An analysis approach of mass and energy balance in a dual-reactor circulating fluidized bed system

An analysis approach considering gas-solids hydrodynamics,reaction kinetics and reacting species nonuniformity together in a dual-reactor system is presented for better understanding its mass and energy balance.It was achieved by a 3-dimensional comprehensive hydrodynamics and reaction model for the dual-reactor system,which was developed from the successfully verified 3-dimensional comprehensive combustion model for one circulating fluidized bed(CFB)system(Xu and Cheng,2019).The developed model and analysis approach was successfully used on a 1 MW circulating fluidized bed–bubbling fluidized bed(CFB-BFB)dual-reactor system.Results showed the sensible and chemical energy between two reactors as well as the energy distributions in each reactor were balanced and they agreed well with the experimental measurements.The analysis approach indicated energy balance had a close relationship with the mass transfer in the CFB-BFB dual-reactor system.It may be applied in a design and operation optimization for a dual-reactor system.

Surface energy balance on the Antarctic plateau as measured with an automatic weather station during 2014

AWS data during 2014 collected at PANDA-N station, on the East Antarctic Plateau, are analysed. Net Short Wave Radiation(QSWR), net Long Wave Radiation(QLWR), sensible(QH), latent(QL) and subsurface or ground(QG) heat fluxes are computed. Annual averages for QSWR, QLWR, QH, QL and QG of 19.65,-49.16, 26.40,-0.77 and 3.86 W·m-2 were derived based on an albedo value of 0.8. QSWR and QH are the major sources of heat gain to the surface and QLWR is the major component of heat loss from the surface. An i terative method is used to estimate surface temperature in this paper;surface temperature of snow/ice is gradually increased or decreased, thereby changing longwave radiation, sensible, latent and subsurface heat fluxes, so that the net energy balance becomes zero. Mass loss due to sublimation at PANDA-N station for 2014 is estimated to be 12.18 mm w.e.·a-1;and mass gain due to water vapour deposition is estimated to be 3.58 mm w.e.·a-1. Thus the net mass loss due to sublimation/deposition is 8.6 mm w.e.·a-1. This study computes surface energy fluxes using a model, instead of direct measurements. Also there are missing data especially for wind speed, though 2 m air temperature data is almost continuously available throughout the year. The uncertainties of albedo, wind speed and turbulent fluxes cause the most probable error in monthly values of QLWR, QH, QL, QG and surface temperature of about ±4%, ±20%, ±50%, ±11% and ±0.74 K respectively.

Glacier mass balance in High Mountain Asia inferred from a GRACE release-6 gravity solution for the period 2002–2016

We provide estimates of glacier mass changes in the High Mountain Asia (HMA) area from April2002 to August 2016 by employing a new version of gravity solutions of the Gravity Recovery and ClimateExperiment (GRACE) twin-satellite mission. We find a total mass loss trend of the HMA glaciers at a rateof –22.17 (±1.96) Gt/a. The largest mass loss rates of –7.02 (±0.94) and –6.73 (±0.78) Gt/a are found forthe glaciers in Nyainqentanglha Mountains and Eastern Himalayas, respectively. Although most glaciers inthe HMA area show a mass loss, we find a small glacier mass gain of 1.19 (±0.55) and 0.77 (±0.37) Gt/a inKarakoram Mountains and Western Kunlun Mountains, respectively. There is also a nearly zero massbalance in Pamirs. Our estimates of glacier mass change trends confirm previous results from the analysisof altimetry data of the ICESat (ICE, Cloud and Land Elevation Satellite) and ASTER (AdvancedSpaceborne Thermal Emission and Reflection Radiometer) DEM (Digital Elevation Model) satellites inmost of the selected glacier areas. However, they largely differ to previous GRACE-based studies which weattribute to our different post-processing techniques of the newer GRACE data. In addition, we explicitlyshow regional mass change features for both the interannual glacier mass changes and the 14-a averagedseasonal glacier mass changes. These changes can be explained in parts by total net precipitation (netsnowfall and net rainfall) and net snowfall, but mostly by total net radiation energy when compared to datafrom the ERA5-Land meteorological reanalysis. Moreover, nearly all the non-trend interannual masschanges and most seasonal mass changes can be explained by the total net radiation energy data. The massloss trends could be partly related to a heat effect due to increased net rainfall in Tianshan Mountains, QilianMountains, Nyainqentanglha Mountains and Eastern Himalayas. Our new results for the glacier mass changein this study could help improve the understanding of glacier variation in the HMA area and contribute tothe study of global change. They could also serve the utilization of water resources there and in neighboringareas.

The mass-balance characteristics and sensitivities to climate variables of Laohugou Glacier No.12,western Qilian Mountains,China

Due to global warming, glaciers on the Tibetan Plateau(TP) are experiencing widespread shrinkage; however, the mechanisms controlling glacier variations across the TP are still rather unclear, especially on the northeastern TP. In this study, a physically based, distributed surface-energy and mass-balance model was used to simulate glacier mass balance forced by meteorological data. The model was applied to Laohugou No. 12 Glacier, western Qilian Mountains, China, during2010~2012. The simulated albedo and mass balance were validated and calibrated by in situ measurements. The simulated annual glacier-wide mass balances were-385 mm water equivalent(w.e.) in 2010/2011 and-232 mm w.e. in 2011/2012,respectively. The mean equilibrium-line altitude(ELA) was 5,015 m a.s.l., during 2010~2012, which ascended by 215 m compared to that in the 1970 s. The mean accumulation area ratio(AAR) was 39% during the two years. Climatic-sensitivity experiments indicated that the change of glacier mass balance resulting from a 1.5 °C increase in air temperature could be offset by a 30% increase in annual precipitation. The glacier mass balance varied linearly with precipitation, at a rate of130 mm w.e. per 10% change in total precipitation.

Coupled heat/mass-balance model for analyzing correlation between excess AlF_3 concentration and aluminum electrolyte temperature

The influence of aluminum electrolyte component on its temperature is an important issue within the field of aluminum reduction with pre-baked cells. The characteristic correlation between excess AlF3 concentration and aluminum electrolyte temperature was explored through the modeling of heat and mass transfer processes in industrial pre-baked aluminum reduction cells. A coupled heat/mass-balance model was derived theoretically from the mass and energy balance of an electrolysis cell, and then was simplified properly into a practical expression. The model demonstrates that if environmental temperature and Al2O3 concentration keep constant, the excess AlF3 concentration decreases with the aluminum electrolyte temperature linearly and its decrease rate is dependent on the heat transfer property of aluminum electrolyte, side wall and cell shell. Secondly, experiments were conducted on site with two industrial cells in an aluminum electrolysis plant. Excess AlF3 concentration and aluminum electrolyte temperature were obtained simultaneously together with other parameters such as Al2O3, CaF2, MgF2 and LiF concentrations. Results show that the maximum absolute error between the tested value and the calculated value of excess AlF3 concentration using the proposed model is less than 2%. This reveals that the coupled heat/mass-balance model can appropriately characterize the correlation between excess AlF3 concentration and aluminum electrolyte temperature with good accuracy and practicability.

A distributed surface energy and mass balance model and its application to a mountain glacier in China

Based on the field observations on Qiyi Glacier during the warm season of 2007,using a digital elevation model(DEM,15 m resolution),we developed a distributed surface energy-and mass-balance model with an hourly resolution.The model described the effect of topography on shortwave solar radiation,and used a new parameterization for glacier albedo.The model was applied to Qiyi Glacier in the Qilian Mountain,China,for the period 20:00 30 June to 12:00 10 October 2007,to simulate the firn-line changes,the temporal and spatial variations of mass balance,and the glacial meltwater runoff.The results indicated that the patterns of altitudinal profile of glacier mass-balance were affected mainly by the altitudinal profile of albedo,and the status of the glacier mass balance was influenced directly by the values of albedo.The parameter sensitivity test showed that the model was sensitive to the air temperature lapse rate and precipitation gradient,and also sensitive to the threshold temperature for solid/liquid precipitation.Furthermore,the climate sensitivity test showed that the mass balance was more sensitive to air temperature than precipitation,and the response of mass balance to air temperature change was nonlinear while the response to precipitation change linearly.The negative mass balance trend of the glacier can not be reversed when precipitation increases by 20%and meanwhile air temperature rises by 1°C.

