Frequency and standards for amine solution replacement in sulfur recovery flue gas purification
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Dear seniors, is there any standard regarding how often the amine solution used for purifying sulfur recovery exhaust gases should be replaced?
I haven’t heard of any standards; we started using MDEA in 1994, and there has never been any intentional release of this substance, nor any purification process. When its concentration drops, we simply add more amine solution, and when the liquid level drops, we add water. Another set of regeneration units was put into operation in 2012, designed solely for treating sulfur-containing exhaust gases; three years later, the concentration of these gases had not decreased, and the liquid level in the system continued to rise. The solution adopted was to discharge the acidic water outside the system. During the major maintenance in 2013, a slight leak was found in one of the tube bundles of the amine liquid cooler, which was sealed, but once operations resumed, the liquid level in the system still rose. There was no other choice; this year, the amine solution was transferred twice to the old centralized amine system in order to replace the contents of that system with fresh amine solution.
Recently, foaming in the amine solution has been severe; we need to add antifoam agents every about 10 days, otherwise the pressure difference between the absorption tower and the regeneration tower increases. Today, the management ordered that the amine solution be replaced.
The foaming of amine solution is highly dependent on the linear velocity of gas in the empty tower; it should generally not exceed 0.7 m/s.
Students* also face the same problem.
It is best not to add antifoam agents casually; the cause of foaming should be identified first. Replacing the amine solution is certainly beneficial for eliminating foaming, but it can easily mask some problems.
There are no specific regulations for this; it is adjusted based on the concentration. Could the increase in the liquid level of the amine solution tank mentioned upstairs be caused by the vapor phase entering the absorption tower having a higher temperature than the liquid phase of the amine solution entering the tower? Adding antifoam agents in such cases is not a advisable approach, as their use may lead to more frequent foaming.
I would like to ask how the flow rate of gas inside the tower is calculated