Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/90—Injecting reactants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8621—Removing nitrogen compounds
  • B01D53/8625—Nitrogen oxides
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J15/00—Arrangements of devices for treating smoke or fumes
  • F23J15/003—Arrangements of devices for treating smoke or fumes for supplying chemicals to fumes, e.g. using injection devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J15/00—Arrangements of devices for treating smoke or fumes
  • F23J15/02—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/206—Ammonium compounds
  • B01D2251/2062—Ammonia
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J2215/00—Preventing emissions
  • F23J2215/10—Nitrogen; Compounds thereof
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J2219/00—Treatment devices
  • F23J2219/10—Catalytic reduction devices
• • 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
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency
  • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Definitions

• the present invention relates to the limitation of emissions of nitrogen oxides in the environment.
• the present invention relates to an improved process for the catalytic reduction of nitrogen oxides to nitrogen.
• Nitrogen oxides, or NOx mainly include nitric oxide (NO) and nitrogen dioxide (NO2).
• NOx can associate with water and produce nitric acid HNO3, which contributes notably to acid rain, photochemical fog, and may be responsible for certain respiratory diseases, such as asthma.
• NOx nitrogen oxides
• HNO3 nitrogen dioxide
• the reduction of NOx emissions into the atmosphere has become a major issue in recent years and is subject to increasingly stringent regulations for industrialists.
• NOx are produced during the combustion of liquid or gaseous fuels, such as hydrocarbons, natural gas, refinery gas, hydrogen, or their mixtures, and escape into the atmosphere through combustion fumes.
• liquid or gaseous fuels such as hydrocarbons, natural gas, refinery gas, hydrogen, or their mixtures
• Such combustions are used in particular for heating, reforming and cracking fluids, hydrocarbon or otherwise, in petrochemical process furnaces.
• heating fluids is meant to preheat and / or heat and / or vaporize and / or overheat fluids.
• Such combustions are also used to achieve the high temperatures necessary for steam reforming reactions or steam reforming, hydrocarbon feeds (SMR, or steam methane reforming in English).
• SMR steam methane reforming
• the vaporeforming consists of the dissociation of hydrocarbon molecules (in particular methane CH 4 ) in the presence of steam and heat (several hundred degrees), and is mainly used in the industry for the manufacture of hydrogen (H 2 ) high purity.
• H 2 hydrogen
• the steam reforming process is carried out in a steam reforming furnace, fed on the one hand with hydrocarbon feedstock and steam, and on the other hand with heat. When the oven is hot, the hydrocarbon feedstock is then injected, mixed with steam, into tubes containing catalyst and passing through the furnace.
• hydrocarbon feeds are hydrocarbons, oils and natural gases.
• the hydrocarbon feedstock is selected from vaporizable hydrocarbons below 250 ° C of various origins, including fossil and plant origin.
• Preferred hydrocarbon feedstocks are natural gas, naphtha, LPG (liquefied petroleum gas), butane, propane, biodiesel, bioethanol, refinery waste gases, and all waste gases in general.
• heat is usually provided by fuel combustion various with air. This combustion is carried out in the zone of radiation (radiant section in English), sometimes also called combustion chamber, through burners, arranged in the top and / or bottom and / or on the side walls of the radiation zone .
• zone of radiation sometimes also called combustion chamber
• the fumes, products of combustion from the burned fuels are for their part evacuated at the exit of the zone of radiation, by at least one flue, through the convection zone (convection section in English), where they are cooled before their release into the atmosphere.
• a preheating system of combustion air is set upstream of the burners.
• the combustion air is preheated by recovering part of the heat available in the flue gases passing through the convection zone, this by means of heat exchangers, of exchanger type for example, these exchangers are called air preheaters.
• the process for reducing nitrogen oxides (also called process P NO ⁇ in the remainder of the description of the invention) is applicable in particular to furnaces for the implementation of petrochemical processes and to furnaces implementing a process of steam reforming.
• process PI will represent indifferently (except in particular cases obvious to the reading of the text) a reforming process implemented in a steam reforming furnace or a process implemented in a petrochemical process furnace .
