Pre-coat filter

Alluvial filtration

Technical

presentation of

a continuous trickling filter

1. Bell
2. Filtering plate||
3. Cake discharge opening
4. Motor for plate rotation
5. Filtering plate washing ramp
6. External residual filtration element (depending on model)
7. Dosing pump for filtering aid
8. Mixing tank for filtering aid, with agitator
9. Main feed pump
10. Flow indicator
11. By-pass

1. |

Main elements

The bell

The filter plates

Tray construction

• :
• a wide-mesh metal frame to support the filtration fabric and drain the filtrate.
• a stainless steel wire or reps fabric. The fabric pore diameters currently encountered are generally between 50 and 120 µm.

Horizontal platforms

Maillaige

reps |

The mixing tank

The feed pump

The dosing pump

The by-pass

The different alluvial filters

Horizontal bell and vertical plate filters

Vertical bell and horizontal plate filters

Alluvial plate filters with hollow frames

Candle filters

Precoat

• :
• To ensure instant clarification
• To facilitate the debatizing of the filter cake

• :
• In all cases, the adjuvant, deposited directly on the substrate, must have a permeability greater than or equal to 1 darcie.
• Never use fine kieselguhr (pink diatomaceous earth) directly, as it is difficult to attach and some of its very fine particles could pass through the support during filtration.
• Use a clear product (water or already filtered wine) to avoid clogging too quickly and to ensure a good cycle length.
• The flow rate through the filter should always be as high as possible (1.5 to 2 times the filtration flow rate) to ensure that the additive is evenly distributed over all the plates.
• Generally speaking, the minimum quantity of filtering agent for the precoat should be 1 kg/m² (up to 2 kg/m² may be used).
• In the case of a precoat in several parts, avoid mixing the filtering agents. In addition, never place a high-permeability diatomaceous earth after a finer diatomaceous earth, as this will form a layer of icing inside the cake, leading to rapid, totally irreversible clogging.

• When filling the filter, leave the air vent open to prevent degradation of the filter cake, as the CO2 will interfere with the installation of the precoat.
• Under normal conditions, when the precoat is in place, the pressure drop is 0.3 to 0.5 bar.

Filtration additive

• :
• Rapid or roughing diatoms Destined

• .
• Medium or clarifying These

• .
• Fine or finishing These

Alluvium

Throughout

the filtration process, the regular addition of kieselguhr makes it possible to

• :
• increase the filtration cycles by delaying clogging
• reduce the differential pressure
• maintain the porosity of the cake as high as possible

Implementation

• :
• Alluviation is carried out with the admixture used to form the last part of the precoat. Never use a diatomaceous earth that is "faster" than the one used to finish the precoat. A layer of icing will form on the inside of the cake, as in the case of a poor precoat.
• The optimum dosage depends on:

- the nature of the particles to be filtered
- the quantity of particles to be filtered (charge)


The type and quantity of additive to be used must be chosen to ensure a slow, steady increase in pressure at the filter inlet. Experience makes these choices easier

Horizontal

plates

loaded with filter cake

Filtration line

Constitution of

the precoat (sizing)

|On

the filtering support, a filtration layer is constituted with a filtration aid which can be kieselguhr (diatomaceous earth), perlite, or even various fibres (cellulose, polyethylene, etc.)

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Alluvionage

A

mixture of wine to be filtered and filter aid is added throughout the filtration process. This superimposes a series of filter layers comprising the filter aid and the retained impurities

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Removing the filter cake at the end of filtration or after clogging.

Depending

on the type of filter, the cake is removed as follows

• :
• by cleaning with water for models with vertical plates
• in paste form or not for models with horizontal plates

In the

latter case, 2 configurations are possible

• :
• automatic by moving the filter elements
• manual by tilting the plates

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Cleaning
Washing is carried out using water pressurised by the general supply pump. The appliance can be fitted with an internal washing ramp, which may or may not be mobile.

The

cleaning discharge is pasty.

Note: Periodic chemical cleaning is necessary to prevent clogging and scaling of the filter elements

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Choosing the right equipment

Resolving malfunctions

• The additive is unsuitable

• - Use a less fine diatomaceous earth
• The alluvium is insufficient

• - Increase the concentration of additive in the mixing tank
• Increase the alluvium flow rate
• The flow rate of the main pump is too high

• -

• Reduce feed pump flow

• - Increase bypass volume

• Admixture unsuitable

• -

• Use a finer diatomaceous earth
• Alluviation is greater than required

• - Reduce the concentration of adjuvant

• - Reduce the flow rate of alluviation
• The flow rate of the main pump is too low

• - Increase the flow rate of the feed

• Alluviation adjuvant is finer than that of the last precoat,
• resulting in
• clogging The concentration of solids increases (e.g. at the bottom of the vat)
• The

• Reduce the impurity load by dilution: Some of the filtered wine is returned to the main pump suction via the bypass.
• This is often necessary when filtering new wines.
• Reduce the inlet flow rate to the bell.
• Increase alluviation by accelerating the flow rate of the dosing pump.
• Increase the concentration of adjuvant in the alluviation tank.
  The

• Activate the air vent frequently, especially in the case of young wines with a high CO2 content
• Avoid pressure surges by handling the valves carefully.