Crystar® FT membranes, using porous re-crystallized silicon carbide (R-SiC), have everything a liquid filtration membrane needs. They are chemically robust and withstand high corrosive solvents, such as strong acids, lye or concentrated NaOH solutions (pH 0 to pH 14), they endure high temperatures with excellent thermal shock resistance and exhibit low fouling behavior, especially to organic matter.

Thanks to these outstanding properties, Crystar® FT filters are optimal for a wide range of filtration applications, including wine and beer clarification, municipal drinking water treatment, oil and gas produced water cleaning, industrial wastewater purification, swimming pool water preparation, as well as other liquid treatment processes.

Crystar® FT membranes can withstand harsh clean in place (CIP) chemical cleaning to fully recover their initial permeability. The cleaning cycles, typically at 40° C to 80° C, can be performed with fast temperature ramp-up and cool down so as to reduce the filtration system downtime. Following cleaning, the filters are practically in an “as new” state. This results in consistent output, reduced maintenance and lower equipment and labor costs. Back flushing or backwashing with air or permeate can also be efficiently carried out thanks to very high permeability of the carrier. These intermediated cleaning operations allow extending the filtration cycles in between CIP’s.

Saint‐Gobain manufactures Crystar® FT filters via a multi‐step process where the membrane is applied onto the channel walls of a porous R-SiC carrier structure. The carrier material is extruded to form honeycombs or multi-channel tubular shapes. The tailored, multi-layer membrane on top of the carrier consists of R-SiC as well, and serves as the functional layer in the filtration process. Two configurations are available.

Crossflow filtration

Figure 1. Tubular crossflow filters are used for the clarification of wine and for the treatment of industrial effluents, among other applications. Source: Saint-Gobain Performance Ceramics & RefractoriesCrossflow filtration uses a selective porous membrane that filters highly loaded liquids for purification or clarification. Tubular crossflow filters have been used for the clarification of wine, along with the filtration of dairy, fruit juices and water, for chemical recovery and for the treatment of challenging industrial effluents.

Crossflow filtration gets its name because the majority of the feed flow travels longitudinally along the surface of the filter channels, whereas the filtered permeate flows radially through the carrier porosity. The structure of the traditional crossflow filters is tubular and consists of a carrier that is the base material, and on top of it is the filtration membrane, which is a thin, porous layer applied on the carrier.

The efficiency of crossflow filtration technology to treat highly loaded and high fouling streams, makes it widely used in industries around the globe. Crystar® FT ceramic membranes are the next generation of ceramic microfiltration.

Dead end filtration

In dead end filtration, all the water that enters the channels of the filter is pressed through the membrane. The filters developed by Saint-Gobain consist of multiple parallel channels that are alternately open and closed at the inlet and outlet faces. The water enters through the inlet channels, is filtered by a membrane with fine pores, passes through the wall of the channel and leaves the filter through the outlet channels.

Figure 2. Dead end filters have parallel channels that are alternatively open and closed. Source: Saint-Gobain Performance Ceramics & Refractories

This filtration technology is more economical than the crossflow one in terms of energy consumption. The high surface area honeycomb geometry is extremely compact. Combined with the specific properties of the R-SiC carrier and membrane, high permeate fluxes can be achieved at low operation pressures, with very good filtration efficiency for microorganisms and suspended solids. Water consumption for backwash operations is very low.

Applications include drinking water production from surface water or groundwater, swimming pool filtration and pretreatment for reverse osmosis in seawater desalination.

Summary

Saint-Gobain Performance Ceramics & Refractories manufactures recrystallized silicon carbide (R-SiC) microfiltration membranes in crossflow and dead-end configurations with several membrane pore sizes, for a wide range of demanding applications. Using advanced R-SiC membranes from Saint-Gobain significantly increased the productivity of filtration processes, reduces the equipment footprint and operating costs and decreases chemical and water usages.

For more information on Crystar® FT membranes, visit our new website, www.crystarfiltration.saint-gobain.com.