Optimal heat pump integration in industrial processes

Abstract

Among the options for industrial waste heat recovery and reuse which are currently discussed, heat pumping receives far less attention than other technologies (e.g. organic rankine cycles). This, in particular, can be linked to a lack of comprehensive methods for optimal design of industrial heat pump and refrigeration systems, which must take into account technical insights, mathematical principles and state-of-the-art features. Such methods could serve in a twofold manner: (1) in providing a foundation for analysis of heat pump economic and energetic saving potentials in different industries, and further (2) in giving directions for experimentalists and equipment manufacturers to adapt and develop heat pump equipment to better fit the process needs. This work presents a novel heat pump synthesis method embedded in a computational framework to provide a basis for such analysis. The superstructure-based approach is solved in a decomposition solution strategy based on mathematical programming. Heat pump features are incorporated in a comprehensive way while considering technical limitations and providing a set of solutions to allow expert-based decision making at the final stage. Benchmarking is completed by applying the method on a set of literature cases which yields improved-cost solutions between 5 and 30% compared to those reported previously. An extended version of one case is presented considering fluid selection, heat exchanger network (HEN) cost estimations, and technical constraints. The extended case highlights a trade-off between energy efficiency and system complexity expressed in number of compression stages, gas-and sub-cooling. This is especially evident when comparing the solutions with 3 and 5 compression stages causing an increase of the coefficient of performance (COP) from 2.9 to 3.1 at 3% increase in total annualized costs (TAC).

A Holistic Methodology for Optimizing Industrial Resource Efficiency

“…Investigation and optimization of the integration of these technologies will require generation and validation of rigorous models followed by reapplication of the techniques discussed throughout this paper to provide highly efficient, integrated bioprocessing systems. Overall, there are nineteen (19) cold process streams (Table A2). In the current state of the mill, they are all being heated with steam.…”

“…The resulting MINLP model contains binary variables addressing investment cost coefficients, choice of working fluid, and equipment. In addition, the equations governing the thermodynamic properties of various working fluids (in modeling Rankine cycles [16] and heat pumping [19]) are non-convex which further increases the difficulty of reaching a global optimum. This has discouraged the authors from using global MINLP optimization frameworks.…”

Critical Analysis of Process Integration Options for Joule-Cycle and Conventional Heat Pumps

“…A recent work [24] has presented a system synthesis method for HP integration in the industry. The method uses a superstructure-based mathematical model, resulting in a Mixed Integer Nonlinear Programming (MINLP) formulation, achieving performance improvements over similar previous methods of up to 30%.…”

A Mixed-Integer Linear Programming Formulation for Optimizing Multi-Scale Material and Energy Integration

“…Mass pinch analysis was first applied for reuse of solvents by El-Halwagi and Manousiouthakis (1989) and later for other material flows such as cooling water (Kim and Smith, 2001), industrial water (Wang and Smith, 1994;Olesen and Polley, 1997), and hydrogen (Towler et al, 1996;Alves and Towler, 2002;Government of Canada, 2002). Related work in the domain by Kermani et al and Wallerand et al also address specific problems such as optimal integration of organic Rankine cycles (Kermani et al, 2018) and heat pumps (Wallerand et al, 2018a) with industrial processes, simultaneous optimization of water and energy (Kermani et al, 2019a), and holistic industrial system design (Kermani et al, 2019b). Industrial retrofit and planning strategies using similar methods have been proposed by Bütün et al (2018Bütün et al ( , 2019, and approaches to heat exchanger network design with utility systems (Ciric and Floudas, 1991) including new solution strategies (Mian et al, 2016) are also of interest within this domain.…”