coal combustion in boilers

[davmuwandi]

i am using coal cobles with a calorific value of 30.1MJ/kg and obtaining an ash with a calorific value of 8.5MJ/kg. this translatates to about 70% coal utilisation. the coal is used on a manually fed fire tube boiler. how good is our performance benchmarking with other coal fired boilers?

 

[mbeychok]

davmuwandi:

I don't understand your posting:

(1) What are coal "cobles"? I've never heard of that term before. Please explain.

(2) The fact that your ash has a heating value about 30% of the coal "cobles" heating value does not necessarily mean that the boiler efficiency is 70%. For example if the total amount of ash is only say 10% of the amount of total coal "cobles" burned, then the total ash only contains 3% of the total heat input to the boiler. You really should tell us how much ash is produced per kg of coal "cobles" burned.

(3) As for the performance of other boilers, typical thermal efficiences may range from 65% to 95% depending on size and how much how much money you want to spend. And most of their heat loss is with the exit flue gas rather than with the ash.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[cub3bead]

I suspect he is using cobles as another word for briquettes.

 

[chicopee]

W/ manually feed fire tube boilers, heat transfer efficiency will be low, somewhere around 60% if you have no economizers, superheaters and combustion air preheaters.