CA1063258A - Determining the concentration of sulphur in coal - Google Patents
Determining the concentration of sulphur in coalInfo
- Publication number
- CA1063258A CA1063258A CA312,918A CA312918A CA1063258A CA 1063258 A CA1063258 A CA 1063258A CA 312918 A CA312918 A CA 312918A CA 1063258 A CA1063258 A CA 1063258A
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- CA
- Canada
- Prior art keywords
- coal
- sulphur
- concentration
- iron
- sample
- 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.)
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- Analysing Materials By The Use Of Radiation (AREA)
Abstract
A B S T R A C T
A method for continuously measuring the concentration of sulphur in coal of the type described, including the steps of bombarding a sample of coal with electromagnetic radiation in the x-ray region of the spectrum to cause the iron atoms in the sample to emit their character-istic fluorescent radiation, detecting said fluorescent radiation, measuring the intensity of said fluorescent radiation, from which measure the concen-tration of iron in the sample is calculated, correcting the concentration of iron to allow for non-pyritic iron in the coal, determining the concen-tration of sulphur present in the coal as iron pyrites from the corrected concentration of iron, and correcting the concentration of sulphur thus found to allow for sulphur present in the coal in organic and sulphatic form to give the concentration of sulphur in the coal. This method has the advantage that it can be applied to coal at the mine head by relatively unskilled personnel.
A method for continuously measuring the concentration of sulphur in coal of the type described, including the steps of bombarding a sample of coal with electromagnetic radiation in the x-ray region of the spectrum to cause the iron atoms in the sample to emit their character-istic fluorescent radiation, detecting said fluorescent radiation, measuring the intensity of said fluorescent radiation, from which measure the concen-tration of iron in the sample is calculated, correcting the concentration of iron to allow for non-pyritic iron in the coal, determining the concen-tration of sulphur present in the coal as iron pyrites from the corrected concentration of iron, and correcting the concentration of sulphur thus found to allow for sulphur present in the coal in organic and sulphatic form to give the concentration of sulphur in the coal. This method has the advantage that it can be applied to coal at the mine head by relatively unskilled personnel.
Description
This application is a divisional of copending application Serial NoO 245,969 filed February 17, 1976.
This invention relates to a method of determining the concentration of sulphur in coalO
It is necessary to know the sulphur content of a given batch of coal in order to be able to supply the correct type of coal for a given useO
For instance coal-burning power stations will only accept coal with a low sulphur contentO Coals with low sulphur contents are also preferred foT use in domestic solid-fuel burning heating systemsO
Previously the sulphur content of a batch of coal has been measured by chemically analysing a sample. This process is time consuming and there is a delay between mining the batch and despatching it either to the appropriate storage bunker or to the appropriate user. This delay involves the inefficient use of intermediate storage~containers.
It is therefore an object of the present invention to provide a method of determining the concentration of sulphur in coal which is easily and quickly operable, and can be applied to the coal as it is minedO
A suitable technique for adaption for this purpose is X-ray fluorescence spectroscopy. When an atom is irradiated with high energy electromagnetic radiation IX-rays) of the appropriate energy its inner elec-tron shells are disturbed and a characteristic fluorescence is observedO The fluorescent radiation has an energy also in the X-ray range and this energy is proportional to the square of the atomic number of the atom, irrespective of the chemical state of combination of the atom. The intensity of the fluorescent radiation is approximately proportional to the concentration of the atom in the matrix. For elements of atomic number 20 and above this is an easily applicable technique. However, for elements such as sulphur (atomic number = 16), the fluorescent radiation is of such an energy that it can be absorbed by other elements of low atomic number such as silicon, aluminium and iron in a matrix and a small variation in the concentration of these elements in a matrix can cause considerable variations in the intensity of the characteristic fluorescent radiation leaving samples having the same sulphur contentO These absorbing elements are commonly found in the ash-forming minerals in coals in amounts which vary considerably from batch to batch. Therefore the determination of the sulphur concentration of the coal by measurement of the intensity of its characteristic fluorescent radiation can be in considerable error.
Sulphur occurs in coal in three forms, vi~ organic~ sulphatic and pyritic (i.e. as iron pyrites), while iron can be classified in co~l as either pyritic or non pyritic. The concentration of the sulphur in the coal can be expressed as follows:-S = (Fe - Fen)O Kl +SO + Ss Where:-S = concentration of sulphur in coal Fe = concentration of iron in coal Fen = concentration of non-pyritic iron in coal Kl = conversion factor to determine the concentration of sulphur in pyritic form ~= 1.1481) SO = concentration of sulphur in organic form Ss = concentration of sulphur in sulphatic form Determination of the concentration of iron (atomic number = 26) in coal by the excitation of its characteristic fluorescent radiation is relative-ly easy since the higher energy radiation is much less absorbed by the ash-forming minerals. Unfortunately, however, the values of Fen, SO and Ss are generally not constant.
We have found that for a given type of coal, the concentration of sulphur in the coal can be reasonably accurately expressed as a function of the intensities of the characteristic fluorescent radiations emitted by the iron and sulphur in a sample of the coal when the sample is bombarded with electromagnetic radiation of appropriate energyO
In particular, we have found that to a good approximation:-S = a ~ bX + cY
Where:-S = concentration of sulphur in the coal sample;
X = intensity of fluorescent radiation emitted by the sulphurin the sample;
Y = intensity of fluorescent radistion emitted by the iron in the sample; and a, b and c are constantsO
The values of a, b and c depend on the test apparatus and the type of coal under test and are determined by placing standard samples of the type of coal under test in the test apparatusO
The sulphur content of an unknown sample may then be determined by measuring the values of X and Y and combining them as indicated aboveO
It is envisaged that more complex mathematical relationships between S, X and Y may result in S being determined more accurately.
Accordingly~ the present invention provides a method for continu-ously determining the concentration of sulphur in coal, which method includes the steps of bombarding a sample of coal with electromagnetic radiation in 2a the X-ray region of the spectrum to cause the iron and the sulphur atoms in the sample to emit their respective characteristic fluorescent radiations detecting said fluorescent radiations, measuring the intensities of said fluorescent radiations and combining said intensities or measures mathemati-cally to produce an output from which the concentration of sulphur in the sample may be determined.
For certain types of coal (hereinafter referred to as 'coal of the type described') the values of Fen, SO and Ss are substantially constantO
In order to determine the concentration of sulphur in coal of the type described the present invention provides a method which includes the steps of bombarding a sample of the coal with electromagnetic radiation in the X-ray region of the spectrum to cause the iron atoms in the sample to emit their characteristic fluorescent radiation, detecting said fluorescent radiation, measuring the intensity of said fluorescent radiation, from which measure the concentration of iron in the sample is calculated, correcting the concentration of iron to allow for any non-pyritic iron in the coal, deter-mining the concentration of sulphur present in the coal as iron pyrites from the corrected concentration of iron and correcting the concentration of sulphur thus found to allow for sulphur present in organic and sulphatic form to give the concentration of sulphur in the coalO
Once the concentration of iron in the sample has been determined the sulphur content could be calculated by handO However, in view of the linear relationship between the concentration of iron and the concentration of sulphur in coal of the type described and since the intensity of fluorescent radiation from the iron is approximately directly proportional to the concen-tration of iron in the coal, it will be appreciated that the scale of a linear intensity meter could be recalibrated to give a direct reading of the sulphur content of any sample, the value of the constant (SO + Ss ~ Fe Kl) for any given type of coal being inserted in the meter by adjusting the scale with respect to the rest position of the needle of the meterO
In order to determine the sulphur content of a large quantity of coal batch sampling may be usedO However, continuous sampling is preferable to minimi~e heterogeneity effectsO
Continuous sampling may be achieved using an apparatus as described in British Patent No. 1,177,067 or any other suitable apparatusO
It is preferred that the sample is ground to a diameter of smaller than 0.5 mmO For coals with low ash content the maximum diameter can be 1 mmO
For coals of the type described it is possible to use particles with a diameter of up to 25 mm, but it is preferred that the diameter should not exceed 5 mm.
