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CHL 794 - PETROLEUM REFINERYENGINEERING
CONVERSIONOFBIOMASSTOLIQUIDFUELS
Submitted by
Aman Agrawal(2009ch10058)
Rituraj (2009CH10094)
Harshit Agrawal(2009CH70136)
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OUTLINE
Feed Composition Biomass
Gasification Syngas Production
Water Gas Shift Reaction Syngas Up gradation
Methanol Synthesis Methanol to Gasoline conversion
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WHY BIOMASS ???
Biomass is:
Abundant
Renewable
Potentially carbon-neutral The only sustainable source of hydrocarbons.
Biomass can:
Fill the gap between energy demand and petroleum
availability in the near to mid term.
Be a renewable source of hydrogen in the long
term.
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ULTIMATE ANALYSISOF BIOMASSFEED
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BIOMASS CONVERSION
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GASIFICATION
o Biomass gasification means incomplete combustion
of biomass resulting in production of combustiblegases consisting of Carbon monoxide (CO),
Hydrogen (H2) and traces of Methane (CH4). This
mixture is called producer gas.
o The production of these gases is by reaction of
water vapour and oxygen through a glowing layer of
charcoal. Thus the key to gasifier design is to
create conditions such that
a) biomass is reduced to charcoal and,
b) charcoal is converted at suitable temperature
to produce CO and H2.
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REACTIONSDURINGGASIFICATION
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GASIFICATION REACTOR
Circulating Fluid Bed Gasifier
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TABLE: GASIFIER OPERATING PARAMETERS, GAS COMPOSITIONS, ANDEFFICIENCIES
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FUELSFROMSYNGAS
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WATERGASSHIFTREACTION
The H2/CO ratio obtained is 0.59 after the
gasification but the desired ratio is about 4.5.
CO+H2O
CO2 +H2
H= -41.1 kj/mol
Operating Conditions:
Temperature 400-500 C
Pressure 1 Bar
Peng-Robinson Fluid Package Mass Flow Rate 18 x 104 kg/hr
Ref: Sorin et al.,2011, Process simulation to obtain a synthesis gas
with high concentration of hydrogen
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SIMULATION STAGESINWATER-GASSHIFT
RXN
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PROCESS STAGES
Reformer: A conversion reactor in which most ofthe methane is reacted with steam and it is
produced hydrogen, carbon monoxide and carbon
dioxide.
o Combustor: A second conversion reactor whichhas as a feeds stream the product of the reformer,
air stream and combustion steam.
o Shift Reactors: A series of equilibrium reactors inwhich the water gas shift reaction occurs.
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INITIALCONDITIONS
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SIMULATION RESULTS
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INFERENCEOF SIMULATIONATDIFFERENT O2
PERCENTAGE
If the content of O2 in the air used in the second
reactor, the combustor, is increased, the content of
hydrogen in the produced synthesis gas is higher.
Also the content of nitrogen which is an inert gas is
decreased (7.99%).
The 50 % O2 content in the air stream ensure the
highest content of hydrogen (63.49%).
The synthesis gas obtained in these conditions has
a better value of calorific power, higher than in thecases in which the content of O2 in the combustion
air is smaller.
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SYNGASTOMETHANOL
Methanol Synthesis The cleaned and conditioned syngas is converted
to methanol in a fixed bed reactor containing acopper/zinc oxide/alumina catalyst. The mixtureof methanol and unconverted syngas is cooled
through heat exchange with the steam cycle andother process streams. The methanol is separated
by condensing it away from the unconverted
syngas. Unconverted syngas is recycled back to
the entrance of the methanol synthesis reactor.
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PROCESSCONDITIONSFORMETHANOL
SYNTHESIS
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The composition of this methanol product is shown
in Table below. After this step, the product is nearly96% methanol, with the remainder being mainly
CO2 and water and small amounts of various
components.
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METHANOLTOGASOLINE: SALIENT FEATURES
Reaction in MTG Reactor :2CH3OH CH3-O-CH3 + H2O H=55.68KJ/mole
Methanol is first dehydrated to dimethyl ether (DME).
Then an equilibrium mixture of methanol, DME and wateris converted to light olefins (C2-C4).
A final reaction step leads to the synthesis of higher
olefins, n/iso-paraffins, aromatics and naphthenes. Theshape selective MTG catalyst limits the hydrocarbonsynthesis to C10 and lighter.
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METHANOLTO GASOLINE CONVERSION
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REACTORPARAMETERS
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PROCESSSPECIFICATIONS
High-quality gasoline is synthesized by catalytic reaction
of methanol over zeolite ZSM-5 between 330-400 C at a
liquid methanol volumetric space time of 0.6-1 hour
Prior to conversion , the crude methanol from the
intermediate storage tank is pumped into the MTGprocess to raise the liquid pressure to 200 psia (1.4
MPa). The methanol is then passed over the ZSM-5
zeolite catalyst in a fluidized bed reactor .
The overall stoichiometric equation in the conversion of
methanol to hydrocarbons is shown below:
n (CH3OH) (CH2) n + n (H20)
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OUTLETRESULTS
Products production (on daily basis)Products % Composition
CH4 1.9
C2-C4 olefins 2
C2-C4
paraffins17
Gasoline
(C5-C9)79
Distillates / diesel -
Oils and waxes -
Oxygenates 0.1
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MTG PROCESS VS FT PROCESS
MTG process selectively converts methanol to highquality gasoline with virtually no sulfur and low benzenewhich can be sold as is or blended in the refinerygasoline pool.
About 90% of the hydrocarbon in methanol is convertedto gasoline as the single liquid product, with theremainder primarily LPG.
The Fisher-Tropsch process produces a broad spectrumof straight-chain paraffinic hydrocarbon which requiresupgrading to produce finished products such asgasoline, jet fuel, diesel fuel, and lube base stocks.
MTG process uses fixed bed reactor where as FTprocess uses slurry bed reactors which are morecomplex
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