Stirred Bed Reactor Research Articles

Flow behavior of polypropylene reactor powder in horizontal stirred bed reactors characterized by X-ray imaging

Horizontal stirred bed reactors (HSBRs) are widely used in the commercial production of polypropylene (PP). Despite their commercial significance, a comprehensive understanding of the flow behavior in HSBRs remains elusive, primarily due to the lack of detailed experimental data. This study investigates the influence of operating parameters on the particle flow behavior of two types of PP reactor powder in a laboratory-scale HSBR using X-ray imaging. Our results indicate that the overall flow behavior and phase holdup in the HSBR are dominated by agitation. Moreover, gas injection through the inlet points at the bottom of the HSBR results in spouting behavior, which can lead to reduced gas-solid contacting and, in extreme cases, complete bypass. Finally, the presence of liquid (in this study, isopropyl alcohol) adversely affects the flow behavior of the PP reactor powder due to liquid bridging at the contact points of particles. Powders that comprise particles with relatively small sizes and dense surface morphology are particularly prone to reduced flow behavior when exposed to liquid.

Study of the Ion-Exchange Capacity of Clinoptilolite for Copper Ions under Ideal Displacement Conditions in the Dynamic Mode

The ionic mechanism of copper ion sorption from an aqueous medium has been confirmed. The study has elucidated the regularities of the process within a stirred bed reactor, where kinetics are limited by the internal diffusion region. Initial sorption curves under dynamic conditions have been obtained.

Particle dynamics in horizontal stirred bed reactors characterized by single-photon emission radioactive particle tracking

Horizontal stirred bed reactors are widely used in the commercial manufacturing of polypropylene. However, a comprehensive understanding of the particle dynamics in horizontal stirred bed reactors remains elusive, primarily due to the lack of detailed experimental data. In this work, we studied the influence of operating parameters on the particle flow dynamics in a laboratory-scale horizontal stirred bed reactor using single-photon emission radioactive particle tracking. The results show that the general solids flow behavior is strongly affected by both the agitator rotation speed and reactor fill level. Operation at low rotation speed and low fill level results in solids flow with poor radial and circumferential distribution due to internal bed circulation. On the contrary, at increased rotation speeds and fill levels, solids motion throughout the bed is continuous resulting in excellent solids distribution. The solids circulation was found to increase for both an increase in rotation speed and reactor fill level. The axial dispersion coefficient, on the other hand, shows a linear relation with the rotation speed, but no conclusive relation between the axial dispersion coefficient and the reactor fill level was found.

Single-photon emission radioactive particle tracking method for hydrodynamic evaluation of multi-phase flows

Evaluation of the hydrodynamics of opaque multi-phase flows remains a challenging task, with implications for various industrial processes such as chemical processing, pharmaceutical, and mineral processing. Understanding how design and operational variables affect the complex behavior of multi-phase flow systems is essential for optimizing processing conditions and improving efficiency. Radioactive particle tracking (RPT) has been a proven measurement technique to evaluate hydrodynamics in multi-phase flow systems. However, a limitation of the classical RPT technique exists in the assumptions made in the simulation of the count rate received by the detectors in correcting for varying flow-induced fluctuations in the volume fraction of the dispersed phase, often encountered in industrial multi-phase flow systems.In this paper, we introduce a fundamentally novel experimental RPT method that directly uses detected incident photon hit locations for the reconstruction of the three-dimensional radioactive tracer particle position. We argue that this approach is inherently more robust as varying attenuation does not affect the reconstruction. The RPT setup consists of three identical γ-radiation slit collimator detectors that are placed equidistantly at 120° intervals. A subsequent calibration-experimentation procedure is established that allows reconstruction of the tracer particle position with spatial accuracy and precision in the order of 1 mm. We demonstrate the applications of this technique in evaluating hydrodynamics in multi-phase systems by characterizing the flow field of industrial-grade polypropylene reactor powder in a laboratory-scale horizontal stirred bed reactor.

