Co-production of Pyrolysis Oil in District Heating Plants: Systems Analysis of Dual Fluidized-Bed Pyrolysis with Sequential Vapor Condensation

Abstract

Flash pyrolysis of biomass yields a liquid applicable as a fuel oil substitute and as a basis for production of chemicals and fuels. Biomass, being a renewable resource, is foreseen to be in increasing demand. An increased usage may lead to scarcity of biomass and emphasizes the need for high-efficiency conversion processes. In this study, the efficiency and capacity aspects of an integration of pyrolysis oil production with a district heating plant by means of dual fluidized-bed technology has been modeled. Further, fractional condensation of the pyrolysis vapors has been applied, enabling part of the condensation energy to be recovered. The concept shows potential for significant pyrolysis oil production while keeping the delivered power and heat constant. The use of excess heat from the pyrolysis production in the district heating net results in a 10% higher overall efficiency than production without heat supply to the district heating net.

Co-production of pyrolysis oil and district cooling in biomass-based CHP plants: Utilizing sequential vapour condensation heat as driving force in an absorption cooling machine

“…The production is planned at 50,000 t/y. Gustavsson and Nilsson [7] investigated the integration of a flash pyrolysis reactor including sequential vapour condensation of the pyrolysis oil in a CHP plant and demonstrated that the potential for producing pyrolysis oil is considerable, especially during the summer months. The proposed plant in Ref.…”

“…The proposed plant in Ref. [7] uses sequential condensation of the pyrolysis oil at different temperature levels. A part of the condenser heat could not be utilized and was discharged as waste heat.…”

“…Models for the heat and mass balances of the flash pyrolysis as well as for the condensation behaviour of the pyrolysis oil produced are taken from a previous published study [7]. The process scheme for the pyrolysis integration, Fig.…”

“…A short summary of the pyrolysis integration is given below, the complete explanation can be found in Ref. [7].…”

“…the air was heated to a maximum 20 C from pyrolysis condenser 2 and then to 10 C below the district heating temperature. The different operating parameters between the pyrolysis integration in this study compared to Gustavsson and Nilsson [7] are shown in Table 1.…”