Combustion Period Research Articles

Environmental and Health Impacts of Crop Residue Burning: Scope of Sustainable Crop Residue Management Practices.

The burning of crop residue in the open field has become a significant concern for climate change mitigation efforts worldwide. This practice has led to air quality impairment, smog, haze, heat waves, and different health problems. These could be avoided by adopting sustainable crop residue management practices (SCRMPs) and enabling farmers to engage in SCRMPs. Assessing the health effects at the household level is critical for understanding this problem and finding a solution. Using the primary dataset of 420 farmers from Punjab, Pakistan, we estimated the incurred impacts and costs of crop residue burning. We calculated the health and environmental benefits associated with adopting SCRMPs by comparing the two groups of farmers (adopters and non-adopters). Furthermore, we used a propensity score matching technique to measure the causal impact of SCRMPs adoption on health costs. The findings showed that a surprisingly large number of farmers are all aware of the adverse effects of residue burning, and many do not burn crop residues and instead use SCRMPs. This study found that households with chronic and non-chronic diseases become acute, and the severity increases during the burning period. They spend USD 13.37 to USD 8.79 on chronic and non-chronic diseases during the burning season, respectively. Consequently, the use of SCRMPs has a positive effect on healthcare costs. Our study findings highlight the meaningful implications for developing a new policy to promote the sustainable utilization of crop residues and enhance their adoption in Pakistan.

Multidimensional Computational Fluid Dynamics Combustion Process Modeling of a 6V150 Diesel Engine

Abstract The smart diesel program requires the engine electronic control unit to consider additional parameters, such as altitude and climatic conditions, in the mapping calibration process. A specially designed environmental simulation cabin, which can simulate environmental conditions at any longitude and dimension, would allow dynamometer testing to be performed indoors. Considering its high cost, a three-dimensional (3D) computational fluid dynamics (CFD) is needed to guide and/or complement experimental researches. As a result, the main objective of this study was to establish a 3D RANS model (i.e., reasonable computational cost and running time) that can provide in-cylinder details and predict the efficiency of a 6V150 diesel engine under varied operating conditions. A sector mesh approach was employed, considering only the compression, combustion, and expansion periods from intake valve closing to exhaust valve opening. The results indicated that the model simulated cylinder pressure agreed well with the experimental data, with relative errors of less than 6% during the primary compression, combustion, and expansion. Further, the model predicted heat release phasing was inconsistent with the experimental results, with absolute errors of less than one crank angle degree for peak pressure location, CA50, and ignition delay. In addition, the multidimensional model captured the effects of environmental pressure and temperature on spray formation (i.e., the dominant phenomenological event). Moreover, the model reasonably reproduced the effects of engine control variables on performance and emissions. All these observations demonstrated the validity of the selection and calibration of geometry, chemistry, and submodels including turbulence, spray, heat transfer, combustion, etc. Overall, the model was deemed capable of predicting combustion characteristics under extreme conditions, including high-temperature, high-cold, and high-altitude environments, which can facilitate the development of smart engines.

Study of effect and mechanism of flame retardation-bursting liability reduction based on chelating water injection wetting agent in coal seam

As coal mines continue to deepen high-intensity mining, the two disasters of coal seam rock burst and spontaneous combustion obviously have a trend of compound occurrence. How to achieve the integrated prevention and control of the two disasters is an important guarantee to realize coal mine safety. As a result, it is very important to select a coal seam water injection additive that can not only reduce the bursting liability, but also prolong the spontaneous combustion period of coal. In this paper, the chelating wetting agent was chosen to soak the coal, and the mass changed and carbon-containing functional groups during the coal oxidation process were studied by thermogravimetric and X-ray photoelectron spectroscopy, and tested the strength of coal by uniaxial compression experiment, and the scanning electron microscopy and low-temperature N2 adsorption were used to analyze the pore structure of coal. The experiment results show that the mass of the raw coal, the mass of the coal soaked in FeSO4 solution, and the mass of the coal soaked in the chelating wetting agent were reduced by 30.01%, 34.62% and 19.00%, respectively. The amount of the carbon–carbon bond and carbon–hydrogen bond decrease and the amount of carbon–oxygen bond increase in the chelating wetting agent soaking coal were less than in the water soaking coal and FeSO4 solution soaking coal. After soaking in the chelating wetting agent, the mechanical properties of the coal were changed, and the uniaxial compressive strength was reduced by 52.55%. The fractal dimension of the coal surface increased from 1.8448 to 1.8575, the average pore diameter in the coal was increased, the specific surface area was reduced, and the number of mesopores also increased. The above results can provide an important theoretical basis for the integrated prevention and control of rock burst-spontaneous combustion compound disaster.

