| With the gradual exploitation of natural gas,the presence of mercury is detected in some natural gas fields.After the high-mercury gas field is mined,it must first be transported to the natural gas processing plant for dehydration and dehydrogenation treatment,and the low-temperature separation process is adopted.After the throttle valve,the pressure is rapidly reduced,generating a large amount of cold energy,reducing the temperature of the natural gas to below-15?.The drastic changes in the temperature and pressure of natural gas in the low temperature separation process cause large amounts of mercury to be precipitated from the natural gas.After long-term operation,a large amount of mercury accumulates at the bottom of the vessel and at the corners of the container.During the maintenance of the equipment,it is difficult for the operator to avoid contact with the air in the container.If exposed to high mercury content,it is extremely vulnerable to the safety of workers.The development and research of mercury-cleaning equipment for mercury-contaminated equipment in China is not yet mature.Therefore,this paper takes the mercury pollution device of KS gas field as the research object,conducts the development of mercury removal agent and performance evaluation experiment,and develops the high efficiency of mercury pollution device for mercury-containing gas field.The amalgamation agent is of great significance for the cleaning of mercury-contaminated equipment in mercury-containing gas fields and the safety protection of maintenance personnel.This paper combines the actuality of natural gas treatment plant engineering to analyze the cleaning process of mercury-contaminated equipment,including spray cleaning method,high-temperature steam cleaning method,chemical circulation cleaning method,peelable coating method and chemical wiping method,etc.The characteristics of the pollution device are finally selected as the cleaning process of the mercury pollution device.The cleaning efficiency of the mercury removal agent is very important in this process.After cleaning,the mercury content inside the container should be less than 20vg/m3.In order to ensure the mercury removal effect of the chemical cycle cleaning process,the KS gas field mercury pollution device was selected as the research object,and the iodide and sulfide were selected for the mercury removal agent development experiment.The experimental results show that the iodide is more efficient than the mercury sulfide.,the reaction is faster,less pollutants are introduced,and it is more suitable as the main component of the mercury amalgamating agent;the potassium iodide concentration is preferably 10%,that is,the added dose of potassium iodide relative to mercury is 16.7g/g(KI/Hg);The concentration is preferably 3%,that is,the dosage of potassium iodide relative to mercury is 5 g/g(I2/Hg);the cleaning temperature is preferably 50?,and the temperature is too high or too low,which leads to a decrease in cleaning efficiency;the concentration of potassium iodide and elemental iodine The ratio needs to be higher than 2:1,otherwise it will cause the elemental iodine not to dissolve completely,which will affect the mercury removal effect.In order to evaluate the practical application effect of the mercury amalgam,the indoor evaluation device was developed to simulate the mercury contamination device cleaning process of the treatment plant.The experimental results show that the mercury concentration in the gas phase after cleaning can be less than 20?g when the dilution ratio of the mercury amalgam is less than 1:20./m3,and the amount of change is small;when the dilution ratio is higher than 1:20,the mercury removal effect is gradually weakened due to the low concentration,which cannot meet the cleaning requirements.Optimize the dilution ratio of the amalgam to 1:10?1:20.After 8 hours of cleaning,the mercury concentration in the gas phase can be reduced to 12-18?g/m3;The amalgamation agent and Amulan DF-30,The combination of SAS60,AES and AEO-9 surfactants has no negative effect on mercury removal.Among them,Amulan DF-30 and AEO-9 surfactants can improve the mercury removal effect(will be wrapped with mercury).The oil concentration and scale of the pollutants are removed.After cleaning,the mercury concentration can be reduced to 6?10?g/m3 and 8?12?g/m3,respectively,which can be used as a component of the compound type amalgam.In order to ensure the feasibility of the mercury amalgam in practical applications,the corrosivity is evaluated.The main materials of the inner wall of KS treatment plant are 22Cr,316L stainless steel,Q345,09MnNiDR,Q245,16Mn,Q235B and 20#steel,which are analyzed by weight loss method and scanning electron microscopy.The experimental results show that 22Cr and 316L are corrosion resistant.The strongest,after 15 days of soaking,the surface is still smooth and flat,no obvious corrosion phenomenon,can adapt to long-time cleaning operation under high concentration;Q345,09MnNiDR,Q245 three materials are less resistant to corrosion than 316L,but after soaking for 7?15 days The weight loss rate of the hanging piece can be kept in a lower range,the surface is relatively flat,and some small etch pits exist.In practice,a high concentration of amalgam can be used for a short time(less than 3 days)of mercury cleaning operation;16Mn,Q235B,20#The three materials of steel have the weakest corrosion resistance.After 7?15 days of immersion,the weight loss rate is high.There are some etch pits on the surface,and the size is obviously larger than other steel materials.In practical applications,it is recommended to dilute the mercury amalgam for a short time(Mercury handling for less than 3 days).In order to ensure that the waste liquid generated after mercury removal has no pollution to the environment after treatment,the chemical sedimentation method is used to carry out indoor experiments on the waste liquid after mercury removal.The experimental results show that the pH is adjusted to 8?8.5,2#heavy metal by successively adding NaOH.Collecting agent to 10 mL/L(1 minute stirring),polyaluminum ferric chloride(PAFC)to 100 mg/L(stirring for 2 minutes)and anionic polyacrylamide(21 million)to 3 mg/L(stirring for 3 minutes),The concentration of mercury in the waste liquid can be reduced from 10000 ?g/L or more to less than 50 ?g/L,and the waste liquid can be sent to the gas field sewage treatment unit after being treated. |
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