化工原理第十章 氣液傳質(zhì)設(shè)備（Chemical engineering principle tenth chapter gas-liquid mass transfer equipment）

1、化工原理第十章 氣液傳質(zhì)設(shè)備（Chemical engineering principle tenth chapter gas-liquid mass transfer equipment）Ppt documents may experience poor browsing on the WAP side. It is recommended that you select TXT first or download the source file to the local machine.Xian Jiaotong University chemical principles of elec

2、tronic coursewareOneThe tenth chapter is gas-liquid mass transfer equipmentComparison and selection of 10.3 tower equipment of 10.1 packed tower and 10.2 plate towerReturnXian Jiaotong University chemical principles of electronic coursewareTwo10.1 packing tower10.1.1 packed tower and packingFirst, p

3、acked tower structure packed tower is a widely used gas-liquid two-phase contact and heat transfer and mass transfer tower equipment, can be used for absorption (Jie Xi), distillation and extraction separation process. The packed tower has the advantages of simple structure, small resistance and eas

4、y to use and has the advantages of corrosion-resistant materials, especially the vacuum distillation system, material or corrosive pressure smaller diameter and smaller tower for treatment in addition, for some relatively large liquid gas distillation or absorption operation, also should adopt the p

5、acking tower.ReturnXian Jiaotong University chemical principles of electronic coursewareThreeTwo, filler type filling in packing tower in the material, it is the main component of the packing tower, its role is to increase the contact area of gas and liquid phases, and improve the liquid turbulence

6、degree for heat and mass transfer. Therefore, the packing should make the gas and liquid contact area larger, the mass transfer coefficient higher, and the flux is large and the resistance is small. The main parameters of filler characteristics are: 1. the specific surface area of 2. porosity is 3.

7、units within the volume of the reactor n filler number 4. 5. dry bulk density and filler packing factor factor 6. mechanical strength and chemical stability and excellent performance of the filler must meet easy manufacture, low cost and other aspects of the request.ReturnXian Jiaotong University ch

8、emical principles of electronic coursewareFourCommonly used fillers can be divided into two categories: individual packing and structured packing. Individual packing by solid solid block, hollow ring packing, surface opening of the saddle, the commonly used construction materials including ceramic,

9、metal, plastic (polypropylene, polyvinyl chloride, glass, graphite, etc.). Ceramic packing corrosion, but fragile, small porosity; metal filler ratio, specific surface area and void flux, high efficiency, but the price of expensive stainless steel, ordinary steel corrosion; plastic filler with large

10、 specific surface area, high porosity, but not high temperature. Some individual fillers used in industry are as follows.Figure 10-2 filler shapeReturnXian Jiaotong University chemical principles of electronic coursewareFiveThree, choose 1, packing packing material selection (1) when the operating t

11、emperature of equipment is low, long-term operation without plastic deformation, in this case, if the system without swelling on plastic may consider the use of plastic, because of its low price and good performance. The operating temperature of the plastic filler is generally no more than 1000C, an

12、d the glass fiber reinforced polypropylene filler can reach 1200C. In addition to concentrated sulfuric acid, concentrated nitric acid and other strong acid, the plastic has better corrosion resistance, but the wettability of the plastic surface to the aqueous solution is poor. (2) ceramic fillers a

13、re generally used in corrosive media, especially at high temperature, but H3PO4 and alkali can not be used for HF and high temperature. (3) metallic materials are generally resistant to high temperature but not corrosion. The general corrosion resistant stainless steel (except C1 acid), but the pric

14、e is more expensive.ReturnXian Jiaotong University chemical principles of electronic coursewareSix2, packing type choice first depends on the process requirements, such as the theory of series, production capacity (volume), allowable pressure drop, material properties (viscosity, gas phase and liqui

15、d phase are suspended or in the production process of polymerization, etc.) and then combined with the filler properties to choose, can meet the requirements for the selected packing technical requirements, technical and economic indicators advanced, easy installation and maintenance. Because the re

