process separation and upgradation

7/31/2019 Process Separation and Upgradation

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XTL Technology for India: Coal, Biomass &Petcoke (Group 1, CHL471, 2nd Semester 2011-12)

Product separation and

upgradationAnanth Govind Rajan

AkshiShubhranshu Kathuria

Ankit Samria

Arjun Singh YadavSahil Singh

Lokesh Meena


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FTReactor

Tail Gas(CO,H2,CO2,C1-C4 HCs)

Water

Condenser

Centrifuge(Separates waxfrom catalyst)

Threephase

Separator

C5 + HCs

UpgradationCracking

S

L

U

R

R

Y

WA

X

cFractionation

CAT

ALYST

Regenerate& Reuse

Converted tosyngas &recycle

Treatment


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Catalyst Separation


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Catalyst Separation

Available techniques: filtration,centrifugation, settling, etc.

Continuous separation process during

normal operation Centrifuge at the end of the run*

Settling tanks avoided due to large settling

times (1-3 hours) to achieve 0.1 wt%* Zhou, P. Z. Status Review Of Fischer-Tropsch Slurry Reactor Catalyst/Wax Separation Techniques;prepared for U.S. DOE Pittsburgh Energy Technology Center in Feb 1991 by Burns and Roe ServicesCorp. under Contract DE-AC22-89PC88400 Subtask 43.02


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XTL Technology for India: Coal, Biomass &Petcoke (Group 1, CHL471, 2nd Semester 2011-

12)

Hydrocyclone

Used for solid-liquid separation

Centrifugal force generated by the motionof the liquid

Used for particles in the size range of 4 to500 microns*

* Coulson and Richardsons Chemical Engineering Vol. 6Engineering Design


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12)

Design of hydrocyclone

Critical particle diameter (d50) for 50% efficiency

Assumed 95% separationefficiency for 50 microncatalyst particle

Cyclone diameter: Dc

= 36 cm,other dimensions w.r.t. figure


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12)

High-pressure filtration

Vertical leaf filtersdesigned for final dischargeof solids in dry or wet state

Fully enclosed and automaticoperation

Chamber contains filter

elements of circular /rectangular shape

* Coulson and Richardsons Chemical Engineering, Volume 2, Fifth edition: ParticleTechnology and Separation Processes


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12)

Design of vertical leaf filter

Assumed constant rate filtration

Pressure drop taken as 1 bar (highpressure)

Residence time taken as 60 s

Obtain filter area as 8.3 m2, quite large

Need to use multiple filtering elements inparallel


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12)

After separation?

Wax of high purity obtained from filtration

Wax sent to hydrocracking unit for furtherprocessing

Catalyst obtained is regenerated andrecycled by making slurry


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12)

Three phase separator


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12)

Vessel SelectionHorizontal separators are chosen over vertical separatorsbecause:

Horizontal separators have greater interfacial areas.

Gravity separation is more effective in horizontal separatorsthan vertical.

Horizontal separators are more economical for normal

hydrocarbons-water separation.

Vertical separators used when liquid is 10-20% by weight ofgas


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12)

The product gas stream from SBCR is at

2200C

This gas stream is cooled to 380C and 15 bar

pressure

The cooled stream is then directed to the

three phase separator

Three phase separator separates the entire

mixture into three new streams:

Unreacted syn gas C1-C4 HCs

C4+ Hydrocarbons (diesel,naphtha)

Water


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Assumptions The fraction of individual component in the final three

streams separated is assumed to be equal.

C7 is considered as the average chain length of C5 to C9

hydrocarbons and these components are treated as one

stream.

C16 is considered as the average chain length of C10 to C22hydrocarbons and these components are treated as one

stream.

