Thermal and Economic Analysis of Multi-Effect Concentration System by Utilizing Waste Heat of Flue Gas for Magnesium Desulfurization Wastewater

Mingwei Yan,Yuetao Shi

doi:10.3390/en13205384

Abstract

Compared with limestone-based wet flue gas desulfurization (WFGD), magnesia-based WFGD has many advantages, but it is not popular in China, due to the lack of good wastewater treatment schemes. This paper proposes the wastewater treatment scheme of selling magnesium sulfate concentrate, and makes thermal and economic analysis for different concentration systems in the scheme. Comparisons of different concentration systems for 300 MW power plant were made to determine which system is the best. The results show that the parallel-feed benchmark system is better than the forward-feed benchmark system, and the parallel-feed optimization system with the 7-process is better than other parallel-feed optimization systems. Analyses of the parallel-feed optimization system with 7-process were made in 300, 600, and 1000 MW power plants. The results show that the annual profit of concentration system for a 300, 600, and 1000 MW power plant is about 2.58 million, 5.35 million, and 7.89 million Chinese Yuan (CNY), respectively. In different concentration systems of the scheme for selling magnesium sulfate concentrate, the parallel-feed optimization system with the 7-process has the best performance. The scheme can make a good profit in 300, 600, and 1000 MW power plants, and it is very helpful for promoting magnesia-based WFGD in China.

Highlights

Limestone-based wet flue gas desulfurization (WFGD), the most popular desulfurization technology used worldwide, leads the world market in installed post-combustion SO2 control technologies, and has about 85% of the market share in China [1,2,3]
Koralegedara et al [6] mainly discussed the application of flue gas desulfurization gypsum in soil improvement and water treatment, and pointed out that there are gaps, like the application of gypsum in landfill leachate treatment, that need to be researched in detail
F130 stands for the forward-feed benchmark system, of which inlet flue gas temperature is 130 ◦ C, P130 stands for the parallel-feed benchmark system, of which inlet flue gas temperature is 130 ◦ C, and so on

Summary

Introduction

Limestone-based wet flue gas desulfurization (WFGD), the most popular desulfurization technology used worldwide, leads the world market in installed post-combustion SO2 control technologies, and has about 85% of the market share in China [1,2,3]. Limestone-based WFGD has many advantages, such as low operating cost, abundant raw materials, and high stability. There are many disadvantages of limestone-based WFGD, such as serious blockage and wear, the byproduct occupying land problem, large water consumption, and air pollution [4]. The byproduct gypsum occupying land problem is more prominent, which gets more attention from scholars in the limestone-based WFGD field. Koralegedara et al [6] mainly discussed the application of flue gas desulfurization gypsum in soil improvement and water treatment, and pointed out that there are gaps, like the application of gypsum in landfill leachate treatment, that need to be researched in detail. Quite a portion of WFGD gypsum has been used in different ways for recent years, Energies 2020, 13, 5384; doi:10.3390/en13205384 www.mdpi.com/journal/energies

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Results

Conclusion