SU1650836A1 - Method of classifying fibrous suspension - Google Patents

Abstract

The invention relates to a technique for sorting fiber suspensions and can be used in the pulp and paper industry. The purpose of the invention is to increase productivity and reduce energy consumption while maintaining the quality of sorting by optimizing the process parameters. The method includes feeding the fibrous suspension under pressure into the body, sorting in the gap between the sieve and the disturbing elements, discharging the filtered fraction through the sieve under the impulse effect on the suspension by the disturbing elements in the bottom layer and removing waste that has not passed through the sieve. The gap between the sieve and the perturbing elements is set to 0.9–4.2 mm, and the pulsed impact on the suspension in the pressurized layer is carried out at a linear velocity of the perturbing elements, defined by the relation k-1 () kr Ukr where v is the linear velocity of the perturbing elements, ms; 6 - a gap between the perturbing elements and the surface of the sieve, m, g (x), the maximum tangential stress required to destroy the floccules in the slurry flow, Pa; gcr — critical value of tangential stress, Pa; уКр is the critical shear gradient for the suspension being processed; К is the dimensionless coefficient taking into account the design features of sorting. 2 Il.

Description

The invention relates to a technique for sorting fiber suspensions and can be used in the pulp and paper industry.

The purpose of the invention is to increase productivity and reduce energy consumption while maintaining the quality of sorting by optimizing the process parameters.

In the method of sorting a fibrous suspension, which includes feeding under pressure into the body, sorting in the gap between the sieve and the perturbing elements,

removal through the sieve of the filtered fraction under impulsive influence on the suspension by disturbing elements in the pressurized layer and removal of waste that has not passed through the sieve, the gap between the sieve and the disturbing elements is set within 0.9-4.2 mm, and the pulsed impact on the suspension in the supplied layer is carried out when the linear velocity of the perturbing elements is determined by the relation

V v 7 (x) „,

where v is the linear velocity of the perturbing elements, ms -1;

b - the gap between the perturbing elements and the surface of the sieve, m;

t (x) is the maximum tangential stress required to destroy floccules in a slurry flow, 3

Tcr — critical value of tangential stress, Pa;

Ukr - critical shear gradient for the treated suspension,

K - dimensionless coefficient taking into account the structural features of sorting.

FIG. 1 shows the sorting of a fibrous suspension for carrying out the sorting method; in fig. 2 shows plots of the technological indicators of the sorting process on the size of the gap between the perturbing elements and the sorting surface.

During the implementation of the sorting method through the pipes 1 and 2, the initial fibrous suspension is fed into the sorting housing 3, after which it advances counter-flow from the periphery to the center along the sorting gap 4 between the filter surface of the sieve 5 and the rotating rotor 6 with perturbing elements 7 , with the gap between the tops of the perturbing elements 7 and the filtering surface of the sieve 5 set within 0.9-4.2 mm. The original suspension entering the gap 4 is subjected to sorting, during which the conditioned fraction of the suspension passes through the perforations of the sieve 5, and the sorting waste retained by the sieve 5 is directed to its central zone, from where they are removed through the branch pipe 8. Sorted the fraction is discharged from the sorting through the port 9. The sowing suspension layer, containing mainly the sorting waste, is pulsed by the disturbing elements 7 of the rotating rotor 6, as a result of which regeneration of the filtering surface of the sieve 5 due to the permanent destruction of this layer. Since the process of destruction of the precursor fiber layer is determined by the ratio of the actual stresses created in the suspension and the tangential stresses characterizing the strength of the structure of the suspension, in the proposed method the linear velocity of displacement of the perturbing elements 7 in the suspension is set in accordance with the ratio

0

five

0

g o

0

five

0

V I /

which determines the lowest energy intensity of the process with optimal quality indicators of sorting.

The ratio is, standing on the left side.

Equality is the actual velocity gradient in the gap between the sieve 5 and the tops of the disturbing elements created in the fibrous pressurized layer as the disturbing elements 7 move relative to the surface of the sieve 5.

Rights part of the equality

t (x) K VI. J Ukr is a gradient

one

The shear, corresponding to the maximum tangential stresses required to destroy floccules and fiber bunches in a suspension, characterizes the strength of the structure of the sorted fiber suspension and determines the minimum velocity gradient in the sorted suspension, which guarantees the complete destruction of structural formations in it.

The dimensionless coefficient K, which takes into account the design features of the sorting used to implement the method, as well as possible variations in the parameters of the rheological characteristics of the sorted suspension, vibrates when setting the speed of the disturbing elements from the interval of values 1 ... 2.

The invention is illustrated by experimental data presented in the table and obtained when implementing the method on groundwood pulp with a grinding degree of 71 ± 3 ° SR at a concentration (x)

10 ± 2 g / l, for which

l

five

0

five

tration

t-cr

15,

Ukrainian 270 s, K 1.5. The data presented show that the selection of the peripheral speed of the rotor sorting in accordance with the equality

r, r.

Claims (1)

Together with the choice of the size of the gap between the perturbing elements of the rotor and the surface of the sieve, the quantitative and qualitative indicators of the sorting process are determined within the specified limits while the energy consumption per process is reduced. The invention of the method of sorting fiber suspension, including feeding it under pressure into the body, sorting in the gap between the sieve and disturbing elements, discharging the filtered fraction through the sieve under pulsed impact on the suspension perturbing elements in the prisit layer, and removing waste that has not passed through a sieve, characterized in that, in order to increase productivity and reduce energy intensity while maintaining the quality of sorting by optimizing the process parameters, the gap between the sieve and perturbing elements is set from 0.9 to 4.2 mm, and the pulsed impact on the suspension in the presowing layer is carried out with the linear velocity of the disturbing elements determined from the ratio veKiIiL uk ъ -Ar where v is the linear velocity of the perturbing elements, ms; K is a dimensionless coefficient that takes into account the design features of sorting. b the gap between the perturbing elements and the surface of the sieve, m; r (x) is the maximum tangential stress required to destroy 0 floccules in a slurry stream. Pa; tcr — critical value of tangential stress, Pa; yCr critical shear gradient for the suspension being processed, b 8 / 2 401 BBg% SS3 E83gSEggggrar Јf 1 234567 6, HH Fi. 1 NH KSm 4 1i