高温陶瓷净化生物质气化粗燃气粉尘试验研究

生物质气化得到的粗燃气含有焦油和粉尘杂质,两者形成的混合物在净化装置的高温区易碳化结焦,在低温区容易凝结成团,因此常规的除尘技术并不适用。针对该问题,本文开发了粗燃气高温陶瓷除尘技术,并考察了生物质原料种类、补燃及反吹等工艺条件对除尘室压降和运行温度的影响。试验结果表明:与木片单独气化比较,采用25%成型颗粒燃料+75%木片(质量比)混合气化可导致除尘室阻力上升1200~1500Pa;高温除尘室最佳操作温度为450~550℃,补燃较反吹是降低除尘室压降更有效的手段,当燃气处理量为260~400m3/h时,补燃空气的最佳流量为10~12m~3/h,此条件下可使除尘室压降稳定在1200Pa左右。陶瓷管燃气除尘设备可实现100h连续稳定运行,除尘器出口粉尘浓度为10~40mg/m~3,粉尘脱除率92.3%~99.8%,焦油脱除率为31.0%~92.5%,且补燃除尘后可燃气体组分浓度基本保持不变。     

岩棉纤维制备气固分离陶瓷材料的性能

以岩棉纤维和淀粉为主要原料,水玻璃为粘结剂,CMC为塑性剂,采用压制成型的方法制备了气固分离陶瓷材料。实验探讨了淀粉含量和烧制温度对材料抗折强度、过滤阻力和气孔率等性能的影响,并采用扫描电镜(SEM)对多孔陶瓷的显微结构进行表征。实验结果表明:当淀粉含量为25%、烧制温度为800℃时,材料抗折强度达7.8 MPa,过滤阻力为172 Pa,显气孔率达72%,脉冲反吹180次后过滤阻力为218 Pa,且后续反吹不再显著上升。     

碳化硅陶瓷膜管高温除尘实验研究

采用自制碳化硅陶瓷膜管对某电厂烟气进行了高温过滤性能和再生效果的实验研究。主要考察了三种陶瓷膜管的处理气量对过滤效率、阻力损失的影响以及反吹再生效果。结果表明,随着含尘烟气量的增加,过滤效率逐渐降低,同时压降损失逐渐增大;复合膜的过滤性能优于单一膜或支撑体,反吹再生效果最佳。     

操作参数对陶瓷过滤管脉冲反吹清灰过程的影响

在由单根陶瓷过滤管组成的实验装置上,利用U形管压差计及压阻式压力传感器分别测定了过滤含粉煤灰气体时滤管内外压差和脉冲反吹时滤管内的瞬态压力. 结果表明,在进入连续稳定循环过程后,单根滤管在各个循环的清灰效率仍存在较大的波动.在过滤参数不变而仅改变反吹参数的情况下,可依据反吹压力波形正压峰值来判断清灰效率的优劣. 同时分析了重要操作参数对反吹压力波形及清灰效率的影响. 指出脉冲宽度对清灰效率几乎没有影响;在满足清灰要求的前提下,再提高反吹压力对清灰并没有明显的改善效果;而过高的过滤速度对清灰效率极为不利,会导致过滤循环操作无法正常进行.     

陶瓷滤芯气体反吹动力学分析

为了优化脉冲反吹效果,对陶瓷过滤器过滤反吹系统的反吹过程进行实验研究和数值模拟,从滤芯轴向压力、速度分布变化方面分析不同反吹压力和不同喷嘴位置高度对反吹过程的影响。模拟结果与实验测量结果基本吻合。结果表明:反吹压力越大效果越好,但基于现实各种因素的考虑,反吹压力不宜过大;反吹过程中滤芯的下半部所受的压力和气流速度均大幅度减小,对反吹效果不利;并根据引射器入口和出口的质量流量得出在反吹过程中改变喷吹距离对反吹有一定的影响。     

高温陶瓷过滤管性能退化建模及实时寿命预测

高温陶瓷过滤管由内部孔径较大的支撑体和外部孔径较小的过滤膜双层结构构成,在实际应用中,存在大量粒径较小的粉尘颗粒,会穿过过滤膜沉积到支撑体内部,脉冲反吹无法有效清除. 因支撑体内颗粒沉积及管壁外残余粉尘层不断压缩,使陶瓷过滤管渗透率不断下降,残余压降逐渐增加。本工作基于高温陶瓷过滤管壁内颗粒沉积特性及残余粉尘层压缩不可直接观测的特点,结合贝叶斯估计理论,利用过滤管运行期间采集的残余压降数据,提出一种基于状态空间模型的过滤管性能退化建模方法。该方法能融入最新采集到的残余压降数据,实时对模型参数进行更新,可对陶瓷过滤管的剩余寿命进行实时预测,同时对陶瓷过滤管剩余寿命的失效概率密度分布及陶瓷过滤管的退化状态变化率进行预测。对某高温试验装置及壳牌煤气化装置中的陶瓷过滤管残余压降分析表明,预测剩余寿命准确率随残余压降数据增加而逐渐增加,后期预测准确率高于95%,且陶瓷过滤管退化状态变化率逐渐变小,与陶瓷过滤管残余压降前期增加快后期增加慢的现象一致。     

气-气混合器的数值模拟及优化设计研究

设计了一种体积小、压降低的新型气-气混合器,用于实现燃气与空气的均匀混合。利用Fluent数值模拟的方法研究了有导流板和无导流板两种情况下气-气混合器内的流场分布及混合效果,发现无导流板时混合器内存在一个旋涡区,混合器出口截面上的混合不均匀度S=0.053 6,空气在混合器中的总压降为960 Pa,空气与燃气进气压差为1 164 Pa;有导流板时混合器内存在两个旋涡区,混合器出口截面上的混合不均匀度S^*=0.045 4,空气在混合器中的总压降为1 109 Pa,空气与燃气进气压差为1 143 Pa。结果表明增设导流板后的气-气混合器整体压降增加约150 Pa左右,但混合效果更优,可实现均匀混合。对于有导流板的混合器结构,随着空气流量增加,压降增长十分显著,混合不均匀度随空气流量的增加而先下降后增长,燃气流量对压降及混合效果影响均不大。     

一种新型超高温气固分离陶瓷材料的制备研究

以普通硅酸铝纤维为骨架材料,加入一定比例的碱金属氧化物和高温陶瓷结合剂,制备出一种新型分离高温含尘气体的多孔陶瓷纤维复合材料.实验研究表明普通硅酸铝纤维中加入1.0wt％碱金属氧化物和10wt％高温陶瓷结合剂,制备出的材料1300℃烧成后具有优异的性能.该材料过滤阻力为143.66 Pa(过滤速度1m/min);抗折强度为5.6 MPa;收缩率为5.41％;气孔率为84.3％;过滤测试环境中粒径大于或等于2.5 μm粒子的过滤效率为99.99％;脉冲反吹40次后过滤阻力增幅为14.8％,且后续反吹不再显著上升.     

陶瓷滤管运行过程中的振动特性测定与分析

为分析实际生产中陶瓷滤管断裂的原因,利用电涡流位移传感器测定了陶瓷滤管在气体反吹时的振动,并测量了操作参数对陶瓷滤管振动的影响. 结果表明,陶瓷滤管在反吹时会产生径向位移,由于陶瓷滤管抗形变能力弱,可能会导致滤管发生断裂;另外,改变反吹压力对滤管振幅影响较大,反吹压力从0.3 MPa升至0.5 MPa时,滤管的振幅增加约40%;而改变过滤速度、脉冲宽度对滤管振幅影响较小,但会影响滤管振动的持续时间.     

