SU1383186A1 - Method of checking ash content of coal - Google Patents

Abstract

The invention relates to indirect physical measurements of coal parameters and can be used for the operational control of coal ash and the creation of an automatic line based on it. The goal is to increase the accuracy. Control. In the method of controlling the ash content, the coal sample is heated, then the electrical resistance is measured successively upon reaching 300. and 350 ° C. The controlled ash content is determined by the logarithmic temperature coefficient of the electrical resistance and the calibration schedule. 5 il.

Description

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The invention relates to indirect physical measurements of coal parameters and can be used for the operational control of coal ash and the creation of an automatic line based on it.

The purpose of the invention is to increase the accuracy of the control.

FIG. 1-4 show graphs explaining the proposed method; in fig. 5 is a diagram of the device implementing the method.

The physical phystors underlying the proposed method are summarized as follows. The electrical conductivity of coal is aesthetically with an increase in the temperature of the coal, and the temperature is the predominant factor in the change in resistance — the change in temperature of the coal: 800.C. Changes the resistance more than 10 times. Resistance depends most strongly on temperature in the range of 250 -.

Within the temperature range of 200 -,. 800 C decimal logarithm of coal resistance varies linearly according to the equation

Ig p a - ILT,

where I is the resistivity, Ohm "m & T ° is the temperature increase, C. The physical meaning of the constant a is the tenth logarithm of the resistance of coal at a certain initial temperature lying in the interval 200-800 C. Constant b plays in this expression role of temperature coefficient

 lg (VP2) DB-TT ° p5d

B

The electrical resistance of coal largely depends on moisture content, but the effect of humidity drops sharply with increasing temperature. Dependence curve

Ig P f (T °). . in the temperature range above 300 for coal, the humidity of which at ordinary temperature does not exceed 22% does not change. Thus, the logarithmic temperature coefficient of resistance is practically independent of humidity. The conclusion made confirms the dependence of the resistance of coal on temperature at their different humidity given in figure 2.

When coal is heated in any way to a temperature of 400 ° C, the structure of coal

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undergoing no radical changes.

Crushing and density of coal occurs at temperatures below 300 ° C.

The anisotropy of the coal has little effect on the magnitude of the resistivity, which is determined along and across the layering.

The electrical conductivity of coal depends on the external electric field only in strong fields, and this effect diminishes with increasing temperature.

All other factors, although affecting the absolute value of resistance, do not affect the magnitude of the temperature coefficient of resistance.

Heating of the coal should be done as quickly as possible. The electrical resistance should be measured immediately after heating to the desired temperature. Due to the ongoing chemical processes and the polarization of the carbon: l, a shutter speed of a few minutes distorts the results.

The ash content of coal, unlike all other factors, strongly affects not only the magnitude of the resistance itself, but also the magnitude of its temperature coefficient. The dependence of the specific resistance of coal with different ash content on temperature is shown in FIG. Ash content less than 10% does not affect; for electrical resistance and temperature coefficient of resistance. An increase in ash content from 12.3 to 61.24% causes strong changes in both resistivity and temperature coefficient of resistance. With a further increase in ash content, the electrical resistance of coal changes with temperature in the same way as the resistivity of the rock.

The dependence of the tenth logarithm of the electrical resistance of coal on the temperature in the temperature range 200 is a straight line with a slope determined by ash. FIG. Figure 4 shows the dependence of the slope (logarithmic temperature coefficient of resistance on ash content, obtained from Fig. 3). This conclusion determines the method for determining ash content from the magnitude of the logarithmic temperature coefficient of resistance.

The ash content of coal according to the proposed method is determined as follows. The sample is filled up, heated to 300 ° C, the resistance of the carbon is determined and memorized at an angle of 300 ° C, the sample is heated up and the resistance of coal 2 is recorded at the temperature determined.

b --- gr o compare the result with the calibrated curve.

The electrical resistance was chosen as the measured parameter, since the measurement of the resistance of coal is governed by GOST. The dependence of the tenth logarithm of electrical resistance on temperature is almost linear, therefore, the logarithmic dependence of the resistance of coal on temperature, which has a constant derivative (constant slope) in the temperature range of 300 -, is used.

A device for determining the ash content of coal (Fig. 5) contains container 1. The bottom of the container is a sieve 2, through which the fine fraction of the coal enters the dispenser 3, which is a funnel. Below the dosing unit, an auxiliary conveyor 4 is located. Above the latter, a limiter 5 of the filling height is located, behind which a sealing shaft 6 is placed. The coal on the auxiliary conveyor is heated by means of a furnace 7 of any design. Temperature measurement is performed remotely using, for example, infrared thermal sensors 8.

Measurement of production resistance using three guide plates 9. Arithmetic logic unit 10 is used to process the information received. The container is equipped with mechanical shovels II.

The device works as follows.

Coal from the process conveyor enters container 1. Its small fraction through sieve 2 enters the funnel of dispenser 3.

The rate of discharge of the coal from the mouth of the funnel of the dispenser is uniform and does not depend on the filling level of the dispenser. After a certain period of time, the sample is stopped.

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is. The conveyor is turned on and approximately a constant amount of coal is leveled on it by the backfill height limiter 5 and ground up by shaft 6. Further movement of the conveyor introduces the sample into the furnace zone 7 and simultaneously in the sample two flow are formed in the sample 9. the effect of transient contacts between coal and has not been noticed. electrodes on resistance, and the crushing and strength of coal only affects up to T; to avoid accidents, the parallel resistance of the two sample streams is measured.

In this position, the conveyor stops and the sample is heated to T 300 ° C. Upon reaching this temperature, the signal of the sensor 8, which is fed to the arithmetic logic unit 10, gives a command to measure the resistance, which is stored. Next, heating to T 350 ° C is performed, and again, by a command determined by the signal of sensor 8, the resistance is memorized. At the same time, a signal is received to advance the conveyor. The used sample is dropped or fed back to the process conveyor. Thus, the operation of the device is intermittent,: and the periodicity is determined by the probability of ash content change, as well as by the furnace power.

The obtained measurement results are processed by an arithmetic logic unit and compared with a curve similar to that shown in Figure 4, refined for a given coal grade.

Claims (3)

1. DRY UGO / 1b 2. Humidity 8.5% 3. INVESTMENT 14.9% c. humidity 2.7 /, fig. g M2 t% SOO 600 / g. J 100 T C I-g VKyu A5 / hail one 10 20 30 5b 60 Fig. Zlnosgpb, "/ in