氨合成塔理论优化模型的数值解及其影响因素分析

Numerical Solution and Influence Factor Analysis of Theoretical Optimization Models for an Ammonia Converter

建立了连续换热式氨合成塔轴向最佳温度和最大合成率的优化模型，采用牛顿迭代法和龙格-库塔法对模型进行了数值解。计算和分析了进塔空速（20000—24000h^-1）、氨摩尔分率（2％～4％）和惰气摩尔分率（10％-14％）对轴向最佳温度和最大合成率的影响。结果表明，提高空速对催化床出口最佳温度和最大合成率的影响可忽略，但可提高氨的产量；提高进塔氨摩尔分率对催化床出口最佳温度的影响可忽略，但使最大合成率或氨净值降低；提高进塔惰气摩尔分率均使催化床出口最佳温度和最大合成率降低。优化模型可直接判断实际工况偏离最佳状态的程度，为氨合成塔的多方案设计或操作的优选提供了重要的理论依据。该方法计算简单、快速、准确。

The optimal mathematical models on the axial optimum temperature and maximum synthetic rate for a continuous heat exchange ammonia converter were established. The Newtonian＇ s iterative method and Runge - Kutta method were used to give the numerical solutions of the models The influences of the entrance space velocity （20 000 -24 000 h^-1 ）, ammonia mole fraction（ 2% -4% ） and inert mole fraction（ 10% - 14% ） on the axial optimum temperature and maximum synthetic rate were calculated and analyzed. The results showed： the influence of increasing space velocity on the optimum temperature and maximum synthetic rate at the outlet of the catalyst bed could be neglected but the ammonia output could be increased; the influence of increasing entrance ammonia mole fractin on the optimum temperature at the outlet of the catalyst bed could be neglected but the maximum synthetic rate or net ammonia value at the outlet of the catalyst bed was decreased ; the increase of inert mole fraction reduced both the optimum temperature and maximum synthetic rate at the outlet of the catalyst bed. The optimal models can directly determine the deviation extent of the practical operation from the optimum state and be the important theratical basis for the selecting among several feasible design or operation schemes of ammonia converter. The method gives a simple , fast and precise calculation.