Ceramic filter

 Synonyms, abbreviations and/or process names

—  High temperature filter

Removed components

—  Dust, particles

Diagram

 

 

 Process description

A ceramic filter operates on the same principles as fabric and compact filters.  The gas flow is fed into a large chamber, into which ceramic filter material is introduced.

The ceramic filter can be made of aluminium oxide, silicon oxide and silicon carbide (amongst others).

Variants 

The material can be implemented in a variety of ways. It is possible to adapt it to fabric, felt-fibre, felt, sintering elements or filter candles.

The table below provides an overview of the various types of implementation:

Filter medium

Filter fabric

Felt-fibre

Fibre elements

Sintering elements

Type

Bag with basket

Bag with support material

Tube, independent

Pipe, candle, independent

Surface weight (g/m²)

1 000 – 2 000

2 500 – 3 500

2 000 – 4 500

12 500 – 22 800

Mechanical properties

Flexible, low tear-resistance

Flexible, low tear-resistance

Half star, average tear-resistance

Tear

resistant

Air permeability

high

average

average

low

The high pressure drop in ceramic elements is reduced by using heterogenic materials such as silicon carbide grains and fibres, but primarily by using a membrane on the carrying system. A 100 – 200 µm heterogenic membrane of silicon carbide grains and ceramic fibres is fitted to the system using a silicon carbide carrying material.

Filtration systems can standardly be fitted with 16, 36, 64, 144 and 256 filter elements. These filter systems can also be placed in a series or parallel set-up.

Efficiency

Residual emissions for the various installations amounts to 1 mg/m³. 

Boundary conditions

—  Flow rate:       2 000 -500 000 Nm3/h
—  Temperature:  < 1 000°C
—  In-coming concentrations:  < 20 g/Nm3

Auxiliary materials

—  Compressed air to clean filter elements;
—  Filter medium. Life-span is determined by the set-up and type of application.

Environmental aspects

Collected substance as residue

Energy use

The energy used by ceramic filters can be compared to that used by fabric filters and is mainly determined by the cleaning system and the filter resistance.

Cost aspects

  • Investment
    — 
    30 000 to 55 000 EUR for 1 000 Nm³/h. Investment costs are linear to gas quantity, considering that costs are
          mainly determined by the filter element [1].
    —  The average cost aspects for a filter element with the dimensions 1000 mm length x 60 mm o.d. x 40 mm i.d.:
          45 EUR [5].
  • Operating costs
    — 
    Personnel costs:    ca. 2 mh/week
    —  Auxiliary and residual materials: In excess of 150 EUR per year for 1 000 Nm³/h [1]. 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
    — 
    Generally the same advantages as fabric filters;
    —  Filter candles have a high dust-separation yield;
    —  Filter candles are modularly constructed and are able to deal with high dust-loads;
    —  In contrast, fibre elements have a relatively low pressure drop, they are cheaper and have a low weight.
  • Disadvantages
    —  Filter candles require a lot of maintenance and are heavy;
    —  Fibre elements that have been woven into the fabric or felt-fibre need to be supported;
    —  Cleaning fibre elements leads to a lot of problems because dust-cake-forming is hindered at high
          temperatures, whereby it begins to swirl again when cleaned – thus becoming difficult to remove;
    —  Less suited to sticky dust;
    —  Temperature fluctuations when cleaning with compressed air;
    —  Risk of explosion in flammable dust ;
    —  Relatively high costs

 Applications

High temperature dust-removal in incineration plants and gasification systems in:

—  Coal-processing industry
—  Waste processing industry
—  Plastic processing

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