Urea denitration in power plants? Where does this urea go after denitration? ? ?

This post was last edited by qugd on 2022-3-8 at 10:49. This is actually the SNCR (Selective Non-Catalytic Reduction) process for selective non-catalytic nitrogen oxide reduction; ammonia was used in the past, but due to the difficulties associated with storing and transporting liquid ammonia, urea was adopted instead. Urea solutions are easy to prepare, and there is no need to worry about explosion safety at the handling site. Urea decomposes at high temperatures in the presence of water to form carbon dioxide and ammonia; ammonia then reacts with nitrogen oxides in the flue gas to produce nitrogen and water. The reaction process is somewhat complex, with a small amount of excess oxygen present in the flue gas also participating in the reaction. Urea decomposition: CO(NH2)2 + H2O ---> CO2 + 2NH3. Ammonia reacts with nitrogen oxides in flue gases that contain excess oxygen: 4NH3 + 4NO + O2 → 4N2 + 6H2O. Combined, these reactions can be expressed as: 2NO + CO(NH2)2 + 1/2O2 → 2N2 + CO2 + 2H2O. In reality, the reactions in flue gases are more complex, as at slightly lower temperatures some nitric oxide is present; nitric oxide also reacts with ammonia to produce nitrogen and water: 6NO + 8NH3 ---> 6H2O + 7N2. The equations haven’t been carefully checked or balanced – this is just a rough approximation.

Thank you for the detailed explanation. In fact, it ends up as nitrogen, returning to nature. In power plants, denitration is essentially the process by which nitrogen oxides are converted into nitrogen

I never imagined that denitration in a power plant would require such a large amount of urea

This post was last edited by qugd on 2022-3-19 at 17:01. From the perspective of the natural biological nitrogen cycle, it is beneficial for plants to have nitrogen that has not been denitrified, as nitrogen oxides can be converted into nitrate and nitrite, which are easily absorbed by plants and serve as good sources of nitrogen fertilizer. However, due to environmental protection requirements, denitrification becomes necessary. One of the first nitrogen sources that plants were able to utilize was the nitrogen oxides formed during lightning storms. It can be said that nitrogen oxides provided by nature were one of the important factors that facilitated the early reproduction and evolution of organisms.

The balanced equation for the reaction of nitrogen dioxide with ammonia to produce nitrogen and water is: 6 NO2 + 8 NH3 ---> 12 H2O + 7 N2

2*600MW+2×350MW 8000 tons

Denitration is still feasible after urea hydrolysis, but when a urea solution is sprayed directly, cyanic acid and nitrous oxide are generated, posing even greater hazards

In 2021, China’s installed capacity for thermal power generation was 1,296.78 gigawatts, representing a year-on-year increase of 4.1%.

A simple calculation shows that 2 tons of urea are required per megawatt. In 2021, China’s installed capacity for thermal power generation was 1,296.78 million kilowatts, representing a 4.1% increase compared to the previous year. 12,967,800 megawatts, with consumption of over 2 million tons per year

The EU emission standard for NOx is 100 mg/m3, while the domestic standard is 50; in actual production, this value ranges from 30 to 40. To improve denitrification efficiency, more ammonia is sprayed, which leads to ammonia leakage. In fact, the impact of ammonia is even greater than that of NOx. The fog in the north is not acidic but alkaline