CN104557435A - Method for separating p-xylene by two-step direct cooling crystallization - Google Patents
Method for separating p-xylene by two-step direct cooling crystallization Download PDFInfo
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- CN104557435A CN104557435A CN201510061295.8A CN201510061295A CN104557435A CN 104557435 A CN104557435 A CN 104557435A CN 201510061295 A CN201510061295 A CN 201510061295A CN 104557435 A CN104557435 A CN 104557435A
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Abstract
The invention relates to a method for separating p-xylene by two-step direct cooling crystallization, for mainly solving the problems of high investment cost, large crystallizer quantity and low heat exchange efficiency in the prior art. According to the technical scheme of the method for separating p-xylene by two-step direct cooling crystallization, a mixed xylene raw material containing 10-40wt% of p-xylene is in direct contact with a low-temperature liquid coolant in a first crystallizer to exchange heat, p-xylene crystal and mixed xylene mother liquor are discharged out of the first crystallizer in the form of size and enter a first filter, and the mixed xylene crystal obtained in the first filter and having high p-xylene content is melted in a melter; and the melted mixed xylene crystal having high p-xylene content enters a second crystallizer and is in direct contact with a low-temperature liquid coolant to exchange heat, so that the above problems are well solved. The method can be used for separating p-xylene.
Description
Technical field
The present invention relates to the method for the direct crystallisation by cooling separating paraxylene of a kind of two-step approach.
Background technology
P-Xylol PX is mainly for the production of basic organic such as pure terephthalic acid PTA, and usual p-Xylol comes from xylol, and this mixture contains four kinds of isomerss: o-Xylol, m-xylene, p-Xylol and ethylbenzene.In order to obtain required high purity p-Xylol and other useful component, they must be carried out separation and purification.The technical process of current industrial separation p-Xylol mainly contains adsorption method of separation and perfectly crystallization process two kinds.In general, when para-xylene concentration is lower in xylol raw material, adopt adsorption method of separation with the obvious advantage; When para-xylene concentration is higher in xylol raw material, adopt perfectly crystallization process advantageously.Perfectly crystallization process wants high feature according to p-Xylol 13.3 DEG C of fusing points compared with other component fusing point (o-Xylol fusing point is-25.2 DEG C, m-xylene fusing point is-47.9 DEG C, ethylbenzene fusing point is-95.0 DEG C) be separated, paraxylene crystals will be separated out at first during the cooling of xylol raw material.
License notification number CN101735001B relates to a kind of method of p-Xylol Crystallization Separation, adopts crystallisation by cooling separating technology to solve the problem of fractionation by adsorption investment height and complicated operation.Public announcement of a patent application CN103333045A relates to the method and apparatus that a kind of p-Xylol is produced, and adopts toluene disproportionation and Crystallization Separation to combine and produces p-Xylol.Public announcement of a patent application CN103772130A relates to a kind of crystallization method of separating paraxylene, and the technical process adopting mother liquor to return solves the problem that energy consumption is large, pre-cooler fouling is serious.Public announcement of a patent application CN104030880A relates to a kind of method of direct crystallisation by cooling separating paraxylene, and indirect cooling process is complicated, number of devices is many, investment and the high problem of process cost to adopt refrigerant direct heat exchange Crystallization Separation p-Xylol to solve.
License notification number CN101735001B of the prior art adopts simulation moving-bed, switch logistics by rotary valve and crystallization and filtration treatment are carried out to material, reach the object of Crystallization Separation p-Xylol, but there is the problems such as the many and investment cost of technical process complexity, number of devices is high in the method.Public announcement of a patent application CN103333045A merely depict and adopts toluene disproportionation and Crystallization Separation to combine the method for producing p-Xylol, its Crystallization Separation still uses the indirect heat exchange type crystallizer of internal structure complexity, and the heat interchanging area of crystallizer can not infinitely increase, the throughput of separate unit crystallizer is limited, when production equipment popularization, exist and need the problems such as multiple stage crystallizer can meet the demands.Public announcement of a patent application CN103772130A adopts indirect heat exchange method, there is the problems such as technical process is long, heat transfer efficiency is low, process cost is high.Public announcement of a patent application CN104030880A solves indirect heat exchange Problems existing, but refrigerant adopts liquid nitrogen or Liquid carbon dioxide, there is refrigerant and is difficult to reclaim or refrigerant recovering long flow path, the problems such as investment cost is high, complicated operation.
The present invention solves this problem targetedly.
