KIST researchers develop scaleable lignin oil treatment process
In South Korea, researchers at the Clean Energy Research Center of the Korea Institute of Science and Technology (KIST) have announced the development of a core solvent-free process technology that could enable mass-production of advanced biofuels such as biojet from lignin oil, which up to now has been difficult to process due to its high viscosity.
Lignin, a component that accounts for 20 to 40 percent of plants such as wood and grass, is largely discharged as waste in the pulp and paper industry. Pyrolysis of this lignin can produce a lignin oil, however, it is difficult to utilize industrially on account of its high viscosity or “stickiness”.
For this reason, pulp mills typically use lignin residues as low-quality boiler fuels directly rather than as high-quality fuels or chemical raw materials.
The development of solvent-free lignin pyrolysis processes is highly desirable because these processes would allow the depolymerized product to be used directly as a renewable energy source and chemical feedstock, without the removal of solvents.
Hydrolyzed lignin oil as the solvent
A team led by Dr Jung-Myeong Ha of the Korea Institute of Science and Technology (KIST) Clean Energy Research Center used hydrocracking to produce hydrolyzed lignin oil to reduce the viscosity of the lignin oil. Acting as a solvent, this hydrolyzed lignin oil is mixed with untreated lignin oil to enable further downstream processing of the lignin oil mix in a continuous process without the need for solvent removal.
At a blend ratio of 30 percent by weight, the viscosity of the lignin oil is significantly reduced – from 750 cp down to 110 cp. By comparison, the viscosity of water is 1 cp and cooking oil is 80 cp.
According to Dr Jung-Myeong Ha, despite the digital revolution, the demand for paperboard and cardboard for packaging boxes has increased due to the surge in courier shipments worldwide.
It was difficult to use lignin waste generated in large quantities in paper mills as a high value-added fuel using the conventional chemical reaction method. From now on, it will be possible for Korea to actively respond to the regulations to reduce greenhouse gas emissions (GHG) that will be strictly enforced, Dr Jung-Myeong Ha said.
The research was conducted by KIST major projects and climate change response technology development projects with the support of the Ministry of Science and ICT. The results have been published in a paper called “Continuous-flow production of petroleum-replacing fuels from highly viscous Kraft lignin pyrolysis oil using its hydrocracked oil as a solvent” in the June 2020 issue of “Energy Conversion and Management” journal.