為了增加鈣基反應劑的使用率，本研究使用內循環式流體化床反應器（Internally Circulating Fluidized Bed Reactor, ICFBR）當作煙道氣除硫（Flue Gas Desulfurization, FGD）反應器，床高及內徑分別為2.5公尺及9公分，床質為矽砂與鈣基粒子的混合物。以ICFBR當作FGD反應器有兩項優點，其一是高的磨損速率可移除鈣基反應劑表面形成的產物層，這樣可以增加鈣基反應劑的使用率及SO2氣體除硫效率。其二是粒子的循環速率及氣體滯留時間可藉由分別調整上升區(Draft tube)及環形區(Annulus)進氣的比例來加以控制。
本研究針對內循環流體化床反應器中鈣基粒子反應劑硫化及磨損、固體粒子循環速率與SO2氣體除硫效率的現象做一探討，其中探討的實驗參數包括相對濕度（RH）、鈣基粒子的粒徑（dpc）、進口SO2氣體濃度（C0）、平均總空床氣速（UT）、上升區與環形區空床氣速差（Ud - Ua）及上升區空床氣速（Ud）等，其中發現：較高的相對濕度有較高的鈣基粒子轉化率，但磨損速率、固體粒子循環速率則較低，操作480分鐘後穩態的除硫效率隨著相對濕度從40至80%會有最大值，當RH = 50、60及70%時除硫效率一開始會下降後上升，最後又會下降到一定值。較小的鈣基粒子粒徑會有較高的磨損速率及固體粒子循環速率。除硫效率隨著粒徑及進口SO2氣體濃度的增加而降低。除此之外，隨著總空床氣速及上升區與環形區空床氣速差的增加，鈣基粒子磨損速率增加，但轉化率下降。總空床氣速固定隨著上升區與環形區空床氣速差的增加，固體粒子循環速率會有最大值的趨勢。較大的上升區與環形區空床氣速差(Ud - Ua)會有較高的穩態除硫效率，這是因為較高的磨損速率造成鈣基反應劑反應性的增加，且較高的磨損速率有較高的煙道氣體處理量。
最後本研究提出一個結合氣固反應的磨損模式來預估鈣基反應劑在內循環流體化床內的磨損量，其預測結果尚能在相對誤差15%以內。除此之外本研究亦提出一個結合鈣基粒子轉化率、磨損速率及氣體分流比例的穩態除硫效率模式來預估內循環流體化床除硫反應器出口的除硫效率，其中假設上升區為氣泡式流體化床，環形區為移動床，最後預測結果與實驗值尚能在相對誤差20%以內。

In this study an attempt was made to use internally circulating fluidized bed reactor (ICFBR) as a flue gas desulfurization reactor. The height of the bed was 2.5 m, and the inner diameter was 9 cm. The bed materials were calcium sorbent and silica sand. One of the special features of the ICFBR is high attrition of the particles in the bed, which would remove the product layer of sulfation and increase the utilization of the calcium sorbent. The other features are easy control of the solids circulation rate and gas residence time in the bed by individually adjusting the gas velocity in the annulus and the draft tube, which would increase the efficiency of the desulfurization process. The effects of the operating parameters including relative humidity, particle size of the calcium sorbent, inlet concentration of SO2, difference superficial gas velocity in the draft tube and the annulus and superficial gas velocity in the draft tube on attrition rate, calcium sorbent conversion, solids circulation rate and SO2 removal efficiency in the ICFBR were investigated. It was found that a higher relative humidity had a higher calcium sorbent conversion, but had a lower attrition rate and solids circulation rate. The removal efficiency of SO2 had a maximum value at steady state when the relative humidity was from 40 to 80%. When RH = 50、60 and 70% RE decreased initially and then increased. After that RE decreased again until a steady state was reached. A smaller particle size of calcium sorbent had a higher attrition rate, a higher solids circulation rate and a higher removal efficiency of SO2. In addition, the effect of the inlet concentration of SO2 on calcium sorbent conversion, attrition rate and solids circulation rate was negligible from 200 ppm to 500 ppm, but the removal efficiency of SO2 was decreased with increasing the inlet SO2 concentrations. Moreover, a higher total superficial gas velocity and a higher difference superficial gas velocity in the draft tube and the annulus had a higher attrition rate, but had a lower calcium sorbent conversion. However, the solids circulation rate might have a maximum value with respect to the difference superficial gas velocity in the draft tube and the annulus at the same total superficial gas velocity in the bed. A higher difference superficial gas velocity in the draft tube and the annulus had a higher removal efficiency of SO2 that was resulted by a higher reactivity of calcium sorbent due to a higher attrition rate. Futhermore, a higher attrition rate had a higher total volume of the flue gas treated.
