Title of Invention	"A FUEL COMBUSTION METHOD "
Abstract	The invention relates to a method for the combustion of a fuel and an oxidant, in which at least one jet of fuel and at least two jets of oxidant are injected. According to the invention, at least one first oxidant is injected at a distance I, at most 20 cm, from the fuel injection point and at least one second oxidant is injected at a distance I2 from the fuel injection point. I2 being grealer than I,. The aforementioned oxidanls are injected in quantities such that the sum of the quantities thereof is at least equal to the stoichiometric quantity of oxidant necessary in order to ensure the combustion of the injected fuel. Moreover, the first oxidant is oxygen-enriched air having a temperature of at most 200°C and the second oxidant is air preheated to a temperature of at least 300°C.

Title of Invention

"A FUEL COMBUSTION METHOD "

Abstract

The invention relates to a method for the combustion of a fuel and an oxidant, in which at least one jet of fuel and at least two jets of oxidant are injected. According to the invention, at least one first oxidant is injected at a distance I, at most 20 cm, from the fuel injection point and at least one second oxidant is injected at a distance I2 from the fuel injection point. I2 being grealer than I,. The aforementioned oxidanls are injected in quantities such that the sum of the quantities thereof is at least equal to the stoichiometric quantity of oxidant necessary in order to ensure the combustion of the injected fuel. Moreover, the first oxidant is oxygen-enriched air having a temperature of at most 200°C and the second oxidant is air preheated to a temperature of at least 300°C.

