Prediction of Ash Behavior and Deposit Formation in Fluidized Bed Combustion of Biofuel Mixtures

2005 ◽  
Author(s):  
Sonja Enestam
Keyword(s):  
Fluidized Bed ◽  
Full Scale ◽  
Fuel Properties ◽  
Operational Experience ◽  
Fuel Quality ◽  
Prediction Tool ◽  
Fluidized Bed Combustion ◽  
Deposit Formation ◽  
Boiler Design ◽  
High Alkali

When moving towards CO2 neutral biofuels, fluidized bed combustion represents a good and flexible combustion technique. Biofuels typically have a high volatile content and varying moisture content. Fluidized bed combustion can provide even combustion conditions regardless of big variations in the fuel quality and fuel properties. However, compared to conventional fuels, biofuels often contain high amounts of chlorine and alkali metals, which set certain challenges for the boiler design. The problems that might occur due to high alkali and chlorine levels in the fuels are mainly slagging, fouling, corrosion and bed sintering. Since the variations in fuel properties between different fuels are big, it is of outmost importance from the boiler manufacturer’s point of view, to be able to predict the behavior of a specific fuel or fuel mixture in a very early stage of boiler design. For this purpose different kinds of calculation and prediction tools are needed. For prediction of slagging and fouling an ash behavior prediction tool has been developed. The prediction routine is based on advanced multi-phase multi-component equilibrium calculations, using the fuel composition and combustion conditions as input. Based on the calculations, the rate of deposit formation, the composition of the deposits and the corrosivity of the deposits at different locations in the boiler can be estimated. The prediction tool can be used in boiler design for defining the optimum arrangement of the superheaters, maximum flue gas temperature in the superheater area and maximum steam temperature. It can also be used for specification of maximum limits of troublesome high alkali, high chlorine fuels in fuel mixtures. In this study the prediction routine has been performed for three biofuels / biofuel mixtures. The calculated results have been evaluated with full scale and pilot scale probe measurements as well as with full scale long term operational experience.

scholarly journals Lab-scale investigation of Middle-Bosnia coals to achieve high-efficient and clean combustion technology

2014 ◽  
Vol 18 (3) ◽  
pp. 875-888 ◽  
Author(s):  
Izet Smajevic ◽  
Nihad Hodzic ◽  
Anes Kazagic
Keyword(s):  
Power Plant ◽  
Fluidized Bed ◽  
Environmental Indicators ◽  
Low Grade ◽  
Plant Design ◽  
Fluidized Bed Combustion ◽  
High Efficient ◽  
Combustion Technology ◽  
Boiler Design ◽  
Clean Combustion

This paper describes full lab-scale investigation of Middle-Bosnia coals launched to support selection an appropriate combustion technology and to support optimization of the boiler design. Tested mix of Middle-Bosnia brown coals is projected coal for new co-generation power plant Kakanj Unit 8 (300-450 MWe), EP B&H electricity utility. The basic coal blend consisting of the coals Kakanj: Breza: Zenica at approximate mass ratio of 70:20:10 is low grade brown coal with very high percentage of ash - over 40%. Testing that coal in circulated fluidized bed combustion technique, performed at Ruhr-University Bohum and Doosan Lentjes GmbH, has shown its inconveniency for fluidized bed combustion technology, primarily due to the agglomeration problems. Tests of these coals in PFC (pulverized fuel combustion) technology have been performed in referent laboratory at Faculty of Mechanical Engineering of Sarajevo University, on a lab-scale PFC furnace, to provide reliable data for further analysis. The PFC tests results are fitted well with previously obtained results of the burning similar Bosnian coal blends in the PFC dry bottom furnace technique. Combination of the coals shares, the process temperature and the air combustion distribution for the lowest NOx and SO2 emissions was found in this work, provided that combustion efficiency and CO emissions are within very strict criteria, considering specific settlement of lab-scale furnace. Sustainability assessment based on calculation economic and environmental indicators, in combination with Low Cost Planning method, is used for optimization the power plant design. The results of the full lab-scale investigation will help in selection optimal Boiler design, to achieve sustainable energy system with high-efficient and clean combustion technology applied for given coals.

Bed Agglomeration During the Fluidized Bed Combustion of Olive Husk

2005 ◽  
Author(s):  
Antonio Cammarota ◽  
Riccardo Chirone ◽  
Fabrizio Scala
Keyword(s):  
Fluidized Bed ◽  
Dynamic Pressure ◽  
Mediterranean Area ◽  
Operating Conditions ◽  
Pressure Gradients ◽  
Fluidized Bed Combustion ◽  
High Propensity ◽  
Olive Husk ◽  
Bed Agglomeration ◽  
High Alkali

The fluidized bed combustion of a biomass residue (olive husk) common in the Mediterranean area has been investigated in a bench scale reactor. The focus of the study was the high propensity of this fuel to give rise to bed agglomeration problems during combustion, as a consequence of the high alkali content of the ash. Bed agglomeration characteristic times as well as temperature and pressure gradients were measured at different operating conditions. In addition, a diagnostic tool based on the measurement of the dynamic pressure signal inside the bed was tested for its capability to predict the bed agglomeration onset.

