Moving Bed Research Articles

Synthesis of 4-Aryl-2-pyrrolidones and β-Aryl-γ-amino-butyric Acid (GABA) Analogues by Heck Arylation of 3-Pyrrolines with Arenediazonium Tetrafluoroborates. Synthesis of (±)-Rolipram on a Multigram Scale and Chromatographic Resolution by Semipreparative Chiral Simulated Moving Bed Chromatography

We report herein a new, practical, and economic synthesis of the phosphodiesterase inhibitor Rolipram on a multigram scale as well as the synthesis of new 4-aryl pyrrolidones and beta-aryl-gamma-amino butyric acids (GABA derivatives) employing an efficient Heck-Matsuda arylation of 3-pyrroline with aryldiazonium tetrafluoroborates. Racemic Rolipram was resolved into its enantiomers using chiral simulated moving bed chromatography having the low-cost microcrystalline cellulose triacetate as a chiral stationary phase.

EVALUATION OF MOVING BED BIOFILM REACTOR TECHNOLOGY FOR ENHANCING NITROGEN REMOVAL IN A STABILIZATION POND TREATMENT PLANT

EVALUATION OF MOVING BED BIOFILM REACTOR TECHNOLOGY FOR ENHANCING NITROGEN REMOVAL IN A STABILIZATION POND TREATMENT PLANTThe Sanitation Districts of Los Angeles County (Sanitation Districts) operate the Palmdale Water Reclamation Plant (WPR) to provide wastewater treatment and disposal services for a city of 140,000. The Palmdale WRP is a secondary treatment system that uses oxidation ponds for BOD stabilization. Partial removal of nitrogen occurs within the facility, primarily as a result of assimilation by algae...Author(s)Jeffery S. WeissMarcos AlvarezChi-Chung TangRobert W. HorvathJames F. StahlSourceProceedings of the Water Environment FederationSubjectSession 25: Leading Edge Research: BNR: Nitrogen RemovalDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2005ISSN1938-6478SICI1938-6478(20050101)2005:14L.2085;1-DOI10.2175/193864705783867035Volume / Issue2005 / 14Content sourceWEFTECFirst / last page(s)2085 - 2102Copyright2005Word count411

Study of Tire Particle Mixing in a Moving and Stirred Bed Vacuum Pyrolysis Reactor

AbstractThe paper studies the motion of scrap tire shreds in a moving and stirred bed vacuum pyrolysis reactor. The reactor configuration is a novel concept. The pattern and the residence time distribution (RTD) of the particle motion in the reactor were investigated using tracers, for different feed rates and blade speeds. It was shown that the particle motion in the reactor is plug flow nature with intermediate dispersion (σ2 = 0.02—0.055). The mean residence time is in the range of 7—23 min, depending on the speed of the blades and the feed rate. The ratio of mean particle speed and the speed of blades vm/vb varied between 0.03 and 0.07.

Increasing the capacity for treatment of chemical plant wastewater by replacing existing suspended carrier media with Kaldnes Moving Bed(tm) media at a plant in Singapore

The Kaldnes biomedia K1, which is used in the patented Kaldnes Moving Bed(tm) biofilm process, has been tested along with other types of biofilm carriers for biological pretreatment of a complex chemical industry wastewater. The main objective of the test was to find a biofilm carrier that could replace the existing suspended carrier media and at the same time increase the capacity of the existing roughing filter-activated sludge plant by 20% or more. At volumetric organic loads of 7.1 kg COD/m3/d the Kaldnes Moving Bed™ process achieved much higher removal rates and much lower effluent concentrations than roughing filters using other carriers. The Kaldnes roughing stage achieved more than 85% removal of organic carbon and more than 90% removal of BOD5 at the tested organic load, which was equivalent to a specific biofilm surface area load of 24 g COD/m2/d. Even for the combined roughing filter-activated sludge process, the Kaldnes carriers outperformed the other carriers, with 98% removal of organic carbon and 99.6% removal of BOD5. The Kaldnes train final effluent concentrations were only 22 mg FOC/L and 7 mg BOD5/L. Based on the successful pilot testing, the full-scale plant was upgraded with Kaldnes Moving Bed™ roughing filters. During normal operation the upgraded plant has easily met the discharge limits of 100 mg COD/L and 50 mg SS/L. For the month of September 2002, with organic loads between 100 and 115% of the design load for the second half of the month, average effluent concentrations were as low as 9 mg FOC/L, 51 mg COD/L and 12 mg SS/L.

