CA1318257C - Process for the separation of solids from suspensions having a high solids content - Google Patents
Process for the separation of solids from suspensions having a high solids contentInfo
- Publication number
- CA1318257C CA1318257C CA000530895A CA530895A CA1318257C CA 1318257 C CA1318257 C CA 1318257C CA 000530895 A CA000530895 A CA 000530895A CA 530895 A CA530895 A CA 530895A CA 1318257 C CA1318257 C CA 1318257C
- Authority
- CA
- Canada
- Prior art keywords
- pressure
- filter
- process according
- container
- solid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000000725 suspension Substances 0.000 title claims abstract description 54
- 238000000034 method Methods 0.000 title claims abstract description 37
- 239000007787 solid Substances 0.000 title claims abstract description 36
- 238000000926 separation method Methods 0.000 title claims abstract description 15
- 238000001914 filtration Methods 0.000 claims abstract description 29
- 239000012065 filter cake Substances 0.000 claims abstract description 17
- 239000007788 liquid Substances 0.000 claims abstract 11
- 239000000706 filtrate Substances 0.000 claims description 9
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 239000000049 pigment Substances 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims description 2
- 150000003839 salts Chemical class 0.000 claims description 2
- 239000004408 titanium dioxide Substances 0.000 claims description 2
- 239000002699 waste material Substances 0.000 claims description 2
- 239000006194 liquid suspension Substances 0.000 claims 2
- 230000000763 evoking effect Effects 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 17
- 150000002500 ions Chemical class 0.000 description 11
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- 235000011149 sulphuric acid Nutrition 0.000 description 3
- 239000001117 sulphuric acid Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- BHMLFPOTZYRDKA-IRXDYDNUSA-N (2s)-2-[(s)-(2-iodophenoxy)-phenylmethyl]morpholine Chemical compound IC1=CC=CC=C1O[C@@H](C=1C=CC=CC=1)[C@H]1OCCNC1 BHMLFPOTZYRDKA-IRXDYDNUSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000006887 Ullmann reaction Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- JCYWCSGERIELPG-UHFFFAOYSA-N imes Chemical class CC1=CC(C)=CC(C)=C1N1C=CN(C=2C(=CC(C)=CC=2C)C)[C]1 JCYWCSGERIELPG-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011085 pressure filtration Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 238000003828 vacuum filtration Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/90—Separation; Purification
- C01B17/901—Recovery from spent acids containing metallic ions, e.g. hydrolysis acids, pickling acids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
- B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
- B01D29/114—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements arranged for inward flow filtration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
- B01D29/76—Handling the filter cake in the filter for purposes other than for regenerating
- B01D29/80—Handling the filter cake in the filter for purposes other than for regenerating for drying
- B01D29/84—Handling the filter cake in the filter for purposes other than for regenerating for drying by gases or by heating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
- B01D29/88—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor having feed or discharge devices
- B01D29/90—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor having feed or discharge devices for feeding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D35/00—Filtering devices having features not specifically covered by groups B01D24/00 - B01D33/00, or for applications not specifically covered by groups B01D24/00 - B01D33/00; Auxiliary devices for filtration; Filter housing constructions
- B01D35/16—Cleaning-out devices, e.g. for removing the cake from the filter casing or for evacuating the last remnants of liquid
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Filtration Of Liquid (AREA)
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
- Preparation Of Clay, And Manufacture Of Mixtures Containing Clay Or Cement (AREA)
- Treatment Of Sludge (AREA)
Abstract
Process for the separation of solids from suspensions having a high solids content ABSTRACT OF THE DISCLOSURE
Solids can be effectively separated from liquid/
solid suspensions having a high solids content by dis-continuous filtration in a pressure filter wherein the suspension to be filtered is first placed in a pressure container, the suspension is then delivered pneumati-cally under pressure from the pressure container into a pressure filter wherein filtration causes a solid-liquid separation, then pressure gas is delivered in the filter removing moisture from the filter cake and for-cing the unfiltrated suspensions to flow back to the pressure container and filtered solids are recoverd.
Le A 23 833
Solids can be effectively separated from liquid/
solid suspensions having a high solids content by dis-continuous filtration in a pressure filter wherein the suspension to be filtered is first placed in a pressure container, the suspension is then delivered pneumati-cally under pressure from the pressure container into a pressure filter wherein filtration causes a solid-liquid separation, then pressure gas is delivered in the filter removing moisture from the filter cake and for-cing the unfiltrated suspensions to flow back to the pressure container and filtered solids are recoverd.
