Modelling and Simulation of SOx and NOx Formation Under Oxy-Coal Combustion Conditions PDF Download
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Author: Michael Müller
Publisher:
ISBN: 9783844040593
Category :
Languages : en
Pages : 164
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Author: Michael Müller
Publisher:
ISBN: 9783844040593
Category :
Languages : en
Pages : 164
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Book Description
Author:
Publisher: Cuvillier Verlag
ISBN: 3736909381
Category : Technology & Engineering
Languages : de
Pages : 180
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Book Description
ABSTRACT The current work briefly reviews the formation mechanisms and reduction approaches of the pollutants SOx and NOx in coal combustion and focuses on the simulation of the lower-cost in-furnace measures ƒ{ the dry additive process (DAP) for SOx reduction and the reburning as well as the advanced reburning (hybrid reburning/SNCR) techniques for NOx reduction. In addition, the influence of sulfur compounds on NOx formation is investigated. The major workings include: Simulation of the dry additive desulfurization process (DAP): Different models ƒ{ shrinking core model (SCM), pore model (PM) and grain model (GM) ƒ{ are implemented to describe the gas-particle reaction. Relevant processes such as the sintering of the additive, the self-retention by coal ash, the thermal equilibrium of the sulfation reaction are accounted for and modeled. A comprehensive model for the DAP with calcium based additives is subsequently established and integrated into a combustion CFD (computational fluid dynamics) code AIOLOS, in both Eulerian and Lagrangian schemes. The model is verified with experiments on a test reactor. Mechanism reduction and simulation of reburning/SNCR Processes: A method for reduction of kinetic mechanisms is introduced. A program tool is developed for automatic reduction of detailed reaction mechanisms. Reduced mechanisms for reburning and hybrid reburning/SNCR processes are developed and implemented into the CFD code. CFD-calculations with the reduced mechanisms are performed and compared with experimental measurements to comprehensively evaluate the simulation approach. It is shown that the detailed simulation is capable of modeling the complex reburning and SNCR processes with acceptable computing time and achieves reasonable results in wide parameter ranges. Study of the influence of sulfur compounds on NOx formation: The effect of SO2 on NOx formation is experimentally investigated and analysed with kinetic mechanisms. It is indicated that the presence of SO2 inhabits the NOx formation and reduce the NOx emissions in normal air-rich combustion. Under air-staging conditions, SO2 addition has no obvious influence on the final NOx emissions.
Author: Muhammad Jahangir Malik
Publisher:
ISBN:
Category : Carbon sequestration
Languages : en
Pages : 136
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Book Description
Growing concerns over greenhouse gas emissions have driven extensive research in carbon capture, storage and sequestration. Oxy-fuel combustion is a promising technology in CO2 capture, as the combustion products consists primarily of CO2 and H2O with contaminants like NOx and SOx. More recently, oxy-fuel combustion under pressurized conditions has gained attention due to its overall higher net efficiency, while decreasing the auxiliary power consumption in the process. The need for a better understanding of the coal combustion in oxy-fuel conditions under elevated pressures and the formation of SOx and NOx in such conditions inspired this research project. In this thesis, the effect of pressurized oxy-fuel combustion on SOx and NOx formation from coal combustion and their removal from the flue gas was investigated. The combustion modelling for lignite coal was conducted in ANSYS Fluent, under oxy-fuel environment at atmospheric pressure and elevated pressures (5 atm, 10 atm, 15 atm). The results showed an increase in SO3 formation and rapid decrease in NO in the flue gas as the pressure was increased in the combustor. At 15 atm, the NOx emissions were found to be below 100 ppm, which is an acceptable concentration of NOx for CO2 transport and storage. In order to investigate the influence of pressure on SOx and NOx in the flue gas in the post-combustion zone, the system was subjected to a temperature profile representative of an actual plant boiler, where the residence time is around 2 seconds. The results showed that the rate of SO2 and NO oxidation to SO3 and NO2, respectively, were influenced by the rate of temperature decrease, and the effect of pressure was not as significant. It was observed that flue gas composition remained constant below 550 K, as all SO3 present in the flue gas converted to gaseous H2SO4. Lastly, simulations for SOx and NOx removal from flue gas via absorption were performed at 15 atm to purify the flue gas to meet the requirements for CO2 transportation. The results showed complete removal of SOx in the form of H2SO4 and SO42- and around 30% NOx removal, mostly in the form of HNO3. A sensitivity analysis was performed on the reflux ratio of liquid in the absorber and the results showed increased NOx removal at lower reflux ratio. The investigation helped conclude that pressurized oxy-fuel combustion results in lower SOx and NOx emissions, and require less sophisticated separation techniques to meet the pipeline threshold for CO2 transportation in storage and sequestration.
Author: A. Tomita
Publisher: Elsevier
ISBN: 9780080440897
Category : Nature
Languages : en
Pages : 340
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Book Description
Over the past decade the topic of emissions reduction and control has remained an important area of research due to the enforcement of various Government policies in an attempt to minimize the impact on the environment. One area in which a great deal of research has been conducted to address this policy is NOx/SOx suppression. However, despite the progress that has been made over this time period, further research into the most effective method of reducing NOx/SOx emissions is still urgently required. In developed countries, a more stringent requirement in the level of emissions (such as is NOx/SOx component of less than 10ppm) will be enforced in the near future. Developing countries will also need a new technology that is effective and that is suited to each countries needs. Additional research and development efforts are thus necessary to meet such requirements. This compendium contains a collection of key papers themed around NOx/SOx emissions from combustion of hydrocarbon resources and the attempts to secure an efficient and effective method for reducing these emissions. These key papers are taken from the journals Fuel, Fuel Processing Technology and Progress in Energy and Combustion Science.
