A hypothesis regarding the use of concentrated sulfuric acid for cleaning – discussions are welcome
Thread Content
This post was last edited by hanzheng666 on 2009-7-28 at 17:33. The treatment of waste acid in the purification process using concentrated sulfuric acid has always been a problem. I have an idea; I’d like to share it for everyone’s discussion. Our company does not use concentrated sulfuric acid for cleaning; if there are any mistakes or shortcomings, please feel free to advise us. The waste acid after purification contains many impurities, such as carbon (solid), sulfurous acid, phosphorous acid, phosphoric acid, etc. Step 1: Add table salt, raise the temperature appropriately, and release hydrogen chloride (which can be recycled) ； In the second step, solid impurities are filtered out, and the filtrate is dried using waste heat (such as conversion heat) to yield crystals (mainly hydrated sodium sulfate). In the third step, the crystal is dehydrated, with some solid alkali being used to remove water from the monomer. To be continued……
This post was last edited by sgh1966 on 2009-7-25 21:32. The purified waste sulfuric acid contains many impurities and has a complex composition; it is possible to carry out analytical treatment on it, but the cost of such treatment is very high, making it not worthwhile. We conducted tests on this waste sulfuric acid; when heated, a large amount of highly unpleasant gases were released, and the remaining substance quickly turned into a viscous substance with a pitch-black color, making it difficult to proceed with any further processing.
The issue of waste acid treatment is indeed a major challenge in concentrated sulfuric acid cleaning technology, hindering the widespread adoption of this technology.
For use as a cleaning agent, we make use of concentrated sulfuric acid by taking advantage of its acidity, as well as by removing sulfur and phosphorus impurities and recycling it for reuse. First, table salt is added and heated to decompose some of the impurity gases; thereafter, sulfur trioxide is absorbed to increase the acid concentration, which is then used again for cleaning purposes. Once the concentration (viscosity) reaches a certain level, the next step is to filter out the solid impurities, and the filtrate is dried using waste heat (such as heat of reaction) to produce crystals (mainly sodium sulfate hydrate). . . . . .
This post was last edited by sgh1966 on 2009-7-26 at 12:02. User on the fourth floor, is there any more detailed information you can share? ! Because the principle is often very simple, but the actual manufacturing process is another matter.
Second option: 1. First, filter the waste acid to remove solid impurities. (An appropriate amount of water can be added to reduce viscosity.) 2. The filtered waste acid solution is treated with calcium hypochlorite (bleaching powder; the amount to be used still needs to be determined), resulting in a mixture of calcium sulfate (insoluble), calcium hydrogen phosphate (soluble under acidic conditions), and calcium chloride (soluble); this mixture remains acidic, right? ). (Calcium carbide slag filtered to remove selenium and iron, along with chlorine, can be used as a substitute for bleaching powder.) 3. Filter the calcium sulfate hydrate crystals and dry them to remove moisture. 4. Add an appropriate amount of slaked lime to precipitate calcium phosphate, then dry and dehydrate it. 5. The calcium chloride solution (containing some calcium hydroxide) is dried to remove water. 6. Calcium sulfate (polishing powder, paper filler, gas desiccant, cement setting regulator); calcium chloride (gas desiccant); calcium phosphate (polymerization buffer). That’s too idealistic, haha – feel free to point out any flaws!
For the recycling of sodium hypochlorite, it is possible to transfer the waste sodium hypochlorite from the waste acid tank to a venturi tube for re-mixing
Suggestions on the concentrated sulfuric acid cleaning process: This process can reduce the amount of water in the system, thereby helping to maintain system water balance and reducing wastewater discharge. However, this method is not necessarily required; our company achieves liquid waste balance by using recycled clean liquids, controlling the amount of water used in mechanical seals, and recycling defective sodium solutions, so there is no need to employ a concentrated sulfuric acid cleaning process. After all, solving one problem may give rise to new ones; one must consider which of the two problems is less severe and choose that one.
Is anyone still paying attention to this issue?