CN104557424B - The method of multistage suspension Crystallization Separation paraxylene - Google Patents
The method of multistage suspension Crystallization Separation paraxylene Download PDFInfo
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- CN104557424B CN104557424B CN201310512340.8A CN201310512340A CN104557424B CN 104557424 B CN104557424 B CN 104557424B CN 201310512340 A CN201310512340 A CN 201310512340A CN 104557424 B CN104557424 B CN 104557424B
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Abstract
A kind of method that the present invention relates to multistage suspension Crystallization Separation paraxylene, the problem that mainly present in solution prior art, energy consumption is big, the present invention uses two-stage crystallization process, first passing through the relatively low first degree crystalline process of temperature and isolate paraxylene from raw material as much as possible to improve the rate of recovery, the secondary crystallization process that recycling temperature is higher reclaims paraxylene from crystalline mother solution;The crystal of firsts and seconds crystallization process is without recrystallizing after being completely melt again, but utilize magma groove to be collected, utilize double pipe heat exchanger that magma groove is carried out temperature control, crystal is made to carry out part fusing wherein, and obtain para-xylene product, magma enters the technical scheme that solid-liquid separator carries out separating after thickening, preferably solves the problem that energy consumption present in prior art is big, can be used for during paraxylene crystallization produces.
Description
Technical field
A kind of method that the present invention relates to multistage suspension Crystallization Separation paraxylene.
Background technology
Paraxylene (PX) is a kind of important Organic Chemicals, be mainly used as producing p-phthalic acid (PTA) and
The raw material of dimethyl terephthalate (DMT) (DMT), PTA is then used for manufacturing polyethylene terephthalate (PET) and poly-to benzene two
The polyester products such as formic acid butanediol ester (PBT).At present, China has become as whole world PX and produces the first big country, and total output accounts for the whole world
More than the 10% of yield, by the end of the year 2011, China has had 13 set PX process units, and aggregated capacity reaches 8,110,000 t/a.In recent years
Coming, China's polyester industrial grows continuously and fast, and is promoted by PET industry, and domestic PTA production capacity is expanded the most rapidly, and PX supplies
Producing expansible demand far from meeting PTA, China PX consumption will maintain the healthy momentum of growth the coming years, and it is short that PX supplies
Scarce situation can exist always, thus has to increase import, and within 2011, China import PX has reached 498.2 ten thousand t, it is contemplated that to 2015
Year will be more than 7,000,000 t.
Separating mixed dimethyl is the main production process of paraxylene.Mixed xylenes mainly by paraxylene, two
Toluene, ortho-xylene and ethylbenzene composition, the boiling point difference between each component is the least, uses rectificating method to be little to obtain high-purity
The PX product of degree, but between these components, fusing point difference is the biggest, can use crystallisation isolated high-purity paraxylene.
Patent US3177265 discloses a kind of method of multistage suspension Crystallization Separation paraxylene, first passes through one-level knot
Brilliant acquisition paraxylene crystals, first degree crystalline process is for improving the paraxylene rate of recovery, and crystallization temperature is relatively low, and due in raw material
Para-xylene concentration is the lowest, and therefore gained paraxylene crystals granularity is the least, and solid-liquid separation effect is poor, final paraxylene crystals
Purity is only 85%~90%.For improving product purity, first degree crystalline gained crystal is all melted by this technique, is then re-fed into
The secondary crystallization process that temperature is higher recrystallizes, to obtain highly purified para-xylene product.This to first degree crystalline
Although the method that crystal recrystallizes after being completely melt again has ensured product purity, but from the perspective of Energy harvesting also
Not being optimum scheme, first refrigeration obtains crystal, then adds heat fusing, and the recrystallization that freezes the most again can increase the energy of crystallization process
Consumption.Only rely on separation of solid and liquid to be usually unable to obtain highly purified para-xylene product, for improving product purity further, generally
Also need to crystal is washed.Cleaning solution is typically toluene or pure liquid para-xylene product, if using toluene to wash
Liquid, then need the separation carrying out paraxylene and toluene just can obtain final product.If using pure liquid paraxylene to produce
Product make cleaning solution, and its benefit is to directly obtain para-xylene product, but risk that may be present is that pure liquid is to two
Toluene product runs into cold paraxylene crystals in washing process can recrystallize precipitation, and then blocking filtration channel, makes washing
Process is difficult to, it is difficult to obtains good clean result, affects product purity.For ensureing crystallization in paraxylene crystallization process
The heat transfer effect of device, needs to use scraper to be scraped by the crystal on heat-transfer surface incessantly, thus inevitably results from big
The thin crystalline substance of amount, when carrying out follow-up separation of solid and liquid, thin brilliant existence can reduce solid-liquid separation effect, and also has the thin crystalline substance of part
Enter in mother liquor, thus cause the loss of para-xylene product.
