Regenerative Thermal Combustors

Aspiration and filtration systems for the abatement of volatile organic substances

CTR Regenerative Thermal Combustors are used for the removal of Volatile Organic Compounds (VOCs) which are present in the airflows extracted from production departments.

The combustion of VOCs occurs in a thermally insulated chamber at a temperature of 750-800°C, TOC output values in the order of 5-20 mg/Nm³ can be obtained. The heat required is supplied by fuel, usually natural gas or LPG.

The Regenerative Thermal combustors owe the adjective “regenerative” to the fact that the heat of exhaust smoke from the combustion chamber is transferred to the ceramic mass contained in a first heat exchange tower; the incoming fumes, passing through a second already warm exchange tower, receive the heat accumulated and supplied by the outgoing fumes. A third chamber in stand-by ensures that there are no polluting fluctuations coming out of the chimney during the inversion phase of chambers.

The design criteria are defined by what is stated in prospectus 1 “Minimum requirements for thermal and catalytic combustion systems” of UNI 11304-2: 2008 regulation, implemented in PC.T: 02 profile of BAT Lombardy (Regional Council Resolution 30 May 2012 – no. 3552), in particular:

• Calculated length of time that the smoke remains in the burner zone between the masses of the two towers in the absence of chlorinated VOCs: t > 0.6 s
• Minimum operating temperature ≈ 750° C in absence of chlorinated volatile organic compounds VOCs.

The Regenerative Thermal combustors can be of various types:

• Bicameral: they have two heat exchange towers, at the time of the inversion of the IN/OUT cycle there’s a moment in which fumes do not pass through the combustion chamber, so there is an emission peak in the funnel. This drawback can be avoided by inserting a compensation chamber where to store fumes at the time of chamber reversal.
• Three-compartments: they have three recovery towers, the third tower in stand-by allows to send purified fumes to the chimney.

When to use the CTR Regenerative Thermal Combustor:

• Processing (and emission) continuous cycle for 24h and at least 5 days a week.
• The concentration of polluting volatile organic compounds VOCs is high (even in the order of 1-2 g/Nm³) and flow rates are low.
• Dust flow less than 5 mg/m³ and a flammable VOC content lower than 25% at LEL point (lower explosion limit). Moreover, if there are organic substances in the form of steam at emission time and condensable at room temperature, they must be separated with appropriate inertial filters and cyclones.
• It’s possible to pre-treat emissions in order to reduce dust content: it’s possible to have coalescence or scrubber systems.
• Protection of suction lines and combustor with suitable ATEX protection systems may be needed.

Operating parameters

• INLET fumes temperature: it depends on the type of dust separator system.
• Fuel consumption: on 10,000 Nm³/h existing systems, consumption will be 18- 22 Nm³/h of methane gas, standard use, with no pollutant.
• Combustion temperature 750-800° C.
• OUTLET fumes temperature: ≈ 80-100° C higher than inlet temperature.