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Fluorocarbon Distillation

 

 

 

 

 

 

Project Background

 

 

 

 

End Client: F2 Chemicals, UK

 

 

 

 

 

 

F2 Chemicals are an established manufacturer of high specification perfluorocarbons for a variety of industries including high purity products for use in semiconductor sector.

 

 

In 2011, JBL provided process engineering services to ETDE Contracting for a design study they were undertaking for F2 Chemicals for the production of a hypergolic halogen based compound. Subsequently JBL was invited by the contractor, now Bouygues Energies and Services, to undertake a series of flowsheeting studies for the distillation of Octafluoropropane manufactured by F2 Chemicals in Preston UK.

 

Octafluoropropane (also known as perfluoropropane, R218 or just 218 is manufactured by F2 Chemicals and marketed as Flutec PP30). It is used extensively by the semiconductor industry in etching processes and chemical vapour deposition (CVD) chamber cleaning to remove dielectric film build up.

 

Octafluoropropane, C3F8 (PP30), is manufactured by the indirect reaction of fluorine gas (F2) with Hexafluoropropylene, C3F6 (HFP).The process is carried out in a reactor followed by distillation.An improved continuous distillation process was required to replace the current batch distillation unit. The new distillation plant was required to have an increased capacity, achieve higher product purity and reduced emissions. The project also required a new dedicated HFP storage area and product filling facility.

 

The studies were undertaken in four phases from 2013 to 2015 and subsequently a facility was designed, built and finally commissioned in 2017.JBL was engaged to provide process engineering services throughout the project. The facility also included Hexafluoropropylene bulk tanker off-loading, reagent storage, handling and reactor feed.

 

Link to F2 Chemicalsí Aerial Video

Photo courtesy of F2 Chemicals Limited

 

Flowsheeting Studies

JBL engaged the services of a capable flowsheet modeller to undertake the flowsheet simulation of the distillation process and associated vapour recovery unit. JBL worked with F2 Chemicals and the contractor to provide the modeller with a specification of requirements. JBL liaised with the modeller throughout each of the study phases. The main objective was to change from the current batch distillation achieving 99.99% product purity to continuous distillation (in campaigns) achieving 99.999% product purity. The new process would also need to reduce emissions of Octafluoroproane.

 

Phase 1

This report presents the results on the initial plate-to-plate simulation for PP30-Distillation and associated vapour recovery unit. The simulation used the NRTL activity co-efficient physical property package as this is recommended for chemical systems. A sense check was made using equation of state methods. The flash calculations for vapour recovery unit were in close agreement. For distillation, the only property methods that were able to generate results were activity coefficient methods similar to NRTL. Equations of state methods were not able to predict vapour-liquid equilibrium. The NRTL method is preferred due to better prediction of liquid phase mixture properties.

 

 

Phase 2

The project specifications for this phase of study included two new components added as part of impurities in the feed stream. One of these components was identified to have tendency for azeotrope formation with the main product. The level of this impurity in the distillation feed would render the 99.999% purity target unachievable. It also identified the risk of impurity accumulation in the vapour recovery system. Binary data was presented to illustrate the problem. The report presented a number of options to resolve this issue.

 

Phase 3

Following a review with F2 Chemicals raw material with an acceptably low level of contaminant was sourced for the fluorination reactor. The flowsheeting exercise was re-run to enable the required product purity to be achieved.

 

Phase 4

This phase of study was primarily different to the previous phases in terms of the underlying objectives. The previous phases were mainly aimed at finding optimal operating conditions and packed bed dimensions to achieve required purity targets. However, this study was aimed at validating the work carried out in past studies for the pre-selected packed bed dimensions based on providing a practical design. The following list represents the main changes introduced to simulation for this phase:

 

       Increased diameters from the theoretical requirements for both distillation columns in order to minimise wall effects.

       Increased pressure in the first distillation column to enable feed to the second column by differential pressure.

       Increased packing heights to make full use of the available height agreed during planning permission.

 

Site Activities

       Liaison with F2 Engineering and Production Personnel

       Redefinition of Control Sequences

       Assistance with FATs and later SATs during water commissioning.

       Prestartup Safety Reviews (PSSR)

       Water Commissioning

       Degreasing

       Chemical Commissioning

       Operator Training

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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