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.

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.

Exergy analyses are essential tools for the performance evaluation of water desalination and other separation systems, including those featuring membrane distillation (MD). One of the challenges in the commercialization of MD technologies is its substantial heat demand, especially for large scale applications. Identifying such heat flows in the system plays a crucial role in pinpointing the heat loss and thermal integration potential by the help of exergy analysis. This study presents an exergetic evaluation of air-gap membrane distillation (AGMD) systems at a laboratory and pilot scale. A series of experiments were conducted to obtain thermodynamic data for the water streams included in the calculations. Exergy efficiency and destruction for two different types of flat-plate AGMD were analyzed for a range of feed and coolant temperatures. The bench scale AGMD system incorporating condensation plate with more favorable heat conductivity contributed to improved performance parameters including permeate flux, specific heat demand, and exergy efficiency. For both types of AGMD systems, the contributions of the major components involved in exergy destruction were identified. The result suggested that the MD modules caused the highest fraction of destructions followed by re-concentrating tanks.

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.

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. 

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.

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.

The purpose of the project was to evaluate membrane distillation as an alternative separation technology for different water purification applications. Membrane distillation (MD) is a unit operation that uses water repellent (hydrophobic) membranes as a barrier for contaminated water. The driving force for the process is the vapor pressure over the membrane achieved by applying temperature differences between a warm and a cold side. The process takes place at temperatures below 100 °C and at ambient pressure. Pilot studies were performed at Hammarby Sjöstadsverk to test the separation of pharmaceutical residues from municipal wastewater after biological treatment as well as final treatment of flue gas condensate. In both cases, most target compounds were separated to a very high degree, often more than 90 %. The project also included energy studies that showed some potential for energy optimisation of the current equipment and provided input for energy efficient set-up, e.g. by using waste heat such as the return flow from district heating. Varying results for the single modules also indicated optimisation potential. The project was performed in cooperation between IVL Swedish Environmental Research Institute, Xzero AB as technology provider, and KTH (Royal institute of technology) for energy studies

In this study, membrane distillation pilot plant facility powered by district heating is considered for removal of drug residues from treated waste water and flue gas condensate treatment. The system consists of five pairs of air gap-MD modules. Three different cases were considered based on the configuration of the MD system in the district heating network. The test results showed that the MD process removes all except two from above thirty five drug residues tested, to below detection limits of the analytical method. The corresponding permeate rate, specific thermal energy consumption, and finally the membrane area required for an anticipated production capacity of 10m³/h were estimated and compared for the cases considered. Concentration tests were also done to get higher amounts of the compounds of interest, with up to 20 times concentrations. Treatment of flue gas condensates from a combined heat and power plant was also done to overcome problems (from previous study) of high permeate pH due to ammonia escape through membrane. Results showed that acidifying the feed sample made it possible to control ammonium slipping through the membrane in to permeate. Removal efficiency of other contaminants was also analysed.