• the present invention responds to the problem identified above by implementing an improved P NO leveraging process, especially less energy consuming and having a lower investment cost than the known methods for reducing the concentration of NOx combustion fumes from a PI process furnace for comparable efficiency.
• the subject of the invention is a process PI for the treatment of a charge in an oven, the process comprising at least: a step of releasing heat by the combustion of liquid or gaseous fuel in the presence of air preheated by at least one circuit preheating of air passing through the convection zone of the fumes one or more times, this step leading to the creation of nitrogen oxides in the fumes, which fumes are discharged into a flue gas through the zone of convection located downstream of the radiation zone (combustion chamber) of said furnace, and a step of selective catalytic reduction of said flue nitrogen oxides, comprising the injection, in the convection zone in which at least one catalyst is present; , a mixture of hot air and ammonia, characterized in that the hot air of
• the process PI is a preheating treatment and / or heating and / or vaporization and / or overheating of hydrocarbon fluids or not, in a petrochemical process furnace.
• this relates to a process PI reforming a hydrocarbon feedstock in the presence of steam in a steam reforming furnace.
• the furnace for carrying out the process PI according to the present invention may correspond to any furnace used in the art by those skilled in the art.
• the oven is powered by any means available in fuel and hot air.
• the furnace is associated with a piping system for bringing each fluid and reagent within it.
• the heat supplied to the furnace (SMR or petrochemical) to operate is preferably obtained by means of burners, located in particular against the walls of the furnace, in particular against the side walls of the furnace, and / or on the floor and / or on the ceiling from the oven. These burners burn fuel in the presence of air to reach the high temperatures required for the various operations.
• fuel means any liquid or gaseous fuel, in particular fossil fuels, hydrocarbons or residual gases from petrochemical processes (or off-gas), which may include gases such as methane and hydrocarbons.
• the oven used in the present invention may be any oven used in the art by those skilled in the art.
• the oven is supplied by any means available in charge (hydrocarbon or other), water vapor and heat (hot air).
• the combustion air that feeds the furnace burners is preheated, before it arrives in the furnace, via at least one air preheating circuit, sometimes two or even three or more.
• the air preheating circuits are preferably supplied with so-called fresh air by fans which draw air outside the installation and inject it into the preheating duct.
• the fresh air circulates in the duct at the level of the air preheaters, a heat exchange occurs between the air and the hot combustion fumes exiting the radiation zone of the furnace.
• the air is preheated while the combustion fumes are cooled. Thermal exchanges will be even more important than the circuit Air preheat passes through the convection zone of the flue gases a high number of times.
• the invention also relates to a method PI as described above, wherein the at least one combustion air preheating circuit is supplied with fresh air using at least one fan.
• the method of the invention is characterized in that the at least one combustion air preheating circuit passes through the convection zone at least once, preferably at least twice (through a air preheater to preheat and cool fumes).
• the at least one air preheating circuit can pass through the convection zone of the fumes three times, four or even five times, the person skilled in the art being able to adapt the process to depending on the required preheating and the size of the installation used.
• Preheaters may pass through the convection zone of the flue gases downstream or upstream of the injection site of the MAA mixture of hot air and ammonia product
• the method according to the invention provides a selective catalytic reduction step of the nitrogen oxides contained in the fumes, to reduce or eliminate their presence in the fumes released into the air.
• selective catalytic reduction within the meaning of the invention is meant a reaction between a product based on ammonia, preferably aqueous, and NOx, in the presence of heat and a catalyst, resulting in the formation of nitrogen N2 harmless, released into the atmosphere.
• the catalyst used may be any catalyst deemed suitable by those skilled in the art. So, according to the process of the invention, a mixture of a product based on aqueous ammonia and hot air from the at least one preheating circuit according to the invention is prepared, this MAA mixture according to the invention being injected directly into the zone. convection. The mixture thus injected comes into contact with the catalyst present in the convection zone; the selective catalytic reduction of NOx present in the fumes then occurs.
