Grate Bar Selection Guide: How to Choose the Pore Structure According to the Fuel Characteristics?

The porosity structure of grate bars plays a crucial role in combustion efficiency and should be carefully matched to fuel properties. For high-ash coal, larger and more numerous pores are preferred to prevent ash accumulation and maintain proper airflow. The increased porosity helps ash particles pass through while sustaining combustion. Conversely, low-ash fuels like anthracite require medium porosity to balance air distribution without excessive fuel fall-through.

Biomass fuels demand special consideration due to their varying particle sizes. Wood chips need moderately spaced pores to accommodate their irregular shape while preventing excessive dropping, whereas pelletized biomass works best with smaller, uniform pores that match pellet diameter. The porosity must allow sufficient primary air for combustion while supporting the fuel bed.

For municipal solid waste (MSW), a dual-porosity approach often works best - larger openings for bulky items combined with smaller pores for fine fractions. This accommodates the heterogeneous nature of waste while ensuring even burning. The porosity should also consider the waste's moisture content, with wetter materials benefiting from slightly enlarged pores to enhance drying.

Liquid and gaseous fuels burning on special grates require minimal porosity, focusing instead on surface area for heat transfer. The pore design here serves more for structural integrity than airflow regulation.

The ideal porosity always balances three factors: adequate air supply for complete combustion, proper fuel retention time, and efficient ash removal. Manufacturers typically offer porosity options ranging from 15% to 40% open area, with the selection depending on comprehensive fuel analysis including particle size distribution, ash content, and moisture levels. Proper matching extends grate life, improves thermal efficiency, and reduces maintenance needs significantly.

Remember that porosity is just one parameter - it must be coordinated with grate bar material, cooling method, and mechanical design for optimal performance with specific fuels.