Understanding the Behavior of Calcium Compounds in Petroleum Coke Fluidized Bed Combustion (FBC) Ash

2006 ◽  
Vol 128 (4) ◽  
pp. 290-299 ◽  
Author(s):  
E. J. Anthony ◽  
L. Jia ◽  
S. M. Burwell ◽  
J. Najman ◽  
E. M. Bulewicz
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Petroleum Coke ◽  
Bound Water ◽  
Mineral Matter ◽  
Fluidized Bed Combustion ◽  
Free Lime ◽  
Size Fractions ◽  
Lime Content ◽  
Calcium Compounds

With growing understanding of the differences between solid residues from the fluidized bed combustion of petroleum coke and of coal, the significance of fuel-derived and sorbent-derived components of the ash has become clearer. It is well documented that hydration of the ashes is necessary prior to disposal or utilization or as a reactivation method. Initially, hydration of the lime was thought to involve water reacting only with CaO to form Ca(OH)2 but when the free lime content of the ashes is looked at before and after hydration, it is apparent that the process is more complex. Detailed analyses have shown that the free lime can decrease and vary within the same ash in different particle size ranges. The complexity of the reactions is reflected in problems with the assessment of the free lime content of the materials and the effect of hydration on different particle size fractions of the ash. The free lime content of the ash is significantly lower than expected based on the elemental analysis. Bed ash from the circulating fluidized bed combustion boilers owned and operated by the Nelson Industrial Steam Company Ltd. (NISCO) was examined in detail to elucidate the fate of calcium in the ash during hydration, using a range of techniques. The objective of the study is to determine the amount of CaO available for hydration/reactivation and to better understand interactions of Ca and other mineral components of the ash. Analysis results indicate that in NISCO ashes up to about 6% of the analytical CaO may be combined as acid soluble and insoluble OCCs (other calcium compounds). This implies up to about 10% less free lime than would be inferred from standard chemical analyses. About 1% of the missing CaO can be present as acid insoluble Ca and Mg vanadates, with up to 2% bound in soluble OCCs. The remaining 3-4% is still not accounted for. It is clear that even very minor quantities of mineral matter, other than CaO or CaSO4, associated mainly with the coarser size fractions, are important. The amount of bound water in the hydrated ash, other than that combined in portlandite or brucite, can be as large as 3-5%. This cannot be ignored when sample mass change on hydration or heating is used as a measure of the extent of CaO to Ca(OH)2 conversion.

Petroleum Coke FBC Ash: A Detailed Look at Calcium in the Ash

2003 ◽  
Author(s):  
E. J. Anthony ◽  
L. Jia ◽  
S. M. Burwell
Keyword(s):  
Chemical Analysis ◽  
Sulfur Content ◽  
Petroleum Coke ◽  
Elemental Analysis ◽  
Current Work ◽  
Free Lime ◽  
Lime Content ◽  
Coke Combustion ◽  
Bed Material ◽  
Calcium Compounds

Petroleum coke combustion is different from coal and its behaviour in an FBC environment clearly illustrates this. Analysis of bed ash from the CFBC boilers owned and operated by the Nelson Industrial Steam Company Ltd. (NISCO) was examined in detail to determine the fate of calcium in the ash using a range of techniques. These analyses have shown a free lime content, which is significantly lower than expected based on the elemental analysis of the bed material. Using different methods of analyses than have been typically used for FBC ashes (coal in particular) it would appear that between 6 to 7% of the total CaO in the samples is combined in the form of acid soluble and insoluble other calcium compounds (OCC). This translates to about 30% less free lime (depending on the ash sulfur content) in the sample than would be calculated based on a standard chemical analysis of the bed ash. This current work has identified about 1% of the missing CaO in the form of acid insoluble Ca and Mg vanadates with perhaps as much as 2% of the remaining missing CaO present as soluble OCC.

Influencing Factors of Hydraulic Property of CFBC Ashes

2012 ◽  
Vol 532-533 ◽  
pp. 282-286
Author(s):  
Yuan Ming Song ◽  
Jing Xiang Liu ◽  
Chao Wang ◽  
Hong He Zhong ◽  
Tian Ding
Keyword(s):  
High Activity ◽  
Fluidized Bed ◽  
Influencing Factors ◽  
Circulating Fluidized Bed ◽  
Great Influence ◽  
Fluidized Bed Combustion ◽  
Hydraulic Property ◽  
Free Lime ◽  
Circulating Fluidized Bed Combustion

The hydraulic property of Circulating Fluidized Bed Combustion (CFBC) ashes has a significant impact on their treatment and re-utilization. The studies on several CFBC ashes show that the hydraulic property of them is obvious, and even the hydraulic rate is so fast that CFBC pastes can harden within several hours after molding. The influencing factors of hydraulic property of CFBC ashes are investigated. The results confirm that the content of the free lime and the high-activity components has great influence on the hydraulic property of CFBC ashes.

A Simulation Study for Fluidized Bed Combustion of Petroleum Coke With CO2 Capture

2003 ◽  
Author(s):  
Jinsheng Wang ◽  
Edward J. Anthony ◽  
J. Carlos Abanades
Keyword(s):  
Power Generation ◽  
Fluidized Bed ◽  
Petroleum Coke ◽  
Co2 Capture ◽  
Low Cost ◽  
Volatile Content ◽  
Fluidized Bed Combustion ◽  
High Carbon ◽  
Overall Efficiency ◽  
Fluidized Bed Combustor

Petroleum coke is regarded as a difficult fuel because of its high sulphur content and low volatile content. However, its low price and increased production, means that there is a powerful economic stimulus to use it for power generation. In this work, a process simulation has been performed as part of a feasibility study on the utilization of petroleum coke for power generation with low-cost CO2 capture. The proposed system employs a pressurized fluidized bed combustor and a calciner. In the combustor itself, the petroleum coke is burned and most of the CO2 generated is captured by a CaO sorbent under pressurized condition to form CaCO3. The CaCO3 is transported into the calciner where limited proportion of the petroleum coke is burned with pure O2, and calcines the spent sorbent back into CaO and CO2. A nearly pure CO2 stream is obtained from the calciner for subsequent disposal or utilization. The predicted overall efficiency of the combustion is near 40%. The proposed system would also be suitable for firing other high carbon and low ash fuel, such as anthracite.

Reactivation Studies on Six Fly Ashes From Commercial CFB Boilers

2005 ◽  
Author(s):  
Y. Wu ◽  
J.-P. Charland ◽  
E. J. Anthony ◽  
L. Jia
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Liquid Water ◽  
Circulating Fluidized Bed ◽  
Absorption Capacity ◽  
Fluidized Bed Combustion ◽  
Fly Ashes ◽  
Commercial Scale ◽  
Circulating Fluidized Bed Combustion ◽  
So2 Absorption

Six different fly ashes from commercial-scale circulating fluidized bed combustion (CFBC) boilers and the carbon-free residues of these ashes were hydrated with liquid water or steam to determine whether hydration could improve sorbent utilization in these samples under fluidized bed combustion conditions. After hydration, for two fly ashes (FA1 and FA6) and three carbon-free samples (FA2-A, FA3-A and FA6-A), the capacity for taking up SO2 showed limited or medium improvement; however, hydration was evidently ineffective in reactivating the remaining samples. It is believed that the reason samples FA6 and FA6-A show a relatively high improvement in SO2 absorption capacity is that these ashes had a larger particle size than any of the other fly ashes examined here. In general, even for these “reactivatable” fly ashes, reactivation by hydration with either liquid water or steam appeared far less promising than for bed ashes, which have been shown to exhibit significant improvement in sulphur capture during re-sulphation. Hydration, whether by steam or liquid water, is not recommended for fly ash, which has a very limited residence time in the boiler due to its small particle size and instead this paper recommends alternative strategies.

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