It is necessary, in order to excite both the iron and sulphur * Coal Industry (Patents) Ltd., published January 7, 19700 fluorescent radiations, for the exiting electromagnetic radiation to have energies in the ranges of 2.5 to 700 keV and 7.2 to 25 keVO These radiations may be provided either by separate isotope sources, or by a "bremsstrahlung"
source, or by an X-ray tube. It is preferred to use separate isotope sources since these are easier to handle. If a "bremsstrahlung" source is used a single semi-conductor detector (e.gO a lithium-drifted silicon detector) should be usedO Otherwise any suitable detector system may be usedO
An apparatus embodying the method of the invention will now be described, by way of example, with reference to the accompanying drawing, which shows a block diagram of the apparatusO
A layer of coal particles 3 of the appropriate maximum diameter is carried on a continuously moving conveyor of the type described in British Patent No. 1,177,067 beneath two isotope sources l and 40 Source 1 comprises iron 55 (5.9 keV), and the radiation 2 from it excites sulphur atoms, and other atoms whose atomic numbers are close to that of sulphur. The fluorescent radiation and the back-scattered radiation 6 from the sample is detected by a proportional counter 7, which gives a signal which is amplified by amplifier 8 and transmitted to pulse amplitude selector 9, which is adjusted to select only those parts of the signal originating from the sulphur in the sampleO
The selected signal on line 11 leaving the pulse-amplitude-selector 9 is then fed to an electronic device 13 as hereinafter describedO
Simultaneously or consecutively, the sample passes under source 4 which comprises plutonium 238 (14 - 17 keV), the radiation 5 from which ex-cites the iron atoms. The fluorescent radiation and the backscattered radiation 6' from the sample is detected by proportional counter 7', to give a signal which is amplified by amplifier 8' and transmitted to pulse-amplitude selector 10 which is adjusted to select only those parts of the signal originating from the iron present in the sample. The selected signal on line 12 leaving pulse-amplitude selector 10 is then combined with the signal on line 11 in electronic device 13 according to the formula:-S = a + bX + cY
where a, b and c are constants, and X and Y are the magnitudes of signals 11 and 12 respectively. Constants a, b and c are determined by calibrating the apparatus with standard samples of coal of the type under testO The out-put signal on line 14 from tle electronic device 13 is then fed to meter 15, having a linear scale 16 and a pointer 170 The signal on line 14 may also be fed to an integrator 19 arranged to produce a digital output 20 at desired intervals and to transmit an output signal on line 21 to operate apparatus for directing the batch from which the sample particles were taken into an appropriate bunker according to its sulphur contentO
If a coal of the type described is being sampled the source 1, detector 6, amplifier 8, pulse amplitude selector 9 and electronic device 13 are disconnected and the signal from the pulse amplitude selector 10 is fed directly to the meter 15, calibrated to display the sulphur concentration or to the integrator l9o The apparatus described above is easy to use and can be operated by an unskilled worker at the pit head. The results obtained using the described method are more consistent and accurate than any previously used non-chemical method, and are obtained much more quickly than by use of chemi-cal methods.
This invention relates to a method of determining the concentration of sulphur in coalO
It is necessary to know the sulphur content of a given batch of coal in order to be able to supply the correct type of coal for a given useO
For instance coal-burning power stations will only accept coal with a low sulphur contentO Coals with low sulphur contents are also preferred foT use in domestic solid-fuel burning heating systemsO
Previously the sulphur content of a batch of coal has been measured by chemically analysing a sample. This process is time consuming and there is a delay between mining the batch and despatching it either to the appropriate storage bunker or to the appropriate user. This delay involves the inefficient use of intermediate storage~containers.
It is therefore an object of the present invention to provide a method of determining the concentration of sulphur in coal which is easily and quickly operable, and can be applied to the coal as it is minedO
A suitable technique for adaption for this purpose is X-ray fluorescence spectroscopy. When an atom is irradiated with high energy electromagnetic radiation IX-rays) of the appropriate energy its inner elec-tron shells are disturbed and a characteristic fluorescence is observedO The fluorescent radiation has an energy also in the X-ray range and this energy is proportional to the square of the atomic number of the atom, irrespective of the chemical state of combination of the atom. The intensity of the fluorescent radiation is approximately proportional to the concentration of the atom in the matrix. For elements of atomic number 20 and above this is an easily applicable technique. However, for elements such as sulphur (atomic number = 16), the fluorescent radiation is of such an energy that it can be absorbed by other elements of low atomic number such as silicon, aluminium and iron in a matrix and a small variation in the concentration of these elements in a matrix can cause considerable variations in the intensity of the characteristic fluorescent radiation leaving samples having the same sulphur contentO These absorbing elements are commonly found in the ash-forming minerals in coals in amounts which vary considerably from batch to batch. Therefore the determination of the sulphur concentration of the coal by measurement of the intensity of its characteristic fluorescent radiation can be in considerable error.
