Decision framework for feasibility analysis of introducing the steam turbine unit to recover industrial waste heat based on economic and environmental assessments

Abstract

With increasing concern of pollution in manufacturing processes, development of advanced green manufacturing technology has drawn a lot of attention. Due to limited energy efficiency in manufacturing processes, a great sum of thermal energy has been directly released and caused environmental problems. It is of great importance to develop advanced manufacturing technology to recover waste thermal energy for promoting sustainability of manufacturing sector. Steam turbine unit is a common equipment for recovering waste thermal energy. The industrial heat recovery process by steam turbine unit brings both economic and environmental benefits. However, the user or the manufacturing enterprise needs to pay a great cost to purchase, install and maintain the steam turbine unit, and the whole life cycle of the unit casts a considerable environmental load. Due to lack of comprehensive research, it is difficult for the user to decide whether should introduce the steam turbine unit for recovering waste thermal energy or not. This paper aims to establish a decision framework which facilitates this decision making procedure by conducting economic and environmental assessments. First, two working modes of the steam turbine unit are investigated and summarized according to the types of energy output - electricity and mechanical driving forces. Second, the economic and environmental assessing models are developed to estimate the potential profit of waste thermal energy recovery from each working mode based on cost-benefit analysis and life cycle assessment. Third, a decision framework composited with nine possible combinations of economic and environmental assessment results is proposed. Finally, a case study in pure terephthalic acid plant shows that the decision framework can quantify the economic and environmental impact of industrial waste heat recovery. The results indicate that the waste heat recovery for the plant is applicable, and payback period is 2.28 years. The proposed decision framework is proved to be meaningful to the feasibility analysis of the waste thermal energy recovery with steam turbine unit. It is an effective technology for improving energy conservation and emission reduction of manufacturing processes operationally.