Spontaneous Ignition Temperature Research Articles

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 pmax 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.

Influence of pre-ignition technology on combustion and explosion characteristics of composite propellants

The slow cook-off test is widely used for analyzing the safety of propellants under accidental thermal stimulation. To examine the influence of the pre-ignition technology of a composite propellant on thermal safety and combustion characteristics, a quantitative evaluation experiment of slow cook-off reaction intensity of a typical composite propellant charge was designed and executed, considering hydroxyl-terminated polybutadiene (HTPB) and hydroxyl‑terminated block copolyether (HTPE) propellants containing ammonium perchlorate (AP) and aluminum (Al). The experimental method for quantitative evaluation of the slow cook-off reaction intensity is highly essential to investigate the safety of ammunition. The influence of pre-ignition on reaction intensity was analyzed at different temperatures, the combustion behavior of the heated propellant was studied using a closed bomb experiment, and the influence of pre-ignition on combustion evolution was analyzed. Finally, the process was characterized by theoretical modeling. The results show that the slider speed was 169.3 m/s when the HTPB/AP/Al propellant was ignited at 234 °C. The slider speed was reduced to 43.4 m/s and 61.8 m/s by pre-ignition at 120 °C and 214 °C, respectively. When the spontaneous ignition temperature of HTPE/AP/Al propellant was 212 °C, the slider speed was 110.5 m/s. Pre-ignition at 120 °C and 192 °C reduced the slider speed to 39.4 m/s and 43.7 m/s, respectively. Pre-ignition can effectively reduce the reaction intensity. Under the same conditions, the reaction strength of HTPE/AP/Al propellant is marginally lower than that of HTPB/AP/Al propellant. In the slow heating process before ignition, with the increase in ignition temperature, when HTPB/AP/Al propellant was pre-ignition at 120 °C and 214 °C, the pressurization time was 9.8 ms and 6.4 ms, respectively, while before ignition, the pressurization time decreased to 5.5 ms. At 120 °C and 192 °C, the pressurization time of HTPE/AP/Al propellant was 50.9 ms and 36.6 ms, respectively, while before ignition, the pressurization time decreased to 26.9 ms. The reduction in ignition temperature decreased the pressure growth rate of propellant during combustion and reduced the pressurization time. A calculation model of the propellant combustion process was established to characterize the growth process of the combustion pressure at different ignition temperatures. This model can effectively predict the combustion evolution of composite propellants after the slow cook-off ignition and aid in ensuring propellant safety.

Оптимизация режимов работы лесопожарной машины

The article considers specialized forest firefighting vehicles required to extinguish forest fires. An overview of modern domestic and foreign forest firefighting equipment and techniques for fighting forest fires is presented. Rapid heating of the cabin enclosure surfaces is a common weakness of the thermal shielding of a forest firefighting vehicle when extinguishing fires in extreme conditions. Therefore, the following issues remain relevant: problem of increasing the forest firefighting vehicle operation efficiency when extinguishing fires; issues of ensuring the operability and optimization of operation parameters and modes; development and creation of new fire protection materials; improving the cabin ergonomics and operator safety. The paper provides substantiation for optimizing the parameters and operation modes of a forest firefighting vehicle on the basis of the given tactical scheme of forest fire extinguishing. The objective function of the mathematical optimization problem is the production capacity, i.e. the area that can be extinguished by a forest fire vehicle. As control factors we consider following parameters of main and auxiliary equipment: capacity of pumps supplying water and foam/water mixtures; water tank capacity; estimated time of forest fire extinguishing and flame retardant properties of the forest firefighting vehicle structure elements, particularly spontaneous ignition temperature of cabin enclosure thermal insulation. The mathematical optimization problem is solved by the analytical method. Methods of computational mathematics and applied programming are used for numerical calculations and software implementation. The solution of the problem enables to calculate the production capacity of a forest firefighting vehicle, determine the required flame retardant properties of the cabin enclosure surfaces and propose new structural fire-resistant materials, recommend the main and auxiliary equipment. Improving the ergonomics of cabins during firefighting will improve the safety of the operator’s working conditions. The effective operation of a forest firefighting vehicle while firefighting reduces the damage to the environment and the losses caused by the destruction of millions hectares of forest. For citation: Pitukhin E.A., Rogozin S.S. Optimizing the Forest Firefighting Vehicle Operation Modes. Lesnoy Zhurnal = Russian Forestry Journal, 2022, no. 6, pp. 139–152. (In Russ.). https://doi.org/10.37482/0536-1036-2022-6-139-152

