Method and device for multi-stage recycling of waste heat of steel billets in pit-shaped steel piling area

Abstract

The invention provides a multi-stage recycling method and device for waste heat of steel billets in a pit-shaped steel piling area. The device mainly comprises a water storage chamber, a water treatment chamber, a flow control system, a pit-shaped steel stacking area peripheral wall internal heat exchange pipeline, a pit-shaped steel stacking area wall body, a steel stacking area peripheral side wall heat exchange pipeline, sleepers, a steel plate, a steel stacking area bottom heat exchange pipeline, a steam parameter feedback system, a steam turbine, a power generator and a condenser. According to the device, cooling water is sequentially subjected to first-stage preheating heat exchange, second-stage heat storage heat exchange and third-stage overheating heat exchange through a heat exchange pipeline in the wall of the pit-shaped steel stacking area, a heat exchange pipeline at the bottom of the steel stacking area and a heat exchange pipeline on the peripheral side wall of the steel stacking area, and then waste heat of the steel stacking area is subjected to multi-stage recovery; and cooling water is gradually heated into superheated steam capable of being used for power generation. The device is simple, efficient, stable and reliable, and is an effective measure for energy conservation and consumption reduction of ferrous metallurgy enterprises.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and specifically relates to a method and a device for recovering waste heat of continuous casting billets in a steel stacking area. Background Art

[0002] In the steel production process, only a few hot steel billets after continuous casting are suitable for direct hot delivery or hot charging and hot delivery, and then transferred to the rolling mill by conveyor rollers to be rolled into slabs or steel coils. Most continuous casting billets do not meet the conditions for direct hot delivery or hot charging and hot delivery, and need to be stored in the steel pile area to cool naturally to room temperature before subsequent processing.

[0003] The temperature of the billet at the outlet of the continuous casting machine is generally above 800℃, and even the temperature of the billet lifted by the overhead crane to the steel stacking area is usually around 750℃. Therefore, a large amount of waste heat of the billet is wasted in the process of natural cooling of the billet to room temperature. In addition, the slabs stored in the steel stacking area are naturally cooled to room temperature in the air, and the required cooling time is usually more than three days, which also reduces the transportation and flow efficiency of the steel stacking area. Therefore, it is urgent to develop a waste heat recovery system to recycle the huge heat released during the cooling process of the billet in the steel stacking area of ​​the steel plant, and at the same time improve the cooling efficiency of the billet in the steel stacking area.

[0004] Chinese patent CN1010778596A develops a waste heat recovery device for hot steel billets, and builds a waste heat recovery furnace consisting of an input roller, a steel pusher, a furnace body, a furnace chamber, a load-bearing track, a circulating water pipeline, a high-pressure container, and an output roller. The waste heat of the hot steel billets is converted into steam and hot water through the circulating water pipeline for power generation and heating needs. However, this device is limited by the volume of the insulation furnace chamber and cannot be used to stack hot steel billets in large quantities. Chinese patent CN111272000A also develops a slab vaporization cooling device and a slab sensible heat recovery power generation system. This device is constructed by constructing insulation walls and insulation upper covers on four sides, and the insulation walls on four sides form a slab stacking area, and then generate and output steam through the heat exchange pipelines on four sides, recovering huge sensible heat for realizing the circulation recovery of slab sensible heat for power generation. The slab sensible heat recovery power generation system using the slab vaporization cooling device mainly includes five main parts: the vaporization cooling device for slab cooling sensible heat, the drum tank, the waste heat power generation system, the desalted water tank, and the thermal deaerator. Both of the above devices can recycle the waste heat of the steel billet for steam power generation, but both require the reconstruction of the surrounding and upper insulation wall structures in the plant, which is time-consuming and labor-intensive. Summary of the invention

