CA1165018A - Analysis of coal - Google Patents
Analysis of coalInfo
- Publication number
- CA1165018A CA1165018A CA000375127A CA375127A CA1165018A CA 1165018 A CA1165018 A CA 1165018A CA 000375127 A CA000375127 A CA 000375127A CA 375127 A CA375127 A CA 375127A CA 1165018 A CA1165018 A CA 1165018A
- Authority
- CA
- Canada
- Prior art keywords
- coal
- rays
- energy
- low energy
- source
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
- G01N23/06—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption
- G01N23/12—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption the material being a flowing fluid or a flowing granular solid
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
- G01N23/06—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption
- G01N23/083—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption the radiation being X-rays
Abstract
"ANALYSIS OF COAL" The present invention relates to a method and apparatus for analysing coal wherein the concentration of ash or mineral matter in said coal is determined from: (i) the result of a measurement in a first energy region of the intensity of X-rays or low energy .gamma.-rays of resulting from at least one scattering interaction in said coal, said first energy region so chosen such that there is significant difference in absorption of radiation per unit weight in coal matter and mineral matter excluding iron, combined with (ii) the result of at least one further measurement at a different energy region of X-rays or low energy .gamma.-rays, resulting from-at least one scattering interaction in said coal, said different energy region(s) so chosen that there is a significant difference in absorption of radiation per unit weight of coal matter and mineral matter, and wherein the relative absorption per unit weights by said coal matter and said mineral matter at any one energy or energy region is significantly different from the absorption at each other energy or energy region.
Description
~6SVI8 The present invention relates to the determination of the ash content of coal or coke employing measurements from X-rays and/or low energy Y-rays.
An accurate knowledge of the composition of coal or coke is very important in many aspects of production or beneficiation and in the utilisation of coal or coke in order to ensure a uniform product and/or batch.
Coal and coke consists of coal matter (oxygen and combustible materials, carbon, hydrogen and a llttle nitrogen and sulphur) and mineral matter (mainly of incombustible aluminium and other silicates, and a little iron sulphide which is partly combustible). Coal ash is the oxidised incombustible residue from the combustion of coal, and is closely ccrrelated with the content of mineral matter.
An accurate knowledge Gf the mineral content of coal is very important in many aspects of coal production, preparation and utilisation. It is especially advantageous to have a continuous monitor of mineral content of coal during coal washing and blending operations, production of coke, and monitoring feed in installations for power generation, metallurgical smelting and gas production.
Coal as mined has a variable heterogeneous minerology and usually a wide particle size distribution. The coal is washed to reduce mineral content and to ensure a more uniform product, and blended to obtain specific characteristics suitable for a particular application requirement. When the mineral content can be monitored continuously, washin~ and blending can be controlled better to ensure a more uniform and lower mineral content and therefore more appropriate characteristics.
An accurate knowledge of the composition of coal or coke is very important in many aspects of production or beneficiation and in the utilisation of coal or coke in order to ensure a uniform product and/or batch.
Coal and coke consists of coal matter (oxygen and combustible materials, carbon, hydrogen and a llttle nitrogen and sulphur) and mineral matter (mainly of incombustible aluminium and other silicates, and a little iron sulphide which is partly combustible). Coal ash is the oxidised incombustible residue from the combustion of coal, and is closely ccrrelated with the content of mineral matter.
An accurate knowledge Gf the mineral content of coal is very important in many aspects of coal production, preparation and utilisation. It is especially advantageous to have a continuous monitor of mineral content of coal during coal washing and blending operations, production of coke, and monitoring feed in installations for power generation, metallurgical smelting and gas production.
Coal as mined has a variable heterogeneous minerology and usually a wide particle size distribution. The coal is washed to reduce mineral content and to ensure a more uniform product, and blended to obtain specific characteristics suitable for a particular application requirement. When the mineral content can be monitored continuously, washin~ and blending can be controlled better to ensure a more uniform and lower mineral content and therefore more appropriate characteristics.
2 -~ ~5~
In ~he specification and claims when describing methods of determining ash content of coal a reference to coal is also a reference to coke. Also, since the content of mineral mat~er is closely related to the content of ash, the content of one can be determined at least approximately from a measuremen~ of the other.
It is known to determine the ash content of coal gravimetrically by burniny a known amount of coal and weighing the residue. In order to reduce errors, a large sample is taken and ground and the sample size reduced in accordance with standard sampling procedures. This method does not permit a rapid continuous monitor of ash content.
Continuous and rapid methods for determining the ash content of coal are known and depend on scatter of particles, or transmission or scatter of X- or iow energy ~ rays~ Such methods are described in Cameron J.F., "measurement of ash content and calorific value of coal with radioisotope instruments" O.R.N.L. llC-10 Vol. ~ P 903, Cameron J.F., CIayton C.G., "Radioisotope Instruments Volume 1" International Series of Monographs in nuclear energy Volume 107, Pergamon Press (1971), Kato M., "Present status of research and appiication of low-energy X- and gamma-ray sources in Japan" O.R.N.L. llC-10 Vol. 2 P 723, Rhodes J.R., "Ore and Coal Analyses using radioisotope techniques"
O.R.N.E. llC-5, P 206 and Vasilev A.G. et al, "Express ash analyser based on the recording of forward scattered gamma rays" Koksi Khimiya 1974 No. 5, P 52. The basis of these methods is that the mean atomic number of the mineral matter constituents is higher ~han that of the coal matter, and that ~ and ~-ray interactions with atoms are atomic number 5~)~.g dependent~ The mean atomic number of mineral matter, however, is not constant, and in practice variations in iron content of the mineral matter cause considerable errors in determination of ash using the above methods.
Neutron techniques can, in principle, be used to determine ash content of coal because these techniques can be used to determine concentrations of the more abundant elements of the coal. Such methods are described in Cameron J.F., "Measurement of ash content and calorific value of coal with radioisotope instruments" O.R.N.L. llC-10 Vol. 2 P 903.