100 percent separation


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12)

Operating ConditionsTemperature 380C

Pressure 15 bar

Inlet flow rates


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12)

Outlet flow rates

Assumptions made during

calculation: Liquid hold up time inside the separator is assumed to be 5

minutes

Vessel volume is considered to be 1.7 times the liquid hold up

Minimum ratio L/D = 3 is chosen


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Calculations

Liquid hold up = Volume occupied by liquid * hold up time

Vessel volume = 1.2*liquid hold up

Back calculations to verify the design parameters calculated Critical velocity of vapor= 0.048((l-v)/ v)^0.5

Max velocity of vapor = 1.7 * critical velocity

Settling velocity of heavy phase in light phase

v= 3.268*dp2*(h- l)/l Re


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12)

Heights of light and heavyphase liquid estimated from

the curve


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Vessel Dimensions obtained

Vessel Diameter = 1.91m ~ 2m

Vessel Length = 5.74m ~ 6m

Vessel crossectional area = 2.87 m2

Vessel volume = 16.48m3


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12)

Fractionation Unit


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12)

Assumptions

The hydrocarbon composition is not known fully nor is theassay data available so we have assumed a Hydrocarbonwhose properties are similar to diesel properties ( average ofthe hydrocarbon composition). Diesel from the reactor is notdivided into AGO so the division is done on the basis of

number of Carbon atoms, assuming each Hydrocarbon (fromC15-C22) has the same mass in the stream. The Steam for various inputs is assumed to be available at

the in the plant. Heat optimization in the unit is not done. Overflash(liquid flow)=3.5 m3/h, at the stage above feed. Pump arounds are not used.


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12)

Table: Assumed HC, Feed Rate

INPUT: Temperature= 700oF Pressure= 50psia

Fraction TrueBoilingPoint Cuts

Assumed HydrocarbonComponent

HC Boiling Point

Flow Rate(kg/h)

Naptha 100-340oF C7H16 210

oF 27600

Diesel 340-550oF C14H30 500

oF 36600

AGO 550-650

o

F C20H42 650

o

F 18300

Waxes - >650oF C36H74 900

oF 17500


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12)

PFD: Fractionation unit

Condenser P= 16psiaCondenser P=6psia

Top Temperature= 300oF

Bottom Temperature=750oF

Condenser temperature=110oF


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12)

Tower Specifications

Tower Height 24m(22.56+extraspacing)

Tower Diameter 3.505m

Side Strippers Diesel AGO

Height 1.85m 1.85m

Diameter 1.067m 1.219m

Condenser Volume

Diameter

Height

63.23m3

3.772m

5.658m

Condenser Duty 5.6e007 kJ/h

Trim Duty 8.301e006kJ/h

Heat Loss 4.77e007kJ/h

Number of trays 37

Bottom Stage Pressure 25.69psia

Steam Flow rate(lb/h)

Bottom Diesel

AGO

3000 500

22.5

Reflux 3.68

Diesel fraction 94.57%

Side Stripper Location

Diesel

AGO

17

29

Iterative procedurefollowed:

1. Changing the number of Trays:

2. Changing the Steam flow rate:3. Location of side strippers:4. The final Pressure was obtained

after sizing the column and hadto be modified according to themaximum P/tray=0.689kPa

*Weighted error


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Tray Specifications Type of Tray: Valve tray

Tray Spacing: 0.6096m Weir Height: 0.508m

Although bubble cap trays are the most

efficient, they are very costly. The sieve traysbeing cheap are not very efficient.Therefore, valve trays are most commonlyused. Valve trays provide high turn downratios with very low liquid weeping


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The higher the reflux ratio, the morevapor/liquid contact can occur in the

distillation column. So higher reflux ratiosusually mean higher purity of the distillate.

As the reflux ratio is increased form theminimum the number of plates decreases,

rapidly at first and then more and more slowlyuntil, at total reflux, the number of plates is aminimum.

Vertical condenser: We can Control liquidlevel(50%) on the condensed liquid while weintroduce vapor at the top


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12)

Pre-fractionation

From 3 Phase Separator Hydrocracking Unit Tower Feed

Diesel 15270 21330 36600

AGO 7630 10670 18300

Naptha 22000 5600 27600

Waxes 0 17500 17500

Temperature 40oC 358 oC 700oF

Pressure 15 bar 3.5Mpa 50psia


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XTL Technology for India: Coal, Biomass &

Petcoke (Group 1, CHL471, 2nd Semester 2011-12)

PFD: Prefractionation train

PFD: Pre-fractionation Unit


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Production of Hydrogen for

upgradation methods

D l h i ti


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Desulphurization- It is the process of removing the sulphur from

naptha or RLNG feed. This is done as sulphur is a poison for the

nickel catalyst which we will be using inreforming section later on.

done in two stages Pre and Final. STAGE -1: HYDROTREATMENT RSH + H2 RH + H2S RSR + 2H2 RH + H2S

Reactor contains beds of Co-Mo catalyst. STAGE -2: H2S formed is absorbed by ZnO absorbers.

