WO2004031474A1

WO2004031474A1 - Method for reducing deposits in industrial systems containing water by addition of hydrophobic organic solvent and tenside

Info

Publication number: WO2004031474A1
Application number: PCT/EP2002/011216
Authority: WO
Inventors: Alfred Pohlen; Gerhard Kern
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-10-07
Filing date: 2002-10-07
Publication date: 2004-04-15
Anticipated expiration: 2005-04-07
Also published as: AU2002346961A1

Abstract

The invention concerns a method for reducing deposits in industrial systems containing water by addition of at least one hydrophobic organic solvent in combination with at least one tenside to the aqueous system either proportional to the volume of water or proportional to the level of any solids transported in the water, wherein the at least one tenside constitutes 0,1 % w/w to 10 % w/w of the overall amount of organic solvent and tenside to be added to the system.

Description

METHOD FOR REDUCING DEPOSITS IN INDUSTRIAL SYSTEMS CONTAINING WATER BY ADDITION OF HYDROPHOBIC ORGANIC SOLVENT AND TENSIDE

Deposits forming within the water circuits in industrial plants on plant are well known to cause problems in the processes for which these plants are used. For instance scale forming on the surfaces of a heat-exchanger will reduce the efficiency of heat-transfer. In a cooling tower system, deposits can lead mechanical breakdown of the cooling surfaces. Particularly in paper machines, for example, deposits forming in the circuits can lead to detachment of these deposits and can lead to defects in the paper sheet or to breaks in production.

The water circuit in a paper machine where the dispersed pa- permaking fibres and other solids are initially separated from the slurry in a forming device to make the paper sheet, usually a continuously moving sieve, is normally called the white-water I (one) circuit. The water in this circuit is recycled and continuously enriched with more papermaking solids. A second circuit where further water is pressed or drawn from the wet paper sheet and treated, for instance, to retrieve lost fibre or to clarify the water for further use is usually called white-water II (two) . Deposits forming in these two circuits can create serious problems for the paper- making process. Further it can be clearly demonstrated that a clean paper machine will have a significantly better runabil- ity than when the white water circuits are clean.

The deposits which tend to form in paper machine water circuits and on parts which come in contact with the circuit contents can be caused by a variety of factors. So, microorganisms often find ideal growing conditions in a paper machine due to the warm temperature and substances present which can act as nutrients. These micro-organisms do not only multiply in the circuit water but also can form slime on sur- faces. Further, many of the additives used in papermaking such as retention aids, charged polymers used for fixing ani- onic trash, sizing agents and wet-strength resins can contribute to the deposit problems. Even natural resins from pulp, either chemical pulp or from mechanical pulp, are a known problem in this respect. Further, if coated paper is broked and re-cycled back into the stock, it brings the synthetic binders used in the coating with it contributing to the problem known as "white pitch".

Further, recycling of waste paper is the cause of some of the most troublesome deposit problems in papermaking today. Not only often contaminated with micro-organisms but due to adhe- sives used for labels, packaging construction etc., waste paper and board is a well known source of deposit causing substances known as stickies.

In patent EP 0 517 316 the addition of a hydrocarbon solvent together with at least one tenside to the pulper of a paper- making system using secondary fibre containing hot melt or pressure-sensitive adhesive contaminants is disclosed. It can reduce the amount of sticky material being liberated from the furnish into the aqueous pulp slurry. This process functions whereby during the pulping processes, where the adhesive tape etc. is separated from the fibres through thermal or mechanical energy, the addition of the solvent and tenside allows better separation of the adhesive contaminants from the fibres whereby the majority of the adhesive substance remains attached to the original substrate, namely the adhesive tape, which would then be removed by mechanical screening. The fibre would pass on in the system with lower levels of contamination.

In patent EP 0 731 776 it is disclosed that an oil-in-water emulsion containing organic solvents and tensides can be added to an aqueous system that transports solids, for instance in a papermaking process, to prevent slime formation and reduce microbiological growth. It is shown that levels of micro-organisms in the water phase can be significantly reduced thus reducing deposits that may be caused by such micro-organisms .

Also, lignosulphonates, as in EP 0 496 905, have been used for deposit control whereby it is set that the growth of microbes can be influenced so that the growth-rate of sessile or slime-forming micro-organisms is reduced and at the same time thus allowing the presence of non-sessile microorganisms to predominate consequently reducing the tendency towards slime deposits but possibly increasing the level of non-sessile (free-swimming) micro-organisms, which anyway should not disturb the process of papermaking. In the process of EP 0 496 905 a reduction in the number of non-sessile microbes is not sought.

Due to ecological concerns, there is progressively increasing pressure to reduce or eliminate the use of potentially harmful or toxic substances used for deposit control in papermaking. Most of the processes used for deposit control already referred to above reflect this trend.

One main and common drawback of the known processes is that each of them addresses only one deposit form, i.e. microorganisms growth and along therewith slime forming, white pitch or stickies. In other words, a biocide can kill or control bugs and control deposits of biological slime. A pitch dispersant can control pitch deposits but would have no effect on biological slime. A bio-dispersant would disperse biological slime (not by killing bugs) but would not protect the surfaces against resins or pitch deposition.

Thus, an object of the present invention is to provide deposit control effect on many types of deposits all at the same time and not on just one specific kind of deposit as other products which have usually to be used in combination. The present invention provides a method for reducing deposits in industrial systems containing water by addition of at least one hydrophobic organic solvent in combination with at least one tenside to the aqueous system either proportional to the volume of water or proportional to the level of any solids transported in the water, characterised in that the at least one tenside constitutes 0,1 % w/w to 10 % w/w of the overall amount of organic solvent and tenside to be added to the system.

Preferred embodiments may be derived from the subclaims .

Thus, the organic solvent is a hydrogen treated petroleum distillate fraction. Up to 20 % of the combination of organic solvent and tenside are preferably derived and replaced by citrus oils. Conveniently the tenside is selected from the group consisting of alkyl benzene sulphonate alcohol amine salt, polyethylene glycolethyl ether, alkyl sulphonsuccinate sodium salt and/or aliphatic alcohol ethoxylate.

In a further preferred embodiment of the invention the organic solvent and tenside are pre-mixed and the mixture contains essentially no water. The organic solvent and the ten- side may be added directly or indirectly into a white water circuit of a paper or board machine or into the circuits of a pulp de-watering machine.

According to the claimed method the components of the additive, i.e. the organic solvent and the tenside do not form an emulsion but discrete small droplets that may adsorb to hydrophobic surfaces. Surprisingly a deposit control effect on many types of deposits can be achieved. With the method of the present invention any of or combinations of various types of deposit control agents can be replaced, making treatment more simple, avoiding toxic substances. According to practical results better long-term results can be achieved compared with conventional combi-systems .

Surprisingly, by comparison of various essentially hydropho- bic liquids with the aim to create a protective layer on the surfaces of the paper machine circuits and parts coming in contact with the process water, it was found that certain specially treated hydrocarbon distillate fractions gave a very efficient protection against deposition of many types of contaminants whilst at the same time preventing or reducing the tendency of micro-organisms to form growths on those surfaces. Furthermore, by addition of small quantities of ten- sides to this hydrocarbon, on addition of a mixture of the components to the white water circuit of a paper machine, the hydrocarbon liquid was dispersed into droplets of such a size that although it still preferentially coated any hydrophobic surfaces in the paper machine thus affording the required protection against deposit formation, there were no hydrocarbon droplets present large enough to cause so called oil- spots in the paper sheet. The invented process has distinct advantages over many conventional systems in that it uses products that when used as in this process are essentially harmless, and that the effect is such that by preventing the contamination from adhering to the surfaces it is independent of the type of contamination whether chemical, from natural or synthetic adhesive materials or from the activities of slime forming micro-organisms.

