Study On Removing Sulfur Dioxide From Flue Gas With Adsorption Method

The global economy is mainly supported by fossil fuels presently. A serious environmental problem of burning coal in power plants is the emission of SO₂ into atmosphere. The SO₂ in the air hurts human's health and causes acid rain, which has been a serious problem for the ecosystem. It is necessary to strengthen the control of SO₂ pollution.The adsorption method features in low investment and energy costs, simple equipments, and without generating secondary pollution, therefore, it is usually considered the most promising method of flue gas desulfurization.The adsorption performance for SO₂ on activated carbon, silica gel, and molecular sieve was studied. Six carbon samples corresponding to different extent of activation were prepared and their desulphurization performance was examined. The results showed that smaller pore size of activated carbon was appropriate to remove SO₂ from flue gas. It was also found that the SO₂ capacity was decided by pore size of adsorbents in testing the performance of three types of silica gels, type A, type B, and type C. Compared to silica gel B and C, silica gel A possessed smaller pore sizes and had the largest breakthrough capacity of SO₂. In addition, The desulfurization performance of molecular sieves such as 4A, ZSM-5 (38) and 13X was tested. It is showed that the pore size of adsodrbents on the removal of SO₂ played a decisive role. With uniform and moderate pore size, 13X displayed good adsorption performance for SO₂. The breakthrough capacity of SO₂ is much larger than that of 4A, ZSM-5 (38), active carbon and silica gel.The factors to affect desulphurization performance of active carbon, silica gel, and molecular sieve were investigated. The factors studied include temperature, pressure, moisture and CO₂ content in flue gas. The results showed that the breakthrough capacity of SO₂ decreased with the rise of temperature and the drop of pressure. The moisture had negative effect on the desulfurization, but the CO₂ content did not interfere SO₂ capture.To improve the desulphurization performance of adsorbents , the surface of adsorbents was modified by the use of active substances. Triethanolamine (TEA) was selected to be loaded on the mesoporous materials of silica gel and SBA-15, and their performance for the removal of SO₂ was studied. the TEA-modified silica, SBA-15 adsorbent sterengthened the chemical adsorption of SO₂; therefore, the SO₂ capacity of adsorbents was greatly improved.Finally, a strong oxidant, H2 O₂ , was used to modify the pore spaces of silica gel and SBA-15. By the characteristics reaction of SO₂ with H₂ O₂ occurred in the nano-pores of adsorbent, the selective adsorption of SO₂ on adsorbent was enhanced significantly. The distinctive pore structure of mesoporous materials provided an ideal place for the reaction of SO₂ and H2 O 2 to occur. So, the capacity of adsorbent for SOwas increased. The results indicated that the H2O₂ modified large pore SBA-15 possessed excellent desulfurization performance, and the maximum capacity of SO reached 300mg.g . In addition, the sorbent had high selectivity and good stability.