FI69101C - FOERFARANDE FOER TILLFOERSEL AV PULVERFORMIG BRAENSLEBLANDNINGTILL BLAESTERFORMOR HOS EN MASUGN - Google Patents

Description

1 69101

The invention relates to iron metallurgy and, more particularly, to a method for feeding a powdered fuel mixture to the flues of a blast furnace.

The method is useful for smelting ingot iron in a blast furnace using injecting coal dust 10 fuel onto the grate.

Coke stocks of coking coal are declining and this is why one of the most urgent problems in blast furnace production is the replacement of coke with a fuel mixture based on non-coking coal, 15 for example coal fuel with sufficient stocks. When using such fuel mixtures, it is particularly important to achieve a uniform supply to the blast furnace flues.

A method is known in the art for feeding 20 fuels of coal dust to the flues of a blast furnace (see

THEY. Dunayev et al., Vduvaniye pylevidnykh materialov v domennye pechi, Moscow, "Metallurgiya", 1977, pp. 96-97), which method comprises transferring the aforementioned fuel to conical manifolds, dividing the fuel stream 25 into a plurality of streams through the outlets. flues.

In the above case, the fuel is unevenly distributed in the flues because the hydraulic resistance values of the exhaust pipes are different.

Also known in the art is a method of feeding a pulverized fuel mixture, disclosed in connection with the description of the apparatus of U.S. Patent No. 3,204,942, comprising charging the discharge chamber with the pulverulent fuel mixture and then continuously passing it through a carrier gas through calibrated orifices of the distributor, 2 69101 streams, after which said mixture is fed through outlet pipes to the flue of the blast furnace.

It is obvious that by using calibrated orifices 5 in the method shown, an equalization of the hydraulic pressure values in the piping is achieved, which improves the uniformity of the fuel distribution in the flue. However, when the pressure in the flue of the blast furnace varies and as a result of wear or clogging of at least one outlet pipe, the uniformity of the distribution of the fuel 10 in the flue is disturbed. The above fact causes the formation of channels in the shaft of the blast furnace and disturbances in the settling of the charged material, i.e. interfering with the optimal process conditions of the smelting process.

Thus, there is a need for a method of feeding a powdered fuel mixture in which the hydrodynamic properties of the exhaust pipes are balanced to ensure an even distribution of the fuel in the blast furnace flue.

The invention provides a method of feeding a pulverized fuel mixture to the blast furnace flues comprising filling the pressurized discharge chamber in batches with a pulverulent fuel mixture, then continuously removing the mixture from the discharge chamber and transferring the mixture to the blast furnace flues. each tube having a total flow of the aforementioned gas 3 to 10 times greater than the main gas flow, and in each tube the product of the total gas flow and the concentration of the powdered fuel mixture therein 30 being kept the same in all flues.

The above makes it possible to equalize the hydrodynamic properties of the pipes, namely to increase the hydraulic resistance of each pipe and thus reduce the response pressure.

II

3 69101 effect of the changes in the flues of the blast furnace and thus improving the evenness of the fuel distribution in the flues.

It is preferable to feed the additional carrier gas into the pipe as a flow directed towards the above-mentioned fuel-5 mixture as it exits the discharge chamber, wherein the additional gas flow rate is kept 0.25 to 1.5 times the critical velocity of its exit flow.

This also allows each tube to increase the total hydraulic resistance and the supply of powdered fuel mixture to the blast furnace flues is more even.

It is advantageous, during the charging of the discharge chamber, to remove a part of the main gas by ventilating it, said gas flow rate being the same as the velocity of the gas 15 entering the discharge chamber together with the fuel mixture to be charged. This allows the fuel mixture distribution process to be stabilized from the discharge chamber and also improves the uniformity of its distribution to the blast furnace flues.

The invention is further illustrated by way of example only with reference to the accompanying drawing, which shows an overview of the supply of a powdered fuel mixture to the flue of a blast furnace.

A flow chart of the application of the cumbersome method of the invention is shown in the accompanying drawing and includes a storage chamber 1; pipe 2 for feeding the fuel mixture to the storage chamber 1; a pipe 3 for removing gas from the thief chamber 1 comprising a filter and a shut-off device; closing chamber 4; a channel 5 connecting the storage chamber 1 to the closing chamber 4; a pipe 6 for equalizing the pressure in the closing chamber 4 and the storage chamber 1; a pipe 7 for supplying gas 30 to the shut-off chamber 4; discharge chamber 8; a pipe 9 for removing a part of the gas from the discharge chamber 8 to the storage chamber 1; a second channel 10 connecting the closure chamber 4 to the discharge chamber 8; a pipe 11 for supplying gas to the discharge chamber 8; feed mixers 12; a passage 13 connecting the discharge chamber 35 8 to the feed mixers 12; a pipe 14 for supplying additional carrier gas to the feed mixers 12; pipes 15 for supplying fuel mixture 4 69101 to the flues 16; a meter 17 for measuring the flow Qk of the gas leaving the closing chamber 4; a meter 18 for measuring the flow rate of the gas removed from the discharge chamber 8; unit 19 for adjusting the flows Qk and the comparator-5 with each other and the flow Qk; a meter 20 for measuring the flow of gas (m / n) fed to the discharge chamber 8 for one pipe 15 (n is the number of pipes 15); a meter 21 for measuring the flow Q of the additional gas flow for each pipe 15; unit 22 for summing the flows 10 μm / n and Qn; concentration meter 23; a unit 24 for multiplying the signals received from the adder 22 and the concentration meter 23; a unit 25 for comparing the signals received from the multiplication unit 24 of each tube and for controlling the flow Qn, a pressure regulator 26 inside the discharge chamber 8.

The powdered fuel mixture is continuously fed from the discharge chamber 8, which is filled in batches with this mixture from the storage chamber 1 through the closing chamber 4. The crushed fuel mixture is fed into the storage chamber 1 via a pneumatic conveyor of the pipe 2 or by gravity. The storage capacity of the storage chamber 1 is selected to be large enough to ensure an uninterrupted supply of the fuel mixture to the blast furnace for at least several hours. At regular intervals, every 6 to 20 minutes, after the shut-off chamber 25 has been emptied, it is isolated from the pressurized discharge chamber 8 by means of a shut-off device placed in the channel 10 and the shut-off chamber is filled with the fuel mixture supplied from the storage chamber 1. The gas removed from the closing chamber 4 is led through a pipe 6 to a storage chamber 1, where it is let into the outside air 30 via a pipe 3 after purification of the gas. When the shut-off chamber 4 is filled with the fuel mixture, it is isolated from the thief chamber 1 and connected to the discharge chamber 8. From the discharge chamber 8 the fuel mixture is fed through a channel 13 to feed mixers 12

5 69101

The even distribution of the powdered fuel mixture in the flues 16 of the blast furnace is carried out by introducing additional gas into each pipe 15, whereby the total flow 1 Q is (3-10) Qm.

5 Reducing the ratio of flows to SQ to less than three does not allow the difference in the hydrodynamic properties of the pipelines to be fully compensated, especially in the case of a large number and relatively long and thus non-uniform distribution of fuel in the flues. Increasing said ratio to more than ten, although it slightly improves the uniformity of the fuel distribution, is undesirable, since a much larger amount of cold gas is then introduced into the grate of the blast furnace. The constant fuel consumption for each flue 16 is performed by varying the total gas flow rate in the appropriate pipeline 15. The magnitude of the additional gas flow rate Qn for each pipeline 15 is determined by considering that the total gas flow product Ti at each flow is equal to its fuel concentration in chimneys, i.e. value r * i _ Q_ - + Q b ...

