US3352745A - Process of separating fibrous pulp into springwood and summerwood fibers by centrifuging - Google Patents

Description

Nov. 14, 1967 v G. E. MALM 3,352,745

PROCESS OF SEPARATING FIBROUS PULP INTO SPRINGWOOD AND SUMMERWQOD FIBERS BY CENTRIFUGING Filed Feb. 27, 1961 PULP I OI/GIMQL Wm WLPI O/P/G/WL PULP INVENTOR ATTORNEYS United States Patent M 3,352,745 PRQQESS 0F SEPARATHNG FIERGUS PULP INTO SPRINGWOQD AND SUMMERWOOD FIBERS BY CENTREFUtEING Gustaf E. Mains, Sundsvall, Sweden, assignor to Svenska Cellulosa Alrtiebolnget, Sundsvall, Sweden Filed Feb. 27, 1961, er. No. 91,890 Claims priority, application Sweden, Feb. 29, 1960, 2,033/60 1 Claim. (Cl. 162-55) The present invention relates to a method of treating fibrous pulp suspensions, containing fibers of different kinds, preferentially suspensions of cellulose pulp containing springwood fibers and summerwood fibers (unbleached, semibleached or all-bleached), in such a manner as will cause the fibers contained in the suspensions to become separated from each other in conformity with p the inherent characters of the fibers. In the present connection fibers of different kinds means such fibers as differ from each other in respect of their morphologic structure and/or specific gravity, specific surface as well as chemical and/or physical properties and which, because of this, when further refined to paper products and/or to packing products and, respectively, to textile fibers, to chemical products etcetera yield different results in respect of the quality and properties of the final product. Examples hereof are the abovementioned springwood fibers and summerwood fibers. The purpose of the separation is to produce, as desired, merely from the obtained fiber fractions or from fractions mixed with each other and/ or mixed with other fractions or pulps, pulps having, for example, different paper-technical properties and, respectively, different derivative-technical properties.

According to the invention the fibrous pulp suspension to be treated is subjected to the action of centrifugal force or centrifugal force in combination with a pumping force and/ or the force of gravity within at least one chamber of treatment connected to a source of suction and/or a source of pressure, for example, a centrifugal or vortex separator, a so-called centricleaner, the various fractions resulting from the separation treatment being then led away from said chamber of treatment in order to constitute, or to be added to, the pulp in which each respective fraction is to be included, after the fibers of such fractions having, if desired, first been, wholly or partly, subjected to further separation and/or mixing with other fractions or pulps. The separation of the fibers-which preferably are suspended in water but which, of course, may be suspended in any other suitable liquid or gaseous medium-can be carried out in one or more steps and under conditions which in each separate case are adapted to the various qualities of pulp to be produced. The chambers of treatment may then be connected in parallel and/or in seriesdirectly and/or in accordance with the principle of so-called cascade connection. The concentration of the fibrous pulp amounts to 0.005-2 percent, preferably to 0.011.6 percent, and preferentially to 0.05-1.3 percent, and the temperature amounts to 0-70 C., preferably to 0-60 C., and preferentially to 1-50 C. The pumping pressure at the inlet end of the chamber of treatment amounts to 02-15 kgs./sq. cm., preferably to 03-12 kgs./sq. cm., and preferentially to 1-8 kgs./sq.,

cm. The counter-pressure, is 0.0- kgs./ sq. cm., prefer- 3,352,745 Patented Nov. 14, 1957 ably 0.0-5 kgs./sq. cm., and preferentially 0.0-2 kgs./sq. cm. The pH-value of the pulp suspension amounts to 1-13, preferably to 2-12, and preferentially to 3-10.

The quantitative proportions of the pulps obtained by the separationthe so-called separated pulpsare adapted to, inter alia, the quantitative proportions and the properties of the components contained in the pulp to be treated-the so-called original pulpand., respectively, to the properties that the separated pulp should have.

