【作者】 王彪；

【导师】 应卫勇； 孙启文；

【作者基本信息】 华东理工大学 ， 化学工艺， 2011， 博士

【摘要】 由甲醇制低碳烯烃是最有希望替代石油路线的新工艺,甲醇制低碳烯烃流化床反应器的研究对于其工艺的开发与完善具有重要的指导意义。论文在反应-再生流化床热模装置中对甲醇制低碳烯烃反应-再生过程,催化剂的微观结构进行研究；建立了甲醇制低碳烯烃循环流化床大型冷模实验装置,研究了循环流化床中的流体力学行为；建立了气固流化床计算流体力学(CFD)模型,改进了传统的曳力模型,采用FLUENT对气固流态化过程进行了数值模拟；结合循环流化床大型冷模实验、反应动力学和传递过程原理,建立了甲醇制低碳烯烃流化床反应器数学模型,并采用MATLAB软件编制成通用程序。建立了反应-再生流化床热模装置,并在该装置上对甲醇制低碳烯烃反应-再生过程进行研究,获得了较佳的反应-再生过程操作条件。在密相段为φ30x320mm及稀相段为φ68×160mmm的流化床反应器中,采用SAPO-34为主要活性成分的催化剂,研究了反应温度、空速(WHSV)、进料组成随反应时间对产物中低碳烯烃(乙烯和丙烯)含量及甲醇转化率的影响,同时在流化床中对失活催化剂进行再生实验,考察了再生催化剂的催化性能,并用XRD、SEM、BET、NH3-TPD、TGA等手段对催化剂进行表征。实验结果表明,在450℃,空速为3h+1,精甲醇(99.5mo1%)进料时,产物中低碳烯烃(乙烯和丙烯)含量高达92.06%；再生催化剂的催化性能良好,微观结构没有发生明显变化,可以循环使用。TGA表征结果表明,600℃是较适宜的再生温度。采用PV6 D光导纤维颗粒速度测量仪和PC6 D光导纤维固体浓度测量仪,在甲醇制低碳烯烃循环流化床大型冷模实验装置上研究了循环流化床中的流体力学行为。在表观气速为0.3930-0.7860m/s,静床高分别取600-1200mm的情况下,以粒径为154～180μm的砂子为固体颗粒,采用PC6 D颗粒速度测量仪与PV6 D固体浓度测量仪对冷模装置中可测量区域的固体浓度分布与颗粒速度分布。考察了不同径向位置(r/R=0,0.1-0.8,0.9),不同轴向位置(500～600mm),不同表观气速(0.3930,0.4912,0.5895,0.6877,0.7860m/s),不同静床高(600mm,800mm,1000mm,1200mm)的条件下冷模装置中固体浓度分布与颗粒速度分布。考察了采用不同形状的气体分布器(环形和枝条型)与不同分布器开孔率(2.5%o和5‰)时冷模装置中颗粒浓度分布与颗粒速度分布。考察了静床高为600mm与800 mm时,枝条型分布器(5‰),表观气速为0.3930-0.6877m/s,颗粒循环通量随表观气速与静床高的变化关系,得出了反应-再生系统物料循环的操作条件。通过对气固流化床流动特性和气固两相流理论分析,建立了气固流化床的计算流体力学(CFD)模型。采用双流体模型,三维非稳态算法在计算流体力学软件FLUENT软件平台上对气固流化床内的流体流动进行了数值模拟。基于最小流态化速度,改进了传统的Syamlal & O’Brien模型,并用C语言编制模型程序嵌入了FLUENT平台中。考察不同条件下气固流化床内流体流动形态的变化；在流动达到稳定后,将模拟值与实验值进行比较。考察网格划分、曳力模型,颗粒剪切粘度、颗粒弹性恢复系数和虚拟质量力等对模型预测能力的影响。同时考察了不同颗粒粒径情况下的流动状况。模拟结果表明：双流体模型可以较好的预测气固流化床中的流动行为,使用改进后的Syamlal & O’Brien曳力模型使模拟计算值与实验值的误差更小,采用三维计算网格、Syamlal固体剪切粘度模型、考虑虚拟质量力可以更好的模拟气固流化床中的流动行为。颗粒弹性恢复系数对计算结果影响较小。结合反应动力学、热力学、大型冷模实验和传递过程原理,建立了甲醇制低碳烯烃流化床反应器数学模型,对采用SAPO-34流化床催化剂的甲醇制低碳烯烃反应结果进行了数学模拟,考察了不同的操作条件对反应产物分布和反应床层压降的影响。计算结果表明：反应温度的升高有助于提高甲醇转化率和产物中乙烯的含量,降低产物中丙烯的含量,增大催化床层的压降；操作压力的升高有助于提高甲醇转化率,降低催化床层的压降；随着空速增大,甲醇转化率降低,床层压降增大；氮气的添加并未对反应结果起到明显的改善作用。更多还原

