化学工程与工艺专业英语 中文不完全版.doc

Unit 16 Evaporation，Crystallization and Drying3. DryingDrying is the removal of water, or other volatile liquids, by evaporation. Most solid materials require drying at some stage in their production. The overriding consideration in the selection of drying equipment is the nature and concentration of the feed. Drying is an energy-intensive process, and the removal of liquid by thermal drying will be more costly than by mechanical separation techniques.3.干燥干燥室用蒸发方法出去水和其他的挥发性液体。大部分在其生产时需要干燥。选择干燥设备的最主要的考虑因素是进料的本质及其浓度。干燥室能源密集型的过程。利用热干燥来除去液体的费用较利用机械技术的费用要高得多。Except for a few specialized applications, hot air is used as the heating and mass transfer medium in industrial dryers. The air may be directly heated by the products of combustion of the fuel used (oil, gas or coal) or indirectly heated, usually by banks of steam-heated finned tubes.除了几种特种的应用之外，热的空气在工业干燥器中用作加热和传质介质。空气可直接用所用燃料（石油、天然气和煤）的燃烧产物加热，或者间接加热，通常通过蒸汽加热的翅片管管道加热。The basic types used in the chemical process industries are:用于化学过程工业中的干燥器基本类型有：Tray dryers Batch tray dryers are used for drying small quantities of solids, and are used for a wide range of materials. The material to be dried is placed in solid bottomed trays over which hot air is blown; or perforated bottom trays through which the air passes. Batch dryers have high labor requirements, but close control can be maintained over the drying conditions and the product inventory, and they are suitable for drying valuable products.板式干燥器 间歇板式干燥器用于干燥少量的固体。所适用的物料范围广。欲干燥的物料位于固体底板上，在固体底板上吹入热空气，欲干燥的物料位于穿了孔的底板上，热空气流经该底板。间歇干燥器劳动力要求高，但干燥条件和产物存货可以得到很好的控制。板式干燥器适合于干燥有价值的产物（品）。Conveyor dryers (continuous circulation band dryers) In this type, the solids are fed on to an endless, perforated, conveyor belt, through which hot air is forced. The belt is housed in a long rectangular cabinet, which is divided up into zones, so that the flow pattern and temperature of the drying air can be controlled. The relative movement through the dryer of the solids and drying air can be parallel or, more usually, counter-current.带式干燥器（连续循环带式干燥器） 该类型的干燥器，固体产物在一个很长的穿孔的传送带上，热空气强制地流过该传送带。传送带被罩在一长的矩形箱内，该箱分成几个区域，以致能控制干燥气体的流型和温度。固体干燥器和干燥空气的相对运动可以是并流的，或者更多的是对流。This type of dryer is clearly only suitable for materials that form a bed with an open structure. High drying rates can be achieved, with good product-quality control. Thermal efficiencies are high and, with steam heating, steam usage can be as low as 1.5 kg per kg of water evaporated. The disadvantages of this type of dryer are high initial cost and, due to the mechanical belt, high maintenance costs.该类型的干燥器只适用于那些形成带式结晶的床层的物料，可实现较高的干燥速率，质量控制容易，热效率高，以蒸汽加热，干燥每1kg蒸发水需要用蒸汽低于1.5kg。该类型的干燥器的缺点为，由于机械传送带、维护费用高，所以首次（最初的）费用高。Rotary dryer In rotary dryers the solids are conveyed along the inside of a rotating, inclined, cylinder and heated and dried by direct contact with hot air gases flowing through the cylinder. In some, the cylinders are indirectly heated.旋转式干燥器 在旋转式干燥器中，固体物质沿着一旋转的倾斜的固体的内部进行输送，通过直接与流经圆柱的热空气而加热、干燥。有时，圆柱间接加热。Rotating dryers are suitable for drying free-flowing granular materials. They are suitable for continuous operation at high throughputs; have a high thermal efficiency and relatively low capital cost and labor costs. Some disadvantages of this type are: a non-uniform residence time, dust generation and high noise levels.旋转干燥器适合于干燥自由流动的粒状的物质，适合用于产量高的连续操作：热效率高，投资费用和劳动费用相对较低。该类型干燥器的一些缺点为：停留时间不统一，产生灰尘，噪声程度较大。Fluidized bed dryers In this type of dryer, the drying gas is passed through the bed of solids at a velocity sufficient to keep the bed in a fluidized state; which promotes high heat transfer and drying rates. Fluidized bed dryers are suitable for granular and crystalline materials within the particle size range 1 to 3 mm. They are designed for continuous and batch operation. The main advantages of fluidized dryers are: rapid and uniform heat transfer, short drying times, with good control of the drying conditions; and low floor area requirements. The power requirements are high compared with other types.流化床干燥器 在该类型的干燥器中，干燥气以足够的速率通过固体床层，以使床层保持在流化状态，该流化状态可提高很大传热和干燥速率。流化床干燥器适合于粒状大小范围为13mm的粒状和晶体状物质。该干燥器可设计为连续操作和间歇操作。流化床干燥器的主要优点：热传递快且均匀、干燥时间短、干燥条件能很好控制、占地面积的要求低。与其他类型的干燥器相比，需要的动力高。Pneumatic dryers, also called flash dryers, are similar in their operating principle to spray dryers. The product to be dried is dispersed into an upward-flowing steam of hot gas by a suitable feeder. The equipment acts as a pneumatic conveyor and dryer. Contact times are short, and this limits the size of particle-that can be dried. Pneumatic dryers are suitable for materials that are too fine to be dried in a fluidized bed dryer but which are heat sensitive and must be dried rapidly. The thermal efficiency of the type is generally low.气流干燥器也称flash干燥器，它们的操作原理与喷雾式干燥器相似。欲干燥的产品由一个合适的进料器分散与向上流动的加热气的蒸汽中。该设备起着气流传送设备和干燥器的作用。接触时间短，（按因素）限制了要干燥的物料颗粒的大小。气流干燥器适合于那些颗粒太小而不能在流化床干燥器中干燥的物料。该类型的干燥剂的热效率一般较低。Spray dryers Spray dryers are normally used for liquid and dilute slurry feeds, but can be designed to handle any material that can be pumped. The material to be dried is atomized in a nozzle, or by a disc-atomizer, positioned at the top of a vertical cylindrical vessel. Hot air flows up the vessel (in some designs downward) and conveys and dries the droplets. The liquid vaporizes rapidly from the droplet surface and open, porous particles are formed. The dried particles are removed in a cyclone separator or bag filter.喷雾式干燥器 喷雾式干燥器一般适合用于液体和稀的淤泥进料，但是可通过设计以处理任何能用泵输送的物料。放置于垂直的圆柱形容器的要干燥的物料，在一喷嘴中或在一圆盘状的原子化器中原子化。热的空气在容器中向上流（在有些设计中向下流）、输送以及干燥液滴。液体从液滴的表面上快速汽化，同时形成有空隙的多孔的颗粒。干燥过的颗粒在旋风（cyclone）分离器中或在袋状过滤器中加以除去。The main advantages of spray drying a