Controlling Operating Parameters Research Articles

Anaerobic Membrane Bioreactors for Municipal Wastewater Treatment, Sewage Sludge Digestion and Biogas Upgrading: A Review

Anaerobic membrane bioreactors (AnMBRs) are formed through the combination of anaerobic digestion and membrane technology. The upgraded technology separates SRT from HRT in the anaerobic digester, shortening the treatment period, reducing the digester’s volume and improving effluent quality. Furthermore, AnMBRs have a strong tolerance for the existing forms of objects and can handle liquids, high-solid materials and gases. Up to now, AnMBRs have been utilized in the treatment of various types of industrial and municipal wastewater, organic solid waste and also biogas upgrading, and they have achieved excellent performance. However, there are few studies which have discussed their multiple utilization, especially following the flow of wastewater treatment. This study summarizes the application of AnMBRs in their diverse roles in the municipal wastewater treatment process. The discussion revolves around energy generation and the fouling issue of AnMBRs in the treatment of municipal wastewater, the digestion of sewage sludge generated in conventional municipal wastewater treatment and the upgrading of biogas after anaerobic digestion. In addition to controlling operating parameters, strategies used to improve the treatment effectiveness are also introduced. Lastly, online methods for preventing membrane fouling, which is the main operational obstacle to AnMBRs’ wider spread, are also discussed. This review aims to provide a fresh perspective on how AnMBRs are utilized in waste treatment.

Synergistic promotion of particulate matter reduction and production performance via adjusting electrochemical reactions in the zinc electrolysis industry

Heavy particulate matter (PM) pollution and high energy consumption are the bottlenecks of hydrometallurgy, especially in the electrolysis process. Therefore, an urgent need is to explore PM reduction methods with production performance co-benefits. This study presents three PM reduction methods based on controlling operating parameters, i.e., lowering electrolyte temperature, H2SO4 concentration, and current density of the cathode. The optimized conditions were also investigated using the response surface methodology to balance the PM reduction effect and Zn production. The results showed that lowering electrolyte temperature is the most efficient, with an 89.0% reduction in the PM generation flux (GFPM). Reducing H2SO4 concentration led to the minimum side effects on the current efficiency of Zn deposition (CEZn) or power consumption (PC). With the premise of non-deteriorating CEZn and PC, GFPM can be reduced by 86.3% at the optimal condition (electrolyte temperature = 295 K, H2SO4 = 110 g/L, current density = 373 A/m2). In addition, the reduction mechanism was elucidated by comprehensively analyzing bubble characteristics, electrochemical reactions, and surface tension. Results showed that lower electrolyte temperature inhibited the oxygen evolution reaction (OER) and compressed gas volume. Lower H2SO4 concentration inhibited the hydrogen evolution reaction (HER) and reduced electrolyte surface tension. Lower current density inhibited both OER and HER by decreasing the reaction current. The inhibited gas evolutions reduced the microbubbles’ number and size, thereby reducing GFPM. These results may provide energy-efficient PM reduction methods and theoretical hints of exploring cleaner PM reduction approaches for industrial electrolysis.

Long-term assessment on performance and seasonal optimal operation of a full-scale integrated multiple constructed wetland-pond system

