Rotation scrubber

Synonyms, abbreviations and/or process names

—  Rundnassentstauber
—  Rotationnassabscheider
—  Nassventilator-Kolonnenwäscher
—  Dynamic scrubber

Removed components

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

Diagram

 

 

Process description

The rotation scrubber is a specific type of dust scrubber. In rotation scrubbers the scrubbing liquid is, via a fast-rotating injection device or rotating sprayer, injected or distributed in small droplets whereby a large contact area is created between droplets and gas. The gas is passed through the cleaning chamber tangentially. Due to centrifugal forces and the rotating sprayer, the particles are pushed to the walls of the scrubber, which means a high separation yield is possible. The separated dust must be dewatered and disposed of.

Variants 

In a “Dynamic scrubber” and “Nassventilator-Kolonnenwäscher” the gas is inputted tangentially at the bottom of the column, whereby rough separation takes place. In the second phase, the gas is made to follow a particular route, which brings it into contact with downward-flowing slurry originating from the next phase. In the third phase, water is injected over the blades of the ventilator, thus creating fine droplets. These droplets bind with the fine particles and stick to the wall, thus creating a slurry that flows downwards.

Efficiency

Depending on the implementation, high removal yields up to 99% can be realised up to the submicron region.

Rotation scrubbers are able to remove particles up to 0.1 µm. Dust particles larger than 1-2 µm are almost completely separated.

Boundary conditions

—  Flow rate:       1,000 -50,000 Nm3/h
—  Temperature:   < 200 °C depending on implementation
—  In-coming concentrations:          a few 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 products which must be dewatered and disposed of.

Energy use

Energy use varies from ca. 2.7 kWh per 1 000 m3 [5]

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. [1, 2, 5]
  • Operating costs
    — 
    Personnel costs:    ca. 0.25 mh/day
    —  Operational costs:  0.4 – 0.5 EUR per 1000 Nm³
    —  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
    — 
    No blockage or fouling of the wash section
    —  Wash water can be re-circulated without risk of blockage
    —  The scrubber has a low pressure drop
    —  Can be used for sticky, explosive and flammable dust
    —  Very high yield, also for sub-micron particles
    —  Able to deal with fluctuating gas flows
    —  Self-cleaning
  •  Disadvantages
    —  The presence of moving parts in the washing section could lead to high maintenance costs
    —  Relatively high energy use
    —  Relatively high investment costs

 Applications

Rotation scrubbers are used when high particle retention is desired, particularly for very small particles encountered in, for example, incinerators for process waste.

Rotation scrubbers are used in a variety of settings, including:

—  The chemical industry, to separate particles and aerosols;
—  The metal industry for various types of waste gases;
—  Waste incineration installations;
—  Gasification processes;
—  Potato-processing industry for the removal of starch;
—  Glass industry;
—  Melting processes in metallurgy;
—  Foundries;
—  Sintering processes;
—  Drying processes;
—  Fertiliser production;
—  Pharmaceutical industry;
—  Plastics industry.

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