LABORATORY GENERATION OF FREE CHLORINE FROM HCL UNDER STRATOSPHERIC AFTERBURNING CONDITIONS

Experiments have been conducted using a low pressure laboratory flame apparatus to examine the chemistry of solid rocket motor (SRM) afterbu rning relevant for stratospheric altitudes. It was found that a signif icant fraction of the HCl injected into H-2-O-2 and H-2-CO-O-2 flames can be consumed, with observed losses of up to 40%. The extent of conv ersion of HCl was found to increase with increasing oxygen:fuel (O/F) ratio and decreasing pressure; the loss at a given O/F was also higher for flames with equal flows of I-I, and CO compared to flames with no CO in the fuel. The major product of HCl reaction was found to be Cl- 2, with no other chlorine-contained products observed via mass spectro metry. Distinct Cl-2 B --> X emission bands were observed along with v ery weak ClO A --> X bands and a bright, white continuum emission that apparently arose from one or more chlorine-containing compounds. The general findings concerning the magnitude of HCl conversion and the fo rmation of Cl-2 are consistent with published modeling results for SRM stratospheric afterburning. This formation of ''free'' chlorine could lead to catalytic destruction of ozone in regions near the path the l aunch vehicle follows during boost through the stratosphere. (C) 1998 by The Combustion Institute.