“…25−27 The increasing NO emissions with excess air ratio were due to the increased concentration of oxygen. Similar results were also found in the studies by Varol et al, 17 Madhiyanon et al, 23 Afacan et al, 28 and Gungor et al 29 There are three general reasons that explain this phenomenon: (1) The nitrogen in the fuel and char is first oxidized to NO in tests with more O 2 . (2) The fuel−NO x reaction is enhanced by the increased oxygen concentration.…”
Section: Emissions Characteristics Of Lwt In Bubblingsupporting
confidence: 78%
“…The LWT used in this study was obtained from an Indonesian power plant. Its output is approximately 10–15 t h –1 , and it is badly in need of disposal. Fluidized-bed (FB) combustion technology has been developed as a clean combustion technology for decades.…”
Section: Introductionmentioning
confidence: 99%
“…Additionally, it is a low-pollution combustion technology, which makes it promising for fuels such as LWT. In our previous work, rheological characteristics of LWT pipeline transportation were studied to determine if LWTs are suitable for use as a slurry . Experimental and kinetic analyses of the combustion characteristics of LWT were also performed, using TG-FTIR to obtain information regarding basic combustion kinetics of LWT. , All of these works demonstrate the possibility of firing LWT in FB systems.…”
In this study, the
combustion and emission characteristics of slurry
from an Indonesian lignite washery tailing (LWT) and a bituminous
coal were studied and compared in both a bubbling fluidized bed (BFB)
and a circulating fluidized bed (CFB). The effects of excess air ratio,
feeding rate, secondary air ratio, and secondary air location on the
flue gas emissions were analyzed to investigate the optimal operating
conditions. The results show that it is feasible to directly fire
LWT slurry in a CFB. The temperature of the dense-phase bed firing
the LWT slurry can reach 800 °C but is lower than that of a normal
BFB/CFB firing coal. Both SO2 and NO emissions of bituminous
coal are higher than those of LWT slurry, but their emission characteristics
are still below the limits for both EU and Chinese regulations. Improved
emission characteristics are observed when firing LWT slurry and coal
in CFB compared to BFB. Two main differences were found between LWT
slurry and coal: (1) Low primary air (PA) flow rates facilitate the
defluidization of the FB combustor when firing LWT slurry. (2) High
feeding rates of LWT slurry may reduce the temperature along FB instead.
These factors should be paid special attention when designing and
operating an FB system. Optimal secondary air (SA) ratios were determined
for both LWT slurry and coal. The SA should not be located near the
distributor. All of the analyses in this study provide useful information
for the design and operation of a commercial FB system.
“…25−27 The increasing NO emissions with excess air ratio were due to the increased concentration of oxygen. Similar results were also found in the studies by Varol et al, 17 Madhiyanon et al, 23 Afacan et al, 28 and Gungor et al 29 There are three general reasons that explain this phenomenon: (1) The nitrogen in the fuel and char is first oxidized to NO in tests with more O 2 . (2) The fuel−NO x reaction is enhanced by the increased oxygen concentration.…”
Section: Emissions Characteristics Of Lwt In Bubblingsupporting
confidence: 78%
“…The LWT used in this study was obtained from an Indonesian power plant. Its output is approximately 10–15 t h –1 , and it is badly in need of disposal. Fluidized-bed (FB) combustion technology has been developed as a clean combustion technology for decades.…”
Section: Introductionmentioning
confidence: 99%
“…Additionally, it is a low-pollution combustion technology, which makes it promising for fuels such as LWT. In our previous work, rheological characteristics of LWT pipeline transportation were studied to determine if LWTs are suitable for use as a slurry . Experimental and kinetic analyses of the combustion characteristics of LWT were also performed, using TG-FTIR to obtain information regarding basic combustion kinetics of LWT. , All of these works demonstrate the possibility of firing LWT in FB systems.…”
In this study, the
combustion and emission characteristics of slurry
from an Indonesian lignite washery tailing (LWT) and a bituminous
coal were studied and compared in both a bubbling fluidized bed (BFB)
and a circulating fluidized bed (CFB). The effects of excess air ratio,
feeding rate, secondary air ratio, and secondary air location on the
flue gas emissions were analyzed to investigate the optimal operating
conditions. The results show that it is feasible to directly fire
LWT slurry in a CFB. The temperature of the dense-phase bed firing
the LWT slurry can reach 800 °C but is lower than that of a normal
BFB/CFB firing coal. Both SO2 and NO emissions of bituminous
coal are higher than those of LWT slurry, but their emission characteristics
are still below the limits for both EU and Chinese regulations. Improved
emission characteristics are observed when firing LWT slurry and coal
in CFB compared to BFB. Two main differences were found between LWT
slurry and coal: (1) Low primary air (PA) flow rates facilitate the
defluidization of the FB combustor when firing LWT slurry. (2) High
feeding rates of LWT slurry may reduce the temperature along FB instead.
