Process and device for recycling waste acid produced in process of producing zoalene

A process for recycling waste acid produced in the process of producing Zoalene, comprising a nitration process, a chlorination process and an ammonization process, wherein the nitration process comprises the following steps:

• putting concentrated sulfuric acid into an enamel reactor (12), starting a mixer (18), putting in ortho-toluic acid and mixing it until completely dissolved, adding nitric acid to the system, controlling the system temperature at 90-100 DEG. C., continuously mixing to react for 0.5-1.5 h after added, and then cooling;
• diluting the liquid with distilled water, then filtering, and then washing and drying the solid to obtain a nitration product 3,5-dinitro-2-methylbenzoic acid;
• putting the waste acid which is diluted and washed in the nitration process into a distillation tower (1), later heating, depressurizing and distilling;
• setting the vacuum degree for depressurizing and distilling the water acid at 0.07-0.1 MPa, putting the acid liquid A obtained by distillation and concentration into a mixing tank (8), and adding new concentrated sulfuric acid to the mixing tank (8), wherein the mass ratio of the acid liquid A to the new concentrated sulfuric acid mixed above is 1-5:1;
• after mixing, putting the mixed sulfuric acid to a reactor to carry out a new nitration reaction;
• recycling and putting the distilled water A which is obtained by heating, depressurizing and distilling into a condenser (15) for cooling, storing the cooled distilled water A in a recycled water storage tank (17), and putting the distilled water A to a diluting pot (13) to dilute the 3,5-dinitro-2-methylbenzoic acid produced in the new nitration process.