Study On Carbon Dioxide Snowed Separation Based On Cellular Automata Method

With the application of carbon dioxide（CO₂）flooding tertiary oil recovery technology and the development of high CO₂content natural gas fields,the proportion of acidic natural gas containing CO₂is increasing in China.If not treated,it will not only cause energy waste,but also aggravate the greenhouse effect when a large amount of CO₂is discharged into the atmosphere.In order to overcome the disadvantages of existing decarbonization methods,this study intends to use the characteristics of CO₂condensation to achieve the separation of CO₂"snowed"in natural gas,which can not only obtain purification gas that meets the requirements,but also realize the capture and recovery of CO₂products.The process of CO₂condensation at the macro scale is determined by the growth of numerous mesoscopic CO₂crystals.Based on investigation of the research,this paper studied the characteristics of CO₂snowed separation at the mesoscopic scale by using the method of cellular automata:First of all,we studied the process of crystal growth of diffusion,phase transformation,nucleation and mass physical process.Crystal growth of CO₂in the gas phase is the nature of sublimation process adsorption flow of particles in the crystal surface roughness is greater than the crystal particles leave the flow of the crystal surface.The Wilson-Frenkel crystal growth model in accordance with CO₂gas phase of crystal growth.Secondly,the cellular automata method is chosen as the mathematical method to simulate the growth of CO₂crystals.In order to solve the crystal growth problem,the spatial division type,grid type and neighborhood type of Cellular Automata were selected,and Netlogo software was used to program the mass transfer diffusion and crystal growth problems involved.Through calculation,the growth morphology and velocity data of H₂O crystal and CO₂crystal are obtained,and the conclusion of the simulation data is consistent with the experimental data in other literatures.Thus,the crystal growth simulation model of cellular automata method is obtained.After CO₂crystal growth model based on the established,by changing the parameters,analysis of temperature,pressure,supersaturation of CO₂and sensitivity to draw the influence of crystal growth.The results are:the impact of temperature,pressure change for CO₂crystal growth is very small,and the saturation effect on CO₂crystal growth is exponential,.Increasing the concentration of CO₂and reducing the environment temperature are reasonable to increase separate efficiency.Finally,after analyzing and calculating the separation intervals at 0.5MPa,1MPa and 2MPa,the Cellular Automata was used to simulate the crystal growth model and analyze the growth rate and size of CO₂crystal,and the technical conditions for the separation of CO₂snowing under such pressure were obtained.The mathematical model of CO₂snowing separation was obtained by data fitting.The average relative error was 4.13%when the calculation results of the mathematical model were compared with the existing experimental data.It is considered that the application of this model to the simulation calculation of the effect of snow separation is feasible,and the prediction and control of the condensation process in the CO₂snow separation technology are realized.