External Reactors Research Articles

Differential Reactor Voltage Based Fault Detection and Classification for Smart DC Microgrid

The primary challenges in the implementation of differential protection techniques are Time Synchronization Error (TSE) due to communication delay and low sensitivity towards High Resistance Faults (HRFs). In this paper, a new technique utilizing the difference in voltage measured across the external reactors connected at opposite ends of the cable is proposed for fault detection and classification of HRFs in islanded and grid connected mode of operation of DC microgrid. Further, to overcome the challenges associated with TSE, which causes differential schemes to mal-operate, the proposed technique determines reactor voltage polarity at opposite ends of the cable to distinguish between internal and external faults. The proposed technique is tested for different types of internal faults and system transients such as external faults, load switching, generation uncertainties etc. to demonstrate sensitivity and accuracy of the proposed technique. Finally, a comparative analysis of the proposed technique is performed with the schemes reported in the literature, which confirms the fast fault detection, high sensitivity for internal HRFs, selectivity and stability of the proposed technique for different operating conditions.

Reduction of excess sludge production by membrane bioreactor coupled with anoxic side-stream reactors

While cleaning wastewater, biological wastewater treatment processes such as membrane bioreactors (MBR) produce a significant amount of sludge that requires costly management. In the oxic-settling-anoxic (OSA) process, sludge is retained for a temporary period in side-stream reactors with low oxygen and substrate, and then it is recirculated to the main reactor. In this way, excess sludge production is reduced. We studied the influence of the rate of sludge exchange between MBR and side-stream anoxic reactors on sludge yield reduction within MBR. Two MBRs, namely, MBROSA and MBRcontrol, each coupled with separate external anoxic side-stream reactors, were run in parallel for 350 days. Unlike MBRcontrol, MBROSA had sludge exchange with the external reactors connected to it. During the investigation over a sludge interchange rate (SIR) range of 0–22%, an SIR of 11% achieved the highest sludge reduction (58%). Greater volatile solids destruction i.e., bacterial cell lysis and extracellular polymeric substance (EPS) destruction occurred at the SIR of 11%, which helped to achieve the highest sludge reduction. The enhanced volatile solids destruction was evident by the release of nutrients in the external anoxic reactors. It was confirmed that the sludge yield reduction was achieved without compromising the wastewater treatment quality, sludge settleability and hydraulic performance of the membrane in MBR.

Hydrodynamic studies in sectionalised external loop air lift reactors

ABSTRACT External loop air lift reactor (EL-ALR) is widely used for multiphase reactions. They offer lower pressure drop and good heat and mass transfer rates compared to conventional bubble column reactors. In the case of fermentation applications where a medium is highly viscous and coalescing in nature, sectionalisation of riser helps in the improvement of the interfacial area as well as the reduction in liquid-phase backmixing. The present work deals with the measurement of the gas hold-up, mixing time, liquid dispersion, Sauter mean bubble diameter over a broad range of superficial gas velocities in sectionalised EL-ALR. Effects of electrolytes and surfactants have also been studied. Different plate designs have been studied for the sectionalisation. The correlations have been proposed for the gas hold-up, liquid circulation velocity, Sauter mean bubble diameter for superficial gas velocities. Abbreviations: EL-ALR: external loop air lift reactor; IL-ALR: internal loop air lift reactor; ADC: analog to digital converter; DAC: digital to analog converter.

Performance Analysis of a Proton Exchange Membrane Fuel Cell Based Syngas.

External chemical reactors for steam reforming and water gas shift reactions are needed for a proton exchange membrane (PEM) fuel cell system using syngas fuel. For the preheating of syngas and stable steam reforming reaction at 600 °C, residual hydrogen from a fuel cell and a certain amount of additional syngas are burned. The combustion temperature is calculated and the molar ratio of the syngas into burner and steam reformer is determined. Based on thermodynamics and electrochemistry, the electric power density and energy conversion efficiency of a PEM fuel cell based syngas are expressed. The effects of the temperature, the hydrogen utilization factor at the anode, and the molar ratio of the syngas into burner and steam reformer on the performance of a PEM fuel cell are discussed. To achieve the maximum power density or efficiency, the key parameters are determined. This manuscript presents the detailed operating process of a PEM fuel cell, the allocation of the syngas for combustion and electric generation, and the feasibility of a PEM fuel cell using syngas.

The role of microbial diversity and composition in minimizing sludge production in the oxic-settling-anoxic process

The oxic-settling-anoxic (OSA) process, which involves an aerobic tank attached to oxygen- and substrate-deficient external anoxic reactors, minimizes sludge production in biological wastewater treatment. In this study, the microbial community structure of OSA was determined. Principal coordinate analysis showed that among the three operational factors, i.e., (i) redox condition, (ii) external reactor sludge retention time (SRText), and (iii) sludge interchange between aerobic and anoxic reactors, redox condition had the greatest impact on microbial diversity. Generally, reactors with lower oxidation-reduction potential had higher microbial diversity. The main aerobic sequencing batch reactor of OSA (SBROSA) that interchanged sludge with an external anoxic reactor had greater microbial diversity than SBRcontrol which did not have sludge interchange. SBROSA sustained high abundance of the slow-growing nitrifying bacteria (e.g., Nitrospirales and Nitrosomondales) and consequently exhibited reduced sludge yield. Specific groups of bacteria facilitated sludge autolysis in the external reactors. Hydrolyzing (e.g., Bacteroidetes and Chloroflexi) and fermentative (e.g., Firmicutes) bacteria, which can break down cellular matter, proliferated in both the external aerobic/anoxic and anoxic reactors. Sludge autolysis in the anoxic reactor was enhanced with the increase of predatory bacteria (e.g., order Myxobacteriales and genus Bdellovibrio) that can contribute to biomass decay. Furthermore, β- and γ-Proteobacteria were identified as the bacterial phyla that primarily underwent decay in the external reactors.

Effects of sludge retention time on oxic-settling-anoxic process performance: Biosolids reduction and dewatering properties

In this study, the effect of sludge retention time (SRT) on oxic-settling-anoxic (OSA) process was determined using a sequencing batch reactor (SBR) attached to external aerobic/anoxic reactors. The SRT of the external reactors was varied from 10 to 40d. Increasing SRT from 10 to 20d enhanced volatile solids destruction in the external anoxic reactor as evidenced by the release of nutrients, however, increasing the SRT to 40d did not enhance volatile solids destruction further. Relatively short SRT (10–20d) favoured the conversion of destroyed solids into inert products. The application of an intermediate SRT (20d) of the external reactor showed the highest sludge reduction performance (>35%). Moreover, at the optimum SRT, OSA improved sludge dewaterability as demonstrated by lower capillary suction time and higher dewatered cake solids content.

Design and Control of the Side Reactor Configuration for Production of Ethyl Acetate

Despite some potential advantages of reactive distillation (RD), reactive distillation may suffer from maintenance/design problems such as catalyst deactivation/replacement and equipment design. In this work, an alternative design, a side reactor configuration, is sought and the process of interest is production of ethyl acetate via esterification. The reactive distillation study by Tang et al. (2005) reveals that almost 90% conversion takes place in the column base of the RD. This naturally suggests a coupled reactor/distillation configuration where all of the catalyst is packed in the bottoms base, denoted as single-reactive tray reactive distillation (RD-SRT). This mitigates the maintenance problem associated with conventional RD. However, simulation results show that, with the same amount of catalyst loading, the SRT configuration cannot achieve the same performance as the RD (∼93% conversion). Another alternative is adding external reactors to the SRT, and this is termed the side reactor configuratio...

Utilization of Heavy Metal Molten Salts in the ARIES-RS Fusion Reactor

ARIES-RS is one of the major magnetic fusion energy reactor designs that uses a blanket having vanadium alloy structure cooled by lithium [1, 2]. It is a deuterium–tritium (DT) fusion driven reactor, having a fusion power of 2170 MW [1, 2]. This study presents the neutronic analysis of the ARIES-RS fusion reactor using heavy metal molten salts in which Li2BeF4 as the main constituent was mixed with increased mole fractions of heavy metal salt (ThF4 or UF4) starting by 2 mol.% up to 12 mol.%. Neutron transport calculations were carried out with the help of the SCALE 4.3 system by solving the Boltzmann transport equation with the XSDRNPM code in 238 neutron groups and a S 8–P 3 approximation. According to the numerical results, tritium self-sufficiency was attained for the coolants, Flibe with 2% UF4 or ThF4 and 4% UF4. In addition, higher energy multiplication values were found for the salt with UF4 compared to that with ThF4. Furthermore, significant amount of high quality nuclear fuel was produced to be used in external reactors.

