Small-scale Reactor Research Articles

Evaluation of parallel milliliter-scale stirred-tank bioreactors for the study of biphasic whole-cell biocatalysis with ionic liquids

As clear structure-activity relationships are still rare for ionic liquids, preliminary experiments are necessary for the process development of biphasic whole-cell processes involving these solvents. To reduce the time investment and the material costs, the process development of such biphasic reaction systems would profit from a small-scale high-throughput platform. Exemplarily, the reduction of 2-octanone to (R)-2-octanol by a recombinant Escherichia coli in a biphasic ionic liquid/water system was studied in a miniaturized stirred-tank bioreactor system allowing the parallel operation of up to 48 reactors at the mL-scale. The results were compared to those obtained in a 20-fold larger stirred-tank reactor. The maximum local energy dissipation was evaluated at the larger scale and compared to the data available for the small-scale reactors, to verify if similar mass transfer could be obtained at both scales. Thereafter, the reaction kinetics and final conversions reached in different reactions setups were analysed. The results were in good agreement between both scales for varying ionic liquids and for ionic liquid volume fractions up to 40%. The parallel bioreactor system can thus be used for the process development of the majority of biphasic reaction systems involving ionic liquids, reducing the time and resource investment during the process development of this type of applications.

The Effect of H<sub>2</sub>S on Hydrogen and Carbon Black Production from Sour Natural Gas

Hydrogen and carbon black production via thermal decomposition of natural gas have been achieved using a carbon black furnace. Direct heat transfer from inert hot gases (argon) introduced into sour gas. The carbon black furnace is a small-scale axial flow reactor. There are 3 main chemical reactions through which carbon black is produced. Finally results indicate that the most influencing factor over these chemical reactions and CH4 and H2S conversions is reactor temperature.

Modelling and simulation of a catalytic autothermal methane reformer with Rh catalyst

A model of a ATR fixed bed reactor with Rh catalyst has been developed and validated on the basis of experimental results. Experiments have been conducted in a small scale reactor and solid temperature profiles have been measured with IR camera. Temperature profiles present high peak temperature at reactor entrance as consequence of the partial separation in space of the reforming and oxidation reactions. Thus, the kinetic model for Rh catalyst refers to an indirect scheme including a shift factor which is crucial for good predictive capabilities of the reactor model. The model validation has been conducted by comparing solid temperature profiles with those obtained experimentally at different feed compositions, total flow rate and preheating temperatures. The model well describes the experimental results in all the investigated operating conditions. The validated model has been then used to analyze the effect of thermal conductivity and of the flow rate on overall reactor performances.

Composting in small laboratory pilots: Performance and reproducibility

Small-scale reactors (<10 l) have been employed in composting research, but few attempts have assessed the performance of composting considering the transformations of organic matter. Moreover, composting at small scales is often performed by imposing a fixed temperature, thus creating artificial conditions, and the reproducibility of composting has rarely been reported. The objectives of this study are to design an innovative small-scale composting device safeguarding self-heating to drive the composting process and to assess the performance and reproducibility of composting in small-scale pilots. The experimental setup included six 4-l reactors used for composting a mixture of sewage sludge and green wastes. The performance of the process was assessed by monitoring the temperature, O 2 consumption and CO 2 emissions, and characterising the biochemical evolution of organic matter. A good reproducibility was found for the six replicates with coefficients of variation for all parameters generally lower than 19%. An intense self-heating ensured the existence of a spontaneous thermophilic phase in all reactors. The average loss of total organic matter (TOM) was 46% of the initial content. Compared to the initial mixture, the hot water soluble fraction decreased by 62%, the hemicellulose-like fraction by 68%, the cellulose-like fraction by 50% and the lignin-like fractions by 12% in the final compost. The TOM losses, compost stabilisation and evolution of the biochemical fractions were similar to observed in large reactors or on-site experiments, excluding the lignin degradation, which was less important than in full-scale systems. The reproducibility of the process and the quality of the final compost make it possible to propose the use of this experimental device for research requiring a mass reduction of the initial composted waste mixtures.