Constructed wetlands as natural process-based water treatment technologies are popular globally. However, lack of detailed long-term assessment on the impact of seasonal variations on their performance with focus on optimal seasonal adjustments of controllable operating parameters significantly limits their efficient and sustainable long-term operation. To address this, a full-scale integrated multiple surface flow constructed wetlands-pond system situated between slightly polluted river water and outflow-receiving waterworks in a subtropical monsoon climate area of middle-eastern China was seasonally assessed over a period of six years. During this period, the removal rate (R) and mass removal rate (MRR) of total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) possessed strong seasonality (p < 0.05). The highest R (%) and MRR (mg/m2/d) were in summer for TN (51.53 %, 114.35), COD (16.30 %, 143.85) and TP (62.39 %, 23.89) and least in spring for TN (23.88 %, 39.36) and COD. Whereas for TP, the least R was in autumn (37.82 %) and least MRR was in winter (9.35). Applying a first-order kinetics model coupled with Spearman's rank correlation analysis, purification efficiency exhibited significant dependence on temperature as nutrient reaction rates constant, k generally increased with temperature and was highest in summer. Meanwhile, the R of TN, TP and COD were positively correlated with influent concentration whiles MRR of TP was negatively correlated with hydraulic retention time but positively correlated with hydraulic loading rate (HLR) (p < 0.05). Also, MRR of COD and TN were positively correlated with mass loading rates (MLR) in summer and autumn. Through linear optimization, the best operating parameters according to the compliance rate were determined and a set of guidelines were proposed to determine the optimal operational change of hydrological index in each season (Spring, 0.1–0.12 m/d; Summer, 0.14–0.16 m/d; Autumn, 0.15–0.17 m/d; Winter, 0.1–0.11 m/d) for efficient and sustainable long-term operation.

Estimating and optimizing wellbore pressure during primary cementing in low pressure and leakage formations

In most realistic situations, casing eccentricity and various fluids injected during primary cementing lead to a significant difference in fluid flow and circulating pressure, compared with a single fluid flowing in the concentric annulus. Ignoring the effect of eccentricity and fluid rheological model on the wellbore circulating pressure results in an inaccurate evaluation and leads to formation leakage, especially for low pressure and leakage formations. To overcome this challenge, firstly, rheological models of various fluids were analyzed using experimental data, including drilling fluid, spacer, and cement slurry. Secondly, the modified correlations of frictional pressure losses for Herschel-Bulkley and Power Law fluids in the eccentric annulus were developed, using the simulation data of computational fluid dynamics software (CFD) and considering the effects of flow behavior index, pipe diameter ratio, and casing eccentricity on the frictional pressure losses. Finally, based on the developed mathematical models, the optimal method of primary cementing and evaluation results were presented, analyzed, and tested in the field with great success. The results demonstrated that the drilling fluid and spacer fluid had the highest goodness of fit for the Herschel-Bulkley model, and the cementing slurry was suitable for the Power Law model. The ratio coefficient of pressure loss in the eccentric to concentric annulus decreased with a decrease of hole size and an increase of casing eccentricity. A 50 percent reduction in frictional pressure loss was evaluated when the casing lies on the borehole wall. Comparing the calculations of the developed correlation with the published correlation in the literature reveals a more accurate evaluation of friction pressure losses in the analyzed case. Combined with the realistic situation of a test well, the density, flow rate, and returning depth of the lead cement slurry were recommended as 1.5 g/cm3, 0.5 m3/min and 4100 m, respectively, according to the leakage pressure of 65.6 MPa that was calculated by the developed mathematical model. Most importantly, the developed method in this paper can accurately predict the variation characteristics of wellbore pressure during the primary cementing process and provide effective guidance in managing downhole pressure in low pressure and leakage formations by real-time adjustment of the most effective and controllable operation parameters.

Um sistema de controle de processos cibernéticos com base em reconhecimento de padrões e computação em nuvem

Abstract: This paper presents a novel simulation model of the Cyber Process Control System (CPCS) by combining pattern recognition and Cloud Computing (CC). This paper's originality arises from its aim to build a cloud computing platform for autonomous machines, and the exploration of manufacturing data to generate interpretable patterns to be used in process control decision making. The combining of Cloud technology and machine learning brings production to Industry 4.0. The proposed system is tested using data Carbon Fiber Reinforced Polymer (CFRP) routing process. The little information available about the manufacturing process of this type of material and the interaction between the production steps makes the manufacturing process quite difficult. This system generates interpretable rules of controllable operating parameters sent to the controller to keep the machining process within the limits of the specifications. The second step is activated during the drifting conditions in the machining step. Also, the simulation of the machining process is illustrated to generate the relations between input and output variables of the machining process. The findings of the corrective actions are illustrated and the interaction between the two industrial steps is simulated. Finally, current and future CPCS and CC applications in Industry 4.0 are discussed.

