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Sorption Processes

Kuttner North America and Luehr Filter are world leaders in the design and supply of state of the art fabric filters with sorption and catalytic technologies for capture of gaseous pollutants along with the particulates.  Gaseous pollutants include, but are not limited to SO2, SO3, HF, HCl, as well as more problematic compounds such as mercury, heavy metals, dioxins and furans.  Luehr Filter technologies have set standards for emissions control together with lowest possible additive consumption rates.  Depending on the target pollutant(s) and required efficiencies, dry or semi-dry sorption techniques can be utilized in single-stage or multi-stage pollution control processes.  Control of NOx via a catalyst system can be combined with the highly efficient sorption processes.

Achieve highest possible emission reduction with Luehr Filter's conditioned particle recirculation (semi-dry scrubbing).

Gaseous Pollutants, SOx, and Acid Gases

Calcium or sodium based additive powders (hydrated lime, sodium bicarbonate, or Trona) are used to control pollutants in the gaseous state.  Additive powders are injected into the dirty exhaust gases along with dust recycled (recirculated) from the fabric filter.  Extremely high efficiency demands are needed from the filter as dust recycling (recirculation) rates of up to x50 can result in extremely high dust loadings into the filter.


High control efficiency for gaseous compounds can only be achieved by three conditions:

  • The reaction time between additive particle and pollutant is increased.

  • Contact between gas molecules and additive particles occurs.

  • Sufficiently thick filter cake, with additive particles, is retained on fabric surface of the filter.

CFD modeling for operation of quench / evaporative cooling tower to optimize temperature upstream of sorption stages

The Luehr Filter dust recycling (particle recirculation) process optimizes all three conditions with a robust mechanical system with extremely high reliability rate.  The combination of flue gas conditioning, additive injection, Conditioning Rotor, reaction chamber, flat-bag filter and particle recirculation has decades of proven performance.  Through the Luehr Filter programs of research & development and continuous improvement, these technologies are constantly challenged to achieve higher levels of performance and reliability while at the same time with reducing additive consumption rates and operating costs.

Mercury (HG) Control

Luehr Filter is a worldwide leader in baghouse design and supply for removal of Hg and gaseous pollutants.

The key factors for efficient and effective Hg control include:

  • Physical contact between Hg and the AC

  • Retention time for the chemical / physical reaction time between the Hg and AC

  • Maximize the usage of the injected AC

  • High collection efficiency

The unique Luehr Filter design incorporates all of these factors - resulting in highly efficient capture of Hg, while minimizing AC injection rates.

Luehr Filter Double-Shaft Mixer system for highest possible emission control efficiency
Luehr Filter Conditioning Rotor system for highest possible emission control efficiency
Dry Sorbent Injection systems (DSI) for introduction additive powders into the flue gases

Dioxins / Furans

Current permit limits for dioxins and furans are measured in nano-grams or pilo-grams.  To achieve such low levels of control, plants must have extremely effective mixing between activated carbon and the exhaust gas and an extremely efficient fabric filter.  Luehr Filter systems are successfully controlling dioxins / furans emissions for the following industries: 

  • Domestic waste incineration

  • Hazardous and sludge waste incineration

  • Secondary aluminum smelting

  • Sintering plants

NOx Control with Selective Catalytic Reduction (SCR)

When NOx reduction requirements are beyond capacity of an SNCR, use of a catalyst system is required.  The Luehr Filter SCR system can be implemented as a stage of the flue-gas treatment process. 


Advantages of the Luehr Filter SCR systems include:

  • Low risk of catalyst poisoning by SOx as the catalyst is downstream of the highly efficient particle recirculation process such that acids are neutralized before reaching the catalyst elements.

  • High catalyst surface area with honeycomb is downstream of the filter stage such that there is no risk of dust blinding.

  • Possible integration of an economizer, Luehr flat-tube heat exchanger, or other heat exchanger, to raise temperature of the flue gas for higher increased control efficiency.

Highest level of NOx control with SCR technology from Luehr Filter
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