Gained Output Ratio Research Articles

Superhydrophobic composite asymmetric electrospun membrane for sustainable vacuum assisted air gap membrane distillation

Membrane distillation (MD) relies on superhydrophobic membranes that must achieve the competing goals of high liquid entry pressure (LEP) and high permeability. In this study, we developed the first superhydrophobic composite electrospun asymmetric membrane using fluorinated graphite (FG). We also provided among the first comparisons of the relative benefits of membrane asymmetry and composite coatings via 3D electrospinning and spraying. FG particles increased the roughness and reduced the zeta potential of the membranes. Superhydrophobic composite membranes had a contact angle of 157° (sliding angle of 7°) and an LEP of 327 kPa. Long-term MD testing revealed that FG particles could increase MD's sustainability while decreasing membrane wetting. Vacuum-assisted air gap membrane distillation (V-AGMD) showed that the composite asymmetric membrane outperformed the non-asymmetric version (composite nanofiber) membrane by 21 % in average water flux and 25 % in average thermal efficiency because of the asymmetric structure of the membrane. The numerical model developed for the V-AGMD system also successfully predicted the water flux generated experimentally from the composite nanofiber and composite asymmetric membranes. Our results confirmed that electrospun asymmetric FG membranes with high contact angle, low sliding angle, high permeability, and high gained output ratio (GOR) would be promising candidates for sustainable MD.

Effect of thermal characteristics on the chemical quality of real-brine treatment through hydrophilic fiber-based low-grade heat-powered humidification-dehumidification process

Considering the increasing demand for desalination plants and their byproduct brine, this study investigated a humidification-dehumidification (HDH) system for treating membrane distillation-generated real high-salinity brine using low-grade heat (45–70 ℃) to explore its feasibility for sustainable energy-efficient minimal liquid discharge. A novel super-hydrophilic fabric was adopted for accelerated humidification, and its impact on brine droplet miscarriage characteristics was evaluated. The influence of the operating fluid thermal properties (cycle 1: air preheating; cycle 2: air and brine dual-fluid preheating; and cycle 3: air post-heating after humidification) on the brine treatment efficiency, energy consumption, and chemical quality of freshwater produced was analyzed in detail to establish their characteristic nexus. It was identified that, during humidification, increasing the brine temperature (up to 55 ℃) influenced its ionic mobility, thereby promoting efficient separation of the salts/minerals and contributing to achieving better freshwater quality. Furthermore, although cycle 3 exhibited improved system thermal efficiency (gained output ratio equal to 1.77), its non-preheated air contributed to a negative effect of the reduced humidity ratio (∼17 g/kg), leading to a lower freshwater productivity of 67% than that of cycle 2 (29 g/kg and 70%). The present study also illustrates a novel effect of evaporative deposition occurring due to air-water interaction on the fabric humidifier surface, with an exploration of its effect on reducing freshwater chemical quality. The freshwater generated from optimum thermal cycle 2 exhibited reduced pH (by ∼63%), sodium (99.9%), chloride (99.9%), toxic boron (99.7%), and other chemical contaminants, thereby satisfying the major international water reuse standards.

Applying energy-exergy, environmental, sustainability, and exergoeconomic metrics and bi-objective optimization for assessment of an innovative tri-generation system

One of the reasons why renewable energies are so attractive compared to fossil fuels is their low environmental impact. In addition, geothermal power plants contribute tremendously to sustainable energy generation for cities despite their lower energy efficiency than fossil fuel plants. The multi-heat recovery will eliminate the applicability defect mentioned. Therefore, this paper studies a novel tri-generation schema with the maximum use of heat loss through a multi-heat recovery technique in two principal processes, namely waste heat-to-power and power-to-H2 and -purified water. A double-flash binary cycle, Rankine cycle, electrolyzer unit, and reverse osmosis desalination system all play a part in the creation of this system. The technical feasibility of the system is scrutinized based on energy-exergy, environmental, sustainability, and exergoeconomic metrics and bi-objective optimization. Generally, 1st separator pressure made the strongest effect on the measured variables among decision variables. The increase in this parameter led to an upward-and-downward behavior of the net electricity and exergetic efficiency; while the cost of products experienced a converse trend. Also, the produced H2 and purified water together with the tri-generation gain output ratio augmented. Changes were not observed in net electricity and purified water with the change in 2nd separator pressure, but the H2 production rate changed significantly. Through bi-objective optimization, net electricity, purified water production rate, and total investment cost rate also significantly increase. Based on the optimum design mode, the CO2 emission rate and the sustainability index are higher than under the base case design.

