Factors Affecting Pulverized Coal Combustion

The main factors affecting the pulverized coal combustion are:

(1) Coal properties (ignition temperature, combustion moisture, ash, coal fineness)

(2) Operating conditions (initial temperature of coal gas flow, a wind rate and wind speed)

(3) Burner structural characteristics

The nature of pulverized coal is the most important factor affecting the combustion of pulverized coal.

2.1.1 Properties of pulverized coal

(1) Volatiles

The greatest impact on the fire is the volatile component, the fire temperature changes with the volatile. The ignition temperature of the pulverized coal gas flow increased significantly, and the heat of ignition also increased. That is, it is necessary to heat the pulverized coal gas stream to a higher temperature for ignition. As a result, low-volatile coal is more difficult to fire and takes longer to catch fire.

(2) Burning water

Coal moisture increases, the ignition temperature also increases .At the same time, the water heating, vaporization must absorb the heat inside the furnace, resulting in lower furnace temperature level, so that the coal powder air entrainment flue gas temperature and flame on the The radiant heat of the pulverized coal gas flow is correspondingly decrease. This is obviously more negative for the fire, but also increases the energy consumption per unit of product. Coal maintaining l.0% to 1.5% water can promote the combustion, but excessive water will hinder the combustion of coal. For each 1.0% increase in coal moisture, the flame temperature is decreased about l0 ~ 20 ℃.

(3) Ash

Coal ash not only cannot heat, but also endothermic in the combustion process. In particular, when low-quality coal with high ash content is burned, since the fuel itself is low in calorific value and fuel consumption increases, a large amount of ash absorbs more heat during ignition and combustion, thereby lowering the furnace gas temperature, The ignition of the powder airflow is delayed, but also the stability of the fire is affected. Calcined dolomite temperature in 1250 ℃, when the ash melting point below this temperature, the rotary kiln calcination zone easy to ring, adverse production.

(4) Fineness

The ignition temperature of the pulverized coal airflow also changes with the fineness of the pulverized coal. The finer the pulverized coal is, the easier the ignition is. This is because in the same pulverized coal fineness, the finer the coal, the larger the surface area of ​​the combustion reaction, while the thermal resistance of coal itself is reduced, and thus heating, the temperature rise of fine coal powder than crude Coal powder fast. This will speed up the chemical reaction, faster to fire. So always in the combustion of fine pulverized coal combustion first. Thus, for difficult to fire the low-volatile coal, coal will be finer grinding, will undoubtedly accelerate its ignition process.

2.2 Rotary kilns calcination of the recommended raw coal

(1) calorific value:> 6000kcal / kg

(2) fineness: 200 mesh, 85% pass rate

(3) Moisture: <2%

(4) Volatiles:> 20%

(5) ash melting point:> 1250 ℃