燃气门站调压过程中水合物防治研究

Research on Prevention and Control of Hydrate Formation during Pressure Regulation of Gas Gate Station

通过改变甲烷、乙烷、丙烷、异丁烷的摩尔分数,分析研究燃气组成对水合物生成条件的影响规律。针对某城市燃气门站2017—2018年出现的冻堵情况,对水合物的生成进行分析。使用HYSYS软件分别建立燃气门站调压计算模型、防治水合物所需的甲醇水相质量分数计算模型,对某城市燃气门站的调压过程进行模拟,研究调压过程中水合物防治。研究结果表明:燃气组成对水合物生成条件存在一定的影响,异丁烷、丙烷对水合物的生成温度有较大影响,且异丁烷影响程度大于丙烷,甲烷、乙烷的变化对水合物生成温度无明显影响;随着压力的升高,燃气组成变化对水合物生成温度的影响相对减弱。研究了通过HYSYS计算燃气调压过程防治水合物生成甲醇注入量的方法,即计算防治水合物生成的甲醇水相质量分数并根据甲醇水相质量分数计算总注入量。通过该方法计算得到某燃气门站调压过程中甲醇水相质量分数为44.5%~49.8%,甲醇的注入量为2.42×10^-4~3.00×10^-4 L/m^3。调压过程压力从3.95 MPa至降2.10 MPa、调压前温度为-6^-10℃时,随着水露点的降低,所需甲醇的量减少,水露点每降低1℃,甲醇的注入量可减少0.05×10^-4~0.07×10^-4 L/m^3。当水露点降至比调压前温度低5~6℃时,调压过程无液态水凝析,因此无需计算甲醇注入量。

By changing the mole fraction of methane,ethane,propane and isobutane,the influence of gas composition on the hydrate formation conditions was analyzed and studied.In view of the freezing blockage of a city gas gate station from 2017 to 2018,the formation of hydrates was analyzed.HYSYS software was used to establish the pressure regulation calculation model of the gas gate station and the mass fraction calculation model of methanol aqueous phase needed to control hydrate were respectively.The pressure regulation process of a city gas gate station was simulated to study the prevention and control of hydrate formation during the pressure regulation.The research results show that the gas composition has a certain influence on the hydrate formation conditions,isobutane and propane have a greater influence on the hydrate formation temperature,the influence of isobutane is greater than that of propane,and the changes of methane and ethane have no obvious influence on the hydrate formation temperature.With the increase of pressure,the influence of the gas composition change on the hydrate formation temperature is relatively weakened.The method of calculating the injection amount of methanol produced by hydrate prevention and control by HYSYS was studied,that is,the mass fraction of methanol aqueous phase for the prevention of hydrate formation is calculated and the total injection quantity was calculated according to the mass fraction of methanol aqueous phase.By this method,the mass fraction of methanol aqueous phase during pressure regulation of a gas gate station is 44.5%to 49.8%,and the injection amount of methanol is 2.42×10^-4 to 3.00×10^-4 L/m^3.When the pressure during the pressure regulation process is reduced from 3.95 MPa to 2.10 MPa and the temperature before the pressure regulation is-6 to-10℃,as the water dew point decreases,the amount of methanol required decreases.For every 1℃decrease in water dew point,the amount of methanol injected It can be reduced by 0.05×10^-4 to 0.07×10^-4 L/m^3.When the water dew point drops to 5 to 6℃lower than the temperature before pressure regulation,there is no liquid water condensation in the pressure regulation process,so there is no need to calculate the methanol injection.