Search results for "Membrane distillation"

Evaluation of Permeate Quality in Pilot Scale Membrane Distillation Systems

2019

In this work, the salinity of permeate obtained with membrane distillation (MD) in pilot scale systems was analyzed. Experiments were performed with three different spiral-wound commercial modules, one from Solar Spring with 10 m2 surface membrane area and two from Aquastill with 7.2 and 24 m2. Intermittent operation meant that high permeate conductivity was measured in the beginning of each experiment, which was gradually decreasing until reaching a constant value (3&ndash

Performance increase of membrane distillation pilot scale modules operating in vacuum-enhanced air-gap configuration

2019

Abstract This paper presents the first experimental evaluation at pilot scale of the operation of vacuum-enhanced air-gap membrane distillation (V-AGMD) using two commercial spiral-wound modules at Plataforma Solar de Almeria's solar desalination test facilities. The main difference between the modules was the channel length (1.5 and 2.7 m) as a result of having different membrane surface area (7.2 m2 and 25.9 m2 respectively) and different number of envelopes. Suction of air from the gap improved the vapour transfer through the membrane pores and the performance of the modules was significantly increased in relation to common air-gap (AGMD) operational mode, especially in the treatment of …

Prediction models to analyse the performance of a commercial-scale membrane distillation unit for desalting brines from RO plants

2018

Abstract Desalting brines from Reverse Osmosis (RO) plants is one of the most promising applications of Membrane Distillation (MD) systems. The development of accurate models to predict MD system performances plays a significant role in the design of this kind of industrial applications. In this paper, a commercial-scale Permeate-Gap Membrane Distillation (PGMD) module was modelled by means of two different approaches: Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). Condenser inlet temperature, evaporator inlet temperature, feed flow rate and feed water salt concentration were selected as inputs of the model, while permeate flux and Specific Thermal Energy Consumpti…

A novel TLC based technique for temperature field investigation in MD channel

2011

Effective recovery of HCl and metals from pickling solutions by cutting-edge membrane technologies

2018

The pickling process is an essential step in the hot-dip galvanizing process.It is performed by immersing manufacturedsteel pieces inacid bathsin order todissolve the oxidized layers. During the pickling process, acid attacks metal oxides on the surface, dissolving them in the pickling bath. Thus, the efficiency of the pickling liquor decreases due to the accumulation of metal salts and the consumption of free acid in the solution. When hydrochloric acid is used,ferrous chloride is producedduring the pickling treatment, reaching concentrations up to 250 g/l, while the acid concentration decreases by 75-85%. A pickling bath in this condition is considered spent [1] due to thevery low picklin…

Some Features of Polymeric Membranes for Water Purification via Membrane Distillation

2011

Polymeric membranes are currently adopted in water purification processes, such as reverse osmosis (RO) and membrane distillation (MD). This latter technique is very promising for separation effectiveness and energy savings. A valuable and effective MD unit must be equipped with polymeric membranes that exhibit specific properties, for example, hydrophobicity, a narrow pore size range, a high water penetration pressure, and a large vapor permeability. In this work, we present and examine the main features of membranes for MD processes, with the aim of experimentally evaluating the related performances. Scanning electron microscopy analysis was carried out for a first estimate of the pore si…

PMRs Utilizing Non–Pressure-Driven Membrane Techniques

2018

In the present chapter it is shown how photocatalytic membrane reactors utilizing membrane processes, which are not pressure driven, can exploit various mechanisms to obtain a substantial improvement of the process. The fundamentals of this particular type of membrane reactors are reviewed including the effects of the most important parameters and the methods and rules of coupling photocatalysis and membrane separation. The survey of the studies on photocatalytic membrane reactors (PMRs) utilizing pervaporation, dialysis, membrane contactors and membrane distillation offers the opportunity of discussing the advantages with respect to PMRs adopting pressure driven membrane processes. Indeed,…

CHARACTERIZATION OF HYDROPHOBIC POLYMERIC MEMBRANES FOR MEMBRANE DISTILLATION PROCESS

2010

Hydrophobic microporous membranes are utilized in membrane distillation (MD) processes, e.g. seawater desalination at moderate temperatures. The vapour permeability of commercial hydrophobic membranes with different pore sizes (0.2-1 micron) was characterized through a simple apparatus designed-on-purpose. A cylindrical vessel had a face closed by the membrane and the other connected to a thin graduate tube. The water level variation in the tube is recorded and related to the vapour flux across the membrane. Measurements were taken in the temperature range 20-80°C. A fan tangential to membrane surface was employed to maintain a constant driving force for vapour transport. Vapour flux did no…

Turbulent heat transfer in spacer-filled channels: Experimental and computational study and selection of turbulence models

2019

Abstract Heat transfer in spacer-filled channels of the kind used in Membrane Distillation was studied in the Reynolds number range 100–2000, encompassing both steady laminar and early-turbulent flow conditions. Experimental data, including distributions of the local heat transfer coefficient h, were obtained by Liquid Crystal Thermography and Digital Image Processing. Alternative turbulence models, both of first order (k-e, RNG k-e, k-ω, BSL k-ω, SST k-ω) and of second order (LRR RS, SSG RS, ω RS, BSL RS), were tested for their ability to predict measured distributions and mean values of h. The best agreement with the experimental results was provided by first-order ω-based models able to …

CFD parametrical study of the spacer geometry for Membrane Distillation

Membrane Distillation (MD) is a thermal process that separates water from aqueous solutions containing non-volatile components such as salt. Water vapor from the hot feed channel permeates through a hydrophobic membrane thanks to a partial pressure gradient, and condenses in the cool channel. One of the main advantages of MD is the easy coupling with renewable resources, as the solar thermal energy. In the various MD configurations developed, net spacers are used in order to support the membrane, thus creating the channels; moreover, they can counteract the side effects of temperature polarization by promoting mixing. However, the presence of the spacer involves an increase of pressure drop…