View
3.315
Download
12
Category
Tags:
Preview:
DESCRIPTION
Feedstock Sources Major Feedstock Impurities Typical Breakdown Cracker Feeds Feedstock vs. Yields (% Wt) Chemistry of Cracking Cracking Furnaces / Conditions Basic Flow Sheet Front End Systems Processes/catalysts/ Absorbents Used in Crackers Acetylene Basic Chemistry Typical Reactor Configurations Steam Cracker C4 Fractions Pyrolysis Gasoline Processes
Citation preview
C2PT Catalyst Process Technology
Summary of design, operation, technology
Ethane usually recovered from natural gas fields mainly USA
Propane/butane recovered from gas fields middle east, Texas etc. Kuwait has a large butane recovery system. Also can come from LNG plants
Refinery naphtha / condensate C5 to C7 paraffin based low octane naphtha from refineries also from natural gas / oil well head production
Light and heavy gas oils refinery based (200 to 350°C) AGO and (350 to 550 °C) VGO
The more paraffinic the feedstock the higher the ethylene yields and the greater the value of the co-products
Sulfur + Cracks in furnaces to give H2S and COS. Mercaptans in C3/C4 cuts,
RSH and thiophenes in gasoline, benzothiophenes in fuel oil Arsenic
+ Organic or arsine + Makes arsine in the furnaces and some remains as organic
Mercury + Metallic / organic + Decomposes to metallic some remains as organic
Ballast water + Sea water from shipping feed stock
Metals + Nickel, sodium, vanadium, iron from heavy feedstocks
FCCU off gas (gas compressor suction, developing trend) + NOx, H2S, amines, SbH3, As , COS, O2, CO2 plus others
Feedstock West Europe
USA Japan World
Ethane 8 57.5 30.5
LPG 11 19 7.5 11
Naphtha 69 9.5 92.5 49
Gas Oil 12 14 8.5
Others 1*
Figures as wt% * Ethanol Brazil and India and Coal based gases Poland
PRODUCTS FEEDSTOCKEthane Propane Butane Naphtha Atm Gas
OilVGO
Hydrogen (95%) 8.8 2.3 1.6 1.5 0.9 0.8
Methane 6.3 27.5 22 17.2 11.2 8.8
Ethylene 77.8 42 40 33.6 26 20.5
Propylene 2.8 16.8 17.3 15.6 16.1 14
Butadiene 1.9 3 3.5 4.5 4.5 5.3
Other C4’s 0.7 1.3 6.8 4.2 4.8 6.3C5 to 200C Gasoline 1.7 6.6 7.1 18.7 18.4 19.3
Benzene 0.9 2.5 3.0 6.7 6.0 3.7Toluene 0.1 0.5 0.8 3.4 2.9 2.9
C9 aromatics - - 0.4 1.8 2.2 1.9Non aromatics 0.7 3.6 2.9 6.8 7.3 10.8
Fuel Oil - 0.5 1.7 4.7 18.1 25
Paraffin C7H16
Primary Cracking C3H8 + 1-C4H8
Dehydrogenation C7H14
Cracked Products
Butadiene C4H6
Secondary Cracking
Propylene C3H6
Propyne C3H4
CH4+ C2H4 2C2H4
Acetylene C2H2
Cyclo additions and Dehydrogenation give aromatics pyrolysis tar and coke
Selectively Hydrogenated Free radical chain reaction initiated in furnace tubes
Halliburton Kellogg Brown &
Root (milli second) Lummus Stone & Webster CF Braun Linde BASF ExxonMobil KTI Technip
Each furnace designer has their own characteristics
Temperature ranges 700°C to 900 °C
Residence times 0.2 ( new units) to 15 secs (older design)
Steam injection into the furnaces minimise coke gives CO formation (C + H2O=CO+ H2) 0.2 to 0.5 wt% feed
Tube outlet pressure 0.5 to 2 bar
T 1 0 2
Feed
Gasoline
Fuel Oil
Caustic wash
Cold Box
H2, CH4
Demethaniser
H2 De-ethaniser Tail End
acetylene
Mixed C4 to splitters
Gasoline Secondary Demethaniser
Ethylene Product
Ethane Recycle
800°C
400°C
-100°C
-50°C
-33°C
60°C
-17°C
120°C
0°C
H2
MAPD Converter
C3 to splitter
Depropaniser Debutaniser
Drier
C2H6 C3H8
Recycle Furnace
Furnace
FRONT END DE_ETHANISER C2H2 Reactors
Driers
T 1 0 2
Cold Box
C3’s, C4’s and pygas C2H4/C2H6
CH4, CO H2
Demethaniser
De-ethaniser
FRONT END DE_DEPROPANISER
Driers
T 1 0 2
C4’s and pygas Depropaniser
C2H2 Reactors
Cold Box
C2H4/C2H6 CH4, CO H2
De-ethaniser
Demethaniser C3H6/C3H8
Gas Compression System
Gas Compression System
Wet Front EndDe-propaniser
Front EndDe-ethaniser
Tail EndDe-ethaniser
H2 32.00 20.00 19.00 -CO 0.07 0.06 0.09 -CH4 9.00 26.00 35.00 1.00C2H2 0.30 0.50 0.90 1.50C2H4 34.00 30.00 38.00 75.00C2H6 22.00 6.30 7.00 22.50C3H4 0.03 0.80 - -C3H6 1.00 9.00 - -C3H8 0.30 8.00 - -C4H6 0.60 0.02 - -C4H8 0.07 - - -C4H10 0.03 - - -
C5+ 0.25 - - -H2O 0.40 - - -
SV (h-1) 5-8000 5-8000 5-8000 1.5-3000P (bara) 15-35 15-35 15-35 15-35T (°C) 70-90 70-90 70-90 40-120
Front end acetylene -( Pd on alumina) De-ethanizer overhead Depropanizer overhead Wet gas
Tail end acetylene -(Pd on alumina) MAPD and butadiene -(Pd on alumina) Methanation catalysts ( Ni on alumina) High activity hydrogenation for C4 or C5 recycle (Pd or HTC) Pyrolysis gasoline -( Ni or Pd on alumina) Ethylene / propylene purification systems Purification
Hg from feed or upstream of Pd catalysts Arsenic from feed or C3 cut or from py gas feed COS hydrolysis in the wet gas system H2S ZnO absorption
SG15/4 or 15/15 equivalent to kg/m3 T in SOR inlet temperature start of run T in EOR inlet temperature end of run Partial pressure NOT same as reactor
pressure Hydrogen terminology
◦ Chemical usage nm3/m3 feed ◦ Solution loss nm3/m3 ◦ MUG-make up gas nm3/hr ◦ Purge gas excess hydrogen to remove
inert gases ◦ Recycle gas rate
LHSV volumes feed/volume catalyst Reactor fill cost gives actual cost for
comparisons ( Catalyst SG)
Life Hours m3 feed/kg catalyst preferred or feed component converted
GHSV care is it actual or normal basis? EIT equivalent isothermal temperature
(WABT) Feed distillations (Check out what they
are) ◦ ASTM ◦ TBP ◦ Sim Dist GLC ◦ Boiling range
Average boiling point Others (Check out what they mean) ◦ MAV ◦ UV ( not only at one wavelength) ◦ Iodine number ◦ Bromine number
Base Intermediate FinalC2H2 + H2 = C2H4 + H2 = C2H6
C2H2 = CH2 CH CH CH2Butadiene
= Green oil
CH3 C CH + H2Methyl Acetylene
= CH3 CH CH2propylene
CH2 C CH2 + H2Propadiene
= CH3 CH CH2propylene
CH2 CH CH CH2 + H2Butadiene
= CH3 CH CH2Butylene
CH2 CH CH CH2Butadiene
= Green oil
Relative reactivitiesC2H2 > C4H6 > C3H4 (MA) >> C3H4 (PD) > C2H4
ConversionC2H2 - Acetylene 100% C3H4 - Methyl Acetylene 90%C3H4 - Propadiene 20% C4H6 - Butadiene 90%
Ethylene Selectivity :
% SC2H4 = 100 - % SC2H6 - % SC4+ - % SC6+
% SC2H6 is the ethane selectivity :
% SC2H6 = {[(C2H6)out –(C2H6)in]/[(C2H2)in-(C2H2)out ]}x 100
% SC4+ is the total C4 selectivity formed (i.e. Cis- andtrans-but-2-enes, but-1-ene and buta-1,3-diene), :
% SC4+ = {[2x(C4'sformed)]/[(C2H2)in-(C2H2)out]} x 100 (2 moles C2H2 1 mole C4’s)
% SC6+ is the total C6 selectivity formed,:
% SC6+ = {[3x(C6'sformed)]/ [(C2H2)in-(C2H2)out]} x 100 (3 moles C2H2 1 mole C6’s)
Important to ask customer his definition, many variations
Catalysts are sock loaded Can be regenerated some in situ
steam/air some offsite No activation step used No of reactors and configuration
depends on plant New units, 25°C −T each reactor Front end units always work in
high CO and excess hydrogen Tail end 2 to 5% excess hydrogen
5 ppm added CO. Susceptible to green oil formation.
