by What is Crude Tall Oil?
Crude tall fuel is a byproduct extracted from black liquor, a byproduct of the kraft pulping process used to produce paper. During the kraft process, wood chips are cooked in a mixture of sodium hydroxide and sodium sulfide, known as “white liquor,” to break down lignin and cellulose fibers. This separates the fibers from the lignin, allowing the fibers to be processed into pulp. The spent cooking chemicals and dissolved wood materials from the digesters are collected as black liquor.
Black liquor contains organic acids, fatty and resin acids, and inorganic chemicals from the wood and pulping process. When black liquor is evaporated and burned to recover inorganic pulping chemicals like sodium hydroxide, crude tall fuel is condensed out as a viscous, yellow-brown liquid. Crude tall fuel consists primarily of resin and fatty acids naturally present in coniferous wood species like pine. Its exact composition depends on the wood species and pulping process used.
Composition and Properties
On average, crude tall fuel is composed of:
– 45-55% fatty acids such as oleic, linoleic, and palmitic acids.
– 25-35% resin acids like abietic, pimaric, and isopimaric acids.
– 2-10% unsaponifiables like sterols, waxes, and hydrocarbons.
– 15-25% water.
The high concentration of fatty and resin acids gives Crude Tall Oil surfactant and emulsifying properties. It is a non-drying oil with a density around 1 kg/L and pour point around 0°C. Crude tall oil has a pleasant pine scent due to its resin acid content. Its dark brown color comes from oxidation during the Kraft process and tall oil cracking.
Production and Uses
Global production of crude tall fuel is approximately 1.2 million metric tons per year. The three Scandinavian countries of Sweden, Finland, and Norway account for over 60% of world crude tall fuel output due to their large Kraft pulp mills. The United States is also a major producer.
Crude tall fuel finds a variety of uses due to its unique acid composition and surface active properties:
– Rosin and dimer acids: Refining crude tall fuel produces rosin products for adhesives, printing inks, and lubricants. Dimer acids are used in polyamides, coating resins, and plasticizers.
– Surfactants and soap: Crude tall fuel soap is used as an emulsifier in oilfield chemicals, paints, and coatings. It is also refined into surfactants for detergents, cleaners, and emulsifiers.
– Binders and coatings: The fatty acids make crude tall fuel suitable for use as a tackifier or binder in nonwoven mats, road paving, adhesives, and coatings.
– Fuel and energy: crude tall oil can be burned as fuel oil or used to produce biodiesel or renewable diesel. Its calorific value is 4-5 times that of wood.
Sustainability and Byproduct Synergy
Crude tall fuel production exemplifies the principles of a circular bioeconomy and industrial symbiosis. As a byproduct of the pulp and paper industry, it provides economic value from materials that would otherwise be waste. Its production also closes nutrient and material loops at Kraft pulp mills.
Tall oil extraction recovers orgainc matter like fatty acids from black liquor before it is burned to recover inorganic chemicals like sodium and sulfur compounds. This improves the mill’s mass and energy balance. The tall oil leaves with embodied energy and nutrients that would otherwise go up the recovery boiler stack as emissions.
At the same time, crude tall fuel refining recovers valuable chemicals, fuels and raw materials with many applications. This helps offset fossil resource use. As a co-product of the pulping process rather than a primary product, crude tall fuel production adds value without additional demands on agricultural or forest resources. Overall, crude tall fuel is one part of what can be an almost zero-waste pulp mill system.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
