Current Issue : October - December Volume : 2018 Issue Number : 4 Articles : 5 Articles
Application of a pre-combustion chamber (PCC) ignition system is one of the methods to\nimprove combustion stability and reduce toxic compounds emission, especially NOx. Using PCC\nallows the operation of the engine at lean combustion conditions or the utilization of low calorific\ngaseous fuels such as syngas or biogas. The paper presents the results of an experimental study of\nthe combustion process in two stroke, large bore, stationary gas engine GMVH 12 equipped with\ntwo spark plugs (2-SP) and a PCC ignition system. The experimental research has been performed\nduring the normal operation of the engine in an industrial compression station. It was observed that\napplication of PCC provides less cycle-to-cycle combustion variation (more than 10%) and nitric oxide\nand carbon monoxide emissions decreased to 60% and 26% respectively. The total hydrocarbon (THC)\nemission rate is 25% higher for the engine equipped with PCC, which results in roughly two percent\nengine efficiency decrease. Another important criterion of engine retrofitting was the PCC location in\nthe engine head. The experimental results show that improvement of engine operating parameters\nwas recorded only for a configuration with one port offset by 45ââ??¦ from the axis of the main chamber.\nThe study of the ignition delay angle and equivalence ratio in PCC did not demonstrate explicit\ninfluence on engine performance....
Carbon dioxide emissions are considered a major environmental threat. To enable power\nproduction from carbon-containing fuels, carbon capture is required. Oxy-fuel combustion technology\nfacilitates carbon capture by increasing the carbon dioxide concentration in flue gas. This study\nreports the results of calcium rich oil shale combustion in a 60 kWth circulating fluidized bed (CFB)\ncombustor. The focus was on the composition of the formed flue gas and ash during air and oxy-fuel\ncombustion. The fuel was typical Estonian oil shale characterized by high volatile and ash contents.\nNo additional bed material was used in the CFB; the formed ash was enough for the purpose. Two\nmodes of oxy-fuel combustion were investigated and compared with combustion in air. When N2\nin the oxidizer was replaced with CO2, the CFB temperatures decreased by up to 100 ââ??¦C. When\noil shale was fired in the CFB with increased O2 content in CO2, the temperatures in the furnace\nwere similar to combustion in air. In air mode, the emissions of SO2 and NOx were low (<14\nand 141 mg/Nm3 @ 6%O2, respectively). Pollutant concentrations in the flue gas during oxy-fuel\noperations remained low (for OXY30 SO2 < 14 and NOx 130 mg/Nm3 @ 6%O2 and for OXY21 SO2\n23 and NOx 156 mg/Nm3 @ 6%O2). Analyses of the collected ash samples showed a decreased extent\nof carbonate minerals decomposition during both oxy-fuel experiments. This results in decreased\ncarbon dioxide emissions. The outcomes show that oxy-fuel CFB combustion of the oil shale ensures\nsulfur binding and decreases CO2 production....
Based on the temperature and O2 concentration in the cement precalciner, co-combustion\nof anthracite and Refuse Derived Fuel (RDF) were investigated using a thermogravimetric analyzer\n(TGA) and a double furnaces reactor. Both the TGA and double furnaces reactor results indicated\nthat the co-combustion characteristics were the linear additive effect in the devolatilization stage,\nwhile it was the synergistic effect in the char combustion stage. During co-combustion, at 900 ââ??¦C,\nNOx released rapidly during the devolatilization stage, but in the char combustion stage the NOx\nformation were inhibited; at 800 ââ??¦C, a large amount of CO formed, which could reduce the NOx.\nIn general, at 900 ââ??¦C and 800 ââ??¦C, the application of co-combustion could lower the NOx emission yield\nand lower the NOx conversion. By combining the combustion characteristics with the XRD results,\nit was indicated that during co-combustion, at 800 ââ??¦C, the SO2 formation reaction was inhibited,\nand the SO2 yield and conversion were quite low....
Direct combustion of solid biomass fuel is one of the most common energy sources in\ndeveloping countries. Evaluation of technology for household biomass pellet fuel combustion is\ncritical, since promoting poorly designed devices may have risks due to exposure to high levels of\nemissions. This study evaluated the effects of various testing conditions on a top-lit forced-up-draft\nsemi-gasifier cooking stove. An orthogonal test was designed with different fuel masses, chamber\nheights, air supply rates, and ending points. The investigation showed that using forced secondary\nair and more fuel tended to improve both thermal and gas emissions performance. The ending\npoints did not have significant effects on thermal efficiency or the carbon dioxide emission factor,\nbut did affect particulate matter emission. A relatively lower chamber height demonstrated better\nperformance on thermal metrics. However, a taller flame had better performance on particulate matter\nemission factors. The results of the indicators reported by different bases, such as fuel mass-based or\nuseful energy-based were also quite different. The study showed that different testing conditions\nhad significant effects on combustion performances. Testing sequences and emission factors should\nbe reviewed and defined clearly when forming testing methods and standards for biomass pellet\nfuel combustion....
Pyrolysis and combustion behaviors of three coals (A, B, and C coals) were investigated\nand their combustion kinetics were calculated by the Freemanââ?¬â??Carroll method to obtain quantitative\ninsight into their combustion behaviors. Moreover, the effects of coal size, air flow, oxygen content,\nand heating rate on coal combustion behaviors were analyzed. Results showed that the three coals\nhave a similar trend of pyrolysis that occurs at about 670 K and this process continuously proceeds\nalong with their combustion. Combustion characteristics and kinetic parameters can be applied\nto analyze coal combustion behaviors. Three coals having combustion characteristics of suitable\nignition temperature (745ââ?¬â??761 K), DTGmax (14.20ââ?¬â??15.72%/min), and burnout time (7.45ââ?¬â??8.10 min)\nwere analyzed in a rotary kiln. Combustion kinetic parameters provide quantitative insights into coal\ncombustion behavior. The suitable particle size for coal combustion in a kiln is that the content of less\nthan 74 Ã?¼mis 60% to 80%. Low activation energy and reaction order make coal, especially C coal, have\na simple combustion mechanism, great reactivity, be easily ignited, and a low peak temperature in the\ncombustion state. Oxygen-enrichment and high heating rates enhance coal combustion, increasing\ncombustion intensity and peak value, thus shortening burnout time....
Loading....