How to treat stainless steel pickling wastewater
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Process components of the pickling section: — Pre-cleaning section (about 3.5 meters) — Sulfuric acid pickling section (about 12 meters) — HF+HNO3 mixed acid pickling section (about 14 meters) — Cleaning section (three stages, about 8 meters) — Drying section (about 4 meters). The wastewater contains chromium and nickel as well; what is the best way to treat it? There are a dozen or so stainless steel manufacturing plants in that industrial area, and if this waste can be properly treated, their business volume will be full this year.
There are two traditional approaches for dealing with pickling wastewater: 1. adding alkali for precipitation, 2. concentrating it to use as a chemical reagent. The costs are all quite high. The challenge in treating stainless steel pickling wastewater lies in removing oil and wax; the COD level in this waste is relatively high, making it difficult to treat. As for chromium and nickel, adding some chemicals can solve the problem!
It can be regenerated through ion exchange; if you’re interested, get in touch with me.
Agree with the view from the second floor: If the volume of water is not large, it is recommended to use a treatment process of coagulation sedimentation plus biological treatment; if the volume of water is large, it is suggested to separate the wastewater into two categories – oily wastewater and mixed wastewater. For oily wastewater, the treatment method should be acid extraction for demulsification, followed by air flotation and biological treatment. For mixed wastewater, coagulation sedimentation plus sand filtration is appropriate
Regarding the topic raised by the original poster, I would also like to ask the experienced colleagues: how should the acidic waste gases emitted by the relevant production units be handled? :Q: Since we are currently in the initial planning stage of such a project, (the sulfuric acid section uses HCL as the raw material instead), and the customer’s factory has not yet been built, they are unable to provide accurate information regarding the concentrations of exhaust gases from that process. I was wondering if any of you with relevant experience could offer some guidance. Thank you! I am initially considering using the alkali washing process; I wonder if that would work? Are there any standard parameter ranges for reference? Thank you!
It can be absorbed using a combined wash tower; the absorption efficiency for acidic gases is over 98%, and the concentration of the acid obtained after absorption can be maintained at above 31%. I am from Hangzhou Zhonghao, and we have successfully installed more than 20 such systems in the PVC industry for the absorption of hydrogen chloride from VCM, where the hydrogen chloride concentration is around 3%. If you need any further information, please contact Qiu Shufeng at 0571-86189107
I have a question for the senior on floor 6: Do you mean that it’s only okay to wash it with water, and not with alkali? Based on your engineering experience, what is the general temperature range of the volatilized gases of this kind? What is the approximate range of their proportion in the total gas? I took a look at the processing methods described on your company’s website; it seems quite complex. Can’t purification be achieved merely through washing with water or alkali? I asked for advice!
I’d like to say a few words too. What should be the concentration of hydrochloric acid in the pickling solution, and what is the temperature? According to our textbooks, hydrochloric acid and nitric acid are both volatile acids. But the volatility of the acid in their dilute aqueous solutions is extremely low. For example, at 25 degrees Celsius, the saturated vapor pressure of hydrogen chloride corresponding to 20% hydrochloric acid is 0.32 millimeters of mercury, while that of water is 14.1 millimeters of mercury. At 25 degrees, the saturated vapor pressure of hydrogen chloride corresponding to 10% hydrochloric acid is 0.0067 millimeters of mercury, while that of water is 20.0 millimeters of mercury. I’m not sure if this will be useful to you.
First neutralize, then adjust to an alkaline pH, and finally oxidize with ozone!