Plan for purging the methanol synthesis system
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Hello, gentlemen. I have a question: is it better to perform purging of the methanol synthesis system on a continuous basis? Is blasting and purging better? What are their respective advantages and disadvantages? Thank you.
First, perform continuous purging, and then carry out explosive purging of the pipes; after purging the containers, manual cleaning is carried out.
I recommend continuous purging; that’s what I have experienced as well. Without explosive purging, continuous purging is cleaner and also less troublesome (in my opinion); explosive purging is too complicated, as the blast disc has to be replaced every time.
Don’t forget to isolate the low-pressure system during purging. Also, remove the instruments and flow meters, blow out the pressure tapping points as well as the instrument pressure guide tubes.
In systems with high pressure, such as those used for methanol synthesis and ammonia synthesis, continuous purging definitely does not result in a thorough cleaning. Our plant’s purging procedure is similar to that on the second floor: it starts with purging at atmospheric pressure, followed by explosive purging, and then manual cleaning. During the normal-pressure purging phase, very little is blown out; the effect of explosive purging is completely on a different level! What is still vivid in my memory is the first explosion at the outlet at the bottom of the synthesis tower; thick clouds of smoke erupted like those from a rocket launch. We, standing 30 meters away, were severely choked by the smoke, and it took over ten minutes for the dust to disperse. The area of ground within 100 square meters around the site of the explosion was completely cleaned of dust. For pipelines of the DN500 size, we use either one 5mm-thick blast plate or two 3mm-thick blast plates; the blast pressure is around 20 bar. The number of times each blast port can be used for blasting depends on the size of the blasting system and the desired blasting effect, and it is generally 30–40 times. But even after such blasting, there is still a layer of dust or rust on the pipe wall during manual cleaning. The crude methanol produced during the initial operation was still very dark (of course, most of it consisted of catalyst powder), to such an extent that even after a year of operation, the methanol upper separator (super filter) has not yet been put into use.
Continuous purging is appropriate; blasting is generally used for new installations
Personally, I think blasting purging is more effective; the main issue with continuous purging is insufficient gas supply. No matter what type of purging is used, care must be taken to isolate it from moving equipment.
For methanol synthesis, continuous and burst purging should be combined; the method that is more appropriate for those specific pipelines should be chosen.
For methanol synthesis, continuous and burst purging should be combined; the method that is more appropriate for those specific pipelines should be chosen.