Download Physical Properties - Coal Combustion - Lecture Slides and more Slides Geochemistry in PDF only on Docsity! 1 Class 4 Physical Properties of Coal Reading Assignment: a. Lee Smith Book, 154-168 b. Article by Merrick (Fuel, 62, 540-546, 1983) 1. Discuss Figure 4.50 in the Lee Smith book. 2. What is meant by porosity, true density, apparent density, and internal surface area? Why are these quantities important in coal combustion? How do they vary as a function of coal rank? How do the these properties vary between chars and coals? 3. Please use your group to find and discuss the model proposed by Merrick for heat capacity. 4. Please show the transient particle energy equation in terms of particle temperature, with appropriate terms for a single coal particle injected into a hot inert gas. Be prepared to describe all of the terms, including thermal radiation. 5. Please compute the number distribution (# vs. diameter in microns) for the following mass distribution: 6. Please compute the heat capacity in J/kg/K of the dried Argonne Premium Wyodak coal at temperatures from 300 K to 700 K. Mesh Size (passing) 400 325 270 250 200 170 150 Weight (%) 5 10 20 30 20 10 5 Figure 4.50 Figure 4.50 Coal Fully cross- linked char Pyrolysis Lignite begins to cross link at lower temps than bituminous coals Evolution of tar breaks bonds Intermediate behavior from Wyodak (subC) and oxidized bituminous coals Particle Densities 1. True Density (He pyncnometry) 2. Apparent Density 3. Bulk Density solidofvolume solidofmass solidinvoidsofvolumesolidofvolume solidofmass bedofvolume solidofmass Vbed = Vsolid + Vvoids in solid + Vvoids between particles True Particle Densities From Gan et al. Fuel, Vol. 51 (1972) docsity.com 2 Apparent Densities • Hg porosimetry – Measure change in Hg volume as pressure increases – Interpret volume change • Tap density – Weigh particles – Place in graduated cylinder – Tap to settle particles – Assume packing factor – Ratio of bulk densities (b/ b,0) equals ratio of apparent densities (a/ a,0) fr om S an di a R ep or t S A N D 88 -8 24 0, C oa l C om bu st io n S ci en ce Q ua rt er ly P ro gr es s R ep or t, Ja nu ar y – M ar ch , 19 88 Apparent Particle Densities From Fletcher Sandia Milestone Report 1.0 0.8 0.6 0.4 0.2 0.0A p p a re n t D e n si ty R a tio ( / o ) 300250200150100500 Particle Residence Time (ms) Hg tap PSOC-1507 PSOC-1445 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 D ia m et er o r D en si ty R at io 350300250200150100500 Particle Residence Time (ms) 1250 K 1050 K d/d o /o PSOC-1451, 106-125 µm Merrick Heat Capacities Computed Heat Capacities (Wyodak Coal) 0 500 1000 1500 2000 2500 3000 300 500 700 900 1100 T (K) c p ( J /k g -K ) 1-stage 2-stage docsity.com