Finally, an attrition rate model proposed in this study could predict the attrition rate satisfactorily. A model to predict the removal efficiency of SO2 at steady state in ICFBR was also proposed. It assumed that the draft tube section was a bubbling fluidized bed while the annulus section was a moving bed. In addition, the effects of the calcium sorbent conversion, attrition rate and gas-bypassing fractions on the removal efficiency of SO2 at steady state were also taken into account in this model. It was found that the values of the removal efficiency of SO2 at steady state predicted by this model agreed with the experimental results.

參 考 文 獻

Ahn, H. S., W. J. Lee, S. D. Kim and B. H. Song, “Solid Circulation and Gas Bypassing in an Internally Circulating Fluidized Bed with an Orifice-Type Draft Tube,” Korean J. Chem. Eng., 16(5), 618-623 (1999).
Allen, T., “Particle Size Measurement,” 4th ed., Chapman and Hall, London (1990).
Babu, S. P., B. Shah and A. Talwalkar, “Fluidization Correlations for Coal Gasification Materials-Minimum Fluidization Velocity and Fluidized Bed Expansion Ratio,” AIChE Symp. Ser., 74(176), 176-186 (1978).
Bernedetto, A. D. and P. Salatino, “Modelling Attrition of Limestone During Calcination and Sulfation in a Fluidized Bed Reactor,” Powder Technol., 95, 119-128 (1998).
Berruti, F., J. R. Muir and L. A. Behie, “Solids Circulation in a Spout-Fluid Bed with Draft Tube,” Can. J. Chem. Eng., 66, 919-923 (1988).
Beverloo, W. A., H. A. Leniger and J. V. De Velde, “The Flow of Granular Solids through Orifices,” Chem. Eng. Sci., 15, 260-269 (1961).
Bhatia, S. K. and D. D. Perlmutter, “Effect of the Product Layer on the Kinetics of the CO2-Lime Reaction,” AIChE J., 29, 79-86 (1983).
Bridgwater, J., in “Fluidization II,” J. F. Davidson, R. Clift, D. Harrison, eds., p. 201, Academic Press, London (1985).
Cheung, L., A. W. Nienow and P. N. Rowe, “Minimum Fluidization Velocity of a Binary Mixture of Different Sized Particles,” Chem. Eng. Sci., 29, 1301-1303 (1974).
Chiba, S., T. Chiba, A. W. Nienow and H. Kobayashi, “The Minimum Fluidization Velocity, Bed Expansion and Pressure-Drop Profile of Binary Particle Mixtures,” Powder Technol., 22, 255-269 (1979).
Chitester, D. C., R. M. Kornosky, L. S. Fan and J. P. Danko, “Characteristics of Fluidization at High Pressure,” Chem. Eng. Sci., 39(2), 253-261 (1984).
Choi, Y. T. and S. D. Kim, “Bubble Characteristics in an Internally Circulating Fluidized Bed,” J. Chem. Eng. Japan, 24, 195 (1991).
Chu, C. Y., K. W. Hsueh and S. J. Hwang, “Sulfation and Attrition of Calcium Sorbent in a Bubbling Fluidized Bed,” J. Hazard. Mater., B80, 119-133 (2000).
Chu, C. Y. and S. J. Hwang, “Attrition and Sulfation of Calcium Sorbent and Solids Circulation Rate in an Internally Circulating Fluidized Bed,” Powder Technol., 127, 185-195 (2002).
