Simulation and Economic Research of Circulating Cooling Water Waste Heat and Water Resource Recovery System

Li Yang,Yunxia Luo,Zhihua Wang,Zhouming Hang,Yunfeng Ren

doi:10.3390/en14092496

Li Yang, Yunxia Luo + Show 3 more

Open Access

https://doi.org/10.3390/en14092496

Copy DOI

Abstract

Industrial circulating cooling water contains a large amount of low-quality energy, which is lost to the environment through cooling towers. It is of great significance and potential to recover the waste heat to improve energy-saving effects and economic efficiency. However, the effect of common water harvesting and energy saving devices is not significant. Heat pumps have been shown to be effective in improving low-quality heat energy in energy conversion systems, although there are not many applications of heat pump scenarios in engineering practice. Based on this, a recovery solution of circulating cooling water waste heat and water resource using lithium bromide absorption heat pump has been put forward. The energy-saving performance of the recovery system was simulated and analyzed using Aspen Plus V10.0 (Bedford, MA, USA) to explore the effects of the parameters of the working medium in evaporators, condensers, absorbers, generators, heat exchangers, etc., and the modelling results indicated that the evaporation pressure and temperature have a great influence on the system COP (coefficient of performance) and can raise the thermal economy of the system. The heat from driving steam and heating capacity both increased with the increase in generating temperature, while the increase in temperature difference between evaporation and condensation inhibits the COP of heat pump systems. Furthermore, economic analyses and comparisons of the recovery solutions were conducted and the recovery solution of circulating cooling water waste heat with heat pump had the best economic performance due to the annual income from the recovery of waste heat and water resource. The static payback period results indicate that the recovery solution from circulating cooling water waste heat with a heat pump has better economic performance than the scenario with a cooling tower. The waste heat recovery solution with a heat pump can improve the thermal economy of the system and has a great guiding significance for engineering practice.

Highlights

IntroductionThe outlet circulating water (316 K) of the power plant flows directly into the cooling tower, cools down to 305 K, and the inlet circulating water from the cooling tower returns to the cooling water main pipe, as in most power plants
Results show that it is feasible to improve the system coefficient of perfordriving mance by optimizing some parameters of waste heat recovery systems using heat. All these results show that it is feasible to improve the system coefficient of pumps performance by optimizing some parameters of waste heat recovery systems using heat pumps in many fields such as the food, paper, electroplating, metal processing and chemical industries, etc., and the suitability depends on the existing environmental and economic framework conditions of the local electricity grid and the COP [30]
The energy-saving performance of a cooling water waste heat recovery system and water resource recovery system of with a lithium bromide absorption heat pump was simulated and analyzed using Aspen plus V10.0 software, and the results indicated that the evaporating pressure and temperature have great influence on the system performance, which can improve the thermal economy of the system

Summary

Introduction

The outlet circulating water (316 K) of the power plant flows directly into the cooling tower, cools down to 305 K, and the inlet circulating water from the cooling tower returns to the cooling water main pipe, as in most power plants. This design scenario established a recovery system of circulating cooling wastewater heat and water resource to recover circulating cooling water to raise the heat efficiency of the system with lithium bromide absorption heat pump technology, which is an important form for low-grade heat energy applications [23]. A certain percentage of circulating cooling water from the 316 K, 5000 t/h main pipe is extracted to enter into the heat pump for precooling, and the precooled circulating water is returned to the main pipe, mingles with the original 316 K circulating water, and enters the cooling tower together.

Results

Discussion

Conclusion