When this process was used to replace a biocide deposit control system is was seen that the micro-organism count rose significantly. Even though after several days running, the paper machine white water circuits showed a 100 times increase in the numbers of aerobic micro-organisms, there was no tendency to increased deposits of biological slime. In another trial where a lignosulphonate deposit control system known to be non-toxic was replaced by the process of this invention, the already quite high bacteria count in the circuit remained at approximately the same level. Even when citrus fruit extracts were. used as part of the solvent component of the product used in this invented process, it was found that no significant difference was measured in the counts of micro-organisms in the aqueous phase of the system being treated. According to what is taught in EP 0731 776, such -solvents in the form of a true oil-in-water emulsion would have a significant reducing effect on measurable level of micro-organisms in the aqueous phase. This demonstrates an important difference in the invented process in that the form of the product added in the invented process is such that it is intended that as much as possible of the solvent component be deposited onto hydrophobic surfaces of the system being treated to reduce the ability of any substance to form deposits on those surfaces. The process is not intended to influence the material being transported by the aqueous phase or the aqueous phase itself but to influence the surfaces, especially the hydrophobic surfaces, that it comes in contact with.

Clearly, the danger that the use of toxic substances represent to any biological waste-water plant treating the paper machine waste water does not apply to this invented process, giving a significant environmental advantage over biocides. Furthermore, no potentially toxic residues as is possible from biocides can collect in the finished paper, an advantage which can be essential in food-packaging paper grades or paper that comes in contact with children.

Further, in the development of deposit control systems for paper machines, it is important to consider that such a system should have as little influence as possible on other systems needed to actually make paper. For instance, due to tendency of some necessary additives to create foam which is very detrimental to the papermaking process, special anti- foam additives must normally be used in the circuit. The products used in the process of this invention have been so formulated that although tensides are present, no significant worsening of foaming problems has been measured and in some trials it was even found that less conventional de-foamer was needed showing that even though the process uses small additions of certain tensides, the process imparts a de-foaming effect in some applications.

Thus the products used in the process of this invention and the way the products are applied can be specifically tailored to the requirements of the situation.

To develop and optimise the invented process including comparison with existing deposit control processes, trials were run on paper machines of various types producing various grades of paper from different raw materials. It is clear that most paper production systems already run at high efficiency levels with respect to machine design or grade of difficulties involved. It was necessary that trials should run for considerable lengths of time to ultimately show that the invented process gave advantages over previous systems. For instance, even 2 years of trials can be needed to demonstrate that seasonal differences in deposit problems are taken into account. Microbial growth is higher in summer and levels of contamination from fresh water can be almost non-existent in deep winter. On the other hand, content of natural resins in pulp can vary enormously throughout year. Additionally, a producer, of for instance packaging board using waste paper, will buy waste from various sources over the time. The trials should be long enough to compensate for these variable factors .

In a paper machine where biocides were used for biological slime control but where problems with resinous deposits were still present, the process of this invention was applied in addition to the biocide in use. During the first 24 hours there were many more problems from resin deposits in the paper than normal but leading rapidly thereafter to a much im- proved runability. The temporary increase in spots demonstrated the cleaning power of the invented process against non-biological deposits in a paper machine essentially under circumstances of good biological slime control whereby eventually the combination of the invented process with a biocide system was more effective that the biocide system alone.

The same improvement was observed in a paper machine where relatively large quantities of oxidising biocide (bro o- chloro dimethyl hydantoin or BCDMH) was being used to treat all fresh water used in the papermaking process and where additional application of the invented process reduced problems of holes in the paper caused by deposits of natural resins from the pulp.

In another paper machine, clarified water derived from white- water II was held in a large sedimentation vessel to allow further solids to sediment out before using this water as process water once again. Due to the time the water stayed in this vessel there was a strong tendency for anaerobic bacteria to grow creating smells. A continual feed of an oxidising biocide, BCDMH solution fed from a "Brominator" tablet dissolving unit, was being added to this vessel to maintain a positive Redox condition and prevent the growth of anaerobic micro-organisms. The primary conventional biocide system being shock-dosed into the main white water circuits of the paper machine was replaced with a continual dosage of a product as in the invented process whereby after a time, less flecks and holes were observed in the paper being produced.

The mixture of hydrocarbon solvents with tensides as relating to the method of this invention can be dosed in appropriate quantities into an aqueous system and measuring the effects in the way described it has been possible to demonstrate that this method is able to successfully solve the problem as set out for this invention. Addition levels of the solvent and tenside mixture to an aqueous system that transports solid . substances such as a paper machine white water circuit can be in the range of 10 to 10000 ppm based on the dry weight of solids contained in the aqueous system, preferably 50 to 500 ppm, typically but more especially from 150 to 400 ppm. In an aqueous system with low levels of solids being transported, the product can be dosed at a typical level of 2 to 25 ppm, preferably 4 to 10 ppm, based on the water volume flowing through the system.

Examples

Example 1. Preparation of a mixture of an organic solvent with tenside

A solution of a blend of surfactants in a solvent mixture was produced by simple mixing whereby the surfactants constituted 2.5 % w/w of the mixture. The components were mixed together for 30 minutes and the resulting product was stored at room temperature.

The solvent used was a de-aromatised white spirit originating as a hydrogen-treated petroleum distillate fraction (naptha) with a boiling range average of 198°C.

Additions by weight :

De-aromatised white spirit 97.5 % isopropanolamine dodecylbenzenesulfonate 0.8 %

Polyethyleneglycol monodecylether 0.7 %

Di (2-ethylhexyl) sulfosuccinic acid, sodium salt 0.6 %

Ci₂ ^_Ci₄ aliphatic alcohol ethoxylate 0.4 %

Example 2. Preparation of a mixture of an organic solvent with tenside A solution of a blend of surfactants in a solvent mixture was produced by simple mixing whereby the surfactants constituted 2.3 % w/w of the mixture. The components were mixed together for 30 minutes and the resulting product was stored at room temperature .

The main solvent used was a de-aromatised white spirit with a boiling range average of 198°C.

Additions by weight:

De-aromatised white spirit 82.8 %

Orange terpene 15.0 % isopropanolamine dodecylbenzenesulfonate 0.7 %

Polyethyleneglycol monodecylether 0.6 %

Di (2-ethylhexyl) sulfosuccinic acid, sodium salt 0.5 %

Cι₂-Cι aliphatic alcohol ethoxylate 0.4 %

Example 3. Prevention of deposits on guide-rolls of a chemical pulp de-watering machine

In a mill producing H₂0₂-bleached cellulose pulp, the guide rolls and the wire of the de-watering machine were prone to severe deposits of natural resins from the pulp. One particular guide roll supporting the de-watering wire was badly affected. It was often necessary to clean this roll by hand once per hour using a petroleum solvent.

The product as described in example 2 was added continually to the pulp stream coming onto the de-watering machine at a rate of 10 ppm based on the volume of pulp flowing onto the de-watering machine.

The de-watering machine could be run without manual cleaning of the guide rolls for up to 2 days continually, thus saving considerable down-time for cleaning. Example 4. Reduction of deposits on the former of a board machine

A multi-cylinder board machine making packaging board from 100% waste paper and board suffered continual problems from deposits especially on the first forming cylinder.

The product as described in example 1 was added continually to the thin-stock coming onto the formers of the board machine. After the first day of treatment, it was seen that all metal surfaces in contact with the treated stock and white- water were clean, meaning that also existing deposits had been cleaned away. This was especially so for the covering wire of the first former which was the main point where problems from deposits were previously apparent.

It was also seen that hydrophilic surfaces in contact with the stock or white water, such as concrete, did not show any significant improvement in the deposit situation.

No significant changes were measurable in the characteristics of the finished board in comparison to board produced without the addition of the deposit control product.

Example 5. Reduction of deposits in the circuit of a fine paper machine using coated broke as part raw material with respect to effect on sizing

A small Fourdrinier paper machine making office and copy paper suffered particularly with white-pitch deposits on many surfaces that came in contact with paper stock or white water, especially in the head-box inner surfaces and on the holey-rolls. It was normal to stop production at least once every two days to clean these deposits away. The machine was supplied with stock which contained up to 50% coated broke from other coating machines in the same works plus fresh liquid pulp from the integrated chemical pulp mill. The sizing with AKD on the machine was critical as due to the pulp mix and other additives used, it was difficult to hold the degree of sizing in specification. The product as in example 1 was dosed into the paper machine at a rate of 400 ppm based on dry paper being produced. Two dosing points were tried in trials. One in the stock before the sizing agent addition and in a later trial one in a point after the sizing agent addition to see if any negative influence on the sizing occurred.

The problems from white pitch deposits were significantly reduced in that it was possible to run for up to one week without stopping and cleaning to remove white pitch deposits from inside the head-box and on the holey-rolls.

No significant changes in the required Cobb of the finished paper or to the slipping (frictional) characteristics that were important to the function of the paper in photo copiers were measurable, whether the product was added before the sizing agent or after.

Example 6. Reduction of problems in a special paper machine caused by pitch by replacing a biocide-dispersant deposit control system

A paper machine making light weight, wood-free speciality paper was suffering badly from deposits caused by use of resin size. A deposit control system was in use consisting of 400 ppm dispersant and 370 ppm biocide based on dry paper weight. A further deposit problem always found on this machine at that time was deposits of spun-fibres building up on the holey-rolls in the head-box. On breaking free, these deposits produced holes and breaks.

The two components of the existing deposit control system were replaced by a single, continual addition of the product as described in example 2 to the water supplying the head-box anti-foam shower at a point directly. by the head-box.

The consequence of the change of deposit control process was that the head-box, especially the lip, was found to be almost clean at each planned shut-down. Secondly, the running period between planned cleaning shut-downs could be extended and also the spun-fibre deposits on the holey-rolls all but disappeared giving a much longer running period before cleaning was necessary.

Example 7. Reduction of breaks, elimination of biocide and cost reduction in an offset paper machine by replacing a biocide/bio-dispersant/pitch- dispersant deposit control system

A fine paper machine was producing office-quality offset printing paper and copy paper at a rate of approximately 380 tons per day. The white water circuits were being treated with biocides with the aim of reducing deposits caused by biological slime. The biocides were being dosed into white water I, white water II and to the machine chest.

A bio-dispersant was also being added to the white water II circuit .

Furthermore, a pitch dispersant product was added to the machine chest aimed at reducing deposits caused by natural resins from the chemical pulp.

Up to this point, the paper machine was stopped on average every 2 week for planned cleaning but also suffered unplanned stops every 5 to 10 days to clean the head-box as deposit growth progressively reduced runability through increased breaks and holes in paper. It was wished to extend the running period of the production, to reduce or eliminate the biocides used for environmental reasons and to allow sales of the thus biocide-free treated paper to new markets and thirdly to reduce the complexity and cost of the deposit control systems used.

A trial was started where the biocides and bio-dispersant being added to the white water circuits of this paper machine were eliminated and a product as in example 2 was added continuously into the profile-regulation dilution water before the cross-flow distributor and to a second dosing point in the water directly feeding the anti-foam shower in the pulsation damper for the stock flow before the stock cross-flow distributor.

The addition levels were 65 ml/minute of product to both dosing locations meaning approximately 400 grams of the products of this invention per dry ton of paper produced.

The addition of pitch dispersant previously added to treat deposits caused by resins was left unchanged at 200 litres per day meaning approximately somewhat over 500 grams of pitch dispersant per ton (g/t) of dry paper.

During the course of the first 8 months running with this deposit control configuration the running period between cleaning stops was increased from 2 weeks to 4 weeks.

After a total of 9 months running with this deposit control configuration, the pitch dispersant was reduced to 100 litres/day or approximately 250 g/t on dry paper produced. After a further 12 months running with the modified deposit control configuration, the pitch control dispersant was eliminated completely.

At this stage in the optimisation, the dosing configuration for the paper machine deposit control was as follows: Product as in example 1: 110 g/t (ppm) based on dry paper production dosed continually into white-water II chest entry pipework. Aim was to keep this system and including clear-filtrate pipework deposit free.

Product as in example 1: 130 g/t (ppm) based on dry paper production dosed continually into machine chest. Aim here was to prevent deposits from natural pitch from the chemical pulp forming deposits on the chest walls and exit pipe-work.

Product as in example 2: 110 g/t (ppm) based on dry paper production dosed continually into the pipe-work leading to the profile regulation water cross-flow distributor. Aim here was to keep the cross-flow distributor for the profile water free of deposits .

Product as in example 2: 110 g/t (ppm) .based on dry paper production dosed continually into the pulsation damper shower - meaning indirectly into the stock cross-flow distributor. Aim here was to keep the stock cross-flow distributor and head-box free of deposits .

Total additions: 460 ppm on dry paper. No biocide addition to the circuits (elimination of 40 kg/d biocide or 105 ppm on dry paper) .

Originally added bio-dispersant no longer added (elimination of approx. 50 kg/d or approx. 130 ppm based on dry paper) .

No additional of originally added pitch dispersant (elimination of 200 1/d additive or approx. 530 ppm on dry paper) .

Total eliminations 765 ppm on dry paper (approximately)

The performance benefits obtained in terms of reduction of breaks per month is shown in the following graphic.

Wet-end breaks in a paper machine making offset paper.

Comparison between biocide / dispersant deposit control (1998) and a solventtenside deposit control process (1999)

Mar Apr May Jun Jul Aug Sep Oct Nov

^■ 1998 biocide — ♦ — 1999 solvent/tenside - - - Trendiine 1998 ^■Trendline 1999

Example 8 Reduction of deposit problems in a special-paper machine making wet-strength paper by addition of a solvent in combination with a tenside to control deposits

A paper machine was producing label paper using wood-free pulp. Various paper grades were being produced in both acid and neutral/lightly alkaline conditions. The process pH changes were to allow certain wet-strength resins to be used depending on the paper grade.

The deposit control system was based on a continual addition of an alkaline solution of a low molecular weight lignosul- phonate product. This system was said to be based on creating a biological equilibrium allowing non-slime-forming microorganisms to predominate over slime-formers.

The papermaking process still suffered from deposit problems although from a variety of reasons thought to be due to the complex and ever-changing papermaking chemistry especially the wet-strength additives. The main problem was severe chemical deposits on the formation wire resulting is frequent cleaning stops . Increases in the addition of the product used in the existing deposit control system to high levels did not improve the deposit situation on the wire.

In a first trial., the continual addition of about 160 ppm of the lignosulphonate product to the white-water I circuit was kept as before but was supplemented by a continual addition of 240 ppm of a product essentially the same as in example 2 to the white water I circuit plus a second continuous addition of 240 ppm of the same product to the profile dilution water early in the pipe-work leading to the cross-flow manifold.

It was immediately seen that the formation wire remained much cleaner allowing a doubling of the running time before cleaning became necessary.

After more than 2 months running with this deposit control configuration, the lignosulphonate product addition was eliminated. The addition rate of the product of the type as in example 2 was left unchanged. No worsening of the deposit situation on the wire was observed. In other words, it remained satisfactory. Measurements of counts of aerobic micro-organisms did not change significantly after the removal of the lignosulphonate product and remained at in the order of 10⁶ cfu/ml.

A trial was then started using a new type of wet-strength resin that meant that the paper machine had to be run under neutral conditions. During an earlier trial where only the lignosulphonate deposit control was used, it was not possible to run for long before the wire was so dirty that production was stopped. This time, with no lignosulphonate product in the system and only the addition of the product of the type as in example 2 in the WW I and in the dilution water dosed at 240 ppm to both locations, there was no significant build up of deposits and the paper machine could run continually with the neutral running conditions and the special wet- strength resin.

