A novel pyroformer system for biomass intermediate pyrolysis with in-situ char-promoted reforming (by char re-circulation) of pyrolysis vapours and potential integration of pyroformer with commercial scale fluidised bed gasifier to enable pyrogasification

• Main Author: Saghir, Muhammad
• Published: Aston University 2018
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760166

Strong scientific evidence shows that anthropogenic greenhouse gas emissions from usage of fossil fuels are responsible for global warming and climate change. Biomass is a sustainable and reliable resource for replacing fossil fuels to produce energy and chemicals through pyrolysis and gasification routes. Pyrolysis of biomass leads to three products i.e. bio-oil, non-condensable gas and char. Gasification of biomass leads to a syngas which consists of hydrogen, carbonmonoxide, carbon dioxide, ,methane, nitrogen water vapour and some C1-C4 gases. The objectives of this thesis included: to conduct tests on a twin-screw pyrolysisreactor (Pyroformer); to evaluate the effects of char recirculation on products; to characterise the bio-oil and char produced and characterise an in-situ blend of biodiesel/bio-oil; and to review the design of the Pyroformer and its coupling with a bubbling fluidised bed gasifier, thus enabling a novel concept of Pyrogasification. To observe the biomass and char flow characteristics, and to calculate the residence time and char to biomass ratio (C/B), cold flow tests were performed ina transparent model of 20 kg/h Pyroformer. Biomass throughput limitations were identified at different feeding rates and C/B.Pyrolysis tests were conducted in a Pyroformer with up to 10 kg/h feeding rates. It was observed that, during pyrolysis of dry digestate pellets, gas yield increased and liquid yield decreased at optimum C/B of 3.1 at 5 kg/h. The organic phase ofbio-oil for MSW had an HHV of 30.3 MJ/Kg and a very low total acid number of 0.2mgKOH/g. ENPlus certified wood pellets and miscanthus pellets were pyrolysed in a 100 kg/h Pyroformer with in-situ blending of bio-oil with biodiesel. Product yield of 21, 32and 47 wt% for liquid, char and gas fractions were observed for wood pellets; and31, 32 and 37 wt% with miscanthus. Bio-oil content in the blend was 19.75 and11.28 wt% for wood and miscanthus derived feed stocks. The heavy metal content in biochars met voluntary biochar standards for soil remediation. A gasifier commissioning test was done with hydrogen, CO, methane and CO2 yields of 13.3,17.3, 4 and 17 vol% at 818 °C.