Volatile Release Rate Research Articles

Pyrolysis and char reactivity of a poor-quality refuse-derived fuel (RDF) from municipal solid waste

The present study focuses on analyzing the pyrolysis and combustion behaviors of a refuse-derived fuel (RDF), which is generated in a MSW treatment plant located in Zaragoza (Spain). Pyrolysis experiments were carried out in a TGA apparatus and a fixed-bed reactor at different peak temperatures (400 and 600°C) and heating rates (5 and 40°Cmin−1). The reactivity towards oxygen of produced chars was also measured in the same TGA device at a heating rate of 10°Cmin−1 and a final temperature of 800°C. Pyrolysis results were significantly affected by peak temperature and heating rate. The found effect of peak temperature on char and fixed-carbon yields as well as on measured properties (H:C and O:C ratios, BET surface area and average pore diameter) was in agreement with previous studies. However, the effect of heating rate, especially on the release rate of volatiles, could be explained by a change in the pyrolysis reaction scheme. The RDF-derived chars obtained at the highest heating rate showed a higher reactivity in air. In addition, an increase in peak temperature also led to a higher reactivity. This result can indicate that the carbon present in the RDF-derived char is dispersed within an ash matrix containing a high number of active sites, the distribution of which could be improved when heating rate (and, to a lesser extent, peak temperature) is increased. The addition of 10wt.% RDF to two-phase olive mill waste prior to slow pyrolysis led to an apparent increase in the carbonization efficiency as well as to an enhancement of the resultant char's reactivity in air.

Clarifying the influence of moisture on the ignition and combustion of wet Victorian brown coal in air-firing and oxy-fuel modes: Part 2: Contribution of gasification reaction to char oxidation rate

This paper is the second part of the study to clarify the influence of moisture in Victorian brown coal oxy-fuel combustion, with a focus on char oxidation and gasification reaction through experimental and modelling efforts. An in-situ high-speed two-colour pyrometer with the wavelength band of 0.85–1.05μm was employed to measure particle temperature in the flat flame burner reactor. The combustion stage of carbon particle was simulated for the transient phenomena with particle heating and radiative heat transfer. The multiple surface reaction single-film approach, including char–O2, char–CO2 and char–steam reactions, was employed and the contribution of individual reactions to carbon consumption rate was determined via matching with the measured particle temperature. Irrespective of the initial moisture content, the extent of char–steam gasification reaction was found to account for ~15% in the air-firing case. This reaction was mainly triggered by the external steam in the reactor, rather than the inherent moisture that resided preferentially as volatile cloud on char particle surface. The combined effect of both char–CO2 and char–steam gasification was significant in oxy-fuel combustion mode, especially for the wet coal. In the oxy-21 case, these two reactions have a total extent of around 8% and 18% on the burning char surface of dried and wet coal, respectively. The char–CO2 gasification is insignificant, because the char particle temperature was low. Increasing the oxygen percentage to 31% in CO2 enhanced the total extent of these two gasification reactions to 28%, based on the mass of total carbon. Such an extent is comparable with the literature. However, the steam gasification rate for brown coal char was far higher, ~26% relative to ~10% for high-rank bituminous coal reported in the literature. This substantiates the strong steam gasification reactivity of Victorian brown coal char. The contribution of inherent moisture to char–steam gasification reaction is crucial in the combustion of wet coal in the oxy-21 case, accounting for ~10%. This is due to the long residence of the unevaporated steam as a thick cloud on the char surface. Increasing the oxygen concentration in CO2 enhanced the char–O2 reaction, the release rate of volatiles and inherent moisture. Therefore, the char–steam reaction caused by the inherent moisture within coal matrix was minimised and eventually diminished in the oxy-31 case.

Analysing chemical attraction of gravid Anopheles gambiae sensu stricto with modified BG-Sentinel traps.

BackgroundCues that guide gravid Anopheles gambiae sensu lato to oviposition sites can be manipulated to create new strategies for monitoring and controlling malaria vectors. However, progress towards identifying such cues is slow in part due to the lack of appropriate tools for investigating long-range attraction to putative oviposition substrates. This study aimed to develop a relatively easy-to-use bioassay system that can effectively analyse chemical attraction of gravid Anopheles gambiae sensu stricto.MethodsBG-Sentinel™ mosquito traps that use fans to dispense odourants were modified to contain aqueous substrates. Choice tests with two identical traps set in an 80 m2 screened semi-field system were used to analyse the catch efficacy of the traps and the effectiveness of the bioassay. A different batch of 200 gravid An. gambiae s.s. was released on every experimental night. Choices tested were (1) distilled versus distilled water (baseline) and (2) distilled water versus soil infusion. Further, comparisons were made of distilled water and soil infusions both containing 150 g/l of Sodium Chloride (NaCl). Sodium Chloride is known to affect the release rate of volatiles from organic substrates.ResultsWhen both traps contained distilled water, 45 % (95 confidence interval (CI) 33–57 %) of all released mosquitoes were trapped. The proportion increased to 84 % (95 CI 73–91 %) when traps contained soil infusions. In choice tests, a gravid female was twice as likely to be trapped in the test trap with soil infusion as in the trap with distilled water (odds ratio (OR) 1.8, 95 % CI 1.3–2.6). Furthermore, the attraction of gravid females towards the test trap with infusion more than tripled (OR 3.4, 95 % CI 2.4–4.8) when salt was added to the substrates.ConclusionMinor modifications of the BG-Sentinel™ mosquito trap turned it into a powerful bioassay tool for evaluating the orientation of gravid mosquitoes to putative oviposition substrates using olfaction. This study describes a useful tool for investigating olfactory attraction of gravid An. gambiae s.s. and provides additional evidence that gravid mosquitoes of this species are attracted to and can be baited with attractive substrates such as organic infusions over a distance of several metres.

Effects of pheromone and plant volatile release rates and ratios on trapping Anoplophora glabripennis (Coleoptera: Cerambycidae) in China.

Native to China and Korea, the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), is a polyphagous wood-boring pest for which a trapping system would greatly benefit eradication and management programs in both the introduced and native ranges. Over two field seasons, a total of 160 flight intercept panel traps were deployed in Harbin, China, which trapped a total of 65 beetles. In 2012, traps using lures with a 1:1 ratio of the male-produced pheromone components (4-(n-heptyloxy)butanal and 4-(n-heptyloxy)butan-1-ol) designed to release at a rate of 1 or 4 milligram per day per component in conjunction with the plant volatiles (-)-linalool, trans-caryophyllene, and (Z)-3-hexen-1-ol caught significantly more A. glabripennis females than other pheromone release rates, other pheromone ratios, plant volatiles only, and no lure controls. Males were caught primarily in traps baited with plant volatiles only. In 2013, 10× higher release rates of these plant volatiles were tested, and linalool oxide was evaluated as a fourth plant volatile in combination with a 1:1 ratio of the male-produced pheromone components emitted at a rate of 2 milligram per day per component. Significantly more females were trapped using the pheromone with the 10-fold higher three or four plant volatile release rates compared with the plant volatiles only, low four plant volatile + pheromone, and control. Our findings show that the male-produced pheromone in combination with plant volatiles can be used to detect A. glabripennis. Results also indicate that emitters should be monitored during the field season, as release rates fluctuate with environmental conditions and can be strongly influenced by formulation additives.

