Reactors In Series Research Articles

Multistage Microfluidic Platform for the Continuous Synthesis of III–V Core/Shell Quantum Dots

AbstractWe present a fully continuous chip microreactor‐based multistage platform for the synthesis of quantum dots with heterostructures. The use of custom‐designed chip reactors enables precise control of heating profiles and flow distribution across the microfluidic channels while conducting multistep reactions. The platform can be easily reconfigured by reconnecting the differently designed chip reactors allowing for screening of various reaction parameters during the synthesis of nanocrystals. III–V core/shell quantum dots are chosen as model reaction systems, including InP/ZnS, InP/ZnSe, InP/CdS and InAs/InP, which are prepared in flow using a maximum of six chip reactors in series.

Biological removal of pharmaceuticals from hospital wastewater in a pilot-scale staged moving bed biofilm reactor (MBBR) utilising nitrifying and denitrifying processes

Hospital wastewater contains high concentrations of pharmaceuticals, which pose risks to receiving waters. In this study, a pilot plant consisting of six moving bed biofilm reactors (MBBRs) in series (with the intention to integrate Biological Oxygen Demand (BOD) removal, nitrification and denitrification as well as prepolishing Chemical Oxygen Demand (COD) for ozonation) was built to integrate pharmaceutical removal and intermittent feeding of the latter reactors aimed for micropollutant removal. Based on the experimental resultss, nitrifying MBBRs achieved higher removal as compared to denitrifying MBBRs except for azithromycin, clarithromycin, diatrizoic acid, propranolol and trimethoprim. In the batch experiments, nitrifying MBBRs showed the ability to remove most of the analysed pharmaceuticals, with degradation rate constants ranging from 5.0 × 10−3 h−1 to 2.6 h−1. In general, the highest degradation rate constants were observed in the nitrifying MBBRs while the latter MBBRs showed lower degradation rate constant. However, when the degradation rate constants were normalised to the respective biomass, the intermittently fed reactors presented the highest specific activity. Out of the 22 compounds studied, 17 compounds were removed with more than 20%.

A model parameter estimation method using Mathematica© applied to transient chemical engineering processes

AbstractIn the present paper, we apply a new approach, based on mainly two built‐in functions of the computer algebra Mathematica©, in order to estimate the parameters of several models that describe various transient (i.e., time‐dependent) chemical engineering processes. These models usually consist of either a set of ordinary differential equations (ODEs) or partial differential equations (PDEs). Basing on experimental data, it is possible to obtain, both readily and accurately, estimates of the values of the parameters involved in such models by adopting the proposed methodology. We illustrate the approach with three case studies, all related to chemical reactors. Actual experimental data, collected by senior students at King Fahd University of Petroleum & Minerals during their core laboratory course (i.e., Chemical Engineering Lab II or CHE 409) are used in the first two case studies: (1) response to a tracer input of three continuous stirred‐tank reactors in series and (2) saponification reaction of ethyl acetate in a batch reactor. In the first case study, the residence time distribution and the mean residence time in each reactor are deduced from the set of gathered data. Reaction order and rate constant are estimated from the experimental findings in the second case study. A more advanced situation, involving the solution of the advection–diffusion equation applied to a tubular micro‐reactor, is considered in the third case study. Data were collected, as part of a Ph.D. research of S. Mejri, using an experimental set‐up at Energy Intensified Reactor Engineering Lab at the University of Warwick, U.K. Here, we obtained an estimate of the relevant dimensionless number namely, the Péclet number.

Ozone treatment process for the removal of pharmaceuticals and personal care products in wastewater

ABSTRACTThis study investigated the degradability of pharmaceuticals and personal care products (PPCPs) by ozonation for the treatment of secondary effluent of a municipal wastewater treatment plant. A set of experiments were conducted in a laboratory using a pilot-scale process consisting of three flow-through reactors in series, by varying the ozone dose (1–9 mg L−1), the hydraulic retention time (5–15 min), and the concentration of ozone injected into the reactors (14–42 mg L−1). Thirty-seven PPCPs were detected in the secondary effluent, which belongs to the use categories of antibiotics, analgesics, antiarrhythmic agents, anticonvulsants, vasodilators, lipid modifying agents, anti-itch drugs, anti-psychotic drugs, insect repellents, bronchodilators, diuretics, peptic ulcer drugs, NMDA receptor antagonists, antifungal drugs, antimicrobial drugs, and antineoplastic agents. These PPCPs were broadly classified into five groups ranging from “sensitive” to ozone (O3) or “unstable” in the ozonation process, to the group of “insensitive” to O3 or “very stable” in the ozonation process. These groups are based on the PPCP concentrations after the ozone treatment and their limit of detection (LOD). Furthermore, this study examined comparatively the effects of the ozone dose, the retention (reaction) time, and the concentration of O3 supplied to the reactors on the degradability of the PPCPs.

IMPACT OF THE HYDRAULIC LOADING RATE ON THE HYDRODYNAMIC CHARACTERISTICS OF AN ANAEROBIC FIXED BED REACTOR TREATING CATTLE SLAUGHTERHOUSE WASTEWATER

The hydrodynamic behavior of an anaerobic fixed bed reactor (AFBR) was evaluated in the treatment of cattle slaughterhouse wastewater. The AFBR was operated at hydraulic retention time (HRT) of 14, 11 and 8 h. Stimulus-response assays were carried out with eosin Y and the experimental data were adjusted to the single-parameter theoretical models of dispersion and N-continuous stirred tank reactors in series. The experimental results of the residence time distribution curves showed that at lower flowrate, the reactor showed plug flow behavior with R2 of 0.88 and number of dispersion of 0.2 for high dispersion (HD). However, at higher and intermediate flowrates, the AFBR behave as a complete mixture flow, with R2 of 0.94 and 0.96, respectively. Residence time distribution curves in the AFBR showed a good approximation of the complete mixing model at hydraulic residence time of 11 h and 8 h, with 5 and 2 N-CSTR reactors in series, respectively. The volume of dead zones corresponding to 43.0%, 37.4% and 11.2% of the volume of the reactor for HRT of 14 h, 11 h and 8 h, respectively, was noted, and hydraulic short-circuiting were not confirmed.

Pilot-scale single-step reactor combining photocatalysis and photo-Fenton aiming at faster removal of Cephalexin

Abstract A solar pilot-scale cascade reactor system with novel Fe TiO2 composite beads possessing unusual characteristics of in-situ dual effect i.e. coupling of photocatalysis and photo-Fenton has been investigated in once-through mode. The cascade arrangement of packed-bed reactors maintained sufficient turbulence in the system besides eliminating the implications of film-diffusion resistance. The synergistic effect (10%) of in-situ dual process over individual processes has significantly reduced the treatment time of a recalcitrant antibiotic, Cephalexin (CEX). The reaction performance of the once-through cascade reactor system (comprising of six packed-bed reactors in series) incorporating in-situ dual effect at optimized conditions i.e. H2O2: 600 mgL−1, flow rate: 50 mLmin-1, with a space time (Ʈ) of 12 min approached to that of plug-flow reactor (PFR). The mineralization of CEX was evaluated through reduction in COD (70%) and TOC (63%) along with generation of anions and evolution of CO2. The treated solution of CEX was completely non-toxic as confirmed through Kirby-Bauer test and bio-assay analysis based on toxicity factor. In addition to this, Fe TiO2 composite beads depicted an excellent recyclability efficiency (>70 recycles) even under continuous flow conditions as confirmed through SEM/EDS, DRS, XRD, XPS and TGA analysis. The overall cost of treatment process was evaluated in detail to visualize the practical feasibility of the presented high performance reactor system.

DC fault protection for modular multi‐level converter‐based HVDC multi‐terminal systems with solid state circuit breakers

The high penetration of renewable energy requires flexible transmission of electrical energy over long distances. Onshore high-voltage DC (HVDC) interconnectors based on overhead transmission lines have already reached an advanced planning stage. These interconnectors could be extended to multi-terminal grids in the second step for higher transmission redundancy and flexibility. Fast and selective protection concepts for fault handling are required to ensure high reliability and continuous operation of these systems. Modular multi-level converters with submodules in half-bridge topology and solid-state HVDC-circuit breakers (SSCB) provide fault clearing within several microseconds to prevent converter blocking. Within this publication, a selective protection concept for SSCB and multi-terminal HVDC systems based on the overhead transmission is developed and analysed. It is based on a combination of local voltage and current signals and does not require communication between grid nodes. Additional series reactors for limiting rising fault currents are not required. Subsequent simulations for validating the protection concept and identifying its limits are carried out in power systems computer-aided design™/electro-magnetic transient design and control™ for an exemplary HVDC system. The combination of overcurrent protection with additional excitation signals enables selective fault clearing for all types of line fault scenarios.

