Model VCEM5100 - Flue Gas Flow Monitor

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The VCEM 5000/51000 represents the latest generation of CODEL’s uni ue flow monitors. These systems measure the velocity of stack gases using a highly accurate time of flight measurement that is derived from a cross correlation analysis of the infra-red emissions of the turbulent gas. Two robust infrared detectors are used for the prime sensing, mounted on the stack or duct typically 1m apart in the direction of flow. High efficiency air curtains are fitted to considerably extend the time between maintenance periods and window cleaning (typically 1 year).

  • Non-contact infra-red sensing
  • Continuous measurement
  • Suitable for hot and dirty gases
  • No limit on upper gas temperature
  • No moving components
  • High availability, low maintenance requirement

  • Large Combustion Plants
  • Small Combustion Plants
  • FGD (Flue Gas Desulphurisation)

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The VCEM 5000/51000 represents the latest generation of CODEL’s unique flow monitors. These systems measure the velocity of stack gases using a highly accurate time of flight measurement that is derived from a cross correlation analysis of the infra-red emissions of the turbulent gas.

Two robust infrared detectors are used for the prime sensing, mounted on the stack or duct typically 1m apart in the direction of flow. High efficiency air curtains are fitted to considerably extend the time between maintenance periods and window cleaning (typically 1 year).

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This technology offers significant benefits over other types of flow measurement devices.

  • Non contact technology enables operation on hot, dusty and aggressive gases
  • It measures directly the bulk gas velocity
  • No moving components delivering low maintenance, and high measurement availability
  • Can operate at gas temperatures in excess of 1000 deg C
  • Equipped with full high and low span automated span checks

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The VCEM 5100 is a standalone unit which can be easily integrated into an existing or proposed CEMS system. It includes a dedicated Data Dislpay Unit for local data interrogation.

The VCEM 5000 is a unit dedicated for use in a CODEL SmartCEM System where all the analysers communicate via a Station Control Unit (SCU). This exports data to the CODEL SmartCEM data logging system, which displays real time data and logs data for historical analysis and regulatory reporting.

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Computation of Total Pollutant Release
Legislation often demands that emission measurements are presented in mg/Nm3 where the expressed volume has been normalised to a standard temperature, pressure and oxygen concentration, and where the effects of dilution by water vapour have been removed.

To compute a measurement of the total pollutant release to atmosphere in kg/hr (or tonnes/annum), it is necessary to know:

  • The pollutant concentration in mg/m3 (mg per actual m3)
  • The hot gas flow in m/s
  • The cross sectional area at the point of measurement in m2

The total release is then calculated as follows:
Mass flow = Mass concentration x Gas velocity x Area of Duct

It is vital that all measurements are made on the same basis. Attempting to make this calculation using an actual hot wet gas flow in m/s and a normalized gas concentration in mg/Nm3 will produce significant errors.

The method used is similar in principle to the technique of flow measurement by the injection of chemical dye or radioactive tracers, where the velocity is derived from the transport time of the tracer between two measuring points a known distance apart. Instead of an artificial tracer being added, the naturally occurring turbulence of the gas stream is used as the tracer.

This flow turbulence causes fluctuations to occur in infrared radiation emitted by the gas. This continuously variable turbulent pattern is monitored by two infra red sensors mounted typically 1m apart along the direction of gas flow. An electronic correlation technique is used to continuously compare the two sensor signals to determine the time delay between them imposed by the gas velocity.



Typical signals from the sensors A and B are shown here. The signal from sensor B shows a strong similarity to that from sensorA but is delayed by a time t, the time taken for the gas to flow from point A to point B

Continuous determination of the sensor signal time delay by the signal processor unit produces a continuous measurement of gas velocity since:

  • Velocity V = L/t

L is the separation distance between the two sensors.

Receiver Unit

  • Operating Principle: Infrared correlation
  • Measuring units: m/s, m3 /s, Nm3 /s, kg/s, tonnes/annum (when connected to a CODEL SmartCEM system)
  • Detectors: Lithium tantalate pyroelectric
  • Receiver separation: 0.5 to 1m
  • For duct diameters: 0.5 to 15m
  • Accuracy: +/- 2% of measurement
  • Linearity: +/- 1% of measurement
  • Response Time: Minimum 10 seconds
  • Measuring Range: Fully selectable from 0-1 up to 0-50m/s
  • Resolution: 0.1 m/s
  • Drift: 0.1 m/s per month
  • Averaging: 4 rolling averages selectable from 10 seconds to 30 days
  • Calibration: Auto low and high span check (US EPA compliant)
  • Ambient Temperature: -20°C to +70°C
  • Flue Gas Temperature: 70°C minimum, No upper limit
  • Power supply: 48V DC from CODEL SmartCEM Station Control Unit (SCU)
  • Construction: Corrosion resistant epoxy coated aluminium housing sealed to IP66
  • Air Purge: Compressed air, 1 litre/sec @ 2bar

Signal Processor Unit (SPU)

  • Construction: epoxy-coated aluminium to IP67
  • Ambient Temperature: -20°C to +50°C
  • Power Supply: 48V DC supplied from CODEL SmartCEM Station Control Unit (SCU)

Outputs from SmartCEM SCU

  • Analogue outputs: 1 x 4-20mA current output as standard, isolated, 500Ω load max, fully configurable
  • Logic Outputs: 1 x volt-free SPCO contacts, 50V, 1A max, configurable as alarm 1 x volt-free SPCO contact, 50V, 1A max, for data valid signal

Compliances

  • EMC: 89/336/EEC directive compliant
  • Low Voltage: 73/23/EEC directive compliant
  • TUV Certified (QAL1): EN 15267 & EN 14181

Services

  • Power: Mains 110 / 230 VAC, single phase, 50/60hz
  • Air Requirement: Clean and dry compressed air, 1 litre/sec @ 2bar

Optional Items

  • Fail-safe Shutter: Automatic shut-off valve in case of compressed air or power failure

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