Combustion, programmed

L. N. Khitrin, Physics of Combustion and Explosion, University of Moscow Press, CIS 1957, trans. Israel Scientific Translations Program, Office of Technical Services, OTS 61-31205, U.S. Dept, of Commerce, Washington, D.C., 1962. 

Control Devices. Control devices have advanced from manual control to sophisticated computet-assisted operation. Radiation pyrometers in conjunction with thermocouples monitor furnace temperatures at several locations (see Temperature measurement). Batch tilting is usually automatically controlled. Combustion air and fuel are metered and controlled for optimum efficiency. For regeneration-type units, furnace reversal also operates on a timed program. Data acquisition and digital display of operating parameters are part of a supervisory control system. The grouping of display information at the control center is typical of modem furnaces. 

New research in combustors such as catalytic combustion have great promise, and values of as low as 2 ppm can be attainable in the future. Catalytic combustors are already being used in some engines under the U.S. Department of Energy s (DOE), Advanced Gas Turbine Program, and have obtained very encouraging results. 

VFO works well in gas turbines. In a nine-month test program, the combustion properties of VFO were studied in a combustion test module. A gas turbine was also operated on VFO. The tests were conducted to study the combustion characteristics of VFO, the erosive and corrosive effects of VFO, and the operation of a gas turbine on VFO. The combustion tests were conducted on a combustion test module built from a GE Frame 5 combustion can and liner. The gas turbine tests were conducted on a Ford model 707 industrial gas turbine. Both the combustion module and gas turbine were used in the erosion and corrosion evaluation. The combustion tests showed the VFO to match natural gas in flame patterns, temperature profile, and flame color. The operation of the gas turbine revealed that the gas turbine not only operated well on VFO, but its performance was improved. The turbine inlet temperature was lower at a given output with VFO than with either natural gas or diesel fuel. This phenomenon is due to the increase in exhaust mass flow provided by the addition of steam in the diesel for the vaporization process. Following the tests, a thorough inspection was made of materials in the combustion module and on the gas turbine, which came into contact with the vaporized fuel or with the combustion gas. The inspection revealed no harmful effects on any of the components due to the use of VFO. 

On the basis of an extended experimental program described in Section 4.1.3, Harris and Wickens (1989) concluded that overpressure effects produced by vapor cloud explosions are largely determined by the combustion which develops only in the congested/obstructed areas in the cloud. For natural gas, these conclusions were used to develop an improved TNT-equivalency method for the prediction of vapor cloud explosion blast. This approach is no longer based on the entire mass of flammable material released, but on the mass of material that can be contained in stoichiometric proportions in any severely congested region of the cloud. 

The major objective of the experimental program was to obtain data that could be used to assess the accuracy of existing models for vapor cloud dispersion. The combustion experiments were designed to complement this objective by providing answers to the question, What would happen if such a cloud ignited ... 

Zeeuwen et al. (1983) observed the atmospheric dispersion and combustion of large spills of propane (1000-4000 kg) in open and level terrain on the Musselbanks, located on the south bank of the Westerscheldt estuary in The Netherlands. Thermal radiation effects were not measured because the main objective of this experimental program was to investigate blast effects from vapor cloud explosions. 

Combustion modifications and postcombustion processes are the two major compliance options for NO., emissions available to utilities using coal-fircd boilers. Combustion modifications include low-NO burners (LNBs), overfire air (OFA), reburning, flue gas recirculation (FGR), and operational modifications. Postcombustion processes include selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). The CCT program has demonstrated innovative technologies in both of these major categories. Combustion modifications offer a less-expensive appiroach. 

The greatest success in new fossil fuel technology has a distant government-aid basis. The combustion turbine is a stationaiy adaptation of the jet engine. The combustion turbine s development and improvement were aided by government militaiy aircraft programs. However, turbine manufacturers independently developed the electric-power version. 

Apart from the provision of various permutations of (chemical-based) boiler water programs, it is common to find water treatment companies supplying value adding chemicals and services in other boiler plant-related areas where their expertise in applied chemical technology can deliver additional economic benefit. Such areas typically include cleaning services for boiler waterside and fireside and the provision of fuel treatments and combustion additives, dust suppressants (for coal and ash handling), acids, and cleaner products. 

In the combustion area, heavy slag and ash may form, preventing the passage of flue gas and blinding tubes. Locations should be precisely noted to provide fireside adjustments or to implement a fuel treatment program. In coal-fired boilers, drums, tubes, and headers should be inspected for abrasion from clinker and fly ash. 

Typically, online cleaning must be carried out fairly slowly and carefully, so that the programs may take 3 to 6 months, perhaps longer, before particularly satisfactory results are achieved. If the boiler is particularly dirty before an online clean is considered necessary, then the combustion efficiency will be lower than desirable. It consequently will take some time before this reduced efficiency improves significantly, and therefore there is an additional fuel cost that must be considered, as well as the cost of the online cleaning program. 

SNCR programs typically employing liquid additive formulations based on urea (carbamide, NH2CONH2), together with stabilizers and modifiers, are particularly useful. The additive is sprayed into the combustion area, after the burner. The use of such additives reduces the NOx level by between 50 and 90% by converting NOx into harmless nitrogen and water. 

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