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Industrial-scale demonstration of a new sorbent reactivation technology for fluidized bed combustors
To minimize the disposal of highly reactive spent sorbent from a fluidized bed combustor, a new method for reactivation has been developed. The method consists of grinding the spent ash in a rotary mill, hydrating the ash with an excess of water, and mixing the wet ground ash with dry solids to absorb the excess water. The mixing process eliminates the formation of a concrete-like product that normally results as wet fluidized bed combustor ash ages. Pilot-scale combustion trials proved to be successful, and the process was scaled up using a 35MWt utility boiler at Purdue University. The test lasted for 3 days and resulted in net reduction of limestone sorbent use of 18%. The results generated in this work have been used to develop an economic evaluation for a 165MWe circulating fluidized bed (CFB) boiler, which projects significant savings due to reduction of limestone supply and ash disposal costs. The evaluation also suggests that the process is cost competitive with other processes, albeit that those processes have not been demonstrated at industrial scale. Furthermore, it also has the potential to make a small net reduction in CO(2) emissions, due to reduced limestone usage. 相似文献
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循环流化床脱硫是目前国内应用最多的(半)干法脱硫技术,但经过多年的运行也暴露出诸如系统可靠性差、循环灰装置易堵塞、湿壁、系统能耗大、运行费用高、脱硫率低等问题。本文就循环流化床脱硫工艺在实际运行中存在的问题进行了分析讨论。 相似文献
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Luis F. de Diego Margarita de las Obras-Loscertales Francisco García-Labiano Aránzazu Rufas Alberto Abad Pilar Gayán Juan Adánez 《International Journal of Greenhouse Gas Control》2011,5(5):1190-1198
CO2 and SO2 are some of the main polluting gases emitted into atmosphere in combustion processes using fossil fuel for energy production. The former is one of the major contributors to build-up the greenhouse effect implicated in global climate change and the latter produces acid rain. Oxy-fuel combustion is a technology, which consists in burning the fuel with a mix of pure O2 and recirculated CO2. With this technology the CO2 concentration in the flue gas may be enriched up to 95%, becoming possible an easy CO2 recovery. In addition, oxy-fuel combustion in fluidized beds allows in situ desulfurization of combustion gases by supplying calcium based sorbent.In this work, the effect of the principal operation variables affecting the sulfation reaction rate in fluidized bed reactors (temperature, CO2 partial pressure, SO2 concentration and particle size) under typical oxy-fuel combustion conditions have been analyzed in a batch fluidized bed reactor using a limestone as sorbent. It has been observed that sulfur retention can be carried out by direct sulfation of the CaCO3 or by sulfation of the CaO (indirect sulfation) formed by CaCO3 calcination. Direct sulfation and indirect sulfation operating conditions depended on the temperature and CO2 partial pressure. The rate of direct sulfation rose with temperature and the rate of indirect sulfation for long reaction times decreased with temperature. An increase in the CO2 partial pressure had a negative influence on the sulfation conversion reached by the limestone due to a higher temperature was needed to work in conditions of indirect sulfation. Thus, it is expected that the optimum temperature for sulfur retention in oxy-fuel combustion in fluidized bed reactors be about 925–950 °C. Sulfation reaction rate rose with decreasing sorbent particle size and increasing SO2 concentration. 相似文献
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旋转喷雾干燥法(SDA)脱硫工艺系统的应用研究 总被引:2,自引:0,他引:2
本文介绍了旋转喷雾干燥法(SDA)脱硫工艺的基本原理、化学过程、主要设备、控制、脱硫副产物、系统运行与维护等,并与石灰石/石膏湿法脱硫工艺、烟气循环流化床工艺进行了比较,给出了脱硫系统投资及运行费用的经济比较。还对SDA脱硫工艺在国内应用中存在的问题进行了探讨。 相似文献
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M. Alonso N. Rodríguez B. González G. Grasa R. Murillo J.C. Abanades 《International Journal of Greenhouse Gas Control》2010,4(2):167-173
Post-combustion carbonate looping processes are based on the capture of carbon dioxide from the flue gases of an existing power plant in a circulating fluidized bed reactor (CFB) of calcium oxide (the carbonator) particles. The calcination of calcium carbonate in a new oxy-fired CFBC power plant regenerates the sorbent (calcium oxide particles) and obtains high purity carbon dioxide. This communication presents experimental results from a small test facility (30 kWt) operated in continuous mode using two interconnected CFB reactors as carbonator and calciner. Capture efficiencies between 70 and 97% have been obtained under realistic flue gas conditions in the carbonator reactor (temperatures around 650 °C). The similarity between process conditions and those existing in CFBC power plants should allow a rapid scaling up of this technology. The next steps for this process development are also outlined. 相似文献
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A combination of biomass treatment, fluidized bed/membrane reactor, and a minimum-suspension fluidized bed reactor is proposed to remove strontium cations from aqueous solutions, such as those generated by nuclear reactors. After conducting a series of screening tests, three adsorbents were selected for their suitability and high adsorptive capacity. The proposed combination uses Chlorella vulgaris in a packed column, followed by the fluidized bed/membrane reactor with bentonite powder in suspension. The membrane is primarily used to retain bentonite powder in the reactor. However, the same can be designed to remove additional amount of contaminant from the aqueous stream. The final separation is carried out in a fluidized bed containing resins that are suspended with minimal airflow. In laboratory scale, a flow rate of 600 ml/h was achieved for 30 min during which period the inlet concentration of 100 mg/l was reduced to 2.5 mg/l at the outlet. Bio-encapsulation with thermophilic bacteria and subsequent separation is proposed at this point in order to reduce the concentration to an even lower level. The proposed separation scheme offers an acceptable solution to removing strontium while minimizing the generation of secondary waste. 相似文献
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Yuefa Wang Zhongxi Chao De Chen Hugo A. Jakobsen 《International Journal of Greenhouse Gas Control》2011,5(3):489-497
A 3D numerical model for gas–solid flow was developed and used to study the sorption enhanced steam methane reforming (SE-SMR) and the sorbent regeneration processes with CaO based sorbent in fluidized bed reactors. The SE-SMR process (i.e., SMR and adsorption of CO2) was carried out in a bubbling fluidized bed. The effects of pressure and steam-to-carbon ratio on the reactions are studied. High pressure and low steam-to-carbon ratio will decrease the conversion of methane. But the high pressure makes the adsorption of CO2 faster. The methane conversion and heat utility are enhanced by CO2 adsorption. The produced CO2 in SMR process is adsorbed almost totally in a relative long period of time in the bubbling fluidized bed. It means that the adsorption rate of CO2 is fast enough compared with the SMR rate. The process of sorbent regeneration was carried out in a riser. An unfeasible residence time is required to complete the regeneration process. Higher temperature makes the release of CO2 faster, but the rate is severely restrained by the increased CO2 concentration in gas phase. The temperature distribution is uniform over the whole reactor. Regeneration rate and capacity of sorbents are important factors in selecting the type of reactors for SE-SMR process. 相似文献
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Zhongyi Deng Rui Xiao Baosheng Jin Qilei Song 《International Journal of Greenhouse Gas Control》2009,3(4):368-375
Chemical-looping combustion (CLC) is a promising technology for the combustion of gas or solid fuel with efficient use of energy and inherent separation of CO2. The technique involves the use of an oxygen carrier which transfers oxygen from combustion air to the fuel, and hence a direct contact between air and fuel is avoided. A chemical-looping combustion system consists of a fuel reactor and an air reactor. A metal oxide is used as oxygen carrier that circulates between the two reactors. The air reactor is a high velocity fluidized bed where the oxygen carrier particles are transported together with the air stream to the top of the air reactor, where they are then transferred to the fuel reactor using a cyclone. The fuel reactor is a bubbling fluidized bed reactor where oxygen carrier particles react with hydrocarbon fuel and get reduced. The reduced oxygen carrier particles are transported back to the air reactor where they react with oxygen in the air and are oxidized back to metal oxide. The exhaust from the fuel reactor mainly consists of CO2 and water vapor. After condensation of the water in the exit gas from the fuel reactor, the remaining CO2 gas is compressed and cooled to yield liquid CO2, which can be disposed of in various ways.With the improvement of numerical methods and more advanced hardware technology, the time needed to run CFD (Computational fluid dynamics) codes is decreasing. Hence multiphase CFD-based models for dealing with complex gas-solid hydrodynamics and chemical reactions are becoming more accessible. Until now there were a few literatures about mathematical modeling of chemical-looping combustion using CFD approach. In this work, the reaction kinetics model of the fuel reactor (CaSO4 + H2) was developed by means of the commercial code FLUENT. The bubble formation and the relation between bubble formation and molar fraction of products in gas phase were well captured by CFD simulation. Computational results from the simulation also showed low fuel conversion rate. The conversion of H2 was about 34% partially due to fast, large bubbles rising through the reactor, low bed temperature and large particles diameter. 相似文献
