Rotary Drum Vacuum Filter (RDVF) Sizing & Cake Dewatering Calculator
Perform industrial solid-liquid separation modeling for continuous rotary drum vacuum filters. Calculate filtration rate, cake thickness, cycle time, drum speed, vacuum air requirements, and dry solids yield using Ruth and Darcy models.
1. Slurry & Filter Operating Parameters
2. Filtration Yield & Dewatering Results
First-Principles Mathematical Derivation of Rotary Drum Vacuum Filtration
Rotary drum vacuum filtration operates via unsteady-state cake deposition across continuously rotating, vacuum-manifolded sectors. Darcy's fundamental filtration law governs cake formation and hydraulic permeation.
1. Ruth Constant-Pressure Filtration Equation
Under a constant applied vacuum differential $\Delta P$, the instantaneous filtrate flux $d(V/A)/dt$ is impeded by cake resistance $R_c = \alpha \cdot c \cdot (V/A)$ and filter medium resistance $R_m$:
Solving the quadratic for specific filtrate volume $(V/A)_{form}$ collected during the submerged period $t_{form} = \frac{60 \cdot \psi}{N}$ (seconds) establishes the cake mass deposited per cycle.
2. Cake Thickness & Solids Deposition
Dry solids mass deposited per square meter is $m_{dry} = c \cdot (V/A)_{form}$ ($kg/m^2$). The resulting wet cake thickness $L_{cake}$ depends on cake dry packing density $\rho_{dry}$ and porosity $\epsilon_{cake}$:
3. Continuous Dry Solids Yield ($Y_{dry}$)
Total dry solids production rate ($kg/h$) accounts for total active drum area $A = \pi D W$ and rotational cycle frequency:
5 Fatal Traps & Engineering Pitfalls in RDVF Operation
1. Sub-Critical Cake Thickness & Scraper Smear Failure
Increasing drum speed (RPM) to chase higher throughput reduces submerged cake form time $t_{form}$. If cake thickness drops below $3\,\text{mm}$, the scraper knife cannot peel the cake; instead, it smears the slurry directly into cloth pores, causing total cloth blinding and cutting output by 90%.
2. Dewatering Cake Cracking & Vacuum Loss
Fine compressible slurries shrink during dry cycle vacuum dewatering, forming fissures that penetrate to the cloth. Air rushes into the cracked zones, dropping system vacuum across the entire drum manifold. Upstream sectors lose suction, discharging wet, sloppy cake into transport bins.
3. Trough Solids Stratification & Agitator Dead-Zones
Heavy mineral concentrates (iron ore, silica) settle rapidly in the slurry vat. Inadequate oscillating pendulum rake agitation allows coarse solids to form a hardened bed in the trough bottom. The drum begins scraping against settled solids, causing motor torque overload trips and ripped filter cloths.
4. Rotary Valve Bridge Seal Air Leakage
The internal rotary distributor valve separates vacuum form, wash, dry, and blow-off sectors using graphite/bronze wear bridge blocks. Operating without adequate lubricated seal flushing causes abrasive wear that allows atmospheric blow-off air to leak into the vacuum zones, destroying vacuum efficiency.
5. Filtrate Vacuum Receiver Barometric Leg Cavitation
If the filtrate receiver seal tank has an insufficient barometric drop leg height ($< 10.3\,\text{m}$ at sea level, or shorter at altitude), filtrate backs up into the vacuum pipework and floods the vacuum pump. Liquid slugging destroys liquid-ring vacuum pump impellers within seconds.