1,721,013 research outputs found
The influence of modular structure on the hydrodynamics of catalytic structured packings for reactive separation processes
No full textResidence time distribution (RTD) and drainage experiments are used to shed light into the hydrodynamics of the catalytic structured packing Katapak-SP11. The liquid flow behaviour and the dynamic liquid holdup were derived from the RTD results and compared with the total liquid holdup derived from the drainage experiments. The liquid considered static from the viewpoint of free-draining experiments becomes dynamic during the normal column operation. The examination of the liquid drainage curves and the consistency of different techniques are discussed. Copyright © 2009, AIDIC Servizi S.r.l
Identification of suspension state using passive acoustic emission and machine learning in a solid–liquid mixing system
Full text linkSolid–liquid mixing is a core operation in many manufacturing processes in the food, cosmetics, pharmaceutical and chemical industries. This work aims to develop an accurate and reliable sensing methodology using passive acoustic emission (PAE) coupled with supervised machine learning (ML) algorithms, to allow identifying and predicting solid–liquid suspension state. Using PAE in process monitoring is beneficial because it is affordable, sensitive, non-intrusive, and suitable for on-line applications. PAE equipment includes a piezoelectric sensor, placed in contact with the system, an amplifier, a filter, an oscilloscope to record the signal and a computer. Experiments were carried out in a fully baffled, flat bottom glass vessel equipped with a PBT impeller. Acoustic signals were recorded with sampling frequency of 750 kHz, impeller speed range 50–1000 rpm and varying solid features, i.e., particle size (dp range 0.250–6 mm), solid loading and solid density (acryl-glass particles). For each classification run, sampled data were pre-processed using Fast Fourier Transform (FFT) to reveal any detailed spectral characteristics of the signal in the frequency domain. Spectra have been filtered and then reduced by selecting the highest variance frequencies. As labelling, established optical measurements were used to classify the acoustic frequency spectra. The frequency data set has been split in training (60%), cross validation (20%) and test (20%) sets and were used, respectively, to build the model, identify the best model parameters (optimisation step), and finally to check the accuracy (test step). The developed technique has shown excellent results in recognizing spectra corresponding to different classes with observed accuracy greater than 99.72%
A mechanistic pressure drop model for columns containing structured packings
No full textA mechanistic model was developed to predict pressure drop and flooding in packed columns equipped with corrugated packing of the regular type. It was developed after considerating the interaction of falling liquid film with the gas phase, based on mass- and momentum-conservation equations. Among the most common structured packings, the behavior of the Mellapak and BX types was analyzed. The aim of this work is to demonstrate how mechanistic models, developed for simple geometry, can also be used to compute pressure drops in cases where the geometry is more complex, as with a structured packing. This approach, based on the geometric characteristics of the packing and measurable parameters such as liquid holdup, enables the development of a basic model by limiting the number of adjustable parameters, which are numerous in all the available models. Because of its nature, this model is extremely easy to extend to different types of structured packings
Liquid-film mass transfer coefficient in column equipped with structured packings
No full textThe effective mass-transfer efficiency in a column equipped with structured packings was investigated experimentally. The packings analyzed in the present work were Sulzer Mellapak 250Y, made of corrugated plastic or metal sheets, and Sulzer BX, made of plastic gauze. In the literature many works have been published on this topic, but they have mainly been oriented toward evaluating overall mass-transfer efficiency or the gas-side coefficient, leaving out closer examination of the liquid-side mass-transfer coefficient. The aim of the present work is to examine liquid film and to identify a relation that allows accurately evaluating the liquid film contribution to overall mass-transfer efficiency. Experimental results showed that column packing height affects the liquid-side mass-transfer coefficient at the usual industrial-scale liquid and gas flow rates. This result agrees with theoretical analysis on stable liquid rivulet flo
Design of complex wire-mesh mist eliminators