Experimental determination of the structure of catalytic micro-combustion flows over small-scale flat plates for methane and propane fuel

Surface oxidation on small-scale catalytic coupons of Pt foil was investigated experimentally for methane/air and propane/air mixtures of varying composition and flow speed. Infrared thermography was used for the measurement of temperature on the catalytic surface in tandem with gas-chromatography/mass spectroscopy measurements of major combustion products and combustion intermediates and particle image velocimetry of the flow field in the vicinity of the catalytic surface. It was shown that the surface reaction develops in three phases. In phase I, very close to the leading edge, a sharp temperature increase occurred on the catalytic surface with simultaneous fast depletion of the gaseous reactants and development of a strong transverse component of the velocity vector. This was followed by phase II in which surface temperature plateaued at a high value, and reactant concentrations remained low. In phase III the non-adiabatic reaction extinguished and, on occasion, reactant replenishment was observed from the free stream. It is suggested that the design of small-scale reactors should proceed by exploiting the intense reaction of phases I and II through boundary layer interruption and not allow the phenomenon to develop all the way into phase III thus achieving miniaturization of the required hardware.

Numerical investigation of heat and mass transfer in the reactor of a plasma-chemical plant purposed for polychlorinated biphenyls treatment

Gas-dynamic and thermal characteristics of the gas flow in the flow part of a small-scale plasmachemical reactor for trichlorbiphenyl decomposition were calculated numerically. The investigations were performed with no regard to the chemical interaction of the components: in the calculations, the treated substance was replaced by a simulator (water steam), water steam was also used as an oxidant. Mathematical model of the flow is based on the complete system of Navier — Stokes equations in the context of axisymmetric task statement, with due regard to the gas flow swirling. The calculation results enabled us to choose the optimum geometrical parameters of the reactor design.

Design of a generator control system for small nuclear distributed generation

Small-scale reactors have recently attracted attention as a potential power generation source for the future. The Regional Energy Research Institute for Next Generation is currently developing a small-scale reactor called Regional Energy rX 10 MVA (REX-10). The current paper deals with a power system to be used with small-scale reactors for multi-purpose regional energy systems. This small nuclear system can supply electric and thermal energy like a co-generation system. The electrical model of the REX-10 has been developed as a part of the SCADA system. REX-10’s dynamic and electromagnetic performance on the power system is analyzed. Simulations are carried out on a test system based on Ulleung Island’s power system to validate REX-10 availability on a power system. RSCAD/RTDS and PSS/E software tools are used for the simulation.

Development of a small-scale reactor system for bioethanol production from agriculture waste geared towards small industries applications in Malaysia

Bioethanol derived from agriculture can be an alternative fuel source to petroleum-based fuel as the fuel hike and supply depreciation. In Malaysia, agriculture waste materials especially from chip industries (such as banana/yam/tapioca) are potential to be one of the feedstock for producing bioethanol. The utilization of the waste feedstock for biofuel production does not disturb the food chain as it is a waste-to-energy concept based. This paper presents the development of an affordable reactor system that is feasible to be applying in Small and Medium Enterprise (SME) in Malaysia. The reactor system concentrated on the fermentation of the feedstock. Based on the experimental results, it is estimated that the yielding percentage of bioethanol is around 14 % for batch production. Moreover, it is estimated that this reactor is able to produce bioethanol around 0.85 L for each batch of production which implied a petrol fuel cost saving for SMEs around 10 % if bioethanol is blended with the fossil fuel.

Characterization of CO 2 hydrate formation by temperature vibration

A method of temperature vibration was proposed to promote CO 2 hydrate formation based on the dual nature of CO 2 solubility in hydrate-forming regions. The effects on carbon dioxide hydrate formation were investigated in a small scale reactor. The results show that the hydrate formation with distilled water in a quiescent system can be improved effectively by temperature vibration, and the pressure drop is increased by 30%. The effect is especially evident with 0.3% sodium dodecyl sulfate (SDS) additive using temperature vibration method, and large amount of hydrates are formed. The rest gas pressure is very close to the phase equilibrium value at setting temperature. Moreover, the pressure drop of CO 2 gas in the reactor is about 2.6 times of that without temperature vibration. With appropriate operation time of temperature vibration, hydrate formation period can be greatly shortened.

