基于CFD-DEM的新型挡板式移动床反应器内Ca(OH)_(2)/CaO热化学储能过程模拟

CFD-DEM-based simulation of Ca(OH)_(2)/CaO thermochemical energy storage process in a novel baffled moving bed reactor

Ca(OH)_(2)/CaO热化学储能技术因其高储能密度和低成本等优势而备受关注,被认为是一种具有潜力的新型储能技术。普通的固定床反应器存在Ca(OH)_(2)颗粒储热速率过低的问题,为改善储能速率,引入了一种挡板式移动床结构,并采用计算流体力学与离散元耦合方法(CFD-DEM)对重力作用下移动反应床内Ca(OH)_(2)颗粒的储热过程进行了研究。相比多孔渗流模型,CFD-DEM更接近真实的流动情况,能提供颗粒尺度的物理信息。结果表明,相同条件下移动床能获得比固定床更高的储能速率,证明了将移动床用作热化学反应器的可行性;移动床内挡板的引入能有效延长颗粒在反应器中的停留时间,从而提高反应器的储能速率与能源利用率,但也会增加气体侧的压降。提高反应器进口气体温度能提高储能速率;在一定范围内提升进口气体流速可提高储能速率,但过高的流速可能引起堵塞,导致储能速率降低;进口固体流量存在最优值,使反应床的总储能速率最高。

The Ca(OH)_(2)/CaO thermochemical energy storage technology has garnered significant attention owing to its attractive features of high energy storage density and cost-effectiveness,positioning it as a promising advancement in energy storage methodologies.Nonetheless,traditional fixed bed reactors may pose challenges with their potential to yield a diminished heat storage rate for Ca(OH)_(2)particles.To address the challenge of low heat storage rate in conventional fixed bed reactor,a novel baffled moving bed structure is introduced.The heat storage process of Ca(OH)_(2)particles in the moving reactor bed under the influence of gravity is studied by using the coupled method of computational fluid dynamics and discrete element method(CFD-DEM).Compared to porous media models,CFD-DEM offers a closer approximation to real flow conditions and provides detailed physical information at the particle scale.The results indicate that the moving bed achieves a higher heat storage rate compared to its fixed bed counterpart under identical conditions,providing evidence for the feasibility of employing a moving bed as a thermochemical reactor.The introduction of baffles in the moving bed is able to extend the particle residence time in the reactor,consequently amplifying both the heat storage rate and energy storage efficiency.However,it concurrently results in an increased pressure drop on the gas side.The simulations under various inlet conditions reveal that elevating the gas temperature at the reactor inlet positively impacts the heat storage rate.Within specific ranges,an increase in the inlet gas flow rate can improve the energy storage rate,albeit with caution against excessively high flow rates that could induce blockages and diminish the overall heat storage rate.Notably,the inlet solid flow rate exhibits an optimum value,maximizing the comprehensive heat storage rate of the reaction bed.