RU2841645C1 - Shaft calcination device for producing hardened pellets from red mud - Google Patents

Abstract

FIELD: performing operations.

SUBSTANCE: invention relates to production of hardened pellets from red mud by firing in shaft furnace. Optimal distribution of heat flow inside the device is achieved due to monitoring and control of temperature created with gas-air mixture by means of PID-control on the basis of data received from thermocouples. Thermocouples are installed in the lining along the filling height of the annealed pellets, the signal from which goes to the PID-controller. In case of temperature drop in upper or lower zones burners operation intensity increases. Wherein said flame shifts subject to gas-air mix combustion intensity to equalize the temperature. Then, reduction reaction occurs in high-temperature zone with no oxygen, while temperature increases due to heat absorption by pellets. Operation of burners becomes less intense.

EFFECT: uniform distribution of heat released during combustion of gas-air mixture takes place; production of pellets with homogeneous structure is ensured.

1 cl, 5 dwg

Description

The invention relates to pelletizing iron ore materials by sintering and can be used in metallurgy to produce hardened pellets.

A device for a drum hot pelletizing unit is known (RU Patent No. 2613116, published on 15.03.2017), including a drum hot pelletizing unit containing a drum body with zones for producing raw pellets, drying, heating, firing and cooling them, a heating device containing a burner unit located in the firing zone, and a flue installed on the unloading side. The heating device is additionally equipped with burners, one of which is installed at the end of the heating zone, and the other - at the beginning of the pellet cooling zone, while the burners are located in the diametrical plane of the drum with an inclination angle of 35-40 ° to the vertical axis. The heating device contains 4-5 burners.

The disadvantage of the device is that the apparatus is of an open type, which does not allow for control of the atmosphere during firing and orderly removal of combustion products.

A shaft annular furnace for heat treatment of small-piece material is known (USSR Author's Certificate No. 183664, published on July 17, 1966), which includes an annular shaft with zones for heating, firing and cooling the material, equipped with annular combustion chambers, and in the walls of which, in the firing zone, channels are made that provide a transverse gas flow through the layer of material, providing the necessary heat exchange between gases and the layer of lump material in all zones of the furnace in the heating and cooling zones in an effective counter-current mode.

The disadvantage of the device is the presence of perforations in the walls of the shaft, which during operation can create deposits of the fired material and thereby limit the evenly distributed movement of the air flow.

A shaft furnace is known (USSR Author's Certificate No. 1717918, published 07.03.1992), which includes a cross-feed of the coolant. For this purpose, gas distribution walls made of beams are installed in the furnace shaft along the height, forming cavities together with the ceilings and refractory walls. Gas ducts connect the inlet and outlet cavities of adjacent gas distribution walls. When the furnace is operating, gases are filtered in a layer of material in one direction regardless of the number of suction stages, therefore the inlet and outlet cavities are located in opposite gas distribution walls, which allows reducing the height of the ceilings and the furnace itself.

The disadvantage of the device is the design of the air duct, with the help of which a screw cross-side flow is organized, which does not ensure the homogeneity of the structure during firing.

A shaft furnace is known (USSR Author's Certificate No. 476427, published on July 5, 1975) comprising a fuel combustion device suspended inside the shaft in the form of a hollow insert installed motionless and having a cylindrical shape in the central part and a conical shape with a perforated surface at the ends, and an air supply pipe. In the proposed shaft furnace, the hollow insert is suspended with the possibility of vertical movement from the drive. A distributor is fixed at the end of the air supply pipe, the holes of which are located coaxially with the holes of the lower end of the insert. The proposed shaft furnace is shown in the drawing. It contains a vertical lined shaft, inside which a fuel combustion device is suspended, made in the form of a hollow insert having a cylindrical shape in the central part and a conical shape with a perforated surface at the ends. An air supply pipe is installed inside the shaft. The hollow insert is suspended freely with the possibility of vertical movement from the drive using a hinge. At the lower end of the air supply pipe, a distributor is fixed, the holes of which are located coaxially with the holes of the lower end of the insert. When the kiln is in operation, a batch consisting of carbonate raw materials and solid fuel is loaded into it. As it descends, the batch is heated by furnace gases. The firing process takes place at a temperature of 1000-1300°C. In the cooling zone, the formed lime is cooled by air supplied from below and unloaded from the kiln. At the boundary between the zone and the heating zone, there is a so-called "reducing zone", in which high-temperature furnace gas, practically no longer containing oxygen, contacts the surface of the hot solid fuel.

