基于草木灰修饰铁矿石载氧体的串行流化床化学链燃烧实验

采用草木灰对铁矿石载氧体进行修饰,在1kWth串行流化床反应器上,以合成气（CO H2 CH4）为燃料进行了化学链实验,对其反应活性进行测试。结果表明：生物质灰修饰铁矿石载氧体在1 kWth串行流化床上表现出较高的反应活性,且反应温度越高,反应活性越好;燃料反应器出口CO和CH4体积百分数显著降低,930 ℃下分别为0.12%和2.63%,与采用纯铁矿石相比分别降低了97.3%和16.0%,CO2捕集效率提升明显,最大值达89.38%;SEM分析表明,反应后的铁矿石颗粒表面出现了晶粒熔融粘接的现象,但生物质灰修饰铁矿石的孔隙结构仍较为明显;EDS分析表明生物质灰修饰铁矿石中K的负载情况较为稳定,没有出现明显的流失现象。     

Thermo‐economic investigation: an insight tool to analyze NGCC with calcium‐looping process and with chemical‐looping combustion for CO2 capture

In this work, three kinds of natural gas‐based power generation processes for CO₂ capture and storage, that is, natural gas‐combined cycle with pre‐combustion decarburization (NGCC‐PRE), NGCC‐PRE with calcium‐looping process, and NGCC‐PRE with chemical‐looping combustion (NGCC‐CLC), are analyzed by Aspen Plus. The effects of two decisive variables (i.e., steam‐to‐natural gas (S/NG) ratio and oxygen‐to‐natural gas (O/NG) ratio) on the thermodynamic performances of individual process, such as energy and exergy efficiencies, are investigated systematically. Based on simulation outcomes, all the three processes are favored by operating at S/NG = 2.0 and O/NG = 0.65. Furthermore, comparisons of individual system efficiencies and exergy destruction contributor are herein involved. The results show that the highest system efficiencies and lowest exergy destruction are achieved in the NGCC‐CLC process. In addition, capital investment, dynamic payback period, net present value, and internal rate of return are used for deciding the economic feasibility and surely are involved in this work for comparison purpose. Copyright © 2016 John Wiley & Sons, Ltd.     

A review of oxy‐fuel combustion in fluidized bed reactors

Presently, there is no detailed review that summarizes the current knowledge status on oxy‐fuel combustion in fluidized bed combustors. This paper reviewed the existing literature in heat transfer, char combustion and pollutant emissions oxy‐fuel combustion in fluidized beds, as well as modelling of oxy‐fuel in FB boiler and gaps were identified for further research direction. Copyright © 2016 John Wiley & Sons, Ltd.     

载氧体几何结构对固定床化学链燃烧影响的实验研究

使用浸渍法制备了球形与拉西环两种内扩散性能不同的铜基载氧体颗粒,在小型固定床反应器上进行了甲烷化学链燃烧实验,分析了球形与拉西环载氧体颗粒在还原反应与氧化反应中的最大温升及所需时间。结果表明：在还原反应中,甲烷进气流量能同时对拉西环载氧体的反应速率与最大温升产生影响,在总流量较大时有必要控制甲烷与氮气进气流量比;在氧化反应中,拉西环载氧体最大温升高于球形载氧体,反应温度的增大对拉西环载氧体最大温升的提升效果优于球形载氧体。     

200‐MW chemical looping combustion based thermal power plant for clean power generation

The present study demonstrates a possible configuration of a 200 MW chemical looping combustion (CLC) system with methane (CH₄) as fuel. Iron oxide‐based oxygen carriers were used because of its non‐toxic nature, low‐cost, and wide availability. We analyzed the effects of different variables on the design of the system. For the air reactor (oxidizer), bed mass is independent, and for the fuel reactor (reducer), it decreases with increase in the conversion difference between the air and fuel reactors. On the other hand, the pressure drop in the air reactor is unchanged, whereas for the fuel reactor, it decreases with the same increase of conversion difference between air and fuel reactors. Also, entrained solid mass flow rate from the air to fuel reactor shows a decreasing trend. Bed mass, bed height, pressure drop, and residence time of the bed materials decrease with increase in the conversion rates in the air and fuel reactors. Residence time of bed material in the air and fuel reactor reduces with increase in the temperature of the air reactor. Copyright © 2011 John Wiley & Sons, Ltd.     

