GB2031297A - Improvements in conveyors - Google Patents
Improvements in conveyors Download PDFInfo
- Publication number
- GB2031297A GB2031297A GB7929330A GB7929330A GB2031297A GB 2031297 A GB2031297 A GB 2031297A GB 7929330 A GB7929330 A GB 7929330A GB 7929330 A GB7929330 A GB 7929330A GB 2031297 A GB2031297 A GB 2031297A
- Authority
- GB
- United Kingdom
- Prior art keywords
- angle
- flight
- solid
- repose
- conveyor
- 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.)
- Withdrawn
Links
- 239000007788 liquid Substances 0.000 claims abstract description 33
- 239000007787 solid Substances 0.000 claims abstract description 33
- 238000000034 method Methods 0.000 claims description 23
- 239000000463 material Substances 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 16
- 239000011343 solid material Substances 0.000 claims description 12
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 238000011084 recovery Methods 0.000 claims description 2
- 238000007670 refining Methods 0.000 claims description 2
- 150000001875 compounds Chemical class 0.000 abstract description 6
- 238000002425 crystallisation Methods 0.000 abstract description 6
- 230000008025 crystallization Effects 0.000 abstract description 6
- 238000001816 cooling Methods 0.000 abstract description 3
- 239000012452 mother liquor Substances 0.000 description 6
- OCJBOOLMMGQPQU-UHFFFAOYSA-N 1,4-dichlorobenzene Chemical compound ClC1=CC=C(Cl)C=C1 OCJBOOLMMGQPQU-UHFFFAOYSA-N 0.000 description 3
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 3
- 239000002178 crystalline material Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000003350 kerosene Substances 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000010960 commercial process Methods 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000007363 ring formation reaction Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/08—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with moving particles
- B01J8/10—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with moving particles moved by stirrers or by rotary drums or rotary receptacles or endless belts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B5/00—Washing granular, powdered or lumpy materials; Wet separating
- B03B5/48—Washing granular, powdered or lumpy materials; Wet separating by mechanical classifiers
- B03B5/52—Spiral classifiers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/18—Details relating to the spatial orientation of the reactor
- B01J2219/182—Details relating to the spatial orientation of the reactor horizontal
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Screw Conveyors (AREA)
- Filling Or Emptying Of Bunkers, Hoppers, And Tanks (AREA)
- Glanulating (AREA)
Abstract
A laboratory crystallization rig comprises a crystallising tube 2 surrounded by cooling jacket 4 and having a feed inlet 5 and overflow outlet 6. Crystallised compound is moved in the direction of the collecting tube 7 by means of helical ribbon conveyor whose angle of flight is selected to exceed the angle of repose of the solids within the liquid medium, but not to exceed 90 DEG . The crystallised compound is melted at the bottom of tube 7 by a heater element 9 and is withdrawn in molten form through melt outlet 8. <IMAGE>
Description
SPECIFICATION
Improvements in conveyors
This invention relates to apparatus for carrying out processes which involve the countercurrent movement of a solid medium and a liquid medium. In particular it relates to conveyors in the form of an
Archimedian screw wherein the helix is one which extends out from the axis or is in the form of a helical ribbon or ribbons coaxial to, but disposed in spaced relationship from the axis (both forms hereinafter referred to as Archimedian screws) which specifically are designed to effect countercurrent movement of a solid and a liquid medium.
In industry there are many instances where it is necessary or desirable to effect countercurrent movement of a solid and a liquid medium. For example, in the treatment of ores it may be desirable to move ground ore countercurrently to a liquid solvent or a liquid reactant. Similarly many processes involving crystalization or precipitation are conveniently carried out in the environment of countercurrent movement of a solid and a liquid phase.
Heretofor Archimedian screw conveyors (as defined above) have not been specifically designed to move a solid medium countercurrently to a liquid medium. Such conveyors have been designed to move material in one direction or to suspend a solid material in a liquid which is pumped through the apparatus carrying the suspended solid in cocurrent flow.
The present invention provides an Archimedian screw conveyor which is specifically designed to move a solid medium in countercurrent relationship to a liquid medium. The countercurrent movement of the liquid may be created solely by the action of the screw, or by an independent force source such as a pump, or by a combination of both.
In accordance with the present invention there is provided an apparatus for carrying out a process which involves the countercurrent movement of a solid and a liquid medium, said apparatus including a conveyor comprising an Archimedian screw or ribbon (as herein defined) having an angle of flight exceeding the angle of repose of the solid medium within said liquid medium, providing always that the angle of flight is less than 90 degrees.