Cook, J. L., S. J. Khang, S. K. Lee and T. C. Keener, “Attrition and Changes in Particle Size Distribution of Lime Sorbents in a Circulating Fluidized Bed Absorber,” Powder Technol., 89, 1-8 (1996).
De Jong, J. A. H. and Q. E. J. J. M. Hoelen, “Cocurrent Gas and Particle Flow During Pneumatic Discharge from a Bunker through an Orifice,” Powder Technol., 12, 201-208 (1975).
Garea, A., J. R. Viguri and A. Irabien,“Kinetics of Flue Gas Desulfurization at Low Temperature: Fly Ash/Calcium (3/1) Sorbent Behavior,” Chem. Eng. Sci., 52(5), 715-732 (1997).
Geldart, D. and A. R. Abrahamsen, “Fluidization of Fine Porous Powders: (a) A Simple Technique for Measuring Particle Density (b) Incipient Fluidization Velocity Using Various Gases,” Chem. Eng. Prog. Symp. Ser., 77(205), 160-165 (1981)
Geldart, D., “Gas Fluidization Technology,” John Wiley & Sons, Chichester (1986).
Gelter, J. K., M. L. Shelton and D. A. Furlong, “Modeling the Spray Absorption Process for SO2 Removal,” JAPCA., 29(12), 1270-1274 (1979).
Gwyn, J. E., “On the Particle Size Distribution Function and the Attrition of Cracking Catalysts,” AIChE J., 15(1), 35-38 (1969).
He, Y. L., S. Z. Qin, C. J. Lim and J. R. Grace, “Particle Velocity Profiles and Solid Flow Patterns in Spouted Beds,” Can. J. Chem. Eng., 72, 561-568 (1994).
Henry, J. M., R. F. Robards and W. L. Wells, “Spray-Dryer Scrubbers for High-Sulfur Coal Combustion,” Environ. Prog., 1(4), 284-290 (1982).
Herb, B., S. Dou, K. Tuzla and J. C. Chen, “Solid Mass Fluxes in Circulating Fluidized Beds,” Powder Technol., 70, 197-205 (1992).
Ho, C. S. and S. M. Shih, “Factors Influencing the Reaction of Ca(OH)2 with SO2,” J. Chin. I. Ch. E., 24(4), 187-195 (1993).
Ho, C. S. and S. M. Shih, “Ca(OH)2 /Fly Ash Sorbent for SO2 Removal,” Ind. Eng. Chem. Res., 31, 1130-1135 (1992).
Irabien, A., F. Cortabitarte and M. I. Ortiz, “Kinetics Model for Desulfurization at Low Temperature Using Calcium Hydroxide,” Chem. Eng. Sci., 45(12), 3427-3433 (1990).
Irabien, A., F. Cortabitarte and M. I. Ortiz, “Kinetics of Flue Gas Desulfurization at Low Temperatures: Nonideal Surface Adsorption Model,” Chem. Eng. Sci., 47(7), 1533-1543 (1992).
Jiang, M. X., T. C. Keener and S. J. Khang, “The Use of a Circulating Fluidized Bed Absorber for the Control of Sulfur Dioxide Emissions by Calcium Oxide Sorbent via in situ Hydration,” Powder Technol., 85, 115-126 (1995).
Jorgensen, C. and J. C. S. Chang, “Evaluation of Sorbents and Additives for Dry SO2 Removal,” Environ. Prog., 6(2), 26-32 (1987).
Judd, M. R. and P. D. Dixon, “The Flow of Fine, Dense Solids Down Vertical Standpipe,” AIChE Symp. Ser., 74(176), 38-44 (1978).
Kim, Y. T., B. H. Song and S. D. Kim, “Entrainment of Solid in an Internally Circulating Fluidized Bed with Draft Tube,” Chem. Eng. J., 66, 105-110 (1997).
Klingspor, J. H., T. Karlsson and I. Bjerle, “A Kinetic of the Dry SO2-Limestone Reaction at Low Temperature,” Chem. Eng. Commun., 22, 81-103 (1983).
Klingspor, J., A. Stromberg, H. T. Karlsson and I. Bierle, “Similarities Between Lime and Limestone in Wet-Dry Scrubbing,” Chem. Eng. Proc., 18(5), 239-247 (1984).
Kunii, D. and O. Levenspiel, “Fluidized Reactor Models. 1. For Bubbling Beds of Fine, Intermediate, and Large Particles. 2. For the Lean Phase: Freeboard and Fast Fluidization,” Ind. Eng. Chem. Res., 29, 1226-1234 (1990).
Kuramoto, M., D. Kunii and T. Furusawa, “Flow of Dense Fluidized Particles through an Opening in a Circulation System,” Powder Technol., 47, 141-149 (1986).
La Nauze, R. D., “A Circulating Fluidized Bed,” Powder Technol., 15, 117-127 (1976).
Lee, S. K., X. Jiang, T. C. Keener and S. J. Khang, “Attrition of Lime Sorbents During Fluidization in a Circulating Fluidized Bed Absorber, ” Ind. Eng. Chem. Res., 32, 2758-2766 (1993).
Levenspiel, O., The Chemical Reactor Omnibook, OSU Bookstore, Corvallis, Oregon, p. 52.12. (1979).
Lin, L., J. T. Sears and C. Y. Wen, “Elutriation and Attrition of Char from a Large Fluidized Bed,” Powder Technol., 27, 105-115 (1980).
Marschall, K. J. and L. Mleczko, “CFD Modeling of an Internally Circulating Fluidized-Bed Reactor,” Chem. Eng. Sci., 54, 2058-2093 (1999).
Mathur, K. B. and N. Epstein, eds., “Spouted Beds,” Academic Press, Inc., New York (1974).
Merrick, D. and J. Highley, “Particle Size Reduction and Elutriation in a Fluidized Bed Process,” AIChE Symp. Ser., 70(137), 366-378 (1974).
Milne, B. J., F. Berruti, and L. A. Behie, “The Internally Circulating Fluidized Bed (ICFB): A Novel Solution to Gas Bypassing in Spouted Beds,” Can. J. Chem. Eng., 70, 910-915 (1992).
Miwa, K., S. Mori, T. Kato and I. Muchi, “Behavior of bubbles in a Gaseous Fluidized Bed,” Chem. Engng., 12(1), 187-194 (1972).
Mori, S. and C. Y. Wen, “Estimation of Bubble Diameter in Gaseous Fluidized Beds,” AIChE J., 20, 109-115 (1975).
Mukadi, L., C. Guy and R. Legros, “Prediction of Gas Emissions in an Internally Circulating Fluidized Bed Combustor for Treatment of Industrial Solid Wasters,” Fuel, 79, 1125-1136 (2000).
Muir, J. R., F. Berruti and L. A. Behie, “Solids Circulation in Spouted and Spout-Fluid Beds with Draft-Tubes,” Chem. Eng. Comm., 88, 153-171 (1990).
Neathery, J. K., “Model for Flue-Gas Desulfurization in a Circulating Dry Scrubber,” AIChE J., 42(1), 259-268 (1996).
Newton, G. H., J. Kramlich and R. Payne, “Modeling the SO2 Slurry Droplet Reaction, ” AIChE J., 36(12), 1865-1872 (1990).
Ormiston, R. M., F. R. G. Mitchell and J.F. Davidson, “The Velocities of Slugs in Fluidised Beds,” Trans. Inst. Chem. Eng., 43, 209-216 (1965).
Ray, Y. C., T. S. Jiang and C. Y. Wen, “Particle Attrition Phenomena in a Fluidized Bed,” Powder Technol., 49, 193-206 (1987).
Richardson J. F., in “Fluidazation,” Davidson J. F. and H. Harrison, eds., p.26 Academic Press, New York (1971)
Rincon, J., J. Guardiola, A. Romero and G. Ramos, “Predicting the Minimum Fluidization Velocity of Multicomponent Systems,” J. Chem. Eng. Japan, 27, 177-181 (1994).
Rowe, P. N., and A. W. Nienow, “Minimum Fluidization Velocity of Multi-Component Particle Mixtures,” Chem. Eng. Sci., 30, 1365-1369 (1975).
