Study On Reaction Kinetics And Simulation Of Shift Reactor Of QCS-01 Sulfur Tolerant Shift Catalyst

The water-gas shift (WGS) reaction is well known since first reports in 1888 and became one of the most important catalytic reactions when the first coal-based ammonia synthesis plant was put into operation. The WGS reaction is an important process in the production of ammonia, hydrogen and methanol, etc. The WGS reaction catalysts have been the subject of extensive studies particularly with regard to accurately predicting catalyst behavior and lifetime. Three classes of catalysts are used almost exclusively in industry: iron oxide-based, copper oxide-based and cobalt-molybdenum oxide-based catalysts. Iron oxide-based catalysts can be operated at the temperature of 350-550℃, which limits the theoretically obtainable CO conversion with unconvertible CO ratio of about 3%(v). The subsequent development of WGS reaction catalysts is the application of copper oxide-based catalysts that are more active at lower temperature of 200-280℃. 0.3 %(v) CO is hardly converted. A disadvantage of both iron oxide-based and copper oxide-based catalysts are highly sensitive towards sulfur contamination of the gas feed. Therefore, some 20 years ago, a new class of sulfur-resistant WGS reaction catalysts-cobalt-molybdenum oxide-based catalysts was proposed and indicated good performance with highly sulfided feeds while operating at further lower temperature. Research Institute of Qilu Branch Co., SINOPEC has developed a series of sulfur-resistant Co-Mo oxide-based WGS reaction catalysts with high activity, lower and wider operating temperature. QCS-01 is one of Co-Mo oxide-based WGS reaction catalysts which can operate under high pressure up to 9 MPa.WGS reaction kinetics of QCS-01 sulfur-tolerant Co-Mo oxide-based WGS reaction catalysts was studied experimentally by using a Berty experimental mixed flow reactor in this paper. The kinetic experiments were carried out under the pressure of 1 - 8.0 MPa and the temperature of 280 480℃. The weight of the catalyst charged was 4.3845g. The space velocity was 2000¹0000h^-1; steam /feed dry gasratio, 0.4¹.7mol/mol; inlet dry gas composition Y_CO2F⁰ in the range of 10^<sup>50 ( mol ) %; and Y_CO2F⁰ 50- 10 (mol) %. A macro-reaction kinetics model wasregressed by non-linear Marquardt least square method from the kinetic experimental data. An exponential macro-reaction kinetics model for QCS-01 sulfur tolerant WGS reaction catalysts at the pressure of 0.8MPa was proposed as follows: ^ 295i27°b^Y^Y^Yc^Y^a - /?) moll(g â–  h)where, frequency factor K0=29.5, activation energyï¿¡=27066 J/mol; and/? indicatesthe degree of the reversible reaction, expressed as: y ywhere, Kp is the equilibrium constant of WGS reaction, and its relation with the reaction temperature isKp = exp(5.0992511 +4764.1 ir^'+5.6273903 xlO³T -2.189647 xlO'T2 +4.17603x10 10r3-1.9439412In7)where, R is gas constant, whose value is 8.314 J/mol â–  K.With mathematical statistics, the correlating degree of the kinetics model developed was checked up by both F method examination and relativity exponent y1examination. The examination results indicate that the kinetics model developed is highly obvious and credible.On the base of WGS reaction kinetic model, a pseudo homogeneous one-dimension mathematics model of WGS packed bed reactor was developed by considering the WGS reaction in the packed bed reactor as an adiabatic process. The model equationsare as follows:dT=nDjw dh 4CPG dYC0 xD2Yvdh AGdYH,0 = dY,Qdh dhdYC0, dYdh dhdh dhThe commercial WGS reaction process using QCS-01 sulfur tolerant catalyst wassimulated. The comparison of simulation results with industrial operation data shows that the simulation results agree well with the industrial operation data, indicating that the mathematics model developed for industrial WGS reaction process can accurately predict the industrial operation. Furthermore the mathematics model of industrial WGS reaction process was applied to investigate the distribution of reactor temperature and CO concentration at the direction of packed bed reactor height. The effect of feed temperature and water steam/gas ratio on CO conversion in the reactor was clarified. The relation of optimum reaction temperature with equilibrium temperature was discussed. The operation of three packed bed reactors in series was optimized and the minimum amount of catalyst needed in each packed bed was obtained for the industrial WGS reaction process using QCS-01 sulfur tolerant catalyst.