US 4,622,922 AGranted

Combustion control method

AssigneeHitachi, Ltd.

InventorsHisanori Miyagaki, Toshihiko Higashi, Atsushi Yokogawa, Yoshihiro Shimada, Nobuo Kurihara, Mitsuyo Nishikawa, Yoshio Sato, Atsumi Watanabe, Yasuo Morooka

Life of this patent

Estimating the term…

patentgrep

Loading patent…

Abstract

A combustion control method wherein manipulated variables or the amounts of fuel and air in at least one combustion zone of a boiler are regulated so that both the amount of nitrogen oxides and the amount of unburned coal in the ash at an outlet of a burner furnace or at least one of them passes the regulation standards and satisfies the requirements for operating a plant. The method is characterized by varying the amounts of fuel and air in performing trial operations on manipulated variables to evaluate the nitrogen oxides at the furnace outlet, the unburned coal in the ash at the furnace outlet and the stability of combustion, and declaring as optimum manipulated variables those amounts of fuel and air used for performing the trial operations which achieve results such that the combustion is found to be stabilized, at least the nitrogen oxides at the furnace outlet satisfy the requirement and the thermal efficiency of the boiler is judged to be at the highest level by a boiler thermal efficiency judging section.

A combustion control method for a furnace, in a boiler, having one or more combustion zones in each of which a burner can be controlled by adjusting the amounts of fuel and air, comprising the steps of:

(a) obtaining a two-dimensional high and low density image having a high and low density regions from a combustion flame and combustion gas in each combustion zone by means of image fiber means and image forming camera means;
(b) estimating for each combustion zone the concentration of NO.sub.x in accordance with the two-dimensional high and low density image obtained from the combustion flame in each combustion zone, and estimating the concentration of NO.sub.x at the outlet of the furnace with the use of the estimated concentration for each combustion zone;
(c) estimating for each combustion zone the amount of unburnt coal in ash in accordance with the two-dimensional high and low density image obtained from the combustion flame in each combustion zone, and estimating the amount of unburnt coal in ash at the outlet of the furnace with the use of the thus estimated amount of unburnt coal in ash;
(d) evaluating the stability of combustion with the use of the two-dimensional high and low density image for each combustion zone;
(e) estimating the thermal efficiency of the boiler upon controlling of the amounts of fuel and air for each combustion zone with the use of a furnace heat transfer model;
and
(f) changing the amounts of fuel and air for each combustion zone when the stability of combustion is satisfactory while either one of the estimated concentration of NO.sub.x at the outlet of the furnace and the estimated amount of unburnt coal in ash thereat exceeds the associated limited value, to allow either one of the estimated concentration of NO.sub.x at the outlet of the furnace and the amount of unburnt coal in ash thereat to satisfy the associated limiting condition while to maximize the boiler efficiency.

4 more elements

Abstract

Claims19