Regenerative Thermal Oxidizer
They are employed for the oxidation of volatile organic compound (VOC) conveyed by air flow produced in production departments and conveyed outside of the working area.
The thermal oxidation of the VOC take place in the combustion chamber, thermally insulated, at a temperature of 750 -850 ° C; it is possible to reduce the output concentration of VOC at 5 -20 mg / Nm3.
The heat required to increasing temperature of combustion chamber (in the starting phase) and to maintain the combustion temperature is supplied from an intake fuel, usually natural gas or LPG.
The combustors are defined by the term “regenerative” since the heat of exhaust smoke from the combustion chamber is used for preheating the ceramic material contained in a first heat exchange tower; incoming fumes, passing over a second exchange tower already in temperature, exchange heat accumulated and provided by the already purified hot fumes. The third room in stand-by ensures that there are no peaks of concentration of VOC in the atmosphere during inversion phase of exchanging rooms.
The dimensional criteria are given in Table 1 “Minimum requirements for thermal and catalytic combustion systems” UNI 11304-2: 2008, incorporated into PC.T board: 02 BAT Lombardia (DGR May 30, 2012 – n. 3552), in particular:
- Residence time in combustion chamber:
- in the absence of chlorinated VOCs: t> 0.6 s
- with Chlorine <0.5%: t> 1 s
- with Chlorine between 0.5% and 2%: t> 2 s
- Minimum operating temperature:
- in the absence of chlorinated VOCs: 750 ° C
- with Chlorine <0.5%: 850 ° C
- Chlorine with between 0.5% and 2%: 950 ° C
The number of exchanging rooms depend on the type of pollutant and the flow of the fumes. The most common configurations are:
- 2-chambers: are constituted by two towers of heat exchange, during the inversion of the IN / OUT cycle will have a few seconds during which the fumes pass not in the combustion chamber so that, not being oxidized, generate an emission peak at the fireplace. This drawback can be obviated by adopting a compensation chamber in which to send the fumes during room inversion.
- 3-chambers: consist of three heat recovery towers; two sections are always in service and the third is stand-by. This configuration allows to send complete oxidized smokes to fireplace.
Optimal use condition of RTO
- 24/5 processing (emission);
- High concentration of pollutants (COT) even of the order of 1-2 g / Nm3, combined with low flow rates of fumes.
- Concentration of powders of less than 5 mg / m3 and amount of VOC less than 25% of LEL. Any organic substances in the form of steam must be condensed before being sent to the RTO by means of suitable inertial filters and / or cyclones.
- It is possible / necessary to pretreat the emission to reduce the content of powders using coalescence filter or scrubber.
- RTO may require the protection of the suction and discharge lines with suitable ATEX systems.
- Inlet smokes temperature: depends on the type of any dedusting system.
- Fuel consumption: existing plants by 10,000 Nm3 / h consume 18 – 22 Nm3 / h of methane, in the absence of pollutant.
- Combustion temperature 750 -800 ° C
- Average stack temperature : ≈ 80-100 ° C higher than the inlet temperature.
COIND may assist the customer in all phases, from design to turn-key RTo; in particular:
- Technical assistance for the part of our responsibility, in relations with the authorities responsible for authorization (AIA, AUA, conference facilities etc)
- Detailed design of RTO (contact times, operating temperature …) based on the real needs of the customer.
- Production in its own workshops of steel structures with a high degree of pre-assembly.
- Acquisition of complementary equipment (burner, gas ramp, inversion valves ..) from selected and qualified
- Companies, capable of providing the necessary product certifications.
- Site installation of RTO.
- After-sales service.