Optimization Of Water Systems In Chemical Industrial Parks With Integrated Regeneration Units

The chemical industrial park（CIP）is an important carrier for the development of China’s chemical industry,and is an important support for the transformation and upgrading of the industry and green and high-quality development.CIPs consume a large amount of water resources,and the environment capacity of the wastewater receiving bodies is limited.The efficient use of wastewater resources has not yet been achieved under the existing production model,resulting in a huge waste of water resources and the increasing of environmental pollution load.In response to these problems,the State Council has issued a policy to accelerate the promotion and application of water-saving technologies and to carry out the whole process of industrial water management in the chemical industry.In order to achieve the goal of sustainable water resources development,this thesis proposes a framework for integrated water system optimization that balances environmental and economic benefits.Based on the perspective of water life cycle,a four-layer structural model of water supply,water usage,water transfer,and wastewater discharge was proposed based on the evolution characteristics of water quality and quantity in the system.Furthermore,it is characterized as the metabolic relationship of the water system resources in CIPs.On this basis,a physical model of the superstructure of the water network system is established by combining the wastewater regeneration unit and the water main model.A mixed integer nonlinear programming（MINLP）mathematical model of the water network is also established.The cost of regeneration units is one of the factors influencing the results of water system optimization.This thesis accounts for the cost factors of regeneration units appropriate to the park case and applies them to the planning study of park-wide water system management in combination with an integrated optimization model.Using the minimum total annua cost and the minimum freshwater flowrate as the optimization targets respectively,the integrated optimization study of multiple efficient utilization scenarios for the water network system was carried out.The results showed that a minimum freshwater flowrate of 100 t/h and a minimum total annual cost of RMB 29.77 million.The effectiveness of unconventional water use for four scenarios under two objectives is discussed and the best scenario under each objective is identified.The metabolic network structure of the water system under two different fresh water supply constraints is also explored.The results of the study show that it is feasible to combine integrated systems engineering optimization with life cycle thinking to achieve efficient water system management analysis.This thesis explores the correlation among the average annual cost of water usage,wastewater discharge,and wastewater quality in a CIP.The proposed integrated and sustainable optimal water management solutions for different scenarios are used as a reference for the park to implement optimal water system management decisions by balancing environmental and economic interests.The results of the study show that without such a program of different options for the optimal management of water resources according to different needs,the added economic burden would be detrimental to the implementation of an actual water management plan.The management options proposed in this study,which are based on life cycle thinking and link water costs,wastewater discharge and wastewater quality simultaneously,can provide a basis for decision making for the park authorities.