Release and migration characteristics of sodium and potassium in high alkali coal under oxy-fuel fluidized bed combustion condition

Fuel ◽  
2020 ◽  
Vol 262 ◽  
pp. 116413 ◽  
Author(s):  
Kaijun Yu ◽  
Xiaoping Chen ◽  
Tianyi Cai ◽  
Jiliang Ma ◽  
Daoyin Liu ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Fluidized Bed Combustion ◽  
Combustion Condition ◽  
And Migration ◽  
High Alkali ◽  
Sodium And Potassium

Assessment of Sorbent Reactivation by Water Hydration for Fluidized Bed Combustion Application

2003 ◽  
Author(s):  
Fabio Montagnaro ◽  
Piero Salatino ◽  
Fabrizio Scala ◽  
Yinghai Wu ◽  
Edward Anthony ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Liquid Water ◽  
Operating Cost ◽  
Bottom Ash ◽  
Full Scale ◽  
Fluidized Bed Combustion ◽  
Research Activities ◽  
Combination Of Methods ◽  
Influence Of Hydration

Disposal of FBC solid residues currently represents one of the major issues in FBC design and operation, and contributes significantly to FBC operating cost. This issue has triggered research activities on the enhancement of sorbent utilization for in-situ sulfur uptake. The present study addresses the effectiveness of the reactivation by liquid water hydration of FB spent sorbents. Two materials are considered in the study, namely bottom ash from the operation of a full-scale utility FB boiler and the raw commercial limestone used in the same boiler. Hydration-reactivation tests were carried out at temperatures of 40°C and 80°C and for curing times ranging from 15min to 2d, depending on the sample. The influence of hydration conditions on the enhancement of sulfur utilization has been assessed. A combination of methods has been used to characterize the properties of liquid water-hydrated materials.

Alternative Bed Materials for High Alkali Fuels

2005 ◽  
Author(s):  
Matts Almark ◽  
Matti Hiltunen
Keyword(s):  
Fluidized Bed ◽  
Particle Sizes ◽  
Fluidized Bed Combustion ◽  
Minimum Level ◽  
Natural Sand ◽  
Suitable Form ◽  
Bed Materials ◽  
High Alkali ◽  
Silicate Layers ◽  
Sodium And Potassium

Fluidized bed combustion of high alkali fuels may cause agglomeration and defluidization of the bed as sodium and potassium react with quartz particles in the bed, forming alkali-silicate layers causing the particles to stick together. In certain cases the use of quartz free bed materials has been shown successful, like “Ofita” in the combustion of the residues from olive oil production in Spain. There are alternatives available to be used as quartz-free bed materials but some of them may be more expensive compared to natural sand. They are not always found in suitable form or particle sizes. Furthermore, the knowledge of the alternatives, and when it would beneficial to use them, is limited. The economics are not always favorable to using the alternative, effective but expensive bed materials since the build-up of harmful elements in bed usually can be avoided with sufficient make-up sand addition. A minimum level of make-up material addition is in any case necessary when combusting fuels with ashes that do not maintain the bed inventory. A study of minerals and materials available in Finland and elsewhere as possible bed make-up materials was carried out. The differences between these materials compared to quartz as a reference are investigated. The economics of the use of the alternative bed materials are discussed.

Application of the Biobed® Upflow Fluidized Bed Process for Anaerobic Waste Water Treatment

1992 ◽  
Vol 25 (7) ◽  
pp. 373-382 ◽  
Author(s):  
R. J. Frankin ◽  
W. A. A. Koevoets ◽  
W. M. A. van Gils ◽  
A. van der Pas
Keyword(s):  
Waste Water ◽  
Water Treatment ◽  
Fluidized Bed ◽  
Waste Water Treatment ◽  
Full Scale ◽  
Upflow Anaerobic Sludge Blanket ◽  
Anaerobic Sludge ◽  
Operational Experience ◽  
Pharmaceutical Waste ◽  
Anaerobic Sludge Blanket

Over the past ten years Gist-brocades has been engaged in anaerobic waste water treatment. An in-depth research program concluded in the construction and operation of three full-scale plants for the treatment of yeast processing and pharmaceutical waste waters. Using the operational experience of the fluidized bed biomass-on-carrier systems and incorporating the strong assets of the Upflow Anaerobic Sludge Blanket (UASB) system features a new process was developed, the so-called Upflow Fluidized Bed (UFB) BIOBED® process, which operation appeared to be very successful over a > 3 year period at full scale. The UFB BIOBED® system combines both characteristics of the UASB and FB processes. Biomass is present in a granular form but conditions with respect to upflow velocities for water and gas approach those of the original Fluidized Bed - biomass on carrier - (FB) system.

scholarly journals Ash deposition behavior of a high-alkali coal in circulating fluidized bed combustion at different bed temperatures and the effect of kaolin

RSC Advances ◽  
2018 ◽  
Vol 8 (59) ◽  
pp. 33817-33827 ◽  
Author(s):  
Yanquan Liu ◽  
Leming Cheng ◽  
Jieqiang Ji ◽  
Qinhui Wang ◽  
Mengxiang Fang
Keyword(s):  
Fluidized Bed ◽  
Combustion Temperature ◽  
Circulating Fluidized Bed ◽  
Ash Deposition ◽  
Fluidized Bed Combustion ◽  
Deposition Behavior ◽  
Zhundong Coal ◽  
High Alkali ◽  
Circulating Fluidized Bed Combustion

This work reports the influence of combustion temperature on the ash deposition of Zhundong coal in a CFB, and evaluates the effect of kaolin.

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