Decrease In Residence Time Research Articles

Modeling and simulation of drying characteristics on flexible filamentous particles in rotary dryers

Experiments were conducted to demonstrate the effects of the drum wall temperature on the heat and mass transfer in rotary dryers. The drying characteristics of flexible filamentous particles in rotary dryers were further explored. In addition, the inlet and outlet temperatures and moisture contents of granular particles were measured. As a result, the good agreement between the simulations and experiments verified the rationale and feasibility of the numerical method. Therefore, the approach was adopted to evaluate the temperature and moisture content of wet granular particles in a rotary dryer in different conditions, for instance, drum wall temperature and rotational speed. The results revealed that the higher drum wall temperature led to hotter particles with lower outlet moisture content. Conversely, the higher rotational speed resulted in cooler particles with higher outlet moisture content due to the decrease of residence time in the rotary dryer.

Evaluation of Phosphorus Filter Media for an Inline Subsurface Drainage Treatment System

Subsurface drainage from agricultural land has been identified as a contributor of both N and P into surface waters, leading to water quality degradation and eutrophication. This study evaluates the ability of P sorption media (PSM; expanded shale, expanded clay, furnace slag, and natural soil) to sorb P in both batch and column tests. Batch sorption tests estimated sorption of 3.4, 1.2, and 0.5 g P kg for expanded shale, expanded clay, and natural soil, respectively. Furnace slag sorption was evaluated for fine (FS), small (FS), and large (FS) particle sizes, with estimated sorption of 6.8, 5.1, and 3.8 g P kg, respectively. Phosphorus removal for the three furnace slag particle sizes and natural soil were tested in flow-through columns operated at residence times of 50, 17, and 7 s. A decrease in residence time reduced P removal in all columns evaluated. Following all trials, the average P removal from influent was 50% for FS, followed by 27% for FS (furnace slag-coated pea gravel), 22% for FS, and 6% for sandy loam-coated pea gravel. The data from this study provides crucial information for developing and sizing an inline tile drainage treatment system to remove P from tile drainage outlets before reaching surface waters.

Nitrogen processing by grazers in a headwater stream: riparian connections

Summary Primary consumers play important roles in the cycling of nutrients in headwater streams, storing assimilated nutrients in growing tissue and recycling them through excretion. Although environmental conditions in most headwater streams and their surrounding terrestrial ecosystems vary considerably over the course of a year, relatively little is known about the effects of seasonality on consumer nutrient recycling these streams. In this study, we measured nitrogen accumulated through growth and excreted by the grazing snail Elimia clavaeformis (Pleuroceridae) over the course of 12 months in Walker Branch, identifying close connections between in‐stream nitrogen processing and seasonal changes in the surrounding forest. Nitrogen processing rates were positively correlated with ecosystem respiration, which was driven by leaf phenology on streamside trees. Snail nitrogen assimilation, growth and excretion were relatively high in spring before leaf emergence, low in summer when canopy shade was extensive and high again in autumn after leaf‐fall. During the time that snails grazed primarily on epilithon (winter, spring and summer), growth and excretion rates followed changes in light and epilithon biomass. In autumn, when snails primarily grazed fallen leaves, leaf‐associated microbes provided large subsidies of nitrogen for the snails. Nitrogen accumulation in snail biomass was greater in the 2 months following leaf‐fall than at any other time of the year. Snails were less important as nitrogen sinks than as sources of recycled nitrogen in Walker Branch. Over the course of the year, snails excreted approximately 12 times more nitrogen than they accumulated in biomass. Nitrogen accrued during growth in spring was subsequently lost in summer when primary production declined and snails underwent tissue loss. Catabolic losses represented >40% of the nitrogen excreted by the snails in summer. Net nitrogen growth efficiency (growth/assimilation), which varied with food availability, was only 8% for the entire year. Neither growth nor excretion was positively correlated with nitrogen concentrations in grazing substrata. Snails achieved high standing crops and were significant contributors to nitrogen spiralling in Walker Branch. On an areal basis, nitrogen in snail biomass (mgN m−2) was two to five times greater than that in epilithon biomass, depending on the season. Snails assimilated and excreted up to 50% of the nitrogen initially taken up by autotrophs and leaf microbes, and they were likely to have additional effects on nitrogen spiraling through egestion and the cropping of assimilative biomass. Primary consumers like Elimia are important catalysts of nutrient movement through headwater streams, decreasing residence times and facilitating fluxes to downstream waters.

