Gas Absorption Enhancement of Carbon Dioxide into Ca(OH)2 Slurries Gas Absorption Enhancement of Carbon Dioxide into Ca(OH)2 Slurries

Gas Absorption Enhancement of Carbon Dioxide into Ca(OH)2 Slurries

  • 期刊名字:天津大学学报(英文版)
  • 文件大小:512kb
  • 论文作者:LU Sumin,MA Youguang,ZHU Chuny
  • 作者单位:State Key Laboratory of Chemical Engineering
  • 更新时间:2020-09-15
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论文简介

Transactions of Tianjin UniversityISSN10064982VoL 13 No, 6DeC.2007Gas absorption Enhancement of Carbon Dioxideinto Ca(oH), SlurriesLU Sumin(卢素敏), MA Youguang(马友光), ZHU Chunying(朱春英), ShEN Shuhua(沈树华)(State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China)Abstract: Chemical absorption of CO, into aqueous slurries of Ca(OH)2 was studied in a stirred ther-mostatic reactor. The intluence of solid loading and stirring speed on absorption rate were investigat-ed experimentally, and the results show that the enhancement factor increases with particle contentdue to the increase of reactive particles in the gas-liquid intertacial region. The absorption processs controlled by the diffusion of gas molecules in slurry. The influence of stirring intensity on en-hancement factor is an integration of gas-liquid and liquid-solid mass transfer variation a novel pre-diction model of enhancement factors was proposed with the partition of interface into two variaus zonesand the prediction values by the presented model are in agreement with the experimental dataKeywords: enhancement factor; gas absorption; mass transfer; theoretical modelCarbon dioxide is a greenhouse gas harmful to the en- was widely accepted or verified due to the complexity of gasvironment, which must be removed from the waste gas pro- absorption in slurries. This paper focuses on the COduced in industrial processes. Various methods [1, 2] have sorption into limestone slurries under different operatingbeen developed for the removal of CO2 from the waste gas of conditions. A new two-zone model was developed to de-industrial emission or other processes. A conventional way scribe the process of CO2 absorption in slurryis CO chemical absorption in aqueous slurries with reactive1 Experimentparticles, such as aqueous Iimestone slurriesMany experimental and theoretical researchesThe experiments were carried out in a thermostatic rebeen reported on the chemical absorption of gas into aque- actor( from Yantai Keli Research Institute of Automaticous slurries sadala et al l3, 4]investigated experimentally the Control Equipment), as shown in Fig. 1. The reactor isabsorption of sulfur dioxide into aqueous slurries of magne- filled with the slurry before each experiment and the liquidsium hydroxide and limestone, and proposed that there ex- was degassed by opening valve 10 until the slurry is equiliistsed two reaction planes in the reactive film zone, but no brated under the vapor pressure of the solvent used. Thensuspending particle was present in the zone between the first valve 10 is closed Open valves 1 and 2 and co is fed intoreaction plane and the gas-liquid interface. Furthermore, vessel 3 and reactor 15 up to a fixed pressure. Valves 1 andthey extended the concept of a thin particle-free zone to the 2 are then closed rapidly. Turn on the motor of the magneticinterpretation of rate data for the simultaneous absorption of stirrer 7 and the absorption is started. Vessel 3 is a refCO2/S02 into calcium hydroxide slurries 5. However, the ence vessel, an SCB3111 pressure difference transducerprediction values were obviously larger than the experimen-( 10 Pa)5 is connected between vessel 3 and reactor 15tal results. Taking into account the marked effect of parti- The transducer signal is transmitted to an acquisition cardcles size on the enhancement of gas absoption, Mehra[6l stud- and recorded on-line by a computer. The growing pressureied theoretically the dissolution process of particles by popu- difference due to the absorption in the reactor is recordedlation balance approach. In spite of the numerous research- on-line as a function of time. The operating conditions arees,no theory or model about gas absorption enhancement listed in Tab. 1Accepted date: 2007-09-06LU Sumin, born in 1967 female, DrSupported by National Natural Science Foundation of China(No. 20176036)CorrespondencetoMAYouguang,E-mail:yema@tu.edu.cn中国煤化Transactions of Tianjin University VoL 13 No 6 2007Co and CacO, takes place only within a thin liquidfm7,8](2) The resistance of mass transfer insecanneglected(3)The particles with equalSUSd in the slurry, and completely immersed into the liquid, and the average distance between the gas-liquid interface and the particles can be estimated according to the film1513Bh。12(4) The gas-liquid interface is divided into two zonesuncovered part(Zone I )and covered part( Zone I)asnown In1gnd the ratefor the1-CO2 inlet valve; 2--Junction valve; 3-Balance tank; 4-Preasure trans- covered part is considered to be equal to that in a homogemitter; 5-Preaeure difference transmitter( connected with the computer) 6- neous reaction system without particlesvalve; 10-vacuum valve; 11--Gae stirrer: 12--liquid stirrer; 13--BafileThen the total gas absorption rate through the entire14--Stainleas steel top: 15-Stainleas steel reactor; 16--Thenmostatic bathgas-liquid interfawntten asFig, Ir吧 for gas absorpt(1-∮)naiAITab 1 Experimental conditionsTemperature/t Initial pressure/kPa Gae purity/% Stiring speed/(rs-I)1599.5NATthe influence of the product CaCO3 on theNAgas absorption, the absorption experiments were carried outSolidby the addition of only CaCO3 particles in pure water. FromFig. 2, the influence of CaCO particles on absorption rate(a) sketch map of mass transfer in the gas-liquid boundary layerof CO, is negligible13131.1◆3rb07_4z(b)Concentration profile of A and B in Zone Ilaco, concentration(mase ratio)%ig. 3 Schematic drawing of mass transier and comumtratioig 2 Variation of enhancement factor with Caco, conceaprole cf A and B in Zone HIn terms of the above assumptions, the mass transfer2 Modeling of absorptionrate is calculated individually in the two zones, and mean-time, the mass transfer is assumed to take place only in theFor the chemical absorption process of Co2 into aque- x-direction in each zoneous slurries of Ca(oh )2, the following assumptions are(1)Zone ImadeThe mass transfer rate in Zone I is equal to that in a(1)The reaction between CO2 and Ca(OH)2 is instan- homogeneous reaction system. For the gas absorption systaneous and irreversible and the chemical reaction between tems accompanied by instantaneous irreversible reaction424方数据LU Sumin et al: Gas Absorption Enhancement of Carbon Dioxide into Ca(OH)2 Slurriesthe rate of gas absorption can be given bvl91Substituting Eg.(10)into Eg.(13)yieldsAl=KCA/1,DBCBsM( CA DB CBSN(3)tanh MOrMDB CBS (14)sin五M6,(2)ZoeⅡwhere 8, can be derived from Eq.(9). Substituting EqsDue to the extremely fast chemical reactioneenA(10)and(11) into Eg.(9), we haveand B, the reaction is thought to take place only at a reacDA CA +dB CBsDB CBStion plane between gas-liquid interface and the particlesinh M8r tanh M5, tanh M(8-8)The concentrations of a and b in the reaction plane are both(15)zero[7, 8, 10, l1].The rate of solid dissolution is enhanced dueThe total gas absorption rate through the entire gas-liqto the reaction by the value ofsiuid interface accordingly can be given byDA CADo C14NA=(1-)k1CA1+DAuAWhen 0

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