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6The article has entered in publishing office 13.01.10. Ed. reg. No. 700
Статья поступила в редакцию 13.01.10. Ред. рег. № 700
PHASE SEPARATION BY MODIFIED MICROSIEVES M. Mutter, P. Schwan, M. Traving, K. Becker, W. Backer
Bayer Technology Services GmbH, 51368 Leverkusen, Germany e-mail: peter.schwan@bayertechnology.com
Referred: 26.01.10 Expertise: 31.01.10 Accepted: 06.02.10
Separation of electrolytes and water from organic phases plays an important role in manufacturing processes. Such separation is mostly performed by centrifugation, coalescence, distillation, spray drying or precipitation. This often requires multi-stage acid/alkali washing followed by washing to neutral reaction, which makes the process more expensive because of large quantities of waste water and high cost of chemicals. Power and equipment costs need to be weighed against the improved quality of products. Often a process enhancement in the upstream part will need to be restricted in favor of a larger particle size in order to achieve an acceptable phase separation later on.
In some dispersion systems with small density differences salts are added before their separation in a mixer settler, which will lead to consequent problems in downstream processes.
The separation process described in the article rests upon the hydrophilic/hydrophobic interaction between separated phases and filter materials. Targeted hydrophobization of filters enables withholding of the aqueous disperse phase, including electrolytes, while the organic phase permeates through the filter.
Successes achieved so far in the purification of biodiesel and polymer solutions can also be applied to the petroleum industry and food processing industry.
Keywords: phase separation, microsieves, filter materials, electrolytes, emulsion, hydrophobic membrane.
РАЗДЕЛЕНИЕ ФАЗ С ПОМОЩЬЮ МОДИФИЦИРОВАННЫХ МИКРОСИТ М. Муттер, П. Шван, М. Травинь, К. Беккер, В. Бэккер
Заключение совета рецензентов: 26.01.10 Заключение совета экспертов: 31.01.10 Принято к публикации: 06.02.10
Очистка электролитов и воды от органической фазы играет важную роль в технологических процессах. Такое разделение в основном осуществляется с помощью центрифуг, методами коагуляции, дистилляции, распылительной сушки или осаждения. Это зачастую требует использования многоступенчатой кислотной или щелочной промывки до нейтральной реакции, что удорожает технологию из-за большого объема сточных вод и дороговизны реагентов. При этом необходимо сопоставлять увеличение расходов на энергию и оборудование с повышением качества продукции. Зачастую усовершенствованием технологии на начальных стадиях приходится жертвовать в пользу большего размера частиц для достижения приемлемого разделения фаз на последующих стадиях.
В некоторые дисперсные системы с небольшой разницей в плотностях перед их разделением в смесителях-осадителях необходимо вводить соли, что ведет к возникновению трудностей при последующей обработке.
В основе процесса разделения, представленного в данной статье, лежит гидрофильное или гидрофобное взаимодействие между разделяемыми фазами и фильтрующими материалами. Придание фильтрам заданных гидрофобных свойств позволяет удерживать водную дисперсную фазу, включая электролиты, в то время как органическая фаза проходит через фильтр.
Достигнутые на сегодняшний день успехи в очистке биодизельного топлива и полимерных растворов также можно применять в нефтеперерабатывающей и пищевой промышленности.
Ключевые слова: разделение фаз, микросита, фильтрующие материалы, электролиты, эмульсия, гидрофобная мембрана.
Martina Mutter studied Process and Environmental Technology at the University of Applied Sciences in Offenburg (Germany 1996-2000) and received her Diploma in Process and Environmental Technology also from this University after joining Bayer AG for 6 month doing the Diploma Thesis about Membrane Adsorber Technology (Leverkusen, Germany 2000-2001). In April 2001 she joined former Bayer AG, today's Bayer Technology Services GmbH in the Competence Center of Chromatography, Extraction and Membrane Technology (Leverkusen, Germany). There she is doing process development research in the fields of membrane technology combined with bio technology, as well as nanofiltration with organic solvents, or as described in the article phase separation with coated membranes/sieves. In 2007 she also started getting a deeper insight in solid/liquid extraction of plant materials (e.g. vegetables or wood).
Martina Mutter
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Michael Traving
Karsten Becker
Peter Schwan
Michael Traving studied Process Technology and Environmental Technology at the University of Kaiserslautern (Germany, 1991-1996). From 1996 to 1999 he did his PhD in Process Technology at the University of Kaiserslautern. In October 1999 Mr. Traving joined the extraction group of the former Bayer AG, today's Bayer Technology Services GmbH. In 2002 he took over a new position in the membrane group in the Competence Center of Chromatography, Extraction and Membrane Technology (Leverkusen, Germany). In 2004 he developed new technologies for pharmaceuticals formulation for 2 years. 2006 Mr. Traving resumed his work in the membrane technology group. He is doing process development research in the fields of membrane technology (gas separation, phase separation and new separation technology using membranes). In 2008 he took over the responsibility of the pilot plants of Bayer Technology Services GmbH.
