Detection and extinguishment approaches for municipal solid waste landfill fires: A mini review

Municipal solid waste (MSW) management is getting more attention in the present scenario. Even though various technologies like incineration, gasification, pyrolysis and waste-to-energy plants have been developed, landfills are still the major disposal option for MSW management. MSW at landfill creates issues that are highlighted at a global level like the fire at Deonar dumping site in Mumbai, India was visible and captured by the space satellites, leading to environmental pollution. Detection and extinguishment of landfill fires at surface and sub-surface in their early stages are the major concern. Thermal imaging camera can be used to know solar radiation effect by identifying the hotspots during the day and the night time for understanding aerobic degradation effect on the surface fire. Sub-surface gas concentrations and its combinations affecting the temperature gradient can be studied for a better understanding of sub-surface fires in their early stages. The use of class 'A' foams with water, which reduces the surface tension of water, can be carried out for landfill fire extinguishment. The application of water in the form of water fog will extract a large amount of heat and block the availability of oxygen for the fire. This mini review presents the sources of fuel, heat, oxidant for landfill fire and its development process, associated pollution on air, water, land and human health due to landfill fire and methods for its extinguishment possibilities.

Optimization of experimental conditions of microbial desulfurization in coal mine using response surface methodology

To reduce the risk of spontaneous combustion during coal storage and transportation, microbial desulfurization technology is used to reduce the content of inorganic sulfur in coal. A strain of Aciditithiobacillus ferrooxidans was purified from coal mine water in Datong, Shanxi Province, and its desulfurization test conditions were optimized. Taking the inorganic sulfur removal rate of coal as the response value. The Plackett-Burman design method was used to screen the main factors affecting the response value. And the response surface method was used to establish the continuous variable surface model to determine the interaction between the factors. The results show that the three main factors affecting the response value and their significance order are temperature > coal particle size > desulfurization time, and the interaction between temperature and coal particle size has the greatest effect. When the temperature is 29.50°C, the coal size is 100 mesh, and the desulfurization time is 11.67 days, the desulfurization effect is the best, and the removal rate of inorganic sulfur can reach 79.78%, which is close to the predicted value, and the regression effect is wonderful.

Prediction of spontaneous coal combustion tendency using multinomial logistic regression

Spontaneous combustion of coal is a complex underground mining disaster, which mainly threats mine safety and efficiency. Several factors usually cause spontaneous combustion of coal, such as gas concentration, ventilation and coal properties. In this study, spontaneous combustion tendencies of coal mines were predicted considering the effective parameters for an underground coal mine in Turkey. Multinomial logistic regression, a multivariate statistical technique, was applied. Gas concentrations (CH₄, CO, O₂) and air velocity were defined as factors affecting spontaneous coal combustion. Fire hazard levels of the coal mines were determined as 'normal situation' and 'potential combustion'. It was observed that CH₄ and CO variables and CH₄ × CO interaction were effective in the formation of clusters. The results indicate that Mine I is more liable to spontaneous combustion than Mine II and Mine III. At the same time, the effects of variations in factors are examined in the study.

Identification of triglycerides in liquid and fire debris samples by triple quadrupole liquid chromatography-mass spectrometry

Analysis of fire debris for triglyceride-based oils may be of interest to fire investigators depending on the circumstances of a particular fire. Such circumstances include accidental or intentionally set cooking oil fires, fires involving triglyceride-based "eco" fire log products, and spontaneous ignition fires that involve drying oils on rags. Many forensic laboratories utilize gas chromatography-mass spectrometry following fatty acid methyl esterification to identify triglyceride residues in fire debris extracts. This study explores an alternate approach, which involves the identification of intact triglycerides by liquid chromatography-mass spectrometry-mass spectrometry (LC-MS/MS). 52 triglyceride-based oils and fats (22 different types) were analyzed by LC-MS/MS using multiple reaction monitoring to investigate variation in triglyceride content between different brands and types of oil and fat. Selected oils were then degraded by exposure to air, typical cooking conditions and/or fire conditions to simulate samples that are typically encountered by Fire Debris Analysts in fire investigation cases. Triglycerides were identified in all pristine and degraded oil samples, and relative peak areas for degraded samples often resembled their pristine oil counterparts. In samples where relative peak area differences were noted, more predominant degradation was observed for triglycerides with a higher proportion of poly-unsaturated fatty acids. Variability in triglyceride content between different brands and types of oil are discussed, as well as factors affecting the identification of triglyceride peaks in commercial oil samples, as compared to the corresponding analytical standard.

Application of Fuzzy Logic for Predicting of Mine Fire in Underground Coal Mine

Background

Spontaneous combustion of coal is one of the factors which causes direct or indirect gas and dust explosion, mine fire, the release of toxic gases, loss of reserve, and loss of miners' life. To avoid these incidents, the prediction of spontaneous combustion is essential. The safety of miner's in the mining field can be assured if the prediction of a coal fire is carried out at an early stage.

Method

Adularya Underground Coal Mine which is fully mechanized with longwall mining method was selected as a case study area. The data collected for 2017, by sensors from ten gas monitoring stations were used for the simulation and prediction of a coal fire. In this study, the fuzzy logic model is used because of the uncertainties, nonlinearity, and imprecise variables in the data. For coal fire prediction, CO, O₂, N₂, and temperature were used as input variables whereas fire intensity was considered as the output variable.The simulation of the model is carried out using the Mamdani inference system and run by the Fuzzy Logic Toolbox in MATLAB.

Results

The results showed that the fuzzy logic system is more reliable in predicting fire intensity with respect to uncertainties and nonlinearities of the data. It also indicates that the 1409 and 610/2B gas station points have a greater chance of causing spontaneous combustion and therefore require a precautional measure.

Conclusion

The fuzzy logic model shows higher probability in predicting fire intensity with the simultaneous application of many variables compared with Graham's index.

Treatment of smouldering coal refuse piles: an application in China

ABSTRACT Coal refuse pile fires are a serious health, safety, and environment hazard. The fires in Guoshan Coal Refuse Pile affect daily life of the local residents. Although conventional fire control methods (water injection, grouting and surface sealing) were used to control the fires, they rekindled soon after the fire-fighting engineering was quitted. Thus, effective methods need to be applied to extinguish the fires completely without reignition. In this paper, the environmental impact of the fire on the local land, water and air is illustrated by sample analysis and photos. The self-potential method, which achieves remote detection from the ground surface, is adopted to delineate the scope of the fires to give support for the efficient and economical extinguishment of them. The three-phase foam containing water, gas and loess is proposed to control and extinguish the fires. The corresponding fire-fighting system is also invented to fit the field work and put out the fires more efficiently and conveniently. The temperature monitoring result shows that the fires are extinguished successfully with no sign of reignition.

Community Citizen Science for Risk Management of a Spontaneously Combusting Coal-Mine Waste Heap in Ban Chaung, Dawei District, Myanmar

Since 2015, a large heap of improperly disposed coal-mine waste in Ban Chaung, Dawei district, Myanmar, has repeatedly spontaneously combusted, affecting an indigenous community. Recently, the regional Myanmar government has compelled the mine to properly manage the mine waste heap, but there is no opportunity for affected villagers to participate. This study empowers the affected villagers to make risk management decisions via a community citizen science approach. First, field investigations were performed with the affected community to identify hot spots at the waste heap releasing gaseous pollutants that may exceed acceptable levels. Next, existing monitoring data previously collected by the community were interpreted as clear evidence of past poor waste management. Information about suppression of existing fire and mine waste storage options was presented to the community for them to make an informed decision about the most appropriate corrective action that should be taken by the mine. The mining company chose to use surface sealing for both suppression of existing fire and on-site storage of the mine waste but did not install any long-term monitoring system. Nevertheless, the community's choice was surface sealing with preventive monitoring together with emergency response, which is the more scientifically appropriate option. This outcome of a science-based risk management decision by the community will be forwarded to the regional government for enforcement. This process of community citizen science is in line with the normative rationale of public participation, which is meant to influence decisions, elevate democratic capacity, and empower marginalized individuals and communities.

CFD modelling of sampling locations for early detection of spontaneous combustion in long-wall gob areas

In this study, computational fluid dynamics (CFD) modeling was conducted to optimize gas sampling locations for the early detection of spontaneous heating in longwall gob areas. Initial simulations were carried out to predict carbon monoxide (CO) concentrations at various regulators in the gob using a bleeder ventilation system. Measured CO concentration values at these regulators were then used to calibrate the CFD model. The calibrated CFD model was used to simulate CO concentrations at eight sampling locations in the gob using a bleederless ventilation system to determine the optimal sampling locations for early detection of spontaneous combustion.

CFD modelling of nitrogen injection in a longwall gob area

This paper describes computational fluid dynamics (CFD) simulations conducted to investigate the effectiveness of N₂ injection in an active panel and a sealed longwall gob area to prevent and suppress spontaneous heating of coal using various injection locations and flow rates. In the active panel simulations, a single longwall panel with a bleederless ventilation system was simulated. The spontaneous heating of crushed coal from pillars was simulated and N₂ was injected from different locations on the headgate side and through boreholes from the surface. The N₂ injection rate at each location was varied between 0.18 m³/s and 0.94 m³/s (380 and 2000 cfm). In the sealed longwall simulations, seal leakage rate was varied to determine its effect on N₂ injection effectiveness. The results of this study should aid mine ventilation engineers in developing more effective N₂ injection strategies to prevent and control spontaneous heating of coal in underground coal mines.