SU846962A1 - Method and apparatus for heating roasting machine - Google Patents

Description

(54) METHOD OF HEATING BURNING MACHINES AND DEVICE FOR ITS IMPLEMENTATION

I

The invention relates to metallurgy. in particular, to methods and devices for burning natural gas in roasting units for ore raw materials in a neutral or weakly reducing atmosphere.

The closest in technical essence and the achieved result to the invention is the method of heating roasting machines, including burning the fuel-air mixture in a vortex flare in the peripheral areas of the pre-chamber with the formation of an internal rarefaction zone and using flue gas as a diluent. The device for its implementation contains a channel for supplying air with a vane swirler and an internal channel for supplying gas with radial holes 1.

The disadvantage is the impossibility of obtaining combustion products of a neutral or weakly reducing composition at an adjustable temperature level of 900 to 1200 ° C. This is due to the fact that the provision of temperatures up to 1200 ° C is achieved by increasing the coefficient of excess air. At the same time, a large amount of free oxygen is present in the combustion products, up to 00%, which excludes the possibility of firing iron ore materials in a neutral or weakly reducing environment.

The purpose of the invention is to expand the range of regulation of the temperature and composition of the combustion products.

This goal is achieved by the fact that the flue gases feed the internal rarefaction zone in the form of an axial flow through a swirling vortex with a variable twist angle of 6p where n is the percentage of oxygen 1 in the ballasting flue gases, 6 is the test ratio.

A device for implementing the method is provided with a central channel for supplying flue gases 15, in which a blade swirl with an adjustable angle of rotation of the blades is placed, installed at a distance from 0.5 to 1.0 gauge of the channel from its outlet orifice.

The essence of the method is as follows.

In the peripheral areas of the pre-chambers, they form a vortex torch in which they organize combustion of the gas-air mixture with coeffiiei-iiOM pacx (,, Ui; “i: i; iyxa, 0 - (0.9 -0.8} When) with NO, 0 form noraduk) (fXipOlil;} -; ipH .i; H ;; CflO: i (/

m; kit, :: op () / |.;. that i8-1e h:) ORS;: Piiiii obzh; e | PD. When iH i; r :; ; iii with d (J, 9- 0,8) 1 products of the don VU k / g: and -. po / ivKTiji ioiodiog g:; reg and CO and 1 j; jr 2 JO rr / ii irn oTC i4: T:): - iH oxygen. what; leth: c.na6oHoccTriH (j;:; iiTe, sredo) -, iianpHMrp, for the magnetising roasting of iron ores. However, in all pp. 1 of the le.ineparvpa (the health of my-products of combustion is close to theoretical and is about; 800 -. 4TU is incomprehensible to the condition of size / size and oil of 5 days; | ud). Increasing the excess of the excess to reduce the air. Fi; rviiiji NS-PERMISSIBLE, since irides to 1: about: 1leepy for the products of combustion freedom l about kis.yurod. In order to reduce the temperature 1), the combustion products are used from () C1b; 1; cooled cooled gases (ballast) in the unit. However, these gases cannot be supplied directly to-soiiy -o-rei; . Thus, to reduce the temperature to 1000 ° C, the amount of ballast should be commensurate with the amount of air supplied to the combustion, the oxygen content in the air-ballast mixture at the same time decreases to 12 / o. Combustion of gas in a mixture with such an oxidizing agent is impossible, therefore, these g-ases are fed into the burner but () are one body; the channel is in the form of axnal oi (i flow with: punching twist, direct | 1io) H1; about 1 oxygen content and tiix gases.

FIG. 1 and 2 are examples of implementations with; state; .on FIG. 3 - the proposed device, a general view.

During the operation of the burner, the air in channel 1 through the supercharger 2 goes to the outlet opening 3 and is intensively mixed with gas streams flowing out of the holes 4. In the prechamber 5, a non-intermittent vortex flow develops, which develops in its peripheral areas, forming an axial flow parts of the prechamber of the rarefaction zone. If the flue gases supplied through channel 6 do not contain oxygen, the air flow rate in the peripheral plume is maintained at the level specified by the technology condition (1.0-0.8), the swing arms 7 are installed along the burner axis, and the flue gases flow out into the central part of the pre-chamber in the form of a bridge pipe. Four zones are formed in the prechamber (see Fig. I). In zone 8, there is an intense gas line with clean air. In zone 9 a stream of flue gases, which do not contain oxygen, develops. Between these zones there is a stagnant zone 10. Smoke gases from zone 9 in the initial part of the pre-chamber do not penetrate into zone 8 and do not interfere with complete and intense burning in the last one. Movement of the fluxes of zones 8 and 9 is carried out in 3 (1 1 1 only after that in zoiit 8. The replication is almost complete, and the cent: al.; ZONY FLOW 9 reaches the end of the iO circulation. In this way, .: ere c) b) a steady torch is created, the rcypenite of which is practically not affected by the center, the ballast flux. The dimensions 30 in the prechamber do not depend on the flow rates and the temperature control of the combustion products and is carried out by changing the amount of injected ballast.