The angle of repose for a particular solid medium in a particular liquid medium is defined as the angle that the solid slurry inclines itself with the horizontal under gravity settling and can be measured easily in laboratory apparatus. Variations in the angle of repose exists for any solid materials depending upon the shape and size of the particular solid material and the amount and nature of the liquid medium.
The angle of flight is defined as the angle the blade makes with respect to the longitudinal axis of the screw and is shown as a in Figure 1 of the accompanying drawing, wherein the arrow 1 indicates the direction of transport of the solid material.
The invention also provides a method of carrying out a process for the treatment or reaction of materials which involves the countercurrent movement of a solid and a liquid medium comprising conducting such process using an apparatus which includes a conveyor comprising an Archimedian screw or ribbon (as herein defined) having an angle of flight exceeding the angle of repose of the solid medium in the liquid medium, providing always that the angle of flight is less than 90 degrees, to produce a desired resultant forward flow of the solid medium relevant to the countercurrent flow of the liquid medium. Preferably the speed of the conveyor is such that the material is maintained in a sedimented or incipient fluidized state so as to minimise back flow of solid material.
The invention further provides a method of constructing a conveyor for use in an apparatus for carrying out a process involving the countercurrent movement of a solid and a liquid medium, said conveyor comprising an Archimedian screw or ribbon (as herein defined) whereby the angle of repose of the solid medium in the liquid medium is measured and the angle of flight of the screw or ribbon is determined in relation to the angle of repose such that the angle of flight exceeds the angle of repose providing always that the angle of flight is less than 90 degrees.
Thus the present invention, as broadly stated above, is derived from the discovery of the relationship of the angle of flight of the blade in an Archimedian screw to the angle of repose of the particular solid medium in the particular liquid medium.
The advantages of the present invention can be exemplified by reference to a number of types of existing commercial processes. One such type of process is where crystallization of a solid material from a mother liquor is carried out under desired conditions involving forward transport of the crystals with countercurrent flow of the mother liquor. In such a process using an Archimedian screw conveyor wherein the angle of flight of the blade is less than the angle of repose of the crystallizing material at a particular point in the conveyor it is possible to develop an undesirable ring formation of the crystalline material due to a predominance of the radial motion of the crystalline material across the tube over the movement along the tube.In accordance with the present invention this can be prevented by measuring the angle of repose of the crystalline material in the mother liquor and adopting an appropriate angle of flight for the blade.
It will be appreciated that the angle of flight may vary along the length of the conveyor to satisfy different process requirements at different points of the conveyor.
The advantages of the present invention can further be illustrated when applied to apparatus of the type discussed in this specification having a bearing section or sections through which the solid medium must be transported. Such a bearing section may occur, for example, between the solid discharge end of the conveyor and another part of the overall apparatus for carrying out a further stage of the process. Aiso in certain types of apparatus the screw or ribbon of the conveyor may be jiscontinuous resulting from a bearing section or sections along the conveyor.
In such apparatus having a bearing section or sections there is a problem in providing adequate transport of the solid material across the gap or bearing section. Although a significant amount of solid
material can be conveyed along the conveyor if the angle of flight is less than the angle of repose,
because of the screw mechanism, when a flow restriction area, such as a bearing section, is reached the
solid material will not adequately be transported across such gap or bearing section. In accordance with
the present invention this problem can be resolved by determining the angle of repose of the solid
material in the liquid medium and adopting an angle of flight for the blade to provide a resultant vector
to cross the bearing section. In some apparatus it is envisaged that the angle of flight will increase
significantly at or approaching a bearing section.
Although the foregoing description is primarily concerned with horizontal conveyors it will be
understood that it also applies to conveyors which are inclined to the horizontal. The effect of inclining
the conveyor will, of course, either increase or decrease the residence time of the solid medium in the
conveyor.
In order to more fully illustrate the invention the following laboratory and pilot experiments were
carried out under the conditions indicated.
EXAMPLE I
Laboratory Determination of angles of Repose
Angles of repose for each material were measured in a laboratory horizontal crystallizer. The
equipment consisted of a 25 cm long 10 cm diameter cylindrical glass crystallizer jacketed by a
rectangular box which allows coolant of the required temperature to be circulated. A ribbon blade stirrer
12 mm wide with zero pitch, that is an angle of flight of 0 degrees, with a 3 mm clearance is driven by a
variable speed motor in which the speed can be varied from 0.5 to 10 rpm. The whole equipment can be
rotated about a swivel pin thereby allowing the angles of repose for crystals in their mother liquors or
appropriate solvent to be measured.