Experimental study of a standalone membrane water desalination unit fully powered by solar energy

In this study, a fully solar-driven water desalination system is designed, fabricated, and tested. The proposed system is designed for remote, isolated areas with limited electricity and freshwater access. For commercial PVDF membranes, the performance of the MD unit is evaluated at various feed temperatures, flow rates, and salt concentrations. In addition, the effect of MD cell design was examined to determine the effect of the obstacles on the feed channel. Increasing the temperature by 20 degrees from 55 to 75 °C enhances productivity by 165 % from 6.2 to 16.4 kg/m2.h. At different operating conditions, the new design of the MD cell with cylindrical obstacles attained higher flux productivity compared to the conventional MD cell design. The maximum attained freshwater output flux was around 15 kg/m2.h at a feed inlet temperature of 65 °C and feed mass flowrate of 66 kg/h for the MD cell with cylindrical obstacles. In the presence of obstacles, a reduction in the specific energy consumption (SEC) by 35–15 % is associated with an increase in the gain output ratio (GOR) by 50–20 % compared to the case of no obstacles. Observations indicate that a small PV module with an area of 0.377 m2 is sufficient to operate the membrane unit for contentious 15 h. Collectively, using solar MD units collectively has the potential to be used for decentralized desalination of water.

Numerical study and experimental validation of a solar powered humidification-dehumidification desalination system with integrated air and water collectors in the humidifier

This paper presents a numerical study and experimental validation of humidification-dehumidification solar desalination unit. This unit consists of a solar evaporator and a tubular condenser. The design particularity of the evaporator is the integration of the humidifier in the solar air and water collectors. A mathematical model based on the heat and mass balances has been developed in the desalination unit. The finite difference method is adopted for discretization of the equations and the resolution is done by MATLAB software. Numerical results are compared with literature and experimental results. An acceptable agreement is observed. A parametric study was conducted to test the influence of the different operating parameters on the unit production and the Gained output ratio GOR. The production of the desalination system increases with air and water temperatures of the water in the evaporator and the inlet humid air temperature at the dehumidifier. It should be noted that the production reaches its maximum value for a feed water mass flow rate in the humidifier of 5.5 kg/h and a cooling water mass flow rate in the dehumidifier of 0.2 kg/s.

Performance evaluation of a novel integrated adsorption desalination system with direct contact membrane distillation plant

Since adsorption desalination (AD) technology has low performance, a hybrid adsorption desalination system with a direct contact membrane distillation plant (AD-DCMD) is proposed for enhanced water production and reduced water cost. In addition to the desalination process, the cooling effect is also produced as a by-product of air conditioning. Two AD-DCMD configurations are investigated, in which the heat released from the AD condenser (configuration 1) and the adsorption process (configuration 2) are utilized to drive the DCMD system. The main performance parameters, such as gain output ratio (GOR), specific daily water production (SDWP), freshwater cost, and coefficient of performance (COP), are investigated. The influential operating parameters are tuned to obtain optimal performance. Results show that GOR values reach 1.48 and 1.6 for configurations 1 and 2, respectively, which is more than the AD system by >117 %. For configuration 2, the SDWP reaches 53 m3/ton per day, higher than the AD system by 136.7 %, at an operating temperature of 90°C. COP was found to be 0.76 and 0.70 for configurations 1 and 2, respectively. Moreover, the freshwater cost of configurations 1 and 2 is 1.72 and 0.92 $/m3, with a reduction of 18.03 and 56.05 %, respectively, compared to the AD system.

