25t/h Flake Type Chain Grate

Product introduction

The grate surface of a flake-type chain grate usually consists of 4~12 parallel chains (similar to the chain structure of a bicycle). Each chain joins several short chain sections together with shovel-shaped bolts, and each section is strung from large rings, small rings, washers, liners and other parts. The grate plates are assembled on the chains with clamp plates; the clamp plates fold back and forth and press against each other, so the plates are arranged in a fish-scale pattern. When the grate plates reach the rear end and turn into the lower return run, they tip over one after another under their own weight and hang upside down on the clamp plates, so that ash and slag are cleared automatically and the plates are cooled.

Adjacent chains are connected by tie rods and sleeves, which keep the chain spacing unchanged.

Scope of application and requirements

Scope of application

This grate is mechanized layer-combustion equipment for boilers and is suitable for boilers with an evaporation capacity of 10~60t/h. It can burn bituminous coal, lignite and peat. Coal is fed automatically from the coal hopper; a pneumatic coal feeder can also be fitted, or the grate can be installed upside down and fitted with a mechanical pneumatic coal spreader, so that it becomes the mechanized suspended-combustion chamber type.

Use requirements

The coal burned on this grate shall meet the following requirements:

(1) The maximum particle size of the coal shall not exceed 40mm; the content of 0~3mm coal fines shall be less than 30%;

(2) The moisture content on a dry basis shall be less than 20%;

(3) The ash content on a dry basis shall not exceed 30%, but shall not be lower than 10%;

(4) The ash deformation temperature shall be higher than 1250℃;

(5) The caking tendency should not be too strong.

(6) If the above coal quality requirements conflict with the coal quality requirements of the coal feeding equipment, the higher requirement shall apply.

The primary air temperature used for this grate shall not exceed 200℃ (it shall not exceed 160℃ when burning anthracite).

Structure and characteristics

The whole grate is divided into seven parts: (1) drive shaft; (2) driven shaft; (3) support (the support is an integral structure with a low ash support plate and friction strips); (4) grate chain; (5) coal hopper; (6) front air baffle; (7) slag stopper. This grate does not include the air supply device of the coal feeding equipment or the grate gearbox.

(1) The working surface of the grate, that is the grate surface, is formed by many grate plates stacked continuously at an incline in a fish-scale pattern, with an air passage section of 8%-10%.

(2) The grate chain is characterised by a large number of chains, and the chains are fixed on the grate chain in groups of five clamp posts. The grate chain is strung and fixed with long shafts and liners, and rollers are threaded between the chains. The rollers mesh with the teeth on the main wheel and drive the sprocket of the transmission grate. The grate is driven by the drive wheel, while the driven wheel slides.

(3) The grate uses zoned air supply. Along the length of the grate it is divided into several large-capacity air chambers, each connected to an air duct. The air entering a chamber slows down through diffusion and fills the whole chamber evenly. Butterfly doors on the air ducts adjust the air pressure in the chambers.

(4) The ash removal device of the air chambers uses push-pull and tie-rod ash doors. Turning or pushing the handle of an ash door drops the ash onto the grate chain below. The grate chain moves on the bottom plate and pushes the ash to the front end of the grate, where it falls into the ash hopper or ash trough.

The ash can also be removed by hand. The push-pull handles pass through the air ducts and sit outside them, and their arrangement matches that of the air ducts: single-side air supply gives single-side ash discharge; double-side air supply gives double-side ash discharge; single-side air supply with double-side ash discharge is also possible.

(5) The seal between both sides of the grate chain and the support uses a labyrinth or contact structure, and coal blocks are placed there to keep coal from leaking into the sides of the grate.

(6) The slag stopping device is of the eagle-iron type. The slag stopper is the eagle iron, placed behind the driven shaft; its head presses on the grate chain under its own weight, and its lower part is mounted on the support and welded to the grate support.

(7) Inspection doors are provided on the slope above the front air baffle for routine inspection, maintenance and ventilation. For natural ventilation, the baffle and the ash doors of the air chambers can be opened.

(8) The coal hopper is mounted on the wall plates on both sides of the support. A coal gate is provided inside the hopper, and the coal bed thickness is adjusted by raising and lowering the coal gate.

Model parameters

Operating features

1. The coal bed contacts the whole grate surface, but the chains are not directly heated, so operation is safe and reliable;

2. The gaps in the grate are extremely small, so little coal leaks; the grate plates are thin and well cooled;

3. The plates can be replaced without shutting down the boiler;

4. Because the chain structure is flexible, a slight deviation in the tooth profile of the sprocket on the drive shaft is self-adjusting in tightness, so good meshing is maintained.