Showing papers by "Steven G. Buckley published in 1998"

Multi-shaft reheat turbine mechanism for generating power

Abstract: A multi-shaft reheat turbine mechanism includes multiple turbines mounted on respective compressor shafts, and catalytic reactors feeding respective ones of the turbines. Fuel is introduced into a low pressure compressor, whereby there is no need to pressurize the fuel. The compressor side of the mechanism emits a compressed air/fuel flow, portions of which are combusted in respective ones of the catalytic reactors. The air/fuel flow traveling from the compressor side to the turbine side passes through a regenerator in heat exchanging relationship with exhaust gas from a low pressure turbine.

Interactions between coal and biomass when cofiring

Abstract: Cofiring biomass with coal is one of the most promising short-term options for reducing the net CO 2 emissions from coal-fired power plants. This paper examines the effects of cofiring biomass and coal on ash deposition, corrosion, and NO x emissions under conditions representative of those found in pulverized-coal (pc) boilers. Experiments were conducted with blends of six different fuels—two types of bituminous coal, two types of straw, switchgrass, and wood. For each fuel, reference tests of unblended fuel establish a baseline to examine the results from the cofiring tests. The deposition rates for the blends of fuels considered by this investigation lay between the measured deposition rates of the unblended fuels. There-fore, cofiring can mitigate some of the fouling difficulties associated with high-fouling coals and biofuels. By accounting for factors other than fuel composition, we can improve our predictions of the effects of cofiring on ash deposition rates. For the fuel blends examined here, available alkali is a relatively good predictor for the ash deposition rate. Sulfation of alkali chlorides is the major interaction that occurs within deposits formed while cofiring. Sulfation reduces the chlorine content of the deposits, potentially reducing the corrosion potential of the deposits. Cofiring biomass can decrease NO x emissions relative to firing unblended coal under typical pc-combustion conditions when the biomass fuel contains little nitrogen There does not appear to be any fundamental synergistic interaction between the coal and biomass that significantly reduces NO x emissions. These measurements demonstrate that cofiring biomass with coal can result in decreased pollutant production, decreased ash deposition, and decreased effective CO 2 , but judicious choices of fuels and operating conditions are required to accomplish these objectives.

Ammonia detection and monitoring with photofragmentation fluorescence

Abstract: Excimer laser fragmentation-fluorescence spectroscopy is an effective detection strategy for NH3 in combustion exhausts at atmospheric pressure and high temperatures. Two-photon photofragmentation of NH3 with 193-nm light yields emission from the NH(A– X) band at 336 nm. There are no major interferences in this spectral region, and the sensitivity is at the parts per billion (ppb) level. Quenching of the NH(A) state radical by the major combustion products is measured and does not limit the applicability of the detection method. Detection limits in practical situations are of the order of 100 ppb for a 100-shot (1-s) average. This technique could prove useful in monitoring ammonia emissions from catalytic and noncatalytic NOx reduction processes involving ammonia injection.

Regenerator type heat exchanger

Abstract: Heat is exchanged between high and low temperature gases in a regenerator type of heat exchanger, wherein the high temperature gas is conducted through a high temperature passage formed in a housing, and the low temperature gas is conducted through a low temperature passage formed in the housing. A porous heat transfer core is rotated such that portions of the core pass sequentially through the high and low temperature passages. The high temperature gas traveling in the high temperature passage is caused to flow through, and heat, a portion of the core disposed in the high temperature passage. The low temperature gas traveling in the low temperature passage is caused to flow through, and be heated by, a heated portion of the core disposed in the low temperature passage. A low pressure zone is established in a chamber situated at each location where the core travels from one of the passages to the other. A pressure in the low pressure zone is lower than pressures-in both of the passages, whereby gases tending to leak from one of the passages to the other are drawn into the low pressure zone and are conducted out of the housing.

in situ measurements of the thermal conductivity of ash deposits

Abstract: Ash deposits reduce heat transfer rates to furnace walls, superheater tubes, and other heat transfer surfaces in coal-fired power plants. The effective thermal conductivity of a porous ash deposit is one important parameter for determining the magnitude of this reduction. In this paper, we report in situ , time-resolved measurements of the effective thermal conductivity of ash deposits formed under conditions that closely replicate those found in the convective pass of a commercial boiler. Experiments were conducted using an Illinois #6 coal and a blend of Illinois #6 coal and wheat straw to determine the thermal conductivity of highly porous, unsintered deposits and to examine the influence of the initial stages of sintering on these deposits. For deposits formed while firing both fuels the measured thermal conductivity of loose, unsintered deposits is 0.15 W/(m K), almost a factor of three greater than that of air under these conditions. The initial stages of deposit sintering and densification are accompanied by a substantial increase in deposit thermal conductivity. Subsequent sintering continues to densify the deposit but has little effect on deposit thermal conductivity. These trends correspond to anticipated effects of sintering on the development of a layered deposit structure and on particle contact efficiency. Measured values of thermal conductivity are also observed to lie between rational theoretical bounds based on deposit porosity and structure.

Energetics to energy: Combustion and environmental considerations surrounding the reapplication of energetic materials as boiler fuels

Abstract: Millions of pounds of waste energetic materials (EM) such as rocket fuel and high explosives are generated every year. Although some of the material can be recycled, much of it is difficult to separate or has little intrinsic value, and some of the material contains hazards such as asbestos and chlorine. Typically this material is disposed of through open burning/open detonation (OB/OD) or in landfills. This wastes the energy content of the fuels and may generate significant pollution. Combustion in an industrial boiler is a compelling alternative disposal option for EM that would capture the energy value in the fuel and also would mitigate many environmental hazards using boiler pollution controls. We examine combustion issues associated with EM, including an evaluation of energy content, NO x production, aluminum combustion behavior, and the fate of asbestos. Although they have lower traditional heating values than typical boiler fuels due to their oxygen content, EM actually contain more energy per unit mass of combustion products. Experiments with a variety of common EM show that NO x production from EM-derived fuels (EMDF) may be quite high. In some cases this arises from a high nitrate concentration, and in others it is from aluminum in the fuel, which burns at very high temperatures. Up to 80% of the fuel-bound nitrogen in trinitrotoluene (TNT) was converted into NO x in our experiments. We demonstrate that staged combustion can effectively control NO x formed by nitrate group decomposition, reducing levels by approximately 60%–65% for a 5% TNT/95% toluene mixture. The high temperatures caused by aluminum combustion create a second concern, damage to the boiler itself. Finally, we give evidence that asbestos incorporated in EMDF from solid rocket motor liners can be rendered nonhazardous by combustion.