Research On The Cause Of Foaming In MDEA Solution Of Desulfurizer For High-sulfur Natural Gas

Natural gas,as a clean and efficient energy sources,the proportion in the energy mix of China is increasing day by day.Our country has gigantic quantities of high sulphurous natural gas,therefore,the exploration and purification treatment technology get rapid development in recent years.Aqueous methyldiethanolamine(MDEA)solution,which has the advantages of negligible corrosion,stabilization,relatively low reaction heat,and highly selective absorption of H2S from a gas stream mixture with CO2,is widely used as a desulphurization agent in the purification plant.However,during the operation process,the foaming of the amine liquid caused by metamorphic pollution is serious.The according problems appear,such as absorbent loss,pipeline corrosion,decreased hydrocarbon yield and fluctuating operation parameters.The issue has become one of the major problems in the purification plant.The pollutant composition in the lean amine from Zhongyuan oil field Puguang purification plant was analyzed.Associating with the component analysis of the feed gas,supplemental water,fresh MDEA material,and MDEA-O2/CO2 degradation of simulated experiment,it provided the type and source of contaminations in this paper.The results showed that F-,Cl-,Br-,SO42,Na+,Ca2+,K+,Mg2+,Sr2+ were mainly controlled by formation water,that a portion of Ca2+,K+,Na+,Cl-,SO42-came from fresh MDEA material,and there were very small amounts of Ca2+,F-,Cl-,SO42-deionized water,that Fe3/Fe2+ were mainly due to corrosion of desulfurization equipment.The test results also showed that CH3COO-,HCOO-,diethanolamine(DEA),1-(2-hydroxyethyl)-4-methylpiperazine(HMP),ethylene glycol(EG),N,N-bis(2-hydroxyethyl)glycine(Bicine),N,N-dimethylethanolamine(DMEA),triethanolamine(TEA)et al were the degradation products of MDEA,that a portion of HCOO-,diethlaminoethanol et al were caused by MDEA material.Solid suspended particles were mainly produced by corrosion of equipments and pipelines,and it existed in the form of FeS mostly.Furthermore,the suspended solids also had MDEA,alkanol amine sulfuric acid esters,amides,amines,aliphatic ethers,polyuria and so on.The foaming ability and foam stability were valuated with the foam height and the foaming break time,respectively.Through the single-factor experiments,it was found that the concentration of these negative ions,such as F-,CH3COO-,C2O42-,S2O32-et al,exerted a depressant action on the foam formation of the 50 wt%MDEA solutions,that activated carbon,FeS,suspended particles,bicine,TEA,EG,DMEA,HMP and other degradation products had exacerbated foaming in alkanolamine desulfurizing solution.When analyzing orthogonal experimental results with grey relational analysis,it showed that the relative importance of factors for foaming ability of MDEA solution,from most significant to least significant:Fe2+,TEA,Bicine,Ca2+,DEA,Mg2+,DMEA,n-dodecane,EG,Sr2+,activated carbon and FeS.And bicine had a serious effect on the foam stability of MDEA solution,then in turn were Fe2+,TEA,Ca2+,DEA,HMP,n-dodecane,Mg2+,DMEA,EG,activated carbon,Sr2+ and FeS.According to the results of single-factor and multiple factors experiments,the main causes for foaming of MDEA solution were obtained.The knowledge acquired will subsequently be used to provide a basis for developing corresponding countermeasures for foaming control.