Letters

Jan. 24, 2005
We have read your review article "Product sulfur specs will determine future refining configurations" (OGJ, Oct. 18, 2004, p. 48). Haldor Topsøe AS is a supplier of ultralow-sulfur diesel (ULSD) catalyst and technology, and we have some comments that we believe will be of interest to the readers of OGJ.

Low-pressure desulfurization

We have read your review article "Product sulfur specs will determine future refining configurations" (OGJ, Oct. 18, 2004, p. 48). Haldor Topsøe AS is a supplier of ultralow-sulfur diesel (ULSD) catalyst and technology, and we have some comments that we believe will be of interest to the readers of OGJ.

Selection of whether to revamp a low-pressure hydrotreater or to build a new hydrotreater is influenced by many considerations, and our licensees have taken different approaches to their ULSD projects based on specific needs.

Several of our licensees have found it more economically attractive to revamp their hydrotreaters even at a very low pressure (30 bar); two examples are BP PLC's Coryton, UK, and ChevronTexaco Corp.'s Pembroke, UK, refineries. The statement, "low-pressure HDS units revamped using high-activity catalyst are a greater technological risk for production of 10 ppm (wt) sulfur diesel" does not reflect our point of view. Revamping a low-pressure hydrotreater for ULSD production is indeed a very viable option.

Due considerations should always be made to hydrogen availability, hydrogen costs, and operating expenditures in general. Topsøe has recently completed a comparison study of the operating expenditures between a 55-bar and a 75-bar hydrotreater unit with a capacity of 66,000 b/sd.

The study showed that the high-pressure unit has additional costs due to higher chemical hydrogen consumption and higher hydrogen solubility loss in the range of $3 million/year compared to the moderate-pressure unit. Taking into consideration the extra catalyst cost, less volume swell, and lower production of fuel gas for the moderate-pressure unit, the operating expenditures of the high-pressure unit was $1.9 million/year more than the moderate-pressure unit.

Topsøe believes that if a hydrotreater is designed with too much conservatism related to pressure, the operators will face too high operating expenditures year after year: $1.9 million/year for 20-30 years is approximately equal to the large investment cost of a new unit itself! We therefore do not believe that "replacing low-pressure hydrotreaters with higher pressure may be the choice of many refiners," but that such statement can only be made on an individual basis after a thorough scoping study.

Such a scoping study can only be performed by a skilful licensor with in-depth knowledge of ULSD kinetics and process, with interaction of the client's strategic and operational expertise.


Morten Schaldemose
Manager
Refining Technology Sales Group

Jesper Rødtjer
Sales Manager
Refinery Technology
Haldor Topsøe AS