DESCRIPTION

Technical Field The present invention refers to a method for the abatement of emissions resulting from the quenching of high temperature coke produced from fossil fuel or coal for use in the steel industry.

The invention also refers to a plant for carrying out said method, as well as to a method for revamping a conventional plant for coke quenching in order to make it suitable for the execution of the method above.

Background Art

It is well known in the art that the production of coke has a fundamental importance in various plants and industrial processes, in particular in plants belonging to the steel industry. The process of coke production contemplates the steps of preparation of a charge of coal, usually fossil fuel or a residual of high-temperature compounds deriving from the fractionation of oil, of power supply in coke oven batteries, of coking and of quenching of the coke obtained.

At the discharging from said oven batteries, the still glowing coal is arranged in apposite quenching railway trucks. The coke shall thus be quenched so that it can be conveyed to the following treatment steps through the conveyor belts of the plant that usually have rubber mats. Once the railway quenching truck has been loaded, it is conveyed towards a plant for the quenching of the coke. A plant for coke quenching, according to a known and currently used method of coke quenching, is schematically illustrated in Figure 1. The plant comprises a station A for coke quenching and a tower B for emitting the vapors generated by quenching. The station A presents a tunnel-like quenching chamber 3 intended to receive a railway truck containing glowing coke and a tower 5 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 liquid (water) to be introduced in the chamber 3. The tower B is in fluid communication with the quenching chamber 3, so as to allow the conveyance of the vapors generated by the coke quenching in chamber 3 and their introduction in the atmosphere.

The quenching is carried out by means of rain-like outpouring of the water contained in the tanks 2 on the coke, which is subjected to a drastic cooling, bringing its temperature from 1000°C to a temperature close to the room temperature. Part of the outpoured water evaporates, producing vapors that are diffused in the atmosphere through the designated tower B.

The cycle is usually repeated every 15-20 minutes, thus presenting an intermittent operation. Indeed, the railway trucks are conveyed from the coke ovens to the quenching plant with a frequency determined from the cycle of the battery ovens in order to allow a regular and more efficient operation of the whole coal coking plant. The coke quenching plant is thus designed so as it can sustain a rhythm as much cadenced and constant as possible.

The quenching process provokes the intermittent introduction in the atmosphere of great quantities of water vapor that, however, contains numerous polluting agents, such as the particulate, i.e. the so-called coke breeze, as well as substances constituting residuals and/or byproducts coming from the previous coking step.

Thus, in this branch the research has been directed towards methods to abate or at least limit the emission of polluting substances brought in the atmosphere by the aforementioned water vapor, with the aim of diminishing the impact on the environment of this specific step of coke treatment. To this end, some processes and relative plants that contemplate a step of treatment and abatement of said water vapor comprising polluting agents have been proposed in the branch. A particular method comprises the partial purification of the water vapor comprising polluting agents and generated by the rain-like water outpouring on the glowing coke by means of at least a series of water vapor interception baffles. Such baffles are arranged near the top of the quenching tower and comprise metal plates inclined with respect to the ascendant flow direction of the vapor. Accompanied by a partial condensation of the water vapor on the above-mentioned metal plates, a partial accumulation of the particulate occurs on them, in order to purify the flow of the exiting residual vapor. Moreover, a further step of cooling and washing of the vapors ascending towards the top of the tower thanks to the water sprayed into the tower through a series of apposite nozzles is contemplated.

Processes of this kind are described for example in patent US 4263099 and in patent application US 2012/0228115.

However, the abatement methods described above present acknowledged drawbacks bound to the need to use additional amounts of water for the condensation of vapors, which in particular should be introduced in spray form thus applying very high pressures. Moreover, according to the described conventional methods, notable emissions of water vapor are however contemplated, which are per se undesirable because of the possible interferences on the microclimate in the region where the plant is located, and moreover comprising polluting substances, among which are particulate and dusts.

Moreover, the production regime and the operation of the following quenching tower is necessarily conditioned by that of the coke oven batteries, which produce coke in an intermittent manner: the processes of coke quenching described in the above mentioned known art documents do not face the problematic relative to the necessity of cooling great volumes of thermal exchange liquid in a short period of time.

Indeed, unless introducing further volumes of low temperature thermal exchange liquid coming from outside the plant, it continues being complicated to carry out such operation in short periods of time (15-20 minutes), i.e. lowering the temperature of the heated heat exchange liquid, usually water, before the arrival of the following railway truck, charged with glowing coke. In terms of a solution to the above-mentioned problems, the patent application WO 2016/083247 suggests a process and a relative plant for abatement of the emissions coming from the high temperature coke quenching. According to the process of WO 2016/083247, firstly, there is an indirect thermal exchange between the coke quenching vapors and a thermal exchange fluid circulating in a tube type heat exchanger installed on a conveyor of such vapors, so as to cause the condensation of said vapors comprising polluting substances.

Subsequently, such heat exchange fluid, so heated, is cooled through a flow of forced air introduced in said conveyor, in order to determine an indirect heat exchange between such heated heat exchange fluid and such forced air flow, cooling the former and heating the latter. However, although being functionally efficient in the abatement of the polluting substances contained in the vapors originated through coke quenching, the process according to application WO 2016/083247 needs a fan of notable dimensions to convey a quantity of air adequate to cool the hot heat exchange fluid before the beginning of the subsequent coke quenching cycle, which significantly increases the realization and operation costs.

The technical problem at the base of the present invention is thus that of providing a method and a plant for abatement of vapors containing polluting substances coming from the coke quenching that allows to effectively abate such vapors and the polluting substances therein contained, in order to be environmentally friendly, with reduced realization and operation costs.

Summary of the invention

Such technical problem is solved, according to the present invention, by a method for the abatement of vapors containing polluting substances coming from coke quenching with energy recovery, wherein the method comprises the steps of:

- cooling glowing coke up to substantial quenching through contact with a quenching liquid, obtaining a quenched coke and a vapor flow containing polluting substances; - conveying said vapor flow towards at least one first heat exchanger of indirect heat exchange and tube type with tubes crossed by a first heat exchange fluid; - carrying out a first indirect heat exchange by means of said at least one first heat exchanger between said vapors and said first heat exchange fluid, obtaining a condensed vapor, comprising said polluting substances, and a heated first heat exchange fluid; - conveying said heated first heat exchange fluid towards at least one second heat exchanger of indirect heat exchange and comprising a second heat exchange fluid;

- carrying out a second indirect heat exchange by means of said at least one second heat exchanger between said heated first heat exchange fluid and said second heat exchange fluid, obtaining a cooled first heat exchange fluid and a heated second heat exchange fluid;

- conveying said cooled first heat exchange fluid towards said at least one first heat exchanger.

Preferably, the aforementioned method for the abatement of vapors containing polluting substances further comprises the step of conveying the aforementioned heated second heat exchange fluid towards a plant for heat energy recovery.

Advantageously, the method according to the present invention, on occasion of the aforementioned indirect first heat exchange, allows to abate effectively a flow of vapors comprising polluting substances, generating a condensed vapor comprising such polluting substances, which can be recovered without being introduced in the environment, and a residual flow, comprising residual vapor and air, substantially free of polluting substances, among which is the particulate and, in particular dusts. Moreover, in an equally advantageous manner, within a second heat exchanger, a second indirect heat exchange between such heated first heat exchange fluid and a second heat exchange fluid is efficiently carried out.

This latter operation, first, allows to effectively cool in short times the heated first heat exchange fluid. The cooled first heat exchange fluid can thus be conveyed towards the first heat exchanger.

This way, the plant wherein the method according to the invention is carried out for the abatement of a flow of vapor comprising polluting substances generated by the quenching of the coke contained in a following railway truck.

Moreover, following such indirect second heat exchange, the method according to the present invention provides a heated second heat exchange fluid, which can be preferably conveyed towards a plant for the heat energy recovery, determining a further advantage in terms of costs of execution of the method according to the invention in an industrial context, as well as of environmental sustainability.

According to a preferred embodiment, the heated first heat exchange fluid coming from such at least one first heat exchanger is conveyed into at least one intermediate containment tank for the containment of said first heat exchange fluid and from this it is conveyed into such at least one second heat exchanger.

In an equally preferred manner, the aforementioned first heat exchange fluid is a liquid, in particular water.

More preferably, during such first heat exchange the heat exchange liquid is heated until it reaches a temperature lower than its boiling temperature: when this first heat exchange liquid is water, it is heated until it reaches a temperature preferably comprised between 85°C and 95°C. In an equally preferred way, such second heat exchange fluid is a liquid, in particular water, more preferably it is water supplied from a natural source, including surface freshwater, groundwater or seawater.

Indeed, the use of groundwater results particularly advantageous since such water supply source has the advantage of maintaining an almost constant temperature throughout the year.

In a similar way, in function of the locality where the process according to the present invention is carried out, it can result particularly advantageous to use seawater, both for the limited temperature range experienced throughout the year and for the natural availability of volumes. According to a further embodiment, such second heat exchange fluid is air. Preferably, in the aforementioned step of conveying such heated second heat exchange fluid towards a plant for heat energy recovery, such heated second heat exchange fluid (heated air) is conveyed towards at least one Cowper stove.

For the purposes of the present invention, with the expression "Cowper stove" it is meant an auxiliary plant of a blast furnace comprising a chamber in turn comprising refractory material capable of storing heat, without being subjected to alterations because of the heat itself or because of the interaction with combustion gases, for example a stone wall cladding inner to the chamber or bricks piled in an alternate manner within the chamber. A Cowper stove normally operates in combination with a fan. Indeed, a Cowper stove is first heated, burning combustion gas and air within the aforementioned chamber, causing the heating of the refractory material; such gas can be gas exiting the blast furnace, or better blast furnace gas. Subsequently, once a sufficient quantity of heat has been absorbed, the aforementioned fan conveys a flow of low temperature air towards the Cowper, which passes through the refractory material contained in it, heating itself. Finally, the so-generated pre-heated flow of air is fed to a blast furnace as combustion air.

Thus, in a fully advantageous manner, the embodiment in question of the method according to the present invention contemplates that a low temperature flow of air - before being fed to at least one Cowper - is subjected to an indirect heat exchange with such heated first heat exchange fluid, heating itself, instead of being directly conveyed towards a Cowper, as differently happens according to the traditional process described in the previous paragraph. This way, the flow of heated air fed to the Cowper requires a lower quantity of heat from the refractory material to reach the desired temperature (for the feeding of a blast furnace), which advantageously translates into a saving of energy connected to the heating of the refractory material with respect to the situation wherein fresh air from the atmosphere is directly fed to the Cowper, as happens according to a conventional process.

According to another preferred embodiment, during the aforementioned step of cooling glowing coke until substantial quenching, such quenching liquid comprises a condensed vapor. Indeed, according to the embodiment in question, the condensed vapor, obtained during the aforementioned step of performing a first thermal exchange, can be recovered and then, after filtering and/ or decantation, used in a fully advantageous way as quenching liquid for the quenching of the coke transported by a following railway truck. This way, a notable saving in environmental terms is determined, since it is not necessary to collect further quenching liquid volumes outside of the plant wherein the process according to the invention is performed.

According to a preferred embodiment, the process according to the present invention can comprise a further step of conveying a flow of air towards the aforementioned at least one first heat exchanger and carrying out, within such at least one first heat exchanger, a thermal exchange between such flow of air and the aforementioned first heat exchange fluid, cooling said first heat exchange fluid and obtaining a flow of heated air, preferably wherein said flow of heated air is conveyed to a plant for heat energy recovery.

Thus, said heated first heat exchange fluid can be cooled both within the aforementioned second heat exchanger during such indirect second heat exchange between such heated first heat exchange fluid and such second heat exchange fluid, both in function of contingent needs, as well as in function of the temperature of the first heat exchange fluid before and/ or after such second indirect exchange - within the aforementioned first heat exchanger, conveying a flow of (fresh) air from the atmosphere in such conveyor and towards such first heat exchanger. Indeed, during the interval of time between the quenching of glowing coke conveyed within a quenching chamber by means of a railway truck and the arrival of a subsequent railway truck containing in turn glowing coke, such first heat exchange fluid should be cooled.

In particular, according to an embodiment of the method according to the present invention, once the glowing coke contained within a railway truck has been quenched, the latter is removed from such quenching chamber and a forced flow of (fresh) air is conveyed within such conveyor, so as to perform the aforementioned indirect thermal exchange between such forced flow of air and such first heat exchange fluid, heating the former and cooling the latter.

More in particular, during this step, the air is heated at a temperature the value of which depends on multiple factors such as the ambient temperature and the sizing of the at least one first heat exchanger, and it is comprised between the value of the ambient temperature and that of the temperature of the first heat exchange fluid before such heat exchange between the latter and such forced flow of air.

Preferably, in an absolutely advantageous manner, the so-generated forced flow of heated air can be conveyed towards a plant for heat energy recovery, so as to achieve a relative, but discreet, economic earning through the recovery of heat from such forced flow of heated air, and coherently reducing the operating costs of the plant wherein the process according to the present invention can be carried out, so as it will be possible to appreciate below.

More preferably, such flow of air can be extracted from such quenching chamber, free after the removal of the railway truck containing cooled and quenched coke.

The aforementioned technical problem is also solved by a plant for the abatement of vapors containing polluting substances resulting from coke quenching with energy recovery, wherein the plant comprises the following units:

- a station for coke quenching having a tunnel-like quenching chamber, comprising an opening for emitting quenching vapors, and a tower in fluid communication with the quenching chamber having on its top or roof a plurality of tanks intended to contain a quenching liquid; - a flow conveyor having an inlet opening for a fluid flow, an outlet opening for a residual flow and at least one draining opening for condensed vapors, wherein such flow conveyor is connected to such quenching chamber so that such inlet opening is situated substantially in correspondence with such outlet opening for the quenching vapors of the aforementioned quenching chamber;

- at least one first heat exchanger of indirect heat exchange and of a tube type with tubes crossed by a first heat exchange fluid, arranged in such flow conveyor;

- at least one second heat exchanger of indirect heat exchange comprising a second heat exchange fluid, wherein such at least one second heat exchanger is arranged externally of such flow conveyor; - at least one pipe for conveying such first heat exchange fluid from such at least one first heat exchanger to the at least one second heat exchanger;

- at least one duct for conveying such first heat exchange fluid from the at least one second heat exchanger to the at least one first heat exchanger.

Preferably, such flow conveyor has a substantially S- shaped structure, comprising an upper or conveying part ending in such inlet opening, a bight- shaped middle part and a substantially straight lower part ending with such outlet opening, wherein such at least one first heat exchanger is situated in such middle part and/ or in such lower part, and wherein such middle part has also an opening for condensate draining of a condensed vapor.

More preferably, the vapor abatement plant according to the present invention comprises a collecting tank for said condensed vapor, in which said collecting tank is in fluid communication with said at least one opening for condensate draining of the above-mentioned flow conveyor and with such plurality of tanks.

Indeed, in line with the method according to the present invention, through such opening for condensate draining, the present plant allows to collect the condensed vapor comprising polluting substances in a collecting tank, which is connected with the aforementioned tanks situated on the tower of the quenching station, in order to allow the conveyance of condensed vapor to such tanks and re-using the same as quenching liquid.

In an equally preferred manner, the plant according to the present invention can comprise an extractor fan, arranged downstream with respect to such outlet opening and in fluid communication with it. Advantageously, such extractor fan improves the conveyance of the vapors comprising polluting substances produced within the quenching chamber inside the conveyor, as well as the conveyance in the atmosphere of the aforementioned residual flow, formed following the aforementioned abatement of a flow of vapor containing polluting substances.

Preferably, such extractor fan is arranged in a pipe, arranged downstream too and in fluid communication with said outlet opening. More preferably, such said pipe comprises in turn a branching tubing for the conveyance of a flow of heated air towards a plant for heat energy recovery.

Moreover, the aforementioned extractor fan, improving the conveyance of the aforementioned flow of vapor comprising polluting substances in the atmosphere, shows itself as particularly useful especially in case of an emergency. For example, a possible emergency situation could occur if glowing coke were cooled again in the chambers before the proper cooling of the aforementioned first heat exchange fluid.

Furthermore, such extractor fan allows to implement the aforementioned embodiment of the process according to the present invention comprising the further step wherein a forced flow of (fresh) air is conveyed towards the at least one first heat exchanger, thereby performing a second indirect heat exchange between such forced air flow and said first heat exchange fluid.

The relative maximum capacity of air of such extractor fan can be opportunely calibrated and regulated, according to the convenience of the operator and with respect to its maximum capacity.

According to a preferred embodiment, the plant according to the present invention can comprise at least one intermediate containment tank for said first heat exchange fluid, wherein said at least one intermediate containment tank is in fluid communication with the aforementioned duct for the conveyance of said first heat exchange fluid from the at least one heat exchanger to the at least one second heat exchanger.

Such at least one intermediate containment tank is arranged along the flow path of said first heat exchange fluid, downstream with respect to the at least one first heat exchanger and upstream with respect to the at least one second heat exchanger, advantageously allowing the temporary stocking of said first heat exchange fluid: for example, after having been heated in the at least one first heat exchanger and before being conveyed towards the at least one second exchanger or after having been cooled in the second exchanger and before being conveyed towards the first exchanger.

Preferably, such at least one intermediate containment tank has a capacity of ca. 250 m ³ .

According to a preferred embodiment, the plant according to the present invention can comprise two intermediate containment tanks, i.e. a first containment tank and an additional second containment tank, both in fluid communication with the aforementioned duct for the conveyance of such first heat exchange fluid from the at least one first heat exchanger to the at least one second heat exchanger. Advantageously, if compared to a plant according to the present invention comprising only one intermediate containment tank having a predefined capacity, a plant equal to the one of the present invention - comprising two intermediate containment tanks each having such predetermined capacity, for example 250 m ³ - allows to perform the aforementioned step of second heat exchange in longer times.

In fact, as anticipated earlier and as will be more apparent from the detailed description, the plant according to the present invention is normally arranged to be compatible with the incoming glowing coke flow coming from the coke ovens, as well as with the intermittent and cadenced release times of the coke trucks containing glowing coke. Likewise, the steps of the method according to the present invention and the elements of the plant which enable them to be executed are suitably arranged to withstand the rhythms of the coke production plant.

The plant according to the present invention, arranged in this way and comprising two intermediate containment tanks, allows to better adapt to the rhythms of production of the coke production plant.

Indeed, once the glowing coke contained within a first railway truck has been quenched, in performing a first indirect heat exchange between a flow of vapor comprising polluting substances, so generated, and a first heat exchange fluid, the latter can be collected from a first intermediate containment tank, opportunely sized to guarantee the supply of a sufficient quantity of first heat exchange fluid such as to guarantee a condensation at least complete of said flow of vapor. The heated first heat exchange fluid is contemporarily collected within the first intermediate containment tank and, subsequently, it is conveyed towards at least a second heat exchanger for the execution of the second indirect heat exchange, in order to cool it. According to the present embodiment of the plant according to the present invention, after the cooling of the glowing coke contained in a successive railway truck, the vapor flow containing polluting substances thus generated can be cooled with the first heat exchange fluid contained in such second intermediate containment tank: this way, the first heat exchange fluid, previously conveyed to the at least one second heat exchanger and to be collected in the first intermediate containment tank, can be kept on to be cooled within the former and collected in the latter, during the cycle of quenching of the coke contained in the successive railway truck being executed. Thus, the present embodiment of the plant according to the present invention allows to perform the above-mentioned step of second heat exchange in at least a double time with respect to the time required for the same step in a plant according to the present invention having only one intermediate containment tank, obtaining this way a larger energy recovery from such heat exchange within such second exchanger. Such at least double time is calculated as the summation of the time available between a first quenching cycle and a second quenching cycle, plus the time necessary to perform the quenching of glowing coke during such second quenching cycle, plus the time that is between the latter and the arrival of a successive (and third) railway truck.

According to a further embodiment, such at least one second indirect heat exchange heat exchanger can be a tube type heat exchanger or a plate heat exchanger.

More preferably, such second heat exchange fluid circulating in such at least one heat exchanger of indirect heat exchange is water or air.

Preferably, when such second heat exchange fluid is air, the plant according to the present invention can further comprise at least one extractor fan, for example a fan, and a connecting pipe for to convey such second heat exchange fluid (air) from such at least one extractor fan to the at least one second heat exchanger, and an outlet pipe to convey hot air from the at least one second heat exchanger to at least one Cowper stove.

Indeed, since the plant according to the present invention finds a particularly convenient installation and an advantageous use in a plant for the manufacture of steel, and since in such typology of industrial plants a certain number of cowpers is commonly present (usually at least three), to each of which an extractor fan for the supply of air is associated, it results extremely advantageous to use such pre-existing elements.

Moreover, as previously explained with reference to the process according to the invention, when the second heat exchange fluid is air, during said second indirect heat exchange, not only the first heat exchange fluid (preferably water) is cooled, but the second heat exchange fluid is also preferably conveyed to the cowpers through said outlet pipe. This way, since pre-heated air is fed to the cowpers, rather than air at room temperature (this last possibility normally happens in a conventional plant for the production of steel), a further advantage in terms of a significant energy saving is accomplished.

It is furthermore to be noted that the environmental conditions do not represent a particular limit for the plant according to the present invention, which can be advantageously dimensioned, in every single one of its parts, in function of the distinctive climate of the region where it is to be installed.

The aforementioned technical problem is also solved by a method for revamping a pre-existing coke quenching plant of the kind comprising a quenching station having a tunnel-like quenching chamber, having on its top or roof a plurality of tanks intended to contain a quenching liquid, and a tower for emission into the atmosphere of the vapors generated from the quenching, comprising the steps of:

- decommissioning and/ or removing said tower,

- providing a flow conveyor having an inlet opening for a fluid flow, an outlet opening for a residual flow and at least one opening for condensate draining,

- connecting such flow conveyor to such quenching chamber so that said inlet opening is situated substantially in correspondence with an outlet opening for the quenching vapors from such quenching chamber,

- providing inside the aforementioned flow conveyor at least one first heat exchanger of indirect heat exchange and of tube type with tubes crossed by a first heat exchange fluid; - providing outside such flow conveyor at least one second heat exchanger of indirect heat exchange, in which a second heat exchange fluid flows;

- connecting said at least one first heat exchanger with such at least one second heat exchanger so that such first heat exchange fluid can be conveyed from such at least one first heat exchanger to such at least one second heat exchanger, and vice versa;

Preferably, the aforementioned method for revamping a pre-existing coke quenching plant comprises the further step of arranging a extractor fan, downstream with respect to and in fluid communication with it.

More preferably, the aforementioned method for revamping further comprises the steps of:- providing a connecting pipe for conveying such second heat exchange fluid from such at least one extractor fan to such at least one second heat exchanger, and connecting such at least one connecting pipe with such at least one extractor fan and with such at least one second heat exchanger; - providing an outlet duct for conveying such second heat exchange fluid from such at least one second heat exchanger to such at least one preexisting Cowper stove, and connecting such outlet duct with such at least one second heat exchanger and with such at least one pre-existing Cowper stove. Further characteristics and the advantages of the present invention will result from the detailed description reported below in form of preferred embodiments, given as an indication and not a limitation with reference to the attached drawings.

Brief Description of Drawin s Figure 1 schematically shows a plant for coke quenching according to the prior art; Figure 2 schematically shows in perspective a plant for the abatement of vapors containing polluting substances coming from the quenching of coke with energy recovery according to the present invention;

Figure 3 schematically represents in perspective a peculiarity of the plant represented in Figure 2;

Figure 4 represents a further different embodiment of a plant for the abatement of vapors according to the present invention comprising an intermediate containment tank and four second heat exchangers for an indirect heat exchange between a first heat exchange fluid and a second heat exchange fluid, wherein the four second heat exchangers are each connected in an independent manner to four cowper stoves.

Detailed description of a preferred embodiment

In Figure 1 it is illustrated a conventional plant for coke quenching that was already previously described with reference to the prior art. With reference to Figure 2, it is shown a plant, generally indicated with 1, for the abatement of vapors coming from the coke quenching with energy recovery, which implements the process according to an embodiment of the present invention.

The plant 1 comprises a quenching station A of a coke having a tunnel-like quenching chamber provided with an opening 4 for the inlet or the intermittent reception of a railway truck (not shown) containing glowing coke. The quenching station A further comprises a tower 5 located above the quenching chamber 3 above an upper opening 7 of said quenching chamber 3 and in fluid communication with it. The tower 5 presents a top or roof 8 wherein a plurality of tanks 2, (in this case two tanks) intended to contain an appropriate quenching liquid, normally water, is arranged.

According to the present invention, the plant 1 comprises a device for the conveyance and the abatement of vapors generated in the chamber 3 due to the quenching of glowing coke by means of the quenching liquid. In the present embodiment, with reference to Figure 3, such device comprises a flow conveyor 9 internally provided with three first heat exchangers 1 1 opportunely distanced between them. Each first heat exchanger 11 is of a tube type one with tubes 12 that cross the flow conveyor 9 from one end to the other in a substantially transversal direction. Such tubes are traversed by a first heat exchange fluid, which is water in the embodiment represented in Figures 2 and 3. Moreover, each first heat exchanger 11 can be made of one or more modules, each in turn comprising tubes 12 organized in a serpentine-like manner or with a single direction of movement, according to the sizing and use. More in particular, the flow conveyor 9 presents a conformation in a substantially "S" shape comprising an upper or conveying part 14 ending with an inlet entrance or opening 10, a bight- shaped middle part 16 and a substantially straight lower part 17, ending with an outlet opening 18. Said upper part 14 comprises a wall or bottom 15 inclined with respect to the ground and sloped.

The conveyor 9 is arranged laterally with respect to the quenching chamber 3, to which it is connected through opportune mounting devices, conventional in themselves, so that the inlet opening 10 is located substantially above the quenching chamber 3 and in lateral proximity of said opening 7.

In the present embodiment, the first heat exchangers 11 are advantageously situated in the bight- shaped middle part 16 and in the lower part 17 of the conveyor 9, which constitute indeed a heat exchange zone, while the upper part 14 functions substantially as a flow fluid conveyor towards the heat exchange zone of the conveyor 9. Moreover, the upper part 14 of the conveyor 9 presents a transversal section larger with respect to that of the intermediate part 16 and of the lower part 17 in order to convey huge intermittent fluid flow rate (quenching vapors) towards the heat exchange zone of the conveyor 9.

The conveyor 9 further presents at least one opening 20 for condensate draining formed on a side of the conveyor 9, the at least one draining opening 20 being located near or at the level of a heat exchanger 11, preferably downstream of the heat exchanger 11 with respect to the flow direction in the conveyor 9. In the present embodiment, it is contemplated a first opening 20 for condensate draining located in the intermediate part 16 downstream of the two heat exchangers 11 present in said intermediate part 16, and a second opening 20 for the condensate draining located in correspondence of the third of the first three heat exchangers 1 1 arranged in the terminal part 17.

More in particular, in the intermediate part 16 a step 21 is formed downstream with respect to the first heat exchangers 11 that extends from one side of the conveyor 9 towards the inside and the top, with the opening 20 for condensate draining of the intermediate portion that is formed in correspondence of such step 21, substantially in proximity with the connection of the step 21 with the side of the conveyor 9 from which it departs.

This way, the step 21 and the respective side of the conveyor 9 advantageously form a collecting and conveying zone for the condensed vapor formed because of the heath exchange with said first heat exchangers 11 towards the opening 20 for condensate draining. In the present embodiment, the step 21 turned towards the inside is connected to a curved upper trait 16a of the intermediate part 16, where the first heat exchangers 11 are present, and to a lower curved trait 16b bending in a direction opposite to said intermediate part 16, the lower trait 16b thus having a minor transversal section (i.e. a section shrinkage) with respect to that of the upper trait 16a.

The plant 1 further comprises a tank 25 (lower) for collecting the condensed vapor in fluid communication with the openings 20 for condensate draining of the conveyor 9 through respective connecting pipes 24. The tank 25 is furthermore in fluid communication with the tanks 2 for the quenching liquid by means of a connecting pipe 27 so as to advantageously use the condensed vapor for the quenching of the coke, thus reducing the supply of further quantities of quenching liquids (water) coming from the outside of the plant.

The plant 1 can also contemplate a system of filtration and deoiling (not represented), in itself conventional, integrated or at least in fluid communication with the lower tank 25 and to purify at least one portion of the condensed vapor collected in the tank 25 before recycling it to the tanks 2 for the quenching liquid. The plant 1 also comprises a pipe 29, located downstream and connected to the outlet entrance 18 of the conveyor, for the conveyance of a residual flow substantially free of polluting substances to a chimney 28 connected with it. The pipe 29 presents an intermediate zone with an increased average diameter, on which inside an extractor fan 31 is set. The extractor fan 31 results substantially positioned along the flow path of such residual flow, having the double function of simplifying the conveyance of the vapors comprising polluting substances produced in the quenching chamber within the conveyor and to send said residual flow toward the chimney 28 for the emission into the atmosphere in case of possible emergency situations.

Moreover, the pipe 29 further comprises a branch tubing 30, i.e. a conduct for the conveyance of a forced flow of heated air towards a plant for the energy recovery of heat, external to the plant according to the present invention, and not represented since fully conventional.

Indeed, with particular reference to the summary, the extractor fan 31 has further function of conveying within the conveyor 9 a forced flow of (fresh) air, collected from the atmosphere by means the aforementioned upper opening 7 of the quenching chamber 3.

In particular, the extractor fan 31 is arranged for the conveyance of said forced flow of air, through its inlet entrance or opening 10, in the conveyor 9, wherein it is heated by contact with the first three heaters 1 1 , generating a forced flow of heated air. Coherently, the pipe 29 is able to receive said forced flow of air, which - with the help of a diverter valve 32 is introduced in such branch tubing 30. Such diverter valve 32 is set at the mouth of the tubing 30, being thus suitable for the opening and closing of the latter, so as to ease the conveyance of the flows of fluid coming from the conveyor 9 alternatively towards the chimney 28 or towards the branch tubing 30.

Plant 1 further comprises a tank 21 for the containment of the first heat exchange fluid intended to flow through the tube bundle of the first heat exchangers 1 1 , each tube bundle having an inlet collector and an outlet collector (not shown) of the first heat exchange fluid in fluid communication with the tank 21 by means of respective connecting tubes 23 having each a free end dipping in the tank 21. This way, the tank 21, the first heat exchanger 11 and the collecting tubes 23 result included in only one circuit for the circulation of the first heat exchange fluid.

Plant 1 further comprises a second heat exchanger of indirect heat exchange and of the plate kind (according to a different embodiment, the second heat exchanger can be suitably a heat exchanger of indirect heat exchange and tube type, as disclosed in advance in the summary, for example a countercurrent heat exchanger), arranged externally with respect to said flow conveyor 9, as evident from Figure 2.

The heat exchanger 36 allows for an indirect heat exchange between the first heat exchange fluid and a second heat exchange fluid circulating in it; with reference to the plant represented in Figure 2, such second heat exchange fluid is water. As disclosed in advance in the summary, such second heat exchange fluid can be sea water, ground water or surface fresh water, for example of a river, depending on the availability of the place where the plant is built.

The heat exchanger 36 is in fluid communication with the intermediate containment tank 21 by means of a connecting pipe 35, able to convey the first heat exchange fluid from the first heat exchangers 11 to the second heat exchanger 36.

Coherently, the connection pipe 35 presents a free end 35a dipping in the tank 21 ; this way, the second heat exchanger 36, as well as the tube 35 itself, results comprised in the aforementioned single circuit for the circulation of the first heat exchange fluid, together with the tank 21 and the first heat exchangers 11.

The plant 1 further comprises a return duct 38, able to convey the first heat exchange fluid from the second heat exchanger to the first heat exchangers. The return duct 38 presents a free end 38a dipping in the tank 21 ; this way, the duct 38 results in turn comprised in the aforementioned single circuit for the circulation of the first heat exchange fluid, together with the tank 21 , to the first heat exchangers 11 and the second heat exchanger 36. At the inlet of the second heat exchanger 36 there is a duct 40, able to introduce a second heat exchange fluid (water, in the present example plant). Once entered in the heat exchanger 36 and carried out the second indirect heat exchange with the first heat exchange fluid, also circulating in the heat exchanger 36, but along a different flow path, the second heat exchange fluid comes out heated by the second exchanger 36 through a duct 41.