Chinese patent " by the method for Xylol Separation by Crystallization paraxylene " (number of patent application:
200910057546.X) by crystalline mother solution overflow by the thin brilliant removal in first degree crystalline device, thus extend crystal at crystallizer
In the time of staying with promote crystal grow up.Although this method can produce the paraxylene crystals of big granularity, but overflow
Mother liquor in be very easy to carry thin crystalline substance, these thin crystalline substances can enter in slurrying tank, does not carry out fine crystal elimination due to slurrying tank, because of
This thin crystalline substance brought into from first degree crystalline device and secondary crystallizer does not ensures that and is completely eliminated, and these thin brilliant existence can affect
To follow-up separation of solid and liquid.Second level crystallizer uses mother liquor overflow equally, and overflowing liquid is directly off crystalline element, and overflowing liquid will
Part can be carried thin brilliant, thus cause the loss of product.
Summary of the invention
The technical problem to be solved is the problem that present in the crystallization of existing paraxylene produces, energy consumption is big, carries
Method for the multistage suspension Crystallization Separation paraxylene of a kind of novelty.
For solving above-mentioned technical problem, the present invention uses technical scheme as follows: mixed xylenes raw material is through mother liquor heat exchanger
Enter in first degree crystalline device after cooling down with forecooler and crystallize;Magma in first degree crystalline device separates through solid-liquid separator I
To paraxylene crystals I and first degree crystalline mother liquor, paraxylene crystals I enters in magma groove, and first degree crystalline mother liquor is divided into two strands,
First strand account for 0~95% the first degree crystalline mother liquor I of weight return in first degree crystalline device, second strand accounts for 5~100% one-level knot of weight
Brilliant mother liquor II leaves crystalline element after raw material is cooled down by mother liquor heat exchanger;Magma in secondary crystallizer is through separation of solid and liquid
Device II isolated paraxylene crystals II and secondary crystallization mother liquor, paraxylene crystals II enters in magma groove, two grades of knots
Brilliant mother liquor is divided into two strands, first strand account for 5~95% the secondary crystallization mother liquor I of weight return in secondary crystallizer, second strand accounts for 5
~95% the secondary crystallization mother liquor II of weight return in first degree crystalline device;Upper strata mother liquor in magma groove is warp after top is flowed out
Again returning to the bottom of magma groove after double pipe heat exchanger heat exchange, the magma in magma groove is discharged from bottom after thickening, through solid
Liquid/gas separator III obtains paraxylene crystals III and filtrated stock after separating, and paraxylene crystals III is warp in solid-liquid separator III
Entering in melted tank after cleaning solution washing, filtrated stock is divided into two strands, first strand account for 5~95% the filtrated stock I of weight return crystalline substance
In stock tank, second strand account for 5~95% the filtrated stock II of weight enter in secondary crystallizer;Paraxylene crystals in melted tank
III heated after fusing, 5~30% weight paraxylene IV scrubbed liquid cooler cooling after return to solid-liquid as cleaning solution
In separator III, 70~95% the paraxylene V of weight leave crystalline element as product.
