Environmental Engineering Reference
In-Depth Information
air, which contains nitrogen, nitrogen oxides can be formed as they are
in gasoline engines. These oxides can almost be eliminated in hydrogen
engines by lowering the combustion temperature of the engine. Some
tests have shown that the air coming out of a hydrogen fueled engine is
cleaner than the air entering the engine. Acid rain, ozone depletion and
carbon dioxide accumulations could be greatly reduced by the use of hy-
After it has been separated, hydrogen is an unusually clean-energy
carrier and clean enough for the U.S. space shuttle program to use hydro-
gen-powered fuel cells to operate the shuttle's electrical systems while the
by-product of drinking water is used by the crew.
Hydrogen could be an alternative to hydrocarbon fuels such as gaso-
line with many potential uses, but it must be relatively safe to manufac-
ture and use. Hydrogen fuel cells can be used to power cars, trucks, elec-
trical plants, and buildings but the lack of an infrastructure for producing,
transporting, and storing large quantities of hydrogen inhibit its growth
and practicality. Although the technology for electrochemical power has
been known since 1839, fuel cells are still not in widespread use. The elec-
trochemical process allows fuel cells have few moving parts. Air compres-
sors are often used to improve the efficiency although there are compres-
sor-less designs.
Fuel cells operate like batteries expect that they combine a fuel, usu-
ally hydrogen, and an oxidant, usually oxygen from the air, without com-
Hydrogen can be obtained from natural gas, gasoline, coal-gas,
methanol, propane, landfill gas, biomass, anaerobic digester gas, other fu-
els containing hydrocarbons, and water. Obtaining hydrogen from water
is an energy intensive process called electrolysis, while hydrocarbons re-
quire a more efficient reforming process.
Hydrogen may be produced by splitting water (H 2 O) into its compo-
nent parts of hydrogen (H 2 ) and oxygen (O). Steam reforming of methane
from natural gas is one way to do this. It converts the methane and other
hydrocarbons in natural gas into hydrogen and carbon monoxide using
the reaction of steam over a nickel catalyst. Another method is electrolysis
which uses an electrical current to split water into hydrogen at the cathode
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