WO2007062257A2

WO2007062257A2 - Trajectory gasifier burners

Info

Publication number: WO2007062257A2
Application number: PCT/US2006/045565
Authority: WO
Inventors: Lloyd E. Weaver
Original assignee: Lew Holdings, Lls
Priority date: 2005-11-28
Filing date: 2006-11-28
Publication date: 2007-05-31
Also published as: WO2007062257A3

Abstract

Burner arrangements (1) for gasifiers or boilers or similar reaction vessels that shoot reactants such as fuel (5) and oxidizer (11) at intersecting angles to combust or react within the reactor cavity but away from inner walls (4) and nozzles (13) to minimize wear and tear on nozzle and cavity refractory in reactors designed to remove solid reactants by gravity below and gaseous reactants within the gas flow above and barrel burner incorporating the same elements.

Description

TRAJECTORY GASIFIER BURNERS

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Ser. No. 60/740,138, filed November 28, 2006.

BACKGROUND OF THE INVENTION

[0002] High temperature oxygen-blown gasifiers experience shortened nozzle or burner life due to burner design. Burners in present slurry fed gasifiers are fluid-cooled metal burner units that combine a curtain slurry and central oxidizer feed much like in a common household boiler, except the oxidizer and fuel feed flows are reversed in gasifier burners. Slurry fuel is fed around the periphery of a center oxidizer (nearly pure oxygen) blast nozzle. Therefore, very hot combustion takes place in very close proximity to the nozzle tips, consuming the nozzles within two months and the upper refractory in less than a year. This requires the gasifier to be shut down often for burner replacements, which is an expensive and time-consuming enterprise, not to mention refurbishing the burners. Refractory placement is an even more expensive proposition.

SUMMARY OF THE INVENTION

[0003] One embodiment of the present invention greatly extends fuel and oxidizer feed port life cycles by blasting fuel mix from one port and oxidizer, such as air or pure oxygen, from another port at an angle to each other to cause intersection or impact (and in this instance once ignited, a self- sustaining reaction occurs) a short distance from the inner wall of the refractor (the exact distance of which can be determined by simulation or actual test). In addition, by locating burners near the bottom of the gasifier, molten slag tends to form away from the gasifier inner wall and advantageously falls by gravity into a molten slag bed or quenching bath ash/slag rejecting lock hopper without contacting the upper walls of the gasifier. The net result can be practically no effect of slag on upper refractory wall surfaces and increased burner and wall refractory life cycles where the most intense gasification reactions occur. A barrel burner arrangement for dry fuel feed is shown that has similar advantages over slurry feed burners.

[0004] One aspect of the invention is based on the simple notion of separating the oxidizer and dry fuel feed flow in highly reactive burners. This version of the invention separates these reactant flows and combines them well away from each respective nozzle causing them to form a trajectory that intersects or impacts with the reacting space but well away from refractory surfaces and the fronts of the nozzles. Initial ignition for self-sustaining reactions can be by high power laser or other hot energy source aimed into the center of the impact space to cause ignition. Gasifiers of this design would have the primary combustion taking place directly over a molten slag bed with the remaining combustion or gaseous byproducts flowing upwards to exit out the top of the reactor. Heavy slag and ash formed would fall to the ash pit or molten slag bed where, in a molten slag bed condition, more oxidizer and energy can be introduced to bum off any remaining carbon while gasifier gas exits the combustion-gasification space at the top area for heat absorption to generate steam or for further gas cleaning and processing as appropriate.

[0005] Such burners or reactor feed assemblies can be located anywhere within the lower combustion space periphery. Fuel with reactive steam and separate oxidizer feeds can be closer together with a narrow intersecting inclusive angle or farther apart depending on what works best. But trajectories would generally be located down low and preferably aimed slightly upwards. Whether they should impact along side each other (i.e., at a small angle) as well as at similar or different velocities to get enhanced eddy reaction or combustion effects can be determined by simulation or actual experiment. Such fuel feed and oxidizer feed rates can be made variable to adjust output or turndown of the gasifier with no affect on the burn point intersection by varying the quantity of individual steam jet blasts. Or₁ if a mechanical fuel slinger is employed, a rather constant fuel feed velocity can be maintained since the slinger peripheral velocity need not change (although it can be made variable if advantageous).

[0006] Another aspect of the invention is based on a combined barrel burner fuel and oxidizer arrangement, which provides better control of combustion and exit velocities, especially in syngas burners which experience very hot burning. By using nearly pure oxygen in the combustion process, better combustion control and longer lived burners can result. The barrel burner version, by virtue of it better control and adjustability, has similar advantages to the intersecting trajectory configuration and is generally preferred with air as oxidizer, while the trajectory version may be preferred with pure oxygen oxidizer, both with pulverized dry fuel feed being used.

