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Technology Profile: Tall Oil Processing

May 1, 2016  

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They exist in the fuel for your cars, the tires you ride on and even the asphalt in the paved street you’re travelling over. And, surprising to some, these constitutes derive from the most unlikely of sources: pine trees.

Or, to be more specific, they are refined from crude tall oil (CTO), a by-product of the kraft pulping process. The components of tall oil (originally from the Swedish “tallolja” for pine oil) have been recognized since the early 1900s, but were largely considered waste. It wasn’t until later in the 20th century that Scandinavians began exploring methods to convert them into useful consumer products.

In fact, many people consider CTO distillation refineries as the pioneers and forerunners of the bioeconomy. Tall oil is a good example of how the global forestry industry has evolved over the past decades from just a lumber and paper products supplier to one that now employs advanced technology that produces a variety of products that seem more likely to be associated with the chemical industry.

For example, Georgia-Pacific Chemicals LLC — a subsidiary of Georgia-Pacific LLC of Atlanta, which began as a wholesale lumber supplier in the late 1920s — is a major refiner of tall oil, producing derivatives that can be used for synthetic lubricants, oilfield chemicals, emulsifiers, rubber processing, asphalt additives, paints and coatings, epoxy additives, plasticizers, metalworking fluids, sealants, pavement marking, book binding, pressure-sensitive tapes and labels, rubber, foundry investment castings, construction and transportation applications and many other applications.

Another tall oil heavyweight is Arizona Chemical Company LCC of Jacksonville, Fla., which has been producing tall oil and turpentine in its facilities at Panama City, Fla., and Springhill, Louis., since 1936. Arizona Chemical developed its refining technology by modifying crude oil fractionating technology.

In the 1960s and 1970s, the company had become a leading supplier of pinebased resins for adhesives and rubber industries, and the largest producer of tall oil fatty acids for the coatings industry. Since then, Arizona Chemical has acquired a variety of refineries in Scandinavia and Europe. It has also opened a research laboratory in China and an office in Moscow. One of the more interesting products that Arizona Chemical has recently developed is its SYLVAROAD RP1000 Performance Additive for use in recycled asphalt pavement (RAP). RAP is simply old asphalt that is ground into an aggregate size. When it’s compacted, the material is able to harden and bind together.

According to Arizona Chemical, incorporating its SYLVAROAD additive within RAP enables the binder or cement infused in the RAP to function with its original capability. The company says the additive can be thoroughly mixed, it’s thermally stable and has a higher flash point at 300 C than bitumen. For asphalt contractors, the economic appeal is clear: a mix containing 60 per cent RAP offers a 25 per cent cost reduction compared to using a 100 per cent virgin mix. Even increasing the content of RAP from 20 to 40 per cent could result in a cost reduction of up to 10 per cent.

This past year, Rotterdam applied Arizona Chemical’s additive to the paving of an experimental bicycle road in the city’s Merwe-Vierhavens (M4H) region, a section dedicated to innovative technologies and urban renewal. The asphalt used for the bike lane is 100 per cent recycled and coupled with the bio-based additive, compatible with M4H’s sustainable objectives. Chemtrade Logistics of Toronto, an international chemical supplier, produces tall oil out of its Prince George, B.C. ,facility, using feedstock from three nearby pulp mills. That tall oil is also used in the manufacture of asphalt, as well as paints, perfumes and other products.

Facility operations manager Rodger Henderson, says it’s not a complicated process. “Crude tall oil is a by-product of the kraft pulping process used by many pulp mills,” says Henderson. “Wood chips are processed in the pulp mill and the by-product is known as black liquor soap skimmings.” Black liquor soap skimmings are transferred to Chemtrade’s site and stored in two 695-cubic- metre storage tanks, where the black liquor settles and is returned to the local pulp mill. The soap skimmings are acidulated in a 300-cubic-metre, brick-lined reactor along with sulfuric acid, separating agent and heat to produce crude tall oil. The batch is then allowed to settle. The oil rises to the top while the spent acid and lignin settle to the bottom. The oil is decanted off the surface layer. The CTO is a mixture of fatty acids, rosin acids with other neutral materials.

It can be further refined through the fractionation process to separate the components of fatty acids and rosin acids and sterols. “CTO is returned back to the kraft mill and is used to heat the kiln as an alternative fuel for natural gas,” explains Henderson. “The other mill we supply uses the oil in the boiler as a fuel source. The oil is also sold on the merchant crude oil market.” Henderson points out the quality of tall oil production, unfortunately, has decreased because of the pine beetle infestation in Western Canada — particularly in British Columbia, Pine trees are generally considered the best source for tall oil, but the Prince George facility has been gradually forced to use spruce as the major source over the past decade because the pine tree supply has been severely affected by the infestation.

