Study On The Crystallization Process Of Sodium Chloride In Ethylene Glycol Desalting Flash Separator

In the development of deep water gas field, the salt content of the produced liquid is high, the glycol solution, which is returned from the pipeline, will contain some salt after absorbing some of the produced liquid. When the glycol solution contains a lot of salt, the salt is easy to be deposited on the inner surface of the container during the regeneration process, and the scaling phenomenon occurs, influencing the heat exchanger effects. Therefore, it is important to study the regeneration and desalination technology of ethylene glycol. The key of the removal of monovalent salts in ethylene glycol solution is to make high solubility salt reache over saturation, then the high solubility salt crystallize. Small crystal particles will be involved in the heating cycle pipeline, depositing and plugging device in heat exchange equipment. In order to avoid the formation of small crystal particles, in this paper, the crystallization process of sodium chloride in ethylene glycol solution was studied. On the basis of experimental research, introducing computational fluid dynamics method to simulate the crystallization process of sodium chloride in ethylene glycol solution of multi phase flow, predicting the particle size distribution of the crystals in the actual operation, and optimizing operation parameters. Based on the simulation of the particle phase volume fraction in the device flash separator, improving the internal structure of flash separator saving the experimental cost at the same time. The following several aspects of the study were carried out:(1) The solubility and solubility of sodium chloride in ethylene glycol solution were determined by laser method, the solubility and super solubility equation were obtained by fitting the experimental data with the Apelblat double logarithm empirical equation. Experimental data of metastable zone are obtained, the results show that the width of metastable zone decreases with the increase of the temperature, and increases with the increase of the initial concentration, in ethylene glycol removal of monovalent salt process, temperature control in between 402.15-417.15K and initial concentration (amount of sodium chloride dissolved per 100g of glycol) control in 4.5?7g/100g ethylene glycol is more appropriate.(2) Using ethylene glycol monovalent salt removal device, the kinetic data of the crystallization of sodium chloride in ethylene glycol solution were obtained by batch dynamic method. The method of moments is used to calculate the particle number balance equation, and the experimental data are fitted to obtain the nucleation rate and growth rate equation of sodium chloride in ethylene glycol solution. The effects of temperature, the degree of saturation and the density of suspended particles on the crystallization process were analyzed and discussed, the results show that to improve the nucleation rate and growth rate of crystallization temperature and supersaturation can increase the crystallization of sodium chloride.(3) Based on the experimental results, the equation of particle number balance for the crystallization of sodium chloride in ethylene glycol solution was solved by the method of grouping. Derived and associated sodium chloride crystallization process nucleation rate and growth rate with mass transfer model, simulating the particle phase volume fraction and crystal size distribution in flash separator crystallization process.(4) Based on the establishment of ethylene glycol removal monovalent salt device flash separator crystallization process simulation model, the effect of various operating parameters on the size distribution of the final product of the crystallization process was investigated and the reasons are analyzed theoretically. By comparing the optimal operating parameters, optimizing operating parameters. The crystallization temperature is 412.15K, feed concentration is 6.0%, feed flow rate is 0.028m/s. By simulating particle phase volume fraction in flash with different separator internal structure, improving the internal structure of flash separator. In order to avoid small crystal particles involving in the heating cycle pipeline, depositing and plugging device in heat exchange equipment.