Research On Vocs Treatment Technology In The Cold Drum District Of A Coking Plant

Nowadays,people are paying more and more attention to the living environment,the desire for the living environment of the clear water and blue sky is getting higher and higher,and the official department has also formulated more and more strict exhaust emission standards.For VOCs tail gas emissions,some places strictly require that the content of non-methane total hydrocarbons[NMHC]in tail gas emissions is less than 50mg/m3.In view of this,many coking plants have begun to transform or rebuild their own exhaust gas purification facilities in order to be able to meet the stringent exhaust emission standards of the national and local governments.This subject was researched and developed under this background,and it came from the actual engineering project of VOCs treatment in the cold drum area of a coking plant.The plant area was originally equipped with an exhaust gas treatment device,which used activated carbon adsorption,and there was no front-end pretreatment process and activated carbon regeneration process,resulting in activated carbon adsorption saturation,frequent replacement,and high operating cost.In view of the shortcomings of the original treatment process,at the same time referring to the process provided by Party A,the original treatment process is optimized and reformed to reduce the system operating cost and ensure that the emissions of the exhaust gas purification system reach the local environmental protection emission limits for a long time.After in-depth research,the current exhaust gas purification system process is "collection of gas collecting tank+oil washing+acid washing+alkali washing+activated carbon absorption/desorption".The use of "collecting gas tank" can mix the exhaust gases uniformly,so as to treat them uniformly;the pretreatment process "oil washing+acid washing+alkali washing" can not only remove a part of VOCs,but also remove other harmful gases such as ammonia and hydrogen sulfide in the tail gas.,So that the subsequent adsorption process can be more durable;the "activated carbon absorption/desorption" process can not only ensure that the exhaust emissions meet the standard emissions within a certain period of time,but also can be rotated to regenerate it,extending the use time of activated carbon and making the entire exhaust The processing system is more stable and efficient.This project is a new project.After dismantling the original exhaust gas treatment system,a new and efficient exhaust gas purification system will be built on the original site.During the process design,the main process equipment oil washing tower and activated carbon adsorption/desorption equipment were studied in detail.The oil washing tower can significantly reduce VOCs in the exhaust gas,and a total of 3 layers of spraying are provided to make the absorption liquid more evenly dispersed in the tower body and improve the absorption efficiency of VOCs.Each layer is filled with 0.5m tower-high Raschig ring packing.Effectively enhance the gas-liquid mass transfer efficiency and prolong the gas-liquid contact time.Seven 120° nozzles are arranged above each layer of packing to promote the absorption liquid to be more evenly dispersed on the packing.The top defogger can effectively capture the tail gas away of washing oil.After the redesign of the activated carbon adsorption equipment,a desorption regeneration process is also added.After the activated carbon is saturated,the activated carbon layer is desorbed and regenerated using 164 ℃ superheated steam in the plant area,so that the activated carbon can be recycled until the service life of the activated carbon is reached to reduce the replacement cost of activated carbon.After the equipment design is completed,the fluent software is used to simulate and optimize it.In contrast,it is found that the 45° conduit inlet flow channel can promote the exhaust gas to be more evenly distributed throughout the tower body,and the "wall flow"phenomenon is weaker,so this inlet channel is selected;And using ANSYS to verify the structure of the adsorption tower,found that the designed adsorption tower can meet the design requirements under various operating conditions.After the construction of the project was completed,the treatment of the exhaust gas purification system was debugged and verified,and it was found that the maximum processing capacity under actual operating conditions reached 7948m3/h,and the system(designed with a processing capacity of 10000m3/h)fully met the requirements.The oil washing system can effectively absorb and remove VOCs in the exhaust gas.After testing,the concentration of non-methane total hydrocarbons in the oil washing outlet pipe is reduced to 299.98mg/m3,compared with 870mg/m3 in the inlet pipe,the tail gas treatment efficiency reaches 65.52%,indicating that the basic Meet the design requirements;the activated carbon adsorption tower can efficiently adsorb VOCs in the exhaust gas,the minimum emission value is much less than 50mg/m3,the overall treatment efficiency of the system is 94.25%,and the single adsorption process can ensure that it is always within 120h(5 days)The discharge time for activated carbon desorption is 9 hours after reaching the standard discharge state,and it is blown through clean and dry hot air for 4 hours and then allowed to stand,so that the next time activated carbon is adsorbed for use.On the whole,the tail gas purification device designed this time basically meets the requirements of the VOCs tail gas treatment project in the cold drum area of the coking plant.