These factors should be paid special attention when designing and
operating an FB system. Optimal secondary air (SA) ratios were determined
for both LWT slurry and coal. The SA should not be located near the
distributor. All of the analyses in this study provide useful information
for the design and operation of a commercial FB system.
“…Figure 8 shows that the viscosities of two CWS samples were relatively high at a low shear rate and then sharply decreased with the increase in the shear rate, which is consistent with the shear thinning characteristic. For further analysis, two rheological models [7,11,27], Herschel–Bulkley equation (3.1) and power-law equation (3.2), were used to fit the shear stress versus shear rate plot.τ=τ0+kγnandτ=kγn,where τ is the shear stress, τ 0 is the yield stress, k is the fluid consistency index, γ is the shear rate and n is the flow behaviour index. Figure 8Relationship between apparent viscosity and shear rate.…”
Section: Resultsmentioning
confidence: 99%
“…Figure 8 shows that the viscosities of two CWS samples were relatively high at a low shear rate and then sharply decreased with the increase in the shear rate, which is consistent with the shear thinning characteristic. For further analysis, two rheological models [7,11,27] royalsocietypublishing.org/journal/rsos R. Soc. Open Sci.…”
Section: Rheological Behaviour Of Cws Prepared With P(ss-co-aa-co-dmdaac)mentioning
In this work, a novel amphoteric copolymer named Poly(sodium p-styrenesulfonate–
co
-acrylic acid-
co
-diallyldimethylammonium chloride) (P(SS-
co
-AA-
co
-DMDAAC)) was synthesized via free radical polymerization. Afterwards, P(SS-
co
-AA-
co
-DMDAAC) was explored for use as a dispersant in coal water slurry (CWS) preparation. The structure of P(SS-
co
-AA-
co
-DMDAAC) was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The synthetic conditions were optimized as the feed ratio of AA to SS was 1 : 1 (for Yulin coal) or 1.5 : 1 (for Yili coal), and DMDAAC dosage was 4.0 wt% (for Yulin coal) and 6.0 wt% (for Yili coal) toward total monomers. The performances of P(SS-
co
-AA-
co
-DMDAAC) as a dispersant for CWS were evaluated by various technologies, such as apparent viscosity, zeta potential, static stability and contact angle measurements. The results revealed that the optimized dosage of P(SS-
co
-AA-
co
-DMDAAC) in CWS preparation was 0.3 and 0.4 wt% for Yulin coal and Yili coal respectively. In this optimum condition, CWS prepared using P(SS-
co
-AA-
co
-DMDAAC) as dispersant showed a typical shear thinning behaviour and excellent stability, which are desired in industries. The rheological models also confirmed the pseudo-plastic characteristics of CWS. Finally, compared with the widely used anionic dispersant naphthalene sulphonate formaldehyde condensate (NSF) and poly(sodium p-styrenesulfonate) (PSS), P(SS-
co
-AA-
co
-DMDAAC) developed in this work exhibited better slurry making performance. The introduction of cationic functional groups promoted the adsorption of the dispersant, which further enhanced the electrostatic repulsion and steric hindrance among coal particles. Accordingly, the viscosity of CWS decreased and static stability enhanced.
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