US3416668A - Table filter washer - Google Patents

Description

Dec. 17, 1968 D. G. LOBLEY 3,416,663

TABLE FILTER WASHER Original Filed June 22, 1964 5 Sheets-Sheet 1 v IITE! I @AAAAQA r-n 24 n 8 I a I I W Dec. 17, 1968 LOBLEY TABLE F ILTER WASHER 5 Sheets-Sheet 2 Original Filed June-22, 1964 Dec. 17, 1968 G. LOBLEY 3,416,668

TABLE FILTER WASHER Original Filed June 22, 1964 3 Sheets-Sheet 3 AAAAAAAAAA W I---------- 'III"''"" United States Patent 3,416,668 TABLE FILTER WASHER Derek Gordon Lobley, St. Bruno, Quebec, Canada, as-

signor to D. & S. Engineering International Limited, Montreal, Quebec, Canada, a Canadian company Continuation of application Ser. No. 377,006, June 22, 1964. This application Aug. 23, 1967, Ser. No. 662,835 3 Claims. (Cl. 210203) ABSTRACT OF THE DISCLOSURE A rotatable table-type pulp thickener unit vertically stacked and readily extended to increase total capacity.

This application is a continuation of application Ser. No. 377,006, filed June 22, 1964, and now abandoned.

This invention relates to a machine for the countercurrent washing and filtration of fibrous, granular and crystalline products and particularly for use in the washing and thickening of pulp stock.

Its greatest application will be in the counter-current washing of soda, sulphate and -N.S.S.C. stocks in kraft and sulphite pulp mills. With sulphate cooked fibre being the predominant product in kraft mills today, the invention will be described in connection with the manufacture of such fibre.

The present method of washing cooking liquor and dissolved solids from sulphate stock is by a countercurrent Washing system, employing two or more filterwashers depending on the number of washing stages required. The stock is fed into one end of the system and proceeds for purposes of this description from left to right in the process. Fresh wash water is applied at the end of the system, and by a series of pumping cycles, is applied to the pulp in a direction opposite to the direction of movement of stock. In this type of operation, is is necessary to dilute between stages, in order that the filter- Washer can pick-up an acceptable sheet for the next stage of washing. The operation can, therefore, be described as continuous, using dilution and displacement washing techniques to remove black liquor and dissolved solids from the pulp.

The effectiveness of the whole cycle is dependent on a number of factors, but the prior aim of the operation is to remove the maximum amount of dissolved solids and liquor with the minimum amount of wash water. By thus so doing, the minimum amount of Water will require to be evaporated prior to the Recovery Furnace, and an obvious power economy will ensue.

A large factor in the overall cost of such a system (commonly called Brownstock Washing) is the space requirement, and the relative inflexibility of operation with stock tonnage fluctuations. For instance, if a system was installed to handle a capacity of 200 tons per day, and the mill required to expaand its facilities to 400 tons per day, duplicate washers would have to be puchased and equivalent floor area provided at much expense.

This invention describes a method in which basically the same machine is used for such a situation, and in which any expansion up to 500 tons per day can be handled without increase in floor space or mechanical drive facilities.

The invention comprises one or more tables of filters rotating with a center shaft and driven from a central power source at the base of the shaft. Each table with its own center shaft section, supporting structure, scroll discharger and discharge chute, are of the same design and construction, thus enabling any multiplicity of five tables to be simply bolted on the bottom table section. For this machine, a total of six tables maximum will be Patented Dec. 17, 1968 deemed practical and commensurate with the torquehorsepower output of the main drive.

Each table will be fed and discharged independently, and conntercurrent washing of pulp up to four stages will be carried out on each table. All washing will be by displacement, none by dilution and the strong liquor and filtrate stages will be separated by an automatic positive clearance type valve at the base of the center shaft.

The object of the invention is to provide a table type pulp thickener unit capable of being stacked one above the other to any desired height and capacity.

A further object of the invention is to provide a common axial drive shaft by means of which the stacked tables are rotated as a unit.

A further object of the invention is to provide means to remove the thickened pulp from each table in the stack and discharge it into a common discharge chute.

A further object of the invention is to provide individual drives for the pulp discharge means at each of the stacked tables.

A further object of the invention is to provide a pulp thickener machine which will take up a minimum of floor space and Where capacity can be added to with a minimum of conversion.

These and other objects of the invention will be apparent from the following detailed specification and accompanying drawings, in which:

FIG. 1 is a front elevation of a typical installation of stacked table pulp thickeners according to the present invention.

FIG. 2 is a partial plan view of the installation shown in FIG. 1.

FIG. 3 is a partial side elevation of the installation shown in FIG. 1 showing the individual drives for the scroll pulp discharge mechanisms.