[0007] There is a turndown limit from maximum flow design whereby the fuel and oxidizer density at the trajectory intersection point would be too low to sustain a flame point. But for all practical purposes, such gasifiers tend to run at or near capacity so turndown is not a primary concern, but component life life cycle is always a concern. Thus, ports and nozzles can be designed with fixed openings for simplicity for full load condition and what turndown is available at that condition can be taken advantage of. Generally, not more than 2:1 turndown with fixed port openings is expected. Present slurry burners also tend to have fixed oxidizer center orifices but variable fuel feed forming an annular or curtain flow outside the oxidizer as they leave the burner, for example. See, for example, U.S. Patent No. 6,358,041 issued March 19, 2002 to Whittaker et al. [0008] The advantages of the burners of the present invention are:

1. Much longer inner reactor wall life due to lower temperatures next to the walls and lessened reactant solids or slag contacting walls.

2. Longer burner life by injecting steam and fuel or inert gas and fuel into the burner space at an angle to the oxidizer so that they intercept at an angle to each other into the combustion space eliminating close proximity of high temperatures burning of these feed nozzles or other undesirable reactant nozzle effects.

3. Better fuel and oxidizer velocity control and having the oxidizer as an annular curtain outside the center well randomized fuel feed forms a well defined flame matrix for more time to finish reaction of the carbon (burning) with the oxidizer compared to slurry feed designs that feed oxidizer in the center blasting apart the flame matrix.

4. In both burner configurations, fuel is fed dry so less steam or water is needed which increases the efficiency of the gasification reaction process.

[0009] The intersecting burner is not limited to just oxidizing reactions whereby any number of feeds intersecting some distance from inner walls within the rector may be advantageous to avoid plugging and excess wear on nozzle parts where processes and/or solid or liquid reactants are drawn off by gravity effects from below and gaseous reactants drown off from above. DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a top down sectional view of a burner or reactor in accordance with one embodiment of the present invention.

[0011] FIG. 2 is a sectional view of a single barrel burner arrangement in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0012] Referring to FIG. 1, reference numeral 1 depicts a burner arrangement used in conjunction with a reactor vessel of a gasifier or boiler burner or the like having an outer wall 2 that may be water cooled and further insulated outside (not shown), insulated refractory 3, and an inner wall 4 of this refractory. Mounted to this reactor vessel is a first tube 6 for providing a dry fuel feed 5 and a second tube 12 for providing an oxidizer stream 11. It should be noted that the present invention is not limited to dry fuel feeds and slurry feeds could also be used and sprayed out of a nozzle (not shown) mounted on the end of tube 6. All the burner arrangements or assemblies around the perimeter of the circular reactor vessel shown are identical; two are shown and more are possible and so only one assembly will be described herein. The invention is not limited to just circular reactor vessels, but any arrangement can be employed including rectangular with burners in corners or even along flat walls as long as there is a clear space for combustion or reactions to occur away from the inner wall area and means to remove solid reactants below and gaseous reactants from above and means to employ spectroscopy measurements. Such spectroscopy measurement means are indicated by reference numerals 16, 17, and 18 and are discussed below, but even gas measurement can be made in the final gas if that is desired, and suitable adjusting algorithms applied by a controller (not shown) to air, fuel, and steam adjustments. All the needed gas constituents for full control over the combustion process are measured by the spectroscopy measurement means 16, 17, and 18 whereby such control procedures (algorithms) and valves and dampers to be manipulated by the controller are well known to those of ordinary skill in the art of burner process control.

[0013] Continuous fuel feed 5 is fed by gravity or screw conveyors from a closed and pressurized vessel into a slinger 6'. Slinger 6' can be a rotary paddle or disk type slinger (see FIG. 2 for example) familiar to those of ordinary skill in the art, or fuel 5 could also be propelled by pressurized steam flow and or inert gases 5' as trajectory mix 9 into a reacting or combusting area 8 within the internal volume or space 7 defined by the reactor vessel. It should be noted that in one embodiment a molten slag bed (not shown) is located directly under the internal volume 7, whereby not only does the hot slag bed assist with combustion in combusting area 8, but also will burn off any residual carbon in the ash or slag that falls by gravity into this molten slag bed under internal volume 7. Also, separate energy can be added to this slag bed to keep it molten which provides another degree of freedom as to combustion temperatures that will be maintained at combusting area 8; that is the ratios of fuel 5, oxidizer 11 , and steam 5' can be such that the combustion temperature maintained within combusting area 8 can be lower than the slagging temperature maintained in the molten slag bed. This is what is meant by there being an additional degree of freedom in gasifier control available by this invention. Also, additives, such as calcium carbonate or iron oxide, can be added with fuel feed 5 to lower the slagging temperature. Such chemicals are well known in the art of gasification as means to lower slagging temperature, especially for hard coals or products being gasified with a high proportion of metals present (such as petroleum coke). Tube 6 would generally be a water cooled metal alloy suitable to high temperature and corrosive environs and have special coatings as needed to this effect and would be attached, such as by welding, to the outside of outer wall 2 and can be removed by cutting away it's outer weld. It would be aimed at installation to form the intersection point within combusting area 8 that is desired. Tube 12 would be similarly installed with capability for removal and repair. [0014] The distance between feed tubes 6 and 12 is one variable determining the location of the combusting area 8, as is their inclusive angle between them, 19. With feed tubes 6 and 12 closer together along outer wall 2 and with a smaller angle 19, these two flows will cascade together earlier to begin to react or combust. Further apart as shown at a more acute angle, and there will tend to be more of a collision reaction or sharper combustion point. Simulation or test will determine which is the best arrangement for a given application.