The disadvantage of the device is that the suspended element, located in the middle of the furnace shaft, during technological movement has a destructive effect on pellets with low strength before firing.

A shaft furnace is known (USSR Author's Certificate No. 153548, published on June 26, 1963), which includes a round concrete foundation slab carrying support columns on which the bed is placed, and on it - the furnace base. The furnace for clarifying the glass mass has a lighting pool, around which there is a working pool connected to the pool by channels. Above the pool there is a vertical chamber for preliminary melting of the batch and a recuperator chamber. The chamber is covered with an overhead arch. Nozzle chambers for feeding fuel and batch into the furnace cavity are laid in the lower developed part of the arch. Under the influence of high temperatures, the dusty mixture of batch and cullet melts, forming tiny drops of glass falling down. During passage through the flame torch, these drops are drawn into threads, which, accompanied by hot exhaust gases, reach the pool. In the pool, the glass mass is cleared of gas inclusions and mixed. The exhaust gases from the furnace cavity rise to the recuperators at a level exceeding the level of the glass mirror.

The disadvantage of the device is that in the shaft of the gas circulation device the walls form vortex flows, which is the cause of build-ups that reduce the area of the flow section.

A shaft circulation furnace for heating section steel is known (USSR Author's Certificate No. 17293, published September 30, 1930), which includes a central conical column with ledges that prevent the sagging of the annealed rods installed around the column in the form of a hollow truncated cone and heated by two independent nozzles, of which the nozzle is installed in a horizontal channel, the continuation of which is the central cavity of the column, opening into the upper part of the furnace, and the nozzle is installed in the lower part of the furnace, communicating by channels with the cavity formed by the heated rods, and for the removal of exhaust gases into the annular bore, channels with branches serve, intended for the supply of part of the gases to the combustion products entering through the channels.

The disadvantage of the device is the removable cap, when raised, the fired material is rapidly cooled, which can cause cracking.

A shaft furnace is known (USSR Author's Certificate No. 809900, published on June 30, 1982), adopted as a prototype, comprising a vertical body connected at the top to a flue, a shaft cover with a device for loading the charge placed on it, a tray, tapholes and an internal lining made of refractory blocks, distinguished in that, in order to increase the yield of refractory metals, the lower part of the body and the tray are equipped with a protective casing connected by a pipe to the internal cavity of the shaft, the flue is made with a valve, and the lining blocks are in the form of a trapezoid, and the shaft body is equipped with screws in sealed caps for radial movement of the lining blocks.

The disadvantage of the device is that in the design the fired material is in close contact with the furnace lining, which can lead to rapid destruction of the lining during unloading of the shaft.

The technical result is the production of pellets of uniform structure.

The technical result is achieved in that the device is installed on a support ring, which is fixed to the base posts, in the lower part, the inner wall of the heat-insulating lining, a layer of structural lining is installed, on top of which a refractory lining is installed, the shaft is divided into a low-pressure chamber, the upper part of which is limited by a grate, a firing chamber which is limited by the height of the shaft refractory ring, and a pumping chamber, which is limited by a drop-shaped cover consisting of a casing and a base, and between them along the perimeter a rib of the cover is fixed, on which, on the front side, a position scale is made with the possibility of precise positioning of the valve, in the center of the cover a ventilation hole is made, in which a valve is installed, with a stop, which is connected to the handle, a lifting mechanism is installed under the cover in a narrowing part, coaxially with the rotary mechanism, through holes are made in the wall of the pumping chamber, in which nozzles of the pumping chamber are installed, which consists of mixer, on which a pressure gauge is installed, and which unites the gas pipeline and the air pipeline, and an automatic damper regulator, which is connected via a cable to the PID controller, and the piezoelectric elements are fixed at the ends of the nozzle mixer pipes, symmetrical through holes opposite each other and equidistant from each other in height are made in the walls of the firing chamber, in which thermocouple bushings are fixed, and thermocouples with the possibility of removal are installed in them, which are connected via a cable to the PID controller, a through hole is made in the wall of the low-pressure chamber, in which a low-pressure chamber nozzle is installed, which consists of a mixer, on which a pressure gauge is installed, and which unites the gas pipeline and the air pipeline, and an automatic damper regulator, which is connected via a cable to the PID controller, a tray is installed inside the lower part of the low-pressure chamber, in the center of which a central hole is made, which coincides with a through hole, which is made in the structural and heat-insulating linings, a chamber is fixed under the device dust collection, in which a cassette with a handle for a replaceable filter is installed, which is fixed under the central opening, while the dust collection chamber is connected through a low-pressure pipeline to the pump.