FIG. 4 is an enlarged partial elevation of the 'top table thickener partly in section to show the discharge scroll, the screen and the water discharge openings.

FIG. 5 is an enlarged vertical section of a typical water discharge valve at the base of the water discharge column.

FIG. 6 is a horizontal cross section through the center column taken on the line 66 of FIG. 1.

FIG. 7 is a horizontal cross section of a typical valve bridge setting.

FIG. 8 is a vertical section through the head box showing the variable slice.

FIG. 9 is a diagrammatic vertical section showing the table elements of FIG. 1 and the method of wash water drainage and dried pulp discharge.

FIG. 10 is a partial plan view taken on the line 1010 of FIG. 9.

Referring to the drawings which illustrate the invention particularly adapted for the filtration and thickening of pulp stock, the machine 5 is formed from two or more table type units A stacked one above the other and rotated by a common drive 6 comprising a motor 7, a reduction gear unit 8 and gearing 9 drivably connecting the reduction gear unit to the drive shaft 10.

Each table unit A comprises its own section of shaft 10, a circular table member 11, mounted about a central hollow column member 12, and consisting of a dished bottom plate 13 (see FIGURE 4) angled upwardly and outwardly from the column member 12 towards an outer vertically disposed peripheral Wall 14. The interior of each table member 11 is divided into sectors 15 by vertically disposed radial Walls 16 (see FIGURES 2 and 4). These walls 16 project upwardly from the inner surface of the dished bottom plate 13 to a level slightly above the level of the juncture of the bottom plate 13 with the peripheral wall 14 to support on their upper horizontal edges 17, a screen 18 (see FIGURES 4 and 9).

Each of the hollow column members 12 has a lower flange 19 (see FIGURE 1) and an upper flange 26 by means of which the individual column members are axially joined to form a continuous water drainage path. The water collected in each of the table sectors is permitted to drain into the hollow column members 12 through apertures 21 formed in the latter (see FIGURE 9).

The drive from each shaft 10 to its associated table member 11 is effected by radial webs 22 connecting the shaft 10 to the inner periphery of the coaxial column member 12. These webs 22 are radially aligned with the radial walls 16 of each table 11 and serve to form individual drainage passages 23 (see FIGURE 6) within the columns 12 for a purpose which will be explained later.

The lower end of the axially aligned and joined column members 12 is provided with a positive clearance valve 24 (see FIGURES 1, 5 and 7) provided with adjustable bridges 25 (shown in FIGURE 7) completely to separate the filtrates and thus prevent contamination between stages. As will be seen more clearly from FIGURE 7, the bridges 25 isolate valve outlets 26, 27, 28 and 29 from each other. A stufling box 30 (see FIGURE 5) is located between the valve 24 and the lower end of the lowermost column member 12 and a second stufling box 31 is radially located between the valve and the drive shaft 10. The valve 24 is located in position by means of jack screws 32 mounted on a sup port structure 33.

Each table unit A includes a framework support comprising four vertical corner members 34 (see FIGURES l and 3) having end flanges 35 by means of which the framework associated with each table unit can be joined together vertically one above the other, and horizontal members 36 and 37 (see FIGURES 1 and 2), secured at their ends to the vertical members 34, form a rectangular structure about each table unit.

A pair of parallel cross members 38 (see FIGURE 2) are located, one on either side of the column member 12 and have their ends joined to the adjacent frame members 36. The uppermost pair of cross members 38 are joined together by a plate 39 on the underside of which is mounted a steady bearing 40 in which is journalled the upper end of the drive shaft 10.

The upper flange 20 of the uppermost section of the column 12 is secured to the shaft 10 by means of a collar 41 (see FIGURE 1).

The downward thrust of the whole machine is taken up in a lower thrust bearing 42.

A pulp discharge scroll 43, provided for each table unit A, is mounted on a shaft 44 supported in bearings 45 and 46 which, in turn, are mounted on the frame and cross members 37 and 38 respectively. These discharge scrolls 43 are disposed at right angles to the axis of rotation of the table members 11 and, as is shown more clearly in FIGURE 9, are located immediately above the top surface of the screen 18. A scroll guard 47 (see FIGURES 2 and 4) located on one side of each of the scrolls 43 serves to pick up the filtered pulp from the screen 18 and prevents pulp from being carried past its associated scroll 43 by the rotating screen 18.

Each discharge scroll 43 has its own individual motor 48 and is rotated by means of a drive 49 connecting the motor 48 with the end of the scroll shaft 44 (see FIGURE 3).

