Conversion of Biomass to liquid fuels

7/30/2019 Conversion of Biomass to liquid fuels

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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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Conversion of Biomass to liquid fuels