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  • 1.
    Kullab, Alaa
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Desalination using Membrane Distillation: Experimental and Numerical Study2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Desalination has been increasingly adopted over the last decades as an option, and sometimes as a necessity to overcome water shortages in many areas around the world. Today, several thermal and physical separation technologies are well established in large scale production for domestic and industrial purposes.  Membrane distillation is a novel thermally-driven process that can be adapted effectively for water desalination or water treatment in industrial applications, due to its potential lower energy consumption and simplicity.

    The general objective of this thesis is to contribute to the technical understanding of membrane distillation as a new technology in water treatment for both industrial and drinking water purposes, as a starting point for further improvement. The thesis includes experimental and numerical investigations that highlight some aspects of the technology application and fundamental aspects.

    In the field of industrial application, an experimental and numerical assessment has been carried out on an Air Gap Membrane Distillation (AGMD) prototype to assess the utilization of the technology in thermal cogeneration plants; in particular, demineralization of water boiler feed water and treating flue gas condensate. The main assessment parameters were water quality and energy consumption. The results from full-scale simulations of a system of 10 m3/hr production capacity,  connected to the district heating network were as follows: 5 to 12 kWh/m3 specific thermal energy consumption, and  0,6 to 1,5 kWh/m3 specific electricity consumption, depending upon the heat source (district heat supply line or low-grade steam).

    For desalination applications, experimental and simulation work was conducted on an AGMD semi-commercial system as part of the EU MEDESOL project. The aim was to evaluate AGMD performance with saline water of 35 g/l NaCl in order to establish an operation data base for simulation of a three-stage AGMD desalination system. Specific thermal energy consumption was calculated as 950 kWht/m3 for a layout without heat recovery, and 850 kWht/m3 for a layout with one stage heat recovery.  The lack of internal heat recovery in the current MD module means that most of the heat supplied to MD system was not utilized efficiently, so the thermal energy consumption is high. This would mean that a large solar field is needed.

    In order to analyze the flow conditions in feed flow and cooling channels, CFD was used as tool to analyze a spacer-obstructed flow channel for different types of spacer geometrical characteristics: flow of attack angle, spacer to channel thickness ratio, and void ratio. Velocity profiles, shear stress, and pressure drop were the main assessment criteria. Results show the flow of attack angle has a very minimum effect on the performance of spacers. The effect of spacer to channel thickness ratio was significant in all assessment parameters. Higher void ratios were found advantageous in promoting flow mixing, but resulted in lower sheer stress and hence reduced heat transfer.

    Physical modifications were implemented on a semi-commercial AGMD prototype to assess experimentally any improvement in its performance. These modifications were mainly focused on reducing the conductive heat transfer losses by modifying the physical support in the air gap that separates the membrane from the condensation surface. In addition, several feed channel spacers were tested and assessed based on their effect in increasing the mass transfer while maintaining or reducing pressure drop. The modifications yielded a two-fold augmentation: slight increase in the distillate mass flow rate (9-11%), and increased thermal efficiency (6%). The pressure drop in the module was reduced by 50% through selecting the appropriate spacer that would achieve the above mass flow rate increase.

  • 2.
    Kullab, Alaa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fakhrai, Reza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    CFD Analysis of Spacer-Obstructed Channels in Membrane DistillationManuscript (preprint) (Other academic)
    Abstract [en]

    Spacers are used in desalination and filtration technologies to enhance the hydrodynamic conditions in flow channels, as well as to provide support and separation of membrane sheets. This paper present the main results of computational fluid dynamics (CFD) simulation for flow in spacer-obstructed flow channel for application in membrane distillation (MD). Flow of attack angle, spacer-to-channel thickness and void ratio were the main geometrical parameters that were studied; velocity profiles, shear stress and pressure drops were the main assessment criteria used for evaluation. Results show the flow of attack angle has a very minimum effect on the performance of spacers. The effect of spacer to channel thickness ratio was significant in all assessment parameters. Higher void ratios were found advantageous in promoting flow mixing, but resulted in lower sheer stress and reduced trans-membrane flux. In practice, the selection of the best case would include a trade-off between the cost of membranes needed to produce the required production and pumping.

