Experimental Research On Removal Of SO₂ And NO_x By A New Combined Spray-and-scattered-bubble Technology

Power generation industry in China is dominated by thermal power.Coal-fired power plants consume a lot of coal in the production process every year,and burn to generate pollutive gas such as SO₂ and NO_x,which can form acid rain and acid fog when flue gas enters the atmosphere,thus causing serious damage to the ecological environment.In order to solve the growing air pollution problems,the government has put forward more stringent ultra-low emission standards.Although the existing removal technology is comparatively mature,there are still problems such as high running cost,poor adaptability for operating condition and difficulty in reaching the standard of emission limitation,etc.Therefore,proposing a technology that combines“near zero emission”with energy conservation and consumption reduction is of great significance to flue gas pollutants treatment.In this paper,a new spray-and-scattered-bubble technology was proposed with the support of the National Key Research and Development Program—“Research and Engineering Demonstration on Integrated Coal-fired Boiler Pollutants?SO₂?NO_x?PM?Control Technology”,and combined with limestone-gypsum wet flue gas removal process to carry out experimental removal of SO₂,which researched the effect of slurry mass concentration,oxidized form,gas flow and SO₂ inlet concentration on the removal efficiency.The results show that:rising absorption slurry mass concentration can increase the desulfurization efficiency,and when mass concentration is 1%,the efficiency could stabilize at around 99.4%,while achieving ultra-low emission.In the same condition,the desulfurization efficiency of forced-oxidation by the spray-and-scattered-bubble technology is higher than that of natural-oxidation.The desulfurization efficiency is basically not affected with the increase of gas flow and SO₂ inlet concentration,which indicates that the spray-and-scattered-bubble technology is adaptable to change in load and coal types.On the other hand,due to the fact that there is NO_x in flue gas and over 95%of the total NO_x is NO which only marginally dissolves in aqueous solution,the removal efficiency of NO_x is extremely low in absorption tower.Thereby,the way that oxidize NO to higher oxidation state which possesses a higher solubility by O₃,then combine with absorption slurry to remove pollutant,is used widely.In this paper,experimental removal of SO₂ and NO_x by the spray-and-scattered-bubble technology based on ozone pre-oxidation was carried out,which researched the effect of O₃/NO molar ratio,SO₂ inlet concentration,liquid/gas ratio and immersion depth of bubbling pipes on the removal efficiency.The results show that:the desulfurization efficiency and the denitration efficiency in the spray-and-scattered-bubble tower are both higher than that in spray tower or JBR in the same condition;With the increase of O₃/NO molar ratio,denitration efficiency increases continuously,but the removal efficiency of SO₂ increases a little;The increase of SO₂ inlet concentration is conducive to the absorption of NO_x,while the desulfurization efficiency is basically not affected;Both the desulfurization efficiency and denitration efficiency rise with the increase of liquid/gas ratio and immersion depth of bubbling pipes.The desulfurization efficiency and denitration efficiency are 99.2%and78.6%respectively in the spray-and-scattered-bubble tower at liquid/gas ratio 5L/m³ and immersion depth 5cm,increasing about 2%of desulfurization efficiency and 10%of denitration efficiency than that in spray tower at liquid/gas ratio 14L/m³,and almost 10%of both than that in JBR at immersion depth 13cm,which indicates that the spray-and-scattered-bubble technology can achieve the purpose of increasing efficiency and decreasing energy consumption.