Temperature SCR for NOx Reduction
Selective Catalytic Reduction (SCR) is the process of NOx reduction that takes place when a NOx source is mixed with ammonia and allowed to react at the surface of the proper catalyst. The liquid ammonia quickly turns into gas, mixes with the NOx gas and the mixture then reacts at the catalyst. The result is the conversion of the mixture to nitrogen gas N2 and water vapor H2O, both harmless atmosphere constituents. The process uses aqueous ammonia, but there is no wet residue or by-product collected: all the reactants leave the system as gases.
Tri-Mer offers three NOx reduction approaches:
- Dry removal with the unique UltraCat catalyst filters for gas temperatures greater than 350°F. This technology features NOx reduction at temperatures lower than conventional Selective Catalyst Reduction (SCR), while also capturing particulate, and offers the option of removing acid gases, mercury, and dioxins. Please view our NOx Control page for more information.
- Conventional stand-alone SCR equipment. Tri-Mer offers both low temperature units that operate in the range of 350°F to 750°F and high temperature units that operation in the range of 600°F to 1100°F. For more information, see below.
- A non-SCR process, wet scrubbing with the Tri-NOx MultiChem system for applications under 350°F with special requirements. See Tri-NOx.
Catalysts are chemically formulated to allow this reaction to occur at different temperature ranges. The most commonly used catalysts require temperatures of 600°F to 1100°F to achieve high levels of effectiveness while consuming reasonable quantities of catalyst material. Tri-Mer offers SCR units in this temperature range. Yet many applications that require NOx reduction do not have gas stream temperatures high enough to make these conventional catalysts effective.
Low Temperature NOx Catalyst
Tri-Mer Corporation also offers SCR equipment that incorporates lower temperature catalysts. These catalysts operate at 350°F to 700°F. They become effective at 350°F, with efficiency climbing to 90% at temperatures higher than 400°F. Low temp SCR makes NOx reduction for boilers, incinerators, and many other applications the smart choice.
The low temperature catalyst is the same catalyst used in the unique UltraCat catalyst filters. (See: Ceramic Filters / Hot Gas Filtration) with one important difference: the catalyst in the filters is micronized powder, distributed throughout the walls of the filters. In the low-temp SCR units, the catalyst is in block form.
When would low-temp SCR be used?
NO reduction at the lower temperatures solves many difficult pollution control problems. It eliminates the need to heat the gas if the source cannot supply sufficient temperature for conventional high-temp SCRs. Many boilers, incinerators, and other sources fall into this category.
All SCR equipment must have inlet streams that are relatively free of particulate. Particulate blocks the reaction sites and can also chemically alter the catalytic reactions. Being fouled with PM is the leading cause of short catalyst life and performance failures. In the case of the UltraCat filters, the micronized catalyst is inside the walls of the filter and thus almost completely protected from particulate.
|Low-temp UltraSCR catalyst blocks.
Ceramic filters capture particulate on the outer surface, with negligible penetration to the interior of the filter media. In contrast, stand-alone low-temp SCR units must be downstream of some form of effective PM removal.
There must be a high-functioning multi-field ESP, a fabric filter baghouse (less feasible as temperatures approach 400°F), or the standard UltraTemp filter, which is effective to 1650°F. (See: Ceramic Filters / Hot Gas Filtration) In rare instances, such as natural gas combustion, PM is inherently low.
Tri-Mer Corporation offers more NOx reduction technologies than any company, worldwide. For more information, please contact: Kevin Moss, (801) 294-5422, email@example.com
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