Numerical Simulation of Pressurized Spouted Fluidized Bed for Coal Semi-Gasification

Numerical simulation study is conducted for a pressurized spouted fluidized bed coal carbonizer, in which hydrodynamics of pressurized spouted fluidized bed, chemical reactions and energy balance are taken into account. The effect of operating conditions such as bed pressure, air and steam mass flow ratio, temperature on product compositions in the bed is investigated. According to the calculated results, bed pressure and bed temperature have the key effects on coal semi gasification.

Analysis of Gas-Solid Flow Characteristics in a Spouted Fluidized Bed Dryer by Means of Computational Particle Fluid Dynamics

In order to grasp the particle flow characteristics and energy consumption of industrial fluidized spouted beds,we conduct numerical simulations on the basis of a Computational Particle Fluid Dynamics(CPFD)approach.In particular,the traction model of Wen-Yu-Ergun is used and different inlet conditions are considered.Using a low-speed fluidizing gas,the flow state of the particles is better and the amount of particles accumulated at the bottom of the bed wall becomes smaller.For the same air intake,the energy loss of a circular nozzle is larger than that of a square nozzle.

Catalytic Partial Oxidation of Methane with Air to Syngas in a Pilot-Plant-Scale Spouted Bed Reactor

On the basis of hydrodynamic and scaling-up studies, a pilot-plant-scale thermal spouted bed reactor (50 mm in ID and 1500 mm in height) was designed and fabricated by scaling-down cold simulators. It was tested for making syngas via catalytic partial oxidation (CPO) of methane by air. The effects of various operating conditions such as operating pressure and temperature, feed composition, and gas flowrate etc. on the CPO process were investigated. CH4 conversion of 92.2% and selectivity of 92.3% and 83.3% to CO and H2, respectively, were achieved at the pressure of 2.1 MPa. It was found that when the spouted bed reactor was operated within the stable spouting flow regime, the temperature profiles along the bed axis were much more uniform than those operated within the fixed-bed regime. The CH4 conversion and syngas selectivity were found to be close to thermodynamic equilibrium limits. The results of the present investigation showed that spouted bed could be considered as a potential type of chemical reactor for the CPO process of methane.

Comparison of numerical simulations and experiments in conical gas–solid spouted bed

Flow behavior of gas and particles in conical spouted beds is experimentally studied and simulated using the twofluid gas-solid model with the kinetic theory of granular flow.The bed pressure drop and fountain height are measured in a conical spouted bed of 100 mm I.D.at different gas velocities.The simulation results are compared with measurements of bed pressure drop and fountain height.The comparison shows that the drag coefficient model used in cylindrical beds under-predicted bed pressure drop and fountain height in conical spouted beds due to the partial weight of particles supported by the inclined side walls.It is found that the numerical results using the drag coefficient model proposed based on the conical spouted bed in this study are in good agreement with experimental data.The present study provides a useful basis for further works on the CFD simulation of conical spouted bed.

Optimization of Draft Tube Position in a Spouted Bed Reactor using Response Surface Methodology

Optimization of draft tube position in a spouted bed reactor used for treatment of wastewater containing low concentration of heavy metals is investigated in this paper. Response surface methodology is used to optimize the draft tube height, the draft tube width and the gap between the bottom of the draft tube and the inlet nozzle. It is observed that the draft tube with a height of 60 millimeter, width of 12 millimeter and the gap of 13 millimeter between its bottom and inlet nozzle, results in optimum value of minimum spouting velocity, measured 45 cubic centimeter per second (2.7 Liter per minute) .

Progress in research of process intensification of spouted beds:A comprehensive review

The development of intensification technology for spouted beds has become a current research focus,and an effective way to improve the efficiency of spouted beds is to reform their structure.Although numerous studies have been conducted on conventional beds,there are few reviews on the comprehensive application of intensification technology for spouted beds.In this paper,we comprehensively review the role of intensification technology in spouted beds for use in hydrodynamics,drying,desulfurization,pyrolysis,coating,biomass and waste gasification,and biomass drying from the perspective of experiment and simulation.Finally,potential problems and challenges in current spouted-bed research are summarized.

Gas Residence Time Distributions in a Spouted Bed

In a spouted bed of 80mm in ID and 1700mm in height, the gas residence time distributions at different radial positions in both spout and annular area were measured with five different kinds of particles as spouting material, air as spouting gas, and hydrogen as tracer. The effects of superficial gas velocity, operating pressure, particle size and its category on gas residence time distribution were discussed. It was found that the gas velocity profile in spout was more uniform than that in annulus. It could be concluded that the gas flow in the spout could be treated as a plug-flow, while that in the annulus inhibited a strong non-ideal flow behavior. Increasing the superficial gas velocity and decreasing the operating pressure, the particle density and its size gave rise to spouting disturbance, thus the measured tracer concentrations vs. time curves fluctuated. The variances of residence time distribution curves could be taken as a measure of the gas fluctuation degree.

Experiments and Modeling of the Preparation of Ultrafine Calcium Carbonate in Spouted Beds with Inert Particles

A novel reaction-drying process was carried out in a spouted bed reactor with inert particles and used to prepare ultrafine CaCO3 particles. Effects of concentrations of CO2 and Ca(OH)2, and reaction temperature on Ca(OH)2 conversion were experimentally investigated. The particle sizes and composition of CaCO3 produced were characterized with transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results indicated that ultrafine CaCO3 particles with mean size of 80 nm could be obtained with this novel process.By modifying the Arrhenius Equation and considering the Ca(OH)2 state, a kinetic model was established to describe the process in the spouted bed. The model parameters estimated from the reaction-drying experiments were found to fit well the experimental data, indicating the applicability of the proposed kinetic model.

Pilot Scale Test to Treat High Concentration Gasification Wastewater Using Catalytic Oxidation and Aerobic Biological Fluid-Bed Combination Process

The gasification wastewater is a kind of typical organic industrial wastewater with high chemical oxygen demand （COD） and ammonia nitrogen, which could not be completely degraded by the traditional physical, chemical and biological method. So it is very important to find an effective treatment process. A combination process of catalytic oxidation with noble metal catalysts and aerobic biological fluid-bed packed with the new ultrastructure biological carriers, which was developed by ourselves, was investigated to treat the gasification wastewater. The pilot scale test with 0.5 m^3/h influent flow was carried out to investigate the performance of this new combination process. The results showed that the effluent COD was 84.02 mg/L, ammonia nitrogen was 14.15 mg/L, and total phenol was 0.20 mg/L, which could completely meet the Grade I of Wastewater Discharge Standard （GB8978-1996）, when the influent average COD was 5 564 mg/L, ammonia nitrogen was 237 mg/L, and total phenol was 1 100 mg/L. The two catalytic reactors could evidently improve the wastewater biodegradability, and the value of BOD5/COD （B/C） increased from 0.23 to 0.413 in the one-stage catalytic reactor and from 0. 273 to 0.421 in two-stage catalytic reactor. The further experiment results showed that the effluent quality of this new combination process could still meet the discharge standard, when the COD loading was 8.65 kg / （m^3· d）. Most of aromatic and heterocyclic compounds were degraded effectively in this combination process.

Prediction of Minimum Spouting Velocity at Elevated Pressures and Temperatures

Minimum spouting velocity （Ums） is one of the most important flow characteristics for proper design and operation of spouted bed reactors. Many correlations for Ums have been published since spouted bed technology was initiated in 1955. In this paper, a new correlation is developed for Ums based on 767 published experimental data covering both high pressure and high temperature conditions. The calculated and the measured results of Ums are in better agreement than other published correlations.

A Preliminary Research on a Plasma Spout-Fluid Bed Reactor

A laboratory-scale plasma spout-fluid bed reactor with a 10 kW DC plasma torch was developed and tested using quartz sand particle and rice hull. The preliminary experimental results including particle recirculation and attrition, bed temperature distribution and stability, as well as biomass gasification system energy balance were presented in this paper. Research results indicated that plasma spout-fluid bed reactor may be a technically feasible reactor for carbonaceous organic material gasification.

CFD-DEM simulation of high density particles fluidization behaviors in 3D conical spouted beds

The spouted bed has been used in the coating process of high-density nuclear fuel particle.The particle fluidization behaviors in pseudo-2D and 3D spouted beds were simulated and validated.The effects of four independent variables(cone angle,particle density,inlet gas velocity,and particle loading)on particle fluidization behaviors in the 3D spouted bed were investigated systematically.The cone angle effect on fluidization mechanism was studied quantitatively first time.A new fluidization quality index was proposed based on the particle entrainment principle,and an extreme value was obtained when the cone angle was 60°,considered to be the optimum value for the 3D conical spouted bed.It was indicated the gas–solid contact efficiency can be kept up if the gas velocity was proportional to ρ_(p)^(0.65) and N_(p)^(0.78) when the particle density or loading was increased.These results will be useful for geometry and operation parameters design of the 3D conical spouted bed and helpful for developing the fluidization mechanism of high-density particles.

非球形湿颗粒导向管喷动流化床流动特性

实际工业生产中颗粒多为非球形颗粒,对颗粒形状效应和液相作用机制的研究不足,是导向管喷动流化床在颗粒涂层改性、包膜等工业应用的关键限制因素。选取粒径、密度相似的球形和圆柱形非球形颗粒为实验物料,对比两种颗粒在不同气速和雾滴引入量下的压力脉动信号频谱分析、信息熵分析,并结合床内气固流动对流型进行划分,绘制非球形湿颗粒流动相图,进而探究喷动流化过程中颗粒形状效应及液相作用机制。相比于球形颗粒,粒径、密度相似的非球形颗粒有较小的最小喷动速度,在喷动过程中有两个及以上较低的主频峰且信息熵较大,显示出非球形颗粒在系统内较高的混乱程度,颗粒之间摩擦、碰撞等降低了导向管内颗粒的固体循环速率。液体的引入增大了环形区颗粒间液桥力,使最小流化速度变大,但液体挥发引起喷动气量增大,使最小喷动速度与最小喷动流化速度减小。在喷动流化流型下引入液体,球形颗粒导向管两端压降ΔpDT的脉动主频降低,而非球形颗粒ΔpDT的主频升高。而且非球形颗粒黏附液体后频谱分析结果显示幅值较大的单一主频峰,表明非球形湿颗粒压力脉动规律性的增强。

怀山药恒温及变温红外喷动床干燥动力学、均匀性及品质特性研究

采用恒温干燥(40,50,60,70℃)和阶段变温干燥(阶段升温和阶段降温)工艺对怀山药进行红外喷动床干燥(IRSBD)处理,研究其对干燥动力学、均匀性及品质特性(质构、复水性能、总酚含量、微观结构和皱缩率)的影响。对怀山药红外喷动床干燥曲线的数学模型拟合结果表明,Midilli模型R2最大(0.99989),RMSE和χ2最小(分别为0.00319和1.69872×10-5),最适合描述怀山药IRSBD动力学。对比不同干燥工艺发现,恒温干燥条件下,提高干燥温度有利于缩短干燥时间,降低能耗。阶段升温干燥能耗仅高于70℃恒温干燥,其干燥均匀性最好,样品总酚含量最高为(85.25±7.41)mg GAE/100 g DW,皱缩率及硬度最低,分别为(74.3±3.96)%和(24.95±7.41)N,且有良好的色泽。阶段降温干燥样品具有较高的平衡复水比和脆度,然而在干燥时间、能耗、均匀性及产品硬度、皱缩率和总酚含量方面没有显著优势。结论:阶段升温干燥是怀山药IRSBD更为理想的干燥工艺。研究结果可为IRSBD技术应用于农产品加工提供理论参考。

咖啡豆红外喷动床干燥对其粉末物性品质、干燥能耗及挥发性成分的影响

为获得高品质干燥咖啡豆,采用红外喷动床组合干燥技术对咖啡豆进行干燥处理,研究不同进口温度和进口风速对咖啡粉色泽、堆积密度、休止角、得粉率、持水能力和水溶性指数、微观结构、干燥能耗及挥发性成分的影响。结果表明,提高进口温度和进口风速可以加快干燥速率,缩短干燥时间,降低干燥能耗。采用顶空固相微萃取-气相色谱质谱联用共检测出7大类(酸类、酯类、醛类、醇类、酮类、杂环类及其他类)挥发性化合物,其中酸类、酯类、醇类、杂环类4类为咖啡豆主要挥发性化合物且含量较高。综合对比得出最佳干燥条件为进口温度75℃,进口风速7.5 m/s,在此条件下,L*值和堆积密度取得最大值,分别为106.59和0.65 g/mL,休止角取得最小值36.87°,得粉率、持水能力和水溶性指数取得最大值,分别为43.43%、5.4 g/g和41.27%,干燥能耗取得最小值336.53 kJ/g,形态结构保存较为完整,壁面光滑平整,检测到的挥发性成分种类最高达70种,含量为38 487.028 49 ng/g(以干基计),咖啡豆综合品质最佳。该研究可为红外喷动床干燥技术在咖啡豆干燥加工及工业化生产中的应用提供参考。

中试脉冲喷动床微波冻干山楂干燥特性与品质特性研究

该文针对传统冻干(conventional freeze-drying,CFD)存在的干燥周期长、能耗大及生产成本高等问题,探究中试脉冲喷动床微波冻干(pulse-spouted bed microwave freeze-drying,PSBMFD)山楂的干燥特性与品质特性,分析代替传统冻干进行商业化应用的可行性。以CFD山楂作为对比,研究了两者干燥时间、能耗、山楂品质及干燥均匀性等方面的差异。结果显示,和CFD相比,中试PSBMFD能耗降低72.49%,干燥周期减少62.39%,较好地保留山楂原有风味,所得山楂产品具有多孔结构和较高质构(硬度20.83 N);在水分含量、色差、收缩率方面,中试PSBMFD实现了山楂产品较高的均匀性(>90%);在营养保留方面,中试PSBMFD山楂具有较高的总酚含量[37.03 mg/g干基,以没食子酸当量(gallic acid equivalent,GAE)计]与抗氧化能力。该中试实验结果为PSBMFD商业化提供了有效的理论基础和技术支持。

肛肠熏洗剂在混合痔术后的应用

目的 探讨自拟中药方肛肠熏洗剂对混合痔患者术后疼痛及创面愈合的影响。方法 选取宁夏医科大学附属中医医院收治的肛肠科混合痔外剥内扎术后患者60例,随机分为2组,每组30例。对照组予以常规术后换药以及药物止痛,试验组在对照组的基础上联合肛肠熏洗剂熏洗治疗。2组患者治疗7 d后比较创面疼痛情况、肛缘水肿情况、创面渗液情况及临床疗效判定。结果 治疗后,试验组临床有效率明显高于对照组,差异有统计学意义(P<0.05)。治疗后,试验组术后创面水肿及渗液积分小于对照组,且术后1、3、5、7 d疼痛积分均低于对照组,差异均有统计学意义(P<0.05)。结论 混合痔术后常规换药以及药物止痛治疗联合肛肠熏洗剂熏洗坐浴临床效果确切,对于术后创口的分泌物有减少作用,能够缓解术后创面水肿和疼痛,促进伤口愈合,使患者症状体征得到有效缓解,加速患者康复。

A new method for identifying flow pattern of spouted fluidized bed by coupling Hilbert-Huang transform characteristics of differential pressure signals in different zones

On a cold spouted fluidized bed,this study compares the characteristic differences in intrinsic mode function(IMF)energy and Hilbert–Huang spectrum between the spout zone and annulus zone under different combinations of spouted gas and fluidized gas flow rates for five typical flow patterns.The energy distribution characteristics under different flow patterns are also analyzed.The Hilbert–Huang spectrum and IMF energy of pressure difference signals exhibit distinct variations in different zones as the flow pattern changes.Moreover,there exists a correlation between the energy in the middle-frequency range and the flow pattern.Leveraging the K-means algorithm,the middle-frequency range energy of IMFs in the spout zone and annulus zone is subjected to clustering analysis,leading to the identification of partition boundaries for each flow pattern.Based on this,a flow pattern identification method of spouted fluidized bed coupled with middle-frequency range energy in spout zone and annulus zone is proposed,which has very high identification accuracy.

四角切圆锅炉的二次风喷口结构优化及应用

300 MW发电机组配备的四角切圆锅炉在深度调峰工况下存在脱硝入口NOx值居高不下、锅炉两侧汽温偏差大、在高负荷工况下水冷壁存在较严重的高温腐蚀等一系列问题,经分析四角切圆锅炉结构特点及左右两侧屏式过热器、屏式再热器的壁温偏差及低负荷时二次风与炉膛压差等运行参数,判断为锅炉二次风配风性能差导致锅炉燃烧动力场偏离设计值。将部分二次风喷口面积局部缩小且辅助风喷口沿炉膛切圆方向偏转7.5°后,锅炉在深度调峰工况下主热、再热汽温分别提升13℃、9℃,左右两侧脱硝入口NOx值平均下降162 mg/m^(3),空预器入口氧量未发生降低,这表明优化的二次风喷口结构可有效提升锅炉性能。