WO2010018315A1

WO2010018315A1 - Oxycombustion chamber

Info

Publication number: WO2010018315A1
Application number: PCT/FR2009/000875
Authority: WO
Inventors: Jérôme Colin; Aii Hoteit; Willi Nastoli; André NICOLLE
Original assignee: Ifp
Priority date: 2008-08-13
Filing date: 2009-07-16
Publication date: 2010-02-18
Also published as: FR2935040A1; FR2935040B1; CN102119298A; EP2310740A1; JP5530441B2; US20110185954A1; JP2011530690A; CN102119298B

Abstract

The invention relates to a combustion chamber that comprises a housing (1) including at least one fuel-injection means (2), at least one oxidant-injection means (3), and at least one means (5) for drawing the combustion fumes, wherein the housing (1) is in the shape of a tube having any cross-section and which is recurved and closed, while the fuel- (2) and oxidant- (3) injection means are provided on the housing (1) so as to be offset by an angle θ defined by each of the fuel- and oxidant-injection positions relative to the centre (C) of the housing, said angle being between 10° and 90°, and wherein the oxidant-injection means is a means for injecting an oxidant consisting of a gas having an oxygen content higher than 90%.

Description

ROOM D ¹ OXY-COM BUSTION

The present invention relates to the field of oxy-combustion, and more particularly to a combustion device whose geometry allows a natural recirculation of fumes and is adapted to the constraints of the oxy-combustion of a liquid or gaseous charge.

Current economic activity as well as increasing energy needs generate, through the use of fossil fuel, increasing emissions of

CO ₂ , greenhouse gas, in the atmosphere. These CO ₂ emissions are strongly suspected of being the source of the observed climatic changes, and in particular of global warming.

One way to reduce these emissions is to capture and sequester the CO ₂ emitted. Nevertheless the additional costs associated in terms of investment and the penalties on the overall efficiency of the equipment are for the moment prohibitive. At present, no economically satisfactory solution is available. Research is therefore being pursued to improve existing technologies, including capture technologies.

Currently, the main CO ₂ capture technologies under study are:

Post-combustion capture, ie the direct capture of CO ₂ present in combustion fumes in air. This capture requires the addition of a dedicated CO ₂ separation unit.

Pre-combustion capture, that is to say the prior capture of CO ₂ on the feed after a first step of conversion to synthesis gas. This conversion generates a gas rich in H ₂ which, once released from its carbon compounds, does not release CO ₂ during its combustion. Oxy-combustion capture: Oxygen is substituted for air for the combustion stages. Thus, at the output of the combustion equipment, high-CO ₂ fumes are available which can then be sequestered directly without having to be treated in a CO ₂ separation unit. On the other hand, a dedicated oxygen production unit is required.

It is this latter oxy-combustion technique which concerns the present invention. Indeed this technique has many advantages: a decrease in the amount of nitrogen oxide (NOx) formed (in the case of pure O ₂ , and absence of nitrogen compounds in the feed), a decrease in amount of fumes generated at iso power, a decrease in heat losses (corresponding to the "useless" heating of nitrogen through the combustion cycle), the concentration of possible pollutants such as nitrogen oxide and the oxide of As sulfur (NOx and SOx) is higher, separation is easier, most components are compressible and the heat of condensation can be used to advantage in the overall process scheme.

However, there are still many problems to solve for oxy-combustion. Indeed, combustion under oxygen (O ₂ ) causes significantly higher flame temperatures that can locally reach 2500 ^° C. In general, under O ₂ , there is observed with the current fuels an additional temperature of between 30% to 45%. % of the temperature obtained in air (in ° C) in an adiabatic configuration. This constraint therefore requires specific technologies, such temperatures not being "manageable" in compact chambers with the usual concepts whatever the alloys and refractories used. One of the preferred solutions to reduce hot spots ("hot spots") is to perform a recirculation of the burnt gases, so as to dilute and homogenize the temperature profile around its average value. This dilution by inert gases and this mixing (the skilled person speaks of training rate to quantify the brewing intensity) thus avoids the formation of hot spots responsible for the localized damage of the walls and / or internal combustion chambers. Recirculation requirements are primarily required for NOx formation and thermal efficiency issues. It should be noted that recirculation requirements are less restrictive for combustion in air than for oxy-combustion.

In addition to being able to influence the homogeneity of the combustion and the temperatures, it is necessary to act on the average temperature by a cooling of the chamber in order to be placed in the temperature window allowing, for example, to minimize the formation pollutants while ensuring good combustion of the load.

Some patents propose devices trying to solve these problems posed by oxy-combustion.

One can quote in particular the patent application US 20050239005. This patent describes a specific burner which highlights the use of a recirculation. It is a low NOx burner that can be used in a conventional combustion chamber such as atmospheric ovens with a wide spacing between burners and internals (tubes, walls, etc.). This device therefore requires specific burners. Injections of fuel and oxidant are made in parallel, which disrupts the recirculation and does not ensure distributed combustion over the entire volume of the chamber.

The patent application WO 2004/065848 relates to a device based on an oval geometry which, although promoting loop recirculation of fumes to dilute the reagents, does not allow a very good homogenization of the combustion. The exchange is made with tubes passing through the chamber which can disturb the recirculation.

US Patent 7318317 discloses a turbine burner for loop recirculation of combustion gases to homogenize combustion. In this device the gases circulate only on a loop, which does not allow a homogeneous recirculation.

The present invention therefore aims to overcome one or more of the disadvantages of the prior art by providing a specific and original arrangement to overcome the constraints specific to oxy-combustion. The combustion chamber therefore has a geometry allowing a natural recirculation of fumes adapted to the constraints of oxy-combustion. In addition, the injection is done at different points to ensure the recirculation and dilution of the reagents, which allows to obtain a distributed combustion over the entire volume of the chamber without using dedicated burners.

For this, the present invention provides a combustion chamber comprising an enclosure having at least one fuel injection means, at least one oxidant injection means and at least one combustion flue extraction means, wherein enclosure in the form of a tube of any section curved on itself and closed and the fuel injection means and oxidizer are disposed on the enclosure so as to be offset by an angle θ, formed by each of the positions of injecting the oxidant and the fuel with the center of the enclosure, between 10 ° and 90 ° and in which the oxidant injection means is an oxidant oxidant injection means which is a gas with a concentration of oxygen greater than 90%.

According to one embodiment of the invention, the enclosure in the form of a tube curved on itself to form a closed circle.

In another embodiment of the invention the chamber in the form of a tube bent on itself so as to form an oval.

According to one embodiment of the invention, the section of the tube is circular, oval or polygonal.

In one embodiment of the invention, the section of the tube is triangular.

In the combustion chamber according to the invention, the withdrawal means is disposed inside the circle formed by the enclosure so as to perform a grazing withdrawal. According to one embodiment of the invention, the fuel injection means are formed by at least one injection nozzle disposed in the radial plane of the enclosure on the outside of the enclosure.

In one embodiment of the invention, the fuel injection pipe forms an angle of inclination α formed by the longitudinal axis of the pipe and the straight line passing through the fuel injection point and tangent to the trajectory. the circulation of gases after the injection point, said angle α being between 5 ° and 80 °.

According to one embodiment of the invention, the fuel injection means are formed by at least two grazing tubes arranged in opposition to the enclosure, a first pipe allowing injection from above the enclosure and a second tubing for injection from below the enclosure.

In one embodiment of the invention the fuel injection pipes form an angle of inclination α ', defined with respect to the longitudinal axis of the pipe and the radial plane of the enclosure, between 5 ° and 80 °.