Summary of the invention
Technical problem to be solved by this invention is the problem that in prior art, investment cost is high, crystallizer quantity is many, heat exchange efficiency is low, provides the method for the direct crystallisation by cooling separating paraxylene of a kind of new two-step approach.The method, for separating of in p-Xylol, has the advantage that investment cost is low, crystallizer quantity is few, heat exchange efficiency is high.
For solving the problem, the technical solution used in the present invention is as follows: the method for the direct crystallisation by cooling separating paraxylene of a kind of two-step approach, by containing p-Xylol massfraction be 10 ~ 40% xylol raw material in First crystallizer with low temperature liquid phase refrigerant direct contact heat transfer, the heat of xylol is absorbed in low temperature liquid phase refrigerant vaporescence, and xylol is lowered the temperature after obtaining the cold of low temperature liquid phase refrigerant and is separated out paraxylene crystals, paraxylene crystals and xylol mother liquor are discharged First crystallizer in a form of slurry and are entered First strainer, paraxylene crystals is separated in First strainer with xylol mother liquor, the xylol crystal of the high p-xylene content that First strainer obtains enters melting tank fusing, the xylol material of the high p-xylene content after fusing enters second crystallizer and low temperature liquid phase refrigerant direct contact heat transfer, the paraxylene crystals of separating out in second crystallizer and xylol mother liquor are discharged second crystallizer in a form of slurry and are entered second strainer, obtain high purity para-xylene product after filtering, the refrigerant of vaporizing in every platform crystallizer returns refrigeration compressor set, and by unit cooler by refrigerant again compressed cooling liquid, the low temperature refrigerant of post liquefaction returns every platform crystallizer and recycles.
In technique scheme, preferably, described every platform crystallizer is all with agitator; Xylol raw material is liquid or the slurry containing partial crystals.
In technique scheme, preferably, the purity of described high purity para-xylene product is 99.8%; In the xylol crystal of high p-xylene content, p-Xylol mass content is more than 60%.
In technique scheme, preferably, described refrigerant is at least one of ethene, propylene, propane, ammonia, cyclopropane and Trimethylmethane.
In technique scheme, preferably, the service temperature of described First crystallizer is-90 ~-50 DEG C, and working pressure is 200 ~ 1050kPaA; The service temperature of First strainer is-90 ~-50 DEG C, and working pressure is 200 ~ 1050kPaA; The service temperature of melting tank is 20 ~ 50 DEG C, and working pressure is 170 ~ 700kPaA; The service temperature of second crystallizer is-40 ~ 25 DEG C, and working pressure is 140 ~ 350kPaA; The service temperature of second strainer is-40 ~ 25 DEG C, and working pressure is 140 ~ 350kPaA.
In technique scheme, more preferably, the service temperature of described First crystallizer is-80 ~-60 DEG C, and working pressure is 400 ~ 850kPaA; The service temperature of First strainer is-80 ~-60 DEG C, and working pressure is 400 ~ 850kPaA; The service temperature of melting tank is 25 ~ 45 DEG C, and working pressure is 300 ~ 600kPaA; The service temperature of second crystallizer is-30 ~ 15 DEG C, and working pressure is 200 ~ 330kPaA; The service temperature of second strainer is-30 ~ 15 DEG C, and working pressure is 200 ~ 330kPaA.
In technique scheme, most preferably, the service temperature of described First crystallizer is-75 ~-65 DEG C, and working pressure is 500 ~ 750kPaA; The service temperature of First strainer is-75 ~-65 DEG C, and working pressure is 500 ~ 750kPaA; The service temperature of melting tank is 30 ~ 40 DEG C, and working pressure is 350 ~ 500kPaA; The service temperature of second crystallizer is-20 ~ 5 DEG C, and working pressure is 260 ~ 310kPaA; The service temperature of second strainer is-20 ~ 5 DEG C, and working pressure is 260 ~ 310kPaA.
In technique scheme, preferably, the temperature entering the low temperature liquid phase refrigerant of First crystallizer is-95 ~-50 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-45 ~ 25 DEG C.
In technique scheme, preferably, in First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 8.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.0 ~ 16.0.
The present invention adopts the direct crystallisation by cooling separating paraxylene of two-step approach.Because the heat transfer efficiency of direct heat exchange is high, crystallizer quantity is the half that prior art adopts indirect heat exchange crystallizer quantity, and the cost of manufacture of the single crystallizer of the present invention is also low than indirect heat exchange crystallizer, therefore the facility investment expense of production equipment is able to further reduction, use the cost of refrigerant to decline 30 ~ 65% simultaneously, achieve good technique effect and good economic benefit.