Optical properties and spectral dependence of aerosol light absorption over the Brazilian Pantanal

Characterizing optical properties of aerosols, particularly the absorption processes, is fundamental for understanding the role of these particles in ecosystems as well as the climate, in general. Currently, changes in precipitation regimes in the southern Amazon basin have resulted in a considerable increase in biomass burning, whereby large amounts of aerosols and gases are emitted into the atmosphere. These increased emissions can impact the ecosystem, modifying mass and energy flows at the surface. This study, motivated by the need for more aerosol observations was the result of a long-term campaign carried out in the Brazilian Pantanal, which provided continuous in-situ measurements of aerosol optical properties between January 2017 and December 2019. From these data, optical properties of aerosols were quantified and analyzed seasonally. Corrected estimates for absorption coefficient (σabs) and Angstrom absorption exponent (αabs) were utilized to characterize the spectral dependence of absorption by aerosols. With additional measurements of the scattering coefficient (σscat), it was possible to evaluate the single scattering albedo (ω0). The mean values for σabs, σscat, ω0 at 525 nm and αabs 370–880 nm during the wet season were 0.66 ± 0.58 Mm−1, 6.16 ± 5.75 Mm−1, 0.90 ± 0.06 and 1.43 ± 0.49, respectively. These values, within measurement uncertainties, were similar to results found in the central Amazon. During the dry season, absorption and scattering increased approximately 88% and 86%, respectively, providing strong evidence for the contribution of local and regional emissions from biomass burning. The values of ω0 did not reveal significant seasonal differences, however, a sharp reduction was observed, medians below 0.8, at the beginning of the burning period, which was associated with more recent local burnings and, therefore, greater absorption. The mean values evaluated for different spectral intervals reveal a strong contribution of brown carbon (BrC) during the dry season, with medians of 1.78 and 0.87 for the intervals of 370–590 nm and 590–880 nm, respectively. This work also quantified BC concentrations for the dry and wet seasons, obtaining mean values of 0.75 ± 0.83 and 0.12 ± 0.09 μgm−3, respectively. In general, a striking similarity was encountered for aerosol optical properties between the Pantanal and the Central Amazon during the wet season. The results presented here characterize the background values for aerosol optical properties in the Pantanal, and the additional effects resulting from biomass burning emissions, therefore providing essential information to assess the effects these particles have on the ecosystem.

Combustion Characterization according to Accelerated Deterioration Temperature of a Non-class 1E Cable

In this study, the temperature effect of accelerated deterioration on combustion characteristics was investigated when accelerating aging a non-class 1E cable for nuclear power plants. The accelerated aging of 40 years was conducted under five temperature conditions of 90 °C, 100 °C, 110 °C, 130 °C and 150 °C. In the early period of combustion when the first peak of the heat release rate emerged, the heat release of the non-aged cable exhibited the largest peak value of 225 kW/m2 while the heat release of the aged cables exhibited a comparatively low first peak value. The first peaks of aged cables decreased as the temperature condition increased. This tendency is considered to emerge from the thermal decomposition and destabilization of long-chained polymer structure when the sheath and insulation of cables are exposed to a thermal degradation environment. Hence, this loosening of the chemical bond and its decomposition severely affected the degradation of the flame retardant performance. In particular, in the combustion characteristics for the aged cables under temperature conditions of 100 °C or higher, the first peak value of the heat release rate did not exceed 200 kW/m2. In the middle period of combustion, the heat release rates of both the non-aged and the aged cables were kept constant at approximately 25-30 kW/m2 without significant change. In the later period of combustion, the second heat release peaks emerged for only non-aged, 90 °C and 100 °C cables because the cables aged under low temperature conditions (90 °C and 100 °C) maintained a certain level of flame retardant performance while those aged above 100 °C did not. Therefore, it can be considered that the higher accelerated deterioration temperature triggers the higher degradation of the flame retardant performance, and 100 °C is a critical temperature that involves the significant degradation effect.

Occupational exposure to air pollutants emitted from in situ burning of offshore oil spills: a large-scale field study.

