阅读说明：本技术 一种稀土回收系统及其回收工艺 (Rare earth recovery system and recovery process thereof ) 是由 张春雷 于 2021-09-16 设计创作，主要内容包括：本发明公开了一种稀土回收系统,包括过滤池、清液池、沉淀池和两个溶解池,所述溶解池内包括具备联动结构的压滤装置和混匀装置。本发明还公开了使用上述稀土回收系统的稀土回收工艺。本发明提供稀土的回收稀土,对溶解池中的压滤结构和混匀结构进行改进,使两者可以进行联动作业,从而提高了压滤效率,以及提高了滤液被充分溶解,实现稀土矿的提取率提高。本发明装置结构简洁,进行稀土回收的工艺方便快捷,可以进行大批量的稀土回收,节省人力物力。(The invention discloses a rare earth recovery system which comprises a filtering tank, a clear liquid tank, a sedimentation tank and two dissolving tanks, wherein each dissolving tank comprises a filter pressing device and a blending device which are in linkage structures. The invention also discloses a rare earth recovery process using the rare earth recovery system. The invention provides a method for recovering rare earth, which improves a filter pressing structure and a uniform mixing structure in a dissolving tank, so that the filter pressing structure and the uniform mixing structure can be operated in a linkage manner, thereby improving the filter pressing efficiency, improving the full dissolution of filtrate and realizing the improvement of the extraction rate of rare earth ore. The device has a simple structure, the process for recovering the rare earth is convenient and quick, the rare earth can be recovered in large batch, and manpower and material resources are saved.)

1. The rare earth recovery system comprises a filter tank, a clear liquid tank, a sedimentation tank and two dissolving tanks, and is characterized in that the dissolving tanks comprise a filter pressing device and a blending device which are provided with a linkage structure, the filter pressing device comprises a filter pressing driving mechanism (40) and a filter pressing rod (29), the filter pressing driving mechanism (40) is arranged in the dissolving tank, and the filter pressing driving mechanism (40) is used for driving the filter pressing rod (29) to filter and press filtrate in the dissolving tank;

mixing device is located the interior bottom surface of dissolving tank, including linkage subassembly (41) that possess cam (15) with set up stirring leaf (38) that are used for stirring dissolving tank internal filtrate in linkage subassembly (41) side, cam (15) are located the below of filter-pressing pole (29) effect down cam (15) take place to rotate.

2. The rare earth recovery system according to claim 1, wherein the filter pressing driving mechanism (40) comprises a movable rod (10) and a slide rail (1), two ends of the movable rod (10) reciprocate in the slide rail (1), the movable rod (10) is connected with the filter pressing rod (29), a through chute (11) is arranged on the movable rod (10), a limiting rod (9) is movably arranged in the chute (11), one end of the limiting rod (9) is connected with a first swing rod (3), the other end of the first swing rod (3) is rotatably connected to a first support (4), and the first support (4) is fixedly arranged on the inner wall of the dissolving tank; a motor is embedded in the first support (4) and used for driving the first swing rod (3) to swing in a reciprocating manner to drive the movable rod (10) and the filter-pressing rod (29) to move up and down; the utility model discloses a dissolving tank, including dissolving tank inner bottom surface, movable rod (10) are close to the one side of dissolving tank inner bottom surface is provided with push rod (37), push rod (37) are kept away from the one end of movable rod (10) is connected with push pedal (28), the one side interval that push pedal (28) kept away from push rod (37) is provided with a plurality of pressure filtration poles (29).

3. The rare earth recovery system according to claim 2, wherein the slide rails (1) are respectively arranged on the inner walls of the dissolving tank, and a first slide way (5) is arranged at one end of each slide rail (1) far away from the inner wall of the dissolving tank; two ends of the movable rod (10) reciprocate in the first slideway (5); two ends of the movable rod (10) are respectively provided with a first sliding block (6), and the first sliding blocks (6) reciprocate in the first slide ways (5); the other end of the first swing rod (3) is rotatably connected to the first support (4) through a first rotating shaft (2), and the motor is used for driving the first rotating shaft (2) of the first swing rod (3) to swing in a reciprocating manner; the extension direction of spout (11) with the activity direction of first slider (6) sets up perpendicularly, wherein one end of spout (11) is equipped with arc recess (7), one side of arc recess (7) is equipped with bellied arc protruding piece (8).

4. The rare earth recovery system according to claim 3, wherein the linkage assembly (41) comprises a fifth support (21), a fifth rotating shaft (23) and a cam (15), the fifth support (21) is fixed on the inner wall of the dissolving tank, two third supports (22) are arranged on one side, away from the inner wall of the dissolving tank, of the fifth support (21) at intervals, a second rotating shaft (12) and the fifth rotating shaft (23) are respectively and rotatably connected onto the third supports (22), a plurality of groups of stirring blades (38) are respectively arranged on the circumferential outer walls of the second rotating shaft (12) and the fifth rotating shaft (23) at intervals, the cam (15) is in linkage with the second rotating shaft (12) and the fifth rotating shaft (23), and the cam (15) drives the stirring blades (38) to rotate when rotating.

