Alfa Laval Research Articles

Pressure-Driven Functional Polymeric Membrane Technology as Athermal Separation Unit Operation in Chemical Engineering : A Review

This manuscript provides an overview of published scientific and trade literatures and a collection of useful reference information on all aspects of membrane science and technology, selected result of experiment applications, and more recent developments in pressure-driven flat sheet membrane (PDFSM) processes as new frontier and athermal separation unit operation in chemical engineering covering general description of the basic principles of membrane separation processes, benefits and drawbacks, and future trends of membrane developments. Meanwhile, experiment results of selected applications of membranes are removing and/or reducing bacteria, and recovering high protein and low fat from skim milk by microfiltration (MF) membrane (Fluoro polymer, 0.45 µm, Alfa Laval) as an alternative to replace heat sterilization, separating and/or concentrating protease enzyme by ultrafiltration (UF) membrane (Polysulphone, 20000 MWCO, DSS), separating target and valuable components in corn steeping water by using nanofiltration (NF) membrane (Thin Film Composite on Polyester, DSS), and separating and/or purifiing ions component in brackish water and sea water by reverse osmosis (RO) membrane (Thin film composite on Polypropylene, DSS).

Lindane removal by membrane nanofiltration

Lindane is the γ-isomer of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) and it has been widely used in the pesticide industry due to its insecticide properties. In the production of lindane, significant quantities of other HCH isomers are generated as byproducts. All these compounds are typically stored in landfills, often with poor management practices. Polyamide membranes, two commercial membranes from Alfa Laval (NF99HF and NF99) and homemade thin film composite membranes prepared by interfacial polymerization on a porous polyimide support, were evaluated for water nanofiltration (NF) of HCH isomers, including lindane. Homemade membranes, with a lindane rejection of 91.3 % and a permeance of 2.7 L·m−2·h−1·bar−1, offered the highest performance in terms of both permeance and rejection. NF99 and homemade membranes were proven to be equally effective in removing α-HCH and β-HCH, showing similar results. Homemade membranes achieved 99.5 and 99.8 % rejections for α-HCH and β-HCH, respectively. Long-term experiments were carried out with NF99 and homemade membranes to assess their stability during filtrations with lindane solutions for up to 214 h. Homemade TFC membrane maintained its initial rejection (ca. 93.5 %) after 214 h, although its permeance decreased over time, ending in 2.5 L·m−2·h−1·bar−1.

Coatings to Reduce Fouling in Plate Heat Exchangers: Two Case Studies

Fouling of heat exchangers in the chemical industry, oil & gas industry, district heating, power plants, among others, results in a loss of performance which leads to production stops for cleaning and therefore increased operation costs. One approach to mitigate fouling is to alter the properties of the metal surface. A coating to be successful in any plate heat exchanger (PHE) application needs to have a good adhesion to the metal but also keep the heat transfer through the metal plates as unaltered as possible. This requires a thin coating with a relatively good thermal conductivity. The plates in a PHE are subjected to plate-to-plate contact point wear when in operation which also puts an extra requirement for the coating. To be suitable, the coating needs to have a good mechanical stability to resist this plate-to-plate wear. Alfa Laval has a long experience in coating plates for diverse applications and in this paper two case studies will be presented. One in the paper industry and the other in the biofuel industry. A new type of multilayer Teflon™ coating from Chemours was used, specifically designed to show excellent fouling release properties along with limited thicknesses (30–50 microns).

Effect of fouling and cleaning upon the surface charge and porosity of polyethersulphone membranes during coffee brew decaffeination

Filtration processes could offer a viable alternative to use of solvents for the production of reduced caffeine coffee beverages (so called ‘half-decaf’) which have recently gained increased commercial attention. However fouling phenomena and membrane deterioration could significantly alter the process performance; hence fouling and cleaning mitigation strategies must be explored by monitoring key membrane properties such as porosity and surface charge. In this study, multiple cycle filtration of coffee brews for the selective reduction of caffeine has been performed. A commercially available synthetic tight ultrafiltration polyethersulphone (PES) membrane (GP95PP – Alfa Laval) and a bespoke loose nanofiltration mixed matrix PES membrane fabricated, were used for three consecutive fouling and cleaning filtration cycles. The impact and mechanisms of fouling and the cleaning protocol effectiveness were investigated using surface charge, porosity, membrane surface and membrane morphology characterization techniques. Streaming potential studies revealed negative surface zeta potential for the membranes in a pH range of ca. 3.5–8.0. The fouled membrane classes exhibited elevated negative charges, which were partially restored to the pristine levels when chemically cleaned, suggesting the presence of residual negatively charged foulants. Porosity studies revealed the presence of a porous cake layer with an increase of average pore size and pore volume, and a decrease of 10–20 % on the BET surface area of the fouled membranes. Presence of key compounds on the membrane surface and structure was confirmed via EDX and FT-IR spectroscopy. Surface roughness along with SEM microscopy verified the uniform deposition of the foulants with absence of bulky particles. The presence of a cake layer was confirmed via SEM cross-sectional images due to selective thick layer thickness increase of the fouled membranes. Flux differences between the membrane classes can be related to the thickness of the top layer. Flux decreases and flux recovery ratios were also reported over multiple cycles and linked with porosity and other surface properties.

