Comparison for Different Types of RTOs
Performance Comparison Table for Different Types of RTOs (Treatment Air Volume: 30000 Nm³/h)
| Performance | Indicator | 2-Chamber RTO | 3-Chamber RTO | Rotary RTO | Remarks |
| Reliability | Number of Valves | 4 | 9 | 1 |
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| Annual Valve Switching Count | 350,000 cycles | 520,000 cycles | / | Rotary valve operates continuously without switching. |
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| Pipeline Pressure Fluctuation | ±200 Pa | ±200 Pa | ±25 Pa |
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| Compliance | Overall Purification Efficiency | 98% | 99.6% | 99.8% |
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| Switching Peak Purification Efficiency | 90% | 98% | 99.8% |
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| Max. Treatable Concentration Range | <1g | <5g | <10g | Emission standard: 20 mg/m³ |
| Energy Efficiency | Surface Area | 160 ㎡ | 230 ㎡ | 100 ㎡ |
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| Inlet-Outlet Temperature Difference | 65°C | 60°C | 30°C |
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| Purging Air Volume | / | 5000 | 3000 | 2-chamber RTO has no purging. |
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| Thermal Efficiency | 90% | 95% | 96% |
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| Startup Heating Time | 2h | 3h | 1.5h | Cold furnace startup. |
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| Self-Sustaining Operating Concentration | 2.3 g/m³ | 2.5 g/m³ | 1.5 g/m³ | Referring to Ethyl Acetate. |
| Economy | Insulation Wool | 28 m³ | 40 m³ | 20 m³ |
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| Regenerative Ceramic Fill Volume | 14.7 m³ | 22 m³ | 15 m³ |
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| Weight | 68 t | 102 t | 60 t |
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| Practicality | Footprint | L12 × W9 | L16 × W9 | L12 × W7 | Meters |
Analysis:
(1) Energy Efficiency:
The surface area of the Rotary RTO is about 45% of that of the three-chamber type, resulting in smaller heat loss from the furnace body. The Rotary RTO requires less regenerative ceramic fill, approximately 68% of that of the three-chamber type, resulting in higher utilization efficiency of the regenerative ceramics per unit time, higher thermal efficiency, lower exhaust gas temperature, and lower natural gas consumption during cold startup. The three-chamber RTO requires repeated "open-close" switching operations, with an annual switching count of 200,000 cycles, meaning an action every 150 seconds. Thus, the heat storage time for each regenerator bed is 150 seconds, allowing heat penetration. The outlet temperature of the regenerator chamber is generally above 80°C. In contrast, the rotary valve operates with continuous, low-speed rotation without switching impacts. The rotary valve operates at a speed of 120 seconds per revolution, meaning each regenerator bed undergoes a "heat storage - heat release" mode exchange every 50 seconds. Therefore, the heat storage time for the regenerator bed is only 50 seconds, preventing heat penetration. The outlet temperature of the regenerator chamber is typically below 40°C.
(2) Practicality:
The Rotary RTO has a smaller footprint, only about half that of the three-chamber RTO.
(3) Investment Cost:
The Rotary RTO has a smaller overall volume, uses less steel, requires only about 70% of the insulation wool and 68% of the regenerative ceramics compared to the three-chamber type, and has fewer connecting pipes, resulting in lower investment costs.
(4) Operating Cost:
* Fuel Gas Consumption: For cold startup, the Rotary RTO consumes less natural gas than the three-chamber type. Furthermore, the startup time for the Rotary RTO is 1.5 hours, compared to 3.0 hours for the three-chamber type. The self-sustaining operating concentration for the Rotary RTO is 1.5 g/Nm³, while it is 2.5 g/Nm³ for the three-chamber type. For waste gases with organic concentrations below 2.5 g/Nm³, the three-chamber RTO requires supplemental natural gas, whereas the Rotary RTO can operate self-sufficiently without consuming natural gas.
* Power Consumption: The main fan and combustion air fan power requirements are similar for both types. The purging air volume required for the rotary valve type is 60% of that for the three-chamber type (resulting in approximately 20% less power). When treating low-concentration waste gas, the combustion air fan for the three-chamber RTO needs to remain on. Although the Rotary RTO features an additional rotating motor, its power is only 1.1 kW for a 30,000 cubic foot air volume unit. Overall, the power consumption of the Rotary RTO is lower than that of the three-chamber RTO.
(5) Development Forecast:
The Rotary RTO demonstrates significant advantages in energy efficiency, practicality, investment cost, and operating expenses. Currently, over 2000 sets of Rotary RTOs are operating stably in the domestic and international markets, successfully applied for VOCs abatement across various industries. The technology is mature and reliable, having gained full market affirmation and recognition regarding its maturity and stability. In the future, Rotary RTOs are expected to largely replace poppet valve RTOs.