Ruiz-Alsop, R. N. and G. T. Rochelle, “Effect of Deliquescent Salt Additives on the Reaction of SO2 with Ca(OH)2,” ACS. Symp. Ser., 319, 208-222 (1986).
Saxena, S. C. and G. J. Vogel, “The Measurement of Incipient Fluidization Velocities in a Bed of Corase Dolomite at Temperature and Pressure,” Trans. Inst. Chem. Eng., 55, 184-189 (1977).
Scala, F., A. Cammarota, R. Chirone and P. Salatino, “Comminution of Limestone During Batch Fluidized-Bed Calcination and Sulfation,” AIChE J., 43(2), 363-373 (1997).
Shamlou, P. A., Z. Liu and J. G. Yates, “Hydrodynamic Influences on Particle Breakage in Fluidized Beds,” Chem. Eng. Sci., 45(4), 809-817 (1990).
Shih, H. H., C. Y. Chu and S. J. Hwang, “Solids Circulation and Attrition Rate and Gas Bypassing in an Internally Circulating Fluidized Bed,” Ind. Eng. Chem. Res., 42(23), 5915-5923 (2003).
Snip, O. C., M. Woods, R. Korbee, J. C. Schouten and C. M. Ven Den Bleek, “Regenerative Removal of SO2 and NOx for a 150 MWe Power Plant in an Interconnected Fluidized Bed Facility,” Chem. Eng. Sci., 51(10), 2021-2029 (1996).
Song, B. H., Y. T. Kim and S. D. Kim, “Circulation of Solids and Gas Bypassing in an Internally Circulating Fluidized Bed with a Draft Tube,” Chem. Eng. J., 68, 115-122 (1997).
Stewart, P. S. B. and J. F. Davidson, “Slug Flow in Fluidised Beds,” Powder Techonl., 1, 60-80 (1967); P. S. B. Stewart, Ph.D. dissertation, Cambridge Univ. (1965).
Stocker, R. K., J. H. Eng, W. Y. Svrcek and L. A. Behie, “Ultrapyrolysis of Propane in a Spouted-Bed Reactor with a Draft Tube,” AIChE J., 35(10), 1617-1624 (1989a).
Stocker, R. K., J. H. Eng, W. Y. Svrcek and L. A. Behie, “Gas Residence Time Distribution Studies in a Spouted bed with a Draft Tube,” in “Fluidization VI,” J. R. Grace, L. W. Shemilt and M. A. Bergougnou, eds., Engineering Foundation, New York, 269-276 (1989b).
Stouffer, M. R., H. Yoon and F. P. Burke, “An Investigation of the Mechanisms of Flue Gas Desulfurization by In-Duct Dry Sorbent Injection,” Ind. Eng. Chem. Res., 28, 20-27 (1989).
Uysal, B .Z., I. Aksahin and H. Yucel, “Sorption of SO2 on Metal Oxides in a Fluidized Bed,” Ind. Eng. Chem. Res., 27, 434-439 (1988).
Vaux, W. G. and A. W. Fellers, “Measurement of Attrition Tendency in Fluidization,” AIChE Symp. Ser., 77(205), 107-115 (1981).
Wen, C. Y. and R. F. Hashinger, “Elutriation of Solid Particles from a Dense-Phase Fluidized Bed,” AIChE J., 6, 220-226 (1960).
Wen, C. Y. and H. Yu, “A Generalized Method for Predicting for Minimum Fluidization Velocity,” AIChE J., 12, 610-612 (1966).
Yang, W. C. and D. L. Keairns, “Studies on the Solid Circulation Rate and Gas Bypassing in Spouted Fluid-Bed with a Draft Tube,” Can. J. Chem. Eng., 61, 349-355 (1983).
徐恆文、廖政一、陳明德、陳瑞燕、溫增文、張瑞進等，“濕式煙道氣除硫技術手冊，”財團法人工業技術研究院，新竹 (1992).
章裕民，“流體化床燃燒脫硫技術，”工業污染防治，30，203-219 (1989).
李百芳、周治雲，“流動床式石灰石粒煙道氣脫硫技術，”工業污染防治，48，75-92 (1993).