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WO2016083247A1 - Method and plant for abatement of emissions resulting from coke quenching with energy recovery from said emissions - Google Patents

Method and plant for abatement of emissions resulting from coke quenching with energy recovery from said emissions Download PDF

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Publication number
WO2016083247A1
WO2016083247A1 PCT/EP2015/077148 EP2015077148W WO2016083247A1 WO 2016083247 A1 WO2016083247 A1 WO 2016083247A1 EP 2015077148 W EP2015077148 W EP 2015077148W WO 2016083247 A1 WO2016083247 A1 WO 2016083247A1
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WO
WIPO (PCT)
Prior art keywords
quenching
heat exchange
flow
conveyor
vapors
Prior art date
Application number
PCT/EP2015/077148
Other languages
French (fr)
Inventor
Antonio Mitidieri
Original Assignee
Antonio Mitidieri
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 Antonio Mitidieri filed Critical Antonio Mitidieri
Publication of WO2016083247A1 publication Critical patent/WO2016083247A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
    • C10B39/00—Cooling or quenching coke
    • C10B39/04—Wet quenching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D47/00—Separating dispersed particles from gases, air or vapours by liquid as separating agent
    • B01D47/05—Separating dispersed particles from gases, air or vapours by liquid as separating agent by condensation of the separating agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D47/00—Separating dispersed particles from gases, air or vapours by liquid as separating agent
    • B01D47/06—Spray cleaning
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
    • C10B39/00—Cooling or quenching coke
    • C10B39/04—Wet quenching
    • C10B39/08—Coke-quenching towers
    • 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

Definitions

  • the present invention relates to a method for abatement of emissions resulting from the quenching of high-temperature coke produced from fossil coal or coal for use in the iron and steel industry.
  • the invention also relates to a plant for implementing the aforementioned method and to a method for revamping a conventional coke quenching plant in order to make it suitable for implementing the aforementioned method.
  • Fossil coal must be necessarily transformed into coke so that it may have characteristics which make it suitable for use in the iron and steel industry, in particular for use in a blast furnace.
  • coke can be used as a fuel to generate the heat necessary for reaching the temperatures required for the reduction of ferrous minerals.
  • Coke also has a sufficient mechanical strength such that it is not prone to crumble during the operations of transportation and charging of the blast furnace and can withstand the high pressures resulting from the weight of the upper layers of material inside said blast furnace.
  • coke has a sufficient porosity to allow the gases to pass upwards and the molten metal to pass downwards.
  • the coke production process involves the steps of preparing a load of fossil coal, feeding the load into batteries of coke ovens, coking and quenching the coke obtained.
  • Coking consists in distillation of the coal, during which it is heated until a temperature of around 1 100°C is reached, avoiding contact with the air.
  • Coke which is the residue of pyrolysis, consists almost exclusively of carbon, in various crystallographic forms, but also contains the inorganic substances initially present in the fossil coal, and part of the sulfur.
  • coking gases and vapors forming the by-products of the process are released, recovered and treated separately.
  • the still glowing coal is conveyed in special quenching freight car.
  • the coke must then be quenched so that it can be transferred to the following treatment steps by means of conveyor belts in the plant which commonly have rubber mats.
  • the quenching freight car Once the quenching freight car has been filled, it is moved towards a coke quenching plant.
  • a coke quenching plant according to a known and currently used coke quenching process, is shown in schematic form in Figure 1.
  • the plant comprises a coke quenching station A and a tower B for discharging the vapors generated by quenching.
  • the station A has a tunnel-like quenching chamber 3 intended to receive intermittently one or more freight cars containing glowing coke and a tower 5 in fluid communication with the quenching chamber 3 which has on its top or roof 8 a plurality of tanks 2 intended to contain the quenching liquid (water) to be introduced into the chamber 3.
  • the tower B is in fluid communication with the quenching chamber 3, so as to allow conveying of the vapors generated by quenching of the coke inside the quenching chamber 3 and the introduction thereof into the atmosphere.
  • Quenching is performed by rain-dripping the water contained inside the tank 2 onto the coke which undergoes extremely rapid cooling down from a temperature of about 1000°C to a temperature close to room temperature. Part of the sprayed water evaporates, producing vapors which are dispersed in the atmosphere by means of the special tower B.
  • two tanks 2 of water with a volume of about 25 m 3 each can be emptied during a time interval of about three minutes. The cycle is repeated every 15-20 minutes and, therefore, the operation is intermittent.
  • the freight cars are conveyed from the coke ovens to the quenching plant with a frequency determined by the cycles of the battery ovens so as to allow regular and more efficient operation of the entire coal coking plant.
  • the coke quenching plant is therefore designed so as to be able to maintain a production rate which is as regular and constant as possible.
  • the quenching process consequently results in the intermittent introduction, into the atmosphere of large quantities of water vapor which, however, contains numerous pollutants including both particulate matter, i.e. that is called coke dust, and substances constituting residue and/or by-products from the preceding distillation step (coking).
  • a particular method envisages the partial condensation of water vapor containing pollutants and generated by rain-dripping the water onto the glowing coke by means of at least one series of baffles for intercepting the water vapor.
  • baffles are positioned close to the top of the quenching tower and comprise metal plates which are inclined with respect to the direction of the rising flow of the vapor.
  • the partial condensation of the water vapor causes, consequently, also a partial accumulation of the particulate on the plates so as to purify the outgoing residual vapor flow.
  • a further step is envisaged where the vapors rising towards the top of the tower are cooled and washed owing to the water sprayed inside the tower through a series of specific nozzles.
  • a further particular method envisages a partial condensation treatment similar to that of the method mentioned above, with the difference that the baffles are partly cooled by means of a liquefied gas.
  • the technical problem underlying the present invention is therefore that of providing a method and a plant for abatement of vapors containing polluting substances resulting from coke quenching, which is able to achieve in a simpler and more effective manner a more complete abatement of vapors containing polluting substances, resulting from coke quenching.
  • This technical problem is solved, according to the present invention, by a method for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors, the method comprising the steps of: - cooling glowing coke through contact with a quenching liquid until substantial quenching occurs, obtaining quenched coke and a vapor flow containing polluting substances;
  • the method according to the present invention comprises the further step of transferring said heated air flow to a plant for heat energy recovery.
  • a plant for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors comprising:
  • a station for coke quenching having a tunnel-like quenching chamber and a tower, in fluid communication with the quenching chamber having on its top or roof a plurality of tanks intended to contain the quenching liquid;
  • a flow conveyor having an inlet opening for a fluid flow, an outlet opening for a flow of non-condensed residue and at least one draining opening for condensed vapors, said flow conveyor being connected to said quenching chamber so that the inlet opening is situated substantially in correspondence of an outlet opening for the quenching vapors from said quenching chamber;
  • Figure 1 shows in schematic form a plant for coke quenching in accordance with the prior art
  • Figure 2 shows in schematic form a perspective view of a plant for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors according to the present invention
  • Figure 3 shows in schematic form a perspective view of a detail of the plant shown in Figure 2;
  • Figure 4 shows in schematic form a perspective view of the same plant shown in Figure 2, but from a different angle. Detailed description of a preferred embodiment
  • Figure 1 shows a conventional coke quenching plant already described above with reference to the prior art.
  • Figure 2 shows a plant, denoted overall by 1 , for abatement of vapors resulting from coke quenching with energy recovery from said vapors, which implements the method according to a mode of implementation of the present invention.
  • the plant 1 comprises a coke quenching station A with a tunnel-like quenching chamber 3 having an opening 4 for intermittent entry or receiving of one or more freight car (not shown) containing glowing coke and an opposite exit opening 6 for the freight car or cars containing quenched coke.
  • the quenching station A furthermore comprises a tower 5 situated above the quenching chamber 3 over an upper opening 7 of said quenching chamber 3 and in fluid communication therewith.
  • the tower 5 has a top or roof 8 on which a plurality of tanks 2 (in the example are shown two tanks) are arranged, said tanks being intended to contain a suitable quenching liquid, normally water.
  • the plant 1 comprises a device for the conveyance and abatement of vapors generated inside the chamber 3 as a result of the quenching of glowing coke by means of the quenching liquid.
  • the plant 1 comprises means 40 for transferring a forced air flow, conventional per se, for example a fan, into said device for the conveyance and abatement of vapors generated inside the chamber 3.
  • a forced air flow conventional per se, for example a fan
  • such a device comprises a flow conveyor 9 provided internally with a plurality of heat exchangers 1 1 , crossed by a heat exchange fluid, suitably arranged at a distance from each other.
  • Each heat exchanger 1 1 is of tube type with tubes 12 which cross the conveyor 9 from one end to the other end thereof in a substantially transverse direction; moreover, each exchanger 1 1 can be formed by one or more modules, in turn comprising tubes 12 organized in the form of a coil or with a single direction, depending on the size and use.
  • the flow conveyor 9 has a substantially S-shaped structure comprising an upper or conveying part 14 ending in the inlet/ entry mouth or opening 10 for a fluid flow, a bight-shaped middle part 16 and a substantially straight lower part 17 ending in an outlet opening 18.
  • Said upper part 14 comprises a wall or bottom 15 inclined with respect to the ground and sloping.
  • Said means 40 for transferring a forced air flow allow to transfer said air flow towards said plurality of heat exchangers for carrying out an indirect heat exchange, using said plurality of heat exchangers, between said air flow and said heat exchange fluid.
  • said means 40 for transferring a forced air flow are in fluid communication with said inlet opening 10, with said conveyor 9 and, preferably, with said upper opening 7 of the quenching chamber 3.
  • the conveyor 9 is arranged along a side of the quenching chamber 3 to which it is connected by means of suitable assembly components, conventional per se, so that the inlet opening 10 is situated substantially above the quenching chamber and laterally next to said opening 7.
  • the heat exchangers 1 1 are advantageously situated in the middle part 16 and in the lower part 17 of the conveyor 9, which form in fact a heat exchange zone, while the upper part 14 acts substantially as a conveyor of fluid flow towards the heat exchange zone of the conveyor 9.
  • the upper part 14 of the conveyor 9 has a cross-sectional area greater than the one of the middle part 16 and of the lower part 17 so as to be able to convey significant intermittent volumes of a fluid flow (quenching vapors or air as will be explained more clearly below) towards the heat exchange zone of the conveyor 9.
  • the conveyor 9 also has at least one draining opening 20 positioned on a wall of the conveyor 9, the at least one draining opening 20 being situated near or at the same level of a heat exchanger 1 1 , preferably downstream of the heat exchanger 1 1 with respect to the direction of the flow inside the conveyor 9.
  • the present embodiment envisages a first draining opening 20 situated in the middle part 16 downstream of the heat exchangers 1 1 present in said middle part 16 and a second draining opening 20 situated in correspondence with the heat exchanger 1 1 arranged in the end part 17.
  • a step 21 is positioned in the middle part 16, downstream of heat exchangers 1 1 , and protrudes from a wall of the conveyor 9 towards the inside and the upper, with the draining opening 20 of the middle part 16 which is positioned in correspondence of this step 21 , substantially close to the connection between the step 21 and the wall of the conveyor 9 from which it protrudes.
  • the step 21 and the respective wall of the conveyor 9 form advantageously a zone for collecting and conveying condensed vapor formed as a result of the heat exchange with said heat exchangers 1 1 towards the draining opening 20.
  • the step 21 directed inwards is connected to an upper curved portion 16a of the middle part 16, where heat exchangers 1 1 are present, and to lower curved portion 16b with a curvature in the opposite direction of said middle part 16, the lower portion 16b having therefore a smaller cross-sectional area (or a narrowing of the cross- sectional area) compared to that of the upper portion 16a.
  • the plant 1 further comprises a lower tank 25 for collecting the condensed vapor in fluid communication with the draining openings 20 of the conveyor 9 by means of respective connection pipes 24.
  • the lower tank 25 is furthermore in fluid communication with the upper tanks 2 for the quenching liquid by means of a connection pipe 27 so as to use advantageously the condensed vapor for coke quenching, thus reducing the net amount of quenching liquid used.
  • the plant 1 can also have a filtration and de-oiling system (not shown), which is conventional per se, in fluid communication with the bottom tank 25 and with the upper tanks 2 in order to purify at least a portion of the condensed vapor collected inside the tank 5 before it is recycled back to the tanks 2.
  • a filtration and de-oiling system (not shown), which is conventional per se, in fluid communication with the bottom tank 25 and with the upper tanks 2 in order to purify at least a portion of the condensed vapor collected inside the tank 5 before it is recycled back to the tanks 2.
  • the plant 1 furthermore comprises a basin 41 for containing the heat exchange fluid intended to cross the tube bundles of the exchangers 1 1 , each tube bundle having an inlet conduit (not shown) and outlet conduit (not shown) for said heat exchange fluid in fluid communication with the basin 41 by means of respective connection pipes 23 each having a free end immersed in the basin 41.
  • the basin 41 , the exchangers 1 1 and the connection pipes 23 form substantially a closed circuit for circulation of the heat exchange fluid.
  • the plant 1 also comprises a pipe 30 for transferring a heated gas flow to a treatment - for example energy recovery - plant, said pipe 30 being connected to the outlet opening 18 of the conveyor 9 by means of a pipe 29. Also provided is a pipe 32 which extends from the pipe 29 so as to transfer a heated gas flow to a chimney 28 connected thereto, and a flow diverter valve 31 in the connection zone between the pipes 29, 30 and 32.
  • the valve 31 can be controlled by a command and control system, conventional per se, with which the plant 1 is provided, so as to deviate the flow from the outlet opening 18 of the conveyor 9 towards the pipe 30 or towards the pipe 32 depending on the operating mode for implementation of the invention.
  • said means 40 for transferring a forced air flow can be positioned up-stream to said flow diverter valve 31.
  • said means 40 for transferring a forced air flow are positioned between said flow diverter valve 31 and the outlet opening 18 of the conveyor 9.
  • said means 40 for transferring a forced air flow can be positioned in correspondence with an inlet/ entry mouth or opening 10 for a fluid flow of said conveyor for the conveyance and abatement of vapors generated inside the chamber 3.
  • the method according to the invention envisages firstly coke quenching inside the quenching station A.
  • a freight car or several freight cars containing glowing coke is/ are moved so as to enter into the quenching chamber 3 through the inlet opening 4 and the quenching liquid (water) contained inside the upper tanks 2 is essentially dripped over the glowing coke.
  • the vapor flow thus generated which contains polluting substances still present in the glowing coke as by-products, exits from the top opening 7 of the quenching chamber 3 and, instead of being discharged as such into the external environment, as occurs in conventional plants, is conveyed through the mouth 10 for introduction into the top part 14 of the conveyor 9.
  • the bottom 15 is, preferably and advantageously, sloping and inclined with respect to the ground so as to allow conveying of said condensate towards the underlying middle part 16, instead of towards the inlet mouth or opening 10. From here the vapors continue along their flow path inside the conveyor 9, encountering the heat exchangers 1 1 in the middle part 16 and in the lower part 17, where the vapors undergo a first heat exchange which results in a substantial condensation cooling of said vapors with formation of a flow of condensed vapors and a flow of not condensed residue.
  • the heat exchange fluid is heated up to a temperature preferably of between 80°C and 90°C and in any case lower than the boiling temperature thereof.
  • the flow of condensed vapors passes out from the conveyor 9 through the draining openings 20 and it is collected inside the tank 25.
  • the condensate can be then recycled directly back to the quenching liquid tanks 2 via the pipe 27 or can be treated beforehand in treatment plants downstream and the treated condensate then recycled back to the tanks 1.
  • non-condensed residue comprising air and, eventually, any not condensed vapor residue
  • the flow of non-condensed residue flows out from the outlet opening 18 of the conveyor 9 reaching the pipe 29 where, with the aid of the diverter valve 31 , it is transferred via a pipe 30 to a treatment plant, for example, for energy recovery.
  • the diverter valve 31 in the case the residual flow output from the opening 18 of the conveyor 9 has not a sufficiently high temperature suitable so as to be conveniently transferred to a treatment plant, by means of the diverter valve 31 , it is transferred via a pipe 32 to the chimney 28 where it is then released into the atmosphere.
  • the diverter valve 31 can be controlled by the command and control system so as to transfer such a residual flow to the chimney 28 instead of to said treatment plant.
  • a forced air flow is transferred into the conveyor 9 towards said plurality of heat exchangers for carrying out an indirect heat exchange, using said plurality of heat exchangers, between said air flow and said heat exchange fluid.
  • the means 40 for transferring a forced air flow can be in fluid communication with said opening 7, said air can be drawn from the quenching chamber 3, which remains empty after removal of the freight car or cars.
  • the air continues along the flow path inside the conveyor 9, encountering the heat exchangers 1 1 in the middle part 16 and in the lower part 17, by means of which a second heat exchange involving heating of said air with formation of a heated air flow and simultaneous cooling of the heat exchange fluid is performed.
  • the air is heated to a temperature, the value of which depends on many factors such as the temperature of the external environment, the size of the exchangers, etc., and it is comprised between the value of the room temperature and the temperature value of the heated heat exchange fluid.
  • the fan is suitably operated and controlled, for example by the command and control system of the plant 1 , so as to transfer the forced air flow after the first indirect heat exchange between the quenching vapors and the exchangers 1 1 present in the conveyor 9.
  • each transfer of air into the conveyor 9 and, consequently, each second heat exchange between the air and the heat exchangers 1 1 is performed in between two successive first heat exchanges between the quenching vapors and the heat exchangers 1 1.
  • the heated air flows out from the outlet opening 18 of the conveyor 9 reaching the pipe 29 where, with the aid of the diverter valve 31, it is transferred via a pipe 30 to a treatment plant, for example, for energy recovery.
  • the diverter valve 31 in the case where the flow of heated air output from the opening 18 of the conveyor 9 has not a sufficiently high temperature suitable so as to be conveniently transferred to a treatment plant, by means of the diverter valve 31 , it is transferred via a pipe 32 to the chimney 28 where it is then released into the atmosphere.
  • the diverter valve 31 can be controlled by the command and control system so as to transfer such a flow of heated air to the chimney 28 instead of to said plant.
  • the method for abatement of vapors containing polluting substances, resulting from coke quenching, with energy recovery from said vapors solves the technical problem and achieves numerous advantages, the first of which is that it is possible to obtain a substantial reduction in the polluting emissions compared to the prior art, owing to nearly complete abatement of the generated water vapor comprising volatile polluting substances and particulate matter.
  • a particularly innovative and advantageous feature is the use, inside the plant, of a single heat exchange device (exchanger) for performing the dual function of abating the vapor resulting from quenching of glowing coke, following a first indirect heat exchange between a heat exchange fluid and said vapor which is in this way condensed, and recovering the thermal energy stored in said heated heat exchange fluid, following a second indirect heat exchange between said heat exchange fluid and air which is in this way heated and subsequently transferred to a heat recovery device.
  • a further advantage is the fact that it is possible to recycle partially the water which is used for coke quenching and transformed into water vapor and then condensed, which in a particular embodiment can be purified before subsequent use.
  • the method according to the present invention allows to achieve the abatement of vapors containing polluting substances, resulting from coke quenching in a plant, ensuring stricter compliance with the environmental standards, with the possibility of heat energy recovery and with production rates compatible with those of an existing coal coking plant, the production capacity remaining the same as the methods according to the prior art.
  • the plant designed to implement the method according to the present invention is able to operate at lower costs compared to the plant needed to obtain such a production capacity using the methods of the prior art; in fact, in the plant according to the present invention, it is possible to recover part of the thermal energy held by the released vapor, with possible reuse during other stages of the production process within which the coke cooling plant operates, and smaller amounts of supply water are requested for each quenching cycle.
  • the plant 1 described above and the associated method according to the invention can be realized and started up ex-novo or integrated with an already existing plant for quenching glowing coke. Therefore, another aspect of the invention also relates to a method for revamping a preexisting quenching plant of the type shown in Figure 1.
  • This pre-existing plant comprises a station A for quenching the coke, having a tunnel-like quenching chamber 3 and a tower 3 in fluid communication with the quenching chamber 3 having on its top or roof 8 a plurality of tanks 2 intended to contain the quenching fluid, and a tower B for discharging the vapors generated by quenching.
  • the method for revamping such a preexisting plant comprises the steps of: - decommissioning and/ or removing said quenching tower B;
  • a flow conveyor 9 having an inlet opening 10 for a fluid flow, an outlet opening 18 for a not condensed residual flow of , and at least one draining opening 20 for condensed vapors;
  • - arranging means 40 for transferring a forced air flow into said flow conveyor 9 towards said at least one heat exchanger 1 1 for carrying out an indirect heat exchange, using said at least one heat exchanger 1 1 , between said air flow and said heat exchange fluid, said means 40 being in fluid communication with said conveyor and, preferably, with said outlet opening for the quenching vapors from said quenching chamber.
  • the revamping method can envisage moreover the provision of a collection tank 25 for the condensed vapor in fluid communication with said at least one draining opening 20 of said conveyor 9 and with said plurality of tanks 2.
  • the revamping method can envisage moreover the provision of a chimney 28 connected to said outlet opening 18 of said conveyor 9 by means of a first pipe 29 and a second pipe 32, providing a third pipe 30 connected to the first pipe 29 and to the second pipe 32 so as to transfer a heated gas flow to a treatment plant, and providing a flow diverter valve 31 in the connection zone between said pipes 29, 30 and 32, controlled by said command and control system so as to transfer said gas flow to said chimney 28 via said second pipe 32 or transfer said gas flow to said treatment plant via said third pipe 30.
  • the revamping method can envisage moreover the provision of a basin 41 for containing the heat exchange fluid intended to cross the tube bundles of the exchangers 1 1 and a plurality of pipes 18 for connection with the inlet conduit and an outlet conduit for the heat exchange fluid of each tube bundle.
  • the revamping method can envisage moreover the provision of a pump for conveying an air flow into said conveyor 9.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Coke Industry (AREA)

Abstract

A method and a plant for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors are described. The method comprising the steps of: - cooling glowing coke through contact with a quenching liquid until substantial quenching occurs, obtaining quenched coke and a vapor flow containing polluting substances; - conveying said vapor flow towards at least one heat exchanger of the indirect heat exchange and tube-bundle type with tubes crossed by a heat exchange fluid; - carrying out a first indirect heat exchange, by means of said at least one heat exchanger, between said vapors and said heat exchange fluid, obtaining a condensed vapor comprising said polluting substances; - conveying an air flow towards said at least one heat exchanger and carrying out a second indirect heat exchange, using said at least one heat exchanger, between said air flow and said heat exchange fluid, obtaining a heated air flow. A method for revamping a pre-existing coke quenching plant for implementing the method described above is also described.

Description

Title: Method and plant for abatement of emissions resulting from coke quenching with energy recovery from said emissions
DESCRIPTION
Field of application The present invention relates to a method for abatement of emissions resulting from the quenching of high-temperature coke produced from fossil coal or coal for use in the iron and steel industry.
The invention also relates to a plant for implementing the aforementioned method and to a method for revamping a conventional coke quenching plant in order to make it suitable for implementing the aforementioned method.
Prior art
It is well-known in art that the production of coke from fossil coal or coal is of fundamental importance in various plants and industrial processes, in particular in plants used in the iron and steel industry.
Fossil coal must be necessarily transformed into coke so that it may have characteristics which make it suitable for use in the iron and steel industry, in particular for use in a blast furnace.
In fact, coke can be used as a fuel to generate the heat necessary for reaching the temperatures required for the reduction of ferrous minerals. Coke also has a sufficient mechanical strength such that it is not prone to crumble during the operations of transportation and charging of the blast furnace and can withstand the high pressures resulting from the weight of the upper layers of material inside said blast furnace. At the end, coke has a sufficient porosity to allow the gases to pass upwards and the molten metal to pass downwards.
The coke production process (coking) involves the steps of preparing a load of fossil coal, feeding the load into batteries of coke ovens, coking and quenching the coke obtained. Coking consists in distillation of the coal, during which it is heated until a temperature of around 1 100°C is reached, avoiding contact with the air. Coke, which is the residue of pyrolysis, consists almost exclusively of carbon, in various crystallographic forms, but also contains the inorganic substances initially present in the fossil coal, and part of the sulfur. During pyrolysis, coking gases and vapors forming the by-products of the process are released, recovered and treated separately.
When removed from said batteries of ovens, the still glowing coal is conveyed in special quenching freight car. The coke must then be quenched so that it can be transferred to the following treatment steps by means of conveyor belts in the plant which commonly have rubber mats. Once the quenching freight car has been filled, it is moved towards a coke quenching plant.
A coke quenching plant, according to a known and currently used coke quenching process, is shown in schematic form in Figure 1. The plant comprises a coke quenching station A and a tower B for discharging the vapors generated by quenching. The station A has a tunnel-like quenching chamber 3 intended to receive intermittently one or more freight cars containing glowing coke and a tower 5 in fluid communication with the quenching chamber 3 which has on its top or roof 8 a plurality of tanks 2 intended to contain the quenching liquid (water) to be introduced into the chamber 3. The tower B is in fluid communication with the quenching chamber 3, so as to allow conveying of the vapors generated by quenching of the coke inside the quenching chamber 3 and the introduction thereof into the atmosphere. Quenching is performed by rain-dripping the water contained inside the tank 2 onto the coke which undergoes extremely rapid cooling down from a temperature of about 1000°C to a temperature close to room temperature. Part of the sprayed water evaporates, producing vapors which are dispersed in the atmosphere by means of the special tower B. By way of example, in the quenching plant shown in Figure 1 , for each cooling cycle, two tanks 2 of water with a volume of about 25 m3 each can be emptied during a time interval of about three minutes. The cycle is repeated every 15-20 minutes and, therefore, the operation is intermittent. The freight cars are conveyed from the coke ovens to the quenching plant with a frequency determined by the cycles of the battery ovens so as to allow regular and more efficient operation of the entire coal coking plant. The coke quenching plant is therefore designed so as to be able to maintain a production rate which is as regular and constant as possible. The quenching process consequently results in the intermittent introduction, into the atmosphere of large quantities of water vapor which, however, contains numerous pollutants including both particulate matter, i.e. that is called coke dust, and substances constituting residue and/or by-products from the preceding distillation step (coking). Although it is possible to attempt purifying the aforementioned water vapor so as to eliminate the pollutants before it is introduced into the atmosphere, owing to the huge amounts of vapor produced per unit of time intermittently by these plants, such a purification operation is in reality very difficult to perform, costly and tends not to produce satisfactory results.
Therefore, in this sector, research has been focused on systems for eliminating or at least limiting the emission into the atmosphere of said water vapor comprising pollutants, with the aim of reducing the environmental impact of this specific coke treatment step. For this purpose, in the sector methods and associated plants which envisage a step of elimination and abatement of said water vapor containing pollutants have already been proposed.
A particular method envisages the partial condensation of water vapor containing pollutants and generated by rain-dripping the water onto the glowing coke by means of at least one series of baffles for intercepting the water vapor. These baffles are positioned close to the top of the quenching tower and comprise metal plates which are inclined with respect to the direction of the rising flow of the vapor. The partial condensation of the water vapor causes, consequently, also a partial accumulation of the particulate on the plates so as to purify the outgoing residual vapor flow. In addition, a further step is envisaged where the vapors rising towards the top of the tower are cooled and washed owing to the water sprayed inside the tower through a series of specific nozzles.
Methods of this type are described, for example, in the patent US 4263099 and the US patent application US 2012/0228155.
However, the abatement methods described above have recognized drawbacks associated with the need to use additional quantities of water for condensation of the vapors, which in particular must be emitted in the form of spray, this resulting in the use of very high pressures. Moreover, by means of some of this conventional method too, considerable amounts of polluted water vapor are nevertheless emitted.
A further particular method, described in the patent US 4294663, envisages a partial condensation treatment similar to that of the method mentioned above, with the difference that the baffles are partly cooled by means of a liquefied gas.
In this case, also, however, the complete abatement of the vapors containing polluting substances is not achieved and moreover the use of liquefied gas for the cooling process results in significant additional costs. Another method for the abatement of vapors resulting from coke quenching is described in the patent application DE 30 01 063 Al . According to this method quenching vapors are condensed in a condensation unit through a specific cooling device, wherein flows a cooling liquid. This cooling device is coupled with a water dripping system, which provides a further condensation/ abatement. The cooling liquid which flows in said cooling device can be cooled outside the condensation unit. Anyway, through this method too, a complete removal of the pollutants from the fluid flow is not achieved. Indeed a combustion unit or a further collecting/ separation step is required, in order not to release any gas except for water or carbon dioxide.
Another method for the abatement of quenching vapors is disclosed in the patent application FR 2 543 885 Al . In this case, several steps of water dripping allow to cool and condense the polluted quenching vapor, which is transformed into liquid and collected. Then, a cooling procedure is envisaged, during which the still hot liquid condensate is cooled, being sprayed in the quenching chamber in countercurrent with a fresh air flow.
The technical problem underlying the present invention is therefore that of providing a method and a plant for abatement of vapors containing polluting substances resulting from coke quenching, which is able to achieve in a simpler and more effective manner a more complete abatement of vapors containing polluting substances, resulting from coke quenching. Summary of the invention
This technical problem is solved, according to the present invention, by a method for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors, the method comprising the steps of: - cooling glowing coke through contact with a quenching liquid until substantial quenching occurs, obtaining quenched coke and a vapor flow containing polluting substances;
- conveying said vapor flow towards at least one heat exchanger of the indirect heat exchange and tube type with tubes crossed by a heat exchange fluid;
- carrying out a first indirect heat exchange, by means of said at least one heat exchanger, between said vapors and said heat exchange fluid, obtaining a condensed vapor comprising said polluting substances;
- conveying an air flow towards said at least one heat exchanger and carrying out a second indirect heat exchange, using said at least one heat exchanger, between said air flow and said heat exchange fluid, obtaining a heated air flow.
Preferably the method according to the present invention comprises the further step of transferring said heated air flow to a plant for heat energy recovery.
The aforementioned technical problem is also solved by a plant for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors, the plant comprising:
- a station for coke quenching having a tunnel-like quenching chamber and a tower, in fluid communication with the quenching chamber having on its top or roof a plurality of tanks intended to contain the quenching liquid;
- a flow conveyor having an inlet opening for a fluid flow, an outlet opening for a flow of non-condensed residue and at least one draining opening for condensed vapors, said flow conveyor being connected to said quenching chamber so that the inlet opening is situated substantially in correspondence of an outlet opening for the quenching vapors from said quenching chamber;
- at least one tube heat exchanger with tubes crossed by a heat exchange fluid, arranged in said flow conveyor, preferably a plurality of tube heat exchangers with tubes crossed by a heat exchange fluid, arranged in said flow conveyor at predetermined distances from each other
- means for transferring a forced air flow into said flow conveyor towards said at least one heat exchanger for carrying out an indirect heat exchange using said at least one heat exchanger between said air flow and said heat exchange fluid, said means being in fluid communication with said conveyor and, preferably, with said outlet opening for the quenching vapors from said quenching chamber.
Further characteristic features and advantages of the present invention will emerge from the description, provided herein below, of a preferred example of embodiment thereof provided by way of a non-limiting example with reference to the accompanying drawings.
Brief description of the drawings
Figure 1 shows in schematic form a plant for coke quenching in accordance with the prior art; Figure 2 shows in schematic form a perspective view of a plant for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors according to the present invention;
Figure 3 shows in schematic form a perspective view of a detail of the plant shown in Figure 2;
Figure 4 shows in schematic form a perspective view of the same plant shown in Figure 2, but from a different angle. Detailed description of a preferred embodiment
Figure 1 shows a conventional coke quenching plant already described above with reference to the prior art. With reference to the figures, Figure 2 shows a plant, denoted overall by 1 , for abatement of vapors resulting from coke quenching with energy recovery from said vapors, which implements the method according to a mode of implementation of the present invention.
The parts of the plant 1 according to the invention which are structurally and/ or functionally equivalent to corresponding parts of the conventional plant according to Figure 1 described above have been assigned the same reference numbers as the latter.
The plant 1 comprises a coke quenching station A with a tunnel-like quenching chamber 3 having an opening 4 for intermittent entry or receiving of one or more freight car (not shown) containing glowing coke and an opposite exit opening 6 for the freight car or cars containing quenched coke. The quenching station A furthermore comprises a tower 5 situated above the quenching chamber 3 over an upper opening 7 of said quenching chamber 3 and in fluid communication therewith. The tower 5 has a top or roof 8 on which a plurality of tanks 2 (in the example are shown two tanks) are arranged, said tanks being intended to contain a suitable quenching liquid, normally water.
In accordance with the present invention, the plant 1 comprises a device for the conveyance and abatement of vapors generated inside the chamber 3 as a result of the quenching of glowing coke by means of the quenching liquid.
According to the present invention, the plant 1 comprises means 40 for transferring a forced air flow, conventional per se, for example a fan, into said device for the conveyance and abatement of vapors generated inside the chamber 3. In the present embodiment, such a device comprises a flow conveyor 9 provided internally with a plurality of heat exchangers 1 1 , crossed by a heat exchange fluid, suitably arranged at a distance from each other. Each heat exchanger 1 1 is of tube type with tubes 12 which cross the conveyor 9 from one end to the other end thereof in a substantially transverse direction; moreover, each exchanger 1 1 can be formed by one or more modules, in turn comprising tubes 12 organized in the form of a coil or with a single direction, depending on the size and use. More particularly, the flow conveyor 9 has a substantially S-shaped structure comprising an upper or conveying part 14 ending in the inlet/ entry mouth or opening 10 for a fluid flow, a bight-shaped middle part 16 and a substantially straight lower part 17 ending in an outlet opening 18. Said upper part 14 comprises a wall or bottom 15 inclined with respect to the ground and sloping.
Said means 40 for transferring a forced air flow allow to transfer said air flow towards said plurality of heat exchangers for carrying out an indirect heat exchange, using said plurality of heat exchangers, between said air flow and said heat exchange fluid.