Le A 23 833
Description
13~ 8~
Process for ~he separa~ion of solids from suspensions S having a high solids conten~
_ The presen~ invention rela~es to a process for the separation of solids from suspensions having a high solids conLent by discon~inuous filtration in pressure filters.
BACKGROUND OF THE INVENTION
SusFensions which have a high solids content can be separa~ed by vacuum filtration or excess pressure filtration. Con~inuous vacuum fil~ra~ion is generally preferred, optionally with precoat layers to provide an accep~able ra~e of filtra~ion (Ullmanns Enzyklopadie d.
techn, Chemie, Verlag Chemie, Weinheim, 4th Edition 1972, Volume 2, pages 188 e~ seq.).
The fil~ration of suspensions of very finely divi-ded solids, however, is often so slow that pressure fil-tra~ion is necessary for separa~ing the solids. Filter presses have proved suitable for this purpose but they have the disadvantage tha~ the overall cost of ~he appara~us employment is high either because, in ~he case of a low degree of automation~ ~he ~ime for emptying ~he filter presses amoun~s to a substantial proportior. of the total charging period (especially when filtering suspensions which have a high solids con~ent) or because, in the case of a high degree of automa~ion, the absolute cost of ~he appara~us is very high.
The specific cos~ of the apparatus based on the surface area of the filter is much more favorable in the ; 35 Le A 23 833 13 3L ~ h ~
case of pressure filters comprising leaf filters or car~ridge filters. These fil~ers have, however, the disadvantage that with each batch, a large volume of container must be filled with suspension before the actual filtration process and must be emptied again after filtration. If the suspension have a solids content of, for example, 10 % by weigh~ or more and the filtra~ion times are shor~ ~in the ran~e of seconds ~o a few minutes) depending on ~he pressure and the permeability of the filter ca~e, then the relatively long time required for filling and emp~ying the filter with the suspension is a very significant factor. For suspensions having a solids content of 10 % by weight or more, ~he volume of the filter housing amounts to 1 to 10 ~imes ~he volume of filtrate obtained per batch, depending on the solids content. Very large, expensive ~ pumps are ~herefore necessary if short filling times are to be achieved, but the frequent on/off switching of such pumps gives rise to considerable problems. To this is added ~he problem tha~ repeated transport of the suspensions through pumps destroys the particles of solids or ~he agglomerates so that ~he suspensions become more difficul~ ~o filter and the removal of moisture from the filter cake also becomes more difficult. For these reasons, pressure filters of the type of leaf or cartridge filters have hardly been usad in the past for the filtra~ion of suspensions with a high solids content, especially when filtration can be carried out with continuously operating vacuum filters.
It was therefore an object of the present invention to provide a process which would be free from the dis-Le A 23 833 13 1 ~
:advantages described above but would make use of the advantages of pressure fil~ers.
BRTEF DESCRIPTION OF THE INVENTION
It has now surprisingly been found that these ob-jects can be achieved if a separate pressure container ~10 is used both for filling the pressure fil~er as in the -original filtratlon pro&ess and the suspension is also discharged into this pressure con~ainer after fil-tration.
The present inven~ion thus relates to a process for the separation of solids from suspensions having a high solids content by discontinuous filtration in pr~ssure fil~ers, in which process the suspension which is to be filtered is conveyed pneumatically from a pressure con-tainer to the pressure filter and the suspension which has not been filtered is returned to be pressure con-tainer after filtration.
The variation of the process according to which thevolume of the pressure container i5 at least 10 % and preferably 10 to 100 % greater than that of the pressure filter is particularly preferred.
BRIEF DESCRIPTION O_ THE DRAWIN5 The Figure illustrates the flow sequence and apparatus used to achieve the improved filtra~ion of the process of this invention, DETAILFD DESCRIPTION
The process according to the invention is described : below with reference to the Figure which illus~rates one possible arrangement for &arrying out the process arcording to the invention.
Le A 23 83 ~ 4 ~ 13~ 3 1 The arrangement illustrated includes a pressure filter (1) which is a leaf or cartridge filter and a pressure container t2) connected thereto, the volume of which container (2) is a~ least 10 %, preferably not less then 50 % greater than the volume of the pressure filter (1). A pump (3) is for feeding the suspsnsion into the pressure container (2). A separating appara-tus (4) is for separating the filtrate from the gasused for removing the moisture from the ~ilter caXe and a separating vessel (5) is for separating the residue of suspension from the gas used for forcing this residue out of ~he filter. The separa~ing apparatus (4) may be a simple vessel, a cyclone separator, a laminar separa-tor, a wire mesh separator, a filter, an EGR or some other known separa~ing apparatus, depending on the nature and the size of the droplets of the filtrate carried along with the gas which has been forced through the filter cake for the removal of its moisture. The separating vessel (5) may be dispensed with if ~he residue is emptied in~o the pressure container (2).
