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  Low nox staged fuel injection burner for creating plug flowUSPTO Application #: 20080096146Title: Low nox staged fuel injection burner for creating plug flow Abstract: A burner for producing a plug-like flow and low NOx emissions. The burner has a central air jet and plural staged fuel jets surrounding the central jet. The ratio of the sum of the momentums of vector components of the staged jets along respective axes parallel to the central longitudinal axis of the central jet to the momentum of the central jet along that axis is within the range of 0.5 to 1.5 and most preferably 0.8. (end of abstract) Agent: Air Products And Chemicals, Inc. Patent Department - Allentown, PA, US Inventors: Xianming Jimmy Li, Mahendra Ladharam Joshi, Aleksandar Georgi Slavejkov USPTO Applicaton #: 20080096146 - Class: 431 9 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080096146. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]The present invention relates to burners for furnaces, and in particular to staged burners for creating a plug-type flow pattern with low nitrogen oxides (NOx) emissions. [0002]Furnaces for ethylene cracking and other industrial processes, e.g., steam-methane reformers, typically make use of burners utilizing fuels such as natural gas, propane, hydrogen, refinery off-gas and other fuel gas combinations of various calorific values. For example, steam-methane reformer furnaces are used to produce hydrogen and carbon monoxide by reforming a hydrocarbon feed with steam and, at times, carbon dioxide at high temperatures. The furnace used for steam-methane reforming can be configured in several different structures. One of the most conventionally used arrangements for such reformer furnaces has vertical reformer tubes arranged in rows. The burners of the furnace can be located on the furnace's floor, its ceiling or its walls. As is known, operating a reformer tube above the desired temperature can cause large decreases in tube life. This, in turn will adversely affect the economics of the plant since the tubes are a substantial portion of the overall cost of the plant and require large expenditures of time and effort to replace one that has failed. Tube hot spots can arise from undesirable furnace flow patterns which cause flame impingement. This is particularly true in a tightly packed furnace with relatively few rows of burners and process tubes where the furnace geometry is such that the flue gas extraction system causes flue gas to cross over the process tubes. Needless to say any crossover within the flame zone should be avoided to maintain equipment life and plant reliability. To that end, establishing an appropriate flow pattern is critical to uniform furnace heating and the concomitant reduction of process tube overheating. Thus, one important criterion for the design of burners where process tube overheating is a concern is to provide a burner that will inherently create what is commonly referred to as a plug-like flow. [0003]Another important criterion for burner design is low NOx emissions. As is known nitrogen oxides are among the primary air pollutants emitted from combustion processes. NOx emissions have been identified as contributing to the degradation of environment, particularly degradation of air quality, formation of smog and acid rain. As a result, air quality standards are being imposed by various governmental agencies, which limit the amount of NOx gases that may be emitted into the atmosphere. One common way of reducing NOx emissions is by means of fuel/oxidant staging techniques, e.g., use of fuel staging burners making use of multiple jets outside and surrounding a central air jet. Other techniques are known for producing low NOx emissions from burners. The following are some exemplary references pertinent to the field of low NOx burners: U.S. Pat. No. 4,531,904 (Sato et al.), U.S. Pat. No. 4,946,382 (Kobayashi et al.) and U.S. Pat. No. 5,823,764 (Alberti et al.) and U.S. Published application 2006/0040223A1 (Ghani et al.). All references cited herein are incorporated herein by reference in their entireties. [0004]While the above mentioned prior art may be suitable for their intended purposes, they nevertheless leave something to be desired from the standpoint of creating a uniform or plug-like flow with low NOx emissions. BRIEF SUMMARY OF THE INVENTION [0005]The subject invention constitutes a staged fuel burner for establishing a plug-like flow, and is particularly useful in furnaces, such as ethylene crackers, reformers, etc. The staged burner comprises a central nozzle and plural staged nozzles. The central nozzle has an orifice producing a jet of air directed along a central longitudinal axis. The staged nozzles surround the central nozzle and each has at least one orifice producing a staged jet. Each staged jet comprises fuel, is directed along a respective longitudinal axis from the nozzle and has a vector component in a direction parallel to the central longitudinal axis. The sum of the momentums of the vector components of the staged jets parallel to the central longitudinal axis is approximately 50% to 150% (preferably 100%, and most preferably 80%) of the momentum of the central jet along the central longitudinal axis. [0006]In accordance with another aspect of this invention there is provided a method of establishing a plug like flow of burning fuel in a furnace. The method entails providing a staged burner comprising a central nozzle and plural staged nozzles surrounding the central nozzle. The central nozzle has an orifice arranged for producing a jet of air directed along a central longitudinal axis. The staged nozzles surround the central nozzle and each has at least one orifice arranged for producing a staged jet. Each staged jet comprises fuel, is directed along a respective longitudinal axis and has a vector component in a direction parallel to the central longitudinal axis. Air is provided to the central nozzle, whereupon the central nozzle produces a jet of air directed along the central longitudinal axis. Fuel is provided to each of the staged nozzles, whereupon each staged nozzles produces a respective staged jet of fuel along a respective longitudinal axes. The sum of the momentums of the vector components of the staged jets parallel to the central longitudinal axis is approximately 50% to 150% (preferably 100%, and most preferably 80%) of the momentum of the central jet along the central longitudinal axis. BRIEF DESCRIPTION SEVERAL VIEWS OF THE DRAWING [0007]The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein: [0008]FIG. 1 is an end view of one exemplary embodiment of a burner constructed in accordance with the subject invention; [0009]FIG. 2 is a sectional view, not to scale, of the exemplary burner taken along line 2-2 of FIG. 1; [0010]FIG. 3A is a sectional view, similar to FIG. 2, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0011]FIG. 3B is a sectional view, similar to FIG. 3A, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0012]FIG. 3C is a sectional view, similar to FIG. 3A, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0013]FIG. 4A is a sectional view, similar to FIG. 2, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0014]FIG. 4B is a sectional view, similar to FIG. 4A, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0015]FIG. 4C is a sectional view, similar to FIG. 4A, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0016]FIG. 5A is a sectional view, similar to FIG. 2, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0017]FIG. 5B is a sectional view, similar to FIG. 5A, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0018]FIG. 5C is a sectional view, similar to FIG. 5A, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0019]FIG. 6A is a sectional view, similar to FIG. 2, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0020]FIG. 6B is a sectional view, similar to FIG. 6A, of another exemplary embodiment of a burner constructed in accordance with the subject invention; [0021]FIG. 6C is a sectional view, similar to FIG. 6A, of another exemplary embodiment of a burner constructed in accordance with the subject invention; Continue reading... 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