Linde Engineering North America Inc.’s Thermatrix® flameless thermal oxidizers (FTOs) provide field proven, high performance, cost-effective solutions for the destruction and removal of a wide range of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs), while generating less than 2 parts per million of nitrogen oxides (NOx). The range of FTOs handle flows from 1 standard cubic foot per minute (scfm) to more than 100,000 scfm — 1 normal cubic meters per hour (Nm3/hr) to 160,700 normal cubic meters per hour — and can be provided as standalone emission control devices through large-scale process treatment systems or process-integrated, turnkey pollution control systems.
The systems are field proven to consistently achieve VOC and HAP destruction efficiencies of 99.99 percent or greater. The unique features of the flameless reactor for fume and liquid abatement are rendering many traditional technologies obsolete because of the reactor’s environmentally friendly high performance.
Designs for Class I, Division 1 or 2 electrical standards allow for virtually unlimited flexibility in unit location. The inherent safety features and energy efficient design allow FTO systems to be integrated directly into many industrial processes and other applications, such as soil remediation, fugitive emissions disposal and as an alternative to open flares.
In the FTO process, organic compounds are oxidized in an inert ceramic bed, without flames or catalysts, into harmless carbon dioxide and water vapor or easily neutralized acid gases. While traditional flame-based thermal oxidation relies on the flame for both fume mixing and reaction, the FTO process completely decouples fume mixing from the oxidation reaction. This allows greater flexibility and control, and eliminates products of incomplete combustion. The absence of catalysts also avoids any chance of poisoning or sintering the matrix.
The matrix
A key element of the FTO process is a porous, inert matrix. This matrix fosters conditions necessary to establish a very efficient and stable reaction zone, allowing flameless oxidation of organic compounds outside their respective flammability limits. The rate of oxidation in this matrix is much faster than with traditional treatment technologies, rendering residence time a nonfactor. In contrast to catalytic oxidizers, pressure drop across the system is very low due to the high void space ratio (70 percent) in the matrix.
Using a matrix to support the oxidation reaction results in several performance, safety and process control related advantages. The three primary attributes of the matrix that promote flameless oxidation are its interstitial geometry (enhances mixing), thermal inertia (promotes stability) and surface characteristics (augments heat transfer). The thermal properties of the matrix allow the pre-reaction area, or “mixing zone,” to be near ambient temperature while the reaction zone is at the appropriate oxidation temperatures.
The properties of the matrix allow for very effective abatement of halogenated organics. Halogenated organics do not affect destruction efficiency or system life as appropriate corrosion-resistant materials are used for each application. Post-reactor acid gas scrubbing can be provided as needed.
Maximum temperatures in the reaction zone remain well below those of a flame, resulting in extremely energy efficient operation with very low formation of thermal NOx.
The process
During initial start-up of the unit, the matrix is preheated and the desired temperature profile is established. Once in profile, the preheater is completely isolated from the system and fume processing can begin. As the fume enters the ambient mixing zone of the reactor, turbulence sufficiently and completely mixes the hydrocarbons and air. The ambient mixing zone, with its large thermal mass, adds to the safety of the system by acting to prevent flashback. As the well-mixed, ambient stream moves through the matrix it is heated to oxidation temperature as it reaches the reaction zone. The matrix design forces the entire fume stream to pass through the reaction zone, which ensures complete destruction of the organic compounds and results in consistently high destruction efficiencies. Heat released by the oxidation reaction is absorbed by the matrix, providing the thermal momentum needed to maintain the process.
Emissions, which vary widely in fume flow and concentration as in batch chemical manufacturing, are ideally suited for the thermally efficient FTO process. Energy, in the form of heat, is stored in the matrix between peaks in organic loading. This buffering capability enables the system to efficiently process fume on very short notice without additional energy input. For intermittent operations, such as those which shut down overnight or on weekends, air flow through the insulated reactor is significantly reduced to help maintain appropriate temperature profile. This operational stand-by, or “ready idle” mode, greatly reduces operating costs and prolongs system life by minimizing thermal cycling.
Control of the FTO is easy and straightforward. The same thermal inertia that buffers system reaction to fluctuating process conditions also provides ample response time to control the reaction. Process control components maintain desired operating temperatures by managing the heating value of the incoming fume. For organic rich or oxygen deficient streams, dilution air is mixed with the fume to maintain the matrix at desired operating temperatures. For lean fume streams, supplemental energy is added to maintain the oxidation reaction. The typical process control scheme is a simple temperature loop controlling the addition of air or fuel to the incoming fume stream.
The GH FTO
The reactor is made up of a refractory lined vessel with a centered inlet dip tube. The ellipsoidal geometry of the reaction zone results in the efficient use of reactor volume. The GH FTO can treat 500 scfm to more than 100,000 scfm of fume (670 to 135,000 Nm3/hr) and is particularly well suited to treatment of halogenated fume. Multiple GH units can be configured in parallel.
The ES-100 FTO
The Thermatrix ES-100 FTO is electrically preheated and consists of a carbon steel, refractory-lined oxidation vessel. The vessel contains three electric resistance heater elements surrounded by the ceramic bed. Fume entering the bottom of the ES-100 is distributed evenly across the bed by a fume distributor.
The ES-100 is offered as a complete, preassembled and compact skid-mounted unit with a footprint of 5 feet by 6 feet with the stack exhausting approximately 15 feet above the oxidizer. The ES-100 meets Class I Division 2 Group D requirements and can be easily adapted to meet Zone I Class IIB T3 requirements. Its simplicity and portability make it a versatile piece of equipment for operation at remote locations near the fume source. The ES-100 is relatively easy to permit and requires minimal time to install and place into operation.
The ES-100 FTO can treat up to 90 scfm (125 Nm3/hr) of fume having 0 to 20 Btu/scf heat content or up to 140 scfm (200 Nm3/hr) of fume having 20 to 40 Btu/scf heat content. Multiple ES-100s can be configured in parallel.
For more information, visit www.lindeus-engineering.com or call (610) 834-0300.
FTO features
• 99.99 percent or greater destruction of efficiency including halogenated organics
• Low nitrogen oxide — less than 2 parts per million
• Undetectable carbon monoxide emissions
• Dioxins and furans emission — less than 0.1 nanograms per normal meter toxicity equivalence
• Destructive process produces no secondary organic waste stream
• Flameless — can be installed in classified areas near the emission source
• Operates below the lower explosive limit
• Stable operation when responding to variable organic loading
• Matrix design prevents potential flashback to process
• Matrix is completely inert — no catalyst to foul
• No internal moving parts or diverting valves
• Integrated microprocessor control
• Treats batch or continuous streams
• Energy efficient operation — self sustaining down to 10 Btu per cubic foot
• Superior turndown capability — reduces operating costs
• Easily permitted
• Energy recovery available
• Can be integrated with acid recovery
