The reason for the sudden large positive pressure of chlorine gas
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This post was last edited by sunjl1981 on 2013-1-6 at 20:13. A few days ago, a large positive pressure suddenly appeared in the chlorine suction system we use at work, which resulted in a chlorine leak and injured one person. However, we were unable to determine the cause. The details are as follows: Before the positive pressure appeared, the diaphragm current increased by 2000A, while the ion membrane current increased by 3000A. Even after this increase, the automatic chlorine control valve still had 50% of its capacity left. The pressure of the raw chlorine was 0.132 MPa (as the temperature of the chilled brine was kept very low). At that time, we were operating two chlorine compressors with a capacity of 110 KW each and one compressor with a capacity of 250 KW. Under normal circumstances, such a situation should not occur when the pressure of elemental chlorine is at 0.132 MPa. Approximately two minutes after the current level increased, a high positive pressure suddenly appeared; we immediately added another chlorine compressor with a capacity of 110 KW, and two minutes later the suction force returned to normal. Under normal circumstances, an increase in current of a few thousand units has little effect on the pumping force; I’m not sure what caused this time, so I hope everyone can help analyze it. The temperature of the wet chlorine gas was also normal at that time. This post was last edited by limingshuguang on 2009-3-9 16:43. ] # ， ， &
After reading the original poster’s description, here is a brief analysis: 1) This issue occurs during the increase in current, which is related to human operation – specifically, whether the chlorine reflux is adjusted in a timely manner (it’s not clear whether the chlorine pressure is regulated automatically or manually when the original poster carries out the current-increase operation) ) 2) The positive pressure of chlorine is due to a problem somewhere between the electrolyzer and the inlet of the chlorine compressor; it could also be an issue in the chlorine treatment section, such as an increase in resistance in the demister. 3) Is this the first time the current is being increased after long-term operation at low load? There may be issues with the coordination of equipment across different work sections. I would also like to ask the original poster: where did the chlorine leak occur, and did the high pressure trigger an automatic shutdown? This post was last edited by yzhms on 2009-3-6 14:06.]
The chlorine compressor was automatically regulated at that time; we did not operate at low load for extended periods. Due to some issues that arose in the ion membrane workshop that day, the current level was reduced by several thousand units. After the repairs were completed, the current level was increased again. One place where leakage occurred was at the chlorine water seal, and another location was a pipe at the top of the waste acid tank that was connected to the atmosphere. We kept an eye on the suction force related to chlorine throughout that time. If the problem was caused by the current level, then the positive pressure should have increased gradually, rather than suddenly. When we checked the historical records, we found that the suction force remained relatively stable before the positive pressure appeared. Last edited by haining on 2009-3-6 14:01
Are there any records regarding the operation of the control valve? If the adjustment range of the automatic valve is insufficient, positive pressure may occur. However, according to the poster’s description, this situation hardly ever happens. Nevertheless, it is still recommended to check whether the valve operates properly to ensure that the same problem does not arise again.
Could there be solid particles falling off and causing blockages?
The possibility of acid or water sealing cannot be ruled out. This is once again the most troublesome issue, as it cannot be verified. It is also related to whether the current rise during electrolysis is too rapid. For example, two systems are upgraded together.
1. The impact of the system’s rising current is superimposed； 2. The optimal operating point for a control valve is around 50%, but it’s not clear what type of valve the poster is referring to ； 3. Check the adjustment curve again to see if it matches, and whether the extent of the adjustment corresponds to the amplitude of the current.
It would be good to have monitors; that way we’d know who is causing the problems. The reflux regulation is normal, but the pressure suddenly increases. Possible reasons include: 1. A sudden blockage in the subsequent processing stage related to chlorine; 2. The outlet valve of the chlorine compressor suddenly opens wider while the inlet valve closes more tightly; 3. An air blockage in the earlier stages: (1) A sudden increase in liquid level during chlorine treatment, such as an increase in the amount of water used for washing or in the circulation volume of sulfuric acid; (2) A blockage in the condensate water. I think options 2 and 3 are the most likely to be caused by human error. Such as the bypass for the automatic reflux control valve of the chlorine compressor. This post was last edited by pzhhuagong on 2009-3-8 13:13]
Whether the opening degree of the control valve matches the actual conditions on site, whether the control valve operates smoothly, whether there is any delay in its ability to respond to adjustments, or whether the PID parameters have been adjusted
"It’s almost impossible for the outlet valve of the chlorine compressor to suddenly open up while the inlet valve suddenly closes; no one was there to operate those valves at that time.
Normally, the chlorine treatment systems for the ion exchange membrane and diaphragm systems are separate; if they are combined, the control system becomes more complex. Possible causes also include water in the diaphragm pipeline creating a water seal, as well as malfunctioning suction instruments (such as water in the signal tube)