Continuous Gas Quality Analysis & Gas Mixing Systems


LNG / N2 blending (liquid / gas-phase)

To ensure imported LNG is compatible with local natural gas specifications, nitrogen is injected. The amount of nitrogen required depends on the imported LNG, as composition varies based on its location of origin.

Nitrogen is produced locally in air separation units, and is considered to be relatively expensive. Reducing nitrogen consumption therefore has a direct impact upon profitability.

Within the contractual bandwidth, gas distributors invoice based on heating value. Nitrogen is added to the LNG to reduce the heating value so too much nitrogen reduces the price of natural gas while also increasing the cost from nitrogen production.

The Hobré WIM COMPASTM F, allows LNG companies to optimize their nitrogen blending thanks to a fast response time, high accuracy and excellent repeatability. The WIM is used for:

  • Blending nitrogen and LNG in the gas phase.
  • Blending different sources of LNG in the liquid phase. (By blending lean and rich LNGs nitrogen injection can be reduced to a minimum.)

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Natural Gas blending

Natural gas distributors have to meet various contractual requirements. Typically, one of the requirements concerns heating value (or Wobbe Index). Often natural gas and/or LNG from different resources are blended to grid quality. Sometimes nitrogen is used to reduce the energy content of rich natural gas. Natural gas distributors are allowed to invoice based on heating value, provided that the heating value is within a prescribed range. This custody transfer is a gas chromatography (GC) application. For gas blending process optimization, a GC with response time in minutes is too slow.

To optimize a blending skid, it is essential to have a rapid response time, along with high accuracy and repeatability. With an accuracy of +/-0.4%, a response time of <5 s, and a repeatability of <0.05%, the Hobré WIM COMPASTM F is the analyzer of choice for this application.  Its benefits include:

  • Unmatched performance, allowing blending close to optimum value
  • High availability
  • Low maintenance requirements (4-8 hours per year)
  • Fast response times, reducing the need for large buffers/retention loops

The fast-responding WIM COMPASTM F, in combination with the Hobré Flow Impact Probe, offers a complete system with a response time of less than ten seconds.


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Gas quality stabilization (at plant in-lets)

The natural gas quality in the grid fluctuates with the source of the gas, which is imported based on demand. In some locations the permitted heating value or Wobbe Index bandwidth is enlarged to create more flexibility in the grid.

Depending on the production process, these natural gas fluctuations can impact the final product quality. Some processes – for instance a glass furnace –  require a very stable temperature and atmosphere. Fluctuations in natural gas composition impact the energy input and air-fuel ratio and result in a loss of production.

The Hobré WIM COMPASTM F is the perfect tool for gas blending process optimization. Designed specifically for industrial users, Hobré has developed a WIM COMPASTM F-based gas stabilization system to control the incoming natural gas quality at the plant level. The incoming natural gas is measured and blended to a fixed quality using nitrogen or air.


  • Inline stabilization of natural gas with no need for big buffers
  • Available for installation in hazardous areas
  • UEL monitoring in case of blending with air
  • Redundant flowmeters with large turn down ratio
  • A proven track record

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Biogas entry management

Whenever biogas is upgraded for injection into the gas grid, a quality analysis is required. Depending on the country, the following parameters need to be checked online: caloric value, Wobbe Index, water dew point, flame stability, and the amounts of CH4, CO2, N2, H2S and O2. Traditionally a gas chromatograph (GC) is used for this, together with a number of sensors. However, GCs are relatively expensive, require carrier gasses, and the analysis takes several minutes.

Hobré has developed a more economical alternative to the GC for these applications, based on the highly successful WIM COMPASTM F – the Hobré Poortwachter. The result is faster analysis based on proven residual oxygen technology, which requires no carrier gases, thereby decreasing the costs for investment and operation.


For more information about the Hobré Poortwachter, please contact us +31 (0)299 420 871.

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