| Gas combustion treatment method and apparatus therefor -> Monitor Keywords |
|
|
  Gas combustion treatment method and apparatus thereforUSPTO Application #: 20060141414Title: Gas combustion treatment method and apparatus therefor Abstract: A gas combustion treatment method for the combustion treatment of an ammonia-containing gas and a hydrogen sulfide-containing gas, the method comprising a first combustion treatment step in which the ammonia-containing gas, together with a fuel, is introduced and burned; a nitrogen oxide reduction step downstream of the first combustion treatment step, in which a portion of the hydrogen sulfide-containing gas or the ammonia-containing gas is introduced and the nitrogen oxides produced in the first combustion treatment step are reduced in a reducing atmosphere; and a second combustion treatment step downstream of the nitrogen oxide reduction step, in which the remaining hydrogen sulfide-containing gas, together with air, is introduced and burned. The present invention provides a combustion apparatus suitable for use as a combustion furnace for off-gases resulting from the wet purification of coal gasification gas. (end of abstract) Agent: Oblon, Spivak, Mcclelland, Maier & Neustadt, P.C. - Alexandria, VA, US Inventors: Masahiro Harada, Makoto Susaki, Kazuo Ishida, Hajime Nagano, Masahiro Hirano, Hiroshi Suzumura, Shintaro Honjo, Yoshinori Koyama, Katsuhiko Yokohama, Mitsugi Suehiro USPTO Applicaton #: 20060141414 - Class: 431354000 (USPTO) Related Patent Categories: Combustion, Mixer And Flame Holder The Patent Description & Claims data below is from USPTO Patent Application 20060141414. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO A RELATED APPLICATION [0001] This application is a divisional of U.S. patent application Ser. No. 10/245,326, filed Sep. 18, 2002, now allowed, which claims priority to Japanese patent application No. 2001-329190, filed Oct. 26, 2001, both of which are hereby incorporated by reference in their entirety. FIELD OF THE INVENTION [0002] This invention relates to gas combustion treatment methods and gas combustion apparatus. More particularly, it relates to a combustion apparatus suitable for use as a combustion furnace for off-gases resulting from the wet purification of coal gasification gas, and a combustion method therefor. BACKGROUND OF THE INVENTION [0003] When coal is gasified and used as a fuel for electric power generation, sulfur compounds (e.g., hydrogen sulfide and carbonyl sulfide) and nitrogen compounds such as ammonia are contained in the product gas. From the viewpoint of environmental protection and corrosion prevention, these compounds are removed in wet purification equipment. The hydrogen sulfide (H.sub.2S) removed in the wet purification equipment is stripped off and discharged as an off-gas containing hydrogen oxide at a high concentration (i.e., H.sub.2S off-gas). Moreover, the recovered ammonia (NH.sub.3) is similarly stripped off and discharged as an off-gas containing ammonia (i.e., NH.sub.3 off-gas). This system is more specifically described below with reference to a flow diagram shown in FIG. 3. [0004] Referring to the flow diagram shown in FIG. 3, hydrogen sulfide present in the product gas is removed with the aid of an amine in the H.sub.2S removal step, and the hydrogen sulfide is released again from the amine. In order to effect the combustion treatment of the resulting regeneration gas containing hydrogen sulfide, the H.sub.2S off-gas has been treated in a common combustion furnace, storage type combustion furnace or the like. As the combustion apparatus used in this combustion step, a storage type combustion furnace has conventionally been chosen and used because, when hydrogen sulfide is burned therein, the amount of SO.sub.3 formed as a by-product is small. [0005] However, storage type combustion furnaces have problems in that they require a valve mechanism for carrying out operation while changing a plurality of flow paths in order to maintain the effectiveness of heat exchange and its operating procedure is troublesome. Moreover, they are disadvantageous from the viewpoint of reliability ensuring freedom from troubles such as failure. That is, since heat exchange is effected when a gas flows through heat reservoirs, it may happen that the temperature of one heat reservoir continues to rise while the temperature of another continues to drop. Accordingly, it has been required to carry out operation while switching a plurality of valves constantly so as to change the gas inlets and outlets for heat reservoirs properly. [0006] On the other hand, when conventional storage type combustion furnaces (at 1,000.degree. C.) are used for the combustion treatment of NH.sub.3 off-gas, the complete combustion treatment of NH.sub.3 cannot be achieved to cause a leak of NH.sub.3 to the downstream side. Although a high combustion temperature (about 1,500.degree. C.) is required to decompose NH.sub.3 completely, the operating temperature of storage type combustion furnaces has been limited to about 1,000.degree. C. owing, for example, to the endurable