PURPOSE: To recover an iron oxide in a sludge as ferric oxide and effectively utilize the sludge by deoiling the sludge, pulverizing the deoiled sludge, washing the pulverized sludge with water and calcining the washed particles in an oxidizing atmosphere.
CONSTITUTION: A petroleum sludge in a ship bottom of an oil tanker contains inorganic impurities, such as iron rust, organic substances, such as petroleum, and foreign materials, such as stone or sand. The above-mentioned sludge is incinerated in a rotary kiln to burn and remove oils. The deoiled sludge is then passed through a classifier to remove contaminating foreign materials and leave various oxides, which are then pulverized to ≤ about 3mm particle diameter in a crusher and further placed in a ball mill. Water is then added to carry out wet pulverization and afford fine particles having ≤ about 1μ average particle diameter. The obtained slurry is stirred in a water washing tank to dissolve and remove impurities, such as CaO or Na2O. The iron oxide slurry of an enhanced purity is subsequently separated and dried in a thickener. The resultant iron oxide is then calcined to wholly convert the various iron oxides into ferric oxide (α-Fe2O3), which is subsequently pulverized to afford high-purity red iron oxide for red pigments.
YOSHIDA HIROHISA
HAYASHI YUKIO
