Process integration study for the use of industrial low grade heat

Abstract

Improving energy efficiency for the process industry has received great attentions due to strong competitiveness in the market and societal demand for sustainable industrial manufacturing. Significant development has been made to develop design methods for achieving efficient use of fuel and raw materials in the generation and utilization of heat and power. Considerable low grade heat in process industries are often wasted without being recovered. This is mainly because the techno-economic impact gained from the heat recovery of low grade heat is much less than that from high grade heat. Therefore, it is necessary to evaluate and screen possible design options for the utilization of low grade heat and provide strategies for implementing energy-efficient process design in industrial practice. Two design aspects will be covered in this paper in the context of integrated design for the recovery of low grade heat in the industrial site. One is to study technologies using low grade heat, for example, heat pump and ORC (Organic Rankine Cycle), which allows identifying the most appropriate way for using waste heat. Site analysis technique has been applied to collectively review the current heat recovery of the industrial plant, to identify how much low grade heat is wasted and to estimate the potential for the further recovery of low grade heat. Modeling and simulation of heat-upgrading and heat-utilizing processes has been made and their characteristics have been considered during the analysis. The other is to integrate the waste heat from the industrial site with local energy systems, in which discontinuous characteristics of energy recovery and heat storage is systematically considered. Energy usage for the local energy systems has been modeled with multi-period representation, which was systematically integrated with the profile of low grade heat provided from the industrial plant. Case studies will be presented to demonstrate how the process integration design method can be applied.