According to one embodiment of the invention, the oxidant injection means are formed by at least one injection nozzle disposed in the radial plane of the enclosure on the outside of the enclosure. In one embodiment of the invention, the oxidant injection pipe forms an angle of inclination β formed by the longitudinal axis of the pipe and the straight line passing through the fuel injection point and tangent to the trajectory. the flow of gas after the injection point, said angle β being between 5 ° and 80 °. According to one embodiment of the invention, the oxidant injection means are formed by at least two grainy tubes, arranged in opposition to the chamber, a first tube allowing injection from above the chamber and a second tubing for injection from below the enclosure.

In one embodiment of the invention, the oxidant injection pipes form an angle of inclination β ', defined with respect to the longitudinal axis of the pipe and the radial plane of the enclosure, between 5 ° and 80 ^th .

In the combustion chamber according to the invention, the withdrawal means forms an angle Y defined with respect to the longitudinal axis of the withdrawal means and the radius of the circle formed by the chamber, and directed in the direction of circulation of the fumes. . According to one embodiment of the invention, the angle y is between 20 ° and 85 °.

According to one embodiment of the invention, the tube has a section whose size is between 100 mm and 2000 mm.

Other features and advantages of the invention will be better understood and will appear more clearly on reading the description given hereinafter with reference to the appended figures given by way of example:

FIG. 1 is a schematic representation of a cross-section of a variant of the device according to the invention,

FIG. 2 is a schematic representation of a profile view of a variant of the device according to the invention, FIG. 3 is a schematic representation of a longitudinal section of the variant of FIG. 2 of the device according to FIG. invention, and Figure 4 is a schematic representation of a side view of a second variant according to the invention.

As illustrated in Figure 1, the combustion chamber according to the invention comprises a housing (1) which has the shape of a tube bent on itself to form a closed circle or a closed oval. A tube is understood to mean an element of elongated, hollow shape, of any cross section. The section of the tube may be in particular circular (9), oval (FIGS. 2 and 3) or polygonal and preferably triangular (9 ^! )

(Figure 4), but also square or rectangle. When the section of the curved tube forming the enclosure is circular (9), it is called a toric chamber.

The enclosure may also be defined as a hollow volume generated by the displacement of any generating surface in the direction of a closed curve representing the location of its centroids.

The dimension d of the section of the tube (for example diameter or side) forming the enclosure is between 100 mm and 2000 mm.

The walls of the combustion chamber are formed of specific alloy such as Haynes 230 ©, Kanthal APM © or MA956 © or alloy HR120 © or any other material of the same type. Externally, these walls may be covered with materials for cooling the reactor from the outside. In this way, the outlet temperature of the chamber is adjusted and the walls are protected from hot spots generated in the chamber. In the case where the chamber would not be cooled using a dedicated device, an internal refractoring of the chamber is also possible. The materials used for refractoring are, for example, ceramics or refractory cements or any other material of the same type. The combustion chamber comprises fuel injection means (2) and oxidant injection means.

When the fuel is liquid, the fuel injection means is a nozzle, and this nozzle is preferably provided with an internal ensuring the ^mixing of the fuel with an atomizing fluid.

When the fuel is gaseous, such as for example natural gas, the injector is a high-speed injector making it possible to reach speeds preferably greater than 100 m / s, for example a commercial RegeMAT® injector used by WS.

The present invention is of course not limited to these two types of fuels and also includes the use of solid fuels. In this case the injector may consist of a rod in which said fuel is transported by a fluid, such as for example steam.

The combustion chamber comprises oxidant oxidant injection means (3) which, in the context of the invention, is a gas with a very high concentration of oxygen, usually greater than 90%, or pure oxygen. .

These oxidant injection means may be an injector, preferably tubular and refractory material.

The injection of oxidant can be assisted by any means, such as by recycled fumes, which has the advantage of accelerating the injection speed of the oxidant, limiting concentration heterogeneities due to oxygen injection. It can also be envisaged to assist the injection of oxidant with water vapor which reduces the formation of unburned solids, such as soot for example.

Typically, the injection of the oxidant is done with a strong impulse which allows to maintain a fast flow of fumes.

