GTC Technology Day 16 April Hotel Le Meridien · Types of PX Crystallization Page 4 GTC Technology...
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Transcript of GTC Technology Day 16 April Hotel Le Meridien · Types of PX Crystallization Page 4 GTC Technology...
C5
Aromatics
Extraction
Toluene
Conversion
Benzene C
olu
mn
Tolu
ene C
olu
mn
Xyle
ne C
olu
mn
Benzene
C6 -C7 raffinate
C9+
Paraxylene
Hydrotreated
Naphtha
Xylene
Isomerization
Catalytic
Reformer
C5
Xyle
ne C
olu
mn
C9+
Refo
rmate
Split
ter
Paraxylene
Recovery
Dehepta
niz
er
Paraxylene Recovery in an Aromatics Complex
GTC Technology DayPage 2
• Boiling points of C8 aromatic isomers are too close for distillation to be used
• Freezing points far enough apart to use crystallization
Boiling Point, °C
Ethylbenzene
Paraxylene
Metaxylene
Orthoxylene
136.0
138.3
139.1
144.3
Freezing Point, °C
-95.0
+13.2
-47.9
-25.2
C8 Aromatic Isomers - Separation Methods
GTC Technology DayPage 3
Suspension Crystallization (GTC’s CrystPX):
– Pure PX is crystallized from a solution of the C8 isomer mixture
– Solid crystals separated from remaining liquid (mother liquor) using centrifuges
– Continuous process
Static Melt Crystallization:
– Solutions containing C8 isomer mixture are repeatedly cooled and heated in tubes to
enrich PX to final purity
– Batch process
Types of PX Crystallization
GTC Technology DayPage 4
1957 first unit built2000 – GTC
partnership with Lyondell
2002 – largest-in-the-world centrifuges and
crystallizers; eliminated external
wash
2006 - Introduced unique slurry system,
(now 2 drums with single point of refrigeration)
Original Arco Process (now Lyondell) was identical in all
practical aspects to Amoco process (now BP)
GTC Partner with Lyondell for CrystPX
GTC Technology DayPage 5
2013 – Isom catalyst produces high purity
benzene at 99.9% without extraction; operates >
70% EB conversion
2014 – Advanced distillation systems to
greatly cut energy consumption in
fractionation sections
2015 – Enhanced mixing system and scraper design
for reduced equipment count
GTC - Leader in innovation
Continued technology advancement
GTC Technology DayPage 6
- 12 licensees, all awarded in competitive bidding
- 4 operational plants with reliable partners
GTC Licensing Experience
GTC Technology DayPage 7
Mixed Xylenes Feed
(from xylene column) CentrifugeCentrifuge
Refrig 1 Refrig 2
Crystallizer
First Stage
Crystallizer
Second Stage
Para-lean xylenes to
isomerization
Paraxylene Product
PX MELT
Wash
PX MELT
(recycle)
(Slurry)
(Slu
rry)
(Cake)
(Cake)
Traditional (1957 vintage) 2-Stage Process for PX Recovery From Dilute Feedstocks
GTC Technology DayPage 8
• Much larger and more reliable equipment:
– First generation process produced ~3,100 MTY / crystallizer
– Modern process produces >100,000 MTY / crystallizer
– Higher speed and more reliable crystallizer scraper system
• PX product washing instead of toluene/C5 wash
• Intermediate process stages via slurry drums to preserve the energy from the cold stage
(gaining an additional stage)
• Single point of refrigeration. No cooling required beyond the crystallizers
Improvements to Process
GTC Technology DayPage 9
Cold Stage
High Purity Paraxylene
Production StageIntermediate Stage
(Cake)
Centrifuge
Centrifuge
Refrig
Crystallizer
Cold Stage
Para-lean Xylenes to
Isomerization
Paraxylene
Product
PX MELT
PX Wash
(Cake)
(Cake)
(Slurry)
(Slurry)
(Slu
rry)
Centrifuge
Slurry
Drum
Slurry
Drum
Mixed Xylenes Feed (from
Xylene Column)
CrystPX Process for PX Recovery from Dilute Feedstocks
GTC Technology DayPage 10
Page 11
Paraxylene
Product
Primary Centrifuge
High Purity Paraxylene Production Section Paraxylene Recovery Section
PX-lean
Filtrate
PX Melt
PX Wash
Feed
Drum
PX Rich Feed
Secondary
Centrifuge
(Cake)
(Cake)
(Slu
rry)
(Slurry)
(Slu
rry)
1- Stage CrystPX Process For PX Recovery From Enriched Feedstocks
GTC Technology Day
• As a mixture of xylenes is cooled, PX crystallization occurs when
the concentration of PX reaches the solubility of PX in the mother
liquor.
• PX crystals separate from solution and leave other xylenes in the
mother liquor. The crystals are nearly pure PX. As temperature
decreases, more and more crystals separate.
