用瞬间快速反应测定气膜和液膜传质系数

1、专业：姓名：刖户9步实验报告二地点：西七二区234课程名称：反应器设计原理实验指导老师：黄灵仙成绩：实验名称：用瞬间快速反应测定气膜和液膜传质系数实验类型：工程实验一实验目的1 .测定氢氧化钠溶液吸收CO2的气液相反应的总传质系数&a及气膜和液膜传质系数kGa,kLa。2 .了解传质和反应对吸收过程控制步骤的影响，并加深对气液相反应过程的认识。二实验原理气液相反应过程是气相反应物进入到液相中进行的反应过程，整个过程是反应和传质相结合的复杂过程，研究气液相反应首先必须了解两相间的传质问题。本实验选用NaOH溶液吸收CO2的瞬间快反应体系，就是要通过简单的实验及理论分析获得有关传质问题的必

2、要信息。在分批式的搅拌鼓泡釜中，该物系进行反应吸收时，化学计量式为：CO2+2NaOH-Na2CO3+hO(A)(B)(C)(D)在一定浓度范围内，此反应过程可以近似为瞬间快速反应，气液界面附近的浓度分布如图1所示，由于A与B一旦接触就立即完成上述反应，使得液侧任一处上A与B都不能同时存在。于是在离界面某一深度Yr处形成一个反应面R；若Cb增加，B的扩散推动力加大，扩散速度也增大，结果使Yr减少，当Cb增加到某一临界浓度Cbc时，反应面将和相界面重合，扩散到界面的A瞬间反应掉了，此时CAi=PAi=0,0yRyL反应吸收过程为气膜传质控制，注意，反应的进行将不影响气相传质系数。为什么？随着吸收

3、过程的进行NaOH(B)最后完全耗尽，此时成为对CO2的纯物理吸收过程。yG图1瞬间反应气液相界面附近的浓度分布根据双膜理论可以写出传质方程：1dnA气相：NAAVdtDgL、/,£(PA"Ai)/RT=kGa(PA-PAi)<YGJa/液相：NAL!(CAi-Ca)=kLa(CAi-Ca)<YLa(2)以气相分压为推动力的总传质方程:*Pa-Pa*Na二一一二KghPa-Pa1HakGakLa*式中Pai=HaCai；Pa=HaCa因此有1kgkGakLa当过程为瞬时反应吸收时，反应面上Ca=Pa=0,kLa随NaOH的浓度而变化，当(4)Cb>=Cbc

4、时，为气膜传质控制，即有NAa=3Pa-0=kGaPA当Cb-0时，成为纯物理吸收过程，则有NAa=KGaPA-P；二HPa二彳PaIHaAkGakLa(6)现对CO2作物料衡算，得到:Pa出=Pa进1VfWRTRT式中；VL釜内液体体积Vg通入气体的流量，假定为常数设釜内气液为全混，则CO2分压Pa=Pa出，CO2的吸收速率可以通过进出口CO?的含量改变来求得,也可以由NaOH的浓度变化求得，本实验采用后一种方法，用电导法测得NaOH溶液的电导随时间的变化,由下式可以求得转化率X时间t的曲线。(8)L。一LX=Lo-L二式中：Lo：起始电导L”：终止时的电导L:t时刻的电导由NaOH浓度随时

5、间的变化率求得:1 c：xNAa=Cbo722所示意。由(3)式可求得某一时刻的Kga,(Pa*t0),然后作KgaCb的关系图，如图图2Kga随Cb的变化根据上述分析，有图2可求得kGa=(KGa)iKgH2kGakLa即得kGa和kLa值，考虑溶液中电解质的影响，CO2在溶液中的亨利常数取HA=32.25atml/gmol三实验流程和实验步骤1.实验流程：1- CO2钢瓶2转子流量计3压缩机4一气体混合器5一搅拌鼓泡釜6电导率仪7记录仪8一搅拌马达9马达调速器10一差压计2 .实验步骤：(1)投放2L浓度0.1N的NaOH溶液入搅拌釜内，开动马达，待混合均匀后，即可开启电导率仪和记录仪，记

6、下初始电导值Loo(2)调节流量计，开始通气(先调好空气流量，再开CO2钢瓶，缓慢打开CO2流量计)。(3)待记录仪上指示浓度(电导率)不下降时，可以停止实验。(4)关闭电导仪和记录仪，切断电源，然后放掉液体，用水清洗搅拌釜。(5)整理实验数据。四实验数据记录及结果1 .原始数据Lo(mm)L0°(mm)P(mmHg)气体流里NaOH溶液备注Vair(l/min)VcO2(l/min)V(l)Cbo(moll-1)0.61420.29961249.567.01.6720.04mmHgT室=25.0CP大气压=761.88巳进=1.67M124"56M101325=32010

