The Pilot Study Of Phenol Recovery From Coal Chemical Industry Wastewater By Pervaporation

Huge amount of coal chemical industrial wastewater is generated during the production of coal chemical industry. The wastewater contains high content of toxic and hazardous substances, and it is difficult to be treated. Nowadays biochemical treatment is most commonly used to treat coal chemical industry wastewater. Phenol and other industrial raw materials are removed as the COD at anaerobic stage.This increases the processing cost, and also a waste of resources. As the unit of preliminary treatment, pervaporation process was introduced to recycle industrial raw materials and reduce the biochemical treatment difficulty to achieve the double effect of resource recycling and improving economic performance of wastewater treatment.In this article, the pervaporation process was used as the unit of physical-chemical treatment of coal chemical wastewater. The separation characteristics of different types of polymer membranes for phenol was investigated, including the highest separation characteristics of pervaporation membrane materials, pervaporation membrane mass transfer and pervaporation treatment of coal chemical wastewater in a pilot study.Several pervaporation membrane materials were investigated in a high concentration of phenol, with the temperature of70℃, and it is found that the order of phenol flux of pervaporation membrane was:PEBA membrane> graft modified PDMS membrane>cross-linking modified PDMS membrane> the PDMS membrane. The order of different membrane materials for phenol separation factor was:graft modified PDMS membrane>cross-linking modified PDMS membrane> the PDMS film> PEBA membrane. The graft modified PDMS membrane appears most suitable for separation of volatile phenol from wastewater.In series resistance model and difference method can effectively describe the controlling factors for the various mass transfer rate. The study found that the flow rate had no effect on mass transfer coefficient of the inside membrane, and mass transfer coefficient was positively correlated to the film outside the boundary layer. When the flow rate was25cm/s, the film rumored transfer coefficient was11×10-6m/s, at the same time membrane mass transfer coefficient of the50μm membrane reached4×10-6m/s. The membrane mass transfer rate is much smaller than the film rumored transfer rate. Therefore, membrane diffusion and mass transfer process can be mainly controlled by reducing the film thickness which will help speed up the mass transfer rate. The relationship of temperature with the membrane inside mass transfer rate accords with the Arrhenius relationship. The temperature was linearly correlated with the film rumored transfer coefficiency.In the pilot study, it is found that pre-treatment and regularly cleaning of the membrane had great effect on separation in dealing with actual wastewater. The controlled conditions in a pilot plant is not harsh for industrial applications which facilitate the promotion of practical applications. Under the optimal conditions of traditional pervaporation pilot test, the system requires two hours to start. The highest phenol removal efficiency was60%, and it was up to66%when the system was pumped with gas.