Developing a water-circulating column photobioreactor for microalgal growth with low energy consumption

A water-circulating column photobioreactor (WCC–PBR) was developed to decrease bubble generation time and mixing time for growing microalgal biomass at low energy consumption. Bubble generation time was decreased by 60.4% and mixing time was decreased by 41.5% owing to an enhanced solution velocity with a water pump. Bubble residence time was decreased by 31.1% and mass transfer coefficient was decreased by 0.4% owing to a reduced distance between air aerator and solution surface. Microalgal growth rate was decreased by 12.7% from 128.9mg/Lday in an air-lifting column photobioreactor (ALC-PBR) to 112.6mg/Lday in a WCC–PBR because of the decrease in residence time of bubbles and an additional shear of cells in a water pump. However, total energy consumption of a WCC–PBR with an air compressor and a water pump was lower by 21.1% than that of an ALC–PBR with only an air compressor.

Diethyl ether pyrolysis study in a jet-stirred reactor

This paper reports new experimental measurements for the pyrolysis of diethyl ether at temperatures between 600 and 1100K under dilute conditions. This work was performed using a jet-stirred reactor at pressures from 26.7kPa (200Torr) to 107.7kPa (800Torr) with dilution in helium, for residence time from 1 to 10s and an inlet fuel concentration from 1 to 5%. Temperature was the parameter with the largest influence on reactivity. The complete destruction of diethyl ether was observed from 1080K. A decrease of residence time and pressure also slightly decreased reactivity, but the effect of pressure remained very limited. Major products were carbon monoxide, methane, ethylene and acetaldehyde. Minor products were ethane, acetylene, propane, propene, ethanol, 1,3-butadiene, and benzene. Two literature models including diethyl ether reactions have been used to simulate these results, with in both cases a satisfactory agreement between experiments and simulations for fuel conversion and the formation of most of the products. Simulations using a literature model for the thermal decomposition of diethyl sulfide indicated that in the studied conditions, the sulfur compound would be completely decomposed at a temperature about 100K lower than the oxygenated reactant.

Morphology and concentration of smoke from fluorinated ethylene propylene wire insulation in microgravity under forced airflow

The production of smoke particles from the jet bursting flame caused by overheating fluorinated ethylene propylene (FEP) wire insulations was investigated. Experiments examining the morphology and volume fraction of the fractal smoke particle aggregates with forced airflow were conducted in a 3.5s drop tower. Gravity level and forced flow were shown to have significant hydrodynamic effects on the pathlines and fractal aggregation of the smoke particles, thus the residence time-dependent flame shape, particle size and concentration have obvious changes. For cases in still air, compared with normal gravity, the jet flame in microgravity has a spherical shape, the mean primary particle and aggregate gyration radius are bigger due to longer residence time, but the fractal dimension maintains at about 1.79, similar to that in the normal gravity level; the calculated smoke volume fraction is also bigger. For cases with force flow in microgravity, the mean primary particle diameter, the mean aggregate gyration radius, and soot volume fraction all decrease with increasing forced flow due to decreasing residence time.

Solvent Dynamics in Solutions of PNIPAM in Water/Methanol Mixtures-A Quasi-Elastic Neutron Scattering Study.