The suspension (26) is delivered by the pump (3) in~o the pressure con~ainer (2) at a rate adjusted by the flow regulator (13) according ~o ~he average fil-tra~ion rate of the batchwise process. The suspension is in~ermittently expalled from the filled container (2) into the filter (1) through the connecting duc~ (27) by ~ means of pressure gas (Z5). The pressure of the gas is maintained until the filter (1) has been filled and a fil~er cake of the required ~hic~ness has been produced on the filter medium.
Le A 23 833 13~82~7 The pressurizing gas used in the process of ~his inven~ion can be any gas whi~h is iner~ ~o the suspen-sion being filt~red. A preferred gas is air but de-pending on the nature of the suspension, steam, ni~ro-gen, argon, carbon dio~ide, helium and other readily available gases are suitable. The ~ r~e (16) ob~ained as a resul~ of this filtration flows through the opened st~p val~e (8) into the separati~g apparatus (4) ~o be discharged f~om there in~o a con~ainer for filtrate.
At the end of the filtration time required for producing the necessary thickness of filter cake, the flow shutter (12l is closed and the flow shutter (6) is opened to admit pressure gas (14) into the part of the filter (1) provided for the suspension. With the aid of the pressure gas, filtration of the suspension may be continued down to the level at which the filter leaves or fllter car-tridges dip into the suspension. The suspension left in the lower part of the filter (1) may then be returned to the pressure container (2) by way of the pipe (27) by releasing pressure gas (24) from the container (2) through the flow shutter (11). Since in this procedure the filter cake becomes much thicker in the lower part ~f the filter (1) than in the upper part of the filter (1), the following procedure is preferred for suspensions which have a high solids content: After the flow shutter (6) has been opened, the flow shutter (11) is opened to such an extent that the suspension flowsr~pidly into the pressure container (2) through pipe (27) but without pressure pulses. The pressure gas (14) introduced through the flow shutter (6) firstl~- forces the suspension out of the filter (1), secondly causes filtration of a small Le A 23 833 ~318~
proportion of the suspension in which the filter elements are still immersed during the stage of rapid emptying, and thirdly removes moisture from the filter cake. The pressure gas (1~) f~d into the fi]ter escapes through the opened flow shutter (8) to the separating apparatus l4) together with the moisture carrièd along with the gas, and separation into filtrate (18) and exhaust gas (19j takes place in the apparatus (4). When the filter cake has been sufficiently freed from moisture, the ~low shutter ~9) is opened and the remaining suspension (21) is forced out of the filter (1). Separation of the suspension (22j from the pressure gas (20) takes place in the separating vessel (5). After removal of the residue (21) of suspension, the flow shutter (6) is closed, the shutter (lO) is opened and the filter cake (23) is discharged from the filter (1). In the case of leaf filters, the cake is discharged from the filtering agent in known manner by rotation or vibration of the leaves. In cartridge filters, which are particularly preferred, the filter cake is discharged by closing of the flow shutter (8) and intermittent injection of pressure gas (15) into 25 the filtrate duct by sudden opening of the shutter (7).
In the cartridge filters, which are preferred, the positioning of the pressure container (2) at a lower level than the filter (1), as shown in the Figure, provides special advantages since no flow shutters are then required 30 in the connecting duct (27) so that vibrations which would occur due to sudden outflow of the suspension from the filter (1) when such a large shutter is opened are thus avoided. Such vibrations could cause part of the filter cake to break away from the filter cartridge and L~ A 23 83 therefore significantly interfere with the process. The arrangement according to the invention, in which the pressure container (2) is placed at a lower level and the filter is emptied under controlled conditions ~y release of pressure from the pressure container by way of the flow shutter (11) prevents such interference with the process.
The embodiment of the process according to the invention in which the pressure container is arranged below the pressure filter is therefore particularly preferred.
