Fuel air supply

Flame Spread The speed at which a flame will cross the surface of a material, influenced by the physical form of the fuel, air supply, the moisture content of the fuel, specific gravity, size and form, the rate and period of heating, and die characteristics/nature of the heat source. A higher flame-spread critically affects the severity of the fire in a given period of time. 

An interesting feature of these high-temperature-calcination apph-cations is the direct injeciion of either heavy oil, natural gas, or nue coal into the fluidized bed. Combustion takes place at well below flame temperatures without atomization. Considerable care in the design of the fuel- and air-supply system is necessary to take full advantage of the fluidized bed, which sei ves to mix the air and fuel. 

As part of a Process Hazards Analysis (PHA). I was required to check a naturally ventilated building containing electrical equipment and a fuel gas supply, for adequate air flow due to thermal forces (stack effect). API RP 500 has a method that they recommend for buildings of l,000fP or less. The building in question was much larger, because ... 

Fig. 3.13 shows the overall efficiency for the [CBTJic, plant plotted against the i.sentropic temperature ratio for various maximum temperatures Tj (and 6= Ty/Ti, with T, = 27°C (3(X) K)). The following assumptions are also made polytropic efficiency, rjp = 0.9 for compressor and turbine pressure loss fraction in combustion 0.03 fuel (methane) and air supplied at 1 bar, 27°C (3(X) K). 

Eq. (6.16) is essentially the same as Eq. (6.8) for the basic STIG plant which, on reflection, is not surprising. If the states 1,2, 3, 4 and 5 and the steam quantity S are all the same then expressions for the work output, the heat input (or fuel energy supply) and the heat rejected are all unchanged. The total amount of heat transferred from the exhaust is also unchanged, but two separate flows, of air and of water/steam, have been raised in enthalpy before entry to the combustion chamber, rather than one (water/steam) in the earlier analysis. 

In the first type, heating of the steam turbine cycle is by the gas turbine exhaust with or without additional firing (there is normally sufficient excess air in the turbine exhaust for additional fuel to be burnt, without an additional air supply). In the second, the main combustion chamber is pressurised and joint heating of gas turbine and steam turbine plants is involved. 

A similar argument can be used for a fuelled semi-closed cycle, assuming that it can be regarded as the addition of an open CBT plant and a closed CHT cycle with identical working gas mass flow rates (and small fuel air ratios). Suppose the latter receives its heat supply from the combustion chamber of the former in which the open cycle combustion takes place. If the specific heats of air and products are little different, then the work output is doubled when the two plants are added together, but the fuel supply is also approximately doubled. The efficiency of the combined semi-closed plant is, therefore, approximately the same as that of the original open cycle plant. 

To complete the. set of possible chemical reactions, consider the combustion of a fuel such as methane with a recirculated flue gas containing m moles of carbon dioxide, but assuming that water vapour has been removed from the recycling flue gas. If the additional air supply (n moles) is assumed to be sufficient for complete combustion, then... 

Air is supplied to the power cylinders by either natural air flow associated with the engine or by some external means. Engines that use no external means of air supply are termed to be naturally aspirated. Those with some external air supply are generally termed supercharged. The horsepower developed by an engine is dependent on its supply of air. The more air mass contained in a cylinder at ignition the more fuel that can be burned and the more horsepower that will be developed by the cylinder. 

Fluidized-bed process incinerators have been used mostly in the petroleum and paper industries, and for processing nuclear wastes, spent cook liquor, wood chips, and sewage sludge disposal. Wastes in any physical state can be applied to a fluidized-bed process incinerator. Au.xiliary equipment includes a fuel burner system, an air supply system, and feed systems for liquid and solid wastes. The two basic bed design modes, bubbling bed and circulating bed, are distinguished by the e.xtent to which solids are entrained from the bed into the gas stream. 

Failure of the utilities and ancillary systems occurs when one or more of tlie following is lost electric power, cooling water or otlier heal removal systems, steam or other heat supply systems, fuel, air, inert gas, or effluent disposal facilities. 

Diesel engines, however, operate on an unrestricted air flow at all speeds and loads to provide the cylinders with an excess air charge. This results in a very lean air/fuel ratio of approximately 90 1 to 100 1 or higher at an idle speed. At the engine s rated speed (full load maximum power output) the air/fucl ratio will drop to 20 1 to 25 1 but still provide an excess air factor here of 10 to 20 percent. This excess air supply lowers the average specific heat of the cylinder gases, which in turn increases the indicated work obtained... 

An independent overriding second low-water control. This will be set below the level control in (2). It will give an audible alarm on shutting off the fuel and air supply and require manual reset before the boiler may be brought back into operation ... 

Steam is the preferred atomizing medium, since it is more economic than compressed air. Steam consumption is typically less than 0.5 per cent of the fuel burnt on a mass basis, although this rises in direct proportion to turndown ratio. On very large burners, the steam flow is modulated in proportion to fuel burnt. Turndown ratios range from about 5 1 for small shell boilers to 12 1 in watertube applications, making this one of the most versatile burners. The steam condition is important in that it must be dry saturated or slightly superheated at the nozzle to avoid condensate formation. On small or non-continuously running plant where no steam is available for start-up a compressed air supply must be provided until steam becomes available from the boiler. 

A drop in steam pressure necessitates an increase in the fuel supplied to the burner and vice versa. However, any change in the quantity of fuel supplied requires a corresponding change in the volume of air supplied to the boiler, and if the fuel-to-air ratio is not balanced within the... 

Two new technologies have reduced the cost of alkali fuel cells to the point where a European company markets taxis that use them. One is the use of CO2 scrubbers to purify the air supply, making it possible to use atmospheric O2 rather than purified oxygen. The other is the development of ultrathin films of platinum so that a tiny mass of this expensive metal can provide the catalytic surface area needed for efficient fuel-cell operation. 

A more sophisticated implementation is full metering control (Fig. 10.6). In this case, we send the signals from the fuel gas controller (FC in the fuel gas loop) and the air flow transmitter (FT) to the ratio controller (RC), which takes the desired flow ratio (R) as the set point. This controller calculates the proper air flow rate, which in turn becomes the set point to the air flow controller (FC in the air flow loop). If we take away the secondary flow control loops on both the fuel gas and air flow rates, what we have is called parallel positioning control. In this simpler case, of course, the performance of the furnace is subject to fluctuations in fuel and air supply lines. 

An explosion and fire occurred in the pipework of a vessel in which dilute butadiene was stored under an inert atmosphere, generated by the combustion of fuel gas in a limited air supply. The inert gas, which contained up to 1.8% of oxygen and traces of oxides of nitrogen, reacted in the vapour phase over an extended period to produce concentrations of gummy material containing up to 64% of butadiene peroxide and 4.2% of a butadiene-nitrogen oxide complex. The deposits eventually decomposed explosively. 

To obtain hygienic combustion, it is essential to adjust the equivalence ratio 0 to an ideal value. This value characterises the ratio of the fuel quantity needed for a stoichiometric combustion to the fuel quantity supplied. In most of the common gas appliances, the air supply slightly exceeds the amount of air needed for complete stoichiometric combustion. The exact value for the surplus of air - often referred to as lambda (X) - depends on the configuration of the burner system in question. 

Generally, the volume fraction of single flue gas compounds for a known combustion system, an adjusted equivalence ratio and a given composition of the fuel gas supplied can be regarded as fixed. In order to adjust the air and gas supply, several different strategies have been developed. The most important strategies to predict correlations between the concentration of flue gas compounds and an ideally adjusted combustion are explained below. 

There can be many different cycle configurations for the hybrid fuel cell/turbine plant. In the topping mode described above, the fuel cell serves as the combustor for the gas turbine, while the gas turbine is the balance of plant for the fuel cell, with some generation. In the bottoming mode, the fuel cell uses the gas turbine exhaust as air supply, while the gas turbine is the balance of plant. In indirect systems, high-temperature heat exchangers are used. 

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