THE ACCURACY OF A SPECTRAFLOW ANALYZER

Abstract

 

SpectraFlow is the only online analyzer on the market free of any radioactive components, neutron generators or lasers. Therefore SpectraFlow is completely safe to operate and no licenses or permits are needed to import, operate and maintain the online analyzer system. This report evaluates at nine different locations the accuracy of the SpectraFlow Analyzer with dynamic comparisons of the XRF at the airslide of raw mills, as well as an absolute comparison of the XRF of crossbelt analyzers after crushers of cement plants. Additionally a dynamic comparison of the results of a Prompt Neutron Activation Analyzer (PGNAA) after a limestone crusher of a cement plant was done. The results of this report show, that SpectraFlow is measuring compared to the XRF reference all constituents very accurately and compared to the PGNAA more accurate. For the process control at the Raw Mill it is essential, that the analyzer delivers very accurate measurement values, as the constituent ranges are very small (e.g. CaO 41% - 45%) compared to an application after the raw material crusher (e.g. CaO 30% - 55%). To control the weight feeders of the additives the measurement results have to be very accurate, real-time (no running averages) and noise-free. A measurement on a belt conveyor is always less accurate than a measurement of raw material on an airslide, due to the consistent grain size and homogeneity of the raw material. Therefore PGNAAs installed before the raw mill are not very efficient to reach very low standard deviations of the Raw Meal, because they have to be installed always on the belt conveyor before the raw mill rather than on the airslide after the mill. SpectraFlow is therefore the most efficient online analyzer for raw mill control.

 

1. Introduction

 

This report shows the result of the SpectraFlow Analyzer compared to the conventional offline method XRF, as well as to Prompt Neutron Activation Analyzer (PGNAA). PGNAAs are highly toxic and dangerous and with the availability of SpectraFlow no longer necessary to operate. All the data in this report is collected over representative time frames and from nine different customer installations.

 

As the results show SpectraFlow is a highly accurate measurement device. The reason for this is:

 

  • Near Infrared is a very sensible analytical method and the ABB Bomem FTIR Spectrometer used in the SpectraFlow Analyzer is the best available on the market, with a very high resolution and an exceptional high precision.
  • SpectraFlow is scanning the raw material surface continuously and delivers an interferogram every 425 milliseconds. These interferograms will be averaged over one minute and a spectra is created. In case of a belt speed of 4 m/s and a belt diameter of 2 meters a single minute result covers an area 480m2 of raw material.
  • After a crusher the raw material is statistically mixed. In case certain constituents are partially segregated to the bottom of the belt, the relation of their occurrence on the top and bottom of the conveyor belt is always linear and with an offset correction this is compensated. On an airslide the raw material is very homogeneous and therefore normally no offset correction is needed. This offsets don’t have to be adjusted and are extremely accurate and stable.
  • A big advantage of the SpectraFlow Analyzer is its surface measurement. Therefore the system is completely independent of belt load and belt speed. No offset corrections have to be done because of changing belt loads.
  • SpectraFlow is measuring the moisture content of the raw material. In case of the belt conveyor application changing moisture contents in the raw material make it necessary to have a highly accurate moisture measurement. SpectraFlow is measuring the moisture content and is correcting the chemical values directly with the corresponding moisture content. These dry values can be compared over days, weeks or years. Therefore the chemical data delivered by the SpectraFlow Analyzer can be perfectly used for optimizing stockpiles built up over several days.

SPECTRAFLOW ANALYTICS LTD I HAERDLISTRASSE 15 I CH-8957 SPREITENBACH I SWITZERLAND

TEL. +41 56 406 12 12 I FAX. +41 56 406 12 10 I NET. info@spectraflow-analytics.com

SPECTRAFLOW ANALYTICS LTD HAERDLISTRASSE 15 CH-8957 SPREITENBACH SWITZERLAND TEL. +41 56 406 12 12 FAX. +41 56 406 12 10 NET. info@spectraflow-analytics.com
SPECTRAFLOW ANALYTICS LTD HAERDLISTRASSE 15 CH-8957 SPREITENBACH SWITZERLAND TEL. +41 56 406 12 12 FAX. +41 56 406 12 10 NET. info@spectraflow-analytics.com