Cross-beam Type Grate

Product introduction

The cross-beam type grate uses cross-beam grate plates with oblique air outlets. The air outlet direction of these grate plates differs from the vertical upward air outlet direction of existing grate plates. The air outlet direction of the ventilation holes of the oblique-outlet cross-beam grate plate forms a certain angle with the vertical. The horizontal velocity of the air as it leaves the grate plates helps the air to spread horizontally in the coal bed and helps the mixing of coal and air, and it reduces coal leakage through the grate.

Scope of application and requirements

Scope of application

The cross-beam type grate is a mechanised layer-combustion device 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 grate is the use of many rigid beams. The grate plates are mounted in the corresponding grooves of the beams, and the beams are fixed to the drive chains. There are usually two drive chains (more can be fitted when the grate is very wide), driven by the sprockets mounted on the front shaft (drive shaft).

It is used in various large boilers, heating and drying equipment and other special equipment. It is suitable for burning bituminous coal, lignite and peat; specially designed incineration equipment can use other fuels such as bagasse and various wastes.

Operating requirements

The fuel medium used in this grate should meet the following requirements:

The maximum particle size of the coal should not exceed 40mm, of which the 0~~5mm fines content should not exceed 50% and the 0~~30mm fines content should be less than 25%.
The moisture content of the coal should be less than 20%, preferably 8~12%.
The ash content of the coal should be less than 30% but not lower than 10%, and the volatile matter should not be lower than 20%.
The ash melting temperature should be above 1250℃.
The coking tendency should be low.
The net calorific value of the coal should be above 4350 kcal/kg.
If the fuel requirements above conflict with the fuel requirements of the coal feed equipment, the highest requirement applies.

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

Structure and characteristics

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

The support frame consists of left and right side plates and front, middle and rear cross beams. The cross beams, the ash removal device and the air chamber partitions form a number of relatively closed large-capacity air chambers; this allows the air volume in each zone of the grate surface to be adjusted and the fuel to burn fully.
The chain consists of chain links, rollers, intermediate guide blocks, chain pins, retaining rings and pin shafts. The chain links are cast with bolt slots, and the beams are fixed with bolts.
One end of the grate is driven by the drive shaft and there is no driven shaft, and the other end is fitted with a guide device; the transition of the chain between the upper and lower guide rails is made by the drive shaft and the guide device. The drive shaft torque is supplied by the grate reducer through the coupling.
The side seals are a horizontal right-angle flow passage side seal and a grate plate side seal; the two sealing lines improve operating safety and reliability.
The ash removal device is of the push-pull type; pull the ash door handle to open the ash door and discharge the fine ash and coal collected in the air chamber.
The layered coal feed device is already used on the coal hopper assembly; the coal entering the furnace is loose and layered and burns fully; the boiler thermal efficiency is raised.
The grate has a compact structure and a rational layout; the grate chain runs inside sealed guide rails, does not carry high temperature and only carries the tension of grate movement; the grate plates made of heat-resistant material contact the burning coal at high temperature on the beams and are free of stress when heated, which extends the service life of the grate.
The grate has no rear shaft and no eagle iron, which lowers the failure rate at the rear of the grate during operation and improves operating efficiency.
The grate chain runs under tension without arching or crawling; chain movement is rolling friction, so the running torque requirement is low and the noise is low.
The grate is well sealed as a whole; air leakage and cross flow between air chambers are prevented. The air volume of each chamber can be adjusted separately, which is convenient in practice.
The grate surface should be flat, and the grate plates overlap each other and are closely arranged to prevent coal leakage and coal dropping; the grate can be replaced easily without shutting down the boiler.

Model parameters

Boiler evaporation capacity	Grate effective area m²	Grate effective length mm	Grate effective width mm	Drive shaft torque N.m	Air inlet method	Ventilation cross-section ratio %	Ventilation resistance pa
20 t/h	23.29	6830	3410	20000	Inlet from both sides	8.5	1000
40 t/h	35.38	7800	4550	30000	Inlet from both sides	8.5	1000
65 t/h	57.6	8150	6960	50000	Inlet from both sides	8.5	1000
75 t/h	63.7	7503	8490	70000	Inlet from both sides	8.5	1000
80 t/h	71.2	8360	8518	60000	Inlet from both sides	8.5	1000
90 t/h	80	9373	8540	70000	Inlet from both sides	8.5	1000
100 t/h	97.71	9165	9570	90000	Inlet from both sides	8.5	1000
130 t/h	126.66	9590	13210	Dual reducer	Constant-pressure air chamber	8.5	1000
160 t/h	153.17	10458	14700	Dual reducer	Constant-pressure air chamber	8.5	1000
200 t/h	185.94	10458	17780	Dual reducer	Constant-pressure air chamber	8.5	1000
260 t/h	248.4	13500	18400	Dual reducer	Constant-pressure air chamber	8.5	1000
300 t/h	295.2	14260	20700	Dual reducer	Constant-pressure air chamber	8.5	1000

Operating features

Rigid structure, the grate plates are not exposed to heat and the beams and chains are not exposed to heat, so it is safer and more durable;
Large effective grate area, low resistance and even air distribution;
Chain movement is rolling friction, so the running torque requirement is low and the friction noise is low;
The grate is well sealed as a whole and prevents air leakage and cross flow between air chambers. The air volume of each chamber can be adjusted separately, which is convenient in practice;
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 plates can be replaced easily without shutting down the boiler;
The ventilation cross-section of the grate is large, generally up to 10%–17%, and combustion is complete;
The grate has no rear shaft and no eagle iron, so the rear of the grate is unlikely to fail inside the furnace.