In technique scheme, the bottom of magma groove is taper;Crystallizer is vertical to scrape wall crystallizer, for cone bottom it
Shape;Crystallizer is double-pipe chiller;Solid-liquid separator is centrifuge, filter or crystal scrubbing tower;Inside double pipe heat exchanger
The inner member such as rotating shaft and scraper is installed;Paraxylene crystals III enters melted in solid-liquid separator III after the washing of scrubbed liquid
In tank, the filtrate of washing process is collected separately and returns in magma groove;Magma in first degree crystalline device is through solid-liquid separator I point
From obtaining paraxylene crystals I and first degree crystalline mother liquor, enter in magma groove after the heated fusing of paraxylene crystals I;One-level
Magma in crystallizer is through solid-liquid separator I isolated paraxylene crystals I and first degree crystalline mother liquor, paraxylene crystals I
Heated fusing rear section or fully enter in secondary crystallizer.
In technique scheme, the crystal of first degree crystalline process and secondary crystallization process, without being completely melt, is sent directly into
Obtain para-xylene product after magma groove carries out part fusing, save the energy consumption of crystallization process.Magma groove is adiabatic operation,
Control the effect of crystal block section fusing in magma groove by the temperature controlling double-tube heat exchanger, after crystal block section fusing, form height
The magma of temperature, the magma of high temperature is more conducive to separation of solid and liquid due to the reduction of liquid phase viscosity;In magma temperature-rise period, due to small grain size
Crystal there is bigger solubility, thus thin crystalline substance can melt at first, improves the degree of supersaturation of liquid phase after thin brilliant fusing, favorably
Continue to grow up in other big granularity crystal, thus follow-up separation of solid and liquid;Gained crystal and cleaning solution after magma intensification
Between the temperature difference reduce, can effectively prevent cleaning solution recrystallization phenomenon in washing process, so that it is guaranteed that clean result and product
Product purity.Magma trench bottom has thickening effect, concentrates magma, can improve the process energy of follow-up solid-liquid separating equipment
Power and stability.The thin crystalline substance that magma groove mother liquor at the middle and upper levels carries returns to magma trench bottom after double-tube heat exchanger heating eliminates,
Both having prevented the deposition of magma trench bottom crystal, and can promote again growing up of other crystal in magma groove, the paraxylene after fusing is
Can enter in secondary crystallizer eventually and recrystallize, not result in product loss.
The method using the multistage suspension Crystallization Separation paraxylene of the present invention carries out the crystallization of paraxylene and produces, and passes through
Arrange magma groove the crystal of first degree crystalline and secondary crystallization is carried out part fusing rather than is completely melt, be greatly saved crystallization
The energy consumption of process, and remain to ensure product purity, the refrigeration of crystallization process can reduce about 17%, the purity of para-xylene product
Can reach more than 99.9%, achieved preferable technique effect.
Accompanying drawing explanation
Fig. 1 is the schematic flow sheet of the method for multistage suspension Crystallization Separation paraxylene of the present invention.
Fig. 2 is the schematic flow sheet of the method for crystallising (US3177265) of existing separating paraxylene.
As described in Figure 1, mixed xylenes raw material 1 enters first degree crystalline device C after mother liquor heat exchanger A and forecooler B cools down
In crystallize;Magma 2 in first degree crystalline device C is female through solid-liquid separator D isolated paraxylene crystals 3 and first degree crystalline
Liquid 4, paraxylene crystals 3 enters in magma groove E, and first degree crystalline mother liquor 4 is divided into two strands, and first strand accounts for 0~95% one-level of weight
Crystalline mother solution 5 returns in first degree crystalline device C, second strand account for 5~100% the first degree crystalline mother liquor 6 of weight through mother liquor heat exchanger A pair
Raw material 1 leaves crystalline element after cooling down;Magma 7 in secondary crystallizer F is through solid-liquid separator G isolated paraxylene
Crystal 8 and secondary crystallization mother liquor 9, paraxylene crystals 8 enters in magma groove E, and secondary crystallization mother liquor 9 is divided into two strands, and first
Stock account for 5~95% the secondary crystallization mother liquor 10 of weight return in secondary crystallizer, second strand accounts for 5~95% secondary crystallization of weight
Mother liquor 11 returns in first degree crystalline device C;Upper strata mother liquor 12 in magma groove E changes through double pipe heat exchanger H after top is flowed out
Again returning to the bottom of magma groove E after heat, the magma 13 in magma groove E is discharged from bottom after thickening, divides through solid-liquid separator I
Obtaining paraxylene crystals 14 and filtrated stock 15 after from, paraxylene crystals 14 is the washing of scrubbed liquid in solid-liquid separator I
Rear entrance melts in tank J, and filtrated stock 15 is divided into two strands, first strand account for 5~95% the filtrated stock 16 of weight return magma groove E
In, second strand account for 5~95% the filtrated stock 17 of weight enter in secondary crystallizer F;Paraxylene crystals 14 in melted tank J
Fusing after heated, 5~30% weight the cooling of paraxylene scrubbed liquid cooler after return to solid-liquid as cleaning solution 18 and divide
In device III, 70~95% the paraxylene of weight leave crystalline element as product 19.