Methanogenic capacity and robustness of hydrogenotrophic cultures based on closed nutrient recycling via microbial catabolism: Impact of temperature and microbial attachment

A biological methanation system based on nutrient recycling via mixed culture microbial catabolism was investigated at mesophilic (37 °C) and thermophilic (55 °C) temperatures. At mesophilic temperatures, the formation of biofilms on two different types of material was assessed. Results showed that with intense mixing the biofilm reactors presented methanogenic capacities (per working volume) 50% higher than the ones operated with suspended cultures. Gas feeding rates of 200 L/L/d were achieved at a H2/CO2 to CH4 conversion efficiency of above 90% by linking two reactors in series. Furthermore the robustness of the cultures was assessed under a series of inhibitory conditions that simulated possible process interferences at full scale operation. Full recovery after separate intense oxygenation and long starvation periods was observed within 2–5 days.

Optimal allocation of series FACTS devices in large‐scale systems

Series FACTS devices, such as the variable series reactor (VSR), have the ability to continuously regulate the transmission line reactance so as to control power flow. This paper presents a new approach to optimally locating such devices in the transmission network considering multiple operating states and contingencies. To investigate optimal investment, a single target year planning with three different load patterns is considered. The transmission contingencies may occur under any of the three load conditions and the coupling constraints between base case and contingencies are included. A reformulation technique transforms the original mixed integer nonlinear programming (MINLP) model into mixed integer linear programing (MILP) model. To further relieve the computational burden and enable the planning model to be directly applied to practical large scale systems, a two phase decomposition algorithm is introduced. Detailed numerical simulation results on IEEE 118-bus system and the Polish 2383-bus system illustrate the efficient performance of the proposed algorithm.

Conceptual design of a new SF6 abatement technology using a multi‐bed series reactor for the production of valuable chemicals free of toxic wastes

AbstractConceptual design using multi‐bed series reactors consisting of catalysts and adsorbent beds was performed for a new SF6 abatement and utilization technology free of toxic chemicals to reduce SF6 emissions and produce valuable products like CaF2 and CaSO4 simultaneously. With process simulation studies using Aspen HYSYS®, comparative studies for a single‐bed reactor (SR‐1), a two‐bed series reactor (SR‐2), and a three‐bed series reactor (SR‐3) revealed that more CaF2 and CaSO4 were produced in multi‐bed series reactors compared to a SR‐1 (SR‐3 > SR‐2 > SR‐1) possibly due to sorption‐enhanced hydrolysis. In addition, lower operating temperatures were observed in multi‐bed series reactors (TSR1 > TSR2 > TSR3) showing the positive effect of using multi‐bed series reactors for a simultaneous SF6 abatement and utilization technology.

Production of acids and alcohols from syngas in a two-stage continuous fermentation process

A two-stage continuous system with two stirred tank reactors in series was utilized to perform syngas fermentation using Clostridium carboxidivorans. The first bioreactor (bioreactor 1) was maintained at pH 6 to promote acidogenesis and the second one (bioreactor 2) at pH 5 to stimulate solventogenesis. Both reactors were operated in continuous mode by feeding syngas (CO:CO2:H2:N2; 30:10:20:40; vol%) at a constant flow rate while supplying a nutrient medium at different flow rates of 8.1, 15, 22 and 30 ml/h. A cell recycling unit was added to bioreactor 2 in order to recycle the cells back to the reactor, maintaining the OD600 around 1 in bioreactor 2 throughout the experimental run. When comparing the flow rates, the best results in terms of solvent production were obtained with a flow rate of 22 ml/h, reaching the highest average outlet concentration for alcohols (1.51 g/L) and the most favorable alcohol/acid ratio of 0.32.

Solid State Fault Current Limiter (SSFCL) in Power System – A Case Study

Increasing generation to meet the load growth and interconnections between systems to improve reliability and power transfer capability are likely to increase the fault current levels. If the resultant short circuit current exceeds the existing equipment rating, they must either be upgraded or replaced or reconfigure its system to reduce the new available fault current. Both of which are very costly or time escalated process. Hence it is preferred to explore the feasibility of utilization of existing equipment with current limiting devices. Current limiting using passive element like series inductor reduces system stability and load flow. To overcome this problem, the series reactor is made to come into services only for the duration of fault. This paper proposes new methods for fast acting current limiting using Solid State Fault Current Limiters (SSFCL) that employs power electronic switches to overcome the limitation of the passive current limiters. Modeling and simulations of these methods are performed on a typical 400 kV power system using PSCAD/EMTDC. The results of which confirm that the fault level can be effectively reduced.

