Anhydrous sulfuric acid: three-effect evaporation; high amount of brine crystals, circulation pump stops operating
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A three-effect MVR evaporation system was installed last year; it was working perfectly until September. Starting in October, salt deposits began to form on the walls of the system, which caused high currents in the three-effect axial flow pumps and even led to their shutdown. Now, it is necessary to shut down the system every 5–6 days for cleaning； When the machine was stopped and the manhole was opened, it was found that there was a large amount of salt deposits on the impeller of the axial flow pump, as well as on the inner walls of the pipes. We seek guidance from experts – this situation is causing serious problems and significantly impacting the company’s production. The process remains unchanged; before September, the raw material was an 10% sulfuric acid solution, and since the end of September, about 5% ammonium dihydrogen phosphate wastewater with a concentration of 5–10% has been added~~~
Materials in industrial and mining applications tend to crystallize, so this pump is not suitable for such applications; considering replacing it with another pump. As for which specific pump to use, we need to wait for experts to give advice
Is it Xingfa’s equipment? Add me and let’s discuss it.
This has never happened before; how can it be said that the operating conditions favor crystallization?
This post was last edited by zuodouwen on 2016-12-20 at 14:06. Regarding the three-effect MVR evaporation system, it’s unclear whether it should be considered a three-effect evaporation system or an MVR evaporation system (normally, an MVR evaporation system cannot be converted into a three-effect system, and moreover, sulfuric acid solutions do not belong to those materials with particularly low boiling point elevations). I’m not entirely sure about the details, so I’ll analyze a few possibilities: One possibility is that the motor used for the pump is of insufficient capacity; a motor with higher capacity should have been selected, but that wasn’t done； The second possibility is that the flow rate of the pump is not chosen appropriately, resulting in poor local heat transfer efficiency; the material sticks together, reducing the area of the heat exchange tubes and increasing resistance, which in turn raises the current required by the axial flow pump motor ； In another scenario, magnesium ions may also be present in the wastewater; these ions react with ammonium dihydrogen phosphate to form an insoluble solid, commonly known as struvite. If this substance gets trapped in the impeller, it’s strange if the pump doesn’t stop working. I’ll analyze these three points. For more details, on-site research is required. QQ: 1035345029
Take a look at the properties of ammonium dihydrogen phosphate: when heated, it decomposes into ammonium metaphosphate, a type of phosphorus fertilizer produced by thermal methods. It’s no wonder that it doesn’t stick to surfaces; for wastewater containing ammonium dihydrogen phosphate, it’s better to find other ways to deal with it. Furthermore, this is clearly a three-effect evaporation system, rather than an MVR system. The solid content in the third effect of three-effect evaporation is high, which makes it necessary to choose an appropriate axial flow pump.
This post was last edited by nickelcp on 2016-12-21 at 22:21. There was no such problem before; the system has always been stable, so there should be no issue with the pump selection； It stopped working again today; upon inspection, it was found that there was a lot of salt on the inner wall of the circulation tube, and there were also many salt deposits at the impeller. The main component in the sample analysis of these salt deposits was ammonium sulfate. Phosphate, as well as magnesium and other elements, are also present in small amounts, less than 1%. The current problem is how salt deposits form on the walls; how can this be resolved? Explain MVR: the system consists of two effects combined with one compressor ； Three-effect system with a higher boiling point elevation; a single compressor is used in conjunction with MVR
The evaporation temperature is only 90 degrees – how can it decompose? Ammonium sulfate is thermally crystallized, so the solid-liquid ratio is naturally high
You can concentrate the acid to 15% before using MVR, which can save a lot of money since MVR is very energy-intensive. I can help you condense it to around 15
Are there any data? Send me the relevant data to take a look, thank you~
Add me on WeChat, 928866853, and I’ll send you the materials
Is the concentration of the steam too high? Causes coking of organic substances
Appropriately reducing the solid-liquid ratio of the materials in the system (below 10%, as this makes it easier to assess the solid-liquid ratio), along with the presence of calcium and magnesium ions, increases the likelihood of scaling; therefore, pre-treatment could be considered.
What was the concentration of sulfuric acid in the water originally?
It’s useless for your company to replace the pump; this problem will still arise over time. You can use the technical electrodialysis provided by our company before evaporation to help alleviate the issues associated with evaporation crystallization. Feel free to contact me if needed; my WeChat ID is 15088793370