Flameless Regenerative Thermal Oxidizer | full electric • e-RTO™ series

Flameless Regenerative Thermal Oxidizers, full electric
DEC.e-RTO™

Flameless Regenerative Thermal Oxidizers (DEC.e-RTO™) are a specific "full electric" (electrified) configuration of a Regenerative Thermal Oxidizer system (RTO™): in the RTO, multiple towers (or chambers) are used to achieve efficient and effective air pollution control. RTOs are widely used in industries such as manufacturing, printing, and chemical processing to comply with environmental regulations and reduce air pollution.

The flameless DEC.e-RTO™ operates on a similar principle to its combustion-based counterpart RTO™, but without the use of an open flame and auxiliary support fossil fuel. Instead, electric heating elements provide the thermal auxiliary energy required to oxidize contaminants (VOCs).

As per the standard Regenerative Thermal Oxidizer system (RTO™), typically two or more towers (ideally 3 or more) are utilized in parallel: the exhaust gas flow is alternated between these towers, allowing for continuous operation; while one tower is used for the oxidation and removal of pollutants, the other tower(s) are undergoing a regeneration cycle to prepare for the next exhaust gas flow.

how it works? • DEC.e-RTO™

Inlet Phase: the contaminated air stream enters the RTO through an inlet duct, and a damper directs the flow into one of the ceramic honeycomb beds.

Preheating Phase: the incoming air passes through the heated ceramic channels (honeycomb), where the thermal energy from the hot exhaust gases is transferred to the incoming air stream. This preheating step helps in reducing the energy consumption of the system.

Combustion Phase: the preheated air stream enters the combustion chamber, where it is further heated to the required temperature (typically between 815°C and 980°C), through electric heater(s); in the presence of oxygen, the VOCs and other pollutants in the air stream undergo combustion, converting them into carbon dioxide (CO₂) and water vapor (H₂O).

Exhaust Phase: the hot, purified air stream exits the combustion chamber and passes through the outlet duct; at the same time, a damper directs the flow into another ceramic honeycomb bed.

Thermal Energy Recovery: the incoming air stream absorbs the thermal energy stored in the ceramic honeycomb bed, which helps in preheating the next batch of contaminated air; this heat exchange process is crucial for the high energy efficiency of RTOs.

This alternating process allows for energy recovery within the DEC.e-RTO™ system: the hot exhaust gases leaving the combustion chamber are passed through a ceramic heat exchanger, known as the "regenerator", in the tower undergoing the regeneration cycle. The regenerator absorbs the heat from the exhaust gases and stores it. During the next cycle, the stored heat is transferred to the incoming cold exhaust gases, reducing the energy consumption of the system.

The use of multiple towers in the DEC.e-RTO™ system provides several advantages, including improved operational efficiency, reduced energy consumption, and continuous operation. It allows for a safe, consistent and reliable treatment of industrial exhaust gases, while optimizing the use of energy resources.

oxidation reaction • DEC.e-RTO™

The oxidation reaction is:

VOCs (C_xH_yO_z) + O₂ + thermal energy = CO₂ + H₂O + (HEAT)

The heat is usually recovered to pre-heat the SLA stream, in order to save on "thermal energy"; if producing extra heat through oxidation of solvents, an energy recovery system (DEC.WHR™) shall be foreseen (typical applications are ranging from heating up air for dryers, steam production, heat tranfer fluid heating, water heating - industrial or sanitary, etc.).

advantages • DEC.e-RTO™

In a regenerative electric thermal oxidizer (e-RTO) with multiple towers, the VOCs are oxidized in the combustion chamber. The hot gas released from the combustion chamber contains thermal energy. This thermal energy is accumulated through the ceramic media bed in one tower. The hot gas then cools down as it exchanges thermal energy with the ceramic media. The cooled gas is then discharged through the stack.

e-RTOs are not equipped with a gas burner: electric heaters are a clean source of heat, producing no thermal NOx and negligible CO generation. This is a significant advantage over gas-fired systems, especially in areas with strict emissions regulations.

The process of accumulating and exchanging thermal energy in the ceramic media bed is called regenerative: this process allows the RTO to operate at a high efficiency, while also reducing the amount of energy required to heat the incoming gas.

Thanks to the specifically designed switching valves, the flow is alternatively reversed: thermal energy is recovered and the flow, in the following cycle, is pre-heated; this cycle is efficiently reducing the auxiliary heat requirement, with self-sustaining operation (with no auxiliary electricity usage) even at low concentrations, thus representing an operational cost reduction.

e-RTOs with multiple towers can operate at a higher efficiency than Direct Thermal Oxidizers (DTO™): the regenerative process allows the RTO to recover heat from the outgoing gas, which can then be used to pre-heat the incoming gas, resulting in lower energy consumptions.

e-RTOs often have a smaller footprint compared to standard RTOs, gas-fired systems.

Hot Gas Bypass module | DEC.HGB™ • DEC.e-RTO™

In case of peaks of concentration, in order for the RTO to correctly perform its duties, to prevent overheating (or oxidation to occur in the ceramic media), the system can be equipped of an automatic hot-gas bypass. The DEC.HGB™ diverts a portion of the hot gases directly from the combustion chamber, bypassing the ceramic media beds.

