Chlorine analysis in refuse-derived fuels (RDF)

Chlorine analysis with NIR spectrometer
Chlorine analysis with NIR spectrometer

The NIR spectrometers uniSPEC2.2MPL, uniSPEC1.9HSI, uniSPEC2.2HSI as well as the fiberoptic hyperspectral cameras uniSPEC1.9FOM and uniSPEC2.2FOM are utilised in quality control of refuse-derived fuels.

The RDF material (fluff) is monitored by process controlled NIR devices. The determination of the weight distribution is achieved by applying statistical methods.

At known total weight, the relative mass contents are calculated by applying the specific weight of the material types. The material composition of the RDF stream is given in weight percent. Identification and
evaluation of the material sorts in the material stream
are the basis for the evaluation of the chlorine value,
humidity and caloric value.


Chlorine analysis

A reliable statistical evaluation of the chlorine content requires a large sample size. Thee realive content of PVC/PVDC related to the total weight can be concluded by the relative mass content and the weight distribution of the total mass. For both material sorts (PVC/PVDC) an average chlorine content is presumed. The method can be used for material streams with different material compositions.

Comparison of RFA and NIR method for chlorine analysis


 
RFA-laboratory measurementsNIR in-line measurements
Chlorine value analysis Direct Indirect
Analysis time A few days between sample drawing and availability of the analysis results Analysis results are immediately available
Analysis mass From heterogeneous solid RDF material mixes a truly representative sample cannot be drawn. Only samples of a few kilogram can be drawn with a justable effort. Usually, the analysed material amount is only about 50 to 150 ‰ of total mass, which is not a representative sample for the total chlorine contents. The NIR in-line methods continuously analyses about 7 to 12 % of total mass assuming an average material layer thickness on the conveyor belt of 15 cm. For this amount the chlorine content, resulting from PVC and PVDC impurities, can be determined.
Example Based on a RDF delivery of 25 tons, the analysed material amount is about 10 – 40 kg. Based on a RDF delivery of 25 tons, the analysed material amount is about 1750 – 3000 kg.


Humidity analysis

Humidity analysis of the RDF material stream is performed for paper, wood and identified plastic composites. The humidity stored in unipolar plastics is small and therefore neglectable. The humidity content is calculated for the polar plastics. The analysis result is given in weight percent.

Determination calorific value

For each identified material type, statistic calorific values are stored in the NIR measurement system. These statistic calorific values are applied to the weight percent of the determined material sorts. The total calorific value is calculated in MJ/kg and provided to the process control. The known total weight of the material stream is a prerequisite for the calculation of the calorific value.

Technical data

Analytical evaluation of granulates and agglomerates

uniSPECx.xQC
uniSPECx.xQC

Determination of material composition


Error rate of identification

Granulate 0,7 % - 1 % Identification error related to the overall material stream
Agglmerate 0,7 % - 1 % Identification error related to the overall material stream
2 % - 4 % Evaluation error based on inhomogeneity