Short residence time of the sorbent in the gas stream and formation of a dense layer of reaction product surrounding its surface influence the sulfur removal efficiency. A practical means of improving the process perf...Short residence time of the sorbent in the gas stream and formation of a dense layer of reaction product surrounding its surface influence the sulfur removal efficiency. A practical means of improving the process performance is to employ fluidized bed reaction in replacement of entrained bed reaction on normally used in cool side desulfurizaiton. This paper describes cold modeling study of a circulating fluidized bed reactor. Several aspects of the problem are discussed: fluidization behavior of CaO, attrition of the sorbent and solids entrainment from the fluidized bed. Mechanisms and key controlling parameters are identified, and an integral model based on rate of attrition and mass balance is developed for predicting steady state mass flows and particle size distributions of the system. A process flow scheme is finally presented for conducting desulfurization tests in the second stage of the study.展开更多
【目的】冷轧含油废水中油、化学需氧量(COD)含量高,可生化性差,传统物理化学法处理冷轧含油废水存在产生大量含油污泥的问题,运行成本高并产生二次污染,而基于污水处理过程中的污泥生物减量化已成为国内外的研究热点和发展趋势。上流...【目的】冷轧含油废水中油、化学需氧量(COD)含量高,可生化性差,传统物理化学法处理冷轧含油废水存在产生大量含油污泥的问题,运行成本高并产生二次污染,而基于污水处理过程中的污泥生物减量化已成为国内外的研究热点和发展趋势。上流式厌氧污泥床(UASB)对较高的有机负荷具有良好的耐受性,且能提高废水的可生化性,有利于解决上述问题。【方法】采用UASB对冷轧含油废水进行了预处理的可行性试验,通过逐渐提高进水有机负荷和油含量来考察UASB对油和COD的去除效果及试验过程中冷轧含油废水可生化性的变化,并探究有机负荷对产气率和颗粒污泥的影响。【结果】当有机负荷为4~12 kg COD/(m^(3)·d),油质量浓度小于500 mg/L时,COD和油平均去除率分别为77.27%和64.13%,产气率可达0.35 m^(3)/(kg COD),可生化性显著提高,且颗粒污泥粒径、污泥沉降性、胞外聚合物(EPS)随有机负荷的增加而提高;当有机负荷增加至13 kg COD/(m^(3)·d)以上,油质量浓度高于500 mg/L时,UASB处理效果急剧下降,颗粒污泥沉降性变差甚至上浮流失。【结论】UASB对有机负荷的波动和油有较好的耐受性,研究结果为UASB代替破乳、气浮等产生大量含油污泥的物理方法进行冷轧含油废水预处理提供了数据支撑。展开更多
文摘Short residence time of the sorbent in the gas stream and formation of a dense layer of reaction product surrounding its surface influence the sulfur removal efficiency. A practical means of improving the process performance is to employ fluidized bed reaction in replacement of entrained bed reaction on normally used in cool side desulfurizaiton. This paper describes cold modeling study of a circulating fluidized bed reactor. Several aspects of the problem are discussed: fluidization behavior of CaO, attrition of the sorbent and solids entrainment from the fluidized bed. Mechanisms and key controlling parameters are identified, and an integral model based on rate of attrition and mass balance is developed for predicting steady state mass flows and particle size distributions of the system. A process flow scheme is finally presented for conducting desulfurization tests in the second stage of the study.
文摘化学链燃烧技术是一种基于固体载氧体颗粒的新型无焰燃烧技术,对于助力碳减排具有重要意义。载氧体颗粒的寿命制约着该技术的进一步应用。文中针对载氧体颗粒的碰撞磨损问题,采用计算流体力学-离散元法(computational fluid dynamics-discrete element method,CFD-DEM)双向耦合数值计算法,建立非规则载氧体颗粒模型,从颗粒速度场、碰撞频率场及碰撞功率场三方面,探究冷态流化床内载氧体颗粒的运动状态、分布特征及碰撞情况。结果表明,冷态流化床内载氧体颗粒呈现上下无序周期性运动,单周期内流化床空间上出现颗粒密相区与稀相区。其中,稀相区颗粒速度大而碰撞频率小,颗粒具有高动能与高重力势能;密相区内颗粒速度小而碰撞频率高,最大碰撞频率对应的颗粒多为大粒径、较小长径比,且颗粒能量低;颗粒最易磨损区即碰撞最大功率区(最大7.8×10^(−8)W)位于颗粒密相区与稀相区的交界面,颗粒碰撞磨损能量由颗粒动能与重力势能累积提供。研究结果揭示了冷态流化床内载氧体颗粒的碰撞磨损机制。
文摘【目的】冷轧含油废水中油、化学需氧量(COD)含量高,可生化性差,传统物理化学法处理冷轧含油废水存在产生大量含油污泥的问题,运行成本高并产生二次污染,而基于污水处理过程中的污泥生物减量化已成为国内外的研究热点和发展趋势。上流式厌氧污泥床(UASB)对较高的有机负荷具有良好的耐受性,且能提高废水的可生化性,有利于解决上述问题。【方法】采用UASB对冷轧含油废水进行了预处理的可行性试验,通过逐渐提高进水有机负荷和油含量来考察UASB对油和COD的去除效果及试验过程中冷轧含油废水可生化性的变化,并探究有机负荷对产气率和颗粒污泥的影响。【结果】当有机负荷为4~12 kg COD/(m^(3)·d),油质量浓度小于500 mg/L时,COD和油平均去除率分别为77.27%和64.13%,产气率可达0.35 m^(3)/(kg COD),可生化性显著提高,且颗粒污泥粒径、污泥沉降性、胞外聚合物(EPS)随有机负荷的增加而提高;当有机负荷增加至13 kg COD/(m^(3)·d)以上,油质量浓度高于500 mg/L时,UASB处理效果急剧下降,颗粒污泥沉降性变差甚至上浮流失。【结论】UASB对有机负荷的波动和油有较好的耐受性,研究结果为UASB代替破乳、气浮等产生大量含油污泥的物理方法进行冷轧含油废水预处理提供了数据支撑。
