Analysing with SOLAS

Analytics

SOLAS will analyse the sample thus taken with the help of an x-ray fluorescence analyser (X-PLORER 9000). The sample to be analysed will be excited by the x-rays generated in a (miniature) x-ray tube, its fluorescence spectrum being absorbed by an energy dispersive detector. From this spectrum the elements contained in the sample (theoretically all elements, including sodium and uranium) can be determined simultaneously. After the measurement has been completed, which may take between about 30 s and 120 s, depending on the application, the measured sample will be discharged from the measuring cell and the measuring cell will be cleaned by an air jet. Following that, the next sample, which has already been collected in the meantime, can be fed into the measuring cell. In order to reduce the absorption of the x-ray fluorescent radiation, SOLAS can be optionally equipped with a helium flushing system that will improve the detection limits, especially those of „light” elements, with spectral lines in the low energy range.

The analysis data thus recorded will be transmitted to the process data capturing and visualisation system WinCC (Siemens). The analyser will use breaks, during which no sampling is required, to calibrate itself with integrated standard material, to carry out automatic checks on certain components, such as the control valves, or to analyse the samples waiting in the automatic feeder system for laboratory samples.

EDXRF-Analyser

Since only a miniature x-ray tube with a low rating is installed in the EDXRF analyser X-PLORER 9000® that has been equipped by apc analytics with the most advanced components and included in the SOLAS system, and since the energy emitted by the photons is low, far less efforts are required to obtain the necessary permits, while the potential risks are considerably lower than for solutions with radioactive sources.
Here are some advantages as compared with radioactive sources:

  •     the generation of radiation can be deactivated;
  •     no toxic materials are used;
  •     the intensity of the radiation generated can be controlled and adjusted;
  •     no effects compromising the analysis, such as a weakening of the excitement (half-life of radioactive sources) need to be taken into account.

The lifetime of the x-ray tube will exceed 10 years during continuous operations.

Calibration

The equipment will usually be calibrated in such a way that samples with analysis data already known are either fed into the suction hole manually or fed into the system via the pneumatically operated sample transport system. Ideally, the contents of the samples thus used for the calibration should cover the entire range of qualities for which SOLAS is employed. During the calibration the x-ray intensities measured by the x-ray fluorescent analyser (count rate for a particular chemical element) will be correlated with the laboratory analysis data. The result in most cases will be simple linear functions between the intensities of the chemical element concerned and the contents in the bulk good.

Contrary to other online analysers, neither the production nor the conveyor belts need to be stopped during the calibration, and the production process will in no way be affected. The results can be verified in an equally easy way.

Long-term stability

After the system has been calibrated in line with the actually intended use, a set of synthetic samples integrated into the system will be measured. This set of samples (pure elements and lithium tetraborate samples) will make it possible to verify the stability of the x-ray fluorescent analyser at any time. Should a problem arise, the original calibration can be restored without having to re-measure new samples with the contents known from the laboratory analyses. Again, the production process will not be affected in any way, either.

Data Processing

All data generated by SOLAS (analysis results, operating messages, alarms etc.) will be visualized in a well-structured form and stored in databases or archives. The system allows recognizing trends speedily, raises the alarm when default limits are exceeded etc. It is possible while running the process to select the calibration function, the sampling location or the sampling mode, respectively, and individual plant components.

The same kind of visualisation will be provided in the client’s computer that is equipped with identical operating elements and that may be remotely located several kilometres away from the system. The presence on site is virtually not required.

Interfaces

As a means of communication with the instrumentation & control (I&C), i.e. the transmission of data and the reception of possible control signals, SOLAS offers several serial options, such as OPC, Profibus, hardware (4-20 mA, floating contacts).