Numerical simulation of fuel reactor for a methane-fueled chemical looping combustion using bubbling fluidized bed with internal particle circulation

Chemical-looping combustion (CLC) is recognized as a promising technique to efficiently and economically capture emitted carbon dioxide in common combustion processes. In this study, the bubbling fluidized bed (BFB) fuel reactor performance of the CLC system was examined through numerical simulation. The reduction reaction performance obtained from conventional BFB fuel reactor and BFB fuel reactor incorporated with internal particle circulation denoted as internal circulation bubbling fluidized bed reactor (ICBFB), were compared under the same fuel flow rate and operating conditions. By using CH₄ as fuel and ilmenite as the oxygen carrier, it was found the reduction reaction can be enhanced by using the ICBFB fuel reactor due to particle circulation. The particle circulation increased the mixing and contact time between fuel and oxygen carrier that produced reduction reaction enhancement. Moreover, the simulation results indicated that higher reduction reaction performance can be achieved by higher reduction reaction temperature and initial oxygen carrier volume fraction.     

Experimental Study and Modelling of Char Combustion under Fluidized Bed Conditions

INTRODUCTIONMailyexperimentshavebeendonetostudytheconversionbehaviorofdifferentcoalsundervariousreactorsandconditions.Someauthorshaveproposeddetailedmodelsfromobservedresults,orfromthealreticalaspects.Twotypemodelsaredevelopedtopredicttheconcelltrationprofilesforthegaseousspeciesaroundaburningcharparticled].In'single--film'models,thecarbonreactdirectlywithoxygentoformCOorCOb.In'double--film'modelsitisassumedthattheoxygendiffusingtowardsthepaxticleisconsumedbeforeitreachesthesuxface.Thep…     

Experiments on chemical looping combustion of coal with a NiO based oxygen carrier

A chemical looping combustion process for coal using interconnected fluidized beds with inherent separation of CO₂ is proposed in this paper. The configuration comprises a high velocity fluidized bed as an air reactor, a cyclone, and a spout-fluid bed as a fuel reactor. The high velocity fluidized bed is directly connected to the spout-fluid bed through the cyclone. Gas composition of both fuel reactor and air reactor, carbon content of fly ash in the fuel reactor, carbon conversion efficiency and CO₂ capture efficiency were investigated experimentally. The results showed that coal gasification was the main factor which controlled the contents of CO and CH₄ concentrations in the flue gas of the fuel reactor, carbon conversion efficiency in the process of chemical looping combustion of coal with NiO-based oxygen carrier in the interconnected fluidized beds. Carbon conversion efficiency reached only 92.8% even when the fuel reactor temperature was high up to 970 °C. There was an inherent carbon loss in the process of chemical looping combustion of coal in the interconnected fluidized beds. The inherent carbon loss was due to an easy elutriation of fine char particles from the freeboard of the spout-fluid bed, which was inevitable in this kind of fluidized bed reactor. Further improvement of carbon conversion efficiency could be achieved by means of a circulation of fine particles elutriation into the spout-fluid bed or the high velocity fluidized bed. CO₂ capture efficiency reached to its equilibrium of 80% at the fuel reactor temperature of 960 °C. The inherent loss of CO₂ capture efficiency was due to bypassing of gases from the fuel reactor to the air reactor, and the product of residual char burnt with air in the air reactor. Further experiments should be performed for a relatively long-time period to investigate the effects of ash and sulfur in coal on the reactivity of nickel-based oxygen carrier in the continuous CLC reactor.     