A duct 41 , also suitable for the possible conveyance of said heated second heat exchange fluid to an energy recovery system, allows the conveyance of the second heat exchange fluid from the heat exchanger 36 to the source of said heat exchange fluid, for example a water reservoir like a lake, a river, an artesian aquifer, or the sea.

The plant according to the present invention as mentioned above can be realized ex-novo or can be realized starting from an already existing plant for the quenching of coke revamped according to the method for revamping according to the present invention.

Indeed, another aspect of the invention refers to a method for revamping a pre-existing quenching plant, for example a plant of the kind represented in Figure 1, so as to obtain a plant wholly comparable with the plant represented in Figure 2.

The elements of the pre-existing conventional system not according to the invention of Figure 1 that are structurally and/ or functionally equivalent to corresponding plant elements according to the above-described invention are given the same reference numerals as those of the invention. The pre-existing plant shown in Figure 1 comprises a coke quenching station A having a tunnel-like quenching chamber 3 and a tower 5 in fluid communication with the quenching chamber 3 which has at its top or roof 8 a plurality of tanks 2 intended to contain the quenching liquid, and a tower B to eject the vapors generated by the quenching of the coke. The steps for implementing the method for revamping for the preparation of a plant according to the present invention are described below, as described above with reference to Figure 2. Before all, the quenching tower B is decommissioned and/ or removed.

Subsequently, a flow conveyor 9 is provided with an inlet opening 10 for the introduction of a fluid flow, with an outlet 18 for a residual stream and at least an opening 20 for condensate draining of a condensed vapor; it is then contemplated the step of connecting the flow conveyor 9 to the quenching chamber 3 so that the inlet opening 10 is substantially positioned in correspondence of a discharge opening 7 for the outlet of the quenching vapors of the quenching chamber 3.

Subsequently, at least one first indirect heat exchanger of indirect heat exchange 11 and tube type, with tubes run by a first heat exchange fluid, in this case a number of three exchangers at predetermined distances, is arranged inside the conveyor 9.

Between the various operations, it is also provided for the arrangement of the tank 25 for the collection of the condensed vapor, as well as for the connection of the latter element with the draining openings 20 of the conveyor 9, as well as with the tanks 2 for the quenching liquid, by means of apposite pipes.

Thus, externally with respect to the flow conveyor 9, it is provided for a second heat exchanger 36 of indirect heat exchange inside which a second heat exchange fluid flows: in the present case, such second heat exchanger is a plate heat exchanger crossed by sea water.

Moreover, it is also contemplated the arrangement of a tank 21 for the containment of the first heat exchange fluid intended to cross the tube bundles of the heat exchangers 11 and a plurality of connecting tubes 18 for the inlet and outlet of the first heat exchange fluid in /out each tube bundle. The plurality of connecting tubes 18 is arranged to be in fluid communication with the tank 21.

Subsequently, the first heat exchangers 1 1 are connected to the second heat exchanger 36 so that the first heat exchange fluid can be conveyed from the first heat exchangers to the second heat exchanger. The operation just described is performed providing a tube 35, which is in fluid communication with the second heat exchanger 36 and has an end dipping in the tank 21. Contextually, the following elements are provided: a return duct 38 for the conveyance of the first heat exchange fluid from the second heat exchanger 36 to the tank 21 ; an inlet pipe 40 for the introduction of the second heat exchange fluid in the second heat exchanger 36; and, an outlet pipe 41 for the outlet of the second heat exchange fluid from the second heat exchanger 36.

Moreover, the method for revamping such as to provide a plant according to the invention, so as represented in Figure 2, contemplates the steps of providing a pipe 29, as well as the connection of this latter with the outlet opening 18 of the conveyor 9, in order to allow the outlet of a non-condensed residual from the conveyor itself.

Then, an extractor fan 31 in an intermediate zone of the tube 29 and a chimney 28 are further provided, and the latter is connected to the tube 29 in order to allow the emission in the atmosphere of said residual flow.

In particular, the pipe 29 so provided is structured in such way to comprise in turn a branch pipe 30, in order to allow the conveyance of a forced flow of heated air towards a plant for the heat energy recovery, external to the plant according to the present invention, and not represented because wholly conventional, as intended by a preferred embodiment of the process according to the present invention.

The plant realized by means of the method for revamping described in the preceding paragraphs and represented in Figures 2 and 3 allows to successfully perform the process of abatement of vapors comprising polluting substances, generated following the quenching of the coke according to the present invention. Indeed, the following was verified.

In a time interval of ca. 4 minutes, first, after the spilling of 20 m^ of water at room temperature on a rail truck comprising glowing coke, a flow of vapor comprising polluting substances is generated.

Then, such flow of vapor enters the aforementioned conveyor and, via contact with the tubes of the first heat exchangers, a condensation liquid comprising polluting substances and a residual flow of air are generated. Simultaneously, such first heat exchange fluid is heated from 20°C to 90°C.

Subsequently, in a time interval of ca. 18 minutes, a volume equal to 250 m3 of a first heat exchange fluid (water) is conveyed to the aforementioned second heat exchanger wherein sea water at a temperature of 36°C is made to flow in countercurrent in a separate fluid circuit.

The first heat exchange fluid is thus made to cross such second heat exchanger, wherein sea water flows with a flow rate of 1000 m^/h.

Because of a second indirect heat exchange with the latter, the first heat exchange fluid reaches a temperature equal to 40°C, so that it can be subsequently re-transmitted to the first heat exchanger, available to perform a first heat exchange during a subsequent cycle.

Simultaneously, the second heat exchange fluid is consequently subjected to a heating at a temperature equal to 46 °C. According to a preferred embodiment, according to the present invention it can be realized a plant 101 so as represented in Figure 4.

Some elements of the plant 101 represented in Figure 4 are structurally and/ or functionally equivalent to corresponding elements of the plant 1 for the abatement of vapors previously described with reference to Figure 2: to such elements are attributed the same reference numbers augmented by one hundred.

Analogously, the plant 101 can be realized by means of a method for revamping according to the present invention similar to that described in the preceding paragraphs. First, a pre-existing quenching tower B is decommissioned and/or dismissed, then a conveyor 109 is made available, which is subsequently connected to the pre-existing quenching chamber 103 by means of the inlet opening 1 10, so as previously described with reference to plant 1.

Thus, three first heat exchangers 111 of indirect heat exchange and tube type are arranged within the conveyor 109, not represented because wholly similar to those already described with reference to plant 1. Thus, four second heat exchangers 136 of the kind of indirect heat exchange and wherein flows a second heat exchange fluid are provided : limitedly to the embodiment represented in Figure 4, such second heat exchange fluid is air. Subsequently, just as for the realization of plant 1 , the present embodiment of the method for revamping according to the invention intends to make available a tank 121a for the containment of the intended first heat exchange fluid, as well as for connecting the latter both with the first heat exchangers 109 (duct 123), and with the second heat exchangers 136 (duct 135), in order to form a single system for the circulation of the first heat exchange fluid (water).

Moreover, return ducts 138 for the conveyance of the first (cooled) heat exchange fluid from each second heat exchanger 136 to the tank 121a are provided. The present embodiment of the method for revamping according to the invention contemplates moreover the arrangement of an additional tank 121b for the containment of the first heat exchange fluid, as well as contemplates the connection of such further tank with the tank 121a, with the first heat exchangers 109 (by means of the tube 123), with the second heat exchangers 136 (by means of the tube 135), as well as with the return duct 138, in order to result integrant part of such system for the circulation of the first heat exchange fluid.

Moreover, the method for revamping for the realization of a plant according to the invention such as represented in Figure 4 contemplates to connect each of the four fans 139 to one of the four second heat exchangers 136, so that each fan 139 is connected to only one of the four second heat exchangers 136. Such operation allows to convey fresh air (second heat exchange fluid) taken from the environment to each of the four second heat exchangers 136. The operation described is operated first by providing connecting pipes 140 for the conveyance of said second heat exchange fluid from each fan 139 to one of the four second heat exchangers 136, and subsequently connecting pipes 140 to each fan 139 and to each heat exchanger 136. Subsequently, each of the four heat exchangers 136 is connected to one of the four pre-existing cowper stoves 150. Such operation allows to convey heated air (second heat exchange fluid) from the second heat exchangers to the cowper stoves 150, in order to make available a plant for the abatement of vapors containing polluting substances coming from the quenching of the coke with energy recovery, integrated and compatible with an existing plant (blast furnace) and realized by means of a particular embodiment of the method for revamping according to the invention, even through the recovery of pre-existing infrastructures (pre-existing coke-quenching plant). The operation described is operated first by providing outlet tubes 141 for the conveyance of the second heat exchange fluid to each of the cowper stoves 150 and, subsequently, by connecting the outlet tubes 141 to each second heat exchanger 136 and to each cowper stove 150.

Moreover, also the method for revamping such as to provide a plant so as represented in Figure 4 contemplates the arrangement of a pipe 129, as well as the connection of the latter with an outlet opening 1 18 of the conveyor 109, in order to allow the outlet of a flow of non-condensed residual from the conveyor itself.

Similarly, an extractor fan 131 in an intermediate zone and a chimney 128 are arranged, connecting the latter to the tubing 129 in order to allow the emission into the atmosphere of said non-condensed residual flow.

Ultimately, from the previous description it is clear that the present invention allows to efficiently realize ex novo or, by means of a method for revamping, of a pre-existing plant for the quenching of the coke, a plant for the abatement of emissions coming from the quenching of the coke with energy recovery.

Such kind of plant results particularly adapted in the execution of a process for the abatement of emissions coming from the quenching of the coke with energy recovery, equally according to the present invention. In general, such process brings numerous benefits, the first of which lies in the fact that it is possible to perform an abatement of vapors coming from the quenching of the coke, comprising polluting substances, in a completely efficient manner, through an indirect heat exchange between a flow of the latter and a first heat exchange fluid.

Then, thanks to a second indirect heat exchange between such first heat exchange fluid and a second heat exchange fluid, it is possible to cool such first heat exchange fluid in an efficient manner not only in terms of cooling of the average temperature of such first heat exchange fluid, but also in terms of execution of such operation in limited time intervals.

Moreover, a further advantage consists in the possibility of recovering energy from such heated second heat exchange fluid by conveying it to an energy recovery system, which can be a cowper, as previously described in detail with reference to a preferred embodiment of the plant according to the present invention, and/or any industrial and/or civil system.

Moreover, from a standpoint of resource economy, the plant and the process for the abatement of vapors containing polluting substances coming from the quenching of the coke according to the present invention can advantageously contemplate the recovery of condensed vapor comprising polluting substances and, after opportune treatments of purification of the liquid, such as conventional and practical techniques of purification and settling, conveying it to the tanks for the coke quenching liquid, in order for it to be re-used. Otherwise said, the plant suitable for the execution of the process according to the present invention contemplates a functioning at inferior costs with respect to a similar plant capable of sustaining the same productive capacity with the methods of the prior art.