Optimum Design of a Column/Side Reactor Process

One of the limitations for reactive distillation to be economically attractive is that the temperature range suitable for reasonable chemical reaction kinetics must match the temperature range suitable for vapor−liquid equilibrium because both separation and reaction occur in a single vessel. This temperature mismatch problem can sometimes be overcome by considering an alternative process flowsheet that features a distillation column linked with several external side reactors. The column operates at a low pressure and temperatures favorable for separation. Liquid sidestreams from trap-out trays at intermediate locations in the column are pumped to external reactors operating at higher pressure and temperatures that are favorable for chemical kinetics. This paper extends our previous work [Kaymak, D. B.; Luyben, W. L. Ind. Eng. Chem. Res. 2004, 43, 8049−8056] to provide a more rigorous steady-state economic optimization of the column/side reactor flowsheet. Results demonstrate that this configuration has b...

Radiation damage studies on the first wall of a HYLIFE-II type fusion breeder

Abstract The radiation damage on the first wall [made of (1) a ferritic steel (9Cr–2WVTa), (2) a vanadium alloy (V–4Cr–4Ti) and (3) SiCf/SiC composite] of an inertial fusion energy (IFE) reactor of HYLIFE-II type is investigated. A protective liquid wall with variable thickness, containing Flibe + heavy metal salt (UF4 or ThF4) is used for first wall protection. The content of heavy metal salt is chosen as 4 and 12 mol%. Neutron transport calculations are performed with the aid of the SCALE4.3 System by solving the Boltzmann transport equation with the XSDRNPM code in 238 energy groups and S8–P3 approximation. A flowing wall with a thickness of ∼60 cm can extend the lifetime of the solid first wall structure to a plant lifetime of 30 years for 9Cr–2WVTa and V–4Cr–4Ti, whereas the SiCf/SiC composite as first wall needs a flowing wall with a thickness of ∼85 cm to maintain the radiation damage limit. Substantial extra revenue can be gained through the insertion of a heavy metal salt constituent into Flibe, which allows breeding fissile fuel for external reactors and increasing energy multiplication (233U with a value of up to 1,000,000,000 $/year or 239Pu for few 100,000,000 $/year).

Design of Distillation Columns with External Side Reactors

Previous work presented a quantitative economic comparison between a reactive distillation process and a conventional multiunit process for systems in which relative volatilities are temperature dependent. A fundamental difference between these two flowsheets is the ability in the conventional process to adjust reactor temperature and distillation column temperatures completely independently, which is not possible in the reactive distillation process. If the temperature required for reasonable reaction kinetics is not in the same range as that in which vapor−liquid phase equilibrium permits the use of distillation, reactive distillation becomes unattractive. This paper explores a third alternative process that can overcome the problem of reaction/distillation temperature mismatch. The column is operated at its optimum temperature (and pressure). Several liquid trap-out trays collect all the liquid coming down from upper trays. These liquids are pumped to external reactors operating at their optimum temper...

04/02774 Microstructural development and radiation hardening of neutron irradiated Mo-Re alloys: Nemoto, Y. et al. Journal of Nuclear Materials, 2004, 324, (1), 62–70