When filtration is carried out on suspensions which give rise to a firmly adhering filter cake or when leaf filters are used, the arrangement of the filter (1) at the same level as the pressure container (2) may provide advantages. An arrangement requiring the installation of a flow shutter in the pipe (27) lies within the scope of the invention since it also enables the filter to be rapidly filled and emptied without the aid of pumps.
Filtration is advantageously always carried out under such conditions that the pressure in the pressure container is higher than that in the pressure filter during filling of the pressure filter and during filtration.
The invention provides special advantages for the filtration of suspensions with a high solids content such as those resulting from the preparation of pigments, (e.g., iron oxide and titanium dioxide pigments) or for the separation of metal salts from sulphuric acid in the conversion of waste acid.
~5 Le A 23 833 ~ 3 ~
-- 8 ~
In such cases, good results are obtained when the pressure in the pressure container is maintained during the process of filtration or even increased until the filter cake acquires the required thickness of 15 to 50 mm.
The advantages of the process according to the invention and of the arrangement of apparatus for this process will now be illustrated by an example without the process according to the invention being limited to this example.
15 Example A Fundabac ~ cartridge fllter (1) of DrM (Switzerland) having a filter surface area of 25 m2 and a volume of 10 m3 was used. In each batcl., 5 t (corresponding to 20 2.9 m3) of a suspension of 1.38 t of metal sulphates in 3.62 t of 65~ sulphuric acid we~e filtered. The batch time was 16 minutes and the rate of filtration there-fore 18.75 t of suspension/h.
The pressure container (2) had a volu~.~ of l6 m3.
25 Before filtration was begun, 80% of the rontainer (2) was filled with suspension (26) by means of the pump (3) (Output: 12 m /h at a counter pressure of 8 bar).
At the onset of the filtration, the flow of suspension was ~djusted to 10.7 m3 per hour by means of a control valve (13). The contents of container (2) were introduced into the filter (1) for 2 minutes by forcing the suspension into the filter (1) through the pipe (27) by means of compressed air (25) at a pressure of 7 bar. The volumetric rate of flo~ through the pipe (27) was 300 m3/h. Intro-3~ duction of suspension into the filter (1) and displacementof air from the filter (1) were immediately followed Le A 23 ~33 ~31~2~
_ 9 _ by the filtration process proper. 2.9 m~ of suspension were filtered over a period of 90 seconds, corresponding to a volumetric flow of 116 m3/h throuqh the pipe (27).
After a total of 3.5 minutes, valve (12) was closed, valve (6) was opened (introduction of air under a pressure of 7 bar) and the pressure in contai.ner (2) was slowly released by opening of the valve (11), The valve (11) was closed after 75 seconds, when the suspension in the filter (1) had reached its lowest level, and the filter cake was blown dry with compressed air (14) for S minutes.
~5 In the laminar separator (4) the filtrate (18) was freed from compressed air which escaped as exhaust air (13).
The valve (9) was then opened and tne residue of suspen-sion in the filter (1) was forced into the separating vessel (5). When compressed air began to leak through, valve (6) was closed, th~ valve (11) was opened,/the pressure in -the filter was released through the valves (8) and (9) and the slide (10) was then opened. After the valve (8) had been opened, the valve (7) was rapidly opened so that the filter cake (23) was discharged by a pulse of compressed air (15).
The duration of the whole batch was 16 minutes.
1.8 t of filter cake having a residual moisture content of 23.4~ and 3.2 t of 65% sulphuric acid, corresponding to 2 m2 of filtrate, were obtained. The thickness of the cake was about 35 mm.
., Le A 23 833
Process for ~he separa~ion of solids from suspensions S having a high solids conten~
_ The presen~ invention rela~es to a process for the separation of solids from suspensions having a high solids conLent by discon~inuous filtration in pressure filters.
BACKGROUND OF THE INVENTION
SusFensions which have a high solids content can be separa~ed by vacuum filtration or excess pressure filtration. Con~inuous vacuum fil~ra~ion is generally preferred, optionally with precoat layers to provide an accep~able ra~e of filtra~ion (Ullmanns Enzyklopadie d.
techn, Chemie, Verlag Chemie, Weinheim, 4th Edition 1972, Volume 2, pages 188 e~ seq.).
The fil~ration of suspensions of very finely divi-ded solids, however, is often so slow that pressure fil-tra~ion is necessary for separa~ing the solids. Filter presses have proved suitable for this purpose but they have the disadvantage tha~ the overall cost of ~he appara~us employment is high either because, in ~he case of a low degree of automation~ ~he ~ime for emptying ~he filter presses amoun~s to a substantial proportior. of the total charging period (especially when filtering suspensions which have a high solids con~ent) or because, in the case of a high degree of automa~ion, the absolute cost of ~he appara~us is very high.