Thermospheric mass density derived from CHAMP satellite precise orbit determination data based on energy balance method

In this article, the energy balance method is used to retrieve thermospheric mass density from CHAMP satellite precise orbit determination(POD) data during 2007–2009. The retrieved thermospheric mass densities are compared with those from accelerometer data and an empirical model. The main conclusions are as follows:(1) Thermospheric mass density can be retrieved from POD data by the energy balance and semi-major axis decay methods, whose results are consistent.(2) The accuracy of the retrieved densities depends on the integration time period, and the optimal period for CHAMP density retrieval from POD data is about 20 minutes.(3) The energy balance method can be used to calibrate accelerometer data.(4) The accuracy of retrieving thermospheric density from POD data varies with satellite altitude and local time.

Geotextile protection of glacier:Observed and simulated impacts on energy and mass balance

The detailed physical processes involved in slowing glacier ablation by material cover remain poorly understood so far.In the present study,using the snow cover model SNOWPACK,the effect of geotextile cover on the energy and mass balance at the tongue of the Urumqi Glacier No.1(Chinese Tien Shan)was simulated between July 12,2022 and August 31,2022.The mass changes and the energy fluxes with and without material cover were compared.The results indicated that the geotextile covering reduced glacier ablation by approximately 68%compared to the ablation in the uncovered regions.The high solar reflectivity of the geotextile reduced the net short-wave radiation energy available for the melt by 45%.Thermal insulation of the geotextile reduced the sensible heat flux by 15%.In addition,the wet geotextile exerted a cooling effect through long-wave radiation and negative latent heat flux.This cooling effect reduced the energy available for ablation by 20%.Consequently,only 37%of the energy was used for melting compared to that used in the uncovered regions(67%).Sensitivity experiments revealed that the geotextile cover used at a thickness range of 0.045-0.090 m reduced the ice loss by approximately 68%-72%,and a further increase in the thickness of the geotextile cover led to little improvements.A higher temperature and greater wind speed increased glacier ablation,although their effects were small.When the precipitation was set to zero,it led to a significantly increased melt.Overall,the geotextile effectively protected the glacier tongue from rapid melting,and the observed results have provided inspiration for developing an effective and sustainable approach to protect the glaciers using geotextile cover.

“链-回-环”系统能质平衡核算及优化

文章以某球团厂200万t“链—回—环”系统为例,根据现场采集到的生产数据,核算得到该系统的热利用率为22.36%,余热回收率为71.62%。优化后得到当喷煤量在5.00~5.40 t/h,煤粉固定碳含量在76%~82%,煤粉燃尽率在97.5%以上时,预热Ⅱ段氧含量可以稳定在14.0%~16.0%,有利于球团矿的氧化且能有效抑制氮氧化物的生成。

表碛覆盖型冰川参数提取方法研究进展

表碛的存在影响了大气与冰川间的能量传输过程,一方面,促进了冰面湖(塘)、冰崖的发育;另一方面,改变了冰川的消融过程和水文模式。利用表碛各项属性和物理参数模型化气候-表碛-冰川间的相互作用和反馈过程能够正确认识表碛覆盖型冰川变化的过程和机理,有助于准确估算和预测冰川物质平衡,进而判断冰川未来演变趋势。本文系统总结和对比了识别表碛范围、提取冰川流速以及获取表碛物理参数的各种技术手段,介绍了表碛覆盖影响下冰川消融模型的原理和应用情况,同时还对这些方法或模型的局限性和发展趋势进行了讨论。表碛覆盖型冰川所处山区地形起伏大、地表变化复杂,为遥感方法识别表碛范围和提取冰川流速带来了诸多困难,如现有表碛识别方法仍无法克服固有干扰因素的影响,而流速提取方法需具备较强抗干扰能力,且配对影像时间基线需尽可能短。当前表碛覆盖型冰川相关研究中关键参数、数据存在大量空缺的状况有望在将来得到改善,冰川动力学过程和表碛动态变化的模型描述将更为精细,冰川物质平衡、径流量等指标的评估和预测也将更为真实准确。

