Thermodynamic Analysis of Hydrogen Production From Coal Char Gasification in Triple-Bed Circulating Fluidized Bed

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Xianan Xiang ◽  
Guangcai Gong ◽  
Chenhua Wang ◽  
Ninghua Cai ◽  
Kun Tang ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Reaction Temperature ◽  
Circulating Fluidized Bed ◽  
Combustion Process ◽  
Pyrolysis Process ◽  
Pyrolysis Gas ◽  
Model Studies ◽  
Gasification Process ◽  
Gasification Efficiency ◽  
Gasification Reaction

Abstract The triple-bed circulating fluidized bed gasifier is a new type of the gasification process in which the combustion process, pyrolysis process, and gasification process of the fuel are carried out in different reactors. The inert heat carrier is used to transfer heat between the reactors. In this way, the gasification efficiency of char is improved since the tar and pyrolysis gas generated in the pyrolysis process will no longer hinder the gasification of the char. The thermodynamic equilibrium model is used to simulate the gasification process of the triple-bed circulating fluidized bed, and the sub-models are established to simulate combustion, pyrolysis, and gasification processes. The simulation results agree well with the experimental values. Besides, the model studies the effects of key parameters such as the gasification reaction temperature and the ratio of steam to C (S/C) on gasification performance. Results showed that higher gasification reaction temperature has a positive effect on gasification performance, S/C may not be too high, and excessive water vapor will directly affect the gasification reaction.

scholarly journals The Design and Operation of a New Clapboard-Type Internal Circulating Fluidized-Bed Gasifier

2005 ◽  
Author(s):  
Zhengshun Wu ◽  
Chuanfang Zhu ◽  
Long-Long Ma ◽  
Chuangzhi Wu
Keyword(s):  
Fluidized Bed ◽  
High Velocity ◽  
Circulating Fluidized Bed ◽  
Wood Chip ◽  
Low Velocity ◽  
Fuel Gas ◽  
Fluidized Bed Gasifier ◽  
Gasification Efficiency ◽  
Gasification Reaction ◽  
Velocity Region

The design and operation of a new clapboard-type Internal Circulating Fluidized-Bed gasifier is introduced in this paper. By setting clapboard in the middle of gasifier, bed layer in gasifier is divided into two regions that have different fluidization velocity, the incompletely reacted fuel or carbon in the high velocity region flows to the low velocity region companying with bed medium, and gasification reaction takes place in this region; still incompletely reacted fuel or carbon returns to the high velocity region in the bottom of gasifier, then gasification reaction further occurs. By this way, internal circulation in the gasifier was formed, gasification reaction time and efficiency increased. The experimental results indicate that gas yield (1.6 ∼ 1.9Nm3/kg fuel), gas heat values (5340kJ/Nm3 for wood chip fuel and 4880kJ/m3 for rice husk), and gasification efficiency (70%) can be obtained using this kind of gasifier in the optimal operational temperature range of 790∼850°C.

scholarly journals Oxy-combustion of biomass in a circulating fluidized bed

2016 ◽  
Vol 37 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Monika Kosowska-Golachowska ◽  
Agnieszka Kijo-Kleczkowska ◽  
Adam Luckos ◽  
Krzysztof Wolski ◽  
Tomasz Musiał
Keyword(s):  
Fluidized Bed ◽  
Ignition Temperature ◽  
Loss Rate ◽  
Circulating Fluidized Bed ◽  
Mass Loss Rate ◽  
Thermal Analyses ◽  
Combustion Process ◽  
Combustion Characteristics ◽  
Lower Maximum ◽  
Maximum Mass Loss

Abstract The objective of this study was to investigate combustion characteristics of biomass (willow, Salix viminalis) burnt in air and O2/CO2 mixtures in a circulating fluidized bed (CFB). Air and oxy-combustion characteristics of wooden biomass in CFB were supplemented by the thermogravimetric and differential thermal analyses (TGA/DTA). The results of conducted CFB and TGA tests show that the composition of the oxidizing atmosphere strongly influences the combustion process of biomass fuels. Replacing N2 in the combustion environment by CO2 caused slight delay (higher ignition temperature and lower maximum mass loss rate) in the combustion of wooden biomass. The combustion process in O2/CO2 mixtures at 30% and 40% O2 is faster and shorter than that at lower O2 concentrations.