• the method according to the invention makes it possible to significantly reduce the energy consumption of the oven, it also makes it possible to reduce the number of equipment necessary for supplying hot air to the mixer. Indeed, thanks to the fan injecting fresh air into the ducts at the beginning of the preheating circuit, and ensuring the circulation of air along the circuit, the air circulating in the preheating circuits is at a pressure greater than that of the oven, whether in the radiation zone or in the convection zone, in order to compensate for the pressure drop in the burners. Therefore, the preheated air fraction of the preheating pipes taken to form the MAA arrives directly to the mixer, the solution of the invention not only makes it possible to eliminate the air fan necessary to supply the mixer with hot air but also to remove the dedicated fresh air preheater.
• the method as described above is characterized in that the injection of the mixture of hot air and ammonia (more generally of ammonia compound) is done in at least one location in the smoke convection zone, upstream of the catalyst, which is held in place in the convection zone by a suitable support.
• the injection of MAA can be done in several locations of the convection zone, upstream of the catalyst, the number of injection sites being directly related to the size of the the installation used.
• the injection site of the MAA can in particular be located between two air pre-heaters passing through the convection zone.
• the process PI as described above is characterized in that the oven is supplied with air preheated by a single air preheating circuit, and in that the hot air used during the step catalytic selective reduction of the nitrogen oxides is taken directly from said single air preheating circuit.
• the method as described above is characterized in that the furnace is supplied with air preheated by two air preheating circuits, and that the hot air used during the catalytic reduction stage selective oxides of nitrogen is taken directly from at least one of said two air preheating circuits.
• the air preheat circuit comprises one, two or more air preheaters, located in the smoke convection zone.
• the hot air used during the selective catalytic reduction step of the nitrogen oxides is taken directly from the air preheating circuit (s), or at the outlet of the first passage of said at least one air preheating in the smoke convection zone, at the outlet of the second passage of the at least one air preheating circuit in the convection zone fumes, either at the outlet of both the first and the second passage of the at least one air preheating circuit in the convection zone of the fumes.
• this also relates to a facility for treating a load in a process furnace comprising at least:
• a process furnace P1 for the treatment of a charge comprising means for supplying fuel, and air; a circuit for preheating the air for supplying the furnace with preheated air passing through the zone of convection of the fumes one or more times,
• a convection zone leading the combustion fumes produced during the combustion of the fuels in the process furnace in which at least one catalyst is present for the selective reduction of nitrogen oxides, preferably maintained in said zone at the using a support medium
• an injector connected to said mixer for injecting said mixture of hot air and ammonia product into said flue gas duct, preferably upstream of the catalyst, either upstream of the catalyst or further upstream of the catalyst.
• supply means any pipe system, conduits, valves, registers, for supplying fuel and preheated air the process oven (also called the oven).
• the means for feeding the oven with preheated air may consist of one, two, three or plus air preheating circuits.
• the hot air supplying the at least one hot air / ammonia product mixer also called the mixer
• the air preheating circuits according to the invention are supplied with fresh air by at least one fan. In this way, as indicated above, the economy of air fans necessary in the known installations to drive the hot air to the at least one mixer, that is to say a saving in energy, cost of the installation, and a saving of space.
• the invention therefore also relates to an installation as described above, characterized in that the at least one air preheating circuit is supplied with fresh air using at least one fan.
• At least one catalyst in the convection zone of the furnace is present at least one catalyst.
• This catalyst is placed inside the flue gas duct, preferably maintained with the aid of a support, and preferably occupying the entire section of the duct, so that all of the flue gases pass through it.
• the catalyst is placed in the convection zone in order to have upstream and downstream air preheaters, the person skilled in the art being qualified to adapt this arrangement so as to obtain a suitable combustion flue gas temperature. to the selective catalytic reduction reaction.
• the flue gas duct transferring the fumes from the radiation zone to the convection zone can be connected to the oven at any time. which level, that is to say above, below, in the middle or at any other level of the radiation zone of the furnace, or even at several places in the zone of radiation of the furnace in particular through several ducts of The fumes can then be combined in one and the same conduit, so that the flue gases can be removed as efficiently as possible.