[0005] 1. Key issues to be addressed

[0006] The problem to be solved by this invention is to recycle the waste heat of steel billets in the steel stacking area in a simpler and more efficient way. Based on the idea of ​​recycling the waste heat of steel billets for steam power generation proposed by predecessors, the present invention designs a multi-stage recycling device for waste heat of steel billets in a pit-shaped steel stacking area. By laying heat exchange pipelines in the wall of the pit-shaped steel stacking area, the bottom of the steel stacking area, and the side walls around the steel stacking area in sequence, the cooling water is subjected to a first-level preheating heat exchange, a second-level heat storage heat exchange, and a third-level superheating heat exchange, and then the waste heat of the steel stacking area is recycled in multiple stages, and the water is heated into high-temperature steam that can be used for power generation. The innovative point of this method is that there is no need to rebuild the insulation furnace cavity in the factory building, and only a simple transformation is required on the basis of the existing pit-shaped area. In addition, water is used to recycle the waste heat of steel billets in multiple stages, making full use of the waste heat of steel billets of different qualities in the steel stacking area for steam power generation, creating economic benefits, and recycling water resources, saving energy and protecting the environment.

[0007] 2. Technical solution

[0008] The technical solution of this invention is as follows: a device for multi-stage recovery and utilization of waste heat of steel billets in a pit-shaped steel pile area, which includes: a multi-stage recovery device for waste heat of steel billets in a pit-shaped steel pile area and a waste heat utilization device. The multi-stage recovery device for waste heat of steel billets in a pit-shaped steel pile area is mainly composed of a water storage chamber, a water treatment chamber, a flow control system, and heat exchange pipelines sequentially laid inside the wall of the pit-shaped steel pile area, at the bottom of the steel pile area, and on the side walls around the steel pile area; the waste heat utilization device is mainly a steam power generation device composed of four main parts: a steam parameter feedback system, a steam turbine, a generator, and a condenser. The specific operation process is as follows: the tap water and the condensed water after steam power generation are passed into the water storage chamber, and then the cooling water in the water storage chamber passes through the water treatment chamber to soften it to prevent the impurities in the water from corroding the pipelines, and then the flow control system adjusts the cooling water flow according to the steam parameter feedback; the cooling water flows into the heat exchange pipeline inside the walls of the pit-shaped steel stacking area for primary preheating and heat exchange. At this stage, the cooling water heats up slowly and the water temperature rises slightly; the cooling water after primary preheating then flows into the heat exchange pipeline at the bottom of the steel stacking area for secondary heat storage and heat exchange. At this stage, the cooling water quickly heats up to Steam state; the steam generated after the secondary heat storage is introduced into the heat exchange pipes on the side walls around the steel pile area for tertiary superheating heat exchange, and continues to heat up to become high-temperature and high-pressure superheated steam that can be used for steam power generation; then the steam parameter feedback system continuously monitors the superheated steam parameters, and continuously feeds back the information to the flow control system to adjust the flow, ensuring a continuous and stable output of superheated steam for steam power generation; the superheated steam drives the steam turbine to rotate, and the steam turbine is simultaneously connected to a generator to generate electricity. The steam that has been generated is cooled into liquid water through a condenser, and then introduced into the water storage chamber for circulation.

[0009] The bottom of the pit-shaped steel pile area is paved with crushed stones, sleepers are laid horizontally at equal intervals on the crushed stones, and then a layer of steel plates is laid flat on the sleepers. When in use, a crane places the hot steel billet on the steel plate.

[0010] The heat exchange pipelines inside the walls around the pit-shaped steel stacking area are used to recover the heat retained in the wall due to the radiation from the steel stacking area indirectly passing through the side wall heat exchange tubes, and then perform primary preheating heat exchange on the cooling water in the heat exchange tubes; the heat exchange pipelines at the bottom of the steel stacking area are close to the bottom steel plate and are laid at the distance between the sleepers. This part of the heat exchange pipeline mainly recovers the waste heat of the steel billet by heat conduction. The heat conduction has a higher speed and efficiency than the waste heat recovery in the form of thermal radiation. The preheated cooling water is subjected to secondary heat storage and heat exchange to quickly heat the cooling water to a steam state; the side wall heat exchange pipelines around the steel stacking area are used to recover the heat directly radiated by the hot steel billets in the steel stacking area, and the steam that has undergone the secondary heat storage and heat exchange is subjected to tertiary superheating heat exchange, so that the steam can reach the temperature and pressure requirements for steam power generation; and check valves are installed between the three parts of the heat exchange pipelines to prevent backflow.

[0011] Cooling water flows into the first-level preheating heat exchange pipeline inside the walls around the pit-shaped steel stacking area and the third-level superheating heat exchange pipeline on the side walls around the steel stacking area from the downcomer and flows out from the upcomer.

[0012] Fins are installed on the outside of the heat exchange tubes. Installing the fins can increase the heat exchange area and improve the waste heat recovery and heat transfer efficiency.

[0013] The steam parameter feedback system mainly continuously monitors the pressure, temperature and flow parameters of the superheated steam.

[0014] The top of the pit-shaped steel stacking area can be covered with a thermal insulation curtain as needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of a multi-stage recovery and utilization device for waste heat of steel billets in a pit-shaped steel pile area;

[0016] Figure 2 This is a diagram of the internal device structure of the pit-shaped steel pile area;

[0017] The components in the attached drawings are marked as follows: 1 is a water storage chamber; 2 is a water treatment chamber; 3 is a flow control system; 4 is a heat exchange pipeline inside the walls around the pit-shaped steel stacking area; 5 is a wall of the pit-shaped steel stacking area; 6 is a heat exchange pipeline on the side walls around the steel stacking area; 7 is a sleeper; 8 is a steel plate; 9 is a heat exchange pipeline at the bottom of the steel stacking area; 10 is a steam parameter feedback system; 11 is a steam turbine; 12 is a generator; and 13 is a condenser. DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with the accompanying drawings through specific implementation cases so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these implementation methods is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0019] Examples

[0020] The method and device of the present invention are specifically described in conjunction with the accompanying drawings: a method for multi-stage recovery and utilization of waste heat of steel billets in a pit-shaped steel pile area, which recovers waste heat of steel billets in multiple stages through heat exchange pipelines sequentially laid inside the wall of the pit-shaped steel pile area, at the bottom of the steel pile area, and on the side walls around the steel pile area to generate superheated steam to drive the steam turbine for steam power generation, efficiently recover waste heat of steel billets, create economic benefits, recycle water resources, and save energy and protect the environment. The specific steps are:

[0021] S1. When a crane hoists a batch of new hot steel billets onto the steel plate (8) laid flat at the bottom of the pit-shaped steel pile area, the temperature of the steel billets is still maintained at 650°C; tap water and condensed water after steam power generation are introduced into the water storage chamber (1) for mixing, and then the cooling water flows through the water treatment chamber (2) for softening treatment. Because there are many impurities in tap water and circulating condensed water, softening treatment can reduce equipment corrosion and pipe blockage.

[0022] S2. The softened cooling water flows through the flow control system (3) and then flows into the heat exchange pipes (4) inside the walls around the pit-shaped steel pile area. Since the walls (5) around the steel pile area are subjected to heat radiation for a long time, some heat will be stored in the walls. The heat exchange pipes in the walls recover this part of heat and perform primary preheating heat exchange on the cooling water in the heat exchange pipes, so that the cooling water temperature is raised from 25°C to 50°C.

[0023] S3. To store hot steel billets, gravel is laid at the bottom of the pit-shaped steel pile area, sleepers (7) are laid horizontally on the gravel at equal intervals, and then a layer of steel plates (8) are laid flat on the sleepers. When in use, a crane places the hot steel billets on the steel plates (8); the heat exchange pipeline (9) at the bottom of the steel pile area is laid under the bottom steel plate (8) and close to the steel plate (8), located at the spacing of the sleepers (7); the cooling water that has undergone primary preheating and heat exchange continues to flow from the heat exchange pipeline in the wall to the heat exchange pipeline (9) at the bottom of the steel pile area for secondary heat storage and heat exchange. Since the heat transfer mode at this stage is heat conduction, the heat exchange rate is faster, so the cooling water is quickly heated to a steam state, and the steam temperature generated is 150°C and the pressure is 1.5±0.02MPa;

[0024] S3. The high-temperature steam after the secondary heat storage and heat exchange is introduced into the heat exchange pipes (6) on the side walls of the steel pile area for the third stage of superheating heat exchange. This stage is used to recover the heat radiated directly from the hot steel billets in the steel pile area to the surrounding areas. The steam is further heated to superheated steam that can be used for power generation. The superheated steam temperature is 200°C and the pressure is 2.0±0.02MPa.