In all cases the injection means are similar to tubings, that is to say circular, oval or polygonal shaped ducts, in the following description.

One of the characteristics of the device according to the invention is that the injection and the withdrawals are done so as to limit the appearance of hot spots. For this purpose, fuel and oxidant are injected in a disjoint manner (without premixing) on the outer axis of the chamber and the angle of incidence of the tubing for injection is optimized so as to avoid any hot gas impact against the walls.

To position the injection means, the tubular implantation constraints are also considered. For the injection of the fuel according to a first variant illustrated in FIG. 1, an injection nozzle is disposed on the outside of the circle formed by the chamber, that is to say in the radial plane (P) of the enclosure. The angle α characterizes the inclination of the tubing and is preferably defined as the angle formed by the longitudinal axis (20) of the tubing and the straight line (21) passing through the injection point and tangent to the axis median circular (A) of the trajectory of the circulation (4) of the gases after the injection point.

However, the construction of a combustion chamber according to the invention requires the welding of several elements and, in certain cases, it is not possible that the injections can be performed exactly on the outside. According to a second variant of the invention, the injection means are thus formed by a system of pairs of tubings (2 ', 2 ") grazing and in opposition with respect to the radial plane (P), as illustrated in FIGS. , 3 and 4. These pipes are arranged to allow an injection from above and below the chamber, considering the section of the tube.The angle α ¹ of these pipes is defined relative to the longitudinal axis tubing (20 ', 20 ") and the radial plane (P) of the enclosure (1).

These angles α and α 'are constrained by the construction limits and by the angle of the spray (8). The angle α corresponds to the inclination required to compensate for the drive and keep an injection centered in the enclosure, it is between 5 ° and 80 °, and preferably between 15 ° and 50 °. The angle α ¹ is between 5 ° and 80 °. The nozzles having a very low flexibility on the flow rates and the air start requiring a large injection amplitude, at least one injection point is specified, but several can be claimed in series. The number of tubes used is thus adjusted to increase flexibility on the flow rates without drastically changing the flow rates per nozzle. The number of tubings is between 1 and 15, and preferably between 2 and 10. This device also improves the fuel distribution, which improves the quality of combustion and avoid the formation of hot spots.

For injecting the oxidant and in particular oxygen (or air for starting), the tubing (3) used is disposed on the outside of the circle formed by the chamber (1), that is to say in the radial plane of the chamber and inclined at an angle β to ensure a resulting circulation after mixing which is in the axis of the enclosure. This angle characterizes the inclination of the tubing and is defined as the angle formed by the longitudinal axis (30) of the tubular and the line (31) passing through the injection point and tangent to the median circular axis ( A) the trajectory of the circulation (4) of the gases after the injection point. It is between 5 ^and 80 ° and preferably between 15 ° and 45 °. In case of implantation problem in the same way as for the injection of fuel, an injection with 2 opposite tubes can be used. These pipes are arranged to allow injection from above and below the enclosure. In this case, the tubes each form an angle β '(not shown) defined with respect to the longitudinal axis of the tubing and the radial plane of the enclosure (1). This angle must be minimal to maximize the induced drive, it is between 5 ° and 80 °

The angle θ formed by each of the injection positions of the oxidant and the fuel with the center of the enclosure, that is to say the angle formed by the straight lines (22, 32) passing through the points of injection of the oxidant and fuel and the center (C) of the enclosure, must be between 10 and 150 ° and preferably between 15 ° and 90 °.

In a preferred embodiment of the invention, the richness defined as the quotient of the ratio of fuel / fuel flow rates in operation and the ratio Combustible / Oxidant to stoichiometry is between 0.5 and 3.

