Steel slag granulation waste heat recovery system

Abstract

The invention discloses a steel slag granulation waste heat recovery system which is characterized in that an air quenching granulation furnace is combined with a fluidized bed boiler, high-temperature flue gas generated in the air quenching process of liquid steel slag enters a flue of the fluidized bed boiler and sequentially exchanges heat with a heated wall in the fluidized bed boiler, and water is preheated for the first time through granulation slag; and then the flue gas enters the flue along the direction opposite to the flowing direction of the flue gas, is heated section by section in different heated walls, and is finally converted into qualified steam. Continuous operation can be achieved, heat in quenched steel slag particles and heat in high-temperature flue gas generated by quenching are reasonably utilized, the utilization rate of the heat is high, the steam yield is large, heat stress for heating feed water is small, and the whole system is stable in operation, small in equipment loss and long in service life.

Description

Technical Field

[0001] The invention belongs to the technical field of energy conservation and environmental protection, and in particular relates to a technology for recycling waste heat from steel slag granulation and metal recovery, so as to improve the comprehensive utilization rate of tailings. Background Art

[0002] Steel slag is a byproduct of the steelmaking process to remove impurities from steel. It includes slag-making agents such as lime, fluorite, deoxidizers, etc.; mud and sand brought in by metal materials; oxides formed by oxidation of aluminum, silicon, manganese, etc. in scrap steel; iron ore, iron oxide, iron-containing sludge, etc. used as coolants or oxidants. The hot steel slag has rich thermal energy and contains about 10% scrap steel and a large number of beneficial chemical elements. The processed steel slag is often used as foundation backfill, road paving, cement raw material, water purifier and steel slag fertilizer.

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

[0004] During the slag treatment process, the structure of dicalcium silicate changes from unstable β type to stable γ type, and the volume increases by 12%. The transformation temperature is generally 630℃~680℃. Free calcium oxide is dissolved into calcium hydroxide in water, and the volume expands and pulverizes. Their transformation process is related to the cooling rate, temperature, pressure, quantity and impurities in the slag. Domestic slag treatment processes include drum method, hot stewing method, hot pouring method, wet air quenching, dry air quenching and other processes. In comparison, the air quenching process has higher processing efficiency, lower operating cost and higher cost performance.

[0005] The slag air quenching technology directly avoids the process of hot stuffiness, crushing and grinding of slag, saving the huge cost of hot stuffiness, crushing and grinding. The air quenching process better eliminates the free calcium oxide in the slag, greatly improving the quality and sales price of the slag. The specific gravity of steel in the high-temperature liquid slag is much greater than that of the slag. The liquid steel sinks to the bottom of the tank. The air quenching technology uses a special granulation system to blow the upper slag liquid into droplets in a closed air quenching chamber, fly along a parabola and fall freely to the slag collection pool. The slag particles are fully in contact with air and / or atomized water vapor during the flight and during the cooling process in the cooling pool, and the free f-CaO and f-Mg0 in the slag are fully eliminated.

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

[0007] Purpose of the invention: In view of the above existing problems and shortcomings, the purpose of the present invention is to provide a steel slag granulation waste heat recovery system.

[0008] Technical solution: In order to solve the above technical problems, the present invention adopts the following technical solution: a steel slag granulation waste heat recovery system, including a fluidized bed boiler, an air quenching granulation furnace and a slag cooler, The fluidized bed boiler comprises a drum assembly and a flue, wherein a superheater assembly, a drum assembly, an economizer and boiler feed water are sequentially arranged in the flue along the direction of flue gas flow; The wind quenching granulation furnace is arranged at the head of the flue, and the flue gas generated by the wind quenching granulation furnace flows through the flue and is discharged; The slag cooler is located below the air quenching granulation furnace and receives the slag discharged from the air quenching granulation furnace; the slag cooler uses desalted water as a heat exchange medium, and the slag cooler is provided with a cooling water outlet, which is connected to the boiler feed water, economizer, drum assembly and superheater assembly in sequence through a pipeline, and discharges steam through the superheater assembly to supply external gas-using equipment.

[0009] Preferably, the drum assembly comprises a drum, a downcomer and an upcomer which are cyclically connected; the upcomer is located in the flue or directly serves as a part of the flue structure, and the downcomer is arranged outside the flue; The middle part of the drum is provided with a high-temperature water inlet and a circulating steam inlet, the top of the drum is provided with a low-temperature steam outlet, and the bottom of the drum is provided with a circulating water outlet; The circulating water outlet is connected to the downcomer, the upcomer and the circulating steam inlet in sequence; the low-temperature steam outlet is connected to the inlet of the superheater assembly; and the high-temperature water inlet is connected to the outlet of the economizer.

[0010] Preferably, the flue is a door-type flue, comprising a first vertical flue, a horizontal flue and a second vertical flue which are connected in sequence; the superheater assembly is arranged in the first vertical flue, the economizer and boiler feed water are arranged in the second vertical flue, and an exhaust outlet is also provided at the bottom of the second vertical flue.

[0011] Preferably, the air quenching granulation furnace includes an air quenching chamber connected to the flue, a chute arranged on the side of the air quenching chamber, and a wind chamber arranged at the bottom of the air quenching chamber. A nozzle is also provided on the upper part of the wind chamber, and the cooling wind blown out by the nozzle can disperse and dissolve the liquid steel slag entering the air quenching chamber.

[0012] Preferably, the bottom of the wind quenching chamber is connected to the wind chamber through an air distribution plate, the wind chamber is connected to a blower, and the air distribution plate is provided with evenly distributed wind hoods.

[0013] Preferably, a slag discharge port is also provided on the air distribution plate.

[0014] Preferably, the exhaust port at the tail end of the flue is connected to the induced draft fan and the bag filter in sequence through a pipeline, and the exhaust port of the bag filter is connected to the air inlet of the air quenching granulation furnace through a blower.

[0015] Preferably, the superheater assembly comprises a high-temperature superheater and a low-temperature superheater arranged in sequence along the flue gas flow direction, and a desuperheater is respectively provided on the pipeline between the high-temperature superheater and the low-temperature superheater and between the low-temperature superheater and the low-temperature steam outlet, and the desuperheater is located outside the portal flue.

[0016] Preferably, the riser adopts a membrane wall structure.

[0017] Preferably, the desuperheater is a water spray type desuperheater; and an air oscillation device for dust removal is provided in the flue.

[0018] Beneficial effects: Compared with the prior art, the present invention combines the air quenching granulation furnace with the fluidized bed boiler, and adopts a fluidized bed boiler with a three-stage door-type flue structure. The high-temperature flue gas generated by the liquid steel slag during the air quenching process 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 steam and hot water of different grades; at the same time, the slag cooler is used to further recycle the heat in the air quenching granulated slag. In addition to the heat dissipation of the equipment, there is almost no heat loss in the entire system. The present invention has a high heat utilization rate, a large steam output, and a small thermal stress of the heated feed water. The entire system runs smoothly, can achieve continuous operation, has low equipment loss, and a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a schematic structural diagram of the steel slag granulation waste heat recovery system of the present invention.

[0020] Among them, the fluidized bed boiler 100, the drum assembly 110, the drum 111, the riser 112, the downcomer 113, the high-temperature water inlet 114, the circulating steam inlet 115, the low-temperature steam outlet 116, the circulating water outlet 117, the portal flue 120, the first vertical flue 121, the horizontal flue 122, the second vertical flue 123, the high-temperature superheater 124, the low-temperature superheater 125, the economizer 126, the boiler feed water 127, the desuperheater 128, the air quenching granulation furnace 200, the air quenching chamber 210, the chute 220, the wind chamber 230, the nozzle 240, the slag discharge port 250, the slag cooler 300, the bag dust collector 400, the induced draft fan 500, the blower 600, and the desalted water tank 700. DETAILED DESCRIPTION

[0021] The present invention is further explained below in conjunction with 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, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0022] like Figure 1 As shown, the dry air-quenching granulated steel slag waste heat recovery system of the present invention includes main equipments including: a fluidized bed boiler 100, an air-quenching granulation furnace 200 and a slag cooler 300.

[0023] The door-type flue 120 of the fluidized bed boiler 100 is in the shape of a "door", and includes two sections of vertical flues and one section of horizontal flue 122, namely the first vertical flue 121, the horizontal flue 122 and the second vertical flue 123. The air quenching granulation furnace 200 is located at the lower part of the first vertical flue 121, and its air quenching chamber 210 serves as the head of the flue, and discharges high-temperature flue gas upward along the flue, passing through the horizontal flue 122 and the second vertical flue 123 in sequence. Along the direction of flue gas flow, a high-temperature superheater 124, a low-temperature superheater 125, a drum assembly 110, an economizer 126 and a boiler feed water 127 are sequentially arranged in the flue of the fluidized bed boiler 100. Among them, the drum assembly 110 is located in the horizontal flue 122, the superheater assembly is located in the first vertical flue 121, and the economizer 126 and the boiler feed water 127 are located in the second vertical flue 123.

[0024] The drum assembly 110 includes a drum 111 disposed at the top of a first vertical flue 121, an ascending pipe 112 disposed in a horizontal flue 122, and a descending pipe 113 disposed outside the door-type flue 120; a high-temperature water inlet 114 and a circulating steam inlet 115 are disposed in the middle of the drum 111, a low-temperature steam outlet 116 is disposed at the top of the drum 111, and a circulating water outlet 117 is disposed at the bottom of the drum 111; the ascending pipe 112 is disposed in the flue, the descending pipe 113 is disposed outside the flue, and the drum 111 is located at the upper end of the flue; The boiler drum 111 is provided with a low-temperature steam outlet 116 at the top, a circulating steam inlet 115 and a high-temperature water inlet 114 at the middle, and a circulating water outlet 117 at the bottom; the low-temperature steam outlet 116 is connected to the low-temperature superheater 125, and the high-temperature water inlet 114 is connected to the economizer 126; the circulating steam inlet 115 and the circulating water outlet 117 are respectively connected to the membrane wall riser 112 and the downcomer 113, forming a circulation loop of steam and water.

[0025] The superheater assembly includes a high-temperature superheater 124 and a low-temperature superheater 125. The low-temperature superheater 125 is connected to the low-temperature steam outlet 116 of the drum 111. The high-temperature superheater 124 collects qualified steam through a high-temperature header and supplies it to the steam turbine for power generation. A desuperheater 128 is provided in the steam pipeline between the high-temperature superheater 124 and the low-temperature superheater 125 and between the drum 111 and the low-temperature superheater 125. The low-temperature superheater 125 and the high-temperature superheater 124 are arranged inside the flue in the opposite direction of the flue gas flow, and the high-temperature header and the desuperheater 128 are arranged outside the flue and connected to the adjacent heating equipment pipelines.

[0026] The slag cooler 300 uses water as a heat exchange medium. The water inlet end of the slag cooler 300 is connected to a deoxygenated water tank, and the water outlet end is connected to the boiler feed water 127, economizer 126, drum assembly 110 and superheater assembly in sequence through pipelines, and finally the main steam is discharged from the high pressure header to supply external steam-using equipment.

[0027] The air quenching granulation furnace 200 is a dry air quenching granulation furnace 200, including a vertical air quenching chamber 210, a chute 220 is provided on the side of the air quenching chamber 210 as a slag liquid inlet, and a wind chamber 230 is provided at the bottom; a plurality of vertical wind caps are provided on the air distribution plate, and the wind caps are made of heat-resistant steel and are mushroom-shaped. The high-pressure wind in the wind chamber 230 is blocked by the top of the wind cap during the process of entering the air quenching chamber 210 upward and changes direction, and becomes blown from top to bottom. This wind blowing from top to bottom can make the slag material falling on the air distribution plate present a fluidized state, avoiding the accumulation of materials. Two slag discharge ports are also provided on the air distribution plate. When the slag discharge ports are opened, the slag material in a fluidized state can be discharged through the slag discharge ports. A nozzle 240 is provided at the upper part of the wind chamber 230. The nozzle 240 blows out cooling air to break up and dissolve the liquid slag entering the wind quenching chamber 210, and performs heat exchange to form high-temperature flue gas that flows upward along the first vertical flue 121, achieving an effect similar to boiler fuel combustion.

[0028] The liquid steel slag from the steelmaking furnace is collected by a slag pot and then transported by a tank truck to the dry air quenching granulation furnace 200 in the slag treatment workshop. At this time, the temperature of the liquid steel slag is about 1450°C. The pot is placed in a sitting position, and then the slag pot is flipped by a tilting device. The liquid steel slag flows into the air quenching chamber 210 through the chute 220. Under the action of the upward cooling wind, the liquid steel slag entering the air quenching chamber 210 is broken up and digested, and most of the heat is released under the action of the cooling wind. Finally, under the action of gravity, it falls back to the bottom of the air quenching chamber 210 along the wall. At the same time, the high-temperature flue gas formed by heat exchange flows upward along the first vertical flue 121, which has an effect similar to the combustion of boiler fuel.

[0029] In order to control the degree of slag digestion, pressure and temperature sensors are set at the hood position. When the amount of slag accumulates to a certain amount and the temperature of the slag reaches a certain value, the slag discharge port is opened for slag discharge. When the slag temperature is around 850°C during slag discharge, a good heat utilization efficiency can be achieved. The slag cooler 300 is further used to recover the sensible heat of the slag particles, so that the slag particles are discharged at a temperature of 60~80°C. At the same time, the circulating water as the working fluid is used as the exchange medium to play a preheating role, achieving the purpose of heat recovery for the entire system.

[0030] Since the temperature of the flue gas decreases in the direction of flow, the low-temperature superheater 125 has a greater heat transfer power than the riser 112 of the drum 111, and can heat the low-temperature steam from the drum 111 to make it superheated steam, reduce exhaust loss, and improve the thermal efficiency of the boiler. The desuperheater 128 can reduce the high-temperature gas to an acceptable range to prevent excessive heat accumulation to ensure the normal operation of the equipment and extend its service life. The high-temperature superheater 124 is located at the front end of the flue and has the strongest heat transfer power. It further heats the high-temperature steam and collects the superheated steam generated from the superheater through the high-pressure header for redistribution and reheating. The low-temperature superheater 125, the desuperheater 128, the high-temperature superheater 124, and the high-pressure header cooperate to maximize the utilization of the boiler thermal effect, produce a large output of qualified steam, and meet the needs of steam power generation equipment.

[0031] After the flue gas enters the second vertical flue 123, although the temperature has dropped, there is still a relatively high amount of heat. The economizer 126 can be used to absorb the heat of the low-temperature flue gas and reduce the exhaust temperature. At the same time, the preheated boiler feed water 127 is further heated to increase the feed water temperature, reduce the wall temperature difference after entering the boiler drum 111, and extend the service life of the boiler drum 111 assembly 110.

[0032] A fly ash collection port is provided at the bottom of the second vertical flue 123 for collecting fly ash deposited in the flue, and an exhaust port is provided on the upper portion of the fly ash collection port, and the exhaust port is connected to the induced draft fan 500, the bag filter, the blower 600 and the air inlet of the dry air quenching granulation furnace 200 in sequence through pipelines, so that the carrier gas can be recycled, thereby reducing waste gas pollution and the cost of gas raw materials.

[0033] In order to prevent the powder ash from sticking to the boiler tube wall, an air vibration device, such as an air cannon, is also provided in the portal flue 120 to vibrate on time.

[0034] The waste heat recovery system of the present invention can generate a large amount of steam of different grades, achieving extremely high heat utilization. The efficiency of the boiler can reach 400 kg steam / ton of slag, with an efficiency of about 85%. The existing conventional steel slag boiler is about 150 kg steam / ton of slag.

[0035] In the present invention, the slag discharged from the slag cooler 300 after cooling is about 60-80°C, the boiler feed water 127 removes the anions and cations in the water, and the normal temperature water enters the economizer 126 at about 120°C, and 20% steam is generated in the economizer 126, and enters the drum 111 with water and gas. The two-stage economizer 126 can increase the heat exchange area and realize the full utilization of steam and water heat.

[0036] The main function of the drum 111 in the present invention is to be used as a gas-liquid separator, the desuperheater 128 controls the temperature, and the water spray directly cools down. In addition to the heat dissipation of the equipment, all other heat is utilized, and there is almost no heat loss.

[0037] The height of the granulating furnace of the present invention accounts for one third of the total height of the first vertical flue 121 on the left; air can be used as cooling wind, and there is no requirement for the type of air.

[0038] The present invention combines the air quenching granulation furnace 200 with the fluidized bed boiler 100. The high-temperature flue gas generated by the liquid steel slag during the air quenching process enters the flue of the fluidized bed boiler 100 and exchanges heat with the heated walls in the fluidized bed boiler 100 in turn. The water is first preheated by the granulated slag, and then enters the flue in the opposite direction of the flue gas flow, and is gradually heated in different heated walls, and finally converted into qualified steam. Continuous operation can be achieved, and the heat in the quenched steel slag particles and the high-temperature flue gas generated by the quenching are reasonably utilized. The heat utilization rate is high, the steam output is large, and the thermal stress of the water supply is small. The whole system runs smoothly, the equipment loss is small, and the service life is long.

[0039] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A steel slag granulation waste heat recovery system, characterized in that: It includes a fluidized bed boiler (100), an air quenching granulation furnace (200) and a slag cooler (300). The fluidized bed boiler (100) comprises a drum assembly (110) and a flue, wherein a superheater assembly, a drum assembly (110), an economizer (126) and boiler feed water (127) are sequentially arranged in the flue along the direction of flue gas flow; The wind quenching granulation furnace (200) is arranged at the head of the flue, and the flue gas generated by the wind quenching granulation furnace (200) flows through the flue and is discharged; The slag cooler (300) is located below the air quenching granulation furnace (200) and receives the slag discharge from the air quenching granulation furnace (200); the slag cooler (300) uses desalted water as a heat exchange medium, and the slag cooler (300) is provided with a cooling water outlet, which is connected to the boiler feed water (127), the economizer (126), the drum assembly (110) and the superheater assembly in sequence through a pipeline, and discharges steam through the superheater assembly to supply external gas-using equipment.

2. The steel slag granulation waste heat recovery system according to claim 1, characterized in that: The boiler drum assembly (110) comprises a boiler drum (111), a downpipe (113), and an uppipe (112) which are cyclically connected; the uppipe (112) is located in the flue or directly serves as a part of the flue structure, and the downpipe (113) is arranged outside the flue; A high-temperature water inlet (114) and a circulating steam inlet (115) are provided in the middle of the boiler drum (111), a low-temperature steam outlet (116) is provided at the top of the boiler drum (111), and a circulating water outlet (117) is provided at the bottom of the boiler drum (111); The circulating water outlet (117) is connected in sequence to the downcomer (113), the upcomer (112) and the circulating steam inlet (115); the low-temperature steam outlet (116) is connected to the inlet of the superheater assembly; and the high-temperature water inlet (114) is connected to the outlet of the economizer (126).

3. The steel slag granulation waste heat recovery system according to claim 1, characterized in that: The flue is a door-type flue (120), comprising a first vertical flue (121), a horizontal flue (122), and a second vertical flue (123) which are connected in sequence; the superheater assembly is arranged in the first vertical flue (121), the economizer (126) and the boiler feed water (127) are arranged in the second vertical flue (123), and an exhaust port is also arranged at the bottom of the second vertical flue (123).

4. The steel slag granulation waste heat recovery system according to claim 3, characterized in that: The wind quenching granulation furnace (200) comprises a wind quenching chamber (210) connected to a flue, a chute (220) arranged on the side of the wind quenching chamber (210), and a wind chamber (230) arranged at the bottom of the wind quenching chamber (210). A nozzle (240) is further arranged at the top of the wind chamber (230). The cooling wind blown out by the nozzle (240) can disperse and dissolve the liquid steel slag entering the wind quenching chamber (210).

5. The steel slag granulation waste heat recovery system according to claim 4, characterized in that: The bottom of the wind quenching chamber (210) is connected to the wind chamber (230) via an air distribution plate, the wind chamber (230) is connected to a blower (600), and evenly distributed wind caps are arranged on the air distribution plate.

6. The steel slag granulation waste heat recovery system according to claim 5, characterized in that: The air distribution plate is also provided with a slag discharge port.

7. The steel slag granulation waste heat recovery system according to claim 1, characterized in that: The exhaust port at the tail end of the flue is connected to the induced draft fan (500) and the bag filter (400) in sequence through a pipeline, and the exhaust port of the bag filter (400) is connected to the air inlet of the air quenching granulation furnace (200) through a blower (600).

8. The steel slag granulation waste heat recovery system according to claim 1, characterized in that: The superheater assembly comprises a high-temperature superheater (124) and a low-temperature superheater (125) arranged in sequence along the flue gas flow direction; a desuperheater (128) is provided on the pipeline between the high-temperature superheater (124) and the low-temperature superheater (125) and between the low-temperature superheater (125) and the low-temperature steam outlet (116); and the desuperheater (128) is located outside the door-type flue (120).

9. The steel slag granulation waste heat recovery system according to claim 2, characterized in that: The riser (112) adopts a membrane wall structure.

10. The steel slag granulation waste heat recovery system according to claim 8, characterized in that: The desuperheater (128) is a water spray type desuperheater; and an air oscillation device for dust removal is provided in the flue.

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