Shell carbon capture project in Alberta breaks new ground, literally

The Alberta oil sands are an enormous resource, but that resource needs a lot of dressing up before ordinary people will buy it. Your car runs on thin, free-flowing liquid fuel, not stuff that is like thickened blackstrap molasses mixed with sand.

“Dressing up” bitumen to the point where gasoline retailers can sell it takes a lot of large-scale, multi-step technology. First, you have to separate the actual hydrocarbon from the sand. Then you have to put hydrogen into the separated hydrocarbon, which in its natural state is more carbon than hydro. An “average” gasoline molecule is C₈H₁₈, and has a carbon-to-hydrogen ratio of roughly 0.44; an “average” bitumen molecule features a ratio more than 18 times as great. That is why bitumen is more like tar than oil, almost more solid than liquid.

So to make bitumen run like a liquid, you have to put hydrogen into it. In oil sands lingo, that is called upgrading. And while hydrogen is the most abundant element in the universe, it does not, on this planet, exist by itself in a form in which you can readily use it. (On Jupiter it’s a different story; there are literally oceans of hydrogen.) That means you have to make it. And by far most man-made hydrogen today is made by splitting methane (CH₄), which is the biggest constituent of natural gas. And that involves a chemical reaction called the water-gas shift (WGS), in which carbon monoxide reacts with water in the form of steam. The WGS produces hydrogen and carbon dioxide (CO₂). You want the hydrogen—that is the whole reason for splitting CH₄.

But you don’t want the CO₂. So what do you do with it? In just about every methane-splitting operation in Alberta, and there are a lot of them, CO₂ is simply dumped into the atmosphere. That is why the oil sands figure so prominently in discussions about climate change and the environment. Demand for oil sands syncrude has been rising along with the world price of petroleum: in fact, the two best things that ever happened to oil sands proponents were the 1973 oil shock, which led to a five-fold increase in the world price of oil, and the Iranian Revolution in 1979, which led to a further dramatic increase. And the current perennial mid-east tensions have also not hurt. Cheap oil is bad for the oil sands—it makes them prohibitively expensive to exploit. That’s why I laugh when I hear environmentalists calling for expensive oil and cheap natural gas. Expensive oil and cheap gas mean lots of oil sands production.

There is however one upgrading operation in the oil sands that soon will not be dumping CO₂ into the air. That is Shell Canada’s Quest project at the company’s Scotford Upgrader near Fort Saskatchewan just north of Edmonton.

The Scotford Upgrader processes close to 300,000 barrels of bitumen per day. Hydrogen is made in three methane cracking units. The process CO₂ from these three units, i.e., the CO₂ made in the WGS part of the methane-splitting process, accounts for about a third of the total CO₂ produced at the site. Under the Quest project, Shell technology will capture about eighty percent of this process CO₂. Shell and its partners will put the CO₂, which Quest project manager Len Heckel told me is over 99 percent pure, into a supercritical state, then into a pipeline for transport to an underground porous rock formation for permanent sequestration.

Under the company’s current agreement with the Alberta government, they will dispose of around 1.5 million metric tons of CO₂ each year, until they have locked 26 million tons of it in the rock.

Here is Shell’s version of how it all works:

The whole idea of carbon capture and sequestration has suffered some setbacks recently. Another Alberta project, involving CO₂ capture from an electricity generator running on pulverized coal, was announced with huge fanfare in 2009, then abandoned with huge embarrassment in April 2012. That was because the project partners could not find a buyer for the captured CO₂.

In Shell’s case, CO₂ is captured from the process emissions of a methane-splitter, not from the combustion exhaust of a coal-fired generator. The chemical separations problems are fundamentally different in each case. In the Shell Quest project, they will separate relatively concentrated CO₂ from hydrogen. The now-abandoned coal-fired generator project involved separating very dilute CO₂ from nitrogen. There also is no buyer for Shell’s CO₂. It is slated for permanent disposal underground. All of the project economics assume that.

As I mentioned, the purity of the captured Quest CO₂ is, according to Len Heckel, fairly high: over 99 percent. If true, that is interesting. I have been running a couple of projects that are looking at splitting CO₂ of similar purity into carbon monoxide (CO), and separating CO₂ from CO. I describe what we intend to do with the CO in this article.

If Shell is producing CO₂ of such good purity, maybe there is value in recycling it instead of putting it all underground. It would certainly improve the economics of similar projects.