Core Differences Between S-Type, Wide, and T-Type Biomass Reciprocating Grate Bars

The S-type, wide and T-type bars are the three most common grate bars for biomass reciprocating grates, and they differ completely in interlocking shape, air volume, slag leakage, fuel pushing and disturbance, and suitable fuel.

1. S-type grate bar

The S-shaped surfaces on both sides overlap and interlock, so when moving and fixed bars slide against each other the overlap always forms a labyrinth seal. Slag leakage is lowest and the bar suits fine biomass such as rice husk, sawdust, chopped straw and palm shell, since fine particles do not drop through the gaps; the sliding motion gives slight stoking and bed disturbance, the gaps are even, primary air is stable, the bar rarely jams and it is the first choice where dust is heavy. The weakness is small ventilation gaps and low total air volume, so oxygen may fall short with high moisture, large wood chips or a thick bed.

It is mostly used on small and medium biomass steam or hot-water boilers and on 6-25t/h SZW biomass reciprocating boilers.

2. Wide bar

The wide bar is a flat wide-faced plate with a larger overlap and greater coverage of grate width per piece, with ventilation slots concentrated at the leading edge. Larger coverage means fewer bars per metre of grate width and less work at overhaul; load capacity is high, suiting log sections, large chips and bark; machining cost is slightly lower and stock is ample. The weakness is weaker interlocking than the S-type, so slag leakage with fine fuel clearly rises; disturbance is weak with almost no automatic clinker breaking, so fuel tends to crust and run short of oxygen locally.

It suits fuel dominated by large wood with little fines, and also the burnout-zone tail grate and low-cost retrofit projects.

3. T-type grate bar

The section is T-shaped, with the face carrying fuel and vertical ribs below improving cooling, and straight-through air channels between bars. Air volume is the largest and permeability the best, so thick beds of wet biomass still get enough oxygen and burn fully; large cooling ribs at the back give good air cooling and high-temperature resistance, so the main combustion zone does not burn out; pushing turns the bed more strongly, suiting clinkering fuel. The weakness is wide gaps and the worst slag leakage with fine biomass, so pure rice husk or fine sawdust should not use it across the whole grate.

It suits high-moisture chips, bark and straw briquettes, the main combustion zone of large biomass reciprocating grates and duties with larger particles and limited fines.

Selection advice

The three types are chosen by fuel particle size and moisture: S-type for fine, dusty fuel where low slag leakage matters; wide bar where large logs, chips and bark dominate or the tail only carries ash; T-type for high moisture, thick beds and clinkering fuel.