In pulverized coal-fired boilers,the coal is ground to a fine powder and is carried into the furnace by an air stream .there are normally two or more pulverizers(in parallel) per boiler. Pulverized coal flow is regulated at the pulverizer, and each manufacturer has a different design requiring different controls. One control arrangement is shown in FIG.1 here, the primary air comes from a pressure fan that blows through the pulverizer, picking up the coal and transporting it to the furnace.
In addition to the controls shown, an air temperature control is required. In this loop, cold and hot combustion air is mixed ahead of the primary air fan to control the temperature of the coal air mixture in the pulverizer. This control is necessary to maintain a maximum safe operating temperature in the pulverizer. This is a simple feedback loop, usually involving proportional control only.
a control arrangement for a bowl-type pulverizer is shown in FIG.1. In this type of pulverizer, the air fan sucks air through the pulverizers with the fan(called an exhauster fan)located between the pulverizer and the burners. The coal-air temperature loop is similar to the one described in FIG.1.
Pulverized Coal-fired Boiler
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