RU2349634C1 - Pulverised coal fuel for blast-furnaces - Google Patents

Abstract

FIELD: chemistry; metallurgy.

SUBSTANCE: pulverised coal fuel for blast-furnaces contains finely ground gas-coal, to whose content is additionally added finely crushed coke breeze, obtained from heat treated inert carriers of gaseous low-sulphur coal. Heat treatment of inert carriers in carried out at temperatures 150-250°C.

EFFECT: intensification of combustion of pulverised coal fuel in the tuyere region, increase in the percentage of substitution of coke with pulverised coal fuel, increase in the production of a blast-furnace and tuyere-zone temperature, decrease in the cost of iron manufacture in blast-furnaces.

3 cl, 3 tbl

Description

The invention relates to ferrous metallurgy, and specifically to blowing pulverized coal in a furnace of a blast furnace, and can be used in the smelting of cast iron in blast furnaces.

Known pulverized coal fuel for blast furnaces, consisting of finely divided lean coal [Metallurg Magazine No. 11, 1965, pp. 33-35].

The disadvantages of known pulverized coal include a low percentage of coke replacement, and since Coke is the most expensive component of a blast furnace charge; therefore, the high cost of producing cast iron.

The closest in technical essence to the claimed fuel is a mixture for the production of metallurgical coke, including gas, fatty, coke, sintering coals and iron-containing additive, while in order to increase the mechanical strength of coke, the remains of the heat treatment process of sulphurous tar are used as a sintering additive in the presence of iron ore concentrate with a softening temperature of 80-100 ° C and a boiling point above 530 ° C with the following ratio of components in the mixture, wt.%:

Sintering additive 2-4 Gas coals 45-55 Fat Coals 17-25 Coke Coals 10-15 Sintering Sintering coals Rest.

[USSR Author's Certificate No. 1703674, cl. СВВ 57/04, publ. 01/07/92]

The disadvantages of the known charge are the insufficient productivity of the blast furnace using known fuel and the insufficient raw material base of fatty coals for the production of the charge, the relatively low productivity of the blast furnace using known fuel, the poor kinetics of burning the charge in the tuyere zone, and therefore the temperature in the tuyere zone is not high enough, the cost of preparing the charge and, consequently, the production of pig iron in a blast furnace.

The basis of the invention is the task of improving pulverized coal fuel for blast furnaces, in which the additional introduction of finely ground coke, obtained from heat treated with an inert carrier of gas coal, with a calculated ratio of components, provides intensification of the combustion of pulverized coal in the tuyere zone, this ensures an increase in the percentage replacing coke with pulverized coal, increasing the productivity of the blast furnace and the temperature in the tuyere zones Expansion raw materials for the production of pulverized coal, reducing the cost of iron making in blast furnaces.

The problem is solved in that in pulverized coal fuel for blast furnaces, including finely ground gas coal, according to the invention, the following differences are provided:

- additionally introduced finely ground coke obtained from heat-treated inert carrier gas gas;

- the components are taken in the following ratio, wt.%:

Gas coal 1-85 Coal Coke Rest

In addition, heat treatment of gas coal with an inert coolant is carried out to a temperature of 150-250 ° C, and coke is obtained from low-metamorphosed low-sulfur gas coal.

The essence of the invention lies in the fact that as the main component of pulverized coal instead of oily deficient fatty coals, finely dispersed coke obtained by the traditional method of layer mowing in industrial coke ovens from gas coal, mainly low metamorphosed low-sulfur, is used.

Before loading into the coking chambers, gas coal is preheated with an inert coolant to a temperature of 150-250 ° C, coked with a coking period of 12-18 hours and a final temperature of 750-1050 + 50 ° C.

The mechanism of influence on the combustion process of finely divided coke in the tuyere zone is that coke is a more active oxidizer of pulverized coal than coal.

Recent studies (DM Khzmalyan, Theory of Furnace Processes. M., Energoizdat, 1990) have shown that when coal is burned, the release of volatile substances is delayed in comparison with heating, i.e. the bulk of the volatiles does not have time to stand out by the moment of ignition of the particles, volatiles burn simultaneously with the combustion of solid particles, small particles of coal (with a diameter of less than 160 microns, which corresponds to the grinding of pulverized coal in the blast furnace process), rich in volatiles, burn without flame burning of volatiles near their surfaces, and the ignition time and rate of burning of particles depend on the temperature of the medium and the density of their material. The process of ignition and burning of dust is determined by the reactivity of the fuel, i.e. physical and chemical structure (density, porosity, etc.). Coke has advantages over any type of coal and anthracite.

In the study of the specific surface of coals of grades G (gas), T (lean), as well as coke, obtained from their 100% low-sulfur gas, low metamorphosed gas coal, the following results were obtained:

Grade G coal has a specific surface 0.7 m ² / g Brand T coal 1.1 m ² / g Coke from 100% gas coal 8.0 m ² / g

Thus, coke from 100% gas coal is more than 11 times the specific surface area of gas coal and 7.5 times higher than lean coal.

In addition, when the temperature in the tuyere zone of the blast furnace is more than 1500 ° С, the process of burning pulverized coal occurs in the diffusion-kinetic sphere (the burning rate is determined not only by the rate coefficient of the heterogeneous chemical oxidation reaction, but also by the rate of supply of the oxidizer to the surface of the burned fuel and its grinding) . These indicators are provided by the proposed pulverized coal fuel, and the replacement in the mixture for injection into the tuyere zone of lean coal with finely ground coke from gas coal significantly increases the temperature in the tuyere zone, and therefore, increases the efficiency of the blast furnace process.

Example

Experimental melting with pulverized coal injection (PUT), consisting of a mixture of brand “G” coals and coke obtained from pre-heat-treated gas coal instead of scarce brand “T” coal, was carried out on an industrial blast furnace, where 15%, 25% was taken 50% of coke from gas coals and, accordingly, 85%, 75%, 50% of brand “G” coal. The supply of PCBs to the tuyere zones of the blast furnace was uniform in time. The operation of the blast furnace in the experimental period was characterized by a stable gathering of charge materials, a stable thermal state of the hearth, which was expressed in insignificant (up to 0.05%) fluctuations in the silicon content at adjacent outlets.

Technological performance of the blast furnace in the experimental period are shown in table 1.

Table 1 Technological performance unit of measurement The composition of the PUT on the coke content,% fifteen 25 fifty Production t / day 2150 2156 2161 Dry coke consumption kg / t 428 418 412 Put consumption kg / t 164 162 160 Blast temperature ° C 1001 989 982 Oxygen consumption m ³ / t 80 74 71 Pressure under the grate atm 1.27 1.26 1.26 Silicon content in cast iron % 0.72 0.72 0.73 Manganese content in cast iron % 0.17 0.17 0.16 Limestone consumption kg / t 132 131 130

The objective of the invention, when choosing the percentage of components in a mixture of PUT, is to maintain quality indicators for ash content (<9%), sulfur content (<0.8%), volatiles yield of not more than 28%, which corresponds to the mastered level of PUT volatiles effective replacement of coke and ensuring the safe operation of the pulverized coal complex.

Proposed in the invention, coke obtained from gas coals, which is part of PUT, when used in a blast furnace, is characterized by a lower content of volatiles in comparison with gas coals of grade “G” and is close in its characteristics to coal of grade “A”, and in terms of sulfur content, indicators are close to grade “G” coal.

The quality indicators of PUT are shown in table 2.

table 2 % coke in Put Ash content,% Sulfur content,% Humidity% The yield of volatiles,% Fractional composition (μm),% <80 > 63 > 63 fifteen 8.1 0.80 0.86 22.96 16,4 9.6 74.0 25 8.3 0.76 0.90 20.32 16.6 9,4 74.0 fifty 8.3 0.72 0.92 17.11 16.1 9,4 74.5

Consequently, the introduction of coke from gas coals into the FCA, while maintaining the volatile content at a basic level, helps to increase the percentage of coke in the mixture and improves the quality of FCA in sulfur content.

A comparative analysis of the performance of brand G gas coal (Zarechnaya mine) used for coking and coke obtained during coking of gas coal is given in table 3

Table 3 No. p / p Component Name Ash content
on a dry mass,% Sulfur content on dry weight, S _d ,% The yield of volatile substances on dry ashless mass, V ^daf ,% Humidity per working mass, W ^z ,% Shrinkage, X mm The thickness of the plastic layer, mm one. Gas coal 7.0 0.5 41.8 9.3 26.0 10.0 2. Coal Coke 10.5 0.65 0.9 8.3 - -

Coke obtained from gas coal has the following technical indicators:

Calorific value for the analytical mass of the bomb O ^a _b = 27700 kJ / kg;

Structural strength according to the Gryaznov method 72.1% Hot reactivity 70-90% Flammability 50-65 sec Bunte Flash Point 500 ° C Specific surface area 8.0 m ² / g

Claims (3)

1. Pulverized coal fuel for blast furnaces containing finely ground gas coals, characterized in that finely ground coke obtained from heat-treated inert carrier of low-sulfur coal is additionally introduced into gas coals, in the following ratio of components, wt.%:
gas coals 1-85 coal coke rest 2. Pulverized coal fuel according to claim 1, characterized in that the heat treatment of gas low-sulfur coals with an inert carrier is performed at a temperature of 150-250 ° C. 3. Pulverized coal according to claim 1, characterized in that the finely ground coke is obtained from gas malometamorphized coals.