On the dehydration of desulfurization gypsum from power plants
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I would like to ask my colleagues: currently, vacuum belt dryers are mainly used for the secondary dewatering of gypsum from desulfurization units in China. I would like to know whether centrifuges are used for this purpose as well If any, please provide details. I am currently working on a project that uses calcium carbide slag as an absorbent for desulfurization, and vacuum belt dryers do not yield good results. Please give me some advice! Thank you.
Vacuum belt dehydration is primarily used in the gypsum-based desulfurization process in large power plants; it is relatively expensive. For smaller and medium-sized facilities, vacuum drum centrifuges for dehydration can be considered.
Can a horizontal spiral centrifuge be used?
Hello, it is necessary to clarify that the issue lies in the fact that what has been produced as a result of desulfurization is not gypsum or its purity is too low. It is recommended to use a filter press or to modify the desulfurization process so that proper gypsum can be obtained.
One problem with desulfurization using calcium carbide slag is that to ensure an effective desulfurization rate, it is necessary to increase the pH level inside the tower; theoretically, this value should be maintained between 6 and 7. At such levels, the oxidation of calcium sulfite becomes problematic, resulting in a large amount of calcium sulfite remaining.
I am also very concerned about this issue. I consulted the engineers at Jingjin Filter Press Group; ordinary plate-and-frame filter presses can reduce the moisture content of desulfurization gypsum to only 70%, while diaphragm filter presses can achieve a moisture content of 60%. The manufacturers of vacuum belt dryers say that after passing through the hydrocyclone, the moisture content is 50%, and it can be reduced to 10%~5% after entering the vacuum belt dryer. The above are merely the manufacturer’s claims
A friend from Zhejiang said that a filter press can reduce the moisture content to below 23% for gypsum dehydration.
What was said upstairs is correct; however, a higher purity of gypsum can be ideal, but it doesn’t have the same advantages as a vacuum filtration machine in terms of performance and ease of use, and it’s not possible to achieve continuous operation with it
For desulfurization projects, both domestic and international, vacuum belt conveyors are used for secondary dehydration whenever gypsum slurry is not discarded. 50% of the fluid flows out at the bottom of the hydrocyclone, and the moisture content can reach around 10% after passing through the vacuum belt dryer. It should be no problem, and there’s no doubt about it. After all, the wet gypsum method for desulfurization is already very mature, with a market share of over 90%. Centrifugal dehydrators can be used, but they are more commonly employed in ammonia-based desulfurization.
My experience and insights: Filter presses are more suitable for handling gypsum slurry; some types of gypsum slurry are difficult to process using vacuum belt conveyors; the moisture content after treatment with centrifuges is higher than that achieved with vacuum belt conveyors.
Reply to 5# lbljlqch: This is determined by the characteristics of the lime process. In the United States, for this process, oxidation inhibition techniques are generally used, and the calcium sulfite slurry produced is discarded after preliminary dewatering.