BURNER PROCESS FOR IRON FUEL COMBUSTION ARRANGEMENT

Abstract

A burner process for iron fuel combustion, comprising the steps of: providing an iron fuel suspension medium comprising iron fuel and oxygen in a suspension solid density of between 2 to 15 kg/Nm.sup.3 and more preferably of between 4 to 8 kg/Nm.sup.3; introducing said iron fuel suspension medium into an iron fuel burner arrangement at a velocity of between 5.5 and 55 m/s and more preferably between 20 and 40 m/s; introducing air from air inlet means into said iron fuel burner arrangement, wherein said air from said air inlet means is introduced with an overall angular momentum ratio between said air and said iron fuel suspension medium of between 3 and 12 and more preferably between 3.8 and 8.9; mixing said iron fuel suspension medium by subjecting it with said air such that an overall oxygen-to-fuel equivalence ratio is obtained between 1.0 and 2.5 and more preferably between 1.2 and 1.8 for obtaining a combustible medium in the said burner arrangement; igniting said combustible medium to provide a combusting iron fuel containing medium.

Claims

1. A burner process for iron fuel combustion, comprising the steps of: (a) providing an iron fuel suspension medium comprising iron fuel and oxygen in a suspension solid density of between 2 to 15 kg/Nm.sup.3; (b) introducing said iron fuel suspension medium into an iron fuel burner arrangement at a velocity of between 5.5 and 55 m/s; (c) introducing air from air inlet means into said iron fuel burner arrangement, wherein said air from said air inlet means is introduced with an overall angular momentum ratio between said air and said iron fuel suspension medium of between 3 and 12; (d) mixing said iron fuel suspension medium by subjecting it with said air such that an overall oxygen-to-fuel equivalence ratio is obtained between 1.0 and 2.5 for obtaining a combustible medium in the said burner arrangement; (e) igniting said combustible medium to provide a combusting iron fuel containing medium.

2. The burner process for iron fuel combustion according to claim 1, wherein the temperature of at least part of the combustible medium obtained in step (e) has a minimum temperature equal to the ignition temperature of the iron fuel.

3. The burner process for iron fuel combustion according to claim 2, wherein the temperature of the iron fuel suspension medium in step (b) is at least approximately equal to ambient air temperature of the burner arrangement.

4. The burner process for iron fuel combustion according to claim 2, wherein upon step (c), (d) and (e) the process further comprises heating with heating means, for heating at least part of said combustible medium to a minimum temperature equal to at least the ignition temperature of the iron fuel.

5. The burner process for iron fuel combustion according to claim 2, wherein said air of said air inlet means are providing at a temperature which is at least approximately equal to the ambient air temperature of the burner arrangement.

6. The burner process for iron fuel combustion according to claim 1, wherein said air inlet means are arranged for directing said air from said air inlet means in a tangential manner, and/or at an angle, with respect to said iron fuel suspension medium, into said iron fuel burner arrangement.

7. The burner process for iron fuel combustion according to claim 1, wherein said iron fuel suspension medium is introduced into said iron fuel burner arrangement at an angle and/or with a swirl.

8. The burner process for iron fuel combustion according to claim 1, wherein said air inlet means are arranged for directing said air in a coaxial manner, and/or at an angle with respect to said iron fuel suspension medium, into said iron fuel burner arrangement.

9. The burner process for iron fuel combustion according to claim 1, wherein said iron fuel suspension medium has a homogeneous distribution in the cross section of iron fuel particles in said medium.

10. The burner process for iron fuel combustion according to claim 1, wherein the iron fuel particles in said iron fuel suspension medium are homogeneously distributed in the cross section with respect to their particles sizes.

11. The burner process for iron fuel combustion according to claim 1, wherein said iron fuel suspension medium has an oxygen concentration of 6-22 vol. %.

12. The burner process for iron fuel combustion according to claim 1, wherein said the iron fuel suspension medium has an enriched oxygen concentration of at least higher than the ambient oxygen concentrations for iron fuel ignition enhancement.

13. The burner process for iron fuel combustion according to claim 1, wherein said air from said air inlets has an oxygen concentration of 6-22 vol. %.

14. The burner process for iron fuel combustion according to claim 1, wherein said iron fuel burner arrangement has a geometry that widens, which provides an approximately constant average axial velocity during nominal load of the flows in the cross-section over the length of the burner arrangement is achieved in step (c) and/or (d).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] FIG. 1 shows in an illustrative manner the steps of the process of burning iron fuel according to an aspect of the present disclosure.

[0051] FIG. 2 shows a schematic overview of the medium flows considered in the calculation of the overall angular momentum ratio.

DETAILED DESCRIPTION

[0052] The present invention is elucidated below with a detailed description.

[0053] In FIG. 1 the four basic and minimal steps are shown in an illustrative manner of a burner process of iron fuel combustion. Combustionor burningof iron fuel is different from the combustion of conventional fuels. Known burning processes suitable for example burning coal, coal-like material, biomass and waste, are not suitable or less suitable for burning iron fuels. Burning iron fuel requires specific process design concepts which are different from these known burner processes. Due to the different chemical and physical properties of iron fuel as compared to conventional fuels, the conventional burner processes do not suffice.

[0054] Iron, just like some other metals, can be burned to generate heat. The iron powder used for such purpose has a particular and preferred particle size or grain size which may lie in the range between 1 and 250 micrometer, and more preferably, between 20 and 150 micrometer.

[0055] To convert iron fuel into heat, the iron fuel is burned in oxygen containing gas, such as air. Preferably, the heat may further be used in a boiler or other means to transport the heat to desired locations, or to convert it into rotational energy, e.g. to generate electricity.

[0056] The combustion of iron fuel is a highly specific process and requires other measures than those of known burner processes of conventional fuels, especially since flame stability is challenging. Moreover, the recovery of the iron oxide or rust to such a degree that it is suitable for regenerating it back into iron powder which again can be used as iron fuel is also challenging. A burner process which meets these requirements, and which thus allows efficient recovery of the rust while having efficient heat transfer is considered even more challenging.

[0057] In FIG. 1 a burner process for iron fuel combustion is shown which meets these requirements and overcomes such challenges. The burner process comprises of several steps and at least the following:

[0058] In a first step, A, the iron fuel suspension medium is provided. The medium may comprise several components but at least comprises iron fuel (iron powder) and oxygen, possibly in a medium completely comprised of oxygen but more likely, containing oxygen and other components. The iron fuel and oxygen are provided in a suspension solid density of between 2 and 15 kg/Nm.sup.3 and preferably between 4 and 8 kg/Nm.sup.3.

[0059] The iron fuel suspension medium with such properties is introduced, in the next step B, into the iron fuel burner arrangement. The speed at which the suspension medium is introduced is at least above 5.5 m/s to assure the particles remain suspended in the airflow, and does not exceed 55 m/s as that would introduce further difficulties in respect of flame stability and especially mixing of the air by the air inlet means.

[0060] The iron fuel suspension medium does not yet meet the requirements which are considered sufficient for combustion of the fuel. Therefore, the suspension medium is subjected to an air flow at step C. The flow is provided by air inlet means which may comprise of one means, or several means and may have one or several (preferably evenly distributed) air inlet ports which introduce the air into the burner arrangement. The air flow mixes with the iron fuel suspension medium to obtain a medium which meets combustion requirements and as such is defined as a combustible medium. The mixing is the result of the air inlet means to introduce the air and direct the air to the suspension medium with a certain impulse creating an angular momentum in the flow. The dimensionless overall angular momentum ratio (I.sub.ratio) between the air and suspension medium flow is calculated using

