EP4159878A1 - Wärmerückgewinnung auf stahlschlacke - Google Patents

Wärmerückgewinnung auf stahlschlacke Download PDF

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Publication number
EP4159878A1
EP4159878A1 EP21199716.8A EP21199716A EP4159878A1 EP 4159878 A1 EP4159878 A1 EP 4159878A1 EP 21199716 A EP21199716 A EP 21199716A EP 4159878 A1 EP4159878 A1 EP 4159878A1
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EP
European Patent Office
Prior art keywords
heat exchanger
slag
heat
steel slag
installation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP21199716.8A
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English (en)
French (fr)
Inventor
Thomas THOELEN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
John Cockerill SA
Original Assignee
John Cockerill SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by John Cockerill SA filed Critical John Cockerill SA
Priority to EP21199716.8A priority Critical patent/EP4159878A1/de
Priority to PCT/EP2022/066563 priority patent/WO2023274754A1/en
Priority to CN202280045946.2A priority patent/CN117897505A/zh
Priority to CA3225178A priority patent/CA3225178A1/en
Priority to EP22734580.8A priority patent/EP4363622A1/de
Publication of EP4159878A1 publication Critical patent/EP4159878A1/de
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B3/00—General features in the manufacture of pig-iron
    • C21B3/04—Recovery of by-products, e.g. slag
    • C21B3/06—Treatment of liquid slag
    • C21B3/08—Cooling slag
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2400/00—Treatment of slags originating from iron or steel processes
    • C21B2400/02—Physical or chemical treatment of slags
    • C21B2400/022—Methods of cooling or quenching molten slag
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2400/00—Treatment of slags originating from iron or steel processes
    • C21B2400/05—Apparatus features
    • C21B2400/066—Receptacle features where the slag is treated
    • C21B2400/07—Receptacle features where the slag is treated open to atmosphere
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2400/00—Treatment of slags originating from iron or steel processes
    • C21B2400/08—Treatment of slags originating from iron or steel processes with energy recovery