Author: Ruksana Moreea-Taha
Publisher:
ISBN:
Category : Coal-fired power plants
Languages : en
Pages : 60
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 113
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Book Description
In this work, both computer simulation and experimental studies were conducted to investigate several strategies for NO(subscript x) reduction under pulverized coal combustion conditions with an aim to meet the stringent environmental standards for NO(subscript x) control. Both computer predictions and reburning experiments yielded favorable results in terms of NO(subscript x) control by reburning with a combination of methane and acetylene as well as non-selective catalytic reduction of NO(subscript x) with ammonia following reburning with methane. The greatest reduction was achieved at the reburning stoichiometric ratio of 0.9; the reduction was very significant, as clearly shown in Chapters III and V. Both the experimental and computational results favored mixing gases: methane and acetylene (90% and 10% respectively) and methane and ammonia (98% and 2%) in order to get optimum reduction levels which can not be achieved by individual gases at any amounts. Also, the above gaseous compositions as reburning fuels seemed to have a larger window of stoichiometric ratio (SR2 0.9) as opposed to just methane (SR2=0.9) so as to reduce and keep NO(subscript x) at low ppm levels. From the various computational runs, it has been observed that although there are several pathways that contribute to NO(subscript x) reduction, the key pathway is NO -- HCN --> NH3 --> N2 + H2. With the trends established in this work, it is possible to scale the experimental results to real time industrial applications using computational calculations.
Author: Hiroshi Tsuji
Publisher: CRC Press
ISBN: 1420041037
Category : Nature
Languages : en
Pages : 425
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Book Description
Maximize efficiency and minimize pollution: the breakthrough technology of high temperature air combustion (HiTAC) holds the potential to overcome the limitations of conventional combustion and allow engineers to finally meet this long-standing imperative. Research has shown that HiTAC technology can provide simultaneous reduction of CO2 and nitric
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
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Book Description
Author: University of Wyoming Research Corporation. Western Research Institute
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
BOC Process Gas Solutions and Western Research Institute (WRI) conducted a pilot-scale test program to evaluate the impact of oxygen enrichment on the emissions characteristics of pulverized coal. The combustion test facility (CTF) at WRI was used to assess the viability of the technique and determine the quantities of oxygen required for NOx reduction from coal fired boiler. In addition to the experimental work, a series of Computational Fluid Dynamics (CFD) simulations were made of the CTF under comparable conditions. A series of oxygen enrichment test was performed using the CTF. In these tests, oxygen was injected into one of the following streams: (1) the primary air (PA), (2) the secondary air (SA), and (3) the combined primary and secondary air. Emission data were collected from all tests, and compared with the corresponding data from the baseline cases. A key test parameter was the burner stoichiometry ratio. A series of CFD simulation models were devised to mimic the initial experiments in which secondary air was enriched with oxygen. The results from these models were compared against the experimental data. Experimental evidence indicated that oxygen enrichment does appear to be able to reduce NOx levels from coal combustion, especially when operated at low over fire air (OFA) levels. The reductions observed however are significantly smaller than that reported by others (7-8% vs. 25-50%), questioning the economic viability of the technique. This technique may find favor with fuels that are difficult to burn or stabilize at high OFA and produce excessive LOI. While CFD simulation appears to predict NO amounts in the correct order of magnitude and the correct trend with staging, it is sensitive to thermal conditions and an accurate thermal prediction is essential. Furthermore, without development, Fluent's fuel-NO model cannot account for a solution sensitive fuel-N distribution between volatiles and char and thus cannot predict the trends seen in the experiment.
Author: Hari Krishna Uggini
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
New regulations like the Clean Air Interstate Rule (CAIR) will pose greater challenges for Coal fired power plants with regards to pollution reduction. These new regulations plan to impose stricter limits on NOx reduction. The current regulations by themselves already require cleanup technology; newer regulations will require development of new and economical technologies. Using a blend of traditional fuels and biomass is a promising technology to reduce NOX emissions. Experiments conducted previously at the Coal and Biomass energy lab at Texas A & M reported that dairy biomass can be an effective Reburn fuel with NOX reduction of up to 95 percent; however little work has been done to model such a process with Feedlot Biomass as a blend with the main burner fuel. The present work concerns with development of a zero dimensional for a low NOX burner (LNB) model in order to predict NOx emissions while firing a blend of Coal and dairy biomass. Two models were developed. Model I assumes that the main burner fuel is completely oxidized to CO, CO2,H20 and fuel bound nitrogen is released as HCN, NH3, N2; these partially burnt product mixes with tertiary air, undergoes chemical reactions specified by kinetics and burns to complete combustion. Model II assumes that the main burner solid fuel along with primary and secondary air mixes gradually with recirculated gases, burn partially and the products from the main burner include partially burnt solid particles and fuel bound nitrogen partially converted to N2, HCN and NH3. These products mix gradually with tertiary air, undergo further oxidation-reduction reactions in order to complete the combustion. The results are based on model I. Results from the model were compared with experimental findings to validate it. Results from the model recommend the following conditions for optimal reduction of NOx: Equivalence Ratio should be above 0.95; mixing time should be below 100ms. Based on Model I, results indicate that increasing percentage of dairy biomass in the blend increases the NOx formation due to the assumption that fuel N compounds (HCN, NH3) do not undergo oxidation in the main burner zone. Thus it is suggested that model II must be adopted in the future work.
