Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
An evaluation of extractive and azeotropic distillation for separation of 1-octene from oxygenates typically produced during Fischer-Tropsch synthesis
Thesis (MEng)--Stellenbosch University, 2024.
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Published: |
Stellenbosch : Stellenbosch University
2025
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867614095554904064 |
|---|---|
| access_status_str | Open Access |
| author | Van der Vyver, Christiaan Steyn |
| author2 | Burger, A. J. |
| author_browse | Burger, A. J. Van der Vyver, Christiaan Steyn |
| author_facet | Burger, A. J. Van der Vyver, Christiaan Steyn |
| author_sort | Van der Vyver, Christiaan Steyn |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description |
Thesis (MEng)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131947 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:46:35.680Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131947 An evaluation of extractive and azeotropic distillation for separation of 1-octene from oxygenates typically produced during Fischer-Tropsch synthesis Van der Vyver, Christiaan Steyn Burger, A. J. Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Fischer-Tropsch process Azeotropic distillation Extractive distillation Separation (Technology) UCTD Thesis (MEng)--Stellenbosch University, 2024. ENGLISH ABSTRACT: The product stream from a Fischer-Tropsch process typically contains a host of different chemical components. The specific composition depends on the thermodynamic conditions, process methodology and catalysts utilised during such synthesis. Effective down-stream separation of the various components can become challenging when the relative volatility, α, of the species is close to unity. Typically, when 0.95 < α < 1.05, simple distillation requires many theoretical stages and high reflux ratios, to the point where it becomes uneconomical. To overcome this problem, close-boiling azeotropic mixtures are usually separated by enhanced (and more complicated) distillation methods, such as extractive distillation and azeotropic distillation. The choice of process is influenced by factors such as cost (primarily), practical limitations, health and safety, and environmental implications. Against this background, this study compared azeotropic distillation with extractive distillation for the separation of a C8 olefin (1-octene) from oxygenates with similar boiling points (α close to one) – as typically derived from Fischer-Tropsch synthesis. Apart from a standard literature survey on the topic, the work entailed the following: (a) a systematic identification and selection of potential entrainers and solvents for azeotropic and extractive distillation, respectively; (b) a detailed simulation of the two processes in Aspen Plus®; (c) and a basic comparison of costs and other factors, for final recommendation of the preferred method. In the systematic chemical screening/selection process, the three most promising (optimum) entrainers/solvents were identified for each of the full-scale azeotropic distillation and extractive distillation systems. In practice, the actual final selection of solvent/entrainer (from the short-list of three) would depend on additional criteria dictated by the operational needs of the specific plant. For azeotropic distillation, the chemical screening process specifically targeted entrainers that could potentially be used in a mixture with water (binary entrainer) to form a water|1-octene|entrainer azeotrope for the separation of 1-octene from oxygenates. The screening analysis considered the following properties: Jacques and Lee relations (infinite dilution activity coefficient), boiling points, toxicity and cost. Among the screened list of entrainers, ethanol, isopropyl-alcohol and methanol stood out as the three strongest (optimal) contenders. The ethanol entrainer was used for simulation of the full-scale azeotropic distillation plant.For the extractive distillation option, solvents have been identified by considering the following properties: selectivity (infinite dilution activity coefficient), boiling points, toxicity and cost. In this case, n-methyl pyrrolidone (NMP), ethylene