The effect of number and dimension in economizer hopper on fly ash capture capabilities and flue gas characteristic

Flue gas and fly ash are by-products of combustion processes within boiler systems. When transported by the flue gas stream, fly ash can cause clogging and corrosion, particularly in the air preheater, which often leads to increased maintenance and the need for component replacement in power plants. To address this issue, the flue gas channel can be redesigned by integrating hoppers that function to separate and trap fly ash particles, thereby preventing their entry into downstream equipment. This study investigates the effect of varying hopper quantities on the efficiency of fly ash capture and the behaviour of flue gas flow using numerical simulations. Four configurations were evaluated: a system without hoppers and systems with 2, 4, and 6 hoppers. Simulation results show that increasing the number of hoppers improves the retention of fly ash in the hopper domain while reducing the mass and percentage of particles that pass through to the air preheater. While the addition of hoppers slightly increases flue gas velocity at the outlet, this change has minimal effect on air preheater performance. However, the pressure drop across the system increases with the number of hoppers, reaching a maximum of 37.94% in the six-hopper configuration compared to the no-hopper setup. Among the configurations, the system with four hoppers offers the best compromise between fly ash capture and system performance, trapping 41.08 kg of fly ash and allowing only 0.81 kg (30.21%) to reach the air preheater, while maintaining the same pressure drop as the six-hopper case.