Steel slag dry-method treatment system and whole-process waste heat recovery process

Abstract

The invention discloses a steel slag dry-method treatment system and a whole-process waste heat recovery process, and belongs to the technical field of steel slag treatment and waste heat recovery. According to the technical scheme, the system comprises a high-temperature section waste heat recovery system, a medium-low temperature section waste heat recovery system and a steel slag secondary separation and tailing digestion system. Firstly, steel slag discharged from a smelting furnace enters a high-temperature section waste heat recovery system, and heat is recovered by adopting a vertical waste heat recovery device through air heat exchange. Afterwards, the steel slag subjected to rolling crushing enters a medium-low temperature section waste heat recovery system, and heat of the steel slag is directly exchanged and recovered through a kiln type waste heat recovery device. And finally, iron-containing materials and tailings are separated from the steel slag through magnetic separation, and the tailings can be comprehensively utilized after being digested by digestion gas. The method has the beneficial effects that the whole-process waste heat recovery of the steel slag discharged from the smelting furnace can be realized, the resource recovery rate is improved, and the problems existing in steel slag treatment in the current steel industry are effectively solved.

Description

Technical Field

[0001] The present invention relates to a dry process for treating steel slag and a full-process waste heat recovery process, belonging to the technical field of steel slag treatment and waste heat recovery. Background Art

[0002] In steelmaking production, for every 1t of crude steel produced, about 100 - 150kg of steel slag is generated. The tapping temperature of the steel slag is as high as 1400 - 1600°C, and the specific heat capacity of the steel slag is 1.2kJ / (kg·°C). If the sensible heat of the steel slag at 1000°C is recovered, then 1.2GJ of heat can be recovered per ton of steel slag, which is approximately equivalent to the heat generated by the complete combustion of 41kg of standard coal, and the market prospect has great potential.

[0003] Currently, the main methods for steel enterprises to treat hot-melt steel slag are hot stamping method, hot splashing method, roll pressing and crushing + hot stamping method, air quenching method, water quenching method, drum method, etc. Most of these methods still focus on recovering metals mainly. That is, after cooling through different processes, and then through processes such as crushing, magnetic separation, and screening, the iron resources in the steel slag are recovered, while the sensible heat of the steel slag is not recovered and utilized.

[0004] In recent years, some steel enterprises have gradually tried to recover the sensible heat of steel slag, mainly adopting two methods of direct heat extraction and indirect heat extraction. However, either it can only treat steel slag with good fluidity, such as the air quenching method and the drum method; or only the waste heat in the low-temperature section of 800 - 200°C in the hot steel slag is recovered, such as the hot stamping method and the water quenching method. Moreover, since this method uses water as a medium to directly contact the steel slag, it not only causes heat loss, but also generates slag-containing waste water and dust-containing steam during the treatment process. Under the increasingly strict environmental protection conditions, perfect wet dust removal and water treatment facilities need to be configured.

[0005] In view of this, it is very necessary to propose a new dry process for treating steel slag. On the one hand, it can realize the full-process waste heat recovery of steel slag, helping steel enterprises to achieve the goal of energy conservation and carbon reduction; on the other hand, it can save the investment in wet dust removal and water treatment facilities and save the floor area. Summary of the Invention

[0006] The object of the present invention is to provide a dry process system for treating steel slag and a full-process waste heat recovery process, which can realize the full-process waste heat recovery of the steel slag coming out of the smelting furnace, and effectively solve the problems existing in the current steel slag treatment in the steel industry.

