Regenerative thermal oxidisers (RTOs) have a unique ability to reuse the thermal energy derived from their operation, ensuring continuity and cutting fuel expenditure. This is one of the major advantages of using an RTO, making it suitable for many energy intensive industries.
But how does an RTO system work? There are four broad steps in the process, which are described below:
Step 1: Initial Heating
Here the regenerative thermal oxidiser unit is heated to combustion temperature using a supplementary fuel source. The fuel source could be diesel or bio-fuel, but propane and natural gas are more commonly used because of their low cost.
Between the initiation of the process (i.e., when heating starts) to the combustion temperature, the RTO system is first cleansed (purged) with fresh air. This continues until the combustion temperature equilibrium is reached. This final temperature is usually within the range of 815°C to 950°C, although heating is sometimes completed in stages to incorporate a pre-treatment stage.
Step 2: Pre-Treatment
Once the desired temperature is reached (around 700*C), the exhaust gas containing VOCs and some other hazardous pollutants are allowed to pass through a specialised thermal ceramic chamber within the first heat exchanger in the RTO unit. This strips out some of the most volatile components.
Step 3: Incineration Of Airborne Contaminants
Once the full combustion temperature is reached, the RTO unit is fed with the pre-treated exhaust air, which contains heavier VOC, metallic compounds and hazardous air pollutants (HAP) to be destroyed. The efficiency of the incineration phase may range from 85-99%.
Step 4: Heat Recovery
The effluent heat generated from incineration is consequently repurposed to operate and sustain combustion temperatures so that there’s no need for additional fuel. In practice, this means that some exhaust runs with a low contaminant levels can be successfully cleansed without the RTO requiring any external power. Recovered heat can also be directed to other systems, either industrial furnaces or kilns, or even to climate control or water heating systems.
Adopting An Appropriate Clean Air Strategy
Regenerative Thermal Oxidisers are one among a number of options available to manufacturers to improve air quality and reduce energy waste. Different manufacturers adopt various solutions on their own or in combination, depending on their business goals, compliance requirements and budget.
RTO’s are discussed in further detail in our e-book: Controlling Air Pollution & Emissions In Manufacturing With After burners & RTO’s, which also explains afterburners, filters and other clean air measures. Download a copy for free by clicking here.