AM-14-56 CO2 Emissions from Hydrogen Plants: Understanding the Options

Description:

In today’s economy with constantly fluctuating supply - demand and price volatility, refiners are faced with challenges on multiple fronts. Crude oil is getting heavier and sourer; and specifications on refinery products are getting more stringent. In addition, regulations on the emission of greenhouse gases are being considered by state and federal governments. While these changes will not progress in a “straight line”, the long term trend is towards lower quality crude oil that requires more hydrogen for refining. Greater hydrogen production from fossil fuels is accompanied by an increase in by-product carbon dioxide (CO2). In the past, hydrogen plants have been designed with economics and reliability as the primary objective functions. While these factors will continue to be very important in plant optimization, it is increasingly important to consider plant designs that also minimize CO2 emissions. This paper will assess the impact of CO2 capture and discuss various options. Carbon dioxide emissions from a steam methane reformer (SMR) can be reduced by minimizing feed and fuel consumption. This option usually entails additional capital expenditure. The less fuel and feed that is consumed, the lower is the amount of by-product CO2. If CO2 capture is needed, or a sink for the CO2 is available, CO2 capture from a SMR can be accomplished using state of the art absorption or adsorption systems. These gas separation processes can be incorporated into the process gas stream either before or after the pressure swing adsorption step. It may also be economic to recover CO2 from the furnace flue gases using absorption systems for postcombustion carbon capture. Various process alternatives for capturing CO2 from a SMR-based hydrogen plant are evaluated. The process economics of these alternatives are evaluated at varying energy prices. Finally, considerations for process selection are discussed.