用瞬間快速反應(yīng)測(cè)定氣膜和液膜傳質(zhì)系數(shù)

精品文檔專業(yè)：姓名：實(shí)驗(yàn)報(bào)告學(xué)號(hào)：日期：地點(diǎn)：西七二區(qū)234課程名稱：反應(yīng)器設(shè)計(jì)原理實(shí)驗(yàn) 指導(dǎo)老師： 黃靈仙 成績(jī)：__________________實(shí)驗(yàn)名稱： 用瞬間快速反應(yīng)測(cè)定氣膜和液膜傳質(zhì)系數(shù) 實(shí)驗(yàn)類型：工程實(shí)驗(yàn)一實(shí)驗(yàn)?zāi)康?. 測(cè)定氫氧化鈉溶液吸收 CO2的氣液相反應(yīng)的總傳質(zhì)系數(shù) KGa及氣膜和液膜傳質(zhì)系數(shù) kGa,kLa。2.了解傳質(zhì)和反應(yīng)對(duì)吸收過程控制步驟的影響，并加深對(duì)氣液相反應(yīng)過程的認(rèn)識(shí)。實(shí)驗(yàn)原理氣液相反應(yīng)過程是氣相反應(yīng)物進(jìn)入到液相中進(jìn)行的反應(yīng)過程， 整個(gè)過程是反應(yīng)和傳質(zhì)相結(jié)合的復(fù)雜過程，研究氣液相反應(yīng)首先必須了解兩相間的傳質(zhì)問題。本實(shí)驗(yàn)選用 NaOH 溶液吸收 CO2的瞬間快反應(yīng)體系，就是要通過簡(jiǎn)單的實(shí)驗(yàn)及理論分析獲得有關(guān)傳質(zhì)問題的必要信息。在分批式的攪拌鼓泡釜中，該物系進(jìn)行反應(yīng)吸收時(shí)，化學(xué)計(jì)量式為：CO2＋2NaOH-- Na2CO3＋H2O（A） （B） （C） （D）在一定濃度范圍內(nèi)，此反應(yīng)過程可以近似為瞬間快速反應(yīng)，氣液界面附近的濃度分布如圖 1所示，由于 A與B一旦接觸就立即完成上述反應(yīng)，使得液側(cè)任一處上 A與B都不能同時(shí)存在。于是在離界面某一深度YR處形成一個(gè)反應(yīng)面 R；若CB增加，B的擴(kuò)散推動(dòng)力加大，擴(kuò)散速度也增大，結(jié)果使 YR減少，當(dāng) CB增加到某一臨界濃度 CBC時(shí)，反應(yīng)面將和相界面重合，擴(kuò)散到界面的 A瞬間反應(yīng)掉了，此時(shí) CAi＝PAi＝0，相界面APA反應(yīng)CB氣面液相PAi相本本體隨意編輯CAiB體yG 0 yR yL z精品文檔反應(yīng)吸收過程為氣膜傳質(zhì)控制，注意，反應(yīng)的進(jìn)行將不影響氣相傳質(zhì)系數(shù)。為什么？隨著吸收過程的進(jìn)行NaOH（B）最后完全耗盡，此時(shí)成為對(duì) CO2的純物理吸收過程。圖1 瞬間反應(yīng)氣液相界面附近的濃度分布根據(jù)雙膜理論可以寫出傳質(zhì)方程：氣相：NA1dnADGPAPAiRTkGaPAPAi(1)VdtYGa液相：NADLCAiCAkLaCAiCA(2)YLa以氣相分壓為推動(dòng)力的總傳質(zhì)方程：PP**NAAAKGaPAPA(3)1HAkGakLa式中PAi=HACAi；PA*=HACA因此有11HA(4)KGakGakLa當(dāng)過程為瞬時(shí)反應(yīng)吸收時(shí)，反應(yīng)面上CA=PA*=0，kLa隨NaOH的濃度而變化，當(dāng)CB>=CBC時(shí)，為氣膜傳質(zhì)控制，即有NAaKGaPA0kGaPA(5)當(dāng)CB- 0時(shí)，成為純物理吸收過程，則有NAaKGaPP*KGaPPA(6)AAA1HAkGakLa現(xiàn)對(duì)CO2作物料衡算，得到：PA出PA進(jìn)1VLCBRT（7）2VG式中；VL——釜內(nèi)液體體積VG——通入氣體的流量，假定為常數(shù)隨意編輯精品文檔設(shè)釜內(nèi)氣液為全混，則CO2分壓P=PA出，CO2的吸收速率可以通過進(jìn)出口CO2的含量改變來(lái)求得，A也可以由NaOH的濃度變化求得，本實(shí)驗(yàn)采用后一種方法，用電導(dǎo)法測(cè)得NaOH溶液的電導(dǎo)隨時(shí)間的變化，由下式可以求得轉(zhuǎn)化率X～時(shí)間t的曲線。LoL(8)XLLo式中：L0:起始電導(dǎo)L∞:終止時(shí)的電導(dǎo)L：t時(shí)刻的電導(dǎo)由NaOH 濃度隨時(shí)間的變化率求得：NAa1CBOx2由（3）式可求得某一時(shí)刻的KGa，（PA*0），然后作KGa～CB的關(guān)系圖，如圖2所示意。KGa(KGa)1(KGa)20 CBC CB圖2 KGa隨CB的變化根據(jù)上述分析，有圖2可求得kGa=(KGa)111HAKGa2kGakLa即得kGa和ka值，考慮溶液中電解質(zhì)的影響，CO2在溶液中的亨利常數(shù)取LHA=32.25atml/gmol隨意編輯精品文檔三實(shí)驗(yàn)流程和實(shí)驗(yàn)步驟實(shí)驗(yàn)流程：1—CO2鋼瓶2—轉(zhuǎn)子流量計(jì)3—壓縮機(jī)4—?dú)怏w混合器5—攪拌鼓泡釜6—電導(dǎo)率儀7—記錄儀8—攪拌馬達(dá)9—馬達(dá)調(diào)速器10—差壓計(jì)實(shí)驗(yàn)步驟：（1）投放2L濃度0.1N的NaOH 溶液入攪拌釜內(nèi)，開動(dòng)馬達(dá)，待混合均勻后，即可開啟電導(dǎo)率儀和記錄儀，記下初始電導(dǎo)值 L0。