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Technology Considerations for Measurement of In-Plant Natural Gas Consumption

The control of in-plant natural gas consumption has become a critical component of strategic energy management measures in process industries. Better information about consumption patterns of natural gas flow to discrete combustion sources creates the opportunity to optimize combustion performance for peak efficiency.

By tracking natural gas, operators can identify combustion units – including boilers, furnaces, kilns and other equipment – that are more efficient and redirect processes accordingly. What’s more, strategic measurement of natural gas consumption can identify how much is being burned and emitted for reporting purposes.

Because gases are compressible, with volume dependent on the pressure and temperature at the point of measurement, tracking gas flow is challenging. Thermal dispersion flow meter technology is an important, yet often overlooked, means of achieving accurate gas flow measurement. While a number of flow meter technologies are commonly used, thermal dispersion mass flow meters can offer significant advantages over more traditional flow meters.

TECHNOLOGICAL CONSIDERATIONS FOR TRACKING NATURAL GAS

Thermal Dispersion Flow Meters

  • No additional instrumentation equipment needed
  • Easily measures low flow rates
  • Higher turndown capabilities
  • Simple installation using NPT connection, flange, compression fitting or retractable probe assembly
  • “Hot tap” installation doesn’t require shut-down
  • Virtually no pressure drop

Orifice Plate

  • High cost of additional instrumentation including temperature transmitter, pressure transmitter and other equipment
  • Differential pressure measurement requires a higher turndown ratio than actually required
  • Loss of signal at lower end of flow rate
  • Placement of unit downstream of pressure regulator can result in insufficient pressure drop and prevent accurate flow measurement

Vortex Flow Meter

  • Need for additional instrumentation including temperature and pressure transmitters
  • Need for smaller pipe size to create vortices complicates installation and may increase pressure drop

Turbine Flow Meter

  • Cleanliness of gas and moving parts in the gas stream limit applicability
  • Requires additional instrumentation for pressure and temperature correction

Ultrasonic Flow Meter

  • Often unsuitable for low-velocity applications, such as measuring natural gas flow to individual combustion sources
  • High cost
  • Additional instrumentation for pressure and temperature gauging is required

Coriolis Mass Flow Meter

  • Often require pipe size reduction to obtain desired range measurement
  • An expensive option for in-plant measurement of natural gas