8t/h Flake Type Chain Grate

Product introduction

The grate surface of a flake-type grate usually consists of 4~12 parallel chains (similar to the chain structure of a bicycle). Each chain is formed by several short chain sections joined together, and each section is threaded by hoe-shaped bolts through parts such as large rings, small rings, washers and liners. The grate plates are assembled on the chains with clamp plates; the clamp plates fold forwards and backwards and press close to each other, arranged in a fish-scale pattern. When the grate plates reach the tail 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 the ash is cleared automatically and the plates are cooled.

Neighbouring chains are connected by tie rods and sleeves so that the chain spacing stays unchanged.

Scope of application and requirements

Scope of application

This grate is mechanized layer-firing equipment for boilers and is suitable for boilers with an evaporation rate of 10~60 t/h. It can burn bituminous coal, lignite and peat. Coal drops automatically from a coal hopper; a pneumatic coal feeder can also be fitted, or the grate can be mounted upside down and equipped with a mechanical pneumatic coal spreader, giving the mechanized suspension-combustion-chamber type.

Operating requirements

The coal quality for this grate should meet the following requirements:

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

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

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

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

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

(6) If the above coal quality requirements conflict with the requirements of the coal feeding equipment on coal quality, the higher one should be taken.

The temperature of the primary air used in this grate must not exceed 200℃ (not more than 160℃ when burning anthracite).

Structure and characteristics

The whole grate is divided into seven parts: (1) driving shaft; (2) driven shaft; (3) frame (the frame 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 retainer. 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 inclination in a fish-scale pattern, with a ventilation section of 8%-10%.

(2) The structural feature of the grate chain is that it has many chains, and the chains are fixed on the grate chain in groups of five clamp plate posts. The grate chain is fixed by long shafts and liners threaded through it, and rollers are threaded between the grate chains. The rollers mesh with the teeth on the main wheel and drive the sprocket of the transmission grate to rotate. The grate is driven by the driving wheel, while the driven wheel runs as a sliding support.

(3) Zoned air supply is used inside the grate. Along the length of the grate it is divided into several large-capacity air compartments, and each compartment is connected to its own air duct. The air entering a compartment slows down through diffusion and fills the whole compartment evenly. Butterfly dampers are provided on the air ducts to adjust the air pressure in the compartments.

(4) The ash removal device of the air compartments uses push-pull and tie-rod type ash discharge doors. When the handle of an ash discharge door is turned or pushed, the ash falls 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 the ash trough.

The ash can also be removed manually. The push-pull handle passes through the air duct and is placed outside it, and its arrangement follows that of the air duct, that is, single-side air supply gives single-side ash discharge; double-side air supply gives double-side ash discharge; and single-side air supply with double-side ash discharge is also possible.

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

(6) The slag retaining device uses the eagle-iron slag retainer. The slag retainer, that is the eagle iron, is placed behind the driven shaft; its head presses on the grate chain by its own weight, and its lower part is mounted on the frame and welded to the grate frame.

(7) To meet the needs of routine inspection, maintenance and ventilation, an inspection door is provided on the slope above the front air baffle. If natural ventilation is required, the air baffle and the ash discharge doors of the air compartments can be opened.

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

Model and parameters

Operating features

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

2. The grate clearance is very small and little coal leaks; the grate plates are thin and the cooling conditions are good;

3. Replacement can be carried out without shutting down the boiler;

4. Because the chain structure is flexible, when the tooth profile of the sprocket on the driving shaft deviates slightly, the tension adjusts itself and good meshing is kept.