| Pyrite-based sulphuric acid plant is the main production progress of making sulfuric acid in China, the pyrite cinder which were produced in this progress were also leached by hydrochloric acid or sulfuric acid to recycle the useful resources in it, but the leaching progress will produce a kind of wastewater which contains large amounts of hydrochloric acid and iron, copper, zinc, arsenic and other heavy metal ions, and this acid waste water were not often being treated resourcefully. This acid wastewater is hard to disposal, when it being discharged without disposal, water, soil, builds and even our body will in danger of being harmed, also the resources in it were wasted. Therefore, it’s very necessary to find an economical and feasible method to treat wasteweter of sulfuric acid residue.In recent years, the vacuum distillation and crystallization method more and more being used for the treatment of industrial wastewater, this method can separating the easily volatile components from wastewater, and separating the high concentration components by crystallization at the same time. So, this method is very suiTab to be used to treat wasteweter of sulfuric acid residue, which contains large amounts of hydrochloric acid and iron.This study using the vacuum distillation and crystallization method to treat wastewater from Huai Yuan mining company in Jianshui country, Yunnan province. The distillation rate and steam concentration changes were discussed in this study, and the concentrations of crystallization were analysed by XPS and XRD progress. Through orthogonal test, the effects of distillation time, distillation temperature and vacuum degree to hydrochloric acid recovery rate, recovery effect of hydrochloric acid concentration and crystallization yield were tested, and obtained the optimum conditions of vacuum distillation, on the basis, this study designed a MVR reduced pressure distillation process, providing an economic and feasible way to treat wasteweter of sulfuric acid residue for pyrite based sulphuric acid enterprises.The main researching contents and results are as followed:(1) Distilled wasteweter of sulfuric acid residue in 115℃, the results showed the distillation could be divided into the high-speed steam of water stage, the accelerate steam of acid stage and thehigh-speed steam of acid stage. When the distillation ended (80% of liquid were distilled), 64.93% of hydrochloric acid was recovered, the mass fraction of recovering hydrochloric acid was about 5.54%, and the crystallization yield was 7.4335g/L, the main component of it was FeCl3.(2) Tested the effects of distillation time, distillation temperature and vacuum degree to hydrochloric acid recovery rate, recovery effect of hydrochloric acid concentration and crystallization yield, and designed a orthogonal test with three factors and five levels. It showed that the optimum experimental conditions is distillation time 130min, distillation temperature of 120℃, vacuum 0.09Mpa, under this conditions, the hydrochloric acid recovery rate is 75.86%, the mass fraction of recovering hydrochloric acid is 6.69%, and crystallization yield is 14.0826g. Considering energy consumption, the optimum technological conditions of distillation time 130min, distillation temperature of 110℃, vacuum 0.06mpa, under this conditions, the hydrochloric acid recovery rate is 77.41%, the mass fraction of recovering hydrochloric acid is 6.71%, and crystallization yield is 11.2373g.(3) Designed a MVR progress with plate evaporator, screen separator and roots type compressor. When it was used to treat wastewater (80t/d) contain 7% hydrochloric acid and 18g/L iron, the process requires preheater heat transfer area for 11.13m2, external electric heating power for the 79.5620kW; plate evaporator heat transfer area for 138.84m2; roots type compressor power for 88.8823kW; size separator is Φ1.41×2.11m, volume for 3.27m2. And the total investment of the device 1797.9 thousands yuan, operating costs for 1235.5 thousands yuan/year, the product can be sold for profit 1211.4 thousands yuan/year, considering the saving of original commission processing costs 500 thousands yuan/year, the process start to profiTab at the 4th years. |
PDF Full Text Request