The Silica-Alumina Based Catalytic Cracking of Bio-oil Using Double Series Reactor

Biomass, especially palms oil empty fruit bunches (EFB) which are abundant in Indonesia can be processed into bio-oil, through pyrolysis process. Bio-oil contains large molecules, thus resulting high viscosity. The use of cracking catalyst such as zeolite, would be beneficial for breaking down the large molecules. Silica-alumina catalyst is one of the mesoporous size catalysts that is expected to improve the quality of products from the catalytic cracking of bio-oil. The objective of this research is to study the effect of the catalyst weight (0-40 gram) on the yield and composition of the product. Bio-oil derived from EFB was upgraded through double series reactor under atmospheric pressure. This configuration will minimize coke formation. The results showed that the weight of catalyst affects the quality and quantity of oil product. With the increased weight of catalyst from 0 to 40 gram, the yield of oil decreased from 42.8 to 22.72%. However, the concentration of gasoline and kerosene increased from 6.61 to 17.02% and 17.53 to 24.53%, respectively. With the raised weight of catalyst, heating value of oil rose from 32 to 36.7 MJ/kg.

Implementation and process analysis of pilot scale multi-phase anaerobic fermentation and digestion of faecal sludge in Ghana

Background. In Ghana, faecal sludge (FS) from on-site sanitation facilities is often discharged untreated into the environment, leading to significant insults to environmental and human health. Anaerobic digestion offers an attractive pathway for FS treatment with the concomitant production of energy in the form of methane. Another innovative option includes separating digestion into acidogenesis (production of volatile fatty acids (VFA)) and methanogenesis (production of methane), which could ultimately facilitate the production of an array of biofuels and biochemicals from the VFA. This work describes the development, implementation and modeling based analysis of a novel multiphase anaerobic fermentation-digestion process aimed at FS treatment in Kumasi, Ghana. Methods. A pilot-scale anaerobic fermentation process was implemented at the Kumasi Metropolitan Assembly’s Oti Sanitary Landfill Site at Adanse Dompoase. The process consisted of six 10 m 3 reactors in series, which were inoculated with bovine rumen and fed with fecal sludge obtained from public toilets. The performance of the fermentation process was characterized in terms of both aqueous and gaseous variables representing the conversion of influent organic carbon to VFA as well as CH 4. Using the operating data, the first-ever process model for FS fermentation and digestion was developed and calibrated, based on the activated sludge model framework. Results and Conclusions. This work represents one of the first systematic efforts at integrated FS characterization and process modeling to enable anaerobic fermentation and digestion of FS. It is shown that owing to pre-fermentation of FS in public septage holding tanks, one could employ significantly smaller digesters (lower capital costs) or increased loading capabilities for FS conversion to biogas or VFA. Further, using the first-ever calibrated process model for FS fermentation and digestion presented herein, we expect improved and more mechanistically informed development and application of different process designs and configurations for global FS management practice.

Operational Efficiency Evaluation of a Setup for Removing Stresses in the Steam Header of PGV-1000 Steam Generator

The effectiveness of a setup for removing stresses in the steam header of a PGV-1000 steam generator is evaluated. The evaluation is based on an investigation of the stress state by means of magnetic anisotropy measurements performed in the zone of the No. 111 weld seam of the hot header of steam generators operating in one of the power-generating units with a V-320 series reactor arrangement. Inspections made it possible to obtain cartograms of the distribution of the difference of the principal mechanical stresses along the perimeter of the weld connection of a PGV-1000 header equipped with a cooling mantle and headers without such a mantle. By means of statistical analysis of the data, a diagram of the distribution of the principal mechanical stresses was obtained. In addition, the distribution of the standard deviation of the principal mechanical stresses as a measure of the dispersion of a random quantity relative to its mathematical expectation was determined.

High solid temperature phased anaerobic digestion from agricultural wastes: Putting several reactors in sequence

High solid anaerobic digestion of agricultural wastes (manure and grass silage) was tested on temperature phased anaerobic digester (TPAD) at lab-scale. A 4days hyperthermophilic hydrolysis was followed by a 15days methanogenesis. The TPAD was divided into 4 or 5 tanks in series without recycling: 2 sectors for hydrolysis (2days HRT each) and 2 or 3 sectors for methanogenesis (5+10 or 3×5days HRT). Two different combinations of temperatures (65°C–37°C, 65°C–55°C) were investigated to assess the process efficiency.For all tested conditions, the TPAD operated steadily with a methane productivity of 235+/−3 mLCH4STPgVS−1. Using four or five reactors in series enabled to identify that during the two first days of hydrolysis, the hydrolysis yield and acidification yield were much higher (22% and 13%, respectively) than during the next two days (2% and 2% respectively). Moreover, concerning methanogenesis it appeared that the retention time may be shortened by 5days with little loss in methane production (11%). In the methanogenic sectors, the uptake of volatile fatty acids and the methane production were higher at 55°C than 37°C.The results suggest that the hydrolytic sector could be limited at 2days HRT, while the methanogenic sector would support a 10days HRT with the feedstocks used.