5. The rare earth recovery system according to claim 4, wherein one end of the second rotating shaft (12) close to the fifth rotating shaft (23) is connected with a second gear (26), one side of the second gear (26) is engaged with a first gear (14), the first gear (14) is arranged on a third rotating shaft (17), and the third rotating shaft (17) is connected with the second rotating shaft (12) through a third swing rod (27); a fourth gear (25) is arranged at one end, close to the second rotating shaft (12), of the fifth rotating shaft (23), a third gear (16) is arranged at one side of the fourth gear (25) in a meshed mode, the third gear (16) is arranged on the third rotating shaft (17), and one end, far away from the first gear (14), of the third rotating shaft (17) is connected with the fifth rotating shaft (23) through a second swing rod (24); a cam (15) is arranged between the first gear (14) and the third gear (16) at intervals, and the center of the cam (15) is fixedly connected to a third rotating shaft (17).

6. The rare earth recovery system according to claim 5, wherein a fourth support (19) is further arranged at an interval on one side of the fifth support (21) far away from the third support (22), a mounting groove is formed in the fourth support (19), the mounting groove is used for being rotatably connected with the boosting roller (18) through a fourth rotating shaft (20), and the circumferential outer wall of the boosting roller (18) is in contact with the circumferential outer wall of the cam (15); the fourth support (19) and the third support (22) are respectively arranged vertically to the fifth support (21); the diameters and the tooth numbers of the third gear (16) and the second gear (26) are consistent, and the diameters and the tooth numbers of the first gear (14) and the fourth gear (25) are consistent; one end of the second rotating shaft (12) far away from the third support (22) and one end of the fifth rotating shaft (23) far away from the third support (22) are rotatably connected to the inner wall of the dissolving tank.

7. A rare earth recovery process using the rare earth recovery system according to any one of claims 1 to 6, comprising the steps of:

s1: collecting rare earth mother liquor, pouring magnesium oxide powder into the rare earth mother liquor, uniformly mixing, and adjusting the pH value to 6.7-7.2 to obtain mixed precipitation slurry;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: adding an acid solution into the rare earth mud precipitate in the dissolving tank until the pH value is 4-4.5, dissolving the rare earth mud precipitate, then performing filter pressing by using a filter pressing device and a uniformly mixing device, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding an alkaline solution into the dissolving tank until the pH value is 5.4-5.8, removing impurities from the filtrate, then performing filter pressing by using a filter pressing device and a uniformly mixing device, and injecting the filtrate obtained after filter pressing into a sedimentation tank;

s5: and (3) injecting a precipitator into the precipitation tank to obtain rare earth carbonate, and recovering the rare earth carbonate.

8. The rare earth recovery process according to claim 7, wherein in S3, oxalic acid and polyethylene glycol solution are added into the rare earth mud precipitate in the dissolving tank in a mass ratio of 1:2-10, the pH value is adjusted to 5-5.5, the precipitate is dissolved, hydrochloric acid solution is added to adjust the pH value to 4-4.5, and the precipitate is dissolved for the second time.

9. The rare earth recovery process according to claim 7, wherein in S4, a suspension of sodium hydroxide and polyacrylamide in a mass ratio of 1:5-8 is added to a pH of 4-4.5, and then a sodium hydroxide solution is added to adjust the pH to 5.4-5.8.

10. The rare earth recovery process according to claim 7, wherein a suspension of sodium carbonate and polyacrylamide is added to S5 in a mass ratio of 1:0.5-2, and sodium carbonate is added to a pH of 6.7-7.2.

Technical Field

The invention relates to the technical field of rare earth recovery, in particular to a rare earth recovery system and a recovery process thereof.

Background

Rare earth minerals exist mainly in mineral form in the earth crust, and there are three main types: as an essential constituent element of a mineral, rare earth is present in the form of an ionic compound in the mineral lattice, and constitutes an essential component of the mineral. The minerals are commonly called rare earth minerals, and rare earth mineral elements are known as industrial vitamins, have irreplaceable excellent magnetic, optical and electrical properties, and play a great role in improving the product performance, increasing the product variety and improving the production efficiency. Because of large action and small dosage of rare earth, the rare earth has become an important element for improving the product structure, improving the technological content and promoting the technical progress of the industry, and is widely applied to the fields of metallurgy, military, petrochemical industry, glass ceramics, agriculture, new materials and the like.