[0015] Similarly, the oxidizer 11 can be blasted under pressure through tube 12 into the combusting area 8, shown as jet flow 11' through an adjustable orifice nozzle 13 located at the end of tube 12. The oxidizer flow 11' impinges with trajectory mix 9 at combusting area 8. Those skilled in the art of nozzle design can create a remote adjustable and fluid cooled nozzle 13 and incorporate it within feed tube 12. However, a fixed nozzle orifice at 13 designed for the maximum load condition will likely be satisfactory for all expected loads to burner arrangement 1.

[0016] An igniter 14 is also mounted to the reactor vessel to provide a means for initially igniting the fuel-oxidizer mixture at the combusting area 8. In one embodiment, the igniter 14 can cause ignition by emitting a high energy laser igniter beam or gas jet 15 aimed at the fuel and oxidizer intersecting point within combusting area 8. Ignition at combusting area 8 will also be assisted by the molten slag bed made molten prior to starting up the burner(s) 1.

[0017] As noted, this reaction principle is designed to spare tube 6, nozzle 13 and/or inner walls 4 any undue wear due to slag deposits or high temperatures, but does not have to be limited to two reactants. Any number of reactants can be aimed to impinge at a point within combusting area 8 with reactive energy 15 supplied continuously or intermittently or only once to initiate self-sustaining reactions. Indeed, energy or reactor source 15 can be any sort of flow (catalytic flows, etc.) as needed to cause reaction away from feed tubes 6 and 12 and reactor inner walls 4. Also, flows 9 and 11' should point upwards to increase contact time for the combustion reaction before slag and ash fall into the molten slag bed. This is a key advantage of molten slag bed design, it not only enables carbon combustion gasification reactions to complete, but the molten bed can readily supply the needed energy to finish combustion and gasification reactions. And combusting areas 8 tend to impinge upon each other in the center, which is also advantageous as it reduces gasifier wall impacts from slag formation.

[0018] The present invention includes fiber optic laser spectrometer technology to measure combustion or reaction gas compounds such as CO, CO2, H2O, O2 and even gas temperature in situ using fiber optic gas purged (for cooling) emitters and receivers 16 and 18, respectively, with powerful laser beam 17 as shown. This technique enables multiple burner operations to be individually sensed and controlled simultaneously within the gasifier to make adjustments in the ratios of fuel 5, steam 5' and oxidizer 11 , respectively, or other reactant ratios as determined by the sensors and known by those skilled in the art of gasifier combustion control. The laser beams 17 for various burner assemblies 1 can be located at a slightly different elevations so that the laser beams do not interfere with one another or igniter beams 15, and can still perform correct measurements for burner fuel air ratio control proposes. Also, more than one set of spectroscopy measurement means 16, 17, and 18 can be employed above a given combusting area 8, if necessary, since such instrumentation can sample multiple (e.g., sixteen or more) points simultaneously, which is enough points to also measure final average gas properties that leave the reactor (not shown). Such sensor systems have been developed, and are manufactured, by ZoIoBOSS.

[0019] As noted, the distance between tubes 6 and 12, and their inclusive angle 19, determine how far from the inner wall 4 the combusting area 8 occurs. This can be any reasonable distance as long as there is not excessive breakup of fuel trajectory mix 9 and/or oxidizer flow 11', or any other reactants, such that combustion or reactions will readily occur at combusting area 8. Such distance can be determined with modern simulation techniques or with prototype burners to obtain the necessary design experience.

