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Saturday, January 16, 2010

Hydrogen Production



All hydrogen production processes are based on the separation of

hydrogen from hydrogen-containing feedstocks. The feedstock

dictates the selection of the separation method. Today, we use two

primary methods to separate hydrogen: thermal and chemical. A third

method, biological, is in the exploratory research and development

phase.



Today, 95% of the hydrogen produced in the U.S., roughly 9 million

tons per year, uses a thermal process with natural gas as the

feedstock. This process, called steam methane reformation (SMR),

consists of two steps: 1) reformation of the feedstock with high

temperature steam supplied by burning natural gas to obtain a

synthesis gas, and 2) using a water-gas shift reaction to form hydrogen

and carbon dioxide from the carbon monoxide produced in the first step.


STEAM METHANE REFORMATION
Step 1: CH4 +H20 => CO + 3 H2
Step 2: CO + H2O => CO2 + H2

To a lesser degree, the U.S. also produces hydrogen electro-chemically

from water when higher purity hydrogen is needed. The

process, called electrolysis, passes electricity through water in an ionic

transfer device to separate water into its hydrogen and oxygen parts.

Renewable technologies, such as wind turbines, can generate

electricity to produce hydrogen from electrolysis with zero greenhouse

gas emissions. In France, an abundance of nuclear power makes

electrolysis a logical, and their most common, method for producing

hydrogen.


ELECTROLYSIS
electricity + 2H2O => O2 + 2H2



All production technologies have a variety of costs and

benefits with regard to the environment, economics, security and other concerns.

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