(i) n * n (i) 25 L- wherein there is a flow of gas fed to the discharge chamber 8; n is the number of pipelines through which the flues are fed from the chamber 8;

Qn is the flow of additional gas per i flue 30 & (i) is P ° ltto: * - nePitc> in the i flue, is kept equal in all flues by changing the value Qn ·

The equality of the value fijjj for all chimneys is preferably generated automatically. To this end, a signal 35 proportional to the quantity O 1 / n and generated by the meter 20 and a signal proportional to the quantity Qn 6 69101 generated by the meter 21 are fed to a summing unit 22 and then to a multiplier unit 24, to which a signal is also applied, which is proportional to the concentration of the fuel mixture in the pipeline as measured by the concentration meter 23.

The signal from the multiplication unit 24 is compared in the comparison unit 25 with the corresponding signals from each other pipeline and, if necessary, an instruction is given to either increase or decrease the additional gas flow rate depending on the sign of the output difference signal of the unit 25. The minimum input is used as a standard value for comparing (for the pipeline with the highest resistance) incoming and side supply of additional gas, while the maximum input /t(.^ (for the pipeline with the lowest resistance) is used in the case of simultaneous supply of additional gas to ensure an exhaust effect .

The additional gas is preferably introduced into each pipe 15 as a flow directed towards the fuel mixture leaving the discharge chamber 8. The velocity pi-20 of this gas stream is set in the range of 0.25 to 1.5 times its critical exit velocity. This allows the pressure in the respective feed mixer 12 to be increased and the total hydraulic resistance of the pipe 15 to increase accordingly, said resistance increasing greater than the pressure variations in the furnace flue area, the pressure-25 variations in the furnace flue area practically having no effect on the total resistance of the pipeline 15

Reducing the velocity of the additional gas stream to less than 0.25 times its critical discharge rate does not give the desired effect because its dynamic pressure is small and the pressure increase in the feed mixer 12 is insignificant. Increasing the carrier gas flow rate to more than 1.5 times its critical discharge rate, while causing an increase in pressure in the feed mixer 12, 35, is disadvantageous due to the increase in energy consumption required to move the fuel mixture and the increase in air blower power.

I! 7 69101

The uniformity of the distribution of the fuel mixture and its uninterrupted blowing into the blast furnace depend to a considerable extent on the uniformity of the supply of the discharge chamber 8. When charging the pressurized discharge chamber 8 with a powdered fuel-5 fuel mixture, in particular with coal dust material, the material in the sealing chamber 4 regularly becomes "spongy". For this reason, the filling of the discharge chamber 8 with the powdered fuel mixture takes place in an unstable manner and lasts for 10-15 minutes. In order to avoid the above-mentioned disadvantages, it is advantageous, when charging the discharge chamber 8, to remove a part of the gas therefrom, the flow rate of this gas being the same as that fed to this chamber together with the fuel mixture to be charged. To this end, when the duct 15 is opened, the supply of dry air or nitrogen gas to the shut-off chamber 4 via pipe 7 and the transfer of the same amount of gas from the discharge chamber 8 through pipe 9 to the storage chamber 1 and then through pipe 3 and filter to the environment are simultaneously connected. Only the equality of the amount of gas 20 fed to the shut-off chamber 4 and the amount of gas removed from the discharge chamber 8 makes it possible to fill it with the fuel mixture and simultaneously distribute said mixture without adversely affecting the pneumatic transfer conditions. Equality of the above flow rates is preferred to be maintained automatically. To this end, the signals from the meters 17 and 18, which measure the flow and quantities, are fed to the unit 19 for comparison and, if there is a difference between the signals, the unit instructs to change the gas flow using a shut-off and control device 30 in the pipe. and no other adjustment is made to it. This is because in order to keep the filling time constant while increasing the working pressure P in the discharge chamber 8, the value of 35 must also be raised. The amount of this increase is set automatically because the position of the shut-off and control device is constant, the flow of gas leaving the pipe 9 increases 8 69101 in proportion to the value where p is the value of the overpressure in the chamber 8. Correspondingly, the value also increases.

