Operational issues of the regeneration tower in wet desulfurization using diethanolamine for liquefied gas
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The liquefied gas in our plant uses diethanolamine wet desulfurization. There has been a problem of excessive hydrogen sulfide for a long time. Please help solve it. The reboiler at the bottom of the regeneration tower uses steam as the heat source, usually around 125 degrees, and the pressure at the top of the tower is 0.1MPa. However, the liquid level and pressure fluctuate greatly, and the sulfur content of the lean liquid also exceeds the standard, so the regeneration effect is not good. What could be the reason?
In my opinion, the liquid level must be stabilized first, and you can check relevant instruments or on-site liquid level; when the liquid level is stable, gradually increase the temperature at the bottom of the tower and the pressure to 0.1MPA to improve the regeneration effect. All in all, if the liquid level is unstable, the pressure will not be stable.
The amine liquid regeneration tower is prone to flooding. If the amine liquid is dirty, the downcomer pipe of the tray may be clogged.； In addition, whether the feed from the flash tank into the tower fluctuates, first stabilize the flow rate. The pressure of hydrogen sulfide in the system must also be stable, and then lower the heating temperature at the bottom of the tower to see if it is stable. ； There are also internal leaks in the poor and rich liquid heat exchangers at the bottom of the tower. ；
In our device, the bottom temperature of the regeneration tower is generally 113 to 114, the top pressure is 0.08MPA, and the circulation volume of the amine liquid is 17T/H. The liquid level control of the regeneration tower uses automatic control, regulating valve PID parameters, and P value settings. is very small, the regulating valve is very sensitive, and basically the liquid level does not fluctuate much, because what goes out from the bottom of the regeneration tower enters the tank, and the pressure fluctuates greatly. It may be that the flash evaporation effect is not good, and MDEA takes the hydrocarbons with it. Is it the reason for the regeneration tower? This post is finally written by * Edited by aoyu0914 on 2008-2-18 16:42 ]
We have lowered the top pressure, but the liquid level still fluctuates greatly, sometimes causing tower flushing. However, if the bottom temperature is too low, the hydrogen sulfide removal effect will not be effective.
I think the following points should be considered: 1. Whether the amine liquid regeneration tower is flooded. Whether the feed temperature of the regeneration tower is too high will cause the bottom temperature to rise to the required heat source when the bottom of the tower is in place. This will cause the vapor phase distribution in the tower to be disordered and the amount of liquid phase falling to the bottom of the tower to be unstable. This will cause the liquid level at the bottom of the tower to fluctuate, and the pressure will also fluctuate. 2. Leakage in the poor and rich liquid heat exchangers at the bottom of the tower. As a result, hydrogen sulfide in lean liquid exceeds the standard and affects the solvent desulfurization effect. 3. The PID of the flash tank outlet regulating valve is inappropriate, and the valve position fluctuates greatly, causing fluctuations in the feed to the regeneration tower. 4. The hydrogen sulfide content of the raw material hydrocarbons is high, which exceeds the processing load of the desulfurization system. 5. The circulation volume is too large, causing the regeneration tower to flood. 6. The solvent contains oil. 7. Solvent foaming.
The amine liquid is dirty, especially the accumulation of heat-stable salts, which has a great impact on operational fluctuations, substandard quality, corrosion and foaming. The author may consider measuring the concentration of solid particles and heat-stable salts in the amine liquid to see the quality of the amine liquid.
LZ, after these problems occurred, what measures did you take and what were the effects? Tell us so that everyone can analyze and discuss them.
The temperature of the lean liquid after cooling must be lowered. A high return temperature is not necessarily good. A pressure of about 0.07 is better. Pay attention to the quality of the amine liquid and clean the amine liquid.