William G. Lloyd

TG/FTIR/MS study of organic compounds evolved during the co-firing of coal and refuse-derived fuels

Complementary thermal analytical techniques were used to analyze gaseous products evolved during the co-firing of coal with refuse derived fuels. The combined thermogravimetric . . . TG rFourier transform infrared FTIR rmass spectrometry MS techniques were employed to study the reaction pathways for the formation of gaseous products during combustion, as well as identify molecular chlorine, HCl, CO, CO , H O and various organic compounds. The discovery 22 of molecular chlorine has led us to look for the possible formation of chlorinated organic compounds in the combustion process. Chlorine and hydrocarbon species are released in the same temperature range and in higher concentrations during fast heating rates compared to relatively slow ones. These results indicate that there may be more opportunities to form chlorinated organic . compounds during the co-firing of coals with refuse-derived fuels RDF at the faster heating rates . that may occur in a fluidized-bed combustor FBC system. q 1999 Elsevier Science B.V. All rights reserved.

Estimates of fluid properties of high volatile bituminous coals

Abstract The fluid properties of 40 high volatile bituminous coals have been studied by Gieseler plastometry, under both ASTM (3 K min −1 ) and isothermal conditions. The Gieseler curves obtained have been analysed with regard to 52 physical, petrographic, and chemical measurements made upon splits of these coals. A number of predictive regressions are developed, including equations predicting ln(maximum fluidity) with R 2 values of 0.927 (3 K min −1 ramp) and 0.935 (isothermal at 420 °C). The significance of the best predictors, and of the signs of their coefficients, is discussed.

The Pd(II)-catalyzed homogeneous isomerization of hexenes

Abstract The isomerization of linear hexenes in alcoholic media, catalyzed by low concentrations of PdCl 2 in the presence of CuCl 2 , has been examined. Effects of reagent concentrations, alcohol and temperature are noted. Values of the rate and equilibrium constants for the ten rate-determining steps have been calculated for reactions in methanol at 30°C. The turnover number for the π-complex group is 48,100 ± 3,800 h −1 . No skeletal isomerization is detected. These isomerizations appear to proceed through π-allylic intermediates.

Co-firing high-sulfur coals with refuse-derived fuel☆

Abstract The fundamental thermal behavior of five materials (Illinois coal #6, Kentucky coal #9, polyvinyl chloride, cellulose and newspaper) has been investigated using the TGA/FTIR/MS system under different combustion conditions. At a fast heating rate, the decomposition temperatures shift towards higher temperatures and the maximum weight loss rates increase by 3–7 times those at the slow heating rate. The gases evolved from the decomposition have been analyzed kinetically. More organic compounds are identified at the faster heating rate. Also, molecular chlorine is observed in the oxidation of PVC. These two species may lead to the formation of chlorinated organic compounds. The results indicate that the TGA/FTIR/MS system can be used to evaluate the effect on the environment of co-firing high-sulfur coal with refuse-derived fuels.

Petrographic observations of Gieseler semi-cokes from high volatile bituminous coals

Semi-cokes from Gieseler plastometry experiments on high volatile bituminous coals conducted under both ASTM 2639 (3°C/min temperature ramp) and isothermal conditions, the latter run at both varied temperatures and at fixed times at a single temperature, were studied for their optical texture. There is some relationship between semi-coke texture and coal rank, with semi-cokes from higher rank coals showing a greater tendency towards the development of a flow texture and, in certain cases, the progression from isotropic to anisotropic semi-coke. Increases in both time and temperature promote a similar tendency towards the development of a flow texture and, in the case of an eastern Kentucky coal, the progression from isotropic to anisotropic semi-coke. Vitrinite types with a greater initial organic sulfur content exhibit flow textures at shorter times than comparatively low-sulfur vitrinite.

Rheological properties of selected bituminous coals

Abstract The rheological behaviour of several bituminous coals has been evaluated by means of a constant torque Gieseler plastometer, utilizing both steadily increasing (3 °C min −1 ) and isothermal (410 °C) temperature conditions. The results indicated that under either thermal treatment, the coals investigated showed predominantly pseudoplastic behaviour. The greatest degree of non-Newtonian behaviour occurred at or near the temperature of maximum fluidity for coals heated at 3 °C min −1 , or within the early stages of melting when isothermal heating was used. Empirical relationships relating the Gieseler fluidities to apparent viscosity were derived from the data.

Isomerization and oxidation of linear hexenes with methanolic Pd(II)

Abstract 1-Hexene, cis -2-hexene and trans -2-hexene all oxidize at the same rate at 30°C to yield 60–62% 2-hexanone along with 3-hexanone and hexanal. trans -3-Hexene reacts similarly, with the product mixture only slightly enriched (by ≈ 5%) in 3-hexanone. Under typical oxidation conditions with 0.010 M of PdCl 2 and CuCl 2 present these hexenes are shown to isomerize rapidly to an equilibrium mixture. The overall oxidation turnover number (TN) is ≈ 10, while for 1-hexene the isomerization TN under these conditions is approximately 3100.

Analytical pyrolysis as a tool for the study of plastic coals

Abstract The technique of analytical pyrolysis has been used to characterize 40 similar mid-rank western Kentucky coals of widely differing ASTM Gieseler plasticity. Certain pyrolysis/g.c. variables were shown to correlate well with both ASTM Gieseler and isothermal plasticity. Highly plastic coals were shown to exhibit certain characteristic peaks in the 450 °C pyrogram which were absent in the pyrogram of the non-plastic coals. Two coals, representing the two extremes in plasticity, were selected for further study. After extraction with solvents such as DMF the characteristic peaks were absent in the 450 °C pyrogram of the extraction residue of the highly plastic coal. These peaks were also shown to decrease with increasing severity of air oxidation of the plastic coal. This technique appears to be a useful tool for the analysis of mid-rank plastic coals and supports the view that the substances contained in the bitumen fraction of these coals are involved in the development of the plastic state.

Thermal studies of (NH4)2 Cr2O7, (NH4)2 WO4, and (NH4)6Mo7O24· 4H2 O deposited on ZrO2

Ammonium molybdate, ammonium dichromate or ammonium tungstate modified zirconia are considered to be catalysts with superacid properties. The activation of these catalysts involves complex chemical changes. In the present study, combined TGA-DTA, TG-MS and TG-FTIR techniques were used to investigate the weight loss and the phase transformations of the solids and to monitor the chemical compounds that evolved under controlled heating in different environments. Through online analysis of the evolved species, some insight into the activation mechanism can be obtained. The phase transformation temperature of zirconia was shifted to a higher temperature when the sample was treated with any of these anions, which indicates that the thermal stability of the catalysts was enhanced.

Rheological inferences from Gieseler plastometry

Abstract The Gieseler constant-torque plastometer can be used to measure apparent slurry fluidities. The dependency of apparent fluidity upon solids fraction conforms to the expectations of slurry rheology. A series of coal-coke blends has been studied isothermally at several temperatures, and the maximum fluidities are found to obey the Arrhenius and Maron-Belner-Robinson relationships. This permits direct estimation of the fluidity of the fluid phase and of the packing fraction of the solids-in-fluid system. The linearity of the coking slope [In(fluidity) versus time], reported 30 years ago by Fitzgerald, probably implies a zeroth-order coking process.