As described in Figure 2, mixed xylenes 1, after heat exchanger 2 cools down, crystallizes in first order crystallizer 11;One-level
Magma 12 in crystallizer 11 carries out separation of solid and liquid by the first solid-liquid separator 13, obtains paraxylene crystals 14 and crystallized
Filter mother liquor 15;Paraxylene crystals 14 enters in second level crystallizer 3 after melting in melted tank 16 and crystallizes, and crystallization is filtered
Mother liquor 15 is discharged after being cooled down mixed xylenes 1 by heat exchanger 2;Magma 4 in second level crystallizer 3 is solid by first
Liquid/gas separator 5 carries out separation of solid and liquid, obtains highly purified paraxylene crystals 6 and crystallization filtrated stock 7;Paraxylene crystals 6
Melting in melted tank 8, the crystal in the first solid-liquid separator 5 is washed by a part as cleaning solution 9, a part of conduct
Para-xylene product 10 is discharged;Crystallization filtrated stock 7 enters in first order crystallizer 11 and crystallizes.
Below by embodiment, the present invention is further elaborated.
Detailed description of the invention
[embodiment 1]
The method for crystallising of multistage suspension Crystallization Separation paraxylene of the present invention.
As described in Figure 1, mixed xylenes raw material 1, temperature is 50 DEG C, and paraxylene content is 24wt%, and flow is
6114kg/h, enters in first degree crystalline device C after mother liquor heat exchanger A and forecooler B cools down and crystallizes, and crystallization temperature is-60
℃;Magma 2 in first degree crystalline device C is through solid-liquid separator D isolated paraxylene crystals 3 and first degree crystalline mother liquor 4, to two
Toluene crystal 3 enters in magma groove E, and the operation temperature of magma groove is 5 DEG C, and first degree crystalline mother liquor 4 is divided into two strands, and first strand accounts for 5%
The first degree crystalline mother liquor 5 of weight returns in first degree crystalline device C, and second strand of first degree crystalline mother liquor 6 accounting for 95% weight is through mother liquor heat exchange
Device A leaves crystalline element after cooling down raw material 1;Magma 7 in secondary crystallizer F is through solid-liquid separator G isolated pair
Dimethylbenzene crystal 8 and secondary crystallization mother liquor 9, crystallization temperature is-8 DEG C, and paraxylene crystals 8 enters in magma groove E, two grades of knots
Brilliant mother liquor 9 is divided into two strands, and first strand of secondary crystallization mother liquor 10 accounting for 85% weight returns in secondary crystallizer, and second strand accounts for 15%
The secondary crystallization mother liquor 11 of weight returns in first degree crystalline device C;Upper strata mother liquor 12 in magma groove E from top flow out after through set
Again returning to the bottom of magma groove E after pipe heat exchanger H heat exchange, the magma 13 in magma groove E is discharged from bottom after thickening, warp
Solid-liquid separator I obtains paraxylene crystals 14 and filtrated stock 15 after separating, and paraxylene crystals 14 is in solid-liquid separator I
Entering in melted tank J after the washing of scrubbed liquid, filtrated stock 15 is divided into two strands, and first strand of filtrated stock 16 accounting for 30% weight returns
Returning in magma groove E, second strand of filtrated stock 17 accounting for 70% weight enters in secondary crystallizer F;Paraxylene in melted tank J
Fusing after crystal 14 is heated, melted tank operation temperature is 30 DEG C, after the paraxylene scrubbed liquid cooler cooling of 20% weight
Returning in solid-liquid separator III as cleaning solution 18, the paraxylene of 80% weight leaves crystalline element as product 19.
