1 granularity 

The most suitable coal particle size for the two-stage gas generator is 25-50mm, which is the size of walnut pieces.

2 Maximum and minimum particle size ratio 

It means that the ratio of the diameter of large coal to the diameter of small coal is less than 2. Reason: The material layer of the two-stage furnace is thicker, about 6 times that of the single-stage furnace. In terms of gas rising resistance, it is much larger than that of the single-stage furnace.Single stage gas generator. If the coal lumps are of uneven thickness, the small coal lumps will block the gaps between the large coal lumps, causing the gas resistance to increase. In high material layers, the resistance will be more significant. Greater furnace bottom pressure is required to overcome.

3 lower limit rate 

 The mass ratio of coal with a particle size smaller than the specified lower limit of particle size in the coal material If there are too many small-grained coals, more pulverized coal and small coal will enter the furnace and block the gas flow gaps.

4 volatiles 

 The two-stage furnace must choose bituminous coal with an appropriate amount of volatile content instead of anthracite, otherwise the retort section of the two-stage furnace will have no effect. Experiments have shown that the most suitable coal volatile content is 20%-35%.

5 Thermal stability and crushing strength

The two-stage furnace requires the coal material to have high thermal stability and high crushing strength. Otherwise, once the coal is heated or squeezed and breaks into small pieces of coal, air flow resistance will occur, which will affect the reaction in the furnace.

6 Roga index 

It refers to the cohesiveness of coal. If the cohesiveness is too great, small pieces of coal will easily stick to large pieces of coal after cracking. As the reaction difficulty increases, the carbon content of the ash may increase. The same is true for the free expansion coefficient.

7 Ash melting point: The temperature at which ash in solid fuel deforms, softens and melts after reaching a certain temperature.

 

In summary, it can be found that the reason why all indicators are important is that they affect the particle size change of coal in the furnace. Any coal with a coefficient that causes the particle size of coal in the furnace to become too small or too large will not work.