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US 5,329,061 AGranted
Crystallization process for para-xylene recovery using two-stage recovery section
AssigneeUop LLC
InventorJohn D. Swift
Life of this patent
Estimating the term…
Abstract
In a combination crystallization/xylene isomerization process for producing para-xylene crystals, the recovery section is modified to accommodate crystallizing and separating para-xylene crystals at two different temperatures (a higher temperature followed by a lower temperature). The benefit is a reduction in the overall energy cost of the process.
Claims17
A crystallization process for producing para-xylene crystals from a mixed xylene feedstock which process comprises the steps of:
- (a) passing at least a portion of said feedstock to a crystallization recovery section comprising:
- (i) a first stage recovery section which produces first stage recovery section para-xylene crystals and first stage recovery section mother liquor at a first temperature;
- and
- (ii) a second stage recovery section which produces second stage recovery section para-xylene crystals and second stage recovery section mother liquor temperature which is lower than said first temperature;
- (b) feeding at least a portion of said first stage recovery section mother liquor to said second stage crystallization recovery section;
- (c) passing at least a portion of said second stage recovery section mother liquor to a xylene isomerization zone containing an isomerization catalyst at conditions sufficient to produce an isomerate comprising an equilibrium xylene mixture and passing a recycle stream comprising said isomerate to said crystallization recovery section;
- (d) passing a purification feed stream comprising said first and second stage recovery section para-xylene crystals to a crystallization purification section to produce a purification section effluent stream comprising para-xylene crystals and purification section mother liquor;
- and
- (e) separating said purification section effluent stream into purification mother liquor and para-xylene product crystals.
6 more elements
A crystallization process for producing para-xylene crystals from a mixed xylene feedstock which process comprises the steps of:
- (a) passing at least a portion of said feedstock to a crystallization recovery section comprising:
- (i) a first stage recovery section which produces first stage recovery section para-xylene crystals and first stage recovery section mother liquor at a temperature of about -35.degree. C. to -50.degree. C.;
- and
- (ii) a second stage recovery section which produces second stage recovery section para-xylene crystals and second stage recovery section mother liquor at a temperature of about -55.degree. C. to -75.degree. C.;
- (b) feeding at least a portion of said first stage recovery section mother liquor to said second stage crystallization recovery section;
- (c) passing at least a portion of said second stage recovery section mother liquor to a xylene isomerization zone containing an isomerization catalyst at conditions sufficient to produce an isomerate comprising an equilibrium xylene mixture and passing a recycle stream comprising said isomerate to said crystallization recovery section;
- (d) passing a purification feed stream comprising said first and second stage recovery section para-xylene crystals to a crystallization purification section to produce a purification section effluent stream comprising para-xylene crystals and purification section mother liquor;
- and
- (e) separating said purification section effluent stream into purification mother liquor and para-xylene product crystals.
6 more elements
A crystallization process for producing para-xylene crystals from a mixed xylene feedstock which process comprises the steps of:
- (a) passing at least a portion of said feedstock to a crystallization recovery section comprising:
- (i) a first stage recovery section which produces first stage recovery section para-xylene crystals and first stage recovery section mother liquor at a temperature of about -35.degree. C. to -50.degree. C,;
- and
- (ii) a second stage recovery section which produces second stage recovery section para-xylene crystals and second stage recovery section mother liquor at a temperature of about -55.degree. C. to -75.degree. C.;
- (b) feeding at least a portion of said first stage recovery section mother liquor to said second stage crystallization recovery section;
- (c) passing at least a portion of said second stage recovery section mother liquor to a xylene isomerization zone containing an isomerization catalyst at conditions sufficient to produce an isomerate comprising an equilibrium xylene mixture and passing a recycle stream comprising said isomerate to said crystallization recovery section;
- (d) passing a purification feed stream comprising said first and second stage recovery section para-xylene crystals to a crystallization purification section to produce a purification section effluent stream comprising para-xylene crystals and purification section mother liquor;
- (e) separating said purification section effluent stream into purification mother liquor and para-xylene product crystals;
- and
- (f) passing at least a portion of said purification section mother liquor to said crystallization recovery section.
7 more elements
Dependencies are inferred from the claim text.