（2）調(diào)節(jié)流量計(jì)，開始通氣（先調(diào)好空氣流量，再開 CO2鋼瓶，緩慢打開 CO2流量計(jì)）。3）待記錄儀上指示濃度（電導(dǎo)率）不下降時(shí)，可以停止實(shí)驗(yàn)。4）關(guān)閉電導(dǎo)儀和記錄儀，切斷電源，然后放掉液體，用水清洗攪拌釜。5）整理實(shí)驗(yàn)數(shù)據(jù)。四 實(shí)驗(yàn) 數(shù)據(jù)記錄及結(jié)果1. 原始數(shù) 據(jù)隨意編輯精品文檔P大氣壓= 761.88 mmHg T室= 25.0 ℃氣體流量NaOH溶液LoL∞PCBO備注VairVCO2V(mm)(mm)(mmHg)(moll-(l/min)(l/min)(l)1)0.6142 0.2996 1249.56 7.0 1.67 2 0.04P進(jìn)=1.671249.56101325=32010PaA1.677761.882.數(shù)據(jù)處理計(jì)算思路：Lo L①用公式X 求出X，Lo L用ORIGIN作X-Θ圖：②利用ORIGIN 的數(shù)學(xué)工具微分得 X/Δθ：隨意編輯精品文檔③用公式NAa 1CBOx求出NAa；2④用公式PA出PA進(jìn)1VLCBA；2VGRT求出P⑤用公式CB=(1-X)CB0求出CB；⑥用公式NAa KGaPA求出KGa。現(xiàn)將結(jié)果列表如下：Θ(s)XNAa(mol/lmCB(mol/l)KGa(mol/lX/ΔθP(Pa)Ain)minatm)183 1 0 0 32010 0 032005.97450.0042928418010.001130.0013560250.9931972732005.97450.000272100.004292841770.001130.00135692950.9931972732005.97450.000272100.004292841740.001130.0013569295隨意編輯精品文檔0.9863945532005.97450.000544210.004292841710.001130.00135682850.986394550.0005442116800320100880.9863945532005.97450.000544210.004292841650.001130.00135682850.9795918332005.97450.000816320.004292841620.001130.00135672750.9795918332005.97450.000816320.004292841590.001130.00135672750.9727891132005.97450.001088430.004292841560.001130.00135662550.9727891132005.97450.001088430.004292841530.001130.00135662550.9659863932001.91340.001360540.008624771500.002270.00272451450.9591836732005.97450.001632650.004292841470.001130.00135632350.9591836732005.97450.001632650.004292841440.001130.00135632350.9523809532001.91340.001904760.008624771410.002270.0027242125隨意編輯精品文檔0.9455782332005.97450.002176870.004292841380.001130.00135612150.9455782332005.97450.002176870.004292841350.001130.001356121532001.91340.008624771320.938775510.002270.0027240.00244898150.9319727832001.91340.002721080.008624771290.002270.00272491850.9251700632005.97450.002993190.004292841260.001130.00135682750.9251700632005.97450.002993190.004292841230.001130.00135682750.9183673432001.91340.003265300.008624771200.002270.00272471650.9115646232001.91340.003537410.008624771170.002270.00272461550.9047619032005.97450.003809520.004292841140.001130.00135652450.904761900.0038095211100320100540.9047619032005.97450.003809520.004292841080