[0007] The technical solution of the present invention is as follows: A dry steel slag treatment system, which includes a waste heat recovery system for the high-temperature section, a waste heat recovery system for the medium- and low-temperature sections, a secondary separation system for steel slag and a tail slag digestion system. The waste heat recovery system for the high-temperature section includes a slag pot, a slag pot tilting device, a roller press thermal crushing device, an enclosure device, a blower, a hot air collecting hood, a cyclone dust collector, a vertical waste heat recovery device, a bag filter, a chimney and a feed pipe. The slag pot tilting device and the roller press thermal crushing device are arranged inside the same enclosure device. The hot air collecting hood is installed on the enclosure device. The slag pot is hoisted by a crane and placed on the slag pot tilting device. The slag pot tilts to pour out the high-temperature steel slag. The roller press thermal crushing device rotates to crush the hot steel slag and push it to the feed opening, and it is sent to the waste heat recovery system for the medium- and low-temperature sections through the feed pipe. At the same time, the blower sends cold air into the enclosure device to exchange heat with the hot steel slag. The hot air is captured by the hot air collecting hood and sent to the cyclone dust collector for rough dust removal. The hot air coming out of the cyclone dust collector enters the vertical waste heat recovery device. After the flue gas coming out of the vertical waste heat recovery device is cooled, it is sent to the bag filter for purification and then discharged through the chimney. The waste heat recovery system for the medium- and low-temperature sections of steel slag includes a No. 1 chain conveyor, a jaw type thermal crusher, a No. 2 chain conveyor, a screening device, a large block scrap steel chute, a large block scrap steel tank, a screen undersize steel slag chute, a kiln type waste heat recovery device, a riser pipe, a steam drum, a circulating pump and a downcomer. The No. 1 chain conveyor sends the hot steel slag to the jaw type thermal crusher for hot slag crushing. The No. 2 chain conveyor sends the crushed hot slag to the screening device. The steel slag on the screen is sent into the scrap steel tank through the large block scrap steel chute and returned to the steelmaking process for recycling. The screen undersize steel slag enters the kiln type waste heat recovery device through the screen undersize steel slag chute. The hot steel slag directly contacts and exchanges heat with the heat exchange pipes installed in the kiln body. The softened water in the heat exchange pipes vaporizes, and the steam-water mixture enters the steam drum through the riser pipe. After steam-water separation, the water in the steam drum is sent to the kiln type waste heat recovery device through the circulating pump and the downcomer. The secondary separation system for steel slag and the tail slag digestion system includes a belt conveyor, a magnetic roller and a storage bin. The belt conveyor receives the steel slag cooled by the kiln type waste heat recovery device and transports the steel slag to the storage bin. The steel slag is magnetically separated by the magnetic roller before entering the storage bin. The selected iron-containing material enters the No. 1 storage bin, and the tail slag enters the No. 2 storage bin and the No. 3 storage bin. One of the No. 2 storage bin and the No. 3 storage bin is used as a storage bin, and the other is used as a digestion bin, which can be used interchangeably. The introduced digestion gas digests the free CaO in the tail slag with residual temperature.

[0008] A slag pot hoisting opening is arranged above the enclosure device. The slag pot hoisting opening is equipped with a switch door, which is opened when hoisting and placing the slag pot and closed when pouring slag and crushing the steel slag.

[0009] The kiln type waste heat recovery device is of a cylindrical structure.

[0010] A dry process for treating steel slag with full-process waste heat recovery. The high-temperature steel slag coming out of the smelting furnace is granulated in a closed device through a roll pressing and crushing device. At the same time, by blowing air into the closed device, heat exchange is carried out with the steel slag. The hot air is sent to a dust collector for rough dust removal. The hot air coming out of the dust collector enters a vertical waste heat recovery device for preheating recovery. The flue gas coming out of the vertical waste heat recovery device is cooled, dust-removed and purified, and then discharged through a chimney. The steel slag after heat exchange in the closed device is sent to a hot crusher for hot slag crushing. The crushed hot slag is sent to a screening device for screening. The steel slag on the screen is returned to the steelmaking process for recycling, and the steel slag under the screen enters a kiln-type waste heat recovery device for preheating recovery.

[0011] The temperature of the high-temperature steel slag coming out of the smelting furnace is 1400 - 1600 °C, and the temperature of the steel slag after heat exchange with cold air in the closed device is 800 - 900 °C. The temperature of the flue gas coming out of the vertical waste heat recovery device is below 200 °C.

[0012] The steel slag after heat exchange in the closed device is sent to a hot crusher and crushed to less than 80 mm.