• Those skilled in the art are competent to adapt the architecture of the furnace and in particular the place of connection of the flue (s) where it wishes that the fumes be removed.
• the preheated air supply of the furnace is carried out by a single air preheating circuit.
• the hot air supplying the at least one mixer is taken directly from said one air preheating circuit.
• the preheated air supply of the furnace is carried out by two air preheating circuits.
• the hot air supplying the at least one hot air / ammonia mixer is taken directly from at least one of said two air preheating circuits.
• said hot air is taken from only one of the two air preheating circuits.
• said hot air is taken from the two air preheating circuits.
• the installation is characterized in that the at least one air preheating circuit passes through the flue gas duct in the convection zone at least once, preferably at least twice .
• the hot air supply of the at least one hot air / ammonia mixer is done by a sampling on at least one air preheating circuit at the outlet of the first passage of the preheating circuit in the smoke convection zone, at the outlet of the second passage of the preheating circuit in the convection zone, or at the output the first and second passages of the preheat circuit in the convection zone.
• mixer in the sense of the invention means any device for homogeneously mixing the hot air ammonia product.
• a device may consist of static equipment (in particular injection nozzle, baffle) or dynamic equipment (in particular propeller, rotor, blade).
• a person skilled in the art is able to adapt the number of mixers he needs to the size. of the installation and the amount of smoke produced.
• small installations will include only one mixer, while larger will include two, three, four or more, each of the mixers being supplied with hot air as described above.
• the number of hot air / ammonia mixture injectors may also vary depending on the size of the installation and the number of mixers that it uses.
• the injector may consist of an injection grid, allowing a homogeneous injection of the MAA into the convection duct.
• the injector is disposed upstream of the catalyst in the convection zone.
• the person skilled in the art can provide for passing, or not, a circuit for preheating water or air, or any other conduit allowing the circulation a heat transfer fluid.
• the MAA injected into the convection zone can thus in turn participate in a preheating.
• the mixture is made from ammonia stored in tanks away from the plant, and sent to the mixer via a drive means, in particular by at least one pump.
• the ammonia can be vaporized before it arrives in the mixer so as to facilitate its mixing with the hot air.
• the plant according to the invention further comprises a means for extracting combustion fumes cooled and purified to nitrogen oxides.
• extraction means may in particular consist of a fan, located at the very end of the convection zone, and for evacuating the fumes in a chimney open to the atmosphere.
• the fumes at the end of the convection zone can also be directed directly into the chimney, the chimney being in this case advantageously above the convection zone.
• the furnace is a petrochemical process furnace capable of preheating and / or heating and / or vaporizing and / or overheating of petrochemical process fluids.
• the furnace is a steam reforming furnace capable of reforming a hydrocarbon feedstock.
• the collected air is already preheated and under pressure thanks to the fresh air fan supplying the air preheating circuit, it can thus directly join the mixer without additional energy supply, the invention thus allows the economy of an air heating system for supplying the at least one hot air / ammonia mixer as well as fans supplying the preheaters with fresh air; this economy represents both a gain in energy and a gain of space.
• the use of hot air taken from the preheating circuit of combustion air avoids the taking of hot fumes directly into the convection duct of fumes, the latter being likely to contain sulfur dioxide, and thus to pollute and / or corrode the mixer (s).
• FIG. 1 and FIG. 2 represent prior art plant diagrams
• FIGS. 3 to 7 show plant diagrams according to the invention.
• the type of process used in the furnace is not specified, it may be a reforming process or a petrochemical process.
• the flue as shown in all of Figures 1 to 7 is connected to the oven in the middle of the radiation zone, it can be at any level; the skilled person is competent to adapt the architecture of the oven.
• FIG. 1 describes an installation as used in the state of the art, comprising an oven 1 allowing the treatment of a load 2 and obtaining a product 3, supplied fuel 5 and preheated air 6 by an air preheating circuit 7, supplied with fresh air 8 by a fan 9.