R f i


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Reforming

Steam reforming of natural gas is the

most common method of producingcommercial bulk hydrogen.

CH4 + H2O CO + 3H2 [H = +206 kJ

mol-1]CO + H2O CO2 + H2 [H = +41 kJmol-1]

CH4 + 2H2O CO2 + 4H2[H =+165

kJmol-1] .Strongly endothermic reaction


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Primary Reformer Main purpose of primary

reformer to converthigher hydrocarbons in tomethane.

To achieve the reaction

temperature, feed isheated in mixed feed coilof convection section ofprimary reformer.

Catalyst Ni(25%) ,Al2O3 (11%) , MgO

Two Catalyst

Beds

Process Gas

Inlet

Process Gas

Outlet


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Operating Conditions

Inlet Outlet

Temperature 500oC 773 oC

Pressure 35.7 kg/cm2 33.4 kg/cm2

Composition(in % Dry basis)

CH4 94.03 13.0

H2 3.48 67.64

N2 1.64 0.55

Ar 0.01 0.01

CO - 8.29

CO2 0.15 10.51C2H6 0.66 -

C3H8 0.03 -


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Secondary Reformers

Mixing and combustion of

reformed process gas withprocess air.

- Mixing of N2- Utilization of O2 by combustion- Temperature raised to 1200 o C

Feed Gas

Process

Air

Reformer Outlet

Ni Al2O3 SiO2 S Volume

Size Shape BulkDensity

9

%

88%


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Operating Conditions

Inlet Outlet

Temperature 773 959

Pressure 33.4 32.8

Air entering in secondary reformer at temperature 5550 C

and pressure 34 kg/cm2

Composition(in % Dry basis)

CH4 13 0.45

H2 67.64 55.92

N2 0.55 23.29

Ar 0.01 0.28

CO 8.29 12.41

CO2 10.51 7.65


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37CO Conversion via Shift Reactions

Temperature (oC)

100 200 300 400 500

1

2

3

4

CO + H2O = CO2 + H2

LTShift

HTShift

Inter-stage

Cooling

0

High Temperature Shift CO Conversion(HTS)


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High Temperature Shift CO Conversion(HTS)

For bulk removal of CO to give CO contents down

to 2-3% Achieved by higher rates of reaction resulting

higher rates of conversionCatalyst:Cu promoted Iron-chrome oxide

Operating temperature range:350-470oC Low Temperature Shift CO Conversion(LTS) For final conversion of CO to typically below 0.3%High conversion achieved since at lower

temperatures equilibrium is more favourable forconversionCatalyst: Copper-Zinc oxide plus Al2O3Operating temperature range:180-270oC

02/07/201238

A erage Operating Conditions


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39Average Operating ConditionsParameters HTS LTS

Temp. In/Out

oC

350/416 190/207

Pressure In/Out Kg/cm2 30.6/30.2 29.6/29.2

CO In/Out

mole %

13.0/2.9 2.9/0.15

H2

mole%

N2

mole%

CO

mole%

CO2

mole%

CH4

mole%

H2O

mole%

HTS in 33.41 14.48 8.41 6.95 0.24 36.50

HTS out 40.32 14.48 1.99 13.27 0.24 29.70

LTS out 42.36 14.48 0.11 14.62 0.24 28.20


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33

W

Process gas

HP Waste

Heat BoilerHP BFW

BFW

Preheater

Trim Heater

Process gas

HTS LTS

Boiler water

Steam & BFWProcess gas

Process gas

350 oC

190 oC

207 oC

416 oC

PFD: CO Conversion


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Hydrocracking


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Hydrocracking Hydrocracking is a chemical

process used to convert heavyhydrocarbons to more useful lowerboiling products.