The specific cos~ of the apparatus based on the surface area of the filter is much more favorable in the ; 35 Le A 23 833 13 3L ~ h ~
case of pressure filters comprising leaf filters or car~ridge filters. These fil~ers have, however, the disadvantage that with each batch, a large volume of container must be filled with suspension before the actual filtration process and must be emptied again after filtration. If the suspension have a solids content of, for example, 10 % by weigh~ or more and the filtra~ion times are shor~ ~in the ran~e of seconds ~o a few minutes) depending on ~he pressure and the permeability of the filter ca~e, then the relatively long time required for filling and emp~ying the filter with the suspension is a very significant factor. For suspensions having a solids content of 10 % by weight or more, ~he volume of the filter housing amounts to 1 to 10 ~imes ~he volume of filtrate obtained per batch, depending on the solids content. Very large, expensive ~ pumps are ~herefore necessary if short filling times are to be achieved, but the frequent on/off switching of such pumps gives rise to considerable problems. To this is added ~he problem tha~ repeated transport of the suspensions through pumps destroys the particles of solids or ~he agglomerates so that ~he suspensions become more difficul~ ~o filter and the removal of moisture from the filter cake also becomes more difficult. For these reasons, pressure filters of the type of leaf or cartridge filters have hardly been usad in the past for the filtra~ion of suspensions with a high solids content, especially when filtration can be carried out with continuously operating vacuum filters.
It was therefore an object of the present invention to provide a process which would be free from the dis-Le A 23 833 13 1 ~
:advantages described above but would make use of the advantages of pressure fil~ers.
BRTEF DESCRIPTION OF THE INVENTION
It has now surprisingly been found that these ob-jects can be achieved if a separate pressure container ~10 is used both for filling the pressure fil~er as in the -original filtratlon pro&ess and the suspension is also discharged into this pressure con~ainer after fil-tration.
The present inven~ion thus relates to a process for the separation of solids from suspensions having a high solids content by discontinuous filtration in pr~ssure fil~ers, in which process the suspension which is to be filtered is conveyed pneumatically from a pressure con-tainer to the pressure filter and the suspension which has not been filtered is returned to be pressure con-tainer after filtration.
The variation of the process according to which thevolume of the pressure container i5 at least 10 % and preferably 10 to 100 % greater than that of the pressure filter is particularly preferred.
BRIEF DESCRIPTION O_ THE DRAWIN5 The Figure illustrates the flow sequence and apparatus used to achieve the improved filtra~ion of the process of this invention, DETAILFD DESCRIPTION
The process according to the invention is described : below with reference to the Figure which illus~rates one possible arrangement for &arrying out the process arcording to the invention.
Le A 23 83 ~ 4 ~ 13~ 3 1 The arrangement illustrated includes a pressure filter (1) which is a leaf or cartridge filter and a pressure container t2) connected thereto, the volume of which container (2) is a~ least 10 %, preferably not less then 50 % greater than the volume of the pressure filter (1). A pump (3) is for feeding the suspsnsion into the pressure container (2). A separating appara-tus (4) is for separating the filtrate from the gasused for removing the moisture from the ~ilter caXe and a separating vessel (5) is for separating the residue of suspension from the gas used for forcing this residue out of ~he filter. The separa~ing apparatus (4) may be a simple vessel, a cyclone separator, a laminar separa-tor, a wire mesh separator, a filter, an EGR or some other known separa~ing apparatus, depending on the nature and the size of the droplets of the filtrate carried along with the gas which has been forced through the filter cake for the removal of its moisture. The separating vessel (5) may be dispensed with if ~he residue is emptied in~o the pressure container (2).
The suspension (26) is delivered by the pump (3) in~o the pressure con~ainer (2) at a rate adjusted by the flow regulator (13) according ~o ~he average fil-tra~ion rate of the batchwise process. The suspension is in~ermittently expalled from the filled container (2) into the filter (1) through the connecting duc~ (27) by ~ means of pressure gas (Z5). The pressure of the gas is maintained until the filter (1) has been filled and a fil~er cake of the required ~hic~ness has been produced on the filter medium.