From the forest to the fuel tank Another significant aspect to crude tall oil production is its very real potential for talloil- based automotive diesel fuel. Until recently, refined tall oil has primarily been applied toward chemically based products. In the past few years, however, several commercial-scale plants have been built to produce diesel using tall oil as feedstock. Not surprisingly, Scandinavia lays claim to the world’s first large-scale production of bio-diesel.

SunPine AB began producing its Preem Evolution Diesel (PED) at its two production facilities in Haraholmen and Gothenburg, Sweden in 2010, and says it has an annual production of about 100 million litres of crude tall diesel. Refining, fractionation and distillation takes place in Haraholmen, producing high cetane (equivalency of octane for gasoline) diesel, after which it is stored at Haraholmen’s deep water port before being shipped south to the Gothenburg facility. There, the diesel is further refined through treatment under high pressure hydrogen into high-quality diesel. In the SunPine refining process, the crude tall oil first goes through an esterification stage in which it is mixed with biomethanol and sulfuric acid.

Then, in a distillation tower, the component is distilled into the main product of CTO and the by-product, pitch fuel. UPM-Kymmene Corp.’s bio-refinery, located in Lappeenranta, about 245 kilometres northwest of Helsinki, Finland, also began commercial production of wood-based renewable “BioVerno” diesel from forestry residue in January 2015. Much of the feedstock is supplied by UPM’s Kaukas pulp and paper mill adjacent to the refinery, which processes about 120 million litres of BioVerno diesel annually.

The finished product is being sold commercially in Finland through two of its largest consumer service station chains, St1 and ABC, and is compatible with all diesel engines. What is significant about this type of diesel fuel is that, unlike first-generation bio-fuels, it is similar in molecular structure to fossil fuel. That means blending limitations don’t apply and distributors are allowed to blend a higher percentage of renewable diesel fuel into regular fossil diesel. For this reason, renewable diesel is recommended by the latest and strictest Worldwide Fuel Charter (WWFC) specification. The WWFC committee is made up of representatives of auto manufacturers from Europe, the United States and Japan, as well as global engine manufacturers.

Its mission is to increase understanding of the fuels and engine technologies and to promote fuel quality harmonization worldwide. Edmonton-based Forge Hydrocarbons Inc., is also interested in the potential of using tall oil as a feedstock to produce diesel fuel. The University of Alberta spin off has been operating a 200,000-litre-per-year pilot plant that can produce high cetane diesel from a variety of feedstocks such as canola and other seed oils, restaurant grease, rendered animal fats and even bio-solids from the residue of Edmonton’s sewage treatment plant, as well as tall oil.

The technology was developed by David Bressler a professor at the U of A’s Faculty of Agricultural, Life & Environmental Sciences and executive director of the Biorefining Conversions Network. The technology was then licensed to Forge Hydrocarbons. “The process is an entirely novel, proprietary and patented approach using free radical chemistry similar to oilsands coking reactions,” says Bressler. “It produces a product that is similar in composition to petroleum-based diesel but without the need for costly hydrogen and catalysts. For generic fats and oils, the feed stock is heated with water to create a mixture of fatty acids and glycerol.

In the case of tall oil feedstock, the tall oil would be anticipated to come as the fatty acid from the pulp industry, so there would be no glycerol recovery step Once the mixture is cooled, the fatty acids are separated from the glycerol and water. Those fatty acids are then heated to a point where the oxygen contained within them is released. “This is the key step that, until now, no one had been able to do in a cost-effective way,” says Bressler. “Once the oxygen is removed, the fatty acid becomes a hydrocarbon. Further processing converts the hydrocarbon into the desired fuel such as gasoline, natural gas, jet fuel, diesel, lubricating oil, solvents and diluents.”

Company president and CEO Tim Haig says tall oil has been used as feedstock during testing phases to produce good, quality diesel. “A product like this is a valuable option for pulp and paper companies. It could offset what the companies are now paying for fuel and energy,” says Haig. “The economics are definitely there, and the reality is the pulp and paper industry is going through some difficult times. So, we have been in discussions with pulp and paper companies, but we haven’t gotten as far yet as building a commercial scale production facility. There are still some issues to work out. “The volumes for feedstock are there in northern Alberta. Since pulp and paper companies are not likely to put up the capital ,we could build the plant ourselves.

But, it’s a very traditional industry and because there’s not a lot of revenue being made at the moment, it’s very hard for them to justify the cost of innovation. But that’s very understandable.” For now, the company has been granted various patents both in Canada and internationally and more patents have been filed. Funding has been awarded to build precommercial plant with capacity to produce 200,000 litres per year. A second, more detailed, feasibility study and market analysis has also been completed along with an initial and engineering design exercise on a pre-pilot.

About the author: Ernest Granson is a Calgary-based writer and editor, and a contributor to PROCESSWest.