Krofta Filter  Krofta Engineering DISSOLVED AIR FLOTATION
Performance: The degree of fractionation and/ or microstraining depends on many factors; inlet consistency, spray pressure, inlet filler content, micron opening size, and particularly fines content of the fiber fraction. The following results can be expected Coarse impurities are separated out. All the water is microstrained.The fiber fraction is retained by the cloth and can be recovered. Changes in fiber content by the KROFTA Spray Filter are minimized so that subsequent clarifiers operate under a uniform load. The KROFTA Spray Filter improves the operation of clarifiers especially floatation ones, as it aerates the effluent making it more adaptable to floatation.
Measurements /Capacities
Type Flow GPM Flow LPM Outside Dimension overall Height
500
132
500
3’ 0”
6’ 0”
1000
264
1000
3’ 0”
6’ 0”
2000
528
2000
3’ 5”
7’ 9”
3000
790
3000
2’ 5”
8’ 2”
4500
1185
4500
6’ 8”
8’ 2”
6000
1580
6000
6’ 8”
9’ 2”
 
DE-INKING PLANTS : Separation of good fibers from fines and ink for a higher yield, less clay content in the stock, and reduced disposal requirements.

BOARD MILLS :
Fractionation of the longer fibers from the effluent for use in the liner stock, while the fine fraction is used in the filler stock.

FINE PAPER and TISSUE MILLS :
Recovery of fiber through the fractionation of the effluent thus reducing total sludge volume.
MICROSTRAINING of the EFFLUENT
for SHOWERS : Used to prevent the plugging of shower nozzles when either clarified or unclarified water is used.
 

SPRAY FILTER (SPRF)
Advantages :

  • Simple operation: few moving parts and very low rpm
  • Self-cleaning: built-in cleaning shower saves down-time
  • No fresh water required: clean ing shower nozzles are an open, non clogging type. Filtered water can be used in the shower
  • Easy maintenance: wide access door allows easy changing of the cloth and access to the interior
  • Inexpensive filter screens
  • Window wiper operated manually is located on inner side of the door.
Purpose :
The KROFTA SPRAY FILTER is specifically designed for the filtration of effluents containing from 20 PPM to 5000 PPM of solids. A fine mesh cloth with openings
from 75-500 microns is used as the filter media, either to separate long fibers from clay and filler or as a safety filter for showers using clarified water. The KROFTA SPRF meets the
need for high throughput units which can handle wide variations of solids content. It is equipped with a cleaning shower which greatly reduces the need to remove the cloth for cleaning.
Entering raw water
 
Operation description
The water to be fractionated enters at (E) with a presssure of about 0.8 kg/cm2(11PSI). Through special nozzles
  1. it is evenly sprayed against a fine plastic cloth
  2. fastened on a drum. The coarse fraction falls down inside the cloth cylinder and is discharged through the pipe, for reuse. The fine fraction passes through the cloth, and is discharged through the pipe, The gear-motor
  3. continuously turns the cloth drum,
  4. The intermittent cleaning shower
  5. Sprays the cloth clean, making it unnecessary to change the cloth for cleaning. For intermittent shower cleaning the filtered water is used. A large front door with a plexiglass panel
  6. Allows easy access to the cloth drum By means of simple fasteners the cloth can be quickly changed.
 
 

Fractionator
 
LOW FILLER CONTENT
HIGH FILLER CONTENT
FLOW
CONSISTENCY
ASH
FLOW
CONSISTENCY
ASH
I/min
g/I
%
I/min
g/I
%
INLET
830
3.3
18.5
900
6.4
69
FINE FRACTION
568
1.4
49.5
717
5.6
61
COARSE FRACTION
262
7.8
8.5
183
10.1
40
Coarse fraction
Fine fraction
 
Fractionation and Fiber Recovery
 
Above Data are for :
26 T/d of good de-inked stock Production
operating with 50 lit/ Wastewater per
kg of final Production
Spray Filter recovers :
From the Wastewater with
low Filler Content 2.7 T/d = 10.4% of Production
high “ . “ 1.5 T/d = 5.8% of Production
Increasing the NET Production of good de-inked stock proportionally
Construction : All parts in contact with the water are built of 304 stainless steel. The access door has a plexiglass window. All bearing's surfaces are made of corrosion-proof plastic materials.
The raw water to be treated for fiber recovery, enters at (A) into the Spray Filter water tank. (Papermachine or De-inking Washer's Effluent)
  • A pump feeds the KROFTA Spray Filter with uniform flow at
  • The coarse fraction (with long fiber)
  • Returns to the stock chest for reuse.
  • The fine fraction
  • Tank, feeding the flotation clarifier. flows into the
 
 
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