Study On Treatment Process Of Mercury-containing Sludge In Gas Field

In recent years,a large amount of mercury-containing sludge has been generated along with the development of mercury-containing gas fields.Mercury and its compounds are highly toxic,mobility,and bioaccumulative,and can damage the environment,endanger the human body,and corrode equipment.Therefore,the mercury-containing sludge in the gas field must be disposed of properly.However,the treatment and technical research on mercury-bearing sludge in the gas field is still immature and lacks theoretical and engineering application experience.So,this paper takes the mercury-containing sludge from KS gas field as the research object,and carries out research on the mercury-containing sludge treatment process in the gas field,which is of great significance for the efficient development of the mercury-containing gas field,the protection of human health and the environment and so on.For the production,characteristics,and process adaptability of mercury-containing sludge from the KS gas field,the overall plan for disposal by a third-party recycling unit after dehydration reduction using the "chemical conditioning-mechanical dehydration-drying"process was selected.By comparing the sludge conditioning agent,concentration,dehydration,and drying,it was determined that the mercury sludge treatment in the KS gas field uses the"chemical conditioning-gravity concentration-decanter dewatering-hollow paddle-type drying machine drying process".The moisture content of the treated sludge was controlled at 40%.In order to understand the sludge characteristics and provide data support for subsequent sludge treatment,the mercury-containing sludge in the KS gas field was taken as the research object,and its yield,physicochemical parameters and particle size distribution were measured.The results showed that the sludge yield was low,the mercury content was high and large fluctuations,dehydration and harmlessness are difficult.The mercury-containing sludge production in the KS gas field is 40m3/d(water content>99%),the absolute dry weight is 92.5-255.6kg/d;the mercury content is 115-585mg/kg.The sludge has a high moisture content,a low relative density,a small particle size,a large sedimentation ratio,a high volatile solids content,and a lot of poisonous and harmful substances in the sludge exceeded the standard.The experimental study on the mercury form and stability of mercury-containing sludge showed that the total mercury content in the sludge was between 115-585 mg/kg,and the content of Hg2+ was the highest,accounting for 82.87%～95.21%,and it contained very little The highly toxic MeHg does not contain EtHg and PhHg.When the sludge drying temperature is less than or equal to 85℃,the mercury content in the sludge remains stable;when the drying temperature is higher than 85℃,the mercury content in the sludge will decrease with the disappearance of the attached body.In order to reduce the treatment of mercury-bearing sludge,sludge conditioning,centrifugation,and drying experiments were carried out on the mercury-containing sludge from the KS gas field.The sludge conditioning agent was APAM-1800 with a dosage of 25 mg/L(it’s mass fraction is 0.1%),and its additive cost is 0.528 million/a.The reasonable rotation speed range of the centrifuge is 2500～3000r/min,and the sludge drying temperature should be 80℃.According to the basic data of the design,the mercury sludge treatment process scheme and device design for the KS gas field have been completed:including sludge collection and concentration,dehydration and drying,tail gas treatment,packaging transport,and sewage return.The unit design feed volume is lm3/h(Water content>99%),the moisture content of the sludge at the outlet of the dryer was 40%,and the sludge weight after treatment was 0.32t/d.And completed the selection of key equipment,such as decanter centrifuges and paddle dryers for mercury-containing sludge treatment equipment.After accounting,the total project investment is 11.625 million yuan,the annual operating cost is 1.129 million yuan,and the annual disposal fee for sludge is 5.28 million.The research results of this dissertation can effectively treat mercury-containing sludge in KS gas field with high water content and high mercury content,which has certain practical application value.