Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
  • D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
  • D21D5/18—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force
  • D21D5/24—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force in cyclones
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04C—APPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
  • B04C5/00—Apparatus in which the axial direction of the vortex is reversed
  • B04C5/14—Construction of the underflow ducting; Apex constructions; Discharge arrangements ; discharge through sidewall provided with a few slits or perforations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04C—APPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
  • B04C9/00—Combinations with other devices, e.g. fans, expansion chambers, diffusors, water locks

Definitions

• the present invention relates in the first place to means for cleaning liquid suspensions, especially fiber suspensions used in paper manufacturing.
• Corresponding present apparatuses are almost solely formed and assembled of hydrocyclones, which due to their in principle simple construction and lack of movable parts have proved to be especially suitable for this kind of cleaning.
• a hydrocyclone operates, as known, by receiving the liquid to be cleaned, the so called feed, and by continuing the rapid rotation so that the lighter particles accumulate to the center, whereas the heavier particles approach the periphery.
• the circulating liquid is distributed and discharged from the cyclone so that the majority thereof escapes through a central discharge opening in the farther part of the cyclone forming a so called accept, whereas the portion with the separated particles circulating in the periphery is delivered towards the top of the cyclone to be discharged as a so called reject.
• cleaning can seldom be carried out completely in one stage or cyclone passage, since the reject still includes separable useful particles which should not be lost and thus the cleaning continues from apparatus to apparatus in the described manner.
• this final reject is not yet discharged straight away because it still includes useful particles, such as coarser fibers and fiber bundles, so called shives, which would be wprth recovering for a secondary object.
• useful particles such as coarser fibers and fiber bundles, so called shives, which would be wprth recovering for a secondary object.
• the amounts of coarse particles that occur in the final reject i.e. sand, metal particles and other coarser scrap is firstly discharged, because they have a harmful influence on the means which will treat the reject material, for example on pumps, but above all, on grinding means and refiners.
• the coarse separation is carried out without any considerable losses in pressure. In other words, it should not cost much to remove the coarse particles in order to collect said rest fibers.
• Another objective of the invention is to produce an apparatus, which is from now on for short called a coarse separator to separate effectively and at low cost these coarse particles from the reject. It can, of course, be maintained that the use range of the coarse separator in accordance with the present invention is not restricted to what is exemplified above, but it can be installed anywhere, where a suspension of light particles, both cellulose fibers and other light particles, can efficiently be removed from sand and other coarser and heavier particles without encountering any significant losses of pressure in the cleaning system.
• Fig. 1 illustrates a total view of the coarse separator from one side and partially sectional
• Fig. 2 illustrates a detail of the separator in a larger scale
• Fig. 3 is a sectional view along line III-III in Fig. 2.
• Fig. 4 illustrates an alternative discharge apparatus for the separated material.
• Fig. 5 finally illustrates a coarse separator in accordance with the invention formed with the outer cleaning stage in the form of additional settling chambers.
• Fig. 1 illustrates a coarse separator 10 in accordance with the invention, in an embodiment applied for treating reject, in, order to separate coarser and wearing particles, such as sand, metal chips, etc.
• the coarse separator 10 comprises two main parts, namely a combined cyclone and settling part 12 and a separate secondary settling chamber or an auxiliary chamber 14.
• the combined cyclone and settling portion 12 comprises a hydrocyclone 15 of a known type, coaxially installed in a cylinder 20, the main cylinder, in which it extends from the top downwards, as shown in Fig. 1.
• the cyclone 15 has usually a feed inlet 16 and an accept outlet 18 and flows downwards, into its so called underflow, a cylindrical reject nozzle 22, through which the reject is discharged to the surrounding cylindrical chamber.
• Its lower part is connected to a discharge apparatus 35 of a sluice type, which is described below and the cylinder 20 comprises in its upper part an overflow opening 25, a so called overflow channel, through which the liquid flowing from the cyclone 15 to the cylinder 20 and ascending upwards in it flows over to the secondary settling chamber 14, as described more closely below.
