(648a) Biomass Pyrolysis Challenge: A Multi-Scale Approach

Authors: 
Sharifzadeh, M., Imperial College London
Shah, N., Imperial College London

Biomass pyrolysis
challenge: A multi-scale approach

Sharifzadeh, Mahdi[1] , Shah, Nilay.

Centre for process Systems Engineering (CPSE),
Imperial College London.

Biomass pyrolysis provides
the cheapest pathway toward renewable liquid fuels. In this presentation, we provide
an overview of our accomplishments at Centre for Process Systems Engineering
(CPSE), Imperial College London, for research into production of fuels and
chemicals from bio-oil, via the pyrolysis pathway. We adapted a multi-scale approach
which spans from the structure of individual molecules to a country-wide supply
chain network [1-5]. The research objective is to improve the overall economy
of the biofuel production and mitigate carbon emissions in order to protect the
environment.

The liquid product of pyrolysis reactions is called biomass pyrolysis
oil, or simply bio-oil. Despite various incentives, bio-oil features some
undesirable properties and is not immediately usable in the current energy
infrastructure. Bio-oil contains a high amount of oxygenates and suffers from a
low calorific value. Furthermore, it is highly acidic leading to thermal
instability and increasing viscosity. Finally, due to high water content it is
immiscible with petroleum-derived fuels. The technology for the removal of
oxygen and other heteroatoms from pyrolysis oil is called ?bio-oil upgrading?. We
propose a novel framework for modelling the kinetics of the involved upgrading
reactions based on connectivity of the oxygen atoms. We demonstrate that this
approach is most effective for representing the highly interactive networks of the
biomass upgrading reactions, involving a large number of species [2].

Furthermore, we conducted a comparative study [2] between two major
bio-oil upgrading technologies, namely hydrodeoxygenation upgrading and
hydrothermal treatment which identified the key characteristics of each
technology. Based on such in-depth insights, we proposed a synergistic reaction
networks which economically produce biofuels and is self-sufficient with
respect to the required hydrogen.

Nevertheless, commercialization of biofuel technologies poses an
important challenge; unlike crude oil, biomass has a high
oxygen content (e.g., 58.28% mass fraction in the case of hybrid poplar). Therefore,
in order to make the biofuels compatible with current energy infrastructures,
the oxygen atoms should be removed resulting in a large amount of inevitable CO2
by-product. For example, in the biomass pyrolysis pathway, from every two
carbon atoms, almost one atom ends up in the CO2 emissions. Therefore,
CO2 utilization is an indispensable element of future biorefineries.
In a follow-up project [3], we developed a new biorefinery scheme based on
processing synergies between bio-oil upgrading and biofuel production from
microalgae. In the proposed scheme, the CO2 generated via biomass
pyrolysis and upgrading is captured using amine solutions and utilized for
microalgae cultivation. We demonstrate that such process integration increases
fuel conversion from 55% to 73%. Nevertheless, CO2 capture and
utilization reduces the CO2 emissions from 45% in the stand-alone
pyrolysis to 6% in the integrated scheme with another 19% in biomass residue
waste streams.

In parallel, we studied the production of commodity products such as
olefins and aromatics from biomass pyrolysis via integrated catalytic
processing [4]. We provide the proof of concept that using such technology,
naphtha can be replaced by biomass pyrolysis oil in conventional olefin
processes. Such a retrofit results in up to 46% reduction in the emission of
greenhouse gases, while the produced biochemicals are still economic in the
current chemical market. 

Finally, we recently studied the biofuel production supply chain.
Several production strategies were considered. They are (1) the centralized
production strategy, where biomass pyrolysis and upgrading are performed at the
same place, (2) the distributed production strategy, where the bio-oil is produced
in distributed production facilities and the bio-oil is delivered to upgrading
centres, and (3) mobile biofuel production where bio-oil is produced in mobile
production facilities and sent to upgrading centres for biofuel production. A
mixed integer linear optimization framework was programmed which enabled
systematic decision-making regarding aforementioned alternative production
strategies. The optimisation results suggested that a combination of
geographically centralized pyrolysis and upgrading centres would suffice for
supply chain management under deterministic conditions. However, under
uncertain scenarios, it is advantageous to deploy mobile pyrolysers to add
extra flexibility to the process operation. Further our analysis suggested that
as the mobile pyrolysers are commercialized and their unit price is reduced,
this technology has the potential to become a key member of future biofuel
supply chains.

References

[1] Sharifzadeh M*, Richards C,
Chadwick D, Shah N (2015). A generalized framework for modeling the kinetics of bio-oil hydrothermal reactions.
In preparation, to be submitted to Biomass & Bioenergy.

[2] Sharifzadeh M*, Richards CJ, Liu K,
Hellgardt K, Chadwick D, Shah N. (2015). An integrated process for biomass pyrolysis
oil upgrading: the synergistic approach. Biomass &
Bioenergy
. 76, 108?117, (Link).

[3] Sharifzadeh M*, Wang L, Shah N,
(2015). Integrated bio-refineries: CO2 utilization for maximum biomass
conversion. Renewable and Sustainable Energy Reviews, 47, 151?161, (Link).

[4] Sharifzadeh M*, Wang L., Shah N.,
(2015). Decarbonisation of olefin processes using
biomass pyrolysis oil. Applied Energy, 149, 404?414, (Link).

[5] Sharifzadeh M*, Cortada Garcia, M,
Shah N., (2015). Supply chain network design and operation under
uncertainty: centralized, distributed, and mobile production of biofuel via
fast pyrolysis and upgrading, (minor revisions required by Biomass &
Bioenergy
).




1
Corresponding author,
Email: mahdi@imperial.ac.uk , Address: Room C603, Roderic
Hill Building, Centre for Process Systems Engineering (CPSE), Department of
Chemical Engineering, Imperial College London, South Kensington, London SW7
2AZ, UK.

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