The solvent dynamics of concentrated solutions of poly(N-isopropylacrylamide) (PNIPAM, 25 wt %) in water/methanol mixtures (85:15 v/v) are measured with the aim of shedding light onto the cononsolvency effect. Quasi-elastic neutron scattering (QENS) with contrast variation has been carried out at temperatures below and above the cloud point by using in the first set of experiments the mixture H2O:d-MeOD (d-MeOD denotes fully deuterated methanol) as a solvent and in the second set of experiments the mixture D2O:MeOH (MeOH denotes methanol). As a reference, bulk H2O, bulk MeOH and the mixtures H2O:d-MeOD and D2O:MeOH (both 85:15 v/v) have been investigated as well. In the PNIPAM solution in H2O:d-MeOD, two water populations are identified, namely strongly and less strongly arrested water. At the cloud point, the former is partially released from PNIPAM. The diffusion coefficient of the latter one is similar to the one in the water/methanol mixture, and its residence time decreases at the cloud point. The PNIPAM solution in D2O:MeOH reveals similar dynamics to the one in H2O:d-MeOD which may reflect that the dynamics of MeOH near the PNIPAM chain is similar to the one of H2O. The similarity may, however, partially be due to H/D exchange between D2O and MeOH. In both PNIPAM solutions, the mean-square displacement of the PNIPAM chain decreases gradually above the cloud point.

Effects of finite-rate droplet evaporation on the extinction of spherical burner-stabilized diffusion flames

Multiscale asymptotic analysis is conducted for spherical burner-stabilized spray diffusion flames with finite-rate droplet evaporation and nonunity Lewis number. The radiative heat loss is considered and the effects of radiation on flame extinction are examined. The structure function of the spray diffusion flame is derived, based on which the effects of finite-rate droplet evaporation on flame radius, flame temperature, and kinetic and radiative extinction limits are assessed. The flame is found to be affected by droplet evaporation in two ways: (1) the latent heat absorbed for droplet evaporation reduces the flame temperature; and (2) the decrease in the flame radius results in the decrease in radiative loss and residence time. For a given the mass flow rate, only the conventional kinetic extinction limit at low reaction Damköhler number exists. The extinction Damköhler number increases with the radiation intensity and it is significantly affected by droplet evaporation. It is found that at higher radiation intensity, the spray flame with the lower vaporization Damköhler number is relatively more difficult to be extinguished than the purely gaseous flame. When the reaction intensity is fixed and the mass flow rate varies, there exists two extinction limits: a kinetic extinction limit at a low-flow rate and a radiative extinction limit at a high-flow rate. Steady burning only exists between these two extinction limits. The flammable zone is shown to be greatly affected by droplet evaporation and is very sensitive to Lewis number.

Simultaneous 10 kHz TPIV, OH PLIF, and CH2O PLIF measurements of turbulent flame structure and dynamics

Simultaneous 10 kHz repetition-rate tomographic particle image velocimetry, hydroxyl planar laser-induced fluorescence (OH PLIF), and formaldehyde (CH $$_2$$ O) PLIF were used to study the structure and dynamics of turbulent premixed flames. The flames investigated span from the classically defined corrugated flamelet regime to conditions at which broadened and/or broken flamelets are expected. Methods are presented for determining 3D flame topologies from the Mie scattering tomography and for tracking features through space and time using theoretical Lagrangian particles. Substantial broadening of the CH $$_2$$ O region is observed with increasing turbulence intensity. However, OH production remains rapid, and the region of OH and CH $$_2$$ O overlap remains thin. Local flame speeds exceeding three times the laminar flame speed are observed in regions of flame–flame interaction. Furthermore, a method of tracking fluid residence time within the CH $$_2$$ O layer is presented and shows that residence time decreases at higher turbulence intensity despite the broader distribution of the CH $$_2$$ O, indicating an increase in local reaction rate.

Transported scalar PDF modeling of oxygen-enriched turbulent jet diffusion flames: Soot production and radiative heat transfer

Turbulent jet flames fueled either by propane or a methane/ethylene blend and burning under different oxygen indexes (OI) in the range from 21% (air) to 100% (pure oxygen), studied experimentally by Wang et al. (2002), were simulated by using an hybrid flamelet/Stochastic Eulerian Field (SEF) method, an acetylene/benzene-based two-equation soot model, and a wide-band correlated-k (WBCK) method to model the spectral dependence of the absorption coefficient of the gaseous radiatively participating species and soot. Emission Turbulent Radiation Interactions (TRIs) are taken into account by means of the PDF method, whereas absorption TRIs are modeled using the optically-thin fluctuation approximation (OTFA). Model predictions in terms of soot volume fraction, radiant heat flux distribution along the wall of the combustion chamber, and radiant fraction are compared with the experimental data of Wang et al. (2002), showing a reasonable agreement. The non-monotonic evolution of the soot production with the OI, increasing sharply when the OI is enhanced from 21% to about 40% and then being significantly reduced as the OI is further increased, and the effects of the fuel sooting propensity, with the propane flames producing much more soot than the methane/ethylene blend flames, are well reproduced by the numerical model. The non-monotonic influence of the OI on soot production can be explained by several competing mechanisms. The soot production tends to be enhanced owing to, on the one hand, the increase in temperature and, on the other hand, a positive feedback between surface growth process and soot surface area observed for moderate level of oxygen enrichment. Oppositely, the soot production tends to be reduced due to a decrease in residence time and an enhancement in the oxidation of both soot precursors and soot particles.

Ability of Single-Rate Models to Predict Solute Distribution Coefficients in Systems with Heterogeneous Sorption Kinetics

Several sorption nonequilibrium models have been developed to gain a better understanding of solute transport in porous media, among which are those that assume a single-rate behavior. In this study, two commonly used single-rate models were fitted to computer-simulated breakthrough data from hypothetical column experiments in which multirate sorption kinetics exist at the pore scale. The objective was to determine how the sorption distribution coefficient (K) predicted using these models depends on the conditions under which the data were obtained. Simulated cases covered a range of experimental conditions and involved compounds with different sorption characteristics and different degrees of sorption rate heterogeneity. Results revealed that, for a system with a multirate sorption behavior, the true K value is under-predicted if the parameter estimation is determined by curve fitting a single-rate model. The extent of deviation between the fitted and true K increases with the decrease in residence time and increase in sorption rate heterogeneity. Functional relationships were developed between the relative reduction in K and solute residence time. Analysis using the relationships developed suggests that a major potential cause of the previously reported discrepancy between batch- and column-determined K could be attributed to the use of single-rate models for parameter prediction.

A multi-geochronological study of the Hakusan volcano, central Japan

The Hakusan volcano, central Japan, is located in a region where two subducting plates (the Pacific Plate and the Philippine Sea Plate) overlap near the junction of four plates adjacent to the Japanese Islands (the Pacific Plate, the Philippine Sea Plate, the Eurasia Plate, and the North American Plate). The Hakusan volcano consists of products from four major volcanic episodes: Kagamuro, Ko-hakusan, and Shin-Hakusan I and II. To date the eruption events of the Hakusan volcano we applied thermoluminescence and fission track methods. 238U(234U)–230Th disequilibrium and 206Pb/238U methods were applied to date the zircon crystallization ages for estimating the magma residence time before the eruptions. The eruption ages we obtained are ca 250 ka for Kagamuro, ca 100 ka and ca 60 ka for Ko-Hakusan, ca 50 ka for Shin-Hakusan I, and <10 ka for Shin-Hakusan II. They are concordant with previous reports based on K–Ar dating. Some of the pyroclastic rocks, possibly originating from Shin-Hakusan II activities, are dated to be ca 36 ka or 50 ka, and belong to the Shin-Hakusan I activity. The zircon crystallization ages show several clusters prior to eruption. The magma residence time was estimated for each volcanic activity by comparing the major crystallization events and eruption ages, and we found a gradual decrease from ca. 500 ky for the Kagamuro activity to ca. 5 ky for the Shin-Hakusan II activity. This decrease in residence time may be responsible for the decrease in volume of erupted material estimated from the current topography of the region. The scale of volcanic activity, which was deduced from the number of crystallized zircons, is more or less constant throughout the Hakusan volcanic activity. Therefore, the decrease in magma residence time is most likely the result of stress field change. 白山火山の活動史を明らかにするために,年代学的研究を行った∘噴火年代を調べるために熱ルミネッセンス法およびフィッション▪トラック法を用いた∘結果はK–Ar法による既報と一致したが,いくつかの新データは活動期の時代区分の再考が必要となることを示した∘またジルコンの結晶晶出年代をU–Pb法,およびU–Th放射非平衡法により求めたところ,ジルコンの結晶晶出は活動期を通し概ね定常的に続いていた∘結晶晶出年代と噴火年代の比較により推定した噴火前の滞留期間と噴火規模には相関があった∘白山の噴火規模は時代に伴い小さくなっていることが知られているが,これは火山としての活動度の低下ではなく応力場の変化によるものと推定した∘

