Gasification of petrochemical sludge in supercritical water

Abstract

In wastewater treatment plants, petrochemical sludge is generated during the treatment of oily industrial wastewaters produced in petrochemical production. Although most of the oil floats on the wastewater, a portion is carried into the sludge with settling solids. The gasification of petrochemical sludge in supercritical water was investigated in a reactor at temperatures of 530–650°C, pressures of 26–42 MPa and residence times of 200–360 s. Pressure change was found to have no significant influence on gasification efficiency. Higher temperatures and longer residence times enhanced gasification efficiency, and lower temperatures favoured hydrogen production. The addition of potassium carbonate increased both the hydrogen fraction and the gas yield. The precipitated alkali in the reactor still showed a high catalytic effect on the subsequent gasification of petrochemical sludge without further alkali addition. The catalytic activity was slightly reduced because the potassium carbonate is transformed to potassium hydrogen carbonate.