Ceramitec has more than met LIPPERT’S expectations.

LIPPERT enjoyed record visitor attendance during the trade show, one some days even requiring extra staff to man the stand. Many contacts were established with po-tential new customers.

One of LIPPERT’S highlights to captivate visitor interest was the innovative universal dip glazing machine for hollowware and flatware with a glazing capacity of 1,600 cups per hour. The machine features article dipping via two numerically controlled axes and fully automated machine loading and unloading.

Another of LIPPERT’S trade show exhibits, a pilot test drying chamber operable with additional microwave support, was met with equally keen interest, especially by manufacturers of sanitary ware and technical ceramics. This pilot test drying chamber allows users to establish drying curves for later transfer to their large production plants.

Another novelty received with visitor enthusiasm was LIPPERT’S innovative new drying system with automated loading and unloading system for the drying pallets. This system is suitable both for tableware and decorative ceramics as well as for technical ceramics.

Ceramitec has more than met LIPPERT’S expectations.

[2009-11-09; 09.00 AM]

Three Case Studies for Rotary Filtration

• Processing of return slip from casting benches
• Glaze overspray from spray booths
• Rinsing water from pressure-casting plants

1. Microfiltration – Cross Flow Filtration:
Microfiltration can be classed as a dynamic filtration process for the separation of a medium (suspension).
Filtration is a mechanical separation process.
Separation is based on the principle of mechanical size exclusion (principle of filtration), i. e. all particles contained in the fluids that are bigger than the pores of the membrane are retained by the membrane.

Driving force in both separating processes is the differential pressure between the flow to and from the filter surface, which ranges between 0.1 and 3 bar. The filter surface material is made of ceramic.

A distinction is made between micro- and ultrafiltration depending on the different pore sizes and membrane structure, as well as on the substances and filter materials involved. Filtration through membranes with a pore size < 0.1 µm is generally termed ultrafiltration, while filtration at pore sizes > 0.1 µm is usually referred to as microfiltration.
A filtered liquid is termed filtrate.
In contrast to static filtration methods, cross-flow filtration systems are capable of clarifying liquids with a relatively high turbid content. This is achieved by applying a cross-flow of around 2.5 to 3 m/sec. to the membrane, which prevents deposition of turbid particles and fast clogging or binding of the membrane (build-up of filter cake).


2. Lippert Rotary Filter

2.1. Description of the Process Sequence:
In the filter unit, ceramic filter disks are threaded onto a hollow shaft.
If the pressure chamber is now set to differential pressure (1 to max. 3 bar), the filtration process begins.
The filtrate "flows" from the outside through the filter disks and via the hollow shaft to be discharged into a filtrate collector tank.

By selection of the appropriate filter fineness, certain particle sizes are retained and conveyed into the waste-water collector tank.
From the waste-water tank, the thickened liquid is fed back to the filtration process. The system operates in a closed circuit.

To prevent the build-up of filter cake on the filter surface, the filter disks are rotated and any particles simply flung off.

With the backwash unit, the filter unit is flushed with water.

The rotary filter is based on a modular design, so that it can be simply adapted to different applications.


Image 1, flow chart


3. Typical Applications

3.1. Slip Processing at Casting
To clean casting bench pipes at set intervals, these are flushed with water. On account of the low sediment load, processing of the residual slip contained has so far been a very complex process.
The sediment load can be precipitated in a settling basin. The water is siphoned off and the sediment must be removed at certain intervals.
Filter press operation is limited in respect of processing slip water with a low sediment load (1.05 kg/dm³) and is very work-intensive.
With the rotary filter, the backwash water with a density of around 1.1 kg/dm³ can be used directly, thickened to around 1.4 kg/dm³.

Advantages:

• automatic process flow
• dissolved sulphates are filtered out with the water
• limited space requirement

• automatic process flow
• total particle fraction is preserved
• limited space requirement

Image 4, densification of glaze-overspray


3.2.1. Test results
In this case, a filter with 2.5 m² filtering area was used for processing the glaze.

With around 180 min, 1.150 l glaze suspension with a density of 1.07 kg/dm³ could be concentrated to a density of 1.62 kg/dm³.
The volume of the glaze with a density of 1.62 kg/dm³ totalled 250l

With this filter, a total daily quantity of approx. 6 m³ glaze suspension can be processed. The recovered glaze totals around 1.9 m³ with a density of around 1.6 kg/dm³.
(Rates must be verified in specific cases. See the start and final density of the glaze listed below)


Image 5, results


3.3. Processing of Rinsing Water in Pressure Casting Plants
After every press cycle, the pressure casting moulds are rinsed with water.
For deep cleaning of the mould, mould cleaning agent is added to the rinsing water at certain intervals, with the aim of increasing mould lifetime.

Based on a water consumption of around 200 l/h for sanitary ware moulds, a water consumption of approx. 5 m³/pressure casting bench per day can be assumed.

Advantages:

• automatic process flow
• uniform water quality
• closed circuit operation, no water consumption
• limited space requirement

3.3.1. Test results
With the use of the rotary filter, the water quality remained unchanged over the entire process duration.
The additives in the rinsing water were recirculated in a closed circuit (reduction of the mould cleaning agents used).
Additionally improved plant safety, as in an incident involving hydraulic oil, the oil could be kept separate from the filter medium and did not contaminate the rinsing water circuit.
With the use of a 2.5-m²-filter, a filter rate of around 500 l/h can be assumed for design purposes.
Based on the consumption values listed above, the rotary filter with 2.5-m² filter area is suitable for treatment of the rinsing water from two pressure casting benches.

4. Final Conclusion
The rotary filter presents a cost-and-energy-efficient solution for the ceramics industry.
Applications with aim of recovering valuable substances such as glaze or slip have previously been very work-intensive.
With cross-flow filtration, payback periods of less than two years can be realized in individual cases.
Owing to higher requirements with regard to abrasion, selection of the filter technology is crucial for the lifetime of the system.

With the use of ceramic filter disks, it is possible to uncouple the differential pressure and overflow rate.

This reduces the wear and is reflected in the long lifetime of the rotary filter.