JPH0738189U - Slit screen basket reinforcement structure - Google Patents

Abstract

(57) [Summary] [Purpose] Even when the plate thickness of the basket of the closed pressurization type slit screen has decreased with the passage of days,
Prevents opening of slits due to the differential pressure between the internal and external pressures of the basket to maintain the dust removal rate and improve the plate life. [Constitution] A slit screen basket in which a central portion in the longitudinal direction of the slit is a sealed pressure type slit screen, and a rod-shaped member of about 4φ is wound around the entire outer periphery of the basket for welding reinforcement.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a reinforcing structure of a closed press type centrifugal type slit screen basket used in a process of selecting a pulp and paper raw material in the pulp and paper industry.

[0002]

[Prior art]

 In the pulp and paper industry, various screens are used to remove foreign matter such as wood binding fibers, pitch, plastics, metal pieces and sand from pulp slurries with a concentration of 0.3% to 2.5%. . Of these, the closed pressure centrifugal type slit screen has a shape as shown in FIG. 5, and a slit is provided in the closed screen body as shown in FIG. The screen basket 1 in which the screen plate 9 is processed into a cylindrical shape is built in, and unselected raw material (pulp) is introduced into the screen basket 1 from the raw material inlet 3 and cut on the screen plate 9 to be installed. The pulp that has passed through the slit-shaped opening 7 is taken out as the selected raw material from the selected raw material outlet 4, while the pulp that cannot pass through the opened opening 7 is the raw material containing a large amount of foreign matter (rejected raw material). This is a device that is discharged from the reject material outlet 5. A scraper blade 2 is rotating inside the basket so that the slit-shaped openings of the screen plate are not blocked by the raw material or foreign matter. In addition, the longitudinal direction of the slit-shaped opening 7 is generally cut parallel to the basket cylinder axis. This is done by the scraper blade 2 moving inside the basket along the screen plate surface. This is to make it easier to remove the clogging in the slit part. Further, since the screen basket is usually weak in structural strength, it is reinforced in multiple stages by the reinforcing ring 6 (see FIG. 5).

When this apparatus is used, the proportion of high-quality pulp as a raw material for selection is determined by the width of the slit-shaped opening 7, and recently, those having a narrow slit width tend to be used. This is because the dust removal technology has advanced and stable use is possible even with narrow slits.

[0004] As a background for this, when the pitch and plastics contained in the chips, which are the raw material of pulp, are contained in the raw material for papermaking, paper breakage troubles in the papermaking process and coating using such paper are performed. Since streaks are generated in the manufacturing process, removing them before they are subdivided will lead to stable operation in papermaking and coating and improvement in the quality of the products obtained. There is knowledge.

The conditions that the screen plate 9 should have are generally as follows. (1) The screen plate is less likely to be blocked and can be used stably. (2) Do not let foreign matter to be removed pass through as much as possible. (3) The strength of the screen plate is sufficient to ensure an appropriate plate life (Paper & Paper Cooperative Paper December 1992 P49-77).

Therefore, many improvements related to these have been proposed in the past. For example, Japanese Patent Publication No. 2-476 discloses that a large number of circular or polygonal depressions should be devised and installed in the land portion of the screen plate surface on the inlet side of the grooved screen (slit) screen plate. It is disclosed that the amount of passing through the screen is increased and the life of the plate is extended while maintaining high dust removal efficiency.

In the centrifugal type slit screen, even if the plate has sufficient strength at the time of manufacture, as the number of days of use elapses, the foreign matter such as sand and metal pieces in the pulp slurry causes the plate thickness to increase. As a result, the strength of the screen plate is reduced and the strength of the screen plate becomes insufficient. Finally, the screen basket swells due to the differential pressure corresponding to the difference between the internal pressure and the external pressure of the basket, and the slit width tends to widen. In such a case, foreign matter in the carefully selected raw materials causes an increase in trouble, so it is necessary to stop the operation once to check the opening of the slit of the plate in use and to correct the slit width. In some cases, partial plate damage may result in unavoidable plate replacement.

