Flammability Research Articles

Process upgradation and kinetic modeling of high-ash non-coking coal flotation using bio-based collector for enhanced clean coal recovery

ABSTRACT The reduction of ash content, contributed by inorganic mineral matter, and recovery of carbon values in a high ash non-coking coal was studied in a laboratory-scale mechanical flotation cell using a bio-collector (PSO) derived from the pumpkin seeds for clean coal recovery. Surface characterization of PSO (GCMS, FTIR) and untreated/PSO-treated coal (contact angle, FTIR) indicated potential interaction between PSO and the coal surface, enhancing its hydrophobicity, while XRD analysis confirmed successful rejection of ash-forming inorganic gangue minerals into tailings, signifying effective clean coal separation from the gangue. The input parameters, such as PSO dosage, frother MIBC dosage, and airflow rate (AFR), were enhanced to attain best process responses, i.e. yield, ash, and fixed carbon of the final clean coal. The use of PSO significantly reduced the ash content of feed coal from 32% to as low as 9.86% in the final clean coal while simultaneously increasing the fixed carbon content from 35% to 61.15% and the gross calorific value from 4966 Kcal/Kg to 6318 Kcal/kg. A clean coal product having high fixed carbon of 61.15% with 11.29% ash content and 70.14% yield was obtained at PSO dosage of 10.73 Kg/t, MIBC dosage of 0.93 Kg/t and at AFR of 2.5lpm. The kinetic study revealed a high recovery of combustible materials (~88%) and low ash recovery (~46%) at a flotation time of 480 seconds. Based on the kinetic model discrimination analysis, it was found that the first-order fits well with the experimental data for combustible and ash recovery. This study illustrates the efficacy of pumpkin seed oil (PSO) as a potential bio-collector for the flotation of non-coking coal, enhancing the coal quality by selectively reducing mineral matter content and leading to substantial economic and environmental advantages.

Chitosan-based films with excellent flame retardancy and highly sensitive fire response for application in self-powered dual fire alarm systems.

The widespread use of flammable building materials severely threatens residential safety. Additionally, traditional fire-alarm systems may fail in complex fire environments due to power disruptions. It is crucial to enhance the flame retardancy of material while establishing effective fire detection and early warning systems. This study prepared a chitosan/gelatin (CG) and LiBr-modified CG (CG-LiBr) composite film using an environmentally friendly water evaporation method. We coated the CG-LiBr film with polytetrafluoroethylene (PTFE), thus a flame-retardant and conductive PTFE-coated film-based triboelectric nanogenerator (PF-TENG) was developed. Notably, the CG-LiBr film exhibits outstanding alarm capabilities, with response times of 0.41 s at 100 °C and 0.4 s under flame attack. Compared to the initial CG, CG-LiBr shows a 24.4 % increase in char residue and a 62.1 % reduction in peak heat release rate. Furthermore, PF-TENG demonstrates excellent voltage output, achieving up to 60.8 V at a vertical contact-separation frequency of 5 Hz. Integrating CG-LiBr's exceptional dual-alarm function into fire protection suits and building materials, along with the development of a fire-alarm system featuring remote signal transmission capabilities, holds considerable promise for enhancing fire safety and developing intelligent early warning systems.

New Insights for Improving Low-Rank Coal Flotation Performance via Tetrahydrofurfuryl Ester Collectors

With the advancement of large-scale coal development and utilization, low-rank coal (LRC) is increasingly gaining prominence in the energy sector. Upgrading and ash reduction are key to the clean utilization of LRC. Flotation technology based on gas/liquid/solid interfacial interactions remains an effective way to recover combustible materials and realize the clean utilization of coal. The traditional collector, kerosene, has demonstrated its inefficiency and environmental toxicity in the flotation of LRC. In this study, four eco-friendly tetrahydrofuran ester compounds (THF-series) were investigated as novel collectors to improve the flotation performance of LRC. The flotation results showed that THF-series collectors were more effective than kerosene in enhancing the LRC flotation. Among these, tetrahydrofurfuryl butyrate (THFB) exhibited the best performance, with combustible material recovery and flotation perfection factors 79.79% and 15.05% higher than those of kerosene, respectively, at a dosage of 1.2 kg/t. Characterization results indicated that THF-series collectors rapidly adsorbed onto the LRC surface via hydrogen bonding, resulting in stronger hydrophobicity and higher electronegativity. High-speed camera and particle image velocimeter (PIV) observation further demonstrated that THFB dispersed more evenly in the flotation system, reducing the lateral movement of bubbles during their ascent, lowering the impact of bubble wakes on coal particles, and promoting the stable adhesion of bubbles to the LRC surface within a shorter time (16.65 ms), thereby preventing entrainment effects. This study provides new insights and options for the green and efficient flotation of LRC.

