纯氢与掺氢天然气节流特性及节流系数预测新方法

Throttling characteristics and throttling coefficient prediction of pure hydrogen and hydrogen-blended natural gas

依托天然气管道掺氢输送,可实现氢能的高效经济储运,天然气节流作为关键环节,掺氢将极大改变节流特性,从而影响管道安全运行。为此,采用数值模拟方法研究了纯氢与掺氢天然气节流特性,并在天然气节流系数经验公式的基础上,建立了三段式节流系数预测新方法。研究结果表明:①纯氢节流特性与以甲烷为主的天然气节流明显不同,纯氢表现为节流负效应;②不同掺氢比时,节流正负效应转变压力不同,天然气中掺氢不超过30%时,对混合气体节流效应转变压力影响较小,但氢浓度更高时,节流效应转变压力随之降低,直至氢浓度80%~92%左右时,气体此后均表现为节流负效应;③节流阀门开度随氢浓度增加而增加,以流量波动时阀门调节范围为限制,天然气掺氢浓度不宜超过30%;③天然气节流系数经验公式仅适用于氢浓度不超过30%的掺氢天然气,在此基础上修正,得到以氢气为主混合气的节流特性预测公式,根据掺氢比提出以0~30%、30%~80%、80%~100%的三阶段公式,可很好地估算纯氢与掺氢天然气节流特性及系数。结论认为,该研究成果可为纯氢与掺氢甲烷混合气体节流系数的估算提供依据,为氢气安全储运提供技术指导。

Hydrogen-blended transportation through natural gas pipelines can realize the efficient and economic transportation of hydrogen energy.Natural gas throttling is a key link,and its throttling characteristics are changed greatly by the blending of hydrogen into natural gas,and thus the safe operation of the pipeline is impacted.In this paper,the throttling characteristics of pure hydrogen and hydrogen-blended natural gas are studied by means of numerical simulation.In addition,a new three-stage throttling coefficient prediction method is established on the basis of the empirical formula of natural gas throttling coefficient.And the following research results are obtained.First,the throttling characteristics of pure hydrogen are obviously different from those of natural gas dominated by methane,and pure hydrogen shows a negative throttling effect.Second,the transition pressure of positive and negative throttling effects varies with the hydrogen blending ratio.When the hydrogen concentration in natural gas does not exceed 30%,it has less effect on the transition pressure of throttling effect of mixed gas,but when the hydrogen concentration is higher,the transition pressure of throttling effect decreases until the hydrogen concentration is about 80%–92%,and then the gas shows negative throttling effect.Third,the opening of a throttle valve increases with the increase of hydrogen concentration.Limited by the regulating range of the valve during flow fluctuation,the hydrogen concentration of natural gas shall not exceed 30%.Fourth,the empirical formula of natural gas throttling coefficient is only applicable to hydrogen-blended natural gas with hydrogen concentration not exceeding 30%.On this basis,the throttling characteristics prediction formula of the mixed gas dominated by hydrogen is obtained.According to the hydrogen blending ratio,a three-stage formula of 0–30%,30%–80%and 80%–100%is proposed,which can well estimate the throttling characteristics and coefficients of pure hydrogen and hydrogen-blended natural gas.In conclusion,the research results can provide a basis for the estimation of throttling coefficient of pure hydrogen and hydrogen-blended methane mixture and a technical support for the safe storage and transportation of hydrogen.