Apr-2008

Delayed coking and LC-Fining technology - a winning combination

The high price of oil and increasing global demand for refined products have resulted in unprecedented refining margins, especially for those refiners processing heavy, high sulphur crudes

Gary M Sieli, Lummus Technology, a CB&I Company
Nash Gupta, Chevron Lummus Global LLC

Article Summary

Many refiners are reinvesting their profits by upgrading existing refining facilities, focusing primarily on the ability to process heavier, higher sulphur and higher naphthenic acid crudes by adding delayed cokers or ebullated bed hydrocracking technologies. For those refiners currently processing light, sweet crudes, the switch to a heavier crude slate and the addition of a delayed coking unit or an ebullated bed hydrocracking unit will significantly increase their refining margin.

 This paper shows how the combination of delayed coking and ebullated bed hydrocracking can significantly increase the conversion capabilities of a refinery versus either technology alone. In particular, the paper shows how the addition of an ebullated bed hydrocracker to a refinery that already includes a delayed coker can improve the economics of the refinery versus the addition of incremental coking capacity. The paper also shows how the addition of a delayed coker to a refinery that already includes an ebullated bed hydrocracker can eliminate the production of heavy fuel oil and improve the refinery economics.

Although the combination of delayed coking and ebullated bed hydrocracking requires more investment, the difference in the total project cost is relatively small when all of the required downstream processes are considered. This project cost difference is offset by the increase in revenue resulting from the incremental conversion.

Introduction
The demand for heavy oil upgrades continues to persist into 2008, with strong activity in the US, Canada, India and Europe. The technology of choice for most of these projects has been delayed coking. There are a number of reasons for this.

Total investment is a primary concern for most refinery upgrade projects. When the two processes are compared, the investment cost per barrel of installed capacity for a delayed coker is usually lower than an ebullated bed hydrocracker. Although this may not be true when all supporting processes and facilities are included in the evaluation (eg, hydroprocessing requirements, coke handling and storage requirements, sulphur recovery and hydrogen production), the perception is often sufficient to impede further evaluation of an ebullated bed hydrocracker.

Furthermore, refiners are comfortable with the delayed coking process. Delayed coking has become a popular residue upgrading technology and the number of refineries utilising it far exceeds the number of refineries utilising ebullated bed hydrocracking. Some refiners will not even consider ebullated bed hydrocracking simply because they have very little knowledge of the process.

Moreover, delayed coking often provides a higher return on investment than ebullated bed hydrocracking projects, but this is dependent on a number of factors including, but not limited to, the specific product slate desired, refinery location, refinery configuration, feed and product pricing, and type of crudes processed. Each refinery upgrade project needs to be evaluated on a case-specific basis.

In some cases, the loss in total C5+ liquid product resulting from coke production can have a negative impact on project economics. For example, when syncrude is the desired product (such as for Canadian Athabasca upgrader projects), the increased revenue resulting from the additional quantity of syncrude produced with ebullated bed hydrocracking technology can be more than sufficient to offset the higher investment cost associated with this process, and therefore generate a more attractive return on investment. In many of these syncrude projects, the coke must be returned to the mine because the location of the upgrader makes it difficult to market the coke. Coke removal can be costly.

In Europe, both processes continue to remain popular. A new ebullated bed hydrocracking unit utilising the LC-Fining process with integrated gas oil hydrocracking has recently come on stream in Finland, while another unit is in the design phase in Bulgaria. The LC-Fining process is a proprietary ebullated bed residue hydrocracking process offered by Chevron Lummus Global and will be discussed in greater detail later in this paper. Existing LC-Fining units in Italy, Poland and Slovakia continue to operate.

New delayed coking units are in various stages of design and construction in Spain, Sweden and Russia, while coker expansions are being considered in other European countries. Existing cokers in Germany, Hungary, Italy, Spain, Romania and Croatia continue to operate as well.

Both processes add incremental revenue to a refiner’s bottom line by converting residue to lighter, higher valued products, and by enabling the refiner to process some quantity of heavy, high-sulphur, lower-priced crude.

This paper presents the results of a study that evaluated and compared the addition of incremental coking capacity versus the addition of an LC-Fining unit to an existing delayed coking refinery looking to increase the quantity of heavy crude oil processed. It also presents the results of a study that evaluated the addition of a delayed coker to a refinery with an existing LC-Fining  unit, with the objective of eliminating bunker fuel oil production and increasing middle distillate production.

Improving refinery profitability by processing heavier crudes
Refinery operations are often characterised in one of two ways: refineries with residue upgrading technologies and those without. For those refiners without this capability, the quantity of heavy, high-sulphur crude that can be processed is limited. The addition of a residue upgrading technology such as delayed coking or ebullated bed hydrocracking will allow these refineries to process larger quantities of heavy, high-sulphur, lower-priced crudes, resulting in increased profitability.