If the flue gases supplied to the burner through the channel 6 contain oxygen, then the cost of air supplied through the channel is reduced to such an extent that the oxygen content in the air-ballast mixture corresponds to the oxygen content during gas combustion with the coefficient of hyuzdukh consumption, 0-0.8. At the same time, if the central note of the flue gases from channel 6 continues to develop in the form of an axial jet, then in the peripheral zones of the prechamber, the reproduction occurs with a lack of oxygen and at a lower temperature, which will not lead to chemical underburning. Due to the decrease in the amount of air in channel 1, the swirling flow in zone 8 decreases and, accordingly, the combustion products of this zone move with the central flow.

In zone 11, with such displacement, combustible CO, H, and soot, as well as oxygen, are observed simultaneously, which is unacceptable under the conditions of roasting.

In order to reduce the oxygen deficiency in the peripheral zone, the blades are turned 7. In this case, the central axial flow from the jetting nozzle is converted into a vortex, the opening angle of which is proportional to the angle of rotation of the blades. In the prechamber two vortex flows are formed: peripheral with constant twist and central with variable (Fig. 2). Changing the opening angle of the central stream, thereby changing the degree of its mixing into the peripheral stream, i.e., the degree of enrichment of the latter with oxygen. This allows oxygen contained in the flue gases to be used for combustion in the peripheral zone, to prevent an increase in chemical underburning in it. f

The magnitude of the deepening of the rotary blades in the Central channel from the outlet in the calibers of its diameter is 0.5-1.0. The depth of the blades is measured from the edge of the outlet n, the central channel 6 to the nearest edge of the rotary blades 7.

When the blades are deepened in channel 6 by less than 0.5 diameters, changing the angle of the blades practically does not change the intensity of the central flow twist, but only spreads it from the center to the periphery of the pre-chamber. When the blades are deeper than 1.0 of the diameter, the mouth of the flow is reduced and a change in the angle of the blades does not cause a proportional change in the opening angle of the central flue gas flow.

Thus, this method of heating consists of the following operations.

1. The fuel-air mixture is supplied to the prechamber along the peripheral channels of the burner and burned in a swirling plume in the wall region with the formation of an internal circulation zone.

2. Flue gases are fed through the central tube of the burner.

3. Set the angle of rotation of the blades in proportion to the amount of oxygen in the ballasting smoke eyes in the expression

 bp where oC is the angle of blade rotation, degrees;

n - the percentage of oxygen in the ballasting flue gas; 6 - experienced coefficient.

4. Changing the ratio of fuel and oxygen in the air-ballast mixture, set the desired For the technology, the composition of the resulting combustion products, and changing the amount of ballast regulate their temperature.

5. In the course of work, they constantly monitor the oxygen content in the ballast and regulate the angle of rotation of the blades, the amount of ballast and clean air.

As a result, combustion products with a temperature of 900-1200 ° C, which do not contain oxygen, and with a controlled amount of reducing gases, CO and Hg, flow out from the pre-chamber of the burning machine.

The method is carried out using a burner, which is mounted on the wall of the kiln 12 and is made of pipes 13-15, which form channels with nozzles: 16 for supplying air, 17 for supplying gas and 18 for supplying flue gases. At a distance of 0.5-1.0 gauge of the central channel from its outlet opening 19, a swirler is installed, the rotating vanes 7 of which through the rod 20 are connected to the drive 21. The channel 22 for supplying gas to the burner mouth ends with wall 23 and has openings 4 for exit gas in the pipe wall 14.

The proposed heating method allows to improve the thermal mode of burning of iron ore materials on conveyor machines. In existing machines, flue gases containing a variable amount of oxygen are not used as an oxidizer in burner devices due to the fact that the required amount of ballast exceeds the allowable limit under conditions of stable combustion. However, the expediency of their use is due to the fact that the creation of a neutral or weakly reducing atmosphere in the heated furnaces of the roasting machines makes it possible to obtain pellets with a magnetite or wustite-magnetite structure, which have high metallurgical properties: durability and a lower tendency to form dust.

The method makes it possible to use flue gases from different parts of the machine and its flues with different oxygen content to reduce the flame temperature, and the design of the burner ensures stable gas combustion.

Claims (2)

1. The method of heating roasting machines, 5 including the combustion of air-fuel mixtures in a vortex flare in the peripheral areas of the prechamber to form an internal rarefaction zone and use flue gases as a diluent, characterized in that, in order to expand the limits of temperature and composition control, the flue gases are fed into the internal rarefaction zone as an axial flow through a swirler with a variable twist angle, 5 where n is the percentage of oxygen in in ballast flue gases, 6 is the test coefficient. 2. A device for carrying out the method according to claim 1, comprising a duct for supplying air with a paddle swirler, 0 an internal channel for supplying gas with radial holes, characterized in that it is aligned with a central channel for supplying flue gases in which the blade vortex is placed at a distance of 0.5-1.0 caliber from its outlet 5. Sources of information taken into account in the examination 1. USSR author's certificate in application No. 2644248, cl. F 27 B 21/00, 1978. J g 1 (rig. / ig.g jg YU (rig. 3