In-situ burning (ISB) could be an effective cleanup method during spills. This study aims to study occupational exposure to pollutants emitted from offshore, large-scale ISB-experiments among personnel on vessels involved in ISB. Six experimental ISBs after release of 4.2-6 m3 crude or refined oils were performed. Air measurements on three vessels were taken of particulate matter (PM) of different size fractions, polycyclic aromatic hydrocarbons (PAH) and volatile organic compounds (VOC). One vessel was located upwind (about 80-140 m) from the burning oil while two work boats were positioned 200-400 m downwind. One of the work boats moved back and forth transverse to the smoke plume while the other followed the edge of the smoke plume downwind. During the burn period (28-63 min) the range of mean concentrations of PM2.5 particles in the closest work boat downwind from the burn (0.068-0.616 mg/m3) was considerably higher than in the upwind vessel (0.0198-0.029 mg/m3) and in the work boat moving downwind at the edge of the visible smoke (0.007-0.078 mg/m3). The particles were mainly in the PM<1 fraction. In the work boat closest to the burn the mean concentration of particulate PAH and VOC was 0.046-0.070 ng/m3 and < limit of detection -17.1 ppm, respectively. The mean PM2.5 levels in the closest vessel varied between 4 and 41 times higher than the 24-hour Norwegian Air Quality Criteria for the general population, indicating that the particulate exposure may impose a health risk for personnel up to 400 m downwind from an ISB. Exposure to VOC and PAH among crew on board vessels both upwind and downwind from the burning was low during these conditions. However, it is recommended that crew on vessels close to and downwind of smoke plumes from oil fires should use half-masks with P3 filters.

A Collection of Airborne Measurements and Analyses of Trace Gases Emitted From Multiple Fires in California

AbstractBiomass burning is an important source of trace gases and particles, and can influence air quality on local, regional, and global scales. With the threat of wildfire events increasing due to changes in land use, increasing population, and climate change, the importance of characterizing wildfire emissions is vital. In this work we characterize trace gas emissions from 12 wildfires and 1 prescribed fire in California between 2013 and 2017, in some cases with multiple measurements performed during different burn periods of a specific fire. Airborne measurements of carbon dioxide, methane, ozone, formaldehyde, water vapor, temperature, and three‐dimensional winds were made by the Alpha Jet Atmospheric eXperiment and have been published at NASA's Atmospheric Science Data Center (https://doi.org/10.5067/ASDC/AJAX/wildfire, Iraci et al., 2021). The majority of these measurements were made as close as possible to each fire and represent fresh emissions from known fire sources. This set of observations from 13 different fires offers the opportunity to explore trace gas emissions over a range of meteorology, fire conditions, and to a lesser extent, vegetation type and drought, and adds to the body of knowledge collected by other investigators and field campaigns.

Impact of biomass burning and stratospheric intrusions in the remote South Pacific Ocean troposphere

Abstract. The ozone mixing ratio spatiotemporal variability in the pristine South Pacific Ocean is studied, for the first time, using 21-year-long ozone (O3) records from the entire southern tropical and subtropical Pacific between 1994 and 2014. The analysis considered regional O3 vertical observations from ozonesondes, surface carbon monoxide (CO) observations from flasks, and three-dimensional chemistry-transport model simulations of the global troposphere. Two 21-year-long numerical simulations, with and without biomass burning emissions, were performed to disentangle the importance of biomass burning relative to stratospheric intrusions for ambient ozone levels in the region. Tagged tracers of O3 from the stratosphere and CO from various biomass burning regions have been used to track the impact of these different regions on the southern tropical Pacific O3 and CO levels. Patterns have been analyzed based on atmospheric dynamics variability. Considering the interannual variability in the observations, the model can capture the observed ozone gradients in the troposphere with a positive bias of 7.5 % in the upper troposphere/lower stratosphere (UTLS) as well as near the surface. Remarkably, even the most pristine region of the global ocean is affected by distant biomass burning emissions by convective outflow through the mid and high troposphere and subsequent subsidence over the pristine oceanic region. Therefore, the biomass burning contribution to tropospheric CO levels maximizes in the UTLS. The Southeast Asian open fires have been identified as the major contributing source to CO from biomass burning in the tropical South Pacific, contributing on average for the study period about 8.5 and 13 ppbv of CO at Rapa Nui and Samoa, respectively, at an altitude of around 12 km during the burning season in the spring of the Southern Hemisphere. South America is the second-most important biomass burning source region that influences the study area. Its impact maximizes in the lower troposphere (6.5 ppbv for Rapa Nui and 3.8 ppbv for Samoa). All biomass burning sources contribute about 15–23 ppbv of CO at Rapa Nui and Samoa and account for about 25 % of the total CO in the entire troposphere of the tropical and subtropical South Pacific. This impact is also seen on tropospheric O3, to which biomass burning O3 precursor emissions contribute only a few ppbv during the burning period, while the stratosphere–troposphere exchange is the most important source of O3 for the mid troposphere of the South Pacific Ocean, contributing about 15–20 ppbv in the subtropics.

