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Capturing CO2 from conventional coal-fired power plant is very costly because of its relatively dilute concentration in the flue gas. One option to reduce the cost of gas separation is to increase CO2 concentration in the flue gas by eliminating nitrogen before combustion and by recycling part of the flue gas. This scheme is known as O2/CO2 recycle combustion. The present work focuses on the implications...
The effectiveness of four Polish lignites as reburn fuels was studied in the laboratory-scale drop-tube furnace. The established rank of the lignites and chars used correlates with concentration of calcium in lignite. A comparison of the reburning effectiveness of partially devolatilized chars with that of the parent lignites showed that the parent lignites achieved a higher NO reduction than the...
An experimental study has been conducted with a fixed bed reactor to simulate, in a laboratory scale, industrial municipal waste incineration using moving grates. Carbon monoxide, nitrogen oxide and temperature measurements have been used to establish the importance of the operating parameters of a municipal waste incinerator in the characteristics of the combustion process. The observation of the...
The potential of calcium magnesium acetate (CMA) as a medium for the simultaneous control of NO x and SO x emissions has been investigated using a pulverized coal combustion rig operating at 80kW. A US and a UK coal of significantly different sulphur contents were used as primary fuel and CMA was injected in solution form into the combustion gases by horizontally opposed twin-fluid...
The adsorption of Hg and NO X on gasifier and combustion by-products was investigated. Carbon-rich fractions were produced by a density separation technique from a gasifier char (GC) and a pulverized coal combustion blended fly/bottom ash (CC) recovered from a pond. Both fractions were subjected to steam activation at 875°C. As-received and activated chars and two commercial carbons developed...
The performance of a suite of different carboxylic salts of calcium, have been assessed as dual NO x /SO x reducing agents. The salts studied include, calcium magnesium acetate (CMA), calcium acetate (CA), calcium formate (CF), calcium benzoate (CB), calcium propionate (CP) and magnesium acetate (MA). The primary fuel was propane operating with a primary zone stoichiometry fixed at...
Model compounds, with a controlled heteroatoms content and well-defined functionalities, were used to study the release of nitrogen compounds from char combustion. In the present work, the mechanisms involved in NO-char heterogeneous reduction were studied with a synthetic coal (SC) char as carbon source. Another synthetic char (SN) without any nitrogen in its composition was also employed in these...
Propane is available commercially for use in conventional internal combustion engines as an alternative fuel for gasoline. However, its application in the developing homogeneous charge compression ignition (HCCI) engines requires various approaches such as high compression ratios and/or inlet charge heating to achieve auto ignition. The approach documented here utilizes the trapping of internal residual...
Computational fluid dynamics is a widely used tool in optimizing natural gas burners, for instance, for emission issues. Especially, a further reduction of NO x emissions is of interest. However, due to computational efforts calculating three-dimensional turbulent flames, there is the necessity for simplified models in order to simulate the combustion reactions and the NO x formation,...
Temperature programmed combustion of a Chinese brown coal before and after demineralization was carried out in a tubular quartz fixed bed reactor. The evolution of NOx during coal combustion has been investigated with an aim of figuring out the influence of indigenous mineral matter in coal as well as the loaded alkali and alkaline earth metals (Na, Ca). The results show that the mineral matter in...
A numerical study of the diluted oxidation of CH 4 was performed to investigate the potential importance of the NO-reburning mechanism in conditions relevant to MILD combustion. It turns out that the NO–HCN conversion reactions are particularly active before auto-ignition. During this period, the nitrogen contained initially in NO is stored in HCN and NH 3 . The extent of this phenomenon...
In this study, computational fluid dynamic (CFD) and kinetic models were used to investigate the relative performances of coal volatiles and natural gas reburning. This modeling approach considers fluid dynamic and non-isothermal effects, which were not considered in past laboratory flow reactor studies. The commercial CFD code FLUENT 6.1 was used to predict the residence times and temperatures for...
The motivation of this study is to explore the feasibility of extending the EGR (exhaust gas recirculation) diluent tolerance for methane/air mixtures with reformer gas (CO and H 2 ). A preheated cylindrical combustion chamber was used to measure the laminar burning velocity of methane/air mixture with variations of EGR diluent, reformer gas, temperature and pressure. The experiments were...
The paper provides an overall assessment of the environmental effects of co-incineration of cutting oil emulsions in cement plants through the quantification of emissions of key pollutants, namely NO x , CO and VOC. Two realistic scenarios are considered. In the first, the cutting oil emulsion is injected directly into the rotary kiln while the second scenario involves injection of the cutting...
The NO 2 , NO (O 2 ) adsorption and temperature programmed desorption (TPD) were studied systematically to probe into the selective catalytic reduction of NO by methane (CH 4 –SCR) over CoH-ZSM-5 (SiO 2 /Al 2 O 3 =25, Co/Al=0.132–0.312). Adsorption conditions significantly affect the adsorption of NO, NO 2 and NO+O 2 . Adsorbed NO species...
This paper presents the comparison of experimental results and computational fluid dynamics (CFD) simulations for a 600MWe industrial pulverised coal power station. The power station measurements were made in a normal combustion mode and in an overfire air (OFA) mode. The agreement between the model and the data collected in the chimney is good; the NO x reduction modelled is in agreement...
Industrial experiments have been performed on a down-fired pulverized-coal 300MWe utility boiler with vent air valve opening of 100% and 40%. The gas temperature distribution along the primary air and coal mixture flow, gas temperature distribution in the furnace, and gas components such as O 2 , CO, CO 2 and NO x in the near-wall region were measured for the first time. The...
For mitigating the emission of greenhouse gas CO 2 from general air combustion systems, a clean combustion technology O 2 /RFG is in development. The O 2 /RFG combustion technology can significantly enhance the CO 2 concentration in the flue gas; however, using almost pure oxygen or pure CO 2 as feed gas is uneconomic and impractical. As a result, this study...
The reactions reviewed here concern those between elemental carbon and NO 2 , N 2 O and NO, sometimes in the presence of oxygen. The section on NO includes only updates to recent reviews. Soots, activated carbons and carbon blacks are more reactive than graphite. The magnitudes of the reaction rates are found to be: NO 2 >N 2 O≈NO≈O 2 . The presence of a...
Combustion simulations were conducted to investigate the parameters controlling the formation of unburned carbon in fly ash from coal reburning in a coal-fired boiler. Unburned carbon (UBC or Loss on ignition, LOI) was generally caused by particles flowing through fuel-rich regions and/or spending insufficient residence time in the furnace. LOI contributions by each individual coal source were identified...
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