Study On Centrifugal Separation Process Of Natural Gas Dewaxing

In recent years,several newly discovered gas field in Xinjiang belong to high wax gas field and the gas is so-called waxy natural gas.The waxy contained in the natural gas is detrimental to the process of exploitation,gathering and transportation and so on.For example,the wax blockage occurred in the process of de-hydrocarbon at low temperature may cause the shutdown of the natural gas treatment.At present,few studies are found on the natural gas dewaxing methods in the world,especially on centrifugal dewaxing technology for natural gas containing wax.The aim of this paper is to study the flow field distribution and gas-liquid separation characteristics during the centrifugal separation process for waxy natural gas.In order to obtain suitable gas-liquid separation conditions,the phase equilibrium of waxy natural gas is calculated and analyzed based on the gas-liquid phase equilibrium theory.Several groups of state equation are used to calculate hydrocarbon mixture phase equilibrium process in a commercial software-MATLAB,and the one with highest accuracy is selected.It is revealed that the suitable condition for separation of natural gas and wax droplets is on the temperature of 10~oC and pressure of 8 MPa.In order to verify the accuracy of the model,commercial software is used to simulate the internal flow field of the axial flow guide vane cyclone separator with the mixture of air and water as medium.The distribution of gas pressure,velocity and turbulence intensity as well as the trajectory of droplets with different particle sizes are analyzed.The separation efficiency and pressure drop under different inlet velocity and droplet size are obtained,and compared with the experimental results in the literature.The results show that the gas-liquid phase separation process can be simulated accurately in the use of the model established.The centrifugal separation process for waxy natural gas is simulated using the established model.The distribution of the wax droplets concentration is characterized and the separation efficiency in the separator is obtained.Meanwhile,the effects of droplet size,inlet velocity,droplet concentration and number of guide vanes on the separation performance are studied.The results are as follows:(1)the separation efficiency increases with the increase of droplet size,inlet velocity and droplet concentration,and decreases with the increase of blade number;(2)the separation efficiency,energy consumption and wear should be taken into consideration together in the design and selection of the separator.Finally,according to the structural characteristics of the axial flow guide vane separator,some theoretical models are selected to calculate the pressure drop,gas phase velocity and wax droplet separation efficiency in different areas of the separator.Compared the theoretical results with the simulation results,it can be seen that the theoretical values of gas phase velocity,cutting particle size and separation efficiency are in good agreement with the simulation values,while the accuracy of the theoretical values of pressure loss needs to be improved.