Title of Invention

" A METHOD OF INCREASING COMBUSTION OF A HYDROCARBON FUEL IN A COMBUSTION CHAMBER OF A FURNACE."

Abstract

Methods and apparatus for combustion of a hydrocarbon fuel in a combustion chamber of a furnace or boiler are presented, the combustion normally using only air as an oxidant, part of the air entering the combustion chamber through one or more burners, and a remaining portion of air entering the combustion chamber at a plurality of locations downstream of the burners. The methods comprise injecting oxygen-enriched gas through a plurality of lances into the combustion chamber at a plurality of downstream locations, the oxygen-enriched gas injected at a velocity ranging from subsonic to supersonic, and the oxygen-enriched gas being present in an amount sufficient to provide an oxygen concentration of no more than 2% on a volume basis greater than when air is used alone as oxidant.

Full Text

1. Field of the Invention: This invention relates to in improved method of incrasing combust of a hydrocastion fuelin a comfustion chow of a furnace 2. Related Art: hi a previous disclosure of the same assignee of the present invention, Air Liquide Serie file 5167, filed November 10, 1999, Application Serial No.09/437,;>26, there was proposed a scheme of oxygen-enrichment in boilers using large amounts of oxygen, up to full oxy-fuel combustion. That patent application involved a certain ratio between the oxygen enrichment and the flue gas recirculation, such that the design boiler parameters are maintained constant. While quite inventive, the above-referenced methods in said patent application may not be desirous in particular industrial heating applications, in particular coal fired boilers, primarily pulverized coal, but with the application to fluidized beds also. Coal combustion results in a potentially large amount of unburned coal in the stack, thus losing a large amount of fuel. Also, due to the incomplete combustion of coal, as well as to the sometimes difficult ignition process, a support fuel such as natural gas is frequently used in significant quantities (from about 10% to about 50% of the total amount of fuel). The ease and completeness of combustion is directly related to the volatile content of the coal, and indirectly related to the percentage of moisture in the coal. In other words, more moisture means more difficult and possibly incomplete combustion, while more volatiles in the coal means more complete combustion. Figure 1 presents in schematic, a prior art combustion chamber 2 in a boiler 4, where the combustion chamber 2 is divided into two major zones: Zone I, as denoted in Figure 1 at 6, represents the area where combustion burners are located, together with air inlets. Combustion air can enter combustion chamber 2 together with a fuel (part of the air is used to transport coal into combustion chamber 2), or in different inlets. Combustion air can be introduced into the boiler partially or totally at this location. More modem schemes use a different air inlet, denoted as Zone II, and noted as 8 in Figure 1, in order to improve the combustion process and to lower the NOx emissions. The combustion scheme illustrated schematically in Figure 1 is termed "staged combustion" since the combustion process occurs in two zones. It is noted that the schematic in Figure 1 is very general, showing a generally horizontal flue gas circulation 10. In general, flue gas circulation can be in any direction (vertical, horizontal, circular, and the like). As illustrated in Figure 1, the combustion process is divided into two major zones: Zone I represents the ignition zone, where the fuel(s) enter the combustion chamber, are heated, and ignite. When coal is of a lesser quality, additional fuel (generally natural gas or fuel oil) is required for a fast ignition. Zone II represents the final region allocated lor combustion. Additional oxidant may be introduced, as mentioned supra. Modem staged combustion schemes allow a significant portion of the oxidant to enter Zone II (between 10% and 50% of the total oxidant). Due to the low pressure of the incoming air in Zone II, the flow patterns of the main flue gas stream are relatively undisturbed, thus the mixing between the two streams is relatively poor, preventing the hill combustion of the fuel. This is represented by the shaded area 16 in Figure 2. Figure 2 illustrates that the mixing zone 16 between the flue gas stream 10 and the balance of the oxidizer in Zone II and exiting into the mixing zone 16 is not total, thus an important part of the fuel will not mix with the oxidant, thus remaining unburned. It would be an advantage if the fuel from Zone I could be mixed with oxidant from Zone II to provide better mixing between fuel and secondary oxidant. Summary of the Invention In accordance with the present invention, methods and apparatus are provided which overcome problems associated with the prior art methods. The present