Proposal and comprehensive analysis of an innovative steam generation system by deep recovery of low-grade waste heat

Abstract

The waste heat generated by industrial processes is often not fully recycled, resulting in a significant amount of wasted energy and thermal pollution. Meanwhile, low-pressure steam plays an important role in industry as many processes consume a large amount of steam. An innovative steam generation system based on the deep recovery of low-grade industrial waste hot water is proposed. The waste hot water first flashes out low-pressure steam, and then drives an organic Rankine cycle to generate mechanical work, which is used to compress the low-pressure steam. A techno-economic model is established. The thermodynamic indicators are calculated under preliminary optimization conditions, and a comparative analysis between the proposed system and other waste heat utilization systems is carried out under the same heat source conditions. The techno-economic analysis shows that the proposed system is better for recycling wasted hot water. The steam generation mass ratio, exergy efficiency, and cost per ton of recycled steam are 2.50%, 44.31%, and 7.67 $/ton, respectively, under the optimized conditions. When the heat source temperature is 100 °C, the exergy efficiency of the proposed system is 37.01% and 60.59% higher than that of the steam generation heat pump system and waste heat power generation system, respectively. Advanced exergy analyses are conducted to determine the actual potential improvement for system components, with the avoidable exergy destruction of the expander showing the largest. This paper proposes an efficient and cost-competitive approach for the deep recovery of low-temperature hot water for producing industrial steam.