DD252889A1 - PROCESS FOR DETERMINING THE ASH CONTENT OF COAL - Google Patents

Abstract

The object of the invention to provide an oak-free method for determining the ash content of coal, taking into account the iron and calcium content based on the X-ray fluorescence analysis, is solved by the X-ray characteristic of the iron and calcium stimulated by X-rays in the energy range of 15 to 25 keV Intensity of the backscattered excitation radiation measured and the measured values are compared with calculated values. The data used to calculate the latter values are varied until sufficient agreement of the measured and calculated intensities is achieved.

Description

Method for determining the ash content of coal Field of application of the invention

The invention relates to a method for determining the ash content of coal taking into account the iron and galium content on the basis of the X-ray fluorescence analysis

Characteristic of the known technical solutions

The classic method for determining the ash content of coal - complete combustion of a weighed coal sample and analysis of combustion residue - is laborious and time consuming and therefore is not usually suitable for process control · It was therefore proposed (GB 965 303) "the ash content means X-ray backscattering. "Although the results are obtained much faster, but their accuracy even for hard coal - insufficient · In addition, a costly Ueukalibrierung of the measuring device is required for coal samples from different sources · The determination of the time when such ÜFeukalibrierung is necessary can only be done via the analysis of comparative measurements in the laboratory ·

In order to exclude the influence of varying iron contents on the measurement result, the ash content, it was proposed (GB 2,056 _e 668) to use X-radiation with two different energies to excite the X-ray fluorescence of the iron and to increase both the intensity of this iron fluorescence radiation and the intensity of the backscattered X-radiation But even that is not enough in all cases to achieve sufficiently accurate results.

 18 9.86-374453

Another proposal (DE-OS 3 306 464) envisages at least the intensities of the X-ray fluorescence radiation of aluminum, calcium, sili- cis and iron, which emits a carbon sample upon irradiation with X-radiation (energy range 1-40 keV) and the intensity of the energy range from 12 to 14 keV backscattered X-radiation and to process these values to a corrected value of the ash concentration · The following equation is used:

^G ash ^A o ^{+ A} 1 · ^ln |

^C ash " ^{the reach} & B ^{e> fce} ash concentration, A _Q , A ₁ - constants,

I., - the intensity of the backscattered radiation, K - constants,

c - the concentration of the elements Al, Si, Ga, Pe mean

The constants are determined from comparisons with the results of chemical analyzes of coal samples. Another possibility is to derive a linear regression equation by using a program in which the results obtained by chemical analysis are systematically compared with variables (counts, vector products of counts and counts of counts), the variables being changed until a large correlation coefficient has been achieved · Zur. By performing this hooting solution, it is first necessary to analyze a large number of samples both by means of the method according to the invention and chemically, the more accurate the equations the larger the number of samples analyzed. The sample preparation requires a fine grinding (<200 bar) ) and pressing (^ 309 MPa) of the coal.

Object of the invention

The object of the invention is a reduction of the effort in determining the ash content of coal by means of X-ray fluorescence analysis »

3 Presentation of the essence of the invention

The object of the invention is to specify an oak-free process for the ash content reduction of coal on the basis of the X-ray fluorescence analysis. , ,

The inventive method consists in the irradiation of the coal samples with X-rays of an energy preferably in the range of 15 to 25 keV and measuring characteristic X-rays in the samples contained chemical elements and the backscattered X-radiation and is characterized in that the intensities of the X-ray fluorescence of the calcium and and comparing these intensities and the intensity of the backscattered X-ray radiation with intensity-proportional values, which were calculated using the average chemical composition of the combustible fraction and the ash of the coal, taking into account the physical interaction mechanisms, and changed the starting values for these calculations so long until sufficient agreement with the measured values ©. is achieved

The process considers coal as one of the four components

- combustible fraction

- Calcium oxide

- Iron oxide and

Ash and calcium oxide and iron content are determined by comparing the measured intensities with the results of a model calculation using the variable parameters of the model to determine the corresponding intensity values, namely Calcium and iron concentration as well as the ash content, are varied until a required or desired adaptation is achieved. "The values of the parameters with which this agreement is achieved represent the result sought. The great advantage of this method is that the data on the average chemical composition of the combustible fraction and the ash residue coming into the model can be changed as desired. Conveniently, these values are taken from existing investigations.

calculation data and other analytical data already available for the eligible

To carry out the method, a device is required which has a radiation source (preferably in the energy range of 15 to 25 keV) for irradiating a material sample, at least one detector for determining the x-ray fluorescence intensities of the elements calcium and iron and the backscattered x-ray radiation and an evaluation unit (eg a microcomputer In addition, a device for displaying or recording the results is suitable. Both simultaneous and sequential spectrometers are suitable, ie those in which the intensities mentioned are determined simultaneously or successively "Also suitable are microcomputers that are equipped with an analog-to-digital converter and can take over the puncture of a spectrometer with the appropriate software and at the same time enable further processing of the measured data n ·