According to the present embodiment, said means 40 for transferring a forced air flow are in fluid communication with said inlet opening 10, with said conveyor 9 and, preferably, with said upper opening 7 of the quenching chamber 3. The conveyor 9 is arranged along a side of the quenching chamber 3 to which it is connected by means of suitable assembly components, conventional per se, so that the inlet opening 10 is situated substantially above the quenching chamber and laterally next to said opening 7.
In the present embodiment, the heat exchangers 1 1 are advantageously situated in the middle part 16 and in the lower part 17 of the conveyor 9, which form in fact a heat exchange zone, while the upper part 14 acts substantially as a conveyor of fluid flow towards the heat exchange zone of the conveyor 9. Moreover, advantageously, the upper part 14 of the conveyor 9 has a cross-sectional area greater than the one of the middle part 16 and of the lower part 17 so as to be able to convey significant intermittent volumes of a fluid flow (quenching vapors or air as will be explained more clearly below) towards the heat exchange zone of the conveyor 9.
The conveyor 9 also has at least one draining opening 20 positioned on a wall of the conveyor 9, the at least one draining opening 20 being situated near or at the same level of a heat exchanger 1 1 , preferably downstream of the heat exchanger 1 1 with respect to the direction of the flow inside the conveyor 9. The present embodiment envisages a first draining opening 20 situated in the middle part 16 downstream of the heat exchangers 1 1 present in said middle part 16 and a second draining opening 20 situated in correspondence with the heat exchanger 1 1 arranged in the end part 17.
More particularly, a step 21 is positioned in the middle part 16, downstream of heat exchangers 1 1 , and protrudes from a wall of the conveyor 9 towards the inside and the upper, with the draining opening 20 of the middle part 16 which is positioned in correspondence of this step 21 , substantially close to the connection between the step 21 and the wall of the conveyor 9 from which it protrudes. In this way, the step 21 and the respective wall of the conveyor 9 form advantageously a zone for collecting and conveying condensed vapor formed as a result of the heat exchange with said heat exchangers 1 1 towards the draining opening 20.
In the present embodiment, the step 21 directed inwards is connected to an upper curved portion 16a of the middle part 16, where heat exchangers 1 1 are present, and to lower curved portion 16b with a curvature in the opposite direction of said middle part 16, the lower portion 16b having therefore a smaller cross-sectional area (or a narrowing of the cross- sectional area) compared to that of the upper portion 16a. The plant 1 further comprises a lower tank 25 for collecting the condensed vapor in fluid communication with the draining openings 20 of the conveyor 9 by means of respective connection pipes 24. The lower tank 25 is furthermore in fluid communication with the upper tanks 2 for the quenching liquid by means of a connection pipe 27 so as to use advantageously the condensed vapor for coke quenching, thus reducing the net amount of quenching liquid used.
The plant 1 can also have a filtration and de-oiling system (not shown), which is conventional per se, in fluid communication with the bottom tank 25 and with the upper tanks 2 in order to purify at least a portion of the condensed vapor collected inside the tank 5 before it is recycled back to the tanks 2.
The plant 1 furthermore comprises a basin 41 for containing the heat exchange fluid intended to cross the tube bundles of the exchangers 1 1 , each tube bundle having an inlet conduit (not shown) and outlet conduit (not shown) for said heat exchange fluid in fluid communication with the basin 41 by means of respective connection pipes 23 each having a free end immersed in the basin 41. In this way, the basin 41 , the exchangers 1 1 and the connection pipes 23 form substantially a closed circuit for circulation of the heat exchange fluid.
The plant 1 also comprises a pipe 30 for transferring a heated gas flow to a treatment - for example energy recovery - plant, said pipe 30 being connected to the outlet opening 18 of the conveyor 9 by means of a pipe 29. Also provided is a pipe 32 which extends from the pipe 29 so as to transfer a heated gas flow to a chimney 28 connected thereto, and a flow diverter valve 31 in the connection zone between the pipes 29, 30 and 32.
The valve 31 can be controlled by a command and control system, conventional per se, with which the plant 1 is provided, so as to deviate the flow from the outlet opening 18 of the conveyor 9 towards the pipe 30 or towards the pipe 32 depending on the operating mode for implementation of the invention.
According to the present embodiment, said means 40 for transferring a forced air flow can be positioned up-stream to said flow diverter valve 31.
Preferably, said means 40 for transferring a forced air flow are positioned between said flow diverter valve 31 and the outlet opening 18 of the conveyor 9.
Alternatively, said means 40 for transferring a forced air flow can be positioned in correspondence with an inlet/ entry mouth or opening 10 for a fluid flow of said conveyor for the conveyance and abatement of vapors generated inside the chamber 3.
With the plant 1 described above, the method according to the invention envisages firstly coke quenching inside the quenching station A. In this connection, a freight car or several freight cars containing glowing coke is/ are moved so as to enter into the quenching chamber 3 through the inlet opening 4 and the quenching liquid (water) contained inside the upper tanks 2 is essentially dripped over the glowing coke. The vapor flow thus generated, which contains polluting substances still present in the glowing coke as by-products, exits from the top opening 7 of the quenching chamber 3 and, instead of being discharged as such into the external environment, as occurs in conventional plants, is conveyed through the mouth 10 for introduction into the top part 14 of the conveyor 9. In particular, inside said top part 14, owing to the contact of the vapor flow with the wall of said conveyor 9 which is at a lower temperature, preliminary and partial formation of condensate may occur. For this reason, the bottom 15 is, preferably and advantageously, sloping and inclined with respect to the ground so as to allow conveying of said condensate towards the underlying middle part 16, instead of towards the inlet mouth or opening 10. From here the vapors continue along their flow path inside the conveyor 9, encountering the heat exchangers 1 1 in the middle part 16 and in the lower part 17, where the vapors undergo a first heat exchange which results in a substantial condensation cooling of said vapors with formation of a flow of condensed vapors and a flow of not condensed residue. During this step, the heat exchange fluid is heated up to a temperature preferably of between 80°C and 90°C and in any case lower than the boiling temperature thereof. The flow of condensed vapors passes out from the conveyor 9 through the draining openings 20 and it is collected inside the tank 25. The condensate can be then recycled directly back to the quenching liquid tanks 2 via the pipe 27 or can be treated beforehand in treatment plants downstream and the treated condensate then recycled back to the tanks 1.
The flow of non-condensed residue, comprising air and, eventually, any not condensed vapor residue, flows out from the outlet opening 18 of the conveyor 9 reaching the pipe 29 where, with the aid of the diverter valve 31 , it is transferred via a pipe 30 to a treatment plant, for example, for energy recovery.
Alternatively, in the case the residual flow output from the opening 18 of the conveyor 9 has not a sufficiently high temperature suitable so as to be conveniently transferred to a treatment plant, by means of the diverter valve 31 , it is transferred via a pipe 32 to the chimney 28 where it is then released into the atmosphere. The diverter valve 31 can be controlled by the command and control system so as to transfer such a residual flow to the chimney 28 instead of to said treatment plant. Once the coke has been cooled (quenched), the freight car or cars containing the cooled coke is/ are removed, being moved out of the quenching chamber 3 via the exit opening 6.
At this point of the method according to the invention, it is required to cool the heat exchange fluid during the interval of time occurring between the emptying of the at least two upper tanks 2 during the current cycle and the start of the next cycle, so as to allow effective condensation of the vapor flow which will be produced during the next cycle.
Then, subsequently, through the means 40 for transferring a forced air flow, a forced air flow is transferred into the conveyor 9 towards said plurality of heat exchangers for carrying out an indirect heat exchange, using said plurality of heat exchangers, between said air flow and said heat exchange fluid. In particular, since the means 40 for transferring a forced air flow can be in fluid communication with said opening 7, said air can be drawn from the quenching chamber 3, which remains empty after removal of the freight car or cars.
From here the air continues along the flow path inside the conveyor 9, encountering the heat exchangers 1 1 in the middle part 16 and in the lower part 17, by means of which a second heat exchange involving heating of said air with formation of a heated air flow and simultaneous cooling of the heat exchange fluid is performed. During this step, the air is heated to a temperature, the value of which depends on many factors such as the temperature of the external environment, the size of the exchangers, etc., and it is comprised between the value of the room temperature and the temperature value of the heated heat exchange fluid. It should be noted that the fan is suitably operated and controlled, for example by the command and control system of the plant 1 , so as to transfer the forced air flow after the first indirect heat exchange between the quenching vapors and the exchangers 1 1 present in the conveyor 9. In other words, each transfer of air into the conveyor 9 and, consequently, each second heat exchange between the air and the heat exchangers 1 1 , is performed in between two successive first heat exchanges between the quenching vapors and the heat exchangers 1 1.
The heated air flows out from the outlet opening 18 of the conveyor 9 reaching the pipe 29 where, with the aid of the diverter valve 31, it is transferred via a pipe 30 to a treatment plant, for example, for energy recovery.
Alternatively, in the case where the flow of heated air output from the opening 18 of the conveyor 9 has not a sufficiently high temperature suitable so as to be conveniently transferred to a treatment plant, by means of the diverter valve 31 , it is transferred via a pipe 32 to the chimney 28 where it is then released into the atmosphere. The diverter valve 31 can be controlled by the command and control system so as to transfer such a flow of heated air to the chimney 28 instead of to said plant.
From the above description it can be seen that the method for abatement of vapors containing polluting substances, resulting from coke quenching, with energy recovery from said vapors according to the invention solves the technical problem and achieves numerous advantages, the first of which is that it is possible to obtain a substantial reduction in the polluting emissions compared to the prior art, owing to nearly complete abatement of the generated water vapor comprising volatile polluting substances and particulate matter.
Moreover, by means of the method according to the invention, differently from that proposed by the prior art, it is possible to recover at least a part of the thermal energy held by the water vapor exiting from the coke quenching chamber, by means of conveyance and condensation of said vapor inside the heat exchanger for heating a heat exchange fluid contained in a closed circuit, said heat exchange fluid being subjected, by means of the same heat exchanger, to subsequent cooling by means of an air flow which, once heated, can be conveyed to an energy recovery device.
Therefore, according to the present invention, a particularly innovative and advantageous feature, also in terms of cost containment, is the use, inside the plant, of a single heat exchange device (exchanger) for performing the dual function of abating the vapor resulting from quenching of glowing coke, following a first indirect heat exchange between a heat exchange fluid and said vapor which is in this way condensed, and recovering the thermal energy stored in said heated heat exchange fluid, following a second indirect heat exchange between said heat exchange fluid and air which is in this way heated and subsequently transferred to a heat recovery device.
A further advantage is the fact that it is possible to recycle partially the water which is used for coke quenching and transformed into water vapor and then condensed, which in a particular embodiment can be purified before subsequent use.
Consequently, the method according to the present invention allows to achieve the abatement of vapors containing polluting substances, resulting from coke quenching in a plant, ensuring stricter compliance with the environmental standards, with the possibility of heat energy recovery and with production rates compatible with those of an existing coal coking plant, the production capacity remaining the same as the methods according to the prior art.
In other words, for the same production capacity, the plant designed to implement the method according to the present invention is able to operate at lower costs compared to the plant needed to obtain such a production capacity using the methods of the prior art; in fact, in the plant according to the present invention, it is possible to recover part of the thermal energy held by the released vapor, with possible reuse during other stages of the production process within which the coke cooling plant operates, and smaller amounts of supply water are requested for each quenching cycle.
The plant 1 described above and the associated method according to the invention can be realized and started up ex-novo or integrated with an already existing plant for quenching glowing coke. Therefore, another aspect of the invention also relates to a method for revamping a preexisting quenching plant of the type shown in Figure 1. This pre-existing plant comprises a station A for quenching the coke, having a tunnel-like quenching chamber 3 and a tower 3 in fluid communication with the quenching chamber 3 having on its top or roof 8 a plurality of tanks 2 intended to contain the quenching fluid, and a tower B for discharging the vapors generated by quenching. The method for revamping such a preexisting plant comprises the steps of: - decommissioning and/ or removing said quenching tower B;
- arranging a flow conveyor 9 having an inlet opening 10 for a fluid flow, an outlet opening 18 for a not condensed residual flow of , and at least one draining opening 20 for condensed vapors;
- connecting said flow conveyor 9 to said quenching chamber 3 so that said inlet opening 10 is situated substantially in correspondence with an outlet opening 7 for quenching vapors in said quenching chamber 3;
- arranging at least one tube heat exchanger 1 1 with tubes crossed by a heat exchange fluid, arranged in said flow conveyor, preferably a plurality of tube heat exchangers 1 1 with tubes 12 crossed by a heat exchange fluid, arranged in said flow conveyor 9 at predetermined distances from each other
- arranging means 40 for transferring a forced air flow into said flow conveyor 9 towards said at least one heat exchanger 1 1 for carrying out an indirect heat exchange, using said at least one heat exchanger 1 1 , between said air flow and said heat exchange fluid, said means 40 being in fluid communication with said conveyor and, preferably, with said outlet opening for the quenching vapors from said quenching chamber.
The revamping method can envisage moreover the provision of a collection tank 25 for the condensed vapor in fluid communication with said at least one draining opening 20 of said conveyor 9 and with said plurality of tanks 2.
The revamping method can envisage moreover the provision of a chimney 28 connected to said outlet opening 18 of said conveyor 9 by means of a first pipe 29 and a second pipe 32, providing a third pipe 30 connected to the first pipe 29 and to the second pipe 32 so as to transfer a heated gas flow to a treatment plant, and providing a flow diverter valve 31 in the connection zone between said pipes 29, 30 and 32, controlled by said command and control system so as to transfer said gas flow to said chimney 28 via said second pipe 32 or transfer said gas flow to said treatment plant via said third pipe 30.
The revamping method can envisage moreover the provision of a basin 41 for containing the heat exchange fluid intended to cross the tube bundles of the exchangers 1 1 and a plurality of pipes 18 for connection with the inlet conduit and an outlet conduit for the heat exchange fluid of each tube bundle.
The revamping method can envisage moreover the provision of a pump for conveying an air flow into said conveyor 9.

Claims

1. A method for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors, comprising the steps of: - cooling glowing coke through contact with a quenching liquid up to substantial quenching, obtaining a quenched coke and a vapor flow containing polluting substances;
- conveying said vapor flow towards at least one heat exchanger of indirect heat exchange and tube type with tubes crossed by a heat exchange fluid - carrying out a first indirect heat exchange by means of said at least one heat exchanger between said vapors and said heat exchange fluid, obtaining a condensed vapor comprising said polluting substances,
- conveying an air flow towards said at least one heat exchanger and carrying out a second indirect heat exchange with said at least one heat exchanger between said air flow and said heat exchange fluid, obtaining a heated air flow, .
2. The method according to claim 1 , comprising the further step of transferring said heated air flow to a plant for heat energy recovery.
3. The method according to claim 2, wherein during said first heat exchange the heat exchange fluid is heated until it reaches a temperature preferably of between 80°C and 90°C and in any case not higher than its boiling temperature.
4. The method according to claim 3, wherein during said second heat exchange the air flow is heated up to a temperature of at least 80°C, preferably up to a temperature between room temperature and the temperature of the heated heat exchange fluid.
5. The method according to any one of the preceding claims, wherein a condensed vapor is used as a quenching liquid in said coke quenching step.
6. A plant for abatement of vapors containing polluting substances resulting from coke quenching with energy recovery from said vapors, comprising:
- a station (A) for coke quenching having a tunnel-like quenching chamber (3) and a tower (5), in fluid communication with the quenching chamber, having on its top or roof (8) a plurality of tanks (2) intended to contain a quenching liquid;
- a flow conveyor (9) having an inlet opening (10) for a fluid flow, an outlet opening (18) for a flow of non-condensed residue and at least one draining opening (20) for condensed vapors, said flow conveyor (9) being connected to said quenching chamber (3) so that the inlet opening (10) is situated substantially in correspondence with an outlet opening (7) for the quenching vapors from said quenching chamber (3);
- at least one tube heat exchanger (1 1) with tubes (12) crossed by a heat exchange fluid, arranged in said flow conveyor (9), preferably a plurality of tube heat exchangers (1 1) with tubes (12) crossed by a heat exchange fluid, arranged in said flow conveyor (9) at predetermined distances from each other
- means (40) for transferring a forced air flow into said flow conveyor (9) towards said at least one heat exchanger (1 1) for carrying out an indirect heat exchange, using said at least one heat exchanger (1 1) , between said air flow and said heat exchange fluid, said means (40) being in fluid communication with said inlet opening (10), with said conveyor (9) and, preferably, with said outlet opening (7) for the quenching vapors of the quenching chamber (3).
7. The plant according to claim 6, wherein said flow conveyor (9) has a substantially S-shaped structure, comprising an upper or conveying part (14) ending in said inlet opening (10), a bight-shaped middle part (16) and a substantially straight lower part (17) ending with said outlet opening (18), said at least one exchanger (1 1) or said exchangers (1 1) being situated in said middle part (16) and/ or in said lower part (17), said upper part (14) of said conveyor (9) having a cross-sectional area greater than the one of said middle part ( 16) and of said lower part (17).
8. The plant according to claim 7, wherein said upper part (14) comprises a wall or bottom (15), sloping and inclined with respect to the ground, to allow the conveying of condensed vapor towards the underlying middle part (16).
9. The plant according to claim 8, wherein said middle part (16) has a step (21) for collecting and conveying said condensed vapor, the step (21) being positioned downstream of the heat exchangers (1 1) and protruding from a wall of said conveyor (9) towards the inside and the upper, said middle part (16) having also an opening (20) for draining said condensed vapor, which is positioned in the correspondence with said step (21), preferably close to the connection between said step (21) and the wall of the conveyor (9) from which it protrudes.
10. The plant according to any one of claims 6 to 9, further comprising a collecting tank (25) for the condensed vapor in fluid communication with said at least one draining opening (20) of said conveyor (9) and with said plurality of tanks (2).
1 1. The plant according to any one of claims 6 to 10, further comprising a chimney (28) connected to said outlet opening (18) of said conveyor (9) through a first pipe (29) and a second pipe (32), a third pipe (30) connected to the first pipe (29) and to the second pipe (32) for transferring a heated gas flow to a treatment plant, and a flow diverter valve (31) in the connection zone of said pipes (29,30,32), controlled by a command and control system in order to transfer said gas flow to said chimney (28) through said second pipe (32) or to transfer said gas flow to said treatment plant through said third pipe (30).
12. A method for revamping a coke quenching plant of the type comprising a quenching station (A) having a tunnel-like quenching chamber (3), having on its top or roof (8) a plurality of tanks (2) intended to contain a quenching liquid, and a tower (B) for emission into the atmosphere of the vapors generated by the quenching, comprising the steps of: - decommissioning and/ or removing said quenching tower (B),
- arranging a flow conveyor (9) having an inlet opening (10) for a fluid flow, an outlet opening (18) for t condensed residual flow and at least one draining opening (20) for condensed vapors, - connecting said conveyor (9) to said quenching chamber (3) so that said inlet opening (10) is situated substantially in correspondence with an outlet opening (7) for the quenching vapors from said quenching chamber (3),
- arranging at least one tube heat exchanger (1 1) with tubes (12) crossed by a heat exchange fluid in said flow conveyor (9), preferably a plurality of tube heat exchangers (1 1) with tubes (12) crossed by a heat exchange fluid in said conveyor (9) at predetermined distances from each other
- arranging means (40) for transferring a forced air flow into said flow conveyor (9) towards said at least one heat exchanger (1 1) for carrying out an indirect heat exchange, using said at least one heat exchanger (1 1), between said air flow and said heat exchange fluid, said means (40) being in fluid communication with said inlet opening (10), with said conveyor (9) and, preferably, with said outlet opening (7) for the quenching vapors of the quenching chamber (3).
PCT/EP2015/077148 2014-11-26 2015-11-19 Method and plant for abatement of emissions resulting from coke quenching with energy recovery from said emissions WO2016083247A1 (en)

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CN110205145B (en) * 2018-04-20 2024-05-28 西安华江环保科技股份有限公司 Wet pressure quenching energy recovery system and method
CN109233876A (en) * 2018-10-15 2019-01-18 中冶焦耐(大连)工程技术有限公司 Three-dimensional water-cooling coke quenching car with bottom single-path water supply and working method thereof
CN109233876B (en) * 2018-10-15 2024-01-09 中冶焦耐(大连)工程技术有限公司 Three-dimensional water-cooling coke quenching car with bottom supplied with water in single way and working method thereof

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