Performance, Exhaust Emissions and Optimization Using Response Surface Methodology of a Water in Diesel Emulsion on Diesel Engine

The use of water in diesel is an alternative to counteracting the increase in nitrogen oxide (NOx) emissions from diesel engines. However, some other criteria such as combustion performance and thermal efficiency were slightly reduced due to the impact of water content in diesel fuel. In other words, optimizing the balance between engine performance and emissions has always been a major problem in automotive industries. The purpose of this article is to demonstrate the use of RSM (response surface methodology) to improve the performance and emissions of a compression ignition (CI) engine which works on 5%, and 10% water mixes dubbed WD5 and WD10. This mixture of water emulsion to diesel is produced by using emulsifier ultrasonic. Tests were then performed on the Isuzu 4JJ1 4-cylinder 3000cc test bed engine with water cooled. Changes to engine load 20% to 50% and speeds of 1000rpm to 3000rpm. Experimental results data is then included in the Design Expert software to analyze the performance, emissions and optimization values using CCD Techniques in RSM. In performance analysis, pure diesel and WD5 are comparable with respect to power, heat efficiency of brakes and brakes of certain fuel consumption (BSFC). At higher loads, increased BTE levels and a neat BSFC drop were found. However, the combustion period is shorter. NOx and CO data slightly decreased with the same increase in water percentage at the same engine speed and load. However, the CO2 data showed a sharp increase with the increase in water content in fuel. Optimum engine operating parameters found as 5% water ratio, 50% of load and 2446 rpm while the best output parameters found as 103.7 Nm. of torque, 26.3 kW power, 43.8% BTE, 172 g/kWh BSFC, 521.8ppm NOx and 3.1% of CO.

Stability, rheological and combustion properties of biodiesel blends with a very-low sulfur fuel oil (VLSFO)

In this study the rheological and combustion properties were evaluated for a very low sulfur fuel oil (VLSFO) with biodiesel added at concentrations of 5, 10, 15 and 20 wt%. The samples were prepared via hand stirring, and blend uniformity was confirmed via sulfur and heat of combustion measurements. Evaluations based on the ASTM D4740 protocols confirmed blend stability (no evidence of visible asphaltene precipitation). The viscosity was significantly reduced with increased biodiesel content, while the boundary lubricity was notably improved by adding 5 wt% biodiesel. Analysis of the combustion results showed that 15–20 wt% biodiesel additions mitigated the premixed-burn spike phenomena observed for VLSFO. Biodiesel concentrations up to 15 wt% were also effective at improving the estimated cetane number and reducing the main combustion delay time and the precombustion burn period. The combination of good blend stability, reduced viscosity, and acceptable combustion properties for low blend levels suggests that biodiesel is suitable for use as a marine fuel for engines that operate on VLSFO.

On the optimization of the double-layer combustion chamber with and without EGR of a diesel engine

This paper focuses on the multi-objective optimization of the fuel injection parameters, combustion chamber geometry parameters and engine operating parameters of a double-layer combustion chamber. Three optimization objectives have been optimized by combining the NSGA-II genetic algorithm and the KIVA-3V program, including the indicated specific fuel consumption (ISFC) rate, NOx and soot emissions. Meanwhile, 10 engine parameters, including two injection parameters, six combustion bowl geometry parameters, compression ratio, and Exhaust Gas Recirculation (EGR) rate, are optimized simultaneously. The results show that the NOx and soot emissions exhibit an apparent trade-off relationship as well as the NOx emission versus ISFC. In addition, response surface analysis is conducted to investigate the influence of the selected parameters on the optimization objectives. It indicates that the retarded injection timing and EGR are conducive to the reduction of the NOx emission. Moreover, the double-layer combustion chamber with an impingement platform can enhance the fuel-air mixing process, and the air utilization rate of the combustion chamber is henceforth improved. Based on our optimization, the high temperature area is widely distributed throughout the double-layer combustion chamber, and most of the soot can be oxidized sufficiently in the main combustion period.