The influence of multiple fouling and cleaning cycles upon the performance of polyethersulphone membrane filters during coffee extract decaffeination

Filtration processes have been applied widely in food processing industry over the recent decades and could offer a viable alternative to the use of solvents in the decaffeination process, comprising low operational costs, high selectivities and mild processing conditions. This paper reports the development and evaluation of the fouling occurring in multiple filtration cycles during the selective reduction of caffeine from coffee brews comparing the performance of (i) a commercially available synthetic tight ultrafiltration (TUF) polyethersulphone (PES) membrane (GP95PP – Alfa Laval) and (ii) a self-made mixed matrix (MMMs) PES membranes (PSCD) fabricated in-house. The effectiveness and performance of the PES MMMs was benchmarked against the commercial 2 kDa PES membranes showing promising results. A cross-flow rig was operated at transmembrane pressures of 2–9 bar and cross-flow velocities (CFV) of 0.04–0.1 m/s at 25 °C. The flux decline and recovery along with changes in the key component rejection and resistances are reported for multiple fouling and cleaning cycles. PSCD exhibited a higher permeate flux of ca. 10.5 L m-2h-1compared to the GR95PP membranes, which exhibited a permeate flux of 6.1 L m-2h-1 over the 29 h filtration period selected, at 9 bar and a CFV of 0.04 m/s. The rejection ratios of the GR95PP and PSCD membranes were monitored for three consecutive filtration cycles, and showed values ca. 30% and 35% for caffeine,> 90% and ∼90% for both polyphenols & proteins, & ∼ 80% for melanoidins, respectively. An effective cleaning protocol was reported, comprised of 0.5 wt% NaOH at 50 °C, exhibiting cleaning efficiencies (CE)> 99%. FT-IR data indicated the presence of key compounds residuals after membrane cleaning. Modification to the membrane surface occurs due to fouling, altering the hydrophobicity. Differences in filtration performance and cleanability between the two classes of membranes are identified and linked to variations in surface and structure properties.

Single‐use centrifugal separator enables intensification of the clarification process in biomanufacturing of recombinant proteins

AbstractBACKGROUNDThe need to produce more biologics at lower costs and hence intensify bioprocessing has significantly improved upstream productivity (cell culture titers ≥3 g L−1 and cell densities ≥20 × 106 cells mL−1), shifting the economic and production bottleneck to downstream manufacturing. The first downstream unit operation is the clarification of the cell culture broth to remove various insoluble (such as cells and cell debris) and soluble (such as host cell DNA and proteins) contaminants, producing a feed stream suitable for further downstream purification. The high cell‐density cultures obtained in modern intensified bioprocessing have made legacy single‐use clarification trains (based primarily on depth filtration of the cell culture broth) ineffective and impractical, significantly increasing the economic and material burden of the clarification process.RESULTSWe have developed and characterized approaches that enable intensification of the clarification operation, by increasing process capacities while reducing material requirements and footprint, for single‐use manufacturing facilities. These approaches are based on primary clarification using the Alfa Laval CultureOne™ centrifuge (a continuous solid discharge disc‐stack centrifuge with a single‐use flow path) followed by secondary clarification using single‐use disposable depth filters. We show that these intensified clarification trains are suitable for processing high cell‐density cultures (6–12% packed cell volume) with significantly high yields (≥90%) and impurity clearance, along with reduced operating costs (30–60% savings).CONCLUSIONIncorporating a single‐use continuous discharge centrifuge into the clarification train enables clarification of high cell‐density cultures in single‐use manufacturing facilities and enhances process economic and environmental sustainability. © 2023 Society of Chemical Industry (SCI).

