FI104817B - Procedure for reducing mucus formation in plants with water circulation systems - Google Patents

Abstract

In the process for reducing slime formation in plants in which water is circulated, a lignosulphonate is added to the water. The lignosulphonate is prepared by a special process and has a special composition which leads the lignosulphonate addition to have a surprisingly good effect.

Description

, 104817

Method for reducing mucus formation in plants with water circulation systems

The invention relates to an improved process for reducing mucus formation in water recirculation plants by adding lignosulfonate to circulating water.

Microorganisms often have ideal reproduction conditions in plant water circulation systems. In particular, the circulating waters of papermaking machines, which are subject to increasing closed loop circulation, are ideally placed for their growth in terms of inorganic and organic nutrient supply, temperature, pH and oxygen content. This results in very strong mucus formation on the walls of the components used in the circulation of circulating water, such as pipes, tanks and pumps. Detachment of the mucus from the walls results in the formation of lumps and holes in the web. This will weaken the web, i.e., the web may tear and thus, inevitably, a machine failure.

Therefore, in the paper industry, traditionally large amounts of biocides are added during production to the paper machine cycle to control bacterial growth. Such biocides are capable of killing bacteria that cause lymphoma. However, biocidal antifouling agents must, for reasons of action and function, be made to have no affinity for the fibers. Thus, they do not remain in the paper but leave the paper mill with the waste water. In addition to bacteria, fungi are also found in circulating water, in addition to which fungicides are used. The known method, also referred to as the "total-kill method", is therefore not only expensive but also leads to environmental load.

For environmental reasons, but also for economic reasons, the papermaking industry has therefore been • 104817 2 aiming to reduce mucus build-up in circulating plants with environmentally friendly yet effective agents.

U.S. Patent 2,551,446 describes the use of a copper salt, for example copper sulfate, to inhibit the growth of microorganisms in water. In order to prevent precipitation of copper sulphate, ligosulphonate is used as a complexing agent. CA application 807 123 discloses the use of a halogenated levulinic acid as a biocide. Since the halogenated levulinic acid is sparingly soluble in water, lignin sulfonic acid and dimethyl sulfoxide are proposed as dispersants. Das österreichische Papier 20, no. 9, 34-35 describes the addition of lignosulfonate together with a biocide to the circulating water of a papermaking machine. Thus, the amount of added biocide can be reduced.

In addition, lignosulfonate is believed to neutralize nutrient metabolites through electrostatic balancing and thus render nutrient delivery inactive. In this way, the activity of the bacteria and thus also the fungal contamination is controlled. According to the said article, "specifically selected and modified lignosulfonate" is used as the biological complexing agent. It is not clear from the article what "specifically selected and modified lignosulfonate" is. In any case, commercially available lignosulphonates are unsuitable for this purpose, as demonstrated by experiments.

EP-A-0 185 963, in the name of this Applicant, describes a method for reducing mucus in water circulation systems employing lignosulfonate having a weight average molecular weight of 4000-7000 and a number average molecular weight of 2000-3000. to achieve good results in reducing mucus formation.

However, it has been found that the known 35 specific lignocelluloses do not fully meet the requirements. It will not work if there is a reduction or absence of flow through the circulating system, for example in certain parts of the equipment.

It is an object of the present invention to remedy this drawback 5 and, in particular, to provide a lignosulfonate product having improved anti-caking properties.

The potency of the known lignosulfonate is believed to be based on its low viscosity and thus low molecular weight. Based on this assumption, 10 were prepared by fractionating even lower molecular weight lignosulfonates. However, these lignosulfonates were little or no better.

The present invention relates to a method for reducing mucus formation in water recycling plants by adding lignosulfonate to circulating water. The process is characterized in that the lignosulfonate is prepared by adding to the acidic charcoal pulp sulphite liquor having a reduced calcium content an amount of calcium hydroxide sufficient to separate 20 part with sodium sulphate and sulfuric acid to separate almost all calcium from the lignosulphonate-containing sulphite liquor in the form of calcium sulphate and possibly concentrating the lignosulphonate-containing sulphite liquor.

Surprisingly, there is a leap-like improvement in the reduction of mucus formation when using the lignosulfonate prepared according to the invention.

; · The use of this lignosulfonate results in a significant improvement of the rupture results during paper machine operation. This is primarily due to the fact that lignosulfonate also has a potent effect in the presence or absence of reduced flow through the circulation system 35. As a logical consequence of the reduced and qualitatively improved layering of paper machine rotations, the susceptibility to interferences in the web due to tearing, lumps, or holes is reduced.

The lignosulfonate used in accordance with the invention has a weight average molecular weight of 8000-15000 and a number average molecular weight of 1000-3000.

Preferably, the lignosulfonate used in accordance with the invention has a weight average molecular weight of about 12,700 and a number average molecular weight of about 1564. In another preferred embodiment, the lignosulfonate to be added preferably has a weight average molecular weight of 8500 and a number average molecular weight of 1500. These lignosulfonates achieve particularly good and stable results. Thus, a lignosulfonate product having a higher molecular weight than the known lignosulfonate product will surprisingly lead to an improvement in the reduction of lympho. This is believed to be mainly due to the amount of oligosaccharides used, which is 12 to 16% by weight.

It is further preferred for the lignosulfonate to be used according to the invention that it is made from wood, which is at least partially composed of coniferous wood, wherein this product contains low, at most 1.0% by weight, reducing sugars. Reducing sugars are known to promote the growth of microorganisms. Preferably, the lignosulfonate product 1 has a degree of sulfonation of 1.2 to 1.5.

A further advantageous feature of the lignosulfonate product used according to the invention is that it contains 40-55% short-chain (1-5 units of pentose and / or hexose) cellulose and its additives, partially degraded by oxidation.

• ·

The lignosulfonate may be added to the water at a concentration of 0.1 to 1.0 g / m 3 in the process of the invention. The lignosulfonate is then continuously administered. Additionally, small amounts of biocides known for this purpose can be added to circulating water to further reduce possible lump formation. The biocide is then added periodically, wherein the duration of the biosodium feed is 4 to 50% of the duration of the lignosulfonate feed.

As the biocide one or more organic sulfur-nitrogen compounds or organic bromine-nitrogen compounds, for example methylene bis-isothiocyanate or carbamates or 2,2-dibromo-2-cyanoacetamide or 3,5-dimethyl-1,3,5-2H, may be used. -tetrahydrotiadiatsiini-2-thione.

The advantage of the method according to the invention will be demonstrated in the following by comparative tests. They compare lignosulfonate (product A) according to EP 0 185 963, commercially available product (product X) and product used according to the invention (product B).

The multiple fractionated and modified product used in accordance with the invention is prepared as follows.

Wood chips are processed under conventional sulphite cooking conditions.

To a sulphite liquor of an acidic sulphite mass (272 parts by weight) having a reduced calcium content and containing 45% solids is added 44 parts by weight of calcium hydroxide [Ca (O) 2]. The separated calcium lignosulfonate having a high molecular weight is separated by filtration.

': 25 To 130 parts by weight of solids is added 22 parts by weight of 36% sulfuric acid (H2SO4). The precipitated calcium sulfate is removed by filtration and the filtrate is concentrated to 40% solids. To it (102 parts by weight) is added 16 parts by weight of sodium sulphate 30 (Na 2 SO 4) and 2.3 parts by weight of sulfuric acid (H 2 SO 4). The calcium sulphate precipitate is removed by filtration and sodium hydroxide is added to the filtrate to adjust the pH to 7.5.

• 100 parts by weight of product solids are obtained; the solution may be further concentrated if desired.

35 • · 104817 6

The product obtained has the following percentage composition:

Total-S 6.3

Other than sulphonate S 0.9 5 Sulphonate S 5.4

Well 11.0

Ca 0.6

Phenol-OH 1.2 0CH3 5.6 10 Sugar 0.5

Na lignosulfonate 43

The product thus obtained has a weight average molecular weight of about 12,700 and a number average molecular weight of about 1570. It will be appreciated that other molecular weights within the claimed range may be obtained by modifying the low described procedure. The proportion of oligosaccharides in the product obtained is about 14% by weight.

Experiment 1

Each of the lignosulfonate products A, B, and X was run for 3 months on a paper machine (300 TATO Produktion, deficient / coated). The average number of web tears was measured as a measure of the bonding of the paper machine roller systems and the control of deposits. Product parameters and results are summarized in Table 1, Table 1.

From the table it can be seen that the lignosulfonate product used according to the present invention can achieve an improvement in the number of tears. The improvement is 10% compared to lignosulfonate EP 0 185 963 and up to 20% compared to commercial lignosulfonates.

Experiment 2

Solutions of lignosulfonate A and B were separately added to cultures of mucus-forming bacteria, such as Pseudomona fluorescens, by viscosity changes as a function of time by capillary flow measurement (glass capillary, fluid volumes fed and weight ratios constant). Simultaneously, a blank test was performed, i.e., a sample without the addition of lignosulfonate-5 was used. The culture solutions were stirred for 100 hours and then the stirrer was stopped. The results are summarized in Table 2.

As can be seen in Table 2, viscosity without the addition of lignosulfonate increases significantly over 100 hours. Instead, the lignosulfonates A and B substantially inhibit the increase in viscosity.

Stopping mixing causes a significant increase in viscosity in cultures to which lignosulfonate A has been added or no lignosulfonate has been added. There is virtually no increase in viscosity in the culture containing the added ligno-15 sulfonate B. Thus, while lignosulfonates A and B are capable of preventing bacterial mucus from forming in systems that move, such as paper machine tubes and troughs that flow through 20 stocks or circulating water, lignosulfonate B used in the invention has the additional effect of preventing mucus formation in non-motile systems. This is very important for those critical zones of the paper machine circulation system which are characterized by a lack of or severely impaired flow. Such sites are usually the first and to a large extent to form mucus.

It goes without saying that the effect of this lignosulfonate used in accordance with the invention is very important for the process. It can significantly improve the number of tears;

At the same time, the improved number of tears means an improvement in the economics of the process, since less unwanted machine breaks are needed.

* «104817 8

table 1

Mg Sulfonation- Oligosacchar-% Degree of tears% / 100 t 5 (%) A 4000-7000 1.2-1.5 25-40 2.75 B 12700 1.2-1.5 12-16 2 , 5 X ± 50,000 0.7 not determined 3.2 10 not specified

Table 2

Product Viscosity Increase () 15 Initial Value 100 hours After 100 hours of mixing after standstill A 1 1.1 3.1 20 B 1 1.1 1.3

No More 1.7 1.7 items • ·

Claims (12)

A process for reducing sludge formation in plants in which water is circulated, in which process 5 to the circulating water is added lignosulfonate, characterized in that the lignosulfonate is prepared by adding to the sulfite liquor an acidic wood sulfite pulp which has a sulfite liquor. reduced calcium content, such an amount of calcium hydroxide sufficient to separate such calcium calcium ligosulfonate having a mole mass value of 8000-15000 and a mole mass number value of 1000-3000 is added by treating the residual soluble portion with sodium and sulfuric acid to separate virtually all calcium in the form of calcium sulphate from the sulphite liquor containing lignosulphonate and by any concentration of the sulphite liquor containing calcium sulphonate. 2. A process according to claim 1, wherein the mass average value of the molar mass of the lignosulfonate is 12700 and the number average number of the molar mass is 1564. 3. A process according to claim 1 or 2, characterized in that the mass average value of the molar mass of the lignosulfonate is 8500 and the number average number of the molar mass is 1500. ·. 25 4. A process according to any of the preceding claims, characterized in that the lignosulphonate product contains 40-55% of short-chain, partly degradation-modified degradation products of cellulose and side materials thereof. 30 5. A process according to claim 4, characterized in that the proportion of oligosaccharides in the lig nosulfonate is 12-16% by weight. Process according to any one of claims 1 to 5, characterized in that the proportion of reducing sugar in the lignosulfonate is not more than 1% by weight. a • · 104817 7. A process according to any of the preceding patent claims, characterized in that the lignosulphonate has a sulfonation degree of 1.2 - 1.5. Process according to any of the preceding patent claims, characterized in that the lignosulfonate is added to the water in an amount of 0.1 - 1.0 g / m 3. 9. A process according to any of the preceding patent claims, characterized in that the lignosulphonate is recovered from wood, which is at least partially strengthened by softwood. 10. A process according to any of the preceding patent claims, characterized in that a biocide is further added. 11. A process according to claim 10, characterized in that the biocide is used in an amount of 0.01 - 2.0 g / t water. Use of a method according to any of the preceding claims, characterized in that it is used for reducing mucus formation in a plant where backwater of paper machines is circulated. 1 • «· <