Relationship Between Feedstock Characteristics and Erosivity of FBC Bed Materials

1992 ◽  
Vol 114 (1) ◽  
pp. 145-151
Author(s):  
A. V. Levy ◽  
B. Q. Wang ◽  
G. Q. Geng
Keyword(s):  
Heat Exchangers ◽  
Major Effect ◽  
Plain Carbon Steel ◽  
Sand Content ◽  
Degradation Mechanisms ◽  
Sharp Transition ◽  
Fluid Bed ◽  
Alkali Compounds ◽  
Bed Materials ◽  
Bed Material

The erosion-corrosion (E-C) metal wastage mechanisms and rates that occur in 1018 plain carbon steel used in tubular heat exchangers of fluid bed combustors (FBC) are discussed. The characteristics of FBC bed material erodent particles such as composition, shape, size, and strength were found to have a major effect on the surface degradation mechanisms and rates that occurred. A total of 16 different bed material particles from ten different FBCs were tested. It was determined that when the particles were strong enough not to shatter when they impacted the steel’s surface, their shape and composition were the most important factors in determining their erosivity. The relative amounts of SiO2, CaO, CaCO3, CaSO4, and alkali compounds in the bed materials were related to the metal wastage by using laboratory mixtures of the compounds as erodents. The ratio of SiO2 to CaO and CaCO3 was especially important in determining the erosivity of the bed materials. It was found that increasing this ratio increased the metal wastage. A sharp transition ratio occurred on either side of which the metal wastages were linear. The slope of the linear curve was low for the lower sand content mixtures and higher for higher sand content mixtures. The transition ratio required a higher CaO content for higher velocity particles.

scholarly journals Relationship Between Feedstock Characteristics and Erosivity of FBC Bed Materials

1990 ◽  
Author(s):  
Alan V. Levy ◽  
B. Q. Wang ◽  
G. Q. Geng
Keyword(s):  
Heat Exchangers ◽  
Major Effect ◽  
Plain Carbon Steel ◽  
Sand Content ◽  
Degradation Mechanisms ◽  
Sharp Transition ◽  
Fluid Bed ◽  
Alkali Compounds ◽  
Bed Materials ◽  
Bed Material

The erosion-corrosion (E-C) metal wastage mechanisms and rates that occur in 1018 plain carbon steel used in tubular heat exchangers of fluid bed combustors (FBC) are discussed. The characteristics of FBC bed material erodent particles such as composition, shape, size and strength were found to have a major effect on the surface degradation mechanisms and rates which occurred. A total of sixteen different bed material particles from ten different FBCs were tested. It was determined that when the particles were strong enough to not shatter when they impacted the steel’s surface, their shape and composition were the most important factors in determining their erosivity. The relative amounts of SiO2, CaO, CaCO3, CaSO4, and alkali compounds in the bed materials were related to the metal wastage by using laboratory mixtures of the compounds as erodents. The ratio of SiO2 to CaO and CaCO3 was especially important in determining the erosivity of the bed materials. It was found that increasing this ratio increased the metal wastage. A sharp transition ratio occurred on either side of which the metal wastages were linear. The slope of the linear curve was low for the lower sand content mixtures and higher for higher sand content mixtures. The transition ratio required a higher CaO content for higher velocity particles.

scholarly journals Experimental Investigation of Oxygen Carrier Aided Combustion (OCAC) with Methane and PSA Off-Gas

2020 ◽  
Vol 11 (1) ◽  
pp. 210
Author(s):  
Viktor Stenberg ◽  
Magnus Rydén ◽  
Tobias Mattisson ◽  
Anders Lyngfelt
Keyword(s):  
Oxygen Carrier ◽  
Silica Sand ◽  
Fuel Conversion ◽  
Fuel Gas ◽  
Bed Temperature ◽  
Bed Materials ◽  
Distribution Plate ◽  
Bed Material ◽  
Gas Conversion ◽  
No Emissions

Oxygen carrier aided combustion (OCAC) is utilized to promote the combustion of relatively stable fuels already in the dense bed of bubbling fluidized beds by adding a new mechanism of fuel conversion, i.e., direct gas–solid reaction between the metal oxide and the fuel. Methane and a fuel gas mixture (PSA off-gas) consisting of H2, CH4 and CO were used as fuel. Two oxygen carrier bed materials—ilmenite and synthetic particles of calcium manganate—were investigated and compared to silica sand, an in this context inert bed material. The results with methane show that the fuel conversion is significantly higher inside the bed when using oxygen carrier particles, where the calcium manganate material displayed the highest conversion. In total, 99.3–99.7% of the methane was converted at 900 °C with ilmenite and calcium manganate as a bed material at the measurement point 9 cm above the distribution plate, whereas the bed with sand resulted in a gas conversion of 86.7%. Operation with PSA off-gas as fuel showed an overall high gas conversion at moderate temperatures (600–750 °C) and only minor differences were observed for the different bed materials. NO emissions were generally low, apart from the cases where a significant part of the fuel conversion took place above the bed, essentially causing flame combustion. The NO concentration was low in the bed with both fuels and especially low with PSA off-gas as fuel. No more than 11 ppm was detected at any height in the reactor, with any of the bed materials, in the bed temperature range of 700–750 °C.

Rice Husk Combustion in a BFBC Using Porous Bed Material

2005 ◽  
Author(s):  
Tadaaki Shimizu ◽  
Takumi Nemoto ◽  
Hotaka Tsuboi ◽  
Toshio Shimoda ◽  
Syunji Ueno
Keyword(s):  
Rice Husk ◽  
Porous Alumina ◽  
Silica Sand ◽  
Stable Operation ◽  
N2o Emissions ◽  
Nox Emissions ◽  
Bed Materials ◽  
Average Size ◽  
Bed Material ◽  
Fluidized Bed Combustor

Rice husk was burned in a bench-scale fluidized bed combustor (53 mm I.D. and 1.3m height) at 1123 K. Silica sand (average size 0.27 mm) was employed as conventional bed material. As an alternative bed material, a kind of porous alumina (average size 0.69 mm) was employed. Unburned gas (CO) emissions were suppressed by employing porous alumina as bed material. NOx emissions from the alumina bed were also suppressed in comparison to the sand bed. N2O emissions were nearly negligible (less than 10 ppm) for both bed materials. During combustion in the sand bed, sudden temperature rise up to 1450 K and increase in pressure drop across the bed were observed. Agglomerates were found in the bed material after the experiments. For the porous alumina bed, such agglomeration trouble did not occur. As conclusion, the present porous alumina was effective for both reduction of pollutants emissions and stable operation.

Icequake streaks linked to potential mega-scale glacial lineations beneath an Antarctic ice stream

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 99-102
Author(s):  
C. Grace Barcheck ◽  
Susan Y. Schwartz ◽  
Slawek Tulaczyk
Keyword(s):  
Mechanical Properties ◽  
Spatial Distribution ◽  
High Porosity ◽  
Back Projection ◽  
West Antarctica ◽  
S Wave ◽  
Frictional Properties ◽  
Ice Stream ◽  
Bed Materials ◽  
Bed Material

Abstract Icequakes radiating from an ice-stream base provide insights into otherwise difficult to observe sub-kilometer-scale basal heterogeneity. We detect basal icequakes beneath an ∼3-km-wide seismic sensor network installed on the Whillans Ice Plain (WIP) in West Antarctica, and we use S-wave back-projection to detect and locate thousands of basal icequakes occurring over 14 and 21 days in January 2014 and 2015, respectively. We find flow-parallel streaks of basal icequakes beneath the WIP, which we conjecture are related to the presence of mega-scale glacial lineations (MSGLs) indicated by ice-penetrating radar, with at least one streak originating in a local trough adjacent to a MSGL. Patterned basal seismicity can be caused by systematic spatial variation in basal pore pressure, bed-material frictional properties, or both. We interpret these flow-parallel icequake streaks as being due to frictionally heterogeneous bed materials in the presence of a streamlined ice-stream bed: bedform ridges correspond to aseismic, high-porosity deforming till, and some troughs to ephemeral exposures of deeper, seismogenic material such as lodged till or older sediments or rocks. Our results are consistent with MSGL formation by either erosion in troughs to expose deeper seismogenic material, or deposition of aseismic high-porosity till in bedform highs. Our results also suggest that evolving subglacial geomorphology can impact basal traction by reorganizing the spatial distribution of basal materials with varying mechanical properties.

Fuel Flexibility and Petroleum Coke Combustion at Provence 250 MW CFB

2003 ◽  
Author(s):  
Thierry Le Guevel ◽  
Philippe Thomas
Keyword(s):  
Sulfur Content ◽  
Petroleum Coke ◽  
Heat Exchangers ◽  
Critical Role ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Cfb Boiler ◽  
Fluid Bed ◽  
Low Sulfur Content

The Provence 250 MWe CFB boiler was originally designed in 1992 for a local coal (Provence lignite) with a high sulfur and high ash content. This large CFB, features a pant leg bottom furnace, 4 cyclones and 4 fluid bed heat exchangers to provide the active temperature control of the furnace and reheated steam final temperature. After start up in 1995 with this local coal, several other fuel types were burnt. Mainly 3 fuels were tested over the last 5 years, on a long term basis, with various degrees of combination with the Gardanne coal up to full firing alone: • a lean coal (Gard, France), low volatile bituminous type, not far from semi anthracite type coals, • an imported coal, representative of low ash low sulfur content imported coal, • a petroleum coke, with a high sulfur content. This last test demonstrates the widest flexibility with regards to fuel reactivity range of a CFB plant with this architecture. The fuel, limestone and ash handling/injection systems were able to cope with this fuel diversity without equipment modifications. Since these tests were conclusive both on the pollutant emissions and on the operating concern, a permit to burn petroleum coke in commercial operation in a 250 MWe CFB boiler has been obtained in December 2001. This paper presents the main features and the results of the petroleum coke tests performed and compare them with the feedback on operating conditions of the boiler and emissions performances for Provence lignite and imported coal. These positive results demonstrate the wide fuel capability of large CFB boilers with this boiler architecture. First, they emphasize the critical role of advanced cyclones to accept fuels with very different reactivities and minimize limestone consumption. Second, these results show the role of the Fluid Bed Heat Exchangers system to control actively the furnace temperature, while controlling the reheated steam temperature without using spray.

scholarly journals Partition of Cu and Pb in a Two-Stage Fluidized-Bed Waste Gasification System

2019 ◽  
Vol 9 (8) ◽  
pp. 1576 ◽  
Author(s):  
Chiou-Liang Lin ◽  
Jing-Dong Chou ◽  
Wang-Chang Weng
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Fluidized Bed ◽  
Operating Temperature ◽  
Two Stage ◽  
Factors Affecting ◽  
Bed Materials ◽  
Major Factors ◽  
Stage 1 ◽  
Bed Material

In this study, a two-stage fluidized-bed gasification system was used to determine the distribution of heavy metal contaminants in simulative waste and evaluate the effect of the bed operating temperature, Equivalence ratio (ER), and Steam/Biomass ratio (S/B) in stage 1. The heavy metal concentrations in bed materials and fly ash were measured in two stages. The results show that as the operating temperature of stage 1 increased, the quantity of heavy metals entrapped by stage 1 bed material decreased, while that captured by stage 2 bed material increased. The less volatile Cu was mostly entrapped in stage 1 bed material. The ER and S/B results show that increasing the ER and S/B caused a slight increase in the concentrations of heavy metals entrapped in stage 1 and stage 2 bed materials. However, the influences of ER and S/B were less than that of temperature. The major factors affecting the heavy metal distribution were the operating temperature and the heavy metal volatility. Stage 2 bed material was able to entrap gaseous heavy metals or particles containing heavy metals by particle filtration and chemical adsorption. Thus, the heavy metals (Cu and Pb) had a downward trend after passing through stage 2.

scholarly journals Effect of Bed Material on Bed Agglomeration for Palm Empty Fruit Bunch (EFB) Gasification in a Bubbling Fluidised Bed System

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4336 ◽  
Author(s):  
Tanakorn Kittivech ◽  
Suneerat Fukuda
Keyword(s):  
Silica Sand ◽  
Empty Fruit Bunch ◽  
Fluidised Bed ◽  
Suitable Alternative ◽  
Heating Value ◽  
Product Gas ◽  
Bed Materials ◽  
Bed Agglomeration ◽  
High Level ◽  
Bed Material

The high level of potassium compounds in Empty Fruit Bunch (EFB) induces ash-related problems, such as bed agglomeration, which is caused by the formation of a low-melting-point sticky compound: K2On·SiO2, especially in fluidised bed gasification using silica sand as bed material. Dolomite was found to be an effective alternative bed material for preventing bed agglomeration by the release of CaO via calcination processes during gasification. CaO acts as a catalyst to inhibit bed agglomeration by possibly enhancing the formation of K2CO3 instead of K2O·nSiO2. Alumina sand was also found to be a suitable alternative bed material to prevent bed agglomeration; however, due to the relatively high density of alumina sand, high gas velocity was needed to ensure good mixing and fluidisation. Using both dolomite and alumina sand as bed materials yielded a product gas having similar higher heating value (HHV) to that when using silica sand (i.e., 3.8–3.9 MJ/Nm3).

Experimental Research on Impacts of Operation Parameters on Agglomeration Characteristics during CFB Biomass Gasification

2014 ◽  
Vol 556-562 ◽  
pp. 375-379
Author(s):  
Xiao Xu Fan ◽  
Li Guo Yang ◽  
Hui Liang Zhang ◽  
Hong Jian Chen
Keyword(s):  
Fluidized Bed ◽  
Biomass Gasification ◽  
High Alumina ◽  
Cotton Stalk ◽  
Air Velocity ◽  
Bed Materials ◽  
Operation Parameters ◽  
Bed Agglomeration ◽  
Bed Material ◽  
Return Valve

The impacts of operation parameters on agglomeration characteristics during biomass gasification in fluidized bed were studied experimentally in a 0.02MWt CFB gasifier using cotton stalk pellet as fuel. The experimental results indicated that among the temperature range (600 °C-800 °C), bed agglomeration would occur after a period running with sand, high alumina bauxite or periclase as the bed material, and potassium gathered on the surface of bed materials. In the process of the fluidized-bed gasification of biomass, air velocity affected the degree of bed agglomeration, and the agglomeration problem in return valve was more serious than that in main bed.

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