Abstract
Good methods enabling quick determination of moisture in wood fuels are lacking. A standardized method generally used by the biofuel industry means drying samples in furnaces during at least 16 hours. The idea of this work has been to investigate if x-ray technique can offer a superior alternative for fast moisture determination. Analysis with x-ray has many advantages. The x-rays go completely through the whole test specimen. Large samples or many sequential samples can rapidly be measured. The penetration is extraordinary good; all parts of the tested mass will be analyzed. The measurement relies on the absorption of gamma photons in the tested mass. The x-ray absorption is carried out deep down in the atoms and therefore is independent of the materials equation of state as temperature, grain size or molecule binding. The disadvantages of the method are the general anxiety which can be for gamma rays, the relative high cost for equipment and the fact that an x-ray tube will wear with time and needs replacement. The method used here for moisture measurement is known as dual energy x-ray. The test sample is simultaneously exposed to transmission of two separate x-ray energies. The two energies are absorbed differently by
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Nordell, Anders;
[1]
Vikterloef, K J
[2]
- Industriellt Utvecklingscentrum i Karlskoga, Karlskoga (Sweden)
- Oerebro Radiofysik AB, Oerebro (Sweden)
Citation Formats
Nordell, Anders, and Vikterloef, K J.
Measurements of moisture content in wood fuels with dual energy x-ray; Maetning av fukt i biobraenslen med dubbelenergiroentgen.
Sweden: N. p.,
2000.
Web.
Nordell, Anders, & Vikterloef, K J.
Measurements of moisture content in wood fuels with dual energy x-ray; Maetning av fukt i biobraenslen med dubbelenergiroentgen.
Sweden.
Nordell, Anders, and Vikterloef, K J.
2000.
"Measurements of moisture content in wood fuels with dual energy x-ray; Maetning av fukt i biobraenslen med dubbelenergiroentgen."
Sweden.
@misc{etde_20068916,
title = {Measurements of moisture content in wood fuels with dual energy x-ray; Maetning av fukt i biobraenslen med dubbelenergiroentgen}
author = {Nordell, Anders, and Vikterloef, K J}
abstractNote = {Good methods enabling quick determination of moisture in wood fuels are lacking. A standardized method generally used by the biofuel industry means drying samples in furnaces during at least 16 hours. The idea of this work has been to investigate if x-ray technique can offer a superior alternative for fast moisture determination. Analysis with x-ray has many advantages. The x-rays go completely through the whole test specimen. Large samples or many sequential samples can rapidly be measured. The penetration is extraordinary good; all parts of the tested mass will be analyzed. The measurement relies on the absorption of gamma photons in the tested mass. The x-ray absorption is carried out deep down in the atoms and therefore is independent of the materials equation of state as temperature, grain size or molecule binding. The disadvantages of the method are the general anxiety which can be for gamma rays, the relative high cost for equipment and the fact that an x-ray tube will wear with time and needs replacement. The method used here for moisture measurement is known as dual energy x-ray. The test sample is simultaneously exposed to transmission of two separate x-ray energies. The two energies are absorbed differently by the sample. The ratio of the absorption in the two respective energies is calculated and from that conclusions on the composition of the material can be drawn. The equipment used in this test is a standard medical apparatus adapted for the study of human body composition. When instead used for measurements of moisture in wood material the discrimination signal is about half of that achieved in the normal medical case. Despite that, the signal has been good enough for giving satisfactory accuracy in the moisture estimation. A little more than sixty approved results are presented in the report comprehending ten different fuel types. The results are grouped into three main categories depending on fuel type, wood fuels, peat fuels and salix including some of the mixed fuels. Provided that the main category is known the moisture content can be determined within one or two percent from the measurements. A complication is that the procedure requires that the fuel type be known. The method offers a relative measurement which means that it relies on calibration against known references. Different types of fuels therefore to some extent need different calibrations. This is basically due to the differences in carbon content which affects the result. With a further development of the method there are ways to overcome this difference in the total absorption resulting in a measurement more or less independent of the fuel type. As the content of carbon as well as of oxygen strongly affects the absorption, one would also in principle be able to calculate the heat content of the fuel. On top of that there is a correlation of the absorption to the mineral content, which opens a possibility to calculate the amount of ash in the material. To reveal these for biofuels highly interesting parameters a substantial effort of software development in the data treatment is required. A fine-tuning of the x-ray energies is also desirable to reach a higher signal ratio for the case moisture in wood, compared to what is possible with the medical equipment. These development steps are regarded fully feasible and are recommended to be taken in the coming work.}
place = {Sweden}
year = {2000}
month = {Apr}
}
title = {Measurements of moisture content in wood fuels with dual energy x-ray; Maetning av fukt i biobraenslen med dubbelenergiroentgen}
author = {Nordell, Anders, and Vikterloef, K J}
abstractNote = {Good methods enabling quick determination of moisture in wood fuels are lacking. A standardized method generally used by the biofuel industry means drying samples in furnaces during at least 16 hours. The idea of this work has been to investigate if x-ray technique can offer a superior alternative for fast moisture determination. Analysis with x-ray has many advantages. The x-rays go completely through the whole test specimen. Large samples or many sequential samples can rapidly be measured. The penetration is extraordinary good; all parts of the tested mass will be analyzed. The measurement relies on the absorption of gamma photons in the tested mass. The x-ray absorption is carried out deep down in the atoms and therefore is independent of the materials equation of state as temperature, grain size or molecule binding. The disadvantages of the method are the general anxiety which can be for gamma rays, the relative high cost for equipment and the fact that an x-ray tube will wear with time and needs replacement. The method used here for moisture measurement is known as dual energy x-ray. The test sample is simultaneously exposed to transmission of two separate x-ray energies. The two energies are absorbed differently by the sample. The ratio of the absorption in the two respective energies is calculated and from that conclusions on the composition of the material can be drawn. The equipment used in this test is a standard medical apparatus adapted for the study of human body composition. When instead used for measurements of moisture in wood material the discrimination signal is about half of that achieved in the normal medical case. Despite that, the signal has been good enough for giving satisfactory accuracy in the moisture estimation. A little more than sixty approved results are presented in the report comprehending ten different fuel types. The results are grouped into three main categories depending on fuel type, wood fuels, peat fuels and salix including some of the mixed fuels. Provided that the main category is known the moisture content can be determined within one or two percent from the measurements. A complication is that the procedure requires that the fuel type be known. The method offers a relative measurement which means that it relies on calibration against known references. Different types of fuels therefore to some extent need different calibrations. This is basically due to the differences in carbon content which affects the result. With a further development of the method there are ways to overcome this difference in the total absorption resulting in a measurement more or less independent of the fuel type. As the content of carbon as well as of oxygen strongly affects the absorption, one would also in principle be able to calculate the heat content of the fuel. On top of that there is a correlation of the absorption to the mineral content, which opens a possibility to calculate the amount of ash in the material. To reveal these for biofuels highly interesting parameters a substantial effort of software development in the data treatment is required. A fine-tuning of the x-ray energies is also desirable to reach a higher signal ratio for the case moisture in wood, compared to what is possible with the medical equipment. These development steps are regarded fully feasible and are recommended to be taken in the coming work.}
place = {Sweden}
year = {2000}
month = {Apr}
}