Production of intermediates (VC4)
Torrefaction is a thermochemical process typically at 200-350 °C in the absence of oxygen, at atmopsheric pressure with low particle heating rates and a reactor time of one hour. The process causes biomass to partly decompose, creating torrefied biomass or char, also referred to as 'biocoal'. Biocoal has a higher energy content per unit volume, and torrefaction followed by pelletisation at the harvest sites facilitates transport over longer distances. It also avoids problems associated with decomposition of biomass during storage. Hence the benefits of torrefaction may outweigh the additional cost in many cases.
An overview of torrefaction technology and market potential is provided in the report:
Carl Wilén, Kai Sipilä, Sanna Tuomi, Ilkka Hiltunen & Christian Lindfors, VTT, 2014
Pyrolysis is another kind of thermochemical decomposition of organic matter by heating. Flash pyrolysis involves rapid heating (1-2 seconds) of fine material up to 500°C. Thermochemical Conversion uses superheated water to convert organic matter to bio-oil. This may be followed by anhydrous cracking/distillation. The combined process is known as Thermal depolymerization (TDP).
Three kind of products can be obtained: a solid (charcoal), a gas and a bio-oil.
A number of research projects and companies are developing innovative processes to turn a wide range of biomass (forestry residues, crop residues, waste paper and organic waste) into stable, concentrated bio-oil (biocrude) that is compatible with existing refinery technology and can be converted into advanced biofuels.
For example, in the HTU® (hydrothermal upgrading) process, originally developed by Shell, biomass is treated with water at high temperature and pressure (300-350°C & 120-180 bar) to produce bio-crude. This can be separated by flashing or extraction to heavy crude (suitable for co-combustion in coal power stations) and light crude, which can be upgraded by hydrodeoxygenation (HDO) to advanced biofuels (Source: Biofuel BV presentation).
EU funded projects
4REFINERY (Scenarios for integration of bio-liquids in existing REFINERY processes) will develop and demonstrate the production of next generation biofuels from more efficient primary liquefaction routes integrated with upgraded downstream (hydro)refining processes to achieve overall carbon yields of >45%. The consortium will aim for successful deployment into existing refineries, including delivering a comprehensive toolbox for interfacing with existing refinery models. Duration: 2017 - 2021.
The BioMates project aspires in combining innovative 2nd generation biomass conversion technologies for the cost-effective production of bio-based intermediates (BioMates) that can be further upgraded in existing oil refineries as renewable and reliable co-feedstocks. The resulting approach will allow minimisation of fossil energy requirements and therefore operating expense, minimization of capital expense as it will partially rely on underlying refinery conversion capacity, and increased bio‐content of final transportation fuels. Duration: 2016 - 2020.
Definitions of 'Fast Pyrolysis Bio-oil' FPBO
In January 2014, a REACH Fast Pyrolysis Bio-Oil (FPBO) consortium was formed in Europe, and determined the following definition for FPBO: "Liquid condensate recovered by thermal treatment of lignocellulosic biomass, at short hot vapour residence time (typically less than about 10 seconds) typically at between 450 - 600°C at near atmospheric pressure or below, in the absence of oxygen."
Properties and composition of FPBO, along with further details of the FPBO REACH consortium, were published in PyNe Newsletter 34 produced by IEA Task 34. A series of handbooks on the Fast Pyrolysis of Biomass have been published by PyNe (Vol 1: ISBN 9781872691077, Vol 2: ISBN 1872691471, Vol 3: ISBN 1872691927).
Standards for fast pyrolysis bio-oil
CEN/TC 19/WG 41 is currently developing standards for fast pyrolysis oils in response to EC mandate M/525 (2013). Three standards will be developed for replacement of heavy fuel oil, light fuel oil and for use of bio-oils in stationary combustion engines. Later, two further technical specifications may also be introduced for use of fast pyrolysis oils as gasification feedstocks and for mineral oil refinery co-processing, as and when required.
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Pyrolysis and torrefaction value chain
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