Energy and economic performance assessment of a solar-assisted regenerative vacuum membrane desalination system

Vacuum membrane water desalination is a promising technology for freshwater production with the advantages of low conduction heat loss and mass transfer resistance, compared to other membrane technologies. Such systems can be driven by solar thermal collectors for green water production, yet there is a lack of dynamic system simulations in the literature to comprehensively assess the energy and economic system performance and evaluate the impact of brine recirculation as a method of regeneration, especially under hot desert climates where solar resources are abundant, but freshwater resources are scarce (e.g., the northern coast of Egypt, considered as the case study here). In this study, a dynamic system simulation model is developed in TRNSYS, where a new “Type” is introduced for the vacuum membrane module. Initial sizing of the system with ∼20 % solar fraction resulted in annual average gained output ratio and specific thermal energy consumption of 2.51 and 133.5 kWh/m3, respectively, with levelized cost of water and payback period of 14.7 USD/m3 and 1.53 years, respectively. By increasing the solar collectors’ area from 8 to 16 m2, the levelized cost of water increased by 14.54 %. The storage volume was highly influential on the solar fraction, which increased by 101.39 % as the volume increased from 0.3 to 0.7 m3. Increasing the membrane area from 0.3 to 0.5 m2 increased the gained output ratio by 76.75 % while decreasing the levelized cost of water by 14.79 %. Internal heat regeneration through brine recirculation enhanced the system performance at lower recirculation ratios. Without recirculation, the levelized cost of water increased by 117.41 % and the system met the daily distillate water demand for only 90 days of the year.

Thermal optimization research of vertical tube climbing film desalination system

Abstract Based on the pinch theory and energy cascade utilization principle, the performance of a multi-effect shipboard vertical tube climbing film desalination system combined thermal vapor compression with different preheating configuration has been analyzed. The mathematical model is established for thermodynamic simulation, in which various thermodynamic losses caused by boiling point elevation and pressure drop are considered, and the effective heat transfer temperature difference and the hot side temperature difference are used to analyze the influences of heating steam temperature, final effect evaporation temperature, and concentration ratio on thermal performance including gained output ratio (GOR)—specific heat transfer area for different preheating configuration. The results show that the internal average effective heat transfer temperature difference determines characteristics of multi-effect distillation (MED) system. While for system with similar average effective heat transfer temperature, the temperature difference of hot side is the controlling parameter. And the energy cascade utilization principle shows the controlling attribute in MED thermodynamic system, as GOR is improved mainly due to utilization of the secondary energy and residual energy of the heating steam for preheating process.

Energy performance and economic assessments of a solar air collector and compression heat pump-integrated solar humidifier desalination system

This article presents the energy performance and economic assessments of a solar air collector (SAC) and compression heat pump (CHP)-integrated solar humidifier desalination system. The influences of solar heat flux, ambient wind speed and ambient temperature on the energy performance of the system are investigated. The quality of distilled water obtained from the system was assessed. The results showed that the proposed configuration has the maximum distillate output of 22.3 l per day in 14 hours of observations during the summer months. Moreover, the system delivers 100 l of hot water at 46 ± 2°C. The effectiveness of a solar humidifier was raised from 0.16 to 0.97. The coefficient of performance of the CHP was fluctuating between 2.40 and 2.77. The gain output ratio (GOR) was raised from 0.9 to 3.35 during the summer months. The proposed system has a payback duration (PBD) of 27.62 months for 14 hours of operation per day during 252 days in a year. The environmental impact assessments revealed that the system will release 32.35 tons of carbon dioxide emissions during 15 years life span. The quality of water obtained from the system was found to be good and suitable for drinking enriched with minerals.

Seawater Greenhouse Equipped with a Novel Solar Humidification-Dehumidification Desalination Unit in MAKRAN Coast: Fabrication and Experimental Study

The purpose of this study is the fabrication and performance evaluation of a new type of solar humidification–dehumidification (HD) desalination unit to supply sufficient fresh water for a seawater greenhouse in the MAKRAN coast in southeast Iran. In the proposed design, a particular type of air-to-air condenser is used. The cold air coming out of the greenhouse ventilation system (fan and pad) in summer and the cold ambient air in winter is used to supply the required cooling of the system. In this way, when cold air passes over the pipes in air-to-air condensers, condensation of water vapor occurs in the moist air inside the pipes, and fresh water is produced. Greenhouse fans, which have an air flow rate of around 20,000 m3/hr, are used to create this air flow. By fabricating two condensers, each using 42 rows of PVC pipes with a diameter of 75 mm, it is possible to produce 400 L of fresh water per day in a 400 m2 greenhouse. The required heating is provided by the solar farm, which includes 96 square meters of flat plate collectors. The steps of unit fabrication are described in detail in this research. However, the effect of greenhouse air temperature and circulating seawater flow rate on freshwater production, energy consumption, and energy intensity are also investigated. By increasing the flow rate of circulating seawater and decreasing the greenhouse air temperature, the production rate of the system increases. When the hot seawater and greenhouse air temperature are 61.7 °C and 26 °C, respectively, the maximum instantaneous production is estimated to be 80 L/h. The energy intensity of the HD desalination unit is varied between 3192 and 4382 kJ/L, and the gain output ratio of the system is around 0.6. The proposed system can be easily paired with conventional greenhouses employing a fan and pad cooling system and produces around 1.25 (L/m2·day) fresh water.

Evaluation of a heat pump coupled two-stage humidification-dehumidification desalination system with waste heat recovery

Humidification and dehumidification (HDH) desalination technology has attracted wide attention in the field of small-scale dispersed fresh water demand, because of its advantages such as simple configuration, low investment, and utilization of low-grade renewable energy and waste heat. In this paper, a heat pump coupled two-stage humidification-dehumidification desalination system with waste heat recovery is proposed, where the waste heat is used to heat the feed seawater of the first-stage humidifier, and the brine leaving the bottom is further heated by the condenser of heat pump and then taken as the feed of the second-stage humidifier, while the evaporator of heat pump is used to recover the heat of humid air from the first-stage dehumidifier. Performance evaluation of the proposed system with various working fluids are conducted regarding the fresh water production mpw, gained output ratio (GOR), recovery ratio (RR), specific entropy generation stot, and unit cost of fresh water production Zpw, and parametric studies are performed to identify the key operating parameters. Results show that the largest entropy generation occurs in evaporator, followed by the first-stage humidifier and condenser. Taking R22 as the working fluids is corresponding to the largest mpw, while the lowest Zpw and stot, and the highest GOR are obtained by R600. Higher spraying temperature of the first humidifier T4 is conducive to improving the mpw and Zpw, but leading to a larger stot. The GOR increases first and then decreases with the rise of T4, and the peak value is 4.57 at T4 = 340.65 K. The mass flow rate ratio of the first stage MR1 has significant effects on the system performance. When MR1 is about 3.5, the mpw, GOR and RR reach the peak. However, the bottom value of Zpw is 8.74 $/m3 corresponding to the MR1 of 2.2–2.5. With the increase of compression ratio (CR) of heat pump subsystem, the mpw, GOR and RR climb up first and then decrease, while Zpw and stot get raised.

A dual-mode system for water purification and cooling using a thermal desalination technique coupled to a heat pump unit

