25t/h Cross-beam Type Grate

Product introduction

The cross-beam grate is a new type of cross-beam grate bar in which an inclined air outlet is applied to the cross-beam grate bar. Unlike existing grate bars, whose air flows vertically upward, the air outlet of the vent holes in the inclined-outlet cross-beam grate bar forms a certain angle with the vertical direction. When the grate air leaves the grate bar it has a horizontal velocity, which helps the air diffuse horizontally in the coal bed, strengthens the mixing of coal and air, and reduces coal leakage through the grate.

Scope of application and requirements

Scope of application

The cross-beam grate is a mechanized layer-firing unit with a compact structure. The cross-beam grate is suitable for boilers with an evaporation capacity of 20~40 t/h and above. Its main structural difference from the chain-belt grate is that it uses many rigid cross beams. The grate bars are mounted in the corresponding grooves of the cross beams, and the cross beams are fixed to the drive chains. There are usually two drive chains (several may be installed when the grate is very wide), driven by the sprockets mounted on the front shaft (drive shaft).

It is widely used in various large boilers and in special equipment such as heating and drying equipment. It is suitable for burning bituminous coal, lignite and peat; specially designed incineration equipment can also burn other fuels such as bagasse and various types of waste.

Operating requirements

The medium used in this grate must meet the following requirements:

(1) The maximum particle size of the coal must not exceed 40mm, of which the content of 05mm coal fines must not exceed 50%, and the content of 030mm coal fines should be less than 25%.

(2) The moisture content of the coal is less than 20%, with 8~12% being optimum.

(3) The ash content of the coal should be less than 30% but must not be lower than 10%, and the volatile matter content must not be lower than 20%.

(4) The ash melting temperature of the coal should be higher than 1250℃.

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

(6) The net calorific value of the coal should be higher than 4350kcal/kg.

(7) If the medium requirements above conflict with the medium requirements of the coal feeding equipment, the highest requirement shall be taken.

The primary air temperature used in this grate must not exceed 200℃.

Structure and characteristics

The complete grate consists of the following components: (1) support frame; (2) grate chain; (3) ash discharge device; (4) side seal; (5) air inlet pipe; (6) rear guide block; (7) front air baffle device; (8) shaft assembly; (9) coal hopper assembly.

(1) The support frame consists of left and right wall plates and front, middle and rear cross beams. Between the cross beams, the ash discharge device and the air chamber partitions, several relatively closed large-capacity air chambers are formed; in this way the air volume to each zone of the grate surface can be adjusted, so that the fuel burns fully.

(2) The chain consists of links passing through rollers, intermediate guide blocks, chain shafts, retaining rings, pin shafts and other parts. Bolt slots are cast on the links, and the cross beams are fixed with bolts.

(3) One end of the grate is driven by the drive shaft and needs no driven shaft, and the other end is fitted with a guide device; the transition of the chain between the upper guide rail and the lower guide rail is accomplished by the drive shaft and the guide device. The drive shaft torque is supplied by the grate reducer through a coupling.

(4) The side seal is a horizontal right-angle flow-channel side seal; together with the side seal of the grate bars, the two sealing lines improve operating safety and reliability.

(5) The ash discharge device is of the push-pull type; by pushing or pulling the handle of the ash discharge door to open the door, the fine ash and coal fines collected in the air chamber can be discharged.

(6) Stratified coal feeding devices are widely used in the coal hopper assembly; the coal entering the furnace is loose and stratified and burns fully, which raises the thermal efficiency of the boiler.

(7) The grate has a compact structure and a rational layout; the grate chain moves inside sealed guide rails, is not exposed to high temperature and only carries the tension of grate movement; the grate bars made of heat-resistant material contact the high-temperature burning coal bed on the cross beams and are not subjected to stress when heated, which extends the service life of the grate.

(8) The grate has no rear shaft and no eagle irons, which reduces the failure rate of the rear part of the grate in operation and improves operating efficiency.

(9) The grate chain runs in a tensioned state without arching or chain climbing; chain movement is rolling friction, so the running torque requirement is low and the noise is low.

(10) The grate has good overall sealing; air leakage and cross-flow between air chambers are prevented. The air volume of each air chamber can be adjusted separately, which is convenient and practical.

(11) The grate surface is flat, the grate bars overlap each other and are closely arranged, which prevents coal leakage and coal dropping; the grate bars can be replaced conveniently without stopping the boiler.

Model parameters

Operating features

1. Good structural rigidity: the grate bars are not exposed to heat, nor are the cross beams and the chains, so operation is safer and more durable;

2. The effective grate area is large, the resistance is low and the air volume is evenly distributed;

3. Chain movement is rolling friction, so the running torque requirement is low and the friction noise is low;

4. The grate has good overall sealing, which prevents air leakage and cross-flow between air chambers; the air volume of each air chamber can be adjusted separately, which is convenient and practical;

5. The grate surface is flat, the grate blocks overlap each other and are closely arranged, so coal leakage and coal dropping are unlikely, and the grate bars can be replaced conveniently without stopping the boiler;

6. The ventilation cross-section area of the grate is large, generally up to 10%-17%, and combustion is very complete;

7. The grate has no rear shaft and no eagle irons, so the rear part of the grate is unlikely to fail in the furnace.