Effect of nozzle type on pulse-jet cleaning performance of ceramic filter tube

The dust-cleaning efficiency of the ceramic filter tube is the key factor to determine the long-term stable operation of the dust removal system, and the type of nozzle significantly influences the performance. In this study, four types of nozzles (injection hole, sudden enlargement nozzle, tubular nozzle, and induction nozzle) are used to conduct comparative experimental study on the dust-cleaning effect of the ceramic filter tube. Using the schlieren technique find that the tubular and induction nozzles can improve the deviation angle of pulse-jet airflow. The injection parameters were set as an injection pressure of 200 kPa, an injection distance of 120 mm and a pulse width of 80 ms in the experiment. Using the sidewall pressure measurement system indicates that the integrated pressure of the sudden enlargement nozzle is the largest, but the uniformity is poor. The comprehensive pressure of the sudden enlargement nozzle is increased by 64.86 %, and the non-uniformity is reduced by 28.62 % compared with those of the induction nozzle. Using the visualization filtration cycle test system implies that the degree of damage and stripping state of the dust layer are directly proportional to the sidewall pressure. Moreover, it is found that the residual pressure drop changes exponentially with the dust removal quality under different nozzle types. These conclusions can help explain the mechanism of dust stripping and provide a basis for the selection of nozzles.     

Dust source identification using MODIS: A comparison of techniques applied to the Lake Eyre Basin, Australia

The impact of mineral aerosol (dust) in the Earth's system depends on particle characteristics which are initially determined by the terrestrial sources from which the sediments are entrained. Remote sensing is an established method for the detection and mapping of dust events, and has recently been used to identify dust source locations with varying degrees of success. This paper compares and evaluates five principal methods, using MODIS Level 1B and MODIS Level 2 aerosol data, to: (a) differentiate dust (mineral aerosol) from non-dust, and (2) determine the extent to which they enable the source of the dust to be discerned. The five MODIS L1B methods used here are: (1) un-processed false colour composite (FCC), (2) brightness temperature difference, (3) Ackerman's (1997: J.Geophys. Res., 102, 17069-17080) procedure, (4) Miller's (2003:Geophys. Res. Lett. 30, 20, art.no.2071) dust enhancement algorithm and (5) Roskovensky and Liou's (2005: Geophys. Res. Lett. 32, L12809) dust differentiation algorithm; the aerosol product is MODIS Deep Blue (Hsu et al., 2004: IEEE Trans. Geosci. Rem. Sensing, 42, 557-569), which is optimised for use over bright surfaces (i.e. deserts). These are applied to four significant dust events from the Lake Eyre Basin, Australia. OMI AI was also examined for each event to provide an independent assessment of dust presence and plume location. All of the techniques were successful in detecting dust when compared to FCCs, but the most effective technique for source determination varied from event to event depending on factors such as cloud cover, dust plume mineralogy and surface reflectance. Significantly, to optimise dust detection using the MODIS L1B approaches, the recommended dust/non-dust thresholds had to be considerably adjusted on an event by event basis. MODIS L2 aerosol data retrievals were also found to vary in quality significantly between events; being affected in particular by cloud masking difficulties. In general, we find that OMI AI and MODIS AQUA L1B and L2 data are complementary; the former are ideal for initial dust detection, the latter can be used to both identify plumes and sources at high spatial resolution. Overall, approaches using brightness temperature difference (BT10-11) are the most consistently reliable technique for dust source identification in the Lake Eyre Basin. One reason for this is that this enclosed basin contains multiple dust sources with contrasting geochemical signatures. In this instance, BTD data are not affected significantly by perturbations in dust mineralogy. However, the other algorithms tested (including MODIS Deep Blue) were all influenced by ground surface reflectance or dust mineralogy; making it impossible to use one single MODIS L1B or L2 data type for all events (or even for a single multiple-plume event). There is, however, considerable potential to exploit this anomaly, and to use dust detection algorithms to obtain information about dust mineralogy.     

200MW乏气送粉机组主蒸汽温度控制优化方案

本文在常规火电厂主蒸汽温度自动控制方案的基础上,对200MW乏气送粉机组的特性进行了分析,结合锅炉主要参数与主蒸汽温度自动控制的相互关系,以及相关的工艺要求,提出了一种新的优化方案。     

DCS在焦炉地面除尘系统中的应用

以和利时DCS系统在某100万t捣固焦炉地面除尘站系统中的应用为例,介绍了袋式除尘系统的工艺流程、工艺联锁与控制要求,并依此制订了基于和利时MACSV系统的详细实现方案。系统具有免维护、除尘效果良好等特点。系统投运后,不仅减少了工人劳动强度,改善了工厂周边环境,并且取得了良好的经济效益和社会效益。     

除尘器智能控制器的开发

针对市场上传统的脉冲袋式除尘器控制器在实际应用中存在的灵活性差、可靠性低等问题，借助于高性能的单片机开发了一种功能完善的通用型控制器。具体介绍了系统的组成和工作原理，详细讨论了通用控制器的硬件组成和软件设计，阐述了系统的性能指标和功能特点，在设计中采用光电耦合器将外部负载驱动电路和控制电路隔离，同时结合看门狗技术提高整个系统的可靠性。     

拆除爆破粉尘控制研究现状与前景

综述了爆破粉尘控制的研究现状,分析了爆破粉尘的特点,对拆除爆破粉尘的控制方法进行了探讨,预测了拆除爆破粉尘控制的发展趋势。文中提出了采用清除积尘、预湿建筑物、爆炸水雾、局部建筑单元蓄水、喷淋等综合除尘方法降低城市控制爆破过程中的粉尘,以减轻和消除爆破粉尘对环境的污染。     

Estimating aerodynamic resistance of rough surfaces using angular reflectance

Current wind erosion and dust emission models neglect the heterogeneous nature of surface roughness and its geometric anisotropic effect on aerodynamic resistance, and over-estimate the erodible area by assuming it is not covered by roughness elements. We address these shortfalls with a new model which estimates aerodynamic roughness length (z₀) using angular reflectance of a rough surface. The new model is proportional to the frontal area index, directional, and represents the geometric anisotropy of z₀. The model explained most of the variation in two sets of wind tunnel measurements of aerodynamic roughness lengths (z₀). Field estimates of z₀ for varying wind directions were similar to predictions made by the new model. The model was used to estimate the erodible area exposed to abrasion by saltating particles. Vertically integrated horizontal flux (F_h) was calculated using the area not covered by non-erodible hemispheres; the approach embodied in dust emission models. Under the same model conditions, F_h estimated using the new model was up to 85% smaller than that using the conventional area not covered. These F_h simulations imply that wind erosion and dust emission models without geometric anisotropic sheltering of the surface, may considerably over-estimate F_h and hence the amount of dust emission. The new model provides a straightforward method to estimate aerodynamic resistance with the potential to improve the accuracy of wind erosion and dust emission models, a measure that can be retrieved using bi-directional reflectance models from angular satellite sensors, and an alternative to notoriously unreliable field estimates of z₀ and their extrapolations across landform scales.     

56m~2电除尘器气流分布及气密性测定分析

本文介绍了贵溪冶炼厂新增备料 ５６ｍ~２电除尘器气流分布及气密性测定分析的方法及过程,指出对新建或大修改造后的电除尘器,在投产前进行气流分布及气密性现场测试调整的必要性。     

中外粉尘监测技术的比较

通过分析粉尘的危害指出进行粉尘监测的意义,讨论了国内外粉尘监测技术方面的研究进展。在法律法规实施、监测仪器精度、监测仪器创新和监测防护措施等方面对我国与国外发达国家进行了比较,找出存在的主要差距,为我国未来粉尘监测技术领域的发展指明了方向。     

粉尘爆炸风险因子分析

基于人机工程原理,从人、机、环境、管理四类因素着手,分析涉及粉尘爆炸场所危害程度的影响因子,得出12个二级影响因子和44个三级影响因素,建立了粉尘爆炸场所风险的层次;提出了基于层次分析评价的粉尘爆炸风险因子评价模型,并对其权重进行分析,得出企业发生粉尘爆炸的风险的主次因素,着重分析了防爆措施和检测系统因素对评价模型中权重的影响,进一步验证采取正确的防爆措施和技术防范,可降低或减缓粉尘爆炸风险等级,减少粉尘爆炸事故。