Refinery Process Catalyst & Molecular Sieve Guide

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Web Site: www.GBHEnterprises.com
GBH Enterprises, Ltd.
Operating Manual
Molecular Sieve
Adsorbents
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 information for its
own particular purpose. GBHE gives no warranty as to the fitness of this
information 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 resulting from reliance on this
information. Freedom under Patent, Copyright and Designs cannot be assumed.

GBH Enterprises molecular sieves are manufactured by CAMChem, which is
ISO 9001 System certified.
Features & Applications
CAMChem Crown Advanced Material Co. , Ltd
Xiabu Industrial Park, Xiangdong District, Pingxiang, Jiangxi, China

LOADING AND START-UP ADSORBENTS AND ADSORPTION UNITS
– Note that before handling the molecular sieve for loading or other purposes,
personnel should read and be conversant with the safety instructions.
– A copy of these instructions is available on request. Remember that molecular
sieves evolve much heat on contact with water.
PHILOSOPHY
Molecular sieves are desiccants which
scavenge water and other small polar
molecules down to very low concentrations,
typically down to 1 ppm or less. The
molecular sieve is loaded into the vessel in
the open air, and in doing so may pick up
inside the vessel or associated pipework.
GBH Enterprises therefore recommend a regeneration of the complete unit after
the unit has been closed-up for the last time and before bringing it on-stream.
This regeneration should also be carried out when the unit has been off line for
maintenance for an extended period of time. In thermal swing applications,
regeneration ensures that the molecular sieve is in a highly active state when the
unit is brought on stream. It involves heating the molecular sieve to above 250°C
(or to 230°C for 3A molecular sieve) in a heated gas stream, which is passed
through the column at the required mass flow rate. The gas provides both heat
and a medium for sweeping away desorbed species from the molecular sieve.
PACKAGING AND INSPECTION
GBH ENTERPRISES molecular sieves are delivered in a variety of packaging,
ranging from 25 kg cartons through 140 kg drums to Big Bags with 600 kg to
1000 kg of product. All these packages contain an inner polyethylene liner which
protects the contents from atmospheric contaminants and moisture.
However the product is a desiccant, and should be stored on site in clean, dry
conditions.

GBH ENTERPRISES molecular sieves are extensively tested before despatch.
Certification and quality control to ISO 9001standards is provided and
guarantees the quality of the product as delivered. Even so, a visual inspection
of the product is recommended before loading into the vessels.
– In the case of the Big Bags, it is simply a
question of undoing the outer and inner liners
on the top of the Big Bag. After inspection,
which should be done under cover, it is
important that the inner plastic liner should be
tied tightly to the outside bag rope to prevent
the liner from falling out during loading.
– With steel drums, it is possible that a vacuum may have developed inside
the drum. To break the vacuum remove the top rim closure and either release the
vent on the top of the drum, or use a screwdriver to pries the lid up and release
the vacuum. Then remove the lid and loosen the inner tie to inspect the
molecular sieve. Re-seal after inspection.
The total delivered quantity should be checked by grade and bead size, and
against the expected total volume of the vessels to be loaded. Should the
molecular sieve appear to be damaged in any way, then please notify GBH
Enterprises for further instruction and assistance.
LOADING
Normally one of two loading configurations are to be used. The bed will either be
made up completely of beads of a single size range; or there will be a two layer
configuration where the bed is made up of approximately 2/3 large beads, and
1/3 small beads. If the bed has a two layer configuration, then the smaller beads
always go at the adsorption outlet end of the column.
With gas phase adsorbers the adsorption outlet is normally the bottom.
With liquid phase adsorbers the adsorption outlet is normally the top.
However this is NOT always the case, and drawings or specifications should
be checked before loading. For further points and recommendations on support
balls, please consult our brochure VULCAN Series A2
ST Advanced Alumina
Support Technology 'Adsorbent Bed Supports' copy available
on request.

1.1 Vessel Inspection
Before loading the molecular sieve it is recommended that
the inside of the vessel is also inspected, particularly
during a re-charge of an existing vessel. The following
checks can prevent major problems from occurring during
operation.
– Ensure the support grid is properly secured in the
bottom of the vessel.
– Inspect the caulking between the screen and the vessel wall.
– Make certain that the screen above the support grid is free of embedded
molecular sieve particles, support material and dust.
– Note the condition of sample taps, thermal wells etc.
– If possible check the calibration of the plant hygrometer probe.
– If the vessel is internally insulated, check the surface for defects.
1.2 Loading of Bottom Support Material
It is normal practice to load a 15 cm / 6 inch layer of inert
balls at the bottom of the adsorber to prevent blinding of the
bottom screen, and to prevent molecular sieve from passing
through this screen.
This may be done by loading through a manway in the lower
section of the tower.
NOTE: The ceramic balls should not be allowed to
free-fall from the top of the tower as they can shatter
when they hit the bottom screen. This may damage
the screen, and may also cause an excessive
pressure drop during operation. Molecular sieve
should not be allowed to free-fall more than about 10
meters.

1.3 Loading of Sieve
There are two basic methods of loading molecular sieve depending on the
packaging in which they are supplied.
– If the molecular sieve is delivered in drums, the material may be loaded by
hoisting individual drums to the top of the tower and tipping them in.
Alternatively a number of drums may be loaded into a hopper, which is
then lifted to the top of the tower and discharged at one go.
– If the molecular sieve is delivered in Big Bags, then individual Big Bags
may be hoisted to the top of the tower. The bottom of the sack is then
slit and the molecular sieve allowed to fall into a loading funnel and into
the vessel.
NOTE 1: Remember that the inner bag is not fixed to the
outer bag, and it is possible for the weight of the molecular
sieve to pull the inner liner into the tower if it is not secured
as above. If this happens, it is essential that the plastic bag
is recovered from inside the tower.
NOTE 2: It is possible for the very dry adsorbent to build up a high static
electricity loading. Therefore in flameproof areas earthing of the bags is
essential.
After all the molecular sieve has been loaded into the vessel, the surface
should be leveled, and a floating screen of approximately 20 mesh
stainless steel placed above the adsorbent. This is extremely important if
ceramic balls are to be placed above the adsorbent as the ceramic balls are
heavier than the molecular sieve, and will fall into the adsorbent bed if not
separated. Note that the bed will settle during service, so the screen should not
be fixed.
1.4 Special Precautions in the Case of PSA and VPSA Applications
In some PSA applications the performance of the molecular sieve is particularly
sensitive to moisture content of the molecular sieve. In such cases protective
measures should be taken from environmental contamination, and it may be
found desirable to flush the column to be loaded with dry air.

It is vital that the molecular sieve is protected from contamination from either
pick-up of moisture from the atmosphere, or from other local airborne
contaminants. The drums should be kept tightly closed until immediately before
loading. After completion of the loading steps which should be done as fast as
possible, the column must be closed in and if necessary flushed with an inert dry
suitable gas. If in any doubt as to the suitability of a particular gas then specialist
opinion should be sought from GBH Enterprises.
1.5 Loading of Top Support Material
Generally a 15 cm / 6 inch layer of support balls is loaded on top of the
molecular sieve bed. This serves to hold the bed down during upflow operation,
and to prevent destructive impingement of the gas stream on the molecular
sieve during down-flow operation. The layer also acts as a distributor of gas
through the molecular sieve.
Loading of this layer should be done by using small buckets, or
by hoisting individual drums to the top of the tower. The balls
should be leveled over the surface area of the screen.
1.6 The vessel should then be closed in ready for process
start-up.
2. START-UP
2.1 Check list before Commencing Start-up
Before commencing Start-up the following plant items must be commissioned
and ready for service:
– the vessels and pipework clean, pressure tested and closed up ready for
service;
– all moving or rotating plant items checked and commissioned;
– the plant checked to ensure all blanks and foreign matter including aids for
construction have been removed;
– pipework and vessels are connected according to the process drawings;
– the various process streams are available for use;
– the instrumentation and any automatic sequencers have been
commissioned (especially any moisture indicators);
– the utilities required for regeneration have been commissioned;
– the vessels and pipework have been lagged as required.

Molecular sieve can adsorb moisture down to very low levels (typically less
than 1 ppm). They also evolve a large amount of heat on contact with water.
Apart from safety considerations, this heat can permanently damage the
molecular sieve. It is important to ensure that there is no possibility of any large
volume of liquid water coming into contact with the molecular sieve beds.
Also during their first exposure to some types of hydrocarbons some grades of
molecular sieve may also adsorb enough of these hydrocarbons to give a
temperature increase of up to 20°C or more.
3. INITIAL REGENERATION
3.1 Regeneration Gas Availability
GBH Enterprises recommend that the initial
regeneration is carried out with the gas stream to be used
in standard plant running. However if this is not
available then a dry nitrogen stream or a dry methane
rich stream (without unsaturated hydrocarbons) may
be used instead.
Note:
– Dry nitrogen is the preferred gas and may already be connected if the vessels
have to be purged of air during commissioning.
– The flow rate may need to be adjusted to allow for any difference in specific
heat from the design stream, but the full designed gas flow rate should be used
to ensure that there is no channelling of the gas flow through the bed.
– Regeneration under plant conditions is generally carried out at a pressure
of 25 / 30 bar or less. If a gas is used at a pressure lower than design, care
should be taken that the pressure drop does not become too high leading to
fluidization of the bed, which may then need repacking, or it can blow the
molecular sieve out of the vessel.
3.2 Initial Regeneration Procedure
a) Turn on the regeneration gas flow and adjust to the required mass flow
rate. Care should be taken to ensure this stream is disposed of safely,
particularly if the next unit up-stream is not yet commissioned and the
regeneration gas stream is vented or flared off.

b) Start up the heating for the gas stream, bringing the temperature up
to specification over a period of say one hour or in accordance with the
suppliers instructions (Maximum three hours). If refractory has to be dried out, or
other commissioning work on other plant items, then this should have been done
beforehand (but see note below on effects of temperature on the molecular
sieve).
c) Maintain heating until the outlet to the bed reaches
a constant temperature within 20-30°C of the inlet.
This outlet temperature should be monitored and
verified during initial start-up. Further the exit gas
stream should also be checked for water content
during initial start-up.
(Typical heating time about 5 hours)
d) Maintain this constant temperature for a period of one hour.
Note that molecular sieve can be degraded by an excessively high temperature.
If heater trials are being undertaken during pre-service regeneration, care should
be taken to protect the molecular sieve from excessive temperatures. A
maximum safe temperature is 325°C.
e) Stop heating.
f) Cool the column down by blowing through DRY cool gas in accordance
with standard plant instructions, until the temperature at the column outlet
reaches a temperature 40-50°C above ambient. (Typical cooling time about 3
hours).
g) Shut in the column ready for start-up on process gas.
h) Repeat the above instructions on each of the columns in turn.

4. PROCESS START-UP
4.1 It is assumed that the molecular sieve has already been regenerated
according to the instructions above.
4.2 The plant will typically be started off at low flow rates and gradually
brought up to design conditions.
GBH Enterprises therefore recommend that the adsorber is placed on a fixed
cycle time during this commissioning phase, unless the switch-over to
regeneration is done by means of a moisture indicator. In this case change-over
should be monitored and verified during the first few cycles.
Regeneration can be done in accordance with the plant manual from the start,
provided gas is available. If not then the regeneration heat time should be
extended until the specified heating maximum outlet temperature is reached.
4.3 At very low flow rates there is a danger of channelling of flow through the
packed beds. In this case an automatic sensor may not see moisture which is
being channeled away in another part of the bed.
4.4 The regeneration should be done with full flow design rates from the start.
This is essential as it reconditions the desiccant for further use in the next
adsorption cycle.
4.5 Automated plant running can be switched in once the flow reaches 50%
design or the minimum turndown flow according to the plant operating manual.
4.6 Outlet streams should be monitored regularly to ensure the required moisture
content is reached.
4.7 Inlet streams should also be monitored regularly to ensure there is no
excessive moisture, oils, dusts or other contaminants reaching the active
molecular sieve surface.
4.8 Automated operation should be switched in when the conditions in
step 6.6 are regularly achieved.

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.
For further Information on “Non-Proprietary” Vulcan Series Process
catalyst absorbents & adsorbents, or recommendations for specific
applications, please contact us.

Refinery Process Catalyst & Molecular Sieve Guide

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