The main technology we are specialising in is hydrothermal liquefaction also known as HTL. Hydrothermal conversion of biomass has been known since the 1970s, with the first pilot plants being built in the following years. During that time, the term hydrothermal liquefaction was used to describe the process of, in simple terms, converting solid (waste) biomass into a liquid product – bio-crude – using high temperature and pressure in the presence of liquid water. Essentially, it resembles the process that has taken place over millions of years in our planet, where sedimented biomass is converted to crude oil, although with the distinct difference that hydrothermal liquefaction takes place in minutes rather than millennia.
In hydrothermal liquefaction, suspended biomass in water is pressurized and heated to temperatures near the critical point of water and kept at this temperature for several minutes. During this process a multitude of reactions take place, including chain scission, hydrolysis, decarboxylation and elimination of water. The latter are responsible for the large drop in oxygen content from the feed stock (50%) to the produced bio-crude (10-15%), as oxygen is eliminated as water and carbon dioxide.
Following the reaction, the process fluid is cooled and depressurized and the phases are separated. The produced oil is separated and if necessary filtered for a minor fraction of solid byproduct (bio-char). The gas phase is emitted and the water phase, containing a range of soluble organics, is valorized by anaerobic digestion to biogas, allowing nutrients to be recovered. In general, the produced oil phase will contain from 70% to 80% of the energy content of the biomass feedstock.
Typical process conditions are 15-20% dry matter in feed with a reaction temperature around 350°C, a pressure around 250 Bar and a reaction in the range of 10 to 20 minutes.
Why hydrothermal liquefaction?
Compared to other technologies, hydrothermal liquefaction has a number of advantages:
- The process does not require a dry feedstock, thereby being less energy intensive compared to gasification, pyrolysis and combustion, and has a higher conversion rate compared to wet processes such as anaerobic digestion.
- It can be used on almost any organic feedstock and works well with wet wastes, such as sewage sludge, agricultural waste and many more.
- The primary output, bio-crude, is of higher quality compared to other processes, and can be upgraded for refining into drop-in fuels – gasoline, diesel, kerosene, heavy fuel oil etc. – using traditional methods.
Bio2Oil has in collaboration with researchers at Aarhus University in Denmark developed a range of unique technologies, which improve on the conversion and energy efficiency of the hydrothermal liquefaction process to achieve greater scaleability, cost efficiency and energy recovery. These include:
- Plug flow reactor – with no constrictions
- A continuous feed pumping allowing pumping of high dry matter streams
- A patented oscillatory flow system improving heat recovery, reducing viscosity and improving plug flow characteristics.
- A proprietary solid state heat recovery system with demonstrated heat recovery up to 85%.
- A unique take of system, eliminating the need for failure prone back pressure regulators.
Bio2Oil has expertise within a range of additional technologies, including:
- Pretreatment of feed streams
- Downstream processing and refining
- Valorization of water soluble products (biogas, etc.)
- Use of the Bio2Oil process for hydrothermal pretreatment, etc.
Contact us for additional information.