  • 3.
    Kullab, Alaa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fakhrai, Reza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental evaluation of a modified air-gap membrane distillation prototype2013In: Desalination and Water Treatment, ISSN 1944-3994, E-ISSN 1944-3986, Vol. 51, no 25-27, p. 4998-5004Article in journal (Refereed)
    Abstract [en]

    Modifications were implemented on a semi-commercial air-gap membrane distillation prototype to assess experimentally any improvement in its performance. The main changes were in the air-gap domain with focus on reducing the conductive heat transfer losses by reducing the physical support that separates the membrane from the condensation surface. Moreover, several feed channel spacers were tested as well and assessed based on their effect in increasing the mass transfer and imposed pressure drop. Results show that the modifications increased slightly the distillate mass flow rate by 9-11% and reduced the conductive heat losses by 20-24%. Spacer effect was found to be mainly in imposed pressure drop within the tested types.

  • 4.
    Kullab, Alaa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Liu, Chuanfeng
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew R.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Solar desalination using membrane distillation: Technical evaluation case study2005In: Proceedings of the Solar World Congress 2005: Bringing Water to the World, Including Proceedings of 34th ASES Annual Conference and Proceedings of 30th National Passive Solar Conference, 2005, p. 2732-2737Conference paper (Refereed)
    Abstract [en]

    Membrane distillation (MD) is a promising desalination technology offering advantages of robustness, scalability, and improved environmental performance as compared to established methods. The aim of this research is to explore the potential of a small scale or stand-alone MD desalination system. The system under consideration consists of an air-gap membrane distillation (AGMD) unit integrated with non-concentrating solar thermal collectors. Scale-up of the MD unit was accomplished via experimental data obtained from an AGMD test facility, and trials were conducted with various feedstock TDS levels, temperatures, and flow rates. Laboratory data obtained from these and other studies demonstrate that MD unit performance is relatively insensitive to variations in feedstock qualities (e.g. pH, TDS levels). Solar data gathered from a case study (Gaza, Palestine) was employed in system simulations. The analysis shows that the system is capable of producing up to 8.5m3/hr of high quality water (< 10 ppm TDS). The power consumption was 150 kWh/m3 (with primary heat recovery), pointing to the need for further studies in ways to utilize low-grade waste heat.

  • 5.
    Kullab, Alaa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental Evaluation of a Modified Air-gap Membrane Distillation Semi-Commercial PrototypeIn: Desalination, ISSN 0011-9164, E-ISSN 1873-4464Article in journal (Other academic)
    Abstract [en]

    Modifications were implemented on a semi-commercial Air Gap Membrane Distillation prototype to assess experimentally any improvement in its performance. These modifications were many focused on reducing the conductive heat transfer losses by reducing the physical support in the air gap that separate the membrane from the condensation surface. Several feed channel spacers were tested as well and assessed based in their effect in increasing the mass transfer and imposed pressure drop. Results show that the modifications increased slightly the distillate mass flow rate by 9-11 % and reduced the conductive heat losses by 20-24 %. Spacer effect was found to be mainly in imposed pressure drop within the tested types.

  • 6.
    Kullab, Alaa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Membrane Distillation and Applications for Water Purification in Thermal Cogeneration: Pilot Plant Trials2007Report (Refereed)
  • 7.
    Kullab, Alaa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Membrane distillation and applications for water purification in thermal cogeneration plants2011In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 76, no 3, p. 231-237Article in journal (Refereed)
    Abstract [en]

