This utility model is an improved double-layer grate vertical positive combustion pressureless boiler. Each grate plate has a convex arc-shaped working surface structure and is operated through a fixed shaft; A bɛ ni rectangulaire movable grates set ye minnu bɛ se ka taa ji pipe grate kan, ka fara coal feeding port kan walasa ka grate movables bila ji pipe grate kan ani slag cleaning port walasa ka grates movables bɔ..