Multiscale modelling of multizone gas phase propylene (co)polymerization reactors—A comprehensive review

AbstractCatalysts and polymerization processes have evolved over the years. Such significant developments have allowed producers to broaden the range of polymer microstructure and process productivity, thereby making it possible to offer a wide range of end‐use properties at a reasonably low cost. However, these advantages in catalyst performance and reactor operation require that we understand as much as possible about reactor operation in the broadest sense. In addition to the fundamental experimental study of polymer chemistry, this means that one needs to develop complete, robust process models. The present paper provides a rapid overview of recent developments in various gas phase propylene (co)polymerization reactors in use today, concentrating on multizone gas phase polypropylene reactors: that is, multizone circulating reactor, fluidized bed reactor with internal circulation, fluidized bed reactor with external circulation, and horizontal stirred bed reactor. We then concentrate on the advances in multiscale modelling of gas phase propylene (co)polymerization reactors, from microscale kinetics at the active sites, to the mesoscale, including physical transport and thermodynamic modelling at the single‐particle level and its boundary layer, up to the macroscale reactor modelling. A systematic guideline used for the selection of appropriate thermodynamic models is proposed for gas phase olefin polymerization processes. Finally, current challenges and remaining issues related with the development of mathematical multiscale modelling are addressed.

Membrane Contactors and Their Application Potential

Nowadays, due to the scarcity of natural resources, there is more pressure on the reuse of materials and the application of circular economy principles. For this purpose, increasingly efficient and energy-saving technologies capable of extracting valuable raw materials from waste streams are needed, thus reducing energy and material dependence on primary resources. One such innovative technology is represented by membrane contactors, which enable mass sharing without the need for phase dispersion within each other, thus achieving lower operational and space requirements, as compared to conventional mass sharing devices (e.g. packed bed, tower column or stirred bed reactors). In addition, membrane contactors are very versatile and can be used not only for the recovery of valuable materials from waste streams in waste management processes (in particular recycling of metals or organics), but also as life-saving devices in biomedical applications (e.g. as extracorporeal blood oxygenation devices).

Intermediate pyrolysis campaign to assess products yield and quality varying biomass particles size, temperatures and composition

Conversely to fast pyrolysis, in which the most abundant product is the pyrolysis oil, intermediate pyrolysis generates comparable amounts of solid, gaseous and liquid products. The present work reports the results of intermediate pyrolysis experiments of lignocellulosic biomass performed in a semi-continuous stirred bed reactor, rated for a nominal capacity up to 1.5 kg h–1 of biomass feed. Bio-oil properties resulted similar to commercial fast pyrolysis oil in terms of organic-rich fraction, but a lower yield was attained. The oil contains an unusual large amount of water, probably due to long residence time and the catalytic effect of the accumulated char into pyrolysis reactor. Char was characterised and evaluated for agriculture applications, while the permanent gases were measured and evaluated as energy carrier for the process itself. These data can potentially be used in the design and modelling of larger-scale unit. [Received: May 6, 2016; Accepted: January 28, 2017]

Effect of biomass ash in catalytic fast pyrolysis of pine wood

Fast pyrolysis experiments of pine wood have been performed in a continuously operated mechanically stirred bed reactor at 500°C. The effects of the pine wood ash were studied by comparing non-catalytic and catalytic experiments (using a ZSM-5 based catalyst) with their ash-added counterparts. To show the case of ash accumulated from the biomass feeding, the results of catalytic fast pyrolysis obtained after eight reaction/catalyst regeneration cycles were included as well. The objective was to distinguish between the ash-catalyst interactions and the catalyst deactivation. The latter may be caused by thermo-mechanical, chemical and/or structural changes in the catalyst; such as poisoning, fouling, and attrition, as well as by coke deposition. Ash concentrations up to ca. 3wt.% relative to the amount of pine wood fed, and ca. 0.002wt.% relative to the amount of bed material, were found to be sufficient to change the distribution and the composition of pyrolysis products. The addition of ash to the catalytic fast pyrolysis, caused a reduction in the yields of both the organics and coke by 2wt.% (on feed basis), while increases of 1wt.% and 4wt.% in the water and non-condensable gases were observed, respectively. The total yield of CO plus CO2 was boosted by more than 10%, while the CO2 production (decarboxylation reactions) was favoured clearly. Moreover, the presence of added-ash suppressed the conversion of sugars and acids – these were more pronounced in the case of accumulated-ash – as well as of the phenols. The catalyst deactivation during the reaction/regeneration cycles is not only related to the presence of ash but also to changes in the structure and composition of the catalyst. To overcome the drawbacks of biomass ash in catalytic fast pyrolysis, either the biomass feedstock has to be leached (ash removal) before being introduced to the process, or the char (which contains a vast majority of the biomass ash) has to be physically removed from the catalyst before the regeneration step.

