Research On Oil-water Separation Technology With The Advection-type Pressurized Dissolved Air Flotation

Dissolved air flotation as a relatively clean and efficient multi-phase separation technology,which is widely used in oil-water treatment and other related fields.As the conventional oil-water separation technology is in low efficiency in emulsified oil wastewater treatment.This study put forward the advection-type pressurized dissolved air flotation for emulsified oily wastewater,and analysis the relation between the distribution of micro bubble size and gas content and the oil removal efficiency in contact zone and dissolved air releaser.The key element of air flotation is the micro bubbles,especially the micro bubbles in the contact zone.The contact zone of advection-type pressurized dissolved air flotation tank is the main place for the micro bubble to collide with the oil droplets,for larger kinetic energy,which can significantly affect the collision efficiency between the micro bubbles and the oil droplets.Based on this,Firstly the theoretical analysis is used to study the formation of pressure dissolved air,the formation of micro bubbles,the energy change in the process of formation and the adhesion behavior between micro bubbles and oil droplets,and then analysis the micro bubble size and gas content of contact zone with different conditions combined with the experimental methods,including micro bubble size and gas distribution rate around the dissolved air releaser and along the height of contact zone.The experimental result shows that the particle size of the micro bubble satisfies the normal distribution generally,decreases with the increasing of dissolved air pressure,and increases along the height of the contact zone.Secondly,the relationship between gas content and micro bubble particle size is analyzed for same experimental parameters,and the gas content distribution around the dissolved gas releaser and along the height of the contact zone are studied in the experiment.The result shows that the gas content distribution reaches the optimum state under the conditions of the optimum dissolved air pressure and the inlet air volume and so on.Last,in order to study the relationship between the distribution of micro bubbles and the effect of oil removal,the study object is self-made emulsified oil wastewater in the laboratory,and the effects of operating parameters,physical parameters,structure parameters and chemical additives on the oil removal efficiency are studied systematically,and so does the relationship between the distribution of micro bubbles and the oil removal efficiency.The experimental result shows that optimum parameters: the dissolved gas pressure is 0.32 MPa,air flow is 0.2L/min,inlet flow of contact area is 300L/h,reflux flow of Saturator is 350L/h,contact zone width is 10 cm,mixing speed is 20r/min.When PAC and PAM are used in coordinated service,adding PAM after PAC with the highest oil removal rate is 85% when the proportion is 1:1;the highest oil removal rate is 80% when the optimal concentration of SDBS is 90mg/L.The highest efficiency was 40% without adding NaCl,the minimum oil removal rate of adding NaCl is about 55%.