Trickle bed reactor Cocurrentflow

Silica-alumina-supported sulfided

NiMo catalyst[112]112) Dieter Leckel, Low-Pressure Hydrocracking of Coal-Derived Fischer-TropschWaxes to Diesel Energy & Fuels 21 (2007) 1425-1431


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Mass balanceIn Kg/hr

Wax 57500

H2 9660

Out

Diesel(C10-C22) 31798

Naptha(C5-C9) 5635

Gases(C1-C4) 2817

waxes 17250

Recycle

H2 9373

Consumed

Wax 40250

H2 287


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Hydrocracking reactor

system[116]

116) Miguel J. Bagajewicz, Refinery Modeling Advanced Chemical EngineeringDesign, 2006


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Reactor design[115][118]

L/D 7

Volume of reactor 185 m3

D 3.2 m

L 23 m

Reactor thickness 223mm+9.5mm(overlay)Material SA 226 F12+SS 347 overlay

Weight around 450 MT

115) OJSC TANECO, http://www.taneconpz.com/en/news/company/index.php?ID=186118) Larsen and toubro, list of offerings for hydrocrackingreactor,http://www.larsentoubro.com/lntcorporate/LnT_Offerings/Product_Template1.aspx?res=P_HED_COFF_SBU_PROD&pid=1530&sbu=66
http://www.taneconpz.com/en/news/company/http://www.taneconpz.com/en/news/company/


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Diesel properties[112]Prorerty Specifications EURO

IVHydrocracked LTFTdiesel

density at 20 C (kg/m3) 820-845 762

viscosity at 40 C(cSt) 2.0-4.5 3.3

flash point, min (C) 62 76

cetane number, min 51 >70

cloud point (C) -10 -18

CFPP (C) -20 -30

sulfur, maximum (ppm) 10


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Naphtha Hydrotreating


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Naphtha Hydrotreating

F-T naphtha has high levels of oxygenates and olefinswhich must be removed prior to reforming .

Oxygenate removal requires temperatures andpressures that would polymerize di-olefins and rapidly

coke-up the hydrotreating catalyst .

Therefore, the hydrotreater design must firstaccommodate the saturation of olefins at lowtemperatures and then the conversion of oxygenates at

higher temperature after the olefin is reduced.


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Hydrotreating Process Conditions :

First Stage Catalyst -- Noble Metal (Pd or Pt on gamma-Al2O3)

LHSV, hr-1-- 4 Pressure(psig) --800

Rx Temperature ,C --160

Second Stage Catalyst -- Base Metal (Ni/Co/Mo on alumina)

LHSV , hr

-1

-- 4 Pressure(psig) -- 800 Rx Temperature ,C -- 380


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Design of Reactor 1:

Operating Conditions: Pressure=800 psig , Reaction

Temperature=1600C

Space Velocity (a) =4 hr-1

Volume Flow rate of Naphtha and Hydrogen (V0)=37.28 m3 /hr

Volume of Reactor =(1/a)*V0=9.325 m3

Diameter of Reactor= 1.41 m Length of Reactor =6.1 m =20.01 ft


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Design of Reactor 2:

Operating Conditions: Pressure=800 psig , Reaction

Temperature=3600C

Space Velocity (a) =4 hr-1

Volume Flow rate of Naphtha and Hydrogen (V0)

=37.1 m3/hr

Volume of Reactor = (1/a)*V0

=9.26 m3

Diameter of Reactor= 1.41 m

Length of Reactor = 6.04 m=19.81 ft


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The Upgrading of Naptha requires further aplatforming process which takes thehydrotreated Naphtha as feed and upgrade itfurther to high octane gasoline

Pl f i Pil Pl


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Platforming process Pilot Plant:

Hydrotreated naphtha was combined withrecycle hydrogen and charged to Platformingreactor.

Reaction Teamperature was controlled wothheating elements surrounding thereactor.Reactor effluent was sent to productseparator where light gases,primarilyhydrogen,was compressed then recycled.

Unlike hydrotreater,the Platforming process pilotplant has to export hydrogen from the gas loopto maintain plant pressure.


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Diesel Hydrotreating

HYDROTREATING


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HYDROTREATING

Hydrotreating is a hydrogenation processused to remove contaminants such asnitrogen, sulfur, oxygen, and metals from

liquid petroleum fractions.

D i id i


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Design considerations

Feed characteristics and variability

Other product quality requirements,

especially cetane index

Catalysts selection

Optimisation of reactor process

variables

C


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XTL Technology for India: Coal Biomass &

Cont

Equipment design requirements

Reliability

Minimising product contamination

Handling of off-spec diesel product

process separation and upgradation

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