Spray and filter technology for the Pulp and Paper Industry

Paper mills are built in locations that have a significant quantity of fresh (river or lake) water, as they use a lot of this commodity. For example, during the first step of production, we found in the products 99 % water and only 1% cellulose.

Often additives must be put into this water (bleaches, glues, silicates, carbonates, soda, etc.).
For this reason, the equipment used is generally made of stainless steel .
The primary source of water (river or lake) has now become secondary (in more industrialized countries) compared to the amount of water reused within the plant, where it is recycled after having been filtered. This is done to satisfy the ever more pressing need to minimize the environmental impact of industrial plants.

Filters are used in the papermaking industry in order to allow water to be recycled and reused, as well as for purifying water for topping up, drawn from wells, rivers, or basins.
Their application extends to the recycling of white water and water saving in applications where it has become necessary.

General features and benefits of these installations:
  • The application of these filters allows a remarkable stability in water quality and so a proper cleaning cloths and felts lengthening the duration, and improving the quality of the finished product.
  • The downtime of the mill becomes shorter, whereas the supply piping to individual users should not be cleaned so often.
  • Significant savings in water with obvious benefits in terms of cost and environmental impact.
  • The filters are automatically cleaned when the differential pressure gauge detects a partial blockage of the cartridge, or after a set time, allowing fully automatic operation without the intervention of personnel.
  • Filtration is mechanical with scrapers or brushes: the counter-washing is only useful to filter disconnected before a canning filter vacuum, so there are no wastes and additional uses of water.
  • The filters mounted after the pumps require a positive pressure very low (5-6 m approx.) .
  • Low waste water as the cleaning cycle lasts approximately 8 seconds during which only 4-5 seconds for the exhaust valve remains open. This allows you to download only the contents of the cartridge.
  • Low pressure drop (0.2-0.3 bar) thanks to the particular shape of the cartridge, also during the cleaning cycle (in time fully open exhaust valve) the loss of flow to the users came in at approximately 25-30 % depending on the supply pressure.


Station pumping fresh water
The fresh water taken from the environment for the reintegration in the production must always be filtered.
In times of drought, in the wells remains a considerable amount of sand, while during periods of heavy rain or when there are floods in rivers and reservoirs, there may be stones, sand in large quantities, branches, weeds, leaves etc.. that dirty blocked canvas, felt, pipes, pumps, nozzles.
The filters used for this purpose have a filter factor which varies between 100 and 500 microns, depending on the type of pollutant in question, and the purpose for which the water is used.

Filtration white water
The most widespread application of filters paper is dedicated to recycling water from under machine. When not used directly in the formation of cellulose, water from under machine is generally sent to filter flotation; it is a large tank where filtration occurs with chemical method - physical flotation unit natural cellulose particles, helped by the chemistry, enables an efficient cleaning method with water "on weir". Flotation unit, met scheme achieves a significant efficiency (50-150 ppm cellulose), but it can enter into crisis if it is not designed for the increasingly high-speed installations in the event of breaking paper on the continued (when the amount of cellulose poured in flotation unit increases).

Others filtrations in production cycle

Application of starch for the paper and connected.
The application of self-cleaning filters for release of water and starch production cycles have led to considerable improvement in the quality of the finished product as well as for greater ease of application (the starch particles in suspension may be too large to could obstruct the passage of pipes and nozzles).

Other applications
The self-cleaning filter was also used for the filtration of the mixture of water and recycled board that the producer uses to produce his paper. The paste to be placed on production is more uniform and easier to distribute.

Advantages and recommendations for this application are:

The filters must be cleaned automatically when the differential pressure gauge detects a blockage of the cartridge, or setting time, allowing the management completely automated and without the involvement of staff.
Filtration is mechanical type with scrapers or brushes: the backwash is useful only disconnect the filter before placing in a storage.
Filters must be fitted after the pump: in fact they need to run a positive pressure of at least 5.6 meters approx. In special cases, the collaboration between us and the paper mill or with the manufacturer of machinery for paper production has put in place before the filtration pump.

The application of these filters allows a remarkable stability in terms of water quality, and therefore better cleaning cloths and felts, which allows a longer life.

Static filters

In some cases more coarse filtration (e.g. 600 microns) is carried out on a large quantity of recycled water, using a large capacity self-cleaning filter, with some static filters being added upstream of critical users (e.g. upstream of sprayer pipes with small diameter nozzles).
This application results cheaper but has the disadvantage of less security, considering that filters must be cleaned manually.

Static filter YMS

The filters are positioned to serve low-pressure spray showers in a process of recycling water (cleaning felt).

Static filter ALSF

The static filters ALSF series (aluminum) and ASF (AISI 316) are positioned just before the spray tube to make additional automatic filtration after automatic filtration.


A large number of spray nozzles is used in paper mills, both in individual applications and more often still, in sprayer pipes that pass through the entire length of the machine.

Nozzles application is therefore combined with sprayer pipe applications, in three ways:
  • Fixed pipe without internal cleaning with standard or self-cleaning nozzles.
  • Fixed pipe with internal cleaning (using brushes, nozzle type C7E, C7C etc.)
  • Oscillating pipe with linear actuators

Nozzles for showers

Pay attention to the choice of material of nozzles for grater durability.


Consists of a closed container (canvas) in a ring, made of a fabric of synthetic fibers. This bed is usually shaken horizontally to allow greater isotropy of the fibers.

95% of the water used is lost in this area. The use of oscillating spray tubes must therefore take continuous water and cellulose rainfall into account.

Natural drainage of the water is assisted by the addition of stops and suction tanks.

The tubes are basically laid out in the following positions (although these may vary for different manufacturers and in relation to plant’s needs):

Oscillating, needle jet, pressure 10-15 bar on the Dandy Cylinder (for cleaning it). This is the mesh cylinder that compacts and smoothes the surface, as well as applying filigree. This is positioned above the canvas. Here our C7 sprayer nozzles are normally used .

Oscillating, needle jet, pressure 35-70 bar on the Suction Cylinder (for cleaning it). This is at the end of the canvas, where it pulls and canvas and provides a suction. Here our C7C type nozzles with a ceramic insert can be used, due to the normally high operating pressure.

Fixed, fan, pressure 2-3 bar, on the canvas head cylinder (at the beginning of the canvas).

Fixed, fan, pressure 1-2 bar, on the coupling cylinder (above the canvas, the final part on the felt side, where the spray is used for moisturising).

The nozzles most often used for the tubes referred to above are the C7 for cleaning, with a brush inside the pipe.


The starch is used to increase strength and rigidity of the paper.
It also helps to prevent the spread of ink. The starch is made from corn, potatoes and wheat flour, to which are added chemicals (copper sulphate, , oxidants, etc.).. The application is made by two cylinders and the starch is sprayed with a hose spray nozzle in a fan, as our types MC2 and MC3.

This is a system that uses a roller press to press the sheet of paper between felt faces (which are also in a ring, like the synthetic canvas). Function: To squeeze out water and compact the sheet of paper.
Various oscillating spray showers with needle jets at pressures of 10 to 25 bar are fitted in this area. (This pressure is often laid down by the felt supplier). These are used for cleaning the felt (each piece of felt has its own). They rinse out fibers and deposits, which is essential in terms of the quality of the paper. These pipes are normally fitted before a suction tank, which is used to take residual water away.
The suction tanks (at the entrance) and some rollers are lubricated by means of fixed low pressure (1-3 bar) sprayer pipes, with very low flow rates.
These are fitted with small diameter fan nozzles. They are used to prevent the felt heating up due to rubbing against a fixed edge or turning around a roller.

This is made up of numerous hot cylinders that have steam pumped into them. The sheet of paper does not come into contact with the cylinders, but rather with the dryer canvasses.
Normally, no pipes are installed at the dry end, however, occasionally there may be an oscillating, medium pressure, needle nozzles.

It can handle synthetic glues, anti-mold products or spread a layer on the surface: the film consists of kaolin (hydrated aluminum silicate) and various carbonates, strongly bound together with starch. The patina is useful for paper designed for specific use. It is caught in by a roller.

Used on washing plant POLYDISC : water goes through wheels which need continuous washing. Self-cleaning nozzles are preferred.

The sheet of paper may be finished by being pressed between metal cylinders. If the sheet is too dry it curls, especially when it comes to cardboard. This ruins the product and results in a significant quantity of waste. Pneumatic atomizer collectors are made for this moisturizing.

When making “tissue” paper (serviettes, handkerchiefs, and toilet paper), hydraulic atomizers are often used to spray small amounts of perfume onto the product.

Hydraulic atomizer nozzles


Needle jet nozzles

Are ideal for cleaning felts, wire, fabrics, rolls and more thanks to their solid stream high impact performance.
They are usually installed on a pipe oscillating pressure between 15 and 40 bar for cleaning cloth. Need for cleaning of fibers and deposits and is essential for the quality of the paper, it is made in the first return of canvass to cash flow between rollers.
In general, the water pressure should be the maximum for very fast machines, and proportionally less for
slower machines.
Normally for this function is installed more than a pipe with a swing speed fixed or variable speed related to the speed of the felt.

For their efficiency it is important to use needle jet nozzles for cutting-edge after the last part of felt. Similar jets are used for Trimming paper for a possible start after break.

Flat jet nozzles

Different models of CD3 nozzles are used to wash rolls on which paper slide after drying.

CD4 model is a fix nozzle, flat jet, pressure 5-15 bar, for endpaper pull down in case of broken of paper in felt zone.
It can be used for operations of abatement trim.

The nozzles model MC2 and MC3 are used to wash with clean water in medium to low pressures.
Ideal for use in the paper mills thanks to its compact shape.

Full cone nozzles

Pipes with nozzles for the overthrow foam can be used in this sector, and usually produce a full cone.

Self cleaning nozzles

In case of presence of fresh water without filtration, often is used a self cleaning nozzle.
For its cleaning is sufficient reduce pressure (about 1,5 – 2 bar) to avoid the accumulation of dirty inside.
They are available with needle jet for cleaning at high pressure and with flat jet for washing at medium-low pressure or lubrication.

Air nozzles

Showers with air nozzles are used for cooling the rollers in drying process after paper release


Pneumatic atomizers are used for paper dampening. These nozzles are used to lubricate paper edges at the end of production run, to avoid cockle.

They have a good humidification.
Regulation of capacity and nebulization type permit to obtain a spray that can reduce scraps in production.


Thanks to the fact of having wheels and to be "autonomous " (just the connection with Rilsan tube and 220V power supply) system EUSPRAY DRY MIST ® can solve many problems related to electrostatic charge in the final stages of working paper..

It can significantly reduce cases of breakage during winding because it has the great advantage of regular capacity, humidification, spray cycle and direction of the spray.

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