Increase in SO2 levels in sulfur flue gas
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In the MDEA solvent regeneration unit, the temperature of the acidic gas at the tower top before it reached the sulfur stage was approximately 45°C. Due to some operational issues (with heating already in use), the temperature of the acidic gas sent outside was kept at around 65–70°C. The flow rate of the acidic gas increased from 3100 to 3600 cubic meters per hour. There was no significant increase in the amount of liquid separated in the acidic gas separation tank. However, the SO2 concentration in the flue gas after passing through the quench tower and absorption tower and entering the incinerator rose from 80 mg/m3 to around 170 mg/m3. Could you help analyze what the main reasons for the increase in SO2 levels in the flue gas might be?
First, test the gas components after the exhaust gas absorption tower to determine whether the hydrogen sulfide level has increased compared to before Calculate the load on the unit and the sulfur production to determine whether they exceed the unit’s maximum capacity, which may result in incomplete conversion of hydrogen sulfide during the Claus reaction and lead to issues downstream ； Check again whether foaming has occurred in the amine solution ； Finally, check whether there are any errors in the emission measurement values.
The hydrogen sulfide level at the top of the absorption tower has increased by 20 mg/m3; the load remains within limits, the amine solution is in normal condition, and the online instruments are functioning properly. What causes the increase?
It is unclear what the process is for the sulfur section before your quench tower, and how the air supply to the sulfur production furnace is controlled.
Has the hydrogen sulfide content in the lean liquid changed? Is ammonia being burned? What is the temperature of the sulfur production furnace? The heat tracing of the pipeline for cleaning acidic gas must not be stopped.
This post was last edited by Meng Tan Jian ④ Frame grass on 2019-11-27 at 12:15. A lot has been said about ammonia content upstairs. 1. High water content and high system pressure are unfavorable for the reaction. 2. High water content leads to a low furnace temperature, which is not conducive to the high-temperature Claus process. 3. High water content hinders the forward progression of the sulfur production reaction. Furthermore, the solubility of water and ammonia is 1 to 800, so it is practically impossible for them to enter the MDEA. The outlet of the thermal regeneration tower is not functioning properly; this may be due to high back pressure in the sulfur production pipeline system. It is recommended to open the valve for the sulfuric acid-containing gas feed.
Primarily, bringing in a large amount of water into the combustion furnace reduces the conversion rate of the Claus reaction. Additionally, rising temperatures cause more carbon dioxide to enter the Claus system, resulting in a low sulfur conversion rate. An increased heat load on the quench tower leads to a rise in the absorption temperature, thereby reducing the desulfurization efficiency.
It should be the effect of acidic gases carrying water on the conversion rate
The expert's reply above is quite comprehensive. Here are two friendly suggestions: 1. Monitor the MDEA concentration as well as the hydrogen sulfide content in the lean solution. 2. A fire in the sulfur tank can also lead to an increase in sulfur dioxide levels.
Is it a centralized regeneration system or separate regeneration towers for sulfur? If centralized regeneration is used, it is necessary to take into account the increase in hydrocarbon content in the regenerated acidic gas due to rising temperatures.