Optimization of Fluidization State of a Circulating Fluidized Bed Boiler for Economical Operation

To reduce the auxiliary power consumption and improve the reliability of large-scale circulating fluidized bed (CFB) boilers, we developed energy-saving CFB combustion technology based on the fluidization state re-specification. A calculation model of coal comminution energy consumption was used to analyze the change in comminution energy consumption, and a 1D CFB combustion model was modified to predict the operation parameters under the fluidization state optimization conditions. With a CFB boiler of 480 t/h, the effect of fluidization state optimization on the economical operation was analyzed using the above two models. We found that combustion efficiency presents a nonmonotonic trend with the change in the bed pressure drop and feeding coal size. There are an optimal bed pressure drop and a corresponding feeding coal size distribution, under which the net coal consumption is the lowest. Low bed pressure drop operation achieved by reducing the coal particle size is not beneficial to SO2 and NOx emission control, and the pollutant control cost increases. The effect of fluidization state optimization on the gross cost of power supply can be calculated, and the optimal bed pressure drop can be obtained.

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Three-Dimensional Modeling and Model Validation of Circulating Fluidized Bed Combustion

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-048 ◽

2003 ◽

Cited By ~ 2

Author(s):

Kari Myo¨ha¨nen ◽

Timo Hyppa¨nen ◽

Jouni Miettinen ◽

Riku Parkkonen

Keyword(s):

Heat Flux ◽

Fluidized Bed ◽

Large Scale ◽

Circulating Fluidized Bed ◽

Combustion Process ◽

Three Dimensional ◽

Hot Water ◽

Combustion Model ◽

Process Conditions ◽

Model Parameters

This paper presents a three-dimensional, steady state combustion model for a circulating fluidized bed (CFB) furnace and several calculation cases which have been used for the validation of the model. The model includes essential submodels to describe the complex combustion process in a circulating fluidized bed boiler. These include the hydrodynamics of the bed, devolatilization of fuel, combustion of char, combustion of hydrocarbons, carbon monoxide and hydrogen, calcination and sulfation, fragmentation and attrition of solids, heat transfer, overall mass balance of the furnace, and three-dimensional balance equations based on the finite volume method. The code was initially developed in 1989, and it has been updated and improved over the years as new methods and new information have become available. The model is used for increasing process knowledge and for studying such phenomena inside the furnace which are often difficult or impossible to study by direct measurements. The knowledge obtained is then applied to optimize boiler design and process performance in terms of efficiency, economy and environmental issues. Reliable experiments and measurements in commercial boilers are used for the validation of the model and for tuning the model parameters. For the validation of a three-dimensional model, extensive profile measurements of the various parts of the furnace are required. This paper presents validation studies for an 80 MWth hot water boiler burning bituminous coal and for a 235 MWe subcritical boiler burning lignite. The measurements with these units included profile measurements of heat flux, pressure, temperature and gas composition under different process conditions. The model was tuned according to the measurements and used for the prediction of the heat flux profile of a large scale supercritical CFB boiler.

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00/03550 Modeling of hydrodynamics of large scale atmospheric circulating fluidized bed coal combustors

Fuel and Energy Abstracts ◽

10.1016/s0140-6701(00)94621-6 ◽

2000 ◽

Vol 41 (6) ◽

pp. 398

Keyword(s):

Fluidized Bed ◽

Large Scale ◽

Circulating Fluidized Bed

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Coupling of a radiative heat transfer model and a three-dimensional combustion model for a circulating fluidized bed furnace

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2014.11.008 ◽

2015 ◽

Vol 76 ◽

pp. 344-356 ◽

Cited By ~ 26

Author(s):

Mohammad Hadi Bordbar ◽

Kari Myöhänen ◽

Timo Hyppänen

Keyword(s):

Heat Transfer ◽

Fluidized Bed ◽

Radiative Heat Transfer ◽

Radiative Heat ◽

Circulating Fluidized Bed ◽

Three Dimensional ◽

Heat Transfer Model ◽

Combustion Model ◽

Transfer Model

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Performance prediction of a large-scale circulating fluidized bed boiler by heat exchangers block simulation

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650914563365 ◽

2014 ◽

Vol 229 (3) ◽

pp. 298-308 ◽

Cited By ~ 5

Author(s):

Taehyun Kim ◽

Sangmin Choi ◽

Jae-Sung Kim

Keyword(s):

Fluidized Bed ◽

Performance Prediction ◽

Heat Exchangers ◽

Large Scale ◽

Circulating Fluidized Bed ◽

Circulating Fluidized Bed Boiler

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Retrofitting 25T/h Pulverized Coal-Fired Boiler Into 35T/h Circulating Fluidized Bed Boiler for Burning Mixture of Coal and Bagasse

18th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2005-78041 ◽

2005 ◽

Author(s):

Han-Ping Chen ◽

Xian-Hua Wang ◽

Shi-Hong Zhang ◽

De-Chang Liu ◽

Yu-Hua Lai ◽

...

