Regarding the issue of fluctuations in the catalytic desorption tower
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I would like to ask the experts where the problems with fluctuations in the desorption tower lie: Recently, these fluctuations have been quite noticeable, and they are mainly manifested as follows: 1. There is a significant amount of water present; the reboiler at the middle section discharges a large quantity of water, similar to the acidic water from the crude gasoline tank； 2. The bottom temperature was reduced from 125 degrees to around 117 degrees (with an operating pressure at the top of the tower of 1.45 MPa); when the temperature increased, the pressure drop in the tower rose significantly, and it became impossible to maintain the liquid level at the bottom of the tower. General situation: 1. The desorption tower is equipped with three reboilers – a middle reboiler and a bottom reboiler (the stabilized gasoline coming from the stabilizer column first passes through the bottom reboiler and then through the middle reboiler for heat exchange); there is also another bottom reboiler that is supplied with heat by steam at 1.4 MPa (the normal pressure in the steam network is around 1.32 MPa, with no fluctuations). It is currently in normal operation ； 2. The water washing water for the rich gas at the compressor outlet has been stopped ； 3. The level measurement between the crude gasoline tank and the condensate oil tank at the compressor outlet is correct, and the liquid level control in both tanks is very stable, at 50±1% ； 4. The C2 content in liquefied gas is 0 ； 5. The water jacket of the reflux drum at the stabilizer top contains a small amount of water. I would also like to ask where the water in the desorption tower comes from in this situation, and whether there is a possibility of salt formation there as well, just like in the distillation tower (the distillation tower is currently operating normally). Thank you all so much!
Can the steam heating circuit of the bottom reboiler be shut down or reduced, to see if the water carryover improves? 1. The source of water contamination is in the rectification tower; the water contamination in the stabilization tower is caused by water present in the raw materials. Therefore, the key is to identify the cause of water contamination in the rectification tower. 2. Is your middle section used as a heat source to generate steam?
The steam from the bottom reboiler cannot be stopped, and its flow rate is around 5 tons; the other two reboilers alone do not have enough heat capacity to handle this amount. Our No.1 Plant uses only the stabilizer bottom as a heat source. Furthermore, during the first few operating cycles, the desorption tower never experienced the problem it has now; back then, there was simply more water in the top of the stabilizer, and the water traps often became full too quickly to be emptied. This water must come from the stripping tower; it’s just that I’ve never understood where the water for the desorption tower comes from.
Did you just drive with water in it? 1. What is the operating pressure of your distillation tower? Determine whether steam leakage is possible, and calculate the material balance for steam and condensed water. 2. Calculate whether the residence time of gasoline in the condensate tank at the compressor outlet is sufficient for oil-water separation; try reducing the oil-water separation interface to 35% to see the effect.
The first point can be used as a basis for judgment, while the second point is more practical!
The steam pressure is around 13.2 kilograms, while the operating pressure in the desorption tower is around 14.5 kilograms. It should be noted that the unit has been operating for several cycles; previously, the temperature at the bottom of the desorption tower was around 125 degrees. In this situation, it is sometimes not possible to drain the water contained in the liquid hydrogen reflux tank at the top of the stabilization tower in time, and this issue has yet to be resolved.
It seems possible that there is a leak in the pipeline
The pressure in the desorption tower is higher than the steam pressure, so it should not be a leak in the reboiler.
If that’s the case, then why is the reboiler’s drain line discharging large amounts of water along with gasoline? Given that the acidity level is roughly the same, there must be some leak somewhere. So why not stop the operation and apply pressure to the reboiler to check for leaks?
Determine whether the steam injection valve at the bottom of the tower has a blind plate installed