振动筛外文资料及翻译

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： 2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, diam 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 the 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., 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 affected. 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 circuits, shown in Fig. 7~64, 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 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 adjusted to produce an acceptableclean 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 the 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 hydro 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 rejecting heavy impurity. The TSR circuit is most effective when thespecific 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 most 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. 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 of 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 capital 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 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 obtained in a single hydro cyclone and two-stage circuits (TSR) are shown by the distribution curves in Fig. 7-65. The sharpness of separation of the two-stage circuit is significantly superior to that of a single hydro cyclone. Also, the sharpness of separation of the two-stage circuit is not nearly as sharp as the separations characteristic of a dense-medium cyclone. It follows then that hydro cyclones are not applicable for difficult-to-clean coal or separations at low specific gravity unless followed by a more effective relearning process. Also, they are not suitable for friable coal or where the refuse particles are platy. Table 7-15 gives detailed performance data for two-stage (TSR) hydro cyclones. These data indicate that in general the specific gravity of separation increases and the sharpness of separation decreases with decreasing particle size.Hydro cyclones may be especially applicable for cleaning -30-mesh (0.6- mm) coal if the coal is not amenable to flotation. However, the Majority of US coals are easily cleaned by flotation. But if the coal is not amenable to flotation because of a slime-coating problem or the coal is oxidized, then hydro cyclones may be a viable alternative. Also if fine pyrite is present in the feed, hydro cyclones are reported to be superior to flotation for lowering the sulfur content of the washed coal.The coarser particles of an easy-to-clean coal with a top size of 1/4 or 3/8 in.(6.3 or 9.5 mm) can be cleaned about as efficiently in a two-stage hydro cyclone circuit as on a concentrating table, but not as efficiently as in a feldspar jig. However, the concentrating table cleans the finer particles much more efficiently than the hydro cyclone. The distribution curves for a two-stage hydro cyclone circuit (TSR) and a concentrating table cleaning a 1/4-in (6.3mm*0) feed are shown in Fig. 7-66. A major advantage of hydro cyclones is that the space requirement is much less than for concentrating tables and jigs, but much more power and water are required. Spiralconcentrators are also used to clean-14-mesh (1.2-mm) coal.A relatively new separator, called the air-spared hydro cyclone, has been developed and can be used to clean opal. It is essentially a porous cylinder without the usual conical section. Feed enters tangentially at the top and spirals downward. Air is introduced through the porous cylinder, and the air bubbles and flotation reagents along with the vortex effect the separation. Coal particles attach to the rising air bubbles and exit the top through a vortex.水力旋流器在选煤方面的应用表7-14，给出了影响入料分选密度和粒度的处理量。