The device of shaft roasting for obtaining pellets reinforced with red mud is explained by the following figure:

Fig. 1. - general view of the shaft roasting device for obtaining hardened pellets from red mud;

Fig. 2 - drying of raw pellets from red mud in a shaft roasting device with an open lid;

Fig. 3 - roasting of pellets from red mud with PID control of the intensity of the nozzles;

Fig. 4 - cooling of burnt pellets from red mud in an air flow;

Fig. 5 - emptying the shaft roasting device for the next cycle, where:

1 - rotary mechanism;

2 - base of the lid;

3 - lid rib;

4 - firing chamber;

5 - cover;

6 - injection chamber nozzle (ICN);

7 - valve;

8 - ventilation hole;

9 - stop;

10 - positional scale;

11 - handle;

12 - cover casing;

13 - bushing for nozzle;

14 - lifting mechanism;

15 - pressure gauge;

16 - piezoelectric element;

17 - automatic damper regulator;

18 - mixer;

19 - gas pipeline;

20 - handle;

21 - pressure chamber;

22 - thermocouple;

23 - air pipeline;

24 - cable;

25 - fireproof lining;

26 - mixer branch pipe;

27 - mine refractory ring;

28 - PID controller;

29 - casing;

30 - loading bowl;

31 - grate;

32 - low pressure chamber;

33 - thermocouple sleeve;

34 - heat-insulating lining;

35 - low pressure chamber nozzle (LPC);

36 - structural lining;

37 - cassette;

38 - pallet;

39 - central hole;

40 - racks;

41 - support ring;

42 - handle;

43 - replaceable filter;

44 - dust collecting chamber;

45 - low pressure pipeline;

46 - base of the device;

47 - pump.

The shaft roasting device for obtaining hardened pellets is mounted on a support ring 41 (Fig. 1), which is secured to the posts 40 of the base of the device 46. The device consists of a vertical body, which is made in the form of a heat-insulating lining 34, which is made of a heat-insulating material laid inside the casing 29. In the lower part, the inner wall of the heat-insulating lining 34, a layer of structural lining 36 is installed, on top of which a refractory lining 25 is installed. The internal visible part of the device is a shaft divided into a low-pressure chamber 32, the upper part of which is limited by a grate 31. The grate 31 is installed in the middle part of the shaft and is secured between the structural lining 36 and the refractory lining 25, with the possibility of installing a loading bowl 30 with a handle 20 on it. A shaft refractory ring 27 is installed between the grate 31 and the walls of the refractory lining 25, the upper part of which is located below the bushings for the nozzle 13. The firing chamber 4 is formed by the walls of the shaft refractory ring 27. The upper part of the shaft is a pumping chamber 21.

In the wall of the low-pressure chamber 32 there is a through hole in which a gas duct is installed, which is made in the form of a low-pressure chamber nozzle (LPCJ) 35. The piezoelectric element 16 is fixed at the end of the mixer pipe 26 in the low-pressure chamber (LPCJ) 35, while it is located inside the low-pressure chamber 32. The low-pressure chamber nozzle (LPCJ) 35 consists of a mixer 18, which is connected to a gas pipeline 19 and an air pipeline 23, an automatic damper regulator 17, which is connected via a cable 24 to a PID controller 28, and a mixer pipe 26. A pressure gauge 15 is installed on the mixer 18.

