外文翻譯--干燥技術(shù)

1、<p><b>　　英文原文</b></p><p>　　Drying Technology</p><p>　　There are three main types of gas-suspension dryers:</p><p>　　Spray dryers, to convert a liquid solution or su

2、spension to a dry, free-flowing powder </p><p>　　Fluid-bed dryers, used to dry wet filter cake, or for pastes and sludges with dry product recirculation </p><p>　　Flash dryers, for a relatively

3、dry, crumbly, non-sticky feed </p><p>　　The type of dryer chosen for any given application depends on both the feed properties and product requirements. Important feed properties are the moisture content, so

4、lids, viscosity, and density, as well as any volatile, flammable, or toxic components. Dried product specifications may include average particle size and particle size distribution, density, moisture content, and residua

5、l volatiles or solvents. Powder characteristics can be controlled and powder properties maintained constant throu</p><p>　　Spray Drying</p><p>　　Spray drying is a three-step drying process invol

6、ving both particle formation and drying. (1) The process begins with the atomization of a liquid feed into a spray of fine droplets. (2) Then a heated gas stream suspends the droplets, evaporating the liquid and leaving

7、the solids in essentially their original size and shape. (3) Finally, the dried powder is separated from the gas stream and collected. Spent drying gas is either treated and exhausted to the atmosphere or recirculated to

8、 the system</p><p>　　The selection and operation of the atomizer is of extreme importance in achieving an optimum operation and production of top-quality powders. There are four main types of atomization:<

9、;/p><p>　　Centrifugal atomization, the most common, uses a rotating wheel or disc to break the liquid stream into droplets. The rotational speed determines the mean particle size, while the particle size distri

10、bution about the mean remains fairly constant in a system. Centrifugal atomizers are available in a large variety of sizes, from laboratory scale to very large commercial units. </p><p>　　Hydraulic pressure-

11、nozzle atomization forces pressurized fluid through an orifice. Multiple nozzles are used to increase capacity. The particle size depends on the pressure drop across the orifice, so that the orifice size determines the c

12、apacity of the system. This type of atomization is simpler than centrifugal, but cannot be controlled as well. It is not suitable for abrasive materials, or materials that tend to plug the orifices. </p><p>

13、　　Two-fluid pneumatic atomization uses nozzles, as well, but introduces a second fluid, usually compressed air, into the liquid stream to atomize it. This type of atomization has the advantage of relatively low pressures

14、 and velocities and a shorter required drying path. It is most often used in small-scale equipment, laboratory or pilot size. </p><p>　　Sonic atomization, not yet widely used, passes a liquid over a surface

15、vibrated at ultrasonic frequencies. It can produce very fine droplets at low flow rates. Current limitations are capacity and the range of different product that can be atomized. </p><p>　　After atomization,

16、 a disperser brings the heated gas into contact with the droplets. The disperser must accomplish three things: mix the gas with the droplets, begin the drying process, and determine the flow paths through the drying cham

17、ber. The drying gas may be heated directly by combustion of natural gas, propane, or fuel oil, or indirectly using shell-and-tube or finned heat exchangers. Electric heaters may be used in small dryers. Industrial radial

18、 fans move the heated gas through the syst</p><p>　　The drying chamber must be sized to allow adequate contact time for evaporation of all of the liquid to produce a dry powder product. Factors that impact t

19、he drying time include the temperature difference between the droplets and the drying gas, and their flow rates. The exact shape of the chamber depends on the drying characteristics and product specifications, but most a

20、re cylindrical with a cone-shaped lower section to facilitate collection of the product.</p><p>　　Finally, proper configuration of the atomizer, disperser, and drying chamber is essential for complete drying

21、 and to avoid the deposit of wet material on the interior surfaces of the dryer. Designs may use co-current, counter-current, or mixed flow patterns.</p><p>　　The powder is separated from the drying gas at t

22、he bottom of the chamber. Most often, the gas exits through an outlet duct in the center of the cone. Heavier or coarser particles will be separated at this point, dropping into the cone to be collected through an air lo

23、ck. Then either cyclones or fabric filters (or both) remove the remaining powder from the exit gas. In systems producing a very fine powder, most of the collection takes place at this point.</p><p>　　Fluid-B

24、ed Drying</p><p>　　Fluid-bed drying is a process in which a gas is forced upward through a bed of moist particles to achieve a fluidized state. The particles are suspended in the gas stream and dry as they f