CIEMAT experimental proposal on lithium ignition in support of DONES licensing (LiFIRE facility)

• Safe handling of lithium should be demonstrated in support of DONES licensing. • LiFIRE facility will study lithium ignition under conditions relevant for DONES. • Outcomes from LiFIRE campaign will support DONES fire protection requirements. • Preliminary design and experimental campaign of LiFIRE facility are presented. In the DEMO-Oriented NEutron Source (DONES) facility, it is expected to use a considerable amount of lithium at an average temperature higher than 300 °C. It is well known that lithium can produce exothermic reactions with several media, generating corrosive and toxic (upon burning) reaction products and with the potential risk of mobilizing radionuclides in little amounts. As a result, lithium represents a hazardous material which must be safely handled under normal operation and, especially, potential accident conditions which involve lithium spills and radioactive releases. Although the burning behavior of lithium has been studied for several decades, there is still a wide dispersion of data regarding its actual ignition temperature. Generally, measurements of the spontaneous or induced ignition temperature of a leakage of molten lithium, pool/spray type, depend on several factors such as metal purity, gas atmosphere composition and relative humidity, sample size or geometrical aspects, and even different treatments, apparatus, and techniques used. A dedicated experimental facility, called “LiFIRE”, is currently under development at the National Fusion Laboratory of CIEMAT with the purpose to quantitatively support the DONES safety analysis on the fire risk in case of lithium leakages, based on the Defense-in-Depth principle, i.e. prevention, detection and mitigation.

Effect of Natural Aging on Oak Wood Fire Resistance.

The paper deals with the assessment of the age of oak wood (0, 10, 40, 80 and 120 years) on its fire resistance. Chemical composition of wood (extractives, cellulose, holocellulose, lignin) was determined by wet chemistry methods and elementary analysis was performed according to ISO standards. From the fire-technical properties, the flame ignition and the spontaneous ignition temperature (including calculated activation energy) and mass burning rate were evaluated. The lignin content does not change, the content of extractives and cellulose is higher and the content of holocellulose decreases with the higher age of wood. The elementary analysis shows the lowest proportion content of nitrogen, sulfur, phosphor and the highest content of carbon in the oldest wood. Values of flame ignition and spontaneous ignition temperature for individual samples were very similar. The activation energy ranged from 42.4 kJ·mol−1 (120-year-old) to 50.7 kJ·mol−1 (40-year-old), and the burning rate varied from 0.2992%·s−1 (80-year-old) to 0.4965%·s−1 (10-year-old). The difference among the values of spontaneous ignition activation energy is clear evidence of higher resistance to initiation of older wood (40- and 80-year-old) in comparison with the younger oak wood (0- and 10-year-old). The oldest sample is the least thermally resistant due to the different chemical composition compared to the younger wood.

Evaluation of Steam-Exploded Wood Pellets Storage and Handling Safety in a Coal-Designed Power Plant

