A hydrogen concentration measurement device is developed for nuclear reactor primary circuits water. Despite the necessity to monitor hydrogen, only one producer offers a really selective hydrogen sensor on the world market because of the complexity of the device preparation when long-term signal stability is required. Therefore, the Mass Transfer Laboratory at UCT Prague shares the experience gained during the sensor development. The results of the amperometric hydrogen sensor laboratory tests are presented, which demonstrate how to improve the sensor durability. An operational test in Dukovany nuclear power plant confirmed a significant improvement of the latest sensor version and showed that a simple principle could be realized in the form of a reliable device for industrial measurements.

The analysis of local values of volumetric mass transfer coefficient, kLa, was performed to identify the effects of local hydrodynamics on the mass transfer rate in multiple-impeller stirred tank reactors. The database of kLa values measured by Dynamic Pressure Method was analysed. The database provides data for two vessel sizes (laboratory and pilot-scale reactor), a wide range of operational conditions (gas flow rate, impeller speed), various impeller geometries and sizes and four different batches including viscous media. The local kLa values in multiple impeller configurations were measured in several positions corresponding to the individual impeller regions. The overall kLa value averaged through the whole volume is considered as the best representation of the correct kLa value. Different hydrodynamic effects on mass transfer rate were obtained in the two end regions. In the bottom region, the local kLa values increase with impeller speed faster than the overall kLa. The opposite behaviour was obtained in the uppermost region corresponding to the decrease of power consumption and the mass transfer rate with increasing surface aeration under high impeller speeds. The best representation of the overall kLa value was obtained in the middle position of the vessel, where the exchange flows bring the liquid saturated to different measure from the end regions. Even if the local kLa data in individual impellers' regions are shifted to the average values due to the inter-impeller exchange flows, the differences between them are still significant. We show the local kLa values by the combination of the data measured at different liquid level heights. The results can be used in the fermenter design with various impeller combinations.

Design and optimization of aerobic fermentation processes in stirred tanks must factor in specific features, such as the formation of gas cavities on the rear of impeller blades and the need for high power input. Here, the ability of a curved-blade impeller to reduce these drawbacks, which are typical of flat-blade impellers, is investigated. The analysis is based on gas holdup distributions and liquid homogenization dynamics collected by electrical resistance tomography in a pilot-scale stirred tank of geometry similar to typical industrial aerated fermenters. A wide range of gas flow rates and impeller speeds in single-impeller and multiple-impeller configurations are considered and the differences arising when a Rushton turbine is replaced with a Bakker turbine are discussed.

In the era of the expansion of hydrogen use, its concentration measurement becomes more important. We further focus on one of the H2 concentration measurement purposes, where the hydrogen diffusion in a solid membrane and in a liquid electrolyte play the key role. To keep optimal process conditions in the primary cooling circuit of nuclear power plants, various chemical species are dosed in. Among the species the concentration of which is monitored in primary coolant, belong oxygen and hydrogen. While plenty of companies offer oxygen sensors suitable for the measurement in the primary coolant, the hydrogen sensor, really selective to H2 concentration, is offered by only one company. It is worth, therefore, accomplishing the development of a hydrogen sensor, which began at UCT Prague in the 1990's and, after several successful measurements in nuclear power plant, interrupted due to fateful events in the research team. We introduce here the results of the first part of contemporary work of the Mass Transfer Laboratory based on new technologies but using the experience from 1990's. Having at disposal modern functional samples to measure both oxygen and hydrogen concentrations, we verified a fair long-term stability of the sensors and, further, we would like to cooperate with an industrial partner to finalize the development of prototypes and start the production of monitoring units.

The mechanically agitated vessels serving as gas–liquid stirred tank reactors are often utilized equipment in the chemical, biochemical, pharmaceutical, and food industry worldwide. When the gas flows through the stirred tank reactor, the liquid level in the tank increases. The amount of encaptured gas is usually expressed as a volumetric fraction of gas in dispersion (also called gas holdup). The gas holdup is one of the main characteristics in the case of gas–liquid contractors because it directly indicates the active interphase area. The most important factors affecting the gas holdup are: vessel and impeller geometry, operational conditions, and chemical properties of the examined system. This work focuses on the viscosity influence on gas holdup formation in laboratory and pilot plant stirred tank reactor at a wide range of experimental conditions. The influence of gas flow rate, impeller type, impeller diameter, batch viscosity, and other operational conditions was tested. The broad experimental conditions were used for establishing chemical engineering correlations that would be viable for the design and scale up.