Flow characteristics of biomass particles in a horizontal stirred bed reactor: Part I. Experimental measurements of residence time distribution

The horizontal stirred bed reactor (HSBR) is a prevalent biomass pyrolysis reactor due to its effective seal, excellent control of temperature and residence time, and capacity to handle a wide range of particle diameters. This paper focused on the effects of various parameters on residence time distribution (RTD) and particle flow behavior in the HSBR. The RTD of biomass particles in a custom-built HSBR was measured using the impulse response method. The effects of operational parameters (including flow rate and agitator rotation rate), material flow properties (characterized by the angle of repose), and design parameters (including the number of blades and blade angle) on solid hold-up, mean residence time (MRT) and relative variance of residence time were investigated. The solid hold-up was affected by the rotation rate, flow rate, blade number, blade angles and material flow properties. The flow rate and material flow properties had a significant influence on the MRT while the effect of the other three parameters on the MRT was minimal. The relative variance was primarily influenced by the flow rate, rotation rate, blade number and material flow properties. The effect of the flow properties on the relative variance was irregular. The inter-particle mixing mainly resulted from agitator stirring. Hence, the inter-particle mixing was enhanced with the increase of the rotation rate and blade number. As such, it is essential to further examine the effect of material flow properties on inter-particle mixing using a modeling approach.

Flow characteristics of biomass particles in a horizontal stirred bed reactor: Part II. Modeling studies on particle residence time distribution and axial mixing

The modeling investigation of the flow and mixing behavior of particles in the horizontal stirred bed reactor was conducted using the axial dispersion model. The axial dispersion coefficients were obtained with different operational and design parameters and flow properties, based on the measured residence time distribution (RTD) in Part I. The axial mixing is considerably enhanced with the increase of the rotation rate, the number of blades and the repose angle. The flow rate made a less important contribution to the variation of the axial mixing while the blade angle rarely affected the axial mixing. This work proposed new design correlations for the model parameters in terms of flow rate, rotation rate, flow properties of materials, number of blades and blade angle, obtained by means of multiple regressions. The model developed in this paper was proved sufficiently accurate to model the RTD of particles in the HSBR by comparison between the numerical simulation and the experimental result of the RTD curve. The simulation of the RTD of particles in the HSBR was then performed with different conditions to investigate the effect of various parameters on the RTD using the model and gave similar trends with the experimental results.

A Bi-component Cu Catalyst for the Direct Synthesis of Methylchlorosilane from Silicon and Methyl Chloride

A bi-component catalyst comprising CuCl and metallic copper was used in the direct synthesis of methylchlorosilane to study the catalytic synergy between the different copper sources. The catalyst exhibited high activity and high selectivity of dimethyldichlorosilane (M2) in the stirred bed reactor. The effect of the proportion of CuCl used was studied and 10%-30% CuCl gave the best yield of M2. The use of CuCl decreased the induction period of reaction, improved the selectivity in the induction stage, and gave a longer stable stage. These results suggest that bi-component catalyst has advantages in the direct synthesis reaction.

Agglomeration Detection in Horizontal Stirred Bed Reactor Based on Autoregression Model by Acoustic Emission Signals

Agglomeration occurring in horizontal stirred bed reactors (HSBR) for polyolefin production has negative impacts on the efficiency of the reactor operation and may sometimes lead to unscheduled shutdown of the plant. In this paper, an autoregression (AR) model based on acoustic emission (AE) technique has been proposed to establish the qualitative relationship between AE signals and agglomeration in the HSBR. In this method, the frequency of AE signal varies with particles of different sizes striking the reactor walls. From the cold model experiments, it was found that AR power spectrum became fluctuant after the addition of agglomerations into laboratorial scale HSBR, and meanwhile the low frequency band energy ratio and the variance of AE signals kept rising. Furthermore, this AE-based AR model was also successfully applied to detect the agglomeration in an industrial HSBR unit, showing that the method could monitor agglomerations in an environmentally friendly manner and with fairly good accuracy.

