GEA Emission Control Equipment GEA SCR Plants

GEA - Leader in DeNOx

Selective catalytic reduction (SCR) is a means of converting nitrogen oxides, also referred to as nitrogen oxides (NOx). When burning coal, petroleum products, natural gas as well as domestic and hazardous waste for industrial production pollutions are created, that are emitted with off gas. Thus, significant amounts of NOx, one of the main pollutants, forms despite optimized combustion. Through the reaction of nitrogen oxides with other atmospheric constituents, ozone is created and leads to the so-called summer smog. Other reaction products such as nitric acid, reach the water and soil with the precipitation in the form of acid rain. The resulting nitrate accumulation has a negative impact on human, plants and animals. For these reasons almost all industrialized countries have adopted laws to strict nitrogen oxide emissions. GEA is a leader in DeNOx plants worldwide and develops and manufactures highly-efficient denitrification systems, individually tailored for different customer needs. Aqueous ammonia solution or urea is injected into the ductwork upstream of the SCR and evaporates immediately. Two-fluid nozzles (ammonia and compressed air) are used for the injection of the ammonia solution. A system of static mixers installed in the ductwork downstream of the ammonia injection points ensure adequate mixing of ammonia. The gas and ammonia mixture enters the unit from the top and exits horizontally at the bottom. A gas distribution system (swirl breaker) ensures adequate gas distribution over the entire cross-section of the unit. The reaction between ammonia and NOX is enhanced by the presence of the catalyst bed located at the bottom of the unit.

The reduction occurs in the presence of the catalyst at a temperature range between 250°C to 380°C (570°F to 716°F).

The main chemical reactions are: 
4 NO + 4 NH3 + O2 -> 4 N2 + 6 H2O (1)
6 NO2 + 8 NH3 -> 7 N2 + 12 H2O (2)

NOx - Removal / Flow Sheet SCR - DeNOx

GEA Bischoff SCR NOx removal Flow Sheet
GEA Bischoff SCR Plant links

Different types of catalyst modules can be selected

GEA Bischoff SCR Cat Modules
The reduction occurs in the presence of the catalyst at a temperature range between 250°C to 380° C (570°F to 716°F).The catalyst bed is cleaned in an intermittent fashion (once or more per 24 hours) with compressed air and steam. A raking arm travels slowly over the catalyst, ensuring efficient cleaning of the top surface and inside the channels.

The catalyst bed is cleaned in an intermittent fashion (once or more per 24 hours) with compressed air and steam. A raking arm travels slowly over the catalyst, ensuring efficient cleaning of the top surface and inside the channels.

The ammonia feed rate is controlled by the NOX outlet concentration of the gas. The resulting products from chemical reactions are nitrogen and water vapor, which constitute the natural components of ambient air, and can be discharged to atmosphere.  

 

Main Benefits

  • Provide highest SCR performance efficiency with minimized ammonia slip
  • Proven reliability over extended years of operation
  • Reduced overall SCR pressure drop
  • Ability to mitigate poisoning of the catalyst and extend the life of catalyst

Soot Blower System

Soot Blower System left

There are sealing profiles in order to secure low ammonia slip.

Testmodule for analyzing activity losses

Testmodule for SCR Catalytic module analyzation
These modules are developed to analyze the module life-time on a regular basis.

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SCR Plant for Cement Industry

For the reduction of the nitrogen oxide emissions from cement plants the selective non catalytic reduction process, SNCR, is usually applied by dosing of ammonia or urea at high gas temperatures. However this process is limited in terms of NOx removal efficiency and produces a fairly high ammonia emission (slip). Therefore GEA is using the advanced SCR technology with catalysts, which reduces the reaction temperature from approximately 1000°C to range of 230°C to 400°C. High reduction rates can be realized with a minimum of ammonia slip. GEA prefers the low dust arrangement.

DeNOx - Comparision of Systems

Advantages and Disadvantages of SCR-Systems

Low DdustSemi LowHigh Dust
Risk of Poisoning++--
Risk of Inkrustations++-
Frequency of Surface Cleaning+++--
Necessary Catalyzer Volume++-
Lifetime of Catalyzer++--
Spec. Investment cost--+
Spec. Operationcost++--

Low Dust Arrangement

GEA Bischoff SCR Configuration low dust arragement cement
Typical low dust SCR parameters:
Temperature250 - 275 °C
Dust load5 - 20 mg/Nm³
Catalyst openings3.5 - 5mm
Catalyst Layers / no cleaning device1 - 2

Such SCR type is in general over the life cycle (CAPEX & OPEX) favorable in comparison to other arrangements.

 

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SCR for Glass Industry

In the glass production sector, GEA provides tailor-made SCR-DeNOx plants, characterized by:

  • High efficient cleaning of deposits on top of catalyst and inside the channels of the catalyst. Top surface is completely cleaned by the rake arm traveling slowly over the complete surface.
  • Cleaning air is heated by routing the compressed air pipes trough the clean gas
  • This cleaning system is able to clean the catalyst also in emergency cases, e.g. power loss, when a higher dust load reaches the SCR.
  • GEA SCR cleaning system secures over long years high cleaning efficiency, seen in various references, resulting in a long time of the catalyst.
  • The SCR is direct after filter therefore no heating needed
  • Selection of catalyst module mainly depending on dust content of SCR inlet

For selenium glass production specific procedures have to be considered

Meanwhile first plants are equipped with high temperature ceramic filter candles with catalytic-heat-dip. GEA is already involved in such development.

However this system is not considered as state of the art, yet.

 

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Fluid Catalytic Cracking (FCC) Units in Refineries

Refineries vary by complexity; more complex refineries have more secondary conversion capability, meaning they can produce different types of petroleum products. Fluid catalytic cracking, a type of secondary unit operation, is mainly producing additional lighter oil fractions out of the crude oil. Here, GEA provides customized gas cleaning systems including specific effluent treatment.

Principal Arrangement of the Gas Cleaning System

GEA Bischoff SCR for FCC Einleitung 3
Remark: Insteat Scrubber and WESP, Dry ESP is also possible

Features of GEA SCRs for FCC

  • No catalyst fouling due to optimized inlet temperature
  • Minimized Ammonia slip / completely removed if there is a down stream scrubber
  • CAPEX and OPEX considerably lower than other DeNOx-Systems for FCC such as Ozone Generation - where additional health and safety aspects have to be considered

 

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