Calorific Value Measurement and Energy Based Lambda Control

The precision Calorimeter CWD2005 PLUS

The energy content of the fuel gas is a key process parameter for the stable operation of industrial furnaces. Changes in the supply source or the increasing admixture of foreign gases (e.g. H2, biogas, liquefied petroleum gas (LPG, LNG)) lead to significant fluctuations in the calorific value.

As these changes usually occur without the knowledge of the end customer and over undefined periods of time, instabilities in the process are rarely attributed to possible correlations.

By continuously determining the energy content and compensating for it with a tailor-made control concept, it is possible to counteract these fluctuations in a controlled manner.

As the exclusive partner of Union Instruments for customers in the glass industry, we recommend the CWD 2005 PLUS calorimeter.

Calorimeter CWD2005 PLUS
Calorimeter CWD2005 PLUS

Why to control Energy Content?

Gas suppliers deliver fuels with varying compositions due to frequent changes of sources of supply

Mixtures of NG with e.g. H2,Biogas, LPG or LNG affect fuel characteristics

This has an impact on 

  • energy content of gas
  • burner’s flame characteristics
  • Air / Oxygen demand

Conclusion: A constant energy input is crucial for a stable melting process. The amount of gas alone is no longer sufficient - the fluctuating calorific value must be included in the calculation. The CWD Calorimeter is ideally suited for this.

Product page: Calorific Value Measurement / Energy Based Lambda Control
Product page: Calorific Value Measurement / Energy Based Lambda Control

Measures for compensation

Reliable online calorific value measurement  (thermal method)

Control of the actual energy input to the process

STG Energy based Lambda Control compensates for variations in gas quality by modifying gas flow and combustion air/oxygen setpoints.

Automatic control possible even for short-term variations

Changes in gas composition
Changes in gas composition

Technical Data CWD2005 PLUS

Continuous measurement of Calorific Value, Wobbe, Density

Measuring accuracy:

  • Natural Gas 30 - 48 MJ/m3 +/- 1,0 % measured value
  • Relative Density: +/- 1,5 % E

Mounted inside indoor cabinet

  • Protection Class IP65
  • Dimensions (WxHxD): 1000 x 1850 x 600mm
  • Exhaust gas connection: 100 mm diameter
  • Max. exhaust gas temp.: 70 °C
  • incl. gas treatment system for dry natural gas
  • incl. calibration gas system
  • Solenoid valve block 2-fold
  • Burner Type H
  • 2x temperature measurement (1x CWD device / 1x ambient temperature)
  • Incl. 3 x analogue outputs (Calorific Value, Wobbe index, Density), 3 relays (com, no, nc), LED continuous light; prepared for Ethernet connection
Calorimeter CWD2005 PLUS
Calorimeter CWD2005 PLUS

Benefits CWD Calorimeter

Precise determination of Calorific Value, Density and Wobbe

All components in the fuel gas (including H2) are considered.

Proven and robust design

Self-monitoring of device and ambient temperatures

Minimal maintenance: only one calibration gas required with low consumption

Provides all necessary raw data for STG's patented "Energy Based Lambda Control" 

Union Instruments
Union Instruments

Scope of supply

Technological consulting

Supplying and installing a complete measuring system with CWD2005 PLUS Calorimeter.

Signal Processing / Combustion Calculation as an integrated module of the Furnace Control System software provides on-line monitoring of

  • Net Calorific value NCV (or: Lower Heating Value LHV)
  • Gross Calorific Value GCV (or: Higher Heating Value HHV)
  • Wobbe Index
  • Stoichiometric air and waste gas flow
  • Dimensionless figures of fuel, acc. to Boie

Optional: Patented STG control concept "Energy Based Lambda Control", see below

Calorific Value and Gas Flow
Calorific Value and Gas Flow

Energy Based Lambda Control

The ever-increasing problem of unpredictable fluctuations in gas quality over the last few years has created a whole new set of challenges for glass melting plant operators.
In order to counteract the resulting instabilities in the melting process in a controlled manner, STG has developed the "Energy Based Lambda Control" and has been using it successfully for several years.

Calorific value measurement detects changes in gas composition.
STG's oxygen probes react to short term changes in the process and are a reliable indicator to detect uncontrolled air ingress.

STG has combined the advantages of both systems and developed an automatic control feature for a stable energy input into the melting process at all times.

The result (patented) speaks for itself:


Compensation for fluctuations in gas quality and uncontrolled air ingress

Constant energy input (MW) into the melting process

Process stability and constant glass quality

Energy saving (fuel and air)

Reduction of energy losses

Reduction of NOx emissions

Limitation of CO emissions

JP Patent Energy Based Lambda Control
JP Patent Energy Based Lambda Control

STG Energy Based Lambda Control for implementation in a Furnace Control System

Available for Siemens / Rockwell (Allen-Bradley)  Furnace Control Systems 

Patented automatic "Energy Based Lambda Control" for a constant energy input into the melting process:

  • Compensation of fluctuations in gas quality
  • Compensation of uncontrolled air flow rates
  • Maintaining the optimum furnace pressure to prevent air ingress into the furnace
  • Calorimeter / Chromatograph monitors the gas quality and provides the control system with the required data for the gas setpoint [MW]
  • Oxygen probes provide rapid feedback on changes to the combustion parameters and act as an indicator of the ingress air XF disturbance variable for the control system to correct the required combustion air flow rate

Full integration into visualisation (S7/WinCC; PCS7; iFIX; FactoryTalk) 

By modification / extension of existing Furnace PLC and visualisation program (e.g. additional faceplates) 

STG requires temporary access to Engineering Station with valid license and currently running program 

Installation and Start Up by STG programmer(s) / Optimisation / Support by remote access

Available for Siemens and Rockwell / Allen- Bradley based Furnace Control

  • either by extension of an existing Control System
  • or as an integral part of a complex Furnace Control System package by STG
Working principle Energy Based Lambda Control
Working principle Energy Based Lambda Control
Werner Bengsch

For CWD Calorimeter get in touch with

Werner Bengsch

Dr. Peter Hemmann

For Lambda Control get in touch with

Dr. Peter Hemmann