DE1561702B - Process for the separation of elongated or flat impurities with a low specific weight from fiber suspensions by hydrocyclones - Google Patents

Description

almost complete separation of the light impurities or splinters is possible, namely under Maintaining normal throughput in the hydrocyclone, d. H. with practically complete utilization its nominal capacity. Preferably the fraction withdrawn from the central tip outlet is used subjected to a further sorting process in a hydrocyclone in a manner known per se. Here are different cascade connections of hydrocyclones for the combined separation of the light ones and heavy contamination possible. The small amount of fiber used in the process of the invention is obtained as a light fraction and in which the light impurities are enriched, can in be sieved or further defibrated in a known manner.

The method according to the invention is illustrated below with reference to some of the drawings Embodiments and explained in more detail with the aid of some numerical examples.

1 to 4 are exemplary embodiments different cyclone separation plants with different combinations of cyclone separators schematically shown;

F i g. 5 shows a graphic representation of the results obtained with operation according to the invention the in F i g. 1 to 4 arrangements shown as well as with splinter separation in a single stage.

In Figs. 1 to 4 the inlet of the fiber suspension, D meant the sequence of a final fraction, which is free of splinters substantially, and E is the flow of the other final fraction, which contains most of the fragment. For each of the four embodiments, the corresponding drawing shows the guide and cascade-like branching or feedback of the inflows and outflows of the interconnected separators that are essential to the invention for the respective embodiment.

Of the in F i g. The curves shown in FIG. 5 give the curves I to IV for the curves shown in FIG. 1 to 4 and line V shows the functional relationship between α and ρ or between b and r for a single hydrocyclone. Here means:

α the ratio between the number of splinters in the end fraction E and in the feed C of the plant;

ρ the degree of splinter separation for each individual cyclone separator, ie the ratio between the number of splinters that are drawn off at the head outlet (light fraction outlet) and the number of splinters fed in at the inlet;

b the ratio between the amount of good fibers in the end fraction E and in feed C of the plant;

r is the degree of fiber loss per cyclone separator, ie the ratio between the amount of good fibers that are also drawn off at the head outlet and the amount of good fibers fed to the inlet.

The values of a, p, b and r can be given in percent, for example.
: From the in F i g. 5 I can read off the a and 6 values of the entire system

corresponding to different values of ρ and r. As tests have shown, a splinter separation rate <2 ρ = 70% and a fiber loss rate r = 20% can be assumed as realistic values for the individual hydrocyclone in operation according to the invention. This results "theoretically, that is, neglecting possible losses in the system:

In the case of the system according to FIG. 1 (curve I):

a = 34 and b = 0.8, ie the end fraction E contains 34% of the splinters and 0.8% of the fibers fed in at C;

In the system according to Fi g. 2 (curve II):

a - 59 and b = 1.2, ie the end fraction E contains 59% of the splinters and 1.2% of the fibers fed in at C;

In the case of the system according to FIG. 3 (curve III):

a = 84 and b = 5.9, ie the end fraction E contains 84% of the splinters and 5.9% of the fibers fed in at C;

In the case of the system according to FIG. 4 (curve IV):

a = 94 and b = 1.8, ie the end fraction £ contains 94% of the splinters and 1.8% of the fibers fed in at C.

The following examples show that the values ρ = 70 Vo and r = 20% assumed above are carefully assumed realistic values which in many cases will be considerably more favorable.

Attempt a

1000 grams of an absolutely dry sulfite pulp, which contained a thousand counted impurities in the form of extensive splinters, were treated according to the invention in a hydrocyclone separator at a substance concentration of 0.5% in such a way that 950 grams of the amount of fiber were removed as a heavy fraction, while the rest of 50 Grams was obtained as the light fraction. The number of splinters in the two fractions was counted; it was 850 in the light fraction and 150 in the heavy fraction. This corresponds to a degree of splinter separation ρ = 85% with a fiber loss r = 5%. In relation to the dry fiber substance, the splinter concentration changed from the original 1000 / kg to 17,000 / kg in the light fraction and 158 / kg in the heavy fraction.

Attempt B

A counter-test was carried out according to the usual procedure, taking 50 grams of the fiber amount as the heavy fraction, while the remainder of 950 grams as the light fraction incurred. The number of splinters from the two factions was counted. It was 950 in the light and 50 in the heavy fraction. So there was no enrichment effect whatsoever.

Even if the values obtained according to test A for a single hydrocyclone are only in exceptional cases can also be realized on a technical scale, it can be done with cascade-like arrangements several hydrocyclones according to FIG. 1 to 4 an optimal separation of the splinters with very achieve low fiber loss with the method according to the invention.