In the wall of the pumping chamber 21 there are through holes in which gas ducts are installed, which are made in the form of pumping chamber nozzles (PCN) 6, consisting of a mixer 18, which is connected to the gas pipeline 19 and the air pipeline 23, and an automatic damper regulator 17, which is connected through a cable 24 to the PID controller 28, and a mixer branch pipe 26. Piezoelectric elements 16 are fixed at the ends of the mixer branch pipe 26 in the pumping chamber (PCN) 6, while they are located inside the pumping chamber 21. Pressure gauges 15 are installed on the mixers 18.

In the walls of the firing chamber 4, symmetrical through holes are made opposite each other and equidistant from each other in height, in which bushings for thermocouples 33 are fixed, and thermocouples 22 are installed in them with the possibility of removal. Thermocouples 22 are connected via cable 24 to PID controller 28.

A drop-shaped cover 5 is installed on top of the device, consisting of a cover casing 12 and a cover base 2, and a cover rib 3 is fixed between them along the perimeter. A refractory lining 25 and a heat-insulating lining 34 are fixed inside the cover. A ventilation hole 8 is made in the center of the cover, into which a valve 7 is installed, with a stop 9, which is connected to a handle 11. On the edge of the cover 3, on the front side, a position scale 10 is made with the possibility of precise positioning of the valve 7. A lifting mechanism 14 is installed under the cover 5 in the tapering part, coaxially with the rotary mechanism 1.

Inside the lower part, a cone-shaped tray 38 is installed on the structural lining 36, made, for example, from refractory steel with a central opening 39, the center of which coincides with a through opening made in the structural lining 36 and the heat-insulating lining 34. A dust collection chamber 44 is fixed under the device, in which a cassette 37 with a handle 42 for a replaceable filter 43 is installed, which is fixed under the central opening 39. The dust collection chamber 44 is connected through a low-pressure pipeline 45 to a pump 47.

The shaft roasting device for producing pellets reinforced with red mud operates as follows.

Raw pellets in loading bowl 30 (Fig. 2) are placed in firing chamber 4 on grate 31 for firing in shaft furnace. In low pressure chamber 32, gas-air mixture supply is switched on through and mixer branch pipe 26, formed in mixer 18 through gas pipeline 19 and air pipeline 23, after which piezoelectric element 16 ignites the flame of gas-air mixture. Pressure control of gas-air mixture in nozzle FKND 35 during pellet drying is performed by means of pressure gauge 15.

Then the cover 5 (Fig. 3) is lowered onto the ends of the device using the lifting mechanism 14. In the injection chamber 21, the supply of the gas-air mixture is switched on through the nozzle of the mixer 26, formed in the mixer 18 through the gas pipeline 19 and the air pipeline 23, after which the piezoelectric element 16 ignites the flame of the gas-air mixture. The FKND nozzle 35 is switched off. The pressure of the gas-air mixture in the FKN nozzles 6 in the firing chamber 4 is monitored using the pressure gauge 15.

In the low-pressure chamber, a vacuum is created, for example, up to 104 Pa, due to the fact that exhaust gases exit through the low-pressure pipeline 45, going to the pump 47. The flame in the pumping chamber 21 leads to an increase in temperature, while heat is absorbed by the pellets, as a result, at the outlet, temperature losses can be from 25 to 30 ° C. The process of aggregation of pellet particles during sintering of the material is accompanied by the formation of slag bridges, the grains are bonded together to form a homogeneous structure. The same temperature is maintained throughout the entire loading height due to the joint operation of the FKN 6 nozzles interacting with the thermocouples 22. From the thermocouples 22, data is sent via cable 24 to the PID controller 28, which sends a signal via cable 24 to adjust the automatic damper controller 17. In the firing zone 4, a gas mixture flow passes through the grate 31, heating the semi-finished product being fired.

Automatic damper regulator 17 (Fig. 4) closes the supply of gas-air mixture to FKN nozzles 6, stopping the firing process. When turning handle 11 to a given value of position scale 10, damper 7 moves to the side and ventilation hole 9 opens, through which air is taken in for cooling pellets. Then the device operates in the air blowing mode through ventilation hole 9 in the center of cover 5. When cooling pellets, scale and small particles are formed on the surface of the product, which fall through grate 31, passing through low-pressure chamber 32, fall on tray 38, and then by means of low pressure through low-pressure pipeline 45 are removed with exhaust gases. Scale and small particles are carried away into dust cleaning chamber 44, and are retained on replaceable filter 43.

