Oil & Natural Gas Projects
Exploration and Production Technologies
Fundamentals of Delayed Coking Joint Industry Project (JIP) Continuation
This project was selected through DOE's solicitation DE-PS26-02FT41422. The
purpose is to better understand refinery coking reactions.
The objectives of this project are to:
- Utilize current micro, batch, and pilot unit facilities to enhance petroleum
coking process understanding.
- Conduct tests with new resids to make optimization models more robust.
- Undertake kinetic experiments to enhance furnace tube modeling and liquid
production while minimizing product sulfur content.
Researchers have completed detailed foaming studies to optimize processes and
minimize upsets. Studies also were conducted of the health, safety, and environment
(HSE) aspects of coking sludge disposal, drum settling, and poor drainage causing
hotspots. The results of these studies will be used as input to enhance computer
programs developed for coking process optimization. These resulting computer
models will be tested against member company refinery data.
Meanwhile, novel designs for removing hydrogen sulfide from furnace gases are
to be studied to establish the feasibility of minimizing or eliminating sulfur
in the liquid products.
University of Tulsa (TU)
The TU Delayed Coker Project (TUDCP) has a "one-of-a-kind" pilot plant
that provides a method to visualize, via a gamma densitometer, coke drum reactions.
This allows study of coke morphology and foaming. The data produced have resulted
in a quench model and a determination of what causes hot spots. The project
also has conducted studies resulting in increased liquid yields, as well as
the ability to change coke morphology.
TU draws on its downstream expertise and the support of 12 member companies
and DOE to understand the coking process. Through TUDCP this gamma densitometer
system provides a method to visualize reactions occurring in the coke drum at
930 F., allowing the study of both morphology and foaming.
This research project is developing robust screening and process optimization
models that result in energy savings as well as maximizing product yields. Increasing
yields in turn enhance refinery margins by reducing coke contaminants-making
the resulting coke better suited for commercial use in the metals and chemical
industries-as well as reducing sulfur in gasoline and diesel fractions to meet
stringent EPA requirements.
This work also has resulted in a better understanding of how coke morphology
is affected by feedstock and processing parameters. Furthermore, the project
results allow for predicting shot-coke formation more accurately and for minimizing
HSE-related concerns by providing insight as to why settling, poor drainage,
and hotspots occur in coke drums.
Foaming studies are providing better understanding of the foaming process and
will result in refinery cost savings through optimized use of antifoams. For
example, reducing the amount of antifoam in the coke drum by $0.10 per ton would
save refiners $5 million per year. In the JIP project, new research areas are
focusing on ways of increasing liquid volumes produced by 20%, changing morphology
to increase product quality, and testing non-silicon-based antifoams that would
save millions of dollars by not fouling catalysts.
Delayed coking evolved steadily over the early to mid-1990s. Its purpose is
to enable refiners to convert high-boiling, residual petroleum fractions to
light products such as gasoline. Coking is the most energy-intensive process
in a modern refinery. Large amounts of energy are required to heat the thick,
poor-quality petroleum residuum to the 900-950 F. required to crack the heavy
hydrocarbon molecules into lighter, more valuable products.
Coke production has increased steadily over the last 10 years, with further
increases forecast for the foreseeable future. A major driving force is the
steady decline in crude quality available to refiners. Crude slates are expected
to grow heavier and with higher sulfur contents, while environmental restrictions
are expected to significantly reduce the demand for high-sulfur residual fuel
oil. Refiners face the choice of purchasing light sweet crudes at a premium
price or adding bottom-of-the-barrel upgrading capability, through additional
new investments, to reduce the production of high-sulfur residual fuel oil and
increase the production of low-sulfur distillate fuels. Because of relatively
moderate intermediate investment and operating costs, delayed coking has increased
Despite its wide commercial use, only a relatively few contractors and refiners
are truly knowledgeable in delayed-coking design, so that this process carries
with it a "black art" connotation. Until recently, expected coker
yields were determined by a simple laboratory test of the feedstock. As a result
of researchers' prior work, a process model was developed that, with additional
work, could be used to optimize existing delayed cokers over a wide range of
potential feedstocks and operating conditions.
A significant amount of data and model development has occurred from the prior
small-scale studies; however, the pilot unit study outcomes are the basis for
the model development effort.
Studies have provided an understanding as to:
- Why and how shot and sponge coke are made.
- How to determine the efficiency of overhead versus bottom drum quenching.
- How to ascertain what are the foaming tendencies of different types of resids.
- What impact operating conditions have on foaming.
- What are the optimum concentrations and strategies to inject antifoam, as
well as how the antifoam partitions.
A unique system was developed that allows one to see coke, liquid, and foam
in the coke drum. Upon completion of the coking process, drum contents are steam-stripped.
The gamma densitometer traces illustrate how the loss of mass occurs during
the stripping process. Material loss resulted in the coke bed slumping by about
10%. This slumping actually caused an increase in the coke bed density, mostly
at the bottom of the bed, but to a lesser extent in the middle. After steam-stripping,
water injection is increased in a controlled manner to cool drum contents. These
data were used to develop a quenching model.
Models, whose robustness is being updated continually, have been developed for
screening, process optimization, kinetics, and quenching. In general, because
the data are scaled up to industry data, refinery coking processes are being
Current Status (August 2005)
This project is in its final year. Sponsors include Baker-Petrolite, ChevronTexaco,
Citgo, ConocoPhillips, GLC, KBC, ExxonMobil, Foster Wheeler, Shell, Marathon,
Suncor, and DOE.
Annual report for 2003
Annual report for 2004
Results reported www.tudcp.utulsa.edu
Project Start: October 1, 2002
Project End: September 30, 2005
DOE Contribution: $1,020,000 (41.8 %)
Performer Contribution: $1,421,000 (58.2 % of total)
NETL-Betty Felber (phone; 918 699 2031 email: firstname.lastname@example.org)
University of Tulsa-Michael Volk (phone; 918 631-5127 email: email@example.com)
Scanning electron micrograph photographs of various shot-coke types.
reactor at TU delayed-coker pilot plant.