CN114833207A - Process method for isothermal treatment and waste heat recovery after strip steel rolling - Google Patents
Process method for isothermal treatment and waste heat recovery after strip steel rolling Download PDFInfo
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- CN114833207A CN114833207A CN202210601198.3A CN202210601198A CN114833207A CN 114833207 A CN114833207 A CN 114833207A CN 202210601198 A CN202210601198 A CN 202210601198A CN 114833207 A CN114833207 A CN 114833207A
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- molten salt
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
- B21B45/0218—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for strips, sheets, or plates
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
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- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
The invention provides a process method for isothermal treatment and waste heat recovery after strip steel rolling, which is characterized in that high-temperature molten salt is adopted to replace aqueous media of laminar cooling and ultra-fast cooling, the rolled strip steel is cooled by utilizing the physical properties of high specific heat, good fluidity and strong heat exchange capability of the high-temperature molten salt, the temperature range of the molten salt is controlled to be 750 ℃, the cooling process is adjusted according to strip steel control, and the process requirement of strip steel variety development is met. The other innovation point of the invention is that the recovery of the waste heat after the rolling of the strip steel solves the problems of periodic operation of steel rolling and discontinuous output of a heat source, the heat of the hot-rolled strip steel is stored by adopting a molten salt energy storage mode, and the steam is output to the outside in a centralized manner to generate electricity, so that the recovery and the utilization of the waste heat after the rolling of the strip steel are realized.
Description
Technical Field
The invention provides a process method for isothermal treatment and waste heat recovery after strip steel rolling, belonging to the field of steel rolling and steel waste heat recovery. The molten salt has good thermal conductivity, viscosity and fluidity, so that the cooling speed is high, the cooling process is stable, the fluctuation control of the transverse final cooling temperature of the strip steel can be realized, the temperature difference between the head and the tail of the strip steel after final cooling can be reduced, and the uniformity of the structure performance of the strip steel is improved. Meanwhile, the invention realizes the recovery of the waste heat after the strip steel is rolled, is an efficient, low-carbon and energy-saving cooling control mode, and is very suitable for variety development and equipment upgrading of hot rolled strip steel and medium plate factories.
Background
The controlled rolling and controlled cooling process of steel is always the key point of industrial research, wherein controlled cooling after rolling plays a decisive role in the structure performance of hot rolled products. In the hot continuous rolling production process, the cooling process after the strip steel is rolled seriously influences the product structure performance, and meanwhile, the cooling mode, the stability of the cooling process and the guarantee capability of cooling equipment become key factors influencing the product quality and are the main key direction of the current hot rolling mill. Meanwhile, steel mills pay more attention to energy conservation in the steel production process, and the recovery of waste heat after steel rolling becomes a flow of key attention.
At present, the post-rolling controlled cooling mode of the hot rolled strip steel is basically water cooling, and the ultra-fast cooling proposed by northeast university and the laminar cooling of Beijing technology university are relatively mature and widely applied. The two cooling modes adopt a high-pressure water jet mode to achieve the purpose of cooling the surface of the hot-rolled strip steel. The technology is widely applied to the production process of a plurality of plate coils and medium plates such as automobile plates, pipeline steel, weathering steel, mechanical steel and the like.
In the conventional laminar cooling of the hot continuous rolling, a cooling area behind a finish rolling stand of the strip steel consists of an upper collecting pipe and a lower collecting pipe, the water amount of a single collecting pipe is manually and automatically controlled, the water spraying amount of the upper collecting pipe and the lower collecting pipe is calculated according to the strip steel speed, the coiling temperature and the like, and the whole controlled cooling process is completed.
The ultra-fast cooling adopts a jet flow impact cooling mode, and adopts a water source with the pressure of 0.3-0.8MPa as jet flow water to ensure the cooling effect on the strip steel. In the existing ultra-fast cooling operation process, the water hammer effect caused by the inertia of medium-pressure water flow can not be avoided all the time, and meanwhile, the effect of damaging cooling equipment is caused.
