Rapid Process and Quality Control in Cement Plants Using Simultaneous WDXRF in Accordance with ASTM C114

Cement production requirements are quite strict. Cost efficiency, reduction of CO2 emission and highest product quality has to be achieved simultaneously. Therefore the process and quality control must become more efficient with even stringent control limits through all steps of the production process from raw materials to the final products. It is possible to perform this task especially well with simultaneous wavelength dispersive X-ray fluorescence (WDXRF) spectrometers, also referred to as multi-channel WDXRF.

These instruments have a dedicated analytical channel for every element of interest, optimized for the concentration range. All the channels work simultaneously resulting in rapid measurement time with very high accuracy and consistency. Since the measurement time is usually less than 60 s, samples from different points in the cement plant can be controlled using a single instrument. The sample may be from raw materials, silos, preheater, calciner, kilns and the final products. The S8 LION has been certified according to ASTM C-114 procedure as a rapid test method for cement analysis proving its capabilities. This method defines the limits for repeatability of the sample preparation and the precision of the calibration of the instrument to ensure that the qualified instrument is capable to perform the analysis as well or better when compared to wet chemical reference methods.

Instrument

The new S8 LION is designed for quality control applications in cement plants, to achieve highest requirements for reliability, sample throughput, and superior analytical performance in combination with ease of use and maximum instrument uptime.

The features of the S8 LION are listed below:

  • The S8 LION has up to 16 element channels, each optimized for the particular element and its respective concentration range, covers all analytical tasks for raw mix, clinker and cement production control by measuring all elements within 60 s or less at the same time, enabling superior sample throughput.
  • The S8 LION’s design is optimized not only for speed but for accuracy also.
  • The instrument has temperature controlled cabinet as well as individual temperature stabilization for every crystal to ensure excellent instrument repeatability in the production environment.
  • The constant vacuum technology in the S8 LION improves lifetime of detector foils and enables excellent precision on light elements.
  • The instrument is designed to be always functional, i.e. 24/7/365 operation under difficult conditions.
  • The loading mechanism with sample swing and sample lift ensures rapid and repeatable positioning with absolute zero tolerance throughout the life-span of the instrument.
  • Reliable handling of pressed pellets is ensured with the help of the SampleCare feature that is based on tube-above-geometry and pre-loading mechanism, which is pressure controlled.
  • The S8 LION is an ideal tool for the cement plant since downtime because of dust and sample debris is considerably reduced.
  • The S8 LION includes the integrated S8 TOOLS software for self diagnostics, automatic system recovery (first aid) and complete service and maintenance access via telephone or TCP/IP (network).
  • TouchControl feature incorporated in the instrument enables ease of use even in difficult environments in an island mode. A PC-based menu interface is no longer required and this feature uses an intuitive “press a button” approach that reduces user training to minutes which is ideal for a production control environment.
  • The standalone instrument can be networked and enable transmission of the results to a level 2 system and also allow the QC manager to analyze the results
  • The S8 LION used for ASTM C-114 is equipped with 10 dedicated channels for the elements Na, Mg, Al, Si, P, S, K, Ca, Ti and Fe.

Sample Preparation

The standards were formed as fusion beads with 1:6 ratio. Seven cement standards from NIST 1880a-1889a series were used. Two sets of the standard samples were prepared on two different days.

Measurement

Measurements were performed on the S8 LION multichannel instrument with 4KW Rh target X-ray tube. The integration time was 60 seconds for all the elements. The instrument was calibrated for analysis of the elements evaluated as oxides such as Na2O, MgO, Al2O3, SiO2, P2O5, SO3, K2O, CaO, TiO2, and Fe2O3. For the accuracy test two fused bead samples were tested every hour for 30 h without intermediate drift correction.

Results

The summary of the accuracy test and the maximum differences between certified and measured data are shown in Table 1.

Table 1. Accuracy test acc. ASTM C114 with three CRM (NIST 1881a, 1888a and 1889a), prepared two times as fused beads