invention involves introducing a high velocity stream of an oxygen-enriched gas into Zone II through a multitude of streams, preferably uniformly distributed for better mixing. "Oxygen-enriched" as used herein, is considered any gas having concentration of oxygen higher than 21% (the oxygen concentration in air). The results of this inventive process are: providing the fuel and/or fuel-rich combustion products with enhanced oxidant (when compared to air), and also impi-oving the mixing Between the fuel and/or fuel-rich combustion products and the oxidant. The combined effect of high oxygen concentration and improved mixing leads to a more effective and complete fuel combustion. One aspect of the invention is a method of increasing combustion of a hydrocarbon fuel in a combustion chamber of a furnace, the combustion normally using only air as an oxidant, part of the air entering the combustion chamber near (preferably in) one or more fuel burners, and a remaining portion of air entering the combustion chamber at a plurality of locations downstream of said fuel burners, the method comprising the steps of injecting oxygen-enriched gas through a plurality of lances into a flue gas in the combustion chamber at the plurality of downstream locations, the oxygen-enriched gas injected at a velocity ranging from subsonic to supersonic, the oxygen-enriched gas being present in an amount sufficient to provide an oxygen concentration in the flue gas of no more than 2% on a volume basis greater than when air is used alone as oxidant. Preferably, the velocity is subsonic for the oxygen-enriched gas in each of the plurality of lances, or in some embodiments the velocity is supersonic for the oxygen-enriched gas in each of tire plurality of lances, in any case the velocity of the oxygen-enriched gas is greater than velocity of air injection. As used herein the term "combustion chamber" includes any area where combustion o f fuel can occur in a furnace or boiler. In other preferred embodiments, some of the oxygen-enriched gas is injected at subsonic velocity in one or more lances while a balance of the oxygen-enriched gas is injected at supersonic velocity through one or more lances. The oxygen-enriched gas is preferably injected through the lances at an angle with respect to a wall of the combustion chamber, the angle ranging from about 20° to about 160° the angle measured in a plane that is perpendicular to the wall. Preferably, the plurality of locations are arranged so that one-half of the lances are on a first wall and one-half of the lances are on a second wall. Also preferred are embodiments where lances on the first wall are separated by distance LL, wherein LL the first wall are positioned a distance 1 from the lances on the second wail, wherein 0 Preferably, the combustion chamber is rectangular, wherein there is one lance on each of four walls of the rectangular combustion chamber, and wherein each lance is a distance L' from a wall wherein an adjacent lance is positioned. Preferably, L' In the embodiments which employ rectangular combustion chambers, the remaining portion of air preferably enters the combustion chamber through one or more rectangular slots, or through one or more substantially circular slots. Other preferred methods are those wherein the oxygen-enriched gas is injected in substitution for the remaining portion of air, and methods wherein said oxygen-enriched gas is injected into the remaining portion of air. A second aspect of the invention is a method of increasing combustion of coal in a combustion chamber of a furnace, the combustion normally using only air as an oxidant, part of the air entering the combustion chamber near (preferably in) one or more fuel burners, and a remaining portion of air entering the combustion chamber at a plurality of locations downstream of the fuel burners, the method comprising the steps of injecting oxygen-enriched gas through a plurality of lances into a flue gas in the combustion chamber at the plurality of downstream locations, the oxygen-enriched gas injected at a velocity ranging from subsonic to supersonic, and the oxygen-enriched gas being present in an amount sufficient to provide an oxygen concentration in the flue gas of no more than 2% on a volume basis greater than when air is used alone as oxidant. As in the first aspect, the injected oxygen-enriched gas is"injected at a velocity greater than the air would have been. Preferred are those methods wherein some of the oxygen-enriched gas is injected at subsonic velocity in one or more lances while a balance of the oxygen-enriched gas is injected at supersonic velocity through one or more lances. Also preferred are methods within this aspect wherein the oxygen-enriched gas is injected through the lances at an angle with respect to a wall of the combustion chamber, the angle ranging from about 20° to about 160°, the angle measured in a plane that is perpendicular to the wall. Preferred