At present, the process for recovering rare earth generally comprises the steps of pumping collected rare earth leaching mine mother liquor into a stirring barrel by a pump, adding magnesium oxide, adjusting the pH value, flowing mixed precipitation slurry into a clarification tank for clarification, discharging supernatant into a liquid preparation tank after clarification, filtering precipitates, adding clear water into filter materials for size mixing, adding acid for dissolution, adding filtrate into a liquid storage tank, adjusting the pH value by NaOH solution, filtering by a plate-and-frame filter press, transferring the filtrate into the precipitation barrel, and adding Na under the stirring state₂CO₃And (4) performing rare earth precipitation and filtering to obtain filter residue, namely rare earth carbonate for separation in a rare earth smelting plant. The filtrate in the process contains impurities, so that the process has the problems of low extraction purity, low extraction rate and the like.

Disclosure of Invention

The invention aims to solve the problems in the prior art, and provides a rare earth recovery system and a recovery process thereof.

Therefore, the invention adopts the following technical scheme.

The invention provides a rare earth recovery system which comprises a filter tank, a clear liquid tank, a sedimentation tank and two dissolving tanks, wherein the dissolving tanks comprise a filter pressing device and a blending device which are in a linkage structure;

the blending device is located the interior bottom surface of dissolving tank, including the linkage subassembly that possesses the cam with set up the stirring leaf that is used for stirring the interior filtrating of dissolving tank in linkage subassembly side, the cam is located the below of filter-pressing pole the filter-pressing pole effect is down the cam takes place to rotate.

Furthermore, the filter pressing driving mechanism comprises a movable rod and a slide rail, two ends of the movable rod reciprocate in the slide rail, the movable rod is connected with the filter pressing rod, a through chute is arranged on the movable rod, a limiting rod is movably arranged in the chute, one end of the limiting rod is connected with a first swing rod, the other end of the first swing rod is rotatably connected to a first support, and the first support is fixedly arranged on the inner wall of the dissolving tank; the motor is embedded in the first support and used for driving the first oscillating bar to oscillate in a reciprocating manner so as to drive the movable rod and the filter-pressing rod to move up and down.

Further, the movable rod is close to the one side of dissolving tank inner bottom surface is provided with the push rod, the push rod is kept away from the one end of movable rod is connected with the push pedal, the one side interval that the push pedal was kept away from the push rod is provided with a plurality of filter-pressing poles.

Furthermore, the slide rails are respectively arranged on the inner wall of the dissolving tank, and one end of each slide rail, which is far away from the inner wall of the dissolving tank, is provided with a first slide way; and two ends of the movable rod reciprocate in the first slide way.

Furthermore, two ends of the movable rod are respectively provided with a first sliding block, and the first sliding blocks reciprocate in the first slide ways; the other end of the first swing rod is rotatably connected to the first support through a first rotating shaft, and the motor is used for driving the first rotating shaft of the first swing rod to swing in a reciprocating manner; the extending direction of the sliding groove and the moving direction of the first sliding block are perpendicular to each other, an arc-shaped groove is formed in one end of the sliding groove, and a protruding arc-shaped protruding block is arranged on one side of the arc-shaped groove.

Further, the linkage subassembly includes fifth support, fifth pivot and cam, the inner wall at the dissolving tank is fixed to the fifth support, the fifth support is kept away from the one side interval of dissolving tank inner wall is provided with two third supports, it is connected with second pivot and fifth pivot to rotate respectively on the third support, just the second pivot with the equal interval of circumference outer wall of fifth pivot is provided with multiunit stirring leaf, the cam with the second pivot with the linkage of fifth pivot sets up, the cam drives the stirring leaf and rotates when taking place to rotate.

Furthermore, one end of the second rotating shaft, which is close to the fifth rotating shaft, is connected with a second gear, one side of the second gear is meshed with a first gear, the first gear is arranged on a third rotating shaft, and the third rotating shaft is connected with the second rotating shaft through a third oscillating bar; a fourth gear is arranged at one end, close to the second rotating shaft, of the fifth rotating shaft, a third gear is meshed with one side of the fourth gear, the third gear is arranged on the third rotating shaft, and one end, far away from the first gear, of the third rotating shaft is connected with the fifth rotating shaft through a second swing rod; a cam is arranged between the first gear and the third gear at intervals, and the center of the cam is fixedly connected to a third rotating shaft;

furthermore, a fourth support is further arranged on one side, away from the third support, of the fifth support at intervals, a mounting groove is formed in the fourth support, the mounting groove is used for being rotatably connected with a power-assisted roller through a fourth rotating shaft, and the circumferential outer wall of the power-assisted roller is in contact with the circumferential outer wall of the cam; the fourth support and the third support are respectively and vertically arranged on the fifth support; the diameters and the tooth numbers of the third gear and the second gear are consistent, and the diameters and the tooth numbers of the first gear and the fourth gear are consistent; one end of the third support is kept away from in the second rotating shaft, and one end of the third support is kept away from in the fifth rotating shaft are rotatably connected to the inner wall of the dissolving tank.