Nitrification activity and community structure of nitrite-oxidizing bacteria in the bioreactors operated with addition of pharmaceuticals

Pharmaceuticals represent a group of the new emerging contaminants, which might influence microbial communities in the activated sludge. Nitrification activity and Nitrospira community structure in the small-scale reactors supplied with different concentrations (0, 50, 200, 500 μg L −1) of the selected pharmaceuticals (ibuprofen, naproxen, ketoprofen, diclofenac and clofibric acid) were evaluated. Ammonia removal was not influenced by selected pharmaceuticals. However, in the two reactors operated with 50 μg L −1 of pharmaceuticals (R50 and R50P), the effluent concentration of N-(NO 2 − + NO 3 −) was significantly higher than in the other reactors. Nitrospira community structure was assessed by terminal restriction fragment length polymorphism (T-RFLP) and by cloning and sequencing of the partial genes for 16S rRNA. Nitrospira spp. were detected in all reactors. The two dominant T-RFs represented the sublineages I and II of the genus Nitrospira. Main shifts were observed in the reactors R50 and R50P, where the T-RF representing sublineage II was much higher as compared to the other reactors. Consistent with this, the Nitrospira sublineage II was detected only in the clone libraries from the reactors R50 and R50P. Our results suggest that the relative abundance of Nitrospira sublineage II could be related to the effluent N-(NO 2 − + NO 3 −) concentration.

Small Scale Reforming Separation Systems with Nanomembrane Reactors for Direct Fuel Cell Applications

Our recent communication focuses on small scale and nanoscale type engineering applications of alumina inorganic membrane reactors and reactor-permeator systems for the conversion of renewable and non-renewable hydrocarbons and methane rich streams into hydrogen rich gas for direct inner application and operation of fuel cell systems. This study elaborates on new nanomembrane reactors for the steam-methane/hydrocarbon reforming and water gas shift reactions, including work in the synthesis, manufacturing, modeling and operation of such microreaction systems. The projected small scale reactors, separators and overall reaction systems are of current significance in the area of multifunctional microreactor and nanoreactor design and operation in connection with the operation of fuel cells for transportation, stationary, and portable power generation applications. An added advantage of such systems is the reactive and separative operations of the fuel cell membrane-processor which are combined to convert the hydrocarbon with steam to valuable fuel gas for continuous fuel cell operation. Moreover, the nanomembrane systems under development have the unique characteristics to perform multiple operations per unit volume, such as to utilize beneficial equilibrium shift principles in reactant conversion and product yield through the removal of permselective species (i.e., hydrogen) via the inorganic membrane out of the conversion/reaction zone. In this way, improved hydrogen and product yields can be achieved which exceed the equilibrium calculated yields. Simultaneously, the reaction products, such as synthesis gas (i.e., H2, CO and CO2) at the reactor exit can be used as fuel in mostly solid oxide and molten carbonate fuel cells. The role of the alumina nanomembrane is also in the main conversion and upgrading sections of these feedstocks in order to overcome existing heat and mass transfer limitations and increase the overall efficiency of the microreactor-fuel cell system.

Energy Efficiency of Conventionally-Heated Pilot Plant Reactors Compared with Microwave Reactors

We report on the energy usage required for one organic reaction in two small pilot plant scale reactors of different vessel designs (both 50 L) conducted in a kilogram scale facility. The background energy consumption of the building and all supporting services was determined beforehand, and this figure used to compensate for the energy usage required for each of six pilot scale batches performed under different conditions at the 20 and 40 L scale. The energy usage data was compared between these large scale batches and with the equivalent laboratory scale batches, including several earlier microwave-heated batches (Moseley, J. D.; Woodman, E. K. Energy Fuels 2009, 23, 5438−5447). The results showed little difference in energy usage between the two pilot plant scale reactors under the different reaction conditions, except on doubling the scale which halved the energy usage per mole. However, the energy efficiency of the laboratory scale reactors was higher than the pilot scale reactors under all reaction conditions on a kilojoule/mole basis. Furthermore, the most efficient microwave reactor operating under optimal conditions was significantly more energy efficient than the pilot scale reactors even up to 40 L.

Reductive Dechlorination of α-, β-, γ-, and δ-Hexachlorocyclohexane Isomers with Hydroxocobalamin, in Soil Slurry Systems

The present study was carried out to test the viability of a method of reductive dehalogenation of α-, β-, γ-, and δ-hexachlorocyclohexane (HCH) in soil slurry systems. The soil slurries were maintained under anaerobic conditions, with titanium(III) citrate as a reducing agent and hydroxocobalamin (vitamin B(12a)) as a catalyzing agent. Experiments were carried out with two soil samples with markedly different characteristics (particularly regarding organic matter content), at a small scale and larger reactor scale. HCH concentration was monitored throughout the 24 h duration of the tests. In the low organic matter soil HCH isomers degraded rapidly, in both the small scale and reactor systems, and undetectable levels (<0.5%) were reached within 5 h. However, complete degradation of HCH isomers was not achieved in soil with high organic matter content, and there were differences between the results obtained in the small scale and reactor systems. In the small scale system, the levels of degradation reached 93, 88, 94, and 91%, for α-, β-, γ-, and δ-HCH, respectively, and the nondegraded HCH was sorbed in the soil. In the reactor system, the reaction stopped after two hours (no more than 65% of any of the isomers was degraded).