A fuzzy logic-based risk evaluation and precaution level estimation of explosive, flammable, and toxic chemicals for preventing damages.

Chemical industries are highly vulnerable to accidental events or terrorist attacks due to their processing, storage, and transportation of explosive, flammable, and toxic materials. Major industrial risks include fire, explosion, and toxic chemical release. An effective risk evaluation system is essential to prevent accidents or terrorist attacks. The proposed system can evaluate the risk of handling hazardous chemicals and determine the appropriate precaution level to prevent accidents using a fuzzy inference system. The inventory size, explosiveness, flammability, and toxicity of the chemicals are used as input variables for evaluating the output variable risk. The defuzzified value of risk indicates the amount of damage it can cause if accidents happen. Using the calculated risk value and the location of the chemical industry as input variables, precaution level can be determined. Security arrangements have been recommended based on the different precaution levels so that industries can take appropriate measures according to the calculated results. This approach helps to protect the environment and save lives from any mishaps.

Double-layer microencapsulation of ammonium polyphosphate and its enhancement on the hydrophobicity and flame retardancy of cellulose paper.

Cellulose paper is a flammable and hygroscopic material, which limits its application. In this paper, melamine-formaldehyde resin (MF) and silane coupling agents were used to microencapsulate ammonium polyphosphate (Si@MFAPP) in turn and added to the fibers suspension to prepare hydrophobic and flame-retardant cellulose paper. It was found that the surface of the ammonium polyphosphate (APP) was smooth with the water solubility of 0.24 g/100 mL. After microencapsulation with MF, the surface of MFAPP became rough, and the solubility was reduced to 0.1 g/100 mL. When further encapsulation with polysiloxanes, the surface showed significantly higher roughness, and a lotus leaf-like microspherical structure was formed. Specifically, its solubility decreased to 0.04 g/100 mL. In addition, the residual char weight of Si@MFAPP at 800 °C was increased from 25.27 % to 38.56 %. The water contact angle (WCA) of MFAPP/Pulp increased from 84.23° to 90.78°, and the limiting oxygen index (LOI) increased from 31.8 % to 34.1 %, meaning that the flame retardancy was obviously raised. The WCA of Si@MFAPP/Pulp enhanced to 96.45°, and the LOI was 34.5 %, meaning that the hydrophobicity was further raised. Therefore, Si@MFAPP significantly improved the flame-retardancy and hydrophobicity of the cellulose paper.

A simultaneous X-ray fluorescence and diffraction analysis method for internal depth profile probing of the volume of material

A simultaneous X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis method for probing the internal depth profile of a material using tungsten target and cadmium telluride (CdTe) detectors is presented. To select a suitable target source, a Geant4 simulation is used to simulate the characteristic X-ray photon numbers produced by metallic materials with atomic numbers ranging from 24 to 92. The fluorescence analysis demonstrates the ability to measure intensity-depth profiles to greater than 500 μm depth in CeO2 powder, at least 400 μm depth in Er2 O3 powder, at least 200 μm depth in WO3 powder and up to 500 μm depth in Bi2 O3 powder. In addition, the diffraction analysis demonstrates the capacity to measure intensity-depth profiles to a depth of greater than 5 mm in silicon powder, at least 2 mm depth in nickel powder and up to 200 μm depth in tungsten powder. This method could be extended to component and phase detection in the safety inspection of flammable and explosive materials.

