Spelling suggestions: "subject:"cembrane reactors"" "subject:"5membrane reactors""
11 |
Membrane fouling of activated sludgeShi, Xinlong. January 2004 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.
|
12 |
Transport of gases across membranesMokrani, Touhami January 2000 (has links)
Thesis (MTech (Chemical Engineering))--Peninsula Technikon, 2000. / Oxygen transport across biofilms and membranes may be a limiting factor in the
operation of a membrane bio-reactor. A Gradostat fungal membrane bio-reactor is one in
which fungi are immobilized within the wall of a porous polysulphone capillary
membrane. In this study the mass transfer rates of gases (oxygen and carbon dioxide)
were investigated in a bare membrane (without a biofilm being present). The work
provides a basis for further transport study in membranes where biomass is present.
The diaphragm-cell method can be employed to study mass transfer of gases in flat-sheet
membranes. The diaphragm-cell method employs two well-stirred compartments
separated by the desired membrane to be tested. The membrane is maintained
horizontally. -The gas (solute) concentration in the lower compartment is measured versus
time, while the concentration in the upper liquid-containing compartment is maintained at
a value near zero by a chemical reaction.
The resistances-in-series model can be used to explain the transfer rate in the system. The
two compartments are well stirred; this agitation reduces the resistances in the liquid
boundary layers. Therefore it can be assumed that in this work the resistance in the
membrane will be dominating.
The method was evaluated using oxygen as a test. The following factors were found to
influence mass transfer coefficient: i) the agitation in the two compartments; ii) the
concentration of the reactive solution and iii) the thickness of the membrane.
|
13 |
A perfluorocarbon-based oxygen delivery system to a membrane bioreactor /Ntwampe, Seteno Karabo Obed. January 2009 (has links)
Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2009. / Includes bibliographical references. Also available online.
|
14 |
Pretreatment and enzymatic hydrolysis of lignocellulosic materialsCheng, Wei, January 2001 (has links)
Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xii, 173 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 138-142).
|
15 |
Hybrid neural networks models for a membrane reactorAl-Yemni, Mohammed. January 1900 (has links)
Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xiii, 112 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 92-94).
|
16 |
Trihalomethane formation in contaminated surface water and its controlby membrane bio-reactorChu, Hiu-ping., 諸曉平. January 2003 (has links)
published_or_final_version / abstract / toc / Civil Engineering / Doctoral / Doctor of Philosophy
|
17 |
A perfluorocarbon-based oxygen delivery system to a membrane bioreactorNtwampe, Seteno Karabo Obed January 2009 (has links)
Thesis submitted in fulfilment of the requirements for the degree
DOCTOR TECHNOLOGIAE: ENGINEERING: CHEMICAL
In the
FACULTY OF ENGINEERING
At the
CAPE PENINSULA UNIVERSITY OF TECHNOLOGY
2009 / The white rot fungus, Phanerochaete chrysosporium strain BKMF-1767 (ATCC 24725),
produces the extracellular enzymes, Lignin peroxidase (LiP) and Manganese peroxidase
(MnP), that constitute the major route for lignin degradation by this organism. LiP and MnP
have also been shown to play a major role in aromatic pollutant degradation. Due to the need
for continuous production of LiP and MnP, a fixed-film bioreactor, classified as a membrane
gradostat reactor (MGR), was developed. The implementation of batch-reactor operational
parameters to the MGR system was found to be ineffective, thus creating the need for further
research to improve the operational aspects of the MGR system to optimise its capabilities
for continuous and industrial-scale operations. The research undertaken in this study,
provides information that can be used to classify the dissolved oxygen (DO) transport
kinetics into immobilised fixed-films of P. chrysosporium. Operational limitations of the MGR
relating to environmental stresses in the bioreactor during operation and to biofilm
deterioration, including limitations of DO mass transport, oxidative stress, trace element
accumulation and polysaccharide storage in the fungal biomass, were evaluated in single
capillary MGR systems (SCMGRs). These conditions were identified as existing in the
continuous MGR systems.
From DO profiles, the oxygen consumption and flux into the biofilms, including the
distribution of DO, was determined to be dependent on the immobilised biofilm’s age.
Younger biofilms showed higher DO distribution than older biofilms even when aeration was
directed to the extracapillary space (ECS) of the reactor against the biofilm’s surface. An
increase in anaerobic zone thickness was observed to be increasing with an increase in
biofilm thickness. Although, DO kinetic parameters were comparable with those obtained in
submerged mycelia pellets, higher oxygen consumption values were observed in biofilms
grown in the SCMGRs. The limitations of MGR were identified as: 1) poor DO distribution in
immobilised biofilms because of b-glucan production and storage in the immobilised
biomass, resulting in ethanol production; 2) the peroxidation of lipids of the biofilms, which in
turn will affect the long-term performance of the biomass caused by oxygenation and 3) trace
element ion accumulation enhanced by b-glucan production. Furthermore, trace element ion
accumulation was higher in the MGRs than in batch cultures using the same nutrient
medium.
The development of a perfluorocarbon (PFC) emulsion for the MGRs to counteract these
limitations was investigated. The compatibility of the emulsion with oxygen-carrying capacity
was shown with an improvement in biomass generation, LiP/MnP production and overall
consumption of primary substrates, mainly glucose and ammonium tartrate, in batch cultures.
The emulsions investigated were based on the addition of oxygen carriers: Perfluorooctyl
bromide (PFOB), Bis-(Perfluorobutyl) ethene (PFBE) and Perfluoropropylamine (PFPA),
using Pluronic F 68 (PF 68) as the surfactant. Concentrations of 10 to 30% (w/v) PFC and
8.5% (w/v) PF 68 were tested successfully in batch cultures. The emulsions containing
10% (w/v) PFCs resulted in improved biomass performance as opposed to emulsions with
higher PFC oil concentrations. An emulsion containing 10% (w/v) PFOB was used to
evaluate its efficacy in the SCMGRs, as the biomass yield and overall enzyme production
were superior to PFPA and PFBE-based emulsions with similar oil concentrations. After
successfully applying PFOB and PF 68 to the SCMGRs, the following results were obtained:
1) reduced ethanol production; 2) reduced trace element accumulation; 3) lower b-glucan
production and 4) improved DO-penetration ratio in immobilised biofilms.
|
18 |
Development and evaluation of woven fabric immersed membrane bioreactor for treatment of domestic waste water for re-useCele, Mxolisi Norman January 2014 (has links)
Submitted in fulfillment of the academic requirements for the Master’s Degree in Technology: Chemical Engineering, Durban University of Technology. Durban. South Africa, 2015. / Increased public concern over health and the environment, the need to expand existing wastewater treatment plants due to population increase, and increasingly stringent discharge requirements, have created a need for new innovative technologies that can generate high quality effluent at affordable cost for primary and secondary re-use. The membrane biological reactor (MBR) process is one of the innovative technologies that warrant consideration as a treatment alternative where high quality effluent and/or footprint limitations are a prime consideration.
MBR processes have been applied for the treatment of industrial effluent for over ten years (Harrhoff, 1990). In this process, ultrafiltration or microfiltration membranes separate the treated water from the mixed liquor, replacing the secondary settling tanks of the conventional activated sludge process. Historically, energy costs associated with pumping the treated water through the membranes have limited widespread application for the treatment of high volumes of municipal wastewater. However, recent advancements and developments in membrane technology have led to reduced process energy costs and induced wider application for municipal wastewater treatment (Stephenson et al., 2000). This report describes a small and pilot scale demonstration study conducted to test a woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) process for use in domestic wastewater treatment. The study was conducted at Durban Metro Southern Wastewater Treatment Works, Veolia Plant, South Africa.
The main objective of this project was to develop and evaluate the performance of an aerobic woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) for small scale domestic wastewater treatment. The experiments were oriented towards three sub objectives: to develop the membrane pack for immersed membrane bioreactor based on WF microfilters; to evaluate the hydrodynamics of WF membrane pack for bioreactor applications; and to evaluate the long-term performance and stability of WFM-IMBR in domestic waste water treatment.
The literature was reviewed on membrane pack design for established commercial IMBR. The data collected from literature was then screened and used to design the WF membrane pack. Critical flux was used as the instrument to measure the WF membrane pack hydrodynamics. Long-term operation of the WFM-IMBR was in two folds: evaluating the performance and long term stability of WFM-IMBR.
The membrane pack of 20 flat sheet rectangular modules (0.56 m by 0.355 m) was developed with the gap of 5 mm between the modules. The effects of parameters such as mixed liquor suspended solids or aeration on critical flux were examined. It was observed that the critical flux decreased with the increase of sludge concentration and it could be enhanced by improving the aeration intensity as expected and in agreement with the literature. Hence the operating point for long term subcritical operation was selected to be at a critical flux of 30 LMH and 7.5 L/min/module of aeration.
Prior to the long term subcritical flux of WFM-IMBR, the operating point was chosen based on the hydrodynamic study of the WF membrane pack. The pilot scale WFM-IMBR demonstrated over a period of 30 days that it can operate for a prolonged period without a need for cleaning. Under subcritical operation, it was observed that there was no rise in TMP over the entire period of experimentation. Theoretically this was expected but it was never investigated before. Good permeate quality was achieved with 95% COD removal and 100% MLSS removal. The permeate turbidity was found to be less than 1 NTU and it decreased with an increase in time and eventually stabilized over a prolonged time.
Woven fibre membranes have demonstrated great potential in wastewater treatment resulting in excellent COD and MLSS removal; low permeate turbidity and long term stability operation. From the literature surveyed, this is the first study which investigated the use of WF membranes in IMBRs. The study found that the small scale WFM-IMBR unit can be employed in fifty equivalence person and generate effluent that is free of suspended solids, having high levels of solid rejection and has acceptable discharge COD for recycle.
