Researchers in Bio4Energy have shown in pilot-scale experiments that pressurised entrained-flow gasification may be used to transform biomass from forestry residue to a synthesis gas rich in chemical energy. This is good news for the researchers and their industrial partners who have been developing the method for the purpose of making biofuel with a low environmental footprint and high energy efficiency.
If the process proves to be as efficient in a future scale up to commercial levels, it could also be good news for the forestry industry at large, looking to use their residual fibre-based process streams in new products. Moreover, it could make forestry residue competitive with black coal in its use in commercial gasification process for making fuels and chemicals, in terms of cold-gas efficiency. This latter is a measure used by researchers of the chemical energy left in the synthesis gas resulting form the gasification process.
The new findings result from two years’ worth of research and development work by Bio4Energy scientists and technicians at the SP Energy Technology Center at Piteå (SP ETC) and the Luleå University of Technology (LTU), both in northern Sweden and leaders in their field.
“It is a milestone in our research. We are very proud with what we have achieved so far”, said Magnus Marklund, CEO at the SP ETC.
“The next step in our applied research will be to optimise the different subsystems in the process, which will render the technology even more viable”, Marklund added.
Fredrik Weiland, a student researcher defending his PhD thesis 26 February at the LTU, has been at the helm of the work to lay bare the parameters of the gasification process itself and looking especially at the high-temperature entrained-flow gasification method in a pilot-scale gasifier at the premises of the SP ETC, in cooperation with Swedish industrial partners IVAB, Biogreen, Sveaskog and Smurfit Kappa. As much as 76 per cent of the chemical energy in the biomass feedstock—saw dust pellets, in this case—were retained in the synthesis gas, Weiland and his colleagues found.
“This is a good, competitive cold-gas efficiency… which can be compared to [that of] the fluidised-bed gasification technique where it reaches about 65 per cent”, said Weiland. However, he pointed out, the energy requirement for biomass milling generally was somewhat higher in entrained-flow gasification compared with that entailed when using a fluidised bed in the gasification process.
Judging from the literature, on a global scale more research has been done on biomass gasification methods using a fluidised bed as a reactor, compared with research having gone into pressurised entrained-flow gasification. However, scientists on the Bio4Energy Thermochemical Platform, of which Marklund and Weiland are part, have opted for developing the latter method both in terms of fundamental knowledge and pre-industrial trials designed to perfect the technology ahead of attempts to scale it up to commercial production levels by industry in the biorefinery sector. Despite its requiring higher temperatures, the scientists believe entrained-flow gasification will win out in the end where the purpose is to make a synthetic fuel. First because this type of gasification can be made to render a highly clean synthesis gas which can be turned directly into biofuel or an energy carrier such as methanol, without adding gas scrubbing as a process step. Second, and as the recent research findings from Bio4Energy would suggest, the scientists believe pressurised entrained-flow gasification can produce fuels which are more energy efficient.
“We have characterised the [pressurised entrained-flow] gasification process to find out at which temperature to run the process, its efficiency and how much of the [biomass] energy ends up in the resulting synthesis gas”, Weiland explained;
“We have also obtained the answer to a range of research questions in terms of temperature and composition of the synthesis gas… This can be of great value for people who look at this from a system’s perspective, for instance to see if producing fuels from the forest is cost competitive” with fossil fuel production.
“Our goal has been to show that it is possible to use a pressurised entrained-flow reactor to gasify pulverised biomass and that this is competitive in terms of cold-gas efficiency, and I feel we have achieved that”, Weiland said.
“But gasification of biomass is not as ‘hot’ as it used to be a number of years ago. This has partly to do with the [low] price of oil and electricity. Long-term incentives are needed”, he said with reference to support measures of the type that governments can grant.
In the picture: Bio4Energy researchers Magnus Marklund and Fredrik Weiland at the SP Energy Technology Center at Piteå.