Simulated Moving Bed Equipment Designs

Simulated Moving Bed or SMB chromatography is a continuous adsorption technique that increases throughput, purity and yield relative to batch chromatography. SMB utilizes a series of columns with periodically moving inlet and outlet ports. This technique has been applied for the production of petrochemicals and sugars, and to a limited extent, pharmaceuticals. The recent surge in SMB research has led to various novel SMB schemes or configurations. This review presents a survey and comparison of SMB schemes and equipment, specifically SMB valve designs, which are needed to implement the various schemes. Illustrated examples include SMBs with three, four, five, eight, nine, or twelve zones, Varicol scheme, Japan Organo process, fast startup and shutdown, and online decoupled regeneration. The SMB valve designs reviewed are classified into central and distributed valves designs, which include two‐way‐valve designs and rotary‐valve designs. We also present a novel SMB design, the Versatile SMB or V‐SMB, which can implement all the novel schemes by using a one‐rotary‐valve‐per‐column design. Select‐Trapping valves are used to interrupt the stream between the columns and to act as a junction that allows streams to be partially or totally added or removed, or to flow through to the next column. The streams can also be redirected to another SMB zone. Compared to other SMB valve designs, the V‐SMB: (1) can be configured for open‐loop, multi‐zone and zone bypass operation; (2) does not require a carousel for column rotation; (3) does not contribute to product contamination; (4) allows independent port switchings, which is required for certain schemes; (5) allows additional columns to be added easily; and, (6) requires only constant speed pumps. The V‐SMB has successfully purified enantiomers, sugars, organic acids, an antibiotic, and biosynthetic human insulin.

DESIGN, CONSTRUCTION, START-UP, AND OPERATION OF A FULL-SCALE SEPARATE STAGE MOVING BED BIOFILM REACTOR NITRIFICATION PROCESS

DESIGN, CONSTRUCTION, START-UP, AND OPERATION OF A FULL-SCALE SEPARATE STAGE MOVING BED BIOFILM REACTOR NITRIFICATION PROCESSStart-up and monitoring data from the first 13 months of operation of a full-scale MBBR for nitrification indicated that the system was capable of achieving the effluent NH3-N objective of 6 mg/L at influent loadings exceeding the design loading (0.84 g/[m2-d]) and an average detention time just under five hours. During warm weather operation, with an average effluent temperature of 18.9°C,...Author(s)Robert A. ZimmermanDon RichardJane M. CostelloSourceProceedings of the Water Environment FederationSubjectSession 4: Meeting the Challenges of Full-Scale Implementation of Hybrid Fixed Suspended Growth Processes (IFAS and MBBR); European and North American Case StudiesDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2004ISSN1938-6478SICI1938-6478(20040101)2004:16L.319;1-DOI10.2175/193864704784147331Volume / Issue2004 / 16Content sourceWEFTECFirst / last page(s)319 - 347Copyright2004Word count264

Drying of Soybean Seeds in a Concurrent Moving Bed: Heat and Mass Transfer and Quality Analysis

The purpose of the present work is to study the simultaneous heat and mass transfer between air and soybean seeds in a concurrent moving bed dryer, based on the application of a two-phase model to the drying process. The numerical solution of the model is obtained by using a computational code based on BDF methods (Backwards Differentials Formulas). The experimental data of air humidity and temperature and of seed moisture content and temperature at the dryer outlet are compared to the simulated values, showing a good agreement. This work also analyzes the effect of the main process variables (drying air temperature, air relative humidity, air velocity and solids flow rate) on the soybean seeds quality during drying. Empirical equations fitted to the experimental data are proposed for predicting the soybean seed quality (germination, vigor and fissures) as a function of the investigated variables.

