固体生物质燃料中氮的测定方法改进探讨

Discussion on the improvement of determination method of nitrogen in solid biofuel

固体生物质燃料及其原料中氮含量的准确测定,对于指导生物质燃料的生产及控制大气污染具有重要的意义。采用凯氏定氮法测定固体生物质燃料中氮含量时,样品的消化催化剂中含有硫酸汞和硒粉等有毒成分,其大量使用易导致环境污染的风险。探讨采用硫酸铜作为催化剂以替代硫酸汞与硒粉并将其用于消化固体生物质燃料样品,针对催化剂量及消化温度等条件进行试验,探讨消化温度与消化时间的关系、不同消化温度下检测结果的精密度、催化剂用量对检测结果的影响以及预烘干法对消泡的作用。通过对样品的含氮量进行国标方法及改进方法的对比测定分析,并对检测数据进行差异显著性统计量t值校验,证明2种方法的检测结果无显著差异。试验结果表明,固体生物质燃料样品经110℃预处理除去水分、以硫酸铜替代硫酸汞与硒粉作为催化剂、采用浓硫酸在390℃温度下进行消化时能缩短消化时间,且采用改进方法测定生物质中氮含量的结果符合国标方法对精密度的要求。

The accurate determination of nitrogen content in solid biofuel and its raw materials are of great significance to production of biofuel and control of air pollution.When the Kjeldahl method is used to determine the nitrogen in solid biofuel,the digestion catalyst of the sample contains toxic components such as mercuric sulfate and selenium powder,and its large-scale use has the environmental pollution risk.Copper sulfate was used as catalyst instead of mercury sulfate and selenium powder to digest solid biofuel samples,regarding to the catalyst dosage and digestion temperature,the experiment was done.The relationship between digestion temperature and digestion time,the precision of detection results under different digestion temperatures,the influence of catalyst amount on detection results and the effect of pre-drying on defoaming were discussed.Through the comparative analysis of national standard method and the improved method for the nitrogen content of the sample,the verification of difference significance statistics t-value for testing data was done,it was proved that there was no significant difference between the two methods.The results showed that the solid biofuel samples were pretreated at 110℃to remove water,copper sulfate was used instead of mercury sulfate and selenium powder was used as catalyst,concentrated sulfuric acid was used to digest at 390℃to shorten the digestion time,the results of the improved method for the determination of nitrogen content in biofuel could meet the precision requirements of the national standard method.