AN APPARATUS FOR DEWATERING AND SQUEEZING MATERIAL

Abstract: An apparatus for dewatering and squeezing treatment of material in form of sludge, suspensions, peat, etc, includes as ending treatment part a screw press section (12-14; 28-30) including a press screw (12, 13; 29, 30) and a sieve mantle (14; 28) surrounding the press screw. An out-feed section (7-10) positioned adjacent a dewatering device such as a drum filter, disc filter, bow sieve, etc, is positioned ahead of the screw press section. This out-feed section includes an out-feed screw (8-10) and a trough (7) surrounding this screw. The press screw (12, 13; 29, 30) and the sieve mantle (14; 28) of the screw press section is an extension of said out-feed screw (8-10) and said trough (7), respectively, and are arranged on the same central line. The dewatering device (5, 6) is provided with an inlet (1-3) for the material to be treated and an outlet means, for instance a scraper (21), for supplying the material from the dewatering device (5, 6) to the out-feed section (7-10).

Description: AN APPARATUS FOR DEWATERING AND SQUEEZING MATERIAL The present invention relates to an apparaus for dewatering and squeezing material in form of sludge, sediment, sus- pensions such as paper pulp, peat, etc. Prior art In fabrics such as pulp and paper industries, water cleaning plants etc, applications exist were dewatering of suspensions takes place from dry substances of some tenths procent up to highest possible dry content, for instance 40-50%. Such dewatering operations are carried out today usually in one or two steps . For dewatering within above mentioned area and in one step wire band presses, some types of cylinder presses and so called sieberdru presses are today preferabely used. The disadvantages with such equipment is that the machines are expensive, require large floor space, are expensive in maintenance, are sensitive for operation disturbances, etc. For dewatering in said area and in two steps for instance different type of filters or drum dewaterε are today used for step 1 and usually screw presses for step 2. The dewatering in step 1 takes place from actual inlet concentration up to for instance 10-12% and in step 2 from this value up to highest possible concentration. Filters or drum dewaters and screw presses used in this connection are considerably simple machines and have accor¬ dingly lower price, are cheaper in maintenance and are machines reliable in running. The disadvantages in dewatering in two steps and in separate machines are, however, above all that the apparatuses must for distribution technical reasons be placed a distance from each other in the fabric meaning that the press material must be transported between the sites of the machines. This results in increased costs for the installation, requires larger building volume, increases the energy requirement for the operation, etc. Our Swedish patent No. 8700658-1 CPubl . No. 456 149) dis¬ closes a screw press consisting of a feed screw and sieve mantle surrounding the feed screw. A feed section is arranged ahead of this screw press and this feed section comprises a feed screw and a sieve mantle surrounding this screw. This first mentioned feed section is formed for dewatering mainly by self-drainage and the section has a rotating sieve mantle provided with means for cleaning holes in the sieve mantle. The present invention The present invention has a press section principally simular to that described and shown in our above mentioned Swedish patent. Beside this, however, the present invention differs essentially from the apparatus according to said patent. Moreover, the above mentioned disadvantages have by the present invention been eliminated by providing a unit in which dewatering and squeezing take place in one machine. Dewatering and squeezing take place in a simple and operatively reliable construction at the same time as the advantages with a compact dewatering function is obtained and the need of intermediate transport devices are eliminated. The characterizing of the invention in order to eliminate the above mentioned -disadvantages and in order "to obtain above mentioned adavantages is that ahead of the screw press section and in direct connection to this section is to a dewatering device in the form of a drumfilter, disc filter, bow sieve, etc, arranged an out-feed section connected to the dewatering device, said out-feed section including an out-feed screw and a trough surrounding this screw and said press screw of said screw press section and its sieve mantle being an elongation of and being arranged on the same central line as the out-feed screw and trough of the out-feed section, respectivily, and that to the dewatering device arranged adjacent the out-feed section is arranged an inlet for the material to be treated and an outlet device for tranferring the material from the dewatering device to the out-feed section. Summing up, the apparatus according to the invention thus consists of a combined dewatering part and screw press part, the dewatering part consisting of a dewatering device such as a filter, a drum dewatering device, a bow sieve, etc, to which is connected an out-feed screw and the screw press part being connected as an elongation to the out-feed screw of the dewatering device. Such a combination according to the invention gives essentual advantages which are not predictable when using each machine itself . Such advantages are for instance the following: - a compact unit resulting in lower investment cost, - smaller space requirement, - lower energy requirement for the operation (no intermediate transport devices, etc), - a unit operating with alternatively positive or negative pressure wherein the press part serves as a sealing plug device against the atmospheric pressure, - simpler guiding of a single unit, - infeed to the screw press in axial direction as distin¬ guished from laterally infeed to a screw press which usually requires separate lateral infeed device and such a lateral infeed device is not required in the apparatus according to the mention, - the connection according to the invention makes it easier to optimize the operation over the apparatus. For instance, the output of the filter can be increased and thereby lower outgoing concentration from the filter be accepted and instead carried out a more powerful dewatering in the screw press part. In for instance machines placed apart from each other in the fabric such a balance in the operation is essentially more complicated to carry out and control. Above mention and other advantages will be evident from the following description of embodiments of the invention with reference to the acompanying drawings. Description of drawings Fig. 1 is a horisontel view showing a combined apparatus of filter/screw press section. Fig. 2 shows a section I-I in Fig. 1. Fig. 3 shows a horisontel view in larger scale of another embodiment of an apparatus according to the invention and shows more in detail the outlet part of the out-feed screw from the filter and the screw press section connected to this part . Fig. 4 shows still another embodiment of an apparatus