Hydrogen Production - PowerPoint PPT Presentation

Loading...

PPT – Hydrogen Production PowerPoint presentation | free to view - id: 4d923a-MDA5Y



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Hydrogen Production

Description:

coal could replace natural gas and oil ... Partial Oxidation Hydrocarbons process can be used to produce hydrogen from heavy hydrocarbons such as diesel fuel and ... – PowerPoint PPT presentation

Number of Views:615
Avg rating:3.0/5.0
Slides: 27
Provided by: LindellRH
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Hydrogen Production


1
Hydrogen Production
  • Hocking College
  • Nelsonville, Ohio

2
One Advantage of using hydrogen
  • One advantage is that it stores approximately 2.6
    times the energy per unit mass as gasoline, and
    the disadvantage is that it needs about 4 times
    the volume for a given amount of energy. A 15
    gallon automobile gasoline tank contains 90
    pounds of gasoline. The corresponding hydrogen
    tank would be 60 gallons, but the hydrogen would
    weigh only 34 pounds.

3
Current global hydrogen production
  • 48 from natural gas
  • 30 from oil
  • 18 from coal
  • 4 from electrolysis of water

4
Primary Uses for Hydrogen Today
  • 1. About half is used to produce ammonia (NH3)
    fertilizer.
  • 2. The other half of current hydrogen production
    is used to convert heavy petroleum sources into
    lighter fractions suitable for use as fuels.

5
Hydrogen Production Processes
  • Steam Methane Reforming
  • Coal Gasification
  • Partial Oxidation of Hydrocarbons
  • Biomass Gasification
  • Biomass Pyrolysis
  • Electrolysis
  • Thermochemical
  • Photochemical
  • Photobiological

6
Steam Methane Reforming
  • most common method of producing commercial bulk
    hydrogen.
  • Most common method of producing hydrogen used in
    the industrial synthesis of ammonia.
  • It is the least expensive method.
  • High temperature process (700 1100 C.
  • Nickel based catalyst (Ni)

7
The Steam Methane Reforming Process
  • At 700 1100 C and in the presence of a nickel
    based catalyst (Ni), steam reacts with methane to
    yield carbon monoxide and hydrogen.
  • 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

8
Purification of Hydrogen
  • Carbon dioxide and other impurities are removed
    from the gas stream, leaving essentially pure
    hydrogen.
  • Endothermic reaction (Heat must be added to the
    reactants for the reaction to occur.)

9
Schematic of the SMR Process
10
Coal Gasification
  • well-established commercial technology
  • competitive with SMR only where oil and/or
    natural gas are expensive.
  • coal could replace natural gas and oil as the
    primary feedstock for hydrogen production, since
    it is so plentiful in the world.

11
Partial Oxidation Hydrocarbons
  • process can be used to produce hydrogen from
    heavy hydrocarbons such as diesel fuel and
    residual oil.
  • Any hydrocarbon feedstock that can be compressed
    or pumped may be used in this technology.

12
Partial Oxidation
  • methane and other hydrocarbons in natural gas are
    reacted with a limited amount of oxygen
    (typically, from air) that is not enough to
    completely oxidize the hydrocarbons to carbon
    dioxide and water.
  • CH4 ½O2 ? CO 2H2 (heat)
  • Exothermic reaction (heat is evolved)

13
Schematic of Partial Oxidation
Partial Oxidation Plant Diagram
14
Thermochemical Production of Hydrogen
  • When water is heated to above 2500 oC, it
    separates into oxygen and hydrogen in a process
    known as thermolysis.
  • However, at such high temperatures, it is
    difficult to prevent the oxygen and hydrogen from
    recombining to form water.

15
Thermochemical Production of Hydrogen
  • Thermochemical water-splitting cycles can lower
    the temperature and help separate oxygen and
    hydrogen products to produce pure hydrogen gas.
  • These cycles can improve the efficiency of
    hydrogen production from 30 for conventional
    electrolysis to around 50 efficiency
  • One of the most promising cycles so far is the
    sulfur-iodine (S-I) cycle.

16
  • Sulfur dioxide (SO2 ) and iodine (I2) are fed
    into the cycle as chemical catalysts..
  • A catalyst lowers the activation energy of a
    reaction without being used up by the reaction.

17
Sulfur-Iodine Thermochemical Cycle
  • In this cycle, sulfur dioxide (SO2) and iodine
    (I2) are feed into the cycle as a chemical
    catalyst.
  • A catalyst lowers the temperature at which the
    reaction will occur without being used up by the
    reaction.

18
There are three steps in the S-I cycle
  • Step 1
  • I2 SO2 2H2O 2HI H2SO4
  • The reaction is run at 120 degrees C.
  • The hydrogen iodide and sulfuric acid are
    separated, usually by distillation.

19
  • Step 2
  • Generation of oxygen and regeneration of SO2.
  • H2SO4 H2O SO2 1/2 O2
  • This reaction is run at 850 degrees C.

20
  • Step 3 Generation of hydrogen and regeneration
    of I
  • 2HI H2 I2
  • This reaction is run at 450 degrees C.

21
SulfurIodine Cycle
  • These reactions can reduce the high temperature
    demands of the thermolysis of water for the
    production of hydrogen gas and can provide a
    mechanism for the separation of oxygen and
    hydrogen products to prevent recombination.

Source Office of Nuclear Energy, Science and
Technology
22
Biomass Production of Hydrogen
  • Hydrogen can be produced numerous ways from
    biomass.
  • Biomass is defined as a renewable resource made
    from renewable materials. Examples of biomass
    sources include
  • gtswitchgrass
  • gtplant scraps
  • gtgarbage
  • gthuman wastes
  • Gasification of biomass could be a way of
    extracting hydrogen from these organic sources.

23
Biomass Production of Hydrogen
  • The biomass is first converted into a gas through
    high-temperature gasifying.
  • The hydrogen rich vapor is condensed in pyrolysis
    oils.
  • These oils can be steam reformed to generate
    hydrogen.
  • This process has resulted in hydrogen yields of
    12 - 17 hydrogen by weight of the dry biomass.
  • When biological waste material is used as a
    feedstock, this process becomes a completely
    renewable, sustainable method of hydrogen
    generation.

24
Electrolysis
  • Electrolysis is the technical name for using
    electricity to split water into its constituent
    elements, hydrogen and oxygen.
  • The splitting of water is accomplished by passing
    a DC electric current through water.
  • The electricity enters the water at the cathode,
    a negatively charged terminal, passes through the
    water and exists via the anode, the positively
    charged terminal.
  • The hydrogen is collected at the cathode and the
    oxygen is collected at the anode. Electrolysis
    produces very pure hydrogen for use in the
    electronics, pharmaceutical and food industries

25
Electrolysis
  • The hydrogen is collected at the cathode and the
    oxygen is collected at the anode.
  • Electrolysis produces very pure hydrogen for use
    in the electronics, pharmaceutical and food
    industries.

26
Photobiological
  • This method involves using sunlight, a biological
    component, catalysts and an engineered system.
  • Specific organisms, algae and bacteria, produce
    hydrogen as a byproduct of their metabolic
    processes.
  • These organisms generally live in water and
    therefore are biologically splitting the water
    into its component elements.
  • Currently, this technology is still in the
    research and development stage and the
    theoretical sunlight conversion efficiencies have
    been estimated up to 24.
About PowerShow.com