7、Pa1.677761.882 .数据处理计算思路：.L.-L.,用公式X求出X,Lo一L二用ORIGIN作X-。图:利用ORIGIN的数学工具微分得AX/A。：用公式NAa1-CBO2LX求出Nah；用公式Pa出=Pa进一IV2Vg1“CbRT求出Pa；用公式Cb=(1-X)CB0求出Cb；用公式NaH=KgHPa求出KGa。4X)B(¥)C(Y)D(Y)我LongNameeXDerivativeUnitsComments1stderivativeofX113310218010.001133177599320.0011341740.99320.0011351710936390.001

8、1361680.98639017165098639一000113e16209795g0.0011391590.979590.0011310156097279一00011311*J-1i一0.00113jn.4K现将结果列表如下:O(s)XAX/A0NAa(mol/lmin)PA(Pa)CB(mol/l)KGa(mol/lminatm)183100320100018010.001130.00135632005.9745200.0042928451770.9931972790.001130.00135632005.974520.0002721090.00429284517

9、40.9931972790.001130.00135632005.974520.0002721090.0042928451710.9863945580.001130.00135632005.974520.0005442180.0042928451680.98639455800320100.00054421801650.9863945580.001130.00135632005.974520.0005442180.0042928451620.9795918370.001130.00135632005.974520.0008163270.0042928451590.9795918370.00113

10、0.00135632005.974520.0008163270.0042928451560.9727891160.001130.00135632005.974520.0010884350.0042928451530.9727891160.001130.00135632005.974520.0010884350.0042928451500.9659863950.002270.00272432001.913410.0013605440.0086247751470.9591836730.001130.00135632005.974520.0016326530.0042928451440.959183

11、6730.001130.00135632005.974520.0016326530.0042928451410.9523809520.002270.00272432001.913410.0019047620.0086247751380.9455782310.001130.00135632005.974520.0021768710.0042928451350.9455782310.001130.00135632005.974520.0021768710.0042928451320.938775510.002270.00272432001.913410.002448980.008624775129

12、0.9319727890.002270.00272432001.913410.0027210880.0086247751260.9251700680.001130.00135632005.974520.0029931970.0042928451230.9251700680.001130.00135632005.974520.0029931970.0042928451200.9183673470.002270.00272432001.913410.0032653060.0086247751170.9115646260.002270.00272432001.913410.0035374150.00

13、86247751140.9047619050.001130.00135632005.974520.0038095240.0042928451110.90476190500320100.00380952401080.9047619050.001130.00135632005.974520.0038095240.0042928451050.8979591840.002270.00272432001.913410.0040816330.0086247751020.8911564630.002270.00272432001.913410.0043537410.008624775990.88435374

14、10.001130.00135632005.974520.004625850.004292845960.8843537410.001130.00135632005.974520.004625850.004292845930.877551020.002270.00272432001.913410.0048979590.008624775900.8707482990.002270.00272432001.913410.0051700680.008624775870.8639455780.00340.0040831997.887930.0054421770.01291979840.850340136

15、0.00340.0040831997.887930.0059863950.01291979810.8435374150.005670.00680431989.801340.0062585030.021551097780.8163265310.007940.00952831981.714740.0073469390.030186768750.7959183670.007940.00952831981.714740.0081632650.030186768720.7687074830.009070.01088431977.689260.0092517010.03448721690.74149659

16、90.01020.0122431973.663780.0103401360.038788736660.7074829930.01020.0122431973.663780.011700680.038788736630.6802721090.007940.00952831981.714740.0127891160.030186768600.6598639460.01020.0122431973.663780.0136054420.038788736570.6190476190.012470.01496431965.577190.0152380950.047433128540.5850340140

17、.01020.0122431973.663780.0165986390.038788736510.5578231290.011340.01360831969.602670.0176870750.043129426480.5170068030.01020.0122431973.663780.0193197280.038788736450.4965986390.01020.0122431973.663780.0201360540.038788736420.4557823130.011340.01360831969.602670.0217687070.043129426390.4285714290.

18、011340.01360831969.602670.0228571430.043129426360.3877551020.01020.0122431973.663780.0244897960.038788736330.3673469390.01020.0122431973.663780.0253061220.038788736300.3265306120.012470.01496431965.577190.0269387760.047433128270.2925170070.011340.01360831969.602670.028299320.043129426240.2585034010.

19、01020.0122431973.663780.0296598640.038788736210.2312925170.011340.01360831969.602670.0307482990.043129426180.190476190.011340.01360831969.602670.0323809520.043129426150.1632653060.011340.01360831969.602670.0334693880.043129426120.122448980.011340.01360831969.602670.0351020410.04312942690.0952380950.

20、01020.0122431973.663780.0361904760.03878873660.061224490.011340.01360831969.602670.037551020.04312942630.0272108840.01020.0122431973.663780.0389115650.038788736000.009070.01088431977.689260.040.03448721五计算与讨论基于上表数据作图如下:CB(mol/l)KGaExpDecIFrt<jfShwtf%.(EsrE一EMOE)如口工可以得到KGa=0.004293mol/1minatmG%2=0.043129mol/1minatm11Ha.,一再根据：=+,H