Neutrons, and the ~-rays produced by neutron interactions with the coal, both penetrate large volumes o coal and hence neutron techniques can be used with relatively large particles of coal. However, determination of concentrations of all the elements required for accurate determination of ash content would, in practice, be very complex because some of the neutron techniques for individual elements are complex.
Techniques are in practice, relatively simple for only a limited number of elements, e.g., iron by neutron capture r-ray techniques as described by FMC Corporation, "Analysis of coal with Cf-252", pages 37 to 39 in Californium Progress, 20 January, 1976 and by Ljunggren K. and Christell R., "On-line determination of the iron cosltent of ores, ore products and wastes by means of neutron capture gamma radiation measurement", page 181 in Nuclear Techniques in Geochemistry and Geophysics, IAEA, Vienna, 1976.
In methods based on scatter o~ ~ particles, the intensity of particles scatter from a material is related to the mean atomic number of the material. As the mean atomic -30 number of coal increases with mineral matter content the intensity of ~ particles scattered from coal is proportional to the ash content. However, large errors occur in this method through variations in iron and moisture content.
In methods based on transmission of X-rays or low energy ~-rays the intensity of the radiation transmitted through a sample of fixed weight per unit area decreases with increasing mass attenuation coefficient of the bulk material. At energies less than about 100 keV the mass attenuation co-efficient changes rapidly with atomic number, which means that the transmitted intensity is sensitive to coal composition.
The ratio of the intensity ~I) of a collimated beam of radiation transmitted through a coal sample of thickness (x) and bulk density (P) to the intensity (Io) in the absence of coal is Io xp( (~i.Ci) p.x) (1) where ~i and Ci are the mass absorption coefficient and concentration (weight fraction) of the ith element in the coal respectively. Now ~ Ci = ~coal matter C coal matter _ + ~mineral matter .C mineral matter (2) where C is concentration and Ccoal matter + Cmineral matter =1 (3) Hence if coal samples to be analysed have mineral matter of essentially constant composition and if the weight per unit area (p.x) of coal is separately measured, and results combined with equations (1), (2) and (3), the concentration of mineral matter and hence the closely correlated ash content are determined.
A high sensitivity to variations in mineral matter content can be obtained with methods employing transmission because the sensitivity to content of mineral matter is proportional to (x) in equation (1).
In methods based on scatter of X- or low energy y-raysl the intensity (I) of radiation scattered from the coal depends on the probability of coherent and Compton scattering, and absorption of X- or low energy ~-rays, within the sample. The optimum energy range for maximum sensitivity to ash is 10 to 20 keV, and in this case k (4) . Ci ) wherein ~i and Ci are the mass absorption coefficient and concentration respectively for the ith element in the coal sample, and k depends on overall geometry and detection efficiency, and output of the low energy ~- or X-ray sourse.
If coal samples to be analysed have mineral matter of essentially constant chemical composition, then mineral matter content and the closely correlated ash content are determined.
Variations in iron content of the mineral matter affect both the X- and low energyy -ray transmission and scatter methods as follows:
~1) If the X-ray energies are chosen below the iron K
shell absorption edge (7,1 keV), the mass absorption coefficient of iron and the mean for the other constituents of mineral matter is about the same and the mineral matter content and hence ash is determined with reasonable accuracy. However, these low energy X-rays are strongly absorbed and the coal must be finely ground (less than 0,3 mm) so that measurements can be made. This is a severe ; 5 ~ ~ ~
limitation in practice for on-line determination.
(2) If the X-ray energies are chosen above the iron K
shell absorption edge, compensation must be made for iron content because iron absorbs far more per unit weight than the absorption per unit weight of the other constituents of the mineral matter. The only compensation currently used for iron depends on excitation of iron K X-rays. This method can only be used on finely ground coal since the X X-rays are greatly absorbed in less than 1 mm thickness of coal.
~ence, unless the case occurs of essentially no variation of iron content o the mineral matter, ~he content of mineral matter and hence ash can only be determined accurately by currently used low energy ~ray and X-ray techniques if the particle size of coal is very small.
It would be expected therefore from the prior art that accurate determination of ash content of coal by X-ray and low energy Y-ray techniques would be unlikely unless the iron content of the ash was constant or the coal particles were finely ground.
The method of the present invention determines ash content even when the iron concentration varies and can be used on relatively large diameter coal particles.
According to the invention the concentration of ash or mineral matter in coal is determined from (i) the result of a measurement in a first energy region of the intensit~ of X-rays or low energy y-rays resulting from at least one scattering interaction in said coal, said first energy region chosen such that there is significant difference in absorption of radiation per unit weight in coal matter and mineral matter excluding iron, ,.. . ) I ~0~ g combined with tii) the result of at least one further ~easurement at a different energy region of the intensity of X-rays or low energy ~-rays, resulting from at least one scattering interaction in said coal, said different energy region(s) so chosen that there is a significant difference in absorption of radiation per unit weight of coal matter and mineral matter and wherein the relative absorption per unit weights by said coal matter and said mineral matter at any one energy or energy region is significantly different from the relative absorption at each other energy or energy region.
The present invention also provides an apparatus for determining the concentration of ash or mineral matter in coal, which apparatus comprises:
(a) a source yielding X-rays or low energy y-rays either of a single energy or multiple energies;
(b) detecting means being associated with said source being capable of detecting X-rays or low energy y -rays resulting from at least one scattering interaction in said coal and being adapted to discriminate between said X-rays or low energy y-rays detected in various energy regions, a first energy region being chosen so that there is significant difference in absorption of radiation per unit weight in coal matter and mineral matter excluding iron and X-rays or low energy y-rays of at least one different energy or energy region so chosen that there is significant difference in absorption of radiation per unit weight of coal matter and mineral matter and that the relative absorption per unit weights by said coal matter and said mineral matter 5 0 :~ ~
at any one energy or energy reqion ls signi~icantly different from the ~elative absorption at each other energy or energy region, (c) shielding means interposed hetween said source and said detecting means, ~hereby reclucing -the intensity of direct source ~-rays ox low energ~ y-rays impinging on said detecting means; and (d) calculating means associated with the outputs of said detecting means to calculate said concentration.
