Pre-reformer Operations Technical Supplement

Post on 01-Nov-2014

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- Process effects of pre-reforming - Process benefits of pre-reforming - Effect of Pre-reformer Inlet Temp on Primary Reformer Efficiency - Services for Pre-reforming Pre-Reforming Problems - Features: Impact of Sulfur - High Temperature Operation - Catalyst Deactivation - Which is Better - High or Low Inlet Temperatures ? - Pre Reformer Loading - Pre-Reformer Installation - Pre-reformer Startup - Catalyst Drying - Catalyst Heating - Reduction

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by Gerard B. Hawkins Managing Director, CEO

C2PT Catalyst Process Technology

Effects: ◦ Steam reforming of higher HC ◦ COx undergoes methanation ◦ WGS (and reforming) to equilibrium

Reforming

CnH2n+2 + n H2O n CO + (2n+1) H2

Water Gas Shift

CO + H2O CO2 + H2

Methanation

CO + 3H2 CH4 + H2O

CO2 + 4H2 CH4 + 2H2O

Moves reforming load from Primary

Better reformer design ◦ Higher thermal efficiency in radiant box ◦ Raises pre-heat temps before carbon formation issues ◦ Feedstock flexibility

Reduced steam export ◦ Heat is recovered from duct

-4.5-4

-3.5-3

-2.5-2

-1.5-1

-0.50440 460 480 500 520 540 560

Pre Reformer Inlet Temperature (°C)

Fu

el R

ate

Ch

ang

e (%

)

Catalyst performance software Catalyst loading techniques Start up advice Data analysis and process modelling ◦ Efficiency gains

Residual life calculations

Steam to carbon ratio ◦ Carbon formation ◦ Wetting

Sintering ◦ high temperature ◦ steam partial pressure

Poisoning ◦ Sulfur, Silica, Arsenic, Lead

Mal distribution ◦ Uniform loading ◦ Install man-way plugs

The catalyst must be resistant to poisoning

00.10.20.30.40.50.60.70.80.9

1

0 0.2 0.4 0.6 0.8 1Bed Depth

Ext

ent o

f Rea

ctio

n

Large Pellet3.2 x 3.2mm

EOR

SOR

Do the benefits of operating pre-reformers at high temperatures outweigh the drawbacks ?

Hydrothermal sintering ◦ Agglomeration of nickel particles causing loss of surface area and

decrease in activity

High Temperatures

Steam

A prescribed ramp rate based on measured parameter. ◦ Minimum bed temp for endotherm present (440°C) ◦ Based on reaction profile length otherwise ◦ Short term to overcome C2+ slip Either method equivalent to about 50°C rise over

life of bed.

Illustration only, not for design

Extremely important to achieve a uniform loading Any zones of low or high voidage will reduce

catalyst life ◦ Check manway plugs

No meshes should be used in the vessel Thermocouples must be positioned correctly and

height recorded Follow loading diagram Loading assistance can be provided (not usual)

◦ VSG-Z101 ◦ Axial flow with 2 Thermowells ◦ 6m3 bed

Inert balls MUST be high purity 99% Alumina, <0.2wt% SiO, Cl free

Drying Heating Startup Reduction (What follows are not detailed instructions!)

For catalyst subjected to low temperatures Dry using Nitrogen 175 to 250°C NG can be used below 200°C 4 to 24 hours (monitor water in KO pot) Dry air, not suitable for prereduced First startup of prereduced

Normally heated using nitrogen Absorbed moisture Initial heating rate, 50°C per hour Max temp differential in bed 100°C At 200°C, 70°C per hour Heating till peak 400°C, min 370°C High circ rate, max pd 2 bar

Warm-up rates Rapid warm-up minimises energy usage/time Traditional constraints of equipment Controllability Limited by mechanical considerations of vessel Catalyst, 150-170oC per hour

Limits on impurities Oxygen 1% vol Carbon Dioxide 1% vol Carbon Monoxide 1% vol Methane 1% vol Hydrogen 1% vol Ethane 100 ppm vol Sulfur 0.2 ppm vol

Holding at temperature Not recommended 2% hydrogen added Temperature reduced to 350°C

When operating temperature has been achieved: Check for build up of carbon oxides and

hydrocarbons Add of 10% Hydrogen Followed by steam Introduce process feed, maintain safe S:C

Ensure feed lines are drained and warmed Vent steam to atmosphere before cutting in

Using NG as heating medium

No impurities Immediate startup 50°C per hour, max differential 100°C At 200°C introduce steam

◦ Min S:C 0.3kg/kg at 200°C ◦ Min S:C 0.5kg/kg at 400°C to 450°C ◦ Increase to design feed and S:C

Unreduced catalyst As supplied - NiO on support Active species - Ni Crystallites Reduction process needed:

NiO + H2 => Ni + H2O

Reduction aspects Bed temperature between 450°C and 500°C (normal op temp) 12 to 16 hours

Hydrogen must be ◦ free of poisons (S, Cl)

Special consideration must be given to the presence in impure hydrogen sources of ◦ oxygen ◦ carbon oxides ◦ hydrocarbons

Reduction procedure Hydrogen set at 15 –25% Slowly increased to 50% (or 100%) Regularly check hydrogen levels Water cooled and collected

Reduction complete 85% of reduction water collected Consumption of hydrogen stopped Temperatures equalised Over 16 hours at bed temps above 450°C

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.

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