Control of the top temperature and kettle temperature in the emergency cooling tower of ethylene plants
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Recently, it has been very difficult to control the top temperature and the temperature inside the reactor of our unit. The top temperature always exceeds 50 degrees, while the temperature inside the reactor is relatively low, at around 72 degrees. Increasing the reflux flow at the top helps to lower that temperature, but the temperature in the middle section doesn’t decrease. One day we increased the recirculation in the middle section and reduced it at the top; both the top temperature and the temperature in the middle section dropped. However, when this situation arose again, this method proved ineffective. It’s really difficult to control quench water towers; I’m hoping that experienced sailors out there can offer some guidance, or provide information regarding the control of such towers. I’d be extremely grateful!
Is it caused by the frequent adjustments made by users of cold water, especially the propylene column in the hot zone and the deethanizer column in the cold zone?
Reply to 2# Front-line employee: Hello, sir. The quench water users aren’t making frequent adjustments. Recently, the top and middle temperatures just won’t drop, as the temperature inside the tank is very low, at around 72 degrees only. Master, I would like to ask you for some experience or information on adjusting the quench tower. Thank you
What about the return flow rate and temperature? Pressure, what is its composition? Here are a few reasons that come to mind: 1: Fluctuations in quench water users. 2: Low return flow. 3: Low cooling water flow, high temperature, or blockage in the cooling water inlet tube bundle of the heat exchanger. 4: High top temperature of the quench oil tower.
Personally, I think it’s necessary to check whether there have been any changes in the composition of the raw materials, as these changes can lead to an increase in the amount of condensed liquid and water that is returned, thereby causing a drop in the temperature at the bottom of the tower. This in turn can result in fluctuations in the oil-water interface level, as well as an excessive amount of oil in the process water. Additionally, it’s important to measure the temperature and flow rate of the cooling water. Check the equipment to see if there is any blockage in the heat exchanger on site.
Reply to 4# Front-line employee: The reflux at the top and in the middle is quite high, higher than the normal values. The heat exchanger can’t be clogged, as it has just been serviced. Our master said it might be caused by flooding or leakage? Is it possible? Thank you,
That’s possible too, but can such a situation occur during maintenance? Was no one there to inspect and accept the equipment?
Check the heat exchange efficiency of the top return heat exchanger, and then measure the flow rate as well
Regarding the operation of the quench water tower, as a shift supervisor, I have encountered the following situations: 1. If the temperature in the reactor is not high but only the temperature at the top of the tower is high, it indicates that this high temperature at the top does not originate from the bottom of the tower. In such cases, it is necessary to check the heat exchange performance of the condenser at the top of the tower; perhaps there is a leak in the heat exchanger, preventing proper heat exchange, or maybe the temperature of the circulating water is too high. One can try flushing the heat exchanger to see if that helps, or open the drain at the top of the circulating water system to allow air to escape. Additionally, it is important to check the suction pressure at the first stage of the compressor. Generally, if this suction pressure is too low, the temperature at the top of the quench water tower will also rise. In such situations, it is possible to contact the personnel responsible for the pyrolysis gas compressor and ask them to increase the suction pressure at the first stage slightly; this approach yields significant results (in fact, it simply involves reducing the compressor’s speed, which is easy to adjust). 2. If both the temperature in the reactor and the temperature at the top are high, I’ve encountered situations where the reactor temperature was 188 degrees while the temperature at the top was close to 48 degrees. Our capacity is only 160,000 tons. In such cases, it’s the cracking temperature in the furnace area that plays a role; we need to lower this temperature. If that doesn’t work, then we have to reduce the amount of oil fed into the furnace. Overall, the rapid cooling position is a balanced one; once this balance is disrupted, adjustments need to be made slowly, without rushing. 3. The final scenario is that even after the aforementioned adjustments, the temperature still doesn’t drop; I suspect there is a problem with the internals of the tower. I’m just an operator, and that’s all I know. I hope it can be helpful to you.
Reply to 9# jr1207: Thank you so much, really.
Reply to 10# fwlovesl: You’re welcome. I’m here to help solve problems, and it’s great to be able to assist everyone. At the same time, I also have many questions that require everyone’s help. This is what Yu Baocai often refers to as \"helping others in order to benefit oneself.\" I hope to encourage one another with all of you.