有固相析出的逆流多效蒸发系统的新设计方法

提出了有固相析出的逆流多效蒸发系统常规设计的一种新方法,将系统的相平衡关系用回归式表达,使模型可以编程用计算机求解;将系统的物料衡算和热量衡算方程组写成矩阵方程的形式,采用迭代法结合矩阵法求解.在常规设计新方法的基础上,提出了系统的优化设计方法,以系统的年总费用最小为优化目标,以生蒸汽压力、冷凝器真空度及各效有效传热温差为决策变量,采用复合形法结合拉格朗日乘子法求最优解.算例表明,生蒸汽压力、冷凝器真空度对优化结果影响显著,优化设计比常规设计可节省年总费用9%左右.算法收敛速度快、收敛稳定性好.

New design method of countercurrent multi-effect evaporation system with solid separation

A new design method of conventional design of countercurrent multi-effect evaporation with solid separation was presented. The equilibrium was correlated to equation and the model could be solved with computer easily. Mass balance and energy balance equations of the system could be expressed in matrix equation. New algorithm, which combined matrix method with iteration method, was presented to solve the conventional design model. Based on the new method of conventional design, the optimum design method was presented. The objective of the optimum design was the minimum total annual cost of the system. Based on decisive variables such as the pressure of fresh vapor, the pressure of condenser and heat-transfer effective temperature difference of vari-effect, the model was solved by the complex method combined with the Lagrangian multiplier method and matrix method. Practical example indicates that the influences of the pressure of fresh vapor and the pressure of condenser on the optimum design was notable. Total annual cost by the optimum design can be decreased by about 9% against that designed by a conventional design. The algorithm increases the convergence speed and stability.