Study of the explosion parameters of vapor–liquid diethyl ether/air mixtures

The knowledge of the vapor–liquid two-phase diethyl ether (DEE)/air mixtures (mist) on the explosion parameters was an important basis of accident prevention. Two sets of vapor–liquid two-phase DEE/air mixtures of various concentrations were obtained with Sauter mean diameters of 12.89 and 22.90 μm. Experiments were conducted on vapor–liquid two-phase DEE/air mixtures of various concentrations at an ignition energy of 40.32 J and at an initial room temperature and pressure of 21 °C and 0.10 MPa, respectively. The effects of the concentration and particle size of DEE on the explosion pressure, the explosion temperature, and the lower and upper flammability limits were analyzed. Finally, a series of experiments was conducted on vapor–liquid two-phase DEE/air mixtures of various concentrations at various ignition energies. The minimum ignition energies were determined, and the results were discussed. The results were also compared against our previous work on the explosion characteristics of vapor–liquid two-phase n-hexane/air mixtures.     

Determination of spontaneous combustion of thermally dried sewage sludge

The general purpose of this research was the determination of self-ignition tendency of thermally dried sewage sludge. Eight Spanish plants located in Madrid, Barcelona and Málaga were selected to develop this study and ten samples were collected. Three different testing methodologies for studying the self-ignition of dusts have been undertaken. Thermogravimetric techniques, self-ignition temperature analyses and UN Division 4.2 tests were developed. The results of these analyses showed the risk of self-ignition during storage and transportation of these substances.     

Ignition and explosion parameters of Colombian coals

The explosivity of coal in Colombia is usually determined by chemical analysis based on the volatile ratio. To improve the assessment of the explosivity of those coals that have led to numerous explosions in Colombian mines, 22 coals from the department of Antioquia were analyzed. Flammability characteristic parameters were determined, such as minimum temperatures and energy for ignition and the lower explosive limit. Also explosion data, ie. Pmax and Kmax values were obtained. In addition, the susceptibility to spontaneous combustion was studied by thermogravimetry and differential scanning calorimetry, together with chemical attack with hydrogen peroxide and also measuring the temperature of ignition of flammable volatiles. Finally the effect of particle size and the percentage range of limestone needed for inerting coal under two different granulometries were determined.     

选煤废物（煤泥）的燃用特性研究

本文研究了选煤厂废弃物──煤泥的着火和燃尽特性，揭示出各种添加剂、温度和几何形状等因素对煤泥成型燃烧利用过程的影响规律，分析探讨了添加剂的助燃机理及其应用可行性，以开发和完善煤泥成型燃烧的综合利用工艺和技术具有一定的参考价值。     

Effects of N2 and CO2 on the flammability of 2,3,3,3-tetrafluoropropene at elevated temperatures

The flammability characteristics of refrigerants are affected by environmental factors, making them prone to flammability and explosion accidents in cooling systems. In this paper, the flammability characteristics of R1234yf–air mixtures with N₂ and CO₂ were investigated comparatively at temperatures between 20 and 50 °C at 80% relative humidity. The lower and upper flammability limits of R1234yf were measured. The limiting oxygen concentration (LOC), critical flammable ratio (CFR), and critical flammable concentration (CFC) of the R1234yf–air mixtures with inert gases were investigated. The paper developed a linear formula between the flammability limit of R1234yf and the temperature. The changes in CFC with different temperatures were negligible for R1234yf. Furthermore, the mixed refrigerant had both non-flammability and the lowest vapor pressure when the CFR of the R1234yf/CO₂ mixture was 2.9. The experimental results were used to propose a new prediction model to estimate the flammability limits of R1234yf. Finally, molecular simulation explained the effect of inert gases on the flammability of R1234yf from a microscopic point of view. The research aimed to provide valid evidence and data for preventing flammable and explosive refrigerant incidents.     

Analysis of the chosen thermal and flammability parameters of dried sewage dust

The hazardous sludge disposal process in the form of landfills requires the determination inter alia of the flammable and explosion properties of dried sewage sludge dust, which has the ability to ignite and spontaneously combust when stored in silos. At a constant furnace surface temperature, the minimum ignition temperature of the sludge dust layer with a layer thickness of 5 mm is 270 °C, and for a layer thickness of 12.5 mm it is 250 °C. Two selected fire extinguishing powders for Class A, B, C and D fires were used in the study to determine the possibility of reducing the susceptibility of dried wastewater to ignition from heated surface, self-ignition and explosion parameters. The most effective extinguishing powder was ABC Favorit, which increased the value of the minimum ignition temperature of the layer (5 mm thick) to 360 °C and the spontaneous ignition temperature of the sludge with this powder increased by 22 °C at 169.6 cm³ in comparison to the sludge without extinguishing powder, respectively. The lowest self-ignition temperature of 136 °C was recorded for the largest tested volume (169.6 cm³) for dried sewage dust without any fire extinguishing powders. The biggest values of p_max and (dp/dt)_max dried sewage dust were recorded 4.8 bar and 113 bar/s respectively. By analysing the obtained test results, it can be assumed that dried sewage dust is a combustible material with properties similar to biomass.     

Combustion hazard of mixing ammonia with nitric oxide

Premixed ammonia/nitric oxide flame was simulated using the Lindstedt 1994 and Miller–Bowman 1989 reaction mechanisms in CHEMKIN. The predicted laminar burning velocities compared well with limited measured values in the literature. The effects of unburnt mixture temperature and pressure on laminar burning velocity, flammability limits, adiabatic flame temperature and species profiles were studied. The unburnt mixture temperature had a positive impact on both the laminar burning velocity and the adiabatic flame temperature, and it extended the ammonia-rich flammability limit. The pressure had a marginally negative influence on the laminar burning velocity, while it had a slightly positive effect on the adiabatic flame temperature.     

Effect of self-inhibition at a flame propagation in rich gaseous mixtures of combustible–air–diluent

An analysis of published experimental data characterizing the influence of diluents of various chemical nature (both halogenated and chemically inert) on upper flammability limits of flammable gases in air (methane and hydrogen have been considered as examples) has been done. Dependences of critical oxygen concentration and critical fuel equivalence ratio _cr for mixtures combustible–air–diluent at upper flammability limits on diluent concentration were determined. The obtained data were interpreted on the basis of the concept of self-inhibition at combustion of rich mixtures of organic combustibles in air. A method for evaluation of relative effectiveness of various inhibitors and for determination of availability of self-inhibitive properties of a combustible gas has been proposed.     

An experimental investigation of an inertization effectiveness of fluorinated hydrocarbons in relation to premixed H2–N2O and CH4–N2O flames

An experimental investigation of an influence of trifluoromethane CHF_3, pentafluoroethane C₂HF₅ and perfluorobutane C₄F₁₀ on near-limit hydrogen-nitrous oxide and methane-nitrous oxide premixed flames was performed. Flammability limits, a maximum explosion pressure ΔP_max, maximum rate of pressure rise (dP/dt)_max, and a laminar burning velocity S_u were determined. The flammability area in the case of N₂O as an oxidizer is substantially wider than for the case of the oxidizer which is the mixture of oxygen and nitrogen with the O₂ content 25% (vol.). The dependences of S_u, ΔP_max and (dP/dt)_max on concentration of the fluorinated hydrocarbons are characterizing by an availability of maxima which positions are close to the peak concentrations of the flammability regions. A qualitative interpretation of the results obtained is given.     

Reconsidering autoignition in the context of modern process safety: Literature review and experimental analysis

Autoignition is regarded as the spontaneous combustion of a fuel without an apparent ignition source. With respect to fires and explosions in the process industries, the autoignition hazard is one that requires management and consideration. Despite the importance of understanding the autoignition hazard, the literature on the topic is often disappointingly sparse and inconsistent. Experimental methods don't adequately represent real-world conditions and are complicated by experimental error, invoking the need for a reconsideration of autoignition as it pertains to process safety. This work utilized the ASTM E659 method to study potential experimental error for the purpose of improving the process safety community's understanding of autoignition phenomena. Of interest to this study were effects of humidity and suspected occurrences of cool flames, two sources of error which have not been fully explained in the literature. For the fuels tested, results show that humidity has only a slight effect on overall autoignition behavior. However, this study's examination of cool flames suggests that they could be a common occurrence in this testing method. Analysis of these experiments show that cool flames can feature significant exothermic effects and are thus of concern from a perspective of risk management. In addition, this work proposes a novel criterion for a more conservative assessment of autoignition experiments, which results in less subjectivity of analysis.