The inhibition of the combustion of carbon and carbon monoxide

Abstract

The presence of small concentrations of inhibitors (CCI,, CL, and HCI) in the air passufp into a bed of burning coke is found to increase the CO content o the combustion &ws at the cxpaw of the CO,. With sufficient inhibitor (> 2.0% CCl,) the effect amounts to almost complete suppression of the formation of CO ,The effect is not due to a promotion of the reduction of CO., d s reaction prorpdhg only to a very Bslpll extent under thc conditions of the ex enments. Further expcnments show that inhibitors can prevent L oxidation of 95 o/ of the co at Ioooo in the prcsence of excess oxygen, if the inhibytor (chlorine) is present in the inlet gases in a concentration greater than a sharply defined critical value (c. 0.5 %). This is an extension to a high tan ture region of the well-known action of halogen compounds on =oxidation at lower temperatures. The inhibition of the oxidation of carbon monoxide is found to be most effective when the area of surface of the silica reaction vessel is greatest and also when the CO and CI, arc preheated together; in an empty reaction tube and with the CO preheated separately from the Cl,, no critical CI, concentration IS found and inhibition is poor.The conclusions from the work on the oxidation of CO are applied ?o the earlier experiments on coke combustion in the presence of inhibitors ; it is inferred from the absence of CO, in the combustion gases produced in inhibited coke combustion, that CO, is not formed as a primary product of the interaction between carbon and oxygen, but is always produced by the oxidation of carbp," monoxide. lliz conception is discussed with reference to the of combustion.The four reactions to be considered in the combustion of Many investigations have been made to decide the relative extent to which these reactions contribute to the overall combustion reaction at different temperatures and under Werent conditions.In particular, experimental evidence has been sought to decide whether the final mixture of CO and CO, obtained by the combustion, arises from an initial CO-formmg reaction (I), or from an initial C0,-forming reaction (2), or, if both are evolved simultaneously, the proportions in which they are produced. In any case, the first formed gas subsequently undergoes oxidizing and reducing reactions (3) and (4, to an extent depending on the chemical and physical nature of the surroundings of the primary reaction, such as the presence of excess oxygen and the temperature and reactivity of the carbon surface. Because of the various chemical and physical conditions that inevitably prevail in such combustion investigations (to name, among many, carbon surface temperature and reactivity), the conclusions of different workers have often been conflicting. The problem has been approached in many ways, but, broadly speaking, from two directions. The first approach has been by experiments involving low pressure and low temperature conditions, to eliminate the complications which reactions (3) and (4) introduce in following the initial reaction. Experiments of t...

Manufacture of silicon tetrachloride from rice hulls

“…It has been found by others (Bridger and Appleton, 1948) that the presence of C12 inhibits the endothermic reduction of COZ to CO. Since reaction (1) is highly exothermic, a temperature wave is produced in the bed.…”

The oxidation of carbon monoxide

“…The finding (see fig. 6) that HCl inhibits the slow oxidation of CO and contracts the glow and explosion peninsulas links with the fact that HCl increases the CO/CO2 ratio in the combustion of solid carbon.17~ 18,19 (ii) The eflect of water vapour.-Our finding that water vapour markedly affects the second explosion limit is in sharp contrast to statements that have repeatedly been made in the literature. We have discussed the matter elsewhere.…”

A literature survey of the chemistry of flame inhibition

“…The oxidation of CO to CO2 is strongly inhibited [13], while the oxidation of C to CO appears to be unaffected [14,15] by halogens or their co mpounds. The oxidation of CO to COz depends in a secondary way on the hydrogen-oxygen chain reaction, since it requires OH and/or H02, according to the reactions CO+ OH~ CO2 + H [16,17] CO+ H02~ CO2+ OH [18,19].…”