Peng, Dr. Ding-Yu

2015 Oil Sands,  Finalist

Optimizing solvent recovery in oil sands processing to create a cleaner future

Mining in the oil sands is complicated enough, even before waste disposal is considered.

Improper disposal of oil sands tailings is economically impractical and environmentally dangerous, because any remaining hydrocarbon solvents are costly and hazardous to clean up. Because of this, oil companies only have one real shot at getting it right.

That’s where Dr. Ding-Yu Peng comes into play. As a world-renowned thermodynamics researcher, companies such as Syncrude rely on his contributions to recover valuable hydrocarbon solvents from tailings streams.

“In the early 1990s, Syncrude approached me to conduct an experimental study of the phase behavior of the tailings streams,” Dr. Peng says. “The tailings stream is a by-product of oil sands recovery, and the tailings mixture will be sent to the pond, but the tailings still have some hydrocarbon solvent and bitumen.”

“The objective of the research is to determine how much of the solvent is left in the stream to be discharged to the pond, and what are the conditions that can be optimized to recover as much of the solvent as possible before the stream is dumped,” Dr. Peng explains.

Dr. Peng says after he determines his findings, he shares the information with engineers who use the results to develop more effective processes and equipment for use in the field.

Devising an experiment

Dr. Peng pursued his Ph.D. in chemical engineering under the guidance of Dr. L.I. Stiel at the University of Missouri-Columbia.  Upon completing his graduate studies, Dr. Peng started to work as a post-doctoral fellow and research engineer under the mentorship of Dr. D.B. Robinson at the University of Alberta, where the well-known Peng-Robinson equation of state was developed and published in 1976.   The equation is instrumental in Dr. Peng’s work today, because his involvement in the creation of the equation strengthens him as an expert in thermodynamics research.

Additionally, by using rigorous thermodynamic principles as the basis of his experiments, Dr. Peng accurately predicts how much solvent will remain after refinement. His findings help engineers develop technology that can be optimized to efficiently remove the largest amount of solvent possible.

“The process deals with low pressure, so it’s very challenging to find the optimum conditions where the maximum recovery can be achieved,” Dr. Peng explains. “So they asked me to complete a rigorous thermodynamics experiment to identify the conditions.”

Dr. Peng says the work is environmentally important because it reduces the overall pollutants that are released into the environment once a project closes, and that’s the ultimate form of motivation for continuing his work.

Reducing environmental impact

Dr. Peng says his main motivator is improving the end result of oil sands production. “The work I do is important because as an engineer I want to improve the process and improve our environment,” Dr. Peng says. “This research program will achieve that objective, because from the company standpoint it’s economical because we recover the solvent and environmentally we will see less emissions from the unwanted pollutants.”

The solvent that Dr. Peng is helping Syncrude remove from the tailing ponds is a hydrocarbon-based solvent. By reducing the amount of hydrocarbons in the tailing ponds, he says the impact goes further than water and atmosphere quality.

“The solvent is a hydrocarbon so when it is sent to the air it will degrade the air, so it’s a pollutant,” Dr. Peng says. As the solvent sits in the tailings pond over time, the residual hydrocarbon components contaminate the water and release into the atmosphere, adding greenhouse gases to the air.

By giving engineers the knowledge they need to remove the solvent before the water makes it to the tailings pond, Dr. Peng’s work has had a profound impact on the environment. While there is an economic benefit, because his work is cost effective and efficient, it is the environmental benefit that is the biggest motivational tool for Dr. Peng.