accor¬ ding to the invention. Description of embodiments The embodiment of a filter having outfeed screw and screw press as shown in Figs. 1 and 2 has a shute 2 for material inlet 1 and a intermediate wall or overflow 3 which delimits the shute 2 from a trough 4 in which a drum 5 is immersed. The drum is covered with a filter cloth 6. On opposite side of the inlet 1 there is a trough 7 for receiving the material path 22 formed on the filter cloth 6 of the filter drum 5. A device for disintegration and outfeed of the material path is arranged in the trough 7. This device consists of a screw core 8, thread sections 9 on the core and pins 10 arranged between these sections. Drive means 11 is arranged for the screw. In the elongation of the outfeed screw 8 there is arranged a device for compression and squeezing of the material. This press section consists of a screw core 12 diverging in the feed direction and a continuous thread helix 13 arranged about the core and surrounded by a perforated sieve cylinder 14. For collecting the water squeezed out through the sieve cylinder 14 there is arranged a sealing mantle 15 and a connection piece 16 for the discharged of the squeezed water. At the material outlet 19 from the press there is a reci¬ procating throttle device 18 by means of which the dry content of the squeezed material can be adjusted. The mate¬ rial is collected in a shaft 17 and falls downwardly for further transport. Bearings for the screw cores 8 and 12 are designated with the reference numeral 20. The water drainaged off the filter drum 5 is discharged through a fall chute 23 and the material layer 22 formed on the drum is directed by means of guard board 21 down into the trough 7. Drive means 24 is arranged for driving the filter drum 5. The filter drum is journalled in two conventional bearings 25. Description of the operation of the invention From a pump or level box, etc, the material to be dewatered is fed through the pipe 1 to the chute 2 and further over the overflow 3 to the trough 4. When the drum 5 rotates, a material layer 22 is deposit on the filter cloth 6. This layer is scraped off the cloth by the guard board or scraper 21 and falls down-wardly on the screw 8-10 in the chute 7. By the fact that preferably the peripherical speed of the screw 8—10 is higher than the speed of the material path, the material path is disintegrated into flakes in the chute 7. Upon the rotation of the screw 8-10 the material is fed forwardly in the screw towards the extension where the press section is arranged. When the material enters the press section 12-14 compression takes place due to the diverging screw core 12 and the successivly decreasing volume per pitch in the feed direction. The water squeezed out from the mate¬ rial is collected in the cylindrical mantle 15 and is dis- charged out through the connection piece 16. An adjustment of the dry content of the outgoing material takes place at the outlet 19 by means of the reciprocating throttle device 18. Thereafter the material falls down-wardly into the shaft 17 for further transport. In the application of the invention many divergencies can be made from the embodiment described above in examplefying purposes . For instance, instead of a dewatering device including a drum surrounding by a sieve cloth (so called drum filter) a de¬ watering device can be used including several laterally positioned cloth-covered discs (so called disc filter) . Also a dewatering device of the type bow sieve with acompanying feed screw having a press device at its outlet part is included in the invention. The invention can also for instance be made as shown in Fig. 3. With press material which are different to dewater it can be necessary that the maintenance time for the press material is prolonged in the screw press section. Under the basic idea of the invention the screw press section can for instance be formed with larger diameter than the feed screw part, wherein preferably the feed screw and the press screw, respectively, are driven with different rotation speed. In the embodiment shown in Fig. 3 the end part for a trough 26 and the screw core for a feed screw 27 diverge to be adapted to an in¬ creased diameter for a sieve tube 28 and screw core 30 with press screw 29, respectively. A useful cone angle 37 can be within the area 0°-60° and preferabely within the area 5°-15°. In order to be able to drive the press screw and the feed screw, respecively, with different rotation speeds in this embodiment, the feed screw is provided with a pin 31 which is journalled in bearing 32 in the press screw. A separate drive of the press screw takes place by means of a drive means 33. Another embodiment of the invention is shown in Figs. 4a and 4b. In this embodiment the dewatering device and the feed screw are provided with a sealing cap 34 whereby the appara¬ tus can be operated under positive pressure and negative pressure, respectively. Such an arrangment makes the deposit and the dewatering of the material 22 on the sieve cloth 6 more effected. In such an embodiment the screw press section 12-15 also serves as gate valve when the material during the press process is compressed, forms a sealing plug and is fed out from positive pressure or negative pressure to atmospheric pressure at 35. Dewater squeezed from the material is passed from the gate to atmoεpharic pressure through a valve means 36. In these embodiment several essential advantages when using the present invention are obtained. Thus, the out coming dry content of the material and/or the productions of the unit can be increased and furthermore the built-in screw press function replaces an otherwise necessary extra gate feeder which is both a complex and expansive equipment. A problem which could exist particularly in the embodiment shown in Fig. 3 is that the material path 22 runs off on the sector surrounding drum 5 resulting in that a larger amount material is temporarily forced down into the feed screw part 8-10 and thereby could cause temporary overload in the following screw press section 29, 30. Such a problem can, however, in i simple way be solved by making the drive means 11 for the feed screw 8-10 with variable rotation speed which is governed by the power required for the operation of the feed screw. When a larger amount of material than normally falls down into the feed screw, the power requirement increases in propotion to the increased amount. At the same time, a time delay naturally exists before new material is supplied from the drum to the feed screw. The guidence can, according to the above, function in such a way that the rotation speed of the feed screw is reduced when the power required for the feed screw increases and that the rotation speed returns to normal value when the power requi¬ rement again decreases. Required time delays for respective functions can be varied within the frame for the operation conditions . Such a guidance function is of course also possible to carry out in such a way that the rotation speed for the feed screw 8-10 is governed according to corresponding principles of the power requirement for the press part 29, 30.

