规整催化剂甲烷化过程数值模拟及反应器设计
发布时间：2018-07-24 21:14
【摘要】：输送床-固定床二段式甲烷化工艺是由输送床和固定床组合而成的,甲烷化反应是放热量高的反应。输送床优传热性能优越,其发生甲烷化反应的床层温度接近等温,大部分原料气在输送床发生反应,剩下小部分没有反应的气体在固定床中发生反应。该工艺中出现的问题是输送床中颗粒相互碰撞带来的颗粒粉末可能会进入固定床中造成传统堆积催化剂空隙的阻塞进而增加床层压降。为避免出现该问题,需要研究低压降甲烷化固定床反应器。低压降甲烷化固定床反应器选用的是规整填料的轴向流反应器。以ANSYS workbench为平台,采用数值模拟的方法分别进行了四部分研究。首先对同样发生表面反应的平板反应器进行模拟,并用相同的方法对单孔道进行模拟。采用单孔道替代多孔道的方法对规整催化剂进行模拟,分别模拟了发生表面反应和体积反应的规整催化剂。第二部分是改变入口温度、入口压力、入口速度、入口浓度等操作参数,分别研究操作参数对固定高度的规整催化剂达到的转化率的影响和达到工艺要求的转化率需要的催化剂高度的影响。第三部分是对发生甲烷化的床层进行研究。研究孔道形状及尺寸对传递、压降、转化率的影响;研究孔道材质和催化剂床层间隙对甲烷转化率的影响;研究达到相同转化率的条件下,流速、尺寸与催化剂用量的关系。第四部分是确定床层流速分别为0.95m/s、1.81m/s对应的固定床的工艺参数与结构尺寸,并对固定床入口结构进行优化。进而对反应器进行强度设计,并利用热-流-固耦合的方式对设计反应器进行强度校核,使最终设计的反应器满足强度需要。研究结果表明:(1)通过验证对比,使用模拟平板甲烷化反应器方法模拟规整催化剂,使用单孔道代替多孔道模拟规整催化剂的方法是正确的。(2)转化率随流速增加而降低;压力越高,转化率越高;入口温度越高,转化率越高,入口温度需要在260℃-320℃之间;固定床入口浓度随前段流化床转化率决定,流化床转化率大于65%,固定床内催化剂不会失活;获得了浓度-流速-转化率关系式。(3)圆形孔道传递效果最好,正方形次之,三角形最差。但三角形孔道压降和转化率最好,圆形孔道最差。孔道尺寸越小转化率越高。对于进料浓度大的规整催化剂,为避免催化剂失活,可以选用金属材料的规整催化剂,并外壁保持恒温。催化剂床层之间的间隙对气体混合没有效果,规整催化剂没有必要设置分段。要达到工艺要求转化率,流速与发生表面反应的规整催化剂用量没有关系。(4)确定了床层内流速为0.95m/s、1.81m/s对应的反应器结构尺寸;需要在反应器内壁增加隔热材料才可以达到强度要求。
[Abstract]:The two-stage methanation process of conveying bed and fixed bed is composed of conveying bed and fixed bed. The methanation reaction is a reaction with high heat release. The bed temperature of the methanation reaction is close to isothermal, most of the feedstock gas reacts in the conveying bed, and a small part of the unreacted gas reacts in the fixed bed. The problem in this process is that the particle powder caused by the collision of particles in the conveying bed may enter the fixed bed resulting in the blockage of the gap of the traditional piling catalyst and thus increase the pressure drop of the bed. In order to avoid this problem, it is necessary to study the low pressure demethanation fixed bed reactor. The fixed bed reactor for low pressure methanation is an axial flow reactor with regular packing. Taking ANSYS workbench as the platform, four parts of research are carried out using numerical simulation method. At first, the surface reaction of the plate reactor is simulated, and the single channel is simulated by the same method. The surface reaction and volume reaction of the regular catalyst were simulated by the method of single channel instead of the multi-pore channel. The second part is to change the operating parameters such as inlet temperature, inlet pressure, inlet velocity, inlet concentration, etc. The effects of operation parameters on the conversion of the regular catalyst with fixed height and the catalyst height required to meet the conversion requirements of the process were studied respectively. The third part is to study the methanation of the bed. The effects of pore shape and size on transfer, pressure drop and conversion rate were studied. The effects of pore material and catalyst bed gap on methane conversion were studied. The relationship between flow rate, size and catalyst dosage was studied under the same conversion rate. The fourth part is to determine the process parameters and structural dimensions of the fixed bed with a flow velocity of 0.95m / s and 1.81m / s, respectively, and optimize the structure of the inlet of the fixed bed. Then, the strength of the reactor is designed, and the design reactor is checked by the thermal-fluid-solid coupling method, so that the final designed reactor can meet the strength needs. The results show that: (1) through verification and comparison, it is correct to use the simulated plate methanation reactor method to simulate the regular catalyst, and to use the single-pore channel instead of the multi-pore channel to simulate the catalyst. (2) the conversion rate decreases with the increase of the flow rate; The higher the pressure, the higher the conversion rate, the higher the inlet temperature, the higher the conversion rate, and the higher the inlet temperature is between 260 鈩，
本文编号：2142674
[Abstract]:The two-stage methanation process of conveying bed and fixed bed is composed of conveying bed and fixed bed. The methanation reaction is a reaction with high heat release. The bed temperature of the methanation reaction is close to isothermal, most of the feedstock gas reacts in the conveying bed, and a small part of the unreacted gas reacts in the fixed bed. The problem in this process is that the particle powder caused by the collision of particles in the conveying bed may enter the fixed bed resulting in the blockage of the gap of the traditional piling catalyst and thus increase the pressure drop of the bed. In order to avoid this problem, it is necessary to study the low pressure demethanation fixed bed reactor. The fixed bed reactor for low pressure methanation is an axial flow reactor with regular packing. Taking ANSYS workbench as the platform, four parts of research are carried out using numerical simulation method. At first, the surface reaction of the plate reactor is simulated, and the single channel is simulated by the same method. The surface reaction and volume reaction of the regular catalyst were simulated by the method of single channel instead of the multi-pore channel. The second part is to change the operating parameters such as inlet temperature, inlet pressure, inlet velocity, inlet concentration, etc. The effects of operation parameters on the conversion of the regular catalyst with fixed height and the catalyst height required to meet the conversion requirements of the process were studied respectively. The third part is to study the methanation of the bed. The effects of pore shape and size on transfer, pressure drop and conversion rate were studied. The effects of pore material and catalyst bed gap on methane conversion were studied. The relationship between flow rate, size and catalyst dosage was studied under the same conversion rate. The fourth part is to determine the process parameters and structural dimensions of the fixed bed with a flow velocity of 0.95m / s and 1.81m / s, respectively, and optimize the structure of the inlet of the fixed bed. Then, the strength of the reactor is designed, and the design reactor is checked by the thermal-fluid-solid coupling method, so that the final designed reactor can meet the strength needs. The results show that: (1) through verification and comparison, it is correct to use the simulated plate methanation reactor method to simulate the regular catalyst, and to use the single-pore channel instead of the multi-pore channel to simulate the catalyst. (2) the conversion rate decreases with the increase of the flow rate; The higher the pressure, the higher the conversion rate, the higher the inlet temperature, the higher the conversion rate, and the higher the inlet temperature is between 260 鈩，
本文编号：2142674
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