To two kinds of traditional cooling methods, laminar flow cooling pressure is low, adopts high flush tank to supply water, and the cooling water supplies to laminar flow cooling device under the effect of dead weight, and water pressure ratio is more stable, and high flush tank possesses the water storage function of transferring flows simultaneously, and water process energy consumption is lower. The pressure of the ultra-fast cooling water is high, and a water pump is generally adopted for directly supplying water. At present, the domestic controlled cooling after rolling of the strip steel basically adopts the two modes, and the method plays a great promoting role in the development of the industry. With the requirement of users on the improvement of product quality, the content of various steel alloys is improved, especially ultra-wide, ultra-thick and ultra-thin products are developed, the potential of a laminar cooling and ultra-fast cooling water cooling mode in the aspect of cold control reaches the limit, the potential reaches the limit in the aspects of structural performance uniformity control, head-to-tail temperature difference, transverse temperature control and plate type control, and the limitation of a water cooling process is exposed on products such as high-grade pipeline steel, automobile plates and weather-resistant steel.
The invention provides a device and a method for controlling cooling and waste heat recovery of rolled strip steel, which are characterized in that high-temperature molten salt is adopted to replace aqueous media of laminar cooling and ultra-fast cooling, the rolled strip steel is cooled by utilizing the physical properties of high specific heat, good fluidity and strong heat exchange capacity of the high-temperature molten salt, the temperature range of the molten salt is controlled to be 750 ℃ and the adjustment is carried out according to the process for controlling cooling of the strip steel. In order to enhance the requirement of molten salt on the rapid cooling of the strip steel, the strip steel is subjected to impingement cooling in a molten salt spraying mode, and the cooling process range of the strip steel is expanded to the maximum extent. The invention has another innovation point that the waste heat of the rolled strip steel is recovered, the molten salt is used as an energy storage material and has very good energy storage characteristic, and after the high-temperature hot rolled strip steel is cooled and subjected to heat exchange, the heat is absorbed by the molten salt and is stored in the high-temperature salt tank, so that the problems of periodic operation of steel rolling and discontinuous output of a heat source are solved.
Disclosure of Invention
The invention provides a process method for isothermal treatment and waste heat recovery after strip steel rolling, which adopts molten salt fluid impingement cooling to replace the traditional process method of high-pressure water ultrafast cooling and laminar cooling, realizes controlled cooling after strip steel rolling, and simultaneously realizes the recovery of waste heat after rolling by utilizing the energy storage characteristic of molten salt. The apparatus arrangement comprises: the molten salt cooling tank, the molten salt isothermal tank, the molten salt input pipeline, the molten salt output pipeline, the molten salt shower, high temperature storage salt jar, low temperature storage salt jar, the molten salt pump, the feed pump, the pre-heater, the evaporative cooler, the over heater, the re-heater, the steam turbine, the generator, deslagging system, dust pelletizing system.
Preferably, a molten salt pump on the low-temperature salt storage tank is started to input molten salt into the molten salt cooling tank through a molten salt input pipeline, the requirement of the temperature process strip steel production process of the molten salt cooling tank is adjusted within the range of 750 ℃ of 100-. The strip steel is cooled according to a preset process, heat is absorbed by fused salt and then stored in a high-temperature salt storage tank, an output fused salt pump is arranged in the high-temperature salt storage tank to lead out the high-temperature fused salt to enter an evaporator, heat output is completed in the evaporator to generate high-variety steam for discharging and generating electricity, waste heat recovery is realized, the evaporator is connected with a low-temperature fused salt tank and is used for storing low-temperature fused salt after heat exchange, the low-temperature fused salt tank is designed with the output salt pump to be connected with the fused salt cooling tank and the fused salt spray pipe, and cooling and waste heat recovery after strip steel rolling are realized.
Preferably, one molten salt cooling tank can be designed, and 2-3 or a plurality of molten salt cooling tanks can be designed according to the requirements of process and production line variety development. The roller way is arranged in the cooling tank, the cooling tank is provided with a molten salt spray pipe, and the flow control in the width direction and the control of the flow field and the temperature field of the cooling tank are realized through the spray pipe, so that the immersed and non-immersed impact cooling of the strip steel is realized. The roller way in the cooling tank can perform variable-frequency speed regulation within the range of 0.1-2m/s, and can also perform reciprocating motion transmission, so as to control the stay time of the strip steel in the molten salt cooling tank and discharge the strip steel out of the molten salt cooling tank after the process requirements are met.
Preferably, the top of the cooling tank is provided with a heat-insulating cover, the heat-insulating cover is provided with a dust-removing hole, the dust-removing hole is externally connected with a spray tower and an axial flow fan, the molten salt cooling tank is guaranteed to be in negative pressure during working, and the requirements on dust removal of the cooling tank and environmental protection of a factory building are met. The diameter of the dust removal hole on the heat preservation cover is at 1000 manges 1500mm, and dust exhausting fan's amount of wind is at 20 ten thousand meters, guarantees the negative pressure of fused salt cooling bath, and the gas wash tower design is outside the factory building, and the top design has spray set, carries out wet dedusting to the flue gas of collecting, and spray water can recycle, carries out salt and water separation after the concentration reaches certain standard.
Preferably, the molten salt flows into the high-temperature salt storage tank after the cooling tank finishes cooling and heat exchange with the strip steel, and the cooling tank and the isothermal tank are both provided with a precipitation pit and a slag filtering device. The molten salt cooling tank realizes cooling and heat exchange of the rolled strip steel, the flow of the sprayed molten salt is in 1500m and 1000 + year, the liquid level of 200mm is formed, and the immersed impact cooling of the strip steel can be realized. And simultaneously, in order to strengthen the flexibility of process control, an outlet valve of the fused salt outflow channel is designed, and the liquid level is adjusted. The fused salt amount that the salt tank design was produced the ability 3-7 times hour steel rolling, and the salt tank design simultaneously has the precipitation hole for the buffer memory of fused salt and the deposit of iron scale, and the precipitation hole can be arranged respectively in the front of salt tank, well back to arrange the filter screen in the precipitation hole, conveniently regularly take out the clearance.
Preferably, the bottom and the side of the salt tank are provided with a plurality of holes and connecting pipelines, so that the molten salt can automatically flow into the high-temperature salt storage tank. The design of the holes takes the circulating amount of the molten salt in the cooling groove into consideration, the outward discharge capacity of 1500m cultivation is guaranteed at 1000-.
Preferably, the high-temperature and low-temperature salt storage tanks are designed with heat insulation systems, the walls of the salt storage tanks are designed into three layers, the inner layer is made of heat-resistant stainless steel, the middle layer is vacuumized, the outer layer is made of carbon structural steel and is integrally insulated by aluminum silicate, the outermost layer is provided with a galvanized plate, and the temperature is controlled within 45 ℃ so as to achieve the purposes of equipment heat dissipation and waste heat recovery.
Preferably, the high-temperature salt storage tank and the low-temperature salt storage tank are both designed with tubular electric heating systems, and the submerged salt pump is arranged at the top of the tank to realize the output of the molten salt. The heating power of the salt storage tank is designed to be 400-600kw, the lift of the salt pump is 20m, and the hourly circulation rate is 80-120m for carrying out the year.
Preferably, an evaporator and a molten salt heat exchanger are designed between the high-temperature salt storage tank and the low-temperature salt storage tank, molten salt in the high-temperature salt storage tank is input into the evaporator and the molten salt heat exchanger through a salt pump, the shell pass of the molten salt is led away, superheated steam and water are led away from the tube pass, the molten salt heat exchanger is connected with a steam drum, high-pressure steam is output outwards to generate power or be connected to the grid, the pressure of the steam is adjustable between 2.0 and 3.5MPa, and the residual steam is connected to the grid to realize waste heat recovery.
Preferably, high-pressure steam generated by the system is introduced into the molten salt cooling tank and the molten salt isothermal tank, and a blowing device of the high-pressure steam is formed on the upper surfaces of the inlet and the outlet of the molten salt cooling tank and the molten salt isothermal tank to seal the molten salt from overflowing out of the molten salt cooling tank or the molten salt isothermal tank along with the strip steel.
Preferably, the fused salt input pipelines of the fused salt cooling tank and the fused salt isothermal tank are 200mm higher than the bottom of the fused salt tank, a precipitation pit, a salt release hole and a valve are designed at the bottom, the salt release hole is communicated with the low-temperature salt storage tank, when the operation is stopped, the fused salt flows back to the low-temperature salt storage tank, and the iron oxide scale enters the precipitation pit for centralized treatment.
The invention has the beneficial effects that:
the invention provides a device and a method for controlling cooling and waste heat recovery after strip steel is rolled, which provide a way for cooling strip steel by high-temperature molten fluid compared with laminar cooling and ultra-fast cooling processes. The laminar cooling and the ultra-fast cooling are limited by the temperature of a water cooling medium in the process of realizing the strip steel cooling, the final cooling temperature fluctuates greatly, the problems of cold impermeability and supercooling are easy to occur, and thermodynamic and kinetic conditions for isothermal transformation of the strip steel cannot be provided after the final cooling. According to the isothermal temperature and time, the strip steel generates pearlite phase transformation, bainite phase transformation, martensite phase transformation and the like, and provides tool guarantee for the development of composite structure steel types such as dual-phase steel, DP steel, TRIP steel, TWINP steel and the like.
Meanwhile, energy storage material fused salt is adopted to replace water to serve as a cooling medium of the strip steel, the recovery of the waste heat of the strip steel is realized, the fused salt has a high heat storage temperature range, stable heat storage capacity, high-variety steam output capacity and continuous heat output capacity compared with water, the rolled waste heat in the periodic and intermittent strip steel production process is converted into the energy storage of a fused salt tank, continuous and high-variety steam is output through a heat exchange system, the concept of energy saving and low carbon in the strip steel production is finally realized, and the method is very suitable for the current strip steel plant to carry out variety development and energy saving project upgrading transformation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic view of controlled cooling and waste heat recovery after rolling of strip steel according to the present invention.
Fig. 2 is a flow chart of waste heat recovery according to the present invention.
The system comprises a 1-molten salt cooling tank, a 2-molten salt isothermal tank, a 3-high temperature salt storage tank, a 4-low temperature salt storage tank, a 5-molten salt pump, a 6-molten salt pump, a 7-water feed pump, an 8-preheater, a 9-evaporative cooler, a 10-superheater, a 11-reheater, a 12-steam turbine, a 13-generator and a 14-condenser.
Detailed Description
The invention provides a method for cooling rolled strip steel and recovering waste heat based on molten fluid isothermal treatment. The apparatus arrangement comprises: the system comprises a molten salt cooling tank, a molten salt isothermal tank, a molten salt spraying system, a molten salt spraying pipe, a high-temperature salt storage tank, a high-temperature salt pump, a low-temperature salt storage tank, a molten salt heat exchange system, a deslagging system and a dust removal system.
Specific parameters of the apparatus
Serial number
Device name
Parameter(s)
1
Length of molten salt cooling tank 1
20m
2
Length of molten salt isothermal tank 2
20m
3
High temperature salt storage tank volume
800m³
4
Volume of low-temperature salt storage tank
1000m³
5
Molten salt circulation capacity
1800m³/h
6
Temperature range of molten salt
100-750℃
7
Power generation capacity
20MW/h
8
Heating power of salt storage tank
2600KW/h
9
Supplying power
380V、4000Kw
10
Dust removal effect
20mg/m³
11
Purity of fused salt after slag removal
99%
The rolled strip steel enters a molten salt cooling tank for cooling through roller way transmission, the requirement of the temperature process strip steel production process of the molten salt cooling tank is adjusted within the range of 750 ℃ of 100 plus materials, the strip steel cooling mode is divided into an immersion type and a non-immersion type, the strip steel surface is cooled through a molten salt spray pipe, the strip steel is cooled according to the preset process, heat is absorbed by the molten salt and then stored in a high-temperature salt storage tank, an output salt pump is arranged in the high-temperature salt storage tank to lead the high-temperature molten salt out to enter a molten salt heat exchanger, the molten salt heat exchanger completes heat output to generate high-variety steam for external discharge power generation to realize waste heat recovery, the molten salt heat exchanger is connected with a low-temperature molten salt tank for storing the low-temperature molten salt after heat exchange, and the low-temperature molten salt tank is provided with an output salt pump connected with the molten salt cooling tank and the molten salt spray pipe to realize cooling and waste heat recovery after rolling of the strip steel.
The molten salt cooling tank is designed to be 2, cooling tank and isothermal tank. The roller way is arranged in the tank, the molten salt spray pipe is arranged in the cooling tank, and the liquid level is controlled through the spray pipe, so that the immersed and non-immersed impact cooling of the strip steel is realized. The roller way in the cooling tank can perform variable-frequency speed regulation within the range of 0.1-2m/s, and can also perform reciprocating motion transmission, so as to control the stay time of the strip steel in the molten salt cooling tank and discharge the strip steel out of the molten salt cooling tank after the process requirements are met.
