Hydrogen ProductionHydrogen Production

Hocking CollegeHocking College

Nelsonville, OhioNelsonville, Ohio

One Advantage of using hydrogenOne Advantage of using hydrogen

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

Current global hydrogen productionCurrent global hydrogen production

48% from natural gas 48% from natural gas

30% from oil30% from oil

18% from coal 18% from coal

4% from electrolysis of water4% from electrolysis of water

Primary Uses for Hydrogen TodayPrimary Uses for Hydrogen Today

1. About half is used to produce ammonia 1. About half is used to produce ammonia (NH3) fertilizer. (NH3) fertilizer.

2. The other half of current hydrogen 2. The other half of current hydrogen production is used to convert heavy production is used to convert heavy petroleum sources into lighter fractions petroleum sources into lighter fractions suitable for use as fuels. suitable for use as fuels.

Hydrogen Production ProcessesHydrogen Production Processes

Steam Methane ReformingSteam Methane Reforming Coal GasificationCoal Gasification Partial Oxidation of HydrocarbonsPartial Oxidation of Hydrocarbons Biomass GasificationBiomass Gasification Biomass PyrolysisBiomass Pyrolysis ElectrolysisElectrolysis ThermochemicalThermochemical PhotochemicalPhotochemical PhotobiologicalPhotobiological

Steam Methane ReformingSteam Methane Reforming

most common method of producing most common method of producing commercial bulk hydrogen.commercial bulk hydrogen.

Most common method of producing Most common method of producing hydrogen used in the industrial synthesis hydrogen used in the industrial synthesis of ammonia.of ammonia.

It is the least expensive method.It is the least expensive method. High temperature process (700 – 1100 °C.High temperature process (700 – 1100 °C. Nickel based catalyst (Ni)Nickel based catalyst (Ni)

The Steam Methane Reforming The Steam Methane Reforming ProcessProcess

At 700 – 1100 °C and in the presence of a nickel At 700 – 1100 °C and in the presence of a nickel based catalyst (Ni), steam reacts with methane based catalyst (Ni), steam reacts with methane to yield carbon monoxide and hydrogen.to yield carbon monoxide and hydrogen. CHCH44 + H + H22O → CO + 3 HO → CO + 3 H22

Additional hydrogen can be recovered by a Additional hydrogen can be recovered by a lower-temperature gas-shift reaction with the lower-temperature gas-shift reaction with the carbon monoxide produced. The reaction is carbon monoxide produced. The reaction is summarized by:summarized by: CO + HCO + H22O → CO2 + HO → CO2 + H22

Purification of HydrogenPurification of Hydrogen

Carbon dioxide and other impurities are Carbon dioxide and other impurities are removed from the gas stream, leaving removed from the gas stream, leaving essentially pure hydrogen. essentially pure hydrogen.

Endothermic reaction (Heat must be Endothermic reaction (Heat must be added to the reactants for the reaction to added to the reactants for the reaction to occur.)occur.)

Schematic of the SMR ProcessSchematic of the SMR Process

REMOVAL OF CO AND CO2

REFOR MER

10% CO

2,000 ppmCO

WATER GAS SHIFT REACTOR

WaterMethane GasolineEthanol

Methanol

<100 ppm CO

O2

H2O

H2FUEL CELL

STACK

Coal GasificationCoal Gasification

well-established commercial technologywell-established commercial technology

competitive with SMR only where oil and/or competitive with SMR only where oil and/or natural gas are expensive.natural gas are expensive.

coal could replace natural gas and oil as the coal could replace natural gas and oil as the primary feedstock for hydrogen production, since primary feedstock for hydrogen production, since it is so plentiful in the world.it is so plentiful in the world.

Partial Oxidation HydrocarbonsPartial Oxidation Hydrocarbons

process can be used to produce hydrogen process can be used to produce hydrogen from heavy hydrocarbons such as diesel from heavy hydrocarbons such as diesel fuel and residual oil.fuel and residual oil.

Any hydrocarbon feedstock that can be Any hydrocarbon feedstock that can be compressed or pumped may be used in compressed or pumped may be used in this technology.this technology.

Partial Oxidation Partial Oxidation

methane and other hydrocarbons in methane and other hydrocarbons in natural gas are reacted with a limited natural gas are reacted with a limited amount of oxygen (typically, from air) that amount of oxygen (typically, from air) that is not enough to completely oxidize the is not enough to completely oxidize the hydrocarbons to carbon dioxide and water. hydrocarbons to carbon dioxide and water.

CHCH44 + ½O + ½O22 → CO + 2H → CO + 2H22 (+heat) (+heat)

Exothermic reaction (heat is evolved)Exothermic reaction (heat is evolved)

Schematic of Partial OxidationSchematic of Partial Oxidation

Partial Oxidation Plant Diagram

Thermochemical Production of Thermochemical Production of HydrogenHydrogen

When water is heated to above 2500 When water is heated to above 2500 ooC, it C, it separates into oxygen and hydrogen in a separates into oxygen and hydrogen in a process known as thermolysis.process known as thermolysis.

However, at such high temperatures, it is However, at such high temperatures, it is difficult to prevent the oxygen and difficult to prevent the oxygen and hydrogen from recombining to form water. hydrogen from recombining to form water.

Thermochemical Production of Thermochemical Production of HydrogenHydrogen

Thermochemical water-splitting cycles can lower Thermochemical water-splitting cycles can lower the temperature and help separate oxygen and the temperature and help separate oxygen and hydrogen products to produce pure hydrogen hydrogen products to produce pure hydrogen gas.gas.

