Decomposition of fossil fuels for Decomposition of fossil fuels for hydrogen productionhydrogen production

Nerijus StriugasNerijus StriugasLithuanian Energy InstituteLithuanian Energy Institute

Laboratory of Combustion ProcessesLaboratory of Combustion Processes

Why the interest in Hydrogen?Why the interest in Hydrogen?

• Hydrogen as an energy carrier:Hydrogen as an energy carrier:– Finite reserves of fossil fuels;Finite reserves of fossil fuels;

– Improves energy efficiency.Improves energy efficiency.

• Environment-friendly energy carrier:Environment-friendly energy carrier:– Reduce Greenhouse Gas Emissions ;Reduce Greenhouse Gas Emissions ;

– Reduce Air Pollution.Reduce Air Pollution.

Hydrogen productionHydrogen productionToday, nearlyToday, nearly all hydrogen production is based on fossil raw materials all hydrogen production is based on fossil raw materials

Natural gas48 %

Water4 %Coal

18 %

Oil30 %

Hydrogen production technologies Hydrogen production technologies from fossil fuelsfrom fossil fuels

• Steam-methane reformingSteam-methane reforming (SMR); (SMR);• Partial oxidation (POX)/Gasification of coal Partial oxidation (POX)/Gasification of coal

and other organics fuels;and other organics fuels;• Hydrocarbons pyrolHydrocarbons pyrolysiysiss;;• Autothermal reforming (ATR).Autothermal reforming (ATR).

SMR – half the hydrogen from water, half SMR – half the hydrogen from water, half from methanefrom methane The conversion efficiencies in this system canThe conversion efficiencies in this system can re reach 65% - 75%ach 65% - 75%

Process chemistryProcess chemistry::• Steam reforming:Steam reforming:

CHCH44+H+H22O O CO+3HCO+3H2 2 [[ΔΔHH=206 kJ/mol]=206 kJ/mol]

• Water-gas shift (WGS):Water-gas shift (WGS):

CO+HCO+H22O O COCO22+H+H2 2 [[ΔΔHH=-41 kJ/mol]=-41 kJ/mol]

• Overall reaction:Overall reaction:

CHCH44+H+H22O O COCO22+3H+3H2 2 [[ΔΔHH=165 kJ/mol]=165 kJ/mol]

POX/Coal and oil gasificationPOX/Coal and oil gasificationThe maximum theoretical efficiencies using pure oxygen is 66.7%The maximum theoretical efficiencies using pure oxygen is 66.7%

Process chemistry for methane:Process chemistry for methane:1)1) CH CH44+1/2O+1/2O2 2 CO+2HCO+2H2 2 [[ΔΔHH=-35.6 kJ/mol]=-35.6 kJ/mol]

and/orand/or

2)2) CH CH44+O+O2 2 COCO22+2H+2H2 2 [[ΔΔHH=-319.3 kJ/mol]=-319.3 kJ/mol]

Process chemistry for coal gasification:Process chemistry for coal gasification:3)3) C+1/2O C+1/2O2 2 CO+2HCO+2H2 2 [[ΔΔHH=-110 kJ/mol]=-110 kJ/mol]

and/orand/or4)4) C+2H C+2H22OO COCO22+2H+2H2 2 [[ΔΔHH=90.1 kJ/mol]=90.1 kJ/mol]

The effluent gas from the The effluent gas from the 11 and and 33 reaction are reaction are processed in WGS reactor for more hydrogen processed in WGS reactor for more hydrogen production.production.

Hydrocarbon pyrolysisHydrocarbon pyrolysisThis is the only method that does notThis is the only method that does not produce carbon dioxide providing the produce carbon dioxide providing the material is decomposed at high enough temperatures in the absence of oxygen.material is decomposed at high enough temperatures in the absence of oxygen.

Process chemistry for methane:Process chemistry for methane:CHCH4 4 C +2HC +2H2 2 [[ΔΔHH=75.6 kJ/mol]=75.6 kJ/mol]

In addition to hydrogen as a major product, the process produces a very In addition to hydrogen as a major product, the process produces a very important by-product – clean carbonimportant by-product – clean carbon..

Autothermal reformingAutothermal reforming Hydrocarbons reforming process in which both exothermic partial oxidation and Hydrocarbons reforming process in which both exothermic partial oxidation and endothermic water-gas shift reaction occur together.endothermic water-gas shift reaction occur together.

Process chemistryProcess chemistry::• Partial oxidation of hydrocarbonsPartial oxidation of hydrocarbons::

CCnnHHm m + + n/2n/2OO22 nnCO + CO + m/2m/2HH22 ;;

• Water-gas shiftWater-gas shift::

CO + HCO + H22O O CO CO22 + H + H2 2 ;;

• Overall reactionOverall reaction::

CCnnHHmm + + n/2n/2OO22 + + nnHH22O O nnCOCO22 + + (n + m/2)(n + m/2)HH22

AirAirFossil fuelFossil fuel

SteamSteam

ReformateReformate

Autothermal reforming reactor for organic Autothermal reforming reactor for organic fuel conversionfuel conversionThe aim of our research is the combined heat and hydrogen production process development.

Organic fuel conversion limits in Organic fuel conversion limits in presence of various catalystpresence of various catalyst

1300

1200

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5001 2 3 4 5

Catalytic conversion

Conversion without catalyst

Ni

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Pd,Pt,CrRuMoW

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re, o C ,

Temperature field in autothermal reactorTemperature field in autothermal reactorFor the hydrocarbons conversion the reactor temperature must be kept in the For the hydrocarbons conversion the reactor temperature must be kept in the range 1200 – 1600 range 1200 – 1600 ooCC

Kinetic simulation resultsKinetic simulation resultsReaction product concentration versus the reactor length, at 1100 Reaction product concentration versus the reactor length, at 1100 ooC C αα=0.48 and =0.48 and initial products composition in mole fraction are: initial products composition in mole fraction are: CHCH44=0.1175,O=0.1175,O22=0.1179,=0.1179,

NN22=0.4375, H=0.4375, H22O=0.3271O=0.3271

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Measured H2 concentration at the 1500 mm from reactor inlet is 8.4 % (vol.)

Simulation result – 9.2 % (vol.)

Kinetic simulation resultsKinetic simulation resultsReaction product concentration versus the reactor length, at 1100 Reaction product concentration versus the reactor length, at 1100 ooC C αα=0.32 and =0.32 and initial products composition in mole fraction are: initial products composition in mole fraction are: CHCH44=0.1=0.1403403,O,O22=0.=0.09850985,,

NN22=0.=0.36153615, H, H22O=0.3O=0.3997997

Measured H2 concentration at the 500 mm from reactor inlet is 9.8 % (vol.)

Simulation result – 9.98 % (vol.)

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CO CO2 CH4

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Schematic of the membrane assembly that Schematic of the membrane assembly that would be used in our research for separating would be used in our research for separating of hydrogen from the product gas mixtureof hydrogen from the product gas mixture

Gas mixture

Activated carbon filter

Membrane

Sweep gas

GC

H2

H2

ConclusionsConclusions

The primary experimental investigation and kinetics simulation of the methane autothermal reforming were performed. The aim of research was to determine optimal process condition for autothermal reforming in order to get maximum H2 concentration in the product gas mixture. Gathered information shows, that the H2 yield increases with decreasing of the air excess ratio and the optimal temperature range in the reactor is 1200 – 1400 oC. The most part of hydrogen (70 – 90%) occurs in the primary reaction zone where the fast exothermal partial oxidation (POX) reaction take place. The remain hydrogen produced in the slow conversion zone where the endothermic water-gas shift reaction occurs.

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