of dense-medium cyclones to remove some o
14、f the low specific gravity coal and thereby reduce the amount of material sent to the dense-medium plant. The hydro cyclones are adjusted to separate at a specific gravity of about 1.35 to 1.40. The advantage is that the capacity of the dense-medium cyclone plant can be smaller, thus reducing capita
15、l and operating costs.Hydro cyclone PerformanceAs mentioned previously, the quality of the washed coal and refuse products can be regulated by changing the diameters of the overflow and underflow orifices. However from a performance standpoint, a ratio of overflow diameter to underflow diameter in a
16、 range of about 1.7 to 2 gives the best results. Performance at lower ratios is inferior. Also, the solids content in the feed to primary and secondary hydro cyclones should range from 8 to 15 % (by weight). Outside this range, either above or below, performance is adversely affected.Separations obt
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