1 sheet of drawings

Claims (2)

1 2 Cellulose, as the fiber bundles in the normal patent claims: 'Bleaching processes are not completely bleached. The "splinters" also affect the strength of the 1. Process for severing elongated paper or pulp web. 5 Since the specific gravity of the named impurities according to specific gravity, such as B. of splinters do not clean themselves from that of the fiber material or or fiber bundles from fiber suspensions differed by little, they are considerably heavier Hydrocyclones with peripheral inlet, central to separate as the so-called severe impurities Tip outlet and central head outlet, cleaning that z. B. from grains of sand, soot, heavy characterized in that the pressure io ren rind particles or the like. For sorting and / or area ratio at the outlets of the suspended fibrous materials different spe- art is set so that the larger part, mint weight and especially for travel at least 60% of the fed pulp, mostly pulp fiber suspensions of heavy Tip outlet and the remainder at the head outlet. Impurities are known in hydrocyclones is pulled. 15 of the usual design, which has a completely or partially conical 2. The method according to claim 1, characterized in that the separating chamber has a peripheral inlet and is marked with that those from the central tip central head outlet at the wider end and central outlet withdrawn fraction in a hydro-tip outlet at the narrower end to be cyclone turn to someone in a manner known per se. With such hydrocyclones the head is more severe Sorting process is subjected. 20 outlet the outlet for the light fraction and the Top outlet the outlet for the heavy fraction; when cleaning fiber suspensions, hydro- -. So far, cyclones have only been operated in such a way that the : cleaned fiber material as a light fraction at the head outlet 25 and the impurities as a heavy fraction on The invention relates to a method for peeling off the tip outlet. By setting separate from elongated or flat perimeters cross-sections. the two omissions can be cleanings with low specific gravity, such as the degree of separation changed and the present z. B. of splinters or fiber bundles can be adapted from fiber ratios (chemical engineer suspensions by hydrocyclones with peripheral 30 technique, 1953, pp. 331 to 341). If found too Inlet, central tip outlet and central head, that the withdrawn heavy fraction besides the outlet. also one called "heavy" impurities In the production of chemical pulp on a certain proportion of light impurities, ie routes are nowadays very high requirements. Splinters, has (Paper Trade Journal, October placed on the purity of the product. A large 35 1952, p. 33), it is generally recognized in the paper and line part of the pollutant technology present in the finished product that with hydrocleaning come from discolored bark-cyclones of the normal type mentioned above and divide or bundle fibers. With the previously known mode of operation, these fiber bundles can occur separately, for example, in that certain sufficient separation of the light contaminants in parts of the wood is not possible due to their particularly strong 40. As a way out of this difficult structure when producing or cooking the cellulose is insufficiently impregnated to separate light contaminants, or that a special type of hydrocyclone is known to treat the wood leading to pulp (Austrian patent 258 692), whose cylinder cellulose digester is uneven . A diametrically opposite peripheral outlet for the knots and branches, possibly with which they contain the accept and a central outlet for the surrounding wood layers, and larger pieces of wood, which has impurities, are created through the peripheral inlet and the separating process following the boiling. Because of the special design and mode of operation that have not yet been deforested or opened up to such an extent, however, the fact that they can be easily frayed, the normal output of such a hydrocyclone is limited.
sometimes separated. In the subsequent sieving, 50 In contrast, the invention is based on the object to which the pulp is generally subjected, the separation of the light-weight mentioned, further wood components and possibly impurities from fiber suspensions are separated from bark parts. Depending on how well the previously existing prejudice with hydrocyclone screens is carried out, the pulp can be of a more conventional design, i.e. with a peripheral inlet and zen or less completely free of the above-mentioned central head and tip outlet.
Be impurities. However, economic This object is achieved according to the invention Considerations a limit up to which the cleaning solves that the pressure and / or area ratio to of the pulp can be forced through sieving. the outlet is adjusted so that the larger It has been shown in practice that even after the part, at least 60% of the supplied fiber material. Sieve a greater or lesser number of 60 at the bottom outlet and the remainder at the head outlet different sizes and similar is flattened. In contrast to the previously practiced operation The hydrocyclone under the term “splitter” is the accepted material at the outlet be summed up. deducted for the heavy fraction. Surprising- These impurities, whose color is between 65 wise, was found to be the can be yellow-brown and almost black, causing splinters for the most part to be located in the abz. B. accumulate in the paper made from the pulp drawn light fraction, so that a Stains and soiling often also very extensive bleached items, in the case of multi-stage operation even