Example 9.Reduction of deposits and prevention of anaerobic smell-causing conditions in a paper machine circuit by use of a solvent/tenside mixture in combination with an oxidizing biocide

A fine-paper grade was being produced on a paper machine where residual solids in the filtrate water from the white water II fibre recovery unit were allowed to settle out in a large volume, conical sedimentation vessel. The flow through this vessel which had a volume of 400 m³/min was approximately 1.5 m³/min. Due to the activity of micro-organisms, there was a tendency for the conditions in this sedimentation funnel to go anaerobic resulting in production of low molecular weight fatty acids from the metabolism of anaerobic bacteria. Furthermore, H₂S was also sometimes measurable contributing to smell and corrosion. The white water I circuit was being treated with a non- oxidizing biocide of the type 2, 2-Dibromo-3- nitrilopropionamid (DBNPA) . Further, a dispersant product was being added to the white water I circuit as part of the deposit control concept.

Another dose of DBNPA biocide was being added to the filtrate after the fibre-recovery before entry into the sedimentation vessel .

It was known that without the DBNPA biocide addition before the sedimentation the water in the sedimentation vessel would become anaerobic and smell-producing substances would begin to form resulting in smell in the finished paper.

The DBNPA addition to the filtrate water was later replaced by an oxidizing biocide, bromo chloro dimethyl hydantoin (BCDMH) added in dissolved form to the filtrate before the sedimentation vessel. The BCDMH oxidizing biocide was intended to eliminate the need for DBNPA whilst contributing an oxidising product to combat anaerobic conditions.

In a trial, the white water I biocide and the dispersant were eliminated and replaced by a single continuous addition of a product essentially the same as that in example 2.

With this combination of products added in this way the paper machine was able to run for 20 days before a cleaning stop was necessary. With the previous process, on average 10 days was possible.

Thus use of the non-oxidizing biocide was eliminated from the white water I circuit and the running period was extended. Example 10. Reduction of deposit problems in a special-paper machine making wet-strength paper by addition of a solvent in combination with a tenside to control deposits

A paper machine used shock doses of biocides for biological slime control but still had problems with resinous deposits in the white water circuits and on the formation wire. Two types of biocide were being shock dosed alternately, the first type, a quaternary ammonium salt - didecyl dimethyl ammonium chloride, the second with bromo nitro propandiol as active ingredient. A product based on a solution of a tenside mixture in a hydrophobic solvent as in example 1 was added continually at 300 ppm (based on dry paper) to the white water I circuit in addition to the existing biocide dose. During the first 24 hours there were many more problems from resin deposits in the paper than normal but leading rapidly thereafter to a much improved runability. The temporary increase in spots demonstrated the cleaning power of the invented process against non-biological deposits in a paper machine essentially under circumstances of good biological slime control. The combination of a process where a solvent/tenside product was continually dosed into the white water in addition to a shock dose of biocide was more effective than the biocide treatment alone.

Claims

1) A method for reducing deposits in industrial systems containing water by addition of at least one hydrophobic organic solvent in combination with at least one tenside to the aqueous system either proportional to the volume of water or proportional to the level of any solids transported in the water, characterized in that the at least one tenside constitutes 0,1 % w/w to 10 % w/w of the overall amount of organic solvent and tenside to be added to the system.

2) The method of claim 1, characterized in that the organic solvent is a hydrogen treated petroleum distillate fraction.

3) The method of claim 1 or 2, characterized in that up to 20 % of the combination of organic solvent and tenside is derived and replaced by citrus oils.

4) The method of claims 1 to 3, characterized in that the tenside is selected from the group consisting of alkyl benzene sulphonate alcohol amine salt, polyethylene gly- colethyl ether, alkyl sulphonsuccinate sodium salt and/or aliphatic alcohol ethoxylate.

5) The method of claims 1 to 4, characterized in that the organic solvent and tenside are pre-mixed and the mixture contains essentially no water.

6) The method of claims 1 to 5, characterized in that the organic solvent and the tenside are added directly or indirectly into a white water circuit of a paper or board machine or into the circuits of a pulp de-watering machine .