Gypsum Dewatering Challenges discussed in the Hot Topic Hour for Thursday, January 24, 2013
Belt filters and vertical basket centrifuges were both analyzed in the Hot Topic Hour yesterday. The right choice depends on the following variables:
§ Volume of material
§ Temperature
§ Particle size distribution "PSD"
§ Concentration of gypsum in the slurry
§ Concentration of Cl- in the feed liquor
The concentration of gypsum in the slurry is a function of pre-filtration. Hydrocyclones are preferred because of the low cost and footprint, but they deliver a more dilute slurry than would a thickener.
Steve Myers, Industry Manager North America Region for Mining & Minerals at ANDRITZ Separation, compared the vertical basket centrifuges (an Andritz product subsequent to the purchase of the division from Krauss Maffei) and the belt filters (a result of the Delkor acquisition). The belt filter is generally the choice for larger installations whereas the basket centrifuge is competitive for smaller installations or where low moisture levels are needed.
Barry A. Perlmutter, President and Managing Director of BHS-Filtration, Inc, compared the new BHS rubber belt filters to the established line of indexing belt filters which are installed for dewatering at coal gasification, grey water, power plants and other critical petrochemical, chemical and mining applications. The advantage of the rubber belt system is the ability to deliver large systems (four times larger than the largest indexing filter system).
Lindy Swan of GKD-USA, Inc. explained that GKD manufactures a high performance, high durability polyester belt that is used in dewatering gypsum slurry on horizontal belt vacuum filters. A new belt design has higher efficiency and throughput and is also less expensive, so it should be considered.
Bob McIlvaine discussed the potential for natural oxidation systems which will result in a difficult to dewater slurry. The advantage is that the calcium sulfite sludge will retain large amounts of liquids. When additional lime is added to the dewatered sludge, the heavy metals are encapsulated. The product can be used for landfill. The loss of gypsum sales revenue is more than offset by the reduced investment in FGD wastewater treatment. So this approach is well suited for older and smaller power plants. The challenge for dewatering suppliers is a decanter centrifuge design which can successfully deal with this difficult sludge.
Bios, Abstracts and Photos
can be seen at:
BIOS, ABSTRACTS, PHOTOS - 1-24-13.htm
The individual presentations are as follows: