Crude Tall Oil A Significant Byproduct The Role of Kraft Pulping Process in Yielding Valuable Co-Products
What is Crude Tall Oil?
Crude tall fuel (CTO) is a dark yellowish viscous liquid that is obtained as a byproduct of the Kraft pulping process in pulp mills. This process recycles pulp fibers and converts them back into paper products. CTO is obtained from the black liquors that are formed during this pulping process. The black liquors contain organic fatty and resinous compounds derived from pine trees. Through acidulation and centrifugal separation, CTO can be fractionated out from these black liquors. CTO constitutes around 15-20% of the organic material content in pine trees that is recovered through this process.
Properties and Composition of Crude Tall Oil
CTO is comprised of fatty and resin acids naturally present in pine trees such as oleic acid, linoleic acid, and abietic acid. It has a total acid number between 170-240 and a density ranging from 0.950-1.020 grams per cubic centimeter. CTO is an excellent emulsifier with a hydrophobic portion containing mostly resin acids and a hydrophilic portion containing fatty acids. The presence of both resin and fatty acids imparts favorable surfactant properties to CTO. It can break down into components that are extensively used across many industries as emulsifiers, dispersants, and additives.
Major Uses of CTO
The main applications of Crude Tall Oil include its use as adhesives, coatings, lubricants, cement additives, flotation agents in mining, corrosion inhibitors and emulsifiers in drilling muds.
Adhesives - Due to its natural resin content, CTO works very well as an adhesive. It is commonly used in the production of ply boards, particleboards, and medium density fiberboards where it acts as an adhesive binder.
Coatings - CTO derivatives function as excellent film-forming agents in paper, paint and fabric coatings. It enhances the water resistance and lubricity of these coatings.
Lubricants - CTO improves lubricity and anti-wear properties of lubricating greases and oils for industrial machinery. It also finds use as a rust inhibitor in metalworking fluids.
Cement additives - Emulsifying properties of CTO make it an effective additive for reducing water demand and improving workability of cement slurries. This enhances cement placement in oil wells.
Mining - As an effective collector and frother, CTO derivatives play a valuable role in the flotation separation process to concentrate valuable minerals in mining operations.
Corrosion inhibition - Derivatives from CTO, like tall oil soaps and fatty acids, act as corrosion inhibitors for ferrous metals in many industrial systems and equipment.
Drilling muds - CTO additives function as lubricity and fluid loss control agents in water-based and oil-based drilling fluids used for oil and gas exploration. This enhances the performance of drilling operations.
Biorefinery Use of CTO
With the rise of biorefineries, CTO is also being explored as a promising feedstock to produce valuable chemicals and biofuels on a commercial scale. Some key applications in biorefining include:
- Biodiesel: CTO derivatives like fatty acid methyl esters can be used directly for producing biodiesel fuel. Oleic and linoleic acids from CTO serve as good substrates.
- Green solvents: Fractionation of CTO allows recovery of terpene derivatives that have applications as green solvents with low vapor pressure and toxicity.
- Biopolymers: Medium and long chain fatty acids from CTO hydrolysis can be utilized to produce biodegradable polymers, resins and plasticizers.
- Bioasphaltenes: Resin acid rich fractions find application as raw materials in road paving, roofing products and carbon material synthesis.
With increasing demand for renewable and sustainable products, biorefining of CTO is an active area of research that can open new markets and applications for this important biobased material. It leverages existing tall oil production infrastructure to diversify product offerings from pulp and paper mills.
Tall Oil Derivatives
Global production of crude tall fuel was estimated at 1.1 million metric tons in 2020 with the market valued at around $1 billion. This market is projected to grow at 3-4% annually driven by expanding use of CTO derivatives across various industries. Scandinavian countries like Finland and Sweden are leading producers along with the US and Canada accounting for the bulk of worldwide CTO supply. Major derivatives obtained from CTO fractionation and treatment include tall oil fatty acids, tall oil rosin, distilled tall oil, dimer acids, and tall oil pitch. Adhesives, coatings, and metal working fluids consume over 60% of the total CTO derivatives produced globally each year. With innovative applications development, the tall oil products market is poised for steady long-term growth.
The versatile properties and numerous uses of crude tall fuel make it an important biobased chemical obtained from the Kraft pulping process. Advances in tall oil refining and fractionation along with growing interest in biorefining applications point to a promising future ahead for this renewable tall oil industry.
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