Reactivity deterioration of NiO/Al2O3 oxygen carrier for chemical looping combustion of coal in a 10 kWth reactor

A relatively long-term experiment for chemical looping combustion of coal with NiO/Al₂O₃ oxygen carrier was carried out in a 10 kW_th continuous reactor of interconnected fluidized beds, and 100 h of operation was reached with the same batch of the oxygen carrier. The reactivity deterioration of the oxygen carriers was present during the experimental period. The reactivity deterioration of reacted oxygen carriers at different experimental stages was evaluated using X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray fluorescence spectrometer. SEM analysis showed no significant change in the morphology of the nickel-based oxygen carrier at the fuel reactor temperature ?940 °C, but loss of surface area and porosity of reacted oxygen carriers was observed when the fuel reactor temperature exceeded 960 °C. The results show that the sintering effect have mainly contributed to the reactivity deterioration of reacted oxygen carriers in the CLC process for coal, while the effects of coal ash and sulfur can be ignored. The oxidization of reduced oxygen carrier with air was an intensive exothermic process, and the high temperature of oxygen carrier particles led to sintering on the surface of oxygen carrier particles in the air reactor. Attention must be paid to control the external circulation of oxygen carrier particles in the interconnected fluidized beds in order to efficiently transport heat from the air reactor to the fuel reactor, and reduce the temperature of oxygen carrier particles in the air reactor. Improvement of reactivity deterioration of reacted oxygen carriers was achieved by the supplement of steam into the fuel reactor. Nevertheless, NiO/Al₂O₃ is still one of the optimal oxygen carriers for chemical looping combustion of coal if the sintering of oxygen carrier is minimized at the suitable reactor temperature.     

循环流化床锅炉燃烧系统动态特性分析

根据循环流化床锅炉(CFBB)的工作特点以及燃烧系统输入和输出过程变量间的耦合关系,讨论了CFBB的蒸汽压力和床温的动态特性。认为引起蒸汽压力变动的主要原因在于燃料量(内扰)和汽轮机调门的变化(外扰);而影响床温变化的主要因素是给煤量、风量、物料循环量的变动,并从传热和燃烧过程分析了这些因素间的相互耦合关系。这对CFBB燃烧自动控制系统的设计与调试,以及整个控制系统的可靠运行都至关重要。     

Parametric study of chemical looping combustion for tri‐generation of hydrogen,heat, and electrical power with CO2 capture

In this article, a novel cycle configuration has been studied, termed the extended chemical looping combustion integrated in a steam‐injected gas turbine cycle. The products of this system are hydrogen, heat, and electrical power. Furthermore, the system inherently separates the CO₂ and hydrogen that is produced during the combustion. The core process is an extended chemical looping combustion (exCLC) process which is based on classical chemical looping combustion (CLC). In classical CLC, a solid oxygen carrier circulates between two fluidized bed reactors and transports oxygen from the combustion air to the fuel; thus, the fuel is not mixed with air and an inherent CO₂ separation occurs. In exCLC the oxygen carrier circulates along with a carbon carrier between three fluidized bed reactors, one to oxidize the oxygen carrier, one to produces and separate the hydrogen, and one to regenerate the carbon carrier. The impacts of process parameters, such as flowrates and temperatures have been studied on the efficiencies of producing electrical power, hydrogen, and district heating and on the degree of capturing CO₂. The result shows that this process has the potential to achieve a thermal efficiency of 54% while 96% of the CO₂ is captured and compressed to 110 bar. Copyright © 2005 John Wiley & Sons, Ltd.     

Characterization of Thai limestone for desulphurization in a fluidized bed combustor

The objective of this study is to determine the chemical kinetics of desulphurization of Thai limestone in an atmospheric fluidized bed combustor (AFBC). The experiments, which employed the batch technique using the limestone samples from six major sources in Thailand, were performed in a laboratory‐scale AFBC. The results obtained were analysed and correlated in the form of apparent reaction rate and deactivation rate constants as a function of operating conditions of the furnace and their properties, respectively. The formulae derived from these correlations were kept as general as possible in order that they could be used as input parameters for the selected mathematical model of desulphurization in an AFBC that is suitable for practical use. The predicted results were in good agreement with the experimental data reported in the literature. Copyright © 2003 John Wiley & Sons, Ltd.     

煤基化学链燃烧串行流化床的冷态试验研究

采用“湍动床＋快速床”作为煤基化学链燃烧（CLC）系统的空气反应器（AR）,鼓泡床作为燃料反应器（FR）,设计了流动密封阀和旋风分离器,分别用于隔绝2个反应器之间的气氛和进行气固分离,在冷态试验装置上分析研究了CLC系统的压力分布、固体循环流量、气体泄漏率及煤灰与循环载体的分离效果．结果表明：该串行流化床反应器之间气氛隔绝性良好,气体泄漏率较低,固体循环流量达到甚至超过设计标准,FR二级旋风分离器的分离效率接近100％,FR中煤灰进入AR的质量分数小于1．55％,煤灰分离效果良好;装置可以长时间连续稳定运行,且操作气速范围较广,自行设计建造的循环流化床作为煤基化学链燃烧试验装置是可行的．     

Optimization of emissions from fluidized bed combustion of coal,biofuel and waste

Several types of fuel can be burned in a fluidized bed. This paper discusses the impact of low‐ or medium‐volatile fuels (coal) and high‐volatile fuels (biomass and waste) on the emissions of NO, N₂O and other pollutants. It is found that high‐ and low‐volatile fuels behave in different ways, and measures to reduce emissions from coal combustion are not necessarily effective for high‐volatile fuels. This forms a basis for various design options. Copyright © 2002 John Wiley & Sons, Ltd.     

The simulation of influence of different coals on the circulating fluidized bed Boiler’s combustion performance

The combustion performance of the boiler largely depends on the coal type. Lots of experimental research shows that different fuels have different combustion characteristics. It is obvious that fuel will change the whole operating performance of Circulating Fluidized Bed Combustion (CFBC). We know even in a pilot-scale running boiler, the measurement of some parameters is difficult and costly. Therefore, we developed the way of simulation to evaluate the combustion performance of Chinese coals in CFB. The simulation results show that, different coals will result in different coal particle diameter and comminution depending on their mineral component and the change will affect the distribution of ash in CFBC system. In a word, the computational results are in accordance with experimental results qualitatively but there are some differences quantitatively.     

The relative performance of alternative oxygen carriers for liquid chemical looping combustion and gasification

The relative performance of different potential liquid oxygen carriers within a novel system that can be configured for either chemical looping gasification or combustion is assessed. The parameters considered here are the melting temperature, the Gibbs free energy, reaction enthalpy, exergy and energy flows, syngas quality and temperature difference between the two reactors. Results show that lead, copper and antimony oxides are meritorious candidates for the proposed systems. Antimony oxide was found to offer strong potential for high quality syngas production because it has a reasonable oxygen mass ratio for gasification. A sufficiently low operating temperature to be compatible with concentrated solar thermal energy and a propensity to generate methane. In contrast, copper and lead oxides offer greater potential for liquid chemical looping combustion because they have higher oxygen mass ratio and a higher operating temperature, which enables better efficiency from a power plant. For all three metal oxides, the production of methane via the undesirable methanation reaction is less than 2% of the product gasses for all operating temperatures and an order of magnitude lower for lead.     

Thermodynamic analysis of H2 production from CaO sorption‐enhanced methane steam reforming thermally coupled with chemical looping combustion as a novel technology

