Patent ID: 8168846

Claim:
A process for the transformation of dangerous waste material containing chromium six into non dangerous waste, characterized by the following steps: transporting the dangerous waste material containing chromium six to a reception hopper feeding a conveyor belt; taking the material to a hammer crusher that reduces a granulometry of the material to pieces having a maximum diameter of one inch; subsequently sending the material through a bucket elevator to a vibratory sieve that feeds a storage silo, wherein the storage silo feeds, in turn, a ball mill; conducting a wet milling process at the ball mill so that about 80% of the material passes through a mesh 200 sieve; classifying the material in a cyclone into fine material and coarse material, wherein the fine material passes to a stirring tank where the fine material is suspended in 50% of water to form a suspension, and the coarse material is separated in the cyclone and returns to the ball mill of the stirring tank; transferring the suspension to reaction reactors; acidifying the suspension with residual sulfuric acid or 98% sulfuric acid until the pH is lowered to a 2.5-3 value; injecting a gas stream of reducing agent to maintain the suspension at a temperature of 80° C. with continuous stirring for four hours; taking a sample to determine whether a chromium six concentration of the suspension is below 0.5 ppm according to a spectrophotometry determination, and if it is determined that the chromium six concentration is below 0.5 ppm: modifying the pH of the suspension to be 8.5-9, taking another sample for a final CRETIB analysis, discharging the suspension to an evaporation pit, and disposing of the suspension.