The Detection of Agglomeration in HSBR Based on the Analysis of an Acoustic Emission Signal

A method of agglomeration detection in horizontal stirred bed reactors was obtained based on the frequency of acoustic emission (AE) signals vary with different sizes of particles stricken on the wall. The AE signal was dealt with by the method of spectrum analysis and wavelet analysis. It was found that the low frequency band energy ratio of AE signals (d6~d7) increased as the agglomerations were added in the reactor. So this method could predict the agglomeration environmental friendly with fairly good accuracy.

Modeling and simulation of polypropylene particle size distribution in industrial horizontal stirred bed reactors

AbstractThis work aims at developing a steady‐state particle size distribution (PSD) model for predicting the size distribution of polypropylene particles in the outflow streams of propylene gas‐phase horizontal stirred bed reactors (HSBR), on the one hand and investigating the effect of the catalyst residence time distribution (RTD) on the polymer PSD, on the other hand. The polymer multilayer model (PMLM) is used to describe the growth of a single particle. Knowing the PSD and RTD of a Ziegler–Natta type of catalyst and polymerization kinetics, this model allows calculating the polymer PSD of propylene polymerization in the HSBRs. The calculated polypropylene PSDs agree well with those obtained from the industrial reactors. The results reveal that both the PSD and the RTD of the catalyst affect the polymer PSD but in different manners. The effect of RTD on the PSD is less significant in the case of a nonuniform size catalyst feed. This model also allows investigating the effects of other process parameters on the polymer PSD under steady‐state conditions, including intraparticle mass‐ and heat‐transfer limitations, initial catalyst size, and polymer crystallinity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Production of hydrogen and light hydrocarbons as a potential gaseous fuel from microwave-heated pyrolysis of waste automotive engine oil

Waste automotive engine oil was pyrolyzed in a continuous stirred bed reactor using microwave energy as the heat source; the yield and characteristics of the incondensable gaseous products are discussed. The recovered gases (41 wt% yield) were found to contain substantial concentrations of light aliphatic hydrocarbons (up to 86 vol.%) that could potentially be used as a chemical feedstock or a fuel source to power the process, or to be reformed to produce hydrogen for use as a second-generation fuel. Examination of the composition of the gases also showed the formation of H2 (up to 19 vol.%) and CO that could also be used as a valuable syngas (with a H2 + CO content of up to 35 vol.%). The high yield of gaseous hydrocarbons can be attributed to the unique heating mode and chemical environment present during microwave-heated pyrolysis. The use of a microwave-heated bed of particulate-carbon showed advantages in transforming waste oil into valuable gases. Hence an environmentally unfriendly waste material can be transformed into a useful resource and serves as an alternative source of hydrogen or hydrocarbon energy. The recovery of valuable gases shows advantage over traditional destructive approaches and suggests excellent potential for recycling problematic waste oil.

Application of the mixture design to decolourise effluent textile wastewater using continuous stirred bed reactor

Important pollutants in textile effluents are mainly recalcitrant organics, colours, toxicants and inhibitory compounds, surfactants, chlorinated compounds (AOX), pH and salts. An aerobic system using a continuous stirred bed reactor (SBR) was continuously operated at constant temperature and fed with textile wastewater (pH 7 and total chemical oxygen demand (COD) 1 700 mg/l).This report is focused on the decolourisation treatment of effluent by a bacterial consortium (Sphingomonas paucimobilis, Bacillus sp. and filamentous bacteria). The influence of the different mixtures of 3 strains on the decolourisation of effluent (cell density fixed at OD600 = 1) was studied using an equilateral triangle diagram and mixture experimental design to assess colour and COD removal during species evolution. With the aid of analysis software (Minitab 14.0), the formulation of pure culture was optimised for several responses and the best formulation obtained. The results suggested that the highest predictable specific decolourisation rate and chemical oxygen demand (COD) were 86.72% and 75.06%, respectively. Regression coefficients between the variables and the responses of decolourisation and COD removal were, respectively, R2 = 72.48% and 54.28%, which indicated excellent evaluation of experimental data by the polynomial regression model. UV-visible analysis confirmed biodegradation of effluent. Keywords : textile wastewater, bacterial decolourisation, response surface, mixture design, SBR