Volatile Release from Whey Protein Isolate–Pectin Multilayer Stabilized Emulsions: Effect of pH, Salt, and Artificial Salivas

Whey protein isolate (WPI) and pectin can form a multilayer at the oil-water interface when they are oppositely charged. In this study, effects of pH, salt, and artificial salivas on emulsion stability and volatile release from multilayer emulsions were investigated. Results showed that emulsions (0.5 wt % WPI, 10 wt % oil) with pectin content ≤0.1 wt % had rapid phase separation at pH 4 and 5, and emulsions with higher pectin content (≥0.2 wt %) had good stability. Due to an electrostatic screening effect, multilayer emulsions collapsed when subjected to ≥150 mM NaCl solutions at pH 5. When diluted with artificial salivas containing salts, mucin, and/or α-amylase, multilayer emulsions showed rapid droplet aggregation. GC headspace analysis found that volatiles had significantly lower initial headspace concentration (C(initial)) in multilayer emulsions, and the C(initial) correlated negatively with pectin content in emulsions. Emulsions at pH 7 had more volatiles released to the headspace than emulsions at pH 5. However, changes in pectin content and pH did not show a significant effect on release rate of most volatile compounds. In salt-treated multilayer emulsions, C(initial) and release rates of volatiles increased with NaCl content. Addition of salivas triggered higher release of hydrophobic volatiles and lower release of hydrophilic volatiles, which was mostly due to dilution effect and saliva-induced emulsion instability.

New application of guayule resin in controlled release formulations

Guayule resin is a by-product of the rubber extraction process from Parthenium argentatum Gray shrubs. When guayule is cultivated to a large extent, it is possible to achieve a production of 200–2000kg/ha of resin in addition to the commercial natural rubber production that is sought for use as hypoallergenic latex. In this paper, we evaluated a new application of guayule resin as a plant-based material for use in the microencapsulation of bioactive volatiles for non-food purposes. Microcapsules and beads were prepared by inverse gelation and oil emulsion entrapment, respectively. The formulations for entrapping volatile compounds (linalool or carvone) consisted of blends of alginate and starch with or without the addition of guayule resin at 1%. The volatile release rate was measured over a 14-day period, and the capsule walls were evaluated with scanning electron microscopy (SEM). Volatile loading was in the range of 4–34.2%. Guayule resin improves the loading of linalool from 5.4% to 13.7% in the capsules, but a similar improvement was not observed for the beads. Alginate microcapsules at 25°C readily released the linalool, and a controlled release over time was observed if guayule resin or starch was added. SEM analysis revealed a well-formed membrane (60μm in cross section) in the microcapsules, and a lower porosity (number of pores) was observed if guayule resin was included in the formulation. Additionally, the pore size of the linalool capsules averaged 4.25μm but 2μm if resin or starch were included in the formulation. Guayule resin improved the performance of the carvone beads, but this effect could not be linked to any particular morphological characteristic observed in the SEM analysis. To provide insight into the use of this new material for encapsulation processes, the interaction of guayule resin with the matrices and volatiles is discussed.

Energy recovery from municipal solid waste via gasification

The quantity of municipal solid waste (MSW) has increased significantly worldwide and its safe disposal is an important concern in present time. In this article, pretreatment and characterisation of MSW from the Bhalswa landfill site (located in Delhi) is presented for green-energy recovery via gasification process. Sampling and physical characterisation of MSW is carried out in terms of combustibles (i.e., fuel, organics, miscellaneous) and non-combustibles (i.e., concrete/stone and recyclables). MSW sample was transformed into energy rich refuse derived fuel (RDF) to facilitate the transformation. For thermochemical characterisation, the proximate, ultimate, TGA pyrolysis thermogram and ash analysis of MSW and RDF were carried out for chemical analysis, fixed carbon, volatile release rate and residual ash. After certain modifications in gasifier design, gasification of waste can be considered to be among the most efficient technology for energy recovery and safe disposal of MSW with ecological harmony.

Influence of Fusarium and Wheat Stem Sawfly Infestation on Volatile Compounds Production by Wheat Plants

Influence ofFusariumand Wheat Stem Sawfly Infestation on Volatile Compounds Production by Wheat PlantsPlants that were infested by the wheat stem sawfly emitted significantly increased amounts of the secondary metabolites linalool, linalool oxide, ß-farnesene, ß-caryophyllene, and 4-heptanone in comparison to uninfested plants. Wheat plants parasitized byFusariumspecies also have emitted volatiles. The amount of volatiles released varied by infective species ofFusariumand volatile patterns varied over time for both sawfly infestation and pathogen infection. Plants that were stressed by both herbivory and pathogens emitted even greater amounts of certain volatiles. Surprisingly, larval sawfly mortality was much greater in plants infected byFusariumspecies, and both mortality and the rate of volatile release varied byFusarium. The role of these plant volatiles are further discussed in the context of defensive plant responses toFusariumand sawfly infestation.