Keyword(s):

Fluidized Bed ◽

Circulating Fluidized Bed ◽

Combustion Efficiency ◽

Economic Benefits ◽

Pulverized Coal ◽

Industrial Wastes ◽

Pollutant Emission ◽

Fluidized Bed Combustion ◽

Circulating Fluidized Bed Boiler ◽

Combustion Technology

In China, there are a large number of pulverized coal-fired industrial boilers, whose steam capacities are usually relatively small. These boilers can burn only high-grade coal and have low combustion efficiency. Furthermore, the combustion emissions, such as SO2 and NOx, pollute the environment severely. Therefore it is very important and urgent to adopt economically efficient and environmentally friendly technologies to retrofit these boilers. At the same time, there are many industrial wastes, such as bagasse, wood waste, rubbish, petroleum coke and so on, need burning disposal in China. Fluidized bed combustion technology is a kind of clear combustion technology, which has many advantages, such as excellence fuel flexibility, high combustion efficiency, low pollutant emission and good turndown capability etc. So, adopting fluidized bed combustion technology, retrofitting pulverized coal-fired boiler into fluidized bed boiler can realize pure burning various wastes or co-firing with coal, which should have great economic benefits and social benefits. And the application prospect of the method is also extensive. The State Key Laboratory of Coal Combustion has successfully retrofitted a 25t/h pulverized coal-fired boiler into circulating fluidized bed boiler with in-bed tubes and downward exhaust cyclone. The retrofitted boiler can burn mixture of coal and bagasse and the steam capacity reaches 35t/h. This paper presents the retrofitting measures and the operation status of the boiler after retrofitting.

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Combustion of Wood Processing Residues in a Circulating Fluidized Bed

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-171 ◽

2003 ◽

Cited By ~ 3

Author(s):

Fernando Preto

Keyword(s):

Fluidized Bed ◽

Pilot Plant ◽

Circulating Fluidized Bed ◽

Combustion Efficiency ◽

Tree Bark ◽

Feed System ◽

Wood Processing ◽

System A ◽

Bed Temperature ◽

High Moisture Level

The combustion of wood processing residues was tested in the 0.8 MWth CANMET Circulating Fluidized Bed Combustor (CFBC) pilot plant. The specific residues tested were three different types of coniferous tree bark (i.e. from different locations to represent a range of possible fuels and fuel properties). Combustion conditions may be summarized as follows: fuel moisture levels 42–60%, fluidizing velocity 2.1–2.4 m/s; bed temperature 785–910 °C; maximum freeboard temperature 980–1070 °C and excess air levels 20–75%. The CFBC unit was able to burn the high moisture level fuels with no detrimental effect. In all trials the residues burned very well, with combustion efficiency greater than 99% based on overhead carbon loss. Emissions measurements were made of the following pollutant species CO, NOx, N2O, SO2, and dioxins and furans. The emissions levels were: 100–130 ppm NOx; <1 ppm N2O; 5–20 ppm SO2 and 400–1800 ppm CO. These emission levels are well below pollution guidelines for all major pollutants except CO. This however can be traced to the non-homogeneous nature of the coarse feed in the pilot plant. The problem can reasonably be addressed in a full-scale unit by a more stable feed system. A preliminary economic analysis of a new 25 MW FBC power plant firing these fuels was performed. Conservative inputs give a cost of 6 cents/kWh for the electricity produced and a economic wood haulage radius of 70 km.

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Simplified Numerical Modeling of Energy Distribution in a Chinese Solar Greenhouse

Applied Engineering in Agriculture ◽

10.13031/aea.12186 ◽

2017 ◽

Vol 33 (3) ◽

pp. 291-304 ◽

Cited By ~ 3

Author(s):

Hui Xu ◽

Yue Zhang ◽

Tianlai Li ◽

Rui Wang

Keyword(s):

Energy Consumption ◽

Northeast China ◽

Field Experiments ◽

Meteorological Data ◽

Calculation Model ◽

Energy Calculation ◽

Coal Consumption ◽

Energy Consumption Analysis ◽

Solar Greenhouse ◽

North Wall

Abstract.Solar greenhouses are widely used in northeast China to grow vegetables in winter. The energy consumption and distribution were determined in field experiments using a solar greenhouse in northeast China by monitoring the environmental factors inside and outside. Each surface inside greenhouse irradiated with incoming solar radiation was calculated. The greenhouse temperature including the front roof, north roof, north wall, canopy, and soil was calculated based on daily meteorological variables forecast by simulation modeling of each part and comparing with the results obtained using individual meteorological data under greenhouse conditions. Chinese greenhouse day and night energy consumption was calculated and compared. During the coldest days, the conduction energy reached 45% by day and 54% at night. The front roof accounted for the conduction energy loss (day: 54%, night: 68%). When the indoor temperature of the greenhouse was maintained above 15°C, the best time for greenhouse heating was around 5 a.m. and total coal consumption in three months was approximately 5.1 t. Results show that this numerical model simulated the various paths of greenhouse energy flow and heating processes. We estimated the specific daily coal consumption to define a comprehensive heating strategy. Keywords: Chinese greenhouse, Energy balance, Energy calculation model, Energy consumption analysis.

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