Effect of pressure and cross-flow velocity on membrane behaviour in red wine nanofiltration

Nanofiltration has found numerous applications in winemaking industry as an effective separation technology, allowing for the recovery and concentration of valuable bioactive compounds from wine/grape by-products, as well as for wine dealcoholization. However, the assessment of membrane fouling remains essential for a stable and sustainable membrane operation. Because of its complex nature, wine components (colloids and solutes such as polysaccharides, polyphenols, proteins) contribute to different mechanisms of fouling. The increase of fouling propensity as well as the conditions that contribute to it - transmembrane pressure and cross-flow velocity – are studied in the present study. Quantitative characteristics as fouling indices are discussed. Results with red wine (Mavrud) nanofiltration are obtained using two NF membranes - Nadir® NP030 P (asymmetric polyethersulfone (PES), MWCO 500 Da) and Alfa Laval NF99HF (thin film composite polyester, MWCO 200 Da). Nanofiltration runs were carried out by a constant-pressure cross-flow filtration system MaxiMem, Prozesstechnik GmbH with a rectangular flat-sheet membrane of 215 cm2 active area.Effect of transmembrane pressure (TMP) (10 to 50 bar) and cross-flow rate (1-3 l/min) on the permeate flux are discussed in view of membrane fouling. Higher operating pressures enhance the permeate flux but may also lead to increased fouling. The two membranes show very different permeate fluxes, the ones measured with NF99HF being 10-20 times higher. Increase in cross-flow velocity improves the hydrodynamic conditions such as shear stress field close to the membrane. The expected positive effect on permeate flux is the more noticeable the more pronounced the fouling. This was shown by two polymer membranes of different molecular weight cut-off exhibiting different susceptibility to fouling.

Evaluation of Nanofiltration Membranes for the Purification of Monosaccharides: Influence of pH, Temperature, and Sulfates on the Solute Retention and Fouling.

Furfural, acetic acid, and sulfates are found in the hemicellulose (HMC) fraction of lignocellulosic biomass. Separation of furfural, acetic acid, and sulfates from monosaccharides by four nanofiltration (NF) membranes was evaluated with a model solution of glucose, xylose, furfural, acetic acid, and sulfates. Results showed that Alfa Laval NF99HF is the most promising membrane to purify monosaccharides, with the retentions of xylose (85%), glucose (95%), and with the minimum sulfate retention. pH has the highest impact on the retention of all solutes and there is no significant effect of temperature on the retentions of sulphates and acetic acid. Lower pH and temperature are favored to maximize the monosaccharide retention and to remove acetic acid while retaining more furfural with the monosaccharides. Moreover, fouling tendency is maximized at lower pH and higher temperatures. According to the statistical analysis, the retentions of glucose, xylose, furfural, sulfates, and acetic acid are 95%, 90%, 20%, 88%, and 0%, respectively at pH 3 and 25 °C. The presence of sulfates favors the separation of acetic acid and furfural from monosaccharides.

Fouling of polyethersulphone ultrafiltration membranes during the decaffeination of ground coffee brews

The production of reduced caffeine coffee beverages (so called ‘half-decaf’) has recently gained increased commercial attention. Ultrafiltration (UF) can offer a viable alternative to the use of solvents in the decaffeination process, also operating at ambient temperatures, and a low operational cost. This paper reports the development and evaluation of the fouling occurring during the selective reduction of caffeine from coffee brews using a commercially available synthetic tight ultrafiltration (TUF) polyethersulphone (PES) membrane (GP95PP – Alfa Laval) with a 2 kDa molecular weight cut off (MWCO). Performance is reported in terms of fluxes, hydraulic resistances, and component rejection ratios. A cross-flow rig was operated at transmembrane pressures of 2–9 bar and cross-flow velocities of 0.04–0.1 m/s at temperatures in the range 25–50 oC. The process is viable: a retentate is produced with a much reduced caffeine concentration whilst still rich in higher molecular weight bioactives. Commercial PES membranes (GP95PP – Alfa Laval) had a permeate flux of 6.5 L m-2 h-1 and a fouling index (FI) of ca 60%. Rejection ratios were ca 30% for caffeine, ≥ 90% for both polyphenols & proteins, & ≥ 80% for melanoidins, over a 29 hr filtration period. Membrane surface modification due to fouling takes place, altering the hydrophobicity. An effective cleaning protocol is reported comprised of 0.5% w/v NaOH at 500 C. The flux decline and recovery are reported for multiple fouling and cleaning cycles.

