1. Analysis basis. 1.1 Definitions. includes Inherent moisture (Im) only

Transcription

1 Coal Conversion Facts & Calculations 1. Analysis basis 1.1 Definitions As Received (AR): Air Dried (AD): Dry Basis (DB): Dry Ash Free (DAF): includes Total moisture (Tm) includes Inherent moisture (Im) only excludes all Moisture excludes all Moisture & Ash The Proximate Analysis of any coal ie the % contents of Moisture, Ash (A), Volatile Matter (VM), Fixed Carbon (FC) - also Sulphur (S) and Calorific Value (CV) - can be expressed on any of the above bases. 1.2 Conversions To obtain: Air Dry Dry Basis As Received multiply AR by: - AD by: - DB by: Where Im: inherent moisture Where Tm: total moisture - [For DAF, multiply DB by /(-A)]

2 Example: Alain DELOYE - Technical Services Manager AR AD DB DAF Tm Im Ash (A) VM FC Sulfur (S) MASS 2.1 Units: Metric ton (t) = tonne = Imperial or Long ton (lt) = Short (US) ton (st) = 1,000 kilograms (= 2,204.6 lb) 1, kilograms (= 2,240 lb) kilograms (= 2,000 lb) 2.2 Conversions: From long ton to metric ton multiply by From metric ton to long ton multiply by From short ton to metric ton multiply by Mt - million tonnes Mtce - million tonnes of coal equivalent (= Mtoe) Mtoe - million tonnes of oil equivalent 3. CALORIFIC VALUES (CV) 3.1 Units: kcal/kg - Kilocalories per kilogram MJ/kg* - Megajoules per kilogram Btu/lb - British Thermal Units per pound * 1 MJ/kg = 1 Gigajoule/tonne (GJ/t)

3 3.2 Gross & Net Calorific Values: Gross CV or 'upper heating value' is the CV under laboratory conditions. Net CV or 'Net Effective Calories' (NEC) is the useful calorific value in boiler plant. The difference is essentially the latent heat of the water vapor produced. 3.3 Conversions Units: From kcal/kg to MJ/kg multiply by From kcal/kg to Btu/lb multiply by kcal/kg = Btu/lb / From MJ/kg to kcal/kg multiply MJ/kg by MJ/kg = kcal/kg / From MJ/kg to Btu/lb multiply MJ/kg by MJ/kg = Btu/lb / From Btu/lb to kcal/kg multiply Btu/lb by From Btu/lb to MJ/kg multiply Btu/lb by Formulas and conversions - Gross/Net : Ref: Net Calorific Value (ASTM D ) The heat produced by combustion of a substance at a constant pressure of 0.1 Mpa (1 Atm), with any water formed remaining as vapor. ISO at constant volume Qv, net,m, J/g = ( Q gr,v,d [ whd ] ) x ( x Tm) - (23.05 x Tm) Qv, net,m, kcal/kg = ( Q gr,v,d [ whd ] ) x ( x Tm) - (5.51 x Tm) ISO at constant pressure Qp, net,m, J/g = { Q gr,v,d [ whd ] x [wod + wnd] } x (1-0.01Tm) x Tm Qp, net,m, kcal/kg = { Q gr,v,d [ whd ] x [wod + wnd] } x (1-0.01Tm) x Tm

4 [ whd ] = H content of the sample less hydrogen present in the moisture w(h)d = w(h) x /-Tm Tm= Total moisture ASTM 5865/3180 at constant pressure Qp(net)ar,J/g = Qp(net)ar,Btu/lb = Qp(net)ar,kcal/kg = Qvar(gross) - (215.5 x Har) Qvar(gross) - (92.67 x Har) Qvar(gross) - (51.47 x Har) Har = total hydrogen where hydrogen includes hydrogen in sample moisture Har = [(Had xMad) x (-Mar)/(-Mad)] x Mar 4. VARIOUS PARAMETERS CALCULATIONS: 4.1 Seyler s Formula: Various parameters of coal can be estimated from the Ultimate Analysis and Calorific Value determinations, using Seyler's formula, and other similar calculations (e.g. Dulong's or Channivala s formulas). Reference: VM daf = 10.61H daf C daf H daf = (Q daf/+vm daf) C daf = [0.59 (Q daf/ VM daf) ] Estimate of the hydrogen content, calculated using Seyler's Formula: wh = w(h) = w(v) = w(a) = qv,gr,m = 0.07 x w(v) x qv,gr,m x [ - Tm - w(a)] is the H content of sample less H contained in moisture, as % mass is the VM content of sample with moisture content Tm, as % mass is the ash content of sample with moisture content Tm, as % mass is the gross CV of sample with moisture content Tm, in j/g Note 1 * Only valid when the calculated H db is greater than 3% *ISO E.3.3 Note 2 ** Only valid when the O daf content is less than 15% ** COAL -Typology -Physics -Chemistry -Constitution D.W. Van Krevelen (third edition 1993) Page 47 Note 3 Can give erroneous results if coal shipments are a blend of low and high rank coals.

5 4.1 Dulong's Formula: Alain DELOYE - Technical Services Manager GCV(db) = 333xC(db) (H(db) - O(db) / 8) + 93xS(db) GCV is in (kj/kg dry basis) - C, H, O, S as percent on a dry basis. Other calculations formulas related to CV: kcal/kg: Net CV = Gross CV H M O MJ/kg: Net CV = Gross CV H M O Btu/lb: Net CV = Gross CV H M O - where M is % Moisture, H is % Hydrogen, O is % Oxygen (from ultimate analysis, also As Received). For typical bituminous coal with 10% M and 25% Volatile Matter, the differences between gross and net calorific values are approximately as follows: 260 kcal/kg 1.09 MJ/kg 470 Btu/lb 5. CO2 EMISSION FACTOR: t/co2/tj = C % As Received x x [NCV/00)] in kj/kg = C % As Received x x [NCV/ /NCV] in kcal/kg Note 1 Coefficient is 3,664 for France. 6. POWER GENERATION: 1 MWh = 3,600 MJ 1 MW = 1 MJ/s 1 MW (thermal power) [MWth] = approx 1,000 kg steam/hour 1 MW (electrical power) [MWe] = approx MWth / 3 A 600 MWe coal-fired power station operating at 38% efficiency and 75% overall availability will consume approximately: - Bituminous coal (CV 6,000 kcal/kg NAR): 1.5 Mt/year - Brown coal (CV 2,250 kcal/kg NAR): 4.0 Mt/year

6 7. MOISTURE: Two Stage Total Moisture Formula (Refer to ASTM / ISO) Two stage total moisture determination is used when the coal sample is too wet to divide or crush without the potential of loosing significant amounts of moisture. Tm ar, % = [Rm ad, % x ( Fm ad, %) / ] + Fm ad % Tm = Total moisture; Fm = Free moisture; Rm = Residual moisture. 8. FUEL RATIO: = Fixed Carbon / Volatile Matter 9. HYDROGEN & OXYGEN In Coal: (Refer to ASTM 3180 / ISO 1170) Inasmuch as hydrogen and oxygen values may be reported on the basis of containing or not containing the hydrogen and oxygen in water (moisture) associated with the sample, alternative conversion procedures are defined below: Hydrogen and Oxygen Factors based on the atomic weight of H20: Hydrogen = Moisture X Oxygen = Moisture X Sources: GWC Coal Handbook, ASTM & ISO Standards & others.