Flash Conditions Research Articles

String flash-boiling in gasoline direct injection simulations with transient needle motion

A computational study was performed to investigate the influence of transient needle motion on gasoline direct injection (GDI) internal nozzle flow and near-field sprays. Simulations were conducted with a compressible Eulerian flow solver modeling liquid, vapor, and non-condensable gas phases with a diffuse interface. Variable rate generation and condensation of fuel vapor were captured using the homogeneous relaxation model (HRM). The non-flashing (spray G) and flashing (spray G2) conditions specified by the Engine Combustion Network were modeled using the nominal spray G nozzle geometry. Transient needle lift and wobble were based upon ensemble averaged X-ray imaging preformed at Argonne National Lab. The minimum needle lift simulated was 5 µm and dynamic mesh motion was achieved with Laplacian smoothing. The results were qualitatively validated against experimental imaging and the experimental rate of injection profile was captured accurately using pressure boundary conditions and needle motion to actuate the injection. Low needle lift is shown to result in vapor generation near the injector seat. Finally, the internal injector flow is shown to be highly complex, containing many transient and interacting vortices which result in perturbations in the spray angle and fluctuations in the mass flux. This complex internal flow also results in intermittent string flash-boiling when a strong vortex is injected and the resulting swirling spray contains a thermal non-equilibrium vapor core.

Assessment of dermal hazard from acid burns with fire retardant garments in a full-size simulation of an engulfment flash fire

There have been concerns that fire-derived acid gases could aggravate thermal burns for individuals wearing synthetic flame retardant garments. A comparative risk assessment was performed on three commercial flame retardant materials with regard to relative hazards associated with acidic combustion gases to skin during a full engulfment flash fire event. The tests were performed in accordance with ASTM F1930 and ISO 13506: Standard Test Method for Evaluation of Flame Resistant Clothing for Protection against Fire Simulations Using an Instrumented Manikin. Three fire retardant textiles were tested: an FR treated cotton/nylon blend, a low Protex® modacrylic blend, and a medium Protex® modacrylic blend. The materials, in the form of whole body coveralls, were subjected to propane-fired flash conditions of 84kW/m2 in a full sized simulator for a duration of either 3 or 4s. Ion traps consisting of wetted sodium carbonate-impregnated cellulose in Teflon holders were placed on the chest and back both above and under the standard undergarments. The ion traps remained in position from the time of ignition until 5min post ignition. Results indicated that acid deposition did increase with modacrylic content from 0.9μmol/cm2 for the cotton/nylon, to 12μmol/cm2 for the medium modacrylic blend. The source of the acidity was dominated by hydrogen chloride. Discoloration was inversely proportional to the amount of acid collected on the traps. A risk assessment was performed on the potential adverse impact of acid gases on both the skin and open wounds. The results indicated that the deposition and dissolution of the acid gases in surficial fluid media (perspiration and blood plasma) resulted in an increase in acidity, but not sufficient to induce irritation/skin corrosion or to cause necrosis in open third degree burns.

Real-Time Monitoring and Assessment of Thermal and Toxicological Risk Associated with Fire Retardant Textiles in a Full-Size Simulation of an Engulfment Flash Fire

A comparative risk assessment was performed on nine commercial flame-retardant materials in garments intended for general occupational use. The assessment evaluated the relative hazards associated with combustion gases during a full engulfment flash fire in accordance with ASTM F1930 and ISO 13506. The materials in the form of whole body coveralls were subjected to propane-fired flash conditions of 84 kW/m2 for a duration of 3 or 4 s. Combustion gas composition and concentrations were measured in the breathing zone of the test manikin in real time by Fourier transform infrared spectrophotometry as was the gas temperature. Results were used to parameterize thermokinetic and toxicokinetic models used to predict both injury and gas exposure. The results indicated that an individual maintaining regular ventilation would receive third degree burns to the upper airway at both durations. In the case of the 4 s burn, third degree injury would reach the larynx, resulting in involuntary apnea, in about 12 s post-ignition. Combustion gas production was high, but of very short duration meaning that exposure was limited by the receptor’s ventilation cycle. Hazards to parties giving aid were limited by rapid declines in combustion gas production and temperature that returned to background concentrations within about 60 s post-ignition. Comparisons made between materials indicated the marked presence of hydrogen chloride, cyanide, and nitrogen dioxide production for the fire retardant (FR) modacrylic blends; cyanide, nitrogen dioxide, and sulfur dioxide for FR cotton; and sulfur dioxide for the FR rayon blends. None of the gas exposures were found to represent a significant risk to health or impedance to survival or escape to the individual wearing the garment, or other persons that may come to their assistance. Particulate antimony was detected in the technologies that use it as a fire retardant, but at concentrations well below anything that could be considered hazardous.

Effect of Arc Electrode Geometry and Distance on Cotton Shirt Ignition

The results of experimental arc testing of a nontreated cotton T-shirt with three different geometrical arc electrode arrangements are presented and discussed. Different geometries of arc electrodes result in different electromagnetic interactions of an arc current with current flowing in arc electrodes, which, in turn, cause very different arc behaviors. The ignition threshold of a T-shirt (arc energy attributed to 50% probability of ignition) was determined using the following: 1) apparatus for mannequin arc test methods ASTM F2621 and IEC 61482-1-1 (Method B) with vertical butted arc electrodes in open air (open arc); 2) apparatus for arc-in-a-box (box) test method IEC 61482-1-2 with vertical butted arc electrodes placed in a box; and 3) nonstandard end-of-line (ejected arc) apparatus with parallel horizontal arc electrodes in open air. Test parameters for the ignition threshold included the following: 1) 4-, 8-, and 16-kA arc current levels for each test apparatus; 2) same distance of 18 in from arc electrodes to the tested T-shirt for all apparatuses; and 3) same arc gap (distance between arc electrodes) except the arc in a box. A strong dependence of the ignition threshold on the electromagnetics was demonstrated by the tests. The T-shirt ignition for the ejected arc demonstrated a longer arc flash boundary distance than that calculated by NFPA 70E or IEEE 1584 calculations, raising a need for strong caution in using non-fire retardant (FR) cotton in arc flash conditions. It is suggested that the electrode configuration should be considered in risk analysis. Reported test results could provide a framework in developing arc flash boundary for ejected arc applications. It is shown that, unlike most cases where the IEEE 1584 calculations and NFPA 70E tables were observed to be conservative, in the ejected arc, calculation results should be used with caution as they are less than conservative.

Using visual evoked potentials for the early detection of amnestic mild cognitive impairment: a pilot investigation.

Amnesic mild cognitive impairment (MCIa) is often characterized as an early stage of Alzheimer's dementia (AD). The latency of the P2, an electroencephalographic component of the flash visual evoked potential (FVEP), is significantly longer in those with AD or MCIa when compared with controls. The present investigation examined the diagnostic accuracy of several FVEP-P2 procedures in distinguishing people with MCIa and controls. The latency of the FVEP-P2 was measured in participants exposed to a single flash condition and five double flash conditions. The double flash conditions had different inter-stimulus intervals between the pair of strobe flashes. Significant group differences were observed in the single flash and two of the double flash conditions. One of the double flash conditions (100 ms) displayed a higher predictive accuracy than the single flash condition, suggesting that this novel procedure may have more diagnostic potential. Participants with MCIa displayed similar P2 latencies across conditions, while controls exhibited a consistent pattern of P2 latency differences. These differences demonstrate that the double stimulation procedure resulted in a measurable refractory effect for controls but not for those with MCIa. The pattern of P2 group differences suggests that those with MCIa have compromised cholinergic functioning that results in impaired visual processing. Results from the present investigation lend support to the theory that holds MCIa as an intermediate stage between normal healthy aging and the neuropathology present in AD. Measuring the FVEP-P2 during several double stimulation conditions could provide diagnostically useful information about the health of the cholinergic system.

