Control of Ash-Related Operational Problems in BFB Combustion of Biofuels and Waste

2003 ◽  
Author(s):  
Sonja H. Enestam ◽  
Marko K. Fabritius ◽  
Seppo K. Hulkkonen ◽  
Jukka T. Ro¨ppa¨nen
Keyword(s):  
Chemical Equilibrium ◽  
Alkali Metals ◽  
Bottom Ash ◽  
Melting Behavior ◽  
Pilot Scale ◽  
Olive Waste ◽  
Boiler Design ◽  
Fuel Mixtures ◽  
High Alkali ◽  
Multi Phase

When moving towards CO2 neutral bio fuels and waste derived fuels, new challenges are set for combustion facilities and technical boiler solutions. A common feature for both bio- and waste fuels is a big variety in composition, often high levels of alkali metals, chlorine and moisture which make these fuels difficult to burn in facilities designed for conventional fuels such as coal, peat and wood. The problems that might occur due to high alkali and chlorine levels in the fuels, are slagging, fouling, corrosion and bed sintering. The Fortum BioMAC BFB boilers are designed especially for difficult, unconventional fuels such as rice husk, olive waste, straw, construction residue, de-inking sludge, etc. The design of each individual boiler is made based on advanced theoretical prediction tools and extensive fuel testing in laboratory and in pilot scale combustion facilities. The theoretical tools consist of a multi-phase multi-component chemical equilibrium model that estimates the slagging/fouling, sintering and corrosion propensity of the fuels/fuel mixtures and of a computational fluid dynamics part. CFD calculations are used to optimize the flow pattern and the temperature of the boiler in order to avoid hot temperatures in the vicinity of refractory linings and cooled surfaces. The chemical equilibrium calculations predict the melting behavior of the fuel ash, which is used as an indicator for the placement of the superheaters. The bottom ash removal is controlled for efficient removal of coarse material, screening and recirculation. The ash related problems of important bio and waste fuels, the analytical procedure of the evaluation of the usability of the fuels and the adaptation of the boiler design are discussed in the paper.

Co-Firing in FBC: A Challenge for Fuel Characterization and Modeling

2003 ◽  
Author(s):  
Maria Zevenhoven ◽  
Bengt-Johan Skrifvars ◽  
Patrik Yrjas ◽  
Rainer Backman ◽  
Christian Mueller ◽  
...  
Keyword(s):  
Prediction Models ◽  
Fluid Dynamic ◽  
Melting Behavior ◽  
Pilot Scale ◽  
Fluidized Bed Combustion ◽  
Formation Behavior ◽  
Ash Formation ◽  
Leaching Experiments ◽  
Fuel Characterization ◽  
Fuel Mixtures

Co-combustion of coal with biomass or firing biomass alone is used more and more in a first step in meeting the Finnish commitments under the Kyoto protocol. A frequently used technique for firing mixtures of fuels is fluidized bed combustion (FBC). Firing coal, co-combustion with biomass or firing biomass alone may, however, lead to unwanted ash-related problems. Prediction of ash formation behavior can help to avoid these problems before taking new fuels into use. Standard fuel analyses have shown to provide insufficient information for proper prediction especially when considering fuel mixtures. In an attempt to minimize the number of lab scale and pilot scale combustion experiments an extensive database is under development. This database contains data used as input for prediction models such as standard fuel analyses, results from stepwise leaching experiments, SEM/EDS analyses of original and partly burned-out fuels and thermodynamic estimations of the melting behavior of the fuels. Today the database contains 51 fuels, i.e. 8 bark fuels, 10 wood fuels, 3 annual biomasses, 8 peats, 6 coals and 16 miscellaneous fuels, such as RDF, sludge, hulls and husks, bagasse and other residues. Standardized fuel analysis is available for all fuels; melting calculations have been carried out for some 33 fuels. SEM/EDS analysis has been carried out for 20 fuels. The extended utilization of these data with computational fluid dynamic modeling (CFD) has proven to be a useful tool in prediction of deposits in FBC boilers. An example of the prediction tool shows the ability of deposit formation prediction.