temperature limits of heat reservoirs comprising mullite and cordierite (high-temperature ceramic materials). [0007] Also from the viewpoint of nitrogen oxide (NOx) reduction, it is necessary to burn NH.sub.3 off-gas at a high temperature (about 1,500.degree. C.), because the denitrification reaction of NO (formed from a portion of NH.sub.3) with NH.sub.3 is pronounced at 1,300.degree. C. or above. On the other hand, the NOx produced in the combustion step includes fuel NOx formed from nitrogen-containing fuels such as ammonia, and thermal NOx formed from atmospheric nitrogen in high-temperature regions (e.g., flames). Since the rate of formation of thermal NOx is enhanced in higher-temperature regions, the amount of thermal NOx produced is increased at high temperatures. However, when a large amount of an ammonia-containing gas is to be treated continuously, it is necessary to use a temperature capable of decomposing NH.sub.3 completely. That is, it has been desired to develop a technique for the treatment of an ammonia-containing gas in which NH.sub.3 is treated at a temperature capable of decomposing it completely and the amount of NOx produced can be reduced. [0008] On the other hand, a direct-burning type combustion apparatus can treat hydrogen sulfide and ammonia at very high temperatures by burning a fuel in a burner section and feeding hydrogen sulfide and ammonia thereto. In connection with this combustion apparatus, a single-stage technique for controlling, for example, the amount of oxygen introduced and thereby burning ammonia under a reducing atmosphere, for example, at a temperature in the vicinity of 1,000 to 1,200.degree. C. has been proposed as a technique for minimizing the amount of NOx produced by the combustion of ammonia. [0009] However, in order to maintain a high temperature of about 1,000.degree. C. or above under a reducing atmosphere, it is necessary to burn a large amount of additional fuel. Moreover, a large-sized combustion apparatus adapted for high-temperature conditions is required, and this is not economical from the viewpoint of operation and equipment investment. Furthermore, in order to solve the above-described problems associated with storage type combustion furnaces and thereby achieve a satisfactory reduction of NOx, it is desirable to burn and decompose ammonia at a high temperature of at least 1,300.degree. C. or above, rather than a temperature in the vicinity of 1,000.degree. C. [0010] When a direct-burning type combustion apparatus is used to burn and decompose ammonia at high temperatures, NOx is produced as a result of high-temperature treatment. Consequently, a suitable measure to reduce NOx with the aid of a reducing agent (e.g., NH.sub.3, H.sub.2S or CO) or the like is required. SUMMARY OF THE INVENTION [0011] In view of the above-described problems, the present inventors made intensive investigations for the purpose of developing a method for the treatment of an ammonia-containing gas and a hydrogen sulfide-containing gas in which these off-gases can be treated at a reduced running cost, the emission of nitrogen oxides (NOx) and the like can be effectively suppressed so as to be lower than required environmental load levels, and the apparatus used therefor is simple and small-sized, has high reliability, and is easy of operation and maintenance. [0012] As a result, the present inventors have now found that these problems can be solved by providing a nitrogen oxide reduction step between the ammonia combustion step and the hydrogen sulfide combustion step and by feeding ammonia gas or hydrogen sulfide gas to the combustion apparatus in two divided portions. The present invention has been completed from this point of view. [0013] That is, the present invention provides a gas combustion treatment method for the combustion treatment of an ammonia-containing gas and a hydrogen sulfide-containing gas, the method comprising a first combustion treatment step in which a fuel and the ammonia-containing gas are introduced and burned; a nitrogen oxide reduction step downstream of the first combustion treatment step, in which a reducing agent (e.g., a portion of the ammonia-containing gas or the hydrogen sulfide-containing gas) is introduced and the nitrogen oxides produced in the first combustion treatment step are reduced under a reducing atmosphere; and a second combustion treatment step downstream of the nitrogen oxide reduction step, in which the hydrogen sulfide-containing gas, together with air, is introduced and burned. In the aforesaid first combustion treatment step, it is preferable to carry out the combustion treatment under an oxidizing atmosphere at 1,300.degree. C. or above. Moreover, in the nitrogen oxide reduction step, it is preferable to introduce a portion of the ammonia-containing gas and reduce the nitrogen oxides produced in the first combustion treatment step under a reducing atmosphere. [0014] In the first combustion treatment step, it is preferable to measure the outlet gas temperature and control the flow rate of the fuel is controlled so that the outlet gas temperature