Ceramic Filters

Description

Caldo ceramic filters are high temperature devices for the continuous removal of particulates from air or other gases. Caldo supply a range of filter sizes and for larger gas flows employ a modular approach, combining several vessels of proven design to achieve the required capacity. The addition of sorbent powder enables the filters to function as dry scrubbers in waste gas applications.

Ceramic Filter Elements

Ceramic filters are distinguished from other hot gas filters because the filtration medium is made in a ceramic material. There are two types of ceramic filter elements: high density, which are based on alumina or silicon carbide granules; and low density, which are based on alumino-silicate or mineral wool fibres. Caldo ceramic filters use only low density alumino-silicate elements.

Stable in Hot and Corrosive Conditions

The ceramic filter element is vacuum formed from alumino-silicate ceramic fibres as a 1000mm long tube, flanged at one end and closed at the other. Its composition is stable under extreme conditions of temperature and/or chemical corrosion. The element can withstand a temperature of 900 degC, but if the housing is fabricated in mild steel the filter operating temperature is limited to 425 degC. Stainless steel construction allows higher temperatures, albeit at a cost. The elements can resist all chemical attack with the exception of HF.

Filter Design

The elements hang vertically in the filter vessel from the header plate, which separates the clean and dirty compartments. The upper photo shows a bank of newly installed filter elements, looking up from below. In use the hot gas is sucked through the filter medium from outside to inside, depositing the particles on the outer surface of the medium. At controllable intervals a sharp pulse of gas is blown back down the inside of the filter element causing a momentary reversal of flow. This reversal causes the accumulated solids to be detached from the outer surface of the filter elements. The solids fall into the hopper section of the vessel from where they may be discharged. The lower photo shows filter elements that have just been cleaned - it can be seen that the cake has detached in patches.

The capacity of the filter is determined by the number of filter elements contained in the filter vessel. Caldo has proven standard designs for a comprehensive range of filter capacities. If the largest filter design is not big enough, 2 or more vessels may be installed in parallel. The photo of the unit fitted to an animal carcase incinerator shows 6 x 256-element vessels.

Data Sheets

Data sheets about ceramic filters, ceramic filter elements, reverse pulse cleaning and other topics are available for downloading on the download page.