[0020] Referring to FIG. 2, the burner arrangement of FIG. 1 does not preclude combining the same elements of FIG. 1 into the single barrel burner arrangement of FIG. 2, but as noted the configuration of the invention represented by FIG. 1 is designed to improve on the life cycle provided by intense pure oxygen oxidizer gasifier burners generally arranged as FIG. 2. Nevertheless, a relatively long lived single barrel burner arrangement is shown in FIG. 2 manufactured of similar materials as in the embodiment of FIG. 1. The barrel burner of FIG. 2 would be arranged perpendicular to a cord of outer wall 2, and although shown horizontal in FIG. 2 for illustration purposes — it would preferably be installed at a slight upward angle. The embodiment of FIG. 2 has advantages over the slurry fed burner depicted in above-mentioned U.S. Patent No. 6,358,041 by providing more adjustability to fuel mix 9 and oxidizer blast 11', respectively. It accomplishes this because even with the constant inside diameter tube diameter of fuel feed tube 6, the exit velocity of fuel mix 9 can be adjusted by the varying the rotational speed of slinger 6', plus it has an adjustable exit orifice 12" to vary oxidizer flow velocity at exit point 11" with varying oxidizer flow rates. On the other hand, above-mentioned U.S. Patent No. 6,358,041 has a constant oxidizer exit orifice diameter which places more limitations to its turndown capability. Also the embodiment of FIG. 2 is configured with fuel blast from the center as a dry and random mixture ready to be dispersed at the exit point 11", which is more advantageous then attempting to form an annular curtain of slurry with oxidizer blasting from a center tube or nozzle as in above-mentioned U.S. Patent No. 6,358,041 to break up that slurry curtain. Thus, the barrel burner of FIG. 2 has flow adjustable advantages, dry fed fuel/air mixing advantages, and will achieve better mixing of fuel and oxidizer and better maintain the "integrity of combustion with a curtain oxidizer and fuel in center matrix" than above-mentioned U.S. Patent No. 6,358,041 , which blasts apart the slurry curtain flow from the burner nozzle face destroying any possibility of maintaining a well formed and well mixed combustion matrix. The embodiment of FIG. 1 has the same flow adjustability advantages over U.S. Patent No. 6,358,041 as well. The embodiment of FIG. 2 is constructed more like a conventional pulverized coal burner with fuel feed 5 and mechanical slinger 6' adding feed velocity to the coal fuel mix 9 and steam jet blast 5'through jet pipe 5" adding to fuel and steam mix 9 velocity through horizontal adjustable (adjust mechanism not shown) fuel feed tube 6 whose inside end slightly inside the end of larger tube 12 end 11" forming the oxidizer blast annular space 12' through which a uniform jet of oxidizer 11 is blasted and ejected as uniform cylindrical ring or annulus stream 11'. The nozzle end of the outer tube 12 is thicker and thus tapered inward such that moving the fuel feed tube 6 towards the tapered inner thicker end of tube 12 decreases the exit oxidizer blast 11' annular space 12", increasing oxidizer blast exit velocity. Or, with lower volumetric flow of oxidizer blast 11 , more turndown capability is available to the barrel burner of FIG. 2 by adjusting tube 6 to close off exit orifice 12" more, thus maintaining constant velocity at lower flows of oxidizer 11. Ignition can be provided by an igniter tube 14 mounted along side the outer tube 12, as shown.

[0021] Further, this invention isn't limited to circular vessels as noted above, and can be applied to any number of reactions requiring multiple feeds, not just combustion or gasification.

[0022] While specific embodiments of the present invention have been described, it should be noted that various modifications thereto can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A burner arrangement (1) for use with a reactor vessel having an inner wall (4), said burner arrangement (1) comprising: means (6) for introducing a fuel stream (5) into said reactor vessel; and means (12) for introducing an oxidizer stream (11) into said reactor vessel, wherein said fuel stream (5) and said oxidizer stream (11) intersect at a combusting area (8) spaced from said inner wall (4).

2. The burner arrangement (1) of claim 1 wherein said means (6) for introducing a fuel stream (5) includes a first tube (6) mounted to said reactor vessel and said means (12) for introducing an oxidizer stream (11) includes a second tube (12) mounted to said reactor vessel.

3. The burner arrangement (1) of claim 2 further comprising a slinger (6¹) for propelling fuel through said first tube (6).

4. The burner arrangement (1) of claim 2 further comprising a source of pressurized gas (5¹) for propelling fuel through said first tube (6).

5. The burner arrangement (1) of claim 2 further comprising an adjustable orifice nozzle (13) located at an end of said second tube (12).

6. The burner arrangement (1) of claim 2 wherein said first and second tubes (6,12) are pointed slightly upwards.

7. The burner arrangement (1) of claim 1 wherein said means for introducing a fuel stream and said means (12) for introducing an oxidizer stream (11) are combined into a single barrel burner arrangement.

8. The burner arrangement (1) of claim 1 further comprising means (16,17,18) for measuring combustion characteristics in said combusting area (8).

9. The burner arrangement (1) of claim 8 wherein said means (16,17,18) for measuring combustion characteristics includes laser spectroscopy devices (16,18).