Comparison of heparin dressing and conventional dressing in second degree burn patients in term of pain relief and wound healing.

Objective: To compare effectiveness of heparin soaked and conventional dressing in Second degree burn patients. Study Design: Randomized Controlled study. Setting: Department of Burn and Plastic Surgery, Teaching Hospital/DG Khan Medical College. Period: November 2019 to October 2020. Methodology: One hundred twenty patients fulfilling inclusion criteria were enrolled and randomly divided into two groups. Group A (60 patients) were treated with Heparin soaked Dressing and Group B (60 patients) with conventional dressing (Silver Sulphadiazine ointment 1%) and were observed up to 3-weeks of post treatment. Outcome measures were noted and was assessed by Visual Analogue scale score for pain relief and complete re-epithelization of wound (&gt;75%) in the two groups. Significance was determined by comparing analgesia doses and total days required to heal in each dressing using chi-square test. Results: One hundred twenty patients were selected with mean age of patients was 14.4+_7.4 and male: female (62.5%:37.5%). Mean TBSA% was 12±1.80. Mean pain score in the group A for Superficial partial thickness burn (SPTB) and Deep dermal burn was 4±1 and 6±1 respectively (P-value &lt;0.001). Total Number of days for re-epithelization in the Group A and Group B (SPTB 13±1 vs. 18 measures in term of pain relief and re-epithelization. Total analgesia requirement in the Group A and Group B (50±20 vs. 116±12mg; P-value &lt;0.000 for Superficial Partial Thickness burn and 46±6 vs. 126±12mg; P-value &lt;0.001 for Deep partial thickness burn) respectively. There was significant difference in Outcome. Conclusion: Heparin soaked dressing is more useful and effective in Second degree burn in term of pain relief and re-epithelization in early post burn period compared to the conventional dressing.

Experimental Investigation about the Effect of Double-Spark Plug Ignition on Combustion Characteristics for Motorcycle Gasoline Engines with a Mild Lean Mixture.

To investigate the effect of double-spark plug ignition (DSI) on the mild lean combustion characteristics of motorcycle gasoline engines, three combustion modes were set up on a gasoline engine for testing, namely, the single-spark plug ignition (SSI) stoichiometric combustion mode (λ = 1, λ represents the excess air coefficient), the DSI stoichiometric combustion mode (λ = 1), and the DSI mild lean combustion mode (λ = 1.1). The results show that the double-spark plug ignition as that in the DSI mild lean combustion mode and DSI stoichiometric combustion mode is more prominent in accelerating the combustion process, reducing the cyclic variation, and improving the lean burn stability. It is verified that the overall effect of double-spark plug ignition on accelerating mildly homogeneous lean combustion is mainly reflected during the early period of rapid burning, which improves the stability of mildly homogeneous lean combustion and extends the lean burn limit. Further, the bench test shows that at a moderate load, the DSI mild lean combustion mode can result in lower brake-specific fuel consumption (BSFC) compared to that of the DSI stoichiometric combustion mode. When using the DSI mild lean combustion mode, the fuel economy can be improved by about 3–6% compared to that when using the SSI stoichiometric combustion mode. And the emission reduction can also be clearly observed when using a three-way catalyst containing rare-earth materials. However, at a low load, limited by combustion stability, for the DSI mild lean combustion mode, λ should not exceed 1.05.

Evidence that modern fires may be unprecedented during the last 3400 years in permafrost zone of Central Siberia, Russia

Recent climate change in Siberia is increasing the probability of dangerous forest fires. The development of effective measures to mitigate and prevent fires is impossible without an understanding of long-term fire dynamics. This paper presents the first multi-site palaeo-fire reconstruction based on macroscopic charcoal data from peat and lake sediment cores located in different landscapes across the permafrost area of central Siberia. The obtained results show similar temporal patterns of charcoal accumulation rates in the cores under study, and near synchronous changes in fire regimes. The paleo-fire record revealed moderate biomass burning between 3.4 and 2.6 ka BP, followed by the period of lower burning occurring from 2.6 to 1.7 ka BP that coincided with regional climate cooling and moistening. Minimal fire activity was also observed during the Little Ice Age (0.7–0.25 ka BP). Fire frequencies increased during the interval from 1.7 to 0.7 ka BP and appears to be partly synchronous with climate warming during the Medieval Climate Anomaly. Regional reconstructions of long-term fire history show that recent fires are unprecedented during the late Holocene, with modern high biomass burning lying outside millennial and centennial variability of the last 3400 years.