These cycles can improve the efficiency of These cycles can improve the efficiency of hydrogen production from 30% for conventional hydrogen production from 30% for conventional electrolysis to around 50% efficiency electrolysis to around 50% efficiency

One of the most promising cycles so far is the One of the most promising cycles so far is the sulfur-iodine (S-I) cycle. sulfur-iodine (S-I) cycle.

Sulfur dioxide (SOSulfur dioxide (SO22 ) and iodine (I ) and iodine (I22) are fed ) are fed

into the cycle as chemical catalysts.. into the cycle as chemical catalysts..

A catalyst lowers the activation energy of a A catalyst lowers the activation energy of a reaction without being used up by the reaction without being used up by the reaction.reaction.

Sulfur-Iodine Thermochemical Sulfur-Iodine Thermochemical Cycle Cycle

In this cycle, sulfur dioxide (SOIn this cycle, sulfur dioxide (SO22) and ) and

iodine (Iiodine (I22) are feed into the cycle as a ) are feed into the cycle as a

chemical catalyst. chemical catalyst.

A catalyst lowers the temperature at which A catalyst lowers the temperature at which the reaction will occur without being used the reaction will occur without being used up by the reaction.up by the reaction.

There are three steps in the S-I There are three steps in the S-I cyclecycle

Step 1: Step 1:

II22 + SO + SO22 + 2H + 2H22O 2HI + HO 2HI + H22SOSO44

The reaction is run at 120 degrees C. The reaction is run at 120 degrees C.

The hydrogen iodide and sulfuric acid are The hydrogen iodide and sulfuric acid are separated, usually by distillation.separated, usually by distillation.

Step 2: Step 2:

Generation of oxygen and regeneration of Generation of oxygen and regeneration of SOSO22..

HH22SOSO44 H H22O + SOO + SO22 + 1/2 O + 1/2 O22

This reaction is run at 850 degrees C.This reaction is run at 850 degrees C.

Step 3: Generation of hydrogen and Step 3: Generation of hydrogen and regeneration of Iregeneration of I

2HI H2HI H22 + I + I22

This reaction is run at 450 degrees C. This reaction is run at 450 degrees C.

Sulfur—Iodine CycleSulfur—Iodine Cycle

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

Source: Office of Nuclear Energy, Science and Technology

Biomass Production of Hydrogen Biomass Production of Hydrogen

Hydrogen can be produced numerous ways from Hydrogen can be produced numerous ways from biomass.biomass.

Biomass is defined as a renewable resource Biomass is defined as a renewable resource made from renewable materials. Examples of made from renewable materials. Examples of biomass sources include:biomass sources include:

>switchgrass >switchgrass >plant scraps >plant scraps >garbage >garbage >human wastes >human wastes Gasification of biomass could be a way of Gasification of biomass could be a way of

extracting hydrogen from these organic sources. extracting hydrogen from these organic sources.

Biomass Production of HydrogenBiomass Production of Hydrogen The biomass is first converted into a gas through The biomass is first converted into a gas through

high-temperature gasifying.high-temperature gasifying. The hydrogen rich vapor is condensed in pyrolysis The hydrogen rich vapor is condensed in pyrolysis

oils.oils. These oils can be steam reformed to generate These oils can be steam reformed to generate

hydrogen.hydrogen. This process has resulted in hydrogen yields of 12% This process has resulted in hydrogen yields of 12%

- 17% hydrogen by weight of the dry biomass. - 17% hydrogen by weight of the dry biomass. When biological waste material is used as a When biological waste material is used as a

feedstock, this process becomes a completely feedstock, this process becomes a completely renewable, sustainable method of hydrogen renewable, sustainable method of hydrogen generation. generation.

ElectrolysisElectrolysis

Electrolysis is the technical name for using electricity to Electrolysis is the technical name for using electricity to split water into its constituent elements, hydrogen and split water into its constituent elements, hydrogen and oxygen. oxygen.

The splitting of water is accomplished by passing a DC The splitting of water is accomplished by passing a DC electric current through water. electric current through water.

The electricity enters the water at the cathode, a The electricity enters the water at the cathode, a negatively charged terminal, passes through the water negatively charged terminal, passes through the water and exists via the anode, the positively charged terminal.and exists via the anode, the positively charged terminal.

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

ElectrolysisElectrolysis

The hydrogen is collected at the cathode The hydrogen is collected at the cathode and the oxygen is collected at the anode.and the oxygen is collected at the anode.

Electrolysis produces very pure hydrogen Electrolysis produces very pure hydrogen for use in the electronics, pharmaceutical for use in the electronics, pharmaceutical and food industries. and food industries.

PhotobiologicalPhotobiological This method involves using sunlight, a biological This method involves using sunlight, a biological

component, catalysts and an engineered system.component, catalysts and an engineered system. Specific organisms, algae and bacteria, produce Specific organisms, algae and bacteria, produce

hydrogen as a byproduct of their metabolic hydrogen as a byproduct of their metabolic processes.processes.

These organisms generally live in water and These organisms generally live in water and therefore are biologically splitting the water into its therefore are biologically splitting the water into its component elements. component elements.

Currently, this technology is still in the research and Currently, this technology is still in the research and development stage and the theoretical sunlight development stage and the theoretical sunlight conversion efficiencies have been estimated up to conversion efficiencies have been estimated up to 24%. 24%.