In the accompanying dra~Jin~s ~Ihich illustrate specific embodiments of the invention, by way of example, FI~JURE 1 is a schematic layout of the apparatus of the present invention;
FIGURE 2 is a graphical illustration of ash content;
FIGURE 3 is another schematic illustration of the ¦ present invention.
In this specification and claims the term "low energy y-rays" means y-rays of such an energy that'the absorption of radiation per unit weight of at least some elements is significantly different ~rom the absorption per unit weight of other elements. Whilst the present invention is described with reference to a single source of X- or low energy y-rays, the source may be a composite one, where two or more radioisotopes either comhined in a single unit or in separate units, which produce a sing1e energy spectrum which is detected by a single detector.
In a preferred emhocliment of the invention the concentration of ash or mineral matter in coal is determined mb/J~ - 9 -~ 1B501~
from the result of a measuremen-t :Ln a :firs-t enercJy reCJion of -the intensity of X-rays or low energy ~-rays resulting from a-t least one scatterinq interaction in said coal, said first ener~y region chosen such that there is significant difference in absorption of radiati.on per unit ~reigh-t in coal matter and mineral matter excluding iron, comhined ~li.th the result of a second measurement at a second energy region of the intensity of X-rays or low enercty y-rays from the same mh/~G7 - 9a -I
0 ~ ~
source as said X-rays or low energy y-rays of said first energy region resulting from at least one scattering interaction ln said coal, said second energy region chosen that the absorption of radiation per unit weight of mineral matter is significantly dif$erent from that of coal matter and that the relative absorption per unit weights by said mineral matter and said coal matter at said first energy region is significantly different from the relative absorption at said second energy region.
In applying the method of the invention, the concentration of mineral matter is sometimes determined by the aforementioned measurements coupled with one or more additional measurements selected from (i~ measurement of weight per unit area or a measurement proportional thereto, or (ii) measurement of bulk density, or a measurement proportional thereto, One of the most common of such methods employs high energy y-rays. Usually, only one of these two measurements is required.
The ash content may be determined in some cases by measurement of the intensities o~ X-rays or low energy y-rays in two separate energy regions of the scattered X-ray or low energy y-rays spectrum wherein the geometry of source, sample and detector is chosen so that the scattered intensity for both beams is essentially independent of bulk density of the coal or is affected proportionately the same by changes in bulk density.
Where the moisture content of the coal or hydrogen
In ~he specification and claims when describing methods of determining ash content of coal a reference to coal is also a reference to coke. Also, since the content of mineral mat~er is closely related to the content of ash, the content of one can be determined at least approximately from a measuremen~ of the other.
It is known to determine the ash content of coal gravimetrically by burniny a known amount of coal and weighing the residue. In order to reduce errors, a large sample is taken and ground and the sample size reduced in accordance with standard sampling procedures. This method does not permit a rapid continuous monitor of ash content.
Continuous and rapid methods for determining the ash content of coal are known and depend on scatter of particles, or transmission or scatter of X- or iow energy ~ rays~ Such methods are described in Cameron J.F., "measurement of ash content and calorific value of coal with radioisotope instruments" O.R.N.L. llC-10 Vol. ~ P 903, Cameron J.F., CIayton C.G., "Radioisotope Instruments Volume 1" International Series of Monographs in nuclear energy Volume 107, Pergamon Press (1971), Kato M., "Present status of research and appiication of low-energy X- and gamma-ray sources in Japan" O.R.N.L. llC-10 Vol. 2 P 723, Rhodes J.R., "Ore and Coal Analyses using radioisotope techniques"
O.R.N.E. llC-5, P 206 and Vasilev A.G. et al, "Express ash analyser based on the recording of forward scattered gamma rays" Koksi Khimiya 1974 No. 5, P 52. The basis of these methods is that the mean atomic number of the mineral matter constituents is higher ~han that of the coal matter, and that ~ and ~-ray interactions with atoms are atomic number 5~)~.g dependent~ The mean atomic number of mineral matter, however, is not constant, and in practice variations in iron content of the mineral matter cause considerable errors in determination of ash using the above methods.
Neutron techniques can, in principle, be used to determine ash content of coal because these techniques can be used to determine concentrations of the more abundant elements of the coal. Such methods are described in Cameron J.F., "Measurement of ash content and calorific value of coal with radioisotope instruments" O.R.N.L. llC-10 Vol. 2 P 903.
Neutrons, and the ~-rays produced by neutron interactions with the coal, both penetrate large volumes o coal and hence neutron techniques can be used with relatively large particles of coal. However, determination of concentrations of all the elements required for accurate determination of ash content would, in practice, be very complex because some of the neutron techniques for individual elements are complex.
Techniques are in practice, relatively simple for only a limited number of elements, e.g., iron by neutron capture r-ray techniques as described by FMC Corporation, "Analysis of coal with Cf-252", pages 37 to 39 in Californium Progress, 20 January, 1976 and by Ljunggren K. and Christell R., "On-line determination of the iron cosltent of ores, ore products and wastes by means of neutron capture gamma radiation measurement", page 181 in Nuclear Techniques in Geochemistry and Geophysics, IAEA, Vienna, 1976.
In methods based on scatter o~ ~ particles, the intensity of particles scatter from a material is related to the mean atomic number of the material. As the mean atomic -30 number of coal increases with mineral matter content the intensity of ~ particles scattered from coal is proportional to the ash content. However, large errors occur in this method through variations in iron and moisture content.