Effects of dispersed multiwalled carbon nanotubes on the micro-explosion and combustion characteristics of 2-methylfuran – diesel mixture droplets

Isolated droplet combustion experiments have been carried out on neat diesel, a 15 vol% 2-methylfuran – 85 vol% diesel mixture (MF15), and nanofuels made from MF15 base fuel with addition of multiwalled carbon nanotubes (MWCNTs) at 25 ppm, 50 ppm, and 100 ppm concentrations (referred to as MF15C25, MF15C50, and MF15C100). Compared to MF15, the nanofuels displayed increased micro-explosion intensity and reduced micro-explosion occurrences, both effects being more pronounced at higher MWCNTs loadings. This behavior is attributed to the higher surface tension and viscosity of the nanofuels compared to that of MF15. The ignition delay decreased from 2.33 s to 1.71 s, the combustion rate constant increased from 0.82 mm2 s−1 to 1.01 mm2 s−1, and the combustion period reduced from 5.31 s to 4.54 s when going from pure MF15 to MF15C50. The improved combustion characteristics can be related to the superior thermal conductivity and large specific surface area of the dispersed MWCNTs in the nanofuels. The combustion characteristics of the nanofuel deteriorate at the highest MWCNTs dosing investigated here, possibly due to nanoparticle agglomeration. Overall, the present results suggest that dosing of MWCNTs at optimum levels improves the thermal efficiency and reduces the NOx emissions upon combustion of MF-diesel blends.

Quantifying the Influence of a Burn Event on Ammonia Concentrations Using a Machine-Learning Technique

Although combustion is considered a common source of ammonia (NH3) in the atmosphere, field measurements quantifying such emissions of NH3 are still lacking. In this study, online measurements of NH3 were performed by a cavity ring-down spectrometer, in the cold season at a rural site in Xianghe on the North China Plain. We found that the NH3 concentrations were mostly below 65 ppb during the study period. However, from 18 to 21 November 2017, a close burn event (~100 m) increased the NH3 concentrations to 145.6 ± 139.9 ppb. Using a machine-learning technique, we quantified that this burn event caused a significant increase in NH3 concentrations by 411%, compared with the scenario without the burn event. In addition, the ratio of ∆NH3/∆CO during the burn period was 0.016, which fell in the range of biomass burning. Future investigations are needed to evaluate the impacts of the NH3 combustion sources on air quality, ecosystems, and climate in the context of increasing burn events worldwide.

Exposure of Malaysian Children to Air Pollutants over the School Day

Children are sensitive to air pollution and spend long hours in and around their schools, so the school day has an important impact on their overall exposure. This study of Kuala Lumpur, Selangor and its surroundings assesses exposure to PM2.5 and NO2, from travel, play and study over a typical school day. Most Malaysian children in urban areas are driven to school, so they probably experience peak NO2 concentrations in the drop-off and pick-up zones. Cyclists are likely to receive the greatest school travel exposure during their commute, but typically, the largest cumulative exposure occurs in classrooms through the long school day. Indoor concentrations tend to be high, as classrooms are well ventilated with ambient air. Exposure to PM2.5 is relatively evenly spread across Selangor, but NO2 exposure tends to be higher in areas with a high population density and heavy traffic. Despite this, ambient PM2.5 may be more critical and exceed guidelines as it is a particular problem during periods of widespread biomass burning. A thoughtful adjustment to school approach roads, design of playgrounds and building layout and maintenance may help minimise exposure.

Research on Initial Prevention of Spontaneous Combustion in Coal Bunkers Based on Fire-Extinguishing and Fireproof Inerting.

