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How AquaVive Technologies solves Wastewater Problems plus “Pitch Control” In Pulp and Paper Production
by Peter Yew

Peter Yew was a key speaker at the UBCM "Water, Storm Water and Wastewater ” Management Conference at the Sheraton Wall Centre, Vancouver, BC, Phone (604.844.1914) or e-mail


The Problem

The content of wood pitch in tree varies from 1.0% to 5.0% (of dry wood), depending on the wood species. After bleaching, the pitch content is reduced to approx. o.15% - 0.20% in the pulp. However, for unbleached grades and mechanical pulp, the content of pitch is considerably higher. The wood pitch is insoluble in water and consists of free fatty acids, resin acids, fatty acid esters of glycerol and sterols, and materials such as sitosterol and betulinol, etc.

Some wood pitch may exist within the fibres but may not cause pitch problems. Again, free pitch will not cause problems, if it does not agglomerate within the system. However, in pulp and paper systems, pitch as colloidal particles has a tendency to agglomerate and may be deposited in the system. The mechanism of pitch deposition includes resin transfer from fibres, fines deposition and deposition of pitch with hydrodynamic shear, evaporation, creaming, coalescence, etc.

The pitch problem is one of the most important factors limiting the efficiency and productivity with washers, bleach plants and paper machines. This is because modern pulp and paper making processes are very sensitive to disturbances. In the washing and bleach plant, pitch can plug washer screens and reduce the efficiency of the washer and increase bleach chemical consumption. Pitch particles in pulp products increase dirt count and reduce pulp brightness. Pulp with big pitch counts leads to paper defects (such as breaks, holes and spots very often caused by pitch deposits) which represent some of the most common complaints of the user/buyer of paper. Thus, pitch control is a critical consideration in pulp and paper production.

The Solution

There are four types of commonly used basic approaches to pitch control. These are : dispersion, adsorption, flocculation and dissolution. The dispersion approach is to stabilize the pitch particles by adding dispersants to protect colloidal action. Pitch particles are eventually washed from the system.

The adsorption approach is to adsorb pitch particles using inorganic minerals. The pitch adsorbed will be carried through the systems as part of the product.

The flocculation approach is to flocculate pitch particles using pitch fixing agents. Here, the pitch particles are retained in the product during drainage.

The dissolution approach is to dissolve pitch particles by surfactants, solvents or a combination of surfactants and solvents. The pitch concentration is reduced and the deposition of pitch is minimized.

Some mills use one approach or a combination of two, three or four approaches to treat pitch problems. The dispersion method will obviously suffer from the closure of the backwater system. The concentration of dispersed pitch can increase to levels at which agglomeration may take place. The pulp from mills using the flocculation method may cause pitch problem in paper machine operation because pitch will be released from the pulp in paper making systems. Also, the flocculation method can result in over-flocculation and sheet formation will deteriorate. Many mills use talc as a pitch adsorbent in brown stock and in paper machine systems to reduce pith problems. However, talc reduces the efficiency of bleaching chemicals since it contains many trace minerals such as Fe, Cu, Al, Mg, etc. These can adversely affect the efficiency of bleaching chemicals, especially in the mills using H2O2. The impurities in talc contribute to rapid decomposition of H2O2 and brightness reversion. In addition, the removal of talc/pitch entities depends on the level of retention, and these entities retained in the products increase product ash, and may cause other deposit problems in paper machine systems. The filler content of the final sheet will increase and therefore strength properties can deteriorate. The dissolution method depends on the selection of proper solvents and surfactants for different systems.

Obviously, these methods for pitch control possess their own limitations and disadvantages.

Pitch Control Agent SF-11 is designed to overcome these limitations and disadvantage. SF-11 is a blend of biodegradable and environmentally correct chemicals. The principal ingredients are natural, non-regulated biomass alcohol's.

It has been demonstrated in North America that mills using products similar to SF-11 for pitch control have been cost effectively producing high quality pulp and paper. SF-11 is being using in many mills abroad and is unmatched in performance and cost effectiveness evidenced by comparative lab bench trials.

For information:
AquaVive Technologies
Suite 303, 7651 Vantage Way Delta BC
Canada V4G 1 A6
Telephone: 604-940.2995
Facsimile: 604.940.2895
e-mail :


Photos courtesy of Tourism Vancouver and Tourism BC