By Anjan Bhattacharya
With India importing largeamounts of high moisture lowrank coal, there is growinginterest in the potential benefits of dryingthe fuel prior to combustion. But what is thebest way of doing this? Arethere advantages in drying the coal at themine before transportation to the powerplant site? The analysis presented herelooks at the add-on benefits of coal dryingat the mine end relative to drying at plantsites, but is agnostic as to the particularcoal drying technology employed.
It is well known that moisture is a majorcause of thermal losses in coal fired boilers.Therefore reduction of the moisturecontent in coal improves boiler efficiency.Reduction of coal moisture also facilitatescoal handling and coal preparation.Drying of high moisture coal to reduceits moisture content and thereby improveboiler performance is a well establishedconcept in principle but when it comes tothe practicalities there are uncertaintiesabout the most suitable drying processesand the economics, currently topicsreceiving attention. Few powerplants around the world using one orother of the available drying methods toreduce the coal moisture, there are alsotrials underway at power plant sites andat laboratories to find the most appropriatetechnologies for coal drying.In India, at present high moisture coal is firedmostly in ‘as received’ condition withoutdrying. Nearly all studies of coal dryingconducted to date assume that the coalwill be dried at the plant site. It meanshigh moisture imported coal would betransported all the way to the plant siteand then dried using fuel or waste heat,if available. In other words, enormousquantities of water are transported tothe plant and then energy isconsumed to evaporate the water.Considering the quantity of waterthat is transported as coal moisture, andtaking into account shipping distances,transportation costs and fuel consumption,it may be worth looking at anotherscenario: what if the coal is dried at themine mouth and then transported? Wouldthis make sense?The issue is examined in the Indian context, but the findings are applicable elsewhere as well.