• the coarse separator in accordance with the invention forms an open system, in other words atmospheric pressure has free access, more precisely to the secondary or auxiliary chamber 14, which is noted by its cylinder 30 pointing openly upwards -and being covered by a lid 32.
• the feed is pumped in at a rather low pressure, 2 to 3 bar, decreasing practically speaking to zero in the accept outlet 18.
• the auxiliary chamber 14 comprises a cylindrical vessel 30, the lower part of which is connected in the same way as that of the main cylinder 20 to a discharge apparatus 35', whereas the upper part as mentioned is open to the atmosphere and covered by the lid 32.
• a pipebend 26 runs from the overflow opening 25 of the main cylinder 20 into the auxiliary chamber 14, which thus receives the liquid flowing out from the cyclone 15 into the main cylinder 20.
• An inwardly extending pipe 40 has been mounted to the reject opening 22 of the cyclone, extending coaxially with the reject opening therethrough to the level s-s where the cylindrical reject opening 22 is transferred to the conical part of the cyclone 15, see Fig. 2.
• the inwardly extending pipe 40 then extends out from the reject opening and bends through the wall of the main cylinder 20 to continue in the auxiliary cylinder 30 and where it ends to a downwardly pipebend 45, which is all evident from Fig. 1.
• the inwardly extending pipe 40 which thus as a whole gets a trunk-like form, and a valve 46 is mounted between both cylinders to regulate the flow through the pipe 40.
• the coarse ⁇ separator in accordance with the invention operates in the following manner.
• the liquid is brought into circulation in the cyclone 15 of the separator simultaneously with the downwardly movement towards the bottom outlet, where the rapidly circulating liquid partly turns and rises upwards along the center of the cyclone, partly flows out through the reject .opening 22, between the inside thereof and the previously described inwardly extending pipe 40.
• the outflowing liquid entrains the coarse particles which are almost immediately slung out towards the inside of the cyclone 15 so as to follow it downwards.
• the movement of the outflowing liquid is dampened rapidly in the main cylinder 20 surrounding the cyclone, and the majority of the separated particles fall towards the bottom of the cylinder.
• the liquid rises in the cylinder so as to flow over through the overflow pipe 25 and through the pipebend 26 into the cylinder 30 of the secondary or auxiliary chamber 14.
• the purpose thereof is thus to form a secondary settling chamber complementing the main cylinder 20, in which chamber the liquid transferred through the overflow pipe 25 is gathered and is brought to settle under smoother conditions, in other words the coarse particles that eventually have not settled in the main cylinder 20 are now given a chance to do so in the auxiliary cylinder 30.
• the circulating liquid generates a vacuum in the center of the cyclone 15 in a known manner, which vacuum extends through the inwardly extending pipe to the auxiliary cylinder 30 so that liquid is drawn from it through the trunk-shaped inwardly extending pipe back to the cyclone 15, as indicated with arrows in Fig. 1.
• the liquid drawn back to the cyclone rises upwards in the center of the cyclone, joins with the liquid directly turning in the bottom outlet and being discharged through the accept outlet 18, free from coarse particles, but entrained with fine particles which are left in the original reject.
• the separated coarse particles are gathered thus to the bottoms of the main cylinder 20 and the auxiliary cylinder 30. From- there they can be transferred out in regular intervals by opening, in case of the main cylinder 20, a slide valve 36 so that the coarse material flows down into a gathering chamber 37. When all the coarse material gathered uptil that moment has flowed down said valve 36 is closed, and a lower slide valve 38 is opened instead and the gathering chamber 37 is unloaded threrethrough.
• the method is applied to the auxiliary chamber 30 which is provided with a valve apparatus 35' comprising a similar, gathering chamber located exactly in the middle between the upper and lower valves.
• valve apparatus 35 or 35' is replaced by an inlet chamber for a screw conveyer 39 which continuously feeds out the separated coarse material which is gathered to the bottom of the cylinder in question.
• the coarse separator in accordance with the invention is set in the optimal drive conditions by regulating the accept outflow (by adjusting the counter pressure in the accept outlet 18) as well as also by regulating the inflow through the trunk pipe 40 by means of the valve 46 mounted therein.
• the liquid level H-H in the auxiliary chamber 30 is caused to settle to an optimal position, which gives a maximal cleaning effect, as can be confirmed by taking a sample of the accept.
• the practical experiments with the separator in accordance with the present invention have proved that the separation effect was very good also with small sand and bark particles which can otherwise be separated only by considerably smaller and more effective hydrocyclones. Additionally saw dust and the like heavier wood particles are separated and gathered into the settling chambers.
• a study of the accept from the separator showed that it was practically speaking free of the sand particles and also no saw dust was to be found in it; the accept comprised only water and fine fiber particles.
• the conical part of the cyclone 15 ends up with a reject portion comprising a cylindrical reject opening 22 with an inwardly extending pipe 40 arranged coaxially therein. It is important that the inner opening of the pipe is at the same level with the s-s level between the conical part of the cyclone and the cylindrical part of the reject opening 22.
• the inwardly extending pipe 40 must thus be either extending upwards in the cyclone 15 or downwards in the reject opening 22, see Fig. 2.
• the coarse separator 10 is, as mentioned, in a condition that it can practically speaking completely separate coarser particles from the flowing liquid, for example, fiber suspension, but in case a hundred per cent separation of these particles, especially very small and hard, such as quartz-type, is desired, the cleaner in accordance with the invention can be "refined” and its separation effect further improved. This can take place in an almost unrestricted extent, as can be seen in Fig. 5, which illustrates a coarse separator 50 in accordance with the invention, in which additional, extra auxiliary chambers or cylinders 60 extend inwards between the original 30 and main cylinder 20 with the cyclone 15.
• Fig. 5 illustrates thus how three such additional auxiliary chambers 60 are installed, and every such chamber is provided with a central intermediary plate or wall 65.
• the overflow from the overflow channel 25 of the main cylinder is supplied to one side of the plate 65 in the first auxiliary chamber 60 and flows downwards along it.
• the plate ends up at a distance from the bottom of the chamber, and it extends upwards to the level of the open upper end of the chamber.
• the liquid flows thus downwards on one side of the plate 65, turns by the bottom of the auxiliary chamber 60, flows then upwards to an upper overflow channel 25' at the same level with main cylinder's overflow channel.
• a second additional chamber 60 is connected subsequent to the first and relative to the current similarly to the first one so that the liquid flows downwards on one side of the plate and upwards along the opposite side of the plate so as to continue further to a third additional chamber 60, in which the flow process is repeated.
• the liquid then continues to a last chamber 30' which corresponds the original single auxiliary chamber 30 in accordance with Fig. 1.
• the inwardly extending pipe 44' from the cyclone 15 extends through - or past - all extra chambers 60 to the final pipebend 45' in the last chamber 30' in order to receive and further transfer the liquid to be redrawn into the cyclone 15.
• the aggregate in accordance with Fig. 5 operates exactly in the same way as the described separator in accordance with Fig. 1 with the exception that a number of additional settling stages are included in the cleaning process.
• the liquid In each of the extra chambers 60 the liquid has the opportunity under its relatively smooth through flow to settle and the separated sedimention is discharged through discharge valves 35', as described above.
• the number of the additional settling stages is determined by how long it is desired in the particular case to run the cleaning process, and as described there is the opportunity to clean the liquid/fiber suspension in this way practically speaking 100 %.
• the described coarse separator is simple and rough in its construction and its lack of constriction in the flow channels decreases the loss of pressure to minimum, and at the same ti- ⁇ e a high through flow capacity becomes possible.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Cyclones (AREA)
• Separation Of Solids By Using Liquids Or Pneumatic Power (AREA)

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• 1989
  • 1989-08-03 SE SE8902661A patent/SE467392B/sv not_active IP Right Cessation
• 1990
  • 1990-07-24 WO PCT/FI1990/000185 patent/WO1991001810A1/en active Application Filing
  • 1990-07-24 CA CA002064104A patent/CA2064104A1/en not_active Abandoned
  • 1990-07-24 US US07/678,291 patent/US5186823A/en not_active Expired - Fee Related

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