Useful heat value

• The gradation of non-coking coal is based on useful heat value (UHV). The classifications are divided into seven grades from A-G.
• UHV is expressed in kcal/kg.
• UHV of grade –A non- coking coal is maximum (> 6200 whereas) grade –G has the lowest value of UHV (1300 – 2400).
• UHV is an expression derived from ash and moisture contents for non-cocking coals as per the government of India notification.

UHV is defined by the formula:
UHV kcal/kg =(8900 -138)× {percentage of ash content + percentage of moisture content}

• In case of coal having moisture less than 2% and volatile content less than 19 %, the UHV value is arrived as above, reduced by 150 kcal/kg for each 1 % reduction in the volatile content below 19% fraction on pro-rata basis.
• Both moisture and ash are determined after equilibrating at 60% relative humidity and 40₀C temperature.