Available experimental data on the dissolution of coal into solvent-hydrogen mixtures were analyzed to obtain a mathematical expression for the rate of dissolution. The rate of dissolution was found to depend exponentially on the hydrogen partial pressure and was proportional to the amount of undissolved organic material per unit volume of slurry. The rate was found also to depend on the type of reactor and coal. The low activation energy for coal dissolution appears to indicate that the dissolution may be controlled by the diffusion of some species in the solution phase. The removal of ash from coal-derived liquids by filtration and centrifugation was examined and the economics of the separation has been analyzed in detail for the COED, SRC, and Synthoil processes. In the SRC process the ash separation represented a major portion of the overall fixed capital investment ranging from 23 to 50% for the SRC process. (auth)
The application of near-surface mounted (NSM) fiber-reinforced polymer (FRP) for shear strengthening of RC beams has attracted abundant research in the past few decades, and a number of strength models for predicting the contribution of NSM FRPs to the shear capacity of strengthened beam have been proposed. In the first of these two companion papers, a total of 12 strength models of NSM FRP shear strengthened RC beams collected from the existing literature have been comprehensively reviewed, while the present paper aims to provide an objective assessment of these models. To this end, the experimental results of 196 RC beams strengthened in shear with NSM FRP bars/strips are collected from the existing literature, as the database for the assessment. The comparisons between the experimental results and predictions by these strength models reveal that the existing strength models all fail to give accurate predictions. The reasons for the inaccurate predictions of these models are also analyzed.
The pulverized coal combustion in both air and oxy-fuel conditions generally experiences successive coal devolatilization and char combustion processes. The effects of these two processes have important influence on the emission characteristics of particulate matter. With some different characteristics of lignite from the higher rank coal, including the high contents of organically bound cations and the apparent char–CO2 gasification reaction upon oxy-fuel combustion, the effects of both coal devolatilization and char combustion processes on the emission characteristics of particulate matter during oxy-fuel combustion of lignite would accordingly be distinctive. A typical Chinese lignite was devolatilized in a N2 or CO2 atmosphere to generate N2–char and CO2–char, respectively. Raw coal and the two chars were burned in a drop-tube furnace under both air and oxy-fuel conditions. Afterward, the yields and inorganic compositions of segregated PM10 were carefully analyzed. The results have shown that the devolatilization in the N2 condition promotes the emission of sub-micrometer particles (PM0.5) and coarse particles (PM1–10) but the devolatilization process in CO2 inhibits their emission. N2–char and CO2–char present entirely different combustion behavior and, thus, reflect the discrepant emission characteristics of PM10. The rough higher yields of PM0.5 and PM1–10 from N2–char combustion compared to raw coal combustion may be driven by the higher particle combustion rate and/or temperature of N2–char. Furthermore, the quite severe gasification reaction of CO2 with char during char preparation results in an inhibited combustion rate of CO2–char, which can explain the case in which much less PM0.5 and PM1–10 are generated from CO2–char combustion than those from raw coal and N2–char combustion. The apparent effects reveal that more detailed work can be continued to further explore this research.
Nowadays, the use of the Digital Image Correlation (DIC) technique has spread and it is being used in several engineering areas to measure displacements. The available data obtained from the DIC measurement to evaluate the bond performance between a Carbon fibre Reinforced Polymer (CFRP) externally bonded to a timber substrate is scarce. From the existing data obtained with other materials, this contactless technique revealed to be quite useful but its accuracy with other well-established techniques, such as the use of electric strain gauges is not well understood yet. Therefore, the current work aims to study the accuracy of 2D DIC measurements with the measurements obtained from the use of strain gauges within a low-cost perspective. To that end, several CFRP-to-timber bonded joints were tested under the single-lap shear test and different bonding techniques were considered as well. Some flaws intrinsically derived from the DIC measurements that complicate the bond assessment, such as the fluctuations in the generated displacements field, are identified, and to bypass this problem a new methodology is proposed. This new methodology is based on two different closed-form solutions that, after defining the local and global bond behaviours of different CFRP-to-timber bonded joints, allowed to eliminate the fluctuations found from the DIC measurements, facilitating the estimation and the comprehension of the full debonding process of the CFRP-to-timber joints, which was achieved with a good proximity to the homologous debonding process derived from the strain gauge measurements.