Effect of needle damage on the release rate of Masson pine (Pinus massoniana) volatiles

The effect of needle damage on the release rate of Masson pine (Pinus massoniana Lamb.) volatiles was examined. Needles were continuously damaged by mechanical damage (MDP) or by feeding of pine caterpillar (Dendrolimus punctatus) larvae (LFP); undamaged pine was used as a control (UDP). Volatiles were collected before damage, and at 16, 24, 40, 48, 64, 72, 88 and 96 h post-damage, and analyzed. The analyses revealed that 19 compounds identified as constitutive volatiles from UDP were terpenes and green leaf odors. The release rate of volatiles from MDP or LFP was higher than that from UDP. At 96 h post-damage, emission from MDP or LFP returned to the same level as that of UDP. Some volatiles, including sabinene, ocimene, limonene-1,2-epoxide, linalool, linalool acetate, germacrene D: -4-ol, farnesol, and (E)-4,8-dimethyl-1,3,7-nonatriene were induced by mechanical damage and/or larval attack. Furthermore, the release rate of linalool acetate, farnesol, or (E)-4,8-dimethyl-1,3,7-nonatriene from LFP was higher than that from MDP. Based on an exact estimation of the proportion of damaged pine needles, a significant linear correlation between the release rate of total volatiles identified and the proportion of damaged needles was found in the case of LFP but not MDP.

Kinetics of devolatilization and oxidation of a pulverized biomass in an entrained flow reactor under realistic combustion conditions

In this paper the results of a complete set of devolatilization and combustion experiments performed with pulverized (∼500 μm) biomass in an entrained flow reactor under realistic combustion conditions are presented. The data obtained are used to derive the kinetic parameters that best fit the observed behaviors, according to a simple model of particle combustion (one-step devolatilization, apparent oxidation kinetics, thermally thin particles). The model is found to adequately reproduce the experimental trends regarding both volatile release and char oxidation rates for the range of particle sizes and combustion conditions explored. The experimental and numerical procedures, similar to those recently proposed for the combustion of pulverized coal [J. Ballester, S. Jiménez, Combust. Flame 142 (2005) 210–222], have been designed to derive the parameters required for the analysis of biomass combustion in practical pulverized fuel configurations and allow a reliable characterization of any finely pulverized biomass. Additionally, the results of a limited study on the release rate of nitrogen from the biomass particle along combustion are shown.

Numerical Studies on Combustion Characteristics of Interacting Pulverized Coal Particles at Various Oxygen Concentration

The two-dimensional laminar combustion characteristics of coal particles at various oxygen concentration levels of a surrounding gas have been numerically investigated. The numerical simulations, which use the two-step global reaction model to account for the surrounding gas effect, show the detailed interaction among the inter-spaced particles, undergoing devolatilization and subsequent char burning. Several parametric studies, which include the effects of gas temperature (1700 K), oxygen concentration, and variation in geometrical arrangement of the particles on the volatile release rate and the char burning rate, have been carried out. To address the change in the geometrical arrangement effect, multiple particles are located at various inter-spacings of 4–20 particle radii in both streamwise and spanwise directions. The results for the case of multiple particles are compared with those for the case of a single particle. The comparison indicates that the shift to the multiple particle arrangement resulted in the substantial change of the combustion characteristics and that the volatile release rate of the interacting coal particles exhibits a strong dependency on the particle spacing. The char combustion rate is controlled by the level of oxygen concentration and gas composition near particles during combustion. The char combustion rate is highly dependent on the particle spacing at all oxygen levels. The correlations of the volatile release rate and the change in total mass of particles are also found.

