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白灰是冶金行业中的重要辅助原料。某公司梁式石灰窑改为气烧窑后,生产过程中存在窑内频繁蓬料及NOx超标问题。若减少天然气用量,生烧比例升高,影响白灰质量;提高天然气用量,则造成排放超标;上梁下方易出现严重蓬料,部分区域下料停滞,导致生产无法持续进行,不得不停窑后在窑壁开孔人工处理结瘤。上述问题严重制约着石灰窑的生产顺稳。以燃烧机理分析为基础、窑内落料过程模拟为切入点,通过对梁式石灰窑煅烧技术的优化改进、优化调整一二次风配比、南北侧区域烧嘴燃气量调整以及燃烧梁增加窑中心供风改造,显著提高了窑内温度场的均匀性,在降低NOx排放量的同时,白灰质量也得以不断提高。 相似文献
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通过对两座100m^3气焦混烧石灰窑的供风系统和出灰系统的改造及炉顶废气回收、除尘、助燃空气预热等改造,对稳定炉况、提高石灰产质量、降低能耗及操作人员的劳动强度都起到了重要的作用。解决了石灰窑气中粉尘对周边环境的污染,以达到节能降耗提高经济效益及社会效益的目的。 相似文献
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为提高并流蓄热式双膛石灰窑生产中石灰石的活性和降低能耗。以200 t/d的双膛石灰窑为研究对象,对采用自定义函数和自定义标量方程编译的局部非热平衡模型和石灰石化学反应模型添加前后的燃料、CO_2、O_2的质量分数分布及温度分布做了对比分析。结果表明:添加前后的燃料、O_2和CO_2质量分数分布趋势一致,添加前燃料和O_2的质量分数比添加后高,CO_2质量分数比添加后低;添加后煅烧带烟气温度分布为1 188~1 612 K,石灰石固体颗粒的温度为1 107~1 398 K,符合设计煅烧温度范围1 123~1 423 K;出口排烟和出料的模拟平均温度与同工况实测值相比,误差在15%以内;石灰窑煅烧窑体的预热带、煅烧带和冷却带的分布高度分别为3.5、6和4.5 m,与设计值基本吻合;添加后获得了设计工况下煅烧窑体中的碳酸钙累积分解率分布图,出窑时的分解率为0.961 5。 相似文献
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以某300 t/d气烧石灰环形竖窑为研究对象,为获得其最佳运行工况并解决窑中煅烧温度分布不均匀的问题,采用数值模拟方法进行研究。将石灰石视为多孔介质、采用自定义标量方程(UDS)编译局部非热平衡模型、窑体中碳酸钙分解反应以源项的形式通过自定义函数(UDF)添加到整个反应过程中,获得的窑体中排烟和出料的模拟平均温度与实测值误差很小(15%),且石灰石固体和烟气的两相温度三带分布图符合实际煅烧过程的温度分布,验证了模拟计算的合理性;在此基础上,对燃料流量、助燃风流量和冷却风流量3参数进行单参数分别分析和正交试验分析。研究表明:燃料流量和冷却风流量对窑体温度场影响较强,而助燃风流量的影响较弱;石灰窑的最佳运行工况为燃料流量、助燃风流量和冷却风流量分别取0.152 4、0.106 7和0.174 6 kg/s。 相似文献
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Sverine Gomes Nathalie Trannoy Philippe Grossel Franoise Depasse Claudine Bainier Daniel Charraut 《International Journal of Thermal Sciences》2001,40(11):1794
The used Scanning Thermal Microscopy (SThM) probe is a thin Pt resistance wire acting as a heat source and as a detector simultaneously. Its energetic balance is investigated by the study of the temperature profile along the probe. A theoretical approach of the measurement, based on this investigation, is then proposed. Simulations with this modelling are shown to predict how the heat, electrically produced in the probe, is dissipated in the probe-sample system. In particular, it is shown that the steady-state of conduction losses to the thermal element support varies versus the thermal conductivity of the sample and can lead to bad interpretations of the measurement. 相似文献
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For optimum design of borehole thermal energy storage (BTES) and ground sources heat pump (GSHP) applications, determination of underground thermal properties is required. The design and economic feasibility (number and depth of boreholes) of these systems need thermal conductivity of geological structure, λ (W m?1 K?1), and thermal resistance of ground heat exchanger, R (K W?1 m). Thermal properties measured in laboratory experiments do not coincide with data of in situ conditions. Therefore, in situ thermal response test equipment has been developed and used in Canada, England, Germany, Norway, U.K., U.S.A. and Sweden to ensure precise designing of BTES systems. This paper describes the results and evaluations of the Adana continual thermal response test measurements. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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After turning on a room heating system (e.g. central heating) a thermal transient phenomenon takes place on the wall–room system, until it reaches a final thermal equilibrium state. The temperature profiles on the wall cross‐section, starting from an initial profile, corresponding to the initial thermal equilibrium state, come gradually through successive intermediate temperature profiles, to a final temperature profile corresponding to the final thermal equilibrium state. These intermediate, nonlinear and time‐dependent temperature profiles characterize the wall thermal transient state and describe the dynamic thermal behaviour of the wall–room system. The mass of the air in the room is negligible, compared to the mass of the surrounding walls, so the dynamic behaviour of the room–wall system is imposed by the corresponding thermal dynamic behaviour of the walls. The influence of this thermal transient state is important for the room heating behaviour because it acts as a thermal flywheel attenuating and smoothing the room temperature variations. In the present work, using the integral method, analytical expressions yielding the temperature profiles, and the duration of the transient state as a function of thermal and structural characteristics have been developed. Conclusions were drawn on the dynamic thermal behaviour of the room–wall system. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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随着新能源汽车的广泛使用,动力锂离子电池的热安全性问题日益突出。本文以Bernardi生热机理为基础,耦合不同物理量,分别从电化学-热耦合模型、电-热耦合模型和热滥用模型来介绍单体电池的热特性。由于电池能量密度的增加与行驶工况复杂程度的提高,动力锂离子电池容易发生热量堆积,甚至造成热失控,对此,文中梳理了商用动力电池包的常用冷却方式。最后,根据对影响电池模组安全性的热失控蔓延机理及实测结果,介绍了阻断单体及基本模块热失控传播的有效方法。 相似文献
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A mobile thermal battery resembling a solar receiver: Innovative design and performance assessment 下载免费PDF全文
An innovative design of a mobile thermal battery resembling the solar receiver is presented. A ternary salt mixture consisting of 52% KNO3, 18% NaNO3, and 30% LiNO3 by wt% is used as the thermal energy storing medium inside the thermal battery. Since the thermal conductivity of the ternary salt mixture is low, aluminum meshes are introduced to create a thermal conduction tree inside the thermal energy storing medium. The actual field data are used in the simulations to resemble the solar irradiation emanating from the parabolic trough and focusing onto the thermal battery outer surface. To improve the uniform heating at the outer surface, the thermal battery rotation along the centerline of the trough is considered. The temperature parameter is introduced to assess the uniform‐like temperature distribution inside the ternary salt mixture. It is found that the use of aluminum meshes improves the heat diffusion in the phase change material of the ternary salt mixture; in which case, it acts like a thermal conduction tree inside the thermal battery. The rotation of the thermal battery results in uniform‐like temperature distribution across the thermal battery cross section and suppresses the excessive temperature rise because of the local heating in the close region of the thermal battery outer surface. 相似文献
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A model study for cyclic thermal loading and thermal performance of a thermoelectric generator 下载免费PDF全文
Thermal cyclic loading influences the life cycle of the thermoelectric device pins because of the thermal stress developed in the pins. Although thermal efficiency improves for different geometric configurations of the device pins, development of thermal stresses limit the selection of pin geometry in practical applications, particularly under cyclic thermal loading. Consequently, in the present study, thermal stress analysis of thermoelectric pins under cyclic thermal loading is carried out. The influence of thermoelectric pin geometry on the stress levels is examined when the device is subjected to the thermal cyclic loading. The predictions of thermal stress distribution are validated with the data presented in the open literature. It is found that pin geometric configuration has a significant effect on the stress levels developed in the pin when subjected to cyclic thermal loading. The pin configuration RA = 1 (parallel pins) results in the minimum value of the maximum von Mises stress in the pins as compared to that corresponding to other configurations. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Rayleigh waves in a half-space exhibiting generalized thermoelastic properties based on Green-Lindsay (G-L), Lord-Shulman (L-S), and classical dynamical coupled (C-D) theories are discussed. The phase velocity of Rayleigh waves in the previous three different theories has been obtained. A comparison is carried out between the phase velocities of Rayleigh waves, displacements, stresses, and temperature as calculated from the different theories of generalized thermoelasticity. The C-D theory is recovered as a special case. It appears, in particular, that the results obtained from G-L theory tend to those of L-S theory as the values of the two relaxation times become closer to each other. The second relaxation time is well pronounced when it becomes larger than the first one. Furthermore, it is found that the thermal relaxation times decrease the speed of the elastic waves and modify the phase velocities of the Rayleigh waves. The results obtained and the conclusions drawn are discussed numerically and illustrated graphically. Relevant results of previous investigations are deduced as special cases. 相似文献