A multi-parameter optimization of the bio-pellet manufacturing process: Effect of different parameters and different feedstocks on pellet characteristics

Biomass pellet fuel is one of the important forms of biomass energy utilization. How to get high quality pellet fuel in the production process is a hot topic of discussion nowadays. Since the quality of biomass pellets is sensitive to the pelletizing conditions, the aim of this research is to investigate the complex relationship between pelletizing conditions, physical quality, and pelletizing energy consumption. In this study, Microalgae, apple tree wood chips, corn cobs and sunflower seed husks were selected for pelletizing in a single pelletization system, with several controlled operating parameters. Subsequently, pellet sample density, durability, and pelletizing energy consumption were tested. A response surface methodology (RSM) multi-objective optimization method was used to develop models for predicting and describing the physical properties of the pellets and the pelletizing energy consumption, and to optimize the operating parameters. The results showed that the optimization results of the four pellet RSM methods corresponded well with the values of the high-quality pellets produced (all ≤5%). Compared to other materials, microalgae can generate high density pellets at lower pressures and thus reduce energy consumption and cost. The microalgal pellet optimal preparation parameters were also obtained via RSM (temperature 108 °C, pressure 76.2 MPa and moisture content 11%). Under the optimal parameters, the pellet durability, density, and pelletizing energy consumption were 96.5%, 1658.4 kg/m3 and 9.19 kJ/kg, respectively. It is clear that raw materials such as microalgae are potential and valuable feedstocks for the production of biomass pellets.

Technical-scale biophotovoltaics for long-term photo-current generation from Synechocystis sp. PCC6803.

A carbon-free energy supply is essential to sustain our future. Biophotovoltaics (BPV) provides a promising solution for hydrogen supply by directly coupling light-driven water splitting to hydrogen formation using oxygenic photoautotrophic cyanobacteria. However, BPV is currently limited by its low photon-to-current efficiency, and current experimental setups at a miniaturized scale hinder the rational investigation of the process and thus system optimization. In this article, we developed and optimized a new technical-scale (~250 ml working volume) BPV platform with defined and controllable operating parameters. Factors that interfered with reproducible and stable current output signals were identified and adapted. We found that the classical BG11 medium, used for the cultivation of cyanobacteria and also in many BPV studies, caused severe interferences in the bioelectrochemical experiments. An optimized nBG11 medium guaranteed a low and stable background current in the BPV reactor, regardless of the presence of light and/or mediators. As proof-of-principle, a very high long-term light-dependent current output (peak current of over 20 µA) was demonstrated in the new set-up over 12 days with living Synechocystis sp. PCC6803 cells and validated with appropriate controls. These results report the first reliable BPV platform generating reproducible photocurrent while still allowing quantitative investigation, rational optimization, and scale-up of BPV processes.

Research on Carbon Emission Index Data of Turbine Unit Based On Variable Parameter Operation

At present, the problem of climate warming caused by greenhouse gases dominated by CO2 has become the focus of global environmental governance, and China is facing severe pressure of carbon emission reduction internationally. In this paper, from the perspective of the operation of coal-fired units, based on the CO2 generation coefficient of unit standard coal consumption, combined with the consumption difference analysis, the influence degree of the main controllable operating parameters such as the pressure, temperature of superheated steam and reheated steam of the units, as well as the boiler exhaust temperature, on Qco2 , that is, the sensitivity of Qco2 to the changes of each parameter is studied. On-site operating personnel of the unit can focus on monitoring and real-time adjustment of controllable operating parameters that have a great impact on Qco2 , so as to ensure that the unit is at a low carbon emission intensity level, thus reducing the total carbon emissions of coal-fired power plants. Finally, through experiments, it is proved that the steam turbine parameter optimization method studied in this paper can provide higher unit efficiency and reduce carbon emission level.

