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Catalytic oxidizers make use of special catalysts to reduce the energy for activating the oxidation reactions of pollutant substances, to reduce fuel consumption.

The catalysts used for this application are based on metal oxides or noble metals.

The catalytic thermal oxidation plants can be designed in different configurations, using:

  • catalysts in the form of pellets or monolithic (honeycomb) for pollution control, for example, in combustion systems complete with thermal recovery in order to further reduce auxiliary fuel consumption;
  • catalyst in the form of random ceramic material (saddles) in regenerative catalytic oxidizers.

The combustion temperature is in the range of 280-400°C depending on the composition of the pollutant substances and therefore after choosing the type of catalyst. The catalytic thermal oxidation plants are very efficient but not very strong as the presence of some pollutants in the air to be treated (for example halogenated compounds, silicons, heavy metals) can deactivate the catalyst, thus “poisoning” it and requiring its replacement. These machines are normally applied in the chemical, pharmaceutical, painting industries and can be equipped with all the pre-and post treatment systems making them useful for the intended purpose.

Features and advantages

  • Electrical switchgear with PLC and remote assistance.
  • Independent combustion system to guarantee correct operation of the plant.
  • Modulating combustion system to maintain the correct operating temperature with different incoming pollutant loads.
  • Structure fully airtight and built with specific steels (AISI 304, 316…).
  • High purification efficiency >99%.
  • Thermal efficiency < 70% in systems with heat recovery unit.
  • Thermal efficiency < 95% in regenerative systems.
  • Reduced production of secondary pollutants (CO, NOx).
  • Possibility of additional heat recovery.
  • Reduced maintenance.

Principles of Operation of Catalytic Combustors

Thermal catalytic oxidation systems can be designed with various configurations, using:

  • Catalysts in the form of pellets or monolithic (honeycomb) structures for pollutant removal, for example, in combustion systems equipped with heat recovery, in order to further reduce auxiliary fuel consumption.
  • Catalysts in the form of loose ceramic material (saddles) in regenerative catalytic oxidizers. There is indeed a regenerative version of the catalytic combustion system, which is ideal for low concentrations.

Depending on the composition of the pollutants and the subsequent choice of the type of catalyst to use, the combustion temperature typically ranges from 280-400°C.

How does a catalytic thermal oxidizer work?

In schematic terms, the operation of the catalytic oxidizer can be described as follows:

  • The polluted gas stream is drawn in by a fan that overcomes the system’s pressure losses; in cases where the flow rate is variable and pressure fluctuations during production need to be minimized, a suction control system (inverter) is added. This system also optimizes energy consumption by adjusting the operation of the system to match production needs.
  • Subsequently, the effluent is preheated in a heat exchanger (flue gas/air) that utilizes the heat from the already purified effluent.
  • This heat exchange system allows for an energy recovery of up to 70%, making it possible for the system to become self-sustaining (i.e., eliminating the need for auxiliary fuel consumption), starting from an inlet concentration of VOCs of 3-4 g/Nm³.

Finally, the heated effluent is directed to the catalyst, where, if necessary, an auxiliary burner increases the temperature before the gas stream passes through the catalyst, ensuring that the desired pollutant removal levels are reached. In the case of regenerative catalytic oxidizers, the purification process remains unchanged, but the heat recovery system is modified. With this version, energy recovery can be pushed up to 95%, enabling the system to become self-sustaining, starting from a concentration of 1.5 g/Nm³.

How is the catalyst selected? What is its lifespan?

The appropriate type of catalyst, both in terms of chemical-physical properties (precious metals or common metal oxides) and geometric design (honeycomb or pellets), is selected based on the organic substances to be removed. With new catalyst formulations, it is now possible to remove even chlorinated or sulfurated organic compounds. Catalytic thermal oxidation systems are highly effective but tend to be somewhat “fragile” because the potential presence of certain pollutants in the air to be treated (such as halogenated compounds, sulfur, silicones, and heavy metals) can “deactivate” the catalyst, or as it is colloquially referred to, “poison” the catalyst, thus necessitating its replacement.

Thermal oxidizers with pre/post treatment

In this condition, appropriate systems are installed, such as cyclones, bag or cartridge filters, Venturi and tower scrubbers, filtering panels, activated carbon adsorbers, various types of demisters or even more complex systems to evaluate for each case.

Plants designed by integrating pre-and post abatement sections to the main oxidizer are used when complex pollutant streams need to be treated with several different technologies. The pre-treatments and therefore the pre-scrubbers are used to preserve the thermal oxidizer both from a mechanical and process point of view, reducing the concentration of particular types of pollutants such as: organic silicone compounds, inorganic acids, inorganic bases, aerosol dust, painting overspray, oily mist and/or condensate droplets

For post-treatments and therefore for the post-scrubbers, rapid cooling systems are typically used such as quenchers followed by tower scrubbers possibly with Venturi-pre-abatement. At times DeNOx SCR or SNCR systems could need to be used to reduce NOx consisting of particular organic compounds such as amines. The various post-abatement systems are applied in the presence of incoming pollutants such as: Halogenated VOC, Sulphurised VOC, Nitrogenous VOC, Silanes or siloxanes

Electric Thermal Oxidizers – OxyTherm Eco2

The electrically powered regenerative thermal oxidizer has the ability to utilize the thermal energy generated during combustion to reduce operational costs and energy consumption of the system itself. Thanks to its high energy recovery, regenerative systems are particularly suitable for applications with low concentrations of VOCs.
Our innovative electric thermal oxidation systems effectively destroy a variety of hazardous industrial pollutants with a destruction efficiency of over 99%.

Features and advantages of electric thermal oxidizers

  • No CO2 production from fuel.
  • No gas connection required.
  • Compact, integrated design with easy installation.
  • Possibility to fully test the system, even hot, in the workshop before shipping.
  • High VOC destruction efficiency >99%.
  • High thermal recovery efficiency and low energy consumption, even with the use of photovoltaic panels.
  • Low maintenance and very high reliability (usage rate >99%).

Plant engineering solutions

  • Turnkey supply.
  • Flexibility in choosing the heating system (burner or electrical resistor).
  • Customised design in case of space restrictions.
  • Secondary heat recovery thanks to our energy recovery solutions.
  • NOx low emission burners.
  • Quenchers and scrubbers for halogenated pollutants.

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