Coal Calculations

Accurate and precise calculations are vital to the success of your coal operation. These calculations are used to calculate various skeleton parameters including ash and calorific value that let you determine the grades of your coal.

SGS global teams of chemists and experts use a range of coal analytical calculations and indexes to arrive at the calorific values, total hydrogen, Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) of your coal sample. Our third party test results and calculations provide you with reliable data that complies with international standards.

The following are some of the interesting protocols and calculations regularly used by SGS coal and coke specialists.

1. Bases Conversion Factors:
   Ref: ASTM D3180 / ISO 1170 - Conversion to different moisture bases
   a. Dry factor (converts AD to Dry) (100-ADM)/100
     Dry = AD / ((100-ADM)/100)
   b. AR factor (converts Dry to AR (100-TM)/100
     AR = Dry x ((100-TM))/100)
   c. DAF factor (converts Dry to DAF) (100-Dry Ash)/100
     DAF = Dry / ((100-Dry Ash)/100)
    
   Where:
   
   TM is Total Moisture
   ADM is Air Dried Moisture (Moisture in the Analysis Sample)
   AR is As Received Basis
   AD is As Determined (Air Dried) Basis
   Dry is Dry Basis
   DAF is Dry Ash Free Basis
   
   
2. 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 losing significant amounts of moisture.
   TMar, % = [RMad, % x (100 - FMad, %) / 100] + FMad %
   M = Total moisture; FM = Free Moisture; RM = Residual moisture
   
   
3. Calorific Value Conversion Factors:
   
   MJ/kg = kcals/kg / 238.846
   MJ/kg = Btu/lb / 429.923
   kcal/kg = MJ/kg x 238.846
   kcal/kg = Btu/lb / 1.8
   Btu/lb = MJ/kg x 429.923
   Btu/lb = kcals x 1.8
   
   
4. CO2 Emission Factor:
   
   t/CO2/TJ = As Received Carbon x 3.667 x [10,000/NCV(p)] in kJ/kg= As Received Carbon x 3.667 x [2388.46/NCV(p)] in kcal/kg
   
   
5. Fuel Ratio
   = Fixed Carbon / Volatile Matter
   
   
6. Hydrogen in Coal: Refer to ASTM 3180 / ISO 1170
   Hydrogen values may be reported if they occur in water (moisture) contained in the sample. There are alternative conversion procedures, reported below:
   
   Use the following conversions to report H including or excluding H in moisture:
   
   Total Hydrogen as-determined (ad): includes H in the analysis moisture
   
   
7. Hydrogen (excluding H in moisture)
   H(dry base) = [Total Hydrogen(ad)-(AMx0.1119)] x (100/(100-AM))
   
8. Hydrogen (including H in moisture)
   H(ar) = [Total Hydrogen(db) x ((100-TM)/100)]+(0.1119*TM)
   
9. ISO 1170 reports H air-dried basis excluding H in the as analyzed moisture.
   H(air-dried) = Total Hydrogen(as-determined) - (Analysis Moisture x 0.1119)
   
   Hydrogen and Oxygen Factors based on the atomic weight of H20
   Hydrogen = Moisture X 0.1119
   Oxygen = Moisture X 0.8881
   
   
10. Net Calorific Value (NCV) Conversion Factors:
    Ref: Net Calorific Value (ASTM D5865-03)
    
    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 1928-1995 at constant volume
    Qv, net,m,J/g =( Q gr,v,d - 206.0 [ wHd ] ) x (1-0.01xMT) - (23.05x MT)
    Qv, net,m,kcal/kg = ( Q gr,v,d - 49.20 [ wHd ] ) x (1-0.01xMT) - (5.51x MT)
    
    ISO 1928-1995 at constant pressure
    Qp, net,m,J/g =
    { Q gr,v,d - 212.2 [ wHd ] - 0.8 x [wOd + wNd] } x (1- 0.01MT) - 24.43 x MT
    
    Qp, net,m,kcal/kg =
    { Q gr,v,d - 50.68 [ wHd ] - 0.191 x [wOd + wNd] } x (1- 0.01MT) - 5.84 x MT
    
    [ wHd ] = H content of the sample less Hydrogen present in the moisture
    w(H)d = w(H) x (100/(100-MT))
    MT= Total Moisture
    
    ASTM 5865/3180 at constant pressure
    Qp(net)ar,J/g = Qvar(gross) - (215.5 x Har)
    Qp(net)ar,Btu/lb = Qvar(gross) - (92.67 x Har)
    Qp(net)ar,kcal/kg = Qvar(gross) - (51.47 x Har)
    Har = total hydrogen where hydrogen includes hydrogen in Sample Moisture
    Har = [(Had-0.1119xMad) x (100-Mar)/(100-Mad)] + 0.1119 x Mar
    
    
11. 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 formula).
    
    Reference:
    
    * COAL -Typology -Physics -Chemistry -Constitution
    D.W. Van Krevelen (third edition 1993) Page 47
    VMdaf = 10.61Hdaf - 1.24Cdaf + 84.15
    Hdaf = 0.069 (Qdaf/100+VMdaf) - 2.86
    Cdaf = [0.59 (Q,daf/100 - 0.367VMdaf) + 43.4]
    
     ** ISO 1928-1995 Part E.3.3
    Estimate of the hydrogen content, calculated using Seyler's Formula
    wH = 0.07 x w(V) + 0.000165 x qv,gr,m - 0.0285 x [ 100 - MT - w(A)
    w(H) - is the H content of sample less H contained in moisture, as % mass
    w(V) - is the VM content of sample with moisture content MT, as % mass
    w(A) - is the ash content of sample with moisture content MT, as% mass
    qv,gr,m - is the gross CV of sample with moisture content MT, in joules/g
    
    Note.1** Only valid when the calculated Hdb is greater than 3%
    Note.2* Only valid when the Odaf content is less than 15%
    Note.3 Can give erroneous results if coal shipments are a blend of low and high rank coals
    
    
12. Dulong's Formula
    GCV(db) = 333xC(db) + 1442(H(db) - O(db) / 8) + 93xS(db)
    GCV is in (kJouls/kg dry basis). C, H, O, S as percent on a dry basis
    

Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR)

When coke descends in the blast furnace, it is subjected to reaction with countercurrent CO2 and abrasion. These concurrent processes weaken the coke and chemically react with it to produce excess fines that can decrease the permeability of the blast furnace burden. SGS conducts CRI and CSR testing to provide high accuracy results with good turnaround times. CRI and CSR tests determine how much energy your coal will produce when being burned in the furnace.

The CRI/CSR test measures coke reactively in carbon dioxide at elevated temperatures and its strength after reaction by tumbling. In the test, 200g of ⅞” x ¾” (19 x 22 mm) sized coke is reacted in a vessel with CO2 gas for 2 hours at 1100°C. The weight loss after the reaction equals the CRI. The reacted coke is then tumbled in an I-shaped tumbler for 600 revolutions at 20 rpm and is then weighed. The weight percent of the + ⅜” coke equals the CSR. Most blast furnaces will require a coke with a CSR greater than 60 and CRI less than 25.SGS is committed to providing accurate, cost effective blast furnace coke analysis for your operation.

SGS is the world leader in coal and coke analysis and testing. The data resulting from our analytical processes ensures optimal recovery rates and performance of your coal or coke.

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  Coal Contacts

  published 02/07/13

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