Coal bunkers are relatively closed systems. Due to their own oxidation characteristics and the increase of temperature, spontaneous combustion will occur beyond the spontaneous combustion period. Moreover, spontaneous combustion of coal bunkers is a disaster caused by multifield coupling, so it is imperative to carry out inerting fire prevention and fire extinguishing. Based on this fact, combined with the actual situation in Huanghua Port, this paper establishes a two-dimensional geometric model of a coal bunker, selects CO2 as the inert gas sprayed in the coal bunker, determines the position of the inert gas port of the coal bunker hopper, and studies the influence of fireproof and fire-extinguishing inerting on coal bunker inerting. The results show that the arrangement of the inert gas port of the bunker hopper outside the bunker is more conducive to the diffusion of CO2 gas in the bunker. In about 35–41 days, the inerting temperature decreases slowly between 345 and 350 K. After 41 days, the maximum temperature of the coal bunker decreases rapidly and the spontaneous combustion of the coal bunker is completely controlled. Under the preset conditions, the best fire inerting time is 32.3 days after coal storage.

Characterization of particle sources and comparison of different particle metrics in an urban detached housing area, Finland

Particulate matter (PM) is emitted from various anthropogenic sources in urban areas affecting the local air quality. The aim of this study was to characterize the sources influencing air quality in detached house area in the Helsinki metropolitan area in Finland, and secondly, to explore the additional value of new particle physical properties to assess the impact of residential combustion on air quality. Measurements were conducted in an urban detached housing area between January and April 2019. Measured particle physical properties were particle number (PN), particle mass (PM1) and lung deposited surface area (LDSA) concentrations and number size distributions. In addition, particle chemical composition was measured using a soot particle aerosol mass spectrometer (SP-AMS; organic compounds, inorganic ions) and an aethalometer (black carbon (BC)). Concentrations of selected monosaccharide anhydrides and polycyclic aromatic hydrocarbons were analysed from the PM10 filter samples. The sources and characteristics of organic aerosol was investigated by applying positive matrix factorization to the mass spectra measured with the SP-AMS. Based on the variations in the measured particle physical parameters, chemical species and meteorology, the measurement period was divided into three sub periods dominated by urban background, wood burning and long-range transport (LRT) aerosols. Highest pollutant concentrations were measured during the wood burning and LRT periods. Wood burning increased the concentrations of all measured species, but the differences were most significant to levoglucosan, benzo(a)pyrene, BC and PM1 that had 12, 10, 6.4 and 3.6 times larger mean concentrations during the wood burning period compared to the urban background period, respectively. LRT affected significantly levoglucosan, PM1 and BC concentrations, since LRT pollutants partly originated from open biomass fires in Eastern Europe. The impact of local wood burning and LRT was quite small to particle number concentrations, whereas LDSA concentrations and size distributions were affected by traffic, wood combustion emissions and LRT. BC concentration correlated with the LDSA concentration during all periods suggesting a common origin. Particle number concentration was a good indicator of local combustion, especially traffic emissions, while the PM1 mass concentration together with secondary particle material was a good measure for the LRT pollutants. Benzo(a)pyrene was found to be a good indicator of local wood burning, but it was not detected in LRT biomass combustion particles.

Optimized neural network to predict the experimental minimum period of coal spontaneous combustion.

The harmful gases produced from coal spontaneous combustion (CSC) can cause the environmental pollution. Being able to predict the experimental minimum period of CSC (EMPCSC) is essential in controlling CSC and effectively reducing harmful gas emissions. To obtain high prediction accuracy, we used three optimization algorithms, namely the genetic algorithm (GA), ant colony algorithm (ACO), and particle swarm optimization algorithm (PSO), to optimize the backpropagation neural network (BPNN). R2, MSE, RMSE, and MAPE were used as evaluation indexes to determine the most accurate prediction model for EMPCSC. Data of 424 coal samples from 15 regions in China were analyzed, with 207 and 217 samples having a spontaneous combustion period of less than 40days (W) and more than 40days (V), respectively. The two groups were further distributed between low-temperature slow oxidation (W0 and V0) and low-temperature fast oxidation (W1 and V1). The results indicated that the prediction performance of the BPNN model optimized using PSO (PSO-BPNN) was better than that of the GA-BPNN and ACO-BPNN models. After optimization through PSO, the goodness of fit (R2) of groups W0, W1, V0, and V1 increased from 0.9180, 0.8746, 0.9987, and 0.9782 to 0.9857, 0.9639, 0.9997, and 0.9994, respectively. Therefore, the results can provide a theoretical reference for selecting the optimal neural network model to predict EMPCSC with high accuracy.