PROCESS FOR DRY COOLING OF COKE WITH STEAM WITH SUBSEQUENT USE OF THE SYNTHESIS GAS PRODUCED

Abstract

A method for the dry quenching of coke using steam with subsequent use of the synthesis gas generated, the method involving the cyclic coking of coal to coke with the coke being sent to a quenching device after being discharged from the coke oven and steam being introduced into the quenching device for dry quenching, thus creating synthesis gas made up of carbon monoxide (CO) and hydrogen (H2) via a water-gas reaction, and the synthesis gas produced being fed to a further application. This method allows the heat generated during coking to be used for the production of useful synthesis gas which, in turn, can be used for a further purpose or in the heating process, thus on the whole achieving an extremely even energy balance throughout the entire process.

Description

The invention relates to a method for the dry quenching of coke by means of steam with subsequent use of the synthesis gas generated, said method involving the cyclic coking of coal to coke with the coke being sent to a quenching device after being discharged from the coke oven and steam being introduced into the quenching device for dry quenching, thus creating synthesis gas made up of carbon monoxide (CO) and hydrogen (H₂) via a water-gas reaction, and the synthesis gas produced being fed to a further application. This method allows the heat generated during coking to be used for the production of useful synthesis gas which, in turn, can be used for a further purpose or used in the heating process, thus on the whole achieving an extremely even energy balance throughout the entire process.

Most methods for the production of coke take place in large coke oven batteries or coke oven banks that comprise conventional coke oven chambers or coke oven chambers of the “heat recovery” or “non-recovery” type. In conventional coke oven chambers the coking gas is collected and processed, while the coking gas in “heat recovery” or “non-recovery”-type coke oven banks is combusted in the coke oven in order to heat said oven. Here, in many embodiments the heating of the coke oven is carried out in several steps in a gas space above the coke cake and in a coke oven sole below the coke oven chamber.

The coking process is performed cyclically, the cycles being charging, coking, discharging and quenching. After coking, the coke is pushed out of the coke oven chamber at a temperature of approximately 1100° C. It is pushed out into a quenching car that collects the coke cake and transports it to a quenching device. In many embodiments this is a wet quench tower, where the coke cake is sprayed with water which evaporates and cools the coke cake to a temperature below the kindling temperature of the coke so that it can be transported in the open air without posing a hazard. After quenching, the temperature of the coke is unevenly distributed in the coke cake but is usually less than 100° C.

DE19614482C1 gives one embodiment of a wet quench tower. This teaching describes a plant for the wet quenching of hot coke in a process for the coking of coal using a coke sluice and a coke transfer chute that is located in a quench tower with a water feed device. On the other side, the chute fits onto a coke quenching car equipped at the bottom end with a coke discharge device and water discharge flaps. The water feed system is located directly at the transfer chute and empties into the coke quenching car, which can be sealed watertightly, and said car is equipped with a control system which keeps the coke discharge flaps closed watertightly while the water is being fed in and opens the water discharge flaps once the water feed has been completed. When water is used for quenching, all of the thermal energy stored in the coke cake is lost without being used.

For this reason, increasing efforts have recently been made to dry quench hot coke using gases instead of water. Here, the gases are passed through the hot coke and collected or extracted until the coke has cooled to a temperature below its kindling temperature. The hot gas is usually passed through a heat recovery unit in which steam is generated, thus recovering the thermal energy. In turn, the steam can be used to drive auxiliary units or to generate electric power. For these purposes, inert gases, such as nitrogen or blast furnace gas, are often used.

WO9109094B1 describes a method for the dry quenching of coke in a quenching chamber with the aid of circulating quenching gas, said method allowing the velocity of the gas corning from the coke to be adjusted so that the grain size of the entrained coke dust particles is less than 3 mm and when the hot quenching gas enters the waste heat recovery boiler the grain size of the entrained coke dust is less than 1 mm, said method involving this gas being passed through a device that consists of a quenching chamber and an antechamber with a round cross section of about equal size and a cylindrical outer casing made of metal, and in particular the roof of the quenching chamber being in an inclined position so that it rises to the hot gas channel, thus increasing the cross section of the annular gas channel above the coke pile enough to allow the gas velocity of the hot quenching gas to be adjusted during quenching so that it remains virtually uniform across the length.

WO8602939A1 describes a method for dry coke quenching using quenching gas, said method involving the coke and the quenching gas being fed in countercurrent direction through a two-stage quencher, the first stage involving quenching to coke temperatures of approximately 800° C. and the quenching gas fed through the second quenching stage containing steam, the quenching gas loop thus being directly coupled with a thermal treatment step in which steam is added so that there is essentially no char burnout, which is achieved by the quenching in the first quenching stage taking place solely by indirect heat exchange between the coke and a coolant via heat exchanger walls and the quenching in the second stage being carried out solely by means of the steam-containing quenching gas.

State-of-the-art methods for dry coke quenching may include a variety of embodiments. EP0317752A2 describes a method for improving the performance of coke dry quenchers which involves hot coke being broken up before entering the quenching shaft. DE3030969A1 describes a method for the dry quenching of hot raw coke that is pushed out of the chambers of a coke oven battery and discharged in a quenching chamber, where it is quenched by means of direct or indirect contact, or both, with a quenching agent, and therefore the raw coke is preclassified into two or more size fractions before entering the quenching chamber and the individual size fractions are subjected to quenching in separate quenching chambers.

Further embodiments relate to the heat recovery or cleaning of the quenching gas. DE2435500A1 describes a method for preheating coking coal using superheated waste heat steam which is generated in a dry coke quencher by the coke releasing, at its highest temperature level, some of its heat to the walls of a steam jacket. DE3217146A1 describes a device for dedusting the loop gas of a coke dry quencher in which the gas inlet channel and the gas outlet channel are located at right angles to each other, the gas outlet channel being directly connected, via a conical expansion, with the inlet opening of the waste heat recovery boiler integrated into the gas loop and a dust collection chamber with an inclined dust discharge area being positioned on the opposite side to the gas inlet channel.

However, the said methods and their embodiments have the disadvantage that during quenching the heat of the coke either cannot be recovered or the heat of the coke can only be inefficiently recovered as during quenching a large gas volume is generated and this needs to be passed through a heat recovery unit, making quenching technically difficult or economically inefficient. For this reason, it would be advantageous to utilise the heat that exists in the pushed coke via an endothermic chemical reaction that makes this energy available in chemical form.

One suitable endothermic chemical reaction is the water-gas reaction with the corresponding water-gas equilibrium. To carry out this reaction, steam (H₂O) is passed through the hot coke, which reacts with the steam (H₂O) to form hydrogen (H₂) and carbon monoxide (CO). This reaction is endothermic and reads:

C+H₂OH₂+CO; ΔH=+131.3 kj/mol

An additional reaction between the steam and the coke to form carbon dioxide and two equivalents of hydrogen is possible but according to the invention it does not generally take place due to suitable metering and a suitable gas velocity of the steam. This reaction is strongly endothermic and can only be carried out with additional heating of the coke.

GB347601A describes a method for the production of a gas mixture made up of nitrogen and hydrogen which is suitable for the synthesis of ammonia and which is produced in a coke quenching device in which the coke is sprayed with water and permeated by air and in which the carbon monoxide is directed into a plant section in which the carbon monoxide is converted into an equivalent of hydrogen via a subsequent conversion of the carbon monoxide using steam. Here, the steam for converting the carbon monoxide comes from the water that is sprayed into the coke cake in order to quench the coke. The application does not describe quenching the coke cake with permeating gaseous steam.

Therefore, the objective is to provide a method that cyclically carbonises coal and uses gaseous steam (H₂O) to dry quench hot coke after a coking cycle, with the steam (H₂O) thus reacting at least partially with the coke to form hydrogen (H₂) and carbon monoxide (CO) according to the water-gas equilibrium, the hydrogen (H₂) obtained being collected and the gas mixture thus obtained being used for a further purpose. In this way synthesis gas is obtained.

According to the invention, coke quenching using steam takes place in a quenching device that is preferably designed as a quenching shaft. Following coking of the coal and completion of the coking process, the coke cake is taken to, or tipped onto, a quenching car, which transports the coke cake to the quenching device. Here, the coke cake is sealed off from the surrounding atmosphere and gaseous steam is passed through it. Preferably, this is done in a vertically upward gas flow direction so that the specifically heavier steam is displaced by the lighter hydrogen during the quenching process. The steam may be a gas mixture in any state and even be in a mixture with other gases, but it is preferably used in pure form.

What is claimed in particular is a method for the dry quenching of coke, in which

• • coal is heated in a coke oven via heating by means of a high calorific gas and coke is obtained via cyclic coking, said coke being pushed out into a coke quenching car on completion of the coking, and
  • the incandescent coke is transported to a coke quenching device in a coke quenching car in which said incandescent coke is quenched to a temperature below the kindling temperature by means of a quenching gas,

and said process being characterised in that

• • gaseous steam (H₂O) is used as the quenching gas under the exclusion of air, said steam reacting at least partially with the incandescent coke (C) according to the water-gas reaction to form synthesis gas made up of hydrogen (H₂) and carbon monoxide (CO), and
  • due to the dry quenching being carried out in a coke quenching device the hydrogenous quenching gas obtained is collected, and
  • the gas mixture thus obtained is used for a further purpose.

The synthesis gas generated may also contain impurities, but if the reaction is carried out correctly, it consists mainly of the constituents hydrogen (H₂) and carbon monoxide (CO).

For implementing the method the steam is preferably generated in a steam boiler. Said steam is kept hot through suitable possibilities for intermediate storage and is then fed into the coke quenching device under pressure using a metering device. In order to prevent condensation of the steam on introduction into the coke quenching device, the feed pipes can, in an advantageous embodiment, be heated. When the steam reacts with the hot coke, hydrogen (H₂) and carbon monoxide (CO) are produced. In a preferred embodiment the gaseous steam used is dry, i.e. there are no adhering water droplets or mist. Via the method according to the invention the thermal energy of the coke that is released during quenching following the coking process is used to generate useful products. As a result, the energy balance of the overall coke production process can be improved.

The synthesis gas generated and the hydrogen contained therein can be used for any further purpose. In one embodiment of the invention use of this gas mixture for a further purpose involves it being added to the fuel gas of the coke oven(s). In this way, the coke oven is heated with the gas generated during quenching of the coke. For this, the hydrogen used to heat the coke oven can be mixed with a hydrocarbonaceous fuel gas before being fed to the coke oven. In an exemplary embodiment the fuel gas is natural gas. In a further embodiment, the fuel gas is coke oven gas. It is also possible to use blast furnace gas from a blast furnace process as the fuel gas instead of a hydrocarbonaceous fuel gas.

In an further embodiment the synthesis gas is subjected to a heat recovery process before being used for a further purpose or being fed to the coke oven for heating purposes. This may, for example, be achieved by passing the gas through a waste heat recovery boiler. In one embodiment of the invention steam is generated during the heat recovery process. In a typical embodiment the steam is then used to generate mechanical energy by driving a turbine. This can, in turn, be used to generate electric power. It is also possible to direct the synthesis gas generated through a heat exchanger in which the steam used for quenching is preheated in countercurrent direction.

In a further embodiment of the invention a water-gas shift reaction is carried out to convert the carbon monoxide (CO) into carbon dioxide (CO₂) after the coke has been quenched with steam (H₂O). As a result, a gas mixture is obtained. This gas mixture mainly consists of hydrogen (H₂) and carbon dioxide (CO₂) and can be easily converted into pure hydrogen, for example by means of pressure-swing adsorption. Here, in one embodiment the steam required for this can be added in excess to the quenching process or added to the synthesis gas already generated. It may also be sprayed in as liquid water after the coke has been quenched.

In a further embodiment of the invention use for a further purpose relates to a conversion of the carbon monoxide with steam and subsequent purification of the hydrogen obtained during the conversion in a pressure-swing adsorption unit. The hydrogen can then be used, for example, in a chemical process in a subsequent application. Pressure-swing adsorption units for the purification of hydrogen from hydrogenous gases are well-known in the state of the art. WO2006066892A1 teaches one example of a method for purifying hydrogen by means of pressure-swing adsorption.

In a further embodiment of the invention the steam is split into at least two part streams for quenching. In one embodiment of the invention a part stream of the steam is introduced into the coke quenching device from below in a vertically upward flow direction and a further part stream of the steam is fed into a part of the shaft in which the coke to be quenched has a temperature of 500 to 900° C. This may, for example, be done via feed nozzles installed in the side of the shaft that inject the steam directly into the coke.

In one exemplary embodiment of the invention the coke quenching device is a coke quenching shaft. In a further exemplary embodiment of the invention the coke quenching device is a coke quenching chamber. In addition, this may, for example, be equipped with an antechamber. The quenching device or the subsequent transfer line for the hydrogen may also be equipped with a dedusting device. This allows the dust to be reduced if a dust-laden coal is used or large amounts of dust are created during quenching.

For it to be used in implementing the method, the coke oven battery or coke oven bank may be of any design and configured in any way. The coke oven battery from which the coke comes and which is heated by the synthesis gas may, for example, be a coke oven battery in which the coking gas is collected and processed. The coke oven bank from which the coke comes may, for example, be a “heat-recovery”-type coke oven battery. Finally, the coke oven bank from which the coke comes may also be a “nonrecovery”-type coke oven battery. Even the coke ovens that are located in a coke oven battery or bank may ultimately be of any design as long as they are suitable for the production of coke and for being heated by synthesis gas when appropriate. The coke pushing may also be carried out at a different coke oven battery or bank from that to which the synthesis gas obtained during quenching is fed, but this is not usual practice.

Furthermore, auxiliary equipment, such as storage tanks for liquids or gases, pumps, valves, heating or quenching equipment, knock-out drums or meters for measuring temperatures or concentrations of gas constituents may be used at any point in the method according to the invention.

The invention has the advantage of utilising the thermal energy of the coke after coking by means of an endothermic chemical reaction and so the thermal energy of the hot coke can be utilised much better than in prior-art methods. Furthermore, the invention has the advantage of providing hydrogen as a useful product without the addition of further energy, thus allowing the energy balance of the overall method to be improved. The environmental compatibility of this method can thus be considerably improved.

The invention is further explained by means of a drawing, this drawing merely representing an exemplary embodiment and not being limited thereto.

FIG. 1 shows a coke oven which serves to carbonise coal. It depicts the coke oven chamber (1) with the coal cake (2), the coke oven chamber doors (3), the primary heating space (4) above the coke cake (2) and the secondary heating space (5) below the coke cake (2). The quenching car (6), which collects the coke cake (2) for quenching, is parked in front of the coke oven chamber (1). Said quenching car (6) is brought in front of the coke quenching chamber (7) and the coke cake (2) is emptied into the coke quenching chamber (7) via a feed flap (7a). Said flap (7a) is closed once the coke quenching chamber (7) has been filled. Steam (8, H₂O) then flows into the coke quenching chamber (7) from below and reacts with the hot coke cake (5a) according to the water-gas equilibrium to form hydrogen and carbon monoxide (9, H₂ and CO) as synthesis gas. The steam (8) is generated via a steam boiler (10) with a downstream metering device (10a). The synthesis gas (9) generated during quenching is extracted in an upwards direction and, following dedusting in a dedusting unit (11), it is directed into the secondary heating space (5) of the coke oven (1) as fuel gas (9a). This is done via a heat exchanger (12), which, in countercurrent direction, preheats the steam (8) fed in to quench the coke (2). Here, it is added to the partially combusted coking gas which has already flowed into the secondary heating space (5) from the primary heating space (4) and combusted. As a result, it contributes to the heating of the coke cake (2) through the floor of the coke oven chamber (1). After combustion, the fully combusted coking gas is exported out of the secondary heating space (5) as waste gas (13) and sent to a gas scrubbing device (14). The cleaned waste gas (14a) is exported from the gas scrubbing device (13) and sent to a heat recovery unit (15). Here, a generator (15a) that generates electric power is driven via a turbine. The cooled waste gas (15b) is exported via a flue (16). The quenched coke (5a) or the coke to be quenched (5a) is discharged via a discharge flap (7b) and sent for final quenching.

LIST OF REFERENCE NUMBERS AND DESIGNATIONS

• 1 Coke oven chamber
• 2 Coal or coke cake
• 3 Coke oven chamber doors
• 4 Primary heating space
• 5 Secondary heating space
• 5a Coke to be quenched
• 6 Quenching car
• 7 Coke quenching chamber
• 7a Feed flap
• 7b Discharge flap
• 8 Steam
• 9 Synthesis gas
• 9a Fuel gas for the secondary heating space
• 10 Steam boiler
• 10a Control valve for steam
• 11 Storage tank
• 12 Heat exchanger
• 13 Waste gas
• 14 Gas scrubbing device
• 14a Cleaned waste gas
• 15 Heat recovery unit
• 15a Generator
• 15b Cooled waste gas
• 16 Flue

Claims

1. Method for the dry quenching of coke in which

coal is heated in a coke oven via heating by means of a high calorific gas and coke is obtained via cyclic coking, said coke being pushed out into a coke quenching car on completion of the coking, and

the incandescent coke is transported to a coke quenching device in a coke quenching car in which said incandescent coke is quenched to a temperature below the kindling temperature by means of a quenching gas,

wherein

gaseous steam (H2O) is used as the quenching gas under the exclusion of air, said steam reacting at least partially with the incandescent coke according to the water-gas reaction to form synthesis gas made up of hydrogen (H2) and carbon monoxide (CO), and

due to the dry quenching being carried out in a coke quenching device the hydrogenous quenching gas obtained is collected, and

the gas mixture thus obtained is used for a further purpose.

2. Method for the dry quenching of coke according to claim 1, wherein use for a further purpose relates to the gas mixture being added to the fuel gas of the coke oven(s).

3. Method for the dry quenching of coke according to claim 2, wherein a hydrocarbonaceous fuel gas is mixed with the synthesis gas used to heat the coke oven before it is added to the coke oven.

4. Method for the dry quenching of coke according to claim 3, wherein the fuel gas is natural gas.

5. Method for the dry quenching of coke according to claim 3, wherein the fuel gas is coke oven gas.

6. Method for the dry quenching of coke according to claim 1, wherein the synthesis gas is subjected to a heat recovery process before being used for a further purpose.

7. Method for the dry quenching of coke according to claim 6, wherein steam is generated during the heat recovery process.

8. Method for the dry quenching of coke according to claim 1, wherein use for a further purpose relates to conversion of the carbon monoxide (CO) contained in the gas mixture using steam (H2O), said carbon monoxide (CO) being converted to carbon dioxide (CO2).

9. Method for the dry quenching of coke according to claim 8, wherein use for a further purpose relates to conversion of the carbon monoxide (CO) using steam (H2O) and subsequent purification of the hydrogen (H2) obtained in a pressure-swing adsorption unit.

10. Method for the dry quenching of coke according to claim 1, wherein the steam for quenching is split into at least two part streams, with one part stream of the steam being fed into the coke quenching device from below in a vertically upward flow direction and a further part stream of the steam being fed into a part of the coke quenching device in which the coke to be quenched has a temperature of 500 to 900° C.

11. Method for the dry quenching of coke according to claim 1, wherein the coke quenching device is a coke quenching shaft.

12. Method for the dry quenching of coke according to claim 1, wherein the coke quenching device is a coke quenching chamber.

13. Method for the dry quenching of coke according to claim 12, wherein the coke quenching chamber is equipped with an antechamber.