[embodiment 2]
The method for crystallising of multistage suspension Crystallization Separation paraxylene of the present invention.
According to the operating condition of embodiment 1, multistage suspension crystallization as described in Figure 1 is used to produce the crystallization side of paraxylene
Method, wherein, the operation temperature of magma groove is 4 DEG C.
[embodiment 3]
The method for crystallising of multistage suspension Crystallization Separation paraxylene of the present invention.
According to the operating condition of embodiment 1, multistage suspension crystallization as described in Figure 1 is used to produce the crystallization side of paraxylene
Method, wherein, the operation temperature of magma groove is 3 DEG C.
[comparative example 1]
The method for crystallising of existing separating paraxylene.
According to the operating condition of embodiment 1, the method for crystallising of employing separating paraxylene as described in Figure 2
(US3177265), its results are shown in Table 1.
Table 1
Comparative run | Embodiment 1 | Embodiment 2 | Embodiment 3 | Comparative example 1 |
The concentration (wt%) of PX in raw material | 24 | 24 | 24 | 24 |
Material flow (kg/h) | 6114 | 6114 | 6114 | 6114 |
First degree crystalline temperature (DEG C) | -60 | -60 | -60 | -60 |
Brilliant slurry groove temperature (DEG C) | 5 | 4 | 3 | — |
Secondary crystallization temperature (DEG C) | -8 | -8 | -8 | -8 |
Crystal particle mean size (μm) | 450 | 450 | 450 | 300 |
The PX purity (wt%) of product | 99.9 | 99.9 | 99.9 | 99.9 |
Energy consumption for cooling (Mkcal/h) | 0.3 | 0.29 | 0.28 | 0.36 |
[comparative example 2]
The method for crystallising of existing separating paraxylene.
According to the operating condition of embodiment 1, use the separation described in Chinese patent (application number: 200910057546.X) right
The method for crystallising of dimethylbenzene, the results are shown in Table 2 for it.
Table 2
Comparative run | Embodiment 1 | Comparative example 1 |
The concentration (wt%) of PX in raw material | 80 | 80 |
Material flow (kg/h) | 6114 | 6114 |
First degree crystalline temperature (DEG C) | -16 | -16 |
Brilliant slurry groove temperature (DEG C) | 5 | 5 |
Secondary crystallization temperature (DEG C) | -1 | -1 |
Crystal particle mean size (μm) | 450 | 400 |
The PX purity (wt%) of product | 99.9 | 99.9 |
Energy consumption for cooling (kg marks oil/ton PX) | 7 | 8.5 |
By comparative example it can be seen that the method for multistage suspension Crystallization Separation paraxylene of the present invention is by arranging
Magma groove carries out part fusing to the crystal of first degree crystalline and secondary crystallization rather than is completely melt, is greatly saved crystallization process
Energy consumption, and remain to ensure product purity, the refrigeration of crystallization process can reduce about 17%, the purity of para-xylene product up to
To more than 99.9%, achieve preferable technique effect.
Claims (9)
1. a method for multistage suspension Crystallization Separation paraxylene, comprises the following steps:
A) mixed xylenes raw material enters in first degree crystalline device after mother liquor heat exchanger and forecooler cool down and crystallizes;
B) magma in first degree crystalline device is through solid-liquid separator I isolated paraxylene crystals I and first degree crystalline mother liquor, to two
Toluene crystal I enters in magma groove, and first degree crystalline mother liquor is divided into two strands, and first strand accounts for 0~95% first degree crystalline mother liquor I of weight
Return in first degree crystalline device, second strand account for 5~100% the first degree crystalline mother liquor II of weight through mother liquor heat exchanger, raw material is carried out cold
Leave crystalline element the most afterwards;
C) magma in secondary crystallizer is through solid-liquid separator II isolated paraxylene crystals II and secondary crystallization mother liquor, right
Dimethylbenzene crystal II enters in magma groove, and secondary crystallization mother liquor is divided into two strands, and first strand accounts for 5~95% secondary crystallization of weight
Mother liquor I returns in secondary crystallizer, second strand account for 5~95% the secondary crystallization mother liquor II of weight return to first degree crystalline device
In;
D) magma groove mother liquor at the middle and upper levels again returns to the bottom of magma groove after top is flowed out after double pipe heat exchanger heat exchange, brilliant
Magma in stock tank is discharged from bottom after thickening, obtains paraxylene crystals III and filter mother after solid-liquid separator III separates
Liquid, paraxylene crystals III enters in melted tank after the washing of scrubbed liquid in solid-liquid separator III, and filtrated stock is divided into two strands,
First strand account for 5~95% the filtrated stock I of weight return in magma groove, second strand account for 5~95% the filtrated stock II of weight enter
Enter in secondary crystallizer;
E) fusing after the paraxylene crystals III in melted tank is heated, 5~30% the scrubbed liquid of paraxylene IV of weight cold
But return in solid-liquid separator III as cleaning solution after device cooling, 70~95% the paraxylene V of weight leave as product
Crystalline element.
