Many chain grate stoker boiler manufacturers use a simple boiler/ buffer control system based on two temperature sensors, one near the top of the buffer vessel and the other near the bottom. it shows the buffer vessel fully charged and fully discharged. The boiler ceases firing when the hot water interface has reached the bottom sensor when charging and firing re-commences when the buffer vessel has discharged to the level of the upper sensor. The problem with this simple control arrangement is that at daily start-up the buffer vessel empties fully before the boiler fires, leaving the auxiliary boiler to provide 100% of the load while the boiler is heating up. The energy consumed during the daily heat-up phase can represent a significant portion of the annual energy requirement and, depending on the boiler, this heat-up phase can take an hour or more before the biomass boiler comes on line.
One of the key components of the chain grate boiler control is the ability of the fuel air control system to maintain sufficient air proportional to fuel to eliminate the possibility of a fuel-rich condition and the possibility of an explosion.Consideration should be given to the effects of fuel,air density,and temperature fluctuations as related to the air flow and the performance of the flow-meter in regulating the fuel air ratio.