Attraction of Astylus variegatus (Germ.) (Coleoptera: Melyridae) by volatile floral attractants

The beetle Astylus variegatus (Germ.) (Coleoptera: Melyridae) is frequently found in flowers feeding on pollen. Responses of A. variegatus to volatile floral attractants were studied in common beans (Phaseolus vulgaris L.) fields. Traps originally designed to capture Diabrotica speciosa (Germ.) (Coleoptera: Chrysomelidae), consisted of plastic bottles (2 L) with 150 holes (5-mm diameter) yellow gold painted and containing inside a plastic strip (3.5 <FONT FACE=Symbol>´</FONT> 25 cm) with Lagenaria vulgaris (L.) powder (0.28% B cucurbitacin - feeding stimulant and arrestant for diabroticites) sprayed with carbaril insecticide. Treatments consisted of 1,4-dimethoxybenzene (one or two dispensers per trap), 1,4-dimethoxybenze + indole, 1,4-dimethoxybenzene + cinnameldehyde and control. Volatile average release rates (over ten days) was approximately 32 mg day-1 per dispenser under laboratory conditions. 1,4-dimethoxybenzene-lured traps caught significantly more beetles than the control, three and seven days after trap setting. Ten days after the onset of the experiment, there were no differences in number of beetles caught by treatments. Captures were higher in the 1,4-dimethoxybenzene + cinnamaldehyde treatment than in 1,4-dimethoxybenzene only in the first assessment. Adding indole to 1,4-dimethoxybenzene did not improve beetle captures.

Part I: Experimental studies on a pulverised fuel stove

This paper is concerned with development of a pulverised fuel stove with improved conversion efficiency and minimal emissions at near constant power level without the use of external power. The design originates from a cylindrical sawdust stove with a central porthole being lit from the bottom. Such a stove will have a flame in port with enhanced sooting tendency. For similar configuration, stable premixed combustion behaviour of the combustible gases from the port of the fuel block (known as the gasification mode) has been achieved by use of air supply through a thin slot at the bottom, for at least 30 min of stove operation. In order to ensure stable combustion of the gases at exit, a metal device is used. In an attempt to extend gasification duration, studies are conducted in single port configuration having air entry from the bottom with a horizontal baffle to control the flow rate. This configuration worked in gasification mode for about 20 min but there have been problems of flame extinction. To overcome these drawbacks multi-port design with vertical air entry is employed with success. The stove has exhibited conversion efficiency in excess of 37% due to well focused nature of flame at exit. CO emission factors are about 12 g (kg fuel) � 1 , a performance superior to conventional biomass stoves (� 45 g kg � 1 ). NOx emission factors are about 1 g kg � 1 fuel which falls in the range of reported data for NOx. Studies with different pulverised leafy fuels have indicated these fuels have lower volatile release rates and therefore exhibit lower power level operation for a given port configuration compared to sawdust fuel. r 2006 Elsevier Ltd. All rights reserved.

Chemistry and geographic variation of floral scent in Yucca filamentosa (Agavaceae)

We identified volatiles from the floral headspace of Yucca filamentosa using gas chromatography and mass spectrometry and analyzed floral scent composition and variation among populations pollinated by different yucca moth species. Twenty-one scent compounds were repeatedly identified and most could be categorized into two major classes: (1) homoterpenes derived from the sesquiterpene alcohol nerolidol and (2) long chain aliphatic hydrocarbons. Two biosynthetic pathways are thus responsible for the majority of floral volatiles in Y. filamentosa. The homoterpene E-4,8-dimethylnona-1,3,7-triene, which is released systemically by higher plants upon herbivory, was the most abundant compound. Two di-oxygenated compounds not previously reported as floral compounds also were detected. No differentiation in floral scent was observed between populations pollinated by different yucca moths, nor was there any correlation between chemical distance and geographic distance among populations. The total release rate of volatiles differed significantly among populations, but not between populations with different pollinators. The combination of unique compounds and low variation in the fragrance blend may reflect highly selective attraction of obligate pollinators to flowers. The observed lack of differentiation in floral scent can putatively explain high moth-mediated gene flow among sites, but it does not explain conservation of odor composition across populations with different pollinators.

Effects of operating parameters on the combustion of medical waste in a controlled air incinerator

Experiments have been performed to investigate the effects of primary chamber preheating temperature and batch size of the waste feed on the combustion of medical waste in a two chamber controlled air incinerator of 50 kg/h nominal capacity. The primary purpose is to determine qualitatively the functional relationships between the key incinerator performance indicators and the above two parameters so that optimum preheating conditions of a pilot incinerator, which has been in trial use at a hospital, may be defined. Three batch sizes were used, namely: 5, 7.5 and 10 kg, with the primary chamber preheating temperature varied from 500 to 800 °C at 100 °C intervals for each batch. The secondary chamber temperature control was set at 900 °C. The results showed that increasing the waste charging temperature and the weight of charge tend to accelerate the rate of volatile gas release, causing a “bottleneck effect” in the secondary chamber and, hence, a negative effect on the overall performance of the incinerator, as reflected in the residual unburned CO in the gases leaving the chamber. Higher charging rates could have been achieved by increasing the combustion air supplied to the chambers. Using CO measurement as a criterion for good combustion makes it possible to determine the optimum incinerator temperature control settings and operating conditions, as well as to assure continuous, efficient, environmentally satisfactory operation. The optimum operating condition for the range of experiments tested appears to be a batch size of 5 kg and a primary chamber preheating temperature in the vicinity of 700 °C.

STUDY ON THE TRANSIENT PROCESS OF WASTE FUEL INCINERATION IN A FULL-SCALE MOVING-BED FURNACE

ABSTRACT The transient process in a full-scale municipal solid waste incinerator was investigated to assess the effect of the grate movement and waste feeding cycles. Inside-bed measurements of temperature and O2 were carried out and an 18-hour record of furnace temperature, airflow, and flue gas compositions was analyzed using discrete Fourier transform. The transient burning process was also simulated numerically by solving the governing equations for both the solid and gas phases. It is found that fluctuations in the furnace temperature and flue gas O2 level correspond to the waste feeding and grate movement cycles, either in phase or out of phase (depending on the length of the cycles), while combustion inside the bed is dominated by a series of big spikes and dips in both local temperature and O2 level. Theoretical calculations indicate that each grate movement causes a surge (by 35%) in the volatile release rate but a depression (by 24%) in the char burning rate. The overall bed-burning rate fluctuates between 90 and 110% of its average.

Gelled emulsion particles for the controlled release of lipophilic volatiles during eating

Gelled emulsion particles are discussed in relation to controlling the release of lipophilic volatiles in the mouth during eating, using a mass spectroscopic technique that enables real time measurement of volatiles on the breath. Our studies have demonstrated that by encapsulating triglyceride oil droplets within biopolymer gelled particles (70–5000 μm), the initial flavour release maxima were reduced by kinetically inhibiting the mass transfer of flavour through the particle. An important feature of this approach was that it was the oil droplets and not the volatiles that were encapsulated. Factors such as particle size, oil phase volume and the partition coefficient of the volatile all affected the rate of volatile release. To control the temporal release profile, gelled emulsion particles have been designed that break down in a controlled manner under physiological conditions in the mouth. The physiological ‘trigger mechanisms’ investigated included mechanical failure, melting and enzyme hydrolysis.

Co-firing of coal and cattle feedlot biomass (FB) fuels. Part II. Performance results from 30 kW t (100,000) BTU/h laboratory scale boiler burner ☆