Reservoir-Fluid Characterization From Tests on Tight Formations

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 164887, ’Reservoir-Fluid Characterization From Tests on Tight Formations,’ by Brian Moffatt, Michael Fawcett, Jaimar Maurera, and Anna Bruzco, Petrophase, prepared for the 2013 European Association of Geoscientists and Engineers Annual Conference and Exhibition incorporating SPE Europec, London, 10-13 June. The paper has not been peer reviewed. Drillstem testing of low-permeability reservoirs is challenging because high-pressure drawdown around the wellbore lowers fluids below saturation pressure and creates two-phase flow into the wellbore. The fluids produced at surface no longer represent the original reservoir fluid. This paper shows the benefits of a careful methodology of data selection and equation-of-state (EOS) modeling to validate data used to characterize the reservoir fluid. Introduction There are significant technical difficulties in capturing representative fluid samples from tight formations. Attempts to flow to surface from tight formations induce a fall in pressure around the well-bore that may take the reservoir oil or gas below its saturation pressure. Two-phase flow in the wellbore can cause significant errors for sampling downhole, although surface sampling can be less prone to error. However, because the gas within the formation is more mobile than liquid, the surface gas/oil ratios (GORs) are higher than those of the native fluid. This can lead to erroneous assumptions about the reservoir fluid if the separator samples are recombined to the prevailing GOR without reference to what is happening in the reservoir. Two case studies are presented that resolve apparently conflicting data and use a wider range of well-test data than single data points to define reservoir fluids. Neither study had the benefit of downhole pressure/depth gradients to corroborate reservoir-fluid properties. Characteristic Test Results for Tight-Formation Drillstem Tests (DSTs) DSTs performed where the flowing bottomhole pressure (FBHP) stays above saturation pressures are ideal for surface sampling or for taking bottomhole flowing samples. However, the low deliverability of tight-formation wells often makes it difficult to establish stable flowing conditions. The FBHP, flowing well-head pressure, and separator conditions may all be unstable, causing difficulties in establishing the correct GOR even when the total wellbore composition is constant. A further complication can arise if the gas rates are too low to lift liquids to the surface. GORs for bottomhole samples (BHSs) are measured in the laboratory by flashing the sample to specified conditions. The same wellstream composition sampled at the surface will normally have a lower GOR because separator conditions favor an increase in stable liquid volume. Surface and bottomhole GORs will match only under identical flashing conditions. Typical GOR characteristics for BHSs and surface samples for a tight formation containing oil are shown in Fig. 1.

Activity in ventral premotor cortex is modulated by vision of own hand in action

Parietal and premotor cortices of the macaque monkey contain distinct populations of neurons which, in addition to their motor discharge, are also activated by visual stimulation. Among these visuomotor neurons, a population of grasping neurons located in the anterior intraparietal area (AIP) shows discharge modulation when the own hand is visible during object grasping. Given the dense connections between AIP and inferior frontal regions, we aimed at investigating whether two hand-related frontal areas, ventral premotor area F5 and primary motor cortex (area F1), contain neurons with similar properties. Two macaques were involved in a grasping task executed in various light/dark conditions in which the to-be-grasped object was kept visible by a dim retro-illumination. Approximately 62% of F5 and 55% of F1 motor neurons showed light/dark modulations. To better isolate the effect of hand-related visual input, we introduced two further conditions characterized by kinematic features similar to the dark condition. The scene was briefly illuminated (i) during hand preshaping (pre-touch flash, PT-flash) and (ii) at hand-object contact (touch flash, T-flash). Approximately 48% of F5 and 44% of F1 motor neurons showed a flash-related modulation. Considering flash-modulated neurons in the two flash conditions, ∼40% from F5 and ∼52% from F1 showed stronger activity in PT- than T-flash (PT-flash-dominant), whereas ∼60% from F5 and ∼48% from F1 showed stronger activity in T- than PT-flash (T-flash-dominant). Furthermore, F5, but not F1, flash-dominant neurons were characterized by a higher peak and mean discharge in the preferred flash condition as compared to light and dark conditions. Still considering F5, the distribution of the time of peak discharge was similar in light and preferred flash conditions. This study shows that the frontal cortex contains neurons, previously classified as motor neurons, which are sensitive to the observation of meaningful phases of the own grasping action. We conclude by discussing the possible functional role of these populations.

The Changing Face of P300 BCIs: A Comparison of Stimulus Changes in a P300 BCI Involving Faces, Emotion, and Movement

BackgroundOne of the most common types of brain-computer interfaces (BCIs) is called a P300 BCI, since it relies on the P300 and other event-related potentials (ERPs). In the canonical P300 BCI approach, items on a monitor flash briefly to elicit the necessary ERPs. Very recent work has shown that this approach may yield lower performance than alternate paradigms in which the items do not flash but instead change in other ways, such as moving, changing colour or changing to characters overlaid with faces.Methodology/Principal FindingsThe present study sought to extend this research direction by parametrically comparing different ways to change items in a P300 BCI. Healthy subjects used a P300 BCI across six different conditions. Three conditions were similar to our prior work, providing the first direct comparison of characters flashing, moving, and changing to faces. Three new conditions also explored facial motion and emotional expression. The six conditions were compared across objective measures such as classification accuracy and bit rate as well as subjective measures such as perceived difficulty. In line with recent studies, our results indicated that the character flash condition resulted in the lowest accuracy and bit rate. All four face conditions (mean accuracy >91%) yielded significantly better performance than the flash condition (mean accuracy = 75%).Conclusions/SignificanceObjective results reaffirmed that the face paradigm is superior to the canonical flash approach that has dominated P300 BCIs for over 20 years. The subjective reports indicated that the conditions that yielded better performance were not considered especially burdensome. Therefore, although further work is needed to identify which face paradigm is best, it is clear that the canonical flash approach should be replaced with a face paradigm when aiming at increasing bit rate. However, the face paradigm has to be further explored with practical applications particularly with locked-in patients.