In methods based on transmission of X-rays or low energy ~-rays the intensity of the radiation transmitted through a sample of fixed weight per unit area decreases with increasing mass attenuation coefficient of the bulk material. At energies less than about 100 keV the mass attenuation co-efficient changes rapidly with atomic number, which means that the transmitted intensity is sensitive to coal composition.
The ratio of the intensity ~I) of a collimated beam of radiation transmitted through a coal sample of thickness (x) and bulk density (P) to the intensity (Io) in the absence of coal is Io xp( (~i.Ci) p.x) (1) where ~i and Ci are the mass absorption coefficient and concentration (weight fraction) of the ith element in the coal respectively. Now ~ Ci = ~coal matter C coal matter _ + ~mineral matter .C mineral matter (2) where C is concentration and Ccoal matter + Cmineral matter =1 (3) Hence if coal samples to be analysed have mineral matter of essentially constant composition and if the weight per unit area (p.x) of coal is separately measured, and results combined with equations (1), (2) and (3), the concentration of mineral matter and hence the closely correlated ash content are determined.
A high sensitivity to variations in mineral matter content can be obtained with methods employing transmission because the sensitivity to content of mineral matter is proportional to (x) in equation (1).
In methods based on scatter of X- or low energy y-raysl the intensity (I) of radiation scattered from the coal depends on the probability of coherent and Compton scattering, and absorption of X- or low energy ~-rays, within the sample. The optimum energy range for maximum sensitivity to ash is 10 to 20 keV, and in this case k (4) . Ci ) wherein ~i and Ci are the mass absorption coefficient and concentration respectively for the ith element in the coal sample, and k depends on overall geometry and detection efficiency, and output of the low energy ~- or X-ray sourse.
If coal samples to be analysed have mineral matter of essentially constant chemical composition, then mineral matter content and the closely correlated ash content are determined.
Variations in iron content of the mineral matter affect both the X- and low energyy -ray transmission and scatter methods as follows:
~1) If the X-ray energies are chosen below the iron K
shell absorption edge (7,1 keV), the mass absorption coefficient of iron and the mean for the other constituents of mineral matter is about the same and the mineral matter content and hence ash is determined with reasonable accuracy. However, these low energy X-rays are strongly absorbed and the coal must be finely ground (less than 0,3 mm) so that measurements can be made. This is a severe ; 5 ~ ~ ~
limitation in practice for on-line determination.
(2) If the X-ray energies are chosen above the iron K
shell absorption edge, compensation must be made for iron content because iron absorbs far more per unit weight than the absorption per unit weight of the other constituents of the mineral matter. The only compensation currently used for iron depends on excitation of iron K X-rays. This method can only be used on finely ground coal since the X X-rays are greatly absorbed in less than 1 mm thickness of coal.
~ence, unless the case occurs of essentially no variation of iron content o the mineral matter, ~he content of mineral matter and hence ash can only be determined accurately by currently used low energy ~ray and X-ray techniques if the particle size of coal is very small.
It would be expected therefore from the prior art that accurate determination of ash content of coal by X-ray and low energy Y-ray techniques would be unlikely unless the iron content of the ash was constant or the coal particles were finely ground.
The method of the present invention determines ash content even when the iron concentration varies and can be used on relatively large diameter coal particles.
According to the invention the concentration of ash or mineral matter in coal is determined from (i) the result of a measurement in a first energy region of the intensit~ of X-rays or low energy y-rays resulting from at least one scattering interaction in said coal, said first energy region chosen such that there is significant difference in absorption of radiation per unit weight in coal matter and mineral matter excluding iron, ,.. . ) I ~0~ g combined with tii) the result of at least one further ~easurement at a different energy region of the intensity of X-rays or low energy ~-rays, resulting from at least one scattering interaction in said coal, said different energy region(s) so chosen that there is a significant difference in absorption of radiation per unit weight of coal matter and mineral matter and wherein the relative absorption per unit weights by said coal matter and said mineral matter at any one energy or energy region is significantly different from the relative absorption at each other energy or energy region.
The present invention also provides an apparatus for determining the concentration of ash or mineral matter in coal, which apparatus comprises:
(a) a source yielding X-rays or low energy y-rays either of a single energy or multiple energies;
(b) detecting means being associated with said source being capable of detecting X-rays or low energy y -rays resulting from at least one scattering interaction in said coal and being adapted to discriminate between said X-rays or low energy y-rays detected in various energy regions, a first energy region being chosen so that there is significant difference in absorption of radiation per unit weight in coal matter and mineral matter excluding iron and X-rays or low energy y-rays of at least one different energy or energy region so chosen that there is significant difference in absorption of radiation per unit weight of coal matter and mineral matter and that the relative absorption per unit weights by said coal matter and said mineral matter 5 0 :~ ~
at any one energy or energy reqion ls signi~icantly different from the ~elative absorption at each other energy or energy region, (c) shielding means interposed hetween said source and said detecting means, ~hereby reclucing -the intensity of direct source ~-rays ox low energ~ y-rays impinging on said detecting means; and (d) calculating means associated with the outputs of said detecting means to calculate said concentration.
In the accompanying dra~Jin~s ~Ihich illustrate specific embodiments of the invention, by way of example, FI~JURE 1 is a schematic layout of the apparatus of the present invention;
FIGURE 2 is a graphical illustration of ash content;
FIGURE 3 is another schematic illustration of the ¦ present invention.
In this specification and claims the term "low energy y-rays" means y-rays of such an energy that'the absorption of radiation per unit weight of at least some elements is significantly different ~rom the absorption per unit weight of other elements. Whilst the present invention is described with reference to a single source of X- or low energy y-rays, the source may be a composite one, where two or more radioisotopes either comhined in a single unit or in separate units, which produce a sing1e energy spectrum which is detected by a single detector.