Pilot scale evaluation of the BABIU process – Upgrading of landfill gas or biogas with the use of MSWI bottom ash

2014 ◽  
Vol 34 (1) ◽  
pp. 125-133 ◽  
Author(s):  
P. Mostbauer ◽  
L. Lombardi ◽  
T. Olivieri ◽  
S. Lenz
Keyword(s):  
Landfill Gas ◽  
Bottom Ash ◽  
Pilot Scale ◽  
Scale Evaluation ◽  
Mswi Bottom Ash

Transformation behavior of alkali metals in high-alkali coals

2018 ◽  
Vol 169 ◽  
pp. 288-294 ◽  
Author(s):  
Yanquan Liu ◽  
Leming Cheng ◽  
Yonggang Zhao ◽  
Jieqiang Ji ◽  
Qinhui Wang ◽  
...  
Keyword(s):  
Alkali Metals ◽  
Transformation Behavior ◽  
High Alkali

Pilot-Scale Study of Multi-Phase Venting from a Vessel at Elevated Pressure and Temperature

2000 ◽  
Vol 78 (6) ◽  
pp. 434-444 ◽  
Author(s):  
J.R. Chen ◽  
C. Lee ◽  
C. Cheng ◽  
W.K. Chou ◽  
T.C. Ho
Keyword(s):  
Elevated Pressure ◽  
Pilot Scale ◽  
Multi Phase

Emission Control of Gaseous Pollutants From Co-Firing of Petroleum Coke and Coal in CFB

2003 ◽  
Author(s):  
Changsui Zhao ◽  
Wenxuan Wang ◽  
Fengjun Wang ◽  
Chuanmin Chen ◽  
Song Han
Keyword(s):  
Petroleum Coke ◽  
Circulating Fluidized Bed ◽  
Pilot Scale ◽  
Molar Ratio ◽  
Gaseous Pollutants ◽  
Emission Characteristic ◽  
Sources Of Pollution ◽  
Excess Air ◽  
Bed Temperature ◽  
Fuel Mixtures

Petroleum cokes including delayed coke, fluid coke, etc. are byproducts of solid residuals from the crude refining process. Using high sulfur petroleum coke as alternative fuel is feasible owing to its high fixed carbon and low ash content, but petroleum cokes are difficult to ignite due to their low volatile content and containing substantial concentrations of vanadium, nickel, nitrogen and sulfur, which can be sources of pollution emission and fireside fouling or corrosion problem. Co-firing petroleum coke and coal in circulating fluidized bed (CFB) is an ideal solution for those problems. Emission characteristic of gaseous pollutants from co-firing petroleum coke and coal is investigated in the paper. Experiments were carried out in a 0.6 MWt pilot-scale CFB combustor with the total height of 12m from the air distributor to the exit of combustor. The concentrations of SO2, NO, N2O, O2, CO2 and CO were measured on line by the gas analyzer. The effect of several parameters, in term of the primary air percentage, air excess coefficient, bed temperature, Ca/S molar ratio and percentage of petroleum coke in mixed fuel on the emission of SO2, NO, N2O is verified in experiments. Experimental results show that SO2 concentration in flue gas reduces with increase in the primary air percentage, excess air coefficient and Ca/S ratio for all kinds of fuel mixtures, whereas NO, N2O concentration rises with increase in the primary air percentage and excess air. When the bed temperature changes, the NO concentration varying trend is opposite to N2O. There is an optimal temperature for sulfur retention. Co-firing of petroleum coke and coal with different mixing ratio in CFB can be stable, efficient and environment friendly.

scholarly journals A Novel Dry Treatment for Municipal Solid Waste Incineration Bottom Ash for the Reduction of Salts and Potential Toxic Elements

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3133
Author(s):  
Marco Abis ◽  
Martina Bruno ◽  
Franz-Georg Simon ◽  
Raul Grönholm ◽  
Michel Hoppe ◽  
...  
Keyword(s):  
Particle Size ◽  
Toxic Elements ◽  
Fine Particles ◽  
Bottom Ash ◽  
Waste Incineration ◽  
Pilot Scale ◽  
Minor Components ◽  
Municipal Solid Waste Incineration ◽  
Potential Toxic Elements ◽  
Main Obstacle

The main obstacle to bottom ash (BA) being used as a recycling aggregate is the content of salts and potential toxic elements (PTEs), concentrated in a layer that coats BA particles. This work presents a dry treatment for the removal of salts and PTEs from BA particles. Two pilot-scale abrasion units (with/without the removal of the fine particles) were fed with different BA samples. The performance of the abrasion tests was assessed through the analyses of particle size and moisture, and that of the column leaching tests at solid-to-liquid ratios between 0.3 and 4. The results were: the particle-size distribution of the treated materials was homogeneous (25 wt % had dimensions <6.3 mm) and their moisture halved, as well as the electrical conductivity of the leachates. A significant decrease was observed in the leachates of the treated BA for sulphates (44%), chlorides (26%), and PTEs (53% Cr, 60% Cu and 8% Mo). The statistical analysis revealed good correlations between chloride and sulphate concentrations in the leachates with Ba, Cu, Mo, and Sr, illustrating the consistent behavior of the major and minor components of the layer surrounding BA particles. In conclusion, the tested process could be considered as promising for the improvement of BA valorization.

Alkali Metals in Circulating Fluidized Bed Combustion of Biomass and Coal: Measurements and Chemical Equilibrium Analysis

2005 ◽  
Vol 19 (5) ◽  
pp. 1889-1897 ◽  
Author(s):  
Michal P. Glazer ◽  
Nafees A. Khan ◽  
Wiebren de Jong ◽  
Hartmut Spliethoff ◽  
Heiko Schürmann ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Chemical Equilibrium ◽  
Alkali Metals ◽  
Circulating Fluidized Bed ◽  
Equilibrium Analysis ◽  
Fluidized Bed Combustion ◽  
Chemical Equilibrium Analysis ◽  
Circulating Fluidized Bed Combustion

Experiment and Mechanism Study on the Effect of Coal Ash on the Capture of Alkali Metals in Zhundong Coal

2017 ◽  
Author(s):  
Hu Xinglei
Keyword(s):  
Alkali Metal ◽  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Alkali Metals ◽  
Coal Ash ◽  
Maximum Efficiency ◽  
Chemical Calculation ◽  
Reaction Interface ◽  
Zhundong Coal ◽  
High Alkali

A large number of Xinjiang Zhundong coal was found in China. Its high content of alkali metals can cause serious fouling/slagging problems which may lead to economic losses. It is significant to control the release of alkali metals from Zhundong coal during the combustion. Si-Al additives are used to capture Na released from the Zhundong coal. In this work, a combination of experimental research and quantum chemical calculation was used to study the effect of coal ash on the capture of alkali metal in Zhundong high alkali Coal and the related mineral evolution mechanism during melting processes. The experiments were done with Zhundong coal/coal ash mixtures at 900–1200°C. The behavior mechanism of coal ash capturing alkali metals was analyzed from the perspective of mineral microstructure features by using XRD, ICP and quantum chemical calculation methods. The results show that during the process of combustions, complex chemical reactions occur among minerals after sodium is released from the coal and captured by the coal ash. The coal ash’s ability to capture sodium in Zhundong high alkali coal rises firstly, and then gradually decreases with the rise of temperature. It shows the best capture performance for sodium at 1000∼1100°C. The maximum efficiency of sodium absorption can reach to 50.6%. The coal ash shows a rather high efficiency compared with other additives. Furthermore, metals in Zhundong coal have opposite directions of migration. The Na, K, Al, Ca, and Mg migrated to the coal ash far away from the reaction interface, and the Fe and Mn were moved to the coal from the reaction interface. The original minerals of Zhundong coal mainly include calcium sulfate hydrate, quartz and kaolinite. Investigating the capture mechanism, it indicates that O (26) and O (22) in kaolinite have electrophilic reaction with Na+ and K+ easily, which would promote the rupture of aluminum-oxygen bonds. The O2- of alkali metal or alkaline earth metal oxide would easily have nucleophilic reaction with Si (6) and Si (8) and prompt the rupture of bridging oxygen bonds (Si-O-Si). Kaolinite would be transformed into some other minerals that contains Na+ or K+ which have trend to form eutectics or evaporate into the flue gas easily, the degree of fouling and slagging on heating surface can be reduced based on these two most easily reaction paths.

Ash deposition and slagging behavior of Chinese Xinjiang high-alkali coal in 3 MWth pilot-scale combustion test

Fuel ◽  
2016 ◽  
Vol 181 ◽  
pp. 1191-1202 ◽  
Author(s):  
Xiaojiang Wu ◽  
Xiang Zhang ◽  
Kai Yan ◽  
Nan Chen ◽  
Jianwen Zhang ◽  
...  
Keyword(s):  
Pilot Scale ◽  
Ash Deposition ◽  
High Alkali
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