Combustion control apparatus for a coal-fired furnace

In a powdered coal combustion furnace in which coal is pulverized by means of a pulverizing mill, and wherein only powdered coal whose grain size is less than a predetermined value is extracted by means of a fine/coarse grain separator, and wherein further said extracted powdered coal is fired within said combustion furnace, a combustion control apparatus for said coal-fired furnace, comprising:

• an evaluating means for qualitatively evaluating density data of nitrogen oxides contained within burning exhaust gases, density data of unburned substances within ash, and power data of said pulverizing mill by using membership functions corresponding to said different data;
• a control rule means containing control rules which define generating control outputs under predetermined situations;
• and
• a fuzzy inference means for searching said control rule means for a control rule that matches an evaluated value produced by said evaluating means and, according to said control rule, infers an optimum control amount for a two-stage combustion air ratio for minimizing said nitrogen oxides within said exhaust gases, and an optimum control amount for said fine/coarse grain separator for minimizing said unburned substances within said ash;
• whereby based upon said optimum control amounts thus inferred, the furnace combustion conditions are optimally controlled so as to maintain said densities of said nitrogen oxides and of said in-ash unburned substances within safe, stable ranges.