Future work should be conducted on energy reduction strategies that can be implemented in WFM-IMBR for wastewater treatment since high energy requirements have been reported by commercial IMBRs.
|
19 |
Evaluation and improvement of dehydrogenation conversion and isomerization selectivity in an extractor Catalytic Membrane ReactorVan Dyk, Lizelle Doreen 03 1900 (has links)
Thesis (PhD (Process Engineering))--University of Stellenbosch, 2006. / Recent advances in inorganic material preparation for membrane fabrication have
extended the use of membranes to high temperature and chemically harsh environments.
This has allowed inorganic membranes to be integrated into catalytic reactors, resulting in
the concept known as Catalytic Membrane Reactors (CMRs). CMRs have overall
important benefits of product quality, plant compactness, environmental impact reduction
and energy savings. It has found use in a broad range of applications including
biochemical, chemical, environmental and petrochemical systems. In these CMRs, the
membranes perform a variety of functions, and consequently they are categorized
according to the primary role of the membrane: extractor, distributor or contactor.
In this dissertation the different uses of an extractor Catalytic Membrane Reactor
(eCMR) are evaluated with the help of model reactions. In the eCMR the primary function
of the membrane is to selectively extract one of the reaction products from the reaction
zone, thereby combining the benefits of separation and reaction in one unit operation. This
can lead to a number of advantages, of which the two most important ones include: (a)
conversion beyond thermodynamic equilibrium in equilibrium restricted reactions and/or
(b) the improvement of product selectivity in consecutive/parallel reaction networks.
The dehydrogenation of isobutane, an equilibrium restricted reaction, was
evaluated in a dense Palladium and a MFI-zeolite/alumina composite eCMR. These two
eCMRs, consisting of a membrane packed with a Pt/In/Ge-MFI-zeolite catalyst, differed
only on the basis of the membrane used. The palladium membrane showed superior
extraction and selectivity capability for hydrogen in the reaction mixture compared to the
MFI/alumina composite membrane. Regardless of these facts, the performances of the Pd
and MFI eCMR, when evaluated at the same reaction conditions, were similar. The
isobutane conversion to isobutene, employing high sweep rates (185 ml/min) could be
increased up to ca. 37 % at 723 K, compared to 14 % in the conventional packed-bed
reactor. The similar performance of the two different eCMRs was evaluated using a
Catalytic Membrane Reactor model. Model results showed that in order for the extractortype
CMR to completely draw benefit from the combination of membrane and catalyst in
the same unit for conversion enhancement, a very active catalyst should be developed, able
to sustain the high extraction ability of the membrane. This was the first time that these two eCMRs were evaluated at similar reaction conditions in order to study the influence of
the nature of the membrane material on the working of the eCMR.
The eCMR was also used to carry out meta-xylene isomerization. This part
focused on the extraction of para-xylene from the meta-xylene isomerization reaction zone
with a MFI eCMR (MFI-zeolite membrane and Pt-HZSM5 fixed-bed catalyst) in order to
improve the reaction selectivity towards para-xylene. Para-xylene is an important
industrial chemical used as a precursor for polyester resin, and in order to meet the paraxylene
demand, ortho- and meta-xylenes are converted via the xylene isomerization
reaction to xylene isomers.
It has been shown that the pore-plugged MFI-zeolite membranes used in this study
can selectively extract para-xylene from a mixture of xylenes. Using an extractor type
catalytic membrane reactor instead of a conventional fixed-bed reactor for meta-xylene
isomerization, can lead to higher para-xylene selectivities. The para-xylene selectivity can
even be improved to 100% if the CMR is operated in the permeate-only mode, but this
comes at a price of lower para-xylene yields. When operated in combined mode (i.e.
mixing both permeate and retentate streams after the reactor), the CMR shows an
improvement on both para-xylene productivity (ca. 10 % maximum at conditions studied)
and selectivity when compared to the conventional reactor. This is the first time paraxylene
selectivity could successfully be improved by employing an extractor Catalytic
Membrane Reactor.
This dissertation also led to the design and construction of a new generation
membrane reactor testing bench, a first in the Department of Process Engineering,
University of Stellenbosch. The bench allows for high temperature evaluation of
membranes and Catalytic Membrane Reactors. The design is simple and easily adaptable
for use to evaluate various different reactions.
|
20 |
Optimising catalyst and membrane performance and performing a fundamental analysis on the dehydrogenation of ethanol and 2-butanol in a catalytic membrane reactorKeuler, Johan Nico 12 1900 (has links)
Thesis (PhD (Process Engineering))--University of Stellenbosch, 2000. / Stricter government regulations and higher energy costs have forced the chemical industry to focus more on environmentally friendly processes and to reduce energy consumption. The main goals of chemical companies are to obtain a high product yield and selectivity, and to reduce unwanted side products. Furthermore, if ractions can be performed at lower temperature, while maintaining the reaction conversion, it will result in large energy savings. Low termperature dehydrogenation reactions (below 300 degrees C) are very selective and do not produce many by-products, but conversion is limited by the reaction equilibrium. The conversion limitations have resulted in the development of alternative processes in recent years for producing alkenes from alkanes and aldehydes or ketones from alcohols....
|
Page generated in 0.0507 seconds