Ash melting type u-firing combustion boiler and method of operating the boiler

摘要

A U-type slag-tap firing boiler includes a combustion furnace (5) formed in a volume so that a temperature of a gas flowing through a slag screen (4) separating the combustion furnace (5) and a radiant furnace (6) disposed below the combustion furnace (5) is maintained in a range that ensures the normal functioning of the slag screen (4) even if air is supplied through a burner (2) into the combustion furnace (5) at an air ratio below 1. NOx generation is reduced by decreasing air supply through the burner (2) into the combustion furnace (5) to below 1, burning pulverized coal in a fuel-rich combustion mode in the combustion furnace (5) to crate a reducing atmosphere therein, and heating the interior of the combustion furnace (5) at a temperature around fluid temperature.