The invention also provides a rare earth recovery process using the rare earth recovery system, which comprises the following steps:

s1: collecting rare earth mother liquor, pouring magnesium oxide powder into the rare earth mother liquor, uniformly mixing, and adjusting the pH value to 6.7-7.2 to obtain mixed precipitation slurry;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: adding an acid solution into the rare earth mud precipitate in the dissolving tank until the pH value is 4-4.5, dissolving the rare earth mud precipitate, then performing filter pressing by using a filter pressing device and a uniformly mixing device, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding an alkaline solution into the dissolving tank until the pH value is 5.4-5.8, removing impurities from the filtrate, then performing filter pressing by using a filter pressing device and a uniformly mixing device, and injecting the filtrate obtained after filter pressing into a sedimentation tank;

s5: and (3) injecting a precipitator into the precipitation tank to obtain rare earth carbonate, and recovering the rare earth carbonate.

Further, in S3, adding oxalic acid and polyethylene glycol solution in a mass ratio of 1:2-10 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5-5.5, dissolving the precipitate, adding hydrochloric acid solution to adjust the pH value to 4-4.5, and dissolving the precipitate for the second time.

Further, in S4, a suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:5-8 is added to a pH value of 4-4.5, and then a sodium hydroxide solution is added to adjust the pH value to 5.4-5.8.

Further, a suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:0.5-2 is added to S5, and sodium carbonate is added to a pH of 6.7 to 7.2.

Specifically, the magnesium oxide powder is 80-90% of industrial grade magnesium oxide powder; the concentration of the sodium hydroxide solution is 5% -10%.

The technical scheme of the invention has the following advantages:

(1) the invention provides a rare earth recovery system, which improves a filter pressing structure and a blending structure in a dissolving tank, so that the filter pressing structure and the blending structure can be in linkage operation, the push rod can move up and down through the up-and-down movement of the movable rod, a push plate connected with the push rod can further move up and down, a filter pressing rod below the push plate can be inserted into filtrate, the filter pressing rod can insert and stir the filtrate, and the filter pressing rod can be used for filter pressing the filtrate; thereby improving the filter pressing efficiency, improving the full dissolution of the filtrate and realizing the improvement of the extraction rate of the rare earth ore.

(2) The recovery process adopts two-step filter pressing, improves the filter pressing efficiency, improves the full dissolution of filtrate, realizes the improvement of the extraction rate of the rare earth ore, can effectively extract and recover the rare earth elements in the electronic product wastes, and effectively reduces the waste condition of the electronic product wastes; meanwhile, the method provided by the invention has the advantages of simple process, high extraction rate and great market prospect.

In the dissolving step S3, firstly, oxalic acid and polyethylene glycol solution are added to dissolve the rare earth mud precipitate, the rare earth mud precipitate is dispersed by using polyethylene glycol, and the oxalic acid preliminarily dissolves the dispersed rare earth mud precipitate to form dispersed suspended precipitate; and then adding hydrochloric acid with stronger dissolving capacity to further dissolve the suspended precipitate, so that the rare earth mud precipitate can be fully dissolved. That is to say, in the step, the polyethylene glycol has a dispersing effect, ether bonds on the molecular surface of the polyethylene glycol have weak negative charges, and oxalic acid and polyethylene glycol solution with the ratio of 1:2-10 can be complexed, so that a mixed solution with a high dissolving effect is formed, and the effect of promoting the dissolution of the rare earth mud precipitate is achieved; and then the mixed solution is matched with hydrogen ions in hydrochloric acid, so that the dissolving capacity of the mixed solution is further improved. If the ratio of the oxalic acid to the polyethylene glycol solution is less than 1:2-10, the oxalic acid and the polyethylene glycol solution are easy to phase separate, and the oxalic acid is difficult to contact with the precipitate, and if the ratio of the oxalic acid to the polyethylene glycol solution is more than 1:2-10, the oxalic acid is difficult to complex with the polyethylene glycol solution.

Meanwhile, in the impurity removal step S4, a suspension of calcium hydroxide and polyacrylamide is added, the filtrate is changed into floccules by the polyacrylamide, the calcium hydroxide is subjected to precipitation reaction with impurities (magnesium ions and the like) in the floccules, and then sodium hydroxide is added to further precipitate the impurities, so that the impurities in the filtrate are sufficiently removed. That is, in this step, the polyacrylamide not only performs flocculation, but also contains amide groups and hydrogen bonds, and can be crosslinked with calcium hydroxide to obtain a polyacrylamide-sodium hydroxide modified product with a network structure, so that the polyacrylamide-sodium hydroxide modified product can be more easily subjected to a precipitation reaction with impurities (such as magnesium ions). If the ratio of the sodium hydroxide to the polyacrylamide is more than 1:5-8, the polyacrylamide is difficult to be connected with the sodium hydroxide, and if the ratio of the sodium hydroxide to the polyacrylamide is less than 1:5-8, the sodium hydroxide is dispersed in the polyacrylamide, so that the sodium hydroxide is difficult to contact with impurities (magnesium ions and the like) and is difficult to have precipitation reaction.

