Coal-fired heating boilers generally use coal-fired hot water boilers. Now, the thermal efficiency of coal-fired hot water boilers can reach 85-89. The specific thermal efficiency depends on the coal-fired boiler model, among which SHW reciprocating grate Coal-fired boilers and DHL angle tube coal-fired boilers have relatively high thermal efficiency. However, the use of coal-fired boilers below 10 tons is now prohibited. If you want to build a new coal-fired boiler, it is best to consult the local Environmental Protection Bureau for detailed boiler prohibition range
Reference: http://www.ranmeiguolu .wang/coalFired-boiler-160/