二甲醚(DME)掺入液化石油气(LPG)中能加速储气罐橡胶密封圈的老化, 存在严重安全隐患, 直接危害消费者安全和利益, 国家明令规定禁止向LPG中掺入二甲醚等化学品作为液化气商品出售, 因此实现LPG中DME含量的快速分析极其重要。 提出一种快速测定LPG中DME含量的新方法, 解决了液化气成分快速测量技术难题。 实验设计和制造了一套精确配制DME液化气溶液的装置和一套基于近红外光谱技术快速测定LPG的分析系统。 该分析系统耐压3.5 MPa, 可方便与高压钢瓶连接, 实现了液化气直接快速测量。 收集了市场上LPG-1(胺前液化气), LPG-2(焦化液化气), LPG-3(脱硫醇后液化气)LPG-4(沧炼催化液化气)共四种液化石油气, 采集其近红外光谱作为背景子空间, 采用称重法配制DME浓度范围1.0%～45.0%。 采用斜投影算法从LPG溶液近红外光谱中提取出不同浓度LPG溶液中DME纯信号, 　使用DME纯信号强度I与浓度c建立标准曲线, 其线性相关系数为0.999　4。 外部验证结果表明, 方法相对误差小于2.0%。 该方法具有操作简单, 快速、 无需建模等优点。

A new analytical method of analyzing dimethyl ether (DME) content in liquefied petroleum gas (LPG) is proposed in this paper. An unsolved problem about quick detection of the composition of LPG has been settled with this method. A set of precise preparation apparatus for DME/ LPG solution and a set of quickly analytical system of LPG based on near infrared technology were designed. The analytical equipment can be conveniently connected to the sampling cylinder because it can bear 3.5 MPa pressure. Oblique projection algorithm was used to separate the pure spectra of DME from that of the LPG’s solutions. The standard curve of the concentration of DME (c) has been built by using the Intensity (I) of pure signal of DME in the LPG solution and the concentrations. The correlation coefficient of the equation is 0.999 4. The result of external validation shows that the relative error is less than 2.0%. The new method has the advantages such as fast, easy and noneed of expensive multivariate modeling.