SU494872A3 - The method of oxidizing roasting pellets - Google Patents

Description

the heated gases are fed at a rate that depends on the speed of the pellets passing through the pre-combustion zone and the rotary kiln, while in the pre-combustion zone, 60 to 80% of magnetite is oxidized to hematite and from 2 to 10% in the furnace, from 62 to 90% of the oxidized granules with a temperature of approximately 1316 ° C are fed from the oven to the refrigerator.

Transporting the pellets through the first cooling zone.

. The flow of air into the first cooling zone is at a rate sufficient to continue, but not to terminate, the oxidation of the magnetite remaining in the granules.

Supplying air flow to the second cooling zone to oxidize the magnetite remaining in the granules to hematite and to cool the granules by heating air and burnt gases passing through the second cooling zone.

Passing heated air and burnt gases through the second cooling zone, through a layer of green granules on a movable grid before moving the granules through the pre-combustion zone for recovery and returning the heat released from the granules during the final oxidation of magnetite to hematite in the granules in the second cooling zone.

It is desirable to include an additional step of reforming the granules discharged from the furnace to the second movable grate for transportation through a group of cooling zones through which air is passed for the final cooling and oxidation of the granules.

It is possible to include another stage of transporting a layer of green granules through the drying zone of the first stage and the drying zone of the second stage, as well as passing heated air and burnt gases from the second cooling zone through a layer of green granules in the drying zone of the first stage to pre-dry the granules before transporting them through drying of the second stage and the pre-combustion zone.

The stage of supplying the mixture of air and burnt gases from the second cooling zone with a temperature of 316 ° C to 371 ° C and passing the mixture through a layer of green granules is also included either in the first stage drying zone or in the second stage drying zone .

According to the technology, the fuel is burned in the furnace in the amount necessary to raise the temperature of the preheated oxidizing gases from 982 ° C to 1316 ° C. The heat energy of these gases is transferred to the ore in the furnace, and the gases released from the furnace enter the pre-combustion zone at the moving grate and have a temperature of 82 ° C to 1093 ° C. Gases are passed through the system in an amount that, together with a certain speed of transportation of pre-combustion pellets and through a furnace, ensures the oxidation of 60-80% magnetite to hematite in the pre-combustion zone and 2 to 10% oxidation of magnetite to hematite in the furnace. From 62 to 90% of oxidized granules with a temperature of 1316 ° C are discharged into the refrigerator. The refrigerator contains two zones that

arranged in series. In the first zone, the passing air, however, does not complete the oxidation of the magnetite, which is formed in the granules that came from the furnace. Said air flow and burnt gases become

preheated (982 ° C) oxidizing gas entering the furnace ..

In the second zone of the refrigerator, the air flow completes the oxidation of the magnetite remaining in the granules and provides some

the cooling of the granules, while the air and combustion products become a stream of oxidizing gas, preheated from 316 ° C to 371 ° C. Heat energy of a gas stream heated to a temperature from 316 ° С to

37GS is recovered by passing this gas stream through a layer of green granules in the drying zone before passing the layer through the pre-combustion zone to carry out the process of heat release from the granules during the final oxidation of magnetite to hematite in the granules in the second cooling zone.

The proposed method makes it possible to reduce fuel consumption by 20–40% compared with the processes currently used in industry.

FIG. 1 shows an apparatus for carrying out the process of the proposed invention with a partial cut; in fig. 2 and 3 variants of the device.

The raw material is prepared for feeding into the apparatus (Fig. 1) using a natural sintering device, which may be a vat for knocking up into lumps or

drum. The feeder feeds green (i.e., untreated) balls or granules of raw materials in the form of a layer onto a gas-tight movable grid 1. Case 2 encloses the space under grid 1 and forms an opening for feeding material. The baffle 3 is located at the top of the housing 2 at a predetermined distance from the grill 1. The baffle 3 divides the space formed by the casing into a drying

chamber 4 and chamber 5 of pre-combustion. A layer of green granules on the grate 1 is fed through the drying chamber 4, then through the pre-combustion chamber 5, and then down into the discharge chute 6 into the inlet 7 of the furnace 8, lined with refractory material.

The rotary kiln 8 is inclined downward from the chute 6 in the direction of the cap 9 which closes the outlet

furnace 8 and separates channel 10 from furnace 8

to the refrigerator 11. A downward-tilted, rotating furnace 8 causes the material coming from the discharge chute 6 to pass through the furnace 8, then enter the cap 9 and through the channel 10 into the refrigerator 11.

The Fridge I is equipped with two blowers 12 and 13, which are driven by variable speed motors 14 and 15. The blowers blow an adjustable amount of air upward through the air chambers 16 and 17 and then through the material into air-permeable rails 18. The baffles 19 and 20 separate the refrigerator 11 to the cooling chamber 21 of the first stage, the cooling chamber 22 of the second stage and the cooling chamber 23 of the third stage along the entire grid 18.

