4
Figure 2. CrystPX Process for Paraxylene Recovery
The next table shows a comparison of the production costs from aromatics complexes using
crystallization and adsorption for paraxylene recovery. The configurations include the xylene
column, paraxylene recovery, and xylene isomerization units.
Table 3. Comparison of Paraxylene Recovery Methods
Using Xylene Based Feedstock
Basis: Paraxylene capacity - 400,000 MTA
Parameter
CrystPX
Adsorption-based
Investment Cost
$130 MM
$170 MM
Cash costs of production, $/ton PX
Raw materials cost
385
385
By-product credits
(55)
(55)
Utility costs
40
30
Fixed/allocated costs
20
25
Total cash cost of production, $/ton PX
390
385
Full Production Cost =
Total cash cost + cost of capital (15 yrs), $/ton PX
433
441
The adsorption unit may have a slightly lower cash cost of production. However, this type
system would require an investment approximately $40MM higher than that with a
crystallization-based aromatics recovery unit. The expenditure of the additional up front
capital, eliminates the long-term cash cost benefit of adsorption, giving investors in a
crystallization-based complex the advantage.
M ixed Xylenes Feed
from Xylene Column
Centrifuge
Centrifuge
Refrig 1
Refrig 2
Crystallizer
First Stage
Crystallizer
Second Stage
First-stage filtrate
to Xylene
isomerization
Paraxylene
Product
PX MELT
PX Wash
PX MELT
