LOGO

HYDROGEN

Introduction

Hydrogen energy is a clean or inexhaustible energy like renewable energy and nuclear energy.

Hydrogen is a secondary source of energy-an energy carrier-which is used to move, store and deliver energy in an easily usable form.

Hydrogen is 75% of the known universe Converting hydrogen into energy is compatible with

existing energy technologies, such as fuel cells, engines, and combustion turbines.

There is no CO2, no CO, no sulfuric acid, no soot, no unburned hydrocarbons, and only very small amounts of NOx are produced (Koroneos et al., 2005).

A Vision of a Hydrogen Future

"I believe that water will one day be employed as fuel, that hydrogen and oxygen which constitute it, used singly or together, will furnish an inexhaustible source of heat and light, of an intensity of which coal is not capable. I believe then that when the deposits of coal are exhausted, we shall heat and warm ourselves with water. Water will be the coal of the future." 

Jules Vernes (1870) L´île mystérieuse

Present uses of hydrogen

Petroleum refining and petrochemical production

Metal processing

Power generation Manufacture of glass

PROPERTY OF HYDROGEN

Hydrogen is a colorless, tasteless gas and it is the lightest chemical substance.

Normal boiling point : 15.5 K The normal melting point :

14.1 K The critical temperature :

30.2 K at a critical pressure of 12.8 atm).

Structure of the hydrogen molecule

1 e 1 e H2

FUEL PROPERTIES OF HYDROGEN

In comparison with an engine burning gasoline, the emission of nitrogen oxides is far less for the engine fueled by hydrogen.

Some oxides of nitrogen (NOx) are formed at very high combustion temperatures (< 2300 K); fortunately, the autoignition temperature of hydrogen is only 858 K.

The bond energy of the H-H bond is 431 kJ/mol. Electron affinity of hydrogen is low (- 72 kJ/mol) The ionization potential of hydrogen is relatively high

(1312 kJ/mol)

Hydrogen burns with a very hot flame and explosion in air:

The higher heating value (HHV) of hydrogen is QHHV = 142.324 kJ/kg or QHHV = 284.648 kJ/kg mol. The lower heating value (LHV) of hydrogen is QLHV = 118.976 kJ/kg mol.

Hydrogen reacts with the reactive metals to produce metal hydrides:

Hydrogen reacts with many metal oxides to produce water and the free metal:

Hydrogen reacts with nitrogen at high pressures (300 to 1000 atm) and at high temperatures (675 to 875 K), in the presence of a catalyst to produce ammonia:

The advantages of hydrogen as a universal energy medium

the combustion of hydrogen results in the formation of steam and liquid water

it is nontoxic and, as an energy carrier, extremely environmentally benign since water is the only exhaust product when hydrogen is converted into energy

it is possible to produce hydrogen from the most abundant chemical on earth: water

it is the most suitable fuel for use in fuel cells transmission of energy in the form of hydrogen is more

economical than through high-voltage AC lines for large distances.

Hydrogen can be used as a feedstock for numerous chemicals

Hydrogen Production Cycle

Crabtree et al., “The Hydrogen Economy,” Physics Today, Dec 2004

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The First Question:Where Does Hydrogen Come From?

95% of hydrogen is currently produced by steam reforming95% of hydrogen is currently produced by steam reforming

Partial Oxidation

Steam Reforming

Electrolysis

Thermochemical

Fossil Fuels

Water

Biomass

currently most currently most energy efficientenergy efficient

requires requires improvementsimprovements

not cost effectivenot cost effective

requires high requires high temperaturestemperatures

Gasification

Microbial

requiresrequiresimprovementsimprovements

slow slow kineticskinetics

Feedstocks Usage in Hydrogen ProductionSource

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Steam Reforming of Methane

Catalysts: Ni, or Au-Ni

CH4 + H2O CO + 3H2 H298 = 206 kJ/mol

Water gas shift reaction

CO + H2O CO2 + H2 H298 = -41kJ/mol

Hydrogen from coal