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  Configuration and process for shift conversionUSPTO Application #: 20060236697Title: Configuration and process for shift conversion Abstract: The inventors discovered that a significant portion of steam in hydrogen production from syngas (and other gases with relatively high CO to H2 ratio) is utilized for temperature control in the shift reactors. Therefore, it is contemplated that the overall steam demand can be significantly lowered by splitting the feed stream in a first and second portion, wherein the first portion is fed to a first shift reactor to form a product that is then combined with the second portion prior to entering a second shift reactor. (end of abstract)
Agent: Robert D. Fish Rutan & Tucker LLP - Costa Mesa, CA, US Inventors: Ashok Rao, Keith Strohler USPTO Applicaton #: 20060236697 - Class: 060645000 (USPTO) Related Patent Categories: Power Plants, Motive Fluid Energized By Externally Applied Heat, Process Of Power Production Or System Operation The Patent Description & Claims data below is from USPTO Patent Application 20060236697. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application claims the benefit of U.S. Provisional Patent application with the Ser. No. 60/439,912 (filed Jan. 13, 2003), which is incorporated by reference herein. FIELD OF THE INVENTION [0002] The field of the invention is hydrogen production, and especially hydrogen production from synthesis gas relates with reduced steam consumption while maintaining predetermined design values for a hydrogen to carbon monoxide ratio. BACKGROUND OF THE INVENTION [0003] Numerous processes are known in the art to produce hydrogen from various materials, including steam reforming of natural gas, syngas, or naphtha, catalytic reforming of heavy straight run gasoline or heavy oils (e.g., fuel oil), and partial oxidation of heavy oils or natural gas. Steam reforming of hydrocarbonaceous material is particularly advantageous due to the relatively simple configuration and relatively robust operation. However, generation of steam for the reforming process requires often relatively large quantities of energy. [0004] To reduce the energy demand for steam production, steam may be internally provided by quenching hot gas from the reformer in direct contact with water as described in U.S. Pat. No. 3,545,926 to Schlinger et al., or U.S. Pat. No. 5,152,975 to Fong. Such configurations may provide a significant reduction in energy consumption for steam production. However, depending on the particular operating conditions, it may be necessary to heat the quenched gas prior to entry into the shift converter, which reduces the energy savings to at least some degree. [0005] Alternatively, the reforming process may be split into two sections in which the feed gas is reformed with steam in the first section and with oxygen in the second section as described in U.S. Pat. Nos. 4,782,096 and 4,999,133 to Banquy. While such configurations generally require less overall steam as compared to a conventional steam reforming processes, several disadvantages nevertheless remain. Among other things, operation of the second section generally requires an oxygen rich gas (typically comprising 80 vol % or even more oxygen), which has to be generated in an air separation or other oxygen enrichment equipment. [0006] Therefore, while various configurations and methods for steam-based production of hydrogen-containing gases are known in the art, all or almost all of them suffer from one or more disadvantages. Consequently, there is still a need to provide improved configurations and methods to reduce energy costs associated with steam consumption in various hydrogen production plants, and especially in steam shifting/reforming, partial oxidation, or gasification plants. BRIEF DESCRIPTION OF THE DRAWING [0007] FIG. 1 is a schematic of an exemplary configuration for hydrogen production from synthesis gas according to the inventive subject matter. [0008] FIG. 2 is a prior art schematic of a known configuration for hydrogen production from synthesis gas. [0009] FIG. 3 is a table indicating composition, flow rate, and temperature of various streams of the configuration of FIG. 1. [0010] FIG. 4 is a table indicating composition, flow rate, and temperature of various streams of the configuration of FIG. 2. [0011] FIG. 5 is a schematic of another exemplary configuration for hydrogen production from synthesis gas according to the inventive subject matter. [0012] FIG. 6 is a table indicating exemplary operating conditions of the configuration of FIG. 5. [0013] FIGS. 7A-7D are tables indicating material balances for first and second stages of cases 1 and 2 of FIG. 6. SUMMARY OF THE INVENTION [0014] The present invention is directed to configurations and methods of H2 production from a feed gas in which the demand for steam or humidification is significantly reduced by splitting the feed gas such that one portion is fed into a first shift reactor and another portion is combined with the first shift reactor effluent before entering a second shift reactor. [0015] In one aspect of the inventive subject matter, a plant includes a first shift reactor and a second shift reactor, wherein the first shift reactor receives a first portion of syngas from a gasification unit or partial oxidation unit to form a first shift reactor effluent, and wherein the second shift reactor receives a combination of the first shift reactor effluent and a second portion of the syngas to form a second shift reactor effluent. [0016] In especially contemplated plants, the second portion of the syngas is combined with the first shift reactor effluent in an amount effective to reduce steam demand by at least 10%, more typically at least 35%, and even more typically at least 45%. Alternatively, where the water is provided to the syngas via humidification of the syngas, it is preferred that the second portion of the syngas is combined with the first shift reactor effluent in an amount effective to reduce water and/or energy consumption of the humidifier by at least 10%, more typically at least 20%, and even more typically by at least 35%. Therefore, especially preferred second portions of the syngas will be between 50 vol % to 75 vol % of the total syngas. [0017] It is still further contemplated that a preferred syngas includes carbon monoxide and hydrogen at a molar ratio of at least 2:1, and that yet another portion of the syngas may be bypassed around the first and second shift reactors for combination with the second shift reactor effluent. Furthermore, suitable plants may also include an acid gas removal unit that is coupled to the second shift reactor to remove carbon dioxide from the second shift reactor effluent. [0018] Therefore, a particularly preferred method of operating a plant will include one step in which a first shift reactor and a second shift reactor are provided. In another step, a syngas stream from a gasification unit or a partial oxidation unit is split into a first portion and a second portion, wherein the first portion is fed to the first shift reactor to form a first shift reactor effluent. In a further step, the first shift reactor effluent is combined with the second portion to form a mixed feed gas, and in yet another step, the mixed feed gas is reacted in the second shift reactor to form a second shift reactor effluent. In such methods, it is particularly preferred that the second portion is combined with the first shift reactor effluent in an amount effective to reduce steam consumption in the first and second shift reactors. With respect to the components, conditions, and further configurations, the same considerations as provided above apply. [0019] Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention along with the drawing. DETAILED DESCRIPTION Continue reading... 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