Pilot-Scale Study on Improving SNCR Denitrification Efficiency by Using Gas Additives

2018 ◽  
Vol 17 (3) ◽  
Author(s):  
Zhou Weiqing ◽  
Liu Meng ◽  
Huang Baohua ◽  
Qiu Xiaozhi
Keyword(s):  
Low Temperature ◽  
Fluidized Bed ◽  
Reaction Temperature ◽  
Temperature Region ◽  
Circulating Fluidized Bed ◽  
Catalytic Reduction ◽  
Pilot Scale ◽  
Incomplete Oxidation ◽  
Optimal Value

Abstract The experiment of improving Selective Non-Catalytic Reduction (SNCR) denitrification efficiency with gas additives (CH4 and C3H8) was carried out in the 50 kW circulating fluidized bed (CFB) pilot-scale equipment. The results show that the denitrification efficiency can reach 20 % when the reaction temperature is 650 °C, and the optimum mole ratio of C3H8/NH3 is 0.5. The denitrification efficiency can exceed 50 % when the mole ratio of C3H8/NH3 is 0.4 and the reaction temperature is 720 °C. However, the CH4 additive does not promote denitrification at this temperature. When the reaction temperature is 760 °C, the optimum denitrification efficiency of CH4 is 60 %, and the required CH4/NH3 is 0.8. Once the amount of CH4 exceeds the optimal value, the denitrification efficiency is suppressed. In addition, the concentrations of N2O and CO in the gas increase significantly with an increase of gas additives. Due to the incomplete oxidation of C3H8, a large amount of C2H4 is produced in the low-temperature region (< 750 °C) of SNCR.

Research on coal-water fuel combustion in a circulating fluidized bed / Badanie spalania zawiesinowych paliw węglowo-wodnych w cyrkulacyjnej warstwie fluidalnej

2012 ◽  
Vol 57 (1) ◽  
pp. 79-92
Author(s):  
Agnieszka Kijo-Kleczkowska
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Combustion Process ◽  
Fuel Combustion ◽  
Waste Materials ◽  
Inert Material ◽  
Process Conditions ◽  
Heat And Mass Exchange ◽  
Water Suspension ◽  
Power Stations

In the paper the problem of heavily-watered fuel combustion has been undertaken as the requirements of qualitative coals combusted in power stations have been growing. Coal mines that want to fulfill expectations of power engineers have been forced to extend and modernize the coal enrichment plants. This causes growing quantity of waste materials that arise during the process of wet coal enrichment containing smaller and smaller under-grains. In this situation the idea of combustion of transported waste materials, for example in a hydraulic way to the nearby power stations appears attractive because of a possible elimination of the necessary deep dehydration and drying as well as because of elimination of the finest coal fraction loss arising during discharging of silted water from coal wet cleaning plants. The paper presents experimental research results, analyzing the process of combustion of coal-water suspension depending on the process conditions. Combustion of coal-water suspensions in fluidized beds meets very well the difficult conditions, which should be obtained to use the examined fuel efficiently and ecologically. The suitable construction of the research stand enables recognition of the mechanism of coal-water suspension contact with the inert material, that affects the fluidized bed. The form of this contact determines conditions of heat and mass exchange, which influence the course of a combustion process. The specificity of coal-water fuel combustion in a fluidized bed changes mechanism and kinetics of the process.

scholarly journals Specific Features of Solid Fuels Combustion in Oxygen Atmosphere with Recirculation of CO2

2015 ◽  
Vol 17 (3) ◽  
pp. 213
Author(s):  
D.A. Melnikov ◽  
G.A. Ryabov
Keyword(s):  
Coal Combustion ◽  
Carbon Capture ◽  
Circulating Fluidized Bed ◽  
Combustion Process ◽  
Carbon Capture And Storage ◽  
Combustion Model ◽  
Coal Pyrolysis ◽  
Char Particle ◽  
Isothermal Kinetic ◽  
Gasification Reaction