Karsten Becker studied Process Engineering at the University of Clausthal (Germany, 1993-1999) and received his Diploma in Process Engineering from this University after joining the Knoll AG for 6 months doing his Diploma Thesis about Simulation and Start-up Assistance of a 2-stage Evaporation Unit in combination with a Rectification.
In October 1999 he joined former Bayer AG, today Bayer Technology Services GmbH in the Competence Center of Chromatography, Extraction and Membrane Technology (Leverkusen, Germany). He is working on the field of unit operation liquid-liquid extraction and liquid-liquid phase separation. His focus is on process development and operational support for production plants. Joining a job rotation program he worked from 2005-2008 in the Engineering Department for active pharmaceutical ingredients of Bayer Technology Services GmbH (Wuppertal, Germany). Since 2008 he is working as specialist for the unit operation extraction technology.
Peter Schwan studied Chemical Engineering at the University of Karlsruhe (Germany, 1990-1996). From 1996 to 2000 he did his PhD in Catalysis at the University of Cape Town (South Africa). In April 2001 he joined the Bayer AG Competence Center of Chromatography and Extraction in Leverkusen. His focus was in the field of chromatography, i.e. Simulated-Moving-Bed Chromatography and Chromatography in biotechnology. From 2005-2005 he joined the Supply Chain Optimization group of Bayer Technology before he worked as Principal Engineer in the Process Technology group of BayerHealthCare, Berkeley (USA) from 2005-2007. In 2007 he rejoined the Bayer Technology Services competence center for Chromatography, Extraction and Membrane Technology with a special interest in membrane and phase separation technology.
Werner Bäcker studied Process and Environmental Technology at the Fachhochschule of Cologne and received his Diploma in Process Technology in 1976. In August 1976 Mr. Bäcker started working in extraction at the Bayer department of Process Technology. In April 2001 he joined former Bayer AG, today's Bayer Technology Services GmbH in the Competence Center of Chromatography, Extraction and Membrane Technology (Leverkusen, Germany).
Mr. Bäcker is an expert in all fields of extraction and phase separation.
Since 2005 he is head of the Competence Center of Chromatography, Extraction and Membrane Technology.
Werner Bäcker
Introduction
Separation of electrolytes and water from organic phases plays an important role in manufacturing processes. Such separation is mostly performed by centrifugation, coalescence, distillation, spray drying or precipitation. This often requires multi-stage acid/alkali washing followed by washing to neutral reaction, which makes the process more expensive because of large quantities of waste water and high cost of chemicals. Power and equipment costs need to be weighed against
the improved quality of products. Often a process enhancement in the upstream part will need to be restricted in favor of a larger particle size in order to achieve an acceptable phase separation later on
In some dispersion systems with small density differences salts are added before their separation in a mixer settler, which will lead to consequent problems in downstream processes.
The separation process described below rests upon the hydrophilic/hydrophobic interaction between separated phases and filter materials (Fig. 1). Targeted
International Scientific Journal for Alternative Energy and Ecology № 4 (84) 2010
© Scientific Technical Centre «TATA», 2010
М. Муттер, П. Шван, М. Травинь и др. Разделение фаз с помощью модифицированных микросит
hydrophobization of filters enables withholding of the aqueous disperse phase, including electrolytes, while the organic phase permeates through the filter.
This membrane phase separation is known in literature for oil/water dispersions, however, successes achieved so far in the purification of biodiesel and polymer solutions can also be applied to the petroleum industry and food processing industry [1-5].
Materials
In addition to hydrophobicity with a sufficient contact angle, filter materials involved in the process should possess high chemical resistance, i.e. resistance to solvents generally at < 70 °C and pH 0-14.
Fig. 3 gives an overview and first evaluation of membranes available on the market. While ceramic membranes are considered the most chemical stable membranes, they lack stability at very high pH, which are commonly found after hydroxide catalyst reaction process. At the same time they have lower permeate fluxes and are more expensive than polymer materials. PP-Membranes are excellent phase separation but lack thermal and chemical stability. However, PP-membranes were successfully used with chlorobenzene and methylene chloride at ambient temperatures. Fluxes here are commonly at 50-100 l/(hm2)
Fig. 1. Phase Separation on a hydrophobic membrane Concept
Fig. 2 shows the concept of phase separation as a hybrid process. Fine dispersion systems or emulsions, such as water in oil (W/O), are separated by means of hydrophobic filters; the continuous organic phase leaves the filter as a stream of highly pure product. This process uses cross-flow filtration. Commonly the required transmembrane pressure ranges between 1-2 bar. The residual concentrated aqueous phase is separated from the organic residue in a smaller settler connected next in line and passed to the next stage. The residue of the organic product solution and the aqueous component is recirculated to the feed stream.
The residual content of water depends on the physical solubility in water. Electrolytes are correspondingly withheld with the aqueous phase. Variations in the product quality are excluded.
Fig. 2. Process Concept of phase separation
Fig. 3. Membrane Selection diagram
Along with commonly used materials, such as polypropylene microfilter membranes, one also uses hydrophobised ceramic membranes.
Outstanding results can also be obtained with coated ultrahydrophobic sieves. In this case, sieves from steel 1.4404 are coated with 5% PTFE dispersion 30-N.
The fluxes were usually 10 to 100 times higher than the PP-membrane with only a slight decrease of selectivity.
Results
The hybrid process was tested on different solvent systems. The test systems included polymer solutions with chlorobenzene and methylene chloride, biodiesel, polyols as well as different product streams with toluene and hydroxylated aromatics, see Fig. 4 for the polyol test system. The membranes were required to remain stable at temperatures of at least up to 60 °C and extreme pH values. In all cases, water separation from the product solution was restricted only by physical solubility. For example, in one polymer solution, the salt content of the
Международный научный журнал «Альтернативная энергетика и экология» № 4 (84) 2010 © Научно-технический центр «TATA», 2010
product stream was reduced from 1 wt% to <5 ppb. As a result, in this case, multi-stage washing can be replaced by single-stage separation. In addition to the decrease in equipment costs, the process makes it possible to reduce the cost of waste water treatment and chemicals.
b c
Fig. 4. a - feed emulsion; b - clear organic product solution after passage through the sieve, salt-free and waterless; c - aqueous phase, including salt and organic residue
Results Biodiesel phase separation
Sample Nr. 1 2 3
Feed pressure bar 0.76 0.8 0.82
Feed temp. °C 31.3 31.6 32.8
Permeation rate kg/m2h 94 108 117
Glycerin-phase in feed wt% 5.7 9.5 11.8
Glycerin-phase in permeate wt% n.a n.a n.a
Solvated glycerin in permeate wt% 0.01 0.01 0.02
Water in feed wt% 0.17 0.18 0.2
Water in permeate wt% 0.06 0.06 0.08
Acidity in feed mg HCl/kg 1657 2433 3498
Acidity in permeate mg HCl/kg 335 371 408
As opposed to conventional processes, soaps and slimes have no adverse effect on the separation through hydrophobic sieves. This makes it possible to avoid preliminary soap extraction process steps.
Conclusions
- Innovative process for separation from fine dispersion systems and residues.
- Separation of dispersion systems with small density differences.
- Efficient single-stage separation process as an alternative to conventional multi-stage acid and alkali washing.
Saving of washing water, smaller quantities of waste water and chemicals.
- Lower equipment costs.
Whereas surfactants can preclude separation in conventional static phase separators, they do not impair the above-mentioned process. This can be illustrated by the separation of fatty acid methyl ester and electrolyte-containing glycerine phase in biodiesel production. The feed stream results from a base catalyst (KOH) transesterification of rapeseed oil with a 25% KOH-Methanol mixture at 35 °C. The two phase system was separated in the lab over a PP-membrane (ID 5.5 mm, L 250 mm, 0.2 ^m pores). The cross flow velocity was 400 kg/h. The separated permeate is a single-phase with only physically solvated glycerine (< 0.1 wt%) and/or water (< 0,1 wt.%). The results are shown in Table.
References
1. Grabosch M. Verfahren und Vorrichtung zur Trennung von Öl/Wasser Gemischen. Pat. DE 4300438, 1994.
2. Meyer H. et al. Method for the separation of an organic phase from an electrolyte-containing aqueous and organic phase. Pat. WO 2008/049548, 2006.
3. Chmiel H. Verfahren und Vorrichtung zur Emulsionsspaltung. Pat. DE 10215 802, 2002.
4. Traving M. et al. Method for Separating Product Mixtures of Transesterification reactions. WO 2008/119489, 2007.
5. Feng, L. et al. Superhydrophobic and super-oleophilic coating mesh film for the separation of oil and water // Angewande Chemie. 2004. Vol. 116. P. 2046.
International Scientific Journal for Alternative Energy and Ecology № 4 (84) 2010
© Scientific Technical Centre «TATA», 2010
