Lesson 22Marine Desalination Plants.ppt

单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,动力工程系,Power Engineering Department,Wuhan Institute of Shipbuilding Technology,Power Engineering Department,Luobin,Lesson,22,Marine Desalination Plants,第,22,课 船用海水淡化装置,A considerable amount of fresh water is consumed in a ship.,船上要消耗大量的淡水。,The crew uses,on average,about 70 liter/person/day and in a passenger ship,consumption can be as high as 225 liter/person/day.,船员平均每天每人需,70 L,淡水，而在客船上，淡水的消耗可高达,225 L/,人,/,天。,Water,used in the machinery spaces,as make up for cooling system losses,may be fresh or distilled,（,water,）,but,distilled water,is essential for steam plant,where there is a water tube boiler,.,机舱用于为冷却系统损失而补给的淡水可以是新鲜的淡水或蒸馏水，而对于水管锅炉的蒸汽装置来说，,蒸馏水,是必不可少的。,Steamship consumption for the propulsion plant and hotel services can be as high as 50 tones/day.,蒸汽机船用于（动力）推进装置和客房服务的淡水消耗每天可高达,50 t,。,It is now common practice to take on only a minimal supply of,potable water,（饮用水）,in port and to make up the rest by,distillation,（蒸馏）,of seawater.,船舶现在普遍的做法是在港口加装极少量的饮用水，通过对海水的蒸馏来补给不足部分。,The saved,storage capacity,（存储容量）,for water,is available for,cargo,（装货）,and increases the,earning power,（盈利能力）,of the ship.,省下的淡水存储容量，可用于装货，从而增加船舶的盈利能力。,A vessel which carries sufficient potable water for normal requirements is required,if ocean-going,to carry distillation plant for emergency use.,如果船舶行驶远洋的话，为正常需求而装载充足饮用水的船舶必需配备蒸馏装置以备应急使用。,The,state of the art,（技术水平）,of distilling plant design has,evolve,d,（发展）,considerably.,蒸馏装置设计的当前技术水平已经有了很大的发展。,A variety of distilling plant designs has been developed from which the most appropriate system,for a given marine power plant,can be selected.,蒸馏装置设计的种类很多，对于给定的船用动力装置来说，最合适的系统都可从中选择。,The,desalination plant,（淡化装置）,designs,most commonly considered for marine use,can be,broadly,（大致地）,classified as those using:,最常见的船用海水淡化装置设计大致分为如下几种：,Flash evaporators,（闪发式蒸发器）,Spray-film evaporators,（喷膜式蒸发器）,Submerged-tube evaporators,（潜管式蒸发器）,Plate-type evaporators,（平板式蒸发器）,Vapor-compression cycles,（蒸汽压缩循环式）,Membrane processes,（膜式）,Flash evaporators,闪发式蒸发器,The,multistage,（多级的）,flash evaporator was a revolutionary design development,because unlike submerged-tube evaporators,which have,heating surface,s,（受热面）,submerge,d,（浸没）,in,boiling,（沸腾的）,seawater,the flash-evaporator concept causes the seawater to flash into water vapor;no boiling occurs on the heat-transfer surfaces.,多级闪发式蒸发器是一革命性的技术设计，因为不像潜管式蒸发器，受热面浸没在沸腾的海水中，闪发式蒸发器使海水“闪发”成水蒸汽，传热面不会发生沸腾。,Flash evaporators became widely accepted for application in marine distilling plants,primarily because of their low operating temperature,as well as they can operate three months or more without feed treatment and without shutdown for cleaning.,闪发式蒸发器被广泛应用在海水蒸馏装置中，主要是因为它们的工作温度低，并且可以连续工作三个月或更长时间而不用对给水进行处理和停机进行清洁。,In addition to being smaller and lighter for a given capacity,the flash-type evaporator is also simpler to operate,which is an advantage from an automatic,standpoint,（立场，角度）,.,在给定的处理容量下，除体积小、重量轻外，闪发式蒸发器还易于操作，这从自动化的角度来看是一个优势。,A flash-type evaporator produces distilled water by discharging heated seawater into a chamber that,is maintained,at a pressure lower than the vapor pressure of the entering heated seawater,and subsequently,condensing,the,flashed,water vapor thereby produced.,闪发式蒸发器是通过将加热后的海水排入蒸发室来产生蒸馏水，蒸发室内的压力低于进入的海水蒸汽压力，随后冷凝由此产生的水蒸气。,Fig.22-1 is a,simplified diagram,（简图）,that illustrates the basic internal construction of a two-stage flash-type distilling plant.,图,22-1,是说明二级闪发式蒸馏装置基本内部结构的简图。,The majority of the flash-type marine units are of the multistage design with,integral,（整体的）,horizontal,（水平的）,condenser tube bundle,s,（冷凝管束）,.,大多数的船用闪发式蒸馏装置设计为多级式，并带有整体水平的冷凝管束。,The heated seawater is introduced,through a flashing device in each stage,to achieve the most effective flashing of,a portion of,（一部分）,the incoming feedwater(heated seawater)into vapor.,加热后的海水通过每一级的闪发装置来实现将部分引入的补给水,(,加热后的海水,),最有效的闪发为蒸汽。,The design of the flashing device is of,critical,（决定性的）,importance because it must provide an,optimum,（最佳的）,feedwater,spray pattern,（喷射形式）,that facilitates the flashing process,and it must also maintain a,pressure differential,（压差）,between,successive,（,接连的,）,stages.,闪发装置的设计极为重要，因为它必须提供最佳的给水喷射形式以利于闪发过程，并且还必须保持相邻两级间一定的压差。,As the feedwater leaves the flashing device,the spray is directed downward in,curtains of,（多层）,water.,随着给水离开闪发装置，喷射是直接以一层层水的形式向下。,The first separation between the flashing vapors and the feedwater occurs at this point.,在此时，闪发而成的蒸汽和给水间进行初次分离。,The downward velocity of the feedwater,directs,all but the fine,droplet,s,（液滴）,to,the lower section of the flash chambers.,给水向下的流速将除细小液滴以外的产物引入闪发室的底部。,The removed droplets that are,entrain,ed,（携带）,in the flashing vapor are removed in the,demister,s,（除雾器）,located in the,upper portion,（上部）,of the distilling plant,after which the vapors pass to the stage condenser.,闪发蒸汽中携带的液滴由位于蒸馏装置上部的除雾器进行清除，然后蒸汽进入该级冷凝器。,sea water feed,condenser,heater,demister,flashed vapor,flashed vapor,distillate,brine discharge,evaporator,The basic internal construction of a two-stage flash-type distilling plant,It is most important that the design,incorporate,（结合，采用）,a,positive seal,（正压密封）,around the demisters to prevent the passage of any,salt-laden,（含盐的）,droplets around the demisters.,最重要的是该设计在除雾器周围采用正压密封，为阻止除雾器周围含盐水滴的通道（防止含盐水滴进入）。,Since the vapor pressure of the heated feedwater,entering the first stage,is higher than the first-stage chamber pressure,a portion of the feedwater flashes into vapor,thereby removing heat from the feedwater until the temperature of the feedwater reaches the,saturation temperature,（饱和温度）,corresponding to the chamber pressure,.,由于进入第一级（蒸发器）的加热过的给水的蒸汽压力大于蒸发器的压力，部分给水闪发为蒸汽，因此，可带走给水的热量，直至给水的温度达到与蒸发器压力相应的饱和温度。,The heated feedwater is evaporated by a pressure reduction instead of a temperature,elevation,（升高）,.,加热的给水是通过压力的降低而不是温度的升高来蒸发的。,After an,equilibrium condition,（平衡条件）,is reached in the first stage,the remaining feedwater(,brine,，盐水,)is introduced into a second stage,that is maintained at a lower pressure than the first,and the process is repeated,.,第一级的平衡条件达到以后，剩下的给水,(,海水,),被引入二级闪发室。二级闪发室的压力比一级的更低，并且在此中重复前述过程。,The distillation process can operate from a positive pressure in the first stage to a,high vacuum,（高真空）,in the last stage,with a stage-to-stage pressure differential being the key to,repeated,（重复的）,flashing.,蒸馏过程可以从第一级的正压到最后一级的高真空范围内进行，级间的压差对于重复的闪发是关键。,The freshwater,distillate,（蒸馏物）,is collected in the bottom of the condenser section of the stage and,a,allowed to flow to the next stage condenser,where it is combined with the distillate from that stage.,淡水蒸馏物收集在每级冷凝器的底部，并且可以允许流入下级的冷凝器，在此与该级的（淡水）蒸馏物混合。,The process is repeated,depending on the number of stages,and the distillate is removed from the last stage by a,distillate pump,（蒸馏水泵，淡水泵）,.,随闪发级数的不同，闪发过程重复（进行），（淡水）蒸馏物在最后一级通过蒸馏水泵排出。,Flash evaporators generally use a“once-through”system,whereby,（通过）,the,entire,（全部的）,seawater feed is preheated through the stage condensers and seawater feed heaters and allowed to flash down through the stages.,闪发式蒸发器通常采用“一次性”系统：送入的全部海水在经过该级冷凝器和海水供给加热器时被预热，并在闪发器中闪发。,The resultant brine from the last stage is pumped overboard.,最后一级产生的盐水通过泵排到舷外。,Approximately 20,gallon,s,（加仑）,of seawater is required for each gallon of fresh water,produced in a once-through flash distilling plant,.,对一次性闪发蒸馏装置，每产生,1,加仑的淡水大约需要,20,加仑的海水。