glycol (EG) and mono-ethanolamine (MEA) were identified as the three most promising solvents. The n-methyl pyrrolidone (NMP) solvent was used for the simulation of the full-scale extractive distillation plant. Following the identification and selection of entrainers and solvents, the research focus shifted towards reliable simulation of the azeotropic and extractive systems. Specific patent-literature exists on the topic, outlining a proposal for commercial implementation of azeotropic distillation (US Patent No. US 2003/0187317 A1). Such data were used to build and re-create the simulation of the patented system in Aspen Plus®, serving as a verifiable foundation for further in-depth simulation, analysis and optimisation of a full-scale azeotropic plant. Along these lines, an extractive system was also simulated, optimised and sized for the same 1-octene recovery. In the chemical selection process, experimental infinite dilution activity coefficient data for various chemical family combinations were obtained from literature. The same infinite dilution activity coefficient data were then generated (estimated) in Aspen Plus® using the UNIFAC Dortmund model. Subsequently, the experimental and estimated values were compared to validate the accuracy of the UNIFAC Dortmund model, before using it in Aspen Plus® for simulation of the re-created patented system and other full-scale systems. For simulation purposes, the full-scale plant feed was chosen to be 60 ton/h, which is well-representative of typical flow rates in the industry. Using the re-created patent simulation as baseline, the full-scale heterogeneous azeotropic system was successfully simulated, optimised and sized with a 1-octene recovery of 99.9%. The optimised entrainer feed flow rate and entrainer feed composition were determined to be at 180 ton/h and a water content of 10 mass% (90 mass% ethanol). An Aspen Plus® simulation was then successfully developed for a similar full-scale extractive distillation system delivering the same 1-octene recovery as the simulated azeotropic system (i.e. 99.9%). The optimised solvent feed flow rate for the extractive system was 60 ton/h. In terms of physical sizing, the diameter of the azeotropic distillation column is approximately double the diameter of the extractive distillation column. On the other hand, the extractive column is approximately double the height of the azeotropic column. The full-scale azeotropic system requires approximately four times more duty and has an approximate six times larger heat exchanger area compared to the extractive system. Although the azeotropic system requires more duty, it uses medium-pressure steam which has a lower utility cost compared to the high-pressure steam required for an extractive system. The NPV range for the full-scale azeotropic system is $0.3 billion – $3.5 billion. The NPV range for the full-scale extractive system is $1.5 billion – $4.7 billion. The IRR range for the full-scale azeotropic system is 1.8 – 19.7%. The IRR range for the full-scale extractive system is 11.2 – 34.4%. The NPV and IRR values at the different 1-octene cost values are higher for the full-scale extractive system compared to the full-scale azeotropic system. The IRR of the full-scale azeotropic system is higher than the hurdle rate at a 1-octene cost value of $1500/ton. The IRR of the full-scale extractive system is higher than the hurdle rate at a 1-octene cost value of $1300/ton. These cost estimates are applicable for the year 2023. Therefore, for a feed rate of 60 ton/h which is well-representative of typical flow rates in the industry, within the limitations of this study, the full-scale extractive system is preferred above the azeotropic system for the recovery of 1-octene from oxygenates. AFRIKAANSE OPSOMMING: Die produkstroom van 'n Fischer-Tropsch-proses bevat tipies 'n verskeidenheid chemiese komponente. Die spesifieke samestelling hang af van die termodinamiese toestande, prosesmetodologie en katalisators wat tydens sodanige sintese gebruik word. Effektiewe afwaartse skeiding van die verskillende komponente kan uitdagend wees wanneer die relatiewe vlugtigheid, α, van die spesies naby aan eenheid is. Tipies, wanneer 0.95 < α < 1.05, vereis eenvoudige distillasie baie teoretiese stadiums en hoë terugvloeiverhoudings, tot die punt waar dit onekonomies word. Om hierdie probleem te oorkom, word naby-kook aseotropiese mengsels gewoonlik geskei deur verbeterde (en meer ingewikkelde) distillasie metodes, soos ekstraktiewe distillasie en aseotropiese distillasie. Die keuse van proses word beïnvloed deur faktore soos koste (primêr), praktiese beperkings, gesondheid en veiligheid, en omgewingsimplikasies. Teen hierdie agtergrond het hierdie studie aseotropiese distillasie vergelyk met ekstraktiewe distillasie vir die skeiding van 'n C8 olefien (1-okteen) van suurstofverbindings met soortgelyke kookpunte (α naby aan een) – soos tipies afgelei van Fischer-Tropsch sintese. Afgesien van 'n standaard literatuuroorsig oor die onderwerp, het die werk die volgende behels: (a) 'n sistematiese identifikasie en seleksie van potensiële meesleurders en oplosmiddels vir onderskeidelik aseotropiese en ekstraktiewe distillasie; (b) 'n gedetailleerde simulasie van die twee prosesse in Aspen Plus®; en 'n basiese vergelyking van koste en ander faktore, vir finale aanbeveling van die voorkeurmetode. In die sistematiese chemiese siftings-/seleksieproses is die drie mees belowende (optimum) meesleurders/oplosmiddels geïdentifiseer vir elk van die volskaalse aseotropiese distillasie- en ekstraktiewe distillasie-stelsels. In die praktyk sal die werklike finale seleksie van oplosmiddel/meesleurder (uit die kortlys van drie) afhang van bykomende kriteria wat deur die operasionele behoeftes van die spesifieke aanleg bepaal word. Vir aseotropiese distillasie het die chemiese siftingsproses spesifiek gemik op meesleurders wat potensieel in 'n mengsel met water (binêre meesleurder) gebruik kan word om 'n water|1- okteen|meesleurder aseotroop te vorm vir die skeiding van 1-okteen van suurstofverbindings. Die siftingsanalise het die volgende eienskappe oorweeg: Jacques en Lee verhoudings (oneindige verdunningsaktiwiteitskoëffisiënt), kookpunte, toksisiteit en koste. Onder die gesifte lys van meesleurders het etanol, isopropiel-alkohol en metanol uitgestaan as die drie sterkste (optimum) mededingers. Die etanol meesleurder is gebruik vir simulasie van die volskaalse aseotropiese distillasie-aanleg. Vir die ekstraktiewe distillasie-opsie is oplosmiddels geïdentifiseer deur die volgende eienskappe te oorweeg: selektiwiteit (oneindige verdunningsaktiwiteitskoëffisiënt), kookpunte, toksisiteit en koste. In hierdie geval is n-metielpirolidoon (NMP), etileenglikol (EG) en mono-etanolamien (MEA) geïdentifiseer as die drie mees belowende oplosmiddels. Die n-metielpirolidoon (NMP) oplosmiddel is gebruik vir die simulasie van die volskaalse ekstraktiewe distillasie-aanleg. Na die identifikasie en seleksie van meesleurders en oplosmiddels het die navorsingsfokus verskuif na betroubare simulasie van die aseotropiese en ekstraktiewe stelsels. Spesifieke patent-literatuur bestaan oor die onderwerp, wat 'n voorstel vir kommersiële implementering van aseotropiese distillasie uiteensit (US Patent No. US 2003/0187317 A1). Sulke data is gebruik om die simulasie van die gepatenteerde stelsel in Aspen Plus® te bou en te herskep, wat dien as 'n verifieerbare grondslag vir verdere in-diepte simulasie, analise en optimalisering van 'n volskaalse aseotropiese aanleg. Langs hierdie lyne is 'n ekstraktiewe stelsel ook gesimuleer, geoptimaliseer en geskaal vir dieselfde 1-okteen herwinning. In die chemiese seleksieproses is eksperimentele oneindige verdunningsaktiwiteitskoëffisiënt data vir verskeie chemiese familie kombinasies uit literatuur verkry. Dieselfde oneindige verdunningsaktiwiteitskoëffisiënt data is toe gegenereer (geskat) in Aspen Plus® met behulp van die UNIFAC Dortmund model. Vervolgens is die eksperimentele en geskatte waardes vergelyk om die akkuraatheid van die UNIFAC Dortmund model te valideer, voordat dit in Aspen Plus® gebruik is vir simulasie van die herskepte gepatenteerde stelsel en ander volskaalse stelsels. Vir simulasiedoeleindes is die volskaalse aanlegvoer gekies om 60 ton/h te wees, wat goedverteenwoordigend is van tipiese vloeitempo’s in die bedryf. Met die herskepte patent-simulasie as basis, is die volskaalse heterogene aseotropiese stelsel suksesvol gesimuleer, geoptimaliseer en geskaal met 'n 1-okteen herwinning van 99.9%. Die geoptimaliseerde meesleurder voer vloeitempo en meesleurder voer samestelling is bepaal om 180 ton/h en 'n water massa-persentasie van 10 massa% (etanol massa persentasie van 90 massa% etanol) te wees. 