Material of refined recycled gas recovery pipeline
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The recovery pipes for refined recycled gas (seamless steel pipes) leak from time to time. Since the recycled gas contains both acids (acetic acid) and bases (ammonia), what type of pipe material would be durable?
Our unit uses ordinary carbon steel pipes; there’s nothing special about them. I’ll replace the pipe once there’s a leak. It’s not that troublesome either. What other materials could be used? Either stainless steel. :D :D :D :D
If acids or alkalis are present, stainless steel is likely to be unsuitable due to its lack of corrosion resistance; plastic pipes or pipes lined with plastic might be a better option.
In the two construction projects I was involved in, the refining and regeneration gas pipelines used were all made of 304 stainless steel; the carbon steel pipelines that had been planned to be purchased were completely useless.
We originally used ordinary carbon steel pipes as well, which leaked frequently, because the recycled gas contained ammonia, acetic acid, as well as CO, CO2, and H2S. Changing it to stainless steel now is indeed much better. This post was last edited by yunanshu on 2008-1-27 13:41]
It used to be carbon steel; the corrosion was too severe. We should use stainless steel now.
It is addressed mainly from two aspects: 1. Change the location where acid is added; it should not be added at the inlet of the reflux tower, but rather after water cooling and before ammonia cooling, and it should be mixed with the copper melt before being introduced into the system. In this way, less acetic acid is distilled in the reflux tower, which reduces acid loss and lowers the load on regenerator recovery. 2. Reform the regenerated gas recovery process: first, use a high-position ammonia absorber for cyclic absorption (the circulating liquid needs to be cooled, and the ammonia absorber as well as the liquid drop pipe should be made of stainless steel); then, use soft water in a packed tower to absorb the ammonia and acids present in the regenerated gas, thereby recovering them. I have adjusted it so that the ammonia output is below 1% in summer. Of course, those with money can use the patented technology for advertising in small fertilizer magazines. 3. Through the above methods, the problems of blockages and corrosion in the hydrogen recovery pipeline are basically resolved.
1. Made of carbon steel; a gas-liquid separator is added at the outlet of the ammonia scrubber or at the inlet of the Roots blower to separate ammonia water from the regenerated gas, thereby reducing corrosion in the regeneration gas pipelines. Pipelines are most prone to corrosion in a gas-liquid mixed state. When installing pipes, try to minimize the number of bends in order to reduce the pipe’s resistance coefficient and lessen erosion corrosion. 2. Modify the ammonia scrubber: those using rectangular saddle rings as packing can be replaced with structured packing, while those using structured packing but having poor absorption efficiency (with an outlet ammonia volume fraction of over 0.5%) can be upgraded to use composite internals. The upper section of the ammonia scrubber shall consist of trays, while the lower section shall use packing for absorption. Reduce the ammonia content in the regenerated gas outlet. 3. Modify the outlet of the reflux tower. To reduce the outlet temperature of the regenerated gas from the reflux tower and the inlet temperature of the ammonia scrubber, external spray of water can be used, with the water being recovered simultaneously. 4. Transforming the equipment associated with the ammonia scrubber allows for the addition of a horizontal cooler and an ammonia water circulation pump. Lower the temperature of the ammonia solution in the ammonia scrubber, thereby reducing the saturated vapor pressure of ammonia in the gas phase within the scrubber. This includes the addition of high-position ammonia absorbers, as mentioned by everyone. Through the above measures, the volume fraction of ammonia in the regenerated gas at the outlet of the control system is kept below 0.3%, so there is no need to worry about corrosion even with carbon steel pipelines. This post was last edited by tm1982yx on 2008-2-16 23:11]
The ammonia recovery systems in our company are made of carbon steel, and they leak everywhere; they’re covered with crystals. Of course, this is inevitable. Currently, only the ammonia recovery section has been upgraded to stainless steel pipes, but the joints are still severely corroded.
Our unit uses ordinary carbon steel pipes; there’s nothing special about them. I’ll replace the pipe once there’s a leak. It’s not that troublesome either. What other materials could be used? Either stainless steel.
Due to the high ammonia content in the regenerated gas, it is recommended to use stainless steel; many manufacturers use 304 pipelines for transportation
The carbon steel pipes we use have hardly ever leaked
It is likely closely related to the ammonia content in the regenerated gas; some manufacturers have an ammonia content in their regenerated gas of over 20 percent, while others have only a few percent, showing a significant difference
The most effective option is 316L material; it can be used for 2 to 3 years without any problems
Our factory originally used carbon steel, but it was in a poor condition. Taking advantage of the major maintenance in April this year, we replaced it all with stainless steel. Hehe~~~
It may also be closely related to the efficiency of the copper washing towers used by various manufacturers