,The flash distilling plant,schematic,（原理图）,illustrated by Fig.22-1 shows that the entering seawater feed is used as the condenser,coolant,（冷却剂）,thereby reducing the quantity of heat which must be added in the seawater heater.,图,22-1,所示的闪发式蒸馏装置原理图表明：进入的海水用来作为冷凝器的冷却水，从而减少在海水加热器中增加的热量。,This feature is shown in more detail in Fig.22-2,which is a flow diagram,for a typical 8,000-,GPD,（,gallons per day,，加仑,/,天）,two-stage,flash distilling plant,.,图,22-2,是一典型的产量为,8 000,加仑,/,天、二级闪发式蒸馏装置的工作流程图，该图较详细地说明了给水的预热特点。,Fig.22-2 A two-stage flash distilling plant,feed line,ejector water pump,distilled water pump,condenser nest,heater nest,demister,As indicated by Fig.22-2,the initial vacuum in the stages is normally created by a high-pressure steam-driven air-ejector vacuum system,but motor-driven vacuum pumps or water-motivated air eductors are sometimes used,where high-pressure steam is not available,.,如图,22-2,所示，各级的初始真空通常由高压蒸汽驱动空气喷射真空系统产生，但是，当无法获得高压蒸汽的时候，也有时使用电动机驱动的真空泵或水动空气喷射器。,The stage condenser bundles are internally,（在内部）,baffle,d,（,vt.,带有挡板）,to direct the flow of noncondensible gases to,vent connection,s,（排气管）,leading to,subsequent,（随后的）,stages or to the air ejector.,该级冷凝器管束内部带有挡板，以将不凝性气体引至排气管，排到下一级或空气喷射器内。,The air ejector is normally of the one-or two-stage,noncondensing type,（非冷凝式）,.It is suitably sized for,the efficient removal of air and noncondensible vapors from the,distiller condenser,s,（蒸馏冷凝器）,.,空气喷射器通常是一级或二级非冷凝式，其尺寸经专门设计，可有效除去蒸馏冷凝器中的空气和不可冷凝的蒸汽。,The seawater heater and separator or built-in air ejector condenser are usually of the multi-pass shell-and-tube type with removable flanged waterboxes.,海水加热器和分离机或内置的空气喷射冷凝器通常是多级壳管式，并有可拆卸的带法兰的水箱。,The seawater flows through the tubes.,海水在管内流动。,The condensers and seawater heater may be provided with,means,for,cathodic protection,（阴极保护）,.,冷凝器和海水加热器可配有阴极保护装置。,The seawater heater is usually designed to maintain the temperature of the feedwater,entering the first stage of the evaporator,between 165 and 175.,海水加热器通常设计用来维持进入第一级闪发器的给水（海水）温度在,165175,之间。,This temperature range is low enough to minimize,scale formation,（结垢）,.,该温度范围足够将结垢降到最低。,The steam,condensate,（冷凝物）,temperature,from the seawater heater,does not exceed 200,under normal operating conditions,.,在正常工作条件下，离开海水加热器的蒸汽冷凝物的温度不超过,200,。,A shell-and-tube distillate cooler,or perhaps another type,is installed,when the evaporator is to provide,potable water,（饮用水）,.,当蒸发器用来提供饮用水时，可装设壳管式或其他形式的蒸馏物冷却器（以冷却蒸馏水）。,The distillate cooler is designed to provide a distillate temperature,leaving the,distilling plant,（蒸馏装置）,of 95 or less with an initial seawater temperature of 85.,蒸馏物冷却器设计用来使蒸馏物的出口温度不大于,95,，而海水的初始（进口）温度为,85,。,Occasionally,this cooler is incorporated,（使用）,as an integral part of the last stage condenser bundle.,有时，该冷却器和最后一级的冷凝器管束做成一体。,Marine distilling plants,incorporate,（加入）,a,solenoid-operated,（电磁控制的）,three-way,dump valve,（,释放阀relief valve,，安全阀,safety valve,）,that is located in the distillate discharge line,.,船用蒸馏装置的排水管路装有电磁三通安全阀。,The valve discharges the distillate to the bilge if the,salinity,（盐度）,of the distillate exceeds 0.25,grain,s,（格令，,0.0648,克，英美制最小重量单位）,of sea salt per,gallon,(,加仑,)(or any other specified preset control point).,如果蒸馏水的盐度超过每加仑,0.25,格令海盐,(,或任何其它设定的控制值,),，该阀会将其排入舱底污水中。,The solenoid is energized by the,salinity-indicating system,（盐度指示系统）,and operates whenever the salinity system is energized,regardless of the position of the cell selector switch on the salinity panel,.,该电磁阀由盐度指示系统激发。不管盐度（控制）面板的电池选择开关位置如何，只要盐度指示系统被激发了，该电磁阀就能工作。,The valve also diverts the flow of distillate to the bilge,upon,interruption,（中断）,of electric current to the salinity indicator,.,该电磁阀还会在盐度指示系统断电时将蒸馏物引入舱底污水中。,A high-salinity,audible alarm,（声音报警器）,is usually installed to indicate the occurrence of a salinity level in excess of preset value.,通常安装高盐度声音报警器以指示盐度超过预设值。,