Abstract:A differential scanning calorimetry (DSC) study on the extraction residues of coals giving different extraction yields (which were prepared by changing the solvent composition of a carbon disulfide-N-methyl-2-pyrrolidinone mixed solvent extraction) was carried out. For the residues from Upper Freeport coal (APCS-1) with extraction yields lower than 30 wt % (daf), an endothermic peak similar to that given by the raw coal was observed around 350°C. This endothermic peak disappeared on the second and third scans,… Show more
“…Extraction Yield. The extraction yields of Upper Freeport coal are plotted against CS 2 vol % in the mixed CS 2 /NMP solvent in Figure . Yields with NMP or CS 2 alone were 18% and 3%, respectively, while the mixed solvent gave higher extraction yields and showed a significant synergistic effect, as shown in Figure .…”
Section: Aggregated Structure Of Upper Freeport Coalmentioning
confidence: 94%
“…Table presents ultimate and proximate analyses of the coals mentioned above. 3 Plots of the extraction yield and swelling ratio with the CS 2 /NMP mixed solvent against NMP vol % in the mixed solvent …”
Section: Aggregated Structure Of Upper Freeport Coalmentioning
confidence: 99%
“…Plots of the extraction yield and swelling ratio with the CS 2 /NMP mixed solvent against NMP vol % in the mixed solvent …”
Section: Aggregated Structure Of Upper Freeport Coalmentioning
Data for the sorption and interaction of alcohols with the coal suggested Upper Freeport coal has a large number of micropores into which relatively bulky reagents could diffuse only marginally; micropores may be molecular voids in the aggregated. The irreversible structural relaxation observed on differential scanning calorimeter (DSC) thermograms at 350 °C is probably very similar in nature to that caused by extraction with highly efficient mixed solvents such as carbon disulfide/N-methyl pyrrolidinone (CS 2 /NMP). Upper Freeport coal must be greatly relaxed (swollen) before solvents have access. A molecular dynamics simulation of relaxation at several temperatures was carried out on a model structure for the aggregated coal. A large change in the volume of the model structure was found between 350 °C and 400 °C, the region in which the irreversible peak was observed in the DSC thermograms. Moreover, in agreement with the experimental results, the structural changes caused by "heating" in the simulation were not reversible. These results suggested that irreversible structural relaxation caused by heating is the result of thermal stabilization of the strained structure of the raw coal.
“…Extraction Yield. The extraction yields of Upper Freeport coal are plotted against CS 2 vol % in the mixed CS 2 /NMP solvent in Figure . Yields with NMP or CS 2 alone were 18% and 3%, respectively, while the mixed solvent gave higher extraction yields and showed a significant synergistic effect, as shown in Figure .…”
Section: Aggregated Structure Of Upper Freeport Coalmentioning
confidence: 94%
“…Table presents ultimate and proximate analyses of the coals mentioned above. 3 Plots of the extraction yield and swelling ratio with the CS 2 /NMP mixed solvent against NMP vol % in the mixed solvent …”
Section: Aggregated Structure Of Upper Freeport Coalmentioning
confidence: 99%
“…Plots of the extraction yield and swelling ratio with the CS 2 /NMP mixed solvent against NMP vol % in the mixed solvent …”
Section: Aggregated Structure Of Upper Freeport Coalmentioning
Data for the sorption and interaction of alcohols with the coal suggested Upper Freeport coal has a large number of micropores into which relatively bulky reagents could diffuse only marginally; micropores may be molecular voids in the aggregated. The irreversible structural relaxation observed on differential scanning calorimeter (DSC) thermograms at 350 °C is probably very similar in nature to that caused by extraction with highly efficient mixed solvents such as carbon disulfide/N-methyl pyrrolidinone (CS 2 /NMP). Upper Freeport coal must be greatly relaxed (swollen) before solvents have access. A molecular dynamics simulation of relaxation at several temperatures was carried out on a model structure for the aggregated coal. A large change in the volume of the model structure was found between 350 °C and 400 °C, the region in which the irreversible peak was observed in the DSC thermograms. Moreover, in agreement with the experimental results, the structural changes caused by "heating" in the simulation were not reversible. These results suggested that irreversible structural relaxation caused by heating is the result of thermal stabilization of the strained structure of the raw coal.
“…In addition, CS 2 was reported 1 to show a high solubility to n -paraffins (aliphatic compounds). It is known that CS 2 alone gives low swelling ratios and extraction yields to any coals. , Investigating how CS 2 serves to enhance the diffusibility of NMP into the coal micropores will be further needed.…”
“…These fragments could not react timely in the combustion furnace and became coke, which also increased the microcrystalline parameters of the unburned coal (Takanohashi et al 1999;Akiyama 2000;Michael 2002). …”
La 2 O 3 is a combustion improver suitable for burning pulverized coal in blast furnace. La 2 O 3 forms the active species La 3? (CO -) 3 that weakens the bridge adhesion of carbon structural units and alters the lattice structures, thus reducing the activation energy of the pulverized coal and accelerating the burning process. Research shows that La 2 O 3 can form the active species La 3? (CO -) 3 , which weakens the bridge adhesion of carbon structural units and alters the lattice structures of the fixed carbon, hence decreasing the activation energy of the pulverized coal and accelerating the burning process.
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