In this novel paper, a technique for hydrogen production route of CaO sorption‐enhanced methane steam reforming (SEMSR) thermally coupled with chemical looping combustion (CLC) was presented (CLC‐SEMSR), which perceived as an improvement of previous methane steam reforming (MSR) thermally coupled with CLC technology (CLC‐MSR). The application of CLC instead of furnace achieves the inherent separation of CO₂ from flue gas without extra energy required. The required heat for the reformer is provided by thermally coupling CLC. The addition of CaO sorbents can capture CO₂ as it is formed from the reformer gas to the solid phase, displacing the normal MSR equilibrium restrictions and obtaining higher purity of H₂. The Aspen Plus was used to simulate this novel process on the basis of thermodynamics. The performances of this system examined included the composition of reformer gas, yield of reformer gas (Y_Rg), methane conversion (α_M), the overall energy efficiency (η), and exergy efficiency (φ) of this process. The effects of the molar ratio of CaO to methane for reforming (Ca/M) in the range of 0–1.2, the molar ratio of methane for combustion to methane for reforming (M(fuel)/M) in the range of 0.1–0.3, and the molar ratio of NiO to methane for reforming (Ni/M) in the range of 0.4–1.2 were investigated. It has been found to be favored by operating under the conditions of Ca/M = 1, M(fuel)/M = 0.2, and Ni/M = 0.8. The most excellent advantage of CLC‐SEMSR was that it could obtain higher purity of H₂ (95%) at lower operating temperature (655 °C), as against H₂ purity of 77.1% at higher temperature (900 °C) in previous CLC‐MSR. In addition, the energy efficiency of this process could reach 83.3% at the optimal conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

440t/h循环流化床锅炉燃烧数值模拟研究

数值模拟是研究工程气固多相流中辅助试验方法的一种强有力的工具,本文采用数值模拟方法,对东锅DG440/13.7 -Ⅱ2型循环流化床锅炉的燃烧进行了研究,计算分析了炉内的流动、温度分布情况,对锅炉的优化设计和运行提供有益的指导.     

结构化载氧体颗粒化学链燃烧内扩散影响模拟分析

采用有限速率模型对CuO/Al_2O_3结构化载氧体颗粒化学链燃烧进行了数值模拟,考察了不同结构化载氧体颗粒模型和进气速度对载氧体化学反应内扩散的影响。结果表明,相比于球形载氧体,环形结构拉西环载氧体内扩散更为容易,反应快,温升高;相比于全活性载氧体,1/4活性和半活性载氧体气体扩散到活性物质距离短,反应更快;增加进气速度能够加速颗粒内扩散,改善反应速率。     

Characterization of ashes from a 100 kWth pilot-scale circulating fluidized bed with oxy-fuel combustion

Oxy-fuel combustion experiments have been carried out on an oxygen-fired 100 kW_th mini-circulating fluidized bed combustion (CFBC) facility. Coal and petroleum coke were used as fuel together with different limestones (and fixed Ca:S molar ratios) premixed with the fuel, for in situ SO₂ capture. The bed ash (BA) and fly ash (FA) samples produced from this unit were collected and characterized to obtain physical and chemical properties of the ash samples. The characterization methods used included X-ray fluorescence (XRF), X-ray diffraction (XRD), char carbon and free lime analysis, thermogravimetric analysis (TGA), and surface analysis. The main purpose of this work is to characterize the CFBC ashes from oxy-fuel firing to obtain a better understanding of the combustion process, and to identify any significant differences from the ash generated by a conventional air-fired CFBC. The primary difference in the sulfur capture mechanism between atmospheric air-fired and oxy-fuel FBC, at typical FBC temperatures (∼850 °C), is that, in the air-fired case the limestone sorbents calcine, whereas the partial pressure of CO₂ in oxy-fuel FBC is high enough to prevent calcination, and hence the sulfation process should mimic that seen in pressurized FBC (PFBC). Here, the char carbon content in the fly ash was much higher than that in the bed ash, and was also high by comparison with ash obtained from conventional commercial air-firing CFBC units. In addition, measurements of the free lime content in the bed and fly ash showed that the unreacted Ca sorbent was present primarily as CaCO₃, indicating that sulfur capture in the oxy-fuel combustor occurred via direct sulfation. Limestone utilization for oxy-fuel combustion in this unit was generally lower than that in industrial-scale air-firing CFBCs, with better limestone performance found during combustion of petcoke running at relatively higher temperatures. The Brunauer–Emmett–Teller (BET) surface area and also the pore volume in the fly ash were much higher than in the bed ash and smaller size pores predominated in the fly ash samples.