El medio ambiente en la minería

EL MEDIO AMBIENTE EN LA MINERIA 134· 2. Acid P1ant Operation The acid plant at Sumitomo' Toyo Smelter started operating in 1971 witb a Chemico-t:ype single contact system. After its successful operation, die single contact system was changed to the double contact system in 1978. The flow sheet of the sulphuric acid plant .al Toyo Smelter is shown in Figure 5. Figure 6 shows the oper<:l.~ion results of the acid. plant since its, start-up ip 1971. As shown in Figure 6, the conyersion ratewas sharply raised and kept at a high level, more than 99.8%, after being ehanged from the single to dquble contact system. Nowadays, a high eonversion rate is maintained de.."pite the inerease of S02 strength due to the oxygen enrichment to the smelter, and the taH gas is kept at about 10 ppmOfS02strength on average, although the peak value currently exceeds 12 percentages of S02 strength, shown in Figure 4. The total S02 emission from Toyo Smelter and Refinery is also rather reduced in spite of the production ¡nerease shown in Figure 6. Asa result, more than 99.9% of the charged sulphur is stably fixed, as shown in Table 6. St&c:k Figure 5. Flow sheet of acid planto 1'0.250 InOWQt"'o