[0013] The innovation points of the present invention are as follows: It can not only realize the full recovery of the sensible heat of the steel slag and avoid energy waste, but also, since the steel slag does not come into contact with water during the whole treatment process, it is a fully dry treatment process. On the one hand, it avoids a large amount of heat being carried away by water, and on the other hand, it can save the investment in wet dust removal and turbidity cycle water treatment. Among them: High-temperature section steel slag waste heat recovery system: After the hot flue gas is dust-removed, it exchanges heat through a waste heat boiler to recover steam. This section recovers the heat of the steel slag between 1500 - 900 °C; Medium and low-temperature section steel slag waste heat recovery system: The temperature of the crushed and granulated steel slag is reduced to 800 - 900 °C. In order to improve the heat exchange efficiency and avoid blockage by large pieces of steel slag, the steel slag is crushed, screened and then enters a high-efficiency heat exchange device, namely a kiln-type waste heat recovery device. This device rotates at a certain speed. During the rotation process, the hot slag directly contacts the heat exchange tubes for heat exchange to recover steam; Three major systems of secondary separation of steel slag and tail slag digestion: In order to ensure the heat exchange effect, no water is sprayed in the first two processes. There is still a large amount of free CaO in the cooled steel slag. After the metallic iron is separated by magnetic separation, it can be returned to the steelmaking process for recycling. The free CaO in the tail slag needs to be digested by introducing digestion gas in the bin before comprehensive utilization can be carried out.

[0014] The equipment or components involved in this process are all marketized general equipment.

[0015] The beneficial effects of the present invention are as follows: The sensible heat of steel slag is recycled through the entire two-stage process, which helps steel enterprises achieve the goal of carbon reduction and efficiency improvement; the steel slag treatment process is a dry process, and water is not required for the steel slag throughout the process, so the turbidity circulating water system in the existing slag smothering process can be cancelled, reducing the investment intensity; the entire steel slag treatment process operates in a closed space and equipment, solving the environmental protection problems existing in the existing steel slag treatment process and meeting the requirements of clean production; the tail slag can be recycled after being digested by the digestion gas, improving the resource recovery rate and meeting the requirements of relevant policies. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic process flow diagram of the present invention.

[0017] The markings in the figure are as follows: high-temperature section waste heat recovery system 1, slag pot 11, slag pot tilting device 12, roller press type thermal crushing device 13, sealing device 14, opening and closing door 141, blower 15, hot air collecting hood 16, cyclone dust collector 17, vertical waste heat recovery device 18, steam drum 19, bag filter 110, chimney 111, feeding pipe 112; medium and low-temperature section waste heat recovery system 2, No. 1 apron conveyor 21, jaw type thermal crusher 22, No. 2 apron conveyor 23, screening device 24, large block scrap steel chute 25, large block scrap steel tank 26, undersize steel slag chute 27, kiln type waste heat recovery device 28, riser pipe 29, steam drum 210, circulation pump 211, downcomer 212; steam drum steel slag secondary separation and tail slag digestion system 3, belt conveyor 31, magnetic roller 32, No. 1 bin 33, No. 2 bin 34, No. 3 bin 35 and digestion gas 36. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be further described below with reference to the accompanying drawings through examples.

