How can ammonium sulfate be modified to enable normal production?
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Since the operation of the ammonium sulfate production line in our factory began, acid leaks have occurred frequently, especially in the mother liquor circulation pipes. Sometimes, dozens of clamps have to be used to seal these leaks, which severely hinders the normal progress of production. The mother liquor circulation pipes in our factory are made of 316L stainless steel; what material could be used as a substitute to effectively address these acid leaks?
If the acidity of the mother liquor is maintained at 3–5 during normal production, there should be no problem using 316L tubing. However, I have encountered such a situation in production: some manufacturers produce pipe fittings that are not stamping products, but rather welded ones. Even if the pipe material is fine, corrosion can still occur if the welding material is substandard. Now we manufacture all our pipe fittings using pipes ourselves, and we use A022 welding material (the one from Sichuan Zigong Atlantic is of better quality). When selecting pipe materials, it is important to pay attention to the differences between American standards and Chinese standards; it is better to choose those that meet Chinese standards. As for other materials, 904 or 904L or Hastelloy are too expensive; they have only been seen in circulation pumps and mechanical seals. Currently, some factories use prefabricated components made of engineering plastics; however, they are rather difficult to clean
There should be no problem using pipes made of material 316L; is there an issue with the manufacturing process?
Please indicate which part of the pipeline is leaking Tubes? Still the weld? Or are they pipe fittings? Currently, 316L stainless steel is still the most commonly used material for the mother liquor circulation pipes in the ammonium sulfate section of coking plants. I wonder how long your factory has been producing ammonium sulfate! If leakage occurs within a short period of time, it is likely due to the material used for the pipes or the welding techniques employed. Stainless steel is generally not very stable, and argon arc welding is usually used during construction in order to minimize heat-affected zones and intergranular corrosion ； Furthermore, if the quality of the stainless steel pipe fittings is not good enough during processing or installation, it will also affect their performance. I suggest you check the material of your pipes. Of course, as a mother liquor circulation pipe that is subject to erosion by ammonium sulfate crystals, the wall thickness should be relatively large.
In our plant, leaks in the mother liquor pipes are mainly caused by leaks at the brackets (due to the welding method used) and flanges (welds); additionally, leaks also occur due to poor gaskets. It has been in production for over a year.
The mother liquor pipes in our factory are made of 1Cr18Ni9Ti; the main problem is that the wall thickness of these pipes thins out as a result of erosion, which leads to leaks.
If there are leaks at the leg joints (welding method) and flange welds, it is definitely a problem with the construction or the material quality. For general stainless steel pipes, the same material must be used when welding to brackets; otherwise, carburization is likely to occur, leading to intergranular corrosion. Intergranular corrosion in stainless steel is devastating ； Of course, it is also possible that the welding process is incorrect (for example: the welding method used is arc welding, the type of welding electrode does not match that of the pipe material, or no proper welding procedures were followed). Please determine whether the above problems exist; the phenomenon you described should be avoidable.
I recommend using fluoroplastic-lined composite pipes; they work well.
The 316L stainless steel material is not as durable as those lined with PTFE; stainless steel is prone to intergranular corrosion. However, the PTFE-lined materials also have their issues – it is necessary to control the expansion coefficient of the pipes properly, otherwise their service life will be short.
Adding to the post on floor 10: At present, our company plans to replace the circulation pipes with steel-lined graphite pipes, in order to increase the expansion coefficient of these pipes and prevent the problems caused by resonance. This should yield better results and extend their service life. The circulation pumps will still be made of steel-lined PTFE material. Previously, our company used 2205 duplex stainless steel for all such components, but that material was completely unsuitable – it has all corroded.
This post was last edited by lxq700918 on 2009-6-18 08:47. We have tried all the methods mentioned above, and the steel framework is still the best option.