Photo-responsive behaviors and structural evolution of carbon-nanotube-supported energetic materials under a photoflash

The photo-responsive behaviors of energetic materials (metal/oxidant) supported by CNTs were investigated under a common photoflash. The remarkable ignition (and/or combustion) was observed in the metal/oxidant/CNT composite with an appropriate ratio, while no obvious change was found in the absence of CNT under the identical flash conditions. The structural characterization indicated that the metallic Zr was oxidized into the corresponding metal oxide (ZrO2) after ignition due to high temperature and the exposure to air ambient. The CNTs showed increased structural defects, indicated by HRTEM and Raman spectra. The enhanced photo-response can be attributed to the absorption capability of CNTs to flash energy and high thermal conductivity, leading to a rapid increase in the internal temperature of composite materials up to ignition temperature within a very short time.

Can indexes be voluntarily assigned in multiple object tracking?

In Multiple Object Tracking (MOT), an observer is able to track 4 – 5 objects in a group of otherwise indistinguishable objects that move independently and unpredictably about a display. According to the Visual Indexing Theory (Pylyshyn, 1989), successful tracking requires that target objects be indexed while they are distinct — before tracking begins. In the typical MOT task, the target objects are briefly flashed resulting in the automatic assignment of indexes. The question arises whether indexes are only assigned automatically or whether they can be assigned voluntarily in a top-down manner. This study compares several ways of specifying which of 8 items are the targets to be tracked. In the Flash condition the target items were flashed, in the Nonflash condition the targets were the items not flashed, and in the Number condition the targets were specified by number (e.g., items numbered 1–4). The results showed no difference between the three conditions, suggesting that tracking was possible with either voluntary or involuntary indexing. The second experiment tested the hypothesis that voluntary indexing is possible only if the target items are visited serially. The conditions were the same as experiment 1 except that the time available for index assignment was too short to allow targets to be visited serially. In this experiment, targets flashed only once (or, in the Numbers condition, remained visible for about 400 ms). The results showed a decrease in tracking performance for the Number condition, but the Flash and the Nonflash conditions did not differ, suggesting that as long as the designation of targets was done rapidly, the observer did not have to visit each target serially in order to index it. These results suggest that indexing can occur both automatically and voluntarily, and without serially visiting them, so long as the items are successfully specified.

Experimental and simulation study of the flash lamp annealing for boron ultra-shallow junction formation and its stability

The application of advanced annealing techniques has emerged as an essential dopant activation step for the formation of ultra-shallow junction in forthcoming complimentary metal-oxide-semiconductor (CMOS) technology. Recent works demonstrated that flash lamp annealing (FLA) is able to provide junctions that are highly activated and ultra-shallow. However, it is found that the thermal budget from the FLA is not enough to fully dissolve the extended defects induced by the pre-amorphizing implant. This affects the junction stability upon post-FLA thermal annealing cycle. In this work, the junction stability is investigated through the de/re-activation behavior of B in the flash-annealed junctions subjected to subsequent isochronal RTA annealing. The experimental results show that a single pulse FLA leads to significant dopant deactivation. It is also found that the deactivation level can be reduced by the additional of flash pulses or eliminated by a spike RTA prior to the FLA. To understand the physics underlying the FLA junction formation and deactivation, junction profiles and activation data are simulated using an atomistic kinetic Monte Carlo (kMC) simulator. The simulated distributions of the defects for various flash conditions are used to study their evolution as well as interaction with dopants. Detailed analyses reveal that large amount of extended defects remains after a single pulse flash annealing. Thus, upon post-FLA thermal annealing, the defects at EOR region emit interstitials toward the surface which deactivate the B through the formation of dopant-defect clusters. For the case of prior RTA schemes, the simulated results show distinct variations in the amount of extended defects and it can be correlated to the different extent of junction stability.

“Hot Helium Flashers” – The Road to Extreme Horizontal Branch Stars

AbstractObservational and theoretical investigations, performed especially over the last two decades, have strongly attributed the far-UV upturn phenomenon to low-mass, small-envelope, He-burning stars in Extreme Horizontal Branch (EHB) and subsequent evolutionary phases.Using our new stellar evolution code – a code that follows through complete evolutionary tracks, Pre-MS to cooling WD – without any interruption or intervention, we are able to produce a wide array of EHB stars, lying at bluer (Teff ≥ 20,000 K) and less luminous positions on HRD, and also closely examine their post-HB evolution until the final cooling as White Dwarfs.HB morphology is a complex multiple parameter problem. Two leading players, which seem to possess the ability to affect considerably positions of HB, are those of: 1.Helium abundance, and 2.mass-loss efficiency on the first giant branch. We focus here on the latter; thus, EHB stars are produced in our calculations by increasing the mass-loss rate on the RGB, to a state where prior to reaching core He flash conditions, only a very small H-rich envelope remains. The core flash takes place at hotter positions on the HRD, sometimes while already descending on the WD cooling curve. We show preliminary results for a range of initial masses (MZAMS = 0.8 − 1.1 M⊙) and for metallicities covering both populations I and II (Z = 0.01 − 0.001). The [M,Z] combinations have been chosen such that the masses would be above and close to typical MS turnoff masses (e.g. the estimation of MTO ≃ 0.85 for NGC 2808), and also so that the ages at HB are of order of 10 ± 5 Gyr.

Flash-Induced Blocking of the High-Affinity Manganese-Binding Site in Photosystem II by Iron Cations: Dependence on the Dark Interval between Flashes and Binary Oscillations of Fluorescence Yield

Incubation of Fe(II) cations with Mn-depleted PSII membranes (PSII(-Mn)) under weak continuous light is accompanied by blocking of the high-affinity, Mn-binding (HAZ) site with ferric cations (Semin, B.K. et al. Biochemistry 2002, 41, 5854-5864). In this study we investigated the blocking yield under single-turnover flash conditions. The flash-probe fluorescence method was used to estimate the blocking efficiency. We found that the yield of blocking increases with flash number and reaches 50% after 7 flashes. When the dark interval between the flashes (Delta t) was varied, we found that the percentage of blocking decreases at Delta t < 100 ms (t 1/2, 4-10 ms). No inhibition of the blocking yield was found at longer time intervals (as with photoactivation). This result shows the necessity of a dark rearrangement during the blocking process (the dual-site hypothesis described in the text) and indicates the formation of a binuclear iron center. During the blocking experiments, we found a binary oscillation of the Fmax elicited during a train of flashes. The oscillations were observed only in the presence of Fe(II) cations or other electron donors (including Mn(II)) but not in the presence of Ca2+. Chelators had no effect on the oscillations. Our results indicate that the oscillations are due to processes on the acceptor side of PSII and to the appearance of "acceptor X" after odd flashes. Acceptor X is reduced by QA- at very high rate (<<2 ms), is not sensitive to DCMU, and is rather stable in the dark (t l/2 approximately 2 min). These properties are similar to those of nonheme Fe(III) (Fe(III)NHI). When Fe(II)NHI was oxidized with ferricyanide (Fe(CN)6), the fluorescence decay kinetics and yield of fluorescence were identical to those observed when the sample was exposed to 1 flash prior to the fluorescence measurement. We suggest that acceptor X is Fe(III)NHI, oxidized by the semiquinone form of QB-. This is similar to the mechanism of "reduction-induced oxidation of Fe(II)NHI" by exogenous quinones reported in the literature. We suggest that involvement of QB- in the oxidation of Fe(II)NHI in PSII(-Mn) membranes is due to the modification of the QB-binding site and increase of its redox potential resulting from extraction of the functional Mn cluster.

