Method for reducing slag content in blast furnace slag treatment circulating water

Abstract

The invention provides a method for reducing slag content in blast furnace slag treatment circulating water, which comprises the following steps: blast furnace red slag and water sprayed from a granulation box are subjected to water quenching in the air to form a mixture, and the mixture falls into a granulation tank at the bottom of a granulation tower. A groove bottom rotational flow plate stirs to form a vortex, the mixture enters a dewatering rotary drum through a side wall slag water pipe, slag-water separation is achieved, slag is carried away through a belt, and hot water is discharged into a hot water groove. Hot water at the bottom of the hot water tank is pumped back to the granulating tank by the recycling pump; hot water on the upper layer of the collecting tank is conveyed to the cooling tower through a granulation return water pump, and is returned to the granulation box for reuse through a granulation pump after being cooled; hot water at the bottom of the tank is pumped by an anti-deposition pump and injected into the granulation tank through pipelines with different heights according to the vortex direction, and the water injection flow speed is reduced along with height reduction, so that the purpose of preventing granular iron from depositing at the bottom of the granulation tank is achieved.

Description

Technical Field

[0001] This invention relates to the field of metallurgical ironmaking equipment technology, specifically to a method for reducing the slag content in circulating water used for blast furnace slag treatment. Background Technology

[0002] Blast furnace slag treatment is a process for treating waste slag discharged from the blast furnace during ironmaking. Currently, the primary method for treating blast furnace slag is water quenching. The water quenching system mainly consists of equipment such as a red slag ditch, granulation box, granulation tower, slag-water pipe, dewatering drum, hot water tank, collection tank, cooling tower, belt conveyor, water pump, valve assembly, and circulating water pipes. Figure 1 As shown, this process transports the slag-water mixture to the granulation tank at the bottom of the granulation tower, and then filters the slag again through the dewatering drum. However, due to the high density of the granulated iron, the angle and water velocity entering the granulation tank have not been properly calculated, and there is no swirl plate to assist. According to the actual situation on the production site, the recirculation pump cannot achieve the slag suspension capacity, the water balance effect is not good, and the ability to reduce the slag content in the slag treatment circulating water needs to be improved.

[0003] Because the granulation tower contains granular iron deposits, and blast furnace maintenance cycles are long and short, slag and iron caking occurs within the tower, reducing its space. This results in a large amount of slag overflowing through the overflow pipe into the hot water tank without passing through the rotary drum filter, causing serious pollution to the water system. With the further use of slag treatment, the slag content in the water increased from 1 g / L initially to 5-20 g / L later, significantly increasing the monthly maintenance workload. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for reducing the slag content in circulating water used for blast furnace slag treatment, comprising: The blast furnace slag falling from the slag ditch reacts with the water sprayed from the granulation box in mid-air, forming a water-slag mixture. This mixture falls into the granulation tank at the bottom of the granulation tower. Swirl plates at the bottom of the granulation tank agitate the mixture into a vortex. The mixture then enters the dewatering drum through the slag-water pipe on the side wall of the granulation tank. The dewatering drum filters the mixture, producing pre-filtered hot water and slag-iron. The slag-iron is transported to the slag heap by belt conveyor, while the pre-filtered hot water is discharged into a hot water tank. The pre-filtered hot water in the hot water tank undergoes a secondary filtration process via overflow. The filtered water enters the collection tank, which contains secondary filtered hot water. The pre-filtered hot water at the bottom of the hot water tank is discharged into the granulation tank for further filtration via a recirculation pump. The secondary filtered hot water on the surface of the collection tank is pumped to the cooling tower for cooling via a granulation return pump and then pumped back to the granulation tank for reuse via a granulation pump. The secondary filtered hot water at the bottom of the collection tank is drawn by an anti-sedimentation pump and injected into the granulation tank in the direction of a vortex through pipes of different heights for further filtration. The water column velocity in the granulation tank gradually decreases from high to low in the pipes of different heights.

[0005] Furthermore, the specific method for pumping water from the bottom of the collection tank into the granulation tank via anti-sedimentation pumps and injecting it into the granulation tank through pipes at different heights in the direction of a vortex is as follows: The direction of the water jet injected into the granulation tank by the anti-deposition pump is the same as the rotation direction of the vortex, and the angle of the water jet injected into the granulation tank by the anti-deposition pump is perpendicular to the central axis of the vortex.

[0006] Furthermore, by controlling the installation angle of the swirl plate, the angle of the vortex center axis of the water-slag mixture in the granulation tank is adjusted, so as to induce the water-slag mixture to be discharged into the slag-water pipe and then enter the dewatering drum.

[0007] Furthermore, the installation angle of the swirl plate is 45°-70°, and the water jet angle injected into the granulation tank by the anti-sedimentation pump is 15°-30°.

[0008] Furthermore, when the water level of the water-sludge mixture in the granulation tank at the bottom of the granulation tower rises to the top of the granulation tower, the water-sludge mixture enters the hot water tank through the overflow pipe.

[0009] Furthermore, the water column flow rate injected into the granulation tank from high to low through the pipes of different heights gradually decreases, which is used to control the flow rate of the water-sludge mixture in the anti-sludge pump to gradually decrease from top to bottom.

[0010] Furthermore, the critical flow velocity of the water-slag mixture that can suspend slag and iron of different particle sizes is obtained based on the Hjulström curve, and the actual flow velocity of the water-slag mixture is controlled based on the critical flow velocity.

[0011] Furthermore, the actual flow velocity of the water-slag mixture is controlled to be 1.2-1.5 times the critical flow velocity.

[0012] Furthermore, the actual flow rate is increased by 20%-30% to prevent the deposition of particles of the corresponding size.

[0013] Furthermore, when the slag and iron particle size is 3-8mm, the actual flow velocity of the water-slag mixture is controlled to be 20-35cm / s.

[0014] The beneficial effects of this invention are as follows: 1. This prevents granular iron deposits from encroaching on the space of the granulation tank, causing slag water to overflow into the system pipeline network. This reduces the slag content in the slag treatment circulating water, thereby reducing wear and balance disruption of circulating water system equipment caused by high slag content and lowering the probability of accidental maintenance. 2. By filtering and reusing water, the water cycle can easily reach a balance, saving water resources. This reduces the likelihood of leaks in the slag treatment circulating water system equipment and lowers energy consumption.

[0015] 3. It can improve water quality by using a sedimentation pump to filter out sediment and treat it again in the circulating water.

[0016] 4. It can maintain water inside the granulation tank in the event of a granulation pump failure to prevent large pieces of red slag from condensing inside the granulation tank.

[0017] 5. It can replace manual cleaning of granular iron deposits inside the granulation tank, reducing labor intensity and improving human resource efficiency. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a graph showing the relationship between particle diameter (horizontal axis) and water flow velocity (vertical axis).

[0019] Attached reference numerals: 1-Red slag ditch, 2-Granulation box, 3-Granulation tank, 4-Dewatering drum, 5-Overflow pipe, 6-Hot water tank, 7-Collection pool, 8-Granulation return water pump, 9-Cooling tower, 10-Granulation pump, 11-Belt conveyor, 12-Slag heap, 13-Anti-sedimentation pump, 14-Swirl plate, 15-Recirculation pump. Detailed Implementation

[0020] The present invention will be further illustrated below with reference to examples and comparative examples.

[0021] A method for reducing the slag content in circulating water for blast furnace slag treatment is based on the core principle of utilizing the dynamic balance between fluid velocity and particle settling velocity to achieve layered and graded treatment of slag particles of different sizes. (Refer to...) Figure 1 ,include: The blast furnace slag falling from the red slag ditch 1 reacts with the water sprayed from the granulation box 2 in mid-air, forming a water-slag mixture. This mixture falls into the granulation tank 3 at the bottom of the granulation tower. The swirl plate 14 at the bottom of the granulation tank 3 agitates the mixture into a vortex. The mixture then enters the dewatering drum 4 through the slag-water pipe on the side wall of the granulation tank 3. The dewatering drum 4 filters the mixture, obtaining preliminary filtered hot water and slag-iron. The slag-iron is transported to the slag heap 12 via a belt conveyor 11. The preliminary filtered hot water is discharged into the hot water tank 6, where it undergoes secondary filtration via overflow. The hot water then enters the collection tank 7, which contains secondary filtered hot water. The pre-filtered hot water at the bottom of the hot water tank 6 is discharged into the granulation tank 3 for further filtration via the recirculation pump 15. The secondary filtered hot water on the surface of the collection tank 7 is pumped to the cooling tower 9 for cooling via the granulation return water pump 8 and then pumped to the granulation box 2 for reuse via the granulation pump 10. The secondary filtered hot water at the bottom of the collection tank 7 is drawn by the anti-sedimentation pump 13 and injected into the granulation tank 3 in the direction of vortex through pipes of different heights for further filtration. The water column flow rate in the granulation tank 3 gradually decreases from high to low through the pipes of different heights.

[0022] In this embodiment, the granulation tank, condensation tower, dehydration drum, etc., all adopt existing known technologies, such as Chinese patents 200520097644.3 and 200610166512.0.

[0023] A vortex is a flow pattern in which a fluid (liquid or gas) rotates around a virtual or real core axis, a spiral motion formed by eddies in water. In this vortex, fluid particles no longer move in straight lines but in circles or spirals. According to Bernoulli's principle, the fluid's rotational speed is fastest at the center of the vortex, resulting in the lowest pressure. The flow velocity is slower and the pressure is higher at the periphery. This pressure difference from the outside in is crucial for maintaining the vortex structure. Furthermore, vortices are usually not purely rotational but accompanied by flow along the core axis, forming a spiral trajectory. In this invention, the vortex is a locally controlled turbulent vortex generated by the jet impact of an anti-settling pump on a fixed-angle swirl plate. Its purpose is not separation, but to create complex mechanical effects through rotational motion, thereby lifting the particles. As mentioned earlier, the center of the vortex is a low-pressure area. The area around the vortex and below the particles is a relatively high-pressure area. If slag or iron is in this flow field, a pressure difference will exist between its upper and lower surfaces. The fluid in the high-pressure area will naturally flow towards the low-pressure area, attempting to balance this pressure difference. This is equivalent to a force "pushing" or "suctioning" the particles from the high-pressure zone (bottom) to the low-pressure zone (vortex center). Since the vortex center is usually accompanied by an upward axial flow, the suction effect generated by this pressure difference is effectively converted into an upward force that lifts the particles and prevents them from settling.

[0024] By employing the above methods, an effective slag-water mixing space is ensured within the granulation tower, preventing granular iron deposits from encroaching on the granulation tank space and causing slag-water overflow into the system pipeline. This avoids high slag content in the slag treatment circulating water, reducing the likelihood of water balance disruption and accident maintenance in the slag treatment system.

[0025] The above-mentioned main process equipment: 1) Red Slag Ditch 1: The ditch and support are made of steel structure. It is lined with silicon carbide plates that are resistant to erosion and wear.

[0026] 2) Granulation box 2: It consists of an orifice plate covered with perforated nozzles, a shell, and pipe connectors. The range of openings on the orifice plate, the size and angle of the openings, and the distribution of the openings are non-uniform depending on the slag flow trajectory and the slag flow cross-section.

[0027] 3) Granulation Tank 3: Located below the condenser tower, it is a cylindrical tank with a diameter of approximately 6m. It contains swirl plates, grids, and water-slag pipes with calculated appropriate angles. The slag-water mixture is further crushed here and flows through pipes into the rotary drum distributor.

[0028] 4) Granulation Tower: Located above granulation tank 3, it is a cylindrical structure with a diameter of approximately 6m and a total height of approximately 30m. It consists of the granulation tower body and a chimney with a diameter of 2m above it, which is higher than the blast furnace exhaust.

[0029] 5) Dewatering Drum 4: The water-slag mixture enters the distributor of the dewatering drum 4 along the slag-water pipe. The slag-water mixture at the bottom of the dewatering drum 4 is lifted and filtered by a dewatering device equipped with a screen plate. When the dewatering drum 4 reaches its highest point, the water and slag fall onto the belt conveyor 11 and are transported to the slag dump 12. The dewatering drum 4 consists of a metal frame, a double-layer filter screen cylinder, and a blade hopper with a filter screen on the inner circumferential wall of the drum. The distributor is a rectangular tube with a variable cross-section. Holes of varying cross-sections are opened at the bottom of the tube. To maintain the shape of the opening cross-section, ceramic wear-resistant liners are embedded. The slag-water flow passes through these lower openings, distributing the slag-water mixture relatively evenly throughout the dewatering drum 4, thereby achieving a better dewatering effect and ensuring uniform screen wear and high efficiency.

[0030] 7) Belt conveyor 11: Belt conveyor 11 passes through dewatering drum 4. The slag and sand dewatered by dewatering drum 4 fall into belt conveyor 11, and then are transferred to slag dump 12 by belt conveyor 11.

[0031] 8) Hot water tank 6: Located below the dehydration drum 4, it collects the hot water filtered from the dehydration drum 4. The hot water tank 6 is made of concrete and is divided into 3 compartments, with the first 2 compartments separated by steel plates. It has a volume of approximately 100 m3 and is equipped with 2 circulating water pumps at the bottom. The recirculation pump 15 pumps the water from the hot water tank 6 back into the granulation tank, where it is filtered again by the dehydration drum 4 to ensure the quality of the water flowing back to the cooling tower 9.

[0032] 9) Collection tank 7: Water in the hot water tank 6 overflows into the collection tank 7. The bottom of the collection tank 7 is equipped with a granulation return water pump 8 and an anti-sedimentation pump 13. The granulation return water pump 8 delivers the hot water to the cooling tower 9 for cooling and recycling. The anti-sedimentation pump 13 sucks out the slag water from the bottom of the collection tank 7 and delivers it back to the granulation tank 3. Through the appropriate angle of the swirl plate 14 in the granulation tank 3 and the calculated pipe diameter angle, the granulated iron particles in the granulation tank 3 are suspended in the water and flow into the dewatering drum 4 along with the slag water through the slag water pipe for dewatering.

[0033] 10) Cooling tower 9: Cooling tower 9 is a device that reduces water temperature by exchanging heat through contact between water and air. It consists of a tower body, a water distribution system, ventilation equipment, a water collection tank, etc.

[0034] 11) Granulation return water pump 8, recirculation pump 15, anti-sedimentation pump 13, granulation pump 10: Granulation return water pump 8, recirculation pump 15, anti-sedimentation pump 13, and granulation pump 10 are water pumps used to transport liquid mixtures containing solid particles. Their working principle is based on centrifugal force, which increases the energy of the solid-liquid mixture through impeller rotation, thereby achieving continuous transportation. Their main characteristics are wear resistance, corrosion resistance, and adaptability to harsh environments.

[0035] 12) Swirl Plate 14: A swirl plate is a fixed blade or baffle assembly with a specific tilt angle installed inside a fluid channel. Its core function is to transform the original straight flow into a rotating, spiraling forward vortex (or vortex flow) by forcibly changing the flow direction and state of the fluid, thereby achieving the purpose of mixing, separating, distributing, or enhancing specific mass transfer processes, and is applicable to existing equipment.

[0036] In a preferred embodiment, the water at the bottom of the collection tank is drawn by an anti-settling pump and injected into the granulation tank through pipes at different heights in the direction of the vortex. Specifically, the direction of the water jet injected into the granulation tank by the anti-settling pump is the same as the rotation direction of the vortex, and the angle of the water jet injected into the granulation tank by the anti-settling pump is perpendicular to the central axis of the vortex. For example, if the installation angle of the vortex plate is 45°-70°, the corresponding angle of the water jet injected into the granulation tank by the anti-settling pump is 15°-30°.

[0037] In a preferred embodiment, the angle of the vortex center axis of the water-slag mixture in the granulation tank is adjusted by controlling the installation angle of the swirl plate, thereby inducing the water-slag mixture to flow into the slag-water pipe and then into the dewatering drum. This promotes the flow of the entire water circulation and prevents the water level in the granulation tower from becoming too high, which would cause slag and iron to overflow into the hot water tank 6.

[0038] In a preferred embodiment, when the water level of the water-slag mixture in the granulation tank 3 at the bottom of the granulation tower rises to the upper part of the granulation tower, the water-slag mixture enters the hot water tank 6 through the overflow pipe 5. This is the handling method when the granulation tower is full, but this will lead to excessive slag and iron content in the hot water tank 6, which is a situation that this patent avoids.

[0039] In a preferred embodiment, the water column velocity injected into the granulation tank from the pipes at different heights gradually decreases from high to low, thus controlling the gradual decrease in the flow velocity of the water-sludge mixture in the anti-settling pump from top to bottom. The high-velocity upper layer is specifically designed to carry large particles. Large particles have a large mass and a fast settling velocity, requiring a strong upward water flow to counteract their gravity, suspend them, and allow them to move with the water flow. This is the primary reason for the existence of the "high-velocity upper layer zone." Maintaining a high flow velocity requires a large amount of energy. Concentrating the high-velocity water flow at the upper inlet, only to treat the most difficult-to-suspend large particles, rather than maintaining a high flow velocity throughout the entire system, significantly saves energy. If large particles settle in the upper layer, it can easily clog the flow channels, causing the entire system to malfunction. The high flow velocity ensures that particles are quickly carried away when they first enter the system. The low-velocity lower layer is optimized for handling fine sludge. After treatment in the upper layer, large particles have been carried to the outlet by the high-speed water flow, and the particles reaching the lower layer are mainly fine sludge particles. Fine particles settle slowly, requiring a very low suspension velocity. A low flow rate in the lower layer is sufficient to handle these fine particles without wasting additional energy. Simultaneously, the lower flow rate helps create a more stable laminar flow, facilitating effective solid-liquid separation in the subsequent dewatering drum and improving dewatering efficiency and quality. Using excessively high flow rates in the lower layer will generate violent turbulence, potentially re-stirring up the settled fine particles, thus negatively impacting the effluent quality and separation effect.

[0040] In a preferred embodiment, the critical flow velocity of the slag-iron mixture capable of suspending slag and iron of different particle sizes is obtained based on the Hjulström curve. The actual flow velocity of the slag-iron mixture is then controlled based on this critical flow velocity, typically 1.2-1.5 times the critical flow velocity. Larger slag-iron particle sizes require higher actual flow velocities. The Hjulström curve guides the control of the actual flow velocity of the slag-iron mixture, improving the slag-water separation effect.

[0041] As a preferred embodiment, referring to Tables 1 and 2, when the slag-iron particle size is 3-8 mm, the actual flow velocity of the water-slag mixture should be controlled at 20-35 cm / s to maintain slag-iron suspension. Pulsed water flow or flow feedback control can be used, and the deposition thickness should be monitored in real time. (Reference) Figure 2 The graph shows the relationship between particle diameter (horizontal axis) and water flow velocity (vertical axis). Considering slag adhesion and bulk density, especially the agglomeration of slag and iron, the actual flow velocity needs to be increased by 20%-30% to prevent the deposition of particles of the corresponding size.

[0042] Table 1

[0043] Table 2

[0044] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for reducing the slag content in circulating water used for blast furnace slag treatment, characterized in that, include: The blast furnace slag falling from the red slag ditch (1) and the water sprayed from the granulation box (2) undergo a water quenching reaction in the air to form a water-slag mixture. The water-slag mixture falls into the granulation tank (3) at the bottom of the granulation tower. The swirl plate (14) at the bottom of the granulation tank (3) stirs the water-slag mixture into a vortex. The water-slag mixture enters the dewatering drum (4) from the slag-water pipe on the side wall of the granulation tank (3). The dewatering drum (4) filters the water-slag mixture to obtain preliminary filtered hot water and slag iron. The slag iron is transported to the slag dump (12) by the belt conveyor (11). The preliminary filtered hot water is discharged into the hot water tank (6). The preliminary filtered hot water in the hot water tank (6) enters the collection pool (7) by overflow. The hot water is collected in the collection tank (7) for secondary filtration. The hot water at the bottom of the hot water tank (6) is discharged into the granulation tank (3) for further filtration by the recirculation pump (15). The hot water at the surface of the collection tank (7) is pumped to the cooling tower (9) for cooling by the granulation return water pump (8) and then pumped to the granulation box (2) for reuse by the granulation pump (10). The hot water at the bottom of the collection tank (7) is drawn by the anti-sedimentation pump (13) and injected into the granulation tank (3) in the direction of vortex through pipes of different heights for further filtration. The water column flow rate in the granulation tank (3) is gradually reduced from high to low through the pipes of different heights.

2. The method for reducing the slag content in circulating water for blast furnace slag treatment according to claim 1, characterized in that, The water at the bottom of the collection tank (7) is drawn by the anti-sedimentation pump (13) and injected into the granulation tank (3) through pipes at different heights in the direction of the vortex. The specific method is as follows: The direction of the water jet injected into the granulation tank (3) by the anti-deposition pump (13) is the same as the rotation direction of the vortex, and the angle of the water jet injected into the granulation tank (3) by the anti-deposition pump (13) is perpendicular to the central axis of the vortex.

3. The method for reducing the slag content in circulating water for blast furnace slag treatment according to claim 1, characterized in that: The angle of the vortex center axis of the water-slag mixture in the granulation tank (3) is adjusted by controlling the installation angle of the swirl plate (14) so ​​as to induce the water-slag mixture to be discharged into the slag water pipe and then into the dewatering drum (4).

4. The method for reducing the slag content in circulating water for blast furnace slag treatment according to claim 3, characterized in that: The installation angle of the swirl plate (14) is 45°-70°, and the water jet angle injected into the granulation tank (3) by the anti-sedimentation pump (13) is 15°-30°.

5. When the water level of the water-slag mixture in the granulation tank (3) at the bottom of the granulation tower rises to the top of the granulation tower, the water-slag mixture enters the hot water tank (6) through the overflow pipe (5).

6. The method for reducing the slag content in circulating water for blast furnace slag treatment according to claim 1, characterized in that: The water column flow rate injected into the granulation tank (3) from the pipes of different heights gradually decreases from high to low, which is used to control the flow rate of the water-slag mixture in the anti-settling pump (13) from top to bottom to gradually decrease.

7. An apparatus for using the method of reducing the slag content in circulating water for blast furnace slag treatment as described in claim 1, characterized in that: The critical flow velocity of the water-slag mixture that can suspend slag and iron of different particle sizes is obtained based on the Hjulström curve, and the actual flow velocity of the water-slag mixture is controlled based on the critical flow velocity.

8. An apparatus for using the method of reducing the slag content in circulating water for blast furnace slag treatment as described in claim 7, characterized in that: The actual flow velocity of the water-slag mixture should be controlled to be 1.2-1.5 times the critical flow velocity.

9. The method for reducing the slag content in circulating water for blast furnace slag treatment according to claim 7, characterized in that: The actual flow rate is increased by 20%-30% to prevent the deposition of particles of the corresponding size.

10. The method for reducing the slag content in circulating water for blast furnace slag treatment according to claim 7, characterized in that: When the slag and iron particle size is 3-8mm, the actual flow velocity of the water-slag mixture should be controlled at 20-35cm / s.

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