Technoeconomic assessment of a fast pyrolysis bio-oil production process integrated to a fluidized bed boiler

The integration of a fluidized bed fast pyrolysis process producing bio-oil to an existing fluidized bed boiler combined heat and power (CHP) plant is presented. The purpose of this work is to assess the cost and performance of the integrated fast pyrolysis bio-oil production compared to a stand-alone fast pyrolysis bio-oil production plant. The reason for integrating bio-oil production into a fluidized bed boiler is to increase overall energy efficiency and profitability and to decrease the production costs of the bio-oil. In the integrated fast pyrolysis concept hot sand from the fluidized bed boiler is used for heating the fast pyrolysis reactor. Simultaneously, fast pyrolysis process byproducts such as char and noncondensable gases are cofired in the CHP boiler together with the primary forest residue boiler fuel. The assessment shows that the integration decreases the primary fuel requirement of the boiler. The integration causes changes in the net power and heat output of the CHP plant, but the integration can still be more profitable than a stand-alone fast pyrolysis process. The differences in pyrolysis feedstock characteristics are important when comparing integration to stand-alone bio-oil production. In this work pine sawdust and forest residue feedstock were evaluated, of which only the forest residue proved to be economically advantageous for integration to a CHP boiler.