Coals of quite different composition, e.g. In the field of reservoir exploration are analyzed. Since any compositions of the combustible fraction and the Asherestes can be entered, are in the event that empirical values or the like on the approximate composition of the coal present, quite fast and for a sighting also sufficiently accurate analysis of coal different Composition possible.

embodiment

To determine the calcium, iron and ash content of lignite, a spectrometer is used which contains a Pu-238 isotope source as the radiation source and an argon proportional counter as a detector. The carbon samples are placed in plastic sample vessels with a thin Mylar beam entry and exit window -

foil used in the spectrometer. The processing of the data is carried out with a microcomputer, which is connected on the one hand to the data output of the spectrometer and on the other hand to a printer or a screen display.

In the calculator, calculated from existing analysis data, a mean chemical composition of the combustible portion of the coal quality to be examined and the ash residue (ash content minus the calcium oxide and iron oxide concentration) entered and stored in the computer according to a program that a model over the composition of the coal from the four components above and the physical processes in the development of Pluoreszenzstrahlung, the scattering of X-radiation as well as the interaction of these radiation with matter is based on the theoretical intensities Yq '' ^Y Pe ^{UOld Y} RS ^a ^ ^"s ^ ¹ ^ "" functions of the mean chemical composition of the ^combustible: xo portion and the ash residue of coal x _D and the calcium oxide (G _{n s)} and iron oxide concentration (θπ, _{Λ n),} and the ash content

j WaU JJ Βρύο

A calculates: ^

^Y Ca ^{= f} Ca ° Ca0, ⁰ Pe ₀ O ₃ , ^A ' ^X B' ^X B?

^Y Pe ^{= f} Pe ⁽ ° Ca0 ' ⁰ PeO' ^AXX ^

^Y RS ^{= f} RS ^(c Ga ⁰ ' ⁰ Pe ₃ O ₃ * ^A » ^X B'

However, these model equations do not take into account the geometry factor, the detector yield, the intensity of the stimulating radiation, and the radiation background. To determine these coefficients, which depend only on the measuring system, a number N of standard samples is required, ie of samples whose composition Z ₀ B _{0 has} been determined as precisely as possible by chemical means. The model data Y 1 for each standard sample i

ss Yp _e and Yβg calculate the correlation of these results

the measured intensities Iq ₃ , l | _e and I ^ _{g of} these standard samples examined:

^ < ^Y Ca ' ^Υ 5β · ^Y RS' ¹ W for i = 1 ... Ii

Fe

¹ RS ^{= s} RS ^(Y Ca » ^Y ? E ' ^Y

for i = 1 ...

The coefficients K _Ca , K _e and. K _RS can be determined z _o B ₀ according to the least squares method <> A comprehensive and precisely analyzed standard sample set can be used for all coal qualities «»

The analysis of a coal sample is carried out as follows: The pit - wet or dried coal (the average water content is stored in the computer over the analytical data in the calculator) and ground up to a maximum grain size of 0.5 mm is placed in a sample vessel and this used in the measuring head of the spectrometer · the sample 100 is irradiated seconds, and the intensities of the calcium and iron fluorescence radiation, as well as the back-scattered X-ray radiation% n _a i "'" Fe * ^ RS determines "These values are automatically directed to the computer, laughing choice The starting values for the calcium, iron and ash concentration and entry into the computer is an expression of the form using the SIMPLEX method

(g _Ca > gp _e »g _RS - weighting factors)

minimized by varying the starting values for the calcium iron and the ash concentration. The values for these three quantities, with which the best fit is obtained, are the result of the analysis and are output.

The computation time largely depends on the speed of the computer, but also strongly on how "good" the selected starting values are. _E Usually, however, the analysis duration is only a few minutes. <> We measured coal of similar quality over a certain period, then the starting values from the range of already analyzed samples are selected and automatically fed to the computer. If the coal quality changes, only the information on the average chemical composition of the coal needs to be changed.

Claims (1)

invention claim Method for determining the ash, calcium and iron content of coal, consisting of irradiating the carbon samples with X-radiation preferably in the energy range of 15 to 25 keV and measuring the characteristic X-radiation of chemical elements contained in the samples and the backscattered X-radiation »characterized in that the intensities of the characteristic X-ray radiation of the calcium and of the iron are determined and these intensities and the intensity of the backscattered X-radiation with the corresponding intensities which are correlated with data on the average chemical composition of the combustible fraction and the ash of the coal, taking into account the physical processes the generation of fluorescent radiation, the scattering of X-rays and the interaction of this radiation with matter are calculated, and the starting values for these calculations are varied until a sufficient Ü match the measured and calculated intensities.