16、gular packing of gas and liquid distribution is uniform, small amplification effect, technical indicators due to random packing,Therefore, the application of regular packing is becoming more and more widespread in recent years, especially for large towers and towers requiring lower pressure, but it

17、is difficult to handle them. For the tower with large production capacity (or large diameter) or high separation requirements and limited pressure drop, it is more suitable to choose the corrugated plate packing, such as styrene ethylbenzene distillation tower, lubricating oil vacuum tower, etc. Som

18、e requirements for the absorption system of liquid holdup higher, generally with random packing. Random packing, comprehensive technical performance is superior to metal saddle ring, cascade ring, followed by Bauer ring, again is Intalox packing.ReturnXian Jiaotong University chemical principles of

19、electronic coursewareSeven3, packing size selection, packing size (diameter, peak height), than the small surface flux (Rong Xu gas velocity), pressure drop, but the efficiency (the theory of half per meter of filler) is also low, so much for the production capacity (processing volume) large tower.

20、Large industrial structured packing towers commonly use wave crest packings with a wave height of about 12mm (the specific surface is about 250m2/m3). The number of theoretical plates or by the limited plant many occasions, small size, high surface filler generally. Large scale grid (grid) fillers a

21、re usually used for easy scaling or easy to precipitate materials and operate at higher gas velocities.ReturnXian Jiaotong University chemical principles of electronic coursewareEightLiu Ti fluid mechanical properties of 10.1.2 packed column in a packed column, the mass transfer performance of gas f

22、low, the flow in the 1 filler layer in packing layer flow and gas flow in the granular layer. 2. The mutual influence of gas-liquid two-phase flow and the increase of gas flow in the dry packing layer of the carrier point will increase the pressure drop according to the order of 1.82.0. 3, packing t

23、ower flooding when the gas volume reached a certain value, the interaction of the two phases appears the malignant development results will lead to flooding phenomenon. At this time of rising air flow drag increase enough to prevent the liquid flows, so the liquid filled bed void, only gas bubble ri

24、sing.ReturnXian Jiaotong University chemical principles of electronic coursewareNineTwo. The hydraulic performance of the packed tower 1. The pressure drop reflects the pressure drop of the packing layer and varies with the type and size of the packing. 2, gas velocity of flooding is usually taken f

25、looding velocity of 50% 80%. The diameter of the packed tower D:3 and the transition from normal to liquid loading are often a smooth curve. 4. The amount of liquid holding liquid refers to the volume of liquid held in its voids in the unit volume packing layer. 5. Wetting rateWetting rate = spray d

26、ensity, liquid volume flow / packing section area = filler ratio, surface filling layer surface area / packing layer volumeD=4Vs PI u=Liquid volume flow, liquid volume flow = packing surface area / packing layer height, packing layer get long circumferenceReturnCalculate the mass transfer performanc

27、e of Xian 1. filler wetting the surface of the filler, three a o G G = 1? Exp? 1.45 () () () calculation of P G k p g a a sigma phase mass transfer coefficient of liquid of 2. mu (= 0.0051) () () (AD) a mu g the principle of P D 3. gas phase mass transfer coefficient K RT G = C () () (AD) aD a p D c

28、ourseware2 W C 0.75 L 0.1 L L 2 LL 13 L 23 L? 12 L P L W L L LV V 0.7 V 13? 2 P V V V VZero Point Zero Five(Sigma alpha Rho LGL 20.2)Zero point fourTenReturnFour, some design indicators Xian 1. filler size generally considered that the above ratio should be at least equal to 8, for the west ring fil

29、ler must be larger. 2. operating gas velocity operating gas velocity can be determined by one of the following two methods: (1) the operating gas velocity is equal to the gas velocity of flooding was 0.50.8 times of the original; (2) according to the production conditions, set the allowable pressure

30、 drop, the pressure will be calculated by reasonable gas velocity. Electric 3.The height of the packing layer height and the height of the sub packing layer are calculated by the number of the mass transfer units or the number of theoretical plates. CoursewareElevenReturnWest tower packing accessory