Thus, the invention makes it possible to separate fibers having different structures and/or properties and compositions, respectively, such as the abovementioned springwood fibers and summerwood fibers. Since, as is well known, fibers of different types-inter alia springwood fibers and summerwood fibers-yield papers of different types it is, thus, possible in accordance with the invention, to produce, as desired, from an original pulp of a normal or of a special type, containing different fiber components, two or more pulps having different properties.

What has been said above also applies to pulps for other purposes, for example, for textile fibers and for fibers intended for chemical products or for packing materials, for example, so-called liners and cardboard.

In the accompanying drawings FIG. 1 is a schematic illustration of a one step separation in a vertix separator of so-called centricleaner, and

FIG. 2 is a schematic illustration of a two step separation.

Referring to the drawings 1 is a typical known conical vortex separator or so-called centricleaner having a tangential inlet 2 for the pulp to be treated, an outlet 3 for the lighter fraction designated pulp 1 and an outlet 4 for the heavier fraction designated pulp II. As appears in FIG. 2 the lighter fraction leaving the centricleaner 1 through the outlet 3, Le. pulp I is delivered into a second centricleaner 1a in which it is again divided into lighter and heavier fractions designated pulps III and V which leave the centricleaner 1a through the outlets 5 and 6 respectively. At the same time the heavier fraction leaving the centricleaner 1 through the outlet 4 i.e. pulp II, is delivered to a third centricleaner 1b in which this fraction is separated into lighter and heavier fractions designated pulps IV and VI which leave the centricleaner 1b through the outlets 7 and 8 respectively.

Some examples, elucidating the application of the invention in connection with the separation of fibers in various kinds of cellulose pulps, are given below.

Example 1.-Separation, in one step, of fibers in unbleached pine sulphate pulp The separation was carried out in one step in a number of vortex separators, so-called centricleaners, at a pulp concentration of about 0.25 percent. The pump pressure of the entering pulp suspension was 3 kgs./sq. cm. with a counterpressure of the leaving pulp suspension amounting to about 0.1 kg./sq. cm. The pH-value of the pulp suspension amounted to 6.5. The temperature was +20 C. The diagram of connections of such a vortex separator will appear from the accompanying FIGURE 1 of the drawing, the analytical data of the pulps being whereas the fraction indicated as pulp II yielded a paper having a low breaking length and a high tear factorthe paper was very porous and bulky.

Example 2.--Separatin, in one step of fibers in bleached pine sulphatepnlp The separation was carried out in the same way as in Example 1. The analytical dataof the pulps will appear from Table 2 (below). Said table shows that by the separation the original pulp has been divided into two fractions possessing entirely different properties. For purifying the fraction indicated by II, which is, in fact, or which may be, not so pure as the pulp indicated by I, a suitable way of proceeding is as follows:

(1) Screening the pulp in a known manner.

(2) Treating the pulp in vortex separators in at least one, preferably in two or more steps, the return connections being used in the manner which is the most suitable one for the pulp or the pulps desired.

Example 3 .S eparation, in two steps, of fibers in unbleached pine sulphate pulp The separation was carried out in two steps in accordance with the diagram of connections appearing from the accompanying FIGURE 2 of the drawing. The concentration of the pulp at the test amounted to 0.3 percent and the temperature amounted to +16 C. The pump pressure of the entering pulp suspension was 3 kgs./sq. cm. and the counterpressure of the leaving pulp suspension amounted to about 0.1 kg./sq.-cm.- The pH-value of the suspension was 6.9. The analytical data of the pulps are found in Table 3 (below), which shows that the connections used'in this case resulted in pulps of entirely different characters. The pulps I, III and V are exceptions, said pulps being rather of the same character. Consequently, in the present case it is possible to restrict oneself to first separating the original pulp into pulps I and II, pulp II being then separated into pulps'IV and VI. Said pulps, IV and VI, may then in their turn be separated in a suitable manner, according to the desiderata existing in respect of the number of qualities and, respectively, the properties of the qualities. Pulp IV and fractions thereof in the. accepted fractions as Well as in the rejected fractions preferably may be screened and/or treated in a vortex separator.

Example 4 .-Separation, in one step, of fibers in unbleached birch sulphate pulp The original pulp was treated under, the same conditions as in Example 1. The analytical data of the pulps will appear from Table 4 (below), which shows that the pulps obtained by the separation-are rather similar to each other and also similar to the original pulp except in respect of the porosity and the volume-weight of the paper made thereof.

Example 5 .---Separation, in one step, of fibers in unbleached spruce snlp/zile pulp The separation was carried out under conditions similar to those in Example 1. The analytical data of the pulps are to be found in Table 5 (below), from which it will appear that the original pulp has been separated into two pulps having different paper-technical properties.

As previously mentioned the vortex separators, the socalled centricleaners, used for the separation, may be connected in parallel and/or in series-directly and/or according to the principle of so-called cascade connection.

TABLE 1.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARATED PULIS, RESIECTIVELY (UNBLEACIIED PINE SULPHATE PULP) Valley beating of dried pulp Fiber Pulp Chlorine meter Degree Time Breaking Burst Tear Folding Porosity; Absorp- Volume number weight, of beating of beating, length, factor factor number see/100 tion, weight,

mgJm. SR min. km. cu. cm. mm. gJcu. cm.

13 0 2.4 16 0 70 0.37 Original pulp 1 5. 5 0. 194 25 10. 4 81 129 4, 000 25 33 0. 45 11.8 91 111 4, 400 390 12 0.70 14 0 39 27 3 44 0. 48 Pulp I 1 -5. 6 0. 160 25 52 10.8 99 4,000 85 21 0.71 45 74 12. 2 96 81 4, 500 900 6 0. 77 13 0 1.3 8 0 80 0.33 Pulp II -5. 2 0. 233 25 50 9.0 70 149 3, 500 19 48 0. 00 45 72 10. 6 85 125 4, 300 150 17 0. 67

1 The pulps screened before being analyzed, screening resi(lne=0.l7

TABLE 2.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARATED PULPS, RESPECTIVELY (BLEACI'IED PINE SULIHATE PULP) Valley beating of dried pulp Whiteness, Fiber Pulp percent meter G.E. weight, Degree of Time of realring Burst Tear Folding Porosity, Absorp- Volume mg./n1. beating, beating, length, factor factor number see/ tion, weight,

S min. km. cu. em. mm. g./eu. cm.

Original pulp 14, 5 0 2. 0 16 1 104 0. 4? 86.0 0. 190 25 35 8.4 66 105 2,900 37 34 0.70 45 57 9. 4 72 90 3,100 640 17 0. 74 15. 5 0 2. 2 l6 1 0. 48 Pulp I 86,1 0.157 25 32 8.5 70 103 2, 700 47 33 0. GS 45 53 9. 5 78 88 3, 400 840 17 0. 74 12. 5 0 1. 4 10 -1 0 110 0. 43 Pulp II 85.6 0.235 25 38 7.8 66 114 2,300 22 41 0. 65 45 56 8. 6 72 99 2, 800 340 20 0. 71

The expression fiber meter weight" means the weight in milligrams of 1 meter length of fibers placed and to emit TABLE 3.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARATED PULPS, RESPECTIVELY (UNBLEACH- ED PINE SULPI-IATE PULP) Valley beating Pulp Degree of Time of Breaking Burst Tear Folding Prosity, Absorp- Volume beating, beating, length, factor factor number sec./l n11. tion, mm. weight,

SR min. km g./cm. cu.

Original pulp 13. 0 3. 4 22 0 75 0.42 25 47 10. 5 81 113 3, 700 36 29 0. 67 45 72 12.0 96 100 4, 400 800 9 O. 72 13 0 3. 2 20 0 81 0. 39 25 49 10. 4 82 118 4,000 26 4O 0. 67 45 74 11. 8 93 101 4, 600 700 11 0. 73 Pulp I 13. 5 0 3. 8 26 1 65 0. 44 25 44 10. 6 81 110 2, 900 38 30 0.68 45 68 12. 2 97 94 4, 500 900 8 0. 73 Pulps separated from pulp 1:

Pulp III 14 0 4. 0 28 1 57 0. 45 25 46 10. 9 84 164 3, 000 65 25 0. 70 45 67 12. 4 9S 2 4, 500 920 7 O. 74 Pulp V 14 0 2. 5 15 0 67 0 42 25 48 9. 9 79 122 8, 800 19 40 0. 65 45 74 11. 7 88 103 4, 400 550 12 O. 70 Pulp II 13 0 2.4 17 .1 0 68 0.36 25 43 9.8 75 127 3, 200 16 44 0.64 45 65 11. 4 90 111 3, 700 420 0. 70 Pnlps separated from pulp II:

Pulp IV 13 0 2. 3 0 89 0.38 49 9. 9 80 124 3, 700 36 0. 67 45 7O 11. 7 90 105 4, 200 550 13 O. 72 Pulp VI 12 0 1. 7 10 0 73 0.32 25 44 9. 0 65 136 2, 300 8 49 0. 62 45 65 10. 7 82 116 3, 300 290 15 0. 65 Pulp I+II 13.5 0 3. 4 21 1. 1 80 0.41 25 48 10.0 84 118 4,000 26 36 0. 67 45 73 11. 7 94 103 4, 400 890 14 0.72 Pulp V+IV 12 0 2. 3 17 0 86 0. 36 25 49 9. 8 79 123 3, 909 22 37 O. 66 45 72 11.7 91 107 4,400 550 15 0. 71

TABLE 4.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARATED PULPS, RESPECTIVELY (UNBLEACHED BIRCH SULPHATE PULP) Valley beating Denomination Degree of Time of Breaking Burst Tear Folding Porosity, Absorption, Volume beating, SR beoting,min. length, km. factor factor number sec./100 cu. nun. weight, gJeu.

cm. cm.

Original pulp 14. 5 0 4. 8 25 1 86 0. 59 25 14 8. 8 57 75 900 27 34 0.71

Pulp I 15.0 0 5. 4 30 3 67 0.61 25 14 9. 2 60 75 800 32 35 0. 74

Pulp II 13.0 0 3. 4 16 106 0.50 25 20 9.2 60 74 950 29 0. 62

TABLE 5.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARAT ED PULPS, RESPECTIVELY (UNBLEACHED PRUCE SULPHITE PULP) Valley beating Denomination Degree of Time of Breaking Burst Tear Folding Porosity, Absorption, Volume beating, SR beating, min. length, km. factor factor number see/100 cu. mm. weight, gJcu.

em. C111.

Original pulp 13. 5 0 6. 5 42 7 58 0. 66 25 1O 9. 1 57 200 14 0. 77 45 21 9. 8 59 1, 200 0 O. 84 Pulp I 14. 5 0 6. 8 46 12 50 0. 67 25 8 9. 6 62 500 12 0. 75 45 17 10. 0 67 1, 200 1 O. 81 Pulp II 12. 0 0 4. 6 31 1. S6 0. 62 25 12 8. 3 54 200 23 O. 73 45 24 9. 2 1, 200 0 0. 80

References Cited Having now described my invention What I claim as UNITED STATES PATENTS new and desire to secure b Letter Patent 's:

Th h V fib d t 2,377,524 6/1945 Samson 209 211 3 P c ss V C C mPI'ISeS eI'lZlng WOO 1n 0 Hesch FOREIGN PATENTS 76,122 10/1954 Netherlands.

DONALL H. SYLVESTER, Primary Examiner.

MORRIS O. WOLK, H. L. MARTIN, R. A. OLEARY,

Examiners.

75 H. CAINE, F. W. LU'ITER, Assistant Examiners.

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