Continuous fermentation of clarified corn stover hydrolysate for the production of lactic acid at high yield and productivity

Significant amount of research has been done on the production of lactic acid from lignocellulosic biomass. However, most of these studies have been restricted to production using pure cultures that require expensive reactor systems operating with high sterility and clean sugar feedstocks translating into high overall processing costs. We produced a stable lactic acid producing culture through extended non-sterile cultivation of a strain of Bacillus coagulans (strain AD) isolated in our laboratory from a thermophilic biogas reactor. The culture operated with complete and consistent production of lactic acid as the only fermentation product in a similar manner to that of the pure culture. In the present study, we assessed the effect of pH and residence times on the continuous fermentation of clarified corn stover hydrolysate for lactic acid production using our stable culture. A continuous fermenter was set up at 50°C with pH conditions ranging from 5.5 to 6.0 and residence times ranging from 6 to 96h. Maximum lactic acid productivity of 3.69g/L/h was found at pH 6.0 and residence time of 6h with a lactic acid yield of 0.95g/g biomass sugars. It was found that the productivity increased with decrease in residence time but there was no significant effect of pH or residence time on the overall lactic acid yield. Maximum lactic acid yield was found to be 1.086g/g biomass sugars at pH 6.0 and a residence time of 24h showing that the culture consumed sugars other than the conventional C5 (xylose) and C6 (glucose) that was used for the yield calculation. Our study shows the potential for high-rate production of lactic acid with low operational costs.

Experimental Study of the Influence of Process Conditions on Tubular Reactor Performance

This work presents an experimental study of the saponification reaction of ethyl acetate by sodium hydroxide in a tubular reactor at 1 atmosphere (atm) of pressure. The objective of this study is to analyze the effect of operating conditions on the rate constant and conversion in order to explore the tubular reactor performance. The temperature, reactant flow rate, and residence time are the parameters considered for analyzing the reactor performance. The steady-state conversion is achieved after a period of 30 minutes. Conversion decreases with the increased reactant flow rate, owing to the resulting decrease in residence time. The rate constant first decreases and then increases with feed flow rate. The rate constant and conversion increase with increased temperature within the studied temperature range. The residence time declines with increased reactants flow rates leading to decreased NaOH conversion. The obtained NaOH conversion values at different temperatures have been compared with literature data. The outcomes of this study may be useful in maximizing the conversion of ethyl acetate saponification reaction for industrial scale synthesis .of sodium acetate and ethanol synthesis in a tubular reactor Keywords: Saponification; Plug flow reactor (PFR); Condu

Assessment of model estimates of land-atmosphere CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; exchange across Northern Eurasia

Abstract. A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land-atmosphere carbon dioxide (CO2) cycling through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary productivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of Northern Eurasia. The retrospective simulations cover the period 1960–2009 at 0.5° resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO2 fluxes derived from site-based eddy covariance measurements as well as regional-scale GPP estimates based on satellite remote-sensing data. The site-based comparisons depict a tendency for overestimates in GPP and ER for several of the models, particularly at the two sites to the south. For several models the spatial pattern in GPP explains less than half the variance in the MODIS MOD17 GPP product. Across the models NEP increases by as little as 0.01 to as much as 0.79 g C m−2 yr−2, equivalent to 3 to 340 % of the respective model means, over the analysis period. For the multimodel average the increase is 135 % of the mean from the first to last 10 years of record (1960–1969 vs. 2000–2009), with a weakening CO2 sink over the latter decades. Vegetation net primary productivity increased by 8 to 30 % from the first to last 10 years, contributing to soil carbon storage gains. The range in regional mean NEP among the group is twice the multimodel mean, indicative of the uncertainty in CO2 sink strength. The models simulate that inputs to the soil carbon pool exceeded losses, resulting in a net soil carbon gain amid a decrease in residence time. Our analysis points to improvements in model elements controlling vegetation productivity and soil respiration as being needed for reducing uncertainty in land-atmosphere CO2 exchange. These advances will require collection of new field data on vegetation and soil dynamics, the development of benchmarking data sets from measurements and remote-sensing observations, and investments in future model development and intercomparison studies.