A pulp discharge chute 50 (see FIGURES 13, 9 and 10) is located vertically alongside the outer periphery of each table member 11 and opposite the outer end 51 (see FIGURE 2) of each discharge scroll 43 thereby to receive the pulp from the scrolls and to carry it downwardly for storage or further treatment.

The pulp stock is fed to each of the table members 11 through a stand pipe 52 (see FIGURE 2) and a branch pipe 53 and thence to a pressure head box 54. The pressure head boxes 54 are designed to distribute the pulp stock evenly on the screens 18 from adjacent the column mem- 4 bers 12 to the peripheral edge of the table members 11 and are located adjacent the scroll guard side of the discharge scrolls 43. The head boxes 54 are each equipped with a variable slice 55 (see FIGURE 8) adapted to control the area of the discharge opening 56 of the head box.

Wash water headers 57, 58, 59 and 60 are located at spaced intervals, as shown in FIG. 2, to feed wash water and recycled liquor through nozzles 61 on to and through the pulp stock spread on the screen 18.

During any wash cycle fresh wash water is applied through header 60 and drained through outlet 29 of the clearance valve 24. This liquor is then applied through a stand-pipe 64 (see FIGURE 2) onto header 59 and after passing through the pulp passes out through valve outlet 28. This liquor is then pumped to a stand-pipe 63 and out through header 58. This liquor will then emerge from valve outlet 27 and is reapplied through stand-pipe 62 to header 57. Strong liquor will then report from valve outlet 26 to strong black liquor storage. The motion of pulp is in the opposite direction and this gives continuous counter-current washing.

A screen cleaning shower header 66 (see FIGURE 2) is located between each scroll 43 and the head box 54 is supplied with strong black liquor from pipe 67.

In operation, each table unit A is assembled complete with its associated table member 11, supporting framework, discharge scroll 43 and wash headers. The lowermost unit A is mounted, through its supporting framework, on pedestals 68 (see FIGURE 1) while the clearance valve 24 is adjusted above the supports 33. The drive shaft 10 is then coupled to the drive 6 through a coupling 69. Subsequent table units A are then added, one above the other to the desired number of units. The topmost unit is then completed by mounting the steady bearing 40 for the upper end of the drive shaft 10.

A single clearance valve unit 24 is sufficient to handle the drainage from each of the table units as the location of the headers over each table are vertically aligned with each other and the drainage water passes down through the drainage passages 23 which are common to the sectors 15 of the tables served by each individual header.

Pulp stock is fed from the pressure head box 54 and its flow on to the screen 18 is controlled to ensure absolute uniformity of pulp distribution across the wire area. Each table is fed and discharged independently, and counterwashing of pulp up to four stages will be carried out on each table. All washing is by displacement, none by dilution and the strong liquor and filtrate stages are separated by the automatic positive clearance type valve 24 located at the base of the centre shaft 10.

A machine of the type above-described can be expanded to handle additional tonnage without an increase in floor space or mechanical drive facilities, and the operation of increasing the capacity by the addition of one or more units A can be carried out with a minimum of shutdown time.

I claim:

1. A table filter washing machine including a plurality of units aligned vertically one above the other, each unit including a stationary supporting structure, a substantially horizontal screen rotatable about a vertical axis, and radially extending walls associated with and rotatable with the screen and defining a series of washing sectors, the filter screens and radially extending walls of the units being coupled together for rotation in unison, means to continuously supply stock to be filtered and washed to each screen, central drainage means surrounded by said screens and having a series of vertically-extending drainage passages into each of which filtrate from vertically aligned sectors drains, discharge means for removing filtered and washed solids from each screen, said screens each being co-axially mounted about and secured to a central column member, each said column member being vertically aligned with and coupled to the underlying column member to form a central column, each column member having a plurality of radially extending webs defining said drainage means, and a drive shaft passing co-axially through the central column, said Webs extending radially outwardly from the drive shaft, and the drive shaft including a plurality of vertically-aligned coupled sections, one for each column member.

2. A table filter washing machine according to claim 1 including filtrate re-circulating means connected to the central drainage means to receive filtrate from sectors at a particular angular position and to supply said filtrate to vertically-aligned sectors at another angular position.

3. A table filter washing machine according to claim 2 wherein said central drainage means is secured to and rotates with said screens, and said filtrate re-circulating means includes a rotary valve co-operating with said drainage passages to collect filtrate from vertically-aligned sectors at said particular angular position.

References Cited UNITED STATES PATENTS 1,229,839 6/1917 Wedge 210-332 1,765,252 6/1930 Vernay 210-330 X 2,127,360 8/1938 Helle et a1.v 210-396 X 3,080,063 3/1963 Krynski et al 210-396 REUBEN FRIEDMAN, Primary Examiner.

U.S.C1.X.R.

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