| OCR Text |
Show Introduction In this environmentally conscious age, increasingly more stringent regulations are being placed on discharges to the atmosphere from industrial processes. Ni trogen oxides have captured considerable attention in recent years because of their adverse affect on the general population via smog, acid rain, and ozone formation. Approximately 30% of acid rain is due to NOx. Other than the automobile, the largest sources of NOx are power plants and industrial processesl • There are currently three generally accepted methods for NOx formation. Thermal NOx is formed by the reaction of nitrogen wi th oxygen at high temperatures. Prompt NOx is formed by the relatively fast reaction between nitrogen, oxygen, and hydrocarbon radicals. Fuel NOx is formed by the direct oxidation of organo-nitrogen compounds contained in the fuel. The overall reactions are as follows: N2 + 02 --> NO, N02 Thermal NOx CH4 + 02 + N2 --> NO, N02, C02, H20 Prompt NOx R3N + 02 --> NO, N02, C02, H20 Fuel NOx With high-quality fuels like natural gas, which contains only trace amounts (if any) of organically bound nitrogen, fuel NOx is not a concern. Oxygen enrichment of air-natural gas combustion processes increases the flame temperature. As a result flame radiation is increased which reduces the amount of energy lost with the exhaust gases. This has several significant commercially demonstrated advantages. Oxygen enrichment can increase production in heating and melting applications, increase energy efficiency, reduce particulates, and reduce total gaseous emissions by substantial reduction of the flue gas volume. At low to intermediate enrichment levels, the higher flame temperatures may also lead to higher NOx formation. It is important to understand how NOx is formed in natural gas combustion processes and the impact of oxygen enrichment on NOx production. With this understanding, combustion control techniques to minimize NOx formation can be identified rather than relying solely on expensive treatment systems. Toward this goal, Air Products is developing a combustion model to predict the importance of various parameters, including enrichment level, on NOx production. This research project is being sponsored by the Gas Research Insti tute. The main tasks are: 1. to develop a computer model to predict the NOx concentrations in the exhaust products of an oxygen enriched air-natural gas flame, -2- |