Asphyxiation effect analysis in confined space of B-type oil pool fire under pressure changes of nitrogen extinguishing system

Nitrogen fire extinguishing system has a significant development space in the modern fire extinguishing because of its environmental protection, energy saving and high stability. To further broaden the application field of nitrogen fire extinguishing system, a shrinkage size model was used as the research object and combined with simulated flow field analysis. A nitrogen fire extinguishing system was characterized for alcohol fire extinguishing efficacy using nitrogen injection pressure as a variable and parameters such as extinguishing time, oxygen concentration, and temperature. Furthermore, diesel and gasoline were used as combustible materials to verify the extinguishing efficacy of pressure variation on Class B oil pool fires. It was found that with the increase of nitrogen injection pressure, the nitrogen extinguishing efficacy gradually increased and then leveled off in the confined space. The asphyxiating oxygen concentrations were 12.2%, 13.2% and 13.7% for ethanol, diesel and gasoline, respectively. Asphyxiating oxygen concentration above limiting oxygen concentration (LOC). For extinguishing Class B oil pool fires in confined spaces, nitrogen extinguishing systems showed excellent fire extinguishing efficiency. They had specific application prospects in the field of protecting underground oil storage tanks and oil wells.

Experimental Study on the Fire Impact of Ceiling Insulation on CPVC Pipes

Fires igniting within a ceiling space often escalate into large-scale fires because of delayed detection times, rapid fire spread, and difficulties in firefighting operations. This study investigated the effect of combustible insulation materials on CPVC piping in sprinkler systems using real-scale fire experiments. Based on the top floor of an apartment, this study focused on insulation materials with the highest fire load among the combustibles in the ceiling space. A field survey and fire tests were conducted, and the experiments with EPS and XPS insulation revealed rapid flame spread and the complete destruction of the CPVC piping owing to high heat intensity. Even PIR insulation, a fire-resistant material, causes the destruction of CPVC piping located directly above the fire source. This confirms that combustible insulation materials within the ceiling have a significant negative impact on the functionality of the CPVC piping, rendering it incapable of performing its intended functions. Therefore, this study suggests alternatives for enhancing the reliability of automatic fire-suppression systems during fires in ceiling spaces.

Layered double hydroxide reinforced thermal expansion fire extinguishing agent for potential solid fire prevention

In this work, phosphorus-decorated Zn-Al-CO3 layered double hydroxide (PLDH) was prepared via a co-precipitation strategy and thus introduced into intumescent flame retardant dispersion to fabricate PLDH-reinforced thermal expansion fire extinguishing agent (FEA@PLDH). It was found that the phosphorus-containing unit was successfully anchored onto the PLDH. The prepared FEA@PLDH solution with a viscosity of 146 mPa·s exhibited good interfacial compatibility with the ethylene-vinyl acetate (EVA) surface. Taking advantage of the synergistic catalytic carbonization and expanded insulating barrier effects of FEA@PLDH, the corresponding coated EVA (EVA-FEA@PLDH1) with 1 wt% of PLDH could form a continuous and compact carbonaceous block layer under fire or high-temperature conditions. Meanwhile, the LOI for EVA-FEA@PLDH1 was increased from 22.0% to 32.0% and reached the UL-94 rating of V0. Moreover, EVA-FEA@PLDH1 showed delayed TTI (77 s) and TPHRR (146 s), with 6% and 44% reductions in THR and TSP, respectively, and 43% increment in residual char, as compared to the EVA-FEA. In addition, fire resistance experiment revealed that EVA-FEA@PLDH1 could withstand the ∼1300 °C flame for 467 s longer than that of the EVA-FEA (171 s). This research provides an intriguing fire extinguishing agent for the potential fire prevention of flammable polymer materials.

Parameters of decomposition and combustion of reed vegetation: 1. Mechanism and kinetics of thermo-oxidative decomposition and pyrolysis

The parameters of decomposition and combustion of reed plants are formulated, which characterize combustible material and are necessary for physical and mathematical modeling of the occurrence and development of a fire, determining the risk of its consequences. According to the results of TGA, the content of the main components in the leaves and stem of the plant was estimated, the mechanism and parameters of the macrokinetics of their thermal-oxidative decomposition and pyrolysis were determined.

OPTIMALISASI BUFFER ZONE SEBAGAI PENGAMAN PERMUKIMAN DI SEKITAR DEPO TANGKI BAHAN BAKAR MINYAK PT. PERTAMINA PLUMPANG, JAKARTA

The fuel storage tanks in Plumpang, North Jakarta, owned by PT. Pertamina Tbk. initially had a land area of ​​153 hectares, with the use of 71 hectares as an operational area and the rest as a buffer zone. However, the buffer zone changed its function to a residential area as a place of residence and economic activities for the community which became increasingly dense accompanied by issues of land ownership status. The Plumpang fuel storage tanks fire incident that occurred several times which caused loss of life and property, is a reminder of the importance of a buffer zone that serves as a separating space between areas at risk of flammable material disasters and residential areas. This paper is the result of research on the analysis of the optimization of land requirements for the Plumpang fuel storage tanks buffer zone, by applying quantitative descriptive methods and spatial mapping of the area using Arcgis software, with reference to fuel depot safety standards. It requires the acquisition of 5.2 hectares of land as a buffer zone area in the form of a safe distance from the safety fence wall, construction of a ditch that functions as an accident pool, and re-arrangement of settlements directly adjacent to the buffer zone.

The effect of burnt nickel-skeletal catalyst man-made raw materials on the сaracteristics of acid-resistant materials

Studies have shown that samples from HCI (the clay part of the tails of gravity of zircon-ilmenite ores), fired at a temperature of 1300 °C, do not meet the requirements of GOST for acid resistance. The introduction of a nickel-skeletal catalyst into the ceramic mass of man-made raw materials in an amount of 40 % reduces the number of plasticity, as with chamotte from 22 to 11 is considered optimal. The use of an optimal amount of man-made raw materials in the production of acid resistant materials makes it possible to obtain products with high physical, mechanical and chemical properties at a firing temperature of 1300 °C, as it contributes to the appearance of new refractory minerals on the diffractogram: corundum, mayenite (12CaO·7Al2O3) and alumomagnesia spinel (MgO·Al2O3), which significantly they improve the technical performance of acid-resistant materials. The presence of the optimal composition of the above minerals in the samples is also confirmed by IR spectra.

Numerical nonlinear structural analysis of a timber truss roof under fire condition

As greenhouse gases continue to rise and environmental impact reduction gains global attention, timber buildings have emerged as a vital asset in the pursuit of a sustainable future. Throughout history, timber has been linked to fire as a flammable material, and there have been numerous reports of out-of-control fires that highlight the importance of fire safety. Hence, the primary goal of this study is to assess the fire resistance of a timber truss roof. As the temperature rises, changes occur in the physical and mechanical characteristics of the timber members, causing the loss of the strength capacity and rigidity of part or the entire truss. Therefore, this research aims to explore the SAFIR computer program to carry out the following analyses: thermal analysis of the timber cross-section; and the structure’s thermo-mechanical analysis. By conducting the first analysis, it becomes possible to calculate the temperature field of timber members’ cross-section in a transient regime, while also obtaining information about the degradation of material properties. The second analysis provides the displacements, internal forces, critical time, and/or critical temperature of the timber truss during collapse. The numerical results obtained here were compared and validated with those from the literature (experimental results). The truss collapse time predicted by SAFIR’s model was quite similar to the one observed in the laboratory. The developed numerical methodology allows for more realistic studies of timber elements or systems, enabling designs based on safety, economy, and sustainability.

Towards synergistic sintering of TiO2/Cu Ceramic/Metal Interpenetrating Phase Composite and its application as structural material for hydrogen combustion

Towards synergistic sintering of TiO2/Cu Ceramic/Metal Interpenetrating Phase Composite and its application as structural material for hydrogen combustion

The flotation deashing separation performance of high-ash fine coal-slime using humic acid depressant and insights to its depressant mechanism