[00001]$I_{ratio}=\frac{I_{air}}{I_{susp}}=\frac{{}_{air}.Math.{\left[v_{air}.Math.\sin \left(\right)\right]}^2.Math.A_{air}.Math.r_{air}.Math.\sin \left(\right)}{\left({}_{susp}+{}_{air}\right).Math.v_{susp}^2.Math.A_{susp}.Math.r_{susp}}$

where [0061] I.sub.x is the respective angular momentum defined by I=.Math.v.sup.2.Math.A.Math.r. It must be noted that the angular momentum is defined as the momentum of the impulse G defined by G=.Math.v.sup.2.Math.A. The latter being equal to the momentum flux J of an inlet multiplied with its surface area. The momentum flux J is defined by J=.Math.v.sup.2. [0062] .sub.air is the air density at the said inlet in kg/m.sup.3. [0063] .sub.susp is the suspension density in kg/m.sup.3 at the said suspension inlet, not including the mass flow of the air in the suspension mixture. [0064] v.sub.air is the velocity of the air inlet(s) in m/s. [0065] v.sub.susp is the velocity of the suspension inlet in m/s. [0066] A.sub.air is the surface area of the said air inlet(s) in m.sup.2. [0067] A.sub.susp is the surface area of the suspension inlet in m.sup.2. [0068] r.sub.susp is area weighted mean radius of suspension flow in meter (assuming uniform distribution for the cross-section of the flow) [0069] r.sub.air is the radial distance from the center of the suspension flow in meter (or centre of the flow) to the mean of the centre of the air inlets (but does not exclude non-mean) and; [0070] and are the angles between the suspension flow and air inlet means as schematically depicted by FIG. 2.

[0071] The burner process according to the present disclosure having a dimensionless overall angular momentum ratio (I.sub.ratio) between the air and suspension medium flow may also be defined by

[00002]$I_{ratio}=\frac{I_{air}}{I_{susp}}=\frac{I_{air}}{I_{susp}}.Math.A_{air}.Math.r_{air}$$I_x=s_x.Math.V_x^2$

[0072] The impulse [kg*m*s{circumflex over ()}1] may be defined by

[00003]$G=m*V$$G=p*V^2*A$

[0073] The angular momentum [kg*m{circumflex over ()}2* *s{circumflex over ()}1] may be defined by

[00004]$I=G*R$$I=m*V*r$$I=p*V^2*A*r$

[0074] And the momentum flux by

[00005]$J=p*V^2$

[0075] The overall angular momentum ratio is between 3 and 12 to ensure the suspension moves sufficiently radially outward (creates angle in FIG. 2), but also such that the radially outward movement of the suspension flow does not become too large such that extreme wear of burner components occurs. Preferably this ratio is between 3.8 and 8.9. The upper limit poses a risk of wear of particles and potential agglomeration and formation of stalagmites/stalactites in the burner arrangement and downstream components.

[0076] Once the suspension medium is mixed, and the combustible medium is obtained, the medium may be ignited. In this way heat is generated, with an iron oxide containing medium as residue, from which the iron oxide can be separated, recovered and regenerated back into iron fuel.

[0077] The following data represents several cases of the suspension and air conditions as experimental data for the present invention and disclosed embodiments. In the example and the cases thereof, it is demonstrated that at least for case 5 a lambda value A or air-fuel ratio, is achieved which is in the preferred ratio of 1.2 and 1.8. Cases 4 and 5 also demonstrate a lambda value by which the claimed effect is achieved, although slightly beyond the preferred ratio bandwidth.

TABLE-US-00001 Cases suspension and air conditions constants rho air @ 293.15K 1.293 angle theta 90 degree A_ratio 9 r_ratio 3 Suspension Air Momentum flux Case rho v_susp v_air J_air J_susp I_ratio Kolom1 [kg/m3] [m/s] [m/s]2 [kg/(m s{circumflex over ()}2)] Kolom2 [] []4 1 15 20 20 517 6517 2.1 0.4 2 6 20 20 517 2917 4.8 2 3 4 20 20 517 2117 6.6 1.5 4 15 20 40 2069 6517 8.6 0.8 5 2 20 20 517 1317 10.6 3 6 10 20 40 2069 4517 12.4 1.22

[0078] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. The scope of the present invention is defined by the appended claims. One or more of the objects of the invention are achieved by the appended claims.