In a preferred emhocliment of the invention the concentration of ash or mineral matter in coal is determined mb/J~ - 9 -~ 1B501~
from the result of a measuremen-t :Ln a :firs-t enercJy reCJion of -the intensity of X-rays or low energy ~-rays resulting from a-t least one scatterinq interaction in said coal, said first ener~y region chosen such that there is significant difference in absorption of radiati.on per unit ~reigh-t in coal matter and mineral matter excluding iron, comhined ~li.th the result of a second measurement at a second energy region of the intensity of X-rays or low enercty y-rays from the same mh/~G7 - 9a -I
0 ~ ~
source as said X-rays or low energy y-rays of said first energy region resulting from at least one scattering interaction ln said coal, said second energy region chosen that the absorption of radiation per unit weight of mineral matter is significantly dif$erent from that of coal matter and that the relative absorption per unit weights by said mineral matter and said coal matter at said first energy region is significantly different from the relative absorption at said second energy region.
In applying the method of the invention, the concentration of mineral matter is sometimes determined by the aforementioned measurements coupled with one or more additional measurements selected from (i~ measurement of weight per unit area or a measurement proportional thereto, or (ii) measurement of bulk density, or a measurement proportional thereto, One of the most common of such methods employs high energy y-rays. Usually, only one of these two measurements is required.
The ash content may be determined in some cases by measurement of the intensities o~ X-rays or low energy y-rays in two separate energy regions of the scattered X-ray or low energy y-rays spectrum wherein the geometry of source, sample and detector is chosen so that the scattered intensity for both beams is essentially independent of bulk density of the coal or is affected proportionately the same by changes in bulk density.
Where the moisture content of the coal or hydrogen
3~ content of the coal matter varies considerably the ash o ~ ~
content of coal can be determined more accurately by combining the method of the invention with a measurement of moisture or hydrogen content. Methods of measuring moisture and hy~rogen in coal are known (viz. neutron scatter or transmission, or capture y-rays from neutron absorption by hydrogen).
The method as described in the preferred embodiment of the present invention also partly compensates for variable amounts of other elements, e.g., calcium or sulur in the mineral matter which have a high mass absorption coefficient compared with the mean for the other mineral matter constituents and hence improves accuracy of analysis for content of mineral matter and hence ash.
The method of the invention may be carried out on coal on a conveyor, in a shute, or in a pipe. The coal may be dry or in a slurry and can be in coarse lumps or finely divided. It is convenient and preferred to apply the method of the invention to a continuous monitoring of ash content of coal but the invention is not so restricted as the method can also be applied to discrete samples of coal.
The energies or energy regions of the X- and low energy ~-rays are chosen in relation to the particular analysis application. For example, in the use of X~ and low energy r-raY to determine the ash content of coal on a conveyor belt, the X-ray energies or low energy ~-ray or energy regions are chosen so that high absorption of X-rays or low energy ~-rays in the thickness of coal occurs and consequently high sensitivity to changes in ash content, but sufficient X-rays or low energy ~-rays tscattered by the coal) reach the detector so that ~ ~5~:~g the X-ray or low energy y-ray intensitie~ can be accurately measured.
Some suitable radioisotopes whlch may be used as sources of the X and low energy ~-rays with the method of the inventiOn are 241Am 153Gd 109cd 155E 145 and 57Co. As well as using their direct radiation the above sources may be used with a secondary target to produce a range of intermediate energy radiation as described in Watt J.S., "~-ray excited X-ray sources" International Journal of Applied Radiation and Isotopes, 1964, Vol. 15, p.617~ Some radioisotopes which may be used as sources of high enexgy y -rays are 133Ba, 137Cs and 60Co. As well as radio-isotope sources, another possible source of X~rays are X-ray tubes but these are considerabiy more complex and expensive.
When the method of the invention is used to determine ash in coal on a conveyor belt it may in some cases be necessary to compensate for slight variations in belt thickness by continuously measuring the thickness of the belt. This could be achieved by conventional radioisotope techniques on the empty return section of the belt.
Preferred embodiments of the invention are described in the following examples with reference to the Figures. Two comments common to each are:
a) Although coal i5 shown on a moving conveyor, it is also possible for measurements to be made on static coal samples, coal passing through a chute or hopper, coal on a continuous sample by-line, etc.l and b) The X~ and/or low energy y-rays scattered by the coal are detected by an energy-sensitive detector, and the ash con~ent is determined by combining measurements of intensity of two or more energy regions selected from the detected X- or low energy y-ray spectrum.
In figure l, coal l on a moving conveyor 2 is viewed by a beam of low energy y- or X-rays from radioisotope source 3. The collimation by the lead shield 4 ensures that the scintillation detector 5 sees X- or low energy y-rays scattered from deeply within the coal and hence analysis for ash is averaged over a considerable depth of coal.
In the simplest case, two energy regions are selected and combined to determine ash content. For example using radioisotope l53Gd and detecting X-rays or low energy ~-rays with a scintillation detector, the intensity of backscattered low energy ~-rays in the two energy regions 27 to 44 keV and 81 to 107 keV were determined. The intensity of the h1gher energy reyion (IHE~ and of the lower energy region were combined and the ash content ~Cash) was calculated from the equation:
Cash IHE
where ~l and a2 are constants determined from least squares analysis. In a group of 14 samples from Utah Development Co's Blackwater Mine in Queensland Australia, ash content was determined to 0.8 wt ~ for samples having ash contents in the range 5 to 18 wt % and iron contents of the ash in the range 6 to 12.6 wt %. These results are shown in Figure 2.
Similarly, in a group of 15 samples from twelve coal mines, which supply coking coal to Australian Iron and Steel 5 0 :~ ~
Pty. Ltd., ~he ash content was determined to an accu~acy of 1.1 wt. % (RMS error3 ash. The ash content range was 10 to 31 wt. ~ with a mean of 17.9 wt. %, and the iron content varied between 0.6 and 4.5 wt. ~ in the ash.
The use of three energy regions in the above example would be of advantage for some coals. 153Gd, 57Co and 241Am are some of radioisotopes suitable for this technique.