25、low along with the gas. Fluid beds can be either cylindrical or rectangular. There are two basic types of fluid-bed designs:</p><p>　　Plug flow fluid beds are used for feeds that are directly fluidizable. Ba

26、ffles in the bed limit mixing in the horizontal direction to maintain plug flow. This type of bed is ideal for removal of bound volatiles or for heating and cooling. The volatile content and temperature vary uniformly as

27、 the solids pass through the bed. Baffle design depends on the shape and size of the bed, with spiral or radial baffles used in circular beds and straight baffles in rectangular. </p><p>　　Back-mixed fluid b

28、eds are used for feeds that cannot be fluidized in their original state, but become fluidizable after a short time in the dryer. The feed is distributed over the bed surface, designed to allow total solids mixing. Produc

29、t temperature and moisture are uniform across the fluidized layer. Heating surfaces may be immersed in the fluidized layer to improve thermal efficiency and performance. </p><p>　　A combination system uses a

30、 back-mixed fluid bed to reduce the moisture level of the wet feed, followed by a plug-flow section to achieve final specifications. This type of arrangement is quite common.</p><p>　　The advantages of fluid

31、ized-bed drying are: relatively long residence times allow high heat-transfer coefficients between the particles and the gas; the ability to closely control product temperature makes fluidized beds ideal for processing t

32、emperature-sensitive solids; and they have the highest thermal efficiency of any gas-suspension drying system.</p><p>　　Disadvantages are: they can process only a limited range of materials; product particle

33、s are relatively large; and there may be difficulty processing needle- or platelet-shaped particles.</p><p>　　Flash Drying</p><p>　　Flash drying forces drying gas through a heater and upward thr

34、ough a duct or flash tube. The high-velocity gas stream instantly suspends the feed, which enters just after the heater, and carries it to the collection equipment, usually cyclones or bag collectors.</p><p>

35、;　　Flash dryers are the simplest gas-suspension dryers, and require the least space. Residence time within the dryer is very short, usually less than 3 seconds. Particles must be quite small, and the best feed is reasona

36、bly dry, crumbly, and not sticky. There are several ways to obtain the required feed qualities:</p><p>　　A cage mill may be used to break up the feed into the required small particles. </p><p>　

37、　If the feed is too wet or pasty, dry solids may be backmixed to create the proper consistency. </p><p>　　An agitated design, using a high-speed disintegrating rotor, will keep all particles moving. This des

38、ign is shorter and larger in diameter than a flash tube, creating a very compact system. </p><p>　　Hybrid Dryers</p><p>　　There are a number of hydrid systems used in applications where a single

39、 system cannot handle the requirements of both the feed and product. The most common are:</p><p>　　Fluidized spray dryers (FSD?) combine spray with fluid bed drying to produce agglomerated products. The top

40、of the system is a spray dryer, atomizing the liquid and contacting it with heated gas. Additional heated gas is introduced at the bottom to create a fluidized bed portion of the drying chamber. This type of dryer will p

41、roduce a dustless, free-flowing agglomerated product. It is ideal for products that must dissolve easily, e.g. food colors, dyestuffs, pigments, and some agricultural chemi</p><p>　　A flash dryer may be used

42、 to remove surface moisture, followed by a fluid bed for removal of bound moisture. </p><p>　　Niro Dryers</p><p>　　The MOBILE MINOR? is a laboratory-scale spray dryer known for its flexibility a

43、nd different levels of control systems. It is used to dry small quantities of solutions, suspensions, and emulsions into representative powder samples. Test results provide important information for selecting the design

44、and technical specification of a given drying project.</p><p>　　The PRODUCTION MINOR? is a larger spray dryer that can be used for pilot testing or small-scale production. It has a choice of atomizers, heati

45、ng systems, and powder discharge.</p><p>　　The Fluidized Spray Dryer (FSD?) was invented and patented by Niro in the early 1980s. It combines fluidization and spray-drying technologies to dry a wide variety

46、of products, including many that cannot be dried using conventional equipment. Advantages include easy control of the size and structure of the particles, making it ideal for agglomerated products, and low powder tempera

47、tures for thermally sensitive materials. It is also very energy efficient.</p><p><b>　　中文譯文</b></p><p><b>　　干燥技術(shù)</b></p><p>　　主要有三種氣體懸浮烘干: </p><p&

48、gt;　　噴霧干燥器,把液體溶液或懸浮于干燥,自由流動的粉末 </p><p>　　流化床干燥機,用干,濕濾餅,或漿和污泥干產(chǎn)品再循環(huán) </p><p>　　閃蒸干燥機,在相當(dāng)干燥,松軟,非飼料粘粘 </p><p>　　該型干燥器選擇任何特定應(yīng)用取決于雙方的飼料性能和產(chǎn)品的要求. 重要飼料性能是水分含量,固形物,粘度,密度,以及任何揮發(fā)性,易燃或有毒成分. 木片產(chǎn)

49、品規(guī)格可能包括平均粒度分布,密度,含水率,殘留揮發(fā)或溶劑. 粉末特性可控制粉末特性保持不變,通過連續(xù)運行. </p><p><b>　　噴霧干燥. </b></p><p>　　噴霧干燥是一個三步走的干燥過程中,涉及兩種粒子形成和干燥. ( 1 )進程始于霧化的液體飼料成噴霧霧滴. ( 2 ) ,然后加熱氣流暫時飛沫 96.3%的液體和離開固體基本上是原來的大小和形

50、狀. ( 3 )最后,干粉分離氣流和收集. 用干燥氣體要么是治療和精疲力竭的氣氛或循環(huán)使用該系統(tǒng). 這三個步驟是由三部分組成:霧化,分散,而干燥室.</p><p>　　選擇和操作的噴霧器,是極端重要性,實現(xiàn)最佳的操作和生產(chǎn)頂級質(zhì)量 粉末. 主要有4種霧化: </p><p>　　離心霧化,最常見的,用一個旋轉(zhuǎn)輪或盤打破液體流成液滴. 轉(zhuǎn)速確定的平均粒徑, 而粒度分布大約平均維持在相當(dāng)穩(wěn)定

51、的系統(tǒng). 離心式霧化器可有多種尺寸,從實驗室規(guī)模比較大的商業(yè)單位. 液壓噴嘴霧化勢力加壓流體通過一個小孔. 多噴頭用來增加容量. 顆粒大小取決于壓降過孔板, 使孔大小決定了系統(tǒng)的容量. 這種霧化簡單得多離心,但無法控制等. 它是不適合研磨材料,或材料,往往堵塞孔口. 雙流體氣動霧化噴嘴的用途,以及如何引進,但第二液,通常壓縮空氣 成液體流霧化. 這種霧化的優(yōu)點在于較低的壓力和速度,縮短干燥所需的路徑. 這是最常用的小型設(shè)備,實驗室或中試

52、規(guī)模. 聲波霧化,尚未廣泛使用,在經(jīng)過了超過液體表面振搗,在超聲波的頻率. 它可以產(chǎn)生非常細微的動作,在低流率. 電流限制能力,以及各種不同的產(chǎn)品,可霧化.</p><p>　　霧化后,使分散的熾熱氣體接觸到液滴. 分散必須完成三件事:混合氣體與霧滴,從干燥過程中, 并確定流路徑通過干燥室. 干燥氣體,可直接加熱燃燒天然氣,丙烷或燃油 或間接使用殼管式或翅片式換熱器. 電加熱器,可用于小型烘干機. 工業(yè)徑向球迷提

53、出了激烈的天然氣通過該系統(tǒng). 烘干室必須大小以便有充裕的時間接觸蒸發(fā)所有的液體產(chǎn)生 一個干粉產(chǎn)品. 因素的影響,干燥時間,包括溫差的霧滴和干燥氣體. 而其流率. 確切庭取決于干燥特性及產(chǎn)品規(guī)格, 但大多數(shù)是圓柱與錐形下段,以方便收集的產(chǎn)品. 最后,妥善配置的噴霧器,播種機, 和干燥室必須徹底干燥,以避免存款濕材料的內(nèi)表面 在吹干. 設(shè)計可利用順流,逆流或混合流模式. 粉末分離的干燥氣室底部. 在多數(shù)情況下,出口氣體通過一個插座導(dǎo)管中心的