Definitions

  • the present invention relates to the field of industrial waste heat recovery from steel slag, in particular with the purpose of producing saturated steam.
  • Waste heat recovery means recovering heat already available on site, for example from hot process exhaust gases, radiative masses, etc. In this way no fuel, and very little electricity coming from the network, are consumed, and operational expenditures are hugely lowered.
  • Steel slag arrives into the pit at high temperature, around 1000°C, and stays in the pit all the time it is cooling in the ambient environment.
  • FIG. 1 shows a solution known from Hui Zhang et al, A review of waste heat recovery technologies towards molten slag in steel industry, Applied Energy 112, Elsevier (2013) 956-966 .
  • This solution developed in Japan in the early 1980s, relates to the single rotating drum process, a technology for dry granulation based on mechanical impact or rolling of slag film by rotating drum.
  • the molten slag is poured onto a rotating drum and is broken up due to direct impact. After that, the disintegrated slag is thrown into a trap under the centrifugal force and then exchanges heat with air in the cooling chamber.
  • the air can be heated to a temperature of 500°C and the heat recovery rate achieves 60%.
  • Document EP 162 182 A1 discloses a method comprising a rolling of the liquid slag between at least two cooling rolls of metal, preferably steel, the temperature of and the distance between the rolls being controlled such that a cohesive slag slab is obtained having a solidified surface layer and a melted central layer, the slab still being sufficiently plastic to be shapable, a shaping in conjunction with the rolling or after the same, of the slab into briquettes and a recovery of heat at least from the shaped briquettes, preferably after these have been separated from each other, via any suitable cooling means or medium.
  • the corresponding apparatus comprises at least two cooling rolls arranged to roll out the liquid slag into a cohesive, shapable slab, means for briquetting the slab and means for recovering heat from the shaped briquettes.
  • Document JP5560871B2 provides a method of efficiently recovering heat energy of steel slag as a gas of high temperature from coagulated slag of high temperature obtained by cooling molten slag.
  • a heat exchanger including a hopper, a belt conveyor for conveying the coagulated slag S charged from the hopper approximately in the horizontal direction, a belt conveyor for conveying the coagulated slag S conveyed by the belt conveyor approximately in the horizontal direction, a gas blowing section for blowing a gas exchanging heat with the coagulated slag S above from a lower part of the belt conveyor, and a gas heating section for heating the gas passing through the belt conveyor by the coagulated slag S falling from the belt conveyor onto the belt conveyor, is used as a heat exchanger exchanging heat between the coagulated slag S of high temperature and the gas, to recover the heat energy from the coagulated slag S as the gas of high temperature.
  • Document EP 2 660 338 B1 relates to an apparatus for assembling molten slag and recovering sensible heat.
  • the apparatus includes: a rotary circular plate which rotates while being cooled by cooling water, and which cools the molten slag dropping onto the top surface thereof so as to convert the molten slag into particle slag and scatter the particle slag; a rotating drum part which rotates while being cooled by the cooling water, which is spaced apart from the side surface of the rotary circular plate, and which collides with the particle slag scattered by the rotary circular part so as to cool the colliding particle slag, thereby moving the cooled particle slag; an inclination-inducing part disposed at a downward incline below the rotation drum part, the inclination-inducing part inducing the colliding particle slag to drop downward; and a sensible-heat recovery casing part connected to the lower portion of the inclination-inducing part to enable the exchange of heat between a cooling medium and the dropping particle
  • heat is recovered from steel slag as inspired from a waste heat recovery solution already designed : recovering the radiative heat emitted by a hot mass by surrounding it by tube-cooled walls inside which evaporating water is flowing. This way to recover heat is very classically found in fired boilers, where furnaces are made up of tube-cooled walls.
  • the present invention aims to provide a cost-efficient technical solution to recover industrial waste heat from molten slag pits while avoiding the above-mentioned drawbacks of prior art.
  • the present invention relates to an industrial installation for recovering waste radiative heat from steel slag, said installation comprising :
  • the installation is further limited by at least one of the following characteristics or by a suitable combination thereof:
  • the present disclosure has the following structural characteristics :
  • FIG. 2 and FIG. 3 The proposed technical solution is shown in FIG. 2 and FIG. 3 .
  • the heat exchanger 6 is placed just above a steel slag pit in order to allow radiative heat recovery in an efficient way. As stated before the heat exchanger 6 must be as close as possible to the steel slag pit radiating surface 2 for allowing the heat exchange, but it must also be kept away to let the truck providing liquid steel slag to discharge its content (not shown). No contact is then allowed between molten slag drop and heat exchanger. Accordingly it requires the ability of the heat exchanger 6 to move up and down. Moreover, very little space is available on the ground around the steel slag pits. Therefore the installation footprint must be as reduced as possible.
  • the steel structure faces several constraints that are typical of this industrial site :
  • Stiffeners 14 are only set on both sides of the structure. In front of the structure, enough space has been foreseen for the molten slag conveying machine. And on the back of the structure enough space has also been foreseen for machines removing cold slag from the pit.
  • the structure height offers the significant advantage of allowing the heat exchanger to work in dry conditions, i.e. without being cooled by a cooler fluid.
  • steel slag logistics cannot often be adapted consequently. What means that steel slag discharge into the pit where exchanger is not cooled anymore cannot often be avoided.
  • the heat exchanger needs to be moved up and down to allow the best radiative heat recovery while protecting the heat exchanger against the machines and the molten steel slag discharge.
  • the solution provided by the present invention for solving this challenge is the use of flexible hoses, as illustrated on FIG. 4 and FIG. 5 .
  • the water flow is preferably divided in several hoses with small diameter instead of being carried by only one big hose.
  • small diameters allow the hoses to keep enough flexibility for this application while being sufficiently robust against pressure and temperature conditions of water.
  • connection between the fixed part and the moving part is advantageously provided at the supply and at the outlet of the heat exchanger.
  • the heat exchanger 6 is made of tube-cooled walls 10, 11 to recover radiative heat. These panels 10, 11 are arranged so that the exchanger forms a cap, looking also like a reversed basket (see FIG. 7 ).
  • This structure forms an enclosure allowing the recovery of heat rays with a better angle than if the heat exchanger were only a plane rectangle. Nevertheless the four vertical sides of the heat exchanger must be short enough in order not to elevate the steel structure too much, what would increase its wind exposure surface area.
  • the walls are supplied with water at their top and a biphasic mixture exits the walls at their top as well.
  • the bottom of the heat exchanger must be as clean as possible to optimize the height of the heat exchanger and futher the height of the steel structure.
  • it makes the routing of the piping simpler, and keeping pipes above the heat exchanger provides a protection against temperature fluctuation and corrosion.
  • Piping carrying inlet and outlet water fluxes are illustrated in FIG. 4 .
  • the heat exchanger 6 is surrounded by a shell made up of steel plates.
  • the function of this shell is multiple :
  • the heat exchanger must also be protected against the highly constraining environment (temperature, corrosion) as for the steel structure.
  • the solution found for this issue is to make tube-cooled walls in « Duplex » stainless steel material, the SA 789 S31803.
  • SA 789 S31803 offers a good protection against corrosion and its behavior against temperature variations is also well suitable for this kind of application.
  • the control system has a classical boiler control architecture, with some specificities for the present application.
  • the installation described in this document aims to recover radiative heat emitted by steel slag by a heat exchanger made of tube-cooled walls.
  • the heat absorbed by the heat exchanger is advantageously used for saturated steam production at low pressure.
  • the heat exchanger is actually an evaporator in which saturated water gets in and is partially evaporated thanks to the recovered heat.
  • the goal is to produce saturated steam at 25 barA from feedwater received at 170°C (50°C below saturation).
  • the steam will enter the steam network.
  • This network carries steam to the receiving process (for example carbon capture process).
  • Heat is available up to 1000°C, and is highly cyclical. Steel slag is discharged in a pit every 20 min (in full load conditions) so that the emitting surface temperature is cyclically fluctuating. The height of the emitting surface is slightly increasing with time since more and more steel slag layers are added. Today, between two unloadings, steel slag in pit is losing heat to the ambient air so that its temperature decreases quite fastly. The implementation of the technical solution disclosed here allows to recover this heat.
  • the important parameter to be controlled is the position of the heat exchanger, which can be lowered to reach a bottom position, or raised to reach a top position.
  • the cold water will fill in the heat recovery system by going through the feedwater control valve 20.
  • This valve will control the water level inside the steam drum depending on the steam production. This control will be performed thanks to flow elements (FE) upstream and downstream the steam drum that measure water and steam mass flows. To assist this control some water level measurements 21 are foreseen on the drum (LT for Level Transmitter, LI for Level Indicator ) .
  • the control valve can be isolated thanks to isolation valves for maintenance purpose.
  • the steam leaving the drum 9 will reach the steam network by passing through another control valve 22 set on the steam piping.
  • This control valve will be adjusted to maintain a constant pressure (25 barA in the studied application) inside the heat recovery system, measured by Pressure Transmitter (PT).
  • PT Pressure Transmitter
  • the second goal of this valve is to generate an isenthalpic expansion of steam so that its temperature becomes slightly higher than the saturation temperature corresponding to the steam network pressure. This margin against the saturated state is useful to compensate the heat losses through the steam network. It will be developed in the section about steam network.
  • the steam piping going to the steam network is equipped with a drain line to evacuate accumulated condensed water if condensation occurred. This phenomenon will typically happen during the boiler start-up phase when hot steam meets cold pipes. Moreover the closeness of the steam with saturated state may lead to some possible condensation.
  • the steam drum is equipped with blowdown lines 23 : one intermittent blowdown line and one continuous blowdown line.
  • the intermittent blowdown line is opened in case of water level increase, in order to help its regulation.
  • This line is typically necessary for system start-up phase during which some water level fluctuations are expected.
  • the steam drum has been designed to limit the water level fluctuations, nevertheless this line is a supplementary security.
  • the continuous blowdown line is continuously draining some water from the steam drum. This allows to evacuate impurities accumulating at the bottom of the drum.
  • the drained water mass flow is typically 1% of the total steam production. To compensate this loss of water, some make-up water must be foreseen, it shall be provided at the deaerator feedwater tank. This tank is set out of steel slag treatment site.
  • the steam drum is equipped with a safety valve 24, to protect the whole heat recovery system against overpressure. If the pressure measured with PT reaches the design limit the safety valve will open and release the produced steam to stop the pressure increase.
  • the heat exchanger is made of tube-cooled walls receiving radiative heat, and carrying evaporating water. It is hanged to a steel structure and is able to move vertically thanks to jacks. In order to allow the relative displacement between the fixed part (the steam drum and the pumps on the steel structure), and the heat exchanger that is moving, flexible hoses are foreseen.
  • the tube-cooled walls are two-passes exchangers 30 : water enters at the top of the boiler, is flowing through the first half of the panel, going from first pass to second pass through the lower header, and flowing upwards through the second half of the wall to leave the heat exchanger at the top.
  • the evaporation circulation is achieved thanks to circulation pumps 40, as mentioned previously.
  • Two pumps able to operate at full load are provided, one operating and one for back-up.
  • Each of the pumps is equipped upstream with filters to avoid soiling. These filters are monitored with pressure difference measurement ( ⁇ PT).
  • ⁇ PT pressure difference measurement
  • pumps can be isolated from the upstream circuit and from the downstream circuit, and are drainable.
  • Water chemistry is a key topic for boiler operation. Indeed steel is subject to corrosion in contact with water or steam.
  • One of the most important parameter involved in the steel corrosion process is water pH. pH regulation is carried out by injection of alkalyzing agents, this is the chemical dosing of the boiler.
  • the water quality monitoring is performed through water sampling. At strategic locations of the boilers some water extractions are foreseen. These extractions will generate water samples intended to be analysed.
  • a nitrogen injection 50 is foreseen on the steam drum, in case of boiler shutdown. This injection of inert gas is for conservation purpose, to protect the boiler against water ingress. Stagnant water is a cause of steel corrosion.
  • This last section is related to the evacuation of dirty water to sewer.
  • the intermittent and continuous blowdown, and also the other drains, are falling to the blowdown tank 60.
  • This tank is equipped with cooling water in order to decrease the water temperature to an acceptable level for the sewer.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
EP21199716.8A 2021-06-30 2021-09-29 Wärmerückgewinnung auf stahlschlacke Withdrawn EP4159878A1 (de)

Priority Applications (5)

Application Number Priority Date Filing Date Title
EP21199716.8A EP4159878A1 (de) 2021-09-29 2021-09-29 Wärmerückgewinnung auf stahlschlacke
PCT/EP2022/066563 WO2023274754A1 (en) 2021-06-30 2022-06-17 Heat recovery on steel slag
CN202280045946.2A CN117897505A (zh) 2021-06-30 2022-06-17 钢渣热回收
CA3225178A CA3225178A1 (en) 2021-06-30 2022-06-17 Heat recovery on steel slag
EP22734580.8A EP4363622A1 (de) 2021-06-30 2022-06-17 Wärmerückgewinnung aus stahlschlacke

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP21199716.8A EP4159878A1 (de) 2021-09-29 2021-09-29 Wärmerückgewinnung auf stahlschlacke

Publications (1)

Publication Number Publication Date
EP4159878A1 true EP4159878A1 (de) 2023-04-05

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EP21199716.8A Withdrawn EP4159878A1 (de) 2021-06-30 2021-09-29 Wärmerückgewinnung auf stahlschlacke

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EP (1) EP4159878A1 (de)
CN (1) CN117897505A (de)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0162182A1 (de) 1982-12-08 1985-11-27 AB Svensk Alunskifferutveckling Verfahren und Vorrichtung zum Stückigmachen flüssiger Schlacken unter gleichzeitiger Wärmerückgewinnung
US5397104A (en) * 1993-11-22 1995-03-14 Altek International Dross compression apparatus
JP5560871B2 (ja) 2010-04-19 2014-07-30 Ｊｆｅスチール株式会社 鉄鋼スラグの熱エネルギー回収方法
CN103981307A (zh) * 2014-05-30 2014-08-13 中冶华天南京工程技术有限公司 移动式热闷渣处理线
CN206755123U (zh) * 2016-12-21 2017-12-15 武学孔 一种钢铁冶金用的蒸汽发生器及其余热利用系统
EP2660338B1 (de) 2010-12-28 2019-04-03 Posco Vorrichtung zur sammlung geschmolzener schlacke und zur wiederherstellung der dafür nötigen wärme
CN112899416A (zh) * 2021-03-17 2021-06-04 中冶节能环保有限责任公司 一种利用钢渣余热的方法

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0162182A1 (de) 1982-12-08 1985-11-27 AB Svensk Alunskifferutveckling Verfahren und Vorrichtung zum Stückigmachen flüssiger Schlacken unter gleichzeitiger Wärmerückgewinnung
US5397104A (en) * 1993-11-22 1995-03-14 Altek International Dross compression apparatus
JP5560871B2 (ja) 2010-04-19 2014-07-30 Ｊｆｅスチール株式会社 鉄鋼スラグの熱エネルギー回収方法
EP2660338B1 (de) 2010-12-28 2019-04-03 Posco Vorrichtung zur sammlung geschmolzener schlacke und zur wiederherstellung der dafür nötigen wärme
CN103981307A (zh) * 2014-05-30 2014-08-13 中冶华天南京工程技术有限公司 移动式热闷渣处理线
CN206755123U (zh) * 2016-12-21 2017-12-15 武学孔 一种钢铁冶金用的蒸汽发生器及其余热利用系统
CN112899416A (zh) * 2021-03-17 2021-06-04 中冶节能环保有限责任公司 一种利用钢渣余热的方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
HUI ZHANG ET AL.: "Applied Energy", vol. 112, 2013, ELSEVIER, article "A review of waste heat recovery technologies towards molten slag in steel industry", pages: 956 - 966

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