embodiments with the second aspect include those methods wherein the plurality of locations are arranged so that one-half of the lances are on a first wall and one-half of the lances are on a second wall; methods wherein lances on the first wall are separated by distance L, wherein L Preferably, the remaining portion of air enters the combustion chamber through one or more rectangular slots, or through one or more substantially circular slots. Preferably, the oxygen-enriched gas is injected in substitution for the remaining portion of air, or the oxygen-enriched gas is injected into the remaining portion of air. A third aspect of the invention is a method of increasing combustion of a hydrocarbon in a combustion chamber of a furnace, the combustion normally using only air as an oxidant, part of the air entering the combustion chamber near (preferably in) one or more fuel burners in a first zone of the combustion chamber, and a remaining portion of air normally entering the combustion chamber at a plurality of downstream locations, the method comprising injecting a first portion of oxygen-enriched gas into the combustion chamber at the plurality of downstream locations, the first portion of oxygen-enriched gas injected at a velocity ranging from subsonic to supersonic, wherein the first portion of oxygen-enriched gas is injected through a centrally located oxygen lance, which injects the oxygen-enriched gas into a flame created at each of the plurality of locations by a second portion of oxygen-enriched gas and a fuel. Preferably, the totality of oxygen-enriched gas is injected at an amount sufficient to provide an oxygen concentration of no more than 2% greater than when air is used alone. As with the previous aspects of the invention, the first portion of oxygen-enhanced gas may be either injected at sub-sonic or supersonic velocity, but in all cases, greater velocity than if air were used alone. Preferred are methods wherein said second fuel is selected from the group consisting of gaseous and liquid fuels, and wherein the second portion of the oxygen-enriched gas has substantially the same concentration of oxygen as the first portion of oxygen-enriched gas; also preferred is when each lance is positioned at a first angle ranging from about 20° to about 160°, the first angle measured in a first plane which is substantially vertical and substantially perpendicular to its corresponding wall. Accordingly the present invention relates to an improved method of increasing combustion of a hydrocarbon fuel in a combustion chamber of a furnace using only air as an oxidant, comprising introducing part of the air into the combustion chamber near one or more fuel burners where it is combusted with the hydrocarbon fuel thereby creating a flue gas, and introducing a remaining portion of air into the combustion chamber at a first velocity at a plurality of locations downstream of the fuel burners where it is combusted with the flue gas, the improvement comprising: injecting oxygen-enriched gas in substitution for the remaining portion of air through a plurality of lances into the flue gas at the plurality of downstream locations, wherein the oxygen-enriched gas has an oxygen concentration of no more than 2% greater than that of air. Brief Description of the'Drawings Figure 1 is a schematic representation of a prior art combustion furnace and method; Figure 2 is a schematic diagram of a prior art combustion furnace and method showing poor mixing between fuel and oxidant injected in Zone II; " Figure 3 is a schematic illustration of an inventive apparatus and method, illustrating mixing between unbumed fuel and oxidant entering from Zone II; Figures 4a and 4b are side sectional and front elevation views, respectively, of one inventive apparatus and method in accordance with the invention; Figures 5a and 5b are side sectional and front elevation views, respectively, of a second apparatus and method embodiment in accordance with the present invention; Figures 6a. and 6b are side sectional and front elevation views, respectively, of another apparatus and method embodiment in accordance with the present invention; Figures 7a and 7b are plan and side sectional views, respectively, of another apparatus and method in accordance with the present invention; Figure 8 is a plan view of another apparatus and method embodiment in accordance with the present invention; Figures 9a, 9b, and 9c, are side sectional, and two alternative front elevation views, . respectively, of another apparatus and method in accordance with the invention; Figures 10a, 10b, and 10c, are side sectional, and two alternative front elevation views, respectively, of another apparatus and method in accordance with the present invention; Figures 11a, 1 lb, and lie, are side sectional, and two alternative front elevation views, respectively, of another apparatus and method embodiment in accordance with the present invention; Figures 12a, 