The electronics used with the scintillation detectors are known art, the main requirement being that the intensity of detected X- or low energy ~-rays can be accurately measured in each energy region. One example of electronics is shown in Figure 1. A high voltage unit 6 polarises the scintillation detector 5, and other equipment comprises amplified-gain stabiliser 7, single channel analysers 8 to select the energy regions, and interface units 9 link outputs from units 8 to a digital computer 10 which scales the electrical pulses and calculates ash content. Alternatively units 8 can be replaced by an analogue to digital converter and multichannel analyser.
In Figure 3, coal 1 on a moving belt 2 is viewed by a beam of X- or low energy y-rays from radioisotope 3. The lead shields 4 and 11 collimate the X- or low energy y-rays from the radioisotope source so that only X- or low energy Y-rays scattered within the coal can be detected by scintillation detector 5.
The electronics is similar to that in Figure 1 and comprises high voltage unit 6, amplifier and gain stabiliser 7, single channel analysers 8, in~er~ace units 9 and digital computer 10.
The ash content o coal is again calculated from measurements of intensity of X- or low energy ~-rays in two (as shown for Figure 3) or more energy regions of spectrum of low energy y- or X-rays scattered in the coal. In some cases a further determination of bulk density or weight per unit area of coal is required to compensate the energy region measurements to give a more accurate determination of ash content.
content of coal can be determined more accurately by combining the method of the invention with a measurement of moisture or hydrogen content. Methods of measuring moisture and hy~rogen in coal are known (viz. neutron scatter or transmission, or capture y-rays from neutron absorption by hydrogen).
The method as described in the preferred embodiment of the present invention also partly compensates for variable amounts of other elements, e.g., calcium or sulur in the mineral matter which have a high mass absorption coefficient compared with the mean for the other mineral matter constituents and hence improves accuracy of analysis for content of mineral matter and hence ash.
The method of the invention may be carried out on coal on a conveyor, in a shute, or in a pipe. The coal may be dry or in a slurry and can be in coarse lumps or finely divided. It is convenient and preferred to apply the method of the invention to a continuous monitoring of ash content of coal but the invention is not so restricted as the method can also be applied to discrete samples of coal.
The energies or energy regions of the X- and low energy ~-rays are chosen in relation to the particular analysis application. For example, in the use of X~ and low energy r-raY to determine the ash content of coal on a conveyor belt, the X-ray energies or low energy ~-ray or energy regions are chosen so that high absorption of X-rays or low energy ~-rays in the thickness of coal occurs and consequently high sensitivity to changes in ash content, but sufficient X-rays or low energy ~-rays tscattered by the coal) reach the detector so that ~ ~5~:~g the X-ray or low energy y-ray intensitie~ can be accurately measured.
Some suitable radioisotopes whlch may be used as sources of the X and low energy ~-rays with the method of the inventiOn are 241Am 153Gd 109cd 155E 145 and 57Co. As well as using their direct radiation the above sources may be used with a secondary target to produce a range of intermediate energy radiation as described in Watt J.S., "~-ray excited X-ray sources" International Journal of Applied Radiation and Isotopes, 1964, Vol. 15, p.617~ Some radioisotopes which may be used as sources of high enexgy y -rays are 133Ba, 137Cs and 60Co. As well as radio-isotope sources, another possible source of X~rays are X-ray tubes but these are considerabiy more complex and expensive.
When the method of the invention is used to determine ash in coal on a conveyor belt it may in some cases be necessary to compensate for slight variations in belt thickness by continuously measuring the thickness of the belt. This could be achieved by conventional radioisotope techniques on the empty return section of the belt.
Preferred embodiments of the invention are described in the following examples with reference to the Figures. Two comments common to each are:
a) Although coal i5 shown on a moving conveyor, it is also possible for measurements to be made on static coal samples, coal passing through a chute or hopper, coal on a continuous sample by-line, etc.l and b) The X~ and/or low energy y-rays scattered by the coal are detected by an energy-sensitive detector, and the ash con~ent is determined by combining measurements of intensity of two or more energy regions selected from the detected X- or low energy y-ray spectrum.
In figure l, coal l on a moving conveyor 2 is viewed by a beam of low energy y- or X-rays from radioisotope source 3. The collimation by the lead shield 4 ensures that the scintillation detector 5 sees X- or low energy y-rays scattered from deeply within the coal and hence analysis for ash is averaged over a considerable depth of coal.
In the simplest case, two energy regions are selected and combined to determine ash content. For example using radioisotope l53Gd and detecting X-rays or low energy ~-rays with a scintillation detector, the intensity of backscattered low energy ~-rays in the two energy regions 27 to 44 keV and 81 to 107 keV were determined. The intensity of the h1gher energy reyion (IHE~ and of the lower energy region were combined and the ash content ~Cash) was calculated from the equation:
Cash IHE
where ~l and a2 are constants determined from least squares analysis. In a group of 14 samples from Utah Development Co's Blackwater Mine in Queensland Australia, ash content was determined to 0.8 wt ~ for samples having ash contents in the range 5 to 18 wt % and iron contents of the ash in the range 6 to 12.6 wt %. These results are shown in Figure 2.
Similarly, in a group of 15 samples from twelve coal mines, which supply coking coal to Australian Iron and Steel 5 0 :~ ~
Pty. Ltd., ~he ash content was determined to an accu~acy of 1.1 wt. % (RMS error3 ash. The ash content range was 10 to 31 wt. ~ with a mean of 17.9 wt. %, and the iron content varied between 0.6 and 4.5 wt. ~ in the ash.
The use of three energy regions in the above example would be of advantage for some coals. 153Gd, 57Co and 241Am are some of radioisotopes suitable for this technique.
