| Typical product suitability | Free-flowing granules, crystals, pellets, and particles that tolerate direct contact with heated air. | Dust-sensitive, oxygen-sensitive, or contamination-controlled products requiring filtered and recirculated process air. | Heat-sensitive, oxidation-sensitive, or solvent-containing products that benefit from lower drying temperatures. | Start with product sensitivity, required atmosphere, and solvent-handling requirements before comparing price. |
| Indicative evaporation capacity | Approximately 50–1,500 kg of water per hour, depending on deck area, air volume, and inlet conditions. | Approximately 50–1,200 kg of water per hour, depending on air-recirculation rate and heat-recovery design. | Approximately 10–500 kg of water per hour, depending on vacuum level, condenser capacity, and product behavior. | Capacity must be confirmed with product moisture data and a pilot or test-bed evaluation. |
| Typical drying-air temperature | 60–180 °C | 50–160 °C | 30–100 °C product-zone temperature, depending on vacuum pressure and product requirements. | Use the lowest practical temperature that achieves the required final moisture and throughput. |
| Indicative thermal energy demand | 700–1,200 kWh per tonne of water evaporated | 550–950 kWh per tonne of water evaporated when air recirculation and heat recovery are properly applied. | 800–1,400 kWh per tonne of water evaporated, including heating and vacuum-system losses. | Actual consumption varies with feed moisture, exhaust humidity, insulation, ambient conditions, and heat-source efficiency. |
| Indicative electrical demand | 8–25 kWh per tonne of water evaporated | 12–35 kWh per tonne of water evaporated, mainly for fans, filters, controls, and air-recirculation equipment. | 20–60 kWh per tonne of water evaporated, mainly for vacuum pumps, condensers, fans, and controls. | Compare electricity separately from thermal energy because the local prices and carbon factors may differ significantly. |
| Heat-recovery potential | Low to moderate; exhaust-air heat recovery can be added but may increase dust-handling complexity. | High; recirculated air, exhaust-air heat exchangers, and controlled purge air can reduce thermal losses. | Moderate; condenser heat may be recovered, but the useful temperature level can be limited. | A heat-recovery system is most valuable where the dryer operates for many hours per year. |
| Main maintenance items | Vibration exciter, bearings, springs, screen or perforated deck, fan, heater, seals, and dust filters. | All open-air items plus recirculation fan, air-locks, higher-grade filters, dampers, ducting, and gas-tight seals. | Vibration exciter, bearings, vacuum seals, condenser, vacuum pump, valves, instrumentation, and product-contact surfaces. | Maintenance complexity rises with filtration, vacuum, solvent recovery, and gas-tight equipment. |
| Routine maintenance labor | Approximately 4–8 technician-hours per operating month, excluding planned shutdowns. | Approximately 6–12 technician-hours per operating month, depending on filter loading and cleaning frequency. | Approximately 8–16 technician-hours per operating month, depending on vacuum-pump and condenser service needs. | These are planning ranges; abrasive, sticky, or corrosive products can increase labor substantially. |
| Typical wear-part replacement interval | Bearings and springs commonly require inspection every 3–6 months; replacement timing depends on load and vibration settings. | Filters may require cleaning or replacement from weekly to quarterly; mechanical components usually follow a 3–6 month inspection cycle. | Vacuum-pump service may be required every 3–12 months; seals and condenser cleanliness require regular inspection. | Use the supplier’s service schedule and confirm availability of local spare parts before purchase. |
| Relative capital cost | Low to medium | Medium to high | High | Include fans, filters, heaters, condensers, controls, installation, utilities, and safety systems in the comparison. |
| Product quality and contamination control | Good for products that can tolerate direct contact with ambient or filtered heated air. | Very good when controlled air quality, dust containment, and reduced cross-contamination are required. | Very good for oxygen-sensitive products and closed solvent recovery, provided the vacuum system is correctly designed. | Validate residence-time distribution, final moisture uniformity, and product-temperature limits through testing. |
| Recommended operating profile | High-volume, continuous operation with moderate product sensitivity and low to medium dust-control requirements. | Continuous production where containment, air recirculation, and energy efficiency justify additional equipment. | Batch or semi-continuous production where product quality and low-temperature drying are more important than maximum throughput. | Calculate total cost of ownership using annual operating hours, energy prices, labor rates, and expected downtime. |