典型寒区流域水文过程模拟及分析

西北高山区寒区流域在全球变化背景下,河川径流发生了明显的变化,定量分析和评估径流变化对制定西部水资源可持续利用有着重要的意义.在VIC模型(含有冻土计算方案)的框架基础上,成功了耦合能量-物质平衡方案,改善了其在寒区冰川流域的水文过程模拟的效果.选择新疆阿克苏河流域作为研究区,验证表明改进后的模型取得比较理想的模拟结果.基于模拟的径流和观测数据,分析了阿克苏河两大支流径流组成及其变化特征.结果表明:1)托什干河冰川区径流占总径流的29.2%,昆马力克河冰川区径流占总径流的58.7%;2)两大支流总径流量近38a均呈增加趋势,托什干河径流增加了43.1%,平均年增加幅度为25.95×106 m3.a-1,昆马力克河径流增加13.1%,平均年增加幅度为14.09×106 m3.a-1;3)低冰川覆盖率的托什干河径流增加完全由于非冰川区径流的增加,高冰川覆盖率的昆马力克河径流增加是冰川区径流和非冰川区径流增加共同作用的结果,其中,总径流增加量中42%是来自于冰川区径流,58%来自于非冰川区径流.

基于能量平衡对额尔齐斯河流域融雪过程的研究

为定量描述额尔齐斯河流域积雪的消融过程,建立了利用基于能量平衡的积雪模型,对流域内库威积雪站2014年1月4日-3月28日积雪的积累和消融过程进行了模拟.结果表明:模型能够很好的模拟出融雪期净辐射能量的变化过程,对雪水当量的模拟结果也非常好,雪水当量的观测值和模拟值之间的Nash系数达到了0.989.在积雪的积累期,雪表的净辐射、感热、潜热通量的绝对值以及地表热通量明显低于积雪的消融期.在积累期,感热和潜热通量以及土壤热通量受到雪层厚度的影响.当雪水当量小于10 mm时,感热和潜热通量的绝对值偏高,土壤热通量的波动性也偏大.在积累期积雪的物质损失全部为升华损失,升华量为2.74 mm;在消融期,积雪的融化量为66.26 mm,升华量为2.04 mm.净辐射对积雪物质损失的贡献达到了83.1%,湍流通量对积雪物质损失的贡献达到16.9%.由于在融化期土壤热通量为正值,因此土壤热通量对融雪没有贡献.

祁连山七一冰川反照率的参数化研究

通过对2006年和2007年暖季消融期七一冰川反照率的观测资料分析,基于冰川反照率的变化规律及其影响因素,根据实测资料的统计建模和验证,初步给出了具有试验基础的冰川反照率多因子参数化公式,其时间分辨率为1h.经检验,2006年和2007年考察期间冰川反照率的模拟值和观测值序列之间的相关系数分别达到了0.901和0.973,平均绝对误差MAE值分别为0.073和0.038,RMSE值分别为0.089和0.052.回归拟合方法得到的冰川反照率参数化公式能较好的反映冰川反照率的日变化和日际变化情况,有望用于冰川表面能量物质平衡的模型模拟之中.

祁连山老虎沟12号冰川表面能量和物质平衡模拟

采用HOCK的分布式能量物质平衡模型对老虎沟12号冰川消融期的物质平衡进行了模拟,时间步长为1 h,空间分辨率为30 m.模型结果利用物质平衡观测数据和气象站观测数据验证,模型模拟时期为2012年6月1日-9月30日.模型模拟结果表明,地形因子对太阳辐射影响相当显著;散射辐射在总辐射中的比例较大为39%,模拟期冰川表面物质平衡为-506 mm w.e..在模拟期整个冰川平均上净辐射占能量收入的84%,感热通量占有16%;消融耗热则是能量的主要支出占有62%,潜热通量占有能量支出的38%.

烟气循环烧结的数值仿真

通过对铁矿烧结过程流动、传热、传质的分析,建立烧结过程热质分析计算的数学模型,并验证计算模型的可靠性。根据常规烧结工艺烟气温度和成分含量的分布特点,基于余热利用和减量排放侧重点的不同提出相应的烟气循环烧结方案,通过模拟计算对比分析烟气循环烧结对于常规烧结工艺的改善作用。研究结果表明:烟气循环烧结工艺能提高上部料层最高温度,使料层最高温度在高度方向上更加稳定,能提高烟气余热利用量,降低烟气脱硫处理量和脱硫负荷,提高烟气脱硫效率。

高层隔震结构单质点模型的地震响应单纯质点法研究

提出了可以快速计算高层隔震结构地震响应的单纯质点法。这种方法基于基底剪力及能量等效原则,建立简化单质点分析模型与原结构模型之间的转换关系及模型参数取值,引入能量平衡方法计算简化分析模型的包络反应,最后利用能量平衡原理及模型参数转换关系,来预测原高层隔震结构的各层地震反应包络值。给出了分析高层隔震结构加速度、隔震层及上部结构的层间变形、层间剪力等预测计算式。通过22层高层隔震结构工程实例来验证单纯质点法的有效性及计算精度,分析结果表明:简化计算结果与多质点模型时程分析法计算结果相当。所提计算方法计算量少,参数取值明确方便,同时具有良好的地震响应分析精度。

焦化炉管内工艺计算数学模型的开发及应用

针对减压渣油在延迟焦化炉管内复杂的流动、反应过程,运用物料、能量及动量平衡,开发了焦化炉管内工艺计算数学模型,可计算渣油沿炉管轴向的组成、温度、压力、汽化分率及转化率分布。结果表明:模型计算值与某炼油厂焦化炉实际操作数据的偏差较小,温度、压力、汽化分率等参数沿炉管的变化规律也与经验认识吻合;模型用于不同注汽工况及加热炉进料波动工况分析,可为延迟焦化加热炉的优化设计及操作提供理论指导。

流化床锅炉床下热烟气点火启动的理论及试验研究──理论模型

本文介绍了我们所建立的流化床锅炉床下热烟气点火启动综合数学模型。模型由描述点火启动过程所涉及的流动、传热和燃烧等物理和化学过程的诸多子模型所构成。本文着重讨论了数学模型中的四个子模型：单颗煤粒多相反应和均相反应模型，氧量平衡计算模型，固相物质平衡计算模型和能量平衡计算模型。计算结果和试验结果进行了对比，两者较为吻合。利用本文模型可对不同容量的流化床锅炉点火启动进行模拟计算，为点火装置设计和运行操作提供合理参数。

基于Ecopath模型的长江口及毗邻水域生态系统结构和能量流动研究

根据2000年和2006年秋季长江口及毗邻水域渔业资源和生态环境调查数据,利用Ecopath with Ecosim软件,构建2个时期的长江口及毗邻水域生态能量通道模型,比较分析了三峡工程蓄水前后长江口及毗邻水域生态系统的结构和能量流动特征。模型包含鱼类、虾类、蟹类、头足类、浮游动物、浮游植物、底栖动物、碎屑等17个功能群,基本覆盖了能量流动的途径。分析结果表明,2006年秋季长江口及毗邻水域生态系统的总生物量、系统总流量比2000年秋季有所下降,碎屑链的重要性略有降低;由于低营养级层次渔获物数量的增加,渔获物平均营养级有所下降。2个时期长江口及毗邻水域生态系统的再循环率较低,仍有较高的剩余生产量有待利用,均处于不成熟的发育期。

高层隔震结构双质点模型的地震响应单纯质点法研究

针对高层隔震结构的双质点简化模型提出了可快速计算其地震响应的单纯质点法,该方法基于基底剪力及能量等效原则来建立简化两质点分析模型与原结构模型之间的转换关系及简化模型的参数取值,推导得到了确定地震反应的两个关键参数:刚度转换系数和质量比。研究基于能量平衡方法提出了高层隔震结构简化分析模型包络反应的计算式,并通过利用能量平衡原理及模型参数转换关系来预测原高层隔震结构的各层地震反应包络值。对22层高层隔震结构工程实例首先进行了双质点模型的转化,其后验证了单纯质点法的有效性和分析精度,分析结果表明新方法计算结果与多质点模型时程分析法计算结果相近,且能包络上部结构各层地震响应。该方法计算量少,参数取值简便,可用于高层隔震结构地震响应的初步分析。