Laval喷管内天然气低温脱除硫化氢机理

Removal mechanism of hydrogen sulfide from natural gas at low temperature in Laval nozzle

为了揭示低温条件下天然气中硫化氢气体超声速凝结特性,为实现天然气超声速旋流分离技术在天然气脱硫化氢领域的应用提供理论依据,建立了甲烷-硫化氢双组分气体超声速凝结流动数学模型,对Laval喷管内不同组分比例条件下甲烷-硫化氢双组分气体凝结流动进行了数值模拟,得出了Laval喷管内温度、压力、速度、成核率、液滴数目、液滴半径、液相质量分数的分布情况。结果表明,随着入口硫化氢含量的增加,入口过冷度增加,更容易达到凝结所需要的极限过冷度,成核发生位置越靠近喉部,且成核区间变窄,极限成核率增大;硫化氢气体凝结释放的潜热对流场产生影响,使得马赫数和过冷度略有降低,之后几乎保持稳定至出口;入口硫化氢含量较高时,硫化氢液滴半径较大,Laval喷管出口液相所占比重较大;而当入口硫化氢含量较低时,液滴半径明显减小,Laval喷管出口液相硫化氢所占比重几乎为0,硫化氢的脱除效率较低。

In order to reveal the supersonic condensation characteristics of hydrogen sulfide gas in natural gas at low temperature and provide theoretical basis for the application of supersonic cyclone separation technology in the field of hydrogen sulfide removal from natural gas,a mathematical model for supersonic condensation flow of methane-hydrogen sulfide binary gas was established,and the condensation flow of methane-hydrogen sulfide binary gas in Laval nozzle with different proportions of components was carried out. The distributions of temperature,pressure,velocity,nucleation rate,number of droplets,radius of droplets and mass fraction of liquid phase in Laval nozzle were obtained by numerical simulation. The results show that with the increase of hydrogen sulfide content in the inlet,the inlet supercooling degree increases,and it is easier to reach the limit supercooling degree required for condensation. The closer the nucleation location is to the throat,the narrower the nucleation interval,and the higher the limit nucleation rate. The latent heat released by hydrogen sulfide gas condensation has an effect on the flow field,which makes the Mach number and supercooling degree decrease slightly,and then almost remains stable to the outlet.When the inlet hydrogen sulfide content is higher,the radius of hydrogen sulfide droplets is larger,and the proportion of liquid phase at the outlet of Laval nozzle is larger;when the inlet hydrogen sulfide content is lower,the radius of liquid droplets decreases significantly,and the proportion of liquid hydrogen sulfide at the outlet of Laval nozzle is almost zero,and the removal efficiency of hydrogen sulfide is lower.