SOLID FUEL COMBUSTION：固体燃料燃烧.ppt

COMBUSTION IN POROUS MEDIA? BY Prof. Dr. Mohammed Hamdan Eng. NABEEL ABO SHABAN CONTENTS PART 1 : Theoretical background Introduction Combustion = Chemical reactions Heating values of fuel fundamentals of combustion PART 2 : Combustion in porous media Porous materials Porous burners Flame propagation Modeling of flame in porous media Terminology Fuel Flame Porous Media Fuel FLAME POROUS MEDIA Is presence of both a persistent solid matrix and avoid space which is occupied by one or more fluid phases within porous media domain . Rocks,ceramics,Human tissue are examples of porous media. Fundamentals of combustion Steps of the combustion process : Heating and drying (evaporation of free and bonded water of the fuel. Pyrolytic decomposition (heat induced decomposition of solid fuel to gaseous, liquid and solid products) Gasification (the solid carbon is converted to gaseous carbon-monoxide) Oxidation (combustion of the produced intermediate gaseous (and liquid) products releasing heat) These different steps are timely and spatial interconnected in existing combustion devices. The combustion technology has to account for these conversion characteristics to ensure an environmentally sound combustion (i. e. complete oxidation). Combustion – Chemical reaction : Fundamental laws Combustible Elements in Fuels : C S H2 CO CH4 C2H4 C2H6 C3H8 ...... Alcans : CnH2n+2 Alcens : CnH2n Aromatics ... Combustion : ? C + O2 ? CO2 S + O2 ? SO2 H2 + ? O2 ? H2O CO + ? O2 ? CO2 CH4 + 2 O2 ? CO2 + 2 H2O C2 H4 + 3 O2 ? 2 CO2 + 2 H2O ........ CnH2n+2 + ? ( 3n + 1 ) O2 ? n CO2 + ( n + 1 ) H2O  Classification of porous burners MATRIX-STABILIZED BURNER (Inside the porous matrix) SURFACE- STABILIZED BURNER (Near or on the porous material surface