CRYSTALLIZATION COLUMN AND CRYSTALLIZATION METHOD

Abstract

A crystallization column and a crystallization method. The crystallization column comprises an upper head (1), a tower body (2) and a lower head (3), wherein a crystallization section (11) is provided with a tray (14); and the tray (14) comprises a tray plate (15) and a plurality of lower crystallization members (17). The top end of the lower crystallization member (17) can form a movable connection with the tray plate (15), so that the two adjacent lower crystallizing members (17) are capable of oscillating collisions. The tray (14) may also comprise a plurality of upper crystallization members (21) extending upwardly from the upper surface of the tray plate (15).

Claims

1. A crystallization column, which comprises an upper head (1) with a gas outlet (4), a tower body (2) and a lower head (3) with a gas inlet (8) and a material outlet (7), the tower body (2) comprises a crystallization section (11); wherein a tray (14) is arranged in the crystallization section (11) and comprises a tray plate (15) extending from the inner wall of the tower body (2) and a plurality of lower crystallization members (17) which are arranged on the lower surface of the tray plate (15) at intervals with each other.

2. The crystallization column according to claim 1, wherein the top end of the lower crystallization member (17) and the lower surface of the tray plate (15) are movably connected, so that two adjacent lower crystallization members (17) may swing and collide.

3. The crystallization column according to claim 2, wherein a plurality of lifting lugs (16) are arranged on the lower surface of the tray plate (15) at intervals; the top end of the lower crystallization member (17) is provided with a hanger (18); the hanger (18) is buckled with the lifting lug (16), so that the lower crystallization member (17) may swing.

4. The crystallization column according to claim 3, wherein the plurality of lifting lugs (16) are uniformly disposed on the lower surface of the tray plate (15), and the plurality of lower crystallization members (17) are connected with the plurality of lifting lugs (16) in one-to-one correspondence.

5. The crystallization column according to claim 4, wherein the lower crystallization member (17) comprises the hanger (18) and a lower cylinder (19); and the radial distance between the cylinder centers of any two adjacent lower cylinders (19) overhanging downward is less than the axial height of the lower cylinder (19).

6. The crystallization column according to claim 5, wherein a cylinder surface of the lower cylinder (19) is provided with a projection.

7. The crystallization column according to claim 6, wherein the projection is a spiny object (20); a plurality of spiny objects (20) radially stretches outward from the cylinder surface of the lower cylinder (19), respectively, so that the lower cylinder (19) forms a mace structure.

8. The crystallization column according to claim 7, wherein the maximum radial stretching length of the spiny object (20) is 1/20 to ? of the axial height of the lower cylinder (19), preferably 1/15 to 1/10.

9. The crystallization column according to claim 7, wherein in the lower cylinder (19) of the mace structure, the height clearance between the upper and lower adjacent spiny objects (20) is 1/20 to ? of the axial height of the lower cylinder (19), preferably 1/15 to 1/10.

10. The crystallization column according to claim 2, wherein the top end of the lower crystallization member (17) is connected to the lower surface of the tray plate (15) through a flexible rope.

11. The crystallization column according to claim 1, wherein the lower crystallization member (17) is an elastic or flexible member with a top end fixedly connected to the lower surface of the tray plate (15); the elastic or flexible member may bend, so that two adjacent lower crystallization members (17) may swing and collide.

12. The crystallization column according to claim 1, wherein the lower crystallization member (17) comprises a lower cylinder (19) and a flexible thread (22), the lower cylinder (19) equipped with the flexible thread (22) forms a torsion wire brush type structure.

13. The crystallization column according to claim 1, wherein one end of the tray plate (15) is connected with the inner wall of the tower body (2), and the other end stretches crosswise and a gas flow gap forms between the stretching end and the inner wall of the opposite side of the tower body (2).

14. The crystallization column of the claim 13, wherein the crystallization section (11) is provided with multiple layers of the trays (14) spaced up and down orderly; the multiple layers of trays (14) are disposed on two sides of the central axis of the tower body (2) and form a left and right staggering arrangement, so that the gas phase may orderly pass through the gas flow gap of each tray plate (15) upward to form bend fluid.

15. The crystallization column according to claim 14, wherein the tray (14) further comprises a plurality of upper crystallization members (21) that stretch upward from the upper surface of the tray plate (15).

16. The crystallization column according to claim 15, wherein in the two adjacent up and down trays (14), a height clearance exists between the top end of the upper crystallization member (21) of the lower tray (14) and the bottom end of the lower crystallization member (17) of the upper tray (14); and the height clearance is preferably 20 mm to 150 mm, more preferably 50 mm to 100 mm.

17. The crystallization column according to claim 15, wherein the upper crystallization member (21) comprises an upper cylinder (23) and a flexible thread (22), the upper cylinder (23) equipped with the flexible thread (22) to form a torsion wire brush type structure.

18. The crystallization column according to claim 17, wherein the upper cylinder (23) is of stainless steel, tetrafluorohydrazine or carbon steel coated with tetrafluorohydrazine; the flexible thread (22) is a material that is not reacted with ammonium hydrogen sulfide and is insoluble in water, preferably any one of carbon fiber, nylon, fluoroplastics or stainless steel wire.

19. The crystallization column according to claim 17, wherein a diameter of the flexible thread (22) is 1 mm to 12 mm; when the flexible thread (22) is of metal material, the diameter of the flexible thread (22) is preferably 1 mm to 3 mm; and when the flexible thread (22) is of non-metal material, the diameter of the flexible thread (22) is preferably 2 mm to 5 mm.

20. The crystallization column according to claim 1, wherein the tower body (2) further comprises a cooling section (10) that is provided with a heat removing component (13); the heat removing component (13) is preferably any one of a shell and tube type evaporative cooler, a plate type heat exchanger, an electrical refrigeration unit and a gas type lithium bromide unit.

21. The crystallization column according to claim 20, wherein the tower body (2) further comprises a feed mixing section (9) located below the cooling section (10); the feed mixing section (9) is provided with a gas phase distributor (12); and the gas phase distributor (12) is preferably an aerator, a plate type gas phase distributor or a trough-pan gas phase distributor.

22. The crystallization column according to claim 1, wherein the upper head (1) is further provided with a water inlet (5); the water inlet (5) is connected with a water distribution pipe (6); and the water distribution pipe (6) is provided with several nozzles.

23. The crystallization column according to claim 22, wherein the water inlet (5) is the gas outlet (4), or the water inlet (5) and the gas outlet (4) are separately disposed, respectively.

24. A crystallization method using the crystallization column of claim 1, wherein gas to be crystallized enters a tower body (2) through a gas inlet (8), the gas to be crystallized reacts to crystallize on a tray (14) of a crystallization section (11), and crystallized gas is discharged out from the gas outlet (4).

25. The crystallization method according to claim 24, wherein the gas to be crystallized entering the tower body (2) is mixed gas of hydrogen sulfide-containing gas and ammonia gas.

26. The crystallization method according to claim 25, wherein the feed molar ratio of the hydrogen sulfide-containing gas and the ammonia gas is 1:1 to 1:2, preferably 5:6 to 2:3.

27. The crystallization method according to claim 25, wherein the reaction crystallization temperature of the hydrogen sulfide-containing gas and the ammonia gas is 0? C.?40? C., preferably 0? C.-20? C.

28. The crystallization method according to claim 24, wherein the crystallization method further comprises: water is added from the top of the tower body (2) to flush the crystal on the tray (14), and mixture of the water after flushing and the crystal outflows from the material outlet (7).

Description

BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings are provided here to facilitate further understanding of the present invention, and constitute a part of this document. They are used in conjunction with the following embodiments to explain the present invention, but shall not be comprehended as constituting any limitation to the present invention. In the figures:

[0022] FIG. 1 is a structural schematic diagram of the crystallization column according to the preferred embodiment of the invention, and the arrows in the figure represent the flowing direction of the gas phase, i.e., forming upward bend fluid;

[0023] FIGS. 2 to 5 are structural diagrams of the tray according to multiple embodiments of the invention;

[0024] FIG. 6 is a structural diagram of the upper crystallization members according to the preferred embodiment of the invention;

[0025]

TABLE-US-00001 Brief Description of the Symbols 1 Upper head 2 Tower body 3 Lower head 4 Gas outlet 5 Water inlet 6 Water inlet distribution pipe 7 Material outlet 8 Gas inlet 9 Feed mixing section 10 Cooling section 11 Crystallization section 12 Gas-phase distributor 13 Heat taking component 14 Tray 15 Tray plate 16 Lifting lug 17 Lower crystallization member 18 Lifting ring 19 Lower cylinder 20 Spiked object 21 Upper crystallization member 22 Flexible thread 23 Upper cylinder

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Hereunder some embodiments of the present invention will be detailed with reference to the accompanying drawings. It should be understood that the embodiments described here are only provided to describe and explain the present invention, but shall not be deemed as constituting any limitation to the present invention.

[0027] In the present invention, unless otherwise specified, the terms of locality, such as upper, lower, top, bottom, etc., are words that describe the positional relation among components and are usually defined in relation to the directions 5 indicated in the accompanying drawings or in relation to vertical or gravity direction; vertical direction refers to the up-down direction of the sheet surface indicated in the figure, and transverse is usually defined in relation to the left-right direction of the approximately horizontal sheet surface indicated in the figure; and inside and outside refer to the inside and outside of the cavity relative to the cavity.

[0028] As shown in the FIG. 1, the invention provides a crystallization column, which comprises an upper head 1 with a gas outlet 4, a tower body 2 and a lower head 3 with a gas inlet 8 and a material outlet 7, wherein the tower body 2 comprises a crystallization section 11; a tray 14 is arranged in the crystallization section 11 and comprises a tray plate 15 approximately and transversely extending from the inner wall of the tower body 2 and a plurality of lower crystallization members 17 which are arranged on the lower surface of the tray plate 15 at intervals with each other.

[0029] The crystallization column of the invention is preferably applied to the gas-gas crystallization reaction, but is not limited to this. The crystallization column can also be used for other gas-liquid reactions. Gas to be crystallized enters the tower body 2 from the gas inlet 8 to produce crystals in the tray 14 in the crystallization section 11, which are attached and crystallized to the lower crystallization member 7 of the tray plate 15; the stripped crystal substances drop or are washed to the material outlet 7 at the bottom of the tower body 2 to be discharged for the next process flow, and gas after reacting is discharged from the gas outlet 4.

[0030] Different from the complex and expensive crystallization apparatus in the prior art, the crystallization apparatus of the invention is simple in structure, i.e., a plurality of lower crystallization members 17 which are hung extend from the tray 14 with large crystallization area; and crystal substances on the lower crystallization member 17 are easily stripped from the lower crystallization member 17 under the disturbance of flowing gas while increasing the crystallization area.

[0031] Wherein the lower crystallization member 17 can form the torsion wire brushed type structure shown as the FIG. 6, and its surface area is large, which is convenient in attached crystallization. The lower crystallization member 7 with the torsion wire brushed type structure can be fixedly or movably connected to the lower surface of the tray plate 15. Or, the lower crystallization member 17 can be an elastic member or a flexible member which is fixedly connected to the lower surface of the tray plate 15, wherein the elastic member or the flexible member can be bent, so that the two adjacent lower crystallization members 17 are capable of oscillating collisions. Or as shown in FIGS. 1 to 5, the top end of the lower crystallization member 17 can form movable connection with the tray plate 15, so that the two adjacent lower crystallizing members 17 are capable of oscillating collisions. When flowing through the lower crystallization member 17, reactant gas is easy in crystallized attachment on its surface, and when the gas phase flows through the lower crystallization member 17, it is necessary to have a certain difference in the flow field or flow velocity, so that the crystal substances attached to the lower crystallization member 17 are non-uniform in distribution. Owing to movable connection between the lower crystallization member 17 and the tray plate 15 and the non-uniform distribution of the crystal substances, it is inevitably to produce the offset of center of gravity for the lower crystallization member 17 under the gravity of the lower crystallization member 17 and the crystal substances as well as the swaying of the gas-phase flowing, resulting in oscillation easily; and once producing collision with the adjacent lower crystallization members 17, the crystal substances will be crushed and stripped to drop the next layer of tray 14 or the bottom of the tower body 2.

[0032] In order to form movable connection, as shown in FIGS. 2 to 5, a retaining ring sliding connection way of lifting rings and lifting lugs is illustrated. Wherein a plurality of lifting lugs 16 are arranged on the lower surface of the tray plate 15 at intervals, the lifting ring 18 is arranged at the top end of the lower crystallization member 17 and is in buckled connection with the lifting lugs 16, so that the lower crystallization member 17 can oscillate. Preferably, a plurality of lifting lugs 16 are uniformly arranged on the lower surface of the tray plate 15, and a plurality of lower crystallization members 17 are in one-to-one correspondence connection to a plurality of lifting lugs 16. Those skilled in the art could know that there are many forms and connecting structures to form the movable connection, which are not limited the buckled ring sliding connection way. For example, the top end of the lower crystallization member 17 can also be connected to the lower surface of the tray plate via the flexible rope, and the two adjacent lower crystallization members 17 can oscillate and collide with each other under air flow blowing or gravity deflection.

[0033] As shown in the FIG. 2, in one preferred embodiment of the lower crystallization member 17, the lower cylinder 19 and the lifting ring 18 connected to the top end of the lower cylinder 19 are included. When the lower crystallization members are in one-to-one correspondence connection to a plurality of lifting lugs 16 which are uniformly arranged, the length of the lower crystallization member 17 and the interval density shall be favorable of oscillation and collision, for example, in many embodiments as shown in the figure, radial distance between the centers of any two adjacent lower cylinders 19 which are overhung downwards is smaller than the axial height of the lower cylinder 19.

[0034] In order to increase the surface area of the lower crystallization member 17 to promote attached crystallization, bulges are also arranged on the surface of the lower cylinder 19. The lower crystallization member 17 according to the other preferred embodiment as shown in the FIG. 3 not only comprises the lower cylinder 19 and the lifting ring 18, but also comprises a plurality of spiked object 20 formed on the surface of the lower cylinder 19, which extend outwards from the surface of the lower cylinder 19 in the radial direction, so that the lower cylinder 19 is in the mace-shaped structure. In addition, as shown in the FIG. 3, the adjacent mace-shaped lower crystallization members 17 are preferably staggered with each other in height, so that during the oscillating collision of the adjacent lower crystallization members 17, the spiked object 20 can align with the crystal substance between the two spiked objects 20 on the other side, making it stripped easily. Similarly, in order to maximize the surface area and facilitate the crystallization and stripping of crystal substances, in many embodiments as shown in the figure, the maximum extension length of the spiked object 20 in the radial direction is 1/20 to ? of the axial height of the lower cylinder 19, with 1/15 to 1/10 preferably. In the mace-shaped lower cylinder, height gap between the upper and lower adjacent spiked objects is 1/20 to ? of the axial height of the lower cylinder, with 1/15 to 1/10 preferably.

[0035] In addition, during the installation of the tray plate 15, one end of the tray plate is connected with the inner wall of the tower body 2, while the other end transversely extends, and a gas circulation gap is formed between the extension end and the inner wall on the opposite side of the tower body 2, the gas phase can pass through the gas circulating gap, and perforated holes are not required to be formed in the tray plate 15. The gas circulating gap is favorable for forming an air flue under guidance to sway the lower crystallization member 17. For example, multiple layers of trays 14 which are sequentially separated up and down are arranged in the crystallization section 11 as shown in the FIG. 1 and are arranged on two sides of the central axis of the tower body 2 (for clarity, it is not shown in the figure) and are arranged right and left in a staggered way, so that the gas phase can pass through the gas circulating gap of each tray plate upwardly to form bend fluid. When flowing along the direction shown as the arrow in the figure to form bend fluid, the gas phase can sway the lower crystallization member 17 on each tray plate 15, which facilitates oscillating collision and crystallization and the stripping of crystal substances. Of course, for the tray plate 15 transversely extends or transversely and obliquely extends from the inner wall of the tray plate 2, it is not limited to the arrangement ways of up-down interval and left-right staggering and is also not limited to multiple tray plates. Single tray plate 15 can also be arranged in the tower body 2 only, and perforated holes can also be formed in the single tray plate 15 to make air flow pass through.

[0036] In the crystallization column as shown in the FIG. 1, in order to increase the crystallization area, the tray 14 also preferably comprises a plurality of upper crystallization members 21, wherein the upper crystallization member 21 extends upwardly from the upper surface of the tray plate 15. As shown in the FIG. 1, gas-phase bend fluid not only can sway the lower crystallization members 17, making them achieve attached crystallization, but can also sway the upper crystallization members 21, thereby greatly increasing the crystallization area. In the upper and lower adjacent trays 14, a height gap is formed between the top end of the upper crystallization member 21 of the lower tray 14 and the bottom end of the lower crystallization member 17 of the upper tray 14, through which the gas phase can easily pass. The height gap ranges from 520 mm to 150 mm preferably, and more preferably ranges from 50 mm to 100 mm.

[0037] As shown in the FIG. 6, the upper crystallization member 21 with the preferred structural form comprises the upper cylinder 23 and the flexible thread 22, wherein the flexible thread 22 is arranged on the upper cylinder 23 to form a torsion wire brushed type structure. Such similar hair brush shape can increase the crystallization area to a great extent, crystal substances are easy to drop, and the surfaces of the dropped crystal substances can also be used as the crystallization attachment surfaces. The upper crystallization member 21 is applied to the embodiment as shown in FIGS. 4 and 5, but the difference between the FIGS. 4 and 5 is that in the FIG. 5, the lower crystallization member 17 with the spiked object 20 is used. In accordance with the reactant gas and the reaction characteristics, the upper cylinder 23 is preferably made of corrosion resistant stainless steel, tetrafluoride or carbon steel outer lining tetrafluoride, the flexible thread 22 is a material which does not react with ammonium hydrosulfide and is water insoluble, which is preferably one of carbon fiber, nylon, fluoroplastics and stainless steel wire. The diameter of the flexible thread 22 approximately ranges from 1 mm to 12 mm. When the flexible thread 22 is made of metals, the diameter of the flexible thread 22 will range from 1 mm to 3 mm preferably; and when the flexible thread 22 is made of non-metals, the diameter of the flexible thread 22 will range from 2 mm to 5 mm preferably.

[0038] In addition, see the FIG. 1, the tower body 2 also comprises a cooling section 10, wherein a heat taking component 13 is arranged in the cooling section 10, which is preferably one of a multitubular evaporative cooler, a plate heat exchanger, an electrical refrigerating unit, a fuel gas type lithium bromide unit. Gas entering the crystallization column from the gas inlet 8 can be cooled via the heat taking component 13 to be close to crystallization reaction temperature, thereby facilitating producing the crystallization reaction at the crystallization section 11 above immediately. For the cooling of the gas to be crystallized, its cooling equipment can also, according to needs, arranged outside the tower body 2. In addition, the tower body 2 also comprises a feed mixing section 9 positioned below the cooling section 10, wherein a gas-phase distributor 12 is arranged in the feed mixing section 9, which is preferably one of an aerator, a plate-type gas-phase distributor or a tank tray type gas-phase distributor. The gas-phase distributor 12 may achieve uniform gas distribution, stable flow field and uniform crystallization. In addition, the upper head 1 is also provided with a water inlet 5, the water inlet 5 is connected with a water inlet distribution pipe 6, and a plurality of spray nozzles is arranged on the water inlet distribution pipe 6. The crystal substances can be washed and dissolved by water sprayed from the spray nozzles to form acidic water, which flows out of a material outlet 7 at the bottom of the tower body 2. The crystal substances are in the fluffy state between the gaps of the torsion wire brushed type upper crystallization members 21, which is extremely easy drop to the tray plate 15 under the impulsion of water injection; As shown in the FIG. 1, the water inlet 5 and the gas outlet 4 can be separately arranged, however, water injection and reaction tail gas discharge are switching operations at different phases, hence, the water inlet 5 and the gas outlet 4 can be preferably the same opening.

[0039] On the basis of the above-mentioned crystallization column, the present invention further provides a corresponding crystallization method, i.e., gas to be crystallized is supplied to the tower body 2 through the gas inlet 8, the gas to be crystallized reacts to crystallize on the tray 14 of the crystallization section 11, and the crystallized gas is discharged from the gas outlet 4. Water is added from the top of the tower body 2 to flush the crystal on the tray 14. Mixture of the water after flushing and the crystal outflows from the material outlet 7.

[0040] Next, it will further illustrate how the crystallization column of the present invention works in conjunction with a specific application. The work procedure of the crystallization column of the present invention is specified by taking processing hydrogen sulfide-containing gas with ammonia gas as an example. The molar ratio of hydrogen sulfide containing gas to ammonia gas is 1:1 to 1:2, with 5:6 to 2:3 preferably. The reaction crystallization temperature of hydrogen sulfide containing gas and ammonia gas is 0? C. to 40? C., with 0? C. to 20? C. preferably.

[0041] First, the acid gas (hydrogen sulfide-containing gas) mixed with ammonia gas enters the crystallization column from the gas inlet 8 of the crystallization column. The gas phase uniformed distributed by a plate-type gas-phase distributor 12 inside the feed mixing section 9 enter into the cooling section 10, passes through a shell and tube evaporative cooler, and realizes cooling with the effect of the liquid ammonia. The liquid ammonia is heated by absorbing heat and becomes ammonia gas to be discharged out from the apparatus or to enter the crystallization column as the ammonia gas reacting with the acid gas. The cooled acid gas mixed with the ammonia gas starts crystallizing on the lower crystallization member 17 of the tray 14. Ammonium hydrogen sulphide crystallizes and adheres to the surface of the lower crystallization member 17 while flowing therethrough. Since there is difference in flowing around when the gas phase flows through the lower crystallization member 17, crystallization and adhering are in a heterogeneous state. Flowing blowing and deflection of the center of gravity of the gas phase causes the lower crystallization member 17 to swing, and once it collides with the adjacent lower crystallization member 17, the crystal shatters and peels off from the lower crystallization member 17 and fall to the next layer of tray 14, greatly increasing the use efficiency of the crystallization column. When crystal in the crystallization column reaches a certain weight, the crystallization tower switches operation. Water is started to be added from the water inlet 5 of the crystallization column to flush and dissolve the ammonium hydrogen sulphide crystal to form the acidic water. The acidic water is discharged out of the apparatus through the material outlet 7 arranged on the lower head 3 of the crystallization column. The water inlet 5 and the gas inlet 8 both can be provided in plural, for example, a plurality of inlets arranged at equal intervals along the circumferential direction.

[0042] Embodiments and comparative embodiments are provided below to verify the crystallization effect of the crystallization column of the present invention.

Embodiment 1

[0043] The crystallization column as shown in FIG. 1 takes the acid gas as the raw material for processing. In the acid gas, CO2 has a volume fraction of 94%, H2S has a volume fraction of 5%, and hydrocarbon has a volume fraction of 1%. The acid gas is first cooled to 20? C. by the cooler, and then uniformly mixed with the ammonia gas. The feed molar ratio of the acid gas and the ammonia gas is 2:3. The mixed material flow enters the crystallization column to obtain the gas phase material flow and the ammonium hydrogen sulphide crystal. The ammonium hydrogen sulphide crystal is deposited within the crystallization column. The result of analysis of the materials is shown in table 1.

Comparative Embodiment 1

[0044] The reaction conditions are the same as those of the embodiment 1 with only difference in replacing the crystallization column of the present invention with a common crystallizer. The common crystallizer is a conventional empty pot, but the crystallizer is ensured to have the same crystallization space with that in the crystallization column of the present invention.

TABLE-US-00002 TABLE 1 Comparison of reaction results of the embodiment and the comparative embodiment Embodiment 1 Comparative embodiment 1 crystallization situation of crystals are uniform, the the sizes of the crystals are ammonium hydrogen particle size is small and irregular, most are in large sulphide easy to wash, and the pieces and not easy to wash, formed acidic water has the formed acidic water has high concentration low concentration, and the volume of the formed acidic water is about 2 times that of the embodiment 1. content of H2S in the 20 100 purified gas (mg/Nm.sup.3) operation period of stably operating for 260 h shutdown processing is apparatus required after operating for 100 h

[0045] As shown in Table 1, the crystallization column of the present invention can operate persistently with an outstanding crystallization effect, the crystal is easy to obtain, the water consumption is low, the gas purification degree is high, energy consumption is reduced, and the crystallization column is especially suitable for separation process of hydrogen sulfide in the carbon dioxide-containing acid gags.

[0046] While some preferred embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the details in those embodiments. Various simple variations can be made to the technical scheme of the present invention, without departing from the spirit of the technical idea of the present invention. For example, for heterogeneous interval distribution of the lower crystallization members 17 and connection not in one-to-one correspondence between the hanger 18 and the lifting lug 16, a single lifting lug 18 may be movably connected with a plurality of hangers 16, and the upper cylinder 23 and the lower crystallization member 17 are not limited to the shown cylinder shape and may be various curved shapes and the like. These simple variations may be deemed as falling into the protection scope of the present invention.

[0047] In addition, the specific technical features described in above embodiments can be combined in any appropriate form, provided that there is no conflict. To avoid unnecessary repetition, the possible combinations are not described specifically in the present invention.

[0048] Moreover, different embodiments of the present invention can be combined freely as required, as long as the combinations don't deviate from the ideal and spirit of the present invention. However, such combinations shall also be deemed as falling into the scope disclosed in the present invention.