Results Angle of
Material Repose
(i) Paradichlorobenzene in its
mother liquor
90% pure 35
93% pure 35
68% pure 40
25% pure 20
(ii) Napthalene in its mother liquor
95% pure 35
85% pure 40
70% pure 55
60% pure 35
EXAMPLE II
Pilot Plant Studies
To simulate countercurrent transport, a pilot rig was constructed. The equipment consisted of an
approximately 2 m long 10 cm diameter cylindrical glass tube fitted with transition pieces to allow the
feeding and discharge of a solid medium consisting of particles of various sizes of polyethylene pellets
ranging from approximately 0.4 to 4.5 mm. The particles were conveyed by double helical ribbons with
a blade width of 1.1 cm and varying angles of flight of 8.5 and 31.0 degrees respectively. Kerosene was
pumped countercurrently at rates between 4.5 litre and 22.5 litres per hour. Ribbon speed could be
varied between 0.5 and 5 rpm. For particles of mean size pf 2.5 mm and a countercurrent flow of approximatley 1 0 litres per hour, the following results were found: Charge of fr-Angle Pellets Solids Discharge
of flight (kgs) (kgs/hr)
1 rpm 2.5 rpm
31.0 2.0 3.73 7.32
8.5 2.6 2.06 4.64
The angle of repose of the solid medium in the kerosene measured was approximately 1 5 degrees.
EXAMPLE lil In order to illustrate the invention in an actual crystallization process a laboratory pilot crystallization rig was constructed as shown in Figure II. This equipment comprises a crystallizing tube 2 with a helical ribbon conveyor 3 therein arranged to turn about the longitudinal axis of the crystallizing tube. The crystallizing tube is provided with a cooling jacket 4, feed inlet 5 for the material to be crystallized and overflow outlet 6. The end of the crystallizing tube 1 opens to a collecting tube 7 which is provided with melt outlet 8 and melter element 9 at or near the bottom thereof. In operation the material to be crystallized and purified is introduced through feed inlet 5 in a form comprising the compound dissolved in its mother liquor at a temperature above the crystallization temperature of the compound.The cooling jacket 4 provides a temperature gradient along the crystallizing tube 2. The compound crystallizes in the crystallizing tube and is moved in the direction of the collecting tube 7 against the countercurrent flow of the feed liquor in the direction of the overflow outlet 6. The crystallized compound passes to the collecting tube 7 where it is melted at the bottom by melter element 9 and withdrawn in molten form through melt outlet 8.
Four crystallization runs were conducted for each paradichlorobenzene and naphthalene. Prior to conducting the runs the angle of repose of the material was determined as described in Example I. Two runs were conducted for each material using a conveyor 3 with an angle of flight less than the angle of repose and two runs for each using a conveyor 3 with an angle of flight greater than the angle of repose.
All other parameters such as speed of the conveyor, rate of feed input and temperature gradient along the crystallizing tube were mainta-ined constant through each set of four runs for the particular material.
The results obtained were as follows:-
% Composition Angle of Conveying Rate or Feed in Mother Angle of Flight - Product Output Material Liquor Repose - a Rate - kgs/hr PDCB 93 35 64.5 12.7 ,. .. ., " 11.6 ,, 32.0 1.3 1.3 I NAPH 85 40 32.0 Nil 64.5 1.0 ,, I ,, ,, 1.0 It will be readily apparent from the above that the use of a conveyor wherein the angle of flight of the blade exceeds the angle of repose of the material provides a far better conveying or product output rate than one wherein the angle of flight is less than the angle of repose.
The present invention finds particular application in the Solid-Liquid Continuous Countercurrent
Purifier described in United Kingdom Patent specification No. 1,275,798 which description is included herein by reference. In the operation of that apparatus it has been found that more efficient transport of the material in the refining and recovery sections of the apparatus is obtained by the application of the present invention whereby the angle of repose of the particular solid in liquid is measured and the conveyor designed and constructed with an angle of flight exceeding the angle of repose.
Claims (6)
1. An apparatus for carrying out a process which involves the countercurrent movement of a solid and a liquid medium, said apparatus including a conveyor comprising an Archimedian screw or ribbon (as herein defined) having an angle of flight exceeding the angle of repose of the solid medium within said liquid medium, providing always that the angle of flight is less than 90 degrees.