Effective inhibition of clay minerals remains a challenge in the flotation separation of fine coal with high ash content. The quest for efficient, environmentally friendly, and cost-effective depressants to improve the flotation efficiency of fine coal-slime has become a focus of current research. Humic acid (HA), a macromolecular organic compound widely present in nature, is known for its non-toxic, low-cost, and biodegradable properties. In this study, the potential selective depressant HA was utilized to enhance the recovery of low-ash clean coal in the coal-kaolinite system. Adsorption and inhibition mechanisms were explored through contact angle measurements, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) methods. Flotation tests demonstrated that HA, at varying dosages, significantly increased combustible matter recovery while reducing ash recovery compared to conventional flotation. Optimal conditions, with an HA dosage of 750 g/t, resulted in a combustible matter recovery of 40.56 % and an ash content of 17.77 % in the clean coal. Contact angle measurements confirmed that high-dosage HA significantly reduces the coal surface hydrophobicity, resulting in a rapid decline in the recovery of combustible matter. It did not significantly alter the contact angle of kaolinite, however, across the entire range of HA dosages. Furthermore, XPS studies revealed that the reduction in hydrophobicity on the coal surface after HA adsorption is mainly attributed to the coverage of surface carbon–carbon/carbon-hydrogen groups (C–C/C–H) and the increased presence of carbonyl groups (C = O). Additionally, the study found that HA predominantly adsorbs on the Si-OH groups of kaolinite. Finally, AFM results showed that the primary mechanism underlying the altered heterocoagulation behavior between coal and kaolinite is HA’s effect on their interaction forces. The optimal flotation results achieved at the HA dosage of 750 g/t are primarily attributed to the consistent presence of repulsive forces during the approach process and weak adhesion forces during the retraction process between coal and kaolinite, thus reducing kaolinite coating on the coal surface. These findings provide a promising direction for utilizing HA to enhance flotation deashing of high-ash coal-slime.

Nitrogen isotopes reveal high NOx emissions from arid agricultural soils in the Salton Sea Air Basin

Air quality management commonly aims to mitigate nitrogen oxide (NOx) emissions from combustion, reducing ozone (O3) and particulate matter (PM) pollution. Despite such ongoing efforts, regulations have recently proven ineffective in rural areas like the Salton Sea Air Basin of Southern California, which routinely violates O3 and PM air quality standards. With over $2 billion in annual agricultural sales and low population density, air quality in the region is likely influenced by the year-round farming activity. We conducted a source apportionment of NOx (an important precursor to both O3 and PM) using nitrogen stable isotopes of ambient NO2, which revealed a significant contribution from soil-emitted NOx to the regional budget. The soil source strength was estimated based on the mean δ15N-NOx from each emission category in the California Air Resources Board’s NOx inventory. Our annual average soil emission estimate for the air basin was 11.4 ± 4 tons/d, representing ~ 30% of the extant NOx inventory, 10× larger than the state’s inventory for soil emissions. Unconstrained environmental factors such as nutrient availability, soil moisture, and temperature have a first-order impact on soil NOx production in this agriculturally intensive region, with fertilization and irrigation practices likely driving most of the emissions variability. Without spatially and temporally accurate data on fertilizer application rates and irrigation schedules, it is difficult to determine the direct impacts that these variations have on our observations. Nevertheless, comparative analysis with previous studies indicates that soil NOx emissions in the Imperial Valley are likely underrepresented in current inventories, highlighting the need for more detailed and localized observational data to constrain the sizeable and variable emissions from these arid, agricultural soils.

Mechanism analysis on carbon-ash separation of coal gasification fine slag by high internal phase emulsion collector

ABSTRACT Coal gasification slag is a solid waste produced in modern coal chemical industry, its mixed characteristics of residual carbon and ash materials restrict its resource utilization. This study focused on improving the flotation effect of coal gasification slag and reducing the consumption of flotation reagents, a water in oil type high internal phase emulsion collector was prepared, and the microstructure, rheology, stability, particle size and other characteristics of the emulsion collector were analyzed. By comparing with the flotation effect of conventional kerosene collector, when the amount of organic liquid is basically equal, the ash content of the tailings increased by 4.02%, the yield of concentrate increased by 9.79% and the recovery of combustible matter increased by 11.11%. When the combustible matter recovery is similar, the emulsion collector can save 13.40% of kerosene. The flotation kinetics test shows that the emulsion collector can significantly improve the flotation speed. By analyzing the flocculating ability of emulsion collectors, emulsion collectors can significantly improve the flocculating ability of particles, thereby improving the flotation effect. The research results have certain guiding significance for improving the flotation efficiency of coal gasification slag.

Study on Natural Characteristics of Coal Gangue Oxidation under the Action of Water.

The exposed accumulation of coal gangue undergoes changes when it is soaked by rainwater, exhibiting varying tendencies for spontaneous combustion in different precipitation regions. This study investigates the effects of moisture on the oxidation and spontaneous combustion of coal gangue in high-sulfur coal gangue from the Qipanjing area of Inner Mongolia. Initially, coal gangue samples were subjected to soaking and air-drying treatments at different moisture contents. The dried coal gangue samples were then placed into a self-designed programmable heating furnace for thermal experiments, during which the gases generated were collected and characterized using gas chromatography. By comparing the oxygen consumption and volume fractions of gases such as CO, CH4, and C2H6 produced from coal gangue treated at different moisture contents, it was found that the low-temperature oxidation characteristics were optimal at a moisture content of 25%. At this level, the initial formation temperatures of gases like CO, CH4, and C2H6 were the lowest, with peak concentrations observed at 390 °C. Conversely, when the moisture content exceeded 70%, a significant amount of combustible material in the coal gangue was dissolved and dispersed by water, leading to a marked decrease in the concentrations of indicator gases produced at 390 °C. In fact, these concentrations fell below those of the control group, which was not subjected to water soaking or subsequent drying. The water immersion treatment also lowered the initial temperature points for the generation of various indicator gases by approximately 15 °C, making spontaneous combustion more likely.

Advancing source apportionment of soil potentially toxic elements using a hybrid model: a case study in urban parks, Beijing, China.

Identifying the source-specific health risks of potentially toxic elements (PTE) in urban park soils is essential for human health protection. However, previous studies have mostly focused on the deterministic source-specific health risks, ignoring the health risk assessment from a probabilistic perspective. To fill this gap, we developed a hybrid model that incorporated machine learning (ML) interpretability into positive matrix factorization (PMF) and probability health risk assessment (PHRA) based on the Monte Carlo simulation. The results indicated that concentrations of soil PTEs except for Mn and Sb were significantly higher than their corresponding background values. Random forest (RF) was regarded as the best ML model to identify key drivers for As, Cd, Cr, Cu, Ni, Pb, and Zn, with R2 > 0.60, but was less effective for other soil PTEs (R2 < 0.49). Specifically, the contributions of the four potential pollutionsources were mixed sources, traffic emission, fuel combustion, and building materials, with contribution rate of 24.88%, 30.56%, 28.99%, and 15.56%, respectively. Fuel combustion contributed the most to non-carcinogenic for children (39.45%), male (43.84%), and female (43.76%), and the non-carcinogenic risk could be considered negligiblefor human. However, building materials was the major contributor to carcinogenic risk for children (36.1%), male (44.9%), and female (43.2%). The integration of the RF model with PMF and PHRA improved the accuracy of the results by identifying and quantifying the specific sources of each soil PTE using the relative importance analysis from the RF model. The results of this study assisted in providing efficient strategies for risk management and control of soil PTEs in Beijing parks.

Molecular level analysis of the influence of natural biomaterials on aviation flame retardant performance

The use of natural biomaterials in flame retardant formulations as sustainable alternatives has gained significant interest in recent years. Given the high-risk environment in which airplanes operate, aviation safety remains a top priority. Flame retardants (FRs) are crucial for preventing or reducing the spread of flames in flammable materials used in aircraft construction and interior furnishings, thus mitigating fire risks. This study aims to analyze the molecular-level influence of natural biomaterials on aviation flame retardant performance, with a focus on lignin. Lignin, a natural polymer derived from plant cell walls, offers an environmentally friendly alternative to conventional synthetic flame retardants. Lignin-based composites can be applied to various aircraft components, such as wings and fuselage. The study employs Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Nuclear Magnetic Resonance (NMR) to investigate the molecular interactions of these biomaterials. Additionally, to assess thermal stability and degradation, Thermo-gravimetric Analysis (TGA) is utilized. The results indicate that lignin enhances flame retardancy by promoting the formation of a protective char layer and improving thermal stability. This research also provides insights into the molecular mechanisms underlying lignin’s effectiveness as a flame retardant and explores its potential in developing high-performance aircraft flame retardants.