Handheld XRF Analysis in the Cement Industry

The use of XRF analysis (X-ray fluorescence) has long been an accepted and recommended technique in the cement manufacturing industry as an analytical tool that provides elemental chemistry. Various types of XRF instruments are used in the cement industry in all stages of cement production from quarry to final product QA/QC. Having the right tools is essential in QA/QC as well as other stages of cement-making, making the cost-effective, easy-to-use, highly accurate elemental analysis method of XRF an essential tool in all cement production facilities. Currently, you will typically find various types of XRF instruments in a cement manufacturing facility, including but not limited to handheld XRF. Contact Bruker to find out how handheld XRF can benefit your cement operations.

 

Standard method ASTM C114 outlines the working requirements for cement analysis instruments.

 

Typical current uses and advances include:

  • Analysis of samples in the field or “at line”
  • Heavy reliance on XRF for production control
  • Innovation in EDXRF (energy-dispersive x-ray fluorescence) hardware has resulted in smaller, more compact instruments with an increasing ability to measure light elements such as magnesium in MgO and Na2O, complementing—and in some stages replacing—already widely used WDXRF instrumentation.

How Can Handheld XRF Instruments Be Used at a Cement Plant?

  • At-line for better control of raw mix blending and clinkerization
  • Spot checks on finished product or clinker shipments in conjunction with a centralized WDXRF analyzer
  • Analysis of raw materials from quarry- such as limestone and clay
  • Analysis of feed stream materials: gypsum, limestone, quartz sand, clay, fuel, pozzolana and fly ash
  • Raw mix control Laboratory-based analysis
  • Checking of adulteration of finished cement

How Are Handheld XRF Analyzers used in the Quarry/Mill?

  • For traditional geochemical applications, such as quarry drill campaigns to establish new source
  • In the field to save time in raw materials extraction
  • Elemental analysis of samples from exploration or blast hole drilling
  • Deposit mapping
  • Grade control
  • Gypsum shipping and incoming inspection
  • Finished mill dosage of Gypsum check

Handheld XRF Calibration Considerations for the Cement Industry

A particular challenge of using handheld XRF in the cement industry is the issue of calibration. Most handheld XRF analyzers come equipped with factory calibrations that carry names like “mining” and “soil.” Often the specifications on these calibrations lead users to believe that they will yield highly accurate results for cement industry samples, but this is often not the case. These One Standard geochemical calibrations can be used for a variety of matrices, but perform best on silicate and aluminosilicate type matrices.

  • Many mining (ore) applications are focused on either oxide or sulfide ore with high metal content
  • As matrices or chemical bonding diverge from the assumed configurations, the measurements will have more error and will eventually become semi-quantitative
  • For raw material cement applications, the major component is carbonate (instead of oxide), so a separate application needs to be developed to get good results on limestone matrices

These calibrations tend to be too generalized and/or calibrated to a matrix that is not similar to the matrices found in cement manufacturing. Since these calibrations rely on mathematic approximations, their accuracy is easily thrown off by changes in matrix or other unexpected changes in values, density, attenuation, etc. One of the mathematical attributes of most generalized factory calibrations (but not Bruker’s) is normalization:

  • Takes the sum of all measured elements and uses multipliers to normalize the concentrations to 100%
  • All elements present in a sample must be either measured or associated by stoichiometry with a measured element
  • Biggest effect is on the largest concentrations

Because normalization is not able to account for the matrix and other changes described above, while maintaining the same level of accuracy, it is best for cement analysis applications to create specific empirical calibrations that take into account the specific matrices and elements typical of cement samples.

Bruker has created an application for the S1 TITAN series which is specifically aimed at this very segment- the “limestone” application is built upon 3 methods:

  1. Carbonate Based materials (Limestone)
    Assuming powders, but able to measure on solid samples with a polymer foil between sample and analyzer, the S1 TITAN reports Mg and Ca as Mg2CO3 and CaCO3 respectively, and the other elements as the standard oxides. The result is normalized by default.
  2. Sulfate Materials (Gypsum)
    Assuming powders, but able to measure on solid samples with a polymer foil between sample and analyzer, The S1 TITAN reports Ca as CaSO4 respectively, and the other elements as the standard oxides. The result is normalized by default. Water content is neglected.
  3. Oxide Materials (Cement)
    Assuming powders, but able to measure on solid samples with a polymer foil between sample and analyzer, the S1 TITAN reports all  elements as the standard oxide, including S and P. The result is not normalized by default. Water content, Carbonate is neglected

These methods will cover a number of applications but ideally they form the basis of local customization.

Bruker also offers the ability to provide custom applications on their Tracer product line. These Tracer-based custom applications are required if you analyze blended cements or have additives such as Fly Ash, Silica fume et al.

Several things should be considered when deciding what type of calibration is best for your specific analysis needs and cement matrices:

  • Calibration Base: powders or solids?
  • What base can be extended (e.g. FlyAsh can be added to standard Cement)
  • Unmeasurable Elements: can they be associated with a measured element by stoichiometry (do you want to normalize)?
  • What is the degree of variation there may be in the measured matrices?
  • What ranges of element concentrations are covered?
  • Select Fundamental parameters or an empirical-based calibration or combine both methods.
  • Understand the limits resulting from the sample preparation (or lack thereof) which affects the “analyzed” layer and therefore the ability of XRF to “see” elements correctly.

Additional considerations should be taken into account when the planned application is in-field analysis, such as at the quarry:

  • Keep the instrument window clean, especially in dusty areas
  • Water and humidity in the sample will change the reading… standardize the measurement approach for the impact of the moisture.
  • When measuring rock faces, try to choose a flat section with no color variation  and ensure it is not wet or covered by plant material
  • Be careful that no sharp edges of rocks puncture the window and damage the detector, consider using the TITAN Detector Shield to protect the window of the instrument

 

Do I Need a Handheld or Benchtop Analyzer for my Cement Application?

 

Advantages of Handheld XRF for Cement Analysis:

  • Little or no sample preparation - can be used on rocks and on coarse or fine powders
  • Can be easily taken to the field and brought to the samples
  • Using direct rock face sample one get a good approximation of the solid rock
  • Quick screening tool
  • Instantaneous results


Limitations of Handheld XRF for Cement Analysis:

  • Large uncertainty – often used for estimating raw material content
  • Light element analysis is difficult due to no vacuum, helium and poor sample quality (Titan cannot see Na (sodium)).
  • Analyzed layer and grain size limits the accuracy of the method

To find the Bruker XRF analyzer that’s best for your cement operation needs, please contact one of our experts in cement analysis. Our experts understand the cement industry as well as cement chemistry, and are available to help you select the most ideal instrumentation to meet your analytical needs and maximize the efficiency of your cement manufacturing business.

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