The combustion chamber also comprises means (5) for withdrawing combustion fumes. This withdrawal means is disposed at a location that does not disturb the circulation of the recirculation gases (4). The withdrawal means (5) is thus disposed inside the circle formed by the enclosure (1), so as to perform a grazing withdrawal. For this, the longitudinal axis (51) of the withdrawal pipe forms an angle Y with the radius (r) of the circle formed at the exit point of the withdrawal means. This extraction pipe is directed in the flue gas flow direction and the angle Y is advantageously between 20 ° and 85 °. In this way, the withdrawal is done in the extension of the circulation (4) fumes. The withdrawal pipe has a diameter S of between 10 mm and 250 mm. During operation of the combustion chamber, a large flow of hot combustion fumes circulates and recirculates continuously in the torus loop. In this case, we are talking about internal recycling as opposed to external recycling techniques (also possible for oxy-combustion). This large flow of smoke is maintained thanks to high injection speeds in the room. As a result, the jets of oxidant and fuel undergo, on entering the chamber, a strong stirring and a high dilution by the fumes. This mixing ensures a contact between the reagents under conditions as dilute and as homogeneous as possible, as well as spreading of the reaction zone over the entire chamber. These fumes are hot enough to ensure self-ignition of the reagents. The fuel is first injected and stirred in the hot fumes. These fumes contain some residual oxygen. As a result, the path of the mixture from the fuel injection point to the oxidant injection (Air or O ₂ ) allows the gas to mix, dilute and partially react.

The oxidant is then injected with a strong impulse. This pulse helps maintain the rapid flow of fumes and additional mixing. The combustion continues throughout the course of the loop.

Some of these fumes are extracted in an area that does not disturb the flow of fumes.

The temperature and the composition of the fumes are substantially homogeneous throughout the enclosure. This temperature is included, in nominal operation, between 600 and 2000 ° C and preferably between 800 and 1500 ⁰ C so as to limit the formation of NOx related to possible parasitic air inlet or to the nitrogen of the oxidizer. The high rate of injection of Air / O ₂ of between 20 m / s and 500 m / s, and preferably between 100 m / s and 250 m / s, maintains a strong entrainment of the gases present in the combustion chamber. This strong recirculation favors the mixing and dilution of the species present so as to set up a combustion distributed as evenly as possible in the volume of the chamber.

The consequences of this type of operation are as follows:

• The combustion takes place in two stages.

• A strong brewing is obtained at the level of the injections.

• The high speed of circulation of hot fumes spreads combustion over the entire volume of the torus and maintains combustion.

This provides a device that prevents the formation of hot spots and provides a combustion volume on the entire combustion chamber.

In addition, the combustion being distributed over the entire enclosure and not concentrated in the form of a flame at the injection points, the temperature never exceeds 2000 ^° C. and the hot zones are located in the center of the chamber. torus. The joint effects of cooling the walls from the outside, the absence of direct impacts of hot gas and the homogeneity of the combustion make it possible to obtain wall temperatures of less than 1000 ^° C.

This arrangement (geometry of the chamber, disjoint injections, central withdrawal) promotes the recirculation of combustion fumes and a homogeneous combustion over the entire volume of the chamber.

The concept imagined is also particularly adapted and interesting to small powers. Indeed, on this power range, the geometry of the chamber according to the invention makes it possible to ensure good recirculation on a small volume whereas the use of pure oxygen causes, on the usual geometries at low power, a generally too weak. This recirculation of gases is due to the centrifugal force that minimizes the ratio of the output gas flow to the recirculated gas flow rate.

In addition, preheating due to the recirculation of hot fumes can extend the flexibility of operations and cover for example a wide range of wealth.

In addition, in small geometries, the high surface area to volume ratio facilitates the possible cooling of the chamber and thus the control of the combustion quality via the control of the average temperature of the chamber.

The possibility of lowering the temperature of the hearth to relatively low temperatures (unlike the combustion chambers in air) without stopping the combustion makes it possible to consider jointly, with appropriate wealth, other applications such as partial oxidation, the production of hydrogen or oxygen compounds, such as methanol.

It should be obvious to those skilled in the art that the present invention should not be limited to the details given above and allow embodiments in many other specific forms without departing from the scope of the invention. . Therefore, the present embodiments should be considered by way of illustration, and may be modified without departing from the scope defined by the appended claims.

Claims

Combustion chamber comprising an enclosure (1) having at least one fuel injection means (2), at least one oxidant injection means (3) and at least one fume extraction means (5). combustion, wherein the enclosure (1) has the form of a tube of any section curved on itself and closed, and the fuel injection means (2) and oxidizer (3) are arranged on the enclosure (1) so as to be offset by an angle θ, formed by each of the oxidant and fuel injection positions and the center (C) of the enclosure (1), between 10 ° and 90 °, and wherein the oxidant injection means is oxidant oxidant injection means which is a gas with an oxygen concentration greater than 90%.

2. Combustion chamber according to claim 1 wherein the enclosure (1) has the shape of a tube curved on itself to form a closed circle. 3. Combustion chamber according to claim 1 wherein the enclosure (1) has the shape of a tube curved on itself to form an oval.

4. Combustion chamber according to one of claims 1 to 3 wherein the section of the tube is circular (9), oval or polygonal.

5. Combustion chamber according to one of claims 1 to 4 wherein Ia section of the tube is triangular (9 ').

6. Combustion chamber according to one of claims 1 to 5 wherein the means (5) for withdrawal is disposed within the circle formed by the enclosure (1) so as to achieve a grazing withdrawal.

7. Combustion chamber according to one of claims 1 to 6 wherein the fuel injection means are formed by at least one injection pipe (2) disposed in the radial plane of the enclosure (1) on the outside of the enclosure (1).

8. Combustion chamber according to claim 7 wherein the fuel injection pipe forms an inclination angle α formed by the longitudinal axis (20) of the pipe and the line (21) passing through the point of fuel injection and tangent to the median circular axis (A) of the path of the circulation (4) of the gases after the injection point, said angle α being between 5 ° and 80 °.

9. Combustion chamber according to one of claims 1 to 6 wherein the fuel injection means are formed by at least two tubing (2 \ 2 ") grazing, disposed in opposition to the enclosure (1), a first tubulure allowing injection from above the enclosure (1) and a second pipe for injection from below the enclosure (1).

10. Combustion chamber according to claim 9 wherein the fuel injection pipes form an angle of inclination α 'defined with respect to the longitudinal axis (20', 20 ") of the pipe and the radial plane of the enclosure (1), between 5 ° and 80 ° C. Combustion chamber according to one of claims 1 to 10 wherein the oxidant injection means are formed by at least one injection pipe (3) arranged in the radial plane of the enclosure (1) on the outside of the enclosure (1).

12. Combustion chamber according to claim 11 wherein the oxidant injection pipe forms an angle of inclination β formed by the longitudinal axis (30) of the pipe and the line (21) passing through the injection point. fuel and tangent to the median circular axis (A) of the path of the circulation (4) of the gases after the injection point, said angle β being between 5 ° and 80 °.

13. Combustion chamber according to one of claims 1 to 10 wherein the oxidant injection means are formed by at least two graining pipes, arranged in opposition to the enclosure (1), a first pipe allowing injection by the above the enclosure (1) and a second pipe allowing the injection from below the enclosure (1).

Combustion chamber according to Claim 13, in which the oxidant injection pipes form an angle of inclination β 1 defined with respect to the longitudinal axis (20 ', 20 ") of the pipe and the radial plane of the pipe. enclosure (1), between 5 ° and 80 ° 15. Combustion chamber according to one of claims 1 to 14 wherein the withdrawal means forms an angle y defined with respect to the longitudinal axis of the withdrawal means and the radius (r) of the circle formed by the enclosure, and directed in the direction of circulation (4) fumes.

16. Combustion chamber according to claim 15 wherein the angle y is between 20 ° and 85 °.

17. Combustion chamber according to one of claims 1 to 1 wherein the tube has a section whose size (d) is between 100 mm and 2000 mm.