Processability‐enhanced bimodal high‐density polyethylene with comb‐branched high‐density polyethylene

ABSTRACTTwo solution reactors in series were utilized to synthesize comb‐branched high‐density polyethylene (HDPE), cbHDPE, where the first reactor prepares vinyl‐terminated HDPE macromers catalyzed by an organometallic catalyst favoring beta hydride transfer and the second reactor copolymerizes HDPE macromers with ethylene using a different organometallic catalyst capable of incorporating macromers. A bimodal HDPE, biHDPE with bimodalities in molecular weight, and hexene content of the desired composition distribution was also prepared in a gas phase reactor using silica supported dual organometallic catalysts. By blending 3% solution‐made cbHDPE into the gas‐phase biHDPE, the resulting trimodal HDPE preserves the excellent stiffness and toughness of the bimodal HDPE while having exceptional melt strength and processability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45755.

Implementation and process analysis of pilot scale multi-phase anaerobic fermentation and digestion of faecal sludge in Ghana.

Background. In Ghana, faecal sludge (FS) from on-site sanitation facilities is often discharged untreated into the environment, leading to significant insults to environmental and human health. Anaerobic digestion offers an attractive pathway for FS treatment with the concomitant production of energy in the form of methane. Another innovative option includes separating digestion into acidogenesis (production of volatile fatty acids (VFA)) and methanogenesis (production of methane), which could ultimately facilitate the production of an array of biofuels and biochemicals from the VFA. This work describes the development, implementation and modeling based analysis of a novel multiphase anaerobic fermentation-digestion process aimed at FS treatment in Kumasi, Ghana. Methods. A pilot-scale anaerobic fermentation process was implemented at the Kumasi Metropolitan Assembly's Oti Sanitary Landfill Site at Adanse Dompoase. The process consisted of six 10 m reactors in series, which were inoculated with bovine rumen and fed with fecal sludge obtained from public toilets. The performance of the fermentation process was characterized in terms of both aqueous and gaseous variables representing the conversion of influent organic carbon to VFA as well as CH 4. Using the operating data, the first-ever process model for FS fermentation and digestion was developed and calibrated, based on the activated sludge model framework. Results and Conclusions. This work represents one of the first systematic efforts at integrated FS characterization and process modeling to enable anaerobic fermentation and digestion of FS. It is shown that owing to pre-fermentation of FS in public septage holding tanks, one could employ significantly smaller digesters (lower capital costs) or increased loading capabilities for FS conversion to biogas or VFA. Further, using the first-ever calibrated process model for FS fermentation and digestion presented herein, we expect improved and more mechanistically informed development and application of different process designs and configurations for global FS management practice.

Passive Reactor Compensated Cascaded H-Bridge Multilevel LC-StatCom

The cascaded H-bridge (CHB) low-capacitance StatCom (LC-StatCom) has a limited operating area in the inductive region compared to a conventional StatCom's V-I characteristic. This limitation for operation in the inductive region is considered to be the biggest disadvantage of CHB LC-StatCom. In this paper, the effect of adding parallel and series reactors on the LC-StatCom system's V-I characteristic is analyzed. Then, a new configuration, which fully compensates for the lost operating area of the LC-StatCom, is introduced. A scaled down single-phase seven-level laboratory prototype is used to confirm practicability of the proposed system.

A green industrial scale di-methyl ether reactor with aiming to CO 2 reduction: staging and multi-objective optimization approach

CO2 and H2O are two important by-products that affect DME production in the reactor. Besides, CO2 is an important air pollutant and may have an impact on global climate change. Therefore, this study tries to increase CO2 conversion along with DME production simultaneously and independently proposing a multi-stage reactor using a multi-objective approach. In this respect, a variety of effective optimization degrees of freedom such as H2O separation ratio, feed temperature, inter-stage cooling temperature, shell temperatures, number of reactors in series and reactor configurations (adiabatic/non-adiabatic fixed bed reactor; (non-)AFBR) at each stage are optimized to improve overall reactor efficiency. An industrial scale catalytic fixed bed reactor is used and the results of the proposed multi-objective multi-stage case are compared with a single-stage single-objective (base case) and single-stage multi-objective optimization one. The comparative test studies clearly demonstrate superiority of the proposed methodology to give optimal solutions with much less CO2 productivity and high DME productivity at the end of the staged reactor. Besides, the simulation results of multi-objective optimization introduced more optimum points as a Pareto front compared to the single objective optimization case.