褐煤锅炉中速磨热平衡计算若干问题的探讨

国内褐煤锅炉中速磨煤机制粉系统热平衡计算以DL/T 5145—2012《火力发电厂制粉系统设计计算技术规定》为主要依据。文章通过对比和分析,探讨了在标准执行过程中煤粉水分和磨煤机出口温度选取、系统散热损失、原煤温度及计入解冻热存在的取值和计算等问题,并提出了合理性建议。

影响熟料标准煤耗因素的定量分析

以国内主力窑型Φ4.8 m×72(74)m、配套5级双系列预热器、熟料产量6000 t/d、熟料标准煤耗100 kg/t为前提,对影响熟料标准煤耗的因素进行定量分析。影响因素有16项,主要因素有煤粉发热量、入窑生料温度、出C_(1)废气温度、出C_(1)氧气(O_(2))含量、出C_(1)一氧化碳(CO)含量、出C_(1)粉尘浓度、冷却机热回收效率、冷却机废气量、系统漏风、熟料形成热、熟料带走热、熟料产量等。文中列出了相关因素变化量对应的煤耗变化指标。

Theoretical calculation of equilibrium Mg isotope fractionation between silicate melt and its vapor

Isotope fractionation during the evaporation of silicate melt and condensation of vapor has been widely used to explain various isotope signals observed in lunar soils, cosmic spherules, calcium-aluminum-rich inclu- sions, and bulk compositions of planetary materials. During evaporation and condensation, the equilibrium isotope fractionation factor （α） between high-temperature silicate melt and vapor is a fundamental parameter that can con- strain the melt＇s isotopic compositions. However, equilib- rium a is difficult to calibrate experimentally. Here we used Mg as an example and calculated equilibrium Mg isotope fractionation in MgSiO3 and Mg2SiO4 melt-vapor systems based on first-principles molecular dynamics and the high- temperature approximation of the Bigeleisen-Mayer equation. We found that, at 2500 K, 625Mg values in the MgSiO3 and Mg2SiO4 melts were 0.141 ±0.004 and 0.143 ±0.003‰ more positive than in their respective vapors. The corresponding 626Mg values were 0.270 ± 0.008 and 0.274 ± 0.006‰ more positive than in vapors, respectively. The general α - T equations describing the equilibrium Mg α in MgSiO3 and Mg2SiO4 melt-vapor systems were： αMg（l）-Mg（g） = 1 ＋ 5.264×10^5/T^2 （1/m - 1/m＇） and αmg（l）-Mg（g） = 1 ＋ 5.340×10^5/T^2 （1/m - 1/m＇）, respectively, Where m is the mass of light isotope, ^25Mg or ^26Mg. These results offer a necessary parameter for mechanistic under- standing of Mg isotope fractionation during evaporation and condensation that commonly occurs during the early stages of planetary formation and evolution.

Heat balance of solar-soil source heat pump compound system

Based on the state-of-the-art studies of solar-soil source heat pump compound system, operation patterns of solar-soil compound system were analyzed, particularly the advantages of parallel operation pattern. It is found that parallel operation pattern is better for solar-soil compound system. Furthermore, the heat balance issue of solar-soil compound system was emphatically analyzed from four aspects, which were annual analysis of heating and cooling load, the heat exchange of ground heat exchanger, capacity determination of solar-assisted heat sottrce and heat balance calculation of solar-soil compound system. Moreover, annual rate of heat balance in a solar-soil source heat pump compound system was calculated with a case study. It is shown that the annual heat unbalance ratio is 19%, which is less than 20%. As a result, the practical solar-soil compound system can basically maintain the heat balance of soil.

Combustion and energy balance of aluminum holding furnace with bottom porous brick purging system

For acquiring the details in aluminum holding furnace with bottom porous brick purging system,efforts were performed to try to find out the potential optimal operation schemes.By adopting transient analysis scheme and constant boundary temperature,combustion in the furnace was investigated numerically using computational fluid dynamics(CFD).The predicted gas temperature shows good agreement with the measured results,and the predicted energy distribution of the furnace is consistent with that obtained from energy balance experiment,which confirms the reliability of the numerical solution.The results show that as the fuel-air mixture temperature rises up from 300 K to 500 K,the energy utilization of the furnace could increase from 34.55% to 37.14%.However,as the excess air coefficient increases from 1.0 to 1.4,energy utilization drops from 34.55% to 29.56%.Increasing the combustion temperature is the most effective way to improve the energy efficiency of the furnace.High reactant temperature and medium excess air coefficient are recommended for high operation performance,and keeping the furnace jamb sealed well for avoiding leakage has to be emphasized.

矿渣立磨系统配置设计研究

矿渣立磨粉磨工艺系统,以其技术先进、生产可靠、系统节能和经济环保等诸多优点,而被国内外工业生产广泛采用。结合中信重工机械股份有限公司设计并已成功运行的矿渣立磨工艺系统的设计配置进行研究。通过对该系统的物流平衡、气流平衡及热量平衡进行计算,得出该系统中关键设备,如热风炉、袋收尘器及排风机等的选型依据参数。