Water ring vacuum pump drainage problem
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VPSA is used for carbon removal in methanol production. I would like to ask the experts: the wastewater from water-ring vacuum pumps used for vacuum creation is acidic; after being pressurized, it is discharged into the circulating water system. Does this cause corrosion to the pipes and pumps?
If the hydrogen sulfide content in the reformate gas is high, it causes the gas to dissolve in water to form weak hydrogen sulfurous acid; this weak hydrogen sulfurous acid can then corrode the pipes in the water system. If the hydrogen sulfide content in the reformate gas is low, and instead carbon dioxide dissolves in water to form weak carbonic acid, then the corrosion of the pipes in the water system by this weak carbonic acid is likely to be less severe. What is the pH value of the acidity? Is a corrosion-resistant pump being used? We found that cast iron pumps are corroded, 304 stainless steel pumps are hardly corroded, while carbon steel pumps are also corroded. If the gas loss is high, that is, the carbon dioxide concentration in the pumped air is low, some cast iron pumps do not suffer from corrosion; whereas if the gas loss is low, that is, the carbon dioxide concentration in the pumped air is high, some 304 stainless steel pumps can still become corroded. It’s best to determine whether the hydrogen sulfide level is high. This post was last edited by CDYANGHAO on 2007-12-24 03:42.]
Just test it and you’ll know; take water samples for analysis!
Or conduct material analysis experiments by using the water discharged to test the materials of the pump casing and impeller; after 24 hours, check whether there is any loss in quality
The pH value is 5.3–5.5, and the hydrogen sulfide content in the exhaust gas is 200 mg/Nm3. The pump impellers are made of carbon steel; the system was originally designed for recirculating water, but due to concerns about pipe corrosion, it is now being used for direct discharge.
The circulating medium can be changed; another liquid can be used in the circulation system. I consulted the manufacturer, and it was stated that any liquid that does not react can be used as the circulating fluid.
With such a high H2S content, acidity can have an impact on the circulating water pipes and related equipment, as the pumps and pipes in the circulating water system are not made of carbon steel. If comprehensive utilization of water is considered, it must be treated before being reused in the circulating water system.
What is the carbon dioxide concentration in the evacuated gas? I think using a circulation tank to store the circulating water, adding alkaline solution to this tank for neutralization, and then using a cooling tower for aeration will allow for the recycling of water. It would be even better to have a set of ammonia coolers, as this would help address the issue of cooling water temperature. This is exactly how the vacuum water circulation system for the VPSA system I designed at a factory in Anhui was implemented.
There should be corrosion in the pipes; the H2S level is too high!
It depends on the drainage volume of your vacuum pump and the volume of circulating water. If the drainage volume constitutes only a small fraction of the circulating water volume, the corrosive effect on the pump and pipes should be minimal
We also use water ring pumps, and we have a decent treatment process. However, you need to first determine the composition of the acidic gas – what it is – before checking whether it’s suitable: call: