Operating Parameters for the Circulating Fluidized Bed (CFB) Pyrolysis of Biomass
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies - IIa: Energy Production (T1-5a)
Keywords: biomass, pyrolysis, CFB, conditions
In general, fluidised bed pyrolysis of biomass is considered as having the highest commercial potential for the thermal treatment of biomass and its transformation into mostly liquid hydrocarbons (tar), together with char and gas. The number of pilot research rigs has risen exponentially during the last decade, with circulating fluidised bed (CFB) prevailing over bubbling fluidised bed applications (BFB).
In this work, a relatively simple model is developed and applied, whereby the basic precept of the pyrolysis is dominated by the heterogeneous thermal decomposition of solid biomass.
Therefore, the CFB can be viewed as a chemical reactor whose performance is mainly affected by parameters controlling gas-solid reactions, i.e. fluid dynamics, contact modes, heterogeneous kinetics etc.
The use of a CFB pyrolysis reactor and associated product upgrading could make small scale operations technically and economically viable.
In the first section of this paper, the kinetics of biomass pyrolysis are reviewed as a result of extensive TGA and DSC experiments.
The hydrodynamics of the CFB are thereafter discussed further to measurements of the residence time distribution of biomass particles in the CFB, and of Positron Particle Tracking of a single biomass radio-actively traced particle.
A design strategy of the CFB for the pyrolysis of biomass is thereafter developed. The main operating parameters are the solids flux and gas velocity in the riser of the CFB.
In view of the required operating conditions for fast pyrolysis (high heat transfer, controlled residence time to avoid secondary cracking of the bio-oil, small biomass particles…), the operation of the CFB in plug-flow mode is favoured. Combined values of the gas velocity and the solids recirculation rate determine the operating conditions for the plug flow regime.
Findings will be summarized into design equations, applied for a pilot 1000 kg/h CFB biomass pyrolysis reactor.
See the full pdf manuscript of the abstract.
Presented Wednesday 19, 16:30 to 16:45, in session Sustainable & Clean Technologies - IIa: Energy Production (T1-5a).
