A three-stage heating system of dual-fuel controlled by negative feedback for fluidized bed fast pyrolysis

Abstract

To ensure the reduction of unnecessary consumption of thermal energy, precise control of the pyrolysis temperature, reasonable use of pyrolysis by-products, and the self-supply of thermal energy in the pyrolysis process, a novel three-stage heating system for pyrolysis was designed, which used liquefied petroleum gas (LPG) and non-condensable gas (NCG) as dual fuels. The programmable logic controller (PLC) adopted the negative feedback to individually control the four key temperatures in the heating system, and finally realized the precise control of pyrolysis temperature. In the case of only LPG to combust, the heating and reaction characteristics of the experimental apparatus were obtained in the initial experiment. The results showed that the heating system had the basis for NCG to replace LPG to combust. From the perspective of saving energy and reducing consumption energy, when LPG and NCG combusted simultaneously and the yield of liquid product was 59%, the self-supply of thermal energy can be realized, that was, reaching the point of energy balance. When the pyrolysis temperature was 500 °C and the packing height was 100 mm/50 mm, the peak value of the combustion gas replacement rate reached 78.2%, and the ideal working conditions were realized at this time.