Sulphur occurs in coal in three forms, vi~ organic~ sulphatic and pyritic (i.e. as iron pyrites), while iron can be classified in co~l as either pyritic or non pyritic. The concentration of the sulphur in the coal can be expressed as follows:-S = (Fe - Fen)O Kl +SO + Ss Where:-S = concentration of sulphur in coal Fe = concentration of iron in coal Fen = concentration of non-pyritic iron in coal Kl = conversion factor to determine the concentration of sulphur in pyritic form ~= 1.1481) SO = concentration of sulphur in organic form Ss = concentration of sulphur in sulphatic form Determination of the concentration of iron (atomic number = 26) in coal by the excitation of its characteristic fluorescent radiation is relative-ly easy since the higher energy radiation is much less absorbed by the ash-forming minerals. Unfortunately, however, the values of Fen, SO and Ss are generally not constant.
We have found that for a given type of coal, the concentration of sulphur in the coal can be reasonably accurately expressed as a function of the intensities of the characteristic fluorescent radiations emitted by the iron and sulphur in a sample of the coal when the sample is bombarded with electromagnetic radiation of appropriate energyO
In particular, we have found that to a good approximation:-S = a ~ bX + cY
Where:-S = concentration of sulphur in the coal sample;
X = intensity of fluorescent radiation emitted by the sulphurin the sample;
Y = intensity of fluorescent radistion emitted by the iron in the sample; and a, b and c are constantsO
The values of a, b and c depend on the test apparatus and the type of coal under test and are determined by placing standard samples of the type of coal under test in the test apparatusO
The sulphur content of an unknown sample may then be determined by measuring the values of X and Y and combining them as indicated aboveO
It is envisaged that more complex mathematical relationships between S, X and Y may result in S being determined more accurately.
Accordingly~ the present invention provides a method for continu-ously determining the concentration of sulphur in coal, which method includes the steps of bombarding a sample of coal with electromagnetic radiation in 2a the X-ray region of the spectrum to cause the iron and the sulphur atoms in the sample to emit their respective characteristic fluorescent radiations detecting said fluorescent radiations, measuring the intensities of said fluorescent radiations and combining said intensities or measures mathemati-cally to produce an output from which the concentration of sulphur in the sample may be determined.
For certain types of coal (hereinafter referred to as 'coal of the type described') the values of Fen, SO and Ss are substantially constantO
In order to determine the concentration of sulphur in coal of the type described the present invention provides a method which includes the steps of bombarding a sample of the coal with electromagnetic radiation in the X-ray region of the spectrum to cause the iron atoms in the sample to emit their characteristic fluorescent radiation, detecting said fluorescent radiation, measuring the intensity of said fluorescent radiation, from which measure the concentration of iron in the sample is calculated, correcting the concentration of iron to allow for any non-pyritic iron in the coal, deter-mining the concentration of sulphur present in the coal as iron pyrites from the corrected concentration of iron and correcting the concentration of sulphur thus found to allow for sulphur present in organic and sulphatic form to give the concentration of sulphur in the coalO
Once the concentration of iron in the sample has been determined the sulphur content could be calculated by handO However, in view of the linear relationship between the concentration of iron and the concentration of sulphur in coal of the type described and since the intensity of fluorescent radiation from the iron is approximately directly proportional to the concen-tration of iron in the coal, it will be appreciated that the scale of a linear intensity meter could be recalibrated to give a direct reading of the sulphur content of any sample, the value of the constant (SO + Ss ~ Fe Kl) for any given type of coal being inserted in the meter by adjusting the scale with respect to the rest position of the needle of the meterO
In order to determine the sulphur content of a large quantity of coal batch sampling may be usedO However, continuous sampling is preferable to minimi~e heterogeneity effectsO
Continuous sampling may be achieved using an apparatus as described in British Patent No. 1,177,067 or any other suitable apparatusO
It is preferred that the sample is ground to a diameter of smaller than 0.5 mmO For coals with low ash content the maximum diameter can be 1 mmO
For coals of the type described it is possible to use particles with a diameter of up to 25 mm, but it is preferred that the diameter should not exceed 5 mm.