Accompanying drawing explanation
Fig. 1 is the schematic flow sheet of the method for the invention.
1 is First crystallizer; 2,12 is low temperature liquid phase refrigerant; 3,13 is refrigeration compressor set; 4,14 is gas phase refrigerant; 5 is xylol raw material; The 6 xylol slurries of discharging for First crystallizer; 7 is First strainer; 8 is the xylol crystal of high p-xylene content; The 9 xylol mother liquors of discharging for First strainer; 10 is melting tank; 15 is the xylol material of high p-xylene content after fusing; 16 is the xylol slurry that second crystallizer is discharged; 17 is second strainer; 18 is para-xylene product; 19 is the xylol mother liquor that second strainer is discharged; 20,21 is agitator.
Below by embodiment, the invention will be further elaborated, but be not limited only to the present embodiment.
Embodiment
[embodiment 1]
The present invention adopts the method for the direct crystallisation by cooling separating paraxylene of two step method, the industrial scale of p-xylene separation device is 100,000 tons/year, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts propane to carry out direct heat exchange crystallisation by cooling separating paraxylene as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 80%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-20 ~-15 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.5 ~ 1:4.5.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-15 DEG C, and working pressure is 286kPaA; The crystal that final second strainer is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 2, and refrigerant use cost declines more than 49%.
[comparative example 1]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 1 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 4.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 2]
According to the condition described in embodiment 1, only the industrial scale of p-xylene separation device changes 200,000 tons/year into, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts propane to carry out direct heat exchange crystallisation by cooling separating paraxylene as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 80%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-20 ~-15 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.5 ~ 1:4.5.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-15 DEG C, and working pressure is 286kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 51%.
[comparative example 2]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 2 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 3]
According to the condition described in embodiment 1, only the industrial scale of p-xylene separation device changes 400,000 tons/year into, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts propane to carry out direct heat exchange crystallisation by cooling separating paraxylene as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 80%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-20 ~-15 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.5 ~ 1:4.5.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-15 DEG C, and working pressure is 286kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 8, and refrigerant use cost declines more than 57%.
[comparative example 3]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 3 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 16.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 4]
According to the condition described in embodiment 1, only the industrial scale of p-xylene separation device changes 1,000,000 tons/year into, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts propane to carry out direct heat exchange crystallisation by cooling separating paraxylene as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 80%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-20 ~-15 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.5 ~ 1:4.5.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-15 DEG C, and working pressure is 286kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 20, and refrigerant use cost declines more than 62%.
[comparative example 4]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 4 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 40.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 5]
According to the condition described in embodiment 2, only the refrigerant of second crystallizer changes propylene into, operational condition is corresponding change also, the industrial scale of p-xylene separation device is 200,000 tons/year, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts propylene as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 75%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-95 ~-90 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-45 ~-40 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.5 ~ 1:4.5.The service temperature of First crystallizer and First strainer is-90 DEG C, and working pressure is 206kPaA; The service temperature of melting tank is 20 DEG C, and working pressure is 170kPaA; The service temperature of second crystallizer and second strainer is-40 DEG C, and working pressure is 142kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 49%.
[comparative example 5]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 5 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 6]
According to the condition described in embodiment 2, only the refrigerant of second crystallizer changes Trimethylmethane into, operational condition is corresponding change also, the industrial scale of p-xylene separation device is 200,000 tons/year, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts Trimethylmethane as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 75%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-55 ~-50 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is 20 ~ 25 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.0 ~ 1:4.0.The service temperature of First crystallizer and First strainer is-50 DEG C, and working pressure is 1027kPaA; The service temperature of melting tank is 50 DEG C, and working pressure is 700kPaA; The service temperature of second crystallizer and second strainer is 25 DEG C, and working pressure is 342kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 50%.
[comparative example 6]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 6 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 7]
According to the condition described in embodiment 2, only the refrigerant of second crystallizer changes ammonia into, operational condition is corresponding change also, the industrial scale of p-xylene separation device is 200,000 tons/year, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts ammonia as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 75%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-15 ~-10 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:10.0 ~ 1:16.0.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-10 DEG C, and working pressure is 282kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 51%.
[comparative example 7]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 7 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 8]
According to the condition described in embodiment 2, only the refrigerant of second crystallizer changes cyclopropane into, operational condition is corresponding change also, the industrial scale of p-xylene separation device is 200,000 tons/year, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts cyclopropane as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 80%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-10 ~-5 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.5 ~ 1:4.5.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-5 DEG C, and working pressure is 288kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 48%.
