Formaldehyde formation in large bore natural gas engines Part 1: Formationmechanisms

Recent testing of exhaust emissions from large here natural gas engines has indicated that formaldehyde (CH2O) is present in amounts that are signific ant relative to hazardous air pollutant standards. In consequence, a detail ed literature review has been carried out at Colorado State University to a ssess the current state of knowledge about formaldehyde formation mechanism s and evaluate its applicability to gas engines. In this paper the followin g topics from that review, which bear directly on formaldehyde formation in natural gas engines, are discussed: (I) post combustion equilibrium concen trations; (2) chemical kinetics: (3) flame propagation and structure: (4) p artial oxidation possibilities and (5) potential paths for engine out forma ldehyde. Relevant data taken from the literature on equilibrium concentrati ons and in-flame temperatures and concentrations are presented in graphical form. A map of possible paths for engine out formaldehyde is used to summa rize results of the review. and conclusions relative to formation and destr uction mechanisms are presented.