Work and Heat Exchange Networks with Energy Identity Changes and Pressure Drop Effects.

BRACCIA, L.; BOTTARI, A.; LUPPI, P.; ZUMOFFEN, D.

Buenos Aires

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

Asociación Argentina de Ingenieros Químicos

Systems that integrate the available processenergy reduce the operating costs by improving the additionalexternal energy consumption. Heat and work are the most common energyforms in any industrial process. These energies are presentin different process streams and can be used through recovery systemssuch as the work and heat exchange networks (WHENs). In the lastyears, several contributions have addressed the synthesis of heat andwork exchange networks (HENs and WENs) simultaneously. These worksintegrated both synthesis tasks into a single optimization problem toobtain the optimal WHEN. Since the simultaneous WHEN synthesisresults in a more complex problem than the individual HEN and WENsynthesis case, the models proposed in the literature have someassumptions and simplifications to facilitate their resolution.Frequently, these assumptions are far from reality and complicate theimplementation of these networks in industrial plants. One of thesesimplifications is neglecting the pressure drop and the heat lossesin theunits. The development of novel simultaneous approaches based ondetailed unit models is one of the major concerns in the processsystems engineering area. In this sense, a detailed superstructure tosynthesize the work and heat exchange networks is proposed in thiswork. Thenew model is obtained by incorporating the pressure drop constraintsinto a MINLP superstructure with identity changes of the processstreams. In the proposed model, the streams alternate their nominalidentities acting as high-pressurecold streams as well as low-pressure hot streams in different stagesof the networks. In addition, the pressure drop modeling is performedconsidering that the process streams can go through the shell or tubeside of the heatexchangers according to the energy requirements and pressure dropeffect. This modeling is performed by including a new set ofconstraints handled by new binary variables into the synthesisproblem. Thus, the proposed superstructure allows to define the heatand work exchanges at each stage of the network, the pressure drop ineach heat exchanger and utility, and the side on which the streams gothrough heat exchangers. In order to analyze the effect of pressuredrop on the work and heat integration and to support the conclusions,a work and heat exchange network is synthesized for an academic casestudy. Finally, the obtained network for this case study is comparedwith previous works where pressure drop is not considered.p { line-height: 115%; margin-bottom: 0.25cm; background: transparent }