Full Text	Staged combustion method using a preheated oxidant The present invention relates to a staged combustion method using a preheated oxidant. In present combustion methods, it is common to recover the energy liberated by the furnaces in order to reduce fuel consumption. The heat convected by the furnace flue gases can be recovered by using waste heat boilers or regenerators. This energy recovery is particularly common for combustion methods in which the oxidant is air. For combustions in which the oxidant is oxygen, it is also advisable to recover the energy. However, techniques valid for air are not directly applicable to oxygen. In fact, the flue gases produced by combustion with oxygen have high moisture contents and may contain a significant quantity of corrosive particles. Two technologies are currently available for preheating the oxygen: US-A-5 807 418 describes a direct heat exchange with the combustion products and the oxidant comprising at least 50% oxygen, according to US-A-6 071 116, an intermediate fluid and a first heat exchanger are used to recover the energy from the burnt gases before restoring this energy to the oxygen via a second heat exchanger. These technologies may raise certain technical problems such as heat exchanger maintenance and service life problems, essentially due to corrosion, the lack of means for measuring and controlling the hot oxygen (no control means compatible with hot oxygen) and the safety problems associated with the use of this hot oxygen. The problem posed by the present invention is to propose a novel combustion method using oxygen as oxidant. and suitable for recovering the energy from the flue gases. Another problem posed by the present invention is to propose a novel combustion method using oxygen as oxidant and suitable for recovering the energy from the flue gases without encountering the problems raised by oxygen preheating. For these purposes, the invention relates to a fuel combustion method in which at least one fuel and at least two oxidants are injected: the first oxidant being injected at a distance Ii, of at. most 20 cm, and preferably of at most 15 cm, from the fuel injection point, the second oxidant being injected at a distance I2 from the fuel injection point, I2 being greater than I1, the oxidants being injected in molar quantities such that the sum of their molar quantities is at least equal to the molar stoichiometric quantity of oxidant necessary to ensure the combustion of the injected fuel, in which the first oxidant is oxygen-enriched air having a temperature of at most 200°C and in which the second oxidant is air preheated to a temperature of at least 300°C. According to the invention, the combustion method is a staged combustion method. This type of combustion consists in introducing the oxidant necessary for combustion of the fuel in the form of at least two separate jets injected at different distances (I1 and T2) from the fuel introduction point in the furnace. The first oxidant is injected in a quantity such that it causes incomplete combustion of the fuel and the gases produced by this combustion between the fuel and the first oxidant still comprise at least part of thefuel. The second oxidant is injected in a quantity such that it completes the combustion of the fuel still present in the gases produced by the combustion between the fuel and the first oxidant. According to the invention, the oxidants are injected in quantities such that the sum of their quantities is at least equal to the st. oichi ometr i c quantity of oxidant necessary to ensure the combustion of the injected fuel. Stoichiometric quantity means the quantity of molecules of oxygen necessary to obtain the complete combustion of the injected fuel. The various oxidants must supply at least all the oxygen necessary for this total combustion of the fuel. According to an essential feature of the invention, the first oxidant injected at. a distance I1 consists of oxygen-enriched air having a temperature of at most 200°C. "Oxygen-enriched air" means air enriched with oxygen so that the; oxygen concentration in the enriched air- is at least 30%, and preferably at least 50%. The oxygen-enriched air is preferably obtained by mixing ambient air with a cryogenic oxygen source. The oxidant injected at. the distance I1 has a temperature of at most 200°C, which means that this oxidant is not preheated, particularly by the energy regenerators from the furnace in which the combustion is implemented. According to another essential feature of the invention, the second oxidant injected at the distance I;> consists of air preheated to a temperature of at least 300°C. The preheating can be carried out by any heat recovery technique using the hot combustion products from the furnace. Thus, the preheated air may be heated by heat exchange with part of the hot combustion products according to any known