“…As a result, there were almost no temperature effects on the absorption of HCl in both the fly ash and bed ash from the combustion of this coal. For the high-chlorine coal (95031), both Figures and show that chloride retention is more favorable at low temperatures. , 3 Effect of bed temperature on the concentration of sulfur in the fly ash of the AFBC system. 4 Effect of bed temperature on the chloride content in the bed ash of the AFBC system.…”
Section: Resultsmentioning
confidence: 97%
“…On the other hand, Figure shows that the Ca/S ratio is more important for the capture of chloride compared to sulfur for the high-chlorine-content coal (95031). It is assumed that the HCl is probably captured in the low bed temperature region when the flue gas is passing through the heat exchange tube region because the reaction between HCl and CaO is more favorable at the lower temperature. , The composition of the fly ash (collected from the wet cyclone) in both cases is Ca(OH) 2 , which is due to CaO reacting with water, CaSO 4 , CaCO 3 , and CaCl 2 . This is the only place CaCl 2 was identified in this study.…”
Section: Resultsmentioning
confidence: 99%
“…For the high-chlorine coal (95031), both Figures 3 and 4 show that chloride retention is more favorable at low temperatures. 11,12 Effects of Coal Chlorine Content on the Retention of SO 2 . Figure 5 shows the results of sulfur dioxide emission from tests with two different coals (95011 and 95031).…”
Two 1000-h burns were conducted with the 12-in. (0.3 m) laboratory AFBC system at Western Kentucky University. Operating conditions similar to those used at the 160-MW AFBC system at the TVA Shawnee Steam Plant located near Paducah, KY, were used. A low-chlorine (0.012% Cl and 3.0% S) western Kentucky No. 9 coal and a high-chlorine (0.28% Cl and 2.4% S) Illinois No. 6 coal were used in this study. Four different metal alloys [carbon steel C1020 (0.18% C and 0.05% Cr), 304 SS (18.39% Cr and 8.11% Ni), 309 SS (23.28% Cr and 13.41% Ni), and 347 SS (18.03% Cr and 9.79% Ni)] were exposed uncooled in the freeboard area at the entrance to the convective pass, where the metal temperature was approximately 900 K. A two-phase investigation was carried out in order to study the fate of chlorine during coal combustion in an AFBC system and to study the susceptibility of boiler components to corrode in combustion gases containing hydrogen chloride. As determined from emission and ash studies, the temperature in an AFBC system plays a key role in the retention of chloride, which is more favorable at low operating temperatures. A small amount of scale failure was observed on the other three samples in both test runs. On the basis of the SEM-EDS mapping results, there was no localized chloride distribution observed on the surface of the coupons, either in the scale failure area nor on the rest of the metal part. Some trace amount of chloride was found but was evenly distributed on the surface of the coupons. There was no concentration of chloride on the spot of scale failure. The scale failure might be due to sulfur attack and/or the effect of erosion. Further study with higher chlorine-content coals for more conclusive information is needed.