• As temperatures continue to decrease, a second component may
reach its solubility limit and begin to crystallize. This temperature is
the eutectic point. Paraxylene crystals under
microscope
How Does PX Crystallization Occur?
GTC Technology DayPage 12
• Crystallizers
• Scraped Surface, Jacketed
• Centrifuges
• Screen Bowl
• Pusher
Major Equipment
GTC Technology DayPage 13
Feeding, distribution & main
dewateringDischarge washing intermediate
dewateringFinal
dewatering
Wash liquid
SolidsFiltrate
100% liquid saturation level
Pusher Centrifuge Cross Section – Details
GTC Technology DayPage 18
Giant Xylene Column
Reformate Xylene
Feed
Para-lean xylenesDeC7 Column
Light Ends
C9+
Adsorption
Toluene
Extract
Raffinate
Desorbent
Desorbent
Finish
Column
Paraxylene
Product
Isomerization
Complicated simulated moving bed;
high risk of failing to meet PX purity
PX Separation Technology – Adsorption
GTC Technology DayPage 21
• Lower installed cost
• Equipment easily procured
• Feed preparation requirements are relaxed, and
insensitive to most common feed impurities
• Highest product purity
• Convenient to add incremental capacity
• No expensive adsorbent and desorbent required
• Simple concept for easy operation
• Lower per-pass recovery results in increased
recycle to Isomerization Unit.
Advantages Disadvantages
Advantages of 2-Stage Crystallization Compared to Adsorption Process
GTC Technology DayPage 22
• Fewer equipment pieces result in the lowest investment cost
• Less equipment leads to lower maintenance and production costs
• Stable operation with simple process controls; product quality maintained by paraxylene wash rate
• Highly efficient refrigeration system requires minimum cooling water consumption
• Turndown operation permissible; operating flexibility and simplicity
• Enriched feedstock results in high recovery
Advantages of 1- Stage Crystallization Process From Enriched Feedstocks
GTC Technology DayPage 23
• Crystallization units often mischaracterized as outdated; however, modern designs
offer:
– Higher equipment reliability and reduced maintenance requirements
– Larger-scale equipment and reduced equipment count
– Higher efficiency based on newer configurations and processing schemes
Crystallization Modern Designs
GTC Technology DayPage 24
Page 25
C5
Aromatics
Extraction
Toluene
Conversion
Tolu
ene C
olu
mn
BenzeneC6 -C7 raffinate
C9+
Paraxylene
Hydrotreated
Naphtha
Xylene
Isomerization
Catalytic
Reformer
Xyle
ne C
olu
mn
C9+
Refo
rmate
Split
ter
Paraxylene
Recovery
Dehepta
niz
er
Benzene C
olu
mn
Xyle
ne C
olu
mn
PRU (Largest-in-the-world commercial size
equipment)
PRU (Largest-in-the-world commercial size
equipment)
PRU “1-time freezing of crystals with optimum
application of refrigerant energy
Distinctives of GTC’s PX Technology
GTC Technology Day
Page 26
C5
Aromatics
Extraction
Toluene
Conversion
Tolu
ene C
olu
mn
BenzeneC6 -C7 raffinate
C9+
Paraxylene
Hydrotreated
Naphtha
Xylene
Isomerization
Catalytic
Reformer
Xyle
ne C
olu
mn
C9+
Refo
rmate
Split
ter
Paraxylene
Recovery
Dehepta
niz
er
Benzene C
olu
mn
Xyle
ne C
olu
mn
“GTC-DWC for Energy
Savings”
BTX
Columns
Reformate
Splitter
Deheptanizer
Xylene Column
(GTC-TWDC
to segregate streams by PX
and EB content)
Distinctives of GTC’s PX Technology
GTC Technology Day
Page 27
C9+
Catalytic
Reformer
C5
Aromatics
Extraction
Toluene
Conversion
Tolu
ene C
olu
mn
BenzeneC6 -C7 raffinate
C9+
Paraxylene
Hydrotreated
Naphtha
Xyle
ne C
olu
mn
Refo
rmate
Split
ter
Paraxylene
Recovery
Dehepta
niz
er
Benzene C
olu
mn
Xyle
ne C
olu
mn
Isom (higher EB
conversion)
Xylene
Isomerization
High-purity benzene by direct
fractionation
Distinctives of GTC’s PX Technology
GTC Technology Day
• Historical traditional method for PX production has been crystallization
• Adsorption processes have enjoyed popularity due to advantages over first-
generation crystallization technologies
• Updated design features, improved equipment, and world-scale designs are making
crystallization once again desirable
• GTC has capable technical staff station locally, to ensure reliable operation
• CrystPX℠ is state-of-the-art for advancement in PX crystallization
Conclusions
GTC Technology DayPage 28