Methanol Converter Types

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

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