复合流化床低阶煤热解制备兰炭的工艺条件

以不同粒径范围的新疆准东煤为原料,在耦合下部流化床和上部输送床的复合流化床中热解制备兰炭,考察了热解温度、过量氧气系数、气化温度、煤颗粒停留时间等对热解产物分布和热解半焦性质的影响. 结果表明,随过量氧气系数、气化温度和颗粒平均停留时间增加,气体产率升高,半焦和焦油产率降低;半焦的比表面积随气化温度升高而增大,而随过量氧气系数增大先增大后减小. 当煤从下部流化床进料时,在过量氧气系数0.11、流化床气化温度850℃、输送床热解温度750℃、流化床内煤颗粒停留时间90 s的操作条件下,可制备出固定碳含量超过83%(w)、挥发分含量低于9%(w)的兰炭.     

多段分级转化流化床提升管速度场的研究

针对流化床煤气化过程中需要长气固接触时间和高固体浓度,开发了耦合灰熔聚流化床和提升管的多段分级转化流化床。为了研究多段分级转化流化床提升管中局部颗粒速度的径向、轴向分布,在不同的操作条件下,采用PV-6型颗粒速度测量仪在冷态实验装置中系统测定提升管内局部颗粒速度。实验结果表明:提升管中任何径向、轴向位置的颗粒速度随着操作气速的增大而增大,随循环量的增加而减小。操作条件对中心区颗粒速度变化的影响明显高于边壁区。颗粒的加速首先发生在提升管中心区域,然后向边壁区域扩展。颗粒速度径向分布的不均匀性沿轴向逐渐增大,并且受操作气速影响比较大。     

热解废水循环流化床焚烧工艺模拟研究

研究了煤热解分级利用多联产工艺产生的热解废水的循环流化床焚烧处理工艺。能量平衡计算结果表明,热解废水进入循环流化床燃烧炉,炉膛温度下降7.6℃。数值模拟了热解废水喷入流化床燃烧炉不同位置的4种工况,各工况炉膛出口温度均下降约16℃,2种计算方法虽有一定偏差,但误差在工程可控范围内。研究结果表明,热解废水送入循环流化床燃烧炉内焚烧的方案可行,能实现热解废水零排放。     

流化床中包覆燃料颗粒的制备及应用

包覆燃料颗粒由燃料核芯、疏松热解炭层、内致密热解炭层、碳化硅层和外致密热解炭层组成.本工作设计建造了不同直径和结构的流化床沉积炉系统,探讨了流化床的结构、气体流量对颗粒流化状态的影响采用化学气相沉积方法生产出的包覆燃料颗粒不仅应用于我国10 MW高温气冷堆燃料元件的制备,而且探讨了包覆燃料颗粒的其它应用.     

稻草及热解半焦颗粒流化特性

研究了稻草及不同温度热解半焦颗粒在内径100 mm、高1000 mm的有机玻璃流化床中的流化特性. 结果表明,稻草颗粒无法单独流化,而其热解半焦颗粒可单独流化;半焦颗粒的最小流化速度随粒径增大而增大,与床层高度无关,筛分粒径为0.45~0.9, 0.18~0.45, 0.125~0.18 mm的半焦颗粒的最小流化速度分别为0.19, 0.16, 0.14 m/s;300~550℃温度范围内稻草热解半焦颗粒的流化特性无明显区别;半焦与稻草颗粒混合流化时,稻草颗粒不大于20%(w)时床层有较好的流化质量,混合颗粒的最小流化速度都随混合颗粒中稻草含量增大而增大.     

双出口分级气流床气化炉内颗粒速度和浓度分布

煤炭分级利用是煤炭高效低碳利用的主要途径之一,提出一种同时制备热解气和合成气的分级气流床气化炉,炉体上部为煤热解室,下部为煤焦气化室。采用PV6M颗粒测速仪对气化炉内固体颗粒的速度和浓度分布进行测量,并运用CFD软件对气化炉内气固两相流场进行模拟。结果表明,在射流发展区域与射流碰撞后的折射流发展区域,颗粒速度较高;边壁区域颗粒速度较低且出现回流现象。在惯性和气流曳力作用下,热解室内大部分颗粒自流进入气化室。热解室上部径向颗粒浓度中心高边壁低;气化室下部径向颗粒浓度中心低边壁高。热解室与气化室进气量比、喷嘴角度及颗粒直径等对气化炉出口颗粒流出量分配有重要的影响。热解室进气量增大,颗粒从热解室出口流出占比先减小后增大;热解喷嘴偏转角与颗粒Stokes数增大,颗粒从热解室出口流出占比减小。     

双出口分级气流床气化炉内颗粒速度和浓度分布

煤炭分级利用是煤炭高效低碳利用的主要途径之一,提出一种同时制备热解气和合成气的分级气流床气化炉,炉体上部为煤热解室,下部为煤焦气化室。采用PV6M颗粒测速仪对气化炉内固体颗粒的速度和浓度分布进行测量,并运用CFD软件对气化炉内气固两相流场进行模拟。结果表明,在射流发展区域与射流碰撞后的折射流发展区域,颗粒速度较高;边壁区域颗粒速度较低且出现回流现象。在惯性和气流曳力作用下,热解室内大部分颗粒自流进入气化室。热解室上部径向颗粒浓度中心高边壁低;气化室下部径向颗粒浓度中心低边壁高。热解室与气化室进气量比、喷嘴角度及颗粒直径等对气化炉出口颗粒流出量分配有重要的影响。热解室进气量增大,颗粒从热解室出口流出占比先减小后增大;热解喷嘴偏转角与颗粒Stokes数增大,颗粒从热解室出口流出占比减小。     

50 MW循环流化床煤炭分级转化多联产技术开发

为了进一步推进煤炭热解分级转化多联产技术工业化应用,实现煤炭清洁高效资源化利用,通过试验研究和理论分析相结合的方法,利用1 MW流化床热解分级转化工业示范装置对煤炭热解分级转化产物的释放及其组分分布特性进行研究,分析了温度、煤种特性对挥发产物煤气产率、焦油产率、煤气组分、煤气热值等的影响,并对煤炭热解-燃烧双流化床协同耦合运行调控特性进行研究,最后以获得的1 MW流化床热解分级转化过程的相关产物转化特性参数及运行特性参数为基础,进行了50 MW循环流化床煤热解燃烧多联产工艺装置设计开发。结果表明,该装置煤气主要成分CH_4与H_2含量分别高达41.97%、28.32%,设计煤种条件下焦油产量3.16 t/h,煤气产量35 262 Nm~3/h,煤气热值达到26.7 MJ/Nm~3,焦油提取率达到90%以上,实现了较高的煤气热值与焦油回收率,为煤炭热解分级转化多联产技术工业化应用提供借鉴。     

低阶煤热解-气化-燃烧TBCFB系统模拟及优化

三塔式循环流化床（TBCFB）是基于低阶煤分质转化利用理念开发的新型工艺系统,包含热解、气化及燃烧三个主反应器。提出了采用半焦颗粒代替石英砂作为循环热载体的新工艺,并使用Aspen Plus建立了基于半焦颗粒的TBCFB系统模拟流程,寻求系统内物料转化和能量利用的适宜操作条件。结果表明,只需燃烧40%的热解半焦,即可满足低阶煤在600℃热解和60%的热解半焦在800.9℃进行水蒸气气化所需热量;与石英砂或高温灰相比,利用热容较高的半焦颗粒作为循环介质可以显著降低热载体循环量,与原煤质量比仅为5.5。综合气化产物组成、低热值和冷煤气效率等指标,适宜的水蒸气与反应半焦质量比为1.5。上述模拟结果对半焦循环TBCFB新技术的工业应用具有一定指导意义。     

低阶煤热解-气化-燃烧TBCFB系统模拟及优化

三塔式循环流化床(TBCFB)是基于低阶煤分质转化利用理念开发的新型工艺系统,包含热解、气化及燃烧三个主反应器。提出了采用半焦颗粒代替石英砂作为循环热载体的新工艺,并使用Aspen Plus建立了基于半焦颗粒的TBCFB系统模拟流程,寻求系统内物料转化和能量利用的适宜操作条件。结果表明,只需燃烧40%的热解半焦,即可满足低阶煤在600℃热解和60%的热解半焦在800.9℃进行水蒸气气化所需热量;与石英砂或高温灰相比,利用热容较高的半焦颗粒作为循环介质可以显著降低热载体循环量,与原煤质量比仅为5.5。综合气化产物组成、低热值和冷煤气效率等指标,适宜的水蒸气与反应半焦质量比为1.5。上述模拟结果对半焦循环TBCFB新技术的工业应用具有一定指导意义。     

Entrainment of coal particles in a gas fluidized bed

Entrainment from an air fluidized bed of coal particles in a 14.5 cm-ID column has been studied. The effects of gas velocity and mean particle size on the transport disengaging height(TDH) and entrainment rate have been determined The entrainment rate increased with the increase in the fluidizing air velocity but decreased with increase in the mean particle size and the column height above the fluidized bed The date of entrainment rate and the TDH have been correlated in terms of Froude and Archimedes numbers.     

Effect of cohesive powders on the elutriation of particles from a fluid bed

The elutriation of fine particles (Group C or A particles in Geldart's classification) from a fluid bed of mixed fine and coarse particles is investigated in a steady state. Al(OH)₃ and alumina and TiO₂ powder of 0.5- were used as fines. FCC, alumina, Al(OH)₃, limestone, silica sand, SiC particles of 44- were used as coarse particles. The paper investigates the effect on the elutriation rate constant of both fine powders and coarse particles (i) of the weight fraction of Geldart C powders in the bed, (ii) of the superficial gas velocity, and (iii) of the size of C powder and size of coarse particles in the bed.The elutriation rate constant of group C or group A particles is not only affected by the properties of the elutriated powders or particles and gas velocity, but also by both the weight fraction and size of C powder in the bed. This finding differs from the elutriation result of A or B particles from a fluidized bed.     

Bed Expansion and Particle Classification in Liquid Fluidized Beds with Structured Internals

The inclusion of a structured packing as internal in a liquid‐solid fluidized bed allows expansion of the liquid velocity operation range before elutriation, promoting the liquid solid contact and mixing. The bed expansion of liquid‐solid fluidized beds provided with structured packing as internals is examined, for solids denser than the liquid phase and within a wide range of operating conditions. A correlation to estimate the bed expansion in liquid‐solid fluidized beds using structured packing as internals is developed. In addition, the feasibility of employing structured packing as internals for favoring classification of different density particles is demonstrated by analyzing the mass elutriated from the column at different liquid velocities for single particles or binary mixtures.     

Optical image analysis of fine coal particles as an aid in optimizing combustion in a fluidized bed

The performance of a fluidized bed combustor is adversely affected by the entrainment of fine coal and char particles. The size distribution of the entrained particles is an indicator of the combustor's performance. Size analysis data may be helpful for optimizing the operating conditions.

An optical image analysis system (TAS, Leitz) was used to analyze the size distribution of char particles elutriated from a small fluidized bed after one single pass. The TAS system discriminates between highly reflecting char particles and low-reflectance ash. The maximum size of the chars produced in these experiments was about 50 μm, almost independent of the type of coal.     

Size distribution of the particles entrained from fluidized beds: Gas humidity effects

Experimental results obtained with 65 μm sand and 69 μm cracking catalyst showed that the smallest particles were not the most easily elutriated from fluidized beds of mixed size particles. This is in contradiction with the assumption applied to existing models for the prediction of the flux and size distribution of particles elutriated from a fluidized bed. The smallest particles cannot be removed by elutriation from a mixture of particles of various sizes. The smallest particles may be agglomerated with larger particles. Increasing the gas humidity, which would presumably reduce electrostatic effects, did not greatly affect the size distribution of the elutriated particles.     

Hydrodynamic behavior of a liquid-solid fluidized-bed reactor for the bioconversion of coal particles to liquid products

A predictive mathematical model based on particle convection and dispersion is presented for a liquid fluidized bed of coal particles. The numerical representation can follow transient behavior of liquid fluidized beds that contain a defined particle-size distribution. The calculations exhibited excellent agreement when compared to experimental transient pressure-drop data from a column containing particles of Illinois No. 6 bituminous coal in the size range of 20–120 μm. In addition, the model was used to simulate the effect of periodic (hourly) liquid velocity step changes on elutriation of small particles from a given particle-size distribution of 34.5–75.5 μm. For the situation tested, the calculations indicate that (a) the column does not reach a steady state between velocity changes and (b) that higher initial particle elutriation rates decay to lower values until no more particles elutriate from the column.     

IMPEDIMENT TO INCIPIENT FLUIDIZATION IN WET BEDS OF POROUS NONSPHERICAL PARTICLES

Fluidized-bed units are efficiently and advantageously employed for drying various wet and sticky particulate materials provided that the bed of such materials can be kept under a fluidized condition. The effect was explored with the incremental addition of water to the bed of nonspherical, porous particles of ceramsite and lignite fluidized with wet air. The limiting fluidization-defluidization point was determined by experiments in a cold model fluidized bed contained in a transparent glass column using wet and dry particles. On the basis of the data amassed, an empirical correlation was developed. This relationship makes it possible to predict the dimensionless excess gas velocity that keeps the wet bed fluidized, as a function of the relative amount of moisture in the bed and the dimensionless particle size.     

IMPEDIMENT TO INCIPIENT FLUIDIZATION IN WET BEDS OF POROUS NONSPHERICAL PARTICLES

Fluidized-bed units are efficiently and advantageously employed for drying various wet and sticky particulate materials provided that the bed of such materials can be kept under a fluidized condition. The effect was explored with the incremental addition of water to the bed of nonspherical, porous particles of ceramsite and lignite fluidized with wet air. The limiting fluidization-defluidization point was determined by experiments in a cold model fluidized bed contained in a transparent glass column using wet and dry particles. On the basis of the data amassed, an empirical correlation was developed. This relationship makes it possible to predict the dimensionless excess gas velocity that keeps the wet bed fluidized, as a function of the relative amount of moisture in the bed and the dimensionless particle size.     

Separation of trace quantities of jetsam in a counter-current fluidized cascade

Data are presented on separations involving systems containing small concentrations of iron particles in sand, and of salt particles in activated carbon, in a bottom-driven 3.66 metre long fluidized cascade. At each fluidization velocity a maximum beneficiation ratio was found at a particular baffle chain velocity. The optimal baffle chain velocity increased with increasing fluidization velocity, and it was larger with 26 mm deep baffles than with 13 mm baffles. An analysis based on a theoretical model led to the conclusion that segregation kinetics are enhanced by the motion of the baffles just above the grid.     

流态化法进行粉体粒度分级实验研究

流化分级是一种有效的粒度分级手段。颗粒群的悬浮速度是流化分级过程中一个重要的操作参数 ,直接影响到分级效率的高低。实验以 11个粒径范围的颗粒群为研究对象 ,在流化床中对颗粒群的悬浮速度进行了测定和研究 ,考察了平均粒径、床层空隙率等因素对颗粒群悬浮速度的影响 ,得出了颗粒群的悬浮速度与颗粒群平均粒径及床层空隙率间的关系曲线 ,为提高粉粒体流化分级的分级效率提供了实验依据