Methodology development in combined interplant heat and water integration for waste heat recovery

Motivation

The growing desire to improve resource efficiency and environmental impact of industrial processes is directly linked to optimal management of heat, mass and power flows. The concept of industrial symbiosis tackles this issue by proposing interplant heat recovery and resource transfer, which can bring economic and environmental benefits to each participating party. A comprehensive methodology is required which can easily be incorporated in the planning of industrial clusters. Therefore, a generic hybrid mixed integer linear programming (MILP) superstructure has been developed to address simultaneous heat, water, and power optimization in interplant operations. Additional concepts are included in the previously proposed water network superstructure [4] to account for the issues related to interplant heat and mass exchange. A cold utility superstructure is included in the water network while a steam network superstructure is modified to better represent the feedwater heaters and heat recovery opportunities.

Method and Results

The proposed methodology is formulated as a mixed integer linear programming (MILP) superstructure, which is based on the previous work of [1], (implemented into the computational framework used in the IPESE group). Given a set, P, of industrial sites (or clusters within each plant), each site i has a set of water unit operations and set of process thermal streams. Several fresh water sources at different temperatures and qualities and wastewater sinks at different temperatures and disposal qualities are available in the plant and thus also in the optimisation. To address the interplant combined heat, water, and power optimization, the methodology is extended to incorporate thermal utilities and the general superstructure is shown in Figure 1.

The proposed methodology was evaluated using a case study encompassing two industrial plants: petrochemical and pulp & paper in [2]. One water tank is available in the petrochemical site (60 ºC) and two are available in the pulp & paper site (35 ºC, 62 ºC). The results were analyzed based on energy and water consumption and total annualized cost (Figure 2). Applying the proposed methodology eliminated the hot utility and further reduced the total water consumption by 14 % in the combination of the two plants.

 

[1] M. Kermani, Z. Périn-Levasseur, M. Benali, L. Savulescu, and F. Maréchal, “An Improved Linear Programming Approach for Simultaneous Optimization of Water and Energy,” in Computer Aided Chemical Engineering, 2014, vol. 33, pp. 1561–1566.

[2] M. Kermani, A. S. Wallerand, I. Kantor, and F. Maréchal, “A Hybrid Methodology for Combined Interplant Heat, Water, and Power Integration,” presented at the 27th European Symposium on Computer Aided Process Engineering, Barcelona, 2017.

Figure 2. Integrated grand composite curve for the optimized interplant case study