8 research outputs found
Experimental and CFD Simulation Techniques for Coal Dust Explosibility: A Review
No full textCoal is a low-cost and high-calorific-value fuel. The coal mining industry worldwide has been suffering from severe accidents due to coal dust explosion hazards since its inception. Statistically, it was observed that 12,489 fatalities had occurred in 104 reported mining accidents from coal dust explosions during 1900–2020. There are numerous methods for detection, prevention, and control of coal dust explosions in mines. The underground mining environment is unpredictable and has an array of variables. These undulating factors make it difficult to prevent or control the coal dust explosion hazard. However, coal mining is done aggressively throughout the world, especially in developing countries as coal is a major source of thermal energy used in power plants contributing to about 38% (IEA, (2019), World Energy Outlook, IEA, Paris https://www.iea.org/reports/world-energy-outlook-2019.) of world electricity. Worldwide, coal dust explosibility studies are carried out in experimental mines, laboratories, and simulations. The complexity, lack of proper infrastructure, and unavailability of laboratory equipment sometimes make it difficult to study coal dust explosibility. The authors have discussed in detail and proposed that the CFD modelling can be a viable option for studying and evaluating coal dust explosibility
A comparative kinetic study between TGA & DSC techniques using model-free and model-based analyses to assess spontaneous combustion propensity of Indian coals
No full textKinetic study of coal was carried out using simultaneous thermal analysis (STA) technique to assess the spontaneous combustion propensity of coal samples collected from various Indian coalfields having both fiery and non-fiery seams. The kinetic parameters were estimated by using both model-free and model-based analysis for both TGA & DSC data. The model-based method comprises four different consecutive reaction steps, viz. A→B→C→D→E for the spontaneous combustion process and the second reaction step (B→C) were used for this investigation. Chemometric analysis was applied to know the relation between the proximate analysis and activation energy of the samples using model-free and model-based techniques. The activation energy for the second reaction step of the model-based method for both TGA and DSC data showed a good relationship with the standard methods i.e., crossing point temperature (XPT) and Tgign of the samples. It indicates that the activation energy values at the oxidation stage (2nd stage) play a significant role in the spontaneous combustion propensity of coal. The study also reveals that the model-based analysis provided better results in comparison to model-free analysis to assess the spontaneous combustion propensity of coal
Review of preventive and constructive measures for coal mine explosions: An Indian perspective
No full textFiredamp and coal dust explosion constitute a lion’s share in mine accidents in a global mining scenario. This paper reports a list of mine explosion disasters since last two decades, a critical review of the different prevention and constructive measures, and its recent development to avoid firedamp and coal dust explosion. Preventive legislation in core coal-producing countries, viz. China, USA, Australia, South Africa, and India related to firedamp and coal dust explosion are critically analysed. Accidents occurred due to explosion after Nationalisation of Coal Mines (1973) in India are listed. Prevention and constructive measures adopted in India are critically analysed with respect to the global mining scenario. Measures like methane credit concept, classification of mines/seams with respect to explosion risk zone, deflagration index; installation of automatic fire warning devices, canopy air curtain technology, explosion-prevention measures, such as fire-retardant materials, inhibitors, extinguishing agent, dust suppressor, and active explosion barrier are discussed in detail to avoid explosion and thereby adhering to zero accident policy due to coal mine explosion
TGA/DSC study to characterise and classify coal seams conforming to susceptibility towards spontaneous combustion
No full textThermogravimetric analysis/differential scanning calorimeter (TGA/DSC) technique along with basic coal characteristics study is carried out for eighty coal samples of Indian coalfields, to determine spontaneous combustion propensity behaviour of coal. TGA study of coal samples indicates that there is an increase in the mass of coal samples in the temperature range 150–350 ℃, which may be due to oxygen adsorption and absorption. The correlation and principal component analysis states that the component of proximate analysis (Mad, VMd, FR, and VR) have an acceptable correlation with the TGA experiments results i.e., Tgsh and Tgign. Multiple fixed nonlinear regression analysis shows that thermogravimetry (TG) experiment results Tgign may be the best index to categorise/classify the coal as per their susceptibility towards spontaneous combustion. The authors proposed four groups of classification as per their propensity towards spontaneous combustion depending upon the moisture (Mad), volatile matter (VMd), and TG ignition temperature from differential thermogravimetric (DTG) curve (Tgign) using hierarchal clustering analysis. The coal samples of different seams from Indian coalfield may be classified into four different clusters, viz. very highly/extremely susceptible (Tgign 320 ℃). The field observations and TGA/DSC experiment results with the following statistical analysis substantiate a similar assessment
CFD modeling to study the effect of particle size on dispersion in 20l explosion chamber: An overview
No full textMine disasters occur predominantly due to methane or coal dust explosion or a combination of both. Among the top ten worst coal mine disasters in India, nine are due to coal dust explosion. The current paper describes a general overview of the parameters causing dispersion leading to coal dust explosion, and computational fluid dynamics (CFD) simulation study to observe the effects of particle size on dispersion in Indian coal mines. Turbulent kinetic energy (TKE) and velocity vector path of dust-air mixture and dust-free air were simulated to understand their effects on coal dust dispersion. The TKE contours and velocity vector paths for dust-free air were uniform and symmetrical due to resistance-free path available. The TKE contours and velocity vector paths for dust-air mixture shows the asymmetrical distribution of contours, due to entrainment of air with dust particles. Vortices were observed in velocity vector paths which gradually diminish on increment of time sequence. These vortices are dead centres where velocity and coal dust particles concentration are both zero
Methodology in early detection of conveyor belt fire in coal transportation
No full textThermal power units are a major source of power generation in India. Belt conveyor is the leading transportation system in a thermal power plant. Belt conveyor fire in a thermal power plant breaks the chain of the transportation system, stops the feeding to the boiler, and often leads to closure of the plant, and thereby impacts the production for several months incurring huge losses. The main aim of this study is to design a model for early detection of belt conveyor fire and its automatic fire suppression system. The proposed model incorporates safety devices and sensors which shall be activated whenever it is necessary. Based on coal characteristics, threshold limit values (TLV) of sensors are defined. Proximate analysis, critical oxidation temperature, fire ladder, and differential scanning calorimetry (DSC) studies were conducted to characterize the five coal samples used in this study collected from Talwandi Sabo Power Ltd. (TSPL), Mansa, Punjab, India. For the coal samples used in this study (with an average moisture content of 7.59 wt %), the average critical oxidation temperature was observed to be 81.3 ⁰C. Further, the fire ladder study indicates that gas sensors like CO and H2 should be installed in the belt conveyor route. Based on laboratory and field investigations an automated model for early detection of fire was proposed which incorporates safety devices, temperature, and gas sensors, and fire suppression mechanisms
Prevention and control of spontaneous combustion/fire in coal stockpiles of power plants using firefighting chemicals
No full textSpontaneous combustion of coal in stockpiles of power plants has a significant problem worldwide which leads to several health hazards, environmental pollution and coal loss. Spontaneous combustion coal stockpiles depend on both endogenous (coal characteristics) and exogenous parameters (stockpile geometry, wind speed, wind direction, local temperature). This paper describes the laboratory experiments to study the suitability of firefighting chemicals on the spontaneous combustion/fire of coal in stockpiles. Coal samples were collected from four different heaps of coal laid in coal storage yards of Talwandi Sabo Power Limited (TSPL), Punjab. This study comprises laboratory analysis i.e., proximate analysis, ultimate analysis, critical oxidation temperature, differential scanning calorimetry (DSC) analysis, gross calorific value (GCV), particle size analysis, and field studies i.e., thermal monitoring of fire-affected area before and after firefighting chemicals. Experiments on mixtures of coal and firefighting chemical having compositions viz. 1, 2, 3, and 5%, were carried out using DSC study for optimization of inhibitors as well as its efficacy. During the laboratory study the chemical composition of 3% was found to be optimum for field application to extinguish coal stockpile fire
