Особенности пожароопасных свойств семян подсолнечника, способов их хранения и тушения

Preparation of fully physically crosslinked double-network gel and its fire prevention mechanism

The spontaneous combustion of residual coal in compound goaf formed by shallow and close coal seam mining is one of the difficulties in mine fire prevention and control. In order to explore the mechanism of spontaneous combustion of residual coal in 22304 working face of Huojitu minefield in Daliuta coal mine, the causes of spontaneous combustion of residual coal in 22304 working face are studied by comprehensively applying the methods of experiment, numerical calculation, and field measurement, the limit parameters of spontaneous combustion of 22304 working face are obtained, and the risk of spontaneous combustion in 22304 working faces is divided. The results show that the critical oxygen concentration of coal in 22304 face is 8%, and the width of inlet airside and return airside of oxidation temperature rise zone in composite goaf is 245 m and 170 m. When the advancing speed of 22304 working face is greater than 7.42 m/d, it can effectively avoid spontaneous combustion in goaf. Finally, the fire prevention and extinguishing measures of composite goaf after temporary shutdown when the working face passes through faults and other geological structures are discussed. The findings have certain reference significance for the division of goaf spontaneous combustion risk areas and the formulation of fire prevention and extinguishing schemes under similar conditions.

The article is devoted to the study of the causes and conditions of spontaneous com- bustion of sulphide ores, which may result in endogenous fires that complicate mining operations in mines, causing enormous material damage to the national economy, and often also leading to human casualties. There are several sulphide-polymetallic deposits in Azerbaijan, the reserves of which were approved back in the days of the USSR. Of these, the Filizchay deposit is the most unique in terms of its reserves and ore composition. The development of other deposits adjacent to the Filizchay deposit, separately, is inexpedient because of their small reserves. However, the development of sulphide-polymetallic deposits in Azerbaijan is complicated by the revealed tendency of industrial types of ores to oxidation and spontaneous combustion. In this regard, there was a need for a special study of the chemical activity of sulphide ores and the phenomena accompanying oxidative processes, taking into account the natural features of the deposits in order to obtain the initial parameters necessary for scientifically based technological solutions for their development. Sulphide ores of sulphide -polymetallic deposits of Azerbaijan significantly differ in material composition, conditions of occurrence and mining technical features of their development from the listed deposits, the issues of spontaneous combustion of which have been studied for a long time. Until now, there are no general criteria for assessing the fire hazard of sulphide ores, suitable for any deposit, since the conditions for the occurrence of underground fires at different deposits are different. It is this circumstance that makes it necessary to conduct special studies for each deposit separately. Therefore, the need for a special study of this problem on the example of the conditions of sulphide-polymetallic deposits in Azerbaijan, which are prone to oxidation and spontaneous combustion, is of great importance. Identification of causes and factors affecting spontaneous combustion of sulphide ores, classification of sulphide-polymetallic deposits of Azerbaijan according to the degree of their tendency to spontaneous combustion by analyzing the collected materials, as well as by the results of studies to determine the oxidative activity of sulphide ores. The article presents the results of experimental studies to determine the oxidative activity and spontaneous combustion of sulphide ores of the Katsdag, Filizchay and Katekh deposits, carried out in laboratory conditions by the method of Institute of Mining named after. A.A. Skochinsky, the basis of which is the determination of the oxygen absorption rate constant. It is known that the susceptibility of ore to spontaneous combustion is determined by its oxidizability at low temperatures and depends on a large number of factors. In this regard, the dependence of the total amount of oxygen absorbed by sulphide ores on time has been studied, it has been established that the rate of oxygen absorption by sulphide ores is long-live and slowly fading, but incessant. On the basis of extensive experimental material, a classification of sulphide ores of Azerbaijan according to the degree of tendency to spontaneous combustion according to low-tempera-ture oxidation is proposed, since it is this that forms the basis of the spontaneous combustion process. The classification is also based on differences in textural and structural features and mineralogical composition of ores. Of great interest is also the influence of the size of the free reacting surface of the ore on the oxidation process. Analysis of ore samples shows that for their spontaneous combustion, the most dangerous are its coarse fractions than the dust. The results of the conducted studies allow a scientifically sound approach to planning the sequence of development and designing mines.

Coal spontaneous combustion (CSC) in goafs, one of the most serious disasters in coal mines, not only wastes resources and destroys the ecological environment, but also causes casualties. As global underground mining gradually shifts to the deep, this problem becomes increasingly prominent. Deep mining is operated in a complex mechanical environment characterized with high stress, high permeability, high temperature, and strong mining disturbance. To avoid stress concentration areas, narrow coal pillars are often utilized in roadway excavation along the goaf. However, narrow coal pillars are likely to fracture and lose stability during the mining process. Consequently, goaf areas of two adjacent working faces might connect, which promotes the CSC risk in the goaf. Most of the current researches are focused on CSC risk areas under shallow mining conditions and the CSC-gas coupling disasters, yet research on CSC risk areas in the goaf triggered by narrow coal pillars under deep mining conditions is rarely reported. Moreover, there is a lack of relevant means to prevent and extinguish fires. This study takes the narrow coal pillar-utilized 130,205 working face in Yangchangwan Coal Mine as the research object. First, the development of coal pillar fractures was simulated by adopting the discrete element method of PFC. Besides, on-site monitoring and FLUENT numerical simulation were conducted to identify CSC risk areas in the goaf of the narrow coal pillar-utilized working face. Finally, a double-pipe liquid CO2 injection technology was proposed for fire prevention and extinguishing. The following beneficial results were obtained. Affected by high stress in deep mining, the coal pillar collapses, which expands the range of the oxidation zone on the return side. Meanwhile, the adjacent goaf is also exposed to CSC risk. Double-pipe liquid CO2 injection can effectively reduce air leakage near the working face and suppress spontaneous combustion of residual coal by inerting the goaf. This study can provide guidance and reference for fire prevention and extinguishing in goafs under the condition of narrow coal pillar-utilized deep mining.

In the coal mining process, injecting nitrogen into thegoaf isan effective method to suppress coal spontaneous combustion, whichis widely adopted due to its significant inhibitory effect and lowcost. Optimizing the injection volume and position of nitrogen iscrucial for enhancing fire prevention and extinguishing efficiencyand reducing safety risks. This study utilized CFD numerical simulationtechnology to investigate the spontaneous combustion risk in the goafof the 81203 working face in Baode Coal Mine under the combined U+ L ventilation and downwind ventilation conditions. The influenceof different nitrogen injection positions and volumes on the distributionof the “three zones” related to coal spontaneous combustionin the goaf was analyzed. By simulating the changes in the oxygenand methane concentration fields in the goaf, this study proposedan optimized nitrogen injection strategy to improve fire preventionand extinguishing efficiency. The results show that setting a nitrogeninjection port 90 m from the working face on the intake side of the81203 auxiliary transport drift and injecting at a rate of 400m3/h meters per hour can achieve the best inhibitory effectand reduce costs.

Extinguishing fires in ecosystems has features compared to extinguishing fires in residential and industrial buildings, due to the composition and structure of combustible materials, which can form many foci of smoldering and have the ability to re-ignite, have a relatively low fire load compared to man-made ones. All this leads to high costs of water for extinguishing, carrying out operations for additional extinguishing of fires that occur after the main extinguishing and sets special requirements for aqueous extinguishing agents for their extinguishing.The paper analyzes the current state of the availability and trends of development in the world and domestic practice of effective water extinguishing agents and technologies for their use. Possible ways to improve recipes and increase the efficiency of fire extinguishing substances are outlined, taking into account, first of all, the criteria of efficiency, economy and environmental friendliness.It is noted that the main direction of increasing the fire extinguishing capacity of water is to create combined fire extinguishing solutions that can combine several methods of extinguishing in one technological operation: cooling, isolation and inhibition, which, other things being equal, reduces fire extinguishing consumption and extinguishing efficiency. An integrated direction of increasing the fire-extinguishing capacity of water can be considered to increase the coefficient of active use of water by reducing the surface tension of the fire-extinguishing solution, increasing the wettability and viscosity of water by introducing appropriate additives, obtaining optimal droplet dispersion.

Background: Fire safety is one of the most important issues in high-rise buildings. The purpose of this study is to assess maximum possible loss in the fire in Central Insurance Building of Islamic Republic of Iran using the layer of protection analysis (LOPA) method.
 Method: In 2017, this analytical study was conducted on the 21-floor building of the Central Insurance in Iran. To identify the hazard sources and assess the maximum possible loss, the authors used the preliminary hazard list (PHL) and layer of protection analysis (LOPA) respectively. In addition, the analysis of the study data was performed based on the 10×10 risk assessment matrix.
 Results: The results of the PHL showed that 26 hazardous conditions and four major sources including structural engineering, fire alarm systems and fire extinguishers, design and maintenance of building safety, and behavioral habits were identified as main hazards of fire in the studied building. The application of the LOPA method showed that highest risk level was associated with the fire caused by the exhaust heat from the engine room (RL=48) and the emergency power generator diesel (RL=40), respectively.
 Conclusion: The findings of this study indicated that calculating the maximum possible loss in the fire of high-rise buildings can help to increase the safety factor. Moreover, the use of the two methods, PHL and LOPA, can be useful in these types of risk assessments.

Aim: The aim of this paper is to present the construction and principle of operation of condensed aerosol generators, as well as a review of their selected characteristics, confirmed in the process of assessment and verification of constancy of performance. The paper describes selected laboratory tests, including those specific to Group A, B and C fires. Introduction: Fixed firefighting systems, in addition to detection systems (fire alarm system) and alarm systems (voice evacuation systems), are one of the pillars of the safety of today's erected, increasingly complex buildings. However, unlike these detection and alarm systems, fire extinguishing systems based on condensed aerosol generators focus on providing an adequate level of protection for property, as they are dedicated to spaces that are not normally occupied. For this reason, emphasis is placed on the reliability of the generators, whose only task is to trigger appropriately at a specific time and fill the protected area with aerosol. Methodology: The theoretical research, such as analysis of literature and legal documents, synthesis, generalisation, inference, comparison and analogy, was used in the development of the paper. A review of selected characteristics validated in the process of assessment and verification of constancy of performance of the analysed products was carried out. Research processes relating to selected parameters of the generators and inherent in the conformity assessment of construction products are presented. Conclusions: It should be noted that, irrespective of their main purpose, condensed aerosol generators, which are a key component of aerosol fire extinguishing kits, can be crucial not only with regard to the safety of the buildings themselves, but also of their users, influencing the containment of a fire in the extinguishing zone where they are installed. Also, important is the awareness of owners and managers of building structures equipped with condensed aerosol generators. Their particular attention should be directed to the specifics of the generator itself and their knowledge of its operating principles. In the next stages of the work, it will be crucial to define the basics related to the connection of the generators to the installation forming a fixed firefighting system, to identify and describe issues related to design, installation and maintenance, and to identify the risks related to the potential exposure of the users of built structures to the extinguishing aerosol.

Computational framework for assessing the fire resilience of buildings using the multi-layer zone model

Fire-retardant foam designed to control the spontaneous combustion and the fire of coal: Flame retardant and extinguishing properties

The numerical simulation is used to research the influence of nitrogen injection on spontaneous combustion in goaf. The spontaneous combustion mathematical model on the coupling of air flow field, oxygen concentration field, and residual coal temperature field was established with nitrogen injection in goaf. Then the software of numerical computation was programmed by Finite Volume Method. Combined with the example, the distributions of air flow field, oxygen concentration field and residual coal temperature field at different nitrogen injection volume were obtained by the software. The results show that the nitrogen injection could effectively prevent the spontaneous combustion fire in goaf and the highest temperature in goaf decreased with the nitrogen injection volume increasing. Finally, the accuracy of the numerical simulation was verified by the temperature observation in field. The achievement of this research is of theoretical and practical significance for the prevention of coal spontaneous combustion in goaf.