2. A method of carrying out a process for the treatment or reaction of materials which involves the countercurrent movement of a solid and a liquid medium comprising conducting such process using an apparatus which includes a conveyor comprising an Archimedian screw or ribbon (as herein defined) having an angle of flight exceeding the angle of repose of the solid medium in the liquid medium, providing always that the angle of flight is less than 90 degrees, to produce a desired resultantfoiward flow of the solid medium relevant to the countercurrent flow of the liquid medium.
3..A method according to claim 2 wherein the speed of the conveyor is such that the material is maintained in a sedimented o.r incipient fluidized state so as to minimise back flow of solid material.
4. A method of constructing a conveyor for use in an apparatus for carrying out a process involving the countercurrent movement of a solid and a liquid medium, said conveyor comprising an Archimedian screw or ribbon (as herein defined) whereby the angle of repose of the said solid medium in the liquid medium is measured and the angle of flight of the screw or ribbon is determined in relation to the angle of repose such that the angle of flight exceeds the angle of repose, providing always that the angle of - flight is less than 90 degrees.
5. A method of designing and constructing the conveyor in a solid-liquid continuous countercurrent purifier described and claimed in United Kingdom patent specification No. 1,275,798 whereby the angle of repose of the particular solid material within the liquid medium in the refining and recovery sections of the purifier is measured and the angle of flight of the screw or ribbon conveyor in each of those sections is determined in relation to the angle of repose such that the angle of flight exceeds the angle of repose, providing always that the angle of flight is less than 90 degrees.
6. A method of designing and constructing the conveyor in an apparatus for carrying out a process which involves the countercurrent movement of a solid and a liquid medium substantially as described with reference to the examples.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPD569178 | 1978-08-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2031297A true GB2031297A (en) | 1980-04-23 |
Family
ID=3767685
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7929330A Withdrawn GB2031297A (en) | 1978-08-28 | 1979-08-23 | Improvements in conveyors |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5561509A (en) |
| AU (1) | AU5002179A (en) |
| BE (1) | BE878456A (en) |
| DE (1) | DE2934363A1 (en) |
| FR (1) | FR2434646A1 (en) |
| GB (1) | GB2031297A (en) |
| IT (1) | IT1121647B (en) |
| NL (1) | NL7906438A (en) |
| SE (1) | SE7907129L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102015009754A1 (en) * | 2015-07-29 | 2017-02-02 | Torsten Heitmann | Crystallizer or reactor and method for the continuous growth of crystals or continuous reaction |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3320595A1 (en) * | 1983-06-08 | 1984-12-13 | Rheinische Braunkohlenwerke AG, 5000 Köln | SCREW CONVEYOR FOR DISCHARGING SOLID RESIDUES FROM DEVICES OPERATED UNDER HIGH TEMPERATURE AND PRESSURE |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS535389A (en) * | 1976-07-06 | 1978-01-18 | Toshiba Corp | Fuel assembly |
-
1978
- 1978-08-28 AU AU50021/79A patent/AU5002179A/en not_active Abandoned
-
1979
- 1979-08-23 GB GB7929330A patent/GB2031297A/en not_active Withdrawn
- 1979-08-24 DE DE19792934363 patent/DE2934363A1/en not_active Withdrawn
- 1979-08-27 BE BE0/196901A patent/BE878456A/en unknown
- 1979-08-27 SE SE7907129A patent/SE7907129L/en not_active Application Discontinuation
- 1979-08-27 FR FR7921434A patent/FR2434646A1/en not_active Withdrawn
- 1979-08-27 NL NL7906438A patent/NL7906438A/en not_active Application Discontinuation
- 1979-08-28 IT IT09521/79A patent/IT1121647B/en active
- 1979-08-28 JP JP10873879A patent/JPS5561509A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102015009754A1 (en) * | 2015-07-29 | 2017-02-02 | Torsten Heitmann | Crystallizer or reactor and method for the continuous growth of crystals or continuous reaction |
| US10661198B2 (en) | 2015-07-29 | 2020-05-26 | Torsten Heitmann | Crystallizer or reactor and method for continuously growing crystals or continuously managing a reaction |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2934363A1 (en) | 1980-03-13 |
| FR2434646A1 (en) | 1980-03-28 |
| SE7907129L (en) | 1980-02-29 |
| IT1121647B (en) | 1986-04-02 |
| BE878456A (en) | 1979-12-17 |
| IT7909521A0 (en) | 1979-08-28 |
| AU5002179A (en) | 1980-03-06 |
| NL7906438A (en) | 1980-03-03 |
| JPS5561509A (en) | 1980-05-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |