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Quench Converter ARC Converter Tube Cooled Toyo MRF-Z Adiabatic Beds
Citation preview
Gerard B. Hawkins Managing Director
• Quench Converter • ARC Converter • Tube Cooled • Toyo MRF-Z • Adiabatic Beds
Exit Catalyst Discharge Chute
Catalyst Discharge Chute
Manway
Manway Inlet
Inert Balls
Vessel Wall
Shot Pipe
Sparge Pipe
Sparge Holes
Mesh
180 200 220 240 260 280 300 320 0
2
4
6
8
10
Temperature (°C)
Met
hano
l Con
cent
ratio
n (m
ol%
)
Max Rate
Curve
Methanol
Equilibrium
MUG
Flash Drum
Separator
• Benefits are ◦ Simple ◦ Reliable ◦ Well proven ◦ Capacity up to 3000 mtpd
• Recover heat into saturator circuit • The catalyst doesn’t see all the gas. • Poor catalyst loading can lead to cold core
developing
• Significant flow mal-distribution • Some zones are cold ◦ Can lose reaction
• Some zones are hot ◦ High byproducts levels ◦ High rate of catalyst deactivation
Cool Normal Normal
Catalyst density
Low flow
• It is not caused by the quench lozenges being poor distributors of the cool incoming gas.
• The reverse is true - the lozenges are very good distributors.
• The problem is that voidage variations across the bed can cause varying flows down different parts of the reactor.
• ARC retrofit developed to overcome problem.
Catalyst Support Plates Individual / Separate
Catalyst Beds
Gas Mixing System
x x xx x x x xx x x xx x x x xx x x x xx x x x xx x x x xx x x x xx x x x xx x x x xx x x xx x x x xx x x x xx x
C a t aly s t be d
Inlet Temperature Exit Temperature
Bed 3 237 °C
Bed 1 223 °C
Bed 4 230 °CBed 3 270 °C
Bed 1 270 °CBed 2 223 °C
Bed 4 260 °C
Bed 2 270 °C
Bed 3 261 °C
Bed 1 251 °C
Bed 4 269 °C
Bed 3 289 °C
Bed 1 291 °CBed 2 262 °C
Bed 2 301 °C
* Figures in red are from current operating records (Sept. '96)
* Figures in black are from ARC design case
Tem
pera
ture
% Methanol
Equilibrium Line Quench Converter
ARC Converter
Increase in Methanol %
0 10 20 30 40 500
50
100
150
200
temperature stand. dev. °C
% in
crea
se in
by-
prod
ucts
QCC + ICI 51-7 ARC + ICI 51-7Ethanol 200 69 ppm
Propanol 71 28 ppmButanol 71 33 ppm
MEK 13 <5 ppmDecane C10 2.6 0.9 ppm
Undecane C11 1.8 0.6 ppmDodecane C12 1.2 0.4 ppmTridecane C13 0.7 0.3 ppm
Comp A Comp A
0 200 400 600 800 1,000 1,200 1,4001,400
1,450
1,500
1,550
1,600
1,650
Days on line
Prod
uctio
n (t
e/da
y)
Key features improved gas mixing no penalty on pressure drop better utilisation of the converter volume minimise the by-product levels
Arc RevampCatalyst Loading
Lozenge removalConverter inspection
Fit ARC internalsCatalyst loading
Bed 5Bed 4Bed 3Bed 2Bed 1
0 7 14 21
activ
ity
days
• ARC converters have exhibited an instability • This is highlighted by inlet and outlet temperatures
varying as per a sine wave • Feedback occurs over warm loop interchanger • Normally stable but can become unstable ◦ Leads to loss of strike in converter
• Action is to reduce circulation rate
Manway
Outlet
Manway
Inlet
Catalyst Discharge Port
Heat Recovery Unit
Crude
Crude Cooler
Loop Interchanger
Syn Gas
Purge
180 200 220 240 260 280 300 320 0
2
4
6
8
10
Temperature (°C)
Met
hano
l Con
cent
ratio
n (m
ol%
)
Max Rate Curve
Methanol Equilibrium
• Cheaper loop with heat transfer and reaction • Smooth catalyst temperature profile • Good catalyst utilisation • Mechanically simple • All converter effluent available at high temperature ◦ Can be used to heat saturator water
• Mixing shall be effective • Mixer should ◦ either not impede loading ◦ or be easy to install and remove.
• Mixer should enhance safe operation and be mechanically robust.
• Leakage of gas bypassing mixer should be minimized.
Steam Outlet
Central Pipe
Catalyst Loading Gas Inlet
Gas Outlet & Catalyst Unloading
BFW Inlet
Cooling Tube
Catalyst
Inert Balls
Outlet Collector
Scallops Adiabatic Beds Cooled Bed
Cooling Tube
180 200 220 240 260 280 300 3203
4
5
6
7
8
9
10
Temperature (°C)
Met
hano
l Con
cent
ratio
n (m
ol%
)
Max RateCurve
MethanolEquilibrium
• 28-32 Bara steam raised • Good approach to equilibrium • Low pressure drop, 0.5 to 0.75 bar • Catalyst discharge complex • Small number of tubes (c.f. Lurgi converter)
Crude
Crude Cooler
Loop Interchanger
Syn Gas
Purge
Steam
180 200 220 240 260 280 300 3200
2
4
6
8
10
Temperature (°C)
Met
hano
l Con
cent
ratio
n (m
ol%
)
Max RateCurve
MethanolEquilibrium
• Cross flow means high heat transfer coefficient ◦ Smaller surface area
• Good utilisation of shell volume • Raised steam at between 30-40 bara • But ◦ Costly (not as expensive as Uhde/Lurgi) ◦ Large interchanger required ◦ Pressure is slightly lower than Uhde/Lurgi
Casale
Horizontal Adiabatic Converter
180 200 220 240 260 280 300 3200
2
4
6
8
10
Temperature (°C)
Met
hano
l Con
cent
ratio
n (m
ol%
)
Max RateCurve
MethanolEquilibrium
• All the gas sees all of the catalyst • Cheap vessels - can be spherical • Vessels can be designed the same ◦ Reduces CAPEX
• But ◦ Large loop interchanger ◦ Multiple vessels (excluding Casale’s Horizontal
Converter) ◦ Beds are shallow and so mal distribution can be a
problem
Relative Catalyst Volumes
Base Case 2800 te/day plant (Chile 3)
Fixed circulation rate (recycle ratio = 4.2)
Reactor Catalyst Volume (m3)
ARC 242
TCC 175
SRC 150
• Loop pressurised to 7 bar with nitrogen • Heated to 180°C • Add small amount of H2 for calibration • Heat to give peak temperature of 220°C • Add hydrogen to 2% • Monitor temperatures • When exotherm profile moves through bed start
soak • Increase H2 and temperature
• Similar to Reduction • Use air instead • Again exothermic • Also requires soak • Can not fully guarantee full oxidation • Procedure is available
Process Information Disclaimer Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the Product for its own particular purpose. GBHE gives no warranty as to the fitness of the Product for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability for loss or damage resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed.