Gaseous emissions from lignosulfonates in dust abatement applications

Concerns over possible gaseous emissions from lignosulfonate dust suppressant agents used on dirt roads prompted an investigation into the possible release of sulfur dioxide and organic vapors. Emissions from eight commercial lignosulfonates products applied to three different soil types were measured in environmental chambers. It was determined that except under extreme soil pH conditions (<1), the release of sulfur dioxide from the application of lignosulfonates to roads is essentially non existent. The odor associated with the application was found to be due to trace amounts of organic compounds mainly of the furfural variety. Levels of odor compounds in these products was significantly lower than the previously reported values for spent sulfite liquors because the majority were removed during processing operations prior to sale.     

Effects of ignitors and turbulence on dust explosions

The aim of this work is in an attempt to increase the understanding of the acting behaviour of pyrotechnic ignitors and their effects on confined dust explosions. Flame visualization has shown that pyrotechnic ignitors can initiate an explosion by instantaneous jet-like volumetric and/or multipoint ignition. Hence, the rate of pressure rise and also the apparent burning velocity will be increased to some extent, depending on the ignitor energy and the reactivity of the mixtures. The ignitor effect is more important for the early stages of flame propagation and would be more significant in small explosion chambers. Thus, for dust explosion tests with various purposes, use of pyrotechnic ignitors should be made carefully, and the ignitor effect must be accounted for in the data interpretation. Turbulence induced by dust dispersion is a dominant factor in affecting dust explosions. At different ignition delays, however, the turbulence influence will be coupled with that of ignitors. This complicates further the interpretation of explosion data measured under turbulent conditions.     

煤矿井下作业场所粉尘浓度的法律管理

煤矿井下作业场所粉尘浓度管理标准的变动，会给煤矿的防尘工作带来很大影响。煤矿防尘工作的好坏主要取决于综合防尘措施的落实、防尘科技的发展状况以及与此相适应的法规标准。脱离实际的防尘标准，只能导致实际工作中的虚夸与浮躁，不利于防尘工作的正常开展     

一维可燃气云燃烧与爆炸的数值模拟

碳氢燃料在空气中形成的可燃气云，点火后容易从燃烧发展为爆轰。本文分别用均匀能量释放模型与能量波模型模拟了可燃气云的能量释放；用高精度、高分辨率的ＴＶＤ格式对有限能量释放速率的一维可燃气云的流体力学守恒方程进行了数值求解，给出了流场压力分布曲线，讨论了两种能量释放模型中影响能量释放速率的主要因素。     

Comparative analysis of test work studying factors influencing pressures developed in vented deflagrations

A test programme was developed to study factors that may influence the maximum pressure during venting developed during deflagration. The factors considered were vent burst pressure, vent mass, ignition source location, discharge ducting, downstream obstructions and water covers.     

Aluminium dust explosion risk analysis in metal workings

The aim of this paper is to present a risk analysis method that can be applied to factories where combustible dust is handled, in the form of raw materials, products or by-products, and therefore at risk to explosion. The work was carried out on site: a consistent number of companies that deal with the surface finishing of objects in aluminium through grinding were examined. The aluminium powder produced as a by-product is generally captured by suction plants and then subjected to dry or wet type abatement. In order to provide a rational approach to the risk assessment and frequency estimation, each company was divided into the so-called fields of study; and four risk assessment topics were identified for each field. A brief review of the methods that are available for the consequence magnitude estimation, regarding both the pressure wave and the launching of missiles, is also provided.     

Explosion temperatures and pressures of metals and other elemental dust clouds

The Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) conducted a study of the explosibility of various metals and other elemental dusts, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating explosion hazards in the minerals and metals processing industries. The dusts studied included boron, carbon, magnesium, aluminum, silicon, sulfur, titanium, chromium, iron, nickel, copper, zinc, niobium, molybdenum, tin, hafnium, tantalum, tungsten, and lead. The dusts were chosen to cover a wide range of physical properties—from the more volatile materials such as magnesium, aluminum, sulfur, and zinc to the highly “refractory” elements such as carbon, niobium, molybdenum, tantalum, and tungsten. These flammability studies were conducted in a 20-L chamber, using strong pyrotechnic ignitors. A unique multiwavelength infrared pyrometer was used to measure the temperatures. For the elemental dusts studied, all ignited and burned as air-dispersed dust clouds except for nickel, copper, molybdenum, and lead. The measured maximum explosion temperatures ranged from 1550 K for tin and tungsten powders to 2800 K for aluminum, magnesium, and titanium powders. The measured temperatures are compared to the calculated, adiabatic flame temperatures.     

New dust explosion venting design requirements for turbulent operating conditions

The 2007 edition of the National Fire Protection Association Standard 68 for Explosion Protection by Deflagration Venting has a new provision to account for the turbulence level in combustible dust or powder processing equipment. This paper explains the development of this new provision for increased deflagration vent area requirements in highly turbulent combustible dust/powder processing equipment. The development includes a review of initial turbulence level effects on vented explosion pressures, and a review of turbulence levels measured in ASTM E1226 and ISO 6184/1 explosion test procedures to determine K_st. A review of operating conditions in some representative spray dryer plant equipment suggests that most equipment of this type probably do not have high enough air flows to require increased explosion vent areas due to turbulence, but some types of equipment with high tangential entrance air flows may well need larger vent areas.     

Ignition tests for electrical and mechanical equipment subjected to hot surfaces

This paper reports some experimental work on hot surface ignition temperatures of dust deposits. Dust layers up to 75 mm in depth were ignited using a modified version of the standard 5 mm layer apparatus. The measured ignition temperatures show good agreement with predictions using the method given in EN 50281-2-1. Ignition temperatures of conical dust deposits over an electrically heated box were not predictable, but were not too dissimilar from the ignition temperatures of the thick layers. Both tests gave adequate reproducibility in round robin tests. Rotating steel wheels in contact, immersed in a dust deposit produce the frictional hot surfaces. A relation between the power lost by friction and the surface temperature developed has been derived. The surface temperatures leading to ignition were close to the ignition temperatures for the conical deposits on the heated box. The similarities between the ignition temperatures of dust deposits in several configurations indicate that a simple test for ignition temperature measurement could have wide application in dusty environments.     

“十一五”期间我国水泥工业的污染减排形势

水泥工业是我国国民经济发展的重要基础性产业,同时也是我国“十一五”期间节能减排的重点行业。对我国水泥工业发展和主要污染物排放现状进行分析后发现,我国水泥工业存在产业梯度转移带来污染转移的风险。同时在现状分析基础上对“十一五”水泥工业污染减排的形势进行了评估。根据保守预测,到2010年,我国水泥工业的粉尘排放量和二氧化硫排放量同比2005年将分别削减29％和13％,根据乐观预测,2010年分别比2005年削减58％和26％。