Fossil Fuel Reforming

Fossil fuel reforming is a technique of generating hydrogen or other useful products from fossil fuels like natural gas. This is accomplished in a processing device known as a reformer which reacts steam at high temperature with the fossil fuel. The steam methane reformer is commonly used in industry to make hydrogen.  There is also interest in the advancement of much smaller units based on similar technology to generate hydrogen as a feedstock for fuel cells.

Steam reforming units

Small-scale steam reforming units to supply fuel cells are presently the subject of research and development, distinctively comprising the reforming of methanol or natural gas but other fuels are also being considered such as propane, gasoline, auto gas, diesel fuel and ethanol. During the switch of the fossil fuel into hydrogen, carbon is emitted into the atmosphere, distinctively as carbon dioxide. Consequently, fuel cell systems using reformed fossil fuels would release substantial amounts of carbon dioxide, so would not make much contribution to decreasing carbon dioxide emissions, as is anticipated to be necessary to tackle global warming.

Steam methane reforming

Steam reforming of natural gas or syngas sometimes referred to as steam methane reforming is the most usual technique of producing commercial bulk hydrogen as well as the hydrogen used in the industrial synthesis of ammonia. It is also the least expensive method. At high temperature and in the presence of a metal based catalyst steam reacts with methane to yield carbon monoxide and hydrogen. These two reactions are reversible in nature.

CH4 + H2O – CO + 3 H2

Additional hydrogen can be recovered by a lower temperature gas-shift reaction with the carbon monoxide produced. The reaction is summarized by

CO + H2O – CO2 + H2

The first reaction is strappingly endothermic the second reaction is slightly exothermic. The United States produces nine million tons of hydrogen per year mostly with steam reforming of natural gas. The worldwide ammonia production, using hydrogen derived from steam reforming was 109 million metric ton in 2004. This SMR process is quite diverse from and not to be confused with catalytic reforming of naphtha an oil refinery process that also produces notable amounts of hydrogen along with high octane gasoline. The competence of the process is around 65% to 75%.

Steam reforming of gaseous hydrocarbons is seen as a potential way to provide fuel for fuel cells. The fundamental concept for vehicle on board reforming is that for instance a methanol tank and a steam reforming unit which would substitute the bulky pressurized hydrogen tanks that would otherwise be necessary. 

Questions:

• What is fossil fuel reforming?
• State the significance of fossil fuel reforming.