Relationships between Chemical Characteristics and Phytotoxicity of Biochar from Poultry Litter Pyrolysis.

Three biochars were prepared by intermediate pyrolysis from poultry litter at different temperatures (400, 500, and 600 °C with decreasing residence times) and compared with biochars from corn stalk prepared under the same pyrolysis conditions. The phytotoxicity of these biochars was estimated by means of seed germination tests on cress (Lepidium sativum L.) conducted in water suspensions (at 2, 5, and 40 g/L) and on biochars wetted according to their water-holding capacity. Whereas the seeds germinated after 72 h in water suspensions with corn stalk biochar were similar to the control (water only), significant inhibition was observed with poultry litter biochars. In comparison to corn stalk, poultry litter generated biochars with higher contents of ash, ammonium, nitrogen, and volatile fatty acids (VFAs) and a similar concentration of polycyclic aromatic hydrocarbons (PAHs). Results from analytical pyrolysis (Py-GC-MS) indicated that nitrogen-containing organic compounds (NCCs) and aliphatic components were distinctive constituents of the thermally labile fraction of poultry litter biochar. The inhibition of germination due to poultry litter biochar produced at 400 °C (PL400) was suppressed after solvent extraction or treatment with active sludge. A novel method based on solid-phase microextraction (SPME) enabled the identification of mobile organic compounds in PL400 capable of being released in air and water, including VFAs and NCCs. The higher phytotoxicity of poultry litter than corn biochars was tentatively attributed to hydrophilic biodegradable substances derived from lipids or proteins removable by water leaching or microbial treatments.

Cloud Shading Effects on Characteristic Boundary-Layer Length Scales

We studied the effects of shading by shallow cumulus (shallow Cu) and the subsequent effect of inducing heterogeneous conditions at the surface on boundary-layer characteristics. We placed special emphasis on quantifying the changes in the characteristic length and time scales associated with thermals, shallow Cu and induced thermal circulation structures. A series of systematic numerical experiments, inspired by Amazonian thermodynamic conditions, was performed using a large-eddy simulation model coupled to a land-surface model. We used four different experiments to disentangle the effects of shallow Cu on the surface and the response of clouds to these surface changes. The experiments include a ‘clear case’, ‘transparent clouds’, ‘shading clouds’ and a case with a prescribed uniform domain and reduced surface heat flux. We also performed a sensitivity study on the effect of introducing a weak background flow. Length and time scales were calculated using autocorrelation and two-dimensional spectral analysis, and we found that shading controlled by shallow Cu locally lowers surface temperatures and consequently reduces the sensible and latent heat fluxes, thus inducing spatial and temporal variability in these fluxes. The length scale of this surface heterogeneity is not sufficiently large to generate circulations that are superimposed on the boundary-layer scale, but the heterogeneity does disturb boundary-layer dynamics and generates a flow opposite to the normal thermal circulation. Besides this effect, shallow Cu shading reduces turbulent kinetic energy and lowers the convective velocity scale, thus reducing the mass flux. This hampers the thermal lifetime, resulting in a decrease in the shallow Cu residence time (from 11 to 7 min). This reduction in lifetime, combined with a decrease in mass flux, leads to smaller clouds. This is partially compensated for by a decrease in thermal cell size due to a reduction in turbulent kinetic energy. As a result, inter-cloud distance is reduced, leading to a larger population of smaller clouds, while maintaining cloud cover similar to the non-shading clouds experiment. Introducing a $$1\,\hbox {m}\, \hbox {s}^{-1}$$ background wind speed increases the thermal size in the sub-cloud layer, but the diagnosed surface–cloud coupling, quantified by characteristic time and length scales, remains.