Membranes extract valuable fibres – turning waste into sellable ingredients

Membrane systems from Alfa Laval are set to be used at a food facility in Denmark to produce healthy dietary fibre from crop leftovers.

Evaluation of Nanofiltration Membranes for Pure Lactic Acid Permeability.

Lactic acid (LA) is an organic acid produced by fermentation or chemical synthesis. It plays a crucial role in the pharmaceutical, food and plastic industries. In the fermentation of, for example, grass silage, LA and different compounds are produced. To purify lactic acid, researchers have tried to investigate membrane technology to achieve a high yield of lactic acid permeance. This study tested four commercially available nanofiltration membranes (NF270, MPF-36, Toray NF, and Alfa Laval NF). Nanofiltration experiments were performed to investigate the rejection levels of lactic acid from a binary solution by using distinct molecular weight cut off membranes. All of the experiments were conducted with a lab-scale cross-flow membrane unit. Different operating conditions (pH, temperature) were studied for each membrane; the optimal process condition was found at 25 °C and pH 2.8. With higher temperatures and pH, an increase in LA rejection was observed. The MPF-36 membrane shows the lowest lactic acid rejection yield of 7%, while NF270 has the highest rejection yield of 71% at 25 °C and pH 2.8. These results will be helpful in the future to understand both the interaction of lactic acid permeance through nanofiltration membranes and process scale-up.

An advanced Grid Diagram for heat exchanger network retrofit with detailed plate heat exchanger design

This paper presents a method for heat exchanger network (HEN) optimisation considering plate heat exchangers (PHEs), incorporating detailed PHEs design. The developed method starts from a mathematical model based on the Advanced Grid Diagram, which can optimise the HEN structure. The model minimises the energy consumption cost with the constraints that enable a solution thermodynamically feasible. Then comes the heat exchanger type selection part, which is provided by a graphical tool helping to identify which types of the heat exchanger are feasible. The feasible temperature range can be easily visualised to avoid the temperature violation of PHEs. This selection part integrates the area calculation and cost calculation with the detailed heat exchanger design. The method has been tested by a case study of crude oil distillation system illustrating that the application of brazed plate heat exchangers (BHEs) of CB series manufactured by Alfa Laval can save 6.6% of the investment cost for new heat exchangers compared with the retrofit plan that only shell-and-tube and double pipe heat exchangers are used.

Alfa Laval AB, Sweden

Alfa Laval AB, Sweden

Alfa Laval AB, Sweden

Alfa Laval AB, Sweden

Investigations on Strategic Element Recovery by an Underground Membrane Pilot Plant from In-Situ Extracted Bioleaching Solutions

Focusing on the selective extraction of the critical raw materials indium and germanium from real bioleaching solutions, extended studies have been carried out using Europe’s first underground hybrid membrane pilot plant (TRL6). In order to transfer former laboratory experiments to pilot scale, NF99 (Alfa Laval) was used for the evaluation of membrane permeance and ion retention. A performance test of microfiltration (MF) and nanofiltration (NF) showed high permeances with low root-mean-square deviation under feed variation (5.2% for MF, 4.7% for NF). Depending on the feed load, a significant permeance drop of up to 57% for MF (3 bar) and 26% for NF (10 bar, 1.1 m s−1) was observed. The NF retention performance showed that, without regular chemical cleaning, the selectivity between the target elements degraded. By introducing acidic-basic cleaning steps, it was possible to keep the retention behavior at an approximately constant level (In 91.0 ± 1.3%; Ge 18.2 ± 5.5%). In relation to the specified target, the best results could be achieved at low pressure (7.5 bar) and a maximum overflow velocity of 1.1 m s−1, with a retention of 88.4% for indium and 8.8% for germanium. Moreover, the investigations proved the functionality and long-term stability of the underground membrane device.