In the precipitation step S5, the suspension of sodium carbonate and polyacrylamide is converted into floc by polyacrylamide, the sodium carbonate is then precipitated with the floc, and then sodium carbonate is added and precipitated with the floc together with the sodium carbonate, so that the filtrate is sufficiently precipitated.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a view showing the construction of a recovery system in example 1 of the present invention;

FIG. 2 is a schematic view showing the structure of a dissolution tank in example 1 of the present invention;

FIG. 3 is a schematic structural view of a filter pressing drive mechanism according to embodiment 1 of the present invention;

FIG. 4 is a front view of FIG. 3;

FIG. 5 is a schematic view showing a partial structure of a filter pressing rod of the filter pressing device in example 1 of the present invention;

FIG. 6 is a schematic structural view of a linkage assembly according to embodiment 1 of the present invention;

FIG. 7 is a schematic view of a portion of the structure of FIG. 6;

FIG. 8 is a schematic view of the structure of a stirring shaft in example 1 of the present invention;

description of reference numerals:

1-a slide rail; 2-a first rotating shaft; 3-a first swing link; 4-a first support; 5-a first slideway; 6-a first slide block; 7-arc groove; 8-arc-shaped convex blocks; 9-a limiting rod; 10-a movable rod; 11-a chute; 12-a second shaft; 13-a second support; 14-a first gear; 15-a cam; 16-a third gear; 17-a third shaft; 18-a power-assisted roller; 19-a fourth support; 20-a fourth rotating shaft; 21-a fifth support; 22-a third support; 23-a fifth rotating shaft; 24-a second swing link; 25-a fourth gear; 26-a second gear; 27-a third swing link; 28-push plate; 29-filter pressing rod; 37-a push rod; 38-stirring blade; 39-a dissolving tank; 40-a filter pressing driving mechanism; 41-linkage assembly.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

The present embodiment provides a structure of a recovery system for rare earth.

As shown in fig. 1, a rare earth recovery system comprises a filtering tank, a clear liquid tank, a sedimentation tank and two dissolving tanks 39, as shown in fig. 2, the dissolving tanks 39 internally comprise a filter pressing device and a blending device with a linkage structure, the filter pressing device comprises a filter pressing driving mechanism 40 and a filter pressing rod 29, the filter pressing driving mechanism 40 is arranged in the dissolving tank 39, and the filter pressing driving mechanism 40 is used for driving the filter pressing rod 29 to filter the filtrate in the dissolving tanks 39;

mixing device is located dissolving tank 39's interior bottom surface, including the linkage subassembly 41 that possesses cam 15 and set up in the stirring leaf 38 that is used for stirring dissolving tank 39 internal filtrate to 41 sides of linkage subassembly, cam 15 is located filter pressing rod 29's below filter pressing rod 29 effect down cam 15 takes place to rotate.

As shown in fig. 3 and 4, the filter pressing driving mechanism 40 includes a movable rod 10, slide rails 1 and first slide blocks 6, the slide rails 1 are respectively disposed on the inner wall of the dissolving tank 39, and a first slide way 5 is disposed at one end of each slide rail 1 away from the inner wall of the dissolving tank 39; two ends of the movable rod 10 are respectively provided with a first sliding block 6, and the first sliding blocks 6 reciprocate in the first slide ways 5; a through sliding groove 11 is arranged on the movable rod 10, and the extending direction of the sliding groove 11 is perpendicular to the moving direction of the first sliding block 6; one end of the sliding chute 11 is provided with an arc-shaped groove 7, one side of the arc-shaped groove 7 is provided with a raised arc-shaped raised block 8, a limiting rod 9 is movably arranged in the sliding chute 11, one end of the limiting rod 9 is connected with a first swing rod 3, the other end of the first swing rod 3 is rotatably connected to a first support 4 through a first rotating shaft 2, the first support 4 is of a triangular structure, and the first support 4 is fixedly arranged on the inner wall of the dissolving tank 39; the motor is embedded in the first support 4 and used for driving the first rotating shaft 2 to rotate. The movable rod 10 is close to the one side of bottom surface is provided with push rod 37 in the dissolving tank 39, push rod 37 is kept away from the one end of movable rod 10 is connected with push pedal 28, push pedal 28 keeps away from the one side interval of push rod 37 and is provided with a plurality of pressure filter rods 29, pressure filter rod 29 keeps away from the one end of push pedal 28 is established to the arc structure.

The first rotating shaft 2 is driven by a motor and then drives the first swing rod 3 to swing, and the first swing rod 3 drives the limiting rod 9 to further swing when swinging, so that the limiting rod 9 can reciprocate in the sliding groove 11 of the movable rod 10, and the first sliding blocks 6 arranged at two ends of the movable rod 10 can reciprocate in the first sliding ways 5 of the sliding rails 1;

further, the push rod connected to the movable rod 10 can move back and forth along with the movable rod; because the slide rails 1 are positioned on the inner walls of the two sides of the dissolving tank 39, the purpose that the push rods 37 move up and down together when the movable rods 10 move up and down is achieved, the push plates 28 connected with the push rods 37 can further move up and down, the filter pressing rods 29 below the push plates can be inserted into the filtrate, the filter pressing rods 29 can insert and stir the filtrate, and the filter pressing rods 28 can be used for filter pressing the filtrate; thereby improving the filter pressing efficiency, improving the aim of fully dissolving the filtrate and realizing the aim of improving the extraction rate of the rare earth ore.

The arc recess and the protruding piece of arc that set up in the spout 11 can effectively improve the smooth and easy nature of activity of gag lever post 9 to reduce push rod 37 and make a round trip the activity the condition that the card went on appears, further reduce the condition that causes filter-pressing efficiency to reduce because of the card went on.

As shown in fig. 6-8, the device includes a fifth support 21, a fifth rotating shaft 23 and a cam 15, the fifth support 21 is fixed on an inner wall of a dissolving tank 39 and is disposed near an inner bottom surface of the dissolving tank 39, two third supports 22 are disposed at intervals on one surface of the fifth support 21 away from the inner wall of the dissolving tank 39, the third supports 22 are respectively rotatably connected with a second rotating shaft 12 and the fifth rotating shaft 23, one end of the second rotating shaft 12 close to the fifth rotating shaft 23 is connected with a second gear 26, one side of the second gear 26 is engaged with a first gear 14, the first gear 14 is disposed on a third rotating shaft 17, and the third rotating shaft 17 is connected with the second rotating shaft 12 through a third oscillating bar 27; a fourth gear 25 is arranged at one end of the fifth rotating shaft 23 close to the second rotating shaft 12, a third gear 16 is meshed with one side of the fourth gear 25, the third gear 16 is arranged on a third rotating shaft 17, and one end of the third rotating shaft 17 far away from the first gear 14 is connected with the fifth rotating shaft 23 through a second swing rod 24; the diameters and the tooth numbers of the third gear 16 and the second gear 26 are consistent, and the diameters and the tooth numbers of the first gear 14 and the fourth gear 25 are consistent; a cam 15 is arranged between the first gear 14 and the third gear 16 at intervals, and the center of the cam 15 is fixedly connected to a third rotating shaft 17; a fourth support 19 is further arranged on one side, away from the third support 22, of the fifth support 21 at intervals, an installation groove is formed in the fourth support 19, the installation groove is used for being rotatably connected with a power-assisted roller 18 through a fourth rotating shaft 20, and the circumferential outer wall of the power-assisted roller 18 is in contact with the circumferential outer wall of the cam 15; the fourth support 19 and the third support 22 are respectively arranged vertically to the fifth support 21. The cam 15 is positioned below the filter pressing rod 29, and the cam 15 is used for jacking up the filter pressing rod 29; the second pivot 12 is kept away from the one end of third support 22, the one end that third support 22 was kept away from to fifth pivot 23 all rotates to be connected dissolve the inner wall of pond 39, just the second pivot 12 with the circumference outer wall of fifth pivot 23 all is provided with multiunit stirring leaf 38 at the interval.

The blending device is mainly used for blending the filtrate in the dissolving tank 39, so that the purpose that the filtrate can be fully subjected to acid-base regulation is achieved;

during operation, under the action of the filter-pressing rod 29, the cam 15 rotates, so that the third rotating shaft 17 is driven to rotate, and then the first gear 14 and the third gear 16 are driven to rotate, the first gear 14 drives the second gear 26 to rotate, the third gear 16 drives the fourth gear 25 to rotate, so that the second rotating shaft 12 and the fifth rotating shaft 23 are driven to rotate, and further the stirring blade 38 is driven to rotate, and the stirring blade 38 can realize the purpose of stirring and filter-pressing the interior of the dissolving tank 39; thus achieving the filter-pressing efficiency of the dissolution tank 39.

