Study On The Preparation Of Ternary Table Active Flocculant And Its Flocculation Mechanism

With the wide application of polymer flooding technology in oil fields,oily wastewater containing residual polymer is produced in these oil fields,which produces a large number of oily floes with strong adhesiveness when treated with cationic flocculant.Due to long-term deposition in equipment and pipelines,viscous flocs will cause serious blockage and affect the normal production of enterprises.Therefore,how to solve the problem of the reduction of viscous floes has become an urgent problem.In this paper,viscous floes was taken as the research object,and its generation mechanism was put forward and verified through a series of experiments.A set of devices for treating flowing wastewater has been set up.The effects of polymer concentration,polymer molecular weight,crude oil concentration,suspended solids concentration and suspended solids size were studied by using cationic flocculant to treat wastewater containing polymer.It was confirmed that polymer concentration in wastewater played a dominant role.A series of characterization experiments,such as IR,further clarified the composition and production process of viscous floes:some cationic flocculants react with partially hydrolyzed polyacrylamide(HPAM)to form polyelectrolyte complexes,while others react with oil droplets to form oil droplet aggregates.Viscous floes are formed by oil droplet aggregates which are enriched and adhered to metals due to the connection of polyelectrolyte complexes.A surfactant flocculant(PDXCn)is designed to reduce the viscous floes by weakening the interaction between flocculant and HPAM.PDXC,was synthesized by copolymerization of dimethyl diallyl ammonium chloride(DM),sodium allylsulfonate(XS)and surfactant monomers(ally]long-chain-alkyl quaternary ammonium salt).Taking oil removal rate and floe adhesion as indexes,the optimum conditions of polymerization were as follows:the surfactant monomer was dimethyl dodecyl allyl ammonium chloride,the mass ratio of DM,XS and surfactant monomers was 100:8:1.5,the concentration of sodium formate was 2000 mg/L,the reaction temperature was 55 C,the concentration of potassium persulfate was 0.5%wt,and the reaction time was 8 h.The oil removal rate of the surfactant flocculant was 98.95%.Compared with cationic flocculants,the floe adhesion decreased by 56.94%.The results of reactivity ratio showed that the copolymer structure is similar to "block sequence".The mechanism of surfactant flocculant was studied.Because of its interfacial activity,PDXCn can not only rapidly change the zeta potential and destroy the electrical double layer,but also reduce the interfacial tension and interfacial film strength of o/W emulsion,and promote the fast convergence of oil droplets to achieve the goal of oil-water separation.The electrostatic attraction within the molecule produced by the anionic monomer of PDXCn makes the long chain of flocculant curl.In addition,the long chain alkyl groups in the main chain will encapsulate some curled cationic groups and f’orm a "shielding" effect,which further weakens the interaction between flocculant and HPAM,and reduces the amount of floes adhering to metal surface.