Modeling of Alternating Current Motor Performance for Increased Production Using Fuzzy Logic Controller

The low productivity experienced in our industries is as a result of not imbibing intelligence in its production mechanism. We know that induction motors are reliable, robust and with good operating characteristics. A means of starting, regulating and controlling operating parameters are very necessary to improve motor efficiency. This low productivity witnessed in our brewery industry is surmounted by modeling of alternating current (a.c) motor performance for increased production output using fuzzy logic controller. To achieve this it is done in this manner, characterizing and modeling a conventional AC motor so as to establish its operational features while working on variable frequency drive (VFD) control model with known production output, designing a rule base for the use of fuzzy controller for a stable and improved production output of AC motor and designing SIMULINK model for the performance of AC motor under operational condition for an increased output using fuzzy controller for a brewery industry. The results obtained are the highest conventional quantity of bottles of beer produced was 3240 while that of fuzzy controller was 3245 at a stable time of 4 through 10 seconds. With these results obtained, it shows there is an improvement in the production capacity in brewery industry when fuzzy controller is incorporated in the system.

Development of a Novel Feedforward Neural Network Model Based on Controllable Parameters for Predicting Effluent Total Nitrogen

Abstract The problem of effluent total nitrogen (TN) at most of the wastewater treatment plants (WWTPs) in China is important for meeting the related water quality standards, even under the condition of high energy consumption. To achieve better prediction and control of effluent TN concentration, an efficient prediction model, based on controllable operation parameters, was constructed in a sequencing batch reactor process. Compared with previous models, this model has two main characteristics: ① Superficial gas velocity and anoxic time are controllable operation parameters and are selected as the main input parameters instead of dissolved oxygen to improve the model controllability, and ② the model prediction accuracy is improved on the basis of a feedforward neural network (FFNN) with algorithm optimization. The results demonstrated that the FFNN model was efficiently optimized by scaled conjugate gradient, and the performance was excellent compared with other models in terms of the correlation coefficient (R). The optimized FFNN model could provide an accurate prediction of effluent TN based on influent water parameters and key control parameters. This study revealed the possible application of the optimized FFNN model for the efficient removal of pollutants and lower energy consumption at most of the WWTPs.

Robust Assessment of Controllable Operating Parameters of Entrained Flow Cogasification of Petcoke with Coal: Considering Some Uncertainties.

This paper is focused on the effects of some controllable operating parameters on the robustness of the coke/coal entrained flow cogasification process considering some uncertainties in it. In the present work, the operating variables were categorized into controllable parameters (CPs) (oxygen and steam concentrations, OC and SC) and hard-to-control parameters (temperature and coal/coke blending ratio) according to the actual modes during the cogasification process. Then, some robust response surface methodology (RSM) models, that is, mean RSM model and variance RSM model, for some important performance indexes [H2, CO, and (H2 + CO) production] with the CPs as independent variables, were found using combined array methodology. Then, the effects of OC and SC not only on the mean but also on the variance of each performance index were systematically investigated. Finally, the cogasification process was robustly optimized using the mean square criterion and desirability function. The result shows that the average production of H2 and that of (H2+ CO) increases with increasing OC but decreases with increasing SC. Additionally, higher OC suppresses the fluctuations in H2 and (H2 + CO) production, while higher SC enlarges the fluctuations in H2 production. Assuming that the variance of temperature in a gasifier is 20 °C and the variance of the coal/coke blending ratio is 5%, the multiobjective robust optimization solutions of OC and SC are 1.56 and 50%, respectively, and a satisfactory performance for high syngas production with low fluctuation can be gained.

