CN102372590B - Crystallization method for preparing para-xylene from xylol - Google Patents
Crystallization method for preparing para-xylene from xylol Download PDFInfo
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- CN102372590B CN102372590B CN201010262033.5A CN201010262033A CN102372590B CN 102372590 B CN102372590 B CN 102372590B CN 201010262033 A CN201010262033 A CN 201010262033A CN 102372590 B CN102372590 B CN 102372590B
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Abstract
The invention relates to a crystallization method for preparing para-xylene from xylol and mainly aims to solve the problem of great energy consumption in the process of crystallization and separation in the prior art. According to the invention, a pulpifying groove is arranged to allow para-xylene crystals obtained in the second stage of crystallisation to enter into a first stage crystallizer after pulpification, which enables the above-mentioned problem to be overcome; the method can be used for industrial production of para-xylene.
Description
Technical field
The present invention relates to a kind of crystallization method of being produced p-Xylol by xylol.
Background technology
P-Xylol is the important source material of polyester industrial, mainly for the production of pure terephthalic acid (PTA) or pure terephthalic acid's dimethyl ester (DMT), and then removing to produce polyester (PET) by PTA and DMT, separating mixed dimethyl is the main production method of p-Xylol.Xylol is mainly comprised of p-Xylol, m-xylene, o-Xylol and ethylbenzene, and the boiling point between each component differs very little, larger but fusing point differs, and can adopt crystallization process separating paraxylene.
Patent US5448005 discloses a kind of crystallization method by being rich in the xylol raw material production p-Xylol of p-Xylol, the method obtains highly purified p-Xylol product by the separation of first step crystallisation process, and reclaims remaining p-Xylol in crystalline mother solution by second stage crystallisation process.Because the purity of p-Xylol crystal product depends on solid-liquid separation efficiency, and the service temperature of second stage crystallisation process is lower, gained magma temperature is also lower, be unfavorable for solid-liquid separation, thereby the highly purified p-Xylol crystal of difficult acquisition, therefore, in this patent, the p-Xylol crystal of second stage crystallisation process gained all melts, and then turns back to first step crystallisation process and carry out recrystallization to improve the purity of p-Xylol product.From the angle of energy utilization, first refrigeration obtains crystal, then melts crystal and freezes and carry out recrystallization, and the Crystallizing process energy consumption of this patent is increased.
Summary of the invention
Technical problem to be solved by this invention is the large problem of energy consumption existing in the existing crystallization method of producing p-Xylol by xylol, and a kind of crystallization method by xylol production p-Xylol of novelty is provided.The method has been saved the energy consumption of sepn process.
In order to solve the problems of the technologies described above, the technical solution used in the present invention is as follows: a kind of crystallization method of being produced p-Xylol by xylol, comprises the following steps:
A) xylol carries out crystallization in first step crystallizer, the clear mother liquor of crystallization in crystallizer flows out from crystallizer top, the clear mother liquor of crystallization is divided into two strands, first gang of clear mother liquor I of crystallization that accounts for 5～95% weight enters in slurrying tank, and second gang of clear mother liquor II of crystallization that accounts for 5～95% weight enters in the crystallizer of the second stage;
B) magma in first step crystallizer obtains p-Xylol crystal I and crystallization filtrated stock I after the first solid-liquid separator separation, p-Xylol crystal I melts after heat exchange, the p-Xylol of 5～30% weight returns to the first solid-liquid separator as washings, and the p-Xylol of 70～95% weight is discharged as product;
C) crystallization filtrated stock I is divided into two strands, and first gang of crystallization filtrated stock I that accounts for 5～95% weight enters in slurrying tank, and second gang of crystallization filtrated stock I that accounts for 5～95% weight enters and in the crystallizer of the second stage, carry out crystallization;
D) magma in the crystallizer of the second stage obtains p-Xylol crystal II and crystallization filtrated stock II through the second solid-liquid separator separation, and p-Xylol crystal II enters in slurrying tank, turns back in first step crystallizer after the mixing of materials in slurrying tank;
E) crystallization filtrated stock II is divided into two strands, and first gang of crystallization filtrated stock II that accounts for 5～95% weight turns back in the crystallizer of the second stage, after second gang of crystallization filtrated stock II that accounts for 5～95% weight and the heat exchange of xylol raw material, discharges;
Wherein, after xylol raw material and second gang of crystallization filtrated stock II heat exchange, enter in slurrying tank, the clear mother liquor of crystallization is 0.1: 1～10: 1 with the ratio of the weight of second gang of crystallization filtrated stock I.
In technique scheme, the service temperature of first step crystallizer is higher than the service temperature of second stage crystallizer; The service temperature of first step crystallizer is-65～13 ℃; The service temperature of second stage crystallizer is-65～13 ℃; The service temperature of slurrying tank is higher than the service temperature of first step crystallizer; Solid-liquid separator is centrifuge separator or crystal washing tower; In xylol, p-Xylol concentration is greater than 20%; The purity of p-Xylol product is at least 99.5%.
In technique scheme, the object that slurrying tank is set is by regulating service temperature and the magma residence time therein of slurrying tank, makes p-Xylol crystal experience therein crystal slaking and crystal sweating process to improve crystal purity.In crystal maturing process, large crystal continues to grow up, and little crystal melts, and the macrobead crystal obtaining will be conducive to follow-up solid-liquid separation process, and crystal purity can be higher.In crystal sweating process, thereby the impurity of crystals will flow out and improves crystal purity after melting.Because the magma after pulp will turn back to first step crystallizer, thereby, the fine crystals having melted in slurrying tank will be in the first step crystallizer recrystallization, thereby can not cause the loss of crystal product, crystal purity can be improved because of recrystallization on the contrary.Arrange after slurrying tank, second stage crystallisation process gained p-Xylol crystal does not just need whole fusings, but after pulp, enters in first step crystallizer, thereby has greatly saved the energy consumption of sepn process.Inevitably some thin brilliant existence in crystallizer, degree of supersaturation is the impellent of crystallisation process, in the thin brilliant process growing, will consume a part of degree of supersaturation, thereby make other larger crystal be difficult to grow into larger crystal, thereby can reduce the mean particle size of whole crystal product, be unfavorable for follow-up solid-liquid separation process.Because the magma in first step crystallizer obtains crystal product after solid-liquid separation, therefore need to eliminate the thin crystalline substance in first step crystallizer.Part magma in first step crystallizer in crystallizer through clarification after, can form on crystallizer top the clear mother liquor of crystallization, the clear mother liquor of these crystallizations is not real clear mother liquor, wherein must contain a large amount of thin crystalline substances, the clear mother liquor overflow of this part crystallization is gone out to crystallizer, be about to thin crystalline substance and shifted out crystallizer, thus make that in crystallizer, other larger crystal can be grown larger.A part enters slurrying tank containing the thin brilliant clear mother liquor of crystallization, after the xylol raw material higher with temperature mixes, temperature raises, contained thin crystalline substance will melt, and the p-Xylol after fusing is separated out recrystallization when turning back to first step crystallizer, thereby can not cause the loss of p-Xylol.A part enters in the crystallizer of the second stage containing the thin brilliant clear mother liquor of crystallization, thin brilliant in the crystal seed in the crystallizer of the second stage, because second stage mould temperature is lower than first step mould temperature, thereby thin crystalline substance will continued growth in the crystallizer of the second stage, thereby improve the crystal size in the crystallizer of the second stage.Use the crystallization method production p-Xylol of being produced p-Xylol by xylol of the present invention, compared with prior art, the energy consumption for cooling of sepn process has reduced more than 19%, and the purity of p-Xylol product reaches 99.9%, has obtained good technique effect.
Accompanying drawing explanation
Fig. 1 is the schematic flow sheet of the crystallization method of existing production p-Xylol.
Wherein, 1-raw material; 2-interchanger; 3-first step crystallizer; 4-one-level crystallization magma I; 5-one-level solid-liquid separator; 6-p-Xylol crystal I; 7-one-level crystallization filtrated stock I; 8-melting tank; 9-washings; 10-p-Xylol product; 11-second stage crystallizer; 12-secondary crystallization magma II; 13-secondary solid-liquid separator; 14-p-Xylol crystal II; 15-secondary crystallization filtrated stock II; 16-melting tank.
Fig. 2 is the schematic flow sheet of being produced the crystallization method of p-Xylol by xylol of the present invention.
Wherein, 1-raw material; 2-interchanger; 3-first step crystallizer; 4-one-level crystallization magma I; 5-one-level solid-liquid separator; 6-p-Xylol crystal I; 7-one-level crystallization filtrated stock I; 8-melting tank; 9-washings; 10-p-Xylol product; 11-second stage crystallizer; 12-secondary crystallization magma II; 13-secondary solid-liquid separator; 14-p-Xylol crystal II; 15-secondary crystallization filtrated stock II; 16-slurrying tank; First gang of one-level crystallization filtrated stock I of 17-; Second gang of one-level crystallization filtrated stock I of 18-; First gang of secondary crystallization filtrated stock II of 19-; Second gang of secondary crystallization filtrated stock II of 20-; 21-slurrying tank magma; The clear mother liquor of 22-crystallization; First strand of clear mother liquor of crystallization of 23-; Second strand of clear mother liquor of crystallization of 24-.
As described in Figure 1, xylol 1, after interchanger 2 is cooling, carries out crystallization in first step crystallizer 3, and the magma 4 in crystallizer 3 carries out solid-liquid separation by the first solid-liquid separator 5, obtains highly purified p-Xylol crystal 6 and crystallization filtrated stock 7.P-Xylol crystal 6 melts in melting tank 8, and a part is washed as the crystal in 9 pairs of the first solid-liquid separators 5 of washings, and a part is discharged as p-Xylol product 10.Crystallization filtrated stock 7 enters in second stage crystallizer 11 and carries out crystallization, and the magma 12 in second stage crystallizer 11 obtains p-Xylol crystal 14 and crystallization filtrated stock 15 through the second solid-liquid separator 13 separation.P-Xylol crystal 14 enters in first step crystallizer 3 after melting in melting tank 16, and crystallization filtrated stock 15 carries out cooling rear discharge by 2 pairs of xylol of interchanger 1.
As described in Figure 2, xylol 1 enters in slurrying tank 16 after interchanger 2 is cooling.The clear mother liquor 22 of crystallization in crystallizer 3 is divided into two strands from flow out on crystallization top, and the clear mother liquor 23 of one crystallization enters in slurrying tank 16, and the clear mother liquor 24 of one crystallization enters in second stage crystallizer 11.Magma 4 in crystallizer 3 carries out solid-liquid separation by the first solid-liquid separator 5, obtains highly purified p-Xylol crystal 6 and crystallization filtrated stock 7.P-Xylol crystal 6 melts in melting tank 8, and one is washed as the crystal in 9 pairs of the first solid-liquid separators 5 of washings, and a part is discharged as p-Xylol product 10.Crystallization filtrated stock 7 is divided into two strands, and one crystallization filtrated stock 17 enters in slurrying tank 16, and one crystallization filtrated stock 18 enters and in second stage crystallizer 11, carries out crystallization.Magma 12 in second stage crystallizer 11 obtains p-Xylol crystal 14 and crystallization filtrated stock 15 through the second solid-liquid separator 13 separation.P-Xylol crystal 14 enters in slurrying tank 16, and the magma 21 in slurrying tank 16 returns in first step crystallizer 3.Crystallization filtrated stock 15 is divided into two strands, and one crystallization filtrated stock 19 turns back in second stage crystallizer 11, and one crystallization filtrated stock 20 is crossed 2 pairs of xylol of interchanger 1 and carried out cooling rear discharge.
Below by embodiment, the present invention is further elaborated.
Embodiment
[comparative example 1]
The existing crystallization method of being produced p-Xylol by xylol
As described in Figure 1, in xylol 1, contain 90% p-Xylol, flow is 14864kg/h, after interchanger 2 is cooling, in first step crystallizer 3, carry out crystallization, Tc is 3 ℃, and the magma 4 in crystallizer 3 carries out solid-liquid separation by the first solid-liquid separator 5, obtains highly purified p-Xylol crystal 6 and crystallization filtrated stock 7.P-Xylol crystal 6 melts in melting tank 8, and temperature of fusion is 20 ℃, and the p-Xylol of 20% weight washs as the crystal in 9 pairs of the first solid-liquid separators 5 of washings, and the p-Xylol of 80% weight is discharged as p-Xylol product 10.Crystallization filtrated stock 7 enters in second stage crystallizer 11 and carries out crystallization, and Tc is-14 ℃.Magma 12 in second stage crystallizer 11 obtains p-Xylol crystal 14 and crystallization filtrated stock 15 through the second solid-liquid separator 13 separation.P-Xylol crystal 14 enters in first step crystallizer 3 after melting in melting tank 16, and temperature of fusion is 20 ℃.Crystallization filtrated stock 15 carries out cooling rear discharge by 2 pairs of xylol of interchanger 1.
[embodiment 1]
The crystallization method of being produced p-Xylol by xylol of the present invention
As described in Figure 2, in xylol 1, containing 90% p-Xylol, flow is 14864kg/h, enters in slurrying tank 16 after interchanger 2 is cooling.Xylol carries out crystallization in first step crystallizer 3, and Tc is 3 ℃.The clear mother liquor 22 of crystallization in crystallizer 3 is divided into two strands from flow out on crystallizer top, and first strand of clear mother liquor 23 of crystallization that accounts for 75% weight enters in slurrying tank 16, and second strand of clear mother liquor 24 of crystallization that accounts for 25% weight enters in second stage crystallizer 11.Magma 4 in crystallizer 3 carries out solid-liquid separation by the first solid-liquid separator 5, obtains highly purified p-Xylol crystal 6 and crystallization filtrated stock 7.P-Xylol crystal 6 melts in melting tank 8, and temperature of fusion is 20 ℃, and the p-Xylol of 20% weight washs as the crystal in 9 pairs of the first solid-liquid separators 5 of washings, and the p-Xylol of 80% weight is discharged as p-Xylol product 10.Crystallization filtrated stock 7 is divided into two strands, and first strand of crystallization filtrated stock 17 that accounts for 74% weight enters in slurrying tank 16, and second strand of crystallization filtrated stock 18 that accounts for 26% weight enters in second stage crystallizer 11 and carry out crystallization, and Tc is-14 ℃.Magma 12 in second stage crystallizer 11 obtains p-Xylol crystal 14 and crystallization filtrated stock 15 through the second solid-liquid separator 13 separation.P-Xylol crystal 14 enters in slurrying tank 16, and the magma 21 in slurrying tank 16 returns in first step crystallizer 3, and the service temperature of slurrying tank is 6.1 ℃.Crystallization filtrated stock 15 is divided into two strands, and first strand of crystallization filtrated stock 19 that accounts for 63% weight turns back in second stage crystallizer 11, and second strand of crystallization filtrated stock 20 that accounts for 37% weight carries out cooling rear discharge by 2 pairs of xylol of interchanger 1.Wherein, the clear mother liquor 22 of crystallization is 08: 1 with the ratio of the weight of crystallization filtrated stock 18.The results are shown in Table 1 for it.
[embodiment 2]
The crystallization method of being produced p-Xylol by xylol of the present invention
Adopt the crystallization method by xylol production p-Xylol as described in Figure 2, wherein, second strand of clear mother liquor 24 of crystallization that accounts for 50% weight enters in second stage crystallizer 11, and all the other operational conditions are identical with embodiment 1, and the results are shown in Table 1 for it.
[embodiment 3]
The crystallization method of being produced p-Xylol by xylol of the present invention
Adopt the crystallization method by xylol production p-Xylol as described in Figure 2, wherein, second strand of clear mother liquor 24 of crystallization that accounts for 75% weight enters in second stage crystallizer 11, and all the other operational conditions are identical with embodiment 1, and the results are shown in Table 1 for it.
Table 1
[comparative example 2]
The existing crystallization method of being produced p-Xylol by xylol
The crystallization method that adopts production p-Xylol as described in Figure 1, wherein, the service temperature of second stage crystallizer is-3.54 ℃, and all the other operational conditions are identical with comparative example 1, and the results are shown in Table 2 for it.
[embodiment 4]
The crystallization method of being produced p-Xylol by xylol of the present invention
Adopt the crystallization method by xylol production p-Xylol as described in Figure 2, wherein, second strand of clear mother liquor 24 of crystallization that accounts for 25% weight enters in second stage crystallizer 11, second strand of crystallization filtrated stock 18 that accounts for 30% weight enters and in second stage crystallizer 11, carries out crystallization, the service temperature of second stage crystallizer is-3.54 ℃, the service temperature of slurrying tank is 63 ℃, second strand of crystallization filtrated stock 20 that accounts for 87% weight carries out cooling rear discharge by 2 pairs of xylol of interchanger 1, the clear mother liquor 22 of crystallization is 0.8: 1 with the ratio of the weight of crystallization filtrated stock 18, all the other operational conditions are identical with embodiment 1, the results are shown in Table 2 for it.
[embodiment 5]
The crystallization method of being produced p-Xylol by xylol of the present invention
Adopt the crystallization method by xylol production p-Xylol as described in Figure 2, wherein, second strand of clear mother liquor 24 of crystallization that accounts for 50% weight enters in second stage crystallizer 11, and all the other operational conditions are identical with embodiment 4, and the results are shown in Table 2 for it.
[embodiment 6]
The crystallization method of being produced p-Xylol by xylol of the present invention
Adopt the crystallization method by xylol production p-Xylol as described in Figure 2, wherein, second strand of clear mother liquor 24 of crystallization that accounts for 75% weight enters in second stage crystallizer 11, and all the other operational conditions are identical with embodiment 4, and the results are shown in Table 2 for it.
Table 2
By comparative example, can find out, under the identical rate of recovery, in the present invention, because gained crystal in the crystallizer of the second stage is without recrystallization again after whole fusings, thereby the energy consumption of whole crystallisation process reduces greatly, by thin brilliant elimination of first step crystallizer, the mean particle size of crystal product has also obtained obvious increase, and product purity is higher.
Claims (3)
1. by xylol, produced a crystallization method for p-Xylol, comprise the following steps:
A) xylol carries out crystallization in first step crystallizer, the clear mother liquor of crystallization in crystallizer flows out from crystallizer top, the clear mother liquor of crystallization is divided into two strands, first gang of clear mother liquor I of crystallization that accounts for 5～95% weight enters in slurrying tank, and second gang of clear mother liquor II of crystallization that accounts for 5～95% weight enters in the crystallizer of the second stage;
B) magma in first step crystallizer obtains p-Xylol crystal I and crystallization filtrated stock I after the first solid-liquid separator separation, p-Xylol crystal I melts after heat exchange, the p-Xylol of 5～30% weight returns to the first solid-liquid separator as washings, and the p-Xylol of 70～95% weight is discharged as product;
C) crystallization filtrated stock I is divided into two strands, and first gang of crystallization filtrated stock I that accounts for 5～95% weight enters in slurrying tank, and second gang of crystallization filtrated stock I that accounts for 5～95% weight enters and in the crystallizer of the second stage, carry out crystallization;
D) magma in the crystallizer of the second stage obtains p-Xylol crystal II and crystallization filtrated stock II through the second solid-liquid separator separation, and p-Xylol crystal II enters in slurrying tank, turns back in first step crystallizer after the mixing of materials in slurrying tank;
E) crystallization filtrated stock II is divided into two strands, and first gang of crystallization filtrated stock II that accounts for 5～95% weight turns back in the crystallizer of the second stage, after second gang of crystallization filtrated stock II that accounts for 5～95% weight and the heat exchange of xylol raw material, discharges;
Wherein, after xylol raw material and second gang of crystallization filtrated stock II heat exchange, enter in slurrying tank, the clear mother liquor of crystallization is 0.1: 1～10: 1 with the ratio of the weight of second gang of crystallization filtrated stock I.
Wherein, the service temperature of first step crystallizer is higher than the service temperature of second stage crystallizer; The service temperature of first step crystallizer is-65～13 ℃; The service temperature of second stage crystallizer is-65～13 ℃; The service temperature of slurrying tank is higher than the service temperature of first step crystallizer.
2. the crystallization method of being produced p-Xylol by xylol according to claim 1, is characterized in that in xylol raw material, p-Xylol concentration is greater than 20%.
3. the crystallization method of being produced p-Xylol by xylol according to claim 1, is characterized in that the purity of p-Xylol product is at least 99.5%.
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Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103880585B (en) * | 2012-12-19 | 2015-09-09 | 中国石油化工股份有限公司 | Produce the crystallization method of p-Xylol |
| CN103880581B (en) * | 2012-12-19 | 2015-12-23 | 中国石油化工股份有限公司 | The crystallization method of p-Xylol |
| CN103880586B (en) * | 2012-12-19 | 2015-09-09 | 中国石油化工股份有限公司 | The multistage crystallization method of p-Xylol |
| CN104230638B (en) * | 2013-06-17 | 2016-04-13 | 中国石油化工股份有限公司 | Suspension crystallization produces the method for p-Xylol |
| CN112225635B (en) * | 2020-11-03 | 2022-09-23 | 中国石油化工股份有限公司 | Device, method and application for crystallization and separation of paraxylene |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1493489A (en) * | 1974-03-11 | 1977-11-30 | Standard Oil Co | Process for the recovery of high purity paraxylene |
| US5448005A (en) * | 1994-04-04 | 1995-09-05 | Mobil Oil Corporation | Crystallization of paraxlene from high purity paraxylene feeds |
| CN101437593A (en) * | 2006-05-24 | 2009-05-20 | 三菱化工机株式会社 | Recovery method and recovery system for crystallization component |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1493489A (en) * | 1974-03-11 | 1977-11-30 | Standard Oil Co | Process for the recovery of high purity paraxylene |
| US5448005A (en) * | 1994-04-04 | 1995-09-05 | Mobil Oil Corporation | Crystallization of paraxlene from high purity paraxylene feeds |
| CN101437593A (en) * | 2006-05-24 | 2009-05-20 | 三菱化工机株式会社 | Recovery method and recovery system for crystallization component |
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