Book - School of Science and Technology

Solid fuel 297Table 11.1 Properties of coal (proximate analysis)VolatilesAir dried, CV (MJ/kg)moistureRank No. % a Type Caking properties (%)Gross Net100 < 10 Very low Non-caking 2 32.4 31.6201 12 Low Non-caking b 1 33.0 32.2202 15 Low Weakly b 1 33.2 32.3204 19 Low Strongly b 1 33.2 32.6300 25 Medium Weakly c 1 33.2 32.3301 25 Medium Strongly c 1 32.9 31.8400 >30 High Very strongly c 2 32.3 31.2500 >30 High Strongly c 2.5 31.5 30.3600 >30 High Medium c 4 30.1 29.1700 >30 High Weakly c 5 29.1 27.9800 >30 High Very weakly c 8 27.9 26.6900 >30 High Non-caking c 10 25.4 24.1a Average for singles. b Sub- and semi-bituminous. c Bituminous.Now that coke is, for practical purposes, no longer available for use as a boiler fuel andsince, except as a matter of passing interest, we are not concerned here with the incinerationof waste products, the principal solid fuel for consideration is coal. Characteristicsof the various categories (or Ranks) which are available are summarised in Tables 11.1and 11.2, the details given being from typical analyses. Size nomenclature is given in Table11.2, the more common grades being Singles and Smalls. The former is the more consistentas to quality and size mixture and is thus the more conveniently handled bymechanical equipment.DeliveryCoal delivery, except to very large industrial users able to take a 400 tonne train load, willnormally be by road either by a 5±20 tonne tipper or by a 15±20 tonne special purposeTable 11.2 Properties of coal (ultimate analysis)Content (%)Rank No. Moisture a Ash Carbon Hydrogen Nitrogen Oxygen Sulphur100 3.5 5 84.5 3.0 1.1 1.8 1.1201 3 5 83.7 3.7 1.3 2.2 1.1202 3 5 83.4 3.8 1.3 2.4 1.1204 3 5 83.1 4.1 1.3 2.4 1.1300 3 5 82.1 4.4 1.4 2.8 1.3301 3 5 81.0 4.5 1.4 3.8 1.3400 4 5 78.5 4.7 1.7 4.2 1.9500 5 5 76.3 4.8 1.6 5.4 1.9600 6.5 5 73.9 4.7 1.5 6.5 1.9700 9 5 71.1 4.5 1.5 7.1 1.8800 11 5 67.8 4.4 1.4 8.5 1.9900 16 5 63.0 3.9 1.3 9.0 1.8a As fired.