Usually one spare in either front or tail end systems. Will vary
Acetylene spec is >10ppm in C2H4. This is <1ppm front end design
Cooling Medium C4 Methanol
Cracked Gas Cracked Gas
FRONT END
Isothermal Adiabatic
TAIL END
Components Average HighC3’s 0.3 0.3N-butane 5.2 2.8Iso-butane 1.3 0.61-butene 16 13.7Cis 2-butene 5.3 4.8Trans 2 –butene 6.6 5.8Iso butene 27.4 22.2Butadiene 37 47.5Acetylenics 0.4 1.8C5’s 0.5 0.5
The LPG stream often further processed. Butadiene can be extracted, selective hydrogenation of raffinates, mono olefins into co polymers, solvents etc, MTBE . Full hydrogenation of C4’s for LPG transportation fuel or recycle to the furnaces.
Feed Tower Optional
C10+ Optional
C5 Optional
C5 Optional
Fuel gas
Rerun Tower Optional
Stabiliser
BTX extraction or Motor Gasoline
1st STAGE 2nd STAGE
C5 Tower Optional
Composition wt%C5-200 °C C6-200 °C C6-C8 Cut
Parrafin / Naphthenes 11.8 7.8 9.7Olefins 5.5 2.4 3.0Diolefins 18.1 8.7 5.9Aromatics
Benzene 28.0 35.2 43.7Toluene 13.9 17.4 21.7
C8 7.2 9.0 11.3Alkenylbenzene
(styrene)3.0 3.8 4.7
C9+ 12.5 15.7 -
Total Aromatics 64.6 81.1 81.4
Sulphur ppm wt 220 180 150
CrudeGasoline
Hydrogenated Hydro-treated
IP (ASTM) °C 40 43 4350% °C 98 100 100EP °C 195 200 200SG 0.83 .832 .835Diene I2gms/100gms 27 1 >0.1Bromine No 75 60 >0.5Total Sulphur ppm 400 400 >1Styrene wt% 5.0 0.1 >0.001RONC 97 97MONC 86 86
Catalyst HTC /Pd NiMo/ CoMo
Temperature In/Out °C 70/120 250/320
Pressure Bar 27-50 27-50LHSV 1 to 3 1 to 3
Some Definitions -2
Purge gas Inlet Temperature
Partial Pressure Hydrogen consumption
Make up gas
Recycle gas
Solution loss in product
Outlet Temperature
EIT =Tin+ (Tout-Tin) x (2/3)
Fresh Feed
Distillation curves
0
50
100
150
200
250
0 20 40 60 80 100
Volume % distilled
Tem
pera
ture
Deg
C
TBP/Sim Dist
ASTM D86
Important to define ASTM { D86 (<350°C EP) or D1160 (> 350°C IP)}, Sim Distillation (HPLC/GLC)
Distillation Data and SG is minimum required to calculate other properties ◦ Average boiling points (TABP,
MeABP, VABP) ◦ K for flash data ◦ MW or hydrogen consumptions
◦ Critical properties (Tc Pc) and heats
of reaction ◦ n-d-m data for aromatic contents
Gives properties of the feeds and products for calculations.
Pilot plant isothermal Plant adiabatic Use Tin conversion too
low Use T out conversion too
high EIT = Tin +(Tout-Tin) x Ι Choose some point to try
to match conversion ◦ will depend on reaction ◦ slow Ι = 0.4 ◦ fast Ι = 0.75 ◦ average Ι = 0.66
Look out for equilibrium operations
Flow FL
Flow RL
Flow RG Flow MG
Conversion Data
455565758595
75 125 175
Temperature Deg C
Conv
ersi
on w
t%
Recommended