[comparative example 8]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 8 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 9]
According to the condition described in embodiment 2, only the refrigerant of second crystallizer changes 50% propylene and 50% propane mixture into, operational condition is corresponding change also, the industrial scale of p-xylene separation device is 200,000 tons/year, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts 50% propylene and 50% propane mixture as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 80%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-25 ~-20 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:3.0 ~ 1:5.0.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-20 DEG C, and working pressure is 267kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 58%.
[comparative example 9]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 9 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 10]
According to the condition described in embodiment 2, only the refrigerant of second crystallizer changes 25% propylene and 25% cyclopropane and 50% Trimethylmethane mixture into, operational condition is corresponding change also, the industrial scale of p-xylene separation device is 200,000 tons/year, in xylol raw material, the weight percent of contained p-Xylol is 25%, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts 25% propylene and 25% cyclopropane and 50% Trimethylmethane mixture as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 75%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-15 ~-10 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:3.0 ~ 1:5.0.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-10 DEG C, and working pressure is 216kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 61%.
[comparative example 10]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 10 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 11]
According to the condition described in embodiment 2, only in xylol raw material, the weight percent of contained p-Xylol changes 10% into, the industrial scale of p-xylene separation device is 200,000 tons/year, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts propane to carry out direct heat exchange crystallisation by cooling separating paraxylene as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 60%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-20 ~-15 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:4.0 ~ 1:6.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.5 ~ 1:4.5.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-15 DEG C, and working pressure is 286kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 30%.
[comparative example 11]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 11 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
[embodiment 12]
According to the condition described in embodiment 2, only in xylol raw material, the weight percent of contained p-Xylol changes 40% into, the industrial scale of p-xylene separation device is 200,000 tons/year, First crystallizer adopts ethene as refrigerant, and second crystallizer adopts propane to carry out direct heat exchange crystallisation by cooling separating paraxylene as refrigerant.In the xylol crystal of high p-xylene content, p-Xylol mass content is greater than 85%, and the purity of high purity para-xylene product is 99.8%.The temperature entering the low temperature liquid phase refrigerant of First crystallizer is-75 ~-70 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-20 ~-15 DEG C.In First crystallizer, the weight ratio of low temperature liquid phase refrigerant and xylol raw material is 1:6.0 ~ 1:8.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.5 ~ 1:4.5.The service temperature of First crystallizer and First strainer is-70 DEG C, and working pressure is 500kPaA; The service temperature of melting tank is 33 DEG C, and working pressure is 410kPaA; The service temperature of second crystallizer and second strainer is-15 DEG C, and working pressure is 286kPaA; The crystal that final filtration device is separated out is 99.8% high purity para-xylene product, and crystallizer quantity is 4, and refrigerant use cost declines more than 65%.
[comparative example 12]
Prior art adopts the indirect heat exchange type crystallizer of internal structure complexity, and under the industrial scale identical with embodiment 12 and operational condition, due to the restriction of the throughput by separate unit crystallizer, crystallizer quantity is 8.And adopting liquid nitrogen as the direct heat exchange technology of refrigerant, its refrigerant use cost is 100%.
Claims (9)
1. the method for the direct crystallisation by cooling separating paraxylene of two-step approach, by containing p-Xylol massfraction be 10 ~ 40% xylol raw material in First crystallizer with low temperature liquid phase refrigerant direct contact heat transfer, the heat of xylol is absorbed in low temperature liquid phase refrigerant vaporescence, and xylol is lowered the temperature after obtaining the cold of low temperature liquid phase refrigerant and is separated out paraxylene crystals, paraxylene crystals and xylol mother liquor are discharged First crystallizer in a form of slurry and are entered First strainer, paraxylene crystals is separated in First strainer with xylol mother liquor, the xylol crystal of the high p-xylene content that First strainer obtains enters melting tank fusing, the xylol material of the high p-xylene content after fusing enters second crystallizer and low temperature liquid phase refrigerant direct contact heat transfer, the paraxylene crystals of separating out in second crystallizer and xylol mother liquor are discharged second crystallizer in a form of slurry and are entered second strainer, obtain high purity para-xylene product after filtering, the refrigerant of vaporizing in every platform crystallizer returns refrigeration compressor set, and by unit cooler by refrigerant again compressed cooling liquid, the low temperature refrigerant of post liquefaction returns every platform crystallizer and recycles.