Le A 23 833 13~82~7 The pressurizing gas used in the process of ~his inven~ion can be any gas whi~h is iner~ ~o the suspen-sion being filt~red. A preferred gas is air but de-pending on the nature of the suspension, steam, ni~ro-gen, argon, carbon dio~ide, helium and other readily available gases are suitable. The ~ r~e (16) ob~ained as a resul~ of this filtration flows through the opened st~p val~e (8) into the separati~g apparatus (4) ~o be discharged f~om there in~o a con~ainer for filtrate.
At the end of the filtration time required for producing the necessary thickness of filter cake, the flow shutter (12l is closed and the flow shutter (6) is opened to admit pressure gas (14) into the part of the filter (1) provided for the suspension. With the aid of the pressure gas, filtration of the suspension may be continued down to the level at which the filter leaves or fllter car-tridges dip into the suspension. The suspension left in the lower part of the filter (1) may then be returned to the pressure container (2) by way of the pipe (27) by releasing pressure gas (24) from the container (2) through the flow shutter (11). Since in this procedure the filter cake becomes much thicker in the lower part ~f the filter (1) than in the upper part of the filter (1), the following procedure is preferred for suspensions which have a high solids content: After the flow shutter (6) has been opened, the flow shutter (11) is opened to such an extent that the suspension flowsr~pidly into the pressure container (2) through pipe (27) but without pressure pulses. The pressure gas (14) introduced through the flow shutter (6) firstl~- forces the suspension out of the filter (1), secondly causes filtration of a small Le A 23 833 ~318~
proportion of the suspension in which the filter elements are still immersed during the stage of rapid emptying, and thirdly removes moisture from the filter cake. The pressure gas (1~) f~d into the fi]ter escapes through the opened flow shutter (8) to the separating apparatus l4) together with the moisture carrièd along with the gas, and separation into filtrate (18) and exhaust gas (19j takes place in the apparatus (4). When the filter cake has been sufficiently freed from moisture, the ~low shutter ~9) is opened and the remaining suspension (21) is forced out of the filter (1). Separation of the suspension (22j from the pressure gas (20) takes place in the separating vessel (5). After removal of the residue (21) of suspension, the flow shutter (6) is closed, the shutter (lO) is opened and the filter cake (23) is discharged from the filter (1). In the case of leaf filters, the cake is discharged from the filtering agent in known manner by rotation or vibration of the leaves. In cartridge filters, which are particularly preferred, the filter cake is discharged by closing of the flow shutter (8) and intermittent injection of pressure gas (15) into 25 the filtrate duct by sudden opening of the shutter (7).
In the cartridge filters, which are preferred, the positioning of the pressure container (2) at a lower level than the filter (1), as shown in the Figure, provides special advantages since no flow shutters are then required 30 in the connecting duct (27) so that vibrations which would occur due to sudden outflow of the suspension from the filter (1) when such a large shutter is opened are thus avoided. Such vibrations could cause part of the filter cake to break away from the filter cartridge and L~ A 23 83 therefore significantly interfere with the process. The arrangement according to the invention, in which the pressure container (2) is placed at a lower level and the filter is emptied under controlled conditions ~y release of pressure from the pressure container by way of the flow shutter (11) prevents such interference with the process.
The embodiment of the process according to the invention in which the pressure container is arranged below the pressure filter is therefore particularly preferred.
When filtration is carried out on suspensions which give rise to a firmly adhering filter cake or when leaf filters are used, the arrangement of the filter (1) at the same level as the pressure container (2) may provide advantages. An arrangement requiring the installation of a flow shutter in the pipe (27) lies within the scope of the invention since it also enables the filter to be rapidly filled and emptied without the aid of pumps.
Filtration is advantageously always carried out under such conditions that the pressure in the pressure container is higher than that in the pressure filter during filling of the pressure filter and during filtration.
The invention provides special advantages for the filtration of suspensions with a high solids content such as those resulting from the preparation of pigments, (e.g., iron oxide and titanium dioxide pigments) or for the separation of metal salts from sulphuric acid in the conversion of waste acid.
~5 Le A 23 833 ~ 3 ~
-- 8 ~
In such cases, good results are obtained when the pressure in the pressure container is maintained during the process of filtration or even increased until the filter cake acquires the required thickness of 15 to 50 mm.
The advantages of the process according to the invention and of the arrangement of apparatus for this process will now be illustrated by an example without the process according to the invention being limited to this example.
15 Example A Fundabac ~ cartridge fllter (1) of DrM (Switzerland) having a filter surface area of 25 m2 and a volume of 10 m3 was used. In each batcl., 5 t (corresponding to 20 2.9 m3) of a suspension of 1.38 t of metal sulphates in 3.62 t of 65~ sulphuric acid we~e filtered. The batch time was 16 minutes and the rate of filtration there-fore 18.75 t of suspension/h.
