Conventional water system optimization often only considered flowrate of fresh water, but ignored flowrates of desalted water, deaerated water, all-level steam and condensate water. The relationship among those types of water is lack of analysis. The minimum freshwater flowrate for the whole water system cannot be determined in one stepvia the conventional water system optimization model. In order to overcome such a limitation, this paper proposed a general model of water-using process including multiple water types, and presented a general superstructure of industrial water network optimization and a related mathematical model. The material balance equations that relate all types of water are integrated in the model. The commercial software, GAMS, was used for modeling and solving a water system for a certain refinery plant. The results of the case study indicate that the flowrate of desalted water is declined and flowrate of reuse water is increased. Thus the total flowrate of fresh water of overall water system is decreased from 489.44 t·h?1 to 283.94 t·h?1 with rain water flowrate keeping unchanged as 469.36 t·h?1 and the water conservation ratio reaches 21.4% on the basis of the summation flowrate of freshwater and rain water. The quantity of water intake per ton crude oil is reduced from 0.649 t to 0.510 t, which approaches the advanced level in China. Case study shows that the freshwater flowrate for the whole refinery water system can be calculated effectivelyvia the proposed optimization model and it demonstrates the applicability of the model.%传统水系统优化往往只考虑了新鲜水用量,而忽视了除盐水、除氧水、各等级蒸汽、蒸汽冷凝水、循环冷却水等类型的水,缺乏对各类型水量关联性的研究.针对这种局限性,提出了包含多种类型水的通用用水过程模型,以及通用炼油厂水系统优化的超结构和相应的数学模型,模型中集成了各装置及各种类型水之间关联的物料衡算方程.利用商业软件GAMS对某炼油厂的水系统进行建模求解,案例分析结果表明,除盐水用量有所下降,回用水用量增加,在优化前后雨水量保持469.36 t·h?1的情况下,系统的新鲜水用量从489.44 t·h?1减小到283.94 t·h?1,以系统新鲜水量和雨水量之和为基准,节水率达到21.4%.加工吨原油取水量从0.649 t减小至0.510 t,接近国内先进水平.案例研究表明,提出的优化模型能够有效地计算整个炼油厂水系统的新鲜水用量,验证了该模型的实用性.
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