SU754284A1 - Method of determining solid fuel combustion temperature - Google Patents

Description

The invention relates to metallurgy and coal industries and can be used both in laboratories and in production conditions, including for determining the ignition temperatures of various metals, explosives, etc.

Known methods for determining the ignition temperature of solid fuels, 'which are based on a comparison of the temperature of the fuel sample with the furnace temperature {ΐ). At the time of ignition, the temperature of the test sample increases sharply. The moment of temperature equalization between them is considered the moment of ignition, and the actual temperature - the temperature of ignition.

There is a method of determining the ignition temperature, which consists in heating the sample and. measuring its temperature at the time of ignition (2).

In this method, the fuel is placed in a reactor inserted into a vertical electric furnace. In the reactor backfill - 3

2

test material is blown, air is blown from top to bottom by a water jet pump. However, due to the need for slow heating of the reactor (0.3 GHz / s), the time for carrying out one determination is about 1 hour. The method does not allow measurements at pieces of more than 5 mm, while in a number of devices burn larger fuel. In addition, the known method does not allow to determine the dependence of the ignition temperature on the heating rate of the sample.

The aim of the invention is to simplify the measurement and expansion of the range of application.

This goal is achieved by the fact that during the heating process, the electric potential of the sample is measured, and the temperature corresponding to the inflection on the potential-change curve is taken as the ignition temperature. before moving it to the plus area and a sharp increase in the positive value. The heating rate of the sample varies from 0.3 to

3

four

.75 ί

30 deg / s, which allows the use of the method · for rapid analysis.

The control of the ignition temperature by inflection on the curve of the change in the electric potential of the sample before it goes into the positive region with a further sharp increase in its positive value is justified by studies that show. that when a solid fuel sample is heated, its electric potential changes in a complex way, with a sharp increase in the positive value at the moment of ignition, which was controlled by the composition of the combustion products, the change in the luminance of the surrounding gas and, in the case of slow heating, by the temperature jump ·. in this moment. The sharp increase in po- ^-, potential of the sample at the time of ignition by intensive development ionization processes at the transition from the oxidation of the fuel to the combustion and, as consequence, increase in the flow of charged particles from its surface.

FIG. 1 shows an installation for implementing the method; in fig. 2 curves of changes in the potential and temperature of the sample when it is heated at a rate of 0.3 deg / s.

The installation includes a vertically positioned electric furnace of resistance 1, in which a heated sample 3 is suspended on thermo5 pair 2. Millivoltmeters 4 and 5 are used to record, respectively, the potential and temperature of the sample.

From the resistance curves of changes in θ potential and temperature (figure 2)

It can be seen that the inflection on the potential change curve before its transition to the positive region and the sharp increase in the positive value correspond to the inflection on the temperature variation curve caused by the ignition of the sample. The ignition temperature, determined according to the schedule, is equal to 800 ° C.

Example. The determination of the ignition temperature was carried out spectrally. pure graphite grade C-3, metallurgical coke and coal grade K. To obtain comparative data, in parallel, we conducted a determination of the ignition temperature of the same fuels by a known method.

The data are given in the table.

Fuel Flash point, determined ¹ by the known method, ° C Flash point, determined by the proposed method at similar speeds, ° C sz 800 880 Coke Kamen 565 550 ny coal 490 500

The method is applicable to large samples, 45 45, since in this case the moment of ignition is recorded not by the temperature jump, which will be smoothed for large samples, but actually by the current from their surface, which increases with the growth of the latter.

The use of abruptly increasing ionization in the ignition of solid fuel to determine the moment of ego onset allows. __

to simplify measurements by eliminating differential thermocouples and improve its accuracy, as well as to determine the ignition temperature of both the individual sample and the fuel layer. In addition, the proposed 60

the method is not critical to the uniformity of air heating and allows significantly (100-100 times) to expand the range of allowable sizes and heating rates of the sample. 65

The method allows, without carrying out preparatory work, to use it both at industrial enterprises and in research laboratories.

Claims (2)

Claim 1. V.T. Monkhov Methods for determining the fire hazard of solids. Μ. , "Chemistry", 1972, p. 104 1. A method for determining the ignition temperature of solid fuels, including heating the Sample and measuring its temperature at the time of ignition, characterized in that, in order to simplify the measurements and expand the application range, the electric potential of the sample is measured during the heating process, and the ignition temperature is determined by its correspondence to the bend on the curve of change "of the potential before its transition to the positive region and a sharp increase in the positive value. five 754284 6 2. The method according to π. Ι, ο t l and h t that the heating rate of the sample varies from 0.3 to 30 degrees / sec. Sources of information taken into account in the examination 2. Schukin P.A., Kazakevich A.P., Mokhnashin A.E. Solid fuel chemistry. 1969, No. 1 (prototype). 1