Preliminary Evaluation of Biological and Physical–Chemical Chromium Removal Mechanisms in Gravel Media Used in Constructed Wetlands

Constructed wetlands have been shown to achieve high chromium and organic matter removal efficiencies when treating tannery wastewaters. Further, findings suggested chromium was potentially binding to iron oxides and microbial surfaces on the wetland media. The purpose of the present study was to distinguish between physical–chemical and biologically mediated removal mechanisms operating on iron-containing media. A total of 12 small-scale reactors were used for testing three conditions: biotic, abiotic aerobic and abiotic anaerobic. All systems were operated in 3-day batches, with the biotic and abiotic aerobic systems operating for 11 batches and the abiotic anaerobic operating for five batches. The results show that biotic systems achieved significantly higher chromium removal efficiencies (83%) than both abiotic treatments (16%). Biotic reactors quickly lowered dissolved oxygen concentrations, removing an average of 53% of the influent organic matter in the process. Redox conditions were affected by microbial metabolism, favouring iron release from the media surface. Findings suggest that microbiological activity catalyses chromium removal from tannery wastewaters. Chromium removals achieved in sterile reactors illustrate that the media influences metal retention in constructed wetlands; however, microbial interactions with both the media and tannery effluent achieve overall greater chromium removal than achieved solely by physical–chemical mechanisms.

Investigation of Lipase-Catalyzed Biodiesel Production Using Ionic Liquid [BMIM][PF6] as a Co-solvent in 500 mL Jacketed Conical and Shake Flask Reactors Using Triolein or Waste Canola Oil as Substrates

The production of biodiesel was investigated using a lipase-catalyzed (Novozym 435) reaction involving methyl acetate and ionic liquid [BMIM][PF6] as a co-solvent. The use of a lipase catalyst removed the need for alkali wastewater removal and treatment, and the methyl acetate and ionic liquid helped prevent deactivation and improve activity and stability of the lipase, respectively. Experiments were carried out in shake flask and jacketed conical reactors. Runs performed in shake flask reactor produced similar fatty acid methyl ester (FAME) yields to previous work using a small-scale reactor (83%), indicating that the reaction can achieve high yields provided that sufficient mixing between the oil and ionic liquid phases occur. The highest yield achieved in the conical reactor was 54% because of the relatively poor mixing in the reactor as a result of two phases present in the mixture. An additional benefit of using ionic liquid as a co-solvent in the process was for its ease of separation of products. Two distinct phases were present at the end of the reaction, with the ionic liquid phase containing the triacetylglycerol byproduct and any unreacted methyl acetate. The byproduct was then separated by washing with water, and the ionic liquid was removed by decantation and reused. FAMEs were also successfully produced from waste canola oil, with a 72% yield achieved in a small-scale reactor and a 30% yield in a 500 mL jacketed conical reactor.

Study of the Design of Data Acquisition and Analysis Systems for Multi-purpose Regional Energy Systems

Recently, the smart grid has become a hot issue and interest in related power sources have increased accordingly. The implementation of a smart grid can enable many generation resources to be linked to the power system, including small-scale reactors for the purpose of co-generation. Research on small-scale reactors is being carried out all over the world. Similarly, Korea is also conducting research on multi-purpose regional energy systems using nuclear energy. This paper proposes a real-time data acquisition and analysis system for small-scale reactors, and is known as the REX-10 (Regional Energy rX 10 MVA). This analysis requires real-time simulations for the power system since it needs data communication with a remote REX-10. A RTDS (Real Time Digital Simulator) has been used for the simulation, and a SCADA/HMI system interfaced with the RTDS is proposed for the purpose of monitoring and control of the regional energy system.