Sample Date Na2O (%) MgO (%) Al2O3 (%) SiO2 (%) P2O5 (%) SO3 (%) K2O (%) CaO (%) TiO2 (%) Fe2O3 (%)
1881a-Lot1 10.02.2009 10:45 0.207 3.029 7.195 22.758 0.143 3.351 1.267 58.794 0.376 3.227
1881a_Lot2 10.02.2009 14:36 0.216 3.021 7.138 22.603 0.143 3.407 1.262 58.599 0.372 3.186
Difference 0.009 0.008 0.057 0.155 0 0.056 0.005 0.195 0.004 0.041
ASTM limit 0.03 0.16 0.20 0.16 0.03 0.10 0.03 0.20 0.02 0.10
passed passed passed passed passed passed passed passed passed passed
Average 0.2115 3.025 7.1665 22.6805 0.143 3.379 1.2645 58.6965 0.374 3.2065
NIST CRM 0.2 3.03 7.17 22.62 0.15 3.42 1.25 58.51 0.37 3.14
Diff to CRM 0.0115 0.005 0.0035 0.0605 0.007 0.041 0.0145 0.1865 0.004 0.0665
ASTM limit 0.05 0.2 0.2 0.2 0.03 0.1 0.05 0.3 0.03 0.1
passed passed passed passed passed passed passed passed passed passed
Sample Date Na2O (%) MgO (%) Al2O3 (%) SiO2 (%) P2O5 (%) SO3 (%) K2O (%) CaO (%) TiO2 (%) Fe2O3 (%)
1888a-Lot1 10.02.2009 10:57 0.147 3.034 4.397 21.636 0.08 2.156 0.568 64.538 0.267 3.155
1888a_Lot2 10.02.2009 14:48 0.143 3.037 4.386 21.656 0.079 2.196 0.574 64.471 0.266 3.13
Difference 0.004 0.003 0.011 0.02 0.001 0.04 0.006 0.067 0.001 0.025
ASTM limit 0.03 0.16 0.20 0.16 0.03 0.10 0.03 0.20 0.02 0.10
passed passed passed passed passed passed passed passed passed passed
Average 0.145 3.0355 4.3915 21.646 0.0795 2.176 0.571 64.5045 0.2665 3.1425
CRM 0.11 3.04 4.34 21.6 0.08 2.17 0.54 64.36 0.27 3.13
Diff to CRM 0.035 0.0045 0.0515 0.046 0.0005 0.006 0.031 0.1445 0.0035 0.0125
ASTM limit 0.05 0.2 0.2 0.2 0.03 0.1 0.05 0.3 0.03 0.1
passed passed passed passed passed passed passed passed passed passed
Sample Date Na2O (%) MgO (%) Al2O3 (%) SiO2 (%) P2O5 (%) SO3 (%) K2O (%) CaO (%) TiO2 (%) Fe2O3 (%)
1889a-Lot1 10.02.2009 10:59 0.17 0.848 3.979 21.348 0.113 2.797 0.607 67.575 0.235 1.985
1889a_Lot2 10.02.2009 14:50 0.173 0.843 3.972 21.32 0.113 2.847 0.621 67.595 0.234 1.954
Difference 0.003 0.005 0.007 0.028 0 0.05 0.014 0.02 0.001 0.031
ASTM limit 0.03 0.16 0.20 0.16 0.03 0.10 0.03 0.20 0.02 0.10
passed passed passed passed passed passed passed passed passed passed
Average 0.1715 0.8455 3.9755 21.334 0.113 2.822 0.614 67.585 0.2345 1.9695
CRM 0.2 0.84 4.02 21.36 0.11 2.78 0.63 67.56 0.24 2
Diff to CRM 0.0285 0.0055 0.0445 0.026 0.003 0.042 0.016 0.025 0.0055 0.0305
ASTM limit 0.05 0.2 0.2 0.2 0.03 0.1 0.05 0.3 0.03 0.1
passed passed passed passed passed passed passed passed passed passed

Precision data for CaO, SiO2 and MgO are shown as an example in the process control charts shown in Figures 1-3 and summarized for all elements in Table 2 for different samples and days.

Table 2. Precision test acc. ASTM C114 for 30 hours, sample alternated with another sample

Date Na2O (%) MgO (%) Al2O3 (%) SiO2 (%) P2O5 (%) SO3 (%) K2O (%) CaO (%) TiO2 (%) Fe2O3 (%)
10.02.2009 19:30 0.556 1.192 5.337 22.305 0.185 2.674 0.908 59.413 0.241 3.378
10.02.2009 20:36 0.558 1.192 5.329 22.295 0.184 2.670 0.910 59.416 0.241 3.376
10.02.2009 21:41 0.553 1.194 5.347 22.288 0.185 2.672 0.909 59.397 0.241 3.375
10.02.2009 22:47 0.547 1.195 5.340 22.294 0.186 2.669 0.908 59.413 0.241 3.376
10.02.2009 23:52 0.553 1.197 5.339 22.295 0.184 2.670 0.909 59.456 0.241 3.378
11.02.2009 00:57 0.552 1.192 5.337 22.307 0.185 2.675 0.907 59.45 0.240 3.377
11.02.2009 02:03 0.549 1.195 5.331 22.291 0.184 2.676 0.909 59.413 0.241 3.374
11.02.2009 03:08 0.547 1.197 5.335 22.317 0.184 2.673 0.909 59.398 0.241 3.374
11.02.2009 04:14 0.554 1.194 5.338 22.299 0.185 2.674 0.910 59.428 0.241 3.377
... ... ... ... ... ... ... ... ... ... ...
11.02.2009 20:34 0.561 1.195 5.347 22.308 0.186 2.682 0.910 59.406 0.241 3.378
11.02.2009 21:40 0.557 1.196 5.339 22.304 0.184 2.684 0.908 59.446 0.241 3.377
11.02.2009 22:45 0.552 1.189 5.340 22.314 0.185 2.683 0.908 59.456 0.241 3.376
12.02.2009 00:56 0.561 1.193 5.336 22.331 0.186 2.688 0.908 59.438 0.241 3.377
12.02.2009 02:01 0.563 1.195 5.330 22.307 0.185 2.683 0.910 59.422 0.241 3.376
Mean value 0.554 1.194 5.339 22.305 0.185 2.678 0.909 59.427 0.241 3.376
Std. dev. 0.005 0.003 0.005 0.011 0.001 0.006 0.001 0.023 0.000 0.001
RSD. 0.92 0.22 0.10 0.05 0.37 0.22 0.11 0.04 0.14 0.04

Process control chart from two days for CaO

Figure 1. Process control chart from two days for CaO

Process control chart from two days for SiO2

Figure 2. Process control chart from two days for SiO2

Process control chart from two days for MgO

Figure 3. Process control chart from two days for MgO

Both precision and accuracy by far exceed the requirements of ASTM C-114 within the shortest measurement time. The S8 LION has a high count rate, which ensures the statistical error is a negligible factor in the total error calculation and therefore the variation of the results from the S8 LION is also negligible. Sample preparation is the only major factor for total error and makes reproducible samples a critical factor for successful process control.

Conclusions

The new S8 LION is a highly successful, quick, analytical instrument that enables superior quality control in advanced cement plants meeting highest demands. It provides quick, precise and very consistent results that will allow close monitoring of the process.

This information has been sourced, reviewed and adapted from materials provided by Bruker X-Ray Analysis.

For more information on this source, please visit Bruker X-Ray Analysis.

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