The electronics used with the scintillation detectors are known art, the main requirement being that the intensity of detected X- or low energy ~-rays can be accurately measured in each energy region. One example of electronics is shown in Figure 1. A high voltage unit 6 polarises the scintillation detector 5, and other equipment comprises amplified-gain stabiliser 7, single channel analysers 8 to select the energy regions, and interface units 9 link outputs from units 8 to a digital computer 10 which scales the electrical pulses and calculates ash content. Alternatively units 8 can be replaced by an analogue to digital converter and multichannel analyser.
In Figure 3, coal 1 on a moving belt 2 is viewed by a beam of X- or low energy y-rays from radioisotope 3. The lead shields 4 and 11 collimate the X- or low energy y-rays from the radioisotope source so that only X- or low energy Y-rays scattered within the coal can be detected by scintillation detector 5.
The electronics is similar to that in Figure 1 and comprises high voltage unit 6, amplifier and gain stabiliser 7, single channel analysers 8, in~er~ace units 9 and digital computer 10.
The ash content o coal is again calculated from measurements of intensity of X- or low energy ~-rays in two (as shown for Figure 3) or more energy regions of spectrum of low energy y- or X-rays scattered in the coal. In some cases a further determination of bulk density or weight per unit area of coal is required to compensate the energy region measurements to give a more accurate determination of ash content.
Claims (24)
- THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
l. A method of analysing coal wherein the concentration of ash or mineral matter in said coal is determined from:
(a) irradiating coal with X-rays or low energy gamma rays and obtaining a single energy spectrum resulting from at least one scattering interaction in said coal, (b) selecting a first energy region from said single energy spectrum, such that there is a significant difference in absorption of radiation per unit weight between coal matter and mineral matter excluding iron, (c) selecting at least one other energy region from said single energy spectrum such that there is a significant difference in absorption of radiation per unit weight between coal matter and mineral matter, and (d) measuring the intensity of the scattered X-rays or low energy gamma rays at said first energy region combined with measuring the intensity of the scattered X-rays or low energy gamma rays at said at least one other energy region and determining the concentration of ash or mineral matter in said coal from these measurements, wherein the relative absorptions per unit weights by said coal matter and said mineral matter at any one said energy region is significantly different from that at each other energy region. - 2. The method as defined in claim l, wherein X-rays or low energy gamma rays are derived from a single source which produces a single energy spectrum which is detected by a single detector.
- 3. The method as defined in claim l, wherein said X-rays or low energy gamma rays are derived from a composite source, where two or more radioisotopes are combined in a single unit which produces a single energy spectrum which is detected by a single detector.
- 4. The method as defined in claim 1, wherein said X-rays or low energy gamma rays are derived from a composite source, where two or more radioisotopes are present in two or more separate units which produce a single energy spectrum which is detected by a single detector.
- 5. The method as defined in claim 1, wherein said concentration is determined from the result of a measurement of said first energy region of the intensity of X-rays or low energy gamma rays resulting from at least one scattering interaction in said coal, combined with the result of a second measurement at another energy region of the intensity of transmission or scatter of X-rays or low energy gamma rays resulting from at least one scattering interaction in said coal.
- 6. The method as defined in claim 1, which further comprises a measurement of at least one of weight per unit area of said coal, or bulk density of said coal, or a measurement proportional to said weight per unit area or said bulk density.
- 7. The method as defined in claim 1, wherein the geometry of said source, coal and detector is chosen so that the scattered intensity of each of said X-rays or low energy gamma rays is essentially independent of bulk density of said coal or is affected proportionally the same by changes in bulk density.
- 8. The method as defined in claim 1, wherein in said coal the moisture content varies considerably, said method further comprising a measurement of moisture or hydrogen content of said coal.
- 9. The method as defined in claim 6, wherein in said coal the moisture content varies considerably, said method further comprising a measurement of moisture or hydrogen content of said coal.
- 10. The method as defined in claim 8 or claim 9, wherein said moisture or hydrogen content is determined by neutron scatter or transmission or by capture gamma rays from neutron absorption by hydrogen.
- 11. The method as defined in claim 1, wherein said source is at least one of 241Am, 153Gd, 109Cd, 155Eu, 145Sm, 57Co.
- 12. The method as defined in claim 11, wherein said at least one of 241Am, 153Gd, 109Cd, 155Eu, 145Sm or 57Co are employed with a secondary target to produce a range of intermediate energy radiation.
- 13. An apparatus for determining the concentration of ash or mineral matter in coal, which apparatus comprises:
(a) a source yielding X-rays or low energy gamma rays either of a single energy or multiple energies;
(b) a detector being associated with said source being capable of detecting X-rays or low energy gamma rays resulting from at least one scattering interaction in said coal and being adapted to discriminate between said X-rays or low energy gamma rays detected in various energy regions of a single energy spectrum, a first energy region being so chosen that there is significant difference in absorption of radiation per unit weight in coal matter and mineral matter excluding iron and at least one other energy region so chosen that there is significant difference in absorption of radiation per unit weight of coal matter and mineral matter and that the relative absorption per unit weights by said coal matter and said mineral matter at any one energy region is significantly different from the relative absorption at each other energy region;
(c) shielding means interposed between said source and said detector, thereby reducing the intensity of direct source X-rays or low energy gamma rays impinging on said detecting means; and (d) calculating means associated with the outputs of said detector to calculate said concentration. - 14. The apparatus as defined in claim 13, wherein said source is a single source of X-rays or low energy gamma rays which produces a single energy spectrum.
- 15. The apparatus as defined in claim 13, wherein said source is a composite source, where two or more radioisotopes are combined in a single unit, which produces a single energy spectrum.
- 16. The apparatus as defined in claim 13, wherein said source is a composite source where two or more radioisotopes are present in two or more separate units which produce a single energy spectrum which is detected by a single detector.
- 17. The apparatus as defined in claim 13, wherein said detecting means detects X-rays or low energy gamma rays of said first energy region and X-rays or low energy gamma rays of one other energy region.