The pressure container (2) had a volu~.~ of l6 m3.
25 Before filtration was begun, 80% of the rontainer (2) was filled with suspension (26) by means of the pump (3) (Output: 12 m /h at a counter pressure of 8 bar).
At the onset of the filtration, the flow of suspension was ~djusted to 10.7 m3 per hour by means of a control valve (13). The contents of container (2) were introduced into the filter (1) for 2 minutes by forcing the suspension into the filter (1) through the pipe (27) by means of compressed air (25) at a pressure of 7 bar. The volumetric rate of flo~ through the pipe (27) was 300 m3/h. Intro-3~ duction of suspension into the filter (1) and displacementof air from the filter (1) were immediately followed Le A 23 ~33 ~31~2~
_ 9 _ by the filtration process proper. 2.9 m~ of suspension were filtered over a period of 90 seconds, corresponding to a volumetric flow of 116 m3/h throuqh the pipe (27).
After a total of 3.5 minutes, valve (12) was closed, valve (6) was opened (introduction of air under a pressure of 7 bar) and the pressure in contai.ner (2) was slowly released by opening of the valve (11), The valve (11) was closed after 75 seconds, when the suspension in the filter (1) had reached its lowest level, and the filter cake was blown dry with compressed air (14) for S minutes.
~5 In the laminar separator (4) the filtrate (18) was freed from compressed air which escaped as exhaust air (13).
The valve (9) was then opened and tne residue of suspen-sion in the filter (1) was forced into the separating vessel (5). When compressed air began to leak through, valve (6) was closed, th~ valve (11) was opened,/the pressure in -the filter was released through the valves (8) and (9) and the slide (10) was then opened. After the valve (8) had been opened, the valve (7) was rapidly opened so that the filter cake (23) was discharged by a pulse of compressed air (15).
The duration of the whole batch was 16 minutes.
1.8 t of filter cake having a residual moisture content of 23.4~ and 3.2 t of 65% sulphuric acid, corresponding to 2 m2 of filtrate, were obtained. The thickness of the cake was about 35 mm.
., Le A 23 833
Claims (15)
1. In the process for separation of solids from liquid/solid suspensions having a high solids content by discontinuous filtration in a pressure filter, the improvement comprises admitting the suspension to be filtered into a pressure container, pneumatically de-livering the suspension from said container into a pressure filter wherein filtration causes a solid-liquid separation, removing the liquid filtrate from the filter and then when the desired amount of solids collect in the filter, subjecting the contents of the filter to a pressure higher than the pressure in said container whereby unfiltered suspension is forced out of the filter and returned to the pressure container, whereupon filtered solids are recovered from the filter.
2. Process according to Claim 1 wherein the volume of the pressure container is at least 10 % greater than the volume of the pressure filter.
3. Process according to Claim 2 wherein the volume of the pressure container is 10 to 100 % greater than the volume of the pressure filter,
4. Process according to Claim 1 wherein the pressure filter is arranged physically higher than the pressure container.
Le A 23 83
Le A 23 83
5. Process according to Claim 1 wherein during the delivery of the suspension from the pressure container into the pressure filter and during filtration, the pressure in said container is higher than the pressure in the filter.
6, Process according to Claim 1 wherein the pressure filter is a leaf filter.
7, Process according to Claim 1 wherein the pressure filter is a cartridge filter,
8. Process according to Claim 1 wherein the solid/
liquid suspension subjected to filtration comprises solid iron oxide or titanium dioxide pigments.
liquid suspension subjected to filtration comprises solid iron oxide or titanium dioxide pigments.
9, Process according to Claim 8 wherein the pressure in the pressure container is maintained substantially constant throughout the solid-liquid separation until a filter cake thickness of 15 to 50 millimeters is obtained,
10, Process according to Claim 8 wherein the pressure in the pressure container is increased during the solid-liquid separation,
11. Process according to Claim 1 wherein the solid/liquid suspension subjected to filtration comprises solid metal salts obtained from waste acid.
Le A 23 833
Le A 23 833
12. Process according to Claim 11 wherein the pressure in the pressure container is maintained substantially contstant throughout the solid-liquid separation until the filter cake thickness of 15 to 50 millimeters is obtained.