    Water treatment is an important auxiliary process in all thermal cogeneration plants. In this context membrane distillation (MD) is a novel technology that has potential advantages in: the ability to utilize low-grade heat instead of electricity; reduced sensitivity to fluctuations in pH or salt concentrations. This research is a continuation of a previously conducted theoretical study where the performance of MD-based water treatment was explored via laboratory testing, system simulations of thermodynamic performance, and economic evaluations. The current paper, encompassing field trials, contains details of a test rig deployed at Idbacken Cogeneration Facility (Nykoping, Sweden) with a five-module MD unit capable of producing 1-2 m(3)/day purified water. District heating supply line was employed for heating while municipal water was used for cooling; feed stocks include municipal water and flue gas condensate. A long-term performance evaluation including thorough chemical testing of product water quality is presented. (c) 2010 Elsevier B.V. All rights reserved.

  • 8.
    Kullab, Alaa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Guillen-Burrieza, Elena
    CIEMAT-Plataforma Solar de Almeria SPAIN.
    Experimental and Simulation of an Air Gap Membrane Distillation SystemIn: Desalination, ISSN 0011-9164, E-ISSN 1873-4464Article in journal (Other academic)
    Abstract [en]

    This paper covers the details and results of experimental and simulation work carried on an Air Gap Membrane Distillation (AGMD) unit, as a part of EU MEDESOL research project. The aim of the experimental work, carried out during a two-week period, was (a) to evaluate the MD performance with saline water (35 g/l NaCl)  establishing an operation data base, and (b) to conduct a system simulation for the design and evaluation of a three-stage MD desalination system. Experimental results shows that production was 30-40% less in the case of using 35 g/l salinity compared with 1 g/l.  Experimental-based simulations of a three step MD system of two arrangement layout were employed to assess the heat demand. Specific thermal energy consumption was calculated as 950 kWht/m3 for a layout without heat recovery, and 850 kWht/m3 for the layout with one stage heat recovery.

  • 9.
    Woldemariam, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Khan, Ershad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kullab, Alaa
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    District Heat-Driven Water Purification Via Membrane Distillation: New possibilities for applications in various industrial processes2016Report (Refereed)
    Abstract [en]

    Water purification is an important separation process that can be found in various industrial applications. Process water quality varies between applications, but the trend of increased reuse or recycling of process streams in combination with stricter emission regulations lead to additional needs for water purification in the future. Membrane technology such as reverse osmosis, ultrafiltration and nanofiltration are often employed. However even if these technologies are mature there is still a need to explore alternatives that can lead to more robust performance, lower energy consumption, reduced environmental effects, and lower costs. Membrane Distillation (MD) is such an alternative. The process is heat driven and can be paired up with district heating when a high degree of purity is desired.The purpose of this project is to develop MD’s role within a district heating perspective. The following three sub-goals have been investigated:Sub-goal

    Sub-goal 1 considered a mapping of water purification in relevant industrial processes. Various possible application areas were identified, including treatment of flue gas condensate, ultrapure water, processes in the food industry, reconcentrating, desalination, and others. Three case studies with relevance to MD driven by district heating were identified for further analysis.Sub-goal 2 encompassed system analyses and optimization studies for the particular case studies:

    • Wastewater treatment at Astra Zeneca in Södertälje. It is theoretically possible to place MD between the district heating network and end users in order to achieve advanced treatment for a smaller wastewater line. The district heating demand would increase by about 7-13%, and costs (excluding retrofitting) are estimated to increase by 60% compared to the available treatment method (activated carbon).• Reconcentrating of ethanol from CO2 scubber water at Agroetanol inNorrköping. The concept involves off-loading of the distillation column via introduction of MD technology. Exchange between steam (distillation column) and district heating (MD system) is roughly balanced which implies significant cost savings potential with MD.• Water purification and reconcentrating at Arla Foods, Kalmar facility. A poor thermal integration yields a high district heating demand for MD in this particular application.For sub-goal 3 experimental investigations were conducted for two MD prototypes. A newer generation of MD prototype showed a marked reduction in heat losses with increase in yield, which in turn leads to lower energy demand.