As shown by the arrows, the cold air supplied by the blower 13 is blown up through the air chamber 17, the grille 18 and the chamber 22 in the pipe 24, which serves as a bypass pipe equipped with a damper 25. The cold air blown by the blower 12 is blown up through the air chamber 16 lattice 18, chamber 21 and channel 10 in the burning cap 9. The burner 26 is mounted in a cap for supplying fuel combustion to raise the temperature of the gases entering the furnace 8 to a predetermined high temperature required for heat treatment The material in the furnace 8. The gas discharged from the upper end of the furnace 8 flows upwardly into the discharge chute biv pre-combustion chamber 5.

A duct 27 is provided in the air supply unit that connects the pre-combustion chamber 5 with the existing chamber 4, which includes a T-shaped connection. One end of it is connected to the expander chamber 28 installed below the grate 1 and the pre-combustion chamber 5 to connect the air chamber 28 of the pipeline 27 to the chamber 5. The other end 29 of the pipeline 27 is connected to the body 2 above the drying chamber 4. Overflow pipe 24 coming from the chamber the second stage 22 of the refrigerator 11 is connected to the pipeline 27 below the air chamber 28.

In line 27 above the bypass line 24 and below the air chamber 28, dampers 30 are installed to control the flow of gas coming from the pre-combustion chamber 5 in line 27.

The exhaust fan 31 is installed in the pipe 27 between the bypass pipe 24 and the external chamber 4 and is designed to force air into the pipe 27 from the chamber 22 of the second stage of the refrigerator 11, as well as to inject gas into the pipe 27 from the furnace 8 to the camera 3, and the mixture of this air and gas is controlled by valves 25 and 30 for feeding into the existent chamber 4. One or several devices, such as a cyclone dust collector 32 with an opening 33 for discharging solid particles, are installed in the pipeline 27 between the bypass pipeline 24 and the fan 31. The inlet 34 to cold air regulating flap 35 nrisoedineno to conduit 27 downstream of the dust collector 32 and above the fan 31 to prevent overheating of the fan 31, the gas that is drawn by this fan. The auxiliary exhaust pipe 36, equipped with a kolnak 37 and a lifting device 38, for lowering and raising the hood above the grating 1 and are the outlet of the chamber 5 for the initial release of gases during fuel combustion by the burner 26 and

closing the dampers 30 to raise the temperature in the furnace 8 to the desired operating temperature.

A third pipe 39 is provided, at one end of which air is installed.

chamber 40 is below lattice 1. Chamber 40 is connected to air chamber 4 between the pre-combustion chamber 5 and the inlet of the drying chamber 4. The other end 41 of the third conduit 39 is connected to

exhaust pipe 42 for exhausting gases to the atmosphere. A drying gas exhaust fan 43 is installed in the pipeline 39 to inject gas into this pipeline and to release this gas through the exhaust pipe 42. A thin dust collector (not shown) can be installed in the pipeline 39. An electrofilter can be used as such a dust collector , gas-tight bags, wet scrubber or inclined dust collectors.

The process for producing solid discrete granules of finely ground magnetite iron ore using the proposed apparatus is a process that begins with the formation of green granules of finely ground ore in the device and the subsequent formation of a layer of granules on the moving grate 1. The granules are sequentially moved through the drying chamber 4 into the chamber Combustion 5. The pellets are processed in a rotary kiln 8, in which fuel is burned by means of a burner 26. The granules are then reformed into a layer on the grid 18 and passed through

chambers 21, 22 and 23 of the refrigerator 11. The air passing through the granules in the first cooling chamber 21 is converted into a stream of heated oxidizing gases flowing in the opposite direction to

movement of the pellets through channel 10 and furnace 8 and

current transverse to the direction of movement

a layer of granules in the drying chamber 4 and in the chamber

pre-combustion 5.

The burner 26 is intended for combustion

a certain amount of fuel in a certain amount of heated oxidizing gases in the furnace 8 to obtain a given amount of oxidizing gas with a temperature of 1148-1366 ° C, and the heated gases are fed depending on the speed of movement

The rpai-Pl through the pre-combustion chamber 5 and the rotary kiln 8, while in the pre-combustion chamber 5 oxidized from 60 to 80% magnetite to hematite and in furnace 8 from 2 to 10%. From oven 8 to refrigerator 11, between 62 and 90% of oxidized granules with a temperature of 1315 ° C are supplied.

Blower 12 is designed to supply air through the cooling chamber 21 depending on the speed of movement of the granules through the first cooling chamber 21 and provides sufficient air to start, but not to complete, the oxidation of the magnetite remaining in the granules. Blower 12 is also intended for supplying the heated oxidizing gas to furnace 8 with a temperature of 982 ° C.

Blower 13 is designed to supply air through the second cooling zone depending on the speed of movement of the granules through the second cooling chamber 22 and provides sufficient air to complete the oxidation of magnetite, remaining in the granules, to hematite. Blower 13 also provides some cooling to the pellets due to the heating of air and exhaust gases passing through the second cooling chamber 22.