The radiation damage on the first wall [made of (1) a ferritic steel (9Cr–2WVTa), (2) a vanadium alloy (V–4Cr–4Ti) and (3) SiCf/SiC composite] of an inertial fusion energy (IFE) reactor of HYLIFE-II type is investigated. A protective liquid wall with variable thickness, containing Flibe + heavy metal salt (UF4 or ThF4) is used for first wall protection. The content of heavy metal salt is chosen as 4 and 12 mol%. Neutron transport calculations are performed with the aid of the SCALE4.3 System by solving the Boltzmann transport equation with the XSDRNPM code in 238 energy groups and S8–P3 approximation.A flowing wall with a thickness of ∼60 cm can extend the lifetime of the solid first wall structure to a plant lifetime of 30 years for 9Cr–2WVTa and V–4Cr–4Ti, whereas the SiCf/SiC composite as first wall needs a flowing wall with a thickness of ∼85 cm to maintain the radiation damage limit. Substantial extra revenue can be gained through the insertion of a heavy metal salt constituent into Flibe, which allows breeding fissile fuel for external reactors and increasing energy multiplication (233U with a value of up to 1,000,000,000 $/year or 239Pu for few 100,000,000 $/year).

Modified APEX reactor as a fusion breeder

An advanced fusion reactor project, called APEX, with improved effectiveness has been developed using a protective flowing liquid wall for tritium breeding and energy transfer. In the modified APEX concept, the flowing molten salt wall is composed of Flibe as the main constituent with increased mole fractions of heavy metal salt (ThF 4 or UF 4) for both fissile and fusile breeding purposes and to increase the energy multiplication. Neutron transport calculations are conducted with the help of the SCALE4.3 SYSTEM by solving the Boltzmann transport equation with the code XSDRNPM. By preserving a self sufficient tritium breeding ratio (TBR > 1.05) for a mole fraction up to 6% of ThF 4 or 12% of UF 4, the modified APEX reactor can produce up to ∼2800 kg of 233U/year or ∼4950 kg of 239Pu/year, assuming the same baseline fusion power production of 4000 MW th, as in the original APEX concept. With 6% ThF 4 or 12% UF 4 in the coolant, the total energy output will increase to 5560 MW th or 8440 MW th, respectively. For a plant operation period of 30 full power years, the atomic displacement and helium production rates remain well below the presumable limits. The additional benefits of fissionable metal salt in the flowing liquid in a fusion reactor can be summarized as breeding of high quality fissile fuel for external reactors and increase of total plant power output.

Neutronics analysis of HYLIFE-II blanket for fissile fuel breeding in an inertial fusion energy reactor

A protective, 60 cm thick flowing liquid wall coolant is investigated as energy carrier, and fusile and fissile breeder medium in an inertial fusion energy (IFE) reactor. Flibe as the main constituent is mixed with increased mole-fractions of heavy metal salt (ThF 4 and UF 4) starting with 2 mol% up to 12 mol%. For a plant operation period of 30 years, radiation damage values were found as DPA=∼65 for 2 mol% heavy metal in the coolant, and remain practically constant with increasing heavy metal fraction, well below the presumable limit of DPA=100. Helium production values are calculated as ∼270 appm for 2 mol% heavy metal fraction, also being far below the limit value of 500 appm and remain at the same level with increasing heavy metal fraction. Such a flowing protective liquid wall extents the lifetime of the rigid first wall structure to a plant lifetime of 30 years. Fissionable metal salt in the flowing liquid enables one to breed high quality fissile fuel for external reactors by a self-sustaining tritium breeding for the fusion plant and increases plant power output.

Gas Holdup in Circulating Bubble Columns with Pseudoplastic Liquids

The contributions of pressure drop due to wall frictional losses to the total gas holdup of two-phase viscous non-Newtonian systems were experimentally investigated using a 150 dm3 circulating bubble column. The column had a downcomer-to-riser cross-sectional area ratio of 0.54 and a dispersion height of 2.5 m. Aqueous solutions of xanthan gum and carboxymethyl cellulose were used to simulate a wide range of rheological properties. The average wall shear stress was estimated from Al-Masry's (1999) correlation for the average wall shear rate in external loop airlift reactors. Pressure drop due to wall shear stress was found significantly contributed by 10–70 % to the total gas holdup. This contribution has always been ignored in the data presented in the literature due to the absence of reliable and simple correlations for the average shear rate and shear stress. Corrections to gas holdup were found necessary for non-Newtonian solutions with concentrations of ≥ 0.5 wt/wt.-%.