Effects of SOA and flash pattern manipulations on ERPs, performance, and preference: Implications for a BCI system

P3 brain–computer interfaces (BCIs) are synchronous communication systems that allow users to communicate interest in a target event by choosing to attend to it while ignoring other events. In such a system, a cogneme refers to the user's response to: “/attend to the event/” or “/ignore the event/”. The present study examined subjects' ability to generate more cognemes per minute (by varying stimulus onset asynchrony or SOA), or requiring fewer cognemes to convey a message (by varying the pattern of stimulus presentation). Both of these have implications for improved information throughput in a P3 BCI. SOAs of 125, 250, and 500 ms were used. Additionally, the conventional “single flash” approach was compared to a new “multiple flash” condition in which half of the stimuli in an 8 × 8 grid were flashed simultaneously. In both conditions, P3-like component amplitudes decreased with faster SOAs at low target probabilities, but the trend did not hold for higher probabilities. The multiple flash condition produced more robust ERPs at the faster speeds. The results also indicate that attend/ignore differences were more apparent following multiple flashes for low target probabilities, but less apparent for high target probabilities. Although information throughput alone does not support the superiority of one approach over the other, only six cognemes are needed in the multiple flash conditions to identify a character, compared to sixteen cognemes in the single flash condition. This suggests that the former approach could operate more rapidly. Thus, the present results suggest that the multiple flash approach may be a more efficient and faster basis for a P3 BCI system.

A 1-kW/cm2 flash KrCl excimer lamp

The amplitude-time characteristics of the emission from a one-barrier flash KrCl excimer lamp and conditions for the maximum luminosity in the UV spectrum range are reported. The best result is achieved for a Ne: Kr: Cl2=50: 1: 1 (torr) mixture. When the lamp is excited by the combined Fitch circuit, the pulse half-height duration 107 ns and the power density E(0,0)=1.1 kW/cm2 are attained.

Temporal modulation enhances the efficiency of spatial offset discriminations by 6-month-olds.

Fourteen- and 24-week-old infants were tested for sensitivity to small position differences under two conditions: (a) the Vernier stimulus was flashed on and off at 1.2 or 4.8 Hz (flash condition); and (b) the Vernier breaks were presented in apparent motion at 1.2 or 4.8 Hz (motion condition). The latter stimulus also contained local flicker cues. Each infant was tested at one temporal frequency with both stimuli. No benefit was shown by 14-week-olds at either temporal frequency from the additional motion and flicker cues. However, 24-week-olds required spatial offsets only one third as large in the motion condition as they required in the flash condition at 4.8 Hz. Ideal observer methodology was used to ensure that the spatial information for both of these discriminations was held strictly equivalent. Increasing sensitivity to flicker and/or motion or uncertainty reduction may underlie the enhancement in discrimination shown by 24-week-olds at 4.8 Hz.

Yz. reduction kinetics in the absence of the manganese-stabilizing protein of photosystem II.

Decay of Signal IIvf of photosystem II (PSII), under repetitive flash conditions, was examined in whole cells of wild-type Synechocystis sp. PCC6803 and in cells of an engineered strain, delta psbO, which lacks the extrinsic 33 kDa manganese-stabilizing protein (MSP). Previous polarographic analysis had shown that O2 release during the S3-->[S4]-->S0 transition of the catalytic cycle is significantly retarded in the delta psbO strain relative to the wild-type [Burnap et al. (1992) Biochemistry 31, 7404-7410]. The present experiments provide evidence that a parallel retardation in the rate of reduction of photooxidized Yz by the H2O oxidation complex is due to the absence of MSP. The half-time of the Signal IIvf component, corresponding to Yz. reduction during the S3-->[S4]-->S0 transition, was estimated to be 1.2 and 6.0 ms in the wild-type and delta psbO cells, respectively.

PAH Emissions from the Fluidized-Bed Incineration of an Industrial Sludge

An industrial waste sludge was incinerated in a laboratory–scale fluidized–bed incinerator and sixteen priority polyaromatic hydrocarbons (PAHs), including the vapor–phase PAHs adsorbed by XAD–2 and the solid–phase ones intercepted by glass fiber filters, were monitored. The experimental parameters were equivalence ratio ( φ = 0.83 and 1.25) and incinerating temperature (500, 600, 700, and 800 °C). The fuel–rich condition was carried out to resemble “fault–mode” operation. The nominal gaseous residence times were in the 0.7–1.2 second range. A gas chromatograph/flame ionization detector (GC/FID) was used to identify the PAHs qualitatively and quantitatively. Three priority PAHs—phenanthrene (PhA), fluoranthane (FluA), and pyrene (Pyr)—were detected in great quantities for all incineration runs. Two other priority PAHs—fluorene (Flu) and anthracene (AnT)—were found only in the solid phase for the fuel–rich run at 500 °C. In general, the PAH levels detected were lower for the runsat higher incineration temperatures and lower equivalence ratio. A comparison of the PAH emission patterns in studies using incinerators of various types and scale showed a difference in PAH concentration in the flue gases of 2 to 3 orders of magnitude. The reason for the high emission level of PAHs in this study might be attributed to the high contents of native PAHs in the incinerated sludge; the short residence time, which was too short to allow the native PAHs to be sufficiently destructed; the rapid heating rate, as in a flash or rapid pyrolysis condition that could accelerate the fusion of organic matters to form PAHs; and a low–to–medium incineration temperature that was not high enough to allow quick destruction of the PAHs. The correlation between log (PAHvapor/PAHsolid) and (1/T) derived from the Langmuir adsorption equation was used to examine the emitted PAHs. Each PAH emitted from the fuel–lean incineration of waste sludge was satisfactorily described if the 500 °C–run data were excluded (at which temperature the organic matter was considered to be under incomplete combustion or oxygen–deficient pyrolysis). Contrarily, the fuel–rich cases gave either poor or no correlation.

Comparative study of the pyrolysis of almond shells and their fractions, holocellulose and lignin. Product yields and kinetics

A comparison between the thermal decomposition of almond shells and their components (holocellulose and lignin) was carried out, considering the yields of the most important products, under flash conditions, and the decomposition kinetics. The yields of the main gaseous products obtained in the fast pyrolysis of almond shells can be reproduced from the yields obtained with holocellulose and lignin. The best results were obtained with CO, water and CO 2. The differences were greater with the minor hydrocarbons, CH 4, C 2H 6, C 2H 4, etc. The kinetics of the slow thermal decomposition (TG-DTG) of almond shells cannot be reproduced by the sum of lignin and holocellulose. The cellulose from almond shells decomposes at lower temperatures than almond shells, and the behavior of isolated lignin is very different from that found when it forms part of the raw material, proving the importance of the interactions between its components.

The Nature And Control Of Geyser Phenomena In Thermal Production Risers

Abstract Efficient application of Steam-assisted Gravity Drainage (SAGD) for bitumen or heavy oil recovery requires production of large fluid volumes, close to the boiling point of water. Flowing or gas/steam lifting such wells is an attractive alternative to rod pumping, but evidence is given that the flow can be unstable, due to the large energy release of flashing water. The instabilities are the same phenomena that drive cyclic eruptions in geothermal geysers. A unique finite difference simulator is used to model and study the transient thermohydraulics of superheated water in an idealized wellbore. It is shown that some form of dynamic wellhead choking system is probably required for satisfactory control of a surface access SAGD well. The advent of horizontal wells for thermal recovery and especially for SAGD has led to the need to produce very large fluid volumes from individual wells, at high temperatures. For optimum SAGD, the temperature in the production liner should be kept close to the steam point at bottomhole pressure (steam trap production control)(l), so as to maintain the steam chamber as deep as possible. Sustained fluid production rates of 300 m3/D or more(2) are anticipated from single producers; at this rate, wellbore heat losses will have a limited cooling effect. In most SAGD applications, then, produced water will flash as pressure declines on the way to the surface. UTF Production Lifting Experience At the AOSTRA Underground Test Facility (UTF)(3), SAGD testing is carried out using horizontal wells that are drilled from a tunnel located below the oil sand reservoir. Steam generation and production treating facilities are on the surface, and standard piping carries fluids to and from the well chambers. The wellheads and production control valves are about 20 m lower in elevation than the production liners. This arrangement takes advantage of gravity to avoid flashing in the wellbore and the tunnel facilities, but production is still subject to flash conditions in the riser, during the 185 m climb to the surface. This was recognized during the design of the Phase A facilities, and it was hoped to exploit the resulting steam lift effect. The underground pump was de-rated and a steam sparge system was installed at the base of the riser to enable the lifting of cold fluids. A summary of experience with this system is shown in Figure 1. This is a scatter plot showing the average riser pressure gradients for about 700 days of Phase A operation, as a function of riser bottomhole temperature. This temperature is expressed in terms of subcooling below the steam point, to account for varying pressure. Most days fall into one of three groups indicated, corresponding to the (I) no flashing, (II) slight flashing, and (III) high enthalpy (est. 15 – 30% quality) conditions. The large gap between regions II and III represents conditions that were avoided due to extreme and persistent instability. In this region, flow consisted of geyser-like eruptions occurring at periods from one-half to several hours.