Break of water seal in Mdea amine liquid storage tank
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The unit is equipped with a decarburization unit, similar to the solvent regeneration unit in sulfur treatment plants; activated MDEA is used to remove carbon dioxide and hydrogen sulfide from the dry gas. The activated MDEA solution is then sent to a solvent regeneration tower for regeneration, and after cooling it is fed into an MDEA storage tank. This tank features a vertical water seal tank as well as a self-acting pressure regulator that introduces nitrogen to keep the pressure in the tank at a positive level. The design pressure of the storage tank is 3000 Pa; the water seal will break in the forward direction when the pressure reaches 1600 Pa. The temperature of the storage tank is kept between 35 and 42 degrees Celsius. The current problem is that the water seal keeps breaking. During summer, from 9:00 a.m. to 4:00 p.m., as the temperature rises, the water seal in the tank breaks (this happens even when the self-acting control valve is not used). After 4:00 p.m., the temperature drops and the pressure returns to around 500 Pa (at this time, a negative pressure occurs if the self-acting control valve is not used). The MDEA storage tank is insulated. Has anyone encountered this issue? How does it should be handled? Additionally, I analyzed the gas inside the mdea tank, and it was all nitrogen. So currently, it is suspected that the solubility of nitrogen in the MDEA solution changes with temperature, resulting in nitrogen precipitating out of the MDEA solution; it’s not clear whether this assumption is correct.
The direction you are suspecting is correct. The solubility of nitrogen in MDEA solution changes with temperature; as the temperature rises, the solubility of nitrogen decreases, causing it to precipitate out of the solution. This increases the pressure inside the storage tank, leading to the breakdown of the water seal. It is recommended to consider adding a pressure regulation system to accommodate the impact of temperature changes on pressure, or to optimize the design of the water seal tank so that it can withstand greater pressure fluctuations and prevent the water seal from breaking. At the same time, maintaining the temperature of the storage tank within a more stable range also helps to avoid this problem. .
The design pressure of this storage tank is only 3000 Pa, which is a bit low; if it were higher, there would be much more operating space.
Indeed, increasing the design pressure of storage tanks can enhance operational flexibility and safety margins, thereby enabling more effective control of internal pressure fluctuations caused by temperature changes. You can consider modifying existing storage tanks or choosing models with a higher design pressure when purchasing new ones. At the same time, ensure that all safety valves and pressure regulation systems can handle higher pressure settings in order to maintain the safe and stable operation of the entire system. .
Light breathing is a normal phenomenon, and breaking the amniotic membrane is part of the normal process, right? Where does the gas go after the seal is broken?
1. The liquid level in the solvent storage tank can be kept low to increase the gas storage space. 2. Add insulation to the storage tank to reduce the impact of external temperature changes. 3. Add an adsorption tank after the positive pressure water seal is breached to prevent hydrogen sulfide from escaping. 4. Prevent large fluctuations in the liquid level of the solvent storage tank, which could affect the pressure in the tank. 5. The pressure at which the water seal breaks is a bit low.
Self-acting control valves cannot effectively stabilize the tank pressure; it is recommended to use a dedicated PV control valve assembly to effectively prevent the breakdown of the water seal