HR: 0800h
AN: NS31B-01    [Abstracts]
TI: Fires in Operating or Abandoned Coal Mines or Heaps of Reactive Materials and the Governing Transport and Reaction Processes
AU: Wuttke, M W
EM: manfred.wuttke@gga-hannover.de
AF: Leibniz Institute for Applied Geosciences, Stilleweg 2, Hannover, D 30655, Germany
AU: * Kessels, W
EM: winfried.kessels@gga-hannover.de
AF: Leibniz Institute for Applied Geosciences, Stilleweg 2, Hannover, D 30655, Germany
AU: Wessling, S
EM: stefan.wessling@gga-hannover.de
AF: Leibniz Institute for Applied Geosciences, Stilleweg 2, Hannover, D 30655, Germany
AU: Han, J
EM:
AF: Leibniz Institute for Applied Geosciences, Stilleweg 2, Hannover, D 30655, Germany
AB: Spontaneous combustion is a world wide problem for technical operations in mining, waste disposal and power plant facilities. The principle driving the combustion is every where the same independent of the different reactive materials: Fresh air with the common oxygen content is getting in contact with the reactive material by human operations. The following reaction process produces heat at a usually low but constant rate. The reactive material in operating or abandoned coal mines, heaps of coal, waste or reactive minerals is most times strongly broken or fractured, such that the atmospheric oxygen can deeply penetrate into the porous or fractured media. Because the strongly broken or fractured medium with air filled pores and fractures is often combined with a low thermal conductivity of the bulk material the produced heat accumulates and the temperature increases with time. If the reactivity strongly increases with temperature, the temperature rise accelerates up to the "combustion temperature". Once the temperature is high enough the combustion process is determined by the oxygen transport to the combustion center rather than the chemical reactivity. Spontaneous combustion is thus a self- amplifying process where an initial small variation in the parameters and the starting conditions can create exploding combustion hot spots in an apparently homogenous material. The phenomenon will be discussed by various examples in the context of the German - Sino coal fire project. A temperature monitoring in hot fracture systems documents the strong influence of the weather conditions on the combustion process. Numerical calculations show the sensitivity of the combustion to the model geometries, the boundary conditions and mainly the permeability. The most used fire fighting operations like covering and water injection are discussed. A new method of using saltwater for fire fighting is presented and discussed. References: Kessels, W., Wessling, S., Li, X., and Wuttke, M. W. Numerical element distinction for reactive transport modeling regarding reaction rate. In Proceedings of MODFLOW and MORE 2006: Managing Groundwater Systems, May 21 - 24, 2006, Golden, CO USA (2006). Kessels, W., Wuttke, M. W., Wessling, S., and Li, X. Coal fires between self ignition and fire fighting: Numerical modeling and basic geophysical measurements. In ERSEC Ecological Book Series - 4 on Coal Fire Research (2007). Wessling, S., Litschke, T., Wiegand, J., Schlömer, S., and Kessels, W. Simulating dynamic subsurface coal fires and its applications. In ERSEC Ecological Book Series - 4 on Coal Fire Reserach (2007). Wessling, S., Kessels, W., Schmidt, M., and Krause, U. Investigating dynamic underground coal fires by means of numerical simulation. Geophys. J. Int. (submitted).
DE: 0500 COMPUTATIONAL GEOPHYSICS (3200, 3252, 7833)
DE: 1600 GLOBAL CHANGE
DE: 4400 NONLINEAR GEOPHYSICS (3200, 6944, 7839)
DE: 6600 PUBLIC ISSUES
SC: Near-Surface Geophysics [NS]
MN: 2007 Joint Assembly