292678 Debottlenecking Gas Dryers and Desiccant Adsorbers
Debottlenecking Gas Dryers and Desiccant Adsorbers
Though Maximization of the Useable Bed Volume with Johnson Screens' SSGTM
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
13th Topical Conference
San Antonio, TX
Introduction:
The following presentation of the Shaped Support Grid (SSGTM) 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, SSGTM 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.
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