Building Block-Based Synthesis and Intensification of Work-Heat Exchanger Networks (WHENS)

Abstract

We provide a new method to represent all potential flowsheet configurations for the superstructure-based simultaneous synthesis of work and heat exchanger networks (WHENS). The new representation is based on only two fundamental elements of abstract building blocks. The first design element is the block interior that is used to represent splitting, mixing, utility cooling, and utility heating of individual streams. The second design element is the shared boundaries between adjacent blocks that permit inter-stream heat and work transfer and integration. A semi-restricted boundary represents expansion/compression of streams connected to either common (integrated) or dedicated (utility) shafts. A completely restricted boundary with a temperature gradient across it represents inter-stream heat integration. The blocks interact with each other via mass and energy flows through the boundaries when assembled in a two-dimensional grid-like superstructure. Through observation and examples from literature, we illustrate that our building block-based WHENS superstructure contains numerous candidate flowsheet configurations for simultaneous heat and work integration. This approach does not require the specification of work and heat integration stages. Intensified designs, such as multi-stream heat exchangers with varying pressures, are also included. We formulate a mixed-integer non-linear (MINLP) optimization model for WHENS with minimum total annual cost and demonstrate the capability of the proposed synthesis approach through a case study on liquefied energy chain. The concept of building blocks is found to be general enough to be used in possible discovery of non-intuitive process flowsheets involving heat and work exchangers.

Computer‐aided process intensification of natural gas to methanol process

“…Because of this phenomena scale representation, building block can generate novel designs without any postulation of candidate designs beforehand. For this reason, building block‐based approach has been implemented to several design and synthesis problems recently 48,51–55 …”

Membrane Separation Process Design and Intensification

“…In this work, we consider only the membrane type boundaries. For other types, please see the previous works. – We define z i , j , s , m F as the variable to indicate which separation phenomenon and enabling material are activated for the horizontal semi-restricted boundary. When z i , j , s , m F is one, there exists a semi-restricted boundary between block B i , j and B i , j +1 with separation phenomenon s and enabling material m . …”

Work Exchange Networks (WENs) and Work and Heat Exchange Networks (WHENs): A Review of the Current State of the Art

“…Recently, Demirel et al 109 proposed a novel method for process design and intensification based on a block superstructure. This novel method has later been applied to WENs and WHENs by Li et al 25 .…”

“… 1967: The Flow Work Exchanger was introduced 10  1983: The Appropriate Placement concept in Pinch Analysis was extended to Heat Engines and Heat Pumps 11, 12  1987: A Superstructure based Optimization Model for integration of Heat Engines and Heat Pumps was introduced 13  1996: The concept of WENs was first proposed 8  2007: The ExPAnD procedure combining Heuristics, Pinch and Exergy Analyses for sub-ambient design was developed 14  2011: A Superstructure and MINLP model based on ExPAnD was developed for offshore LNG production 15  2014: A Superstructure based MINLP Optimization Model for WHENs was suggested 16  2014: A Graphical Approach to WEN design was proposed 17  2015: New insight was developed for Appropriate Placement of Compressors and Expanders with a corresponding manual Design Procedure 18-21  2018: An extensive Superstructure for WHENs was proposed 22  2019: A decomposed approach to WHENs based on first identifying optimal Thermodynamic Paths for streams with pressure change was suggested 23  2019: An extended Superstructure for WENs was proposed 24  2019: A Building Block based synthesis method for WHENs was proposed 25 This review presents the state-of-the-art in the literature, as well as challenges and future directions for WENs and WHENs. These research fields are still at an early stage of development and the corresponding literature is rather limited compared with HENs.…”