VCM synthesis, washing, and acid treatment
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How is the acid used in water washing during VCM synthesis by the calcium carbide method typically treated? It seems that some factories sell it directly as a commodity, but this acid contains mercury. Other factories use distillation methods; the results are said to be good, but what is the efficiency of these methods? Is their operation stable? This post was last edited by wang*neng on 2009-3-20 at 11:37
Conventional acid digestion yields good results: 32% hydrochloric acid is reduced to 22% dilute acid, which is then absorbed back by the system to be converted into concentrated acid for reuse in the process. There is in-depth analysis: 25% hydrochloric acid is reduced to below 1%, and it is recycled. This project has been implemented, but it has not been used yet.
For the treatment of this waste acid, many manufacturers currently use distillation processes to recover vinyl chloride and hydrogen chloride from it. This post was last edited by wang*neng on 2009-3-20 15:23]
The best approach is to separate hydrogen chloride and then regenerate vinyl chloride
31% hydrochloric acid was diluted to 22% dilute acid using conventional acid dilution. 22% dilute acid is then absorbed back into the system to become concentrated acid for reuse. With in-depth analysis, it means reducing 22% hydrochloric acid to below 1%, and then absorbing it.
Our facility uses hydrochloric acid distillation to convert the acid into hydrogen chloride; acids with a concentration of 25–30 are sent to the concentrated acid tank, while those with a concentration below 25 are sent to the dilute acid tank for absorption and reuse. Last edited by shizhiyong001 on 2009-3-25 09:44.]
Our company first removes about 31% of the acid, reducing its concentration to 26.6%, and then uses advanced purification methods to bring it down to 0.07%. However, both of these processes are currently under development
Conventional acid leaching yields good results: 32% hydrochloric acid is used to reduce the concentration to 22% in dilute acid; for more intensive leaching, 22% hydrochloric acid is used to lower the concentration to below 1%. This is exactly what we do in our workshop.
After neutralization, it is sent to the wastewater treatment plant where it is treated with sodium sulfide; the results are very good, so this option worth considering. :handshake
Under alkaline conditions, treating the mercury with sodium sulfide can reduce its concentration to below 0.05 mg/l, meeting the **emission standards. :lol
We have also sold this acid; others buy it mainly for rust removal. Once we install analysis equipment, we won’t sell it any more