Sulfuric acid production has decreased; seeking expert help!
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Currently, the company’s two sulfuric acid production systems are operating normally. The sulfuric acid system built six years ago is experiencing production issues; this system generates acid from the flue gases resulting from the roasting of zinc sulfide ore, and it uses a 3+1 two-turn two-absorption process along with an acid washing procedure. As a result of these problems, the daily acid production has decreased by about 10 tons. After investigation, it was found that: 1. The outlet pressure of the foam tower is higher than the normal value ； 2. The inlet pressure of the drying tower is higher than the normal value ； 3. The inlet pressure of the main fan (tail fan) is higher than the normal value ； 4. The acid concentration in the drying tower is higher than that of the finished acid ； 5. An irritating odor also occasionally emanates from the roasted ore outlet; it is likely sulfur dioxide. Before this, an anode protection unit was used to replace a plate heat exchanger as a coolant; operation was normal for two days after the replacement. It is now suspected that there is a blockage in the pipes within the system, and although the foam tower was cleaned, there was no improvement. Another possible cause could be equipment aging. I would appreciate it if experts could advise on the specific procedures for maintenance and identify the root cause of the problem. Thank you very much! :handshake
Is the furnace gas cooled by an intercooler or a plate heat exchanger? If it is an intercooler, there is a high likelihood of blockages. I’ve encountered a plant that also produces zinc acid, where the resistance in the intercooler reached 300 millimeters of water column.
They were all layout-type coolers; later, the plates of the heat exchanger in the primary absorption tower became perforated and damaged, so an anode-protection acid cooler was installed. Currently, the drying section and the secondary absorption section use plate-type coolers, while the primary absorption section uses an anode-protection acid cooler. However, it has only been a few days since this replacement was made, so blockages are unlikely. It is suspected that the problem lies in the system between the main fan and the foam tower, but there isn’t enough time for a shutdown for major repairs; therefore, it’s necessary to identify the issue and carry out repairs on a single unit, otherwise the losses resulting from a shutdown would be even greater. :handshake
Your plant’s sulfuric acid system is going to be shut down for maintenance. Before shutting it down, measure the resistance of each piece of equipment; those with high resistance should be given special attention during cleaning. During the shutdown, clean the waste heat boilers and dust removal equipment, as well as devices such as the foam tower electrostatic precipitators. If there is a large amount of sublimated sulfuric acid sludge in the dry absorption tower, it also needs to be cleaned.
I’m asking whether your plant’s purification section uses intercoolers or plate heat exchangers. If intercoolers are used, there is a high likelihood of blockages. Dry-suction acid coolers do not affect the system resistance.
Oh! Hehe, yes, an intercooler would be a good option. It’s likely that this equipment hasn’t been cleaned or maintained for a long time; leaks were simply sealed up and production continued as usual.
In sulfuric acid production, temperature and pressure are the most important factors. The pressure in several of your key equipment units is higher than normal; it is recommended to check ahead of the foam tower – there might be a blockage there, or the foam tower itself could be blocked. If the resistance cannot be reduced, it is recommended to stop the machine for maintenance.
In my opinion, the fundamental reason for the reduced sulfuric acid production is either a leak of sulfur dioxide or the failure of the sulfur dioxide in the system to reach the converter, which leads to increased system resistance. However, if the sulfur content in the calcination system remains unchanged, then it’s not the system resistance that causes the drop in production. If the sulfur content in the calcination system decreases, then production will drop as well. Another factor could be an excessively high concentration of acid during drying, along with too low acid temperature, which results in excessive dissolution of sulfur dioxide. I’d like to hear everyone’s opinions on this
The previous system was clogged, resulting in a reduced gas flow
Based on these 4 analyses of 1, 2, 3, and 5, it seems that ash accumulation has occurred in the outlet pipeline of the baking furnace. If time permits, an inspection and cleaning should be carried out; once the blocked area is cleared, the production volume should return to normal. As for Article 4, it’s purely a matter of operation; just make some adjustments.