Capture of CO2 From Hydrogen Plants (Chevron)

CATEGORY: CARBON CAPTURE 
Capture of CO2 From Hydrogen Plants (Chevron)

Type	Patent
Inventor	Raja A. Jadhav
URL	Free Full Text Source:  http://www.google.com/patents/US20140186257
Assignee	Chevron U.S.A. Inc.
Patent Number	US20140186257 A1
Issue Date	Jul 3, 2014
Abstract	The invention includes a process which eliminates or reduces the CO2 emissions from a steam methane reforming and autothermal reforming plant. The process preferentially uses temperature swing adsorption units which are employed to purify the hydrogen stream instead of more conventional solvent based aMDEA plants to remove the CO2 from the gas stream when creating a higher purity hydrogen stream. BACKGROUND OF THE INVENTION Steam methane reformer (SMR) plants often a widely employed in refineries to supply H2 for various product upgrading operations. The SMR process produces a large amount of CO2 which must be cleaned from hydrogen stream. In steam methane reformer plants and solvent based aMDEA is used to remove the CO2 from the hydrogen stream. Newer conventional hydrogen plants may use pressure swing adsorption (PSA) units to purify the CO2 from the hydrogen stream. In both these units large amounts of CO2 at low concentration and pressure are emitted from the SMR furnace. Capture of this CO2 using a post combustion amine based technology such as aMDEA is expensive. Autothermal reformer (ATR) units may be used to produce CO2-free hydrogen at reduced costs. However, they require expensive air separation unit (ASU) to produce the oxygen. Also, the ASU requires a large amount of power, which itself results in additional CO2 emissions. A recent patent application US 2010/0080754 teaches a method of reducing the CO2 emissions from the steam methane reformer plant by employing a temperature swing adsorption (TSA) unit in place of a traditional PSA unit. After the shift reactors, the fuel gas stream is sent to an aMDEA unit to remove majority of the CO2 In the gas stream. The CO2-free fuel gas stream is next sent to a TSA unit, which produces high-purity H2 by adsorbing CO, CH4 and any remaining CO2 on an adsorbent. The TSA adsorbent bed is next regenerated by using high pressure and high temperature natural gas and steam and the off-gas is sent to the steam methane reformer as a high pressure feed. The steam methane reformer furnace is fueled by a portion of the pure hydrogen product. The patent, however, does not address how to reduce CO2 emissions from an SMR plant that does not have an amine absorber upstream of the TSA unit.