Solid biofuels are currently used in increasing volumes to replace fossil equivalents. Next to the traditional wood-derived fuels, the advancement of biomass upgrading technologies like steam explosion (SE), followed by pelleting, further broadens the variety of materials on the market. This thermochemical and mechanical upgrading improves greatly the general properties of such fuels (homogeneity, energy density, water resistance, biological decomposition, grindability, pneumatic transport, etc.) and at the same time offers the possibility for co-production of green chemicals/biorefinery processing. However, these alternative SE-material pellets have different properties from the fossil counterparts with regard to dust formation, dielectric, ignitability, and explosive characteristics, hence posing an increased risk of fire and explosion in handling, transport, and storage of the biosolid fuels. These divergent properties need to be properly addressed before their large implementation in the industry. To shed more light on the variability of such material properties, several batches of SE pellets varying in bulk density and subjected to different handling and storage conditions were evaluated. This was done using a number of standardized equipment and following industrial standard measurement methodologies to compare steam-exploded material with standard white wood pellets and reference coals. The main body of the work focused on the explosivity of dust generated in the handling of the pellets, studied using a Hartmann tube, coupled with a high-speed camera to evaluate the sensitivity [minimum ignition energy (MIE) and minimum explosive concentration (MEC)] and the severity maximum flame front velocity (FFVmax) of explosions of the generated SE-pellet dust. Thermogravimetric analyses (TGA) was used to measure and compare the ignitability of dust layers of SE-pellet dust vs coal and as a function of co-mixture. Finally, the SE-pellet self-heating behavior was addressed using the standard “basket method” and compared with that of a commercial coal sample. The results show that the SE pellets produce very low levels of dust even after extensive weathering, hence limiting the explosion potential. The MIE and MEC of SE-pellet dusts exhibited similar values compared to those of the parent raw biomass material; however, the FFVmax revealed lower values when compared to that of the parent raw biomass. Also, the self-heating propensity is very low as the pellets are basically immune to biological degradation, while the spontaneous ignition temperature is high and in the range of nonhazardous bulk materials.

Температура займання та самозаймання найпоширеніших деревних порід териконів

Екологічна небезпека шахтних породних відвалів в умовах урбанізованого середовища є високою. Для її оцінювання у кожному конкретному випадку потрібно проводити екологічний моніторинг для розроблення природоохоронних заходів з мінімізації негативних їх чинників. Наголошено на чинниках, які призводять до самозаймання вугільних відвалів, та на підставі наукових джерел детально описано хімізм досліджуваних процесів. Окиснення і горіння породних відвалів супроводжується значним виділенням водяної пари, яка є мінералоутворюючим середовищем для більшої частини мінералів: сульфатів, гідрокарбонатів, карбонатів, фосфатів, арсенатів. Окрім цього, внаслідок окиснення виділяється вуглекислота, нітроген оксид (IV), який з водою утворює нітратну кислоту. У разі нестачі кисню в осередках горіння в парогазових викидах міститися сірководень, вуглеводні, амоніак, оксид карбону (II). Акцентовано увагу на тому, що важливе значення в процесах окиснення належить сірці. Окиснення вугілля посилюється на дрібних частинках, через збільшення площі поверхні, що доступна для окиснення. Висвітлено, що найнадійнішим способом захисту від самозаймання вугільних відвалів є створення на їх поверхні рослинного покриву. Процес формування рослинного покриву є дуже важливим, адже при цьому відбувається як накопичення важких металів у рослинах, так і зв'язування субстрату їхніми коренями й кореневищами, що зменшує процес вивітрювання та вимивання породи, яка містить велику кількість важких металів. Встановлено показники температури займання та самозаймання зразків деревних порід відвалів вугільних шахт згідно з ДСТУ8829:2019. Дослідження показників займання та самозаймання твердих речовин і матеріалів здійснювали у весняний та літній періоди. Досліджуваними об'єктами були проби листя та деревина з терикону шахти Нововолинського гірничопромислового району (Волинська область, м. Нововолинськ). Встановлено, що для сосни звичайної температура займання становить: +225 °C, а самозаймання +475 °C. Температура займання берези повислої +260 °C, дуба звичайного +275 °C, козячої верби +280 °C, температура самозаймання – берези повислої +470 °C, дуба звичайного +475 °C, верби козячої +473 °C. Температура займання берези повислої, дуба звичайного, верби козячої ніж сосни звичайної робить їх перспективними породами дерев для запобігання самозайманню вугільних відвалів.

Modelling air injection in shale oil reservoirs: physical process and recovery mechanism

In this paper, reservoir simulation approach is conducted for qualitative analysis on EOR mechanisms of air injection in shale oil reservoirs. Effects of oxygen molecular diffusion, reaction enthalpy, activation energy, reaction scheme, and flowing well-bore pressure on the well performance of air injection are examined in detail. Results show that oxygen molecular diffusion has great effect on spontaneous ignition temperature, heat transfer and oil recovery, which should be considered in simulating air injection in shale oil reservoir for better understanding the real mechanisms. Reaction enthalpy and activation energy can significantly affect ignition temperature, but not on the production performance. High oil recovery can be favourably achieved when the crack reaction dominates, while the combustion reaction exhibits a negative effect on production performance. The development scheme with lower flowing well-bore pressure is more favourable for the air injection process. In-situ combustion and heat transfer cannot sustain due to the air low injectivity. More hydraulic fractures as well as an improved understanding of fracture and its distribution is helpful for enhancing air injectivity to better perform synergic recovery mechanisms of air injection in shale reservoirs. [Received: January 2, 2017; Accepted: June 25, 2018]