The value of the pressure p in the discharge chamber 8 represents the main parameter which determines the transfer of the fuel mixture from the chamber 5 to the blast furnace 5 and is set according to the desired value of this flow rate, the pressure in the blast furnace chimneys and the pipeline resistances. The total consumption of the fuel mixture is checked according to the change in mass in the chamber 8, which is measured by means of strain gauges using conventional equipment. The value of the pressure P is kept constant by means of the pressure regulator 26 using the closing and regulating device of the pipeline 11.

The invention is further illustrated by the following representative examples.

15 Example 1

The method was applied in a pilot plant for blowing coal dust fuel into a blast furnace with a volume of 1,033 m 2.

4

The pressure in the blast furnace was 20 * 10 Pa. The pressure in the discharge chamber was 25 * 10 Pa. The pressure variation in the blast furnace hor-, 4 us was ± 2 * 10 Pa. The length of each pipe measured from the feed mixer to the flue was 100 m, the diameter 25 mm, 4 the hydraulic pressure was 2.5 * 10 Pa and the fuel concentration 3 3 in them was 0.06 m / m.

The filling chamber 4 with a capacity of 2 m 2 (see drawing) was filled with coal dust fuel at normal atmospheric pressure. Compressed air was introduced into the sealing chamber 4 for the flow Q of said air.

3 K

at 120 m / h. When the pressure in the closing chamber had reached 30 * 10 * Pa, the closing piece of the channel 10 was opened, whereby the closing chamber 4 and the discharge chamber 8 were connected. At the same time, a valve was opened in the duct 9 connecting the storage chamber and the discharge chamber 8, and gas was also removed from the rigid one at a flow of 120 m / h. In this case, the ta-35 underwent an efficient filling of the discharge chamber 8 with fuel in the form of coal dust. The pressure in the discharge chamber 8 remained practically constant because the flow rate of the removed gas li 9 69101 was the same as the flow rate of the gas introduced into it. The above made it possible to fill the discharge chamber in 3-5 minutes and stabilize the pressure and the amount of material in it.

5 The gas flow was maintained at 20 m / h # while the additional gas Qn flow rate was 160 m ^ / h, i.e. eight times greater than Qm · The supply of additional gas to the supply mixers 12 was carried out towards the corresponding supply of the gas-fuel mixture at a speed of 200 m / s. The hydraulic resistance of the pipelines 15 4 10 increased to 5 * 10 Pa and had grown considerably larger than the pressure fluctuations in the blast furnace chimneys 16, thus allowing the fuel supply variations to be reduced to 5%.

Example 2 Using the same equipment, additional gas was fed according to the procedure shown in the direction of the fuel mixture at a speed of about 300 m / s. The hydraulic resistance at the inlet 4 of the pipe 15 increased to 9.5 * 10 Pa due to the pressure increase in the feed mixer 12. The degree of unevenness of the supply of coal dust fuel at the same back pressure variation values (2 · 104 Pa) was 3.6%.

Claims (3)

10 691 01 A method for feeding a pulverized fuel mixture into the flues of a blast furnace, comprising filling a pressurized discharge chamber 5 in batches with a pulverulent fuel mixture, then continuously removing the mixture from the discharge chamber and transferring this mixture to the blast furnace flues by gas. introducing additional gas into each pipe (15) with an e of said total gas flow 3-10 times greater than the main gas flow and in each pipe (15) the product of the total gas flow and the concentration of the pulverulent fuel mixture therein is kept the same in all 15 chimneys. A method according to claim 1, characterized in that the additional gas is introduced into the pipeline (15) as a flow directed towards the above-mentioned fuel mixture, wherein the flow rate of the additional gas is kept 0.25-1.5 times its critical outlet rate. A method according to claim 1 or 2, characterized in that during the filling of the discharge chamber (8) a part of the gas is removed therefrom, the gas flow being the same as the flow of the gas introduced into the discharge chamber (8) together with the fuel mixture fed thereto. of