13. Process according to Claim 11 wherein the pressure in the pressure container is increased during the solid-liquid separation.
14. Process according to Claim 1 wherein at least a portion of the liquid removed from the filter is sub-jected to a gas-liquid separation.
15. Process according to Claim 1 wherein moisture is removed from the recovered solids while still in the filter by contacting the solids with a flow of pressur-ized gas.
Le A 23 833
Le A 23 833
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19863606986 DE3606986A1 (en) | 1986-03-04 | 1986-03-04 | METHOD FOR SEPARATING SOLIDS FROM SOLID-SUSPENSIONS |
| DEP3606986.8 | 1986-03-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1318257C true CA1318257C (en) | 1993-05-25 |
Family
ID=6295429
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000530895A Expired - Fee Related CA1318257C (en) | 1986-03-04 | 1987-03-02 | Process for the separation of solids from suspensions having a high solids content |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0235689B1 (en) |
| AU (1) | AU585134B2 (en) |
| CA (1) | CA1318257C (en) |
| DE (2) | DE3606986A1 (en) |
| FI (1) | FI89874C (en) |
| NO (1) | NO166621C (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0362428B1 (en) | 1988-10-06 | 1992-12-23 | KRONOS TITAN-Gesellschaft mbH | Process and apparatus for the treatment of a sulfuric-acid solution containing ferrous sulfate |
| NL1023398C2 (en) * | 2003-05-13 | 2004-11-16 | Amafilter Bv | Method and device for filtering an unfiltered residual content in a filter device for liquids. |
| DE102006046214B3 (en) * | 2006-09-29 | 2008-04-30 | Siemens Ag | Fluid collection device |
| DE102010016394A1 (en) * | 2010-04-12 | 2012-05-10 | Solar Und Vakuum Technologie (Svt) A.G. | Solid/liquid mixtures dehumidifying and cleaning method, involves supplying liquid from separating bottom to storage tank, and cooling down heating plates as condensate over drain pipe while providing cleaned vapor |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA981595A (en) * | 1972-06-15 | 1976-01-13 | Dorr-Oliver Incorporated | Defouling ultrafiltration cells |
| DE2831607A1 (en) * | 1978-07-19 | 1980-01-31 | Peter Ueberall | Filter with automatic cleaning action - using air cushion used to backflush element at regular intervals, for use on car wash plants |
| DD159605A1 (en) * | 1981-06-11 | 1983-03-23 | Helmut Hartmann | METHOD AND DEVICE FOR MULTI-STAGE FILTRATION OF PHOTO BAGS |
| BR8301830A (en) * | 1982-04-12 | 1983-12-20 | Amsted Ind Inc | FILTERING APPLIANCE AND PROCESS TO SEPARATE SOLIDS IN SUSPENSION IN A LIQUID |
| US4469594A (en) * | 1982-11-12 | 1984-09-04 | Harnischfeger Corporation | High pressure hydraulic system and self-cleaning filter assembly therefor |
-
1986
- 1986-03-04 DE DE19863606986 patent/DE3606986A1/en not_active Withdrawn
-
1987
- 1987-02-18 NO NO870642A patent/NO166621C/en unknown
- 1987-02-19 DE DE8787102365T patent/DE3772222D1/en not_active Expired - Lifetime
- 1987-02-19 EP EP87102365A patent/EP0235689B1/en not_active Expired - Lifetime
- 1987-03-02 FI FI870897A patent/FI89874C/en not_active IP Right Cessation
- 1987-03-02 AU AU69655/87A patent/AU585134B2/en not_active Ceased
- 1987-03-02 CA CA000530895A patent/CA1318257C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE3606986A1 (en) | 1987-09-10 |
| FI870897A0 (en) | 1987-03-02 |
| FI870897A (en) | 1987-09-05 |
| AU585134B2 (en) | 1989-06-08 |
| NO870642L (en) | 1987-09-07 |
| AU6965587A (en) | 1987-09-10 |
| EP0235689B1 (en) | 1991-08-21 |
| FI89874B (en) | 1993-08-31 |
| DE3772222D1 (en) | 1991-09-26 |
| EP0235689A3 (en) | 1988-11-17 |
| FI89874C (en) | 1993-12-10 |
| NO166621C (en) | 1991-08-21 |
| EP0235689A2 (en) | 1987-09-09 |
| NO870642D0 (en) | 1987-02-18 |
| NO166621B (en) | 1991-05-13 |
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| Date | Code | Title | Description |
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| MKLA | Lapsed |