Modeling Study on Effects of Liquid Propylene in Horizontally Stirred Gas‐Phase Reactors for Polypropylene

AbstractModeling study was carried out for JPP‐HORIZONE, which has horizontally stirred gas reactors in which the heat of polymerization is removed by vaporization of liquid propylene (LPP). The effects of LPP were estimated by the model which has a couple of continuous stirred bed reactors different in propylene form, gas of liquid, combined with a less stereospecific catalyst as a probe. LPP affects isotacticity further than catalyst efficiency in the developed model. Observed isotacticity was lower than that estimated by the model without LPP, which can be explained only by the presence of LPP.

Agglomeration detection based on attractor comparison in horizontal stirred bed reactors by acoustic emission sensors

AbstractIn industrial propylene polymerization technology of Innovene and Chisso, agglomeration of polymer particles in horizontal stirred bed reactors (HSBR) has significant negative impacts on the reactor efficiency. If the hydrodynamic change could be detected early enough, then large chunks may not be formed nor cause an unscheduled shutdown of the plant. A novel non‐invasive acoustic emission (AE) technique combined with an attractor comparison method is presented. It is based on the comparison of the time series of AE signals acquired from a normal state with the time series measured during operation of the bed. The nature of the method is to determine whether or not two time series are generated by the same mechanism. A statistical characteristic S is used to test the null hypothesis that the two multidimensional probability distributions are identical. Experiments were carried out at room temperature in a 475 mm i.d. laboratory HSBR. The results demonstrated that the method is sensitive to small changes in the particle size distribution. It is, therefore, indicated that the proposed method not only can offer “early and accurate warning,” but also has the potential to locate the agglomeration in HSBR with multiple AE sensors. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Synthesis of Isopropyldichlorosilane by Direct Process

Direct reaction of elemental silicon with a gaseous mixture of isopropyl chloride (1) and hydrogen chloride in the presence of copper catalyst using a stirred bed reactor equipped with a spiral band agitator gave isopropyldichlorosilane having a Si-H bond (2a) as a major product and isopropyltrichlorosilane (2b) along with chlorosilanes, trichlorosilane and tetrachlorosilane. A process for production of 2a was maximized using the 1:0.5 mole ratio of 1 to HCl and smaller size of elemental silicon at a reaction temperature of 220 °C. When a reaction was carried out by feeding a gaseous mixture of 1 [12.9 g/h (0.164 mol/h)] and HCl [2.98 g/h (0.082 mol/h)] to a contact mixture of elemental silicon (360 g) and copper (40 g) under the optimum condition for 45 h, 2a among volatile products kept up about 82 mol % until 35 h and then slowly decreased down 68 mol % in 45 h reaction. Finally 2a was obtained in 38% isolated yield (based on 1 used) with an 85% consumption of elemental silicon in a 45 h reaction. In addition to 2a, 2b was obtained as minor product along with chlorosilanes, trichlorosilane, and tetrachlorosilane. The decomposition of 1 was suppressed and the production of 2a improved by adding HCl to 1.

Catalyzed and Promoted Direct Reaction of Ethyl Chloride with Silicon Using Stirred-Bed Reactor

In this paper a stirred-bed performed of the copper catalyzed synthesis of ethylchlorosilanes from silicon and ethyl chloride was described. A Si-catalyst mixture prepared by reaction of CuCl and Si was employed. The compositions of products were mainly ethyltrichlorosilane, diethyldichlorosilane, and ethyldichlorosilane and mainly depended on the extent of Cu in the mixture and the reaction temperature. A promoting effect on the extent of adsorption was observed on the addition of certain additives. The kinetic data revealed the direct depended of the reaction rate on C2H5Cl pressure.