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Low pressure drop purifier for nitrogen, methane, and argon removal from syngasRelated Patent Categories: Chemical Apparatus And Process Disinfecting, Deodorizing, Preserving, Or Sterilizing, Chemical Reactor, Ammonia SynthesizerLow pressure drop purifier for nitrogen, methane, and argon removal from syngas description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060239871, Low pressure drop purifier for nitrogen, methane, and argon removal from syngas. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application is a divisional to co-pending U.S. patent application Ser. No. 10/604,404, filed on Jul. 17, 2003. FIELD [0002] The present embodiments relate generally to methods and apparatus to improve production of synthesis gas for manufacturing ammonia. The present embodiments reduces pressure losses in a nitrogen-wash purifier unit BACKGROUND [0003] Processes for manufacturing ammonia from a hydrocarbon and air, via a hydrogen/nitrogen synthesis gas (syngas), are well known. Extraneous syngas components typically include inert gases from the air and/or the hydrocarbon feed, such as argon and methane. When excess air is used in the syngas production, nitrogen is also present in stoichiometric excess, and must be removed from a raw makeup syngas stream or purged from an ammonia synthesis loop to maintain a desired ammonia synthesis reactor feed composition. [0004] In the prior art, some syngas production methods use excess air and cryogenic syngas purification, which relies on a syngas pressure drop upstream of purification for refrigeration. The pressure drop is subsequently made up in a compressor that raises the syngas to ammonia synthesis loop pressure. This type of method also reduces the rate of recycle or purge gas flow from the ammonia reactor loop due to the upstream removal from the makeup syngas of inerts such as argon and methane in the syngas purification. [0005] Other methods of ammonia synthesis use high-activity catalyst in the ammonia synthesis reactor. Purge gases are eliminated via a hydrogen enrichment process operating on a sidestream of the syngas recycled to the synthesis loop compressor. The total recycle flow is roughly three times the volumetric flowrate of the makeup syngas. [0006] Other methods use air separation to provide oxygen-enriched air such that reforming produces a synthesis gas with higher hydrocarbon slip than in other ammonia manufacturing systems. A higher concentration of nonreactive gas in the ammonia synthesis is managed by purging from a residual syngas stream following recovery of ammonia product. This type of method unloads front-end gas reforming reactors, at the expense of including air separation, but ostensibly enables a smaller purge stream process after ammonia synthesis. [0007] Other methods are centered on an integrated process system for synthesizing methanol and ammonia that uses a nitrogen wash by cryogenic fractionation to purify ammonia syngas, with refrigeration supplied externally and providing no recovery of expansion power in the process. [0008] The present embodiments meet these needs. BRIEF DESCRIPTION OF THE DRAWINGS [0009] The detailed description will be better understood in conjunction with the accompanying drawings as follows: [0010] FIG. 1 is a schematic process flow sheet showing prior art syngas purification using an upstream syngas feed to drive an expander and extract syngas energy as work to achieve auto-refrigeration. [0011] FIG. 2 is a schematic process flow sheet of an embodiment of the present invention, using expansion of a nitrogen-rich liquid waste stream to generate auto-refrigeration in the process. [0012] FIG. 3 is a schematic process flow sheet showing an alternate embodiment of the present invention wherein syngas feed or liquefied waste gas can be expanded across a liquid expander for refrigeration. [0013] FIG. 4 is a block flow diagram of an embodiment of the invention showing low pressure drop nitrogen removal integrated in an ammonia synthesis process with secondary reforming with excess air and heat-exchanging reforming. [0014] FIG. 5 is block flow diagram of an alternative embodiment of the invention showing low pressure drop nitrogen removal integrated in an ammonia synthesis process with conventional primary steam reforming and secondary reforming with excess air [0015] The present embodiments are detailed below with reference to the listed Figures. DETAILED DESCRIPTION OF THE EMBODIMENTS [0016] Before explaining the present embodiments in detail, it is to be understood that the embodiments are not limited to the particular embodiments and that they can be practiced or carried out in various ways. [0017] The present embodiments provide methods to purify syngas. Syngas, as an example, occurs in ammonia manufacturing processes. The methods use cryogenic distillation to purify syngas, and obtain refrigeration for the distillation from waste fluid expansion using a liquid expander to recover mechanical work from the waste fluid. These methods reduce the pressure losses in the syngas stream and concomitantly reduce compression costs and power relative to similar prior art ammonia processes utilizing nitrogen and inerts removal. [0018] The methods are applicable in grassroots plant design, and can also be applied to retrofit existing synthesis gas systems to improve process performance and economics. In the retrofit, for example, the lower pressure drop of the present embodiments can allow process modification for reforming with excess air and nitrogen removal from the makeup syngas without expensive modification or replacement of the synthesis loop and/or makeup gas compressors. [0019] In an embodiment, the present embodiments provide methods to purify syngas, including: (a) introducing a raw syngas stream containing excess nitrogen to a feed zone in a distillation column; (b) expanding a liquid bottoms stream from the distillation column through a liquid expander with a work output to form a cooled waste fluid stream; (c) rectifying vapor from the feed zone in the distillation column to form an overhead vapor stream of reduced nitrogen and inerts content; (d) cooling the overhead vapor stream in indirect heat exchange with the cooled waste fluid stream to form a partially condensed overhead stream and a relatively warm waste fluid stream; (e) separating the partially condensed overhead stream into a condensate stream and a purified syngas vapor stream of reduced nitrogen and inerts content; and (f) refluxing the distillation column with the condensate stream. The method can also include cooling the raw syngas stream by expansion across a Joule-Thompson (J-T) valve in advance of the introduction to the feed zone. Additionally, the method can include cooling the raw syngas stream in cross-exchange against the warm waste fluid stream and against the purified syngas vapor stream. In this embodiment, adjusting the flow to the liquid bottoms stream expansion controls liquid level in the distillation column. Continue reading about Low pressure drop purifier for nitrogen, methane, and argon removal from syngas... Full patent description for Low pressure drop purifier for nitrogen, methane, and argon removal from syngas Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Low pressure drop purifier for nitrogen, methane, and argon removal from syngas patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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