化工专业英语第五篇翻译

Distillation 蒸馏

The separating operation called distillation utilizes1 vapor and liquid phases at essentially the same temperature and pressure for the coexisting zones. Various kinds of device such as dumped2(倾倒;堆放) or ordered3 packings4 and plates5 or trays5 are used to bring the two phases into intimate （亲密的；隐私的）contact. Trays are stacked（叠，层叠）one above the other and enclosed（装入）in a cylindrical shell to form a column6. Packings are also generally contained（包含；容纳）in a cylindrical shell between hold-down7 and support plates.

称为蒸馏的分离操作是利用蒸汽相和液体相在基本相同的温度和压力下相互接触进行的。各种设备，诸如散装的或者整砌的填料以及塔板或者塔盘用于使两相充分接触。一块塔盘置于另一块之上并装入一个圆筒中形成一座塔。填料一般也是装入圆筒中的支承板与压板之间。

1. Continuous Distillation (Fig.7) 连续蒸馏

The feed material, which is to be separated into fractions1, is introduced at one or more points along the column shell. Because of the difference on gravity between vapor and liquid phases, liquid runs down the column, cascading2(成瀑布状落下；溢流) from tray to tray, while vapor flows up the column, contacting liquid at each tray.

需要分离为几个馏分的物料从塔壳上的一个位置，或者几个沿塔高分布的位置进入塔中。因液相与汽相的重度不同，液体一块塔板接一块塔板地溢流而下，同时蒸汽相则向上流动，在每一块塔板上与液体接触。

Liquid reaching the bottom of the column is partially vaporized in a heated reboiler (再沸器)to provide(保持) boil-up(煮开), which is sent back up the column. The remainder（残余物；剩余部分）of the bottom liquid is withdrawn（采出）as bottoms （残留物，残渣，下脚料）, or bottom products. Vapor reaching top of the column is cooled（冷却）and condensed（冷凝）to liquid in the overhead （在高处，在上的）condenser（冷凝器）. Part of the overhead stream is withdrawn as distillate, or overhead product.

到达塔底的液体在持续加热沸腾的再沸器中部分汽化，产生的蒸汽又返回到塔中并沿塔上升。塔底液体的剩余部分作为下脚料或者底部产品采出。上升到塔顶的蒸汽在顶端的冷凝器中冷却并凝结为液体。顶部液体的一部分作为馏出物或者说是塔顶产品采出。

This overall（全部的，全面的）flow pattern in a distillation column provides countercurrent （逆流的，相反的）contacting of vapor and liquid streams on all the trays through the column. Vapor and liquid phases on a given tray approach1 thermal, pressure , and composition equilibrium to an extent （is）dependent2 upon the efficiency of the contacting tray.

在精馏塔中的这种普遍的流动模式使蒸汽流和液体流在塔内的所有塔板上逆流接触。在一块指定的塔板上，相互接触的汽液两相在热量，压力和组成上接近平衡的程度取决于这块板的效率。

The lighter (lower-bioling) components（组分）tend to concentrate（浓缩；集中）in the vapor phase, while the heavier (higher-boiling) components tend toward the liquid phase. The result is a vapor phase that becomes richer in light components as it passed1 up the column and a liquid phase that becomes richer in heavy components as it cascaded1 downward. The overall separation achieved between the distillate（馏出液）and the bottoms（残液）depends primarily on the relative volatility（挥发度）of the components, the number of contacting trays, and the ratio2 of the liquid-phase flow rate to the vapor-phase flow rate. If the feed is introduced at one point along the column shell, the column is divided into an upper section, which is often called the rectifying（修整，提纯，精馏）section, and a lower section, which is often referred to as the