Review of Advanced Technology of Flue Gas Desulphurization

Simultaneous removal of SO2 and NOx from flue gas by low-temperature adsorption over activated carbon

An exceptional phenomenon has been observed that SO₂ and NO_x in flue gas can be effectively adsorbed over activated carbon with a surprising capacity at cold temperatures with the presence of oxygen. In this study, the adsorption characteristics of NO and SO₂ over activated carbon at 80, 20, 0, and − 20 is experimentally investigated. Without the presence of oxygen, adsorption of NO is negligible. In the presence of oxygen, NO can be oxidized to NO₂ over activated carbon which leads to the co-adsorption of NO/NO₂ within the adsorption bed. Catalytic oxidation of NO over activated carbon can be significantly enhanced at cold temperatures, leading to an extraordinary increase of adsorption capacity of NO. With an initial concentration of NO = 200 ppmv and a space velocity of 5000 h⁻¹, the average specific capacity increases from 3.8 to 169.1 mg/g when the temperature decreases from 80 to – 20 ℃. For NO–O₂ co-adsorption, the specific capacity increases along the adsorption bed due to the increasing NO₂ concentrations. The adsorption capacity of SO₂ is also significantly enhanced at cold temperatures. With an initial concentration of SO₂ = 1000 ppmv, the specific capacity increases from 12.9 to 123.1 mg/g when the temperature decreases from 80 to – 20 ℃. A novel low-temperature adsorption (LAS) process is developed to simultaneously remove SO₂ and NO_x from flue gas with a target of near-zero emission. A pilot-scale testing platform with a flue gas flowrate of 3600 Nm³/h is developed and tested. Emission of both SO₂ and NO_x is less than 1 ppmv, and the predicted energy penalty is about 3% of the net generation.

A review of NOx and SOx emission reduction technologies for marine diesel engines and the potential evaluation of liquefied natural gas fuelled vessels

Due to intensive marine activities and the use of low-quality fuel oils, the marine transport accounts for a considerable part of air pollution in the transportation sector. Although ships provide the convenient transportation, they exhaust a large number of hazardous pollutants, especially nitrogen oxides (NOx) and sulfur oxides (SOx), which have a significant side effect on environment and human health. To alleviate the impact of global shipping on the environment, international maritime organization established the more stringent emission regulations from Tier I to Tier III in order to reduce emissions from ships. As a result, various emission reduction technologies need to be developed in order to meet more stringent regulations in the future and reduce the pollutant emissions. Under this background, it is indispensable to examine the existing emission reduction technologies when exploring another possible method to reduce the pollutant emissions. Based on a significant number of related literatures, it is general to utilize the marine alternative fuels to reduce the pollutant emissions. Especially, liquid natural gas (LNG) is considered to be one of the most promising marine alternative fuels due to its economy and environmentally friendly features. This review thus aims to summarize the different emission reduction technologies of marine diesel engines through three reduction paths of fuel optimization, pre-combustion control and exhaust after-treatment. Furthermore, the utilization of LNG in the marine diesel engines are evaluated comprehensively from three aspects of environmental protection, energy structure and economic benefits. At the end, some suggestions on the future research are given based on the extensive review on the state-of-the-art literature.