12b, and 12c, are side sectional, and two alternative front elevation views, respectively, of another apparatus and method embodiment in accordance with the present invention; and Figure 13 is a schematic illustration of a preferred apparatus and process in accordance with the invention wherein enhanced oxidant is injected in with the fuel in Zone I. Description of Preferred Embodiments The combined effect of enhanced oxygen concentration and improved mixing leads to a more effective and complete fuel combustion. Figure 3 illustrates the process schematically where the enhanced oxidant is injected in Zone II at 8, forming an enriched oxidant mixing zone 14 which greatly improves the combustion efficiency. Figures 4-12 illustrate specific embodiments of injection of oxygen-enriched gas. Figure 4a illustrates a side sectional view, and a front elevation view, Figure 4b, of one apparatus and method embodiment of the invention. A furnace wall or burner block 300 has a front face 302 which faces a combustion chamber. Oxygen-enriched oxidant enters into pipe 301 and traverses through a converging, diverging nozzle 200, having an exit 201. As illustrated in Figure 4b, there typically are multiple pipes 301 having exits 201, Figure 4b illustrating a case where there are three pipes 301 and three exits 201. The injection points are located preferably on the same wall of the combustion chamber and separated from the air injection points. The velocity (Vox) of the oxygen-enriched oxidant stream (400) is preferably within the range of 0.75 Mach up to about 5 Mach, and more preferably ranging from about Mach 1 to about Mach 2. The high momentum oxidant jet 400 entrains flue gases as depicted in Figure 4a to create a mixing zone 401. The high momentum oxidant jet entrains flue gases rich in fuel into a high oxygen concentration zone to complete combustion. Typically, if Vs is the sonic velocity of the main oxidant stream in the conditions of use in the furnace, then the following condition will be present with the oxidant stream 400: Vs Figures 5a and 5b illustrate another embodiment of the invention where oxygen-enriched oxidant is injected in pipe 100 in Zone II of the combustion chamber using the same configuration described in Figure 4a; however, the oxidant stream velocity exiting pipe 100 is below sonic velocity of the local air stream. Thus, in this embodiment, the following relationship exists: 0.1 x Vs Another embodiment is depicted in Figures 6a and 6b. As depicted in Figure 6a, a first portion of oxygen-enriched oxidant enters pipe or conduit 100, producing an oxidant stream 400b. The oxidant exiting pipe 100 is subsonic in velocity following the relationship: Vox shown from the direction "C" in Figure 6a. The front elevation view in Figure 6b depicts three injector pipes 100, three fuel pipes 110, and three outer oxidant injector pipes 120. As with the previous embodiments, the injection points are preferably located on the same wall of the combustion chamber and preferably separated from the air injection points by distance ranging from a few meters up to about 50 meters, depending on the combustion chamber and furnace dimensions. Figures 7a and 7b present plan and side sectional views, respectively, of another embodiment of the present invention. In this embodiment, four oxidant lances are installed on two opposing walls of a combustion chamber to provide a more homogenous oxidant distribution within the combustion chamber. Four injection points 100, 100', 100a, and 100a' are provided. Velocity of the oxidant streams injected in these four injectors may range from • 0.75 Mach up to Mach 5, preferably ranging from 0.7 Mach to Mach 3. The angle a is as before with regard to previous embodiments, while the angle (3 as depicted in Figure 7b is generally within the range of 20° to about 160°. The angle (3 may be different from the angle a but is preferably the same as the angle a. Illustrated in Figure 7a is the distance LL and the distance 1. LL is defined as the distance between two adjacent oxidant lances, for.example, 100a and 100a' in Figure 7a. Preferably the following relationship exists: LL Figure 8 illustrates another embodiment of oxygen-enriched oxidant injected in Zone II of a combustion chamber. In this embodiment, the oxidant lances 100, 100a, 100b, and 100c are installed on four walls of a combustion chamber 300, 300a, 300b, and 300c, respectively. This embodiment provides a more homogenous and turbulent oxidant distribution. Figure 8 illustrates a rectangular combustion chamber, but the same injection arrangement could be applied in a cylindrical combustion chamber. The velocities of the various oxidant streams emanating from lances 100, 100a, 100b, and 100c maybe the same or different, but in each case the following relationship holds: Vox each individual oxidant lance 100, 100a, 100b, and 100c, again independently ranges from about 20° to about 160°. Again, a is defined as the angle between the oxidant lance symmetry axis and the combustion wall surface. Another angle is defined in Figure 8a, angle y, there being shown y1,y2,y3 and 74. Angle 8 is defined as the angle between the oxidant lance symmetry axis and the combustion wall surface in a plane perpendicular to which the angle a is measured. The angle y in each independent case ranges from about 20° to about 160°. There is also defined in Figure 8 lengths L1, Lo2 L3, and L4. The length L1 is the distance between the respective oxidant lance and its closest wall surface, with the following relationship holding true: Li Figures 9a, 9b, and 9c, illustrate schematically a side sectional view, and two alternative front elevation views depicted by front elevation "E" in Figure 9a. hi Figure 9a, oxygen-enriched oxidant enters a pipe 100, wherein the oxygen-enriched gas is injected directly into an air stream traversing through through-hole 500 in furnace wall 300. Oxygen-enriched gas traverses through pipe 100 and through a converging, diverging nozzle 200 and exits with supersonic velocity ranging from about 1 Mach up to about 5 Mach, preferably from about 1 Mach to about 3 Mach. The high momentum oxidant jet 400 entrains air and flue gases rich in fuel into a high oxygen concentration zone to complete combustion. Depicted in Figures 9b and 9c are two alternative front elevation views, which differ primarily in the shape of the through-hole for air. in Figure 9b, through-hole 500 is a slot, whereas in Figure 9c, the through-hole 500a is a circular pattern. Figures 10a, 10b, and 10c, show a design similar to that depicted previously in Figures 9a, 9b, and 9c, except that the oxidant-emiched gas emanating from pipe 100 travels through a straight nozzle 202, and therefore, Vox follows the relationship: 0.1 x Vs Figures 11a, lib, and lie, illustrate yet another embodiment of the invention. In Figure 11a, oxidant enters through a pipe 100 directly into an ah stream which traverses through a through-hole 500 in furnace wall 300. Oxygen-enriched stream flowing through pipe 100 is injected perpendicularly (as illustrated via arrows) to the flow of air through a nozzle 600. The oxygen-enriched gas, being mjected perpendicular to the flow of air, improves the mixing of air with the high oxygen concentration gas. The velocity of the injected oxygen-enriched stream follows the following relationship: 0.1 x Vs Figures 12a, 12b, and 12c illustrate yet another embodiment of the apparatus of the invention wherein oxidant-enriched gas is injected in Zone II of the combustion chamber. In this embodiment, the oxidant is used as the driving fluid while injected into an ejector through a pipe 100 having a pipe exit 102. The oxidant is preferably mjected through multiple ejectors, in order to improve the mixing between air and the high-oxygen concentration gas, and also to extend the high oxygen concentration zone further into the combustion chamber. An ejector nozzle 700 is provided for this purpose. The velocity of the oxygen-enriched stream (Vox) niay be sonic or subsonic, following the relationship: 0.1 x Vs Figure 13 illustrates schematically a process and apparatus of the invention where a combined scheme is proposed. Here, enhanced oxidant is introduced both into Zone I, lanced into the fuel stream, and into Zone ll, tlrrough one of the means described in Figures 4-12. Enhanced oxidant is injected at 350 into Zone H and at 352 in Zone I. The impact of the WE CLAIM: 1. A method of increasing combustion of atleast a hydrocarbon fuel in a combustion chamber of a furnace using only air as an oxidant, comprising introducing part of the air into the combustion chamber near one or more fuel burners where it is combusted with the hydrocarbon fuel thereby creating a flue gas, and introducing a remaining portion of air into the combustion chamber at a first velocity at a plurality of locations downstream of the fuel burners where it is combusted with the flue gas, the improvement comprising: injecting oxygen-enriched gas in substitution for the remaining portion of air through a plurality of lances into the flue gas at the plurality of downstream locations, wherein the oxygen-enriched gas has an oxygen concentration of no more than 2% greater than that of air. 2. Method as claimed in claim 1 wherein some of said oxygen-enriched gas is injected at subsonic velocity in one or more of said lances while a balance of said oxygen-enriched gas is injected at supersonic velocity through one or more of said lances. 3. Method, as claimed in claim 1 wherein, said hydrocarbon fuel used is coal. 4. Method as claimed in any of the preceding claims wherein said velocity is subsonic for said oxygen-enriched gas in each of said plurality of lances. 5. Method as claimed in any of the preceding claims wherein said velocity is supersonic for said oxygen-enriched gas in each of said plurality of lances. 