2. the method for the direct crystallisation by cooling separating paraxylene of two-step approach according to claim 1, is characterized in that described every platform crystallizer is all with agitator; Xylol raw material is liquid or the slurry containing partial crystals.
3. the method for the direct crystallisation by cooling separating paraxylene of two-step approach according to claim 1, is characterized in that the purity of described high purity para-xylene product is 99.8%; In the xylol crystal of high p-xylene content, p-Xylol mass content is more than 60%.
4. the method for the direct crystallisation by cooling separating paraxylene of two-step approach according to claim 1, is characterized in that described refrigerant is at least one of ethene, propylene, propane, ammonia, cyclopropane and Trimethylmethane.
5. the method for the direct crystallisation by cooling separating paraxylene of two-step approach according to claim 1, it is characterized in that the service temperature of described First crystallizer is-90 ~-50 DEG C, working pressure is 200 ~ 1050kPaA; The service temperature of First strainer is-90 ~-50 DEG C, and working pressure is 200 ~ 1050kPaA; The service temperature of melting tank is 20 ~ 50 DEG C, and working pressure is 170 ~ 700kPaA; The service temperature of second crystallizer is-40 ~ 25 DEG C, and working pressure is 140 ~ 350kPaA; The service temperature of second strainer is-40 ~ 25 DEG C, and working pressure is 140 ~ 350kPaA.
6. the method for the direct crystallisation by cooling separating paraxylene of two-step approach according to claim 5, it is characterized in that the service temperature of described First crystallizer is-80 ~-60 DEG C, working pressure is 400 ~ 850kPaA; The service temperature of First strainer is-80 ~-60 DEG C, and working pressure is 400 ~ 850kPaA; The service temperature of melting tank is 25 ~ 45 DEG C, and working pressure is 300 ~ 600kPaA; The service temperature of second crystallizer is-30 ~ 15 DEG C, and working pressure is 200 ~ 330kPaA; The service temperature of second strainer is-30 ~ 15 DEG C, and working pressure is 200 ~ 330kPaA.
7. the method for the direct crystallisation by cooling separating paraxylene of two-step approach according to claim 6, it is characterized in that the service temperature of described First crystallizer is-75 ~-65 DEG C, working pressure is 500 ~ 750kPaA; The service temperature of First strainer is-75 ~-65 DEG C, and working pressure is 500 ~ 750kPaA; The service temperature of melting tank is 30 ~ 40 DEG C, and working pressure is 350 ~ 500kPaA; The service temperature of second crystallizer is-20 ~ 5 DEG C, and working pressure is 260 ~ 310kPaA; The service temperature of second strainer is-20 ~ 5 DEG C, and working pressure is 260 ~ 310kPaA.
8. the method for the direct crystallisation by cooling separating paraxylene of two-step approach according to claim 1, is characterized in that the temperature of the low temperature liquid phase refrigerant entering First crystallizer is-95 ~-50 DEG C; The temperature entering the low temperature liquid phase refrigerant of second crystallizer is-45 ~ 25 DEG C.
9. the method for the direct crystallisation by cooling separating paraxylene of two-step approach according to claim 1, is characterized in that the weight ratio of low temperature liquid phase refrigerant and xylol raw material in First crystallizer is 1:4.0 ~ 8.0; In second crystallizer, the weight ratio of the xylol material of low temperature liquid phase refrigerant and the high p-xylene content after melting is 1:2.0 ~ 16.0.
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| CN113144660A (en) * | 2021-02-05 | 2021-07-23 | 成都思达能环保设备有限公司 | Crystallization method and system |
| CN115160100A (en) * | 2021-04-02 | 2022-10-11 | 中国石化工程建设有限公司 | System and method for producing ethylbenzene from C8 aromatic hydrocarbons |
| CN115177969A (en) * | 2021-04-02 | 2022-10-14 | 中国石化工程建设有限公司 | System and method for separating ethylbenzene from C8 aromatic hydrocarbon |
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| CN113144660A (en) * | 2021-02-05 | 2021-07-23 | 成都思达能环保设备有限公司 | Crystallization method and system |
| CN115160100A (en) * | 2021-04-02 | 2022-10-11 | 中国石化工程建设有限公司 | System and method for producing ethylbenzene from C8 aromatic hydrocarbons |
| CN115177969A (en) * | 2021-04-02 | 2022-10-14 | 中国石化工程建设有限公司 | System and method for separating ethylbenzene from C8 aromatic hydrocarbon |
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