Talk about the service life of our own magnesium nitrate method concentrated nitric acid heater
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Let’s talk about the service life of our own magnesium nitrate method concentrated nitric acid heater. In the early stage of operation, because the inlet liquid pipe of the heater was not modified, it leaked after 20 days.； After modification, it can basically be used for about 1 year.
Then we have a longer time than you. We first leaked after using it for more than 2 years. We opened it and checked that the guide plate under the magnesium nitrate liquid pipe had fallen off. The heat exchange tube was blocked and the baffle plate was welded and now there is no leakage in use. Our nitrate control is still a bit high and not ideal yet.
Then you control it better than us. I wonder how high your nitrate content is? Our current nitrate content is ~0.3%,
I wonder if there are few people working on nitric acid in the forum? Or is it because everyone is unwilling to discuss it? Why is there so little discussion about nitric acid?
It should be because there are few people engaged in it. When I attended the annual meeting of the nitric acid industry, there were very few young people and very few old comrades knew about the Haichuan Chemical Forum.
It feels like a single tree cannot make a forest. I hope everyone can discuss it more.
Materials with severe corrosion in the gas phase need to be further improved. Duplex stainless steel can be used, and the effect should be better. Dilute magnesium contains nitrate, which must be strictly controlled.
“Isn’t it too expensive to use duplex stainless steel? In fact, just use white steel.
Let me ask if the white steel is made of 316L stainless steel. The main cause of leakage and shutdown is the leakage of the inner core of the heater (a large amount of steam entering the system).
The nitrate content of 0.3 is indeed a bit high, but ours is usually 0.4, haha, the heater leaks every day.
White steel refers to the abbreviation of all ordinary stainless steel.
If it is ordinary stainless steel, it will probably leak quickly. The corrosion of high-temperature dilute nitric acid is very strong. When the heater leaks in a small amount, it will not affect the concentration of the finished acid, but the dilute magnesium concentration will decrease, causing an increase in evaporation steam consumption. (Direct steam is used to make sulfuric acid to thicken the nitric acid.) However, if the leakage is large, it will affect the system negative pressure and reduce the concentration of the finished acid.
It seems there are so few people in the nitric acid industry
The key is to maintain the stability of the steam. If the steam fluctuates greatly, the nitrate content will become relatively high. Secondly, you can change the feed pipe of the heater to feed from the top to the side and install an arc baffle on the heat exchange tube, which can effectively slow down the corrosion rate of the equipment.
Are there any manufacturers that make nitric acid-resistant kettles? Can you recommend them?