The Research Of Comprehensive Treatment Method On Methanol-containing Wastewater In Changbei Gasfield

Since the methanol wastewater contains a large amount of condensate oil,suspended solid as well as other organic matter composition et.al in Changbei gas field,the quality and volume of water vary greatly,and emulsifying phenomenon is very serious.Additionally,present treatment technique is not perfect,the treatment method is not reasonable and the quality of water does not match with pretreatm ent reagent.Based on the above reasons,fouling and blockage of the sewage treatment and methanol regeneration system is very serious,the quality of treated water and recovery of methanol is unqualified.According to the nature of the composition of methanol sewage,it's needed that the research of comprehensive treatment method on wastewater is carried out to provide basic data for normal operation of sewage treatment system.In this paper,with wastewater treatment system and reclamation of methanol system as an object,variety of chemical analysis methods and means are used to analyze the nature of the composition of sewage and causes of emulsion in detail.And the operation effect of each device in existing sewage treatment system is also analyzed and evaluated.Then the reasons that sewage treatment is not up to standard as well as all kinds of generated problems are determined.Based on the above,the sewage treatment process and the formula of water treatment agent as well as the operation parameters of methanol regeneration tower are optimized.The results showed that:(1)Methanol-containing wastewater is weak acid,the content of condensate oil and suspended solids is higher and varys greatly(the content of condensate oil is 681.7?4139mg/L,suspended solids is 204?447mg/L),suspended particle size is smaller(median particle size is 5?12 microns);(2)The main problems of present sewage treatment system is determined.The quality and volume of water do not match with the type and dose of pretreatment reagent.The settling tank's role of flocculation sedimentation is not ideal.The average content of iron ions is 66.9mg/L,condensate oil is 278.94mg/L and suspended solids is 264mg/L in the sedimentation tank outlet;(3)By increasing the density of the floc,the problem of high emulsification and floating floc is solved,and the best water treatment agent formulations is determined:the dosage of barite powder whose particle size is 120?200 mesh is 100mg/L,H2O2 is 156mg/L,NaOH is 142mg/L,PAC is 100mg/L,and PAM whose molecular weight is 12 million is 2mg/L.The content of suspended solids and condensate oil is lower than 50mg/L in treated water;(4)The problem that the water volume doesn't match with the dose of water treatment agents is solved by making the water pump and dosing pump run at the same time;(5)The operation parameters of rectification tower are optimized with Aspen HYSYS process simulation software.Under the condition of new operation parameters,methanol content in rectification tower is more than 95%at top and less than 0.1%at bottom.