[0019] Refer to the attached Figure 1, a dry steel slag treatment system, which includes a high-temperature waste heat recovery system 1, a medium- and low-temperature waste heat recovery system 2, and a secondary steel slag separation and tail slag digestion system 3. The high-temperature waste heat recovery system 1 includes a slag pot 11, a slag pot tilting device 12, a roller press thermal crushing device 13, an enclosure device 14, a blower 15, a hot air collecting hood 16, a cyclone dust collector 17, a vertical waste heat recovery device 18, a bag filter 110, a chimney 111, and a feeding pipe 112. The slag pot tilting device 12 and the roller press thermal crushing device 13 are arranged inside the same enclosure device (14), and the hot air collecting hood (16) is installed on the enclosure device (14). The slag pot 11 is hoisted by a crane and placed on the slag pot tilting device 12. The slag pot is tilted to pour out the high-temperature steel slag, and the roller press thermal crushing device 13 rotates to crush the hot steel slag and push it to the feeding port, and then it is sent to the medium- and low-temperature waste heat recovery system 2 through the feeding pipe 112. At the same time, the blower 15 sends cold air into the enclosure device 14 to exchange heat with the hot steel slag. The hot air is captured by the hot air collecting hood 16 and sent to the cyclone dust collector 17 for rough dust removal. The hot air coming out of the cyclone dust collector 17 enters the vertical waste heat recovery device 18. After the flue gas coming out of the vertical waste heat recovery device 18 is cooled, it is sent to the bag filter 110 for purification and then discharged through the chimney 111. The medium- and low-temperature steel slag waste heat recovery system 2 includes a No. 1 chain conveyor 21, a jaw thermal crusher 22, a No. 2 chain conveyor 23, a screening device 24, a large scrap steel chute 25, a large scrap steel tank 26, a screened steel slag chute 27, a kiln-type waste heat recovery device 28, a riser pipe 29, a steam drum 210, a circulating pump 211, and a downcomer 212. The No. 1 chain conveyor 21 sends the hot steel slag to the jaw thermal crusher 22 for hot slag crushing. The No. 2 chain conveyor 23 sends the crushed hot slag to the screening device 24. The steel slag on the screen is sent into the scrap steel tank 26 through the large scrap steel chute 25 and returned to the steelmaking process for recycling. The screened steel slag enters the kiln-type waste heat recovery device 28 through the screened steel slag chute 27. The hot steel slag directly contacts and exchanges heat with the heat exchange tubes installed in the kiln body. The softened water in the heat exchange tubes vaporizes, and the steam-water mixture enters the steam drum 210 through the riser pipe 29. After steam-water separation, the water in the steam drum is sent to the kiln-type waste heat recovery device 28 through the circulating pump 211 and the downcomer 212. The secondary steel slag separation and tail slag digestion system 3 includes a belt conveyor 31, a magnetic drum 32, and a storage bin. The belt conveyor 31 receives the steel slag cooled by the kiln-type waste heat recovery device 28 and transports the steel slag to the storage bin. The steel slag is magnetically separated by the magnetic drum 32 before entering the storage bin. The selected iron-containing material enters the No. 1 storage bin 33, and the tail slag enters the No. 2 storage bin 34 and the No. 3 storage bin 35. One of the No. 2 storage bin 34 and the No. 3 storage bin 35 serves as a storage bin, and the other serves as a digestion bin and can be used interchangeably. The introduced digestion gas 36 digests the free CaO in the tail slag with residual temperature.

[0020] In this embodiment, refer to Figure 1, A dry steel slag treatment system and a full-process waste heat recovery process, including a high-temperature waste heat recovery system 1, a medium- and low-temperature waste heat recovery system 2, and a steel slag secondary separation and tail slag digestion system 3.

[0021] Reference Figure 1 , The high-temperature waste heat recovery system 1 includes a slag pot 11, a slag pot tilting device 12, a roller press thermal crushing device 13, a sealing device 14, a blower 15, a hot air collecting hood 16, a cyclone dust collector 17, a vertical waste heat recovery device 18, a steam drum 19, a bag filter 110, a chimney 111, and a feeding pipe 112.

[0022] Reference Figure 1 , The medium- and low-temperature waste heat recovery system 2 includes a No. 1 chain conveyor 21, a jaw thermal crusher 22, a No. 2 chain conveyor 23, a screening device 24, a large-piece scrap steel chute 25, a large-piece scrap steel tank 26, a screen-under steel slag chute 27, a kiln-type waste heat recovery device 28, a riser pipe 29, a steam drum 210, a circulation pump 211, and a downcomer 212.

[0023] Reference Figure 1 , The steel slag secondary separation and tail slag digestion system 3 includes a belt conveyor 31, a magnetic roller 32, a No. 1 bin 33, a No. 2 bin 34, a No. 3 bin 35, and a digestion gas 36.