The design of cooling bath top has the heat preservation lid, and the heat preservation lid design has the dust removal hole, and dust removal hole allies oneself with spray column and axial fan outward, guarantees that fused salt cooling bath during operation is the negative pressure, reaches the requirement to cooling bath dust removal and factory building environmental protection. The diameter of the dust removal hole on the heat preservation cover is at 1000-.
And after the molten salt cooling tank finishes cooling and heat exchange of the strip steel, the molten salt flows into the high-temperature salt storage tank, and the salt tank is provided with a precipitation pit and a slag filtering device. And carrying out cooling and heat exchange on the rolled strip steel by the molten salt cooling tank, carrying out 1500m thin film evaporation and high-flow salt transportation pump of the low-temperature salt storage tank, and forming a liquid level of 150 thin film evaporation and 200mm above a roller way in the salt tank by combining the sprayed molten salt flow with the high-flow salt transportation pump of the low-temperature salt storage tank, so that the immersed impact cooling on the strip steel can be realized. Meanwhile, the flow and the injection angle of the spray pipe are adjusted for the flexibility of strengthening process control, the molten salt spray amount at the edge, the quarter and the middle in the width direction is controlled, the temperature difference is reduced, and the uniformity of the structure performance and the plate shape are improved.
The bottom and the side of the salt tank are provided with a plurality of holes which are connected with pipelines, so that the molten salt can automatically flow into the high-temperature salt storage tank. The design of the holes considers the circulation amount of the molten salt in the cooling groove, the outward discharge capacity of the 1500m thin-walled cultivation is guaranteed at 1000-.
The high-temperature and low-temperature salt storage tank is designed with a heat insulation system, the wall of the salt storage tank adopts a three-layer design, the inner layer is made of heat-resistant stainless steel, the middle layer is vacuumized, the outer layer is made of carbon structural steel, the outer layer is subjected to integral heat insulation by adopting aluminum silicate, a galvanized plate is added on the outermost layer, and the temperature is controlled within 45 ℃.
The high-temperature salt storage tank and the low-temperature salt storage tank are both designed with tubular electric heating systems, and submerged salt pumps are arranged on the top of the tanks to realize the output of molten salt. The heating power of the salt storage tank is designed to be 400-600kw, the number of the salt pumps is 20, the lift is 20m, and the hourly circulation rate is 80-120m during the high-speed cultivation.
A fused salt heat exchanger is designed between the high-temperature salt storage tank and the low-temperature salt storage tank, fused salt in the high-temperature salt storage tank is input into the fused salt heat exchanger through a salt pump, the fused salt flows away from a shell pass of the fused salt heat exchanger, superheated steam and water flow away from a tube pass, the fused salt heat exchanger is connected with a steam drum and outputs high-pressure steam to the outside to perform power generation or steam grid connection, the pressure of the steam is adjustable between 2.0 and 3.5MPa, and waste heat recovery is realized.
Example 1
The invention provides a device and a method for cooling after rolling strip steel and recovering waste heat, wherein the device and the method realize the controlled cooling after rolling the strip steel by adopting the molten salt fluid impingement cooling to replace the traditional process method of high-pressure water ultrafast cooling and laminar cooling, and simultaneously realize the recovery of the waste heat after rolling by utilizing the energy storage characteristic of molten salt. The invention is applied to the cold-rolling transformation of hot rolled strip steel production line and the development process of DP steel.
Steel grades that can be developed such as table
Steel grade
Stands for steel grade
Carbon structural steel
Q195 Q275
High-quality carbon structural steel
08、08Al、10~45、65Mn
Low alloy structural steel
Q345 Q460
Low-alloy high-strength structural steel plate
Q500D/E、Q550D/E、Q620D/E、Q690D/E
Steel plate for engineering machinery
A681, StE460, HITEN540 SA-780 LE, etc
Wear-resistant steel plate
NM360, NM400, etc
Steel plate for building structure
Q460GJ C/D/E
Steel for automobile beam
16MnL、16MnReL、10TiL、LG510L
Structural steel for bridge
Q235q、Q345q
Steel for pressure vessel and boiler
16Mng、20Mng、20g、09MnNiDR13、12MnNiVR、15CrMoR、12CrMoVg、15CrMog
Structural steel for ship
A、B、D、A32、A36
Pipeline steel
S290～S555
Molten salt cooling tank and isothermal tank process for typical steel grades
Pipeline steel
Automobile beam steel
Engineering machinery steel
Hull steel
Bridge steel
Molten salt cooling tank
650-750℃
670-720℃
670-720℃
650-750℃
670-720℃
Molten salt isothermal tank
300-400℃
150-250℃
240-360℃
400-500℃
400-500℃
The strip steel is cooled to a ferrite phase transition region through the cooling of the molten salt cooling tank, the content of ferrite is controlled through controlling the residence time of the molten salt cooling tank, then the strip steel enters the isothermal tank to carry out the next step of structure transformation, the unconverted austenite provides thermodynamic and kinetic conditions, and martensite phase transformation, bainite phase transformation and pearlite phase transformation occur, so that the process requirements of different varieties are met.
Table typical steel grade pattern control and texture property fluctuation
Pipeline steel
Automobile beam steel
Engineering machinery steel
Hull steel
Bridge steel
Tissue fluctuations
±5%
±5%
±5%
±5%
±5%
Performance fluctuations
±20MPa
±25MPa
±30MPa
±20MPa
±25MPa
Transverse unevenness
2mm/m
3mm/m
2.5mm/m
2.2mm/m
4mm/m
Longitudinal unevenness
2mm/m
3mm/m
2.5mm/m
2.5mm/m
3mm/m
Sickle bend
3mm/12m
4mm/12m
3.5mm/12m
3.3mm/12m
3mm/12m
The invention replaces laminar cooling, can meet the variety development requirement and waste heat recovery of a strip steel mill, and has the specification coverage range of products as follows:
thickness of the strip steel: 1.2-25.4 mm;
width of the strip steel: 900 to 2130 mm
The inner diameter of the steel coil is as follows: 762 mm
The external diameter of the steel coil: max.2100mm min.1200mm
The quality of the steel coil is as follows: max.38t
Mass per unit width: max.22kg/mm
Transverse cutting middle plate
Thickness of the steel plate: 4.0-25.4 mm
Width of the steel plate: 850 to 2130 mm
Length of steel plate: 2000-16000 mm
Meter waste heat power generation system parameter
Parameter(s)
High-temperature salt storage tank
Volume 800m for harvest
Low-temperature molten salt tank
Volume 950m full bloom
Salt pump
20, single hourly flow rate 150m
Evaporator with a heat exchanger
Hourly steam production of 40t
Fused salt
Adopts mixed salt of nitrite, nitrate and carbonate, the melting point is 90 DEG C
Generator set
The steam turbine steam inlet parameter of the power generation sub-group is 8MPa with the maximum high-pressure parameter, the steam inlet enthalpy h0 is 3200 kJ/kg, the steam turbine internal efficiency is 0.8, the actual steam exhaust enthalpy hc of the steam turbine is 2200 kJ/kg, and the power generation power of the steam turbine is calculated to be 30 MW.
Low pressure steam
2.0-3.0MPa, and is merged into a heating power pipe network after temperature and pressure reduction
The annual output of the steel coil is 441 ten thousand tons, the transverse cutting middle plate is 50 ten thousand tons, the hot rolling comprehensive yield is 98 percent, the annual waste heat recovery heat power is converted into 8000 ten thousand yuan RMB, and the steel coil becomes a typical online heat treatment and high-efficiency energy-saving strip steel production line.
Comparative example 1
The traditional laminar flow cooling hot rolling production line comprises high and medium steel and alloy steel, carbon structural steel, low alloy high-strength steel, IF steel, high weather-resistant structural steel, pipeline steel, hot rolling dual-phase steel and the like. Thickness of strip steel in specification coverage range: 1.2-25.4 mm; width: 900 to 2130 mm.
Control of plate type and structural property fluctuation of typical steel grade of surface conventional laminar cooling
Pipeline steel
Automobile beam steel
Engineering machinery steel
Hull steel
Bridge steel
Tissue fluctuations
±10%
±10%
±10%
±15%
±10%
Performance fluctuations
±30MPa
±35MPa
±40MPa
±30MPa
±30MPa
Transverse unevenness
4mm/m
4mm/m
3mm/m
5mm/m
5mm/m
Longitudinal unevenness
4mm/m
5mm/m
5mm/m
4mm/m
5mm/m
Sickle bend
5mm/12m
6mm/12m
4mm/12m
5mm/12m
6mm/12m
The annual output of the steel coil is 450 ten thousand tons, the middle plate of the transverse cutting is 60 ten thousand tons, the probability of disqualification of the laminar cooling plate is increased, in addition, the performance is disqualified due to the unstable cooling process, the comprehensive yield of the hot rolling is 97 percent, and the waste heat recovery after the rolling cannot be realized.
Comparative example 2
The production line for ultra-fast cold and hot rolling comprises high and medium steel and alloy steel, carbon structural steel, low-alloy high-strength steel, IF steel, high weather-resistant structural steel, pipeline steel, hot-rolled dual-phase steel and the like. Thickness of strip steel in specification coverage range: 1.2-25.4 mm; width: 900 to 2130 mm.
Plate type control and structure property fluctuation of ultra-fast cooling typical steel grade
Pipeline steel
Automobile beam steel
Engineering machinery steel
Hull steel
Bridge steel
Tissue fluctuations
±15%
±15%
±15%
±15%
±15%
Performance fluctuations
±35MPa
±40MPa
±45MPa
±35MPa
±35MPa
Transverse unevenness
5mm/m
4mm/m
4mm/m
6mm/m
6mm/m
Longitudinal unevenness
5mm/m
5mm/m
5.5mm/m
5mm/m
6mm/m
Sickle bend
6mm/12m
7mm/12m
5mm/12m
6mm/12m
7mm/12m
The annual output of the steel coil is 430 ten thousand tons, the middle plate is transversely cut by 60 thousand tons, the probability of disqualification of the plate shape due to ultra-fast cooling is increased, in addition, the performance is disqualified due to unstable cooling process, the comprehensive yield of hot rolling is 96%, and the waste heat recovery after rolling cannot be realized.
Item
Recovery of heat energy
Recovery rate of heat energy
Target strip properties
Example 1
30Mw
60%
Stabilization
Comparative example 1
0
0
Instability, abnormal tissue and pattern problems
Comparative example 2
0
0
Compared with products developed by a conventional laminar cooling and ultra-fast cooling production line, the structural performance uniformity and the plate shape control of the products developed by the invention are greatly improved, and the recycling of the waste heat after rolling is realized.
Claims (10)
1. A process method for isothermal treatment and waste heat recovery after rolling of strip steel is characterized in that the traditional process method of high-pressure water ultrafast cooling and laminar cooling is replaced by molten salt fluid impingement cooling, so that cold control after rolling of strip steel is realized, and meanwhile, the energy storage characteristic of molten salt is utilized to realize recovery of waste heat after rolling, and the equipment device comprises: the molten salt cooling tank, the molten salt isothermal tank, the molten salt input pipeline, the molten salt output pipeline, the molten salt shower, high temperature storage salt jar, low temperature storage salt jar, the molten salt pump, the feed pump, the pre-heater, the evaporative cooler, the over heater, the re-heater, the steam turbine, the generator, deslagging system, dust pelletizing system.
2. The process method for the isothermal treatment and the waste heat recovery after the rolling of the strip steel as claimed in claim 1, wherein a molten salt pump on a low-temperature salt storage tank is started to input molten salt into a molten salt cooling tank through a molten salt input pipeline, the molten salt overflows to a molten salt output pipeline to enter a high-temperature salt storage tank after being filled with a certain liquid level, the strip steel is conveyed to the molten salt cooling tank through a roller way to be cooled after passing through a finishing mill, the strip steel cooling mode is divided into an immersion mode and a non-immersion mode, the surface of the strip steel is cooled through a molten salt spray pipe, the strip steel is cooled according to a preset process, heat is absorbed by the molten salt and then stored in the high-temperature salt storage tank, an output molten salt pump is arranged in the high-temperature salt storage tank to lead the high-temperature molten salt out to enter an evaporator, the evaporator completes heat output to generate high-variety steam for discharging power generation, waste heat recovery is realized, the evaporator is connected with the low-temperature salt storage tank for storing the low-temperature molten salt after heat exchange, the low-temperature molten salt tank is provided with an output salt pump connected with the molten salt cooling tank and the molten salt spray pipe, so that the cooling and waste heat recovery after the strip steel is rolled are realized.
3. The process method for isothermal treatment and waste heat recovery after strip steel rolling according to claim 1, wherein a roller way is arranged in a molten salt cooling tank, molten salt spray pipes are arranged in the cooling tank, and the cooling uniformity of the strip steel in the transverse direction is controlled by the number of spray pipe nozzles.
4. The process method for isothermal treatment and waste heat recovery after rolling of strip steel as claimed in claim 1, wherein the cooling tank is designed with a heat-insulating cover, the heat-insulating cover is designed with a dust-removing hole, and the dust-removing hole is externally connected with a spray tower and an axial flow fan, so as to ensure that the molten salt cooling tank is in negative pressure during working, and meet the requirements of dust removal of the cooling tank and environmental protection of plants.
5. The process method for isothermal treatment and waste heat recovery after rolling of the strip steel as claimed in claim 1, wherein the strip steel enters a molten salt isothermal tank after exiting a molten salt cooling tank, and enters a high-temperature salt storage tank after molten salt in the isothermal tank is cooled and heat exchanged with the strip steel.
6. The process method for isothermal treatment and waste heat recovery after rolling of strip steel as claimed in claim 1, wherein the high-temperature and low-temperature salt storage tanks are designed with heat preservation systems, the walls of the salt storage tanks are designed with three layers, the inner layer is made of heat-resistant stainless steel, the middle layer is vacuumized, the outer layer is made of carbon structural steel, the outer layer is made of aluminum silicate for overall heat preservation, and the outermost layer is provided with a galvanized plate, and the temperature is controlled within 45 ℃.
7. The process method for isothermal treatment and waste heat recovery after rolling of strip steel according to claim 1, wherein the high-temperature salt storage tank and the low-temperature salt storage tank are both designed with tubular electric heating systems, and submerged salt pumps are arranged on the top of the tanks to realize output of molten salts.
8. The process method for the isothermal treatment and the waste heat recovery after the strip steel rolling is characterized in that a molten salt heat exchange and an evaporator are designed between a high-temperature salt storage tank and a low-temperature salt storage tank, molten salt in the high-temperature salt storage tank is input into a molten salt heat exchanger and the evaporator through a salt pump, the molten salt flows through a shell pass of the heat exchanger, superheated steam and water flow through a pipe pass, the molten salt heat exchanger is connected with a steam drum, high-pressure steam is output to the outside to generate electricity, and the residual steam is connected to the grid to realize waste heat recovery.
9. The strip steel post-rolling isothermal treatment and waste heat recovery process method according to claim 1, characterized in that high-pressure steam generated by the system is introduced into the molten salt cooling tank and the molten salt isothermal tank, and purging devices for the high-pressure steam are formed on the upper surfaces of the inlet and the outlet of the molten salt tank to seal molten salt overflowing with the strip steel out of the molten salt cooling tank or the isothermal tank.
10. The process method for the isothermal treatment and the waste heat recovery after the strip steel is rolled according to claim 1, wherein a molten salt input pipeline of the molten salt cooling tank and the molten salt isothermal tank is 200mm higher than the bottom of the salt tank, a precipitation pit, a salt discharge hole and a valve are arranged at the bottom, the salt discharge hole is communicated with the low-temperature salt storage tank, when the process is stopped, the molten salt flows back to the low-temperature salt storage tank, and iron oxide scales enter the precipitation pit for centralized treatment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210601198.3A CN114833207A (en) | 2022-05-30 | 2022-05-30 | Process method for isothermal treatment and waste heat recovery after strip steel rolling |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210601198.3A CN114833207A (en) | 2022-05-30 | 2022-05-30 | Process method for isothermal treatment and waste heat recovery after strip steel rolling |
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| CN114833207A true CN114833207A (en) | 2022-08-02 |
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| CN202210601198.3A Withdrawn CN114833207A (en) | 2022-05-30 | 2022-05-30 | Process method for isothermal treatment and waste heat recovery after strip steel rolling |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116287664A (en) * | 2023-05-15 | 2023-06-23 | 江苏永钢集团有限公司 | High-speed wire on-line heat treatment equipment and process based on energy recycling |
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2022
- 2022-05-30 CN CN202210601198.3A patent/CN114833207A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116287664A (en) * | 2023-05-15 | 2023-06-23 | 江苏永钢集团有限公司 | High-speed wire on-line heat treatment equipment and process based on energy recycling |
| CN116287664B (en) * | 2023-05-15 | 2023-08-08 | 江苏永钢集团有限公司 | High-speed wire on-line heat treatment equipment and process based on energy recycling |
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Application publication date: 20220802 |
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