多气源管网天然气发热量赋值计算方法研究

Research on Calculation Method of Natural Gas Calorific Value Assignment in Multiple Gas Source Pipeline Networks

为解决浙江省多气源环状天然气管网在线气相色谱仪损坏或未配备色谱仪的情况下,无法与下游用户进行能量计量贸易交接的问题,研究出一套天然气能量赋值算法,替代设备无法正常工作时给出合理的天然气热值。在直管段和多支路的不同管网结构类型情况下,通过拟合管段压力和管段流量之间的经验公式,建立各相连管段的流量与压差之间的关系,并建立站点气体组分与上下游管道两端站点压差和气体组分之间的关系,从而可以实时计算得到天然气热值。根据天然气能量间接测定法,通过溯源上下游的方式,在已知相邻站点压力、流量和组分的情况下,能够推算出本站天然气发热量。选取了浙江省典型天然气站场对本赋值算法进行验证,与实际热值测量值相比,计算值偏差在0.6%以内,满足GB/T 18603中A级计量站的赋值发热量最大允许误差的要求,能够保障贸易计量工作的顺利开展。

In order to solve the problem of energy measurement and trade handover with downstream users in Zhejiang Province's multi source circular natural gas pipeline network when the online gas chromatograph is damaged or not equipped with a chromatograph,a natural gas energy assignment al-gorithm has been developed to provide a reasonable natural gas calorific value when the equipment cannot work normally.In the case of different pipe network structures in straight and multi branch pipe-lines,the relationship between the flow rate and pressure difference of each connected pipe section is established by fitting the empirical formula between the pressure of the pipe section and the flow rate of the pipe section.The relationship between the gas composition at the station and the pressure differ-ence and gas composition at both ends of the upstream and downstream pipelines is also established,so that the natural gas calorific value can be calculated in real time.According to the indirect measure-ment method of natural gas energy,by tracing upstream and downstream,the heat generation of natu-ral gas at this station can be calculated when the pressure,flow rate,and composition of adjacent sta-tions are known.A typical natural gas station in Zhejiang Province was selected for validation of this as-signment algorithm.Compared with the actual calorific value measurement value,the calculated value deviation is within 0.6%,which meets the maximum allowable error of assigned calorific value for Class A metering stations in GB/T 18603 and can ensure the smooth progress of trade measurement work.