Method for controlling NOx concentration in exhaust gas in combustion facility using pulverized coal

A method for controlling an NOx concentration in an exhaust gas in a combustion facility that uses a pulverized coal as a fuel, comprising, in the following order:

• measuring a reaction velocity of each of a plurality of chars represented by ki and corresponding to a plurality of types of pulverized coals;
• determining a relationship between the NOx concentration in the exhaust gas and the reaction velocity ki for the each of the chars in the plurality of chars;
• blending the plurality of the types of the pulverized coal, to obtain a blended pulverized coal, wherein a blending ratio of the plurality of the types of the pulverized coal is determined by using, as an index, a reaction velocity of the char of the blended pulverized coal, which is represented by kblend and which corresponds to a target NOx concentration or below, on the basis of the relationship;
• and
• supplying the blended pulverized coal to the combustion facility as the fuel of the combustion facility wherein the reaction velocity of the each of the plurality of the chars, ki, is determined by:
• drawing a curve of a time change of weight loss for the each of the plurality of the types of the pulverized coals under the condition of a plurality of temperatures by using a thermal balance;
• and dividing inclination of a tangent of the curve by a measured partial pressure of oxygen, thereby determining the reaction velocity of the each of the plurality of the chars, ki at the respective temperatures.