Promoted Ignition-Combustion Tests with Structured Aluminum Packings in Gaseous Oxygen with Argon or Nitrogen Dilution at 0.1 and 0.6 MPa

摘要

High-surface-area aluminum structured packings are finding a wide use in the cryogenic distillation of air. An experimental program was performed to determine the oxygen compatibility of commercial packings. In particular, the influence of pressure increase up to 0.6 MPa (6 bar absolute) and the effect of the replacement of nitrogen by argon as O_2-diluting gas were investigated. Additionally, the impact of reducing the sheet thickness from 0.2 mm to 0.1 mm was tested. The packing samples weighing 120-250 g were ignited on top by a 3 g thermite pill, resulting in a combustion channel which was either contained within the sample or passed through it. Incidents causing a noticeable downward widening of the channels were evaluated as "promoted combustion." Typically, a promoted combustion occurred when the weight loss of corrugated sheet exceeded 10%. The increase of pressure reduces the O_2-threshold concentration for propagated combustion, as expected. Reducing the thickness of the sheets from 0.2 mm to 0.1 mm affects the O_2-threshold concentration only slightly. A replacement of N_2 by Ar as O_2-diluting gas at 0.6 MPa shifts the O_2-threshold somewhat beyond accuracy, but the extent of combustion in O_2/N_2-mixtures is much more substantial than in O_2/Ar-mixtures. Thus a complete destruction of the Al-samples is reached in O_2/N_2-mixtures at much lower O_2-concentrations.