The gas suction rate of a conventional liquid-gas ejector pump was measured on a modular pilot plant unit utilizing convergent nozzles and a water-air system. Hydraulic character-istics were measured for various water flow rates, suction and discharge pressures, and ejector geometries, covering a wide range of configurations and operating conditions. The device configurations, providing the most stable and reproducible results, were identified. The air flow rates measured with these configurations were correlated by a simple, three-parameter correlation with a relative standard deviation (RSD) of 11%. The performance and behavior of the ejector in less stable configurations are discussed and the recommendations for the design of optimally operating units are provided. Finally, the correlation is tested against available literature data. The ejectors with comparable geometry agree well with the proposed correlation (within 20% RSD). The reasonable agreement with the discussed differences is found for other literature data. This comparison results in the validation of the proposed correlation to provide a safe prediction of minimal gas entrainment in units of various geometries, orientation and operating conditions. (c) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. The gas suction rate of a conventional liquid?gas ejector pump was measured on a modular pilot plant unit utilizing convergent nozzles and a water?air system. Hydraulic characteristics were measured for various water flow rates, suction and discharge pressures, and ejector geometries, covering a wide range of configurations and operating conditions. The device configurations, providing the most stable and reproducible results, were identified. The air flow rates measured with these configurations were correlated by a simple, threeparameter correlation with a relative standard deviation (RSD) of 11%. The performance and behavior of the ejector in less stable configurations are discussed and the recommendations for the design of optimally operating units are provided. Finally, the correlation is tested against available literature data. The ejectors with comparable geometry agree well with the proposed correlation (within 20% RSD). The reasonable agreement with the discussed differences is found for other literature data. This comparison results in the validation of the proposed correlation to provide a safe prediction of minimal gas entrainment in units of various geometries, orientation and operating conditions.

Microorganisms are used in various fermentation processes for the production of biochemicals and food. These types of processes take place predominantly in mechanically agitated vessels. An important transport characteristic is the volumetric mass transfer coefficient k(L)a. Many correlations are available in the literature to estimate parameters in a gas-liquid system; however, three-phase systems are not sufficiently described. The experiments were carried out under laboratory conditions in a single-impeller mechanically agitated vessel with an internal diameter of 0.29 m. The solid phase was either cellulose, with two different particle sizes, or glass beads. An updated correlation is proposed that could be adopted in the design and scale-up of agitated devices operating in the presence of solid particles.

Stirred tank reactors are one of the crucial equipments in the chemical, biochemical, pharmaceutical, and food industries. The design of mechanically agitated vessels contains two main tasks: to find appropriate geometry of the system (such as vessel shape, impeller types, and others) and to choose suitable driving force that would supply required power input for operational conditions reach. The ungassed power input prediction is necessary for the effective industrial design of the engine. The ungassed power input depends on many variables such as tank geometry, used impeller type, and properties of the batch. This work focuses on the influence of the batch composition, impeller type, and impeller diameter on ungassed power consumption. Experiments were performed in laboratory and pilot plant scale vessels while using various operational conditions (such as impeller type, impeller diameter, batch viscosity, and others). Due to a wide range of operational conditions, the obtained results could be transferable to other systems with similar geometry up to industrial conditions.

Volumetric mass transfer coefficient (kLa), is the critical transport characteristic in the design of mechanically agitated contactors. Prediction of kLa is nowadays mostly based on literature correlations. Our aim is to establish suitable kLa correlations for different types of devices that would be based on the experimental data set. In our previous work, the correlation for kLa prediction in coalescent batch were described only for Rushton turbines (Petříček et al., 2019). Now, we aim at the description of one universal correlation that would be viable for mechanically agitated contactors in coalescent batch for several impeller types with different diameters and their combinations on a common shaft. The measured transport characteristics were summarized into correlations. This correlation shape can be used to predict transport characteristics in industrial-scale vessels under a wide range of operational conditions.

Mass transfer processes are one of the most important operations in chemical, biochemical, and food industries worldwide. In the processes that are controlled by the gas-liquid mass transfer rate, the volumetric mass transfer coefficient k L a becomes a crucial quantity. The dataset was measured with the aim to create a correlation for k L a prediction in a non-coalescent batch under the wide range of experimental conditions. The dynamic pressure method, which was reported as physically correct in the past, was chosen to be the method for experimental determination of k L a. Our previous work targeted the k L a dependencies in viscous and coalescent batches resulting in correlations that are viable for the broad range of process conditions. We reported that the best-fit correlation is based on the hydrodynamic parameter circumferential velocity of impeller blades in the case of non-coalescent liquids in the vessel equipped by single or multiple impellers at a constant D/T ratio (diameter of the impeller to the inner diameter of the tank). Now, we focus on the influence of various impeller diameters on transport characteristics (mainly k L a) in a non-coalescent batch. The experiments are carried out in a multiple-impeller vessel equipped with Rushton turbines (of four diameters) and in both laboratory and pilot-plant scales. Various impeller frequencies and gas flow rates are used. We examine the suitability of the hydrodynamic description, which was reported in the past, to predict k L a also when the D/T ratio changes. We show that the correlation based on the energy dissipation rate better fits the experimental data and predicts k L a values more accurately in the case of varying D/T values. This correlation could be adopted in the design and scale-up of agitated devices operating with non-coalescent batches.