'n Aspen Plus® simulasie is toe suksesvol ontwikkel vir 'n soortgelyke volskaalse ekstraktiewe distillasie stelsel wat dieselfde 1-okteen herwinning as die gesimuleerde aseotropiese stelsel lewer (d.w.s. 99.9%). Die geoptimaliseerde oplosmiddel voer vloeitempo vir die ekstraktiewe stelsel was 60 ton/h. In terme van fisiese grootte, is die deursnee van die aseotropiese distillasiekolom ongeveer dubbel die deursnee van die ekstraktiewe distillasiekolom. Aan die ander kant is die ekstraktiewe kolom ongeveer dubbel die hoogte van die aseotropiese kolom. Die volskaalse aseotropiese stelsel vereis ongeveer vier keer meer arbeid en het 'n ongeveer ses keer groter hitteruiler area in vergelyking met die ekstraktiewe stelsel. Alhoewel die aseotropiese stelsel meer arbeid vereis, gebruik dit mediumdruk stoom wat 'n laer nuts-koste het in vergelyking met die hoëdruk stoom wat vir 'n ekstraktiewe stelsel benodig word. Die NPV-reeks vir die volskaalse aseotropiese stelsel is $0.3 miljard – $3.5 miljard. Die NPV-reeks vir die volskaalse ekstraktiewe stelsel is $1.5 miljard – $4.7 miljard. Die IRR-reeks vir die volskaalse aseotropiese stelsel is 1.8 – 19.7%. Die IRR-reeks vir die volskaalse ekstraktiewe stelsel is 11.2 – 34.4%. Die NPV en IRR waardes by die verskillende 1-okteen koste waardes is hoër vir die volskaalse ekstraktiewe stelsel in vergelyking met die volskaalse aseotropiese stelsel. Die IRR van die volskaalse aseotropiese stelsel is hoër as die hinderniskoers by 'n 1-okteen koste waarde van $1500/ton. Die IRR van die volskaalse ekstraktiewe stelsel is hoër as die hinderniskoers by 'n 1-okteen koste waarde van $1300/ton. Hierdie koste ramings is van toepassing vir die jaar 2023. Daarom, vir 'n voer tempo van 60 ton/h wat goed-verteenwoordigend is van tipiese vloeitempo’s in die bedryf, binne die beperkings van hierdie studie, word die volskaalse ekstraktiewe stelsel bo die aseotropiese stelsel verkies vir die herwinning van 1-okteen van suurstofverbindings. Masters 2025-04-30T10:23:53Z 2025-04-30T10:23:53Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131947 Stellenbosch University 158 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Fischer-Tropsch process Azeotropic distillation Extractive distillation Separation (Technology) UCTD Van der Vyver, Christiaan Steyn An evaluation of extractive and azeotropic distillation for separation of 1-octene from oxygenates typically produced during Fischer-Tropsch synthesis |
| title | An evaluation of extractive and azeotropic distillation for separation of 1-octene from oxygenates typically produced during Fischer-Tropsch synthesis |
| title_full | An evaluation of extractive and azeotropic distillation for separation of 1-octene from oxygenates typically produced during Fischer-Tropsch synthesis |
| title_fullStr | An evaluation of extractive and azeotropic distillation for separation of 1-octene from oxygenates typically produced during Fischer-Tropsch synthesis |
| title_full_unstemmed | An evaluation of extractive and azeotropic distillation for separation of 1-octene from oxygenates typically produced during Fischer-Tropsch synthesis |
| title_short | An evaluation of extractive and azeotropic distillation for separation of 1-octene from oxygenates typically produced during Fischer-Tropsch synthesis |
| title_sort | evaluation of extractive and azeotropic distillation for separation of 1 octene from oxygenates typically produced during fischer tropsch synthesis |
| topic | Fischer-Tropsch process Azeotropic distillation Extractive distillation Separation (Technology) UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131947 |
| work_keys_str_mv | AT vandervyverchristiaansteyn anevaluationofextractiveandazeotropicdistillationforseparationof1octenefromoxygenatestypicallyproducedduringfischertropschsynthesis AT vandervyverchristiaansteyn evaluationofextractiveandazeotropicdistillationforseparationof1octenefromoxygenatestypicallyproducedduringfischertropschsynthesis |