Working principles and characteristics of chain grates and cross-beam grates

Chain grates and cross-beam grates are two common industrial boiler grates; their working principles differ, and so do their suitable fuels and maintenance needs.

How a chain grate works

A chain grate consists of a drive sprocket, an idler sprocket and a chain running around both, with many grate bars mounted on the chain; fuel is spread evenly on the bars at the front and carried into the furnace as the chain turns slowly. Air boxes below the grate supply air, which flows up through the gaps between bars, meets the fuel and burns; as the fuel travels backwards it passes through drying, volatile release and coke combustion.

Features of a chain grate

The chain grate has a relatively simple structure, runs stably and reliably, feeds continuously and burns evenly, and adapts well to lump coal and granular biomass. Its limits are that the bar motion can distribute fuel unevenly, leaving local incomplete combustion that lowers efficiency, and that bars wear after long service and need periodic maintenance and replacement.

Structure and features of a cross-beam grate

A cross-beam grate is built from a series of transverse beams carrying the grate bars. Fuel also enters at the front, and during combustion air is supplied through ducts between the beams to provide oxygen. The bars are held more firmly and can carry greater fuel weight and combustion impact, suiting large-lump, high-ash fuel; air distribution is more even, which raises combustion efficiency and cuts unburned loss. The drawbacks are a more complex structure, higher manufacturing and installation cost and stricter demands on installation precision and maintenance skill; a failed beam or bar is harder to repair and may need a long shutdown.

Selection points

Choosing a grate type means weighing fuel characteristics, boiler capacity, operating cost and maintenance requirements so that the boiler runs steadily while meeting production energy demand.