STEAMING PROCEDURE FOR VULCAN STEAM REFORMING CATALYSTS

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STEAMING PROCEDURE FOR VULCAN STEAM REFORMING
CATALYSTS
Plant Note Book Series:
PNBS-0603
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STEAMING PROCEDURE FOR VULCAN STEAM REFORMING CATALYSTS
CONTENTS
0 SCOPE
1 INTRODUCTION
2 PROCEDURE
3 SUMMARY

STEAMING PROCEDURE FOR VULCAN STEAM REFORMING CATALYSTS
0 SCOPE
This procedure is applicable for VULCAN series catalysts to recover from
sulfur poisoning and/or carbon formation incidents.
1 INTRODUCTION
Steaming of steam reforming catalysts can be used to attempt to recover
from incidents which have led to carbon lay down on the catalyst surface.
Steaming has also been demonstrated to remove traces of certain poisons
from the surface of the catalyst and sulfur in particular. Quite frequently
carbon formation results in conjunction with sulfur poisoning. The
effectiveness of the steaming procedure depends on the severity and
circumstances of the incident, however. Carbon formation tends to cause
hot bands around one third down the reformer tubes and may cause
pressure drop build up.
Steaming will often reverse these effects especially where the
hydrocarbon feed is relatively light when most of the carbon results from
thermal cracking between the catalyst tablets.
Heavy carbon formation particularly from heavier feeds leads to polymeric
carbon within the catalyst structure and this may lead cracking of the
catalyst tablets such that the tablets remain largely intact while the carbon
is present but, when the carbon is removed by steam, the tablets can
disintegrate leading to catastrophic pressure drop rise.

2 PROCEDURE
In case steaming is required in the steam reformer, a minimum steam flow
equivalent to 30~40% of the design steam flow should be maintained.
The minimum value will depend on the plant design and the ability to
control firing to maintain acceptable tube temperature. If possible, the
reformer outlet process gas temperature should be maintained above
780°C (1436°F) subject to the reformer design constraints to increase the
effectiveness of the steaming process.
Particularly on top-fired furnaces, the high exit temperature is the means
of ensuring that the inlet temperature is hot enough to drive the carbon
gasification rate. The reformer inlet temperature should be maintained
very close to the design value.
It is also advised to add a small known flow of nitrogen gas admitted at the
inlet of the reformer. This will enable collection of a dry gas sample at the
outlet of the reformer at periodic intervals. An hourly sample frequency is
suggested but this will depend on analytical capability.
During steaming, the reformer outlet sample should be analyzed for CO2,
CH4, H2S & SO2 and the nitrogen provides a means of quantifying the
amount of these components arising in the steaming process.
The oxides of carbon are expected to increase from the time steaming is
started, attain peak values and then taper off to near asymptotic levels.
After the asymptotic values are reached, the exit temperature should be
increased from 780°C (1436°F) by 10° C (18°F) and maintained until two
further samples are taken over a period of at least two hours.
Assuming the carbon oxide level does not increase, steaming may be
stopped and preparations made for re-commissioning the plant.
If the carbon oxides level is not steady, steaming should be continued until
a steady level is observed over the course of 2 – 3 analyses. Typically, the
CO2 level will reduce to a level in the low ppmv.
Depending on the level of the problem and the temperature available
for steaming, this process will be complete in 12 – 24 hours.

In particularly severe cases where steam alone is not taking the
process to completion, an air/steam regeneration can be considered.
This must be done with care to avoid over-heating the catalyst.
GBH Enterprises can advise on the appropriate procedure.
During steaming, the firing should be even throughout the furnace as
far as possible to ensure that all the tubes are hot enough to allow for
carbon gasification. Also, the pressure drop and condition of the
reformer tubes must be monitored closely to prevent over
temperature and the potential for failure of the tubes.
The condition of the reformer tubes should be monitored visually
once every hour and these observations recorded. Also, if any
adjustments are made to firing, the reformer tubes should be
visually inspected as these changes are made.
After maintaining the steaming conditions, an appropriate level of
catalyst reduction is necessary. The reduction procedure is influenced
by the catalyst type and duration of steaming. A separate procedure
is available from GBH Enterprises advising on this which is found in the
Operating Manual for the installed catalysts.
After completion of reduction of reformer catalyst, hydrocarbon may be
admitted to the reformer following the standard procedure described in the
Operating Manual for the installed catalysts.

3 SUMMARY
Steaming the Reformer
Maintain a steam flow of approximately 70-80 te/h
A small amount of nitrogen should be added at the inlet of the reformer
If possible keep the reformer outlet temperature above 780°C
Keep the reformer inlet temperature around 520°C
Analyze every 2 hours
CO2
CH4
H2S
SO2
CO2 should increase when steaming is started
CO2 will reach a peak and then slowly start decreasing
When CO2 becomes level, increase reformer exit temperature to 790°C
Continue steaming until CO2 becomes steady
Closely monitor pd throughout the steaming process
Visually inspect the reformer tubes every hour
Steaming should last between 12-24 hours

STEAMING PROCEDURE FOR VULCAN STEAM REFORMING CATALYSTS

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STEAMING PROCEDURE FOR VULCAN STEAM REFORMING CATALYSTS