Humidification-dehumidification is one of the most suitable small-scale desalination methods based on air humidification and condensation. The major energy-consuming components for a humidification-dehumidification process are a heat source for the humidifier and a cooling source for the dehumidifier. To improve the performance of these processes, the fluids were preheated using different energy sources or waste heat. In recent years, preheating air or saline water using heat from a heat pump's condenser has been explored to improve the system's performance and to produce cooling and desalination simultaneously. However, separate heat exchangers and additional solar collectors/heaters were used to preheat the second fluid. In this work, the air-cooled condenser of a heat pump has been replaced by an evaporative condenser and used as a humidifier. This configuration has been scarcely explored in the literature and requires a single heat exchanger to preheat the fluids. On the other hand, the heat pump's evaporator was used to produce low-temperature coolant, circulated through a cooling coil where the humid air from the evaporative condenser is cooled and dehumidified to produce fresh water and cooling simultaneously. This modification ensures reduced space requirement and better system performance than other heat pumps coupled to humidification-dehumidification systems for simultaneous cooling and desalination. Also, the present system operates flexibly to switch between desalination and cooling mode (mode-1) to cooling mode (mode-2). Towards this, a mathematical model of the system has been developed and analyzed under various operating conditions. The system's performance, which includes desalination yield, cooling output, gained output ratio, and coefficient of performance under each mode of operation, is studied for different ambient conditions and evaporator temperatures. The maximum desalination yield, cooling output, gained output ratio, and coefficient of performance of mode-1 are 4.55 LPH, 0.82 kWth, 3.79, and 0.75, respectively. The maximum cooling output and COP of mode-2 are 3.79 kWth and 3.82, respectively. The exergy efficiencies for mode-1 and mode-2 are 32.7 % and 29.7 %, respectively.

Neural networks for predicting air gap membrane distillation performance

The hollow fiber air gap membrane distillation (AGMD) has recently attracted tremendous attention for desalination and wastewater treatment due to its high packing density, low conductive heat loss, and latent heat recovery capability. Utilizing fast and accurate modeling tools to predict MD performance can result in the further development of desalination technologies. However, simple and time-saving prediction models to assess the AGMD performance were not abundant. Herein, AGMD performance, including permeate flux (J) and gained output ratio (GOR) was predicted through multiple linear regression (MLR) model, back propagation neural network (BP ANN) and radial basis function neural network (RBF ANN) under different hot temperatures (Th), coolant temperatures (Tc), feed flow rates (F), and feed concentration (c). A total of 30 sets of data were used to train the proposed models, the other 10 external validation datasets not used for training the models were applied to validate the prediction accuracy. The results depicted that RBF ANN (SPREAD = 30, N = 30) showed greatest prediction performance (R2 = 0.99–1) compared with BP ANN and MLR models (R2 = 0.98–0.99; R2 = 0.89–0.97). The computing time consumption of RBF ANN was higher than BP ANN. According to the Mean impact value (MIV) analysis, Th had the strongest effect on J and GOR. Increasing Th and decreasing c both had positive impacts on J and GOR, but increasing Tc or F resulted in a trade-off influence. A genetic algorithm (GA) was employed to optimize J and GOR simultaneously, the optimum J and GOR could reach 6.00 kg/m2·h and 7.70 respectively. In this study, the three prediction models proved their abilities to predict AGMD performance and further provide guidance in the actual membrane distillation water treatment process.

Multi-sections solar distiller integrated with solar air heater: numerical investigation and experimental validation

ABSTRACT A numerical investigation for a solar air heater integrated with a multi-section solar distiller has been conducted with a novel design of solar distiller with interior sections. A mathematical description of the solar distiller is made and solved with a MATLAB code. The air flow in the solar air heater, the water height in the solar distiller, and the number of interior sections have all been studied. To validate the numerical system, an experimental system was built. The theoretical model and the experiment performed appear to be in satisfactory correlation. The best working conditions occur when the system is run with a lower air flow rate, a lower saline water height, and a greater number of interior sections with productivity reaching 1242.6 ml/m2 per day, a gain output ratio (GOR) about 0.622 and air heater efficiency about 35%. In the normal case of output salinity between 0 and 500 ppm, the cost was reduced by 96.7%, and by 96.3% in the case of four interior sections. Water cost reduction is also observable at the same output salinity, with 54.1% at 0 ppm and 62.4% at 200 ppm between number of interior sections = 0 and 4.

Study on the synergistic heat transfer of double boundary layers in the jacketed vacuum membrane distillation process

During the process of membrane distillation (MD) heat recovery, due to the adverse effects of the heat exchange boundary layer and membrane surface boundary layer, the latent heat is hindered in its transfer and ultimately leading to the loss of heat recovery and mass transfer capacity of the system. In this study, a novel type of jacketed hollow fiber vacuum membrane distillation module (J-HF-VMD-M) has been successfully developed. It has the dual functions of “feed evaporation” and “vapor condensation”, which is helpful in reducing the volume and complexity of the system. Based on the structural characteristics of the jacketed module, a “Synergistic heat transfer model of double boundary layers” (SHT-DBL Model) is proposed for the first time. Compared with the previous “independent heat transfer” method between boundary layers, the “synergistic heat transfer” can overcome the above challenges more effectively. Compared with the non-heat recovery process in experimental range, the equivalent membrane distillation flux of the jacketed-type heat recovery process increased by 246.1 %, especially the gain output ratio increased by 145.1 %, and the corresponding increment is more significant than that of the traditional heat recovery process.

Performance analysis of a pilot-scale modified air heated and dual heated humidification-dehumidification desalination system

Humidification-dehumidification (HDH) desalination systems offer an effective decentralized solution to meet the potable water demands of small and medium - size communities. Amongst many HDH configurations, the modified air heated and dual heated HDH cycles have demonstrated promising results in several studies based on small lab-scale setups, where the pilot scale experimental data are lacking in literature. In this study, the performance of both modified air heated and dual heated cycles are experimentally investigated using a new pilot-scale system to benchmark the performance for scaling-up the HDH system. The concept of heat rate ratio is explored practically in a new approach by splitting up the energy supply between water and air streams in the dual heated cycle. Both cycles operate in closed-air open-water cycle. In the modified air heated layout, humid air is heated after the humidifier, whereas in the dual heated mode, both water and air are heated simultaneously before and after the humidifier. The effects of changing the mass flowrate ratio on the performance dynamic indices, including productivity, gained output ratio, product cost, recovery ratio, top system temperature, specific energy consumption, and heat capacity ratio of both configurations are investigated. Results indicate that the dual heated system performs better than the modified air heated cycle, with a maximum freshwater production rate of 117.2 kg/day and 72.7 kg/day for dual the heated and modified air heated cycles, respectively. Dual heated system also recorded peak recovery ratio of 2.24 % while modified air heated cycle attained a highest RR of 1.26 %. Furthermore, the estimated peak gained output ratio for modified air heated and dual heated cycles are 0.53 and 0.74, respectively. The dual heated cycle also recorded the lower freshwater cost of 0.055 $/kg, while the best product cost for the air heated cycle is 0.079 $/kg of freshwater.

Multistage Surface-Heated Vacuum Membrane Distillation Process Enables High Water Recovery and Excellent Heat Utilization: A Modeling Study

Surface-heated membrane distillation (MD) enhances the energy efficiency of desalination by mitigating temperature polarization (TP). However, systematic investigations of larger scale, multistage, surface-heated MD system with high water recovery and heat recycling are limited. Here, we explore the design and performance of a multistage surface-heated vacuum MD (SHVMD) with heat recovery through a comprehensive finite difference model. In this process, the latent heat of condensation is recovered through an internal heat exchanger (HX) using the retentate from one stage as the condensing fluid for the next stage and an external HX using the feed as the condensing fluid. Model results show that surface heating enhances the performance compared to conventional vacuum MD (VMD). Specifically, in a six-stage SHVMD process, 54.44% water recovery and a gained output ratio (GOR) of 3.28 are achieved with a surface heat density of 2000 W m-2, whereas a similar six-stage VMD process only reaches 18.19% water recovery and a GOR of 2.15. Mass and energy balances suggest that by mitigating TP, surface heating increases the latent heat trapped in vapor. The internal and external HXs capture and reuse the additional heat, which enhances the GOR values. We show for SHVMD that the hybrid internal/external heat recovery design can have GOR value 1.44 times higher than that of systems with only internal or external heat recovery. Furthermore, by only increasing six stages to eight stages, a GOR value as high as 4.35 is achieved. The results further show that surface heating can reduce the energy consumption of MD for brine concentration. The multistage SHVMD technology exhibits a promising potential for the management of brine from industrial plants.

Thermodynamics analysis of a novel absorption heat transformer-driven combined refrigeration and desalination system

Preservation of food and medicines below sub-zero temperatures is the need of the present times. To achieve the required temperature using renewable energy, a waste heat-driven vapour absorption refrigeration system can be implemented. Majority of the available waste heat is available in the low temperature range i.e. between 60–80 °C, which cannot be directly used to provide refrigeration. Therefore, an absorption heat transformer (AHT) is coupled with the VARS (Vapour absorption refrigeration system) system which increases temperature of this waste heat, and the upgraded heat is utilized to produce required refrigeration effect. Further, the rectifiers’ waste heat of the absorption system will be used to power humidification-dehumidification (HDH) desalination cycle. Although all these three components (AHT, VARS, and HDH) have been studied individually, but they have never been combined altogether. This paper presents a mathematical model for the proposed system and its validation against published available literature. The performance parameters such as coefficient of performance, gain output ratio and refrigeration effect of the system is evaluated at different evaporator and desorber temperatures. For 300 kW waste heat at 80 °C, evaporator (VARS) temperature of −10 °C, the system reported 70 kW of refrigeration effect is provided with 20 kg/hr of distillate production rate. An exergy destruction of 82.64 kW has been reported for total input exergy of 142.2 kW, for refrigeration capacity of 157 kW.

Wet Flue Gas Desulphurization (FGD) Wastewater Treatment Using Membrane Distillation

The use of waste incineration with energy recovery is a matured waste-to-energy (WtE) technology. Waste incineration can reduce the volume and mass of municipal solid waste significantly. However, the generation of high volumes of polluting flue gases is one of the major drawbacks of this technology. Acidic gases are constituents in the flue gas stream which are deemed detrimental to the environment. The wet flue gas desulphurization (FGD) method is widely employed to clean acidic gases from flue gas streams, due to its high efficiency. A major setback of the wet FGD technology is the production of wastewater, which must be treated before reuse or release into the environment. Treating the wastewater from the wet FGD presents challenges owing to the high level of contamination of heavy metals and other constituents. Membrane distillation (MD) offers several advantages in this regard, owing to the capture of low-grade heat to drive the process. In this study the wet FGD method is adopted for use in a proposed waste incineration plant located in Ghana. Through a mass and energy flow analysis it was found that MD was well matched to treat the 20 m3/h of wastewater generated during operation. Thermal performance of the MD system was assessed together with two parametric studies. The thermal efficiency, gained output ratio, and specific energy consumption for the optimized MD system simulated was found to be 64.9%, 2.34 and 966 kWh/m3, respectively, with a total thermal energy demand of 978.6 kW.

Solar powered hybrid desalination system using a novel evaporative humidification tower: Experimental investigation

Experimental investigation of a hybrid-solar desalination system consisting of a humidification–dehumidification unit and a solar distiller unit. At El Mahalah city- Egypt in climatic conditions, experimental work was performed under real thermal conditions in September 2021. A new design of helical humidifier and multi-section solar distiller has been tested. There is good agreement between the predicted and measured changes in water production and performance parameters. According to testing and operating parameters, the system's highest productivity was 6.7 kg/m 2 per day at a production cost of 10.4 $/m 3 . System performance was tested and represented by system efficiency, humidifier efficiency, and gain output ratio (GOR). The system efficiency, humidifier efficiency, maximum gain output ratio, and exergy efficiency reached 95%, 98%, 1.65, and 7.2%, respectively. The proposed hybrid desalination system gives an adequate operational compatibility between the HDH method and solar energy. • An experimental study for a solar hybrid desalination system has been conducted. • The highest productivity of the proposed system was 6.7 kg/m 2 per day. • The overall system efficiency reached 95% with an average water cost of 10.4 $/m 3 . • Exergy efficiency and maximum GOR reached 7.2% and 1.61, respectively. • A novel humidifier design was demonstrated with an efficiency reached 98%.