Identification of the optimal pressure levels in steam networks using integrated combined heat and power method

The integration of the utility system with all the plants of an industrial site is a major task for targeting the Minimum Cost of the Energy Requirement (MCER). Defining the target in terms of cost rather than in terms of energy introduces the problem of integrating the combined heat and power systems and especially the steam network. Furthermore, the integration of the utility system defines the complete list of streams that has to be considered for the Heat Exchangers Network (HEN) design or retrofit. In this paper, we present a method for computing the Integrated Combined Heat and Power (ICHP) target of industrial processes. The approach is based on the analysis of the shape of the balanced Grand Composite Curve of the process and the utilities. The ICHP target is an improvement of the rules for the appropriate placement of the combined heat and power engines. The method proposed, based on the application of the Carnot cycle, allows estimation of the combined power production potential of the system and identification of the optimal pressure levels of the steam network. From these results, the Minimum Cost of Energy Requirement target is computed by considering a model (presented elsewhere) for the integration of the steam network. Using a simplified example which originated from an industrial application, we show the benefits in terms of energy costs that might be obtained from the ICHP approach and its incidence on the rules for energy efficiency optimization of industrial processes. (C) 1997 Elsevier Science Ltd.