54、錐. 較重或粗顆粒將會分開,在這一點上, 墜入錐可通過收集空鎖. 然后要么旋風(fēng)或織物過濾器(或兩者)來清除殘留的粉末從出口氣. 在系統(tǒng)產(chǎn)生非常微細粉末,大部分的收集發(fā)生在這一點.</p><p><b>　　流化床干燥 </b></p><p>　　流化床干燥過程中的氣體被迫通過向上一床濕顆粒實現(xiàn) 沸騰狀態(tài). 這些微粒懸浮在氣流和干燥,因為他們流隨氣. 流化床可分為圓

55、柱形或長方形. 有兩個基本類型的流化床設(shè)計:</p><p>　　堵塞流病床被用作飼料,是直接發(fā)霉. 擋板床攪拌限制在水平方向上保持堵塞水流. 這種床是理想的搬遷勢必揮發(fā)或加熱和冷卻. 揮發(fā)量與溫度變化一致的固體通過床底下. 擋板的設(shè)計取決于形狀和尺寸的床, 螺旋或徑向隔板采用圓形床和直擋板的長方形. 返混流化床用作飼料,不能流于原始狀態(tài), 但成為發(fā)霉后,在很短的時間干燥. 飼料派發(fā)超過床面,旨在讓總固體混合.

56、產(chǎn)品的溫度和濕度都是一刀切流化床層. 受熱面,可沉浸在流態(tài)化層,以提高熱效率和業(yè)績. </p><p>　　組合系統(tǒng)采用返混流化床,以減少水分含量的濕飼料 其次是一個插件流斷面,以達到最終規(guī)格. 這種安排是司空見慣. 優(yōu)點流化床干燥如下: 較長的停留時間,讓高傳熱系數(shù)與粒子間的氣體; 能密切控制產(chǎn)品溫度使得流化床理想的加工溫度敏感固體; 他們有最高的熱效率氣體懸浮干燥系統(tǒng). 缺點是:它們能過程只是一個范圍有限的材

57、料; 產(chǎn)品顆粒較大; 并有可能難以處理針頭或血小板形顆粒. </p><p><b>　　速干 </b></p><p>　　速干勢力干燥氣體通過一個加熱器,向上通過導(dǎo)管或閃光燈管. 高速氣流瞬間停止飼料,其中大部分進入剛剛加熱器 縹緲,它的采集設(shè)備,通常旋風(fēng)或袋收藏. 閃蒸干燥機是最簡單的氣體懸浮烘干機,并要求最少的空間. 居留時間內(nèi)干燥,是非常短,通常小于3秒.

58、粒子必須相當(dāng)小,而最好的飼料是合理的干燥,松軟,不發(fā)粘. 有幾種方法,以取得所需的飼料品質(zhì):</p><p>　　籠子軋機可用于擊破飼料成所需的小顆粒. 如果飼料過于潮濕或糊狀,干物質(zhì)可backmixed創(chuàng)造適當(dāng)?shù)囊恢滦? 激動的設(shè)計,采用高速粉碎轉(zhuǎn)子,會讓所有粒子. 這個設(shè)計是較短時間和較大的直徑比閃光燈管,創(chuàng)造一個非常緊湊的系統(tǒng). </p><p><b>　　混合式干燥機

59、</b></p><p>　　有一些氫化系統(tǒng)在應(yīng)用中,一個單一的系統(tǒng),不能處理的要求,既 飼料和產(chǎn)品. 最常見的有: </p><p>　　流化床噴霧干燥器(消防?)結(jié)合噴霧流化床干燥制粒生產(chǎn)的產(chǎn)品. 頂級的系統(tǒng)是一個噴霧干燥機,霧化液接觸,并與熾熱氣體. 新增天然氣加熱介紹,在底部形成流化床部分的干燥室. 這種烘干機將產(chǎn)生一個無塵,自由流動的壓塊產(chǎn)品. 它是理想的產(chǎn)品,必須解

60、散容易,例如: 食用色素,染料,顏料,以及一些農(nóng)業(yè)化學(xué)品. 一個旋轉(zhuǎn)閃蒸干燥機,可用于去除表面水分,然后由流化床去除一定水分. </p><p><b>　　Niro干燥 </b></p><p>　　移動輕微?是一個實驗室規(guī)模噴霧干燥機已知的靈活性和不同層次的控制系統(tǒng). 它是用來干少量溶液,懸浮,乳液為代表的粉末樣本. 測試結(jié)果提供了重要信息,為選擇設(shè)計和技術(shù)規(guī)格,