Adapting A Process Used To Make Sugar And Paint To The Alberta Oilsands

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Oilsands/ heavy oil costs must be reduced, and better technology is one way to do that. This week the Bulletin looks at some of the technologies that are being developed. Many were presented at the dmg :: events-organized  World Heavy Oil Congress in Calgary earlier this fall.

WorleyParsons Limited, the Australian engineering company, believes a process used in other industries for decades could replace most lime softeners used in the Alberta oilsands.

Most thermal oil operations in Alberta use lime softeners to treat produced water that’s recycled into the once-through steam generators. But lime softeners are expensive, complicated and prone to process upsets.

WorleyParsons dubbed its proposed alternative to lime softeners its high-temperature front-to-back central processing facility (FTB-CPF), so named because it touches most of the steps involved in steam production. At the heart of the FTB design is a high-temperature electrocoagulation (EC) process which the company says is unique.

First patented in 1906, electrocoagulation uses an electric current to remove total suspended solids (TSS), heavy metals, emulsified oils and other contaminants from water.

“The electrocoagulation chemistry itself is not new to the chemical industry. It has been applied for the last 100-odd years in various other applications. But we are bringing it into the Alberta heavy oil industry for the first time,” says Ashutosh Nischal, process engineering manager with WorleyParsons Canada.

Existing applications include the manufacture of sugar, paint and some pharmaceuticals, ore separation, cooling-tower blowdown treatment and AA batteries.

The science is simple — you use iron anodes and pass current through them, and the iron goes into solution and precipitates out silica, organics and dissolved minerals (magnesium and calcium) which give the water its hardness. If the water is too hard, then additional ion exchanger capacity may be required.

Improved steam quality, reliability

Nischal says the main goal is to improve reliability and steam quality. Cleaner water means greater reliability, which means more of the boiler feed water gets converted to steam.

“If you improve the quality of water going to the steam generators, they have high reliability of steam production. And because you have high reliability of steam production, and much cleaner water coming through the OTSGs — the once through steam generators — the operators are then able to produce a higher-quality [steam], more reliably.”

By better water quality, Nischal means less silica and organics: “Those are the two components that really impact the water and the steam generation’s reliability.”

Treating blowdown more cheaply

Removing silica and total organic carbon could also save money spent on treating and handling blowdown water (any water that doesn’t get converted to steam as it passes through the OTSGs). WorleyParsons believes removing silica and organics could save $5 million a year in related operating and maintenance costs, based on a 35,000-bbl-a-day SAGD plant with a steam/oil ratio of three.

“So currently operators spend up to $5 million [a year] in treating or handling their blowdowns — and they don’t have to with our [design],” says Nischal.

Less disposal

Compared to lime softening, WorleyParsons says its FTB design would save about 32 per cent in capital costs and about 15 per cent in operating costs.

“The electrocoagulation is a simpler, cleaner process with a lower amount of waste produced,” Nischal says.

Compared to lime softeners, electrocoagulation produces as little as one-fifth as much solid waste that has to be sent to an industrial landfill. And with a further investment, WorleyParsons says it can more effectively integrate a zero liquid discharge system at a facility. That way, operators would have only industrial landfill disposal (solid waste) and no liquid waste, so they wouldn’t need disposal wells.

Also, higher steam quality means less liquid disposal for those facilities that use disposal wells.

WorleyParsons says its FTB design would produce 90 per cent steam quality. (In Alberta thermal oil operations the steam quality is typically about 75-80 per cent.) Ninety per cent steam quality means that for every 100 kilograms of water fed into steam generators, 90 kilograms would be converted to steam and 10 kilograms would remain as water. Some of that remaining water can be further flashed to make utility steam. Leftover water — with its high concentration of impurities — is currently disposed of, usually in disposal wells.

So if WorleyParsons’s design can produce 90 per cent steam quality instead of, say, 80 per cent — in other words, convert 90 (instead of 80) kilograms of every 100 kilograms of water to steam—then the amount of blowdown water would be cut in half. That’s before any flashing and/or evaporation processing to further concentrate the volume of waste sent to disposal.

Also, the higher the steam quality, the lower the greenhouse gas emissions — a major consideration as the industry faces increased carbon penalties.

So WorleyParsons is offering a solution to reduce the blowdown disposal challenges. It’s impossible to eliminate all the blowdown because there will always be one or two per cent that still has to be disposed of to rid the system of concentrated salts.

With electrocoagulation the main waste stream would be a sludge, consisting mostly of silica with lesser amounts of dissolved organics and mineral salts. Because iron is consumed in low amounts during the electrocoagulation process, the reduced amount of solid waste generated would be mainly an iron silica sludge. This could be disposed of in the regulated industrial landfills that now take the greater volumes of sludge from lime softeners.

Can parallel lime softeners

WorleyParsons’s FTB design is intended as an alternative to lime softeners at future plants. The company isn’t expecting producers to rip out existing lime softeners in which major capital investments have already been made.

However, there is a retrofit option. If a thermal oil operator is doing an expansion or de-bottlenecking, WorleyParsons could add its units to supplement existing lime softeners.

Several de-bottlenecking add-on designs have been created to operate in parallel with existing lime softeners and evaporators, and at smaller, less complex facilities that use only ion exchange to treat fresh/brackish water.

WorleyParsons says these add-on designs use key components of its overall FTB-CPF design to operate in parallel with existing water treatment processes. The goal is to improve water reuse, reduce freshwater or groundwater makeup, improve steam quality and increase the quantity of steam to the field while being able to lower the volume of blowdown sent to disposal.

Pilot

Small volumes of produced water have been treated in the lab, and the next step would be a field pilot at process operating conditions. WorleyParsons is seeking a thermal oil operator to collaborate with to provide a pilot site.

“It’ll be a small trailer-mounted pilot. We are attempting [to] minimize the cost of bringing it to a site,” says Nischal. “And that’s the development that we are currently working on.”

Any pilot would probably run for three to six months. WorleyParsons wants to test various water qualities and combinations of blends.

Ultimately, the company would like to install the test skid at multiple sites, but it needs the first pilot to prove the concept and give producers confidence there is an alternative to lime softeners.

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