共查询到20条相似文献,搜索用时 250 毫秒
1.
通过分析煤粉的矿物结构可知,研磨后煤粉中的矿物可分为独立矿物和细分散状矿物两种类型.煤粉燃烧后大部分独立矿物形成飞灰中的玻璃微珠,而细分散矿物形成硅铝质微珠和铁质微珠.此外,由飞灰中未燃碳的结构分析可知,粉煤灰中未燃尽的碳大部分以单体形式存在于粉煤灰中.粉煤灰作为一种新的资源,若将其中的未燃碳通过分选分离出来,并进一步分选提纯,获得高质量、高价值的产品,则可大量节约能源.另外,粉煤灰的含碳量越低,资源化程度越高,价值越大. 相似文献
2.
一次风速度对煤颗粒群着火特性影响的实验研究 总被引:1,自引:0,他引:1
利用Hencken型平面携带流反应器,研究了一次风速度对两种高挥发分褐煤和一种贫煤射流着火特性的影响.实验结果表明,低雷诺数(Re=878)条件下,贫煤煤粉气流先后发生外层单颗粒着火燃烧和内层颗粒群着火燃烧,煤粉颗粒着火和燃烧轨迹十分规则.但在高雷诺数(Re=4,392)条件下,贫煤煤粉气流更难形成群燃火焰,呈现出暗红色火焰.随着一次风速度的增加,尽管煤粉颗粒的停留时间减小,但湍流强度的增加使颗粒加热速率以及挥发分析出的强化作用占主导,使得煤粉气流的着火距离减小.此外,群燃火焰在挥发分聚集到一定程度后产生,是颗粒群燃烧的特有现象,而煤种挥发分含量的增加和有效聚集有利于群燃火焰的出现. 相似文献
3.
4.
5.
6.
针对某循环流化床锅炉运行中存在返料系统与旋风分离器效果差等问题,采用CPFD数值模拟法讨论床料粒径大小和给煤偏置的设置对锅炉稳燃及旋风分离器失衡问题的影响.结果表明:颗粒粒径过大时炉膛内易结渣、流化效果不良且内循环不佳,无法形成良好的稀密相分布.同时煤粉粒径对炉内燃烧影响显著,因煤粉对床料颗粒夹带量不同,粒径越大的床料颗粒煤粉对其夹带能力越小,导致上部稀相区温度偏高.研究得出调整给煤设置参数是保证锅炉稳燃,同时解决左右旋风分离器不平衡的有效措施.其中最佳给煤偏置为左、中、右分别为1.93、2.93和3.93 kg/s. 相似文献
7.
填充床储能是一种很有发展前景的热能储存技术,它具有可降低存储成本和提高太阳能热系统开发效率等优点。研究人员多采用球形的储能单元,而圆柱体在储能填充床换热中有其独特的优势,因此基于圆柱形和拉西环形两种柱状颗粒,建立了一种潜热储能填充床的三维模型,采用数值模拟的方法分别研究两种柱状颗粒组成的填充床的储能性能,分析了储能填充床的直径比对其性能的影响。研究表明,填充床直径比越大,其储能性能越好。同时研究了圆柱形储能单元高度和拉西环形储能单元孔径对储能性能的影响。结果表明,在研究范围内,由高度为3 mm的圆柱形储能单元和孔半径1.50 mm的储能单元分别组成的填充床储能速率最高。 相似文献
8.
以获取准确的煤粉燃烬率,掌握煤粉加热炉燃烧状态为研究目的,提出基于数学建模的煤粉加热炉燃烧状态模拟方法。通过构建连续性方程、能量方程、动量方程、湍动能耗散率方程以及湍动能方程,描述煤粉加热炉内煤粉的燃烧过程。将煤粒在加热炉中的燃烧过程分为两个阶段,第一个阶段为热解挥发阶段,第二个阶段为残碳氧化阶段,依据双挥发反应模型构建热解挥发模型,对原煤热解挥发过程进行模拟。设置边界条件,进行实验研究,结果表明:颗粒粒径与煤粉燃烬率之间呈反比关系,温度与煤粉燃烬度之间成正比关系。所提方法的模拟结果与实际结果之间的拟合度较高,说明其模拟结果更加准确,可以促进工业加热中煤粉加热炉燃烧状态优化。 相似文献
9.
10.
融合一种新式燃烧理念的多孔介质发动机,能够实现发动机的均质、高效和稳定燃烧.为加深对两种形式多孔介质发动机燃用液体燃料着火特性的了解及探讨影响其各自压燃着火的因素,用改进的KIVA-3V对两种形式的多孔介质发动机燃用异辛烷的工作过程进行了模拟,并讨论了多孔介质初始温度、多孔介质结构对两种形式发动机压燃着火的影响.计算结果表明,压缩比一定时,多孔介质初始温度是决定两种形式多孔介质发动机能否实现压燃着火的重要因素;与永久性接触型发动机相比,在较低的多孔介质初始温度下,即可保证周期性接触型发动机实现压燃着火;多孔介质结构通过改变多孔介质内气固两相换热及弥散作用影响两种形式多孔介质发动机的压燃着火. 相似文献
11.
《能源学会志》2020,93(2):679-694
The catalytic behavior of alkali vapor on unburned pulverized coal (UPC) prepared from bituminous coal, anthracite, semi coke and coke have been investigated. Experiment results show that the alkali metal vapor has catalytic effect on the gasification reaction of UPC. The catalytic effect of coke UPC is the most obvious, followed by anthracite UPC and bituminous coal UPC. Semi coke UPC is the least catalyzed by alkali metals but its gasification reactivity is the best. As the concentration of alkali metal vapor increases, the alkali metal content adsorbed by UPC increases, and there may be a phenomenon of saturated adsorption. The amount of alkali metal adsorbed is between 2% and 6%. AUPC has the highest ability to adsorb alkali metals, and SUPC is the weakest, which may be related to the minerals (CaO, Al2O3) in the coal ash. Changes in stomatal parameters are not the main factors affecting the catalytic effect. The results of X-ray diffraction experiments show that alkali metal aluminosilicate exists in the ash of coal after adsorption of alkali metal, and the average stack height of carbon atoms decreases significantly. The alkali metal catalytic gasification reaction is mainly achieved by destroying the carbon basic structural unit. The alkali metal nepheline and the interlayer compound may be the main catalytic substances, and the destructive ability of alkali intercalation is obviously stronger than that of alkali nepheline. The catalytic mechanism of alkali metals on unburned coal and the destruction mechanism of alkali metals on carbon crystals were discussed. It can provide reference for reducing alkali metal corrosion on coke and improving pulverized coal utilization rate. 相似文献
12.
Masashi Nishizawa Takayuki Morito Makoto Matsuura Hideyuki Aoki Takatoshi Miura 《亚洲传热研究》1996,25(4):238-253
The steam outflow rate and temperature distribution in a packed bed of coal particles were measured and compared with the results of a numerical analysis in order to determine the steam flow behavior in a coke oven chamber. The moisture-controlled and size-graded pulverized coal particles were packed in a cylindrical stainless steel vessel with steam flow pipes at both ends of the vessel. The upper end of the vessel was heated from 293 K to 653 K with constant heating rate of 3 K/min and maintained at 653 K. The numerical analysis, which was based on a new concept of the evaporation/condensation behavior, was conducted in an axisymmetrical coordinate system. The unsteady heat conduction equation in the solid phase and the mass, momentum, and energy conservation equations in the gas phase were solved simultaneously. The condensed water in the bed is assumed to be static and a part of the solid phase under the assumption of local thermal equilibrium. Estimated results on the temperature distribution and the steam outflow rate are quantitatively in good agreement with experimental results and the model performance is verified. The steam flow toward the heated side decreases the heat transfer rate to the inside, while the flow toward the insulated side increases it. © 1997 Scripta Technica, Inc Heat Trans Jpn Res 25(4): 238–253, 1996 相似文献
13.
14.
15.
16.
流化床-煤粉复合燃烧锅炉的炉膛传热计算方法 总被引:2,自引:2,他引:0
针对流化床-煤粉复合燃烧锅炉的特点,在综合考虑流化床、火焰和受热面之间换热的基础上,推导了流化床-煤粉复合燃烧锅炉炉膛传热计算的基本方程,得到了复合燃烧锅炉炉膛传热计算的零维模型半径验法。以某75t/h树皮流化床-煤粉复合燃烧锅炉为例,进行了炉膛传热计算。图1表6参5 相似文献
17.
18.
19.