Pump 47 (Fig. 5) is switched off in low-pressure pipeline 45, removal of exhaust gases stops and the pressure inside the shaft equalizes with the surrounding pressure. Then cover 5 is raised using lifting mechanism 14 and moved to the side using rotary mechanism 1. Loading bowl 30 with finished product is removed from the furnace shaft. After that, the cover is closed again and cleaning air blowing is carried out through all FKN nozzles 6 and FKND nozzle 35, pump 47 is switched on, which begins removing exhaust gases through low-pressure pipeline 45. During blowing, fines and scale particles are separated from the internal surfaces of firing chamber 4, injection chamber 21 and low-pressure chamber 32, which are subsequently collected on replaceable filter 43. Then cassette 37 with replaceable filter 43 is removed from the chamber of replaceable filter 44, and a clean replaceable filter 43 is installed in its place.

Optimal distribution of heat flow inside the device is achieved by monitoring and regulating the temperature created by the gas-air mixture using PID control based on the data from the thermocouples. Thermocouples are installed in the lining along the height of the backfill of the fired raw material, the signal from which goes to the PID controller. In case of a drop in temperature in the upper zone, the intensity of the burners increases. the flame shifts in the right direction depending on the intensity of combustion of the gas-air mixture and the flow temperature is equalized. Then, in the high-temperature zone, in the absence of oxygen, the reduction reaction occurs, and the temperature increases due to the absorption of heat by the pellets. The burners work less intensively. Thus, the heat released during combustion of the gas-air mixture is distributed evenly.

Optimal heat flow distribution inside the device in turn ensures a high degree of reduction during firing and, as a consequence, obtaining a homogeneous structure of the raw material, which directly affects the crushing strength tests. This result is achieved due to exothermic reduction reactions in a zone with a relatively high temperature with a reduced presence of oxygen.

Claims (1)

A shaft roasting device for producing hardened pellets from red mud, comprising a vertical body, a flue, a cover, a tray, a casing, an internal refractory lining, characterized in that that the device is installed on a support ring, which is secured to the base posts, in the lower part of the inner wall of the heat-insulating lining a layer of structural lining is installed, on top of which a refractory lining is installed, the shaft is divided into a low-pressure chamber, the upper part of which is limited by a grate, a firing chamber, which is limited by the height of the shaft refractory ring, and a pumping chamber, which is limited by a drop-shaped cover consisting of a casing and a base, and between them along the perimeter a rib of the cover is fixed, on which a position scale is made on the front side with the possibility of precise positioning of the valve, in the center of the cover a ventilation hole is made, in which a valve with a stop is installed, which is connected to the handle, a lifting mechanism is installed under the cover in the tapering part, coaxially with the rotary mechanism, through holes are made in the wall of the pumping chamber, in which pumping chamber nozzles are installed, which consist of a mixer on which a pressure gauge is installed and which combines the gas pipeline and the air pipeline, and an automatic damper regulator, which is connected via a cable to the PID controller, and the piezoelectric elements are fixed on the ends of the nozzle mixer pipes, symmetrical through holes opposite each other and equidistant from each other in height are made in the walls of the firing chamber, in which bushings for thermocouples are fixed, and thermocouples with the possibility of removal are installed in them, which are connected via a cable to the PID controller, a through hole is made in the wall of the low-pressure chamber, in which a low-pressure chamber nozzle is installed, which consists of a mixer, on which a pressure gauge is installed and which combines the gas pipeline and the air pipeline, and an automatic damper regulator, which is connected via a cable to the PID controller, a tray is installed inside the lower part of the low-pressure chamber, in the center of which a central hole is made, which coincides with a through hole, which is made in the structural and heat-insulating linings, a dust collection chamber is fixed under the device, in which a cassette with a handle for a replaceable filter, which is fixed under the central hole, while the dust collection chamber is connected via a low-pressure pipeline to the pump.