Benzol Refining Spent Acid Regeneration Research

There are more than 40 enterprises in China with the approximate capacity of processing 0.7million tons crude benzol every year. Sulfuric acid wash or scrubbing method is adopted as the main crude benzol refining methodology in China that can further produce approximately 50 thousand tons waste acid per year. At present, there are two methods to make use of the waste acid: 1) Discharge directly. This way not only pollutes the water source and environment, but also corrodes the sewers seriously and wastes the valuable chemical industry material resource. 2) Being used to produce ammonia sulfate. However, this operation process will encounter a lot of difficulties resulting in low quality ammonia sulfate when the untreated waste acid is used to make ammonia sulfate. Therefore, more and more attention is being paid to the treatment of waste acid.A lot of research work carried out both in China and abroad has been reviewed on the treatment of waste deposits. Considering the status in quo of domestic coke making industry, this paper puts forward a number of methods for decontaminating waste acid, which include the following:(1) Roasting MethodBy making use of the convenient research environment, i.e. JINING Minsheng Coal Chemical Processing Co. owns a sulfuric acid factory, the project employs the roasting method to process the waste acid.The waste acid of 40⁵5% concentration is pumped into a boiling-bed roaster and roasted in the boiling bed. The results of this test reveal that this method can treat waste acid effectively.(2) Extraction MethodThis method is based on the similitude and compatibility principle. Sulfuric acid is separated by transferring the organics in the waste acid to the extracting agent. After the extraction process the COD_cr number in waste sulfuric acid falls down from 13.56×10⁴mg/L to 9.61×10⁴mg/L, and the percentage of COD_crremoval can reach up to 30%. However, this method is limited by the problems such as difficulty of extracting agent recovery and secondary pollution. Further research work is still in demand. (3) Oxidation MethodThe organic deposits in waste sulfuric acid are oxidized and resolved with the help of the oxidant, the remainders of which become CO2, H2O and NOX that can be separated from sulfuric acid. The above process is called oxidation method by which the waste sulfuric acid is purified and recovered. Experimental results have shown: the direct oxidation method consumes too much oxidant with the result of high expense, so it is impossible to be adopted in industry widely. Nevertheless the dilution oxidation method can treat waste acid more efficiently, from which the CODcr number in waste sulfuric acid falls down from 13.56×10⁴mg/L to 6.23×10^mg/L, and the percentage of CODcr removal arrives at about 95% at the optimum technical conditions. This method has got the advantages of easy operation, no secondary pollution and good economy. Therefore it could be easily extended to industry.