- 18. The apparatus as defined in claim 13, further comprising:
(e) first measuring means to measure at least one of weight per unit area of said coal and/or bulk density of said coal, or a measurement proportional to said weight per unit area or said bulk density.
the output of said first measuring means being associated with said calculating means. - 19. The apparatus as defined in claim 13, wherein the geometry of said source, coal and detecting means is chosen so that the scattered intensity of each of said X-rays or low energy gamma rays is essentially independent of the bulk density of said coal or is affected proportionally the same by changes in bulk density.
- 20. The apparatus as defined in claim 13, when used to determine the ash or mineral matter concentration in a coal having a considerably variable moisture content, further comprising;
(e) second measuring means to measure moisture or hydrogen content of said coal;
the output of said second measuring means being associated with said calculating means. - 21. The apparatus as defined in claim 18, when used to determine the ash or mineral matter concentration in a coal having a considerably variable moisture content further comprising:
(f) second measuring means to measure moisture or hydrogen content of said coal;
the output of said second measuring means being associated with said calculating means. - 22. The apparatus as defined in claim 20 or claim 21, wherein said second measuring means measures neutron scatter or transmission or capture gamma rays from neutron absorption by hydrogen.
- 23. The apparatus as defined in claim 13, wherein said source is at least one of 241Am, 15Gd, 109Cd, 155EU, 145Sm, 57Co.
- 24. The apparatus as defined in claim 23, wherein said at least one of 241Am 153Gd 109Cd 155Eu 145Sm or 57Co is employed with a secondary target to produce a range of intermediate energy radiation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPE307980 | 1980-04-10 | ||
| AUPE3079 | 1980-04-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1165018A true CA1165018A (en) | 1984-04-03 |
Family
ID=3768485
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000375127A Expired CA1165018A (en) | 1980-04-10 | 1981-04-09 | Analysis of coal |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5710441A (en) |
| AU (1) | AU6917381A (en) |
| CA (1) | CA1165018A (en) |
| DE (1) | DE3114668A1 (en) |
| GB (1) | GB2073884B (en) |
| ZA (1) | ZA812363B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4710946A (en) * | 1985-08-06 | 1987-12-01 | Amoco Corporation | Method and apparatus for X-ray video fluoroscopic analysis of rock samples |
| US5506406A (en) * | 1993-05-17 | 1996-04-09 | Atomic Energy Corporation Of South Africa Ltd. | Method and apparatus for determining the concentration of a heavy element in a rock face |
| CN101349658B (en) * | 2008-09-17 | 2010-11-03 | 丹东东方测控技术有限公司 | Fast analysis method of coal ash separating line |
| CN102128840B (en) * | 2010-11-30 | 2013-11-06 | 湖南大学 | Method for automatically recognizing coal ash |
| CN102749344B (en) * | 2012-06-19 | 2016-03-16 | 内蒙古立信测控技术有限公司 | A kind of coal ash detection method based on single radioactive source |
| CN104764755B (en) * | 2015-04-20 | 2017-07-28 | 清华大学 | The device that uranium content and grade of coal are controlled in lime-ash after on-line prediction coal burning |
-
1980
- 1980-04-10 AU AU69173/81A patent/AU6917381A/en not_active Abandoned
-
1981
- 1981-04-09 GB GB8111227A patent/GB2073884B/en not_active Expired
- 1981-04-09 ZA ZA00812363A patent/ZA812363B/en unknown
- 1981-04-09 CA CA000375127A patent/CA1165018A/en not_active Expired
- 1981-04-10 DE DE19813114668 patent/DE3114668A1/en not_active Withdrawn
- 1981-04-10 JP JP5325081A patent/JPS5710441A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5710441A (en) | 1982-01-20 |
| ZA812363B (en) | 1982-04-28 |
| GB2073884A (en) | 1981-10-21 |
| DE3114668A1 (en) | 1982-04-01 |
| AU6917381A (en) | 1981-10-15 |
| GB2073884B (en) | 1984-08-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4090074A (en) | Analysis of coal | |
| US6130931A (en) | X-ray fluorescence elemental analyzer | |
| US4314155A (en) | Method and apparatus for elemental analysis employing combination of neutron inelastic scattering and γ ray scattering | |
| CA1157169A (en) | Annihilation radiation analysis | |
| US4566114A (en) | X- and γ-Ray techniques for determination of the ash content of coal | |
| Lim et al. | On-line coal analysis using fast neutron-induced gamma-rays | |
| US4414472A (en) | Method for determining the solids weight fraction of a slurry | |
| Sowerby et al. | Development of nuclear techniques for on-line analysis in the coal industry | |
| CA1165018A (en) | Analysis of coal | |
| CA1193371A (en) | Neutron method for elemental analysis independent of bulk density | |
| Fookes et al. | On-line determination of the ash content of coal using a “Siroash” gauge based on the transmission of low and high energy γ-rays | |
| US3353021A (en) | Apparatus and process for continuous measurement of moisture in moving coal by neutron thermalization | |
| Qi et al. | A novel automated separator based on dual energy gamma-rays transmission | |
| Cywicka-Jakiel | Fast-neutron and gamma-ray transmission method for coke-humidity determination | |
| Sowerby | Bulk analysis of coal | |
| GB2054140A (en) | Improvements to X- and gamma -ray Techniques for Determination of the Ash Content of Coal | |
| AU600461B2 (en) | Neutron and gamma-ray moisture assay | |
| Sowerby | On-line and bulk analysis of coal and metalliferous ores | |
| Lim et al. | Neutron techniques of on-line analysis in the Australian mineral industry | |
| Lim et al. | On-belt analysis of ash in coal | |
| CA1150860A (en) | X- and m-ray techniques for determination of the ash content of coal | |
| Sowerby | Combination neutron and γ ray method of elemental analysis | |
| Salgado et al. | Current status of nucleonic gauges in Portugal | |
| Hall et al. | Continuous monitoring of coal by a neutron moisture meter | |
| Borsaru et al. | Advanced Techniques for On-Line Monitoring of Brown Coal Quality |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |