How to use Rotary Dryer Heat& Mass Balance Calculator
- Enter Wet feed throughput (t/h) and adjust the options as needed.
- Run the tool and inspect its results, evidence and limitations.
- Copy or download the result, then verify it against the actual website, source data or business records.
Try a concrete example
In a metallurgical slag powder and industrial quartz sand drying project, wet feed rate is 30.0 t/h with 22.0% initial wet-basis moisture, targeting 1.50% final moisture. The combustion furnace supplies hot flue gas at 650.0 °C, exhaust ID fan outlet temperature is 105.0 °C, and ambient reference temperature is 20.0 °C in an industrial heavy-duty rotary dryer (drum length-to-diameter ratio L/D = 7.50): Based on thermal and mass conservation, bone-dry solid matrix rate is 23.40 t/h, yielding 23.76 t/h dried product; hourly water evaporation W is 6.24 t/h (6,243.66 kg/h water removed); total system heat duty is 5275.4 kW (18.99 GJ/h, including 12% shell surface radiation and air in-leakage allowance); required hot flue gas normal flow is 27,249.4 Nm³/h (gas mass flow 35,151.7 kg/h); at a design volumetric evaporation intensity of 32.0 kg water/(m³·h), required active drum volume is 195.1 m³; recommended rotary drum geometry is Φ2.1m × 15.8m; exhaust flue gas dew point safety margin is 57.0 °C (confirmed safe, well above water vapor saturation dew point, eliminating baghouse moisture condensation and acid blinding risks). Product moisture re-absorption and baghouse mud blinding are reliably prevented.
How to interpret results
Industrial rotary dryer heat and mass balance and flue gas sizing calculation is the thermodynamic foundation for process engineering in mineral tailings drying, cement slag grinding, FGD gypsum processing, coal preparation, and biomass pelletization. Inside the rotating shell, complex lifting flights cascade material to form dense, uniform curtains that engage in intense convective and radiative heat and mass transfer with hot combustion gases. Inaccurate thermal sizing either causes massive fuel waste or causes downstream baghouse filters to cross acid/water dew points, inducing severe fabric blinding that chokes system draft. This calculator applies thermodynamic heat balance and psychrometric principles to compute water evaporation rates, heat duty, normal flue gas flow, drum dimensions, and exhaust dew point safety margins.
Frequently asked questions
What are the differences between co-current and counter-current rotary dryer flow configurations?
Flow directions, temperature gradients, and material compatibilities define clear boundaries: First, co-current flow (gas and solids flow in the same direction): At the drum feed head, high-temperature gas (600–800°C) contacts cold, wet feed; extreme thermal gradient drives rapid surface flash evaporation. Toward the discharge end, gas cools substantially while dry product encounters mild temperatures, keeping discharge solids cool (60–90°C) and preventing overheating or auto-ignition; ideal for coal dust, refractory minerals, slag, quartz sand, and heat-sensitive materials. Second, counter-current flow (gas and solids flow in opposite directions): Hottest gas contacts the driest product at the discharge hood, maximizing mean log temperature difference (LMTD) and thermal efficiency; ideal for high-temperature tolerant aggregates, clays, and ores requiring ultra-low final moisture (< 0.5%), though discharge dust carryover is higher.
How is exhaust gas temperature set, and why must the acid dew point safety margin be protected?
Exhaust temperature governs system thermal efficiency and filtration integrity: First, stack heat loss and economy: Lower exhaust temperature retains more sensible heat inside the dryer, raising thermal efficiency (every 15°C reduction cuts fuel consumption by ~1.5%–2%). Second, acid dew point blinding disaster: Dryer exhaust carries high moisture concentrations (100–200 g/m³ dry air). If exhaust drops below 85–90°C, encountering localized casing chill or ambient air in-leakage drops gas below water and sulfur acid dew points (typically 55–65°C). Water vapor condenses into acid slurry on fabric filter bags, cementing dust into an impermeable crust that reverse pulses cannot dislodge, causing pressure drop to spike and shutting down production. Therefore, engineering standards mandate exhaust temperatures maintain at least 25–35°C margin above dew point.
What role does volumetric evaporation intensity Av play in rotary dryer drum sizing?
Volumetric evaporation intensity Av is the empirical benchmark for drum geometry: First, definition: Av represents the mass of moisture evaporated per hour per cubic meter of active drum volume (kg water/(m³·h)). Second, typical bulk material design windows: For granular, high-temperature tolerant materials like slag and quartz sand, direct co-current drying achieves Av of 25 to 40 kg/(m³·h); for sticky sludge or agglomerating plastic clays, Av derates to 15 to 25 kg/(m³·h). Third, volume and aspect ratio sizing: Total required active volume is V = W / Av. Combining this with an established length-to-diameter ratio L/D of 6.0 to 9.0 yields exact drum diameter D and shell length L, avoiding oversized capital expenditures.
How do interior lifting flights affect cascading material curtain formation and heat transfer?
Lifting flights are the core functional components for efficient gas-solid heat exchange: First, flight functionality: Driven by slow shell rotation (2–6 rpm), interior flights scoop bed material from the invert and shower it across the gas cross-section, generating dense cascading curtains that multiply gas-solid contact area hundreds of times. Second, segmented flight zone architecture: The feed entry features steep helical screw flights to advance sticky wet feed and prevent throat clogging; the intermediate drying zone incorporates radial quadrant, cross-shaped, or folding flights to maximize dispersion; the discharge end features bare shell or retention rings to settle coarse particles and minimize dust carryover into the exhaust duct.