Modelling air injection in shale oil reservoirs: physical process and recovery mechanism

In this paper, reservoir simulation approach is conducted for qualitative analysis on EOR mechanisms of air injection in shale oil reservoirs. Effects of oxygen molecular diffusion, reaction enthalpy, activation energy, reaction scheme, and flowing well-bore pressure on the well performance of air injection are examined in detail. Results show that oxygen molecular diffusion has great effect on spontaneous ignition temperature, heat transfer and oil recovery, which should be considered in simulating air injection in shale oil reservoir for better understanding the real mechanisms. Reaction enthalpy and activation energy can significantly affect ignition temperature, but not on the production performance. High oil recovery can be favourably achieved when the crack reaction dominates, while the combustion reaction exhibits a negative effect on production performance. The development scheme with lower flowing well-bore pressure is more favourable for the air injection process. In-situ combustion and heat transfer cannot sustain due to the air low injectivity. More hydraulic fractures as well as an improved understanding of fracture and its distribution is helpful for enhancing air injectivity to better perform synergic recovery mechanisms of air injection in shale reservoirs. [Received: January 2, 2017; Accepted: June 25, 2018]

Preliminary Flammability Assessment of Sea Buckthorn from The Netherlands Compared to Known Flammable Shrubs of the Southern and Western US

Sea buckthorn (Hippophae rhamnoides) is a common coastal species in The Netherlands that potentially burns with extreme energy levels. In this region of Europe that is experiencing increases in wildfire events, the need to gain a greater understanding of energy released when this species burns will improve fire behavior predictions. The objective of this study was to conduct an initial investigation into the foliage flammability of sea buckthorn to a common southern United States native shrub known for its flammability, yaupon (Ilex vomitoria), and two common dominant shrub species in California chaparral, chamise (Adenostoma fasciculatum), and manzanita (Arctostaphylos spp.). Flammability parameters were evaluated using thermogravimetric analysis (TGA) and oxygen bomb calorimetry to estimate relative spontaneous ignition temperature (RSIT), gas-phase maximum mass loss rate (GP-MMLR), gas-phase combustion duration (GP-CD), volatile matter%, fixed carbon%, ash%, and net heat content (NHC). Sea buckthorn exhibited similar ignitability ( GPMMLR) to yaupon. Sea buckthorn and yaupon shared similar NHC values and subsequent fire behavior outputs. Proximate analysis for VM% and FC% were varied, but low ash% values correlated with slightly lower RSIT’s for sea buckthorn and chamise. Anecdotal information from a 2019 prescribed burn along the coast of The Netherlands highlighted significant fire behavior, and shows similarities with these species in two North American ecosystems.

COMPARISON OF POTENTIALALLY DANGEROUS FACTORS WITH THE USE OF RARE AND GASILY VEHICLE

A detailed analysis of the potentially dangerous factors in the use of diesel, gasoline, methane and propane-butane fuels was carried out in cars. A detailed analysis of potentially dangerous factors when using diesel, gasoline, methane and propane-butane fuels in automobiles has been carried out. 6 options of fuel usage are considered: a tank with g asoline and a system supplying it to the carburetor and further to the engine cylinders, a tank with diesel fuel and the system feeding it to the engine cylinders, gas cylinder installation when installing cylinders with methane on the roof of the car, gas cylinder installation when mounting cylinders with methane in the luggage compartment of the car, gas installation when installing cylinders with propane-butane mixture on the roof of the car, gas installation when installing cylinders with propane-butane mixture in the cargo compartment of the car. Meanwhile, the potential danger while the vehicle is in motion is analyzed, as well as while it is in the open parking lot and in the garage. As the initial data, the common operation period was taken - in summer with the temperature of 30°C and possible fuel leakage with the probability of formation of an explosive mixture. Nonane is taken as a model when considering gasoline, and Pentadecane is used for diesel fuel.
 It was noted that the gasoline self-ignition temperature ranges from 255°С to 435°0С, the lower concentration limit of petrol explosiveness can be considered as 0.76% vol., while under selected conditions indoors, gasoline vapor can reach the concentration of up to 0.8 vol. %. The relative vapor density of diesel fuel betting the same conditions is 8.52 kg/m3. With the explosion, the pressure in the closed volume will reach 5.2 atm.
 It was noted that the gasoline self-ignition temperature ranges from 210°С to 370°0С, the lower concentration limit of petrol explosiveness can be considered as in % vol., while under selected conditions indoors, gasoline vapor can reach the concentration of up to 0.13 vol. %. With the explosion, the pressure in the closed volume will reach 5.0 atm.
 The self-ignition temperature of methane is 537°C, the lower concentration limit of explosiveness of this gas is 5.28% (vol). The vapor density of methane at the temperature of 300°C (303K) is 0.64 kg/m3, which is significantly less than the density of air. The explosion pressure in the closed volume will reach 7.7 atm.
 The propane-butane mixture used in summer contains about 40% of propane and 60% of butane. Spontaneous ignition temperature of propane is 4700C, butane is 4050C. The calculated lower explosion limit of this mixture is 1.5% (vol), and the vapor density of mixture at the temperature of 300°C is 2.1 kg/m3, which is almost twice the density of air under the same conditions. The calculated explosion pressure in the closed volume will reach 8.3 atm.
 It was concluded that when using certified equipment which is professionally installed, methane, which cannot accumulate in the lower part of the room or any compartment, is much safer than propane-butane and, especially, than gasoline or diesel fuel, as vapor densities of both are more than air density.

Study on Sensitivity Differences of Critical Spontaneous Ignition Temperature between Alcohol and Hydrocarbon Fuels Based on Reaction Pathway

In this article, the critical spontaneous ignition temperature of both hydrocarbon and alcohol fuel was acquired on a constant volume combustion bomb platform by slowly heating the inner charges, and then followed by using the CHEMKIN-PRO software to simulate the auto-ignition-dominated characteristic and parameter sensitivity of the two kinds of fuels. Results revealed that in different conditions, the critical spontaneous ignition temperature of methanol changed dramatically, with a maximum temperature of 50 K, while the counterpart temperature of n-heptane remained an invariable value of 553 K within a large changeable scope of temperature, and only a maximum temperature of 10 K was observed. The maximum difference of spontaneous ignition temperature between methanol and n-heptane reached 270 K. At the same time, a minimum difference of 170 K was obtained as well. The complete reaction of methanol requires 5 steps, involving 6 components and 11 elementary reactions. However, for the comparative part-n-heptane, more than 20 main self-ignition reactions were involved, which indicated that the whole reaction process of n-heptane has more reaction pathway branches and it was much more complicated compared to methanol. The differences of the reaction pathways triggered a considerable distinction of critical self-ignition temperature between the two charges, making a “step-by-step” spontaneous ignition combustion mode possible. In this way, a further high-efficient and clean combustion can be available to cater to much more stringent emission regulations in the future.

페놀의 연소특성치의 측정 및 예측

The fire and explosion properties necessary for waste, safe storage, transport, process design and operation of handling flammable substances are lower explosion limits(LEL), upper explosion limits(UEL), flash point, AIT( minimum autoignition temperature or spontaneous ignition temperature), fire point etc., An accurate knowledge of the combustion properties is important in developing appropriate prevention and control measures fire and explosion protection in chemical plants. In order to know the accuracy of data in MSDSs(material safety data sheets), the flash point of phenol was measured by Setaflash, Pensky-Martens, Tag, and Cleveland testers. And the AIT of phenol was measured by ASTM 659E apparatus. The explosion limits of phenol was investigated in the reference data. The flash point of phenol by using Setaflash and Pensky-Martens closed-cup testers were experimented at 75℃ and 81℃, respectively. The flash points of phenol by Tag and Cleveland open cup testers were experimented at 82℃ and 89℃, respectively. The AIT of phenol was experimented at 589℃. The LEL and UEL calculated by using Setaflash lower and upper flash point value were calculated as 1.36vol% and 8.67vol%, respectively. By using the relationship between the spontaneous ignition temperature and the ignition delay time proposed, it is possible to predict the ignition delay time at different temperatures in the handling process of phenol.