Analysis of the experimental ballast water treatment system

The object of research is the experimentally created model of the accompanying ballast water treatment systems (BWTS) at the Danube Institute of the National University «Odessa Maritime Academy». (Izmail, Odessa region, Ukraine). The study is aimed at assessing the compliance of ballast water quality standard D-2 ballast water operational cycles by disinfection and purification. One of the most problematic places of the presented research is the renewal (acquisition) of a separate node segmentation of the experimental BWTS with attraction of certain material support (investment). In particular, it is the scaling of BWTS, presentation in the state market of Ukraine, abroad (competition), qualitative assessment, certification at the level of the Ukrainian Sea Ports Administration (USPA), the register of maritime shipping. Elimination of the above «problem-tasks» will contribute to the collective research support, opinion and effective steps of professionals-researchers, in particular, in the maritime industry (experts IMO – International Maritime Organization, professors, academicians TAS – Transport Academy of Sciences). Also, compatible contribution of significant research results to separately oriented projects (European, Ukrainian) with attraction of investors, mentors, maritime industry business. The research used modern practices of design of such accompanying BWTS, referring to innovative methods, methodologies of global production of such structures of famous world brands, for example, Alfa Laval, Wartsila, OceanSaver, Hyde Marine, Industrie de Nora, etc. Researchers have qualitatively and consistently studied the generally accepted series of technological processes for ballast water treatment, observing classical according to the analytical review of literature sources and in the modern coverage (state) of similar stages of ballast water decontamination/cleaning. Qualitative expression of the received result is a number of conducted researches of disinfection/purification of sea outboard water in laboratory conditions on experimental BWTS. Thanks to the latter the reliability of the presented data is provided, which coincide (are identical) with trustworthy, established by the BW quality standard D-2, that are specified in discussion and conclusion of the given work.

Alfa Laval AB, Sweden

Alfa Laval AB, Sweden

Study of Acid Whey Fouling after Protein Isolation Using Nanofiltration.

In this paper, nanofiltration (NF) of acid whey after isolation of proteins was studied. Two membranes were tested: NF-99 (Alfa Laval) and DL (Osmonic Desal). Based on previous measurements that determined the highest efficiency in separating lactic acid and lactose whey, the pH was adjusted to 3. First, the most appropriate transmembrane pressure (TMP) was determined based on the highest flux measured. The TMP range was 5–25 bar for the DL membrane and 10–30 bar for the NF-99 membrane. The temperature was kept at 4 °C using a thermostat. The mechanisms of membrane fouling were investigated. The Hermia models and the modified Tansel model were applied to study the fouling mechanism and to determine which membrane would foul earlier and more severely, respectively. The most suitable TMP was determined at 20 bar. Despite the 1.4 times higher flux of the sample at DL, the fouling rate was higher when NF-99 was used. The results showed that the Tansel model is suitable for predicting the fouling time of protein-isolated whey by nanofiltration.

Plate heat exchanger design for the utilisation of waste heat from exhaust gases of drying process

The vapour condensation is typical for processes of waste heat recovery from exhaust gases. It complicates the selection of condensers and requires reliable correlations for estimation of heat transfer coefficients and pressure drop in the unit. In the presented paper, a novel model was elaborated to be applied for commercially produced plate heat exchangers (PHEs) assembled from plates with different geometries of corrugations, which accounts the change of process parameters at the main corrugated field, in PHE collectors and channels distribution zones. The process of waste heat recovery from exhaust gases after tobacco drying is discussed in the case study. The pilot unit assembled with PHE of TS-6MFG type manufactured by Alfa Laval was installed at a tobacco factory. The examined condensing media was an incoming air-steam mixture with 10% of air content and temperature equal to 140 °C. The comparison of modelling results and data of industrial operation has shown good accuracy of prediction. It allowed recommending obtained correlations and developed mathematical model for the design of plate heat exchangers in applications with heat utilisation from exhaust gases after drying processes in the industry, with a considerable saving of heat energy. In the considered example, it is up to 640 kW or 2090 kJ/kg of exhaust gases.

Новейшие разработки Альфа Лаваль в области обезвоживания осадка на декантерных центрифугах

Рассмотрены разработанные компанией Alfa Laval инновационные технологические решения, воплощенные в декантерной центрифуге Aldec G3. Для обезвоживания осадков сточных вод компания Alfa Laval изготавливает два вида современных декантерных центрифуг (всего их более 12 типов для применения в различных сферах: от пищевой промышленности и биофармацевтики до обезвоживания нефтешламов или отвальных хвостов горнодобывающей промышленности). Использование декантерной центрифуги Aldec G3 обеспечивает максимальное сокращение совокупных издержек на обезвоживание осадков сточных вод. Описаны виды ремонтных работ декантерных центрифуг, осуществляемые в единственном на территории России сертифицированном по стандартам ISO сервисном центре Альфа Лаваль.