Hydrogen production from methane reforming: Thermodynamic assessment and autothermal reactor design

In this study, a comparative thermodynamic analysis of methane reforming reactions is conducted using an in-house code. Equilibrium compositions are calculated by two distinct methods: (1) evaluation of equilibrium constants and (2) Lagrange multipliers. Both methods result in systems of non-linear algebraic equations, solved numerically using the Scilab ( www.scilab.org) function “fsolve”. Effects of temperature, pressure, steam to carbon ratio (S/C) (steam reforming), CH 4/CO 2 ratio (dry reforming), oxygen to carbon ratio (O/C) (oxidative reforming) and steam to oxygen to carbon ratio (S/O/C) (autothermal reforming) on the reaction products are evaluated. Comparisons between experimental and simulated data, published in the literature, are used to validate the simulated results. We also present and validate a small-scale reactor model for the autothermal reforming of methane (ATR). Using this model, the reactor design is performed and key operational parameters are investigated in order to increase both H 2 yield and H 2/CO selectivity. The reactor model considers a mass balance equation for each component, and the set of ordinary differential equations is integrated using the Scilab function “ode”. This ATR reactor model is able to describe the influence of temperature on methane conversion profiles, aiming to maximize hydrogen production. The experimental results and the model presented good agreement for methane conversion in all studied temperature range. Through simulated data of methane conversions, hydrogen yields and H 2/CO selectivity, it is observed that the best reaction temperature to maximize the yield of hydrogen for the ATR reaction is situated between 723 and 773 K. Inside these bounds, 50% of methane is converted into products. Also, the experimental data indicates that the Ni catalyst activity is not compromised.

Simulation of the Effectiveness Factor for a Tri-Lobular Catalyst on the Hydrodesulfurization of Diesel

Typical models to estimate effectiveness factors include sphere, cylinder, slab and strong internal diffusion limitations models. However, a reliable model for complex-irregular catalyst shapes is still lacking. Therefore in this work a new approach is proposed which makes simultaneous use of the 1D and GC models to approximate a 3D problem in order to determine the effectiveness factor of a tri-lobular catalytic on a HDS reaction involving diesel. The restrictive internal diffusion phenomena were examined at the cross-section of the catalyst including the effects of its shape. Simulation for the HDS reaction involved the consideration of a small scale reactor using industrial operating conditions. Effects of the intrinsic kinetic, considering strong internal diffusion effects, were calculated through well established computational algorithms. Mathematical simulations of the reaction effectiveness using a given feed-stock of diesel are described completely for a tri-lobular particle considering organic sulfur compound for molecular diffusion, pore size, shape and radial transport across the section of the catalyst and results were validated with models and data published in the literature of typical analysis.

Effect of adding carbon fiber textiles to methanogenic bioreactors used to treat an artificial garbage slurry

To compare the performances and microbial populations of methanogenic reactors with and without carbon fiber textiles (CFT), we operated small-scale (200 ml) reactors using a slurry of artificial garbage. For both types of reactors, the organic loading rate (OLR) was stepwisely and rapidly increased in the same manner. Start-up period was shortened by adding CFT. Reactors with CFT showed greater efficiency for removal of suspended solid and volatile suspended solid than reactors without CFT at a long hydraulic retention time (HRT) between 8 and 13 days. The reactors with CFT maintained stable methane production at an OLR of 15.3 g dichromate chemical oxygen demand (CODcr)/l/day and DNAs from microorganisms were highly concentrated in adhering fractions on CFT. As shown by quantitative PCR analysis, the proportions of methanogenic archaea were conserved more than 25% in adhering fractions on CFT in reactors with CFT. By contrast, reactors without CFT showed accumulation of volatile fatty acid and deteriorated at an OLR of 2.4 gCODcr/l/day. Methanogenic proportions dropped to 17.1% in suspended fractions of reactors without CFT. Denaturing gradient gel electrophoresis (DGGE) analysis revealed that all archaeal DGGE bands in both types of reactors were related to methanogens, but more bands were observed in reactors with CFT. Thus the higher performance of reactors with CFT likely reflects the greater abundance of microorganisms and methanogenic diversity.

Modeling Temperature Profiles of a Catalytic Autothermal Methane Reformer with Nickel Catalyst

In this work, a one-dimensional heterogeneous model for the autothermal reforming of methane in a catalytic (Ni/Al 2 O 3 catalyst) fixed-bed reactor is proposed. The kinetic model implements an indirect reaction scheme and includes a reduction factor that is dependent on the oxygen concentration. Such a factor delays the reforming and water-gas shift reactions, with respect to the oxidation reactions. Experiments at different steam-to-methane ratios and feed flow rates were conducted in a small-scale reactor to identify and validate the proposed mathematical model. To this end, temperature profiles in the solid phase were measured with an infrared camera. The agreement between experimental data and model predictions is very good for all the investigated operating conditions. In particular, the model predicts the strong separation between the oxidation and the experimentally observed reforming zones well.