Intensification of the degradation of Acid RED-18 using hydrodynamic cavitation

Abstract In this work degradation of Acid Red-18 (AR-18) was examined in the hydrodynamic cavitation reactor. Orifice plates with different holes geometry are used to determine the optimum plate to carry out the degradation based on cavitation number. The obtained optimum orifice plate is used as a cavitating device on varying parameters like initial AR-18 concentrations, pH, temperatures, and operating pressures of the reactor. A photocatalyst (TiO2) was prepared by the sol-gel method and used in combination with H2O2 to intensify the degradation of AR-18. The obtained optimum condition of hydrodynamic cavitation was again used in the ultrasonic cavitation reactor for the comparison. Hydrodynamic cavitation (orifice) given the highest degradation as compared to Hydrodynamic cavitation (Venturi) and Ultrasonic Cavitation with and without the use of TiO2. At TiO2(300 mg/L) dose, 88.1%, 70.4% and 64.8% degradation is obtained in HC-O, HC-V and UC reactor at initial AR-18 concentration (15 ppm), pH (3), Operating temperature (35 °C), and H2O2(300 mg/L). Hence the use of an advanced oxidation process can be successfully used with hydrodynamic cavitation to intensify the degradation of Acid Red-18 under the controlled operating parameters.

Numerical and experimental investigation of the effect of operating conditions on performance of PVT and PVT-PCM

Irradiations incident on the photovoltaic module are converted only 15–20% into electrical energy and remaining are transformed into heat and drop electrical efficiency. Therefore, to harness both the thermal and electrical energy, hybrid photovoltaic thermal system is an optimum option. Moreover, phase change materials add more advantages of PV cell cooling and heat storage. A novel thermal collector has been designed as PVT and PVT-PCM systems to improve the heat transfer and performance. The 3D numerical analysis is done with COMSOL Multiphysics® software, and is validated at different volume flow rates of 0.5LPM to 3LPM, by experimental investigation at conditions of keeping the inlet water and ambient temperature at 27 °C and solar irradiation at 1000 W/m2. The experiment is carried out in indoor weather under controlled operating parameters and conditions with passive cooling of the module. Maximum 12.4% and 12.28% electrical efficiency of PVT is achieved numerically and experimentally respectively. Similarly, 12.75 and 12.59% electrical efficiency for PVT-PCM is obtained for experimental and numerical cases respectively. For PVT system, 10.13 and 9.2% electrical performance is improved. For PVT-PCM the electrical performance improvement is obtained as 12.91 & 12.75% numerically and experimentally respectively.

Establishing a practical method to accurately determine and manage wellbore thermal behavior in high-temperature drilling

As deeper reservoirs are pursued around the globe, the oil and gas industry has shown a keen interest in high-temperature operations, despite the significant drilling problems such operations pose. In order to formulate guidelines to manage wellbore temperatures accurately and maintain drilling safety, it is crucial to develop a method to quantitatively identify the effects of various parameters, both controllable and uncontrollable, on circulating fluid temperature through sound statistical methods with field validations. In this paper, the transient heat transfer mechanisms of each region of wellbore and formation were investigated. Based on the first law of thermodynamics, a set of transient heat transfer models were developed and solved using the fully implicit finite difference method. The change in the thermal behavior of the wellbore and formation was analyzed to ascertain the range of change in the sensitivity parameters. Using the Monte Carlo simulation technique, the input parameters were treated as uniform, and triangular distributions were applied to estimate the probability distribution of the bottom-hole temperature. The contributing factors of the bottom-hole temperature were ranked based on their level of influences as fluid heat capacity, formation thermal conductivity, inlet temperature, flow rate, and fluid density. The research findings from this study provides a quantitative evaluation of each parameter’s relative significance to circulating fluids temperatures during oil and gas wells or geothermal well drilling operations and therefore provides practical guidance in managing downhole temperatures by identifying the most effective and controllable operation parameters.

