Char particle fragmentation and its effect on unburned carbon during pulverized coal combustion. Quarterly report, January 1, 1993--March 31, 1993

Technical Report · Thu Apr 01 04:00:00 EST 1993

DOI:https://doi.org/10.2172/10172467· OSTI ID:10172467

Diaz, R; Mitchell, R E

Additional samples of synthetic char were produced and characterized. These chars were prepared with lycopodium to polymer mass ratios of 0:1, 1:2, and 1:8. Combined with the char prepared with a lycopodium to polymer of 1:4 that was discussed last quarter, we now have synthetic chars varying in porosity from 17% to 37%. These chars will be used in the forthcoming char fragmentation experiments. Using both a tap density technique and mercury intrusion porosimetry on synthetic char with no macropores, a value of 0.39 was determined for the bed void fraction of tightly packed particles in the 75--125 {mu}m size range. The true density of the synthetic char was found to be 1.58 g/cc using helium pycnometry. From these measurements, the apparent density and porosity for each batch of char were determined. The mechanical grinding procedure was refined to obtain a greater size fraction of particles in the 75--125 {mu}m size range of interest. An investigation of the log-normal distribution function for describing the measured particle size distribution was performed. It was noted that a log-nominal distribution function adequately described the breadth and mean size of the size classified particles but does not completely capture the wings of the distribution. The log-normal distribution will be useful, however, in describing the changing distribution that results from mass loss and fragmentation, phenomena that tend to shift the distribution to smaller sizes. Preliminary experiments were performed with the pressurized thermogravimetric analyzer (PTGA). Combustion in air of synthetic chars having 17% and 24% porosity revealed that the overall particle burning rates of the chars were essentially the same. In the combustion tests, temperature was ramped from 300 K to 1173 K at 25{degrees}C/min. This indicates that under these conditions there were no diffusional resistances to particle burning.

• Research Organization: Stanford Univ., CA (United States). Dept. of Mechanical Engineering
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG22-92PC92528
• OSTI ID: 10172467
• Report Number(s): DOE/PC/92528--2; ON: DE93018928
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
014000
CHARS
CHEMICAL REACTION KINETICS
COAL
COMBUSTION
DISTRIBUTION
FRAGMENTATION
PARTICLE SIZE
PARTICULATES
POROSITY
PRESSURIZATION
PROGRESS REPORT
PULVERIZED FUELS
THERMAL GRAVIMETRIC ANALYSIS