technique of the prior art. According to a variant of the method of the invention, at least two oxidants are injected at a distance Ii of at most ]5 cm, one, called primary, being injected in a mixture with the fuel or close to the fuel, and the other, called secondary, being injected at a distance from the fuel. "In a mixture" means that the primary oxidant and the fuel are premixed before being intj-oduced in the combustion zone. This premixing can be carried out by injecting the primary oxidant and the fuel into a cavity, said cavity terminating in the combustion zone. "Close to" means that the primary oxidant is the oxidant introduced at the point closest to the fuel introduction point among all the oxidants injected during the combustion method. The secondary oxidant is introduced at a distance from the fuel, that is at a distance Iisecondary from the upper fuel introduction point at the distance Iiprimary defined between the primary oxidant and fuel introduction points. The primary oxidant and the secondary oxidant may have different oxygen concentrations; preferably, the primary oxidant has a higher oxygen concentration thari the secondary oxidant. The quantity of oxidant injected by the primary oxidant jet preferably represents 2 to 50% of the stoichiometric quantity of oxygen necessary to ensure the combustion of the injected fuel. The quantity of oxidant injected by the secondary oxidant jet and the oxidant jet injected at the distance I2 may represent 50 to 98% of the stoichiometric quantity of oxygen necessary to ensure the combustion of the injected fuel. In this variant, the secondary oxidant may be divided into a plurality of secondary oxidant jets, which may be injected either all at the same distance Iisecondary from the fuel jet, or at different distances Iisecondary from the fuel jet, these distances remaining shorter than 20 cm, preferably shorter than 15 cm. According to a particular embodiment of the invention, the oxidant injected at the distance I2 may be divided into a plurality of oxidant jets. The method according to the present invention may be applied to any type of combustion furnace and particularly to heating furnaces, glass-melting furnaces, and melting furnaces for ferrous or nonferrous metals. By the implementation of the method as previously described, it has been observed that, although the method uses air containing nitrogen, the NOx emissions remain low and compatible with environmental release standards. In any case, they remain lower than the contents obtained for the same burner exclusively using preheated oxygen. The method according to the invention hence has neither the drawbacks of preheated oxygen, nor those of combustion with air. Furthermore, the use of enriched air limits refractory wear. Claims 1. A fuel combustion method in which at least one fuel and at least two oxidants are injected: at least one first oxidant being injected at a distance I[ of at most 20 cm, and preferably of at most 15 cm, from the fuel injection point, at least one second oxidant being injected at a distance I2 from the fuel injection point, I2 being greater than I-it the oxJdants being injected in quantities such that the sum of their quantities is at least equal to the steichiometric quantity of oxidant necessary to ensure the combustJon of the injected fuel, characterized in that the first oxidant is oxygen-enriched air having a temperature of at most 200°C and in that the second cxidant is air preheated to a temperature of at least 300°C. 2. The method as claimed in claim 1, characterized in that the air is enriched with oxygen so that the oxygen concentration in the enriched air is at least J. The method as claimed in either of claims 1 and 2, characterized in that the oxygen-enriched air is obtained oy mixing ambient air with a cryogenic oxygen source. The method as claimed in one of the preceding claims, characterized in that the preheated air is heated by heat exchange with part of the hot combustion products. The method as claimed in one of the preceding claims, characterized in that at least two first oxidants are injected at a distance Ii of at most 20 cm, and preferably of at most 15 cm, one, called primary, being injected in a mixture with the fuel or close to the fuel, and the other, called secondary, being injected at a distance from the fuel. The method as claimed in the preceding claim, characterized in that the quantity of oxidant injected by the primary oxidant jet represents 2 to 50% of the stoichiometric quantity of oxygen necessary to ensure the combustion of the injected fuel. The method as claimed in either of claims 5 and 6, characterized in that the secondary oxidant is divided into a plurality of secondary oxidant jets. The method as claimed in one of the preceding claims, characterized in that the second oxidant injected at the distance l2 is divided into a plurality of oxidant jets.

