Ricardo Alvarez

A new integrated membrane process for producing clarified apple juice and apple juice aroma concentrate

An integrated membrane process for producing apple juice and apple juice aroma concentrates is proposed. The process involves the following operations: an integrated membrane reactor to clarify the raw juice; reverse osmosis (RO) to preconcentrate the juice up to 25°Brix; pervaporation (PV) to recover and concentrate aroma compounds, and a final evaporation step to concentrate apple juice up to 72°Brix. These operations were tested in laboratory and pilot plant units. Promising results were obtained with the membrane operations involved. In order to have an economic process assessment, the pilot plant units were assembled into an integrated unit and operated with raw apple juice. The products were more clear and brilliant than apple juice produced by conventional methods. The integrated membrane process also seemed to be more advantageous on the basis of economics than the conventional one.

Salicylic acid production by electrodialysis with bipolar membranes

Abstract Production of salicylic acid from sodium salicylate was carried out by electrodialysis (ED) using bipolar membranes (BPM). The process feasibility was tested using a laboratory ED-cell with a membrane area of 40 cm 2 . The performances of two commercial bipolar membranes (Tokuyama Soda and Stantech membranes) are compared. Current efficiencies for salicylic acid and caustic soda production are close for both bioolar membranes (80–90%), but differences are observed with respect to energy consumption which are related to the electrical characteristics of the membranes.

Effect of ionic strength on rinsing and alkaline cleaning of ultrafiltration inorganic membranes fouled with whey proteins

Abstract The rinsing and alkaline cleaning of an ultrafiltration (UF) inorganic membrane fouled with whey proteins was investigated. The progression of both processes was assessed by membrane hydraulic resistance restoration and fouling deposit removal. The amount of protein removed during rinsing is quite significant, as compared to the total amount removed during rinsing and cleaning. Increased ionic strength of the rinsing solution, by means of NaCl addition, resulted in an impressive increase of calcium removal during the rinsing step. This can be probably attributed to calcium/sodium ion exchange. The effect of increased calcium removal on rinsing and cleaning efficiency was not significant. The kinetics of rinsing and cleaning were also considered.

Recovery and concentration by electrodialysis of tartaric acid from fruit juice industries waste waters

Abstract: Electrodialysis (ED) has been used as a membrane technique to con-centrate tartaric acid from ion exchange regeneration waters obtained in grapejuice treatment. The initial ion tartrate concentration in these streams variesbetween 1 and 10 kg m~3 and can be concentrated more than 60% (53E2kgm~3after 13300 s). Permeate Nux of other common ionic components has beenshown. Optimum intensities and current efficiency have been calculated with syn-thetic solutions. A mathematical approach has been used to predict Ðnal tartaricacid concentration and electro-osmotic e†ects.J. Chem. Technol. Biotechnol. 70, 247E252 (1997)No. of Figures: 5. No. of Tables: 4. No. of Refs: 15Key words: tartaric acid, electrodialysis, waste waters, recovery, fruit juice NOTATIONA Membrane area per cell-pair (m2)C Solute concentration (mol m~3)F FaradayIs constant (A s eq~1)i Current density (A m~2)J Massic solute Nux (kg m~2 s~1)JwVolumetric water Nux (m s~1)m Anion mass (kg)n Number of cell-pairs (dimensionless)N Normality (eq m~3)S Electrode surface (m2)t Time (s)V Batch or solution volume (m3)a Constant in eqn (2) (m~3 g~1)b Constant in eqn (2) (s m~3 g~1)g Current efficiency (dimensionless)Subscriptsc Related to the concentrated streamw Related to water transport

Permeate flux prediction in apple juice concentration by reverse osmosis

This work studies apple juice concentration by reverse osmosis (RO) using polyamide tubular membranes at different operating conditions. Permeate flux has been predicted by using the solution-diffusion model combined with the film model. Good agreement was found between the experimental values and the ones calculated by using both models. Pressure was found to be the most important variable controlling the process. Physico-chemical analyses were made in order to evaluate the quality of concentrated apple juice.

Skimmed milk demineralization by electrodialysis: Conventional versus selective membranes

Abstract Electrodialysis (ED) is a membrane technique that is useful in the demineralization of dairy products. In this work, experimental results obtained in batch electrodialysis of skimmed milk are presented. Two kinds of membranes were used: the first kind were conventional membranes in PVC and the second were monovalent ion selective membranes which are now available on the market. This latter type of membrane permits the transport of monovalent ions but limits the passage of large ions which have a high valency. The limiting current was measured as a function of feed flow into the stack. The results obtained when using both types of membranes were compared for elimination rate of K + , Na + , Cl −1 , Ca 2+ , Mg 2+ and PO 4 3− ions as well as for current efficiency and electric power consumption in the separation process.

Detection of Sags, Swells, and Interruptions Using the Digital RMS Method and Kalman Filter with Fast Response

A fast detection algorithm for sags, swells and interruptions is developed in this paper. The proposed method is based on the combination of the digital RMS technique and the Kalman filter. The union of these methods allows using the main advantages of Kalman filter and RMS techniques and helps rejecting the extreme drawbacks of Kalman filter. The proposed approach can be applied to dynamic voltage restorers, dynamic sag correctors, uninterruptible power supplies, and other compensation topologies for power quality improvement

Electrodialysis in the separation of dilute aqueous solutions of sulfuric and nitric acids

Abstract Dilute aqueous mixtures of sulfuric and nitric acids were electrodialyzed with the aim to separate and concentrate both acids. The stack was fitted with heterogeneous or homogeneous membranes, the former untreated, the latter with a low transport number of bivalent anions. Changes in concentration were analyzed in terms of the normalized concentration C * = C/C ° as a function of the relative mass concentration of the slower ion in the diluate, X dS = C dS /( C dS + C dN ). The results show that such a separation is possible and more efficient with treated membranes.

Caseinomacropeptide behaviour in a whey protein fractionation process based on α-lactalbumin precipitation

This work studied the behaviour of caseinomacropeptide (CMP) in a whey protein fractionation process based on the selective precipitation of α-lactalbumin (α-la) in an acid medium. Three different acids (hydrochloric, citric and lactic) and different operating conditions (protein concentration, temperature and pH) were considered to perform the precipitation step. Under the optimised precipitation conditions obtained for α-la (pH 4, 55°C, initial α-la concentration around 12 g/l) CMP presents quite similar behaviour to that observed for β-lactoglobulin (β-lg), namely remaining in the supernatant fraction. However, at a lower pH value (3.5) the amount of precipitated CMP increases up to 72% when citric acid is added. This behaviour could be due to the fact that CMP is close to its isoelectric point, which allows a supernatant fraction enriched in β-lg that is almost free from the rest of proteins in sweet whey.

Reverse osmosis of whey. Determination of mass transfer coefficients

Abstract Experimental data are reported for the reverse osmosis (RO) of reconstituted whey from ultrafiltrated whey powder, using the following conditions: Temperature 15°C, differential pressure range 2.0–5.0 MPa and pH=5.1–9.0. Using the osmotic-pressure model, mass transfer coefficients and solid concentration at the membrane surface are determined for the RO process.