In a low-pressure boiler using a screw-feed retort stoker, what area is NOT considered a combustion zone?

In a low-pressure boiler using a screw-feed retort stoker, the cutoff grate zone is not considered a combustion zone because its primary function is to control the flow of fuel and maintain the desired fuel bed thickness rather than facilitate the actual combustion process.

The ignition zone is where fuel first catches fire, and the burning zone is where the sustained combustion happens, producing heat and flue gases. The combustion chamber, on the other hand, is the enclosed space where the combustion process takes place and where combustion gases travel.

The cutoff grate zone is specifically designed to separate the solid fuel from the burning and ignition zones, allowing for the effective control of combustion rate and emissions, reinforcing its role as a non-combustion area. Understanding these distinct zones within a boiler helps operators manage combustion efficiency and adherence to safety standards.