Full Text

Staged combustion method using a preheated oxidant
The present invention relates to a staged combustion method using a preheated oxidant.
In present combustion methods, it is common to recover the energy liberated by the furnaces in order to reduce fuel consumption. The heat convected by the furnace flue gases can be recovered by using waste heat boilers or regenerators. This energy recovery is particularly common for combustion methods in which the oxidant is air.
For combustions in which the oxidant is oxygen, it is also advisable to recover the energy. However, techniques valid for air are not directly applicable to oxygen. In fact, the flue gases produced by combustion with oxygen have high moisture contents and may contain a significant quantity of corrosive particles. Two technologies are currently available for preheating the oxygen:
US-A-5 807 418 describes a direct heat exchange with
the combustion products and the oxidant comprising at
least 50% oxygen,
according to US-A-6 071 116, an intermediate fluid
and a first heat exchanger are used to recover the
energy from the burnt gases before restoring this
energy to the oxygen via a second heat exchanger.
These technologies may raise certain technical problems such as heat exchanger maintenance and service life problems, essentially due to corrosion, the lack of means for measuring and controlling the hot oxygen (no control means compatible with hot oxygen) and the safety problems associated with the use of this hot oxygen.
The problem posed by the present invention is to propose a novel combustion method using oxygen as oxidant. and suitable for recovering the energy from the flue gases.
Another problem posed by the present invention is to propose a novel combustion method using oxygen as oxidant and suitable for recovering the energy from the flue gases without encountering the problems raised by oxygen preheating.
For these purposes, the invention relates to a fuel combustion method in which at least one fuel and at least two oxidants are injected:
the first oxidant being injected at a distance Ii, of at. most 20 cm, and preferably of at most 15 cm, from the fuel injection point,
the second oxidant being injected at a distance I2 from the fuel injection point, I2 being greater than I1, the oxidants being injected in molar quantities such that the sum of their molar quantities is at least equal to the molar stoichiometric quantity of oxidant necessary to ensure the combustion of the injected fuel, in which the first oxidant is oxygen-enriched air having a temperature of at most 200°C and in which the second oxidant is air preheated to a temperature of at least 300°C.
According to the invention, the combustion method is a staged combustion method. This type of combustion consists in introducing the oxidant necessary for combustion of the fuel in the form of at least two separate jets injected at different distances (I1 and T2) from the fuel introduction point in the furnace. The first oxidant is injected in a quantity such that it causes incomplete combustion of the fuel and the gases produced by this combustion between the fuel and the first oxidant still comprise at least part of thefuel. The second oxidant is injected in a quantity such that it completes the combustion of the fuel still present in the gases produced by the combustion between the fuel and the first oxidant. According to the invention, the oxidants are injected in quantities such that the sum of their quantities is at least equal to the st. oichi ometr i c quantity of oxidant necessary to ensure the combustion of the injected fuel. Stoichiometric quantity means the quantity of molecules of oxygen necessary to obtain the complete combustion of the injected fuel. The various oxidants must supply at least all the oxygen necessary for this total combustion of the fuel.
According to an essential feature of the invention, the first oxidant injected at. a distance I1 consists of oxygen-enriched air having a temperature of at most 200°C. "Oxygen-enriched air" means air enriched with oxygen so that the; oxygen concentration in the enriched air- is at least 30%, and preferably at least 50%. The oxygen-enriched air is preferably obtained by mixing ambient air with a cryogenic oxygen source. The oxidant injected at. the distance I1 has a temperature of at most 200°C, which means that this oxidant is not preheated, particularly by the energy regenerators from the furnace in which the combustion is implemented. According to another essential feature of the invention, the second oxidant injected at the distance I;> consists of air preheated to a temperature of at least 300°C. The preheating can be carried out by any heat recovery technique using the hot combustion products from the furnace. Thus, the preheated air may be heated by heat exchange with part of the hot combustion products according to any known technique of the prior art.
According to a variant of the method of the invention, at least two oxidants are injected at a distance Ii of
at most ]5 cm, one, called primary, being injected in a mixture with the fuel or close to the fuel, and the other, called secondary, being injected at a distance from the fuel. "In a mixture" means that the primary oxidant and the fuel are premixed before being intj-oduced in the combustion zone. This premixing can be carried out by injecting the primary oxidant and the fuel into a cavity, said cavity terminating in the combustion zone. "Close to" means that the primary oxidant is the oxidant introduced at the point closest to the fuel introduction point among all the oxidants injected during the combustion method. The secondary oxidant is introduced at a distance from the fuel, that is at a distance Iisecondary from the upper fuel introduction point at the distance Iiprimary defined between the primary oxidant and fuel introduction points. The primary oxidant and the secondary oxidant may have different oxygen concentrations; preferably, the primary oxidant has a higher oxygen concentration thari the secondary oxidant. The quantity of oxidant injected by the primary oxidant jet preferably represents 2 to 50% of the stoichiometric quantity of oxygen necessary to ensure the combustion of the injected fuel. The quantity of oxidant injected by the secondary oxidant jet and the oxidant jet injected at the distance I2 may represent 50 to 98% of the stoichiometric quantity of oxygen necessary to ensure the combustion of the injected fuel. In this variant, the secondary oxidant may be divided into a plurality of secondary oxidant jets, which may be injected either all at the same distance Iisecondary from the fuel jet, or at different distances Iisecondary from the fuel jet, these distances remaining shorter than 20 cm, preferably shorter than 15 cm.
According to a particular embodiment of the invention, the oxidant injected at the distance I2 may be divided into a plurality of oxidant jets.
The method according to the present invention may be applied to any type of combustion furnace and particularly to heating furnaces, glass-melting furnaces, and melting furnaces for ferrous or nonferrous metals.
By the implementation of the method as previously described, it has been observed that, although the method uses air containing nitrogen, the NOx emissions remain low and compatible with environmental release standards. In any case, they remain lower than the contents obtained for the same burner exclusively using preheated oxygen. The method according to the invention hence has neither the drawbacks of preheated oxygen, nor those of combustion with air. Furthermore, the use of enriched air limits refractory wear.