No full textKnitted wire-mesh mist eliminators have widespread application in many industrial plants. Despite their extensive use, the open literature regarding them:is really limited. Some experimental data and mechanistic models have been published for common knitted wire-mesh mist eliminators formed from a single metal pad. This type of mist eliminator can be used in most distillation and absorption columns, but because of the poor removal efficiency, cannot be used in operations involving acid mist, fine fog resulting from liquid condensation from a saturated vapor, oil mist from compressed gases, and natural-gas dehydration applications. Moreover, other possible problems may arise when the separator is fed with high liquid and gas flow rates, because these conditions can induce flooding in the mist eliminator: In both of these cases, common wire-mesh mist eliminators do not perform satisfactorily, and therefore complex wire-mesh mist eliminators have to be installed to improve separation efficiency or to increase allowable liquid loadings while avoiding flooding phenomena. This article presents a mechanistic model based on a set of new experimental data obtained by investigating performance of commercial complex eliminators
Conventional and complex knitted mesh mist eliminators
No full textKnitted wire mesh mist eliminators have a widespread application in many industrial plants as they assure an optimum cost/performance for many applications compared with other separation devices. Complex mesh pads allow the performance and the range of applications of conventional wire mesh pads to be extended. In recent years, increasing research effort has been dedicated to the experimental investigation of both common and complex mesh pads and to the development of reliable design models that are essential for the design and optimization of complex separation units
Design of wire mesh mist eliminator
No full textKnitted wire mesh mist eliminators are used extensively in many industrial plants. Their widespread application is essentially due to the low cost and efficient removal of entrained liquid droplets from vapor and gas streams. Despite the broad range of entrainment removal applications, open literature an this topic is limited. All the available design relations are based on semiempirical equations with an uncertain range of application. In this work, a set of new experimental data was obtained by investigating the performances of commercial eliminators, and a mechanistic model is presented. Comparison between experimental data and the proposed model shows that it can be used to predict separation efficiency both for horizontal and vertical arrangements
Effect of residence time and energy dissipation on drop size distribution for the dispersion of oil in water using KMS and SMX+ static mixer
No full textThe Planar Laser Induced Fluorescence technique was used to determine the drop size distribution of oil dispersed in water at the inlet and outlet of two static mixer geometries (KMS and Sulzer_SMX+) equipped with either 6 or 12 elements. A mineral oil (Lytol®), three times more viscous than the water continuous phase, was used as the dispersed phase. The oil flow rate was kept constant through all experiments forcing the drop detachment from the secondary inlet. The L–L system was very dilute ( ̃0.05–0.0007% v/v O/W) to avoid coalescence phenomena. The flowrate of the continuous phase (water) was altered giving values of Reynolds number from 2000 to 12,000, covering high transitional and turbulent flow regimes. Increasing the flow rate of the continuous phase, the detached oil drops from the secondary inlet decreased in size as expected. However, same drops after flowing a length of 0.4 m of an empty pipe reached a constant size. To investigate a wider range of energy dissipation and residence time, the presence of static mixers has been investigated. Pressure drops, hence energy consumed, were measured to compare the different set ups and drop size distributions. The results show that by increasing the flow rate, the drop size decreased up to a critical point, beyond which oil droplet size reduction became inefficient. The collected data were then used to derive a methodology to identify the optimal flow conditions and choice of static mixer device to achieve best drop size reduction with less energy per unit mass
Measurement of activity-coefficients at infinite dilution of chlorinated solvents in commercial polyethylene-glycol ethers
No full textAmong the suggested scrubbing liquids, alkylene glycol dialkyl ethers are especially suitable because of their favorable properties. Activity coefficients at infinite dilution are reported in the literature only for single absorption liquids, but generally in industrial applications stabilized mixtures of these substances are used. In this work two commercial products were considered: Genosorb 300 and Genosorb 1843, mixtures of polyethylene glycol dimethyl ethers and of polyethylene glycol dibutyl ethers, respectively. Gas-liquid chromatography was chosen for the es:perimental determination of the activity coefficients at infinite dilution, in the temperature range between 42 and 90 degrees C, of commonly used organic solvents, belonging in particular to the halocarbon class
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