The method of multistage suspension Crystallization Separation paraxylene the most according to claim 1, it is characterised in that the end of magma groove
Portion is taper.
The method of multistage suspension Crystallization Separation paraxylene the most according to claim 1, it is characterised in that crystallizer is vertical
Formula scrapes wall crystallizer, for taper bottom it.
The method of multistage suspension Crystallization Separation paraxylene the most according to claim 1, it is characterised in that crystallizer is set
Pipe crystallizer.
The method of multistage suspension Crystallization Separation paraxylene the most according to claim 1, it is characterised in that solid-liquid separator
For centrifuge, filter or crystal scrubbing tower.
The method of multistage suspension Crystallization Separation paraxylene the most according to claim 1, it is characterised in that casing type heat exchanging
Device is internally installed rotating shaft and scraper inner member.
The method of multistage suspension Crystallization Separation paraxylene the most according to claim 1, it is characterised in that paraxylene is brilliant
Body III enters in melted tank after the washing of scrubbed liquid in solid-liquid separator III, and the filtrate of washing process is collected separately and returns to
In magma groove.
The method of multistage suspension Crystallization Separation paraxylene the most according to claim 1, it is characterised in that first degree crystalline device
In magma through solid-liquid separator I isolated paraxylene crystals I and first degree crystalline mother liquor, paraxylene crystals I is heated
Enter in magma groove after fusing.
The method of multistage suspension Crystallization Separation paraxylene the most according to claim 1, it is characterised in that first degree crystalline device
In magma through solid-liquid separator I isolated paraxylene crystals I and first degree crystalline mother liquor, paraxylene crystals I is heated
Melt rear section or fully enter in magma groove.
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US3177265A (en) * | 1961-05-22 | 1965-04-06 | Standard Oil Co | Process for the recovery of paraxylene |
US5498822A (en) * | 1994-04-04 | 1996-03-12 | Mobil Oil Corporation | Single temperature stage crystallization of paraxylene |
CN101941882A (en) * | 2009-07-06 | 2011-01-12 | 中国石油化工股份有限公司上海石油化工研究院 | Method for separating p-xylene from mixed xylene |
CN101941883A (en) * | 2009-07-06 | 2011-01-12 | 中国石油化工股份有限公司上海石油化工研究院 | Method for preparing p-xylene by separating and crystallizing mixed xylenes |
CN102372591A (en) * | 2010-08-23 | 2012-03-14 | 中国石油化工股份有限公司 | Crystallization method for p-xylene production |
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Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3177265A (en) * | 1961-05-22 | 1965-04-06 | Standard Oil Co | Process for the recovery of paraxylene |
US5498822A (en) * | 1994-04-04 | 1996-03-12 | Mobil Oil Corporation | Single temperature stage crystallization of paraxylene |
CN101941882A (en) * | 2009-07-06 | 2011-01-12 | 中国石油化工股份有限公司上海石油化工研究院 | Method for separating p-xylene from mixed xylene |
CN101941883A (en) * | 2009-07-06 | 2011-01-12 | 中国石油化工股份有限公司上海石油化工研究院 | Method for preparing p-xylene by separating and crystallizing mixed xylenes |
CN102372591A (en) * | 2010-08-23 | 2012-03-14 | 中国石油化工股份有限公司 | Crystallization method for p-xylene production |
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