IDENTIFICATION OF VOLATILE ORGANIC COMPOUNDS IN GASEOUS POURING EMISSIONS

摘要

The use of sand and chemical binders to make moulds and cores generates gaseous emissions, the composition of which varies according to the chemistry of the process. The objectives of the study were to identify the compounds - in particular the variousVOCs - present in the gases resulting from the pouring of liquid metal at different temperatures, in moulds made with sand and various chemical resins or of green sand with an addition of seacoal. The various experiments were performed at the CTIF testing station under experimental conditions. The arrival of molten metal in a mould made with chemical resins induces a thermal shock that causes the release of gases by degradation of the organic compounds in contact with the molten metal. The heat flux that advances in the sand entails the evolution of the most volatile organic compounds during this period, simultaneous with condensation of a part of them inside the mould. As a result, the least labile organic molecules condense in the sand step by step as the heat advances in the mould, then ore volatilised. Free-radical chemical reactions occur in the mould and at its perimeter. The gases contain aldehydes, ketones, alcohols, acids, aromatic compounds (phenol and its derivatives), and esters. In green sand moulding, the volatile organic compounds found are extremely varied; most of them are also found with the chemical bonding processes. The diversity of the compounds evolved during pouring is due in large pan to molecular recombinations.