Oxygen-enriched combustion

Taking a coal-fired furnace as an example, oxygen-enriched combustion merely increases the temperature of the flame and improves the efficiency of fuel utilization. The solid unburned residues present in the flue gases after normal combustion can be burned completely, thereby reducing the darkness of the flue gases as well as emissions of particulates and dust. However, in terms of greenhouse gas emissions, the flue gas emissions generated during oxygen-enriched combustion should remain largely unchanged; there might be less CO, but more CO2, while SO2 levels are likely to stay similar These are merely my humble personal opinions, meant simply to serve as a starting point for further discussion!

For beginners learning this*, many studies state that the purpose of using oxygen is to capture carbon dioxide; the reduction in smoke emissions should not be very significant. After all, so much coal is burned, and the only difference is the higher oxygen content. As a result, the total volume of gases entering might decrease, so the amount of smoke emitted is likely to go down as well

Oxygen-enriched combustion is already well-established in the glass furnace industry. For several of our company’s projects involving waste heat recovery from glass production, oxygen-enriched combustion technology is used in the glass furnaces. Typically, nitrogen is first removed from the air, and the resulting \"nitrogen-free\" air is then fed into the furnace for combustion. Since the oxygen content in this air is high after nitrogen removal, this combustion technique is referred to as oxygen-enriched combustion. Due to the higher oxygen content, less air is required for combustion, which in turn results in reduced flue gas emissions. As a result, waste losses are minimized and the combustion efficiency increases. In addition, there are full-oxygen combustion technology, electric furnace technology, etc., all of which are effective methods for improving heat utilization efficiency.

The amount by which the flue gas volume decreases can be calculated based on the fuel properties~:P

This post was last edited by gzlzhx on 2013-1-13 at 15:53. Has anyone worked on the oxygen-enriched combustion technology for cement kilns? If so, could anyone share any relevant information? Contact via in-site message

Just do a fuel combustion calculation by yourself and you’ll understand. With pure oxygen, about 71% of the nitrogen in the air is removed. As for oxygen enrichment, I’ve heard that combustion is carried out with an oxygen concentration as high as 30%. The comprehensive economic cost needs to be taken into account. Operating oxygen production cost and one-time investment cost. There are also many furnaces in steel mills that use air or gas for preheating; the heat recovery rate in such cases is already quite high, so oxygen enrichment needs to be considered carefully.

From an economic perspective, oxygen-enriched combustion in ordinary factories and boilers is most cost-effective at around 30%. The effectiveness of oxygen-enriched combustion in the current market is indeed practical. Oxygen-enriched combustion can help save energy, especially in industries with high energy consumption such as thermal power plants, fertilizer factories, ammonia synthesis plants, and cement factories, which are all part of the large-scale combustion sector. The key at present is a cost-effective and practical technology for producing oxygen-enriched air. It is recommended to search for: membrane oxygen enrichment, pressure swing adsorption, magnetic energy oxygen enrichment.

Combustion with an amount of air exceeding the theoretical amount is considered oxygen-enriched combustion; it is generally used in direct combustion systems. The more air that is added, the greater the energy waste

If the pure oxygen + flue gas recycling method is used, the amount of flue gas is significantly reduced, as using pure oxygen instead of air (21% O2 and 79% N2) as an oxidizing agent prevents the introduction of large amounts of N2. The components in the flue gas are mainly high-concentration CO2 and H2O (without N2); by removing the water through condensation, high-concentration CO2 (over 90%) can be obtained. In the metallurgical industry, when oxygen-enriched combustion is used, a certain amount of pure oxygen is added to the air supplied, thereby increasing the oxygen concentration (to 30%-40%). This helps to raise the combustion temperature and thus improves combustion efficiency. Additionally, since less N2 from the air is introduced, the amount of flue gas generated is reduced; however, this amount is still greater than that produced by the combustion method using \"pure oxygen + flue gas recycling\".

Using too much oxygen is simply not cost-effective! Therefore, what the original poster mentioned about reducing smoke emissions is merely a theoretical idea; in reality, it’s completely impossible to achieve ； Moreover, reducing the amount of smoke significantly would lead to a too great decrease in the air flow rate inside the furnace or kiln, which would have adverse effects! In systems like cement pre-decomposition kilns, it’s necessary to support the raw material, and convective heat exchange is used in boilers! In reality, many problems have an impact on the whole system once something changes!