will be not less than a predetermined temperature. Moreover, in the nitrogen oxide reduction step or the second combustion treatment step, it is preferable to measure the outlet nitrogen oxide concentration and control the flow rate of the ammonia-containing gas or hydrogen sulfide-containing gas introduced into the nitrogen oxide reduction step is controlled so that outlet nitrogen oxide concentration will be not greater than a predetermined concentration. [0015] The present invention also provides a gas combustion apparatus for the combustion treatment of an ammonia-containing gas and a hydrogen sulfide-containing gas, the apparatus comprising a first combustion section in which the ammonia-containing gas, together with a fuel, is introduced and burned; a nitrogen oxide reduction section located downstream of the first combustion section, in which a portion of the hydrogen sulfide-containing gas is introduced and the nitrogen oxides transferred from the first combustion section are reduced under a reducing atmosphere; and a second combustion section located downstream of the nitrogen oxide reduction section, in which the remaining hydrogen sulfide-containing gas, together with air, is introduced and burned. It is desirable that the gas combustion apparatus has a structure in which the cross section of the gas flow path extending from the first combustion section to the nitrogen oxide reduction section is made smaller than the cross sections of the first combustion section and the nitrogen oxide reduction section and in which a radiation shield is provided between the nitrogen oxide reduction section and the second combustion section. [0016] The present invention can provide a three-stage combustion apparatus in which the combustion treatment of off-gases resulting from the purification of coal gasification gas can be carried out very efficiently. [0017] In a system using the combustion apparatus of the present invention, NH.sub.3 off-gas and H.sub.2S off-gas are subjected to combustion treatment in the same combustion apparatus. When NH.sub.3 off-gas is burned in a high temperature range (about 1,500-1,600.degree. C.), the production of NOx is suppressed to a low level. Accordingly, at the initial stage of the combustion apparatus of the present invention, NH.sub.3 off-gas is first subjected to perfect combustion treatment under an oxidizing atmosphere and thereby converted into nitrogen and water. Since H.sub.2S off-gas can be treated in a low temperature range (800.degree. C. or above), H.sub.2S off-gas is subjected to combustion treatment under an oxidizing atmosphere and thereby converted into water (H.sub.2O) and sulfur dioxide (SO.sub.2) after the combustion treatment of NH.sub.3 off-gas. [0018] Since the combustion treatment of ammonia (NH.sub.3) produces some nitrogen oxides (NOx), a portion of the H.sub.2S off-gas or NH.sub.3 off-gas is by-passed and introduced in the presence of NOx immediately after the combustion of ammonia. Thus, at the second stage comprising a nitrogen oxide reduction step, NOx is reduced to N.sub.2 under a reducing atmosphere, resulting in a reduced NOx concentration. [0019] The three-stage combustion apparatus of the present invention is divided into three stages. Starting from its upstream end for gas introduction, the first stage comprises a first combustion section for burning NH.sub.3 off-gas, the second stage comprises a nitrogen oxide reduction section for reducing NOx, and the third stage comprises a second combustion section for burning H.sub.2S off-gas. This three-stage construction makes it possible to carry out the combustion treatment of NH.sub.3 off-gas and H.sub.2S off-gas in the same combustion apparatus while giving low environmental load values. [0020] Since the present invention enables the sequential combustion treatment of NH.sub.3 off-gas and H.sub.2S off-gas, the necessity of treating them separately is eliminated to bring about a simplification of the treatment system. Moreover, by burning NH.sub.3 off-gas, the cost for the disposal of ammonia water is made unnecessary. Furthermore, by providing a bypass section for H.sub.2S off-gas or NH.sub.3 off-gas, the production of NOx is reduced. In addition, the effect of heat recovery from combustion furnace waste gas can be expected. Continue reading... Full patent description for Gas combustion treatment method and apparatus therefor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Gas combustion treatment method and apparatus therefor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Gas combustion treatment method and apparatus therefor or other areas of interest. ### Previous Patent Application: Burner plate and burner assembly Next Patent Application: Intra-oral mirrors Industry Class: Combustion ### FreshPatents.com Support Thank you for viewing the Gas combustion treatment method and apparatus therefor patent info. IP-related news and info Results in 7.3335 seconds Other interesting Feshpatents.com categories: Canon USA , Celera Genomics , Cephalon, Inc. , Cingular Wireless , Clorox , Colgate-Palmolive , Corning , Cymer , |
||