The mining technology of gob-side entry retaining without a coal pillar is gradually becoming a mature and increasingly important mining technology. As it maintains the roadway near goaf, the air leakage should be greater than a U-type ventilation system in goaf, so it is prone to cause coal spontaneous combustion problems. CO2 is an inert gas, and it is usually used to prevent spontaneous combustion and extinguish coal fire. However, there is a lack of research on characteristics and safety of CO2 for the mining technology of gob-side entry retaining without the coal pillar. In this paper, the indexes of influencing factors were proposed on gas, pipelines, and mining technical parameters. Using a three-dimensional physical model of coal stope, the gas migration law of CO2, the relationship between gas injection rate and the oxidation zone area, and the safety of the CO2 inerting technology were analyzed. The results indicate that the O2 concentration is diluted between the working face and the injection port, especially in the air intake side. Furthermore, the CO2 injection rate is an important parameter to the fire prevention and extinguishing technology. When the gas injection rate ranges from 240 to 720 m3/h, the oxidation zone area varies from 7380 to 14 760 m2, and the gas injection rate grows exponentially with the area of the oxidation zone. Moreover, the redundant CO2 gas flows to the retaining roadway, and it reduces the O2 concentration, resulting in asphyxia accidents of miners. The research results are helpful to balance the relationship between inert gas injection and production safety and provide guidance for the practical application of the inert gas fire prevention technology.

Judging development trends in coal spontaneous combustion (CSC) accurately has long been a global problem. Once a CSC phenomenon is found, the coal temperature tends to reach or exceed the critical temperature. To address this problem, the CSC characteristic parameter testing device is used to simulate the air reduction environment after the coal low temperature oxidation reaches the critical temperature, and long-flame coal was tested. The results show that the gas index can be used to judge the development trend and the characteristic temperature point for the initial stage of CSC. The development of oxidation at low temperature can be effectively predicted by using the composite indexes-Graham (G), CO/CO2 and 100× (C2H4/CO). Based on this information, a multi-index early warning method for comprehensive classification was proposed. The results have guiding significance for determining the development trend of CSC fires and fire prevention and extinguishing work. [Received: August 10, 2019; Accepted: May 26, 2020]

To address the environmentally friendly issue of fire prevention and extinguishing materials in coal mines, a new biomass gel material was prepared using sodium carboxymethyl cellulose (CMC) as the matrix, ferro aluminum citrate (Fe-AlCit) as the cross-linking agent, and gluconic acid-δ-lactone (GDL) as the pH modifier. Through performance tests of gel micromorphology, thermal stability, viscoelasticity and yield stress, it was found that the CMC-3 gel material with a ratio of 2.5% CMC + 4% Fe-AlCit +2% GDL had a dense surface structure, good thermal stability and moderate viscosity, which was the most suitable for pipeline transport. A metal coordination bond favorable to the stability of CMC-3 gel is formed by the carboxylate ion in CMC and the double high-valent metal ions Fe3+ and Al3+ dissociated by Fe-AlCit. CMC-3 gel exhibits excellent fire prevention and extinguishing properties. The results of the programmed warming experiments showed that the inhibition rate of the coal sample treated with CMC-3 gel against CO and C2H4 gases reached 44.84% and 46.57% at 220°C, respectively, and the growth rate of the activation energy in the first and second stage reached 17.63% and 22.68%, respectively, which plays a significant inhibitory role. The infrared spectroscopy test showed that after adding CMC-3 gel, the content of -OH and Ar-C-O in the coal samples was reduced by 49.58% and 40.82%, respectively, and the content of stable C=C in the aromatics was increased by 6.14%, which effectively blocked the coal-oxygen chain reaction and reduced the tendency of coal spontaneous combustion. The thermogravimetric test showed that the characteristic temperature points of the coal sample treated with CMC-3 gel were all increased to different degrees. The fire extinguishing test showed that CMC-3 gel could significantly reduce the temperature of coal sample and extinguish the coal fire quickly. Moreover, the CMC-3 gel material also has excellent self-healing properties, which can self-repair the damaged network through the abundant reversible hydrogen and ionic bonds inside the gel in only 90 s. The study has certain guiding significance for the development of efficient and environmentally friendly self-healing mining fire prevention and extinguishing materials.

Comparative study of single inert gas in confined space inhibiting open flame coal combustion