Flow Control, Flow Control March 2019

Application Corner By David W Spitzer Chemical composition of natural gas A game of alphabet soup S ometimes the obvious is not quite evident Have you specified a flowmeter for natural gas service in your career I suspect that a few individuals routinely specify natural gas flowmeters while many others have specified a handful of such flowmeters in their careers and the remainder has not specified any flowmeters for natural gas service Regardless of where you fall in this spectrum consider how you would describe the process fluid in your specification The obvious choice would be natural gas and you would be in good company if this was your response However natural gas is not a pure substance but rather a naturally occurring gas that largely contains methane but can also contain significant amounts of other combustible and inert gases The North American Energy Standards Board NAESB suggests that a typical natural gas composition consists of 949 percent methane 25 percent ethane 16 percent nitrogen 07 percent carbon dioxide 02 percent propane 003 percent each of iso butane and normal butane 01 percent oxygen 001 percent each of iso pentane normal pentane and hexanes and a trace of hydrogen However NAESB suggests that these percentages can vary considerably such as 87 to 96 percent methane 18 to 51 percent ethane or 13 to 56 percent nitrogen In short the chemical composition of natural gas at a given location is determined by the nature of its source and treatment Further the composition of the natural gas can be different than typical NAESB natural gas and can vary over time as its source ages and or changes Therefore its physical properties such as its density heat content and thermal properties can be different and vary over time This reality begs one to question whether these potentially large differences from a typical NAESB composition can affect the measurement of the flow of natural gas Read more on this topic next month FC David W Spitzer is a principal at Spitzer and Boyes LLC which offers engineering focused market research writing editing white papers strategic marketing consulting distribution consulting seminars and expert witness services for manufacturing and automation companies Spitzer has written more than 400 technical articles and 10 books about flow measurement instrumentation and process control He can be reached at 845 623 1830 or via spitzerandboyes com 8 March 2019 Flow Control