Pyrolysis of spent coffee grounds using a screw-conveyor reactor

The fast pyrolysis of spent coffee grounds using a compact, transportable, screw conveyor reactor for producing bio-oil was studied. A two-factor, five-level, central composite response surface experiment was completed to formulate a statistical model that relates reactor temperature (429–550°C) and residence time (23–42s, controlled by the screw rotation rate) to bio-oil yield and quality. Regression analysis of model fits with experimental data showed that temperature and residence time had a significant effect (p<0.05) on bio-oil yield. Highest bio-oil yield (61.8%) was observed at 500°C while the highest char yield (20.6 % w/w) was produced at the lowest temperature of 429°C. Bio-oil yields increased with screw speed and decreasing residence time. The model predicted a maximum liquid yield of 61.7% and an accompanying char yield of 17.1% at 505°C (778K) and 70rpm. In addition to containing oxygenated organic compounds typical of bio-oils, spent coffee bio-oil also contains more hydrophobic compounds (>20% peak area) such as fatty acids, fatty acid esters, medium-chain paraffins, olefins, and caffeine. Because of the abundance of spent coffee grounds and the quality of its bio-oil, this waste stream offers potential as a valuable bioenergy feedstock.

An oxygen permeable membrane microreactor with an in-situ deposited Bi1.5Y0.3Sm0.2O3−δ catalyst for oxidative coupling of methane

In this study, a novel catalytic hollow fibre membrane microreactor (CHFMMR) was developed using a micro-structured La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) hollow fibre as an oxygen separation membrane as well as a functional substrate for in-situ deposition of a Bi1.5Y0.3Sm0.2O3−δ (BYS) catalyst using a sol–gel method for oxidative coupling of methane (OCM) reaction. A nano-thickness BYS catalytic layer (300–500nm) was successfully deposited onto the microchannel walls throughout the whole hollow fibre. The differences in the OCM performances between the in-situ sol–gel prepared CHFMMR and a washcoat CHFMMR are highlighted. The performance of such CHFMMR is found to be strongly dependent on the properties of BYS and the reaction conditions. When the particle size of BYS was reduced to nano-sizes and was uniformly dispersed, the performance of such CHFMMRs changes drastically, in which higher oxygen permeation rate and methane conversion were obtained. A decrease in residence time was observed to give a better C2+ selectivity and C2+ yield, achieving a maximum value of 79% and 39%, respectively at 900°C. To the best of our knowledge, the C2+ yield obtained in this study is the highest value reported so far. The C2+ productivity rate of the in-situ design CHFMMR was observed to be nearly four times higher than that of the washcoat CHFMMR due to the better accessibility of reactants towards lattice/active site of the uniform BYS catalytic layer.

CFD Numerical Simulation of Biodiesel Synthesis in a Spinning Disc Reactor

Abstract In this paper a two-disc spinning disc reactor for intensified biodiesel synthesis is described and numerically simulated. The reactor consists of two flat discs, located coaxially and parallel to each other with a gap of 0.2 mm between the discs. The upper disc is located on a rotating shaft while the lower disc is stationary. The feed liquids, triglycerides (TG) and methanol are introduced coaxially along the centre line of rotating disc and stationary disc. Fluid hydrodynamics in the reactor for synthesis of biodiesel from TG and methanol in the presence of a sodium hydroxide catalyst are simulated, using convection-diffusion-reaction species transport model by the CFD software ANSYS©Fluent v. 13.0. The effect of the upper disc’s spinning speed is evaluated. The results show that the rotational speed increase causes an increase of TG conversion despite the fact that the residence time decreases. Compared to data obtained from adequate experiments, the model shows a satisfactory agreement.