Wet dust scrubbing - general

Synonyms, abbreviations and/or process names

—  Wet dust collector
—  Scrubber
—  Dust scrubber

Removed components

—  Dust, particles: fine, sticky, hygroscopic
—  Inorganic gaseous components

Diagram

Process description

Working principle

Wet dust scrubbing is a variation on wet gas scrubbing. The two most common techniques are the venturi and rotation scrubbers. In wet dust scrubbing, the dust is separated by intensively mixing flue gases with water. For further information please refer to the relevant technique sheets.

Design data

The liquid-gas ratio (L/G) in a dust scrubber is the relationship between the volume of scrubbing liquid and the volume of gas flow. For dimensioning purposes, and to evaluate the workings of a dust scrubber, it is important to know how much liquid is required per m³ to realise the required residual emission. However, the L/G ratio is not only determined by the required residue emission, but also partly by the concentration of the to-be-removed substance(s) in the gas stream. The desired L/G relationship is thus determined by the selected scrubbing system, the properties of the to-be-cleaned gas and the requirements set for residual emissions.

Variants

Venturi scrubber (vortex scrubber), rotation scrubber, spray chamber, wet cyclone .

Efficiency

High removal yields up to 99% can be realised up to the submicron region.

Boundary conditions

—  Flow rate:           720 – 100 000 Nm3/h
—  Temperature:       4 - 370 °C
—  In-coming concentrations:    1 -115 g/Nm3

Auxiliary materials

Water and possibly auxiliary products to increase sedimentation.

Environmental aspects

Waste water must be treated or discharged into the sewer network.

Residual materials which must be dewatered and disposed of.

Energy use

Depends on variant (See specific technique sheets)

Cost aspects

  • Investment
    —  For a very basic spray washer, investment costs for a to-be-treated gas stream of 10 000 Nm³/h amount to ca.
          50 000 EUR or 5 000 EUR per 1 000 Nm3/h. For other capacities, a scale-up factor to the power of 0.3 should
          be used. [Source 1, 2, 5]
  • Operating costs
    —  Personnel costs:       ca. 0.25 mh/day (control + maintenance)
    —  Operational costs:     0.4 – 0.5 EUR per 1 000 Nm³ [5]
    —  Auxiliary and residual materials: The separated dust must be dewatered and disposed of. The water must be
          treated prior to being discharged. Transport costs for the separated dust are determined by the type of residue.

                        Inert: ca. 75 EUR/ton
                        Chemical: 150 – 250 EUR/ton

Advantages and disadvantages

  • Advantages

Depends on variant (see specific technique sheets)

  • Disadvantages

Depends on variant (see specific technique sheets)

Applications

See specific technique sheets for the concerned variants.

References

  1. Factsheets on Air-emission reduction techniques, www.infomil.nl, Infomil
  2. Common waste water and waste gas treatment and management systems in the chemical sector. BREF document, European IPPC Bureau, http://eippcb.jrc.es
  3. Elslander H., De Fré R., Geuzens P., Wevers M. (1993). Comparative evaluation of possible gas purification systems for the combustion of household waste. In: Energie & Milieu, 9
  4. Work-book on environmental measures: “Metal and electro-technical industry” (1998 ). VNG publishers
  5. Supplier information
  6. VDI 3679, Nassabscheider für partikelförmige stoffe