[0025] S4. Continuously monitor the temperature, pressure, flow rate and other information of the superheated steam generated through the steam parameter feedback system (10), and feed back to the flow control system (3), and adjust the cooling water flow rate to ensure the continuous and stable output of the superheated steam used for steam power generation;

[0026] S5. After the superheated steam flows through the steam parameter feedback system (10) to monitor the parameters, it drives the steam turbine (11) to rotate and operate. The steam turbine is simultaneously connected to the generator (12) to generate steam power. The steam generated by the steam power generation then flows through the condenser (13) for cooling. The steam is cooled to liquid cooling water and circulates to the water storage chamber (1) for recycling, which can save a lot of water resources.

[0027] In addition, cooling water flows into the downcomer from the first-level waste heat exchange pipeline inside the walls around the pit-shaped steel stacking area and the third-level superheat heat exchange pipeline on the side walls around the steel stacking area, and flows out from the riser; fins are installed on the outer walls of the heat exchange pipelines to increase the heat exchange area and improve the heat exchange rate; the top of the pit-shaped steel stacking area can be covered with an insulation curtain as needed.

[0028] The above is only an embodiment of the present invention with better effects, and is not intended to limit the scope of the present invention. Any simple deformation or equivalent transformation made by any technician based on the content of the present invention, or directly or indirectly applied in other related technical fields, is included in the scope of the present invention.

Claims

1. A multi-stage recovery and utilization device for waste heat of steel billets in a pit-shaped steel pile area, characterized in that: The device mainly comprises a water storage chamber (1), a water treatment chamber (2), a flow control system (3), heat exchange pipes inside the walls around the pit-shaped steel pile area (4), the wall of the pit-shaped steel pile area (5), heat exchange pipes on the side walls around the steel pile area (6), sleepers (7), steel plates (8), heat exchange pipes at the bottom of the steel pile area (9), a steam parameter feedback system (10), a steam turbine (11), a generator (12), and a condenser (13). By sequentially laying hot water exchange pipes inside the walls of the pit-shaped steel pile area, at the bottom of the steel pile area, and on the side walls around the steel pile area, the cooling water is subjected to primary preheating heat exchange, secondary heat storage heat exchange, and tertiary superheating heat exchange, and then the waste heat of the steel pile area is recovered in multiple stages, and the cooling water is heated into superheated steam for power generation.

2. The device for multi-stage recovery and utilization of waste heat of steel billets in a pit-shaped steel pile area according to claim 1 is characterized in that: The heat exchange pipeline (4) inside the wall of the pit-shaped steel pile area recovers the heat stored in the wall of the steel pile area for a long time, and performs primary preheating heat exchange on the cooling water in the heat exchange pipe, so that the cooling water temperature is increased from 25°C to 50°C; the heat exchange pipeline (9) at the bottom of the steel pile area performs secondary heat storage heat exchange through heat conduction, and the preheated cooling water is quickly heated to water vapor, the steam temperature is 150°C, and the pressure is 1.5±0.02MPa; the heat exchange pipeline (6) on the side walls around the steel pile area is used to recover the heat directly radiated by the hot steel billets in the steel pile area, and performs tertiary superheating heat exchange on the water vapor, and the high-temperature water vapor is quickly heated to superheated steam that can be used for power generation, the superheated steam temperature is 200°C, and the pressure is 2.0±0.02MPa.

3. The device for multi-stage recovery and utilization of waste heat of steel billets in a pit-shaped steel pile area according to claim 1 is characterized in that: Check valves are installed between the three parts of the heat exchange pipelines, namely, the heat exchange pipelines (4) inside the walls around the pit-shaped steel pile area, the heat exchange pipelines (9) at the bottom of the steel pile area, and the heat exchange pipelines (6) on the side walls around the steel pile area, to prevent backflow; fins are installed on the outside of the heat exchange tubes to increase the heat exchange area and improve the heat exchange efficiency.

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