Research subjects

Thermal Conversion Processes

Thermal conversion processes include combustion, gasification, pyrolysis, torrefaction and hydrothermal conversion. In our research we investigate sustainable routes and technologies to convert biomass into energy and fuels. Another focus is on the valorization of waste streams into both fuels and raw materials. An example is the production of oil and minerals via the pyrolysis of paper sludge. Future fuels can be derived from solar and wind energy. For hydrocarbon fuels we need a sustainable carbon source and a challenging option is to capture CO2 from ambient air.

people involved

example research

Ultra fast pyrolysis of used car tyres

Project description
Each year, 800,000,000 tires are discarded, containing approximately 3,500,000 tons of valuable fillers, mainly carbon black. Within the EU, currently more than half of this material is still incinerated. In view of the diminishing resources and resource efficiency, environmental issues and the enormous quantity of waste tires, cradle‐to‐cradle loops have to be elaborated for sound processing of this waste stream. In order to open new markets in high demanding applications including tires, new technologies have to be developed for the recovery of a higher quality carbon black. Besides, other rubber additives like zinc, threatened by scarcity, as well as energy have to be reused. Additionally, the envisaged process is more climate-neutral than production of new materials.  

In this project, a new innovative process for waste tire recycling will be developed. The process will convert used tires by a new thermochemical ultra fast pyrolysis process, and will produce a high quality nano-structured carbon black and valuable fuels: both can be used as raw materials for an energy-efficient production of new sustainable tires. The latter also requires tailoring of processing and compounding with the recycled carbon black to achieve material properties comparable to those of virgin material. An initial study showed the feasibility and potential for a breakthrough in quality compared to conventional pyrolysis carbon black, using an innovative technology which is significantly more cost-effective than the conventional pyrolysis processes.


Direct CO2 capture from ambient air

Project description
Carbon dioxide is by many considered the building block of the (transportation) fuel and (chemical or agricultural) industry of the future. Carbon dioxide can be used to produce liquid fuels and chemicals, that are currently produced from fossil carbon sources. The use of carbon dioxide as a raw material for chemicals and fuels opens the door for truly sustainable products, if sustainable energy sources are used for the conversion.

Two types of carbon dioxide sources can be used as a raw material: carbon dioxide captured for concentrated sources and carbon dioxide captured from air. Of the two, the former is limited in availability and location. The latter can be obtained anywhere in the world where a need is present, while the effort needed for capturing carbon dioxide from air is not much higher than that needed to capture carbon dioxide from a concentrated source.

Previous research at the University of Twente, funded by ANTECY BV, has resulted in the development of a promising process and technology and the filing of multiple patents regarding the capture and release of carbon dioxide from air. The project proposed is aimed at creating more fundamental knowledge on the process of capturing carbon dioxide from air in general as well as specifically with regard to the process developed in the previous process thus aiding the up scaling of the technology in practice. 


Enhanced catalytic fast pyrolysis of biomass

Project description
The Enhanced Catalytic Pyrolysis (EnCat) project presents and investigates a new concept for the production of high-quality bio-oil and a high yield. Because of a novel biomass pre-treatment step to be developed the concept is suitable for both woody biomass and biomass residues from agriculture, etc. The pretreated biomass will be pyrolysed in a reactor making use of deoxygenation catalysts.

Simultaneously, CO2 will be captured with sorbents and via the water-gas-shift reaction in-situ hydrogen will be produced. After cleaning, the oil vapours will be mildly hydrogenated to produce a high-quality bio-oil. The high-quality oil will be used for combustion tests in both a diesel engine and a gas turbine for combined power and heat generation. Parallel to this, the bio-oil will be further upgraded by a new method of downstream hydrogenation under high pressure for production of high-grade transportation fuels.


Recovery of minerals and fuels from paper slugde via flash pyrolysis

Project description
At its workshop in Arnhem, Alucha is currently developing a 100 kg/h mobile container unit to treat and recycle paper sludge. Paper sludge is the largest waste stream in the paper industry. The waste stream is produced by the water treatment plants in paper mills. Currently there is no sustainable solution to treat this waste stream. With the new advanced pyrolysis technology, they aim to recycle the minerals (such as Kaolin, calciumcarbonate) in the paper sludge (about 50% of the stream). The other 50% consist of paper fibers that will be converted into bio-oil.

The PDEng project will consist of modelling and optimizing the pyrolysis process for further upscaling. The patent pending reactor has now been designed for 100 kg/h capacity. The project consists of developing a CFD model for the reactor. The results from operational tests with the pilot plant during 2017 can be used to verify and validate this CFD model. The PDEng trainee can participate in these tests together with the Alucha team. Based on this validation, the reactor can be further designed, improved and finally upscaled to 1000 kg/h. Next to reactor design, the optimization of the energy efficiency of the pyrolysis process will be part of the project.


Demonstration of PyRos technology

Project description
Biomass contains carbon and hydrogen is thus the most important sustainable energy source for the production of liquid hydrocarbons. Flash pyrolysis provides the opportunity to convert biomass (e.g. woody or agriculture residues) in a few seconds into a liquid product. However, this pyrolysis product has a limited number of applications because of some problematic properties like corrosivity, high viscosity, instability and low energy density. Recently, research at the UT has shown that the application of catalysts in the pyrolysis process itself can significantly improve the properties of the oil product. Via a deoxygenation process the heating value can be increased to higher values such as 34 MJ/kg. The challenge of this DEMONSTRATOR-project to test this catalytic pyrolysis process in a pilot-plant with the so called PyRos technology a cyclone reactor with integrated separator for fines). 


Recovery of carbon and glass fibers for new products and fuels

Project description
Recovery of materials and energy is one of the pillars of a sustainable society. Carbon and glass fiber based materials are used for many products and in many forms. The recovery of carbon and glass materials is important for the industry to get green credits and to reduce costs. In this project the focus is on the recovery of carbon fibers from reinforced composite plastics, and on the recovery of glass fibers used in a wide range of different applications such as wind turbine blades, automotive applications, and boats. For both materials the problem is that the fibers are mixed with other components such as plastics, rubber or metals. Mechanical recovery from the waste streams is not successful as the resulting products do not meet the specs for reuse in high-quality products. 

The goal of the present project is to recover carbon and glass fibers from waste streams via a new flash pyrolysis technology. The focus is on recovering carbon fibers from composite materials and glass fibers from polyester waste streams in an energy efficient way and to produce high-quality fibers and fuels for new applications and products.


Supercritical aqueous reforming (SCAR) of digestate and sewage sludge into green gas

Project description
Biomass gasification in supercritical water is a rather new and challenging process. The reactions take place at high temperatures, high pressures in a water environment. The design of the reactor is important with respect to complete conversion of the reactants and avoiding the production of by-products that can plug or damage the reactor. Because of the use of wet biomass (sewage sludge) heat exchange between products and reactant is required for a high process efficiency. Heat transfer, hydrodynamics and phase changes are important aspects for an optimum design of such a heat exchanger. For both the reactor and heat exchanger mathematical models will be developed and validated against experimental data of the pilot-plant. The models will be used for further optimization of the reactor and heat exchanger.


Pretreatment/torrefaction of biomass

Project description
In the project TKI BBE Invent/Pre-treatment the viability of (partly) replacing fossil fuels by torrefied biomass is investigated. The project was divided in 4 work packages:

  1. Biomass selection, conditioning and supply
  2. Development of robust, flexible and safe production processes
  3. Inventory product requirements for logistics and end-use
  4. Optimization and standardization product quality

The work done by the University of Twente was part of work package 4, and covered the following topics:

  • Desk study mass and energy balances of integrated torrefaction and pyrolysis
  • Lab-scale batch and continuous experiments using various woody biomass streams and straw
  • Pilot-scale pyrolysis experiments

 The main objective was an assessment of the combination of the torrefaction and pyrolysis processes.


contact person

Ir. E.A. Bramer (Eddy)
Assistant professor