| Synthesis of Heat exchanger networks is one of the important technologies to reduce chemical energy consumption.Along with the development of chemical industrial parks,the diversity of energy use in the parks has become an issue that must be considered in heat exchanger networks.Waste heat utilization technologies(absorption refrigeration,organic Rankine cycle,heat pumps,etc.)can convert waste heat into cold,heat and electricity,and become the focus of attention in inter-plant heat exchanger networks.At present,the study of integrating waste heat recovery systems directly or indirectly into heat exchanger networks has been widely carried out,while indirect integration with the help of steam and global coupling of inter-plant heat exchange networks,utility system allocation,and waste heat utilization technologies achieved with the help of steam have not been reported.Therefore,this paper considers the operability and safety of the inter-plant heat exchanger network.A global heat integration study for industrial parks based on inter-plant indirect heat integration is carried out,which can simultaneously realize inter-plant heat exchanger network integration,utility distribution and waste heat utilization technology configuration.This paper focuses on the advantages,disadvantages and applicable scenarios of centralized and distributed waste heat recovery modes.Specifically,the following studies are conducted in this paper.(1)A global heat integration method for industrial parks based on mathematical programming ideas is proposed.By exploring the potential interactions between the inter-plant heat exchanger network,steam system,cooling water system,and absorption refrigeration cycle system,a total-site heat integration superstructure is established and a mixed-integer nonlinear programming model is formulated based on it.In this model,steam generated from the hot process stream,and utility steam is used as a heat source to heat the cold stream and drive the absorption refrigeration cycle system.Finally,the case study shows that the proposed global heat integration approach considering waste heat utilization can significantly reduce the overall investment in the park by 30.4% and has better economic benefits.(2).On the basis of considering only absorption refrigeration cycle in Chapter 2,a waste heat recovery cycle system containing three thermal cycles: organic Rankine cycle,absorption refrigeration and electric compression refrigeration is proposed and integrated with the heat exchanger network and utility system of the industrial park simultaneously.Considering the variability of energy supply and demand in different plants in the park,two modes of centralized and distributed waste heat recovery cycle system configurations are proposed,and superstructure models and mathematical programming models are solved for the different modes to obtain the integrated system structure and operating parameters.The effectiveness of the proposed method is demonstrated by two cases studies,and the applicable scenarios for the two waste heat recovery cycle modes are revealed by comparing and analyzing the economic performance of the total site systems.It is concluded that the two waste heat recovery cycle configuration modes do have specific conditions of applicability,that is,the distributed mode is the better choice if the utility cost plus transportation cost of the entire system dominates the total cost,conversely,the centralized mode is recommended.The results also indicate that the inter-plant distance is an important factor affecting decision making,so sensitivity analysis is subsequently conducted and indicates that the distributed mode is preferable only if a specific threshold of inter-plant distance is exceeded.(3)The concern for heat integration in the park is not only energy saving and consumption reduction,but also the safety and stability of the integrated structure is crucial.Therefore,network correlation analysis is further conducted on the basis of the integration framework of centralized and distributed waste heat utilization systems in the park to provide guidance for the smooth and resilient operation of the park network coupling structure.The analysis of the cases shows that the average value of the Interdependence index of the distributed mode is 0.543,which is much larger than the average value of the centralized mode interdependence index of 0.383,indicating the stronger interdependence of the former,which improves the resilience and fault resistance of the designed network. |
