Introduction
Fire in Goafs (mines) is considered to be a potential environmental and health risk throughout the globe. Although, plenty of conventional fire extinguishing methods has been proposed in the past, yet they contain side effects. The authors in propose a novel fire management system using expansion form for fighting with fire at the top of goafs. The system contains a jet device for adding foaming agent produced by foam generator. The foam is powered by water pressure and compressed gas that are intrinsically safe for operating in mines. The expansion foam propels itself upwards to extinguish fire at the top of the goaf. It is advisable to inject foam in goaf in suitable intervals less than the half life of the foam.
Coal industries face self-ignited mine fires as a serious challenge around the world. As a result of these fires, a huge inventory of coal becomes unavailable for extracting useful energy. Self-ignition occurs owing to physiochemical processes taking place in mines. The exothermic reaction between coal and oxygen liberates a lot of heat and this heat generates fire if it is not properly exchanged with the environment. To prevent goaf fire, traditional means like grouting, infusing gelatum and inert gases, and adding spraying resistance agent have been proposed in the past. The article under discussion proposes expansion foam for fire fighting in mines owing to its properties like having high apparent viscosity, large interfacial area between gas and liquid, low density. Another related research work shows that aqueous three-phase foam possesses tremendous coal fire fighting capabilities.
Main Points of Article
Expansion foam for fire suppression is more effective, readily available, less costly, and environment friendly.
The article discusses fire characteristics of mines. Three regions span the area of goaf namely fissure zone, caving zone, and bent deformation zone. Continuous stream of oxygen is available for coal burning inside goaf owing to the masses of fracture aisles in the caving zone. Fire rapidly starts as heat is accumulated to a certain value.
The article presents the challenge of extinguishing fire at the top of the goaf, generally restricted by the gravity of infusion material and limited diffusion area. Expansion foam is suitable for fire suppression in mines by utilizing pipelines and drill holes. It gets accumulated around the infusion points until covering the whole goaf.
Foam preparation methodology is presented along with the foam preparation device. Then, suitable operating conditions for foam preparation are discussed. Author also provides foam expansion profile in a figurative manner.
The mentioned article justifies the choice of expansion foam as a fire suppressant and provides idea about its effectiveness.
The article also discusses idea of driving foam into goaf in regular intervals taking into account its half life. During initial phase of fire fighting, the foam volume reduces significantly and then slows down a bit after some time.
Intended Audience of the Article
The tone of the article is professional and contains technical details about fire suppression in underground mines. The author presents preparation and usage method of expansion foam that interests the people of this very field. Therefore, the intended audience of this article is people researching the horizons in the field of fire protection technology.
Issues Addressed in the Article
The article under discussion considers fight suppression for underground mines as a major issue for coal industries worldwide. Improper management of coal goafs leads to fire as exothermic heat rises to a certain limit. The authors report drawbacks of conventional fire fighting material and draw favors for expansion foam as an effective material for this very purpose. Although this effort will go a long way in solving fire management issues for coal goafs, yet research efforts are not saturated and needs further exploration for minimizing catastrophic effects of fire in top of coal goafs.
The most important contribution of this research work is addressing of the problems associated with the conventional fire fighting methods proposed in the literature. The ease of implementation of expansion foam in mines will solve many industrial scale problems for coal utilization around the globe.
Application of Information of Article to Course Material
The reviewed article presents solution to a major problem of fire fighting in coal industries today.This topic provides a good idea about practical fire management systems and how they are applied in industries. The concepts and ideas developed in this article support information studied in fire protection technology course.
Explanation of Main Points
Most of the details of the paper have already been discussed previously. However, we will shed some light on implementation of expansion foam in underground mines.
The first step in expansion foam fire fighting implementation is preparation of an appropriate mixture of foaming agent and water. Then, compressed gas is used to convert this liquid solution into gas-liquid form. Foam delivery pipe drives the solution into goaf. This method of driving foam is suitable as it doesn’t involve any electrical pumping action, thus negating any chance of electric sparks. The design meets the highest standards of industrial safety. Compressed nitrogen is used as a gas source because of its ease of availability and inert nature.
The adding device of the foaming agent and foam generator are key parts of the fire suppression system under study. The adding device comprises a jet nozzle, diffuser, throat, suction pipe, suction import, filter, and a needle valve. Jet nozzle creates a vacuum for driving foam into mine. Venturi principle is used to suck foam in required proportion with water. The authors described the arrangement with the help of an experimental setup. The results depict the effectiveness of expansion foam for extinguishing fire. The expansion foam could easily reach the incompact areas in the goaf which would otherwise stay under fire if conventional methods were used. The gas-liquid volume should be applied in an appropriate ratio to cover the affected areas suitably.
Choice of intervals for infusing foam in goafs is very important. For this purpose, half-life of the foam material dictates retention time of foam in mine. If this time is too short, it will not help in fire extinguishing. Experimental setup is provided to test the choice of half-life of foam material. Good foam accumulation is possible if foam is infused into goaf in a discontinuous manner.
In short, the research work proposed in article provides revolutionary idea to manage fire fighting in mines where coal gets ignited if heat is not dissipated at the top. The idea is practicable and economically viable also. The results also show why this idea is preferable over conventional fire suppression methods. By applying these ideas, the utilization of coals through mining will improve significantly for solving energy crisis.
References
Lu, X. a. (2015). Experimental investigation of fire extinguishment using expansion foam in the underground goaf. Arabian Journal of Geosciences , 9055--9063.
Qin, B. a. (2014). Aqueous three-phase foam supported by fly ash for coal spontaneous combustion prevention and control. Advanced Powder Technology , 1527--1533.