31、 structure including packing support plate, liquid distributor, liquid distributor, liquid gas, an inlet and outlet device etc. Intersection 1, support plate large chemical engineering principle (c) strip riser gas electronic (b) gas lift (a) grid plate Lesson 10-5 supporting components of packingTw

32、elve10.1.3 packing tower attachment structure(c)ReturnXian Jiaotong University chemical principles of electronic coursewareThirteen2. Liquid distributor (1) tubular sprinklerB A B A (a) AA(c)B B(d) (b)Fig. 10-6 tubular sprinklerReturnXian Jiaotong University chemical principles of electronic coursew

33、areFourteen(2) the lotus type sprinkler sprinkler disc (3)(4) slot type distributorFig. 10-9 slot sprayerReturnXian Jiaotong University chemical principles of electronic coursewareFifteen4, in order to avoid other operation due to gas velocity fluctuations of the filler by impulse and damage, often

34、in the packing layer is arranged on the top of filler plate or block, otherwise it may make the performance of the filler layer structure and the tower deteriorated sharply, broken filling may also be substituted into the gas and the liquid outlet pipe caused by the obstruction. The gas filler tower

35、 inlet configuration should consider fluid intrusion, more important is to facilitate gas evenly into the filler layer, the common way is the center position of the turret so that the intake pipe extends to the tower section, the tube end as downward sloping downward curved incision or bell. For lar

36、ge, should take more effective measures. Sometimes, the demister is equipped with baffle demister, screen demister and so on. Liquid exports should ensure the formation of tower liquid seal, and can be placed with gas.ReturnXian Jiaotong University chemical principles of electronic coursewareSixteen

37、10.2 plate towerReturnLiquidLiquidLiquid float valveTower type 10.2.1 West profile plate tower right: an Jiaotong University (a) for bubble column; industry (b) as the original sieve tray; (c) for the float valve tower; (d) for a fixed type tongue tower; physical and electrical (E) for floating spra

38、y tower. Sub coursewareSeventeenA air flow (b) airflow (c)LiquidLiquid float plateFlow diagram (d) figure 10-11 commonly used plate towerAir flow (E)ReturnThe operation principle of 10.2.2 An Tongchang west tower plate to form three different states in the range of turn plate above: near the plate l

39、iquid layer at the bottom is bubbling zone, as shown in (1); the chemical liquid layer surface is the froth zone, as shown in (2); the original is in the liquid entrainment zone the top layer as shown in the physical space, (3). Electronic coursewareEighteenReturnXi PI Anta diameter can be according

40、 to the flow equation, i.e. V = Du 4 4Vs D= u so PI P L? U = Umax calculation C sigma Rho G C sigma Rho G working principle of gas velocity value should press type correction: C = 20 (electric) Sigma Sigma C courseware2 sEstimation of the diameter of 10.2.3 plate towerTwentyZero point twoNineteenRet

41、urnXian Jiaotong University chemical principles of electronic coursewareTwenty10.2.4 plate flow form of the downcomer tray tower plate used to liquid flow patterns are the following: 1. single overflow in Figure 10 - 14 (a). 2. double flow patterns are shown in Figure 10 - 14 (B).3.U shape overflow

42、type, as shown in Figure 10 - 14 (C). 4. four overflow type, as shown in Figure 10 - 14 (D).(a)(b) figure 10-14 flow pattern of tray(c)(d)ReturnXian Jiaotong University chemical principles of electronic coursewareTwenty-oneThe common structure of 10.2.5 trayInvalid zone of WCSeveral areas of various

43、 plate layout 1. plates can be roughly divided into three areas: the downcomer occupied part called overflow area; plate open space called bubble zone; Figure 10 - 15 in the shadow part is called the invalid area.Aa overflow zone in Af bubbling zone of overflow zoneLWSchematic diagram of wsdiagram 1

44、0-15 common structure of tower plate WSReturnWest 2. drop Guan An (1) and liquid drop tube in tube to drop the residence time of general requirements for residence time more than 3 5S, which is calculated by the formula: Af H T downcomer volume m3 tau = = m3 s / Ls volumetric flow rate of liquid che