  • 10.
    Woldemariam, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kullab, Alaa
    KTH.
    Khan, Ershad Ullah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    District heating-driven membrane distillation in industrial-scale bioethanol production: Techno economic study2016Conference paper (Refereed)
    Abstract [en]

    In this study, membrane distillation integrated with district heating network has been investigated for applications in a bioethanol production plant. The specific application considered was recovery of ethanol from CO2 scrubber water, where the main objective of this study was to develop an air gap membrane distillation system that is driven by heat from district heating network, to offload the distillation column. Experiments on membrane distillation lab unit along with data from the industry were used to assess the technologic and economic feasibilities of this system. Comparisons were also made between the distillation columns and membrane distillation units in terms of heat demand and economic savings. Results of the study showed that MD can be a competitive technology for ethanol concentration depending on availability of low-grade heat like district heating or waste heat.

  • 11.
    Woldemariam, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kullab, Alaa
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Khan, Ershad Ullah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Recovery of ethanol from scrubber-water by district heat-driven membrane distillation: Industrial-scale technoeconomic study2018In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 128, no SI, p. 484-494Article in journal (Refereed)
    Abstract [en]

    Membrane distillation (MD) integrated with a district heating network (DHN) to supply the heat demand has been investigated in a bioethanol production plant (BP). The specific application considered here is ethanol recovery from fermentation off-gas (CO2) scrubber water, where the main objective of this study was to develop an air gap MD system that is driven by heat from DHN, thereby offloading the steam-driven distillation column. Experiments conducted on an MD laboratory facility combined with data from the bioethanol industry were used to assess the technological and economic feasibility of this integrated MD-DHN-BP system. Comparisons were also made between the distillation column and MD units regarding heat demand and economic savings. Results of the study showed that MD could be a competitive technology for ethanol recovery given that low-grade heat such as from district heating network or waste heat is accessible.

  • 12.
    Woldemariam, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kullab, Alaa
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    District heat-driven water purification via membrane distillation: New possibilities for applications in Pharmaceutical Industries2017In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045Article in journal (Refereed)
    Abstract [en]

    Here, we presented a novel industrial application for membrane distillation (MD) in a pharmaceutical production facility’s wastewater treatment plant (WWTP). Two semi-commercial air gap MD module designs (Xzero and Elixir500) were studied for comparison, with experimental results of product yield and heat demand up-scaled for inclusion in system simulations. District heating was considered to drive the 3 m3/h capacity MD process, with heat recovery employed in various process streams and for heating purposes in offices. The selected configurations show a high degree of thermal integration with an increase of yearly district heating purchases of 2-13%. Economic assessments of the full-scale MD system indicate that unit costs of purification would be $1.3/m3 and $7/m3 for Elixier500 and Xzero MD modules respectively. Module heat losses should be considered in the future design of MD systems since the heat demand contributed to up to 77% of the specific costs.

  • 13.
    Woldemariam, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kullab, Alaa
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Membrane distillation pilot plant trials with pharmaceutical residues and energy demand analysis2016In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 306, p. 471-483Article in journal (Refereed)
    Abstract [en]

    In this study, an air gap membrane distillation (AGMD) system at pilot scale is applied for purification of effluent from a municipal wastewater treatment plant. A district heating network (DHN) is considered as a heat source for the membrane distillation system. Removal performance of pharmaceutical residuals, specific heat demand, and economic assessments were analyzed on the membrane distillation plant. Almost all targeted pharmaceutical compounds were removed to a very high degree, often below the method detection limit. The heat requirement for the MD process could be sufficiently supplied by the low-temperature district heating return line. Specific heat demands for the AGMD ranges from 692 to 875 kWh/m3 without heat recovery and as low as 105 kWh/m3 when heat recovery is possible. Different approaches to integrating the MD within the DHN system were analyzed; the advantages and shortcomings of each are discussed with emphasis on the MD system’s capacity requirement and annual heat demand. The thermoeconomic analyses from this study presented the potential for energy optimization regarding heat recovery and module design improvement of the current MD equipment.

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