天然气管道输送混氢天然气的可行性

将氢以一定比例掺入天然气作为家用燃料使用，被认为是减少温室气体排放的途径之一，而利用现有发达的天然气管网输送混氢天然气（HCNG）至终端用户则被视为可行的方法；但由于氢气与天然气在物理化学性质方面存在着差异，HCNG有可能对燃气终端用户以及管道输送工况造成较大的影响。鉴于我国目前尚未出台HCNG作为燃料及其输送的相关标准，为此采用德尔布指数法、韦弗指数法、高沃泊指数与高热值法分别对天然气在不同混氢比下的燃气互换性和燃烧特性进行了评估分析，同时基于HYSYS软件和相似原理建立管道模型，分析了氢气的混入对天然气管道和压缩机运行工况的影响。研究结果表明：①随着混合气体中氢气体积分数的增加，燃具的热负荷下降，燃气的火焰传播速度急剧增大，燃具发生回火的风险增大，并以此确定对于天然气管道供应系统来说混氢天然气的最大混氢体积比不应超过27%；②氢气的混入虽然能提高管道的输气能力，但当管网和压缩机联合运行时其平衡工作点对应的压力和流量都将减小，反而会降低管道的输气能力。结论认为，该成果为天然气管道输送混氢天然气的可行性研究提供了基础数据。

Feasibility analysis on the transportation of hydrogen–naturalgasmixtures in natural gas pipelines

Hydrogen that is mixed with natural gas at a certain proportion is used as a domestic fuel, which is one of the ways to reduce greenhouse gas emission. And one feasible method is to use the existing developed natural gas pipeline networks to transport hydrogen–naturalgasmixtures (HCNG) to end-users. However, hydrogen and natural gas are different in physical and chemical properties, and HCNG may have greater negative effects on end-users and pipeline transportation conditions. So far, no any standard related to HCNG as a fuel and its transportation has been issued in China. To deal with this situation, this paper evaluated and analyzed the gas interchangeability and combustion characteristics of natural gas at different hydrogen mixing ratios by using the Delbourg method, Weaver method, Wobbe index, and calorific value method. In addition, a pipeline model was established on the basis of the HYSYS software and similarity principle, and the influence of hydrogen adding on the working conditions of natural gas pipelines and compressors was analyzed. And the following research results were obtained. First, with the increase of the volume fraction of hydrogen in HCNG, the thermal load of a gas appliance decreases, the flame propagation speed of gas increases sharply and the tempering risk of the gas appliance increases. And it is accordingly determined that as for natural gas pipeline supply systems, the HCNG's maximum hydrogen volume ratio shall not exceed 27%. Second, hydrogen adding can increase the gas transmission capacity of a pipeline, but the pressure and flow rate corresponding to its equilibrium operating point will drop when the pipeline network and compressors are operated jointly, which will lead to the reduction of gas transmission capacity instead. In conclusion, the research results provide the basic data for the feasibility study on the transportation of HCNG in natural gas pipelines.