As the concentration of volatile organic compounds (VOCs) in the incoming stream increases, the combustion chamber temperature rises due to the additional heat generated by the combustion process. When the temperature reaches a pre-set safety limit, the DEC.HGB™ module is automatically enabled, allowing a portion of the hot exhaust gases, to directly bypass the ceramic media beds and exit to the exhaust stack (FGS). By diverting the hot gases, the DEC.HGB™ module safeguards the ceramic media from exposure to excessively high temperatures. This is crucial because the media plays a vital role in preheating the incoming air stream and maintaining the overall efficiency of the RTO.

The DEC.HGB™ components directly exposed to the high-temperature exhaust gases (around 900°C) are typically constructed from special high-grade materials like Stainless Steel or Inconel.

In essence, the DEC.HGB™ module acts as a safety mechanism and a way to optimize RTO performance. It prevents damage to the ceramic media while ensuring the RTO can continue to function effectively even during abnormal or unexpected spikes in VOC concentration.

Waste Heat Recovery module | DEC.WHR™ • DEC.e-RTO™

When the process conditions allows (e.g. when VOC in the emission stream reaches higher than normal), and the DEC.HGB™ module is installed, the diverted hot stream, can be used for beneficial purposes. DEC.WHR™ module acts as a secondary heat recovery.

DEC.WHR™ secondary heat recovery provides additional energy saving:

heating thermal oil for industrial processes;

heating water for various applications;

recovering heat to generate steam;

recovering heat to generate electricity.

By utilizing this waste heat, the facility may further reduce its reliance on traditional fuel sources like natural gas or propane. The specific application chosen will depend on factors like the facility's existing needs and the temperature of the recovered heat stream. This could translate to significant cost savings on the energy bill, leading to a more competitive operating cost structure.

DEC.WHR™ essentially allows the RTO to operate with a "closed-loop" approach for thermal energy. This reduces the overall energy demand of the system, making it more efficient. A more efficient system translates to lower operating costs and a smaller environmental footprint.

Overall, waste heat recovery in RTOs offers a compelling solution for manufacturing facilities. It lowers operating costs, enhances efficiency, improves sustainability, and even offers potential revenue generation opportunities. These combined benefits can significantly improve a facility's competitive advantage in today's market.

Waste To Energy module | DEC.WTE™ • DEC.e-RTO™

By utilizing the solvent waste as fuel in the RTO, the system requires less external fuel to maintain the oxidation temperature. Instead of paying for solvent waste disposal, the facility can utilize it as a fuel source, potentially creating a cost-saving opportunity.

thermal oxidation | incinerators • GHG and by-products

Whenever you have to face a non-recoverable stream of VOCs, a XTO™ • thermal oxidizer could be the solution: sometimes the VOC stream composition may result too complex to be recovered or the quantity of solvents is not interesting to go for a SRU™ • solvent recovery units.

An oxidizer is handling the transformation of the pollutant(s) into different products, with a reduced environmental impact. However, it is important to consider the resulting GHG emissions, when selecting a VOC oxidizer; the amount of GHGs generated by a thermal oxidizer depends on the type of VOCs being treated, its quantity, the needed quantity of fuel to be added for sustaining the oxidation reaction and the selected oxidizer process configuration.

Any oxidizer will have to deal with all or most of the following issues:

VOCs emission (= non complete oxidation);

CO₂ emission (= GHG, possible taxation);

CO emission (= GHG, non complete oxidation);

NO_x emission (= nitrogen oxides, as a result of N₂ presence);

N₂O emission (= nitrous oxide);

Dioxin emission (as a result of possible chlorinated compounds );

High temperature emission (as a result of non complete thermal energy recovery).

These emissions contribute to climate change and should be taken into account when assessing the overall environmental impact of the system.

As mentioned earlier, oxidizers typically require a significant amount of energy to operate: if this energy comes from non-renewable or carbon-intensive sources, it will dramatically contribute to environmental degradation and offset any of the potential benefits of VOC emission reduction.

thermal oxidation | incinerators • greenwashing

Greenwashing will occur when a company promotes an oxidizer as an environmentally friendly or sustainable technology for VOC emissions control, while neglecting to address other significant negative aspects of its environmental impact, such as greenhouse gas (GHG) emissions and harmful by-products.

Greenwashing can happen when a company portrays an oxidizer as a comprehensive and eco-friendly solution to VOC emissions, creating the perception that it is a sustainable option without considering the complete environmental picture. While oxidizers can help reduce VOC emissions, they can have negative consequences that should not be overlooked.

To avoid greenwashing, companies shall provide transparent and comprehensive information about the environmental impact of their VOC emission control systems: this includes addressing greenhouse gas (GHG) emissions, harmful by-products, and the energy efficiency of the system. By doing so, companies can ensure that consumers have an accurate understanding of the technology's environmental implications and make informed decisions.

Thermal oxidizer, Thermal incinerator, Oxidation equipment, Regenerative thermal oxidizer, Catalytic oxidizer, Recuperative thermal oxidizer, GHG, CO2, NOx, CO, N2O, direct-fired thermal oxidizer, Afterburner, Air pollution control, Industrial exhaust treatment, Volatile organic compounds (VOCs), Hazardous air pollutants (HAPs)