PX-PlusTM XP Aromatics
Application The PX-Plus XP process is an integration of the PX-Plus process and the Badger/Niro para -Xylene -Xylene Crystallization process. This technology converts toluene to a high purity para -xylene -xylene product and a high purity benzene co-product. The para -xylene -xylene is purified to 99.9+ wt-% via single-stage crystallization and a wash column. Benzene purity is 545-grade by fractionation. The PX-Plus process selectively disproportionates toluene to benzene and xylenes. The process is -selective, with the product having a para -xylene -xylene para -selective, concentration in the xylene fraction of nearly 90%. Thus the PX-Plus process can increase the para -xylene -xylene concentration in the feed to the crystallizer. This increased para -xylene -xylene concentration allows recoveries from a single-stage crystallizer to increase from 65% to more than 80%. The Badger/Niro para -Xylene -Xylene Crystallization process recovers high-purity para -xylene -xylene from aromatics streams. This technology is particularly attractive when the feed has more than 70% para -xylene -xylene concentration. Recoveries greater than 80% have become possible with single-stage crystallization from the PX-Plus unit.
exchanger, are air cooled and condensed, and sent to the product separator separator,, where recycle hydrogen is recovered. The separator liquid is sent to the stripper column, where light by-products are removed overhead. The stripper bottoms stream is sent to a benzene-toluene-xylene (BTX) fractionation unit. In the fractionation section, stripper bottoms are fed to a benzene column where the benzene product is recovered overhead and the A 7+ is sent to a toluene column. The toluene is then sent overhead and recycled to the PX-Plus unit. The bottoms are sent to the xylene column, where the heavy tail is rejected and the concentrated xylenes are taken overhead for the crystallized feed. In the Badger/Niro crystallization unit, the xylenes are fed to a single-stage crystallization section that uses continuous suspension crystallization. The crystallizers create a slurry of high-purity para -xylene -xylene crystals in mother liquor. This slurry is fed to Niro wash columns where the crystals are mechanically pushed upward and the mother liquor washed away countercurrently from the crystals with high-purity -xylene. The slurry leaves the wash column and para -xylene. enters a heat exchanger where the crystals are melted for the final product.
Process description The PX-Plus XP process is composed of three processing steps:
Selective toluene disproportionation, via the PX-Plus process Fractionation for recovery of recycle toluene and benzene product The Badger/Niro para -Xylene -Xylene Crystallization process, where single-stage crystallization and crystal wash columns are used.
In the PX-Plus unit, fresh toluene is combined with recycle toluene and mixed with recycle and makeup hydrogen. This feed is heat exchanged against the fixed-bed reactor effluent and passed through a fired heater where it is raised to reaction temperature. The reactants exit through the feed-effluent
PX-Plus XP Process Benzene Toluene Column Column
Xylene Column
Benzene
para -Xylene -Xylene
Hydrogen Lights Ends Toluene
Badger/Niro Crystallization
PX-Plus
Mother Liquer
Heavies
A r o m a t i c s
PX-Plus XP
2
Process performance
Commercial experience
The table below shows typical PX-Plus XP process performance.
Badger Technologies and Niro Process Technology combined their crystallization and wash column technologies in 1993. In 1997, UOP started offering the PX-Plus process for licensing and in 1999 announced the PX-Plus XP Process. This new process is the latest in a series of technology advances that allow para -xylene producers to gain and maintain a significant advantage by enabling rapid, low-cost capacity expansion, and high yield purification.
Yields:
Toluene conversion per pass Light ends, wt-% Benzene yield, wt-% para -xylene yield, wt-% para -xylene recovery para -xylene purity, wt-%
30% 7.5 43.4 35.6 93.5 99.9
At 30% toluene conversion, the PX-Plus XP process produces less than 8 wt-% light ends per pass. Also the mixed xylenes in the reject stream can be sent to a Parex unit for additional PX production.
Case study
Overall Material Balance, KMTA Charge Products Light ends Benzene para -xylene Mixed xylenes Heavies (A9+)
PX-Plus XP technological services are available on request. For more information, contact your local UOP representative or our Des Plaines sales office: e-mail:
[email protected] fax: +1-847-391-2253 phone: +1-847-391-2000
Basis: 558 KMTA toluene feed Feedstock Properties, KMTA Toluene Hydrogen
For more information
558 4 562 42 244 200 64 12
Economics Economics: Capital investment for erected unit (including initial load of catalyst). US$, MM
57
Utilities (normal operation) Electricity, kW 4310 High pressure steam, MT/hr 62 Medium pressure steam, MT/hr 94 Low pressure steam, MT/hr 2 3 Cooling water, m /hr 682 Fuel, MMkcal/hr 13 1 Note: 1 Under normal operations of the PX-Plus unit, a fuel credit of 40.4 MMKcal/hr from the stripper off gas will result in a net export of 27.4 MM Kcal/hr.
UOP LLC
25 East Algonquin Road Des Plaines, IL 60017-5017 U.S.A. www.uop.com
© 2006 UOP LLC. All rights reserved. The information in this document should not be construed as a representation for which UOP assumes legal responsibility, or an authorization or recommendation to practice a patented invention without a license. UOP 4680-13 1106AR0Ab