Methods for improving the strength and rigidity of the screen plate to solve these problems include (1) increasing the plate thickness of the plate, (2) reducing the spacing between the reinforcing rings, and (3) Although there are reinforcement ribs, etc., regarding (1), there is concern that the passage flow rate may decrease due to an increase in the passage resistance of the pulp raw material, and the plate may become clogged. There is. With regard to (2), due to restrictions on the processing accuracy and strength of the reinforcing ring, a reduction in the slit opening area corresponding to the thickness of the reinforcing ring will reduce the flow rate and increase the manufacturing cost. With regard to (3), the rib blocks the flow of raw material and increases the resistance. At present, it is difficult in terms of machining technology to insert ribs so as to prevent the swelling of the screen plate and to allow the raw material flow to pass smoothly. Furthermore, in this case, an increase in resistance and a decrease in the opening area are unavoidable, which causes a decrease in flow rate and an increase in manufacturing cost. As described above, any of the methods described in (1) to (3) has its problems in solving problems.

[0009]

[Problems to be solved by the device]

 The object of the present invention is a closed pressure type centrifugal type slit screen, which prevents the opening due to the differential pressure between the inside and outside pressures of the basket to remove dust even when the plate thickness decreases after the number of days of use of the plate has passed. It is intended to provide a reinforcing structure at a low cost that can maintain the rate and significantly improve the plate life.

[0010]

[Means for Solving the Problems]

 The present invention is a closed pressure type centrifugal type slit screen, in which a plurality of slits are provided by cutting each in parallel to the cylindrical axis of one screen basket, the longitudinal direction of the slits of the slit group This is a reinforcing structure for a slit screen basket characterized in that a rod-shaped member is wound around the entire outer periphery of the basket in the center portion of the slit screen basket.

[0011]

[Action]

 According to the reinforcing structure of the present invention, the rod-shaped member, which is reinforced by winding the central portion of the slit screen basket in the longitudinal direction of the slit around the entire outer circumference of the basket, is supported at the central portion of the slit. In addition, since the bending is greatly reduced, it is possible to prevent the opening due to the pressure difference corresponding to the difference between the inner pressure and the outer pressure of the screen basket, and to remove the wood binding fibers, pitch, plastics, etc. to the selected raw material side. Prevents foreign substances from entering and improves plate life significantly. Further, since the basic basket has sufficient strength, the strength of the reinforcing structure may be such that it supports the central portion in the longitudinal direction of the slit and prevents the slit from expanding outward. As described above, a round bar having a diameter of about 4 mm can be sufficiently used as the bar-shaped member. Further, as shown in FIGS. 2 to 4, since the slit opening is not directly closed by the rod-shaped member which is reinforced by winding the slit substantially in the center in the longitudinal direction, the selected raw material flows out in the form of wrapping around the obstacle, It has no effect on the flow rate and screen pressure loss. The rod-shaped member generally has a circular cross-sectional shape, but other shapes may be used as long as they can be evenly wound around the basket.

[0012]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is of course not limited thereto. 1, 2, 3 and 4 show an embodiment of the present invention, FIG. 1 is a perspective view of a slit screen basket 1, which includes a reinforcing ring 6 (also see FIGS. 2 and 3) in seven stages. The screen plate 9 is divided into two parts and is slit. The screen plate 9 (see also FIGS. 2, 3 and 4) is made of SUS304L and has a thickness of 8 mm. The basket 1 has an outer diameter of 772 mm, a height of 833 mm, and a slit-shaped opening 7 (see FIGS. 1 to 4). A slit width of 0.4 mm (for unbleached softwood raw material) or 0.254 mm (for unbleached hardwood raw material), a slit length of 67 mm, and a cut number of 5 / inch were used. Reinforcement was performed by winding a round bar (reinforcing member 8) of SUS304L of the same material as the basket material and a diameter of 4 mm around the outer periphery of the screen plate 9 around the central portion in the longitudinal direction of the slit. TIG welding that pulls with a chain block so that it does not come loose during winding, generates an arc between the tungsten electrode and the base metal in an inert gas stream, and adds a welding rod to perform welding. The spot welding was performed at intervals of about 200 mm. FIG. 4 is a cross-sectional view of the screen plate 9, and FIG. 5 is a side view of the screen plate 9, but when the reinforcing member 8 is welded to the screen plate, the slit opening 7 is not blocked as much as possible. I was careful.

[0013] Unbleached unbleached softwood kraft pulp (NUKP) and high kappa unbleached softwood craft pulp that have not been carefully selected using the apparatus shown in FIGS. 1 to 4 (examples) and 5 to 6 (comparative examples) Table 1 shows the operation data of Examples and Comparative Examples using the same raw material when (NUKP) and bleached unbleached hardwood kraft pulp (LUKP) were subjected to primary screen treatment. The actual number of screens for NUKP and LUKP is multiple, but the data is shown as the number per unit. Table 2 shows the results obtained by fractionating some of the same raw materials as above using a laboratory flat screen (using 10 CUT plates for NUKP and 8 CUT plates for LUKP).

[0014]

[Table 1]

[Table 2] Note) Calculation formulas for selection rate and dust removal rate 1. Selection rate = outlet throughput / inlet throughput × 100 2. Dust removal rate = ((inlet treatment amount x flat screen residue)-(outlet treatment amount x flat screen residue)) / (inlet treatment amount x flat screen residue) x 100 The operation of the screen is shown in Fig. 6. This is a method in which the valves for the selected raw material outlet 4 and the reject (raw material containing a large amount of foreign matter) outlet 5 are each controlled at a remote flow rate. If the screen differential pressure (pressure difference between the inlet and the outlet) becomes too large, the plate will be blocked. In this case, the adjustment is performed by throttling the outlet valve. Incidentally, the screen differential pressure is usually operated at a maximum of 0.7 to 0.8 Kg / cm ² . In addition, for the determination of the content level of foreign matter in the screen selection raw material, a large foreign matter with a diameter of 0.5 mm or more, a large foreign matter with a length of 3 mm or more, or a foreign matter with a lightly dotted spot on the tip of a pencil is good quality. If there are a large number of selected pulp raw materials, thoroughly check the foreign material content in the selected raw materials from each screen, stop the screen causing the above foreign substances, and correct the slit opening. . Using the conventional screen basket (Fig. 5), which does not have the rod-shaped member like the present invention, but is divided into 7 steps by only the reinforcing ring 6 and slitted, the screen can be removed in about 6 months. The frequency of correcting slit openings has increased. Therefore, as a result of using the screen basket reinforced by using the present invention, even after two years have passed, there are almost no cases of accidents where large foreign matter is mixed or the foreign matter content rate becomes large due to the opening due to the screen differential pressure. lost. As a result, quality and operation are stable, and the life of the screen plate is significantly extended. Regarding the treatment amount and the occurrence of blockage of the plate, no change was observed before and after the reinforcement, as seen from the operation data, and the results were good.

[0015]

[Effect of device]

 As described above, according to the present invention, the screen basket of the centrifugal system is reinforced, and as a result, the material flow rate is maintained almost the same as before the reinforcement, while the good foreign substance content level is maintained for a long period of time. The result is that the life of is greatly extended. In other words, the level of inclusion of foreign matter does not increase the slit opening due to the pressure difference between the inside and outside of the basket even if the plate thickness decreases with the lapse of days of use. The phenomenon of increase in the number of times will disappear, and the operation will be extremely stable.

[Brief description of drawings]

FIG. 1 is a perspective view of a slit screen basket in which a plate outer peripheral surface is reinforced according to the present invention.

FIG. 2 is a partially enlarged view of a side surface of a screen plate according to the present invention.

FIG. 3 is a sectional view of a screen plate according to the present invention (Y-
(Y arrow view).

FIG. 4 is a sectional view of a screen plate (X-
X arrow view).

FIG. 5 is a perspective view of a slit screen basket according to the prior art.

FIG. 6 is a conceptual diagram of a conventional closed press type centrifugal type slit screen.

[Explanation of symbols]

 1: Screen basket 2: Scraper blade 3: Raw material inlet 4: Selected raw material outlet 5: Rejected raw material outlet 6: Reinforcement ring 7: Slit-shaped opening 8: Rod-shaped member 9: Screen plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Kitabatake 1 Oji-cho, Kasugai-shi, Aichi Shin-Oji Paper Co., Ltd. Kasugai Mill

Claims (1)

[Scope of utility model registration request] 1. A hermetically sealed pressure-type centrifugal type slit screen, in which a plurality of slits are provided by cutting each in parallel to the cylindrical axis of one screen basket, the slits of the slit group have a long length. A reinforcing structure for a slit screen basket, characterized in that a rod-shaped member is wound around the entire outer circumference of the basket in the center in the direction.