Flake Type Chain Grate

Product introduction

The flake-type grate surface usually consists of 4~12 parallel chains (similar to the chain of a bicycle). Each chain is built from small links joined by hoe-shaped bolts; a small link consists of a large ring, a small ring, a spacer and a liner. The grate plates are fitted to the chains with clamp plates, and the clamp plates fold forwards and backwards and close on each other, so the surface looks like fish scales. When the grate plates reach the tail end and turn downwards into the return run, they tip over one after another under their own weight and hang on the clamp plates, so the ash is removed automatically and the plates are cooled.

Neighbouring chains are joined by tie rods and sleeves so that the chain spacing stays constant.

Scope of application and requirements

Scope of application

This grate is mechanized layer-firing equipment for boilers and suits 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 be fitted instead, or the grate can be inverted and matched with a mechanical pneumatic spreader, which turns it into a mechanized model with a suspension combustion chamber.

Operating requirements

The coal used in this grate should meet the following requirements:

The maximum lump size of the coal does not exceed 40mm; the content of 0~3mm coal powder is less than 30%;
Moisture on a dry basis is less than 20%;
The ash content is not more than 30%, but not less than 10%;
The ash deformation temperature should be above 1250℃;
The caking tendency is weak.
If these coal requirements conflict with the coal requirements of the coal feeding equipment, the higher requirement applies.

The primary air temperature for this grate must not exceed 200℃ (not more than 160℃ when anthracite is burned).

Structure and characteristics

The whole grate is divided into seven parts: (1) driving shaft; (2) driven shaft; (3) frame (a one-piece structure with a low ash support plate and friction strips); (4) grate chain; (5) coal hopper; (6) front air baffle; (7) slag stopper. The air supply device of the coal feeding equipment and the grate gearbox are not part of this grate.

The working surface of the grate, that is the grate surface itself, is formed by many grate bars laid continuously at a slope in a scale pattern, and the air passage section is 8%–10%.
The grate chain consists of several chains, and each chain is fixed to the grate chain by one set of five clamp posts. The grate chain is held together by long shafts and liners, and rollers are fitted between the chains. The rollers mesh with the teeth on the main wheel and drive the grate sprocket. The grate runs as the driving wheel pushes it, while the driven wheel slides.
Air is supplied in sections inside the grate. Along its length the grate is divided into several large air chambers, and each chamber is connected to its own air duct. The air entering a chamber spreads out, slows down and fills the chamber evenly. Butterfly dampers on the air ducts adjust the air pressure in the chambers.
The ash removal device of the air chambers uses push-pull ash gates and tie-rod ash gates. When the ash gate handle 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 of the grate, where it drops into the ash hopper or the slag trough. Ash can also be removed by hand. The push handle passes through the air duct and sits on the outside of the duct, and it is laid out in the same way as the air ducts: air supplied on one side means ash discharged on one side, air supplied on two sides means ash discharged on two sides, and air supplied on one side with ash discharged on two sides is also possible.
The seal between the two sides of the grate chain and the frame uses a labyrinth or a contact structure, and coal blocks are placed on both sides to keep coal from leaking in at the sides.
The slag blocking device is an eagle-iron type slag stopper. The slag stopper, that is the eagle iron, sits behind the driven shaft; its head rests on the grate chain under its own weight, its lower part is mounted on a bracket, and the bracket is welded to the grate frame.
An inspection door is set on the slope above the front air baffle for daily inspection, repair and ventilation. For natural ventilation, open the air baffle and the ash gates of the air chambers.
The coal hopper is mounted on the side wall plates of the frame. A coal gate is fitted inside the hopper. The coal bed thickness is adjusted by raising or lowering the coal gate.

Model parameters

Boiler evaporation rate	Grate effective area m²	Grate effective width mm	Shaft extension length (to grate centre line) mm	Output shaft end diameter mm	Number of air chambers
2 t/h	3.04	1040	802	Φ60	3
4 t/h	5.97	1332	1050	Φ80	5
6 t/h	7.36	1560	1089	Φ80	5
8 t/h	8.26	2000	1425	Φ80	4
10 t/h	10.5	2000	1470	Φ95	6
15 t/h	15.57	2664	1835	Φ100	5
20 t/h	22.08	3434	2079	Φ120	6
30 t/h	27.39	3804	2400	Φ130	6
40 t/h	35.44	4544	2771	Φ130	7

Operating features

The coal bed touches the whole grate surface, but the chains are not heated directly, so operation is safe and reliable;
The gaps in the grate are very small, so little coal leaks through; the grate plates are thin and cool well;
They can be replaced without stopping the boiler;
Because the chain structure is flexible, when the sprocket teeth on the driving shaft are slightly uneven, the chain adjusts its own tension and keeps good meshing.