Claims: CLAIMS 1. An apparatus for dewartering and squeezing treatment of material in form of sludge, sediment, suspensions such as paper pulp, peat, etc. , which apparatus is ended by a screw press section ( 12-1 ; 28-30) , from which dewatered and squeezed material is discharged through an outlet (19;35) and squeezed water is discharged through an outlet (16;36), and which includes a press screw (12, 13 ; 29 , 30) and a sieve mantle C14;28) surrounding the press screw, c h a r a c t e r i ¬ z e d in that ahead of the screw press section ( 12-14; 28-30) and in direct connection to this section is 'to a dewatering device (5,6) in form of a drum filter, disc filter, bow sieve, etc, arranged an out-feed section (7-10) connected to the dewatering device (5,6), said out-feed section (7-10) including an out-feed screw (8-10) and a trough (7) sur¬ rounding this screw and said press screw (12 , 13 ; 29 , 30) of said screw press section ( 12-1 28—30) and its sieve mantle (14;28) being an elongation of and being arranged on the same central line as the out-feed screw (8-10) and trough (7) of said out-feed section (7-10), and that to the dewatering device (5,6) arranged adjacent the out-feed section (7-10) is arranged an inlet (1-3) for the material to be treated and an outlet device (21) for transferring the material from the dewatering device (5,6) to the out-feed section (7-10). 2. An apparatus according to claim 1, c h a r a c t e r i ¬ z e d in that the out-feed screw (8-10) of said out-feed section ( 7-10) is fixed to the press screw ( 12 , 13 ;29 , 30) of said screw press section (12-14;28-30) . 3. An apparatus according to claim 1, c h a r a c t e r i ¬ z e d in that said out-feed screw (8-10) and said press screw ( 12, 13 ;29 ,30) are driven by the same drive means (11) . 4. An apparatus according to claim 1 , c h a r a c t e r i ¬ z e d in that the out-feed screw (8-10) of said out-feed section (7-10) and the press screw ( 12 , 13 ; 29 , 30) of said press section ( 12-1 ; 28-30) are journalled in each other for rotation with different rotation speed. 5. A device according to claim 4, c h a r a c t e r i z e d in that said out-feed screw (8-10) and said press screw ( 12 , 13 ; 29 , 30) are driven by separate drive means (11;33) . 6. An apparatus according to any of the preceding claims, c h a r a c t e r i z e d in that the sieve mantle (28) of said screw press section ( 12-14; 28-30) and the core (30) of its press screw (29,30), respectively, have at the inlet to the screw press section larger diameter than the trough (7) of said outfeed section (7-10) and the core (8) of its out-feed screw (8-10), respectively, and that the transition between said trough (7) and sieve mantle (28) and said cores (8,30), respectively, are cone-shaped. 7. An apparatus according to any of the preceding claims, c h a r a c t e r i z e d in that the out-feed screw (8-10) of said out-feed section (7-10) is driven with a peripherical speed higher than the speed of the material path in the trough (7) . 8. An apparatus according to any of the preceding claims, c h a r a c t e r i z e d in means (18-20) at the outlet of said screw press section ( 12-14 ;28-30) for controlling the dry content of the discharged material. 9. An apparatus according to any of the preceding claims, c h a r a c t e r i z e d in a cap (34) surrounding the apparatus for operating the apparatus under positive pressure or negative pressure. 10. An apparatus according to any of the claims 3-9, c h a r a c t e r i z e d in means for guiding the rotation speed of said out-feed screw C8-10) independent of the power required for said out-feed screw (8-10) or said press screw (12, 13;29,30) .

Inventors: BERGGREN TORSTEN LENNART, BERGGREN, TORSTEN, LENNART
Applicants: HEDEMORA AB
Application year: 1990
Main classification: D21F1
IPC codes: B01D29, B01D33, B01D36, B30B9, C02F11, D21F1