| The alkanolamine solvent method is the most commonly desulfurization method in natural gas purification system recently.The methyldiethanolamine(MDEA)solution is widely used as a desulfurization solvent because of its high desulfurization efficiency,good thermal stability and low energy consumption of regeneration.In the long-term use of MDEA solution,the accumulation of impurities,degradation of foaming and deterioration,resulting in a significant decrease on desulfurization efficiency and unqualified temperament.This study focused on severe deterioration of MDEA solution in a purification plant of northern Shaanxi,and there is no rapid and accurate detection and evaluation methods in the production process,lack of purification measures for the deep removal of heat-stable salts,and the reduce of deacidification capacity ability caused by the continuous accumulation of organic impurities.Therefore,the deep purification of MDEA desulfurization solutions has been carried out,and the research results as follows.(1)Established a set of qualitative analysis and quantitative detection methods for all kinds of impurities in MDEA fluids.The degree and deterioration cause of amines are evaluated with turbidity,viscosity,chromaticity,p H,conductivity,solid suspensions,heat-stable salts and organic impurities,etc.and use the self-designed indoor simulated deacidification apparatus to evaluate the effect of deep purification of MDEA solutions.In addition,the HYSYS software was used to simulate the desulfurization system,the model correlation between the indoor deacidification ability of the MDEA solution and the temperament of the industrial product was established by combining the indoor deacidification and on-site production.Furthermore,the bridge between the experimental results and industrial parameters is built.(2)A new method of amphoteric ion exchange resin was proposed on the basis of a single anion exchange resin for the deep purification of amine liquid.A strong base weak acid PS-3 amphoteric resin was prepared,and its pore structure,surface area,exchange capacity and FT-IR were also characterized.The isothermal adsorption characteristics and adsorption selectivity of heat-stable salt ions in amine liquids were studied by using the resin.Moreover,the adsorption thermodynamics and adsorption kinetics on the PS-3 resin were studied with Fe3+ and C2O42-as the object.The results show that PS-3 resin has a large adsorption capacity and good ion adsorption performance.Its isothermal adsorption law is consistent with the Langmuir model,and has high selectivity for high-valent ions and organic acid ions.Adsorption kinetics and thermodynamics indicate that ion adsorption on PS-3 resin is an exothermal spontaneous process with external diffusion as a control step and reduced the confusion,and its adsorption kinetic behavior is accordance with the Lagergren's pseudo-second model.(3)Using decompression distillation method to deeply purify the deteriorating MDEA solution.The purification effects of vacuum degree,heating temperature and distillation time on organic impurities was investigated.The order of MDEA recovery rate was optimized by response surface analysis method,which was distillation time > heating temperature > system vacuum degree.The optimum conditions are the system vacuum degree of 90.3k Pa,the heating temperature of 150°C,and the distillation time of 17.31 min.The MDEA yield was94.72%.Under this condition,the appearance of MDEA solution was significantly improved,and the recovery was close to the predicted value.In addition,a decompression distillation simulation based on Aspen Plus was also carried out.The indoor experiments were designed and validated by DSTWU and Rad Frac module,respectively.The results illustrate that the decompression distillation simulation was also have a good reliable to deal with the deep purification of large quantities of MDEA solution. |
PDF Full Text Request