“…As a result, there were almost no temperature effects on the absorption of HCl in both the fly ash and bed ash from the combustion of this coal. For the high-chlorine coal (95031), both Figures and show that chloride retention is more favorable at low temperatures. , 3 Effect of bed temperature on the concentration of sulfur in the fly ash of the AFBC system. 4 Effect of bed temperature on the chloride content in the bed ash of the AFBC system.…”
Section: Resultsmentioning
confidence: 97%
“…On the other hand, Figure shows that the Ca/S ratio is more important for the capture of chloride compared to sulfur for the high-chlorine-content coal (95031). It is assumed that the HCl is probably captured in the low bed temperature region when the flue gas is passing through the heat exchange tube region because the reaction between HCl and CaO is more favorable at the lower temperature. , The composition of the fly ash (collected from the wet cyclone) in both cases is Ca(OH) 2 , which is due to CaO reacting with water, CaSO 4 , CaCO 3 , and CaCl 2 . This is the only place CaCl 2 was identified in this study.…”
Section: Resultsmentioning
confidence: 99%
“…For the high-chlorine coal (95031), both Figures 3 and 4 show that chloride retention is more favorable at low temperatures. 11,12 Effects of Coal Chlorine Content on the Retention of SO 2 . Figure 5 shows the results of sulfur dioxide emission from tests with two different coals (95011 and 95031).…”
Two 1000-h burns were conducted with the 12-in. (0.3 m) laboratory AFBC system at Western Kentucky University. Operating conditions similar to those used at the 160-MW AFBC system at the TVA Shawnee Steam Plant located near Paducah, KY, were used. A low-chlorine (0.012% Cl and 3.0% S) western Kentucky No. 9 coal and a high-chlorine (0.28% Cl and 2.4% S) Illinois No. 6 coal were used in this study. Four different metal alloys [carbon steel C1020 (0.18% C and 0.05% Cr), 304 SS (18.39% Cr and 8.11% Ni), 309 SS (23.28% Cr and 13.41% Ni), and 347 SS (18.03% Cr and 9.79% Ni)] were exposed uncooled in the freeboard area at the entrance to the convective pass, where the metal temperature was approximately 900 K. A two-phase investigation was carried out in order to study the fate of chlorine during coal combustion in an AFBC system and to study the susceptibility of boiler components to corrode in combustion gases containing hydrogen chloride. As determined from emission and ash studies, the temperature in an AFBC system plays a key role in the retention of chloride, which is more favorable at low operating temperatures. A small amount of scale failure was observed on the other three samples in both test runs. On the basis of the SEM-EDS mapping results, there was no localized chloride distribution observed on the surface of the coupons, either in the scale failure area nor on the rest of the metal part. Some trace amount of chloride was found but was evenly distributed on the surface of the coupons. There was no concentration of chloride on the spot of scale failure. The scale failure might be due to sulfur attack and/or the effect of erosion. Further study with higher chlorine-content coals for more conclusive information is needed.
“…Based on the stoichiometry of the sulphur capture reaction with calcium oxide, a theoretical limestone feed of one mole calcium per mole of sulphur would be enough for complete sulphur capture. However, the molar volume of the reaction product CaSO 4 is about three times greater than the molar volume of CaO, therefore complete conversion of the adsorbent particle is impossible, because sulphation only proceeds at the outer shell of the CaO particle (Bramer, 1995) and formation of CaSO 4 causes pore mouth closure and reaction stops before all the CaO is consumed by the reaction (Marsh and Ulriehson, 1985). This sulphation pattern is commonly referred to as the unreacted-core model (DamJohansen, 1987;Dam-Johansen et al, 1991;Laursen et al, 2001).…”
“…In addition, it can be seen from Figure 9 that with the increase in CO/O 2 reaction ratio, the ratio of NH 3 to NO increases because the amount of oxygen involved in reaction R2.7 increases with an elevating oxygen concentration, and the Industrial oxidation is difficult to observe. 26,37 Model prediction for the formation of NO and N 2 O from the oxidation of NH 3 in CO/O 2 is shown in Figure 10; the conversion rate of NH 3 into NO is relatively high, and the NO concentration is maintained at 150 ppm even under the condition of 0.5% O 2 concentration. However, under this condition, the prediction of N 2 O is quite different, and only at a lower temperature can about 1 ppm of N 2 O be generated, which needs to be improved.…”
Accurate prediction of NO x formation is of great significance for NO x emission control. The model of NO and N 2 O in air-staged combustion is established in this study, creatively associates the important reactions involving NO and N 2 O, and successfully predicts the secondary increase of NO during air-staged combustion and the occurrence of N 2 O in the high-temperature zone. The model correlates CO with the reduction of NO in the reduction zone and the generation of N 2 O, successfully predicting the downward trend of NO in the reduction zone. The formation mechanism of NO and N 2 O was further explored by simulating the combustion atmosphere. The results show that the increase in oxygen concentration can promote the oxidation of NH 3 to NO. In the CO/O 2 combustible atmosphere, NH 3 will be converted into a high ratio of NO and a certain amount of N 2 O. The addition of NO did not increase N 2 O formation. N 2 O can be formed through the direct oxidation of CO(NH 2 ) 2 and also can be generated by reaction of NO with NCO; the significant increase in the production of N 2 O in the second stage indicates the important role of NO in N 2 O formation.
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