【Abstract】 Methanol-to-olefins process is the most hopeful new process instead of petroleum route process, so research of fluidized bed reactor for methanol-to-olefins process is of importance for continuous development and improvement of the process. The dissertation gives some results about reaction-regeneration process of methanol-to-olefins in fluidized bed and micro-structure of catalysis. Cold model experimental facility of gas-solid circulating fluidized bed for methanol-to-olefins process is established and flow behavior in gas-solid circulating fluidized bed is studied. Computational fluid dynamics model of gas-solid fluidized bed is established and gas-solid flow behavior is simulated by software FLUENT by means of modified drag coefficient model. Mathematical model of fluidized bed reactor for methanol-to-olefins process is founded combining with cold model experiments in the gas-solid circulating fluidized bed, reaction kinetics and transport process principles. The model equations are programmed using software MATLAB.Experimental equipment of reaction-regeneration fluidized bed for methanol-to-olefins process is established and optimized operating conditions of reaction-regeneration process are obtained according to the research of reaction-regeneration process for methanol-to-olefins process in the experimental equipment. In order to study the process of methanol-to-olefins, the SAPO-34 is used as the main active component in a fluidized bed reactor with dimensions of 030 mm×320 mm for its dense section and 068 mm×160 mm for its thin section. The effects of reaction temperature, WHSV and feed composition on ethylene, propylene selectivity and methanol conversion are investigated; at the same time, the deactivated catalyst after use is regenerated in the fluidized bed and the catalytic performances of the regenerated catalyst is investigated too. The results indicate that, under optimal conditions for proceeding operation methanol-to-olefins:i. e. temperature of 450℃, WHSV of 3 h1a and feed methanol composition of 99.5%(mol), the total selectivity of ethylene and propylene can reach 92.06%. The catalyst SAPO-34 and the regenerated catalyst are characterized by means of XRD, SEM, BET, NH3-TDP and TGA, respectively. It is found that, after regeneration, the microstructure and the catalytic performance of the regenerated catalyst has no evident change, and it can be used repeatedly. The TGA characterization indicates that the 600℃is the optimal regeneration temperature.Flow behavior in gas-solid circulating fluidized bed is studied in cold model experimental facility of gas-solid circulating fluidized bed for methanol-to-olefins process via a PC-6D solid concentration analyzer and a PV-6D particle velocity analyzer. Solid concentration and particle velocity distribution in cold model experimental facility are studied with a mixture of sand ranging from 154 to 180μm diameter used as the fluidizing particles, different superficial gas velocities ranging from 0.3930 to 0.7860 m/s and different initial bed height ranging from 600 to 1200mm using air as the fluidizing gas. Local solid concentrations and particle velocity under 10 operating conditions are measured at 10 radial positions (r/R=0.0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9) on 10 axial levels (500,600,700, 800,900,1000,1100,1200,1400,1600mm),4 initial bed height (600,800,1000,1200mm) and 4 superficial gas velocities (0.3930,0.4912,0.5895,0.6877,0.7860m/s). Solid concentration and particle velocity distribution in cold model experimental facility are discussed with four types of distributors employed in the experiment:5%o circle distributor,5%o branched pipe distributor,2.5%o branched pipe distributor and 2.5%o circle distributor. Particle cycle flux is studied with different superficial gas velocities ranging from 0.3930 to 0.7860 m/s, different initial bed height ranging from 600 to 800mm and 5%o branched pipe distributor used. Optimized operating conditions of particle cycle flux for reaction-regeneration process are obtained.Computational fluid dynamics model of gas-solid fluidized bed is established according to analysis of flow behavior in gas-solid fluidized bed and theory of gas-solid flow. Gas-solid flow behavior in fluidized bed is simulated by software FLUENT by means of multi fluid model for two phase and 3d unsteady state algorithm. Syamlal & O’Brien model is modified based on minimum fluidization velocity and modified Syamlal & O’Brien model is added in software FLUENT via C programming language. Flow behaviors in gas-solid fluidized bed are discussed under different operations and models, the simulated results are compared with experimental results. Effects of meshing, drag models, particle shear viscosity, particle coefficient of restitution and virtual mass force on predictive power of computational fluid dynamics model are discussed. Simultaneously the flow behaviors using different particle diameters are studied. The results indicate that flow behaviors can be simulated by computational fluid dynamics model. the result with modified Syamlal& O’Brien drag model,3d mesh, Syamlal particle shear viscosity, regard of virtual mass force can simulate the flow behavior of gas-solid fluidized bed better. The effect of particle coefficient of restitution on the simulated result is small.Mathematical model of fluidized bed reactor for methanol-to-olefins process is founded combining with cold model experiments in the gas-solid circulating fluidized bed, reaction kinetics and transport process principles, the results of methanol-to-olefins reactions using catalysis SAPO-34 in relative steady period are simulated. Effects of operated conditions on product distribution and pressure drop are discussed. The results indicate that high temperature can increase the selectivities of ethylene and propylene, methanol conversion and pressure drop; high operated pressure can increase methanol conversion and decrease pressure drop; high space velocity can increase pressure drop and decrease methanol conversion; effects of nitrogen on results of reactions are unconspicuous.更多还原