Steel slag double-roll on-line treatment method and steel slag double-roll on-line treatment system

Abstract

The present invention relates to a double-roller online processing method and a double-roller online processing system for steel slag, which comprises the following steps: S1, high-temperature steel slag discharged from a slag outlet of an electric furnace enters a double-roller pretreatment device, carbon powder and bauxite are added into the double-roller pretreatment device to perform high-temperature reduction modification on the high-temperature steel slag, and waste heat is recovered at the same time; S2, the steel slag after waste heat recovery by extrusion enters a crushing device for stirring, crushing and waste heat recovery; S3, the crushed steel slag discharged from the crushing device enters a horizontal vibration digestion device, CO2 and H2O are sprayed into the horizontal vibration digestion device to thermally stew and digest CaO in the steel slag; S4, the steel slag after thermal stewing and digestion is transported to a slag storage chamber, and the steel slag after aging treatment is transported to a set position for secondary treatment; S5, the waste gas discharged from the horizontal vibration digestion device enters a waste heat boiler for heat exchange cooling, and the dust removal and filtration system removes dust from the waste heat boiler so that it is mixed with steam for recycling.

Description

Technical Field

[0001] The present invention relates to the technical field of steel metallurgy, and in particular to a double-roller online processing method and a double-roller online processing system for steel slag. Background Art

[0002] Currently, the comprehensive utilization of steel slag, a smelting waste product discharged from the steelmaking industry, has become a major challenge for steel mills. Due to the huge amount of slag produced and the lack of effective comprehensive utilization methods, the comprehensive utilization rate of steel slag has been low. Currently, it is mainly used as road material, backfill material, and raw materials for cement and concrete.

[0003] Steel slag is also a high-quality waste heat resource. The temperature of liquid steel slag is 1450-1650℃, the specific heat capacity is 1.2kJ / (kg·℃), and the thermal enthalpy value can reach 2000MJ / t, which is equivalent to 61kg of standard coal.

[0004] In essence, steel slag is a resource that can be recycled. However, in large-scale applications, steel slag suffers from poor volume stability, low gelling activity, and large chemical fluctuations, which reduce its utilization rate and efficiency. Steel slag is mainly composed of calcium, magnesium, iron, silicon, and small amounts of oxides of aluminum, sodium, and manganese. The chemical composition of converter and electric furnace steel slag is shown in Tables 1 and 2:

[0005] Table 1 Chemical composition of converter slag

[0006]

[0007] Table 2 Chemical composition of electric furnace slag

[0008]

[0009] Due to varying steelmaking processes and requirements, the chemical composition of steel slag fluctuates somewhat, but it primarily consists of oxides such as CaO, SiO2, Fe2O3, FeO, Al2O3, MgO, MnO, and P2O5. CaO is the primary oxide in steel slag, typically comprising 40% to 60%, and serves primarily as a calcium source. The f-CaO (free calcium oxide) and f-MgO (free magnesium oxide) contained in steel slag expand upon hydration, a significant factor affecting the stability of steel slag. Hydration of f-CaO in steel slag produces Ca(OH)2, increasing the volume of the slag by 1.98 times, while hydration of f-MgO in steel slag produces Mg(OH)2, increasing the volume of the slag by 2.48 times. Therefore, the use of steel slag in concrete has significant limitations and is not suitable for excessive slag content. Excessive slag content can easily cause concrete cracking, leading to structural damage and posing a significant safety hazard.

[0010] The main reasons why steel slag is difficult to promote and apply on a large scale are: (1) The excessive amount of lime added during steelmaking causes the steel slag to contain a large amount of free calcium oxide, which is easy to expand and cause damage when used as building materials; (2) Steel slag contains a certain amount of hydraulic cementing minerals such as tricalcium silicate and dicalcium silicate, but the content is small and the activity is poor, which makes it difficult to meet the technical requirements of the cement and concrete industries for auxiliary cementing materials; (3) Steel slag contains a large amount of iron minerals such as dicalcium ferrite and RO phase, which leads to high power consumption when grinding steel slag to prepare steel slag powder. Therefore, improving the volume stability and hydraulic cementing properties of steel slag is the key to achieving large-scale application of steel slag in road engineering, backfill engineering and cement and concrete industries.

[0011] Therefore, slag treatment should have four goals:

[0012] 1) Reduce the free CaO content in steel slag to below 1% and improve the stability of steel slag;

[0013] 2) Recover metallic iron from the slag and reduce RO phase oxides in the slag;

[0014] 3) Under high temperature conditions, it reacts with steel slag to produce more hydraulic cementitious minerals such as tricalcium silicate, dicalcium silicate and tricalcium aluminate;

[0015] 4) Recover waste heat from steel slag.

[0016] Currently used slag stabilization processes include hot pouring, air quenching, drum method, atmospheric pressure pool hot stuffing, and roller crushing-waste heat hot stuffing. The hot pouring method requires a large footprint, has a long treatment cycle, produces large amounts of steam and generates unorganized emissions, resulting in a high level of free calcium oxide (CaO) in the treated slag. The air quenching method can only process liquid molten slag with good fluidity. For converter slag, the high viscosity of the liquid slag makes it difficult for the air quenching method to achieve a slag treatment rate exceeding 50%. The drum method can also only process slag with good fluidity, causing significant wear and tear on the equipment. The atmospheric pressure pool hot stuffing method requires less space and can process any liquid or solid slag. The treated slag has a low free calcium oxide content, but the treatment cycle requires 24 hours. While the slag roller crushing-waste heat hot stuffing method can quickly eliminate free calcium oxide in the slag, it cannot effectively improve the hydraulic cementitious properties of the slag.

[0017] The main reason for the low hydraulic gelling property of steel slag is that the content of SiO2, Al2O3 and CaO in the steel slag produced after steelmaking is low, making it difficult to generate more hydraulic gelling minerals such as tricalcium silicate, dicalcium silicate and tricalcium aluminate. Therefore, to improve the hydraulic gelling property of steel slag, more hydraulic gelling minerals such as tricalcium silicate, dicalcium silicate and tricalcium aluminate can be generated with steel slag under high temperature.

[0018] Regardless of whether it is waste heat recovery, hot stewing pulverization or roller crushing, the steel slag treatment method basically belongs to the category of physical treatment methods of "cooling - crushing - magnetic separation". Although it can achieve the purpose of recovering the waste heat of steel slag, recovering the metal in the slag and further utilizing the tailings, there are still problems such as insufficient utilization of high-temperature sensible heat, low recovery of iron oxides in the steel slag, and low proportion of gelling phase.

[0019] The prior art provides a method for processing hot molten slag and a waste heat utilization device. The roller crusher consists of a closed, insulated structure with a built-in roller press. Cooling water in embedded water channels continuously exchanges heat with heat sources ranging from low to high temperatures through a unit composed of different roller presses. The water does not come into direct contact with the slag, resulting in clean steam that does not corrode the pipes. Roller crushing prevents the formation of aggregate on the roller surface. This technology has the following problems:

[0020] 1) Steel slag easily sticks to the cooling roller and is not easy to fall off;

[0021] 2) The slag treatment process is ineffective, hindering its secondary use. This is primarily due to: failure to reduce free CaO in the slag, resulting in poor slag stability; failure to reduce FeO in the slag to recover metallic iron; and failure to increase the amount of gelling minerals in the slag.

[0022] There is also a method and device in the prior art that uses water and carbon dioxide to achieve slag quenching and waste heat recovery. Carbon dioxide and water vapor are mixed; the mixed gas is sprayed into the fluidized bed heat exchanger through the injection system and enters the gas circulation pipeline through the waste heat boiler; part of the gas returns to the gas injection system, and the rest is passed into the air distribution plate; the molten metallurgical slag is introduced into the fluidized bed heat exchanger for gas quenching, and the generated slag particles are suspended under the action of the air flow; the high-temperature gas enters the waste heat boiler for heat exchange, forming low-temperature gas that enters the gas circulation pipeline; when the slag particles are below 800°C, an exothermic reaction occurs; when the temperature of the high-temperature gas is 450±5°C, CO2 is added; when the material temperature is below 150°C, the gas injection system is turned off; the device includes a slag chute, a fluidized bed heat exchanger and a gas injection system. This technology has the following problems:

[0023] 1) The treatment process consumes too much CO2 and H2O steam, which also require additional heat sources for heating, resulting in high energy consumption;

[0024] 2) The processed steel slag is inconvenient to collect and clean.

[0025] The existing technology also has a comprehensive treatment system for roller crushing of steel slag with pressurized self-decomposition of waste heat and waste heat recovery and utilization, in which the molten steel slag is poured from the slag pot into the roller crushing treatment device; the air supply device blows room temperature air into the roller crushing treatment device to cool the molten steel slag; the roller crushing device crushes the large crusted steel slag and simultaneously turns the molten steel slag at the bottom to the surface; the air cooling and crushing are repeated until the molten steel slag is broken into lump steel slag; the hot air generated after heat exchange enters the waste heat recovery and utilization device for power generation or heating; the lump steel slag is sent to the waste heat pressurized self-decomposition treatment device through the chute to stabilize the steel slag. This technology has the following problems:

[0026] 1) Steel slag roller crushing - waste heat pressure heating method can quickly eliminate free calcium oxide in steel slag, but it cannot effectively improve the hydraulic gelling property of steel slag;

[0027] 2) The efficiency of steel slag waste heat recovery in this technology is relatively low, mainly because air is first used to exchange heat with steel slag, and then the air is used to exchange heat with water to form steam. The number of heat exchanges is large and the energy loss is high.

[0028] Therefore, the inventors, relying on their many years of experience and practice in related industries, have proposed a double-roller online processing method and a double-roller online processing system for steel slag to overcome the defects of the prior art. Summary of the Invention

[0029] The purpose of the present invention is to provide a double-roller online processing method and a double-roller online processing system for steel slag, which can efficiently recover the sensible heat of steel slag and the iron in the slag; eliminate free calcium oxide in the steel slag to improve the stability of the steel slag, meet the subsequent use requirements of the steel slag as a cement admixture, and improve the recovery rate of the steel slag; increase the minerals such as tricalcium silicate, dicalcium silicate, and tricalcium aluminate in the steel slag to improve the hydraulic gelling properties of the steel slag, meet the subsequent use requirements of the steel slag as a cement admixture, and improve the recovery rate of the steel slag.

[0030] The object of the present invention is achieved by providing a double-roller online slag processing method, comprising the following steps:

[0031] S1. High-temperature slag discharged from the slag outlet of the electric furnace enters a double-roll pretreatment device, into which carbon powder and bauxite are added to perform high-temperature reduction modification on the high-temperature slag and simultaneously recover waste heat. The double-roll pretreatment device is connected to a waste heat boiler, which recovers waste heat from the high-temperature slag.

[0032] S2, the steel slag after being squeezed and heat recovered by the double-roll pre-treatment device enters the crushing device for stirring, crushing and heat recovery;

[0033] S3. The crushed slag discharged from the crushing device enters the horizontal vibration digestion device, and the CO2 and H2O injected into the horizontal vibration digestion device are used to heat and digest the CaO in the slag;

[0034] S4, the steel slag after hot stewing and digestion is transported to the slag storage chamber, and the steel slag is aged for a set time. The aged steel slag is then transferred to a set location for secondary treatment;

[0035] S5. The exhaust gas discharged from the horizontal vibration digestion device enters the waste heat boiler for heat exchange cooling. The dust removal and filtration system removes dust from the exhaust gas from the waste heat boiler so that it is mixed with steam for recycling.

[0036] In a preferred embodiment of the present invention, in step S1, at the inlet of the double-roll pretreatment device, carbon powder for reduction modification and bauxite for steel slag modifier are sprayed synchronously with the high-temperature steel slag, the injection amount of carbon powder is less than or equal to 5% of the amount of high-temperature steel slag, and the injection amount of bauxite is less than or equal to 5% of the amount of high-temperature steel slag. The carbon powder reduces the high-temperature steel slag, and the bauxite modifies the high-temperature steel slag.

[0037] In a preferred embodiment of the present invention, in step S1, the high-temperature steel slag, carbon powder and bauxite flowing into the double-roll pretreatment device first pass through at least one group of double-roll structures provided in the double-roll pretreatment device, wherein a first heat exchange medium channel is provided in the double-roll structure, and the double-roll structure performs extrusion cooling and heat exchange on the high-temperature steel slag.

[0038] In a preferred embodiment of the present invention, in step S2, the crushing device includes a drum crusher, and the steel slag cooled, heat-exchanged and squeezed and crushed by the double-roller structure flows downward to the drum crusher below the double-roller structure. A second heat exchange medium channel is provided in the drum crusher, and the drum crusher cools and rotationally crushes the steel slag.

[0039] In a preferred embodiment of the present invention, in step S2, the steel slag is struck by the drum crusher and flies toward an impact crushing bed located on one side of the drum crusher. A third heat exchange medium channel is provided in the impact crushing bed, and the impact crushing bed cools and impact-crushes the steel slag.

[0040] In a preferred embodiment of the present invention, in step S1, the twin-roll pretreatment device includes a heat exchange device, in which a heat exchange medium is provided to recover waste heat from the high-temperature steel slag, and the heat exchange medium includes a steam-water saturate or liquid metal.

[0041] In a preferred embodiment of the present invention, in step S3, the horizontal vibration digestion device performs a slow forward and fast return motion to drive the slag forward.

[0042] In a preferred embodiment of the present invention, in step S5, the exhaust gas discharged from the horizontal vibration digestion device is drawn into the combustion sedimentation chamber, the slag particles carried in the exhaust gas are further settled in the combustion sedimentation chamber, and the CO gas in the exhaust gas undergoes secondary combustion with the mixed air in the combustion sedimentation chamber to release heat. The flue gas after sedimentation and secondary combustion enters the waste heat boiler for heat exchange cooling, and the generated steam enters the steam drum and heat accumulator for storage.

[0043] The object of the present invention can also be achieved by providing a steel slag twin-roller online processing system for use in the aforementioned steel slag twin-roller online processing method; the steel slag twin-roller online processing system comprises:

[0044] A twin-roll pretreatment device is provided below the slag outlet of the electric furnace, and is used to perform high-temperature reduction modification and waste heat recovery on the high-temperature steel slag using carbon powder and bauxite; the twin-roll pretreatment device comprises at least one twin-roll structure, each of which is provided with a first heat exchange medium channel, and is used to cool, exchange heat, and crush the high-temperature steel slag;

[0045] A crushing device is provided below the double-roll pre-treatment device, and is used to stir and crush the steel slag after the double-roll pre-treatment device has extruded and recovered the waste heat, and to recover the waste heat;

[0046] A horizontal vibration digestion device, which is arranged at the outlet of the crushing device in a vibrating and cyclically movable manner, and is used to receive and thermally digest the steel slag discharged from the crushing device;

[0047] A composite nozzle for compositely spraying CO2 and H2O steam into the horizontal vibration digestion device;

[0048] a slag storage chamber, provided at the outlet of the horizontal vibration digestion device, for receiving and storing the steel slag discharged from the horizontal vibration digestion device;

[0049] a waste heat boiler, connected to the double-roll pretreatment device, the crushing device and the horizontal vibration digestion device, for recovering waste heat from high-temperature steel slag;

[0050] The dust removal and filtering system is connected to the waste heat boiler and is used to remove dust from the exhaust gas from the waste heat boiler. The exhaust gas after dust removal is mixed with steam for recycling.

[0051] In a preferred embodiment of the present invention, the double-roll pretreatment device includes a heat exchange device and a pretreatment shell. A steel slag inlet is provided at the top of the pretreatment shell. At least one group of double-roll structures is provided in the pretreatment shell below the steel slag inlet. Each of the double-roll structures includes two cooling extrusion rollers rotating in opposite directions. An extrusion crushing channel is formed between the two cooling extrusion rollers of each double-roll structure. A first heat exchange medium channel is provided in each of the cooling extrusion rollers, and the first heat exchange medium channel is connected to the heat exchange device.

[0052] In a preferred embodiment of the present invention, the crushing device includes a drum crusher, the drum crusher includes a drum body, tooth nails are provided on the outer wall of the drum body, a second heat exchange medium channel is provided in the drum body, and the second heat exchange medium channel is connected to the heat exchange device.

[0053] In a preferred embodiment of the present invention, an impact crushing bed is provided on one side of the drum crusher, a third heat exchange medium channel is provided in the impact crushing bed, and the third heat exchange medium channel is connected to the heat exchange device; the impact crushing bed cools and impact-crushes the steel slag; and an outlet hole is provided at the bottom of the impact crushing bed.

[0054] In a preferred embodiment of the present invention, the crushing device is a crocodile crushing bed, a second heat exchange medium channel is provided in the crocodile crushing bed, and an outlet hole is provided at the bottom of the crocodile crushing bed.

[0055] In a preferred embodiment of the present invention, an inlet baffle is provided at the steel slag inlet of the pretreatment shell, and a carbon powder injection pipe and a bauxite injection port are sealed and penetrated through the inlet baffle.

[0056] In a preferred embodiment of the present invention, the horizontal vibration digestion device includes a heat delivery trough for carrying steel slag, and the heat delivery trough moves and circulates under the drive of a resonant driver; a fourth heat exchange medium channel is provided in the side wall of the heat delivery trough, and the fourth heat exchange medium channel is connected to the heat exchange device; the top of the heat delivery trough is detachably connected to a sealing cover.

[0057] In a preferred embodiment of the present invention, the composite nozzle is sealed and penetrated through the side wall of the heat delivery trough.

[0058] In a preferred embodiment of the present invention, the composite nozzle is sealed and penetrated through the sealing cover.

[0059] In a preferred embodiment of the present invention, a waste gas collecting device is provided at the end of the horizontal vibration digestion device, and the waste gas collecting device is connected to the combustion settling chamber, and the combustion settling chamber is connected to the waste heat boiler.

[0060] As described above, the steel slag twin-roller online processing method and the steel slag twin-roller online processing system of the present invention have the following beneficial effects:

[0061] The steel slag treatment method of the present invention can efficiently recover the sensible heat of steel slag and the iron in the slag; eliminate free calcium oxide in the steel slag to improve the stability of the steel slag, meet the subsequent use requirements of the steel slag as a cement admixture, and improve the recovery rate of the steel slag; increase the hydraulic gelling properties of the steel slag by adding minerals such as tricalcium silicate, dicalcium silicate, and tricalcium aluminate in the steel slag, meet the subsequent use requirements of the steel slag as a cement admixture, and improve the recovery rate of the steel slag; the present invention can be used to solidify and seal CO2 emitted by the steel industry to reduce carbon emissions; the present invention can process slag online without the need for slag transportation, thereby reducing the heat loss and transportation cost of the slag; the waste heat heat exchange method of the present invention adopts a closed-loop heat exchange method, and the heat exchange medium does not directly contact the steel slag, which is safer and cleaner.

[0062] The double-roll pretreatment device and crushing device in the present invention can realize the reduction modification, waste heat recovery and crushing of steel slag, and the steel slag treatment effect is better; the double-roll pretreatment device of the present invention is arranged below the slag outlet of the electric furnace, and can process steel slag online without the need for steel slag transport, thereby reducing the heat loss and transportation cost of the steel slag; the crushing device of the present invention can realize stirring during the steel slag treatment process, with better dynamic conditions and a shorter steel slag treatment cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0064] in:

[0065] Figure 1 : It is a schematic diagram of Example 1 of the steel slag double-roller online processing system of the present invention.

[0066] Figure 2 :for Figure 1 Cross-sectional view at AA in the middle.

[0067] Figure 3 :for Figure 1 Enlarged view of point I in the middle.

[0068] Figure 4 : It is a schematic diagram of Example 2 of the steel slag double-roller online processing system of the present invention.

[0069] Figure 5 :for Figure 4 Enlarged view of point II in the middle.

[0070] In the picture:

[0071] 1. Double roller pretreatment device;

[0072] 11. Double-roller structure; 12. Heat exchange device; 13. Pretreatment shell; 14. Drum crusher; 141. Drum body; 142. Tooth nails; 15. Impact crushing bed; 16. Alligator crushing bed; 17. Inlet baffle; 18. Carbon powder injection pipe; 19. Bauxite injection port;

[0073] 2. Composite nozzle;

[0074] 3. Horizontal vibration digestion device; 31. Heat delivery trough; 32. Fourth heat exchange medium channel; 33. Sealing cover; 34. Horizontal bracket; 35. Support; 36. Screw;

[0075] 4. Slag storage room;

[0076] 5. Waste heat boiler;

[0077] 6. Dust removal and filtration system;

[0078] 7. Combustion settling chamber;

[0079] 8. Booster fan;

[0080] 91. Slag outlet of electric furnace; 92. Steel slag. DETAILED DESCRIPTION

[0081] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0082] The specific embodiments of the present invention described herein are intended only to illustrate the present invention and are not to be construed as limiting the present invention in any way. In light of the present invention, a skilled person may conceive of any possible variations based on the present invention, all of which should be considered to fall within the scope of the present invention. It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be an intermediate element at the same time. The terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to mechanical or electrical connections, or to internal communication between two elements, and may be directly connected or indirectly connected through an intermediate medium. A person of ordinary skill in the art can understand the specific meanings of the above terms based on the specific circumstances. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0083] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended only to describe specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0084] The present invention provides a double-roller online processing method for steel slag, comprising the following steps:

[0085] S1. High-temperature slag 92 discharged from the slag outlet 91 of the electric furnace enters the double-roll pretreatment device 1. Carbon powder and bauxite (existing technology) are added to the double-roll pretreatment device 1 to perform high-temperature reduction modification on the high-temperature slag and simultaneously recover the waste heat from extrusion. The double-roll pretreatment device 1 is connected to a waste heat boiler 5 (an existing boiler system can be used), which recovers the waste heat from the high-temperature slag.

[0086] Specifically, although existing steel slag treatment technology can quickly eliminate free calcium oxide in steel slag, it cannot effectively reduce FeO in the slag to recover metallic Fe, nor can it improve the hydraulic gelling properties of steel slag, which is not conducive to the next step of steel slag recycling and application.

[0087] In the present invention, the reduction modification of high-temperature steel slag mainly adopts a mixture of carbon powder and bauxite to perform reduction modification treatment on the steel slag.

[0088] The main mechanism of reduction modification of carbon powder and steel slag is as follows:

[0089] FeO+C=Fe+CO (T≥721.6°C).

[0090] Bauxite can effectively combine with the oxides in steel slag, promoting the full reaction of coke and iron-containing oxides. In addition, Al2O3 in high-alumina bauxite reacts with CaO in steel slag to generate a large amount of gelled phase tricalcium aluminate.

[0091] 3CaO+Al2O3=3CaO·Al2O3.

[0092] At the entrance of the double-roll pretreatment device 1, carbon powder for reduction modification and bauxite for steel slag modifier are sprayed synchronously with the high-temperature steel slag. The amount of carbon powder sprayed is less than or equal to 5% of the amount of high-temperature steel slag, and the amount of bauxite sprayed is less than or equal to 5% of the amount of high-temperature steel slag. The carbon powder reduces the high-temperature steel slag, and the bauxite modifies the high-temperature steel slag.

[0093] The twin-roll pretreatment device 1 reduces FeO in the high-temperature steel slag to Fe, and converts the free CaO in the steel slag into gelling substances such as tricalcium silicate, dicalcium silicate and tricalcium aluminate. At the same time, the temperature of the steel slag is cooled from 1500-1600°C to below 800°C, and the waste heat of the steel slag is recovered.

[0094] Furthermore, in step S1, the high-temperature steel slag, carbon powder and bauxite flowing into the double-roll pretreatment device 1 first pass through at least one group of double-roll structures 11 arranged in the double-roll pretreatment device 1. The double-roll structure 11 is provided with a first heat exchange medium channel, and the double-roll structure 11 extrudes, cools and exchanges heat on the high-temperature steel slag.

[0095] Furthermore, in step S1, the double-roll pretreatment device 1 includes a heat exchange device, in which a heat exchange medium is arranged to recover the waste heat of the high-temperature steel slag. The heat exchange medium includes a steam-water saturated product or liquid metal. If liquid metal is used, the liquid metal and the high-temperature steel slag undergo a primary heat exchange, and the steam-water saturated product and the liquid metal undergo a secondary heat exchange.

[0096] The heat exchange medium can preferably be a liquid metal for primary heat exchange, followed by secondary heat exchange with the steam-water saturated product in a liquid metal heat exchange device. Liquid metal is an alloy material formed by a combination of various metal materials with low melting points, such as gallium, indium, and tin. It has low and adjustable melting points (-5°C to 300°C), high boiling points (>2000°C), high thermal conductivity, stable physical and chemical properties, a low expansion coefficient, a high boiling point, no volatility, and is non-toxic and environmentally friendly. Its heat transfer efficiency is more than 10 times that of traditional working fluids and can be driven by an electromagnetic pump.

[0097] S2, the steel slag after being squeezed and heat recovered by the double-roll pre-treatment device enters the crushing device for stirring, crushing and heat recovery;

[0098] Furthermore, in step S2, the crushing device includes a drum crusher and an impact crushing bed. The steel slag that is squeezed, cooled and heat-exchanged by the double-roller structure flows downward to the drum crusher below the double-roller structure. A second heat exchange medium channel is provided in the drum crusher, and the drum crusher cools and rotationally crushes the steel slag.

[0099] The steel slag is hit by the drum crusher and flies to the impact crushing bed located on one side of the drum crusher. A third heat exchange medium channel is provided in the impact crushing bed, and the impact crushing bed cools and impact-crushes the steel slag.

[0100] The double roller structure 11 cools the temperature of the slag from 1500-1600℃ to below 1000℃, and then enters the crusher and impact crushing bed for further cooling and crushing. The temperature of the slag at the outlet of the impact crushing bed can be reduced to below 800℃.

[0101] The crushing device can also adopt a crocodile crushing bed.

[0102] S2. The crushed slag discharged from the crushing device enters the horizontal vibration digestion device 3. The CO2 and H2O injected into the horizontal vibration digestion device 3 are used to heat and digest the CaO in the slag.

[0103] Specifically, the horizontal vibration digestion device 3 adopts a horizontal vibration hot stewing bed, and the horizontal vibration digestion device 3 performs a slow forward and fast return movement to drive the steel slag to move forward.

[0104] CO2 and H2O steam are sprayed into the horizontal vibrating hot stewing bed. Under the action of CO2 and H2O steam, the free CaO in the steel slag is further digested. The specific reaction formula is as follows:

[0105] CaO(s)+H2O(g)=Ca(OH)2;

[0106] CO2(g)+Ca(OH)2=CaCO3(s)+H2O(g);

[0107] CaSiO3(s)+CO2(g)=CaCO3(s)+SiO2(s);

[0108] 2CaO·SiO2(s)+2CO2(g)=2CaCO3(s)+SiO2;

[0109] The injected CO2 can be derived from the CO2 removed from coal gas during the shaft furnace direct iron reduction process. This method allows for solid storage of industrial CO2 emissions, helping to reduce carbon emissions. The H2O steam can be generated from waste heat recovered from steel slag. This H2O steam is generated by heat exchange with steel slag, eliminating the need for an additional heat source and reducing steam production costs.

[0110] S3, the steel slag after hot stewing and digestion is transported to the slag storage chamber 4, and the steel slag is aged for a set time. The aged steel slag is transported to a set location for secondary treatment;

[0111] Specifically, the steel slag after hot stewing and digestion is transported to the slag storage chamber 4 for further aging treatment under the drive of the horizontal vibration digestion device 3. After about 1 to 2 hours of aging treatment, the steel slag can be transferred to the secondary processing line.

[0112] S4. The exhaust gas discharged from the horizontal vibration digestion device 3 enters the waste heat boiler 5 for heat exchange cooling. The dust removal and filtration system 6 (the existing flue gas dust removal and filtration system can be used) removes dust from the exhaust gas from the waste heat boiler 5 so that it is mixed with steam and recycled.

[0113] Specifically, a waste gas collection device is installed at the end of the horizontal vibration digestion device 3. The high-temperature waste gas (300-400°C) after sufficient heat exchange with the steel slag is drawn into the combustion and settling chamber 7. The slag particles carried in the waste gas can further settle in the combustion and settling chamber 7. At the same time, the waste gas may contain a certain amount of CO gas, which can undergo secondary combustion with the mixed air in the combustion and settling chamber 7 to release heat. The flue gas after settling and secondary combustion enters the waste heat boiler 5 for heat exchange and cooling, and the generated steam enters the steam drum and heat accumulator (existing technology) for storage.

[0114] The exhaust gas from the waste heat boiler 5 enters the dust removal and filtration system 6 and then passes through the booster fan 8 to be mixed with steam and recycled.

[0115] The steel slag treatment method of the present invention can efficiently recover the sensible heat of steel slag and the iron in the slag; eliminate free calcium oxide (f-CaO) in the steel slag to improve the stability of the steel slag, meet the subsequent use requirements of the steel slag as a cement admixture, and improve the recovery rate of the steel slag; increase the tricalcium silicate, dicalcium silicate, tricalcium aluminate and other minerals in the steel slag to improve the hydraulic gelling properties of the steel slag, meet the subsequent use requirements of the steel slag as a cement admixture, and improve the recovery rate of the steel slag; the present invention can be used to solidify and seal CO2 emitted by the steel industry to reduce carbon emissions; the present invention can process slag online without the need for slag transportation, thereby reducing the heat loss and transportation cost of the slag; the waste heat heat exchange method of the present invention adopts a closed-loop heat exchange method, and the heat exchange medium does not directly contact the steel slag, which is safer and cleaner.

[0116] like Figures 1 to 5 As shown, the present invention provides a steel slag double-roller online processing system for use in the aforementioned steel slag double-roller online processing method; the steel slag double-roller online processing system comprises:

[0117] The twin-roll pre-treatment device 1, located below the slag outlet 91 of the electric furnace, is used to perform high-temperature reduction modification, waste heat recovery, and stirring and crushing on the high-temperature steel slag 92 using carbon powder and bauxite. The twin-roll pre-treatment device 1 includes at least one set of twin-roll structures 11, each of which has a first heat exchange medium channel. The twin-roll structures 11 are used to cool, exchange heat, and crush the high-temperature steel slag.

[0118] The crushing device is arranged below the double-roll pretreatment device 1, and is used to stir and crush the steel slag after the double-roll pretreatment device 1 has extruded and recovered the waste heat, and to recover the waste heat;

[0119] A horizontal vibration digestion device 3 is provided at the outlet of the crushing device in a vibrating and cyclically movable manner, and is used to receive and thermally digest the steel slag discharged from the crushing device;

[0120] The composite nozzle 2 is used for compositely spraying CO2 and H2O steam to the horizontal vibration digestion device 3;

[0121] The slag storage chamber 4 is provided at the outlet of the horizontal vibration digestion device 3 and is used to receive and store the steel slag discharged from the horizontal vibration digestion device 3;

[0122] The waste heat boiler 5 (an existing boiler system can be used) is connected to the double-roll pretreatment device 1, the crushing device and the horizontal vibration digestion device 3 to recover the waste heat of the high-temperature steel slag;

[0123] The dust removal and filtration system 6 (an existing flue gas dust removal and filtration system may be used) is connected to the waste heat boiler 5 and is used to remove dust from the waste heat boiler 5. The waste gas after dust removal is mixed with steam and recycled.

[0124] Although existing steel slag treatment technology can quickly eliminate free calcium oxide in steel slag, it cannot effectively reduce FeO in the slag to recover metallic Fe, nor can it improve the hydraulic gelling properties of steel slag, which is not conducive to the next step of steel slag recycling and application.

[0125] The double-roll pretreatment device and crushing device in the present invention can realize the reduction modification, waste heat recovery and crushing of steel slag, and the steel slag treatment effect is better; the double-roll pretreatment device of the present invention is arranged below the slag outlet of the electric furnace, and can process steel slag online without the need for steel slag transportation, thereby reducing the heat loss and transportation cost of the steel slag; the crushing device of the present invention can realize stirring during the steel slag treatment process, with better dynamic conditions and a shorter steel slag treatment cycle; the steel slag waste heat exchange method of the present invention adopts closed-loop heat exchange, and the heat exchange medium does not directly contact the steel slag, which is safer and cleaner.

[0126] Further, if Figure 1 、 Figure 4 As shown, the double-roll pretreatment device 1 includes a heat exchange device 12 and a pretreatment shell 13. A steel slag inlet is provided at the top of the pretreatment shell 13. At least one set of double-roll structures 11 is provided below the steel slag inlet in the pretreatment shell 13. Each double-roll structure 11 includes two cooling extrusion rollers rotating in opposite directions. An extrusion crushing channel is formed between the two cooling extrusion rollers of each double-roll structure 11. A first heat exchange medium channel is provided in each cooling extrusion roller, and the first heat exchange medium channel is connected to the heat exchange device 12.

[0127] A heat exchange medium is set in the heat exchange device to recover the waste heat of the high-temperature steel slag. The heat exchange medium includes steam-water saturated product or liquid metal. If liquid metal is used, the liquid metal and the high-temperature steel slag undergo primary heat exchange, and the steam-water saturated product and the liquid metal undergo secondary heat exchange.

[0128] The heat exchange medium can preferably be a liquid metal for primary heat exchange, followed by secondary heat exchange with the steam-water saturated product in a liquid metal heat exchange device. Liquid metal is an alloy material formed by a combination of various metal materials with low melting points, such as gallium, indium, and tin. It has low and adjustable melting points (-5°C to 300°C), high boiling points (>2000°C), high thermal conductivity, stable physical and chemical properties, a low expansion coefficient, a high boiling point, no volatility, and is non-toxic and environmentally friendly. Its heat transfer efficiency is more than 10 times that of traditional working fluids and can be driven by an electromagnetic pump.

[0129] like Figure 1 、 Figure 3As shown, in embodiment 1 of the present invention, the crushing device includes a drum crusher 14, which is in a high-speed rotating operation state; the drum crusher 14 includes a drum body 141, and tooth nails 142 are provided on the outer wall of the drum body 141. The tooth nails 142 can hit and crush the falling steel slag, and a second heat exchange medium channel is provided in the drum body 141.

[0130] An impact crushing bed 15 is installed on one side of the drum crusher 14. A third heat exchange medium channel is provided within the impact crushing bed 15, which is connected to the heat exchange device 12. The impact crushing bed 15 cools and crushes the slag. An outlet port is provided at the bottom of the impact crushing bed 15. The high-speed rotation of the drum crusher 14 forces the slag to fly toward the impact crushing bed 15. At a certain speed, the slag hits the impact crushing bed 15, further crushing it. The drum crusher 14 and the impact crushing bed 15 crush the slag while recovering its waste heat.

[0131] like Figure 4 、 Figure 5 As shown, in the second embodiment of the present invention, the crushing device adopts a crocodile crushing bed 16, a second heat exchange medium channel is provided in the crocodile crushing bed 16, and an outlet hole is provided at the bottom of the crocodile crushing bed 16. The crocodile crushing bed 16 crushes the steel slag and recovers the waste heat of the steel slag.

[0132] Further, if Figure 1 、 Figure 3 、 Figure 4 、 Figure 5 As shown, an inlet baffle 17 is provided at the slag inlet of the pretreatment shell 13, and a carbon powder injection pipe 18 and a bauxite injection port 19 are sealed through the inlet baffle 17. The inlet baffle 17 is a baffle made of high-aluminum refractory material.

[0133] Further, if Figure 2 As shown, the horizontal vibration digestion device 3 can adopt a horizontal vibration hot stewing bed, including a heat delivery trough 31 for carrying steel slag, and the heat delivery trough 31 moves and circulates under the drive of the resonant driver; a fourth heat exchange medium channel 32 is provided in the side wall of the heat delivery trough 31, and the fourth heat exchange medium channel is connected to the heat exchange device 12; the top of the heat delivery trough 31 is detachably connected to the sealing cover 33. The heat delivery trough 31 is a welded structure of the heat exchange medium channel, which can recover the waste heat in the steel slag while processing the steel slag. The sealing cover 33 is enclosed with thermal insulation material and is fixed to the heat delivery trough by bolts, which is convenient for disassembly and maintenance. A rubber sealing plate is provided between the sealing cover 33 and the heat delivery trough 31.

[0134] In this embodiment, the horizontal vibrating hot stewing bed is driven by a resonant driver to drive the horizontal bracket 34 around the screw 36 fixed on the support 35 to perform slow forward and fast return motion.

[0135] Further, if Figure 1 、 Figure 2 、 Figure 4 As shown, a composite nozzle 2 is sealed and penetrated on the side wall of the hot delivery trough. Composite nozzles for spraying CO2 and H2O steam are provided on both sides of the horizontal vibrating hot stewing bed. The sprayed CO2 and H2O can further digest CaO in the slag.

[0136] Further, if Figure 2 As shown, a composite nozzle 2 is sealed and penetrated on the sealing cover 33. A composite nozzle 2 is set on the top of the horizontal vibrating hot stewing bed to spray CO2 and H2O steam.

[0137] Furthermore, a waste gas collecting device is provided at the end of the horizontal vibration digestion device 3 , and the waste gas collecting device is connected to the combustion settling chamber 7 , and the combustion settling chamber 7 is connected to the waste heat boiler 5 .

[0138] After sufficient heat exchange with the steel slag, the high-temperature exhaust gas (300-400°C) is drawn into the combustion and settling chamber 7, where the slag particles carried by the exhaust gas are further settled. The exhaust gas may also contain a certain amount of CO, which can undergo a secondary combustion with the mixed air in the combustion and settling chamber 7 to release heat. After settling and secondary combustion, the flue gas enters the waste heat boiler 5 for heat exchange and cooling, and the generated steam is stored in the steam drum and heat accumulator (existing technology).

[0139] As described above, the steel slag twin-roller online processing method and the steel slag twin-roller online processing system of the present invention have the following beneficial effects:

[0140] The steel slag treatment method of the present invention can efficiently recover the sensible heat of steel slag and the iron in the slag; eliminate free calcium oxide (f-CaO) in the steel slag to improve the stability of the steel slag, meet the subsequent use requirements of the steel slag as a cement admixture, and improve the recovery rate of the steel slag; increase the tricalcium silicate, dicalcium silicate, tricalcium aluminate and other minerals in the steel slag to improve the hydraulic gelling properties of the steel slag, meet the subsequent use requirements of the steel slag as a cement admixture, and improve the recovery rate of the steel slag; the present invention can be used to solidify and seal CO2 emitted by the steel industry to reduce carbon emissions; the present invention can process slag online without the need for slag transportation, thereby reducing the heat loss and transportation cost of the slag; the waste heat heat exchange method of the present invention adopts a closed-loop heat exchange method, and the heat exchange medium does not directly contact the steel slag, which is safer and cleaner.

[0141] The double-roll pretreatment device and crushing device in the present invention can realize the reduction modification, waste heat recovery and crushing of steel slag, and the steel slag treatment effect is better; the double-roll pretreatment device of the present invention is arranged below the slag outlet of the electric furnace, and can process steel slag online without the need for steel slag transport, thereby reducing the heat loss and transportation cost of the steel slag; the crushing device of the present invention can realize stirring during the steel slag treatment process, with better dynamic conditions and a shorter steel slag treatment cycle.

[0142] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A double-roller online slag processing system, characterized in that: The steel slag double-roller online processing system includes: A twin-roll pretreatment device is provided below the slag outlet of the electric furnace, and is used to perform high-temperature reduction modification and waste heat recovery on the high-temperature steel slag using carbon powder and bauxite; the twin-roll pretreatment device comprises at least one twin-roll structure, each of which is provided with a first heat exchange medium channel, and is used to cool, exchange heat, and crush the high-temperature steel slag; A crushing device is provided below the double-roll pre-treatment device, and is used to stir and crush the steel slag after the double-roll pre-treatment device has extruded and recovered the waste heat, and to recover the waste heat; A horizontal vibration digestion device, which is arranged at the outlet of the crushing device in a vibrating and cyclically movable manner, and is used to receive and thermally digest the steel slag discharged from the crushing device; A composite nozzle for compositely spraying CO2 and H2O steam into the horizontal vibration digestion device; a slag storage chamber, provided at the outlet of the horizontal vibration digestion device, for receiving and storing the steel slag discharged from the horizontal vibration digestion device; a waste heat boiler, connected to the double-roll pretreatment device, the crushing device and the horizontal vibration digestion device, for recovering waste heat from high-temperature steel slag; a dust removal and filtration system, connected to the waste heat boiler, for removing dust from the exhaust gas from the waste heat boiler, and mixing the dust-removed exhaust gas with steam for recycling; The twin-roll pretreatment device includes a heat exchange device and a pretreatment shell. A slag inlet is provided at the top of the pretreatment shell. At least one twin-roll structure is provided in the pretreatment shell below the slag inlet. Each twin-roll structure includes two cooling extrusion rollers rotating in opposite directions. An extrusion crushing channel is formed between the two cooling extrusion rollers of each twin-roll structure. A first heat exchange medium channel is provided in each cooling extrusion roller, and the first heat exchange medium channel is connected to the heat exchange device. The crushing device is a crocodile-type crushing bed, a second heat exchange medium channel is arranged in the crocodile-type crushing bed, and an outlet hole is arranged at the bottom of the crocodile-type crushing bed.

2. The steel slag twin-roller online processing system according to claim 1, characterized in that: The crushing device includes a drum crusher, which includes a drum body. Tooth spikes are provided on the outer wall of the drum body. A second heat exchange medium channel is provided in the drum body, and the second heat exchange medium channel is connected to the heat exchange device.

3. The steel slag twin-roller online processing system according to claim 2, characterized in that: An impact crushing bed is provided on one side of the drum crusher, a third heat exchange medium channel is provided in the impact crushing bed, and the third heat exchange medium channel is connected to the heat exchange device; the impact crushing bed cools and impact-crushes the steel slag; an outlet hole is provided at the bottom of the impact crushing bed.

4. The steel slag twin-roller online processing system according to claim 1, characterized in that: An inlet baffle is provided at the steel slag inlet of the pretreatment shell, and a carbon powder blowing pipe and a bauxite blowing port are sealed and penetrated through the inlet baffle.

5. The steel slag twin-roller online processing system according to claim 1, characterized in that: The horizontal vibration digestion device includes a heat delivery trough for carrying steel slag, and the heat delivery trough moves and circulates under the drive of a resonant driver; a fourth heat exchange medium channel is provided in the side wall of the heat delivery trough, and the fourth heat exchange medium channel is connected to the heat exchange device; the top of the heat delivery trough is detachably connected to a sealing cover.

6. The steel slag twin-roller online processing system according to claim 5, characterized in that: The composite nozzle is sealed and penetrated through the side wall of the hot delivery trough.

7. The steel slag twin-roller online processing system according to claim 5, characterized in that: The composite nozzle is sealed and penetrated through the sealing cover.

8. The steel slag twin-roller online processing system according to claim 5, characterized in that: An exhaust gas collecting device is provided at the end of the horizontal vibration digestion device. The exhaust gas collecting device is connected to the combustion sedimentation chamber, and the combustion sedimentation chamber is connected to the waste heat boiler.

9. A double-roller online processing method for steel slag, characterized in that: The slag double-roller online processing system according to any one of claims 1 to 8 is used for implementation; the system comprises the following steps: S1. High-temperature slag discharged from the slag outlet of the electric furnace enters a double-roll pretreatment device, into which carbon powder and bauxite are added to perform high-temperature reduction modification on the high-temperature slag and simultaneously recover waste heat. The double-roll pretreatment device is connected to a waste heat boiler, which recovers waste heat from the high-temperature slag. S2, the steel slag after being squeezed and heat recovered by the double-roll pre-treatment device enters the crushing device for stirring, crushing and heat recovery; S3. The crushed slag discharged from the crushing device enters the horizontal vibration digestion device, and the CO2 and H2O injected into the horizontal vibration digestion device are used to heat and digest the CaO in the slag; S4, the steel slag after hot stewing and digestion is transported to the slag storage chamber, and the steel slag is aged for a set time. The aged steel slag is then transferred to a set location for secondary treatment; S5. The exhaust gas discharged from the horizontal vibration digestion device enters the waste heat boiler for heat exchange cooling. The dust removal and filtration system removes dust from the exhaust gas from the waste heat boiler so that it is mixed with steam for recycling.

10. The twin-roll online slag processing method according to claim 9, characterized in that: In step S1, at the entrance of the double-roll pretreatment device, carbon powder for reduction modification and bauxite for steel slag modifier are sprayed synchronously with the high-temperature steel slag. The amount of carbon powder sprayed is less than or equal to 5% of the amount of high-temperature steel slag, and the amount of bauxite sprayed is less than or equal to 5% of the amount of high-temperature steel slag. The carbon powder reduces the high-temperature steel slag, and the bauxite modifies the high-temperature steel slag.

11. The twin-roller online slag processing method according to claim 10, characterized in that: In step S1, the high-temperature steel slag, carbon powder and bauxite flowing into the double-roll pretreatment device first pass through at least one group of double-roll structures provided in the double-roll pretreatment device, wherein a first heat exchange medium channel is provided in the double-roll structure, and the double-roll structure extrudes, cools and exchanges heat on the high-temperature steel slag.

12. The twin-roller online slag processing method according to claim 11, characterized in that: In step S2, the crushing device includes a drum crusher. The steel slag cooled, heat-exchanged and squeezed and crushed by the double-roller structure flows downward to the drum crusher below the double-roller structure. A second heat exchange medium channel is provided in the drum crusher, and the drum crusher cools and rotates and crushes the steel slag.

13. The twin-roll online slag processing method according to claim 12, characterized in that: In step S2, the steel slag is struck by the drum crusher and flies to the impact crushing bed located on one side of the drum crusher. A third heat exchange medium channel is provided in the impact crushing bed, and the impact crushing bed cools and impact-crushes the steel slag.

14. The twin-roller online slag processing method according to claim 9, characterized in that: In step S1, the twin-roll pretreatment device includes a heat exchange device, in which a heat exchange medium is provided to recover waste heat from the high-temperature slag, and the heat exchange medium includes a saturated steam-water substance or liquid metal.

15. The twin-roller online slag processing method according to claim 9, characterized in that: In step S3, the horizontal vibration digestion device performs a slow forward and fast return motion to drive the slag forward.

16. The twin-roll online slag processing method according to claim 9, characterized in that: In step S5, the exhaust gas discharged from the horizontal vibration digestion device is drawn into the combustion sedimentation chamber, and the slag particles carried in the exhaust gas are further settled in the combustion sedimentation chamber. The CO gas in the exhaust gas undergoes secondary combustion with the mixed air in the combustion sedimentation chamber to release heat. The flue gas after sedimentation and secondary combustion enters the waste heat boiler for heat exchange and cooling, and the generated steam enters the steam drum and heat accumulator for storage.

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