A relatively new mesoporous silica sorbent for environmental protection applications (i.e., mesoporous spherical-silica particles [MSPs]), was modified by N- [3-(trimethoxysilyl)propyl]ethylenediamine (EDA) solution and was tested for its potential in the separation of carbon dioxide (CO 2 ) from flue gas. The CO 2 adsorption capacity of MSP and MSP(EDA) increased with temperature from 20 to 60°C but decreased with temperature from 60 to 100°C. The mechanism of CO 2 adsorption on both samples is mainly attributed to physical interaction regardless of temperature change. The MSP(EDA) have good adsorption performance as compared with EDA-modified zeolite or granular activated carbon conducted in this study and many types of silica sorbents reported in the literature. The cyclic CO 2 adsorption showed that spent MSP(EDA) could be effectively regenerated at 120°C for 25 min and CO 2 adsorption capacity of MSP(EDA) was preserved during 16 cycles of adsorption and thermal regeneration. These results suggests that MSP(EDA) are efficient CO 2 sorbents and can be stably used in the prolonged cyclic operation. INTRODUCTIONThe carbon dioxide (CO 2 ) capture and storage (CCS) technologies from flue gas are considered to be completely feasible means to lessen the global warming issue. 1 Various CO 2 capture technologies, including absorption, adsorption, cryogenics, membranes, and so forth, have been investigated. 2 Among them, the absorption-regeneration technology has been recognized as the most matured process so far, with the amine-based or ammonia-based absorption processes receiving the greatest interest. [3][4][5][6][7] However, because the energy penalty to regenerate liquid amine or ammonia in the absorption process is high due to the high heat capacity of liquid amine/ammonia and large amount of water, 2 other technologies are being investigated throughout the world. The Intergovernmental Panel on Climate Change (IPCC) special report concluded that the design of a full-scale adsorption process might be feasible. 8 Possible CO 2 sorbents investigated in the literature include activated carbon, 9 -11 X-type zeolites, 12,13 carbon nanotubes (CNTs), 11,14,15 SBA-15 mesoporous silica sorbents, 16 -19 and mesoporous molecular sieve MCM-41. 20 -23 Mesoporous spherical-silica particles (MSPs), which were modified from the MCM-41 materials, 24 are a relatively new sorbent for environmental protection applications. 25 The MSPs possess advantages of much faster preparation time, higher packing density, and lower pressure drop than MCM-41 because of their well -defined spherical shape. 26 These advantages make MSPs more practical

The Industrial Technology Research Institute has developed a 30 kWth moving bed chemical looping system for hydrogen production. Methane is supplied as a fuel to the reducer, and steam is supplied to the oxidizer to produce hydrogen. An iron-based oxygen carrier is used circulating between the reactors. In this study, the mechanical strength, attrition rate, and conversion rate of the oxygen carrier were tested at two Fe2O3 levels of content (40 and 60 wt %) calcined at temperatures of 1100 and 1300 °C. The oxygen carrier with the lower iron content presented the higher conversion rate of 72% at both calcination temperatures. The mechanical strength (170.5 N) and attrition rate (0.3%) of the oxygen carrier with a low Fe2O3 content were higher at the higher calcination temperature. Further, the oxygen carriers were circulated in the 30 kWth moving bed chemical looping system under ambient and high-temperature conditions. The oxygen carrier with two Fe2O3 content levels (40 and 60 wt %) at the calcination temperature of 1200 °C was employed in the attrition rate test conducted in the chemical looping system. Under the ambient temperature conditions, the average attrition rate of the oxygen carrier with a lower Fe2O3 content was lower (0.16%) than that of the oxygen carrier with a higher Fe2O3 content (0.24%). Moreover, the test results show the operating temperature has a lower level of influence on the attrition rate of the oxygen carrier.

Mercury speciation and distribution in a 660-MW tangential-fired utility boiler in Taiwan burning Australian and Chinese bituminous coal blends was investigated. Flue gases were simultaneously sampled at the selective catalytic reduction (SCR) inlet, the SCR outlet, the electrostatic precipitator (ESP) outlet, and the stack. Samplings of coal, lime, bottom ash/slag, fly ash, and gypsum slurry were also conducted. Results indicated that flue gases at the inlet to SCR contained a great potion of particle-bound mercury (Hg(p)), 59-92% of the total mercury. Removal of mercury was not observed for the SCR system. However, repartitioning of mercury species across the SCR occurred that significantly increased the portion of elemental mercury (Hg0) to up to 29% and oxidized mercury (Hg2+) to up to 33% in the SCR outlet gas. Overreporting of Hg(p) at the inlet of SCR may cause the observed repartitioning; the high ammonia/nitric oxide circumstance in the SCR unit was also speculated to cause the mercury desorption from ash particles and subsequent reentrance into the gas phase. ESP can remove up to 99% of Hg(p), and wet flue gas desulfurization (FGD) can remove up to 84% of Hg2+. Mercury mass balances were calculated to range between 81 and 127.4%, with an average of 95.7% wherein 56-82% was in ESP fly ash, 8.7-18.6% was retained in the FGD gypsum, and 6.2-26.1% was emitted from the stack. Data presented here suggest that mercury removal can be largely enhanced by increasing the conversion of Hg0 into Hg(p) and Hg2+.

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