• the radiation zone or combustion chamber 4 is connected to a zone convection device 10 allowing the evacuation of the combustion fumes 11 produced in the radiation zone 4 during combustion, said combustion fumes 11 comprising, inter alia, nitrogen oxides.
• the fresh air 8 is injected through the fan 9 into the air preheating circuit 7, which passes through the convection zone 10 twice with the exchangers (air preheaters) 24, 26.
• the installation further comprises a mixer 12 of hot air 13 and ammonia 14.
• the ammonia is stored in a tank 15 connected to a pump 16 supplying the mixer 12 with ammonia 14.
• the hot air 13 comes from a heater 17 supplied with fresh air 8 by a fan 18.
• Said mixer 12 is associated with an injection grid 19 for injecting said mixture of hot air 13 and ammonia 14 in the combustion fumes 11 at said at least one convection zone 10 comprising at least one catalyst 20.
• the injection grid 19 is placed in the convection zone 10 upstream of the catalyst 20 Finally, the combustion fumes cooled and purified to nitrogen oxides are expelled into a chimney 22 open to the atmosphere, possibly with the aid of a fan extractor 21.
• FIG. 2 also describes an installation according to the prior art, identical in every respect to FIG. 1, with the difference that the hot air supplying the mixer 12 is replaced by combustion fumes 11 taken in the convection zone 10, using a fan 23 and after the catalyst 20.
• FIG. 3 describes an installation according to the invention, in which the references are identical to those of FIG. 1, with the difference that hot air
• FIG. 4 describes an installation according to the invention, in which the references are identical to those of FIG. with the difference that the hot air 13 supplying the mixer 12 is directly taken from the air preheating circuit 7, at the outlet of the air preheater 26, via a pipe 27 directly connecting said preheating circuit 7 to said mixer 12.
• the temperature of the air taken at the outlet of the second air preheater is generally between 250 and 600 ° C.
• FIG. 5 describes an installation according to the invention, in which the references are identical to those of FIG. 1, with the difference that the hot air 13 supplying the mixer 12 is directly taken from the air preheating circuit 7 , both at the outlet of the first air preheater 24, and at the outlet of the second air preheater 26.
• FIG. 6 describes an installation according to the invention, identical to the installation of FIG. the difference that the injector 19 is placed downstream of an exchanger 28 (commonly called convection beam) whose purpose is the preheating and / or heating and / or vaporization and / or overheating of a fluid other than the combustion air, more precisely the injector 19 is placed between the exchanger 28 and the catalyst 20.
• an exchanger 28 commonly called convection beam
• FIG. 7 describes an identical installation to the installation of FIG. 4, with the difference that the injector 19 is placed upstream of an exchanger (convection beam) 28.
• the skilled person may according to another alternative (not shown) remove the fresh air fan 18 for the selective catalytic reduction process of NOx when the combustion air used for combustion in the radiation zone is not preheated through the convection zone and use the fan 9 both to bring fresh air to the radiation zone (as combustion air) and to the mixer 12 of the selective catalytic NOx reduction process.
• it will preferentially use a preheater on the air duct used for the selective catalytic reduction.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Analytical Chemistry (AREA)
• Oil, Petroleum & Natural Gas (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=39580688

Family Applications (1)

Country Status (7)

Families Citing this family (12)

Family Cites Families (15)

• 2007
  • 2007-12-05 FR FR0759569A patent/FR2924623A1/fr not_active Withdrawn
• 2008
  • 2008-12-04 EA EA201070678A patent/EA201070678A1/ru unknown
  • 2008-12-04 WO PCT/FR2008/052202 patent/WO2009080937A2/fr not_active Ceased
  • 2008-12-04 EP EP08864483A patent/EP2219763A2/de not_active Withdrawn
  • 2008-12-04 CN CN2008801193574A patent/CN101888895A/zh active Pending
  • 2008-12-04 US US12/745,157 patent/US20110005438A1/en not_active Abandoned
• 2010
  • 2010-05-21 ZA ZA2010/03632A patent/ZA201003632B/en unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events