Milne problem for linearly anisotropic scattering and a specularly reflecting boundary

The radiation damage on the first wall [made of (1) a ferritic steel (9Cr–2WVTa), (2) a vanadium alloy (V–4Cr–4Ti) and (3) SiCf/SiC composite] of an inertial fusion energy (IFE) reactor of HYLIFE-II type is investigated. A protective liquid wall with variable thickness, containing Flibe + heavy metal salt (UF4 or ThF4) is used for first wall protection. The content of heavy metal salt is chosen as 4 and 12 mol%. Neutron transport calculations are performed with the aid of the SCALE4.3 System by solving the Boltzmann transport equation with the XSDRNPM code in 238 energy groups and S8–P3 approximation.A flowing wall with a thickness of ∼60 cm can extend the lifetime of the solid first wall structure to a plant lifetime of 30 years for 9Cr–2WVTa and V–4Cr–4Ti, whereas the SiCf/SiC composite as first wall needs a flowing wall with a thickness of ∼85 cm to maintain the radiation damage limit. Substantial extra revenue can be gained through the insertion of a heavy metal salt constituent into Flibe, which allows breeding fissile fuel for external reactors and increasing energy multiplication (233U with a value of up to 1,000,000,000 $/year or 239Pu for few 100,000,000 $/year).

Underutilization of loop reactors due to desorption

Loop reactors or circulating bubble columns are considered to be promising multiphase contactors to conduct biochemical and chemical reactions due to flexibility in their design, their low power requirement and low fluid shear stresses in these reactors. A generalized model for external loop airlift reactors (EL-ALRs), accounting for axial variations in holdups of the gas and liquid phases and total pressure, is employed, to predict the performance of these reactors when used for slow liquid phase reactions. As the liquid travels upward in the riser, the decrease in the local pressure due to reduction in the static head of liquid reduces the saturation concentration of the solute (coreactant transferred from the gas phase) in the liquid phase. At certain locations in the riser, especially in the top portion of the riser, the liquid phase concentration of the solute may exceed the local saturation level resulting in desorption of the reactive solute. This undesired situation leads to underutilization of the EL-ALR as far as conversion of the absorbed reactant is concerned. The effects of design parameters, such as the height to diameter ratio, area ratio, and sparger location, and operational parameters, such as superficial feed gas velocity, composition of the feed gas, kinetic coefficient, and top pressure, on the performance of the EL-ALR are examined in considerable detail. Existence of optimum values of height-to-diameter ratio, sparger location in the downcomer, area ratio, and top pressure for minimization/obviation of desorption, maximization of net rate, and maximization of net rate per unit power consumption is established. The importance of proper selection of the key design and operating parameters for EL-ALRs for optimal performance of these is demonstrated.

A Corona Discharge Treater using a 30kHz 5kW IGBT Inverter.

Corona discharge treaters have been used to treat surface of polyethylene films and to improve affinity for inks. The features of a resonant inverter system using IGBT's for corona discharge treaters developed in this paper are as follows. (1) No external reactors or capacitors are necessary because a series resonant circuit is composed of a leakage inductor of a step-up transformer and a capacitor between discharge electrodes of the treater. (2) A three-phase diode rectifier can be used because the output power is controlled by adjusting output power factor of the inverter. (3) A capacitor is connected between a collector and emitter of IGBT's to reduce switching losses.An optimal design of the capacitor is done by utilizing an analog circuit simulator. The authors propose an equivalent circuit of the IGBT because there may be no exact IGBT model for analog circuit simulators. The validity of the equivalent circuit is verified by comparing experimental results with simulated ones. As a result, it is shown experimentally that the optimal capacitor, which is determined by the simulation developed in this papaer, leading to higher efficiency.

Rapid ethanol fermentation with immobilized Zymomonas mobilis in a three stage reactor system

Using the Zymomonas mobilis NRRL B 14023 strain for ethanol fermentation with immobilized cells the combination of two external loop reactors followed by a plug flow reactor was the most effective reactor configuration. A maximal productivity of 92 and 108 g/l·h at practically complete sugar consumption was obtained with Carrageenan and Alginate catalysts respectively. Due to the high dilution rate nonsterile operation for extended periods of weeks was possible.