Claims
1. A fuel combustion method in which at least one
fuel and at least two oxidants are injected:
at least one first oxidant being injected at a distance I[ of at most 20 cm, and preferably of at most 15 cm, from the fuel injection point,
at least one second oxidant being injected at a distance I2 from the fuel injection point, I2 being greater than I-it
the oxJdants being injected in quantities such that the sum of their quantities is at least equal to the steichiometric quantity of oxidant necessary to ensure the combustJon of the injected fuel, characterized in that the first oxidant is oxygen-enriched air having a temperature of at most 200°C and in that the second cxidant is air preheated to a temperature of at least 300°C.
2. The method as claimed in claim 1, characterized
in that the air is enriched with oxygen so that the
oxygen concentration in the enriched air is at least
J. The method as claimed in either of claims 1 and 2, characterized in that the oxygen-enriched air is obtained oy mixing ambient air with a cryogenic oxygen source.
The method as claimed in one of the preceding
claims, characterized in that the preheated air is
heated by heat exchange with part of the hot combustion
products.
The method as claimed in one of the preceding
claims, characterized in that at least two first
oxidants are injected at a distance Ii of at most 20 cm,
and preferably of at most 15 cm, one, called primary,
being injected in a mixture with the fuel or close to the fuel, and the other, called secondary, being injected at a distance from the fuel.
The method as claimed in the preceding claim,
characterized in that the quantity of oxidant injected
by the primary oxidant jet represents 2 to 50% of the
stoichiometric quantity of oxygen necessary to ensure
the combustion of the injected fuel.
The method as claimed in either of claims 5 and
6, characterized in that the secondary oxidant is
divided into a plurality of secondary oxidant jets.
The method as claimed in one of the preceding
claims, characterized in that the second oxidant
injected at the distance l2 is divided into a plurality
of oxidant jets.

Documents:

3169-delnp-2006-Abstract-(08-05-2012).pdf

3169-delnp-2006-abstract.pdf

3169-delnp-2006-Claims-(08-05-2012).pdf

3169-delnp-2006-claims.pdf

3169-delnp-2006-Correspondence Others-(08-05-2012).pdf

3169-delnp-2006-Correspondence Others-(16-05-2012).pdf

3169-delnp-2006-correspondence-others 1.pdf

3169-delnp-2006-correspondence-others.pdf

3169-delnp-2006-description (complete).pdf

3169-delnp-2006-Form-1-(08-05-2012).pdf

3169-delnp-2006-form-1.pdf

3169-delnp-2006-form-18.pdf

3169-delnp-2006-Form-2-(08-05-2012).pdf

3169-delnp-2006-form-2.pdf

3169-delnp-2006-Form-3-(16-05-2012).pdf

3169-delnp-2006-form-3.pdf

3169-delnp-2006-form-5.pdf

3169-delnp-2006-GPA-(08-05-2012).pdf

3169-delnp-2006-gpa.pdf

3169-delnp-2006-Petition-137-(16-05-2012).pdf

« Previous Patent

Next Patent »

Patent Number

263387

Indian Patent Application Number

3169/DELNP/2006

PG Journal Number

44/2014

Publication Date

31-Oct-2014

Grant Date

27-Oct-2014

Date of Filing

02-Jun-2006

Name of Patentee

L'AIR LIQUIDE, SOCIETE ANONYME A DIRECTOIRE ET CONSEIL DE SURVEILLANCE POUR L'ETUDE ET........CLAUDE

Applicant Address

75 QUAI D'ORSAY, F-75321 PARIS CEDEX 07, FRANCE.

Inventors:

#	Inventor's Name	Inventor's Address
1	REMI PIERRE TSIAVA	71 RUE ANDRE BRETON, 91250 ST. GERMAIN-LES-CORBEIL, FRANCE.
2	BERTRAND LEROUX	3 PASSAGE DE I'INDUSTRIE, 92130, ISSY-LES-MOULINEAUX, FRANCE.
3	CHRISTIAN IMBERNON	1 RESIDENCE PLEIN SUD, 94320 THIAIS, FRANCE

PCT International Classification Number

C03B 5/235

PCT International Application Number

PCT/FR2004/050650

PCT International Filing date

2004-12-06

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0351061	2003-12-16	France