The direct demands of industry`s process and wastewater treatment applications over the last twenty years have accelerated the development of variable volume membrane (diaphragm) filter plate technology.
Diaphragm Filter Plates
An intensive analysis into the present-day requirements for a diaphragm filter plate in conjunction with the experience of competent users in the field preceded the development of the Klinkau diaphragm filter plate.
The three prominent requirements of diaphragm filter plate technology is to
- Increase cake solids over conventional dewatering devices
- Reduce the filtration cycle time to increase production yield
- Improve cake washing capabilities to increase product yield
The Klinkau diaphragm filter plate product line was developed to meet and exceed these requirements as well as improve other demands of the liquid / solid filtration marketplace.
The final volume of the diaphragm filter plate chamber after the squeeze cycle will vary depending on many factors such as slurry filtration characteristics, slurry feed time , slurry feed pressure, filter cake compressibility, squeeze pressure, and squeeze time, etc.
Advantages of Diaphragm Filter Plate Technology
Solid / liquid filtration can be accomplished by various techniques, such as centrifuges, rotary drum vacuum filters, belt filter presses, recessed chamber filter presses and also diaphragm filter presses.
Quite often, the final selection of a filtration method is determined by the requirement for the degree of dryness of the filter cake and the quality of the filter cake composition.
Some years ago, the results achieved on a standard recessed chamber filter press were quite acceptable until the Diaphragm filtration technology created better cake quality with higher solids content.
The two techniques - conventional recessed chamber filtration and diaphragm filtration differ in one major important point:
The final dewatered cake is a result of mechanical squeezing by the diaphragm.
In a conventional recessed chamber filter press, the filter cake is formed in layers until the chamber is completely filled with solids. As the filter cake is being formed, its permeability and flow rate decrease as the solids increase in the chamber. Intense compressible products reduce the cake permeability causing long filtration cycles and increased operating costs.
Reduced Cycle Times
The significant advantage of the diaphragm filter plate technique is that the pressure filtration phase is conducted in only the efficient stage of the filtration cycle.
The unproductive phase of the pressure filtration, where the flow rates are already greatly reduced, is replaced by squeezing with the diaphragm.
In most conventional recessed chamber filtration cycles, the majority of the cake is formed in the first half of the cycle time.
The diaphragm plate technique allows the flexibility to vary the final cake volume based upon process conditions.
Increased Cake Dry Solids
During the diaphragm squeezing cycle, the porosity of the filter cake decreases notably, so that additional dewatering occurs.
With conventional pressure filtration, the cake next to the filter cloth is drier than in the center due to uneven distribution of pressures in the filter cake.
The diaphragm squeeze technique will provide an even spread of pressure so that a homogeneous porosity is created within the cake.
The average grade of dewatering is profoundly higher with diaphragm filtration technology compared to recessed chamber filter plate filtration.
Diaphragm filter plate technology can produce final cake solids 30% to 100% greater than conventional recessed chamber filter plate filter presses.
Due to shorter filtration cycle times and increased final cake solids, the filtration process efficiency (yield) can be improved up to 100%.
Improved Cake Wash Capability
Cake wash after filtration is a major requirement in many filtration applications.
The purpose of cake washing is to displace the remaining liquid in the filter cake with another liquid (mainly water) or reduce the concentration of soluble chemicals in the solid matter of the filter cake.
The application of utilizing the diaphragm filter plate technique will provide homogeneous porosity within the filter cake.
The cake wash results are optimized by pre-squeezing the filter cake before the wash cycle has begun. The pre-squeeze step ensures a homogeneous filter cake and eliminates the potential for wash liquid flow channeling.