Experimental Study of Continuous Separation of 1‐1′‐Bi‐2‐Naphthol Enantiomers by an Eight‐Column Simulated Moving Bed System

The separation of 1,1′‐bi‐2‐naphthol racemic mixtures, using the eight‐column simulated fmoving‐bed (SMB) method with chiral columns of Pirkle D‐phenylglycine and each column length of 10 cm, was investigated experimentally in this study. A quick method was used to determine the optimal operating conditions for the SMB system. This was based on the “triangle theory,” and good separation conditions were found based on the experimental results of a series of SMB experiments conducted around the complete separation region of the “triangle theory.” The optimal operating conditions for each of the solvent composition systems (hexane/IPA = 90/10, 80/20, 70/30) were found, and the effect of solvent compositions on the SMB system performance was studied based on the above quick method. Good system performance (with purity and recovery higher than 97% and productivity higher than 0.44 mg/min of each isomer) was achieved using 80/20 hexane/IPA as eluent, which was found to be a suitable solvent composition for our SMB system.

Enhanced Methanol Yields from the Direct Partial Oxidation of Methane in a Simulated Countercurrent Moving Bed Chromatographic Reactor

A laboratory-scale simulated countercurrent moving bed chromatographic reactor (SCMCR) for the direct, homogeneous partial oxidation of methane to methanol has been constructed and tested. Reaction conditions were evaluated from independent experiments with a single-pass tubular reactor. Separation was effected by gas−liquid partition chromatography with 10% Carbowax on Supelcoport. At the optimal reaction conditions of 477 °C, 100 atm, and feed methane-to-oxygen ratio of 16, the methane conversion in the SCMCR was 50%, the methanol selectivity was 50%, and the methanol yield was 25%. Factors affecting methane conversion were investigated. Possible ways to improve the methane conversion, and hence the methanol yield, are discussed.

Multiobjective Optimization of Simulated Countercurrent Moving Bed Chromatographic Reactor (SCMCR) for MTBE Synthesis

The paper addresses the multiobjective optimization of a simulated moving-bed chromatographic reactor (SCMCR). The selection of the operating parameters such as the length and number of columns, switching time, and liquid flow rates in different sections is not straightforward in an SCMCR. In most cases, conflicting requirements and constraints govern the optimal choice of the decision (operating or design) variables. A mathematical model that predicts single-column experimental results well was modified for MTBE synthesis in an SCMCR. Thereafter, a few simple multiobjective optimization problems were solved that included both existing and designstage SCMCRs using a nondominated sorting genetic algorithm (NSGA). Optimal design and operating conditions for three cases of practical relevance are studied in this work, namely, (a) simultaneous maximization of the purity and yield of MTBE; (b) simultaneous maximization of the purity and yield of MTBE, together with minimization of the total amount of adsorbent/ catalyst required; and (c) maximization of the purity of MTBE with simultaneous minimization of the eluent consumption, to illustrate the procedures and interpret the results obtained. Paretooptimal solutions were obtained in all cases, and moreover, it was found that the performance of the SCMCR could be improved significantly under optimal operating conditions.

Simulated moving bed chromatography (SMB) for application in bioseparation.

Simulated Moving Bed (SMB) technology is of rising interest in the field of bioseparation. This is particularly due to its advantages such as reduction of solvent consumption, high productivity and final purities as well as low investment costs in comparison to eluent chromatography. SMB units can operate under high productivity overloaded conditions. This leads to non-linear competitive adsorption behavior, which has to be accounted for when designing and optimizing new SMB separations. The so called "Triangle Theory", which is briefly reviewed in this chapter, provides explicit criteria for the choice of the operating conditions of SMB units to achieve the prescribed separation of a mixture characterized by Langmuir, modified Langmuir and bi-Langmuir isotherms. The application of the SMB-technique to the downstream processing of biotechnological products requires some specific changes to meet the special demands of bioproduct isolation. Some exemplary applications are given including separations of sugars, proteins, monoclonal antibodies, ionic molecules and optical isomers and for desalting.