6. Method as claimed in any of the preceding claims wherein the oxygen-enriched gas is injected through said lances at an angle with respect to a wall of the combustion chamber, said angle ranging from 20° to 160°, said angle measured in a plane that is perpendicular to the wall. 7. Method as claimed in any of the preceding claims wherein said plurality of locations are arranged so that one-half of said lances are on a first wall or said combustion chamber and one-half of said lances are on a second wall of said combustion chamber, said first and second walls being parallel. 8. Method as claimed in claim 8 wherein lances on said first wall are separated by a distance as hereindescribed LL, wherein LL 9. Method as claimed in claim 7 wherein said lances on said first wall are positioned a distance from said lances on said second wall, wherein 0 10. Method as claimed in any of the preceding claims, wherein the combustion chamber is rectangular having four walls. 11. Method as claimed in claim 10 wherein there is at least one lance on each of said four walls of said rectangular combustion chamber. 12. Method as claimed in claim 11 wherein each lance is a distance as hereindescribed L' from a wall wherein an adjacent lance is positioned, and L' 13. Method as claimed in claim 11 wherein each lance is positioned at a first angle ranging from 20° to 160°, said first angle measured in a first plane which is vertical and perpendicular to its corresponding wall. 14. Method as claimed in claim 13 wherein each lance is positioned at a second angle ranging from 20° to 160°, said second angle measured in a plane perpendicular to the first plane. 15. Method as claimed in any of the preceding claims wherein the remaining portion of air enters the combustion chamber through one or more rectangular slots, at least one of said lances positioned in each of said rectangular slots. 16. Method as claimed in any of the preceding claims wherein the remaining portion of air enters the combustion chamber through one or more circular slots, at least one of said lances positioned in each of said substantially circular slots. 17. Method as claimed in any of the preceding claims wherein the oxygen-enriched gas is injected in substitution for said remaining portion of air at least one of said plurality of downstream locations. 18. Method as claimed in any of the preceding claims wherein said oxygen-enriched gas is injected into said remaining portion of air. 19. A method, as claimed in any of the preceding claims wherein it comprises increasing combustion of a first hydrocarbon fuel in a combustion chamber, the combustion normally using only air as an oxidant, part of the air entering the combustion chamber through one or more first hydrocarbon fuel burners in a first zone of the combustion chamber, and a remaining portion of air entering the combustion chamber at a plurality of locations downstream of said first hydrocarbon fuel burners, the method comprising injecting a first oxygen-enriched gas into the combustion chamber at said plurality of locations, the first oxygen-enriched gas being in an amount sufficient to provide an oxygen concentration of no more than 2% greater than when said air is used alone, and wherein the first oxygen-enriched gas is injected through a lance at a velocity, said lance injecting said first oxygen-enriched gas into a flame created by a second oxygen-enriched gas and a second hydrocarbon fuel.Method as claimed in claim 19 wherein said velocity is subsonic. 20. Method as claimed in claim 19 wherein said velocity is supersonic. 21. Method as claimed in claim 19 wherein said second hydrocarbon fuel is selected from the group consisting of gaseous, liquid, and particulate fuels. 22. Method as claimed in claim 19 wherein said second oxygen-enriched gas has the same concentration of oxygen as said first oxygen-enriched gas. 23. Method as claimed in claim 19 wherein each lance is positioned at a first angle ranging from 20° to 160°, said first angle measured in a first plane which is vertical and perpendicular to its corresponding wall. 25. A method of increasing combustion of a hydrocarbon fuel substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

1380-delnp-2003-abstract.pdf

1380-delnp-2003-assignment.pdf

1380-delnp-2003-claims.pdf

1380-delnp-2003-complete specification (as files).pdf

1380-delnp-2003-complete specification (granted).pdf

1380-delnp-2003-correspondence-others.pdf

1380-delnp-2003-correspondence-po.pdf

1380-delnp-2003-description (complete).pdf

1380-delnp-2003-drawings.pdf

1380-delnp-2003-form-1.pdf

1380-delnp-2003-form-19.pdf

1380-delnp-2003-form-2.pdf

1380-delnp-2003-form-3.pdf

1380-delnp-2003-form-5.pdf

1380-delnp-2003-gpa.pdf

1380-delnp-2003-pct-210.pdf

1380-delnp-2003-pct-301.pdf

1380-delnp-2003-pct-304.pdf

1380-delnp-2003-pct-308.pdf

1380-delnp-2003-pct-332.pdf

1380-delnp-2003-pct-402.pdf

1380-delnp-2003-pct-409.pdf

1380-delnp-2003-pct-416.pdf

1380-delnp-2003-petition-137.pdf

abstract.jpg