Dust explosion incidents and regulations in the United States

The U.S. Chemical Safety and Hazard Investigation Board (CSB) investigated three fatal dust explosions that all occurred in 2003. These explosions caused the deaths of 14 people and injured hundreds more. Two of the facilities were damaged beyond repair, and several hundred employees lost their jobs.

CSB's investigations revealed that the explosions had common causes, despite their geographic and industrial diversity. Consequently, CSB commissioned a study of combustible dust fire and explosion hazards. This paper presents a summary of CSB's findings and recommendations developed during that study.     

Determination of the maximum effective burning velocity of dust–air mixtures in constant volume combustion

The reactivity of a combustible dust cloud is traditionally characterized by the so-called K_St value, defined as the maximum rate of pressure rise measured in constant volume explosion vessels, multiplied with the cube root of the vessel volume. The present paper explores the use of an alternative parameter, called the maximum effective burning velocity (u_eff,max), which also is derived from pressure–time histories obtained in constant volume explosion experiments. The proposed parameter describes the reactivity of fuel–air mixtures as a function of the dispersion-induced turbulence intensity. Procedures for estimating u_eff,max from tests in both spherical and cylindrical explosion vessels are outlined, and examples of calculated values for various fuel–air mixtures in closed vessels of different sizes and shapes are presented. Tested fuels include a mixture of 7.5% methane in air, and suspensions of 500 g/m³ cornstarch in air and 500 g/m³ coal dust in air. Three different test vessels have been used: a 20-l spherical vessel and two cylindrical vessels, 7 and 22 l. The results show that the estimated maximum effective burning velocities are less apparatus dependent than the corresponding K_St values.     

Modelling Seasonal Dynamics from Temporal Variation in Agricultural Practices in the UK Ammonia Emission Inventory

Most ammonia (NH₃) emission inventories have been calculated on an annual basis and do not take into account the seasonal variability of emissions that occur as a consequence of climate and agricultural practices that change throughout the year. When used as input to atmospheric transport models to simulate concentration fields, these models therefore fail to capture seasonal variations in ammonia concentration and dry and wet deposition. In this study, seasonal NH₃ emissions from agriculture were modelled on a monthly basis for the year 2000, by incorporating temporal aspects of farming practice. These monthly emissions were then spatially distributed using the AENEID model (Atmospheric Emissions for National Environmental Impacts Determination). The monthly model took the temporal variation in the magnitude of the ammonia emissions, as well as the fine scale (1-km) spatial variation of those temporal changes into account to provide improved outputs at 5-km resolution. The resulting NH₃ emission maps showed a strong seasonal emission pattern, with the highest emissions during springtime (March and April) and the lowest emissions during summer (May to July). This emission pattern was mainly influenced by whether cattle were outside grazing or housed and by the application of manures and fertilizers to the land. When the modelled emissions were compared with measured NH₃ concentrations, the comparison suggested that the modelled emission trend corresponds fairly well with the seasonal trend in the measurements. The remaining discrepancies point to the need to develop functional parametrisations of the interactions with climatic seasonal variation.     

粉尘爆炸事故模式及其预防研究

随着粉体工业的发展,粉尘爆炸发生的危险性也随之增大。为了探讨粉尘爆炸发生的规律,笔者对粉尘爆炸发生的点火源类型、事故原因进行了统计、排序;在对已发生的典型的粉尘爆炸事故分析的基础上,总结、归纳了影响粉尘爆炸发生的,诸如粉尘自身的可燃性、粉尘所处的状态、粉尘所处的外部环境等因素;提炼出了7种粉尘爆炸事故模式,并对各种模式下粉尘爆炸发生的条件、机理进行了初步研究分析,然后提出了相应的事故预防措施。笔者所研究的成果,对粉体工业的安全生产具有实际的指导作用,对今后防灾决策的深入研究也具有一定的参考价值。     

Estimating receptor sensitivity to spatial proximity of emissions sources

Spatial proximity of emissions sources to receptors may affect sensitivity to potential adverse human health effects. This research investigates whether receptor sensitivity to the location of emission sources can be utilized efficiently to minimize health risk in selecting sites for industrial enterprises, thermal electric stations, etc. A sensitivity function that is independent of the location of pre-existing emission sources is derived and applied to Minsk, Belarus. The function estimates exposures based on weather and climatic conditions as well as the distribution of population density at a given locality. Arraying prospective sites based on their sensitivity function magnitude provides a technique for minimizing health risk based on receptor sensitivity to the spatial proximity of atmospheric emissions sources.     

Evaluation of the First Phase of Sulfur Dioxide and Nitrogen Oxides Provisions of the 1990 Clean Air Act: A Plant-Based Approach

Electric power generating plants that use coal were among the key targets of Title IV of the 1990 Clean Air Act. Under the first phase of the act, 110 coal-fired electric power plants were required to reduce their sulfur dioxide emissions by 1995 and nitrogen oxide emissions by 1996. Phase 2 of the act requires even greater reduction of sulfur dioxide emissions by 2000 and nitrogen oxide emissions by 2008. This study examines whether the 107 targeted plants (three plants went off-line) have achieved the desired sulfur dioxide and nitrogen oxide emission levels. The analysis of sulfur dioxide is based on data from 1990, 1995, and 1999. The findings show that although sulfur oxide increased by 3% from 1995 to 1999, it decreased by 45% over the 1990–1999 period at the firm level for the targeted firms. The findings also indicate that the overall reduction in sulfur dioxide was achieved by utilizing low sulfur coal and by purchasing emission allowances. So far as nitrogen oxides are concerned, there has been a reduction of 14% over the 1990–1999 period, of which 7% was achieved during the 1995–1999 period. An evaluation of emissions at the plant level indicates that several plants do not meet the emissions level for sulfur dioxide or nitrogen oxides. These results provide a mixed scorecard for reduction in emissions both for sulfur dioxide and nitrogen oxides. Even though there is reduction in the emissions on an overall basis at the firm level, several plants that have not been able to reduce emissions deserve special attention to meet the goals of the act in reducing emissions.     

Allocating anthropogenic pollutant emissions over space: application to ozone pollution management

An inventory of volatile organic compound (VOC) and nitrogen oxides (NOx) emissions is an important tool for the management of ground-level ozone pollution. This paper has two broad aims: it illustrates the potential of a geographic information system (GIS) for enhancing an existing spatially-aggregated, anthropogenic emissions inventory (EI) for Tucson, AZ, and it discusses the ozone-specific management implications of the resulting spatially-disaggregated EI. The main GIS-related methods include calculating emissions for specific features, spatially disaggregating region-wide emissions totals for area sources, and adding emissions from various point sources. In addition, temporal allocation factors enable the addition of a multi-temporal component to the inventory. The resulting inventory reveals that on-road motor vehicles account for approximately 50% of VOC and NOx emissions annually. On-road motor vehicles and residential wood combustion are the largest VOC sources in the summer and winter months, respectively. On-road motor vehicles are always the largest NOx sources. The most noticeable weekday vs. weekend VOC emissions differences are triggered by increased residential wood combustion and increased lawn and garden equipment use on weekends. Concerning the EI's uncertainties and errors, on-road mobile, construction equipment, and lawn and garden equipment are identified as sources in the most need of further investigation. Overall, the EIs spatial component increases its utility as a management tool, which might involve visualization-driven analyses and air quality modeling.     

室内皮带上煤机除尘系统改造设计

针对某公司热电厂皮带上煤机除尘系统所存在的问题,进行了全面的改造设计,取得了良好的除尘效果。     

除尘管道磨损与防磨措施

讲述了除尘管道磨损的危害,对磨损的形成机理及其影响因素进行了分析,提出了防止磨损的技术措施,提供了一种新型结构的防磨弯头.     

Climate change in Asia: issues and policy options

This article provides a brief review of some of the policy issues facing the Asian region with respect to climate change and its economic consequences. The environmental consequences of Asia's economic rise threaten the future growth of the region. Despite recent economic expansion, Asia will be one of the areas of the world most vulnerable to climate change. While Asia currently contributes moderately to greenhouse gas emissions, the potential for increases in emissions is significant. National and regional policy options, including abatement and adaptation, are examined as strategies for tackling the likely effects of climate change. This study recommends that national initiatives that have no 'regrets' properties be a priority area for further research so that they can be implemented as soon as possible. It is envisaged that in the short to medium term, identifiable no regrets policies can be a useful tool for reducing emissions and vulnerability to climate change in developing regions such as Asia.