It is necessary, in order to excite both the iron and sulphur * Coal Industry (Patents) Ltd., published January 7, 19700 fluorescent radiations, for the exiting electromagnetic radiation to have energies in the ranges of 2.5 to 700 keV and 7.2 to 25 keVO These radiations may be provided either by separate isotope sources, or by a "bremsstrahlung"
source, or by an X-ray tube. It is preferred to use separate isotope sources since these are easier to handle. If a "bremsstrahlung" source is used a single semi-conductor detector (e.gO a lithium-drifted silicon detector) should be usedO Otherwise any suitable detector system may be usedO
An apparatus embodying the method of the invention will now be described, by way of example, with reference to the accompanying drawing, which shows a block diagram of the apparatusO
A layer of coal particles 3 of the appropriate maximum diameter is carried on a continuously moving conveyor of the type described in British Patent No. 1,177,067 beneath two isotope sources l and 40 Source 1 comprises iron 55 (5.9 keV), and the radiation 2 from it excites sulphur atoms, and other atoms whose atomic numbers are close to that of sulphur. The fluorescent radiation and the back-scattered radiation 6 from the sample is detected by a proportional counter 7, which gives a signal which is amplified by amplifier 8 and transmitted to pulse amplitude selector 9, which is adjusted to select only those parts of the signal originating from the sulphur in the sampleO
The selected signal on line 11 leaving the pulse-amplitude-selector 9 is then fed to an electronic device 13 as hereinafter describedO
Simultaneously or consecutively, the sample passes under source 4 which comprises plutonium 238 (14 - 17 keV), the radiation 5 from which ex-cites the iron atoms. The fluorescent radiation and the backscattered radiation 6' from the sample is detected by proportional counter 7', to give a signal which is amplified by amplifier 8' and transmitted to pulse-amplitude selector 10 which is adjusted to select only those parts of the signal originating from the iron present in the sample. The selected signal on line 12 leaving pulse-amplitude selector 10 is then combined with the signal on line 11 in electronic device 13 according to the formula:-S = a + bX + cY
where a, b and c are constants, and X and Y are the magnitudes of signals 11 and 12 respectively. Constants a, b and c are determined by calibrating the apparatus with standard samples of coal of the type under testO The out-put signal on line 14 from tle electronic device 13 is then fed to meter 15, having a linear scale 16 and a pointer 170 The signal on line 14 may also be fed to an integrator 19 arranged to produce a digital output 20 at desired intervals and to transmit an output signal on line 21 to operate apparatus for directing the batch from which the sample particles were taken into an appropriate bunker according to its sulphur contentO
If a coal of the type described is being sampled the source 1, detector 6, amplifier 8, pulse amplitude selector 9 and electronic device 13 are disconnected and the signal from the pulse amplitude selector 10 is fed directly to the meter 15, calibrated to display the sulphur concentration or to the integrator l9o The apparatus described above is easy to use and can be operated by an unskilled worker at the pit head. The results obtained using the described method are more consistent and accurate than any previously used non-chemical method, and are obtained much more quickly than by use of chemi-cal methods.
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for continuously measuring the concentration of sulphur in coal of the type described, including the steps of bombarding a sample of coal with electromagnetic radiation in the x-ray region of the spec-trum to cause the iron atoms in the sample to emit their characteristic fluorescent radiation, detecting said fluorescent radiation, measuring the intensity of said fluorescent radiation, from which measure the con-centration of iron in the sample is calculated, correcting the concen-tration of iron to allow for non-pyritic iron in the coal determining the concentration of sulphur present in the coal as iron pyrites from the corrected concentration of iron, and correcting the concentration of sulphur thus found to allow for sulphur present in the coal in organic and sulphatic form to give the concentration of sulphur in the coal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA312,918A CA1063258A (en) | 1975-03-14 | 1978-10-10 | Determining the concentration of sulphur in coal |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB10713/75A GB1494549A (en) | 1975-03-14 | 1975-03-14 | Determining the concentration of sulphur in coal |
| CA245,969A CA1064165A (en) | 1975-03-14 | 1976-02-17 | Determining the concentration of sulphur in coal |
| CA312,918A CA1063258A (en) | 1975-03-14 | 1978-10-10 | Determining the concentration of sulphur in coal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1063258A true CA1063258A (en) | 1979-09-25 |
Family
ID=27164338
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA312,918A Expired CA1063258A (en) | 1975-03-14 | 1978-10-10 | Determining the concentration of sulphur in coal |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1063258A (en) |
-
1978
- 1978-10-10 CA CA312,918A patent/CA1063258A/en not_active Expired
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