fixed-bed combustion

Fixed-bed combustion involves burning lumps of coal, typically between 3 and 50 millimeters in size, placed on a grate. Preheated air is blown from beneath the bed to burn the fixed carbon, while additional air is introduced above the bed to combust released volatiles. This method is characterized by a slower heating rate, resulting in combustion times of 45 to 60 minutes per particle. Due to grate size limitations, fixed-bed combustors are generally restricted to industrial and smaller-scale power plants, with an upper limit of approximately 100,000 megajoules per hour. The coking properties of coal and the presence of fine particles can affect airflow and require measures like tempering to ensure efficient combustion.1