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RESEARCH PAPERS

Waste-Heat Recovery in Batch Processs Using Heat Storage

[+] Author and Article Information
S. Stoltze, J. Mikkelsen, B. Lorentzen, P. M. Peterson, B. Qvale

Laboratory for Energetics, Technical University of Denmark, Building 403, DK-2800 Lyngby, Denmark

J. Energy Resour. Technol 117(2), 142-149 (Jun 01, 1995) (8 pages) doi:10.1115/1.2835330 History: Received March 10, 1994; Revised January 07, 1995; Online January 22, 2008

Abstract

The waste-heat recovery in batch processes has been studied using the pinch-point method. The aim of the work has been to investigate theoretical and practical approaches to the design of heat-exchanger networks, including heat storage, for waste-heat recovery in batch processes. The study is limited to the incorporation of energy-storage systems based on fixed-temperature variable-mass stores. The background for preferring this to the alternatives (variable-temperature fixed-mass and constant-mass constant-temperature (latent-heat) stores) is given. It is shown that the maximum energy-saving targets as calculated by the pinch-point method (t ime a verage m odel, TAM) can be achieved by locating energy stores at either end of each process stream. This theoretically large number of heat-storage tanks (twice the number of process streams) can be reduced to just a few tanks. A simple procedure for determining a number of heat-storage tanks sufficient to achieve the maximum energy-saving targets as calculated by the pinch-point method is described. This procedure relies on combinatorial considerations, and could therefore be labeled the “combinatorial method” for incorporation of heat storage in heat-exchanger networks. Qualitative arguments justifying the procedure are presented. For simple systems, waste-heat recovery systems with only three heat-storage temperatures (a hot storage, a cold storage, and a heat store at the pinch temperature) often can achieve the maximum energy-saving targets. Through case studies, six of which are presented, it is found that a theoretically large number of heat-storage tanks (twice the number of process streams) can be reduced to just a few tanks. The description of these six cases is intended to be sufficiently detailed to serve as benchmark cases for development of alternative methods.

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