The use of cattle manure (referred to as feedlot biomass, FB) as a fuel source has the potential to both solve waste disposal problems and reduce fossil fuel based CO 2 emissions. A co-firing technology is proposed where FB is ground, mixed with coal, and then fired in existing, pulverized coal-fired boiler burner facilities. A research program was undertaken in order to determine (i) fuel characteristics, (ii) combustion characteristics when fired along with coal in a small scale 30-kW t (100,000 BTU/h) boiler burner facility, and (iii) combustion and fouling characteristics when fired along with coal in a large pilot scale 150-kW t (500,000 BTU/h) DOE-NETL boiler–burner facility. Part I presented a methodology for fuel collection, fuel characteristics of the FB, its relation to ration fed, and the change in fuel characteristics and volatile oxides due to composting. Part II addresses the pyrolysis characteristics of coal, FB, and blend and presents results on the performance of 90:10 coal:FB (PC) blend as fired in a 30-kW t boiler–burner unit. The boiler–burner unit is made of steel and lined with a cast ceramic liner for long duration operation and a commercial feeding system is used for firing the coal and the blend. Thermogravimetric analyses (TGA) performed on coal, FB, and 90:10 coal:FB blend reveal that biomass will start releasing gases at 273 °C (523 °F) which is about 100 °C (212 °F) lower than that of coal. The maximum rate of volatile release is about 0.000669 kg/s kg for FB while that of coal is 0.000425 kg/s kg. The experiments revealed that the 90:10 blend burns more completely in the boiler, due to the earlier release of biomass volatiles and higher amount of volatile matter in FB. The NO x emission for coal was 290 ppm, 0.162 kg/GJ (0.3768 lb/mm BTU) and 260 ppm, 0.1475 kg/GJ (0.343 lb/mm BTU) for the 90:10 blend at 10% excess air. Even though the effective N content of the blend increased by 18%, compared to coal the NO x emission decreased which is attributed to the higher VM of FB and more N in the form of NH 3. However, due to limited residence time and higher VM, the CO emission increased from 15,582 ppm, 5.29 kg/GJ (12.305 lb/mm BTU) to 22,669 ppm, 7.81 kg/GJ (18.16 lb/mm BTU) when fuel was switched from coal to 90:10 blend. Large scale pilot plant tests performed at the 150-kW t facility (DOE-NETL) reveal increased falling potential for the blend compared to coal (Part III), emissions were negligible.

Temperatures of Wood Particles in a Hot Sand Bed Fluidized by Nitrogen

The thermal history undergone by cylindrical beech wood particles, injected in a sand bed fluidized by nitrogen has been recorded. Experiments have been carried out by varying particle diameter (d = 2−10 mm) and bed temperature (Tr = 712−1107 K). The rate of volatile release becomes significant for temperatures above 625−650 K and is always completed for temperatures below 675−825 K. Devolatilization causes a strong reduction in the heating rate which, at the particle center and for the most intense reaction activity, is comprised between 0 and 25 K/s. For the conditions typical of fast pyrolysis (bed temperatures of 800−1100 K and particle sizes of 2−6 mm), the yields of char are 10−18% and the devolatilization times (corresponding to a conversion of 95%) 18−45s. Furthermore, in qualitative agreement with previous analyses carried out for coal particles, these are well predicted by an empirical power-law relation: tv = 0.8e1525/Trd1.2 s, over the entire range of experimental conditions examined.

Effect of Hydrogen Sulfide on Organic Sulfur Behavior in Coal and Char during Heat Treatments

The effect of hydrogen sulfide on organic sulfur behavior has been investigated for subbituminous and bituminous coals during heat treatments in free-fall and fixed-bed reactors. The organic sulfur content in the solid phase was observed to increase, even with the rapid release of volatiles. The change in the amount of sulfur and its rate of increase were found to be approximately inversely related to the carbon content of the raw coal and volatile matter release rates. Increases in sulfide and thiophene forms were identified by sulfur K-edge X-ray absorption near-edge structure analysis for the hydrogen sulfide-adsorbed chars. Langmuir's adsorption isotherm was found to characterize the effects of hydrogen sulfide concentration on the uptake behavior of sulfur by rapid pyrolysis chars in nitrogen streams containing hydrogen sulfide at 1073 K in a fixed bed. Gasification of the hydrogen sulfide-adsorbed char showed a lower conversion of sulfur from the solid phase to the gaseous products compared to the loss of carbonaceous substances from the gasified chars.