This shaking grate has flanges assembled on square bars. A key wrench rocks a bar and its flanges to disturb the fuel bed and help loosen ash. This calculator reports a selected steady heat balance against an assumed gross grate heat flux; it does not determine burnout, clinker risk or grate suitability.
Shaking-Grate Selected Heat-Flux Reference
Explore the fuel rate and area implied by selected steady heat-flux assumptions with a square-bar grate illustration.
Equation Used
- Useful output, useful/gross fraction, HHV and gross grate heat flux are constant selected values.
- HHV is entered in kJ/kg and fuel rate is reported in kg/h.
- The selected reference area is uniformly exposed to the selected gross heat flux.
- Combustion, materials, loads, operations and safety are excluded.
The selected heat flux does not predict grate burnout.
Flanges and square bars
Hiscox figure 204 shows flanges strung on square bars to form the grate sections. A key wrench at the front turns a bar to shake or dump its section. The animation shows one section being rocked while the others remain in their supports.
What the calculator determines
Select useful output Q, useful/gross fraction η, fuel HHV H and assumed gross grate heat flux qʺ. The calculator reports implied fuel rate, gross heat input, implied reference area and the gross-to-useful ratio 1/η.
Selected steady heat balance
Qin = Q/η; ṁ = 3600Q/(ηH) for H in kJ/kg; A = Qin/qʺ; and gross/useful = 1/η.
Selected-input arithmetic
For Q = 180 kW, η = 0.65, H = 31,000 kJ/kg and qʺ = 700 kW/m², gross input is about 276.92 kW, implied fuel rate 32.16 kg/h, reference area 0.396 m² and gross/useful ratio about 1.538.
Heat balance and grate design
Heat flux alone does not establish burnout. Actual grate design requires product data and analysis of fuel, ash, clinker, air distribution, draft, bed depth, emissions, bar materials and temperature, thermal expansion, loads, operating sequence and safety.
Questions
Does the reference area size a grate?
No.
Does qʺ predict burnout?
No.
Are the bar angles recommended?
No; they are illustrative.
References & Further Reading
- Wikipedia contributors. Fire-tube boiler. Wikipedia
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