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Procedure

Graphic overview of downstream processes for exhaust air purification. Divided into two main categories: Decomposition with biological oxidation and thermal oxidation - as well as separation with SIMASOLVENT, condensation, adsorption and absorption.

Procedure at a glance

The exhaust air purification processes downstream of paint shops or painting processes can generally be divided into 2 groups. On the one hand, those in which the pollutants are decomposed and thus destroyed and, on the other hand, those processes in which the pollutants are separated and thus removed from the exhaust air unchanged in their chemical structure.

  • Biological oxidation

    Decomposition of pollutants through metabolism of microorganisms


    Biofiltration

    Microorganisms are located on a fixed bed which is exposed to the exhaust air.

    • Main area of application: Odor reduction
    • Suitable for VOC load: up to 1gC/Nm³
    • OC separation efficiency: up to 99
    • Suitable for exhaust air volume flow: up to 100,000 Nm³/h


    ADVANTAGE

    • Low energy requirement
    • No additional emissions
    • High efficiency


    DISADVANTAGE

    • constant supply of nutrients
    • VOCs must be biodegradable
    • Conditioning of the scrubbing liquid necessary (pH value)

    Bioscrubber

    Microorganisms are in an aqueous phase. The VOCs are absorbed into the aqueous phase and can thus be broken down.

    • Main area of application: odor reduction
    • Suitable for VOC loads: up to 5gC/Nm³
    • OC separation efficiency: up to 97
    • Suitable for exhaust air volume flow: up to 100,000 Nm³/h


    ADVANTAGE

    • Low energy requirement
    • No additional emissions
    • High efficiency

    DISADVANTAGE

    • constant supply
    • VOCs must be biodegradable
    • exhaust air conditioning may be necessary before cleaning

     

  • Thermal post-combustion (TNV)

    Combustion, i.e. oxidation of the VOCs in a combustion chamber with a supply of fuel or self-burning (autothermal)

    Possibility of heat recovery by preheating the exhaust air flow using recuperative heat exchangers and downstream heat exchangers for water heating.

    • Main area of application: Reduction of VOC emissions
    • Suitable for VOC load: above 1 gC/Nm³
    • VOC separation efficiency: up to 99.8%
    • Suitable for exhaust air volume flow: up to 100,000 Nm³/h


    ADVANTAGE

    • Wide range of applications
    • Fast start-up possible
    • Autothermal operation possible


    DISADVANTAGE

    • high primary energy requirement (compared with RNV)
    • low thermal efficiency (compared with RNV)
    • additional CO, CO2, NOx emissions (post-treatment may be necessary)

     

  • Regenerative afterburning (RNV)

    Combustion, i.e. oxidation of the VOCs in a combustion chamber with fuel supply or self-combustion (autothermal)

    Possibility of heat recovery by preheating the exhaust air flow using recuperative heat exchangers

    • Main area of application: Reduction of VOC emissions
    • Suitable for VOC load: 1-10 gC/Nm³
    • OC separation efficiency: up to 99.8%
    • Suitable for exhaust air volume flow: up to 100,000 Nm³/h


    ADVANTAGE

    • High thermal efficiency (compared with TNV)
    • Autothermal operation possible (concentrations above 1-2 gC/Nm³)
    • Wide range of applications


    DISADVANTAGE

    • only for continuous operation (thermal inertia of the storage tank)
    • additional CO, CO2, NOx emissions (post-treatment may be necessary)

     

  • Catalytic post-combustion (KNV)

    Combustion, i.e. oxidation of the pollutants in a catalytic converter with the addition of fuel or self-combusting (autothermal); fuel consumption can be reduced by using a catalytic converter

    Possibility of heat recovery by preheating the exhaust air flow using recuperative heat exchangers

    • Main area of application: Reduction of VOC emissions
    • Suitable for VOC loading: up to 5 gC/Nm³
    • VOC separation efficiency: up to 99.8%
    • Suitable for exhaust air volume flow: up to 100,000 Nm³/h


    ADVANTAGE

    • Lower NOx emissions (compared with TNV & RNV)
    • Autothermal operation possible (concentrations above 1-3 gC/Nm³)


    DISADVANTAGE

    • limited area of application (catalyst poisons)
    • additional CO and CO2 emissions (post-treatment may be necessary)
    • high investment costs for catalysts

     

  • Adsorption

    Accumulation or deposition of pollutants on solid interfaces (e.g. activated carbon); use of disposable carbon (subsequent disposal), or regeneration for multiple use possible

    Adsorbent: Exhaust air flows through a bed of activated carbon, for example, causing VOCs to accumulate in the activated carbon

    • Main area of application: Reduction of VOC emissions; concentration for downstream cleaning processes
    • Suitable for VOC loading: up to 20 gC/Nm³
    • VOC separation efficiency: up to 99
    • Suitable for exhaust air volume flow: up to 100,000 Nm³/h


    ADVANTAGE

    • Low energy requirement
    • No additional emissions
    • Buffer function, therefore suitable for fluctuating concentrations
    • Recovery of VOCs possible


    DISADVANTAGE

    • limited applicability (adsorption capacity of VOCs)
    • Additional energy requirement for possible regeneration
    • Replacement of the adsorbent (even with regenerable adsorbent)

     

     

  • Absorption

    Absorption of the pollutant in a liquid carrier medium; subsequent expulsion of the VOCs by thermal treatment of the carrier medium

    • Main area of application: Reduction of VOC emissions; recovery of expensive solvents
    • Suitable for VOC loading: up to 50 gC/Nm³
    • VOC separation efficiency: up to 98
    • Suitable for exhaust air volume flow: up to 100,000 Nm³/h


    ADVANTAGE

    • No additional emissions
    • Recovery of VOCs possible


    DISADVANTAGE

    • Limited applicability (VOCs must be soluble)
    • complex system technology and handling
    • additional energy required for regeneration

     

  • Condensation

    Condensation of VOCs by cooling the exhaust air

    Exhaust air is cooled by a cooling unit in a cooling coil until VOCs condense

    • Main area of application: Reduction of VOC emissions; recovery of expensive solvents
    • Suitable for VOC load: above 5 gC/Nm³
    • VOC separation efficiency: up to 98
    • Suitable for exhaust air volume flow: up to 5,000 Nm³/h


    ADVANTAGE

    • No additional emissions
    • Recovery of VOCs possible


    DISADVANTAGE

    • Selective condensation often not possible
    • High concentration necessary
    • additional energy requirement for cooling unit

     

SIMAKA Energy and Environmental Technology GmbH

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