Technological Study On Refinery Alkaline Residue Wastewater Disposed By Cascade Reducing Method

Focusing on the high COD value, high chroma and stench of alkaline residue wastewater of oil refineries in Ningxia, the present work designs a combining process of concentrated sulfuric acid neutralization-activated carbon adsorption-steam distillatio based on gradual reduction process to deal with the refining alkaline residue wastewater in order to reach requirements of wastewater discharge in oil refinery. The experiment results demonstrate that the process is feasible. And the optimum conditions are determined by single factor analysis and orthogonal experiment. The paper performs the design of the material balance and the main equipment selection, as well as economic evaluation. It concludes the following conclusion by analyzing experimental results:The most appropriate operational parameters are conluded from concentrated sulfuric acid neutralization experimen, and they are room temperature, with 25/1 volume ratio of alkaline residue wastewater and concentrated sulfuric acid, and 2-hour reaction time. Under these conditions, the study results show that the COD value of alkaline residue wastewater is reduced from 147288 mg/L to 84320 mg/L.The most proper operational parameters are concluded from activated carbon static adsorption experiment. In other words, adsorption temperature should be 20 ℃, adsorption time 6 hours, protential hydrogen value 8.0, volume ratio of activited carbon and wastewater 1/3.3, oscillation frequency 140 round per minut. Under these circumstances, the study results show that the COD value of alkaline residue wastewater is decreased to 14950 mg/L. For one thing, the adsorption kinetics is consistent with pseudo-secondary adsoption model; for another, the adsorption isothermal curve is consistent with the Freundich adsorption isothermal model. Undinalbly, the adsorption process is spontaneous and exothermic. In addition, the most proper operational parameters of active carbon dynamic adsorption experiment concludes room temperature, and that protential hydrogen value is 8.0, feed flow rate 6.52 milliliters per minute, packing layer height 26 centimeters, and inside diameter 3.2 centimeters. In this way, the adsorption is conducted in 21.5 minutes, the average COD value of alkaline residue wastewater is reduced from 84320 mg/L to 15000 mg/L.The best operational parameters of steam distillation experiment are as follows:with protential hydrogen 6.7, with distillation time 100 minutes, and with steam temperature 120℃. The study results show that the COD value of alkaline residue wastewater was reduced from 15000 mg/L to 1690 mg/L.The results indicate that a ton of alkaline residue wastewater is treated with the cost of 1806 yuan, which is more economical and environmental than the present treatment method in oil refinery industry. The experiment results can be provided for pilot plant as a technology basis, which is useful to other medium and small oil refinery industries.