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Anaerobic treatment has become a technically as well as economically feasible option for treatment of liquid effluents after the development of reactors such as the upflow anaerobic sludge blanket (UASB) reactor, expanded granular sludge bed (EGSB) reactor, anaerobic biofilter and anaerobic fluidized bed reactor (AFBR). Considerable effort has gone into developing mathematical models for these reactors in order to optimize their design, design the process control systems used in their operation and enhance their operational efficiency. This article presents a critical review of the different mathematical models available for these reactors. The unified anaerobic digestion model (ADM1) and its application to anaerobic biofilm reactors are also outlined. 相似文献
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The objective of this study was to determine the technical feasibility of green sand reclamation using attrition in a gas–solid fluidized bed. Reclamation of foundry sand is becoming important as it may help solve concerns related to transportation and dumping of the used sand, and reduce production costs by recycling sand. The crucial step in green sand reclamation is the removal of small clay particles that are bound to the sand particles.For this study two different types of green sand were used and supplied by two different foundries. Tests were performed in a fluidized bed equipped with an attrition nozzle operating at pressures of either 350 or 550 kPa (50 or 80 psig). Attrition experiments for one green sand were performed on either unburned or burned (calcined) green sand, to determine the effect of prior calcination of the green sand on its reclamation potential by attrition. Calcination temperatures of over 700 °C were employed, and the results suggest that calcination facilitates the removal of clay from the green sand.Green sand was analyzed for clay and organic content, acid request, and particle size before and after attrition. Attriting calcined green sand produces the best results. Also experiments conducted at the highest attrition pressure of 550 kPa gave good results. According to the mass balance, the mass lost during the attrition process may be limited to less than 14%, and this could be considered acceptable. The volume of air required for the attrition nozzle is rather high and this may adversely affect the economics of the process. 相似文献
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A. Charitos C. Hawthorne A.R. Bidwe S. Sivalingam A. Schuster H. Spliethoff G. Scheffknecht 《International Journal of Greenhouse Gas Control》2010,4(5):776-784
Calcium looping (CaL) is a promising post-combustion CO2 capture technology which is carried out in a dual fluidized bed (DFB) system with continuous looping of CaO, the CO2 carrier, between two beds. The system consists of a carbonator, where flue gas CO2 is adsorbed by CaO and a regenerator, where captured CO2 is released. The CO2-rich regenerator flue gas can be sequestered after gas processing and compression. A parametric study was conducted on the 10 kWth DFB facility at the University of Stuttgart, which consists of a bubbling fluidized bed carbonator and a riser regenerator. The effect of the following parameters on CO2 capture efficiency was investigated: carbonator space time, carbonator temperature and calcium looping ratio. The active space time in the carbonator, which is a function of the space time and the calcium looping ratio, was found to strongly correlate with the CO2 capture efficiency. BET and BJH techniques provided surface area and pore volume distribution data, respectively, for collected sorbent samples. The rate of sorbent attrition was found to be 2 wt.%/h which is below the expected sorbent make-up rate required to maintain sufficient sorbent activity. Steady-state CO2 capture efficiencies greater than 90% were achieved for different combinations of operational parameters. Moreover, the experimental results obtained were briefly compared with results derived from reactor modeling studies. Finally, the implications of the experimental results with respect to commercialization of the CaL process have been assessed. 相似文献
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Erik Jerndal Tobias Mattisson Ivo Thijs Frans Snijkers Anders Lyngfelt 《International Journal of Greenhouse Gas Control》2010,4(1):23-35
Chemical-looping combustion is a novel combustion technology with inherent separation of the greenhouse gas CO2. The technology uses circulating oxygen carriers to transfer oxygen from the combustion air to the fuel. In this paper, oxygen carriers based on commercially available NiO and α-Al2O3 were prepared using the industrial spray-drying method, and compared with particles prepared by freeze-granulation. The materials were investigated under alternating oxidizing and reducing conditions in a laboratory fluidized bed, thus simulating the cyclic conditions of a chemical-looping combustion system. The particles produced by spray-drying displayed a remarkable similarity to the freeze-granulated oxygen carriers, with high reactivity when the bed was fluidized and similar physical properties when sintered at the same temperature. This is an important result as it shows that the scaling-up from a laboratory production method, i.e. freeze-granulation, to a commercial method suitable for large-scale production, i.e. spray-drying, did not involve any unexpected difficulties. A difference noticed between the spray-dried and freeze-granulated particles was the sphericity. Whereas the freeze-granulated particles showed near perfect sphericity, a large portion of the spray-dried particles had hollow interiors. Defluidization was most likely to occur for highly reduced particles, at low gas velocities. The apparent density and crushing strength of the oxygen carriers could be increased either by increasing the sintering temperature or by increasing the sintering time. However, the fuel conversion was fairly unchanged when the sintering temperature was increased but was clearly improved when the sintering time was increased. 相似文献
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《International Journal of Greenhouse Gas Control》2007,1(2):158-169
Chemical-looping combustion (CLC) is a combustion technology where an oxygen carrier is used to transfer oxygen from the combustion air to the fuel, avoiding direct contact between air and fuel. Thus, CO2 and H2O are inherently separated from the rest of the flue gases and the carbon dioxide can be obtained in a pure form without the use of an energy intensive air separation unit. The paper presents results from a 3-year project devoted to developing the CLC technology for use with syngas from coal gasification. The project has focused on: (i) the development of oxygen carrier particles, (ii) establishing a reactor design and feasible operating conditions and (iii) construction and operation of a continuously working hot reactor. Approximately, 300 different oxygen carriers based on oxides of the metals Ni, Fe, Mn and Cu were investigated with respect to parameters, which are important in a CLC system, and from these investigations, several particles were found to possess suitable qualities as oxygen carriers. Several cold-model prototypes of CLC based on interconnected fluidized bed reactors were tested, and from these tests a hot prototype CLC reactor system was constructed and operated successfully using three carriers based on Ni, Fe and Mn developed within the project. The particles were used for 30–70 h with combustion, but were circulated under hot conditions for 60–150 h. 相似文献
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A study of the effluent of an anaerobic fluidized bed reactor acclimated to 2,4,5-TCP was made in order to determine the metabolic pathway and reaction rate limiting step of 2,4,5-TCP. The wastewater with about 2500 mg L−1 COD and 50 mg L−1 2,4,5-TCP was biodegraded by anaerobic digestion, and the intermediate analyzed by HPLC and GC/MS. The results showed the degradative metabolic pathway of 2,4,5-TCP, under anaerobic conditions, to be: 2,4,5-TCP→3,4-DCP→3-CP→phenol→benzoate. For the rate limiting step, the accumulated concentration of 3,4-DCP was higher than other intermediates for Anaerobic Toxicity Assay (ATA) and Biochemical Methane Potential (BMP) tests. From the anaerobic fluidized bed reactor, analyses showed the chloride at the ortho-position was removed very quickly after 2,4,5-TCP entered the reactor. As for the intermediate products, 43% of 3,4-DCP was not decomposed and of the 3-CP only 6.4% left. This shows that the rate limiting step of 2,4,5-TCP was the dechlorination of 3,4-DCP. 相似文献
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Ziegler CK 《Environmental management》2002,29(3):409-427
The stability of cohesive sediment deposits during a rare storm is a critical component in the evaluation of remedial options
at a contaminated sediment site. Estimating scour depths during a rare storm, and the resulting contaminant concentrations
in the surficial layer of the bed, is necessary for comparing the efficacy of various remedial alternatives. Evaluation of
sediment stability is accomplished using sediment transport analyses that employ quantitative procedures. Qualitative analyses
or conceptual models can be useful for developing and validating quantitative analysis tools; however, qualitative techniques
alone generally are insufficient for conducting defensible remedial alternative evaluations. The level of analysis used for
a specific site depends on data availability, required level of accuracy, and time and budget constraints. A tier 1 analysis
involves the use of approximate equations to produce order-of-magnitude estimates of scour depths during a rare storm. The
second tier of this analysis scheme employs the development and application of a sediment transport model to evaluate bed
stability. State-of-the-science sediment transport models have been effectively used as management tools for evaluating remedial
options at several contaminated sediment sites. It should not be presumed that rare storm events cause catastrophic impacts
at the site under review. Two case studies demonstrate that a rare storm is not necessarily catastrophic; significant increases
in surficial bed concentrations caused by reexposure of elevated concentrations buried at depth in the bed will not necessarily
occur during a rare storm. However, it is important to note that sediment stability is site-specific. 相似文献