In mechanically agitated gas–liquid contactors design, transport characteristics such as volumetric mass transfer coefficients, power input, and gas hold-up often become the key parameters. Therefore, their values should be estimated as precisely as possible. The power input is usually used as the scale of energy dissipation for other characteristics. The goal of this work is to establish reliable power input correlations for industrial processes design, where the coalescent batch is used. The experiments were carried out in a pilot-plant and laboratory vessel. Different types of impellers, as well as their different diameters, were used, and also the combinations of radially and axially pumping impellers on a common shaft. Energy consumption was measured in a multi-impeller vessel with different impeller frequencies and several gas flows. Correlation equations describing the behavior of individual impellers were evaluated. The correlations we suggested can be used for impeller power prediction in industrial scale vessels under a wide range of operational conditions.

Volumetric mass transfer coefficients, k(L)a, just as power input are considered as essential parameters for mechanically agitated gas-liquid contactors in relation to their optimization and design. The knowledge of power input is crucial for the prediction of other mass transfer characteristics. A power input correlation is created for the industrial design of the process with a non-coalescent batch that would be appropriate for a broad range of operational conditions. The recommended resulting correlation is able to predict the power input for impellers in industrial-scale design for a significant scope of operational conditions.

The volumetric mass transfer coefficient (kLa) plays a crucial role in industrial design in the case of the process controlled by gas–liquid mass transfer. Prediction of kLa is nowadays mostly based on literature correlations. Our research goal is to establish suitable kLa correlations for different types of devices that would be based on the experimental dataset. This article aims at the description of one universal correlation that would be viable for mechanically agitated gas–liquid contactors and also for pneumatically agitated gas–liquid contactors such as airlift reactor.

The volumetric mass transfer coefficient k(L)a becomes the crucial parameter for mechanically agitated fermenters design. Prediction of k(L)a is commonly based on literature correlations. In the case of coalescent liquids, literature-based correlations don't provide results with acceptable scatter. Our aim is to establish viable k(L)a correlations for coalescent liquids that would be based on great experimental data set obtained using Dynamic Pressure Method, the physical correctness of which was verified earlier. In our previous work, the k(L)a dependencies on process conditions in a viscous liquid were described in terms of an appropriate correlation. Now, we aim at the description of dependency between impeller diameters and transport characteristics in coalescent batch. The measurements were performed in multiple-impeller vessels of both laboratory and pilot-plant scale, and for various experimental conditions (impeller frequencies, gas flow-rates, impeller diameters). The studied impellers were Rushton turbines with diverse diameters. On the base of experimental results, the accurate correlation for k(L)a prediction in coalescent batch for industrial devices was suggested. Both the experimental technique and the correlation shape could be used for an industrial design of fermenters with coalescent batches. (C) 2018 Elsevier Ltd. All rights reserved.

The transient and steady pervaporation of 1-butanol-water mixtures through a poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membrane was studied to observe and elucidate the diffusion phenomena in this high-performing organophilic glassy polymer. Pervaporation was studied in a continuous sequence of experiments under conditions appropriate for the separation of bio-butanol from fermentation broths: feed concentrations of 1.5, 3.0 and 4.5 w/w % of 1-butanol in nutrient-containing (yeast extract) water, temperatures of 37, 50 and 63 °C, and a time period of 80 days. In addition, concentration polarization was assessed. As expected, the total flux and individual component permeabilities declined discernibly over the study period, while the separation factor (average β = 82) and selectivity towards 1-butanol (average α = 2.6) remained practically independent of the process conditions tested. Based on measurements of pervaporation transients, for which a new apparatus and model were developed, we found that the diffusivity of 1-butanol in PTMSP decreased over time due to aging and was comparable to that observed using microgravimetry in pure vapor in 1-butanol. Hence, despite the gradual loss of free volume of the aging polymer, the PTMSP membrane showed high and practically independent selectivity towards 1-butanol. Additionally, a new technique for the measurement and evaluation of pervaporation transients using Fourier transform infrared spectroscopy (FTIR) analysis of permeate was proposed and validated.

This paper refers on the hydraulic and mass-transfer characteristics of several high capacity structured packings Raschig Super-Pak (RSP250Y, RSP350Y, RSP500Y) under absorption conditions. Measurements were performed in column with inner diameter 0.15 m. The comparison with data published in Rejl et al. (2015) for structured packing Raschig Super-Pak 250Y performed in column with inner diameter 0.29 m allows unique assessment of column diameter effect on hydraulic and mass-transfer characteristic of packings. Such study should provide an answer whether is it possible to acquire or under which experimental conditions obtain a reliable hydraulic and mass-transfer characteristics of packing on the columns, from industrial point of view, with small diameter. Obtained characteristics on packings with three different geometric areas enable the evaluation of geometric area effect on the hydraulic and mass-transfer characteristics.

Unbaffled stirred tanks are increasingly recognized as a viable alternative to common baffled tanks for a range of applications such as biochemical, food or pharmaceutical processes where the presence of baffles is undesirable for some reason. In this work, the mass transfer performance of unbaffled stirred tanks with pitched blade turbine, operating either in up-pumping or down -pumping mode, was investigated. The influence of impeller size and liquid viscosity were also investigated. The mass transfer intensity was measured by means of the Simplified Dynamic Pressure. Method: The measurements concerned both coalescent and non-coalescent (viscous) batches. Results: confirm that increasing apparatus size has a slightly positive effect on gas-liquid mass transfer coefficient. It was also found that when the PBT is operating in the up pumping mode the formation of surface oscillations, which lead to undesired instabilities of the whole apparatus, is conveniently minimized. In the super-critical regime, the unbaffled tanks provide a performance comparable with that of the standard (baffled) bioreactors at the same power dissipation, which makes them a viable alternative for general fermentation operations and other gas-liquid reactions. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

We present a novel approach to the determination of the distillation packed bed height utilizing procedure involving new mass-transfer and hydrodynamics models for structured packings. Our approach is based on: a) advanced analyses of the distillation data utilizing composition profiles (instead of HETP); b) measurement and separation of the non-ideal hydrodynamics influence on the packed bed efficiency; c) utilization of the data acquired with proven absorption test methods with non-air (kG) and non-aqueous (kL) systems. The parameters of the here presented model are derived from the experimental data acquired with i.d. 150 mm distillation & absorption column and might be modified and supplemented when industrial scale experimental data and data for more packing types are available.

The interest in the process industry on unbaffled stirred tanks has greatly expanded in the last years because they may bring about significant advantages in a number of applications, including biochemical, food and pharmaceutical processes where the presence of baffles is undesirable for several reasons. Despite their application potential, unbaffled vessels still lack fundamental information, due to the fact that only recently their capabilities have started being dug out. The lack of information on scale up effects is possibly the main reason hindering practical applications.In this work the influence of vessel size and liquid viscosity on the mass transfer performance in unbaffled stirred vessels, is investigated. As regards the first issue (scale-up) quite surprisingly results show that comparable mass transfer coefficients may be obtained in larger vessels, for a given power input per unit volume, with typical kLa values up to 2×10−3s−1 in ungassed conditions and of 2×10−2s−1 in gassed conditions. This is opposite to expectations based on the fact that the exchange surface in subcritical conditions only grows with D2 while volume grows with D3. Notably, the same result is obtained at an increased liquid viscosity (a feature often exhibited by biological cultivation broths) and confirms that unbaffled stirred tanks should be regarded as a strong candidate for industrial applications.Finally, also at the larger scale, in the super-critical regime unbaffled tanks are found to provide a performance comparable with that of standard (baffled & sparged) stirred tanks, hence resulting in a viable alternative to baffled tanks for all gas–liquid processes and bio-processes.

Transport characteristics such as volumetric mass transfer coefficients, k(L)a, power input, P and gas holdup, epsilon(G), are the key parameters in the design of mechanically agitated gas-liquid contactors. For their successful design, values of the key parameters can be estimated using empirical correlations. The goal of this work is to complete a complex study to investigate the behavior of k(L)a, P and epsilon(G) in multiple-impeller vessels in non-coalescent viscous batch. We used the dynamic pressure method (DPM). The experiments were conducted in multiple-impeller vessels of both laboratory and pilot-plant scale, which enabled the scale-up studies. Several impeller types with different diameters and their combinations on a common shaft were used in the vessel, under various impeller tip speeds and gassing rates. For all impeller combinations, the gassed and ungassed power consumption, gas hold-up and volumetric - mass transfer coefficient were measured in viscous batch. The measured transport characteristics were summarized into correlations. Several literature correlations were judged, using these extensive datasets. In addition to this, new correlation shapes were also established. The correlation given by and p(g)/V-L = K-1(p(v/)V(L))(K2) vs(K3) gave fairly good prediction of the impeller power. The correlation of this shape can also be employed to calculate the power dissipated in the bottom and upper stages of the multiple-impeller vessel. Correlation epsilon(G) = K-1 (p(g)/V-L)(K2) vs(K3), based on the theory of isotropic turbulence was shown to be reliable for various impeller types. For non-coalescent viscous batch, it is worth using correlation based on power dissipation k(L)a = K-1(p(TOT))(K2) v(s)(K3) ilp This correlation shape can be used to predict transport characteristics in industrial scale vessels under a wide range of operational conditions. (C) 2018 Elsevier Ltd. All rights reserved.