The heated air and exhaust gases from the second chamber 22, cooling with a temperature of about 315-371 ° C, flow through conduit 24 into the layer of green granules on the grate 1 in the drying chamber 4 for recovery and return to the process of heat release from the granules during the final oxidation of magnetite to hematite in the granules in the second cooling chamber 22.

Thus, the heat released during the final transformation of magnetite into hematite in the first two chambers 21 and 22 of the refrigerator 11 is returned to the process. However, a significant portion of this heat (i.e., heat from the second chamber 22) returns to the process, mine furnace, where the gases must be heated to higher temperatures, thereby reducing fuel consumption. After the granules of the cooling chambers 11, 22 and 23 pass through the granules, they are sufficiently cooled and sent to storage.

The apparatus (shown in Fig. 2) further comprises a fourth conduit 44 for bypassing gases coming from the furnace around the pre-combustion chamber 5 and for supplying these gases to the drying chamber 4 and 1FW pipeline 27 for circulating gases of the mixed gas-air streams around the drying chamber 4.

The fourth pipe 44 includes flaps 45 and is connected to the opening 46 above grill 1 in the pre-combustion chamber 5 by the first end. This fourth pipe 29 provides means for removing gas from the pre-combustion chamber 5 to bypass material - and inlet this gas into pipe 27 at the site 47 which

located above the overflow pipe 24 and the dust separator 32. The cold air inlet 48 with the valve 49 is designed to regulate the flow of 5 mixed air passing through the cold air hole 48 into the pipe 44.

The fifth pipeline 50 includes a valve 51 and is connected at one end to the pipeline 27 in the area between the fan 31 and 10 by the drying chamber 4, and the other end to the pipeline 39 above the fan 43.

The operation of this apparatus (FIG. 2) for carrying out the process corresponds to the operation of the apparatus shown in FIG. 1. Except that the excess heat released during the conversion of magnetite to hematite is discharged through conduit 44, and from 60 to 80% of magnetite to hematite is oxidized in the pre-combustion chamber 5. The hot gases discharged through conduit 44 are mixed with the hot gases in the overflow pipe 24 (these gases are the result of the final exothermic transformation of magnetite to hematite in the cooling zone 22) and this mixture of hot gases which are mixed with air in a ratio of 62% and 38%, is fed at a temperature of from 316 to 321 ° C in the drying chamber 4.

Any temporary additional heat supply 0 to the chamber 4 is carried out by opening the valve 51 and withdrawing a certain amount of gas from the pipeline 27 through the third bypass pipeline 50 to the pipeline 39 and the exhaust pipe 42.

5 In FIG. Figure 3 shows another embodiment of the apparatus, but with some modifications. The housing 2 above the moving grate 1 is equipped with baffle plates for two-stage drying. The drying chamber 52 (upper figure) is followed by the drying chamber 53 (lower figure) of the second stage. The bypass pipeline 24 is equipped with a branch 54 for supplying hot gas through the pipeline 37 to the drying chamber 53 and a branch 5 55 for supplying the hot gas to the drying chamber 52.

The gases emitted from the furnace 8 are transferred via the bypass pipeline 44 to the bypass outlet 55 and to the air chamber 56 below the chamber 52. The overflow pipe 44 is also divided into two outlets 57 and 58. The outlet 57 is connected to the pipeline 27 to supply hot gas to a drying chamber 53, and a branch 58 is connected to an inlet outlet 54 for supplying hot gas to the drying chamber 52. The gas is exhausted from the drying chamber 52 through conduit 59, which is equipped with a fan 60, and is released into the atmosphere through exhaust pipe 61.

The operation of the apparatus shown in FIG. 3,

differs from the apparatus depicted in

FIG. 2 so that, overflowing heat, derived from

pre-combustion chambers 5 into hot gases withdrawn from cooling zone 22,

served in one of the chambers or in both chambers (drying chamber 52 of the first stage or chamber 53 of the second stage).

Thus, each apparatus can be used to carry out the process of oxidizing calcination of pellets. In each of the apparatus described, the heat released during the final conversion of magnetite to hematite in the first two zones 21 and 22 of the refrigerator 11 returns to the process, and a significant part of this heat (i.e., heat from zone 22) returns to the process a furnace in which gases must be heated to very high temperatures, thereby reducing fuel consumption by 20–40% or more.

Subject invention

The method of oxidizing roasting of pellets of magnetite ores, including drying

temperature of 316-317 ° C and heating at 982– 1093 ° C on a movable grid, processing in a furnace at 1148-1346 ° C, air cooling in a two-zone cooler, and drying and heating are carried out

a mixture of exhaust gases and air heated in the cooling zone, characterized in that, in order to increase the strength of the pellets and reduce fuel consumption, magnetite is oxidized in heating zones,

processing and cooling respectively by 60-80%, 2-10% and 10-38%.

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