Besides air and single gases, such as O2, N2, H2, etc., there are many gas mixtures being measured and controlled on a daily basis in different industries. One of the most common ones is natural gas used as a fuel or even biogases from decomposition of waste and organic material. There are also gases that are measured to control emissions or as part of environmental laws and restrictions.
- NATURAL GAS: The cleanest burning fossil fuel, natural gas trails electricity as the second most used energy source in industry. Industrial demand accounts for 40 percent of total natural gas demand, the highest of any sector. With a multitude of industrial uses, natural gas is consumed primarily in pulp and paper; metals manufacture; power generation; petroleum refining; stone, clay and glass manufacture; chemicals production; plastic resin production; and food processing.
Natural gas flow at a gas production plant is monitored to provide flow measurement from each individual well. The main custody transfer meter is positioned downstream from where the flow from individual lines is combined. See also liquified gases.
- DIGESTER GAS FLOW (BIOGAS): In the anaerobic decomposition process, organic matter is converted into stable solids and energy-rich gas, mainly methane (60%) and carbon dioxide (40%). A combustible hydrocarbon of high fuel value, methane can serve as a fuel for in-plant heat exchangers, blower engines or other systems, marketed to the local industrial community, or burned off.
Safe and reliable flow measurement is essential in the collection, disposal or re-use of methane gas. Because methane is highly combustible, flow instrumentation must be certified for operation in these hazardous locations.
- FLARE STACKS, EXHAUST & WASTE GAS FLOW: Industrial waste exhaust gases are present in a wide variety of compositions from benign to toxic. Measurement of the flow of these later gases is often required for reporting environmental emissions, including flared hydrocarbon gases. Off-gases are vapors emitted from extraction and treatment systems that are discharged directly to the atmosphere, captured or destroyed.
Thermal dispersion flowmeters are ideal instruments for flare flow measurement due to low flow sensitivity and high turndown. Consideration must be given to changes in gas composition, abruptness of flow change, low pressures, and a wide range of velocities.