Pyrolysis and Combustion of Refuse-Derived Fuels in a Spouting−Moving Bed Reactor

A reactor with two reaction zones (pyrolyzer and combustor) is developed, which is proposed for the thermal disposal of solid wastes, especially RDFs (refuse-derived fuels). A model RDF was used to evaluate the performance of the reactor. The RDF is continuously fed to the spouting−moving bed pyrolyzer in which the RDF partially combusts to supply heat for pyrolysis of the RDF at low temperature, then the pyrolysis product burns with secondary air at high temperature in the upper combustor. A special connector cascades the two parts to a vertical configuration, where secondary air is introduced. The effect of operating parameters, such as spouting air and auxiliary air, as well as secondary air flow rate on the pyrolyzer temperature, pyrolysis gas composition at different positions, combustor temperature, and emissions of CO and NOx in flue gas, are studied.

Enantioseparation through Supercritical Fluid Simulated Moving Bed (SF-SMB) Chromatography

In this work, the first enantioseparation in a SF-SMB unit, i.e., a simulated moving bed (SMB) operated under supercritical conditions, is reported. Complete separation of the two enantiomers of tetralol was achieved both in the pressure-gradient mode (where a pressure gradient is imposed along the four sections of the unit) and in the isocratic mode (where the pressure is kept constant). However, an almost 3-fold increase in productivity could be achieved in the pressure-gradient rather than the isocratic mode. The obtained results are explained and rationalized using recently developed design criteria for SMBs, the so-called “triangle theory”, which have been properly extended to allow for different pressure values in the different sections of the unit.

Economic design criteria for cooling solid beds

Moving beds are widely employed in cooling particulate solids for process requirements. In this paper a moving cooling bed design optimization approach is developed which is based on total cost minimization and considers either capital investment (bed structure, trolleys and fans) and operating expenses (blowers operation and trolleys motion). Resorting to a previously developed heat exchange simulation model, to an optimization algorithm and to properly developed cost functions the optimal set of design variables, namely bed width, length, depth, advancement speed and cooling air flow rate, are chosen on the basis of the given set of input data, including solid inlet flow rate, temperature and physical characteristics, in order to respect the required solid exit temperature and other constraints at the minimum total cost. After outlining the adopted solution method some optimized results are shown to highlight the capabilities of the proposed approach. A sinter cooling bed of Riva/ILVA steel works in Italy is assumed as reference case study. Results show that expected savings could range around 10% to 25% of total annual cost when an optimized design is adopted.

Further Studies of the Oxidative Coupling of Methane to Ethane and Ethylene in a Simulated Countercurrent Moving Bed Chromatographic Reactor

An experimental and mathematical modeling study of a simulated countercurrent moving bed chromatographic reactor for oxidative coupling of methane to ethane and ethylene is reported. The experiments were done in a laboratory-scale three-section simulated moving bed reactor. Operating conditions were deduced from independent experiments in a microcatalytic fixed-bed reactor and from adsorber dynamics studies. With a YBa2Zr3O9.5 catalyst and activated charcoal adsorbent, the sum of the ethane and ethylene yields at optimum simulated moving bed operating conditions was 45%. Numerical simulations of the reactor performance were done and compared with experimental results.

MOVING BED CHROMATOGRAPHY

Moving bed chromatography, and simulated moving bed chromatography has been known for over 50 years, but has recently become important in the isolation of pure substances where the components are very similar, as in the case of enantiomers and in the isolation of substances which would be difficult or impossible by other means. The first example of moving bed chromatography was in the separation of pure acetylene from methane oxidation products, reported in 1956. Subsequently, in 1958, the separation of pure benzene from coal gas was described using gas liquid chromatography and a moving bed system. The movement of solely the chromatographic packing proved difficult to control and an alternative method using circular columns with moving ports to simulate the moving bed proved to be partially successful. Eventually, the circular columns were replaced by a group of static packed columns connected in series by a rotary valve that simulated a moving bed. This device proved very successful and was developed further, the disc valve eventually being replaced by low dead volume unit valves under computer control. Today, effective simulated moving bed chromatographic systems are becoming available, but it is still left to the operator to determine the optimum operating conditions, and that can often be difficult and tedious.

Treatment of High Strength Wastewater in Thermophilic Anaerobic-Aerobic Moving Bed Biofilm Reactors

Moving bed biofilm reactors were used for the thermophilic (55°C) anaerobic-aerobic treatment of a constructed high strength wastewater based on molasses. The anaerobic reactors were started with mesophilic inoculum, while the subsequent aerobic reactors were started without inoculation. The total amount of anaerobic biomass (suspended and attached) in the reactors stabilised at around 3 g VSS l−1. Substrate utilisation rates up to 4.2 kg soluble chemical oxygen demand (SCOD) (kg VSS·d)−1 were obtained at loading rates to the anaerobic biomass up to 16.4 kg SCOD (kg VSS·d)−1. Volumetric removal rates up to 7.6 kg SCOD m−3d−1 were achieved at loading rates up to 30 kg SCOD m−3d−1 in the anaerobic reactors. The maximum loading capacity however, was not evaluated during the study. Average sludge yields of 0.25–0.28 kg VSS (kg SCODremoved)−1 were achieved in the anaerobic reactors. The total amounts of aerobic biomass varied between 1.1 and 2.5 g VSS l−1. A maximum aerobic substrate utilisation rate of 4.6 kg SCOD (kg VSS·d)−1 was achieved at an aerobic biomass loading rate of 18.4 kg SCOD (kg VSS·d)−1. Volumetric removal rates up to 6.8 kg SCOD m−3d−1 were achieved at loading rates up to 27 kg SCOD m−3d−1 in the aerobic reactors. The maximum obtainable removal rates per biomass or volume were not reached during the study.

Determination of the Overall Heat Transfer Coefficient in a Vacuum Pyrolysis Moving and Stirred Bed Reactor

A novel moving and stirred bed reactor with a high heat transfer capacity has been operated to achieve the thermal decomposition of used tyre particles under vacuum. The overall heat transfer coefficient determined in this reactor reaches 200–250 W m−2K−1, a value exceeding the levels obtained in conventional rotary kilns and multiple hearth furnaces. In order to design large scale stirred bed vacuum pyrolysis reactors, both experimental and theoretical studies were carried out to understand the heat transfer mechanism and to determine the heat transfer coefficient in the reactor as a function of the operating conditions. In this work, the heat transfer coefficients under different agitation speeds up to 22.5 rpm were measured. The heat transfer coefficient was found to increase with the agitation speed, proportionally to (1/tmix)1/2. A Schliinder's modified model was used to describe the correlation between the heat transfer coefficient and the operating conditions. Calculation of the partial heat transfer coefficients during the three pyrolysis evolution periods revealed the influence of the chemical reactions, the phase change and the feedstock thermal property variation on the overall heat transfer coefficient during the vacuum pyrolysis of tyre particles.

Experimental analysis of a chiral separation through simulated moving bed chromatography

An eight column HPLC-Simulated Moving Bed (SMB) laboratory unit for the separation of enantiomers has been built and operated. The separation of the enantiomers of the Tröger’s base compound on triacetylcellulose has been considered as model separation. First the thermodynamics of adsorption has been characterised on a single analytical chromatographic column, then the separation has been scaled- up to the SMB laboratory unit. SMB experiments with different operating parameters, i.e., switch time and flow rates, have been run in order to analyse the separation performance of the laboratory unit. The experimental results are discussed in the light of the triangle theory for SMB operation.

Design of Counter-Current Moving Bed Reactor for CVD Coating of Ultra-Fine Particles.

A new counter-current type of moving bed reactor was devised for AlN coatings of Si 3 N 4 fine particles in the form of agglomerates by chemical vapor deposition. The influence of process parameters, such as reaction time and temperature, input concentration of gas precursor, and the agglomerate size, was investigated in relation to total quantity of deposited AlN inside the agglomerates. A simplified reactor model was used to analyze the deposition data. As a result, the conversion of Si 3 N 4 particles to their composite with AlN increased with increasing temperature and concentration of AlCl 3 reaction gas and with decreasing agglomerate size. Thus, it has become possible to produce a sort of surface modified ultra-fine particle at certain coating ratios continuously.