A novel process for coke wastewater gasification quenching: Energy and exergy analysis

The rapid quenching of hot coke from coke ovens to prevent oxidation is important for coke storage and transportation. We studied a novel process for coke wastewater gasification quenching (CWGQ) in a shaft furnace, which was proposed recently. In the CWGQ process, wastewater is sprayed into the lower part of the furnace, where it is heated and evaporates into steam that then reacts with coke to generate water gas. A one-dimensional model was developed to simulate the in-furnace heat transfer and reaction. The energy/exergy flow of the CWGQ system was calculated and compared with coke dry quenching (CDQ) system. The net income and efficiency of exergy of the CWGQ system are about 2.1 times and 1.5 times of those of the CDQ system. For CWGQ process, the more wastewater injection, the better exergy efficiency and wastewater treatment. The effect of intermediate steam extraction on exergy efficiency and wastewater treatment is opposite. The wastewater treatment reaches the maximum (0.202 t-water/t-coke) when all superheated steam is extracted at lower flue. For the largest exergy efficiency, the best rate of steam extraction is 0.4. This study suggests that CWGQ process is a promising alternative technology for coke quenching and wastewater treatment.