Volatile yield

The effect of heating rate on evolution of volatiles is most clearly evidenced in the case of woody biomass, which has been shown to have a volatile yield of greater than 90% when small particles are rapidly heated to 1200°C and to have a volatile yield of only 65% when large particles are slowly heated to 500°C in the commercial charcoal-making process. 

The single-rate approach defined by Eq. (9.43) adequately captures the increasing rate of devolatilization at higher temperatures, but fails to account for the observed change in the volatiles yield as a function of temperature. To capture this, Kobayashi et al. [42] proposed the use of two competing reaction... 

In a moist Hatboro silt loam, volatilization yields of 50 and 90% were found after 6 h and 6 d, respectively. In a dry Norfolk sand loam, 12% volatilization was reported after 50 h (Glotfelty et al., 1984). The average half-lives for lindane in aerobic and flooded soils under laboratory conditions were 276 and 114 d, respectively (Mathur and Saha, 1977). In field soils, the half-lives ranged from 88 d to 3.2 yr with an average half-life of 426 d (Lichtenstein and Schulz, 1959, 1959a Lichtenstein et al., 1971 Voerman and Besemer, 1975 Mathur and Saha, 1977). 

The coal, 78% C daf, was heated in the direct introduction system of the spectrometer to the end temperature of 500 C this led to volatilization yield of the coal corresponding to its mobile phase content which was app. 30 wt % org. mat. 

An alternate process for the synthesis of this amide involved holding at reflux for 16 h a solution of 10 g of MDA as the free base in 20 mL fresh ethyl formate. Removal of the volatiles yielded an oil that set up to white crystals, weighing 7.8 g. 

The spacing B of coal feed points (Figure 9) should be such that the air flowing in the cross-section TTr of the volatile plume should be sufficient to oxidize the volatiles. The fraction fv of the stoichiometric air requirement needed to consume the volatiles will depend upon the volatile yield and composition (76, 79, 80). A typical value for fv is about 0.4. A fraction fa of about 0.1 of the stoichiometric air is used to transport the coal. The oxygen requirements of the volatiles is then satisfied when... 

Solomon, P. R., Hobbs, R. H., Hamblen, D. G., Chen, W., La Cava, A. and Graff, R. A., "Correlation of Coal Volatile Yield with Oxygen and Aliphatic Hydrogen", Fuel, (to be published) ... 

A plug flow char combustion model was used to predict the combustion efficiencies of SRC under simulated commercial boiler operating conditions. Inputs were based on the volatile yields and char characteristics measured in the CMHF. 

The TGA char reactivity data indicate that the CSD SRC has a relatively low reactivity (similar to KHB coal). However, the extremely high volatile yields of the CSD SRC (illustrated in DTFS and CMHF results below) leaves very little char for subsequent burnout and results in a high overall combustion efficiency. 

Ge reduced burning rate of carbon, K final volatile yield, %... 

Badzioch [I] summarized the volatile yields in the pioneering studies carried out at relatively low temperatures in a publication on rapid pyrolysis containing three introductory... 

Menster et al. [8] used electrical pulse heating to apply a heating rate of nearly 10" °C/s to a number of coals. The total volatile yield from low-rank hVC and hVA coals displayed a maximum in the temperature region 700-800°C. The peak volatile yields exceeded the volatile matter contents of the coals as determined by the standard ASTM method. 

Within a few AU of the Sun solar heating causes vigorous sublimation of volatiles yielding the formation of a 10 km coma and gas and dust... 

Petrological estimates of emption yields of sulfur and, to a lesser extent, halogens have received much attention, partly because they offer a means to assess the volatile yield for historic and ancient emptions. The search for suitable host phenocrysts requires careful microscopic... 

Wallace et al. (1995) and Wallace (2001) have explored this issue in detail, and ScaiUet et al. (1998, 2003) and ScaiUet and Pichavant (2003) have advanced petrological modeUng approaches to circumvent the problem by estimating the volatile contents contained in the vapor phase prior to emption. Another problem with petrological estimates of volatile yields is that they scale linearly with the emption magnitude, which is often only poorly constrained from the rock record. This is especially tme in cases where tephra dispersal is very widespread, perhaps largely at sea, and where substantial burial, erosion or redeposition limit efforts to identify original thicknesses of sediment in the field. 

Fuel Oil.—North American fuel oils show a rather steadily progressive increase in density and heat value and decrease in volatile yield as we advance from the East toward the West and Southwest. Eastern oils are paraffin base ... 

Comparisons of yields of total headspace volatiles from vegetative tissues of tobacco and wheat Quantitative estimates of headspace total volatile yields are summarized in Table II. 

Cleavage of N-bmzyl-linked tertiary amines fi om a support with a-chloroetliyl chlorofomiate/MeOH to yield secondary amines 6 An excess of an amine was first coupled to Merrifield resin suspended in DMF (if the amine was added as a hydrochloride, then 20 equiv. of DIPEA was added). The mixture was stirred for 17 h at 50 °C. The substitution level was found to be >0.6 mmol (>85%). To a suspension of the resin in 1,2-dichloropro-pane, 10 equiv. of a-chloroefhyl chloro formate was added and the suspension was stirred for 3 h at rt. The resin was then filtered off and fhe filtrate was concentrated to dryness. The residue was redissolved in MeOH and the solution was refluxed for 3 h. Evaporation of the volatiles yielded the secondary amine 6 as its hydrochloride. The isolated yield varied from 70% to 95 %, depending on the type of amine. 

In contrast to the results obtained with bituminous coals, the weight-loss curve of subbituminous coal exhibited no peak instead, it reached a plateau in Figure 2. From 800° to 1000°C the volatile yield remained level at about 42 wt % of the coal. Beyond this region the production of volatiles increased sharply. The fact that the devolatilization curve of subbituminous A coal differs distinctly from those of bituminous coals indicates a need for further study of other subbituminous coals and lignites. Low rank materials such as these are of interest in coal gasification because their reserves are abundant and because they are situated in deposits with shallow ground cover. 

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