Experimental study on dynamic characteristics of biomass straw pyrolysis driven by concentrated solar energy
[Objective]The extensive combustion of fossil fuels results in increasingly severe environmental pollution,greenhouse gas emissions,and other related challenges.As a result,it is imperative to vigorously advance the development and utilization of renewable energy sources to foster clean and efficient energy utilization.As a promising green technology,biomass pyrolysis driven by concentrated solar energy will optimize the usage and storage of renewable energy.By harnessing solar radiation as a heat source for biomass pyrolysis reactions,it produces high-quality syngas,bio-oil and bio-char,consequently creating an opportunity to integrate solar energy into the broader energy system,catering to diverse needs.However,challenges arise owing to the fluctuating radiation intensity and complex chemical processes involved in the solar-driven pyrolysis reaction.Understanding the release patterns of biomass pyrolysis products,under different radiant flux densities becomes crucial for exploring the influence characteristics of radiation on dynamic pyrolysis energetic and chemical transformation processes.To thoroughly investigate the dynamic generation rules and benefits associated with the solar pyrolysis products of straw biomass,we have designed and constructed a specialized experimental platform.This platform is specifically tailored for direct biomass pyrolysis powered by high-flux concentrated solar energy.[Methods]A high-energy flow solar simulator is used to generate simulated solar rays.These rays,produced by several xenon lamps,are reflected through an ellipsoidal mirror and concentrated on the reaction bed.This process creates a high-temperature,high-radiation environment.We use a newly designed thermochemical reactor to drive biomass pyrolysis.We monitor the dynamic reaction process with a gas pretreatment system and an online gas analyzer.To ensure clarity in our experimental conditions,we adopt a grayscale method based on a"Lambert target + CCD camera"system,which indirectly measures the distribution characteristics of radiant energy density.Additionally,we strategically place thermocouples throughout the reaction space to monitor temperature characteristics.We use wheat straw as the biomass sample to investigate the characteristics of solar-driven pyrolysis under different energy flux densities.[Results]The solar simulator of our experiment generated a high-temperature spot with an average energy flux density of 757 kW/m2 at an electric power of 6.0 kW.This achieved maximum temperatures and pyrolysis reaction heating rates of 870℃and 25℃/s,respectively.Our results reveal that increasing the radiation intensity of the light source enhances the release of pyrolysis products H2 and CO.By increasing the electric power of the solar simulator from 1.5 kW to 6.0 kW,the yields of H2 and CO increased by 13.8%and 18.0%,respectively.Furthermore,the peak times for CO and H2 concentrations in pyrolysis gas were reduced by 67%and 71%,respectively.This suggests that augmenting the radiation intensity significantly accelerates biomass pyrolysis reactions.Moreover,the peak concentration levels of H2 rose to 11.48%from 1.49%,and the CO peak concentration increased to 11.61%from 1.59%,indicating a substantial enhancement in pyrolysis reaction rate.[Conclusions]Our research provides valuable insights into the efficient solar-driven pyrolysis conversion of straw biomass and the rational design of solar reactors.
solar thermochemicalbiomass pyrolysissolar reactordynamic reaction characteristics
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