Boiler Losses Affecting Coal Fired Boiler Efficiency
Boiler efficiency will vary over a wide range, depending on a great variety of factors and conditions. The difference between the efficiency secured in any boiler trial and the perfect efficiency, 100 per cent, includes the losses, some of which are unavoidable in the present state of the art, arising in the conversion of the heat energy of the coal to the heat energy in the steam. These losses may be classified as follows:
1. Loss due to fuel dropped through the grate.
2. Loss due to unburned fuel which is carried by the draft, as small particles, beyond the bridge wall into the setting or up the stack.
3. Loss due to the utilization of a portion of the heat in heating the moisture contained in the fuel from the temperature of the atmosphere to 212 degrees; to evaporate it at that temperature and to superheat the steam thus formed to the temperature of the flue gases. This steam, of course, is first heated to the temperature of the furnace but as it gives up a portion of this heat in passing through the boiler, the superheating to the temperature of the exit gases is the correct degree to be considered.
4. Loss due to the water formed and by the burning of the hydrogen in the fuel which must be evaporated and superheated as in item 3.
5. Loss due to the superheating of the moisture in the air supplied from the atmospheric temperature to the temperature of the flue gases.
6. Loss due to the heating of the dry products of combustion to the temperature of the flue gases.
7. Loss due to the incomplete combustion of the fuel when the carbon is not completely consumed but burns to CO instead of CO2. The CO passes out of the stack unburned as a volatile gas capable of further combustion.
8. Loss due to radiation of heat from the boiler and furnace settings.
Obviously a very elaborate test would have to be made were all of the above items to be determined accurately. More information about coal fired boiler efficiency calculation and coal fired boiler losses, please consult our online customer service.