Device for steel slag granulation waste heat recovery

Abstract

The utility model discloses a device for steel slag granulation preheating recovery, which comprises a fluidized bed boiler and an air quenching granulation furnace, the fluidized bed boiler comprises a boiler barrel assembly and a gate-type flue, and a channel of the gate-type flue is circular and comprises a first vertical flue, a horizontal flue and a second vertical flue which are communicated in sequence. According to the utility model, the air-quenching granulating furnace is combined with the fluidized bed boiler, and high-temperature flue gas generated in the air-quenching process of liquid steel slag of the fluidized bed boiler adopting a three-section gate-type structure flue enters the flue of the fluidized bed boiler and sequentially exchanges heat with a superheater assembly, an economizer and boiler feed water in the fluidized bed boiler; heat in quenched steel slag particles and high-temperature flue gas generated by quenching is fully utilized, steam and hot water of different grades are obtained, the utilization rate of the heat is high, the steam yield is large, the thermal stress for heating feed water is small, and the whole system runs stably.

Description

Technical Field

[0001] The utility model belongs to the technical field of energy conservation and environmental protection, and in particular relates to a technology for recycling waste heat from granulating steel slag and metals, thereby improving the comprehensive utilization rate of tailings. Background Art

[0002] Steel slag is a byproduct of the steelmaking process, produced to remove impurities from steel. It contains slagging agents such as lime, fluorite, and deoxidizers; mud and sand carried over from the metal; oxides formed by the oxidation of aluminum, silicon, and manganese from scrap steel; and iron ore, scale, and iron-containing sludge used as coolants or oxidants. Hot steel slag is rich in thermal energy and contains approximately 10% scrap steel, along with numerous beneficial chemical elements. Processed steel slag is often used for foundation backfill, road paving, cement raw materials, water purifiers, and steel slag fertilizer.

[0003] The purpose of slag treatment is to pulverize the slag as quickly as possible, separate the scrap metal from the slag, and reduce the free calcium oxide (f-CaO) in the slag, so as to recover as much metal as possible from the slag and improve the comprehensive utilization rate of the tailings.

[0004] During the slag treatment process, the structure of dicalcium silicate transforms from the unstable β-type to the stable γ-type, increasing its volume by 12%. The transformation temperature is generally between 630°C and 680°C. Free calcium oxide dissolves in water to form calcium hydroxide, which expands and pulverizes. This transformation process is related to the cooling rate, temperature, pressure, quantity, and impurities within the slag. Domestic slag treatment processes include drum quenching, hot stewing, hot pouring, wet air quenching, and dry air quenching. By comparison, air quenching offers higher efficiency, lower operating costs, and a more cost-effective price-performance ratio.

[0005] Slag air quenching technology bypasses the slag heating, crushing, and grinding steps, saving the significant costs associated with these processes. The air quenching process effectively eliminates free calcium oxide from the slag, significantly improving its quality and sales price. The specific gravity of steel in the hot liquid slag is much greater than that of the slag, causing the liquid steel to sink to the bottom of the tank. Air quenching technology uses a special granulation system within a sealed quenching chamber to disperse the upper slag into droplets. These droplets travel along a parabolic trajectory and free-fall to a slag collection tank. During this flight and while cooling in the cooling tank, the slag particles come into contact with air and / or atomized water vapor, effectively eliminating the free f-CaO and f-MgO in the slag.

[0006] The existing technology mainly uses waste heat recovery devices to convert the heat in the large amount of high-temperature flue gas generated during steel slag air quenching to steam. For example, CN111947116A discloses a system for recovering steel slag waste heat and steam based on combined air-water quenching. The system uses water-carrying quenching air as the power for steel slag granulation, air as the medium for recovering steel slag waste heat, a steel slag air quenching waste heat boiler with a water-cooled wall as the steel slag radiation heat recovery device, an economizer as the steel slag convection heat recovery device, a moving fluidized bed as the steel slag cooling and conveying device, and a heat accumulator as a load buffer device to implement combined air-water quenching to recover steel slag waste heat. This system that combines water-cooled walls and economizers to recover steel slag waste heat suffers from low steam production. Summary of the Invention

[0007] Purpose of the invention: In view of the above-mentioned existing problems and shortcomings, the purpose of this utility model is to provide a device for granulating, preheating and recovering steel slag.

[0008] Technical solution: In order to solve the above technical problems, the utility model adopts the following technical solution: a device for recovering waste heat from slag granulation, comprising a fluidized bed boiler and an air quenching granulation furnace, wherein the fluidized bed boiler comprises a drum assembly and a portal flue, wherein the portal flue has a rectangular channel cross-section and comprises a first vertical flue, a horizontal flue, and a second vertical flue that are connected in sequence;

[0009] The boiler drum assembly includes a boiler drum, an ascending pipe, and a downcomer. The boiler drum is located at the top of the first vertical flue. The ascending pipe adopts a membrane wall structure. The horizontal flue is composed of four sealed membrane wall ascending pipes. The downcomer is located outside the door-type flue. A high-temperature water inlet and a circulating steam inlet are provided in the middle of the boiler drum. A low-temperature steam outlet and a circulating water outlet are provided at the top and bottom of the boiler drum, respectively.

[0010] The air quenching granulation furnace is connected and arranged at the lower part of the first vertical flue, and adopts a cyclone separation structure, including an inverted conical air quenching chamber, a chute along the side wall of the air quenching chamber for tangentially feeding the steel slag into the air quenching chamber, an air chamber arranged at the bottom of the air quenching chamber, and a plurality of nozzles arranged on the air chamber. The cooling air blown by the nozzles can disperse and dissolve the liquid steel slag entering the air quenching chamber.

[0011] A superheater assembly is provided in the first vertical flue, an economizer and a boiler feed water unit are provided in the second vertical flue, and an exhaust port and a water supply port are provided at the bottom of the second vertical flue;

[0012] The water supply port is connected to the boiler feed water and economizer in sequence through pipes, and then connected to the high-temperature water inlet of the boiler drum; the circulating water outlet of the boiler drum is connected to the riser after passing through the downcomer, and the outlet of the riser is connected to the circulating steam inlet through a pipe; the low-temperature steam outlet is connected to the superheater assembly through a pipe, and the outlet of the superheater assembly collects qualified steam through a high-pressure header and supplies it to the steam turbine for power generation.

[0013] Preferably, the superheater assembly includes a high-temperature superheater and a low-temperature superheater arranged in sequence along the flue flow direction.

[0014] Preferably, a desuperheater is provided on the pipelines between the high-temperature superheater and the low-temperature superheater, and between the low-temperature superheater and the low-temperature steam outlet, respectively, and the desuperheater is located outside the portal flue.

[0015] Preferably, the downcomer is connected to each pipeline of the riser through a distributor, and the inlet of the riser is arranged at the bottom.

[0016] Preferably, the four walls of the first vertical flue are also provided with membrane wall risers.

[0017] Preferably, the height of the air quenching granulation furnace accounts for one third of the total height of the first vertical flue.

[0018] Preferably, an air vibration device for dust removal is provided in the flue.

[0019] Preferably, the nozzle is of hood type.

[0020] Beneficial effects: Compared with the existing technology, the utility model combines the air quenching granulation furnace with the fluidized bed boiler, and adopts a fluidized bed boiler with a three-stage door-type structure flue. The high-temperature flue gas generated during the air quenching process of the liquid steel slag in the fluidized bed boiler enters the flue of the fluidized bed boiler, and exchanges heat with the superheater components, economizer and boiler feed water in the fluidized bed boiler in turn, making full use of the heat in the quenched steel slag particles and the high-temperature flue gas generated by quenching to obtain different grades of steam and hot water. The heat utilization rate is high, the steam output is large, the thermal stress of the heated feed water is small, and the entire system runs smoothly. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural diagram of the steel slag granulation preheating and recovery device described in the present invention.

[0022] Among them, the first vertical flue 1, the horizontal flue 2, the second vertical flue 3, the boiler drum 4, the riser 5, the downcomer 6, the high-temperature water inlet 7, the circulating steam inlet 8, the low-temperature steam outlet 9, the circulating water outlet 10, the air quenching granulation furnace 11, the air quenching chamber 12, the chute 13, the wind chamber 14, the nozzle 15, the slag discharge port 16, the high-temperature superheater / 7, the low-temperature superheater 18, the economizer 19, the boiler feed water 20, the exhaust port 21, the water supply port 22, and the desuperheater 23. DETAILED DESCRIPTION

[0023] The present invention is further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0024] like Figure 1 As shown, the utility model is used for the slag granulation preheating and recovery device, including a fluidized bed boiler and an air quenching granulation furnace, the fluidized bed boiler includes a drum assembly and a door-type flue, the channel of the door-type flue is circular, including a first vertical flue, a horizontal flue and a second vertical flue connected in sequence;

[0025] The boiler drum assembly includes a boiler drum arranged at the top of the first vertical flue, a membrane wall riser forming the horizontal flue, and a downcomer located outside the door-type flue; a high-temperature water inlet and a circulating steam inlet are provided in the middle of the boiler drum, and a low-temperature steam outlet and a circulating water outlet are provided at the top and bottom of the boiler drum respectively;

[0026] The air quenching granulation furnace is connected to the lower part of the first vertical flue and adopts a cyclone separation structure, including an inverted conical air quenching chamber, a chute for tangentially feeding the material into the air quenching chamber along the pipe wall of the air quenching chamber, an air chamber arranged at the bottom of the air quenching chamber, and a plurality of wind cap-type nozzles arranged on the air chamber. The cooling wind blown out by the nozzle can disperse and dissolve the liquid steel slag entering the air quenching chamber; at the same time, the slag material falling into the bottom of the air quenching chamber can be fluidized, which is convenient for slag discharge.

[0027] The first vertical flue is provided with a superheater assembly including a low-temperature superheater and a high-temperature superheater. The second vertical flue is provided with an economizer and boiler feed water connected in sequence. The bottom of the second vertical flue is also provided with an exhaust port and a water supply port.

[0028] The water supply port is connected to the boiler feed water and economizer in sequence through pipes, and then connected to the high-temperature water inlet of the boiler drum; the circulating water outlet of the boiler drum is connected to the riser after passing through the downcomer, and the outlet of the riser is connected to the circulating steam inlet through a pipe; the low-temperature steam outlet is connected to the low-temperature superheater and the high-temperature superheater in sequence through pipes, and then extracted from the outlet of the high-temperature superheater, and qualified steam is collected through the high-pressure header and supplied to the steam turbine for power generation.

[0029] As a preferred embodiment, desuperheaters are installed on the pipes between the high-temperature superheater and the low-temperature superheater, and between the low-temperature superheater and the low-temperature steam outlet, respectively. Each desuperheater is located outside the portal flue. The desuperheaters can reduce the high-temperature gas to an acceptable range, preventing excessive heat accumulation, thereby ensuring normal operation of the equipment and extending its service life.

[0030] The downcomer is connected to the various pipes of the riser through a distributor, and the riser's inlet is located at the bottom. High-temperature water drawn from the boiler drum enters the bottom of the riser through the downcomer, flows evenly under the distributor (which may use a tube sheet structure), and is heated by the rising flue gas to form steam, which then returns to the boiler drum through the circulating steam inlet.

[0031] This utility model combines an air-quenching granulation furnace with a fluidized bed boiler. The high-temperature flue gas generated by the air-quenching process of liquid steel slag enters the flue of the fluidized bed boiler, where it sequentially exchanges heat with the boiler's heated walls (membrane walls). Water is first preheated by the granulated slag before entering the flue in the opposite direction of the flue gas flow. The water is gradually heated within the different heated walls before ultimately converting into qualified steam. This system enables continuous operation, effectively utilizing the heat from both the quenched steel slag particles and the high-temperature flue gas generated during quenching. This results in high heat utilization, high steam production, and minimal thermal stress on the feedwater. The entire system operates smoothly, with minimal equipment loss and a long service life.

[0032] The fluidized bed flue of this utility model is rectangular, reducing the difficulty of membrane wall manufacturing. Furthermore, the air-quenched granulation furnace utilizes a cyclone separation structure. The raw slag enters the granulation furnace tangentially, retaining the majority of the material inside the furnace, significantly reducing carryover of dust. Furthermore, the cyclone separation structure of the granulation furnace increases the flue gas flow rate, preventing dust from adhering to the boiler tube walls.

[0033] The above description is only a preferred embodiment of the present invention, and it is certainly not intended to limit the scope of rights of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and changes without departing from the principles of the present invention, and these improvements and changes are also considered to be within the scope of protection of the present invention.

Claims

1. A device for recovering waste heat from slag granulation, characterized by: It includes a fluidized bed boiler and an air quenching granulation furnace. The fluidized bed boiler includes a drum assembly and a door-type flue. The channel cross-section of the door-type flue is rectangular and includes a first vertical flue, a horizontal flue, and a second vertical flue that are connected in sequence. The boiler drum assembly includes a boiler drum, an ascending pipe, and a downcomer. The boiler drum is located at the top of the first vertical flue. The ascending pipe adopts a membrane wall structure. The horizontal flue is composed of four sealed membrane wall ascending pipes. The downcomer is located outside the door-type flue. A high-temperature water inlet and a circulating steam inlet are provided in the middle of the boiler drum. A low-temperature steam outlet and a circulating water outlet are provided at the top and bottom of the boiler drum, respectively. The air quenching granulation furnace is connected and arranged at the lower part of the first vertical flue, and adopts a cyclone separation structure, including an inverted conical air quenching chamber, a chute along the side wall of the air quenching chamber for tangentially feeding the steel slag into the air quenching chamber, an air chamber arranged at the bottom of the air quenching chamber, and a plurality of nozzles arranged on the air chamber. The cooling air blown by the nozzles can disperse and dissolve the liquid steel slag entering the air quenching chamber. A superheater assembly is provided in the first vertical flue, an economizer and a boiler feed water unit are provided in the second vertical flue, and an exhaust port and a water supply port are provided at the bottom of the second vertical flue; The water supply port is connected to the boiler feed water and economizer in sequence through pipes, and then connected to the high-temperature water inlet of the boiler drum; the circulating water outlet of the boiler drum is connected to the riser after passing through the downcomer, and the outlet of the riser is connected to the circulating steam inlet through a pipe; the low-temperature steam outlet is connected to the superheater assembly through a pipe, and the outlet of the superheater assembly collects qualified steam through a high-pressure header and supplies it to the steam turbine for power generation.

2. The device for recovering waste heat from slag granulation according to claim 1, characterized in that: The superheater assembly includes a high-temperature superheater and a low-temperature superheater which are sequentially arranged along the flue flow direction.

3. The device for recovering waste heat from slag granulation according to claim 2, characterized in that: Desuperheaters are respectively provided on the pipelines between the high-temperature superheater and the low-temperature superheater and between the low-temperature superheater and the low-temperature steam outlet, and the desuperheaters are located outside the door-type flue.

4. The device for recovering waste heat from slag granulation according to claim 1, characterized in that: The downcomer is connected to each pipeline of the riser through a distributor, and the inlet of the riser is arranged at the bottom.

5. The device for recovering waste heat from slag granulation according to claim 1, characterized in that: The four walls of the first vertical flue are also provided with membrane wall risers.

6. The device for recovering waste heat from slag granulation according to claim 1, characterized in that: The height of the air quenching granulation furnace accounts for one third of the total height of the first vertical flue.

7. The device for recovering waste heat from slag granulation according to claim 1, characterized in that: An air vibration device for dust removal is provided in the flue.

8. The device for recovering waste heat from slag granulation according to claim 1, characterized in that: The nozzle is of hood type.

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