Exploration of the causes of corrosion in chlorine compressors

With the same problem, there will definitely be acid residue, even though the acid is changed frequently. After investigating the problem that arose in our company, we found that it was due to insufficient capacity; however, the capacity decreased as well because of the grooves on the disk. The final solution was to install another small Naisch pump, which resolved the issue. Still, the replacement allowed Lang Caixia to make a profit. Actually, the technology behind these disks isn’t very advanced, but their price is high; presumably no one would dare to take the risk, especially new users.

Let’s conduct an analysis of the moisture content in the chlorine gas; it seems that the drying effect is not sufficient. It is recommended to use secondary or tertiary sulfuric acid for drying – 95% sulfuric acid can be used to dry the wet chlorine gas, followed by drying with 98% sulfuric acid.

A typical characteristic of HCI corrosion is that it causes corrosion in a direction parallel to the compression force, resulting in ridges similar to those in fields. There’s no good solution to this; if high-quality materials are used, their cost is too high, so frequent replacements are necessary. :lol

We use three-stage drying, which works well; the chlorine content remains within acceptable levels, and tests are conducted daily. Our approach is to reuse 95% of the acid that has been used in the chlorine compressor in the chlorine drying tower.

It seems we’re facing the same problem, and the solution is the same. But the price we pay for this is too high. We have taken the issue of acid residues into account; therefore, from the very beginning we have imposed strict requirements on the acid used in the chlorine compressors, specifying that only absorbed acid should be used and no mineral acids. Thus, corrosion is not entirely due to acid residues. We also replaced the discs, but they no longer achieve the original performance. We plan to install a filter at the inlet of the circulating acid; I’m not sure if this will increase the resistance and whether it will still work. Also, could anyone recommend a filter that can meet these process requirements while having low resistance, in order to improve our process?

Didn’t it say on the second floor: actually, the technology behind these discs isn’t very advanced, but their price is high. Changing it frequently isn’t a solution either! The boss won’t let you do that either, right? It’s better to solve the problem at its root. :)

We were really troubled by this issue at the time, and things got awkward between me and Nasser as well. However, the results of the discussions and analyses at that time pointed to the manufacturer’s fault and the acid slag. You should know that back then, 98% of our units were also replaced frequently. Based on our current operational experience, replacing the acid regularly is one approach; what’s really important is that the operators on site use their experience to control the temperature of the acid properly. Erosion is inevitable. However, installing a filter is not very feasible, as scouring of the disk will still be inevitable. Our company has seen good results by using a small Naeff pump for diversion; if such equipment is already available, it worth considering. There was also a small incident: at that time, Siemens was already being used in our company, back in 2001. Check whether the sealing rings of your machine seals are O-rings or wedge rings. This is also very important

Well, this one. There’s something wrong with the acid temperature of yours. A larger acid flow rate can be designed. Ask them at NASH-ELMO to increase the compressor clearance.

I’m not an expert in equipment; I’ll check whether the seal is an O-ring or a wedge ring, and then get back to you.

Do you mean the acid flow rate as the circulating acid flow rate through the cooler? Additionally, is there any fixed ratio required between the flow rate of acid circulating through the cooler and the amount of acid inside the pump casing? I believe that if the flow rate of acid is low, even if the temperature of the acid after passing through the cooler is normal, the temperature inside the pump casing will still be above 60 degrees, which can cause corrosion to the equipment. This is my personal opinion; I’m not sure if it makes sense, so please point out any mistakes.

Our machine seal’s sealing rings are O-rings, with a total of 5 O-rings for the stationary and rotating rings. Is there any difference in performance between O-rings and wedge rings?

I will first set the range; under these operating conditions, it is better to use an O-ring. Our company has a total of six Siemens chlorine compressors for primary and secondary compression; at the beginning of operation in 2001, their performance was not satisfactory. One of the reasons is frequent leakage of the mechanical seal; the root cause of this leakage lies in the use of PTFE wedge rings. These wedge rings are hard, and under the action of acidic residues they wear down the shaft sleeve. Any gap that results leads to leakage, which necessitates either replacing the shaft sleeve or spraying Hastelloy on that area. But in an environment of worshipping foreign things at that time, no one thought of replacing the wedge ring. It was a blind spot at that time. Since neither party had a solution for this issue (replacing the shaft sleeves multiple times required money and time), we had to use O-rings as a substitute on our own, and the result was very good. And from there, it was expanded upon, and communication was carried out with foreigners. Although the foreigners said nothing at the time, that marked a turning point – from then on, all the machine seals featured O-rings, and the foreigners indeed had a high sense of pride. This set of equipment is quite mature in terms of its use within our company at present; if there are any issues, feel free to discuss them together. However, due to some issues, the KKK turbines used in the subsequent expansion equipment turned out to be quite effective.

You are absolutely right. It is the acid temperature returning to the compressor that is crucial. However, a higher acid flow rate in the cooler can reduce the temperature of the acid entering the compressor. It’s equivalent to shifting the acid temperature inside the compressor downward. A reduction of about 5 degrees each would be quite significant. The corrosion rate of stainless steel due to nicotinic acid also increases rapidly and sharply around 60 degrees Celsius. Not to mention the high-velocity acid under the small gap at the distribution disk.

Thank you for the introduction. As a token of gratitude, I’d like to tell you that we also use domestically produced mechanical seals; a set of silicon carbide mechanical seals costs only a few thousand yuan. Less than half of the import amount.

Could you provide a detailed explanation of the bypass operation of the Nagaoka pump? Your experience would be very useful to us. :handshake