Flexible and Economic Dispatching of AC/DC Distribution Networks Considering Uncertainty of Wind Power

In order to cope with the uncertainty power and consumption problems in AC/DC distribution networks after accessing high-permeability renewable energy source (RES), a flexible economic dispatching method for the AC/DC distribution networks considering the uncertainty of wind power is proposed based on the flexibility operation theory. First, considering the flexibility of regulation range, speed, and time, the source-network-load flexibility resources of AC/DC distribution networks are quantitatively evaluated. An evaluation index and a calculation method of the operation flexibility for the AC/DC distribution networks are defined. Then, based on the nonparametric kernel density estimation and confidence interval method, the constraints transformation of flexibility requirement in distribution networks considering the uncertainty of wind power is implemented. Finally, a multi-objective day-ahead flexible and economic dispatching model of the AC/DC distribution networks is established, which takes the operation economy and voltage quality of distribution networks as the objective function and the controllable operation parameters of voltage-source converters (VSCs) and AC/DC networks as the decision variables. The modified IEEE-33 system with flexible multi-terminal interconnection is simulated and analyzed. The result shows that the proposed method further improves the node voltage level and the RES consumption level and reduces the network losses and the total dispatching cost while ensuring the AC/DC distribution network to cope with the fluctuation of the system uncertainty.

Preparation of Electrosprayed Microporous Membranes

Polytetrafluoroethylene (PTFE) which is also called as “TEFLON” is a synthetic fluoropolymer of tetrafluoroethylene that has wide applications due to its differentiating properties. In this study, different PTFE dispersions for preparation of polytetrafluoroethylene mesoporous active membranes doped by basalt and carbon particles which were created in high voltage electrostatic field has been studied. The adjusting of process parameters of common electrospinning system (Nanospider) for preparation of membranes with tunable porosity created by nanofibrous assembly (electrospinning) and interconnected particles (electrospraying) has also been investigated. The nanoparticles based on milled basalt and carbon was used for activation and achieving of special effects. Superhydrophobic Polytetrafluoroethylene (PTFE) microporous membranes with different surface structures were obtained by controlling operating parameters in the electrospinning process. The diameters and microstructure of the PTFE microporous membrane were characterized by scanning electron microscopy. The contact angles on the microporous membranes were evaluated by static micro-drop observation, and a modified Yang equation was applied to analyze the contact angles. The superhydrophobic PTFE microporous membranes were also tested for thermal properties. As a result of this study, optimized PTFE blend solutions were identified. The results also revealed that the specific surface area was the key factor affecting the contact angles. The thermal properties revealed that thermal conductivity was higher and thermal resistance was lower for carbon and basalt doped membranes.

Big-Data-Mining-Based Improved K-Means Algorithm for Energy Use Analysis of Coal-Fired Power Plant Units: A Case Study.

The energy use analysis of coal-fired power plant units is of significance for energy conservation and consumption reduction. One of the most serious problems attributed to Chinese coal-fired power plants is coal waste. Several units in one plant may experience a practical rated output situation at the same time, which may increase the coal consumption of the power plant. Here, we propose a new hybrid methodology for plant-level load optimization to minimize coal consumption for coal-fired power plants. The proposed methodology includes two parts. One part determines the reference value of the controllable operating parameters of net coal consumption under typical load conditions, based on an improved K-means algorithm and the Hadoop platform. The other part utilizes a support vector machine to determine the sensitivity coefficients of various operating parameters for the net coal consumption under different load conditions. Additionally, the fuzzy rough set attribute reduction method was employed to obtain the minimalist properties reduction method parameters to reduce the complexity of the dataset. This work is based on continuously-measured information system data from a 600 MW coal-fired power plant in China. The results show that the proposed strategy achieves high energy conservation performance. Taking the 600 MW load optimization value as an example, the optimized power supply coal consumption is 307.95 g/(kW·h) compared to the actual operating value of 313.45 g/(kW·h). It is important for coal-fired power plants to reduce their coal consumption.

