Stokers
A common solution for feeding solid fuels into boilers is through the use of stokers. Stokers were first used in the 18th century to burn coal. Since then they have evolved from crude machines to sophisticated electromechanical components that can rapidly respond to changes in boiler output demand and provide good fuel handling capabilities and turndown, defined as the ratio of maximum to minimum fuel flow rate. Firing systems that involve stokers must be integrated into the boiler design in order to optimize combustion and heat recovery and to minimize emissions. Stoker systems are typically categorized into either underfeed or overfeed systems (Oland, 2002).