(45g) Debottlenecking Gas Dryers and Desiccant Adsorbers

Debottlenecking
Gas Dryers and Desiccant Adsorbers

Though Maximization of the Useable Bed Volume with Johnson
Screens' SSG^TM

Benjamin
Schmitt, PE

Senior Mechanical Engineer, Technology

Michael
Ekholm, PE

Applications and Product Design Manager

Johnson Screens Inc. ? St. Paul, MN

AIChE
Spring Meeting, April 2013

13^th
Topical Conference

San Antonio, TX

Introduction:

The following presentation of the
Shaped Support Grid (SSG^TM) releases additional supporting data and
updates to the initial presentation given by Robert G. Norell at the 2010 AIChE
Spring Conference. 

Limitations on ethylene dryers and desiccant
adsorbers can create bottlenecks in the production process which can lead to a
need for increased dryer and adsorber capacity.  Capital intensive investments may be necessary
in order to eliminate the bottleneck which may include the addition of an
additional vessel.  With limits on the plot
plan, this may not be a workable solution. 
Adding to the problem is the amount of time consumed in engineering,
planning and construction, which can have negative effects on the operation of
the ethylene unit.  Increased desiccant
volume and operational efficiency can increase the unit's production with
minimal capital expenditures.  Johnson
Screens', patent pending, SSG^TM can add the increased process
efficiency and cycle life necessary to extend the operating capability of the
unit.

Extending the operation, though
debottlenecking, can be achieved by maximizing the time before breakthrough of
the media bed.  There are three primary
functions that maximize the breakthrough time:

·        
Proper gas distribution in both normal operation
and regeneration conditions which maximizes the bed utilization.

·        
Increased molecular sieve or desiccant bed
volume are achieved through the elimination of traditional bed supports
comprised of support grids and beams. 
The support interface for the screen configuration also allows for
thermal expansion typically present in vessels with a thermal cycle as part of
the process.  The design allows for
thermal cycling without the risks of seal or structural failure inherent in
other solutions. 

·        
Minimizing the bed volume consumed by the
distribution and support system increases the net desiccant volume lost when
utilizing alternative bed supports.

Johnson Screens SSG is designed to provide the industry with an alternative, cost
effective, approach to increasing capacity. 
Supporting data and preliminary case studies will be depicted to
quantify the benefits that are achievable through the implementation of the SSG. 

Conclusions:

The use of a Johnson Screens SSG provides a reliable immediate
solution to reduce capacity bottlenecks. 
The SSG increases the bed
volume, when compared to traditional bed support arrangements comprised of
grids and beams.  The increase in desiccant
volume will allow for increases in feed flow rate and/or adsorbtion cycle time.  The SSG
maximizes the flow distribution during desiccant regeneration, maximizing the
utilization of the complete cross section of the vessel.  This solution can be implemented in both new
and existing vessels, providing consistency in design between planned increases
in performance of current vessels and future expansions. 

The modular design of the SSG allows for easy installation and
maintenance.  Connection of the SSG to the vessel is performed within
the outlet nozzle, eliminating all welding on the pressure vessel and
eliminating any need for recertification of the pressure vessel after
installation.  The design allows for ease
of dismantling for inspection of the vessel head during routine maintenance and
inspections.  The low profile will also
reduce interference with any required media exchanges.  The design package of the SSG provides the end user with a
holistic solution that fulfills debottlenecking needs with limited capital
expenditures. 

Biography of Speaker:

Benjamin Schmitt is a Senior
Mechanical Engineer in Johnson Screens' Hydrocarbon Processing Industry
Technology Group.  Ben graduated from
North Dakota State University in 2004 with a Bachelor of Science degree in
Mechanical Engineering.  He currently
working toward his Master's in Business Administration from Hamline
University.  Ben is member of AIChE and
is a registered professional engineer in the state of Minnesota.