<p>Aspects of coal combustion have been experimentally studied under oxyfuel conditions, one of the promising technologies for carbon capture and storage (CCS). Here, the thermogravimetric analysis (TGA) method was chosen as an experimental technique. Coal pyrolysis tests performed under an O<sub>2</sub>/CO<sub>2</sub> atmosphere were compared with a conventional O<sub>2</sub>/N<sub>2</sub> environment in terms of reaction rate and total volatile yield. Combustion of the resulting chars in the corresponding atmospheres revealed somewhat different combustion rates with a less vigorous reaction in the O<sub>2</sub>/CO<sub>2</sub> medium. The two manipulated factors – namely, the inherently different char reactivities due to the different atmospheres they were obtained in and the different atmospheres of the actual combustion process – were distinguished by performing another series of tests with chars pyrolysed under identical conditions using a standard routine. These chars also showed a weaker reaction in O<sub>2</sub>/CO<sub>2</sub> atmosphere, which was attributed to the lower binary diffusion coefficient of the O<sub>2</sub>/CO<sub>2</sub> pair. The activity of the char – CO<sub>2 </sub>gasification reaction in an O<sub>2</sub>/CO<sub>2</sub> environment was also investigated and revealed some contribution of this reaction to the conversion process. This was particularly noticeable at temperatures above 750 °C and under an internal diffusional controlled regime (zone II), implying displacement of oxygen out of the char particle pore volume, which allowed free reaction of CO<sub>2</sub> on the developed pore surface. Non-isothermal kinetic analysis of the intrinsic kinetics of the oxidation reaction in O<sub>2</sub>/CO<sub>2</sub> revealed no particular difference compared to the O<sub>2</sub>/N<sub>2</sub> medium, at least when the char-CO<sub>2 </sub>reaction was inhibited. The obtained data were used to develop a coal combustion model under O<sub>2</sub>/CO<sub>2</sub> conditions, which was then incorporated as a combustion module into circulating fluidized bed (CFB) computation software.</p>

scholarly journals Analysis and Discussion on Burning Low Calorific Value Fuel of Circulating Fluidized Bed Boiler

2021 ◽  
Vol 329 ◽  
pp. 01074
Author(s):  
Yi Yan
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
High Reliability ◽  
Combustion Process ◽  
Calorific Value ◽  
Utilization Rate ◽  
Energy Structure ◽  
Actual Process ◽  
Circulating Fluidized Bed Boiler ◽  
Power Stations

China's coal-dominated energy structure will not change in a short time. In order to implement the relevant national policies on energy conservation and emission reduction, it is a good response to adopt circulating fluidized bed boilers in coal-fired power stations. Circulating fluidized bed boiler adopts fluidized combustion, which has high reliability and high utilization rate because of its special combustion mode and particle recycling device. For the low calorific value inferior fuel which is difficult to burn in common boiler, CFB boiler also has certain adaptability and compatibility. In this background, this article with coal gangue as the representative of the inferior coal are discussed its application in the circulating fluidized bed boiler, the combustion process, boiler equipment and special fly ash produced by combustion is proposed that often appear in the three aspects of problems, and accordingly put forward the solution and optimization measures, provides reference for the actual process.

Evolution of the Structure and Mechanical Strength of a Coal Particle During Combustion in the Atmosphere of Air and the Mixture of Oxygen and Carbon Dioxide / Ewolucja Struktury Oraz Wytrzymałości Mechanicznej Ziarna Węgla Podczas Spalania W Atmosferze Powietrza Oraz Mieszaninie Tlenu I Dwutlenku Węgla

2013 ◽  
Vol 58 (3) ◽  
pp. 673-690
Author(s):  
Piotr Pełka ◽  
Grzegorz Golański ◽  
Paweł Wieczorek
Keyword(s):  
Carbon Dioxide ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Sudden Change ◽  
Combustion Process ◽  
Ambient Air ◽  
Hard Coal ◽  
Atomic Force ◽  
Coal Particles ◽  
The Moment

Abstract The research was conducted on the basis of four different types of hard coal and one type of brown coal. There are typical coals commonly used as fuel in Polish CFB boilers. The combustion process was conducted at a temperature of 850°C and the atmosphere of ambient air as well as in the mixture of oxygen and carbon dioxide in different proportions. The research was carried out using specially prepared cubical coal particles with measurements of 15×15mm and also 10×10 mm. The change of the mechanical properties was analyzed based on three parameters, i.e. compression strength, Vickers hardness and fracture toughness. The analysis was supplemented by microscopic images of the surface of the particles using an atomic force microscope. The results obtained clearly indicated the mechanical changes of the coal during its combustion, particularly at the moment of ignition of the char. Moreover, the results correlate very well with the processes of coal comminution that have been described by other authors (Basu, 1999; Chirone et al., 1991) during combustion in the circulating fluidized bed and also explain the sudden change of susceptibility to erosion in the conditions with and without combustion. The measured values can be used as strength parameters in the modelling of the mass loss of coal particles in conditions of circulating fluidized bed combustor that are hard to describe.

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