A Method for Reduction of Carbon-dioxide Emission by Soot Deposition (II)

Promotion of Soot Deposition by Air Addition

Abstract

A method for reduction of carbon dioxide emission due to the use of hydrocarbons as fuels consisting in a pre-deposition of part of the carbon content in the fuel into soot was tested for industrial application. As a basic research, the influences of the amount of air added to the fuel and the temperature to which the mixture is heated up on the soot pre-deposition when methane is the fuel were investigated. Below 1500K, addition of 30% of air led to the largest soot pre-deposition; the addition of this relative large amount of air promotes soot formation because the active species needed for the first step of that process, the conversion of methane into methyl radicals, are produced through reactions activated by oxygen; further addition of air promotes the oxidation of carbon into carbon monoxide and carbon dioxide, lowering the soot deposition. At temperatures higher than 1500K, thermal decomposition of methane causes the reactions to proceed very fast, and the addition of air reduces the soot deposition. Concretely, conversion of 30% of the carbon content in the fuel into soot can be easily controled at temperatures below 1500K with addition of convenient amounts of air; and the conversion of 50% of the carbon into soot can be obtained at reaction temperatures above 1550K.