振动筛外文资料及翻译

2012 届届 华北科技学院华北科技学院 本 科 毕 业 设 计 外 文 翻 译 翻翻 译译 题题 目目 Hydrocyclone in the coal cleaning applications 姓姓 名 名 丁清珍 学学 号 号 5 专业班级 专业班级 矿物 B081 院院 部 部 环境工程学院 指导教师 指导教师 张秀梅 2012 年年 6 月月 20 日日 Hydrocyclone in the coal cleaning applications TABLE 7 14 Effect of Geometry and Concentration of Feed Solids on throughput for a 1 6 in diam hydro cyclone cleaning 1 4 in Varying 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 sheets Soon 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 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 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 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 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 Performance As 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 Spiral concentrators 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 旋流器直径为 1 4 in 表 7 14 入料 底流口 直径 in 溢流口 直径 in 入料口 直径 in 处理量 t h 10 20 751 501 231 8 9 81 753 001 232 9 9 81 753 003 004 5 17 31 753 003 008 9 改变旋流器溢流口和底流口的距离 例如 降低分选精煤的灰分可以通过 减小旋流器溢流口的距离 减小溢流管的长度 或者增大底流口的直径 增大 入料量会降低分选效率 因此 分选精煤的产率和灰分的关系表明了只有保证 恒定的入料量才能保证洗选精煤的质量 处理量影响着旋流器的几何尺寸 包括溢流口的尺寸 底流口的尺寸 入 料口的尺寸和入料量 这些参数的影响如表 7 14 改变入料压力是一个改 变旋流器参数的简单方法 然而对改变精煤的产率和灰分的影响不明显 而且 会增加抽水成本 还会导致煤的泥化现象 流程图流程图 随着旋流器的发展 很明显它毫不逊色于其他的分选设备 因此 为了提 高性能 两段分选的旋流器 如图 7 64 被开发了出来 最早的两段分选旋流 器叫第二段再选或者叫 TSR 从第一段旋流器出来的产品只是简单的在第二段 再选 从两段旋流器溢流口出来的煤被混合当作洗选精煤产品 从第二段旋流 器底流出来的物料被视为洗选尾矿作为矸石 最近的有一种设备 一种从旋流 器第二段出来的产品被循环作为第一段的入料 在两段旋流器的溢流循环 TSOR 这种从旋流器的第一段被作为调节产品所要求精煤 第二段作为调节尾 矿中保证没有错配物 从旋流器第二段的溢流出来的物料包含本该进入到第二 段旋流器底流的错配物 所以返回到第一段旋流器进行再次循环洗选 在两段 旋流器底流循环 TSUR 这种从第一段旋流器的底流出来的物料被作为最终的 尾矿矸石 第二段的底流出来的物料再次进入到第一段作为第一段的入料 从 第二段溢流出来的产品被作为最终的洗选精煤产品 上述的其中每个流程都有优点 取决于入料的粒度组成 和所要求的精煤 产品质量 TSOR 流程能更有效地回收分选精煤 而 TSUR 流程更有效地排除重 产物 当两段旋流器分选的比重类似时 TSR 流程是最有效的流程 相反 TSOR 和 TSU 的性能取决于两段旋流器的分流量 在目前 TSOR 是应用的最为普遍的一种流 程 有人提出一种改进的 TSR 流程是从第一段主选底流出来的物料被再次分选 浓缩代替第二段旋流器分选 入料 精煤 尾煤 TSR 入料 精煤 精煤 尾煤 尾煤 入料 TSOR TSUR 图7 64 旋流器分选工艺流程 有一些厂用跳汰机分选块煤 利用旋流器分选细粒的煤 一种方法是用煤 用振动筛筛分的筛下物 通常 1 4 英寸 的煤用旋流器分选 另一种方法是用 煤用振动筛筛分出粗粒煤 细粒度的煤用旋流器分选 旋流器也被运用到重介质分选中去分选出一些含煤少的贫矿 以降低选煤 厂重介质的消耗 旋流器可以调节的分选密度大概在 1 35 1 40 之间 这样的 优点是大大的降低了分选过程中所需重介质的体积 节约了资金和运营的成本 水力旋流器性能水力旋流器性能 正如上文以前 对洗精煤产品质量和垃圾 可通过改变调节溢出和下溢口 的直径 但是从性能的角度来看 溢流直径到底流直径的比例范围为约 1 7 至 2 为最好 较低的比率性能为低劣产品 此外 在原料中固体物含量 一段和 二段水力旋流器应定为 8 至 15 重量 此范围以外 高于或低于 性能将 产生不利影响 分离获得的水力旋流器和一个两阶段的电路 TSR 是由图所示 的分布曲线 两个阶段的电路分离清晰度明显优于单一的水力旋流器 另外 这两个阶段的电路分离清晰度几乎没有像重介质旋流器特点鲜明 由此得出结 论 水力旋流器应用于难以清洁煤或低比重的适用 除非更 有效的再分选过 程 此外 他们没有合适的煤或者易碎的煤矸石颗粒板状 表 7 15 给出了详细的两个阶段 TSR 的水力旋流器的性能数据 这些数 据表明 在一般的分离增加 分离小颗粒的清晰度的减少 水力旋流器可能会 适合分选 30 目 0 6 毫米 的煤 如果煤不浮选 然而 美国多数煤浮选煤 很容易分选通过浮选 但是 如果煤炭 不受外界因为黏涂层问题浮选或煤被 氧化 然后水力旋流