45、mical (2) of the downcomer the shape of A A class electric principle (a) circular (b) Figure 10 - 16 segmental downcomer sketch mapsF fTwenty-twoReturnXian Jiaotong University chemical principles of electronic coursewareTwenty-three3. overflow weirWe downcomer how HW HT H0 sieve plate overflow weir

46、LW Af Aa Ws Af R x WdFig. 10-17 schematic diagram of single overflow trayLW weir length: in order to make the liquid flow uniformly through the tray, the single overflow is generally consideredDouble overflowLW = 0.6 0.8 DLW = 0.5 0.7 DThe maximum liquid flow on the weir should not exceed 100 130m3/

47、 (MI h).ReturnXian Jiaotong University chemical principles of electronic coursewareTwenty-fourHeight of liquid layer on 4. weirsHow = 2.84 (Lh 23) LW5. the liquid gets resistance through the downcomerHC = 0.153 (Ls 2) LW H06. the distance between downcomer and lower plate H0H0 generally, the resista

48、nce should not exceed 25mm when the liquid passes through the downcomer. In addition, should be immersed in the liquid layer to keep the liquid seal to prevent gas into the downcomer, so the value should be less than the weir high h w, usually from H? H = 6 13mmW 0ReturnXian Jiaotong University chem

49、ical principles of electronic coursewareTwenty-fiveThe opening 1. tower structure design of 10.2.6 plate plate to make the plate utilization rate is high, many of the triangle mesh (see Figure 10 - 21). When the hole spacing and aperture are determined, the ratio of the opening area to the area of t

50、he opening area of the plate is calculated by the lower form:Alpha =A0 d = 0.907 (0) 2 Aa tTD0The opening area can be calculated for the single overflow trays: for the double overflow traysX Aa = 2x R 2? X 2 + R 2 sin? 1 RFigure 1021 screen schematic arrangementThe total number of sieve holes on the

51、 tray can be calculated by n:1185 x 105 n= Aa = n Aa 2 TX x Aa = 2x R 2? X 2 + R 2 sin? 1? 2X1 R 2? X12 + R 2 sin? 1 r rReturnXian Jiaotong University chemical principles of electronic coursewareTwenty-six2. weir weir design considered in section 10.2.5, the tower plate weir can be designed accordin

52、g to the following requirements: General tower, tower should make the supernatant layer height (weir height + flow weir height) between 50 100mm, i.e.0.100? How = HW = 0.050 how?When the vacuum is high or the pressure is very small, hL 25mm, at this time how = 6 15mm. When the liquid flow is large,

53、the weir can not be set. 3. other structural downcomer, internal weir, receiving disc and stability zone, edge area and so on, according to the 10.2.5 section design.ReturnCalculation of 1. tray pressure drop of fluid mechanics of West 10.2.7 sieve tray (fluid resistance) to the pressure drop of the

54、 tower plate is composed of three parts as follows: (1) the dry pressure drop; F (1- alpha)? P = 0.051 I C P L (2) through the pressure drop of liquid layer;The pressure drop through the liquid layer is calculated according to the effective liquid layer resistance he (3) the pressure drop caused by

55、the surface tension. The pressure drop caused by surface tension is generally negligible, so it is important to be composed of the first two items, i.e., P = P dry + P liquid courseware220 dry 20Twenty-sevenReturn2. screen several operating limit of Xian (1) leakage leakage point F0 4.51=0.00848 (d

56、= - 0 + 1.27 (hL + 27.9) Jiaotong University) (2) entrainment? U 730.0057? U (E = 0.22) = Sigma? 12 (H? H) Sigma? H H?. (3) no more than the original design flooding plate spacing plate tower in the physical requirements in the downcomer liquid column height H 0.5 0.6 times, H D is less than or equa

57、l to (0.5 0.6) H T courseware3.2 G 3.2 G V T f T fDHTTheTwenty-eightReturnXian Jiaotong University chemical principles of electronic coursewareTwenty-nineThe load performance diagram of the 3. plate tower is plotted on the upper and lower limits of the operation of the tray, which is called the load performance diagram.Gas / (m 3 /h)Operating point a A C D B f e D(1) the center