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Papermachine Cleaning Chemicals - Technical Papermaking

Wire conditioner

Wire conditioner is sprayed on to the wires of the fourdrinier machine. The job of the wire conditioner is to coat the wire and prevent stickie’s, glues, pitch and other tacky substances from binding with the wire plugging the holes in the mesh. Blocked parts on the wire will inhibit drainage leading to weight and moisture deviations as well as holes/ weak spots in the sheet. these will cause a lot of issues on the paper machine.

When problems occur on the paper machines wire like marks from stickie’s and hot melts a caustic chemical clean on the headbox can remove the hot melts. Caustic soda is used because it breaks down inorganic materials like chalk, ash and stickie’s.

Felt conditioner

Felt conditioner works in a similar way to the wire conditioner helps prevents stickie’s and pitch from attaching to the felt and blocking the felt. An excessive amount of pitch on the felts not only hinders dewatering but sticks off a small amount of fibers. After time this will build up and cause defects in the sheet, potentially leading to breaks.

Chemical felt cleaning and conditioning

Chemical precipitates found in the press section are inorganic as well as organic. The organic or hydrophobic types include rosin size, wet strength resin, and pitch and hydrocarbon oil. Inorganic precipitates include clay, calcium carbonate.  
Generally speaking, chemicals for cleaning felts are applied using either a continuous or a shutdown cleaning method. Continuous cleaning effectively keeps the felt open during its run rather than relying on the more difficult job of cleaning a plugged felt.

Chemical felt washes are done more infrequently on PM3/6 than on PM4, usually if the machine has been shut for a while a chemical wash is usually done but on crawl speed to allow better penetration of the chemicals in the felt. Using a lower speed allows the chemicals to bed in and reacts with the dirt and contaminates.

 Acid

Acid is used in two ways on the machines, continuously dosing and shock dosing. The acid is used continuously on all of the machines to help keep the felt open, rather than relying on the shock cleaning on a closed felt.
The Shock dosing is done at a high concentration of acid, it is important to ensure the water is running, neat acid will melt the felts.

Acid is used to clean the felts and to neutralise the caustic that has been previously dosed. The acid is dosed through the chemical sprays on the felts. Acid is dosed for ten mins with 5 mins flushing time after. The acid removes the broken down pitch, fines etc. in the felts. The acid is delivered in a higher concentration when shock dosed and more dilution water is added when the acid is used continuously to keep the felts cleaned. The caustic id a alkaline which is on the opposite spectrum to the acid.

Caustic Soda

Caustic is used to treat the felts. The chemical is shock dosed through the chemical sprays onto the felts to break up the pitch, ash, fines and dirt collected in the felts. The caustic is applied for 10 mins on each of the felts. The issue with caustic being used on the felts is the chemical can cause the felt to close up, reducing the efficient of water removal. After the chemical dosing the lines are flushed with fresh water to clean the pipe work and sprays.

 Anti-Scale Chemical

Anti-Scale chemical is important chemical because the papermaking process is water based. Scale is made up of minerals (mainly chalk and limestoneare composed mainly of calcium carbonate (CaCO3), magnesium hydroxide (Mg(OH)2), and calcium sulfate (CaSO4)) within the water precipitating out and building up within water systems.

Industrial water systems using hard water can experience breakdowns as the scale builds up in pipes, boilers, water tanks etc. To maintain the level of scale within the water systems a chemical is doses at specific points to dissolve/ break down the chalky deposits preventing build up and ultimately costly breakdowns.

The effects of scale

Can restrict the flow through pipes as the internal diameter decreases as the scale builds up in the pipe.
Scale impairs the heat exchange between metals into the water. this reduces the cooling/ heating efficiency and can lead to the metal components over heating. This causes issues with the drying cylinders requiring more steam to dry the paper because not al heat can be transferred through the cylinder if a build up of scale occurs.


Below is a list of all the dosing points in the site. There are problematic areas that scale is likely to build up and can cause catastrophic breakdowns for example. If the dosing to the pump seal water failed the pumps can clog up with scale, pumping would be reduced and the mechanical could seize. 

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