气固分离膜材料的制备及性能

采用无机陶瓷纤维制备气固分离膜,利用短长径比的纤维在支撑体上制备过滤膜层,对膜层的过滤阻力、滤后空气含尘量以及反吹再生性能等进行测试。经对比发现,采用长径比为8~14的硅酸铝纤维制成的过滤膜性能最佳。在1 m/min的过滤风速下该膜层的初始阻力为108 Pa,经0.6 MPa的气压循环反吹300次后的平衡阻力为145 Pa,滤后空气含尘量为195μg/m~3。对0.03~0.06 MPa的反吹压力清灰后的平衡阻力进行了测试,0.06 MPa的反吹压力下平衡阻力为146 Pa,与0.6 MPa反吹后的平衡阻力相仿,所以反吹压力≥0.06 MPa时即可达到最佳反吹效果。     

气固错流移动颗粒床过滤器压降特性研究

研究了错流移动颗粒床过滤器操作压降与过滤介质特性、表现过滤气速、颗粒层移动速度和床层粉尘沉积量之间的关系。结果表明，无粉尘沉积时，床层压降可以用Ergun方程计算。颗粒层移动速度的变化并不会造成床层压降的显著变化。除尘过程中，床层内粉尘沉积量随气体中粉尘浓度的增大、颗粒层移动速度的减小而增加，同时将导致床层压降的显著增大。错流移动床除尘操作压降可以用带修正项的Ergun方程计算，其修正项为比沉积率和颗粒层空欧率的函数。在实验数据范围内，该方程的计算结果与实验数据最大偏差小于15％。     

基于CFD-DEM方法的净化器流场模拟与结构优化

针对空气净化器能耗高的问题,使用离散元方法(DEM)在吸附滤网中建立随机堆积柱形活性炭模型,采用计算流体力学(CFD)方法对空气净化器内部流场进行数值模拟,在模拟与实验验证的基础上,考察了压降最小、流场最均匀的吸附滤网结构。结果表明,空气净化器压降主要发生在轴向,活性炭吸附滤网中回流、沟流现象严重,流体阻力是其他两种滤网的3倍。边数对多边形填充孔结构吸附滤网内压降与流场均匀性无影响,当孔结构改为圆形时,压降减小约52 Pa,节能18.4%(49 W);当孔直径由8 mm增至12 mm,压降减小约48 Pa,节能19.4%(45 W);滤网间距对空气净化器压降无影响,圆形、小孔径的吸附滤网内流场最均匀。     

陶瓷过滤管管壁内气体流动的LBM并行模拟

采用格子Boltzmann方法,编制并行程序,计算了陶瓷过滤管管壁内的流体流动,从微观角度对滤管多孔介质结构内的流动进行分析。以陶瓷过滤管管壁扫描电镜图片为基础,根据实际滤管的厚度,确定计算中的多孔介质结构。分析了无膜滤管微细通道内的速度及压力随入口参数的变化情况以及多孔介质结构对速度的影响,给出了压力沿滤管厚度方向的变化曲线;分析了有膜滤管内的流动情况,给出了压力变化曲线,由计算结果可知,滤膜压降占滤管压降的比例较大。对过滤管微孔结构内流动的研究,可为陶瓷过滤管的性能优化提供理论指导。     

摇摆对气液并流模式立体旋流筛板压降的影响研究

以空气-水为实验介质,在喷淋密度78～182 m³·(m²·h)^-1、气相动能因子1.19～2.77 m·s^-1·(kg·m^-3)^0.5、摇摆幅值Θ=5°～15°、周期T=8～20 s的条件下,测定了气液并流模式下立体旋流筛板(TRST)的压降,考察了气液通量、塔板数量、位置和方式对压降的影响,并与直立和倾斜工况对比。结果表明：增加倾斜及摇摆角度干板压降略微下降;摇摆时的湿板压降介于直立和倾斜之间,受摇摆角度影响较大,基本不受周期影响;增大气量有利于抵抗倾斜及摇摆的影响,而增大液量会使倾斜及摇摆的影响作用加剧。整体上,塔板顺、逆向安装时的湿板压降分别在100 Pa和170 Pa以内,而逆向安装的变化率约为顺向的2倍,这是由于逆向安装下改变了气液流动方向,增大了能量损失。建立了气液并流摇摆工况下TRST的湿压降预测模型,相对误差在15%以内。     

Computer aided fuel cell design and scale-up,comparison between model and experimental results

The present work illustrates the employment of an Automatic Scale-up Algorithm (ASA) to design a 200 cm² multiple serpentine (MS) flow field for a Polymer Electrolyte Fuel Cell (PEFC). With a fixed fuel cell active area and total pressure drop, the algorithm provides the flow-field design solution characterized by a specific set of parameters including channel width, rib width, channel height, covering factor, number of switchbacks, Reynolds number and pressure drop. It is known that a correlation exists between the mass flow passing through the electrode and the pressure drop, influencing the fuel cell performance. A pressure drop range from 5 to 45 kPa with steps of 5 kPa has been investigated. Numerical simulations performed on each geometry set have permitted a comparison of the flow-field total pressure drop with the analytical compressible calculation, and to evaluate the mass flow rate passing through the electrode and in the flow field channels separately. A comparison between ASA and CFD results has highlighted that the methodology is able to find a flow-field geometry that matches target geometrical and fluid dynamic requirements. A better agreement between the Automatic Scale-up Algorithm and direct CFD pressure drop calculation has been obtained taking into account the gas compressibility effects. The increase of the mass flow rate vs flow-field total pressure drop is also reported. A better understanding of the gas shorting phenomenon has been achieved by CFD post-processing, in terms of gas velocity profiles and pressure drop between adjacent channels. Since the gas shorting is a pressure driven effect, the total mass flow rate percentage passing through the porous backing has been related to the shorting velocity and geometrical parameters of the porous backing; moreover proportionality between “shorting” pressure drop and ratio of flow field total pressure drop and switchback number has been highlighted.     

Water flooding and pressure drop characteristics in flow channels of proton exchange membrane fuel cells

Water flooding of the flow channels is one of the critical issues to the design and operation of proton exchange membrane fuel cells (PEMFCs). The liquid water and total pressure drop characteristics both in the anode and cathode parallel flow channels of an operating PEMFC were experimentally studied. The gas/liquid two-phase flow both in the anode and cathode flow channels was observed, and the total pressure drop between the inlet and outlet of the flow field was measured. The effects of cell temperature, current density and operating time on the total pressure drop were investigated. The results indicated that the total pressure drop in the flow channels mainly depends on the resistance of the liquid water in the flow channels to the gas flow, and the different flow patterns distinguish the total pressure drops in the flow field. Clogging by water columns result in a higher pressure drop in the flow channels. The total pressure drop measurement can be considered as an in situ diagnoses method to characterize the degree of the flow channels flooding. The liquid water in the cathode flow channels was much more than that in the anode flow channels. The pressure drop in the cathode flow channels was higher than that in the anode flow channels. During the fuel cell operation, the cell performance decreased gradually and the pressure drop both in the anode and the cathode flow channels increased. The rate of flooding at the cathode side reached 49.56% under experimental conditions after 78 min of operation. However, it was zero at the anode side.     

超重力旋转床微米级粉尘脱除实验研究

以超重力旋转床作为除尘设备,用超细滑石粉模拟工业微米级粉尘,考察旋转床除尘的分离效率和设备压降.在气量500～700 m~3/h、液量0.6～1.0 m~3/h、转速560～1 400 r/min、平面丝网层数为3的条件下,除尘总效率均大于97%,设备总体压降不超过490 Pa.超重力旋转床相对于其他除尘设备,显示了高效除尘和低压降性能.     

陶瓷球填料生物滴滤塔降解甲苯废气

The Purification experiments of waste gas containing low concentration toluene were made in trickling biofilter with ceramic spheres. The effects of liquid flow rate,gas flow rate,pH of circulation liquid, and toluene concentration in inlet gas on the purification efficiency of trickling biofilter were investigated. The pressure drop of the trickling biofilter was also measured during experiments.Increasing liquid flow rate and gas flow rate resulted in the decrease of purification efficiency of trickling biofilter. The highest purification efficiency of trickling biofilter was found at the circulation liquid pH of 7. The porosity of the packing material at the inlet of gas was higher than that at the outlet of gas in biofilter after continuous operation in 50 days. The decrease in the porosity of packing material caused a great increase in the pressure drop of the biofilter.