Example 2

The embodiment provides a rare earth recovery process, and the rare earth recovery system provided in embodiment 1 includes the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 6.7, and the pH value of the supernatant reaches 6.7;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding oxalic acid and polyethylene glycol solution in a mass ratio of 1:2 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5, adding hydrochloric acid solution to adjust the pH value to 4, carrying out secondary dissolution on the precipitate, then carrying out filter pressing through a filter pressing device and a uniformly mixing device provided by the invention, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:5 into the dissolving tank to a pH value of 4, adding a sodium hydroxide solution to adjust the pH value to 5.4 so as to remove impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry by a filter pressing device and a uniformly mixing device, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: adding suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:0.5 into a precipitation tank, adding sodium carbonate, testing the pH value of mother liquor, and if the pH value is less than 6.7, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 6.7, wherein the precipitation end point is the filter residue, namely the rare earth carbonate.

Example 3

The embodiment provides a rare earth recovery process, and the rare earth recovery system provided in embodiment 1 includes the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 7.2, and the pH value of the supernatant reaches 7.2;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding oxalic acid and polyethylene glycol solution with the mass ratio of 1:10 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5.5, adding hydrochloric acid solution to adjust the pH value to 4.5, dissolving the precipitate for the second time, then performing filter pressing through a filter pressing device and a uniformly mixing device provided by the invention, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:8 into the dissolving tank to a pH value of 4.5, adding a sodium hydroxide solution to adjust the pH value to 5.8 so as to remove impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry through a filter pressing device and a uniformly mixing device, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: adding suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:2 into a precipitation tank, adding sodium carbonate, testing the pH value of the mother liquor, and if the pH value is less than 7.2, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 7.2, wherein the precipitation end point is the filter residue, namely the rare earth carbonate.

Example 4

The embodiment provides a rare earth recovery process, and the rare earth recovery system provided in embodiment 1 includes the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 7.0, and the pH value of the supernatant reaches 7.0;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding oxalic acid and polyethylene glycol solution with the mass ratio of 1:5 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5.2, adding hydrochloric acid solution to adjust the pH value to 4.2, dissolving the precipitate for the second time, then performing filter pressing through a filter pressing device and a uniformly mixing device provided by the invention, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:6 into the dissolving tank to a pH value of 4.5, adding a sodium hydroxide solution to adjust the pH value to 5.5, removing impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry through a filter pressing device and a uniformly mixing device, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: adding suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:1.2 into a precipitation tank, adding sodium carbonate, testing the pH value of mother liquor, and if the pH value is less than 6.8, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 6.8, wherein the precipitation end point is the filter residue, namely the rare earth carbonate.

Example 5

The embodiment provides a rare earth recovery process, and the rare earth recovery system provided in embodiment 1 includes the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 7.0, and the pH value of the supernatant reaches 7.0;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding oxalic acid and polyethylene glycol solution with the mass ratio of 1:8 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5.2, adding hydrochloric acid solution to adjust the pH value to 4.2, dissolving the precipitate for the second time, then performing filter pressing through a filter pressing device and a uniformly mixing device provided by the invention, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:7 into the dissolving tank to a pH value of 4.5, adding a sodium hydroxide solution to adjust the pH value to 5.5, removing impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry through a filter pressing device and a uniformly mixing device, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: adding suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:1.5 into a precipitation tank, adding sodium carbonate, testing the pH value of mother liquor, and if the pH value is less than 6.8, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 6.8, wherein the precipitation end point is the filter residue, namely the rare earth carbonate.

Example 6

The embodiment provides a rare earth recovery process, and the rare earth recovery system provided in embodiment 1 includes the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 6.8, and the pH value of the supernatant reaches 6.8;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding oxalic acid and polyethylene glycol solution in a mass ratio of 1:2 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5, adding hydrochloric acid solution to adjust the pH value to 4, dissolving the precipitate for the second time, performing filter pressing by a plate-and-frame filter press, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:5 into the dissolving tank to a pH value of 4, adding a sodium hydroxide solution to adjust the pH value to 5.4, removing impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry through a plate-and-frame filter press, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: adding suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:0.5 into a precipitation tank, adding sodium carbonate, testing the pH value of mother liquor, and if the pH value is less than 6.7, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 6.7, wherein the precipitation end point is the filter residue, namely the rare earth carbonate.

Example 7

The embodiment provides a rare earth recovery process, and the rare earth recovery system provided in embodiment 1 includes the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 7.2, and the pH value of the supernatant reaches 7.2;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding oxalic acid and polyethylene glycol solution in a mass ratio of 1:10 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5.5, adding hydrochloric acid solution to adjust the pH value to 4.5, dissolving the precipitate for the second time, performing filter pressing by a plate-and-frame filter press, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:8 into the dissolving tank to a pH value of 4.5, adding a sodium hydroxide solution to adjust the pH value to 5.8, removing impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry by using a plate-and-frame filter press, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: adding suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:2 into a precipitation tank, adding sodium carbonate, testing the pH value of the mother liquor, and if the pH value is less than 7.2, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 7.2, wherein the precipitation end point is the filter residue, namely the rare earth carbonate.

