生物质秸秆在聚光太阳能驱动下的动态热解特性实验

Experimental study on dynamic characteristics of biomass straw pyrolysis driven by concentrated solar energy

太阳能驱动生物质热解是重要的热化学互补技术,可将太阳能转化为高品质合成气中的化学能,并实现高效化学存储。为探究太阳能热解过程中的能量及化学转化特性,该文设计搭建了太阳能驱动生物质热解实验平台,并开展了太阳能驱动小麦秸秆热解实验研究。结果表明太阳能模拟器可提供平均能流密度为757 kW/m^(2)的高温焦斑,热解反应的最高温度和最大瞬时加热速率分别达到870℃和25℃/s。太阳能模拟器输入电功率由1.5 kW提升至6.0 kW,反应气体产物的质量百分比由24.7%上升至54.4%,对应的H_(2)动态浓度峰值(体积百分比)将由1.49%增加至11.48%,CO动态浓度峰值(体积百分比)由1.59%增加至11.61%,增大入射光能流密度有效促进了H_(2)、CO等燃料气体的生成,并能提高反应速率。研究结果将为太阳能驱动秸秆生物质的高效热解转化和太阳能反应器设计提供参考。

[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/m^(2)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 H_(2)and CO.By increasing the electric power of the solar simulator from 1.5 kW to 6.0 kW,the yields of H_(2)and CO increased by 13.8%and 18.0%,respectively.Furthermore,the peak times for CO and H_(2)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 H_(2)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.