In production, what should be done if the level gauge of the CO2 stripping tower malfunctions (shows distorted readings)?
Thread Content
After the system was fed with material and just as the synthesis tower began to discharge its product, it was observed that the level gauge in the CO2 stripping tower was fluctuating significantly. We adjusted the control valve for the effluent from the CO2 stripping tower to 70% of the corresponding production load. At this time, we paid close attention to the load on the low-pressure circulation system; whenever the pressure increased, we immediately reduced the opening of this control valve. Through trial and error, we increased the system’s load until it reached full capacity. It was found that whether we increased or decreased the opening of the control valve for the CO2 stripping tower effluent, the liquid level reading remained stable or showed little variation. This led us to initially conclude that there was an issue with the accuracy of the level gauge. When we contacted the electrical and instrumentation staff to investigate, they said that the lower limit setting of the level gauge had been adjusted during maintenance work. Following discussions between the production department and our workshop supervisors, the original minimum design parameters were restored; however, this still did not meet the requirements of normal production. Meanwhile, the temperature of the liquid coming out of the CO2 stripping tower was also too high (given our high production load, it is possible that this temperature could approach the process specification of 175°C). Even after adjusting the control valves, no significant changes in the temperature were observed. I wonder, if you were Haiyou, 1. how would you handle it? 2. Is a low limit always designed for the liquid level gauge of the CO2 stripping tower in every manufacturer’s equipment? So what should this lower limit be? Please reply! ! ! ! ! This post was last edited by lxq700918 on 2009-2-14 23:16.]
It should be judged based on the following points: 1. The pressure of the high-pressure drum and the amount of steam used; 2. The temperature difference before and after the liquid discharge pressure regulator in the stripping tower, as well as the liquid discharge temperature and low-pressure in the distillation tower. 3. In the case of overheating in the stripping tower, it is necessary to determine whether the overheating is caused by an excessive opening degree of the liquid discharge valve during synthesis Is it again the full or low level of the stripping liquid that causes uneven distribution of carbon dioxide in the stripping tower, leading to overheating? 4. Have the instrumentation staff check whether the thermometer is functioning properly. If the temperature still exceeds the limit, the system has to operate at reduced capacity.
First of all, thank you to Durian for your participation. There are also a few points I mentioned when initiating this topic: 1. Under the corresponding production load, the opening degree of the liquid outlet control valve in our synthesis tower hardly changes; as for the opening degree of the liquid outlet control valve in the stripping tower, it can be determined based on the pressure in the circulation system and the temperature after the liquid pressure reducing valve； 2. Have you set a lower limit design for the liquid level in the stripping tower? In our production processes, we also tried adjusting the discharge control valve of the synthesis tower accordingly, but the stripping tower still experienced overheating. The liquid level in the synthesis tower was difficult to control while maintaining the desired conversion rate, N/C ratio, and H/C ratio. We also adjusted the opening degree of the liquid discharge control valve – increasing it caused the pressure in the low-pressure circulation system to rise rapidly, while decreasing it resulted in only a modest drop in the circulation system’s pressure. Additionally, there was little change in the temperature after the liquid discharge pressure reducing valve (I’m referring to comparisons made when making adjustments of 5%). Once again, thank you! ! ! ! ! This post was last edited by lxq700918 on 2009-2-15 19:23.]
If the level gauge of the stripping tower becomes inaccurate, it is necessary to manually maintain the opening of that valve based on the current load temporarily. Since the heating steam for our stripping tower comes from the exhaust gas of the compressor, a disruption in the feed to the stripping tower could very likely cause the compressor to shut down due to high exhaust pressure. At this time, strict attention should be paid to changes in steam pressure. If the stripping tower is filled with liquid, it can cause overpressure in the high-pressure system. The handling principle should be to keep the liquid level in the stripping tower full rather than empty. Handle the instrument as soon as possible. Do not force the equipment; it’s not worth it and can easily cause damage to the equipment.
Hehe! Yes, different process flows may require different focus areas when problems arise. But in terms of production, a malfunction in the liquid level gauge of the air lift tower means that either an excessive or insufficient liquid level can pose a serious threat to production! Added to this are the issues with our instrument operators’ handling, which have not yet been properly resolved. I hope the level gauge can be fixed as soon as possible! ! ! ! !
The level gauge in a stripping tower is usually an isotope level gauge, with a low probability of failure. If it occurs, the opening degree of the liquid discharge valve should be adjusted manually according to the load level, and adjustments should be made as needed by referring to indicators such as the low-pressure value and the temperature of the liquid discharged from the stripping tower, in order to maintain production; meanwhile, the instrumentation staff should be contacted promptly for handling. The liquid level range in the stripping tower is small, and the adjustment range is limited as well, but the control is strict. During normal production, it is generally kept at around 50%; some manufacturers keep it at around 30% or even lower, in order to prevent high levels of biuret. The specific liquid level should be determined based on the actual conditions at the respective facility. If it is too low, cross-ventilation occurs, which can also be detected from the throttling sound and vibration of the liquid outlet control valve; this requires on-site experience. To prevent large fluctuations in the liquid level of the stripping tower, it is necessary to maintain a stable flow rate of carbon dioxide gas, in order to avoid fluctuations in the liquid level caused by shocks. Sometimes, even if the liquid level is kept at an appropriate level, shocks from carbon dioxide can still lead to air leakage and low or high pressures. Finally, it is recommended to analyze the stripping efficiency and consider whether the carbon dioxide gas distributor has been overturned or damaged, resulting in large fluctuations in liquid level. Personal opinion.
Let me say a few things: 1. I have also encountered situations where the level gauge in the stripping tower failed to function. The solution we adopted (from the instrumentation side) was to swap the two signal receivers of the stripping tower’s level gauge online in order to resolve the issue. (The two signal receivers of the stripper level gauge one display the normal level while the other provides an alarm for high level; during online replacement, control is achieved through the cycle pressure, the temperature of the liquid exiting the stripper, and the shut-off valve of the regulator valve for that liquid.) ) 2. As for the lower limit setting for the liquid level gauge in the stripping tower, if it relates to the process parameters, we have such a setting; it is generally set at 40%. As for the lower limit setting for the liquid level gauge signal receiver, I’m not sure about that.