Impact of thermal loading on selected chemical and morphological properties of spruce ThermoWood

Physico-chemical changes to ThermoWood produced from Norway spruce (Picea abies L.) with the dimensions 20 mm × 20 mm × 10 mm were evaluated as a function of thermal loading at a flame ignition temperature (FIT) and spontaneous ignition temperature (SIT). The extractives, cellulose, holocellulose, and lignin contents were determined by wet chemistry methods. Carbohydrates and cellulose changes were investigated by high-performance liquid chromatography and size exclusion chromatography. The dimensional characteristics of the fibers (length, width, and shape factor) were measured. After thermal loading, an increase in both the cellulose (FIT – 33.1%, SIT – 64.6%) and lignin (FIT – 28.3%, SIT – 63.4%) contents and a decrease in the extractives content (approximately 8% to 9%) were observed. The increase in the cellulose content was attributed to structural changes (carbonization and crosslinking). The lignin content increased because of condensation and its greater thermal stability compared with carbohydrates. After the thermal treatment, saccharides content was lower due to degradation of non-glucosic saccharides (mainly pentosans – 51.3%). The cellulose degree of polymerization decreased by 40.8% during thermal loading at the FIT and by up to 75.4% at the SIT. Thermal loading of ThermoWood samples caused a significant decrease of fibers average width.

Comparison of thermal properties of the fast-growing tree species and energy crop species to be used as a renewable and energy-efficient resource

The energy stands of fast-growing tree species and crops are a prospective resource of renewable energy to the future. The paper focuses the assessment and comparison of the thermal properties of selected species of fast-growing trees (Paulownia tomentosa, Salix viminalis clone Tora, Populus × euramericana clone MAX 4) and energy crops (Sida Hermaphrodita, Arundo donax, Miscanthus × giganteus), as well as ash content (mass%). The following fire and thermal and properties were tested: spontaneous ignition temperature, gross caloric value, heating value. Besides those parameters, the elemental composition and ash content of the samples tested were analyzed. The results showed the energy crops to be much more effective for energy production than the energy trees. It is mostly due to higher yields harvested in a relatively short time, increased share of fiber, as well as higher energy efficiency. The highest heating value (energy potential) in case of energy crops showed Miscanthus × giganteus (16.29 ± 0.14 MJ kg−1), which had the lowest ash content (2.67 ± 0.08 mass% on average). The highest heating value in case of fast-growing tree species showed Paulownia (16.40 ± 0.18 MJ kg−1), which also had the lowest ash content (0.75 ± 0.05 mass% on average), while the Populus had the highest one (2.58 ± 0.24 mass% on average).

КИНЕТИЧЕСКИЙ ПОДХОД ПРИ РАСЧЕТЕ ПАРАМЕТРОВ ПОЖАРОВЗРЫВООПАСНОСТИ ГАЗОВЫХ СМЕСЕЙ МЕТАНА С ХЛОРОМ

Purpose. The computational method of indexes of fire-and-explosion hazard of gas mixtures a kinetics and the mechanism of chemical interaction which is based on a heat conduction equation and considering is considered. This method allows to define indicators of fire-and-explosion hazard of substances which can enter among themselves chemical reaction. That methods where for definition of indexes of fire-and-explosion hazard of substances use a structure of molecules do not allow and can be applied only to one homologous series. Methods. Calculation of indicators of fire-and-explosion hazard was carried out by means of the mathematical model of thermal ignition developed by authors in the environment of MATLAB. Researches were conducted for gas mixes of methane, chlormethane and dichloromethane with chlorine at ignition of these mixes heat and ultra-violet light, in a cylindrical vessel of long 0.04 m, with a diameter of 0.036 m. For creation of model the chemical kinetics of elementary reactions of these mixes is considered. Coefficients of heat conductivity and thermal capacity for initial composition of mix paid off, and during chemical transformations considered their change from temperature. Results of calculation were compared to experimental data. Findings. By means of model of thermal ignition for mixes of methane, chlormethane and dichloromethane with chlorine concentration limits of photoignition and critical intensity of ultra-violet light have been set. For chlormethane mix with chlorine the minimum phlegmatizing concentration of four-chloride carbon is defined, and for methane with chlorine spontaneous ignition temperature is calculated. Results of calculation of indicators of fire-and-explosion hazard for these mixes enough with a good accuracy coincide with experimental data. Conclusions. The model of thermal ignition which is based on the equation of heat conductivity and considering kinetics and the mechanism of chemical reaction authentically reflects a physical picture of ignition and gives the chance for chlorine mixes with methane and its chlorderivatives to estimate such parameters as: concentration limits of photoignition, critical intensity of UV-light, minimum phlegmatizing concentration and temperature of spontaneous ignition. This method has shown a possibility of calculation of indicators of fire-and-explosion hazard of gas substances for kinetic data on the mechanism of chemical interaction and to constants of speed of elementary reactions.

Fuel Cells and the Self Ignition Temperature of Hydrogen

The theoretical open circuit voltage of 1.23V has never been observed for low temperature fuel cells, while excellent agreement with theory is found for SOFCs. Apparently, one has overlooked that spontaneous fuel cell reactions of H2 and O2 cannot occur below the Spontaneous Ignition Temperature (585°C). A hypothesis is presented for the electrochemical low temperature combination of H2 and O2 based on the formation of Hydroxyl. A steady state OCV of 0.876V is obtained for fuel cells operating at 25°C. This hypothesis is supported by many experiments. Apparently, the Spontaneous Ignition Temperature separates the two regimes of fuel cell conversion: 2H2 + O2 => 2H2O at high and H + O => HO at low temperatures.

Модификация аддитивно-группового метода для описания показателей пожарной опасности предельных углеводородов: температур вспышки и самовоспламенения, энтальпии испарения

Модификация аддитивно-группового метода для описания показателей пожарной опасности предельных углеводородов: температур вспышки и самовоспламенения, энтальпии испарения

The development of a model for the prediction of polymer spontaneous ignition temperatures in high pressure enriched oxygen across a range of pressures and concentrations

High pressure enriched oxygen is used in a wide number of areas, including aircraft, medical breathing apparatus, diving, mining and mountaineering operations. It is also used for a number of industrial processes, but is most commonly used for combustion. Where the pressure or concentration of oxygen is increased well above that of atmospheric, oxidation reactions occur more readily, and at a faster rate, relative to those under atmospheric conditions. Thus the criteria used for polymer selection is key to preventing, or at least limiting, the possibility of a catastrophic oxygen incident which endangers both property and human life. In this work spontaneous ignition temperature (SIT) data obtained in high pressure enriched oxygen from both differential scanning calorimetry and oxygen bomb testing are compared. A model is derived to enable the calculation of a SIT of a non-metal at any pressure and oxygen concentration using existing test data from other pressures. This has been shown to work with reasonable success for most materials tested, being validated using the comparison of test data from the oxygen bomb test and Pressurised Differential Scanning Calorimetry (PDSC) testing. These results may indicate the suitability of a PDSC for safety testing in the future. Further work is needed to increase the data base of ignition test data from PDSCs, and thermodynamic constants to allow for the direct comparison, and to assess the suitability of this apparatus for safety testing of more materials.

Test and study on spontaneous ignition temperature of a Philippine coal

Temperature programmed method is adopted to study spontaneous combustion of a Philippine coal. A tested sample exposed to the air and a reference sample isolated from the air are placed and heated in an oven. When the tested sample temperature reaches a certain value, spontaneous combustion occurs, causing the temperature increase curves of the two samples separating. Two different holders, isothermal copper tube and stainless steel basket, are used respectively to simulate two different temperature and oxygen concentration boundary conditions. The results show that spontaneous ignition temperature of the coal in the isothermal tube only with top cover ventilation is about 120°C, while that of the sample in the basket with six-surface ventilation is about 100°C. Additionally, as the temperature of the sample in the basket is higher than 40°C, the temperature increase curve deviates from the original trend due to heat release from oxygen adsorption.