Example 8

The embodiment provides a rare earth recovery process, and the rare earth recovery system provided in embodiment 1 includes the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 7.0, and the pH value of the supernatant reaches 7.0;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding oxalic acid and polyethylene glycol solution in a mass ratio of 1:5 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5.2, adding hydrochloric acid solution to adjust the pH value to 4.2, dissolving the precipitate for the second time, performing filter pressing by a plate-and-frame filter press, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding a suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:6 into the dissolving tank to a pH value of 4.5, adding a sodium hydroxide solution to adjust the pH value to 5.5, removing impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry by using a plate-and-frame filter press, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: adding suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:1.2 into a precipitation tank, adding sodium carbonate, testing the pH value of mother liquor, and if the pH value is less than 6.8, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 6.8, wherein the precipitation end point is the filter residue, namely the rare earth carbonate.

Example 9

The embodiment provides a rare earth recovery process, and the rare earth recovery system provided in embodiment 1 includes the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 7.0, and the pH value of the supernatant reaches 7.0;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding oxalic acid and polyethylene glycol solution in a mass ratio of 1:5 into the rare earth mud precipitate in the dissolving tank, adjusting the pH value to 5.2, adding hydrochloric acid solution to adjust the pH value to 4.2, dissolving the precipitate for the second time, performing filter pressing by a plate-and-frame filter press, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding a suspension of calcium hydroxide and polyacrylamide in a mass ratio of 1:6 into the dissolving tank to a pH value of 4.5, adding a sodium hydroxide solution to adjust the pH value to 5.5, removing impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry by using a plate-and-frame filter press, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: adding suspension of sodium carbonate and polyacrylamide in a mass ratio of 1:1.2 into a precipitation tank, adding sodium carbonate, testing the pH value of mother liquor, and if the pH value is less than 6.8, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 6.8, wherein the precipitation end point is the filter residue, namely the rare earth carbonate.

Comparative example 1

The rare earth recovery process provided by the comparative example comprises the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 7.0, and the pH value of the supernatant reaches 7.0;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding a hydrochloric acid solution into the rare earth mud precipitate in the dissolving tank to adjust the pH value to 4.2, then performing filter pressing through a plate-and-frame filter press, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding a sodium hydroxide solution into the dissolving tank to adjust the pH value to be 5.5, removing impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry through a plate-and-frame filter press, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: and adding sodium carbonate into the precipitation tank, testing the pH value of the mother liquor, and if the pH value is less than 6.8, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 6.8, wherein the precipitation end point is obtained, and the filter residue is the rare earth carbonate.

Comparative example 2

The rare earth recovery process provided by the comparative example comprises the following steps:

s1: collect 250m³Leaching rare earth mine mother liquor (test pH is 4.8), pumping the mother liquor into a stirring barrel, starting stirring, adding magnesium oxide (industrial grade, 85% MgO) while pumping the mother liquor, testing the pH value of supernatant, and if the pH value is not high, adding magnesium oxide (industrial grade, 85% MgO) into the supernatant<Magnesium oxide is added at 7.0, and the pH value of the supernatant reaches 7.2;

s2: draining the mixed precipitation slurry to a filtering tank, standing and filtering in the filtering tank, then draining clear liquid above the filtering tank to a clear liquid tank, and discharging the rare earth mud precipitate at the bottom in the filtering tank to a dissolving tank from a mud discharge port;

s3: slowly adding a hydrochloric acid solution into the rare earth mud precipitate in the dissolving tank to adjust the pH value to 4.8, then performing filter pressing through a plate-and-frame filter press, draining the filtrate to the next dissolving tank, and collecting filter residues for later use;

s4: adding a sodium hydroxide solution into the dissolving tank to adjust the pH value to be 5.8, removing impurities from the filtrate, standing for 1 hour, performing filter pressing on bottom sediment slurry through a plate-and-frame filter press, and injecting the filtrate obtained after filter pressing into a settling tank;

s5: and adding sodium carbonate into the precipitation tank, testing the pH value of the mother liquor, and if the pH value is less than 6.8, adding a small amount of sodium carbonate until the pH value of the mother liquor reaches 7.2, wherein the precipitation end point is obtained, and the filter residue is the rare earth carbonate.

Test examples

The rare earth carbonates obtained in examples 2 to 9 and comparative examples 1 to 2 were calculated and the settlement data is shown in table 1 below, and it can be seen from table 1 that the recovery rates of examples 2 to 9 were 97.2 to 98.9%, which are far greater than those of the comparative examples.

TABLE 1

	Percent recovery%
		Example 2	98.5
Example 3	98.1
		Example 4	98.9
Example 5	98.4
		Example 6	97.2
Example 7	97.5
		Example 8	97.4
Example 9	97.2
		Comparative example 1	95.2
Comparative example 2	95.4

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.