Preliminary Characterization of Corn Cob Ash as an Alternative Material for Ceramic Hollow Fiber Membrane (CHFM/CCA)

Currently, exchanging trends in the expensive usage of ceramic materials such as alumina, zirconia etc. into economical ceramic raw sources have been studied extensively over the last decade for various technological applications. Despite the fact that this ceramic compound or elements offer a great performance and stability, especially at high temperature and corrosive or acidic conditions, the basic commercial price of this compound which is a little bit higher have hindered the used of these materials. Thus interest in fabricating of bio-ceramic membrane using corn cob ash, an agricultural by product not only offered the development of new low cost materials but also able to enhance better properties and performance. The suitability of corn cob ash as an alternative material for ceramic hollow fiber membrane fabrication (CHFM/CCA) as a main substrate was investigated via combined phase inversion and sintering technique based on several controlled operating parameters. The effects of selected bore fluid (5, 10, 15 and 20 mL/min) and different sintering temperature (800˚C, 900˚C, 1000˚C, 1100˚C) towards membrane structure and properties were observed and studied. Interestingly, analysis of the SEM morphology showed that the potential of the main constituents of corn cob ash which highly consisted of silica, alumina and calcium oxide are able to improve the properties of CHFM/CCA by lowering sintering temperature (1000˚C) as compared to the standard CHFM bodies which normally has sintering temperature higher than 1200 oC. Thus, the used of corn cob ash not only able to enhance better ceramic properties but also able to reduce sintering temperature. Reduction in energy consumption with slightly reduced sintering temperature also will offer a better sustainable process through recycling abundant waste materials as well as the emphasis on the green resources. In respect, the bio-material of corn cob ash is capable to replace the commercial ceramic membrane materials for membrane applications by considering the availability of this agro waste product as the main crops in most countries in the world.

INFLUENCE OF PAD GEOMETRY MODIFICATION ON THE PERFORMANCE OF THRUST BEARINGS LUBRICATED WITH MAGNETORHEOLOGICAL FLUID

Magnetic fluids belong to the class of controllable materials. The influence of magnetic fields on this type of substance results in a change in its internal structure and an almost immediate change in its rheological properties. The ability to control the rheological characteristics in a very wide range, in combination with the ease of generating and controlling the magnetic field, creates the possibility of using this type of substance in systems with controlled operating parameters. The use of magnetic fluids in bearings may allow the design of some types of bearings to be simplified and enable efficient, fast, and precise control of the system operation, with a much shorter response time and higher stiffness than is the case with conventional sliding friction bearings. The paper presents the results of experimental tests carried out on a laboratory stand designed for thrust bearings lubricated with magnetic fluids. The analyses carried out concerned the determination of how the pad surface modification of the slide bearing, lubricated with magnetorheological fluids, influences the system performance parameters.

Aroma recovery of beer flavors by pervaporation through polydimethylsiloxane membranes

AbstractFive commercial beers and their corresponding no‐alcohol presentations have been analyzed in terms of five aroma compounds: three alcohols and two esters (isobutyl alcohol, ethyl acetate, 2‐methyl butanol, 3‐methyl butanol, and isoamyl acetate). Substantial reductions of volatile aroma compounds have been encountered in these nonalcoholic beers. Pervaporation of these aromas in order to allow their recovery has been tested through two commercial membranes with polydimethylsiloxane active layers (Pervatech and Sulzer). Total fluxes are higher through the Pervatech membrane while individual aroma ones are similar for both the membranes. Mass recovery is higher for the Pervatech membrane for most of the aromas whereas their enrichment factors are better for the Sulzer membrane. The rest of the beer profile modulates to some extent the general trends referred. Mass recoveries and enrichment factors from 5 to 35% were obtained for the aromas tested. Mass recovery and enrichment factors could be improved by increasing membrane area or time of treatment.Practical applicationsPervaporation is a membrane technique which effectiveness has been proven to separate volatile organic compounds from aqueous mixtures. It could be useful in beer industry in a significant way, helping nonalcoholic beers to improve their organoleptic characteristics. In a near future, by controlling operating parameters involved in the full process, it will be possible to introduce this technique into the factories and produce a tastier and better quality beer by minimizing the lack of valuable aroma compounds.