Intalysis - Technology for online analysis

Technology

How does it work?

Microwave moisture analysers work on the principle that water has a very high dielectric constant compared to many materials.  When microwaves come into contact with moist materials they slow down (and hence change phase) and weaken (attenuate) as the energy is transferred to the material.

The LFM3 Moisture Analyser is based on this principle.  Put simply, it measures the change in phase and attenuation of a microwave passing through a moist material.

Microwaves are influenced in their intensity and speed of propagation by the presence of free water molecules.  By measuring the decrease in intensity (attenuation) and the decrease in speed (by the change of phase) it is possible to infer the moisture content.

Since phase shift and attenuation also depend on the amount of material present, a measurement of the mass loading on the belt is required to compensate or “normalise” the microwave measurements.  This is generally provided by a beltweigher.  Where a belt scale is not available, Intalysis can provide alternative solutions using scanning lasers and ultrasound bed height indicators.

More Information

Advantages of the LFM3 Moisture Analyser technology

  • The TPX digital signal processing capability enables very precise frequency emission and measurement.  The very low power transmission of less than 100 nano-watts ensures EMC compliance in all countries
  • Thorough material analysis which is inherently more accurate than surface measurement (NIR) and local measurement (Microwave resonance)
  • Remote monitoring and control is available via dial up interface
  • Effective in highly attenuating environments or high precision applications
  • Rugged, light-weight construction
  • Continuous moisture measurement

LFM3 Moisture Analyser Brochure

Alternative moisture analysis technologies

Technology Applications Advantages Disadvantages
Microwave Transmission systems
  • Granular material on conveyor belts
  • Managing dust extinction and maximum moisture limits
  • Measuring “dry tonnes” for mass balance reconciliation
  • Measuring critical process applications such as filtration, pelletising
    and sintering
  • Samples a representative sample e.g. through material on conveyor belts
  • Low power versions are considered very safe due to low emission of electromagnetic
    radiation
  • Suitable for conveyor applications
  • Has limits as to the depth of the material being measured
  • Cannot measure chemically combined water
  • Cannot measure thick beds of highly attenuating materials such as coke,
    pure magnetite or manganese ore
Microwave Resonance Systems
  • Concrete batch plant applications
  • Cheaper than Transmitter Receiver systems
  • Suitable for bin installations
  • Limited in high moisture systems
  • Cannot be used with high attenuation materials e.g. iron ore
  • Cannot be used with sticky materials
Near Infra Red (NIR)
  • Typically used in the food and tobacco industries. Some multi channel
    units have wider applications
  • Usually the most generic moisture analysers
  • Can be low cost depending on number of frequencies being analysed
  • Only measures surface moisture. Most suitable applications are in installations
    within a closed environment where surface moisture is representative of average
    moisture
  • Readings can be affected by grading of material, atmospheric dust/fog
    and light penetration of enclosure
Nuclear
  • Best used where material is highly conductive (coke, magnetite) and sinter
    mixtures
  • Tend to be specialist instruments that can be used where material is highly
    conductive (coke, magnetite) and sinter mixtures
  • Work on the principle that fast neutrons are preferentially slowed down
    by hydrogen atoms
  • Shieldings and warnings are necessary
  • Measures total hydrogen content including chemically bound hydrogen. This
    leads to difficulties with hydrated oxides of iron e.g. hematite and goethite