[0024] In this embodiment, the converter slag tapping temperature is 1400 - 1600 °C, the slag production is 50 t / h, and the 16 m 3 After receiving the hot slag, the slag pot 11 is transported to the slag treatment workshop and hoisted by the workshop crane and placed on the slag pot tilting device 12. The slag pot is tilted to pour out the steel slag, and the roller press thermal crushing device 13 rotates to crush the hot steel slag and push it to the feeding port, and then it is sent to the medium- and low-temperature waste heat recovery system through the feeding pipe 112. The slag pot tilting device 12 and the roller press thermal crushing device 13 operate in a completely enclosed space. There is a slag pot hoisting port above the sealing device 14, and a switch door is installed at the slag pot hoisting port, which is opened when hoisting and placing the slag pot and closed when pouring slag and crushing the steel slag. The blower 15 sends cold air into the inside of the sealing device 14 through the air inlet to exchange heat with the hot steel slag. The temperature of the steel slag drops from 1400 - 1600 °C to 800 - 900 °C. The hot air is captured by the hot air collecting hood 16 and sent into the cyclone dust collector 17 through the air duct for rough dust removal. The hot air coming out of the cyclone dust collector enters the vertical waste heat recovery device 18, and a steam drum 19 is installed on the upper part of the waste heat recovery device 18. The temperature of the flue gas coming out of the vertical waste heat recovery device drops below 200 °C, and it is sent to the bag filter 110 for purification and then discharged through the chimney 111. The high-temperature waste heat recovery system generates 13 t / h of steam.

[0025] The No. 1 apron conveyor 21 sends the steel slag at a temperature of 800 - 900 °C to the jaw-type hot crusher 22 for hot slag crushing, crushing the steel slag to less than 80 mm. The No. 2 apron conveyor sends the crushed hot slag to the screening device 24. The sieve plate of the screening device 24 is heat-resistant above 1000 °C. The steel slag on the sieve enters the scrap steel tank 26 through the large-piece scrap steel chute 25 and returns to the steelmaking process for recycling. The steel slag under the sieve enters the kiln-type waste heat recovery device 28 through the under-sieve steel slag chute 27. The kiln-type waste heat recovery device is a cylindrical structure with a length of 20 m and a diameter of 3 m, rotating at a speed of 0.5 - 1.5 r / min. The hot steel slag continuously enters the kiln-type waste heat recovery device 28 and directly contacts and exchanges heat with the heat exchange tubes installed in the kiln body. The softened water in the heat exchange tubes vaporizes, and the steam-water mixture enters the steam drum 210 through the riser 29. After steam-water separation, the water in the steam drum is sent to the kiln-type waste heat recovery device 28 through the circulating pump 211 and the downcomer 212. The medium and low temperature section waste heat recovery system generates 10 t / h of steam.

[0026] The temperature of the steel slag coming out of the low temperature waste heat recovery system drops to 180 - 200 °C and is transported to the magnetic drum 33 by the belt conveyor 32. The steel slag is magnetically separated by the magnetic drum 33 before entering the bunker. The selected iron-containing material enters the No. 1 bunker 34, and the tail slag enters the No. 2 bunker 35 and the No. 3 bunker 36. The proportion of the tail slag with a particle size ≤ 20 mm is not less than 70%. The No. 3 bunker is used as a digestion bunker to introduce digestion gas to digest the free CaO in the tail slag with residual temperature. The digested tail slag can be comprehensively utilized as raw materials for roads and building materials, and the iron-containing materials are returned to the steelmaking process as cold materials for recycling.