.001130.0013565245隨意編輯精品文檔0.8979591832001.91340.004081630.008624771050.002270.00272441350.8911564632001.91340.004353740.008624771020.002270.00272431150.8843537432005.97450.00429284990.001130.0013560.004625851250.8843537432005.97450.00429284960.001130.0013560.0046258512532001.91340.004897950.00862477930.877551020.002270.0027241950.8707482932001.91340.005170060.00862477900.002270.00272491850.8639455731997.88790.00544217870.00340.004080.012919798370.8503401331997.88790.00598639840.00340.004080.012919796350.8435374131989.80130.006258500.02155109810.005670.00680454370.8163265331981.71470.007346930.03018676780.007940.00952814980.7959183631981.71470.008163260.03018676750.007940.0095287458隨意編輯精品文檔0.7687074831977.68920.00925170720.009070.0108840.034487213610.7414965931973.66370.010340130.03878873690.01020.0122498660.7074829931973.66370.03878873660.01020.012240.011700683860.6802721031981.71470.012789110.03018676630.007940.00952894680.6598639431973.66370.013605440.03878873600.01020.0122468260.6190476131965.57710.015238090.04743312570.012470.01496499580.5850340131973.66370.016598630.03878873540.01020.0122448960.5578231231969.60260.017687070.04312942510.011340.01360897560.5170068031973.66370.019319720.03878873480.01020.0122438860.4965986331973.66370.020136050.03878873450.01020.0122498460.4557823131969.60260.021768700.04312942420.011340.0136083776隨意編輯精品文檔0.4285714231969.60260.022857140.04312942390.011340.01360897360.3877551031973.66370.024489790.03878873360.01020.0122428660.3673469331973.66370.025306120.03878873330.01020.0122498260.3265306131965.57710.026938770.04743312300.012470.01496429680.2925170031969.60260.04312942270.011340.0136080.028299327760.2585034031973.66370.029659860.03878873240.01020.0122418460.2312925131969.60260.030748290.04312942210.011340.013608779631969.60260.032380950.04312942180.190476190.011340.0136087260.1632653031969.60260.033469380.04312942150.011340.013608678631969.60260.035102040.04312942120.122448980.011340.0136087160.0952380931973.66370.036190470.0387887390.01020.012245866隨意編輯精品文檔31969.60260.0431294260.061224490.011340.0136080.03755102760.0272108831973.66370.038911560.0387887330.01020.01224485631977.68920 0 0.00907 0.010884 0.04 0.034487216五計(jì)算與討論基于上表數(shù)據(jù)作圖如下：可以得到KGa=0.004293mol/lminatmkGa=0.043129mol/lminatm再根據(jù)：11HA，HA=32.25atml/gmol，得：KGa2kGakLakLa