Claims

1. A dry steel slag treatment system, characterized in that: It includes a high-temperature waste heat recovery system (1), a medium- and low-temperature waste heat recovery system (2), and a secondary separation of steel slag and tail slag digestion system (3). The high-temperature waste heat recovery system (1) includes a slag pot (11), a slag pot tipping device (12), a roll press thermal crushing device (13), an enclosure device (14), a blower (15), a hot air collecting hood (16), a cyclone dust collector (17), a vertical waste heat recovery device (18), a bag filter (110), a chimney (111), and a feeding pipe (112). The slag pot tipping device (12) and the roll press thermal crushing device (13) are arranged inside the same enclosure device (14). The hot air collecting hood (16) is installed on the enclosure device (14). The slag pot (11) is hoisted by a crane and placed on the slag pot tipping device (12). The slag pot is tilted to pour out the high-temperature steel slag. The roll press thermal crushing device (13) rotates to crush the hot steel slag and push it to the feeding opening, and it is sent to the medium- and low-temperature waste heat recovery system (2) through the feeding pipe (112). At the same time, the blower (15) sends cold air into the enclosure device (14) to exchange heat with the hot steel slag. The hot air is collected by the hot air collecting hood (16) and sent to the cyclone dust collector (17) for rough dust removal. The hot air coming out of the cyclone dust collector (17) enters the vertical waste heat recovery device (18). After the flue gas coming out of the vertical waste heat recovery device (18) is cooled, it is sent to the bag filter (110) for purification and then discharged through the chimney (111). The medium- and low-temperature steel slag waste heat recovery system (2) includes a No. 1 chain conveyor (21), a jaw thermal crusher (22), a No. 2 chain conveyor (23), a screening device (24), a large-piece scrap steel chute (25), a large-piece scrap steel tank (26), a screened steel slag chute (27), a kiln-type waste heat recovery device (28), a riser pipe (29), a steam drum (210), a circulating pump (211), and a downcomer (212). The No. 1 chain conveyor (21) sends the hot steel slag to the jaw thermal crusher (22) for hot slag crushing. The No. 2 chain conveyor (23) sends the crushed hot slag to the screening device (24). The steel slag on the screen is sent into the scrap steel tank (26) through the large-piece scrap steel chute (25) and returned to the steelmaking process for recycling. The screened steel slag enters the kiln-type waste heat recovery device (28) through the screened steel slag chute (27). The hot steel slag directly contacts and exchanges heat with the heat exchange pipes installed in the kiln body. The softened water in the heat exchange pipes vaporizes, and the steam-water mixture enters the steam drum (210) through the riser pipe (29). After steam-water separation, the water in the steam drum is sent to the kiln-type waste heat recovery device (28) through the circulating pump (211) and the downcomer (212). The secondary separation of steel slag and tail slag digestion system (3) includes a belt conveyor (31), a magnetic drum (32) and a silo. The belt conveyor (31) receives the steel slag cooled by the kiln-type waste heat recovery device (28) and transports the steel slag to the silo. The steel slag is magnetically separated by the magnetic drum (32) before entering the silo. The iron-containing material selected enters the No. 1 silo (33), and the tail slag enters the No. 2 silo (34) and the No. 3 silo (35). One of the No. 2 silo (34) and the No. 3 silo (35) serves as a storage silo, and the other serves as a digestion silo, which can be used interchangeably. The introduced digestion gas (36) digests the free CaO in the tail slag with residual temperature.

2. The dry treatment process of steel slag and the full-process waste heat recovery process according to claim 1, characterized in that: Above the closing device (14), there is a slag ladle lifting port. The slag ladle lifting port is equipped with a opening and closing door, which is opened when lifting and placing the slag ladle, and closed when pouring the slag and crushing the steel slag.

3. A dry process for treating steel slag and a full-process waste heat recovery process according to claim 1, characterized in that: The kiln-type waste heat recovery device (28) is of a cylindrical structure.

4. A dry process for treating steel slag with full-process waste heat recovery, characterized in that: The high-temperature steel slag coming out of the smelting furnace is granulated by a roll crushing device in a closed device. At the same time, by blowing air into the closed device, heat exchange is carried out with the steel slag. The hot air is sent to the dust collector for rough dust removal. The hot air coming out of the dust collector enters the vertical waste heat recovery device for preheating recovery. The flue gas coming out of the vertical waste heat recovery device is cooled, dust-removed and purified, and then discharged through the chimney. The steel slag after heat exchange in the closed device is sent to a hot crusher for hot slag crushing. The crushed hot slag is sent to a screening device for screening. The steel slag on the screen is returned to the steelmaking process for recycling, and the steel slag under the screen enters the kiln-type waste heat recovery device for preheating recovery.

5. A full-process waste heat recovery process for dry treatment of steel slag according to claim 4, characterized in that: The temperature of the high-temperature steel slag coming out of the smelting furnace is 1400 - 1600 °C, and the temperature of the steel slag after heat exchange with cold air in the closed device is 800 - 900 °C.

6. A full-process waste heat recovery process for dry treatment of steel slag according to claim 4, characterized in that: The temperature of the flue gas coming out of the vertical waste heat recovery device is below 200 °C.

7. A full-process waste heat recovery process for dry treatment of steel slag according to claim 4, characterized in that: The steel slag after heat exchange in the closed device is sent to a hot crusher and crushed to less than 80 mm.

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