Combustion control

W. R. Seeker, W. S. Lanier, and M. P. Heap, Municipal Waste Combustion Study Combustion Control of MSW Combustors to Minimi Emissions of Trace Organics, EER Corporation, Irvine, Calif., 1987. 

Combustion. The burning of soHd, Hquid, and gaseous fuels as a source of energy is very common. Using sufficient and reHable combustion controls, this process seldom causes serious problems. However, some combustion processes are deHberately carried out with an inadequate oxygen supply in order to obtain products of incomplete combustion. Explosive mixtures sometimes occur, and then flashback is a serious problem. 

Wet-Throwaway Processes. By 1978, three wet-throwaway systems were in commercial operation lime scmbbing, limestone slurry scmbbing, and dual alkah (1). Time/limestone wet scmbbing (Fig. 11) remains the most common post-combustion control technique appHed to utiHty boilers (67). The waste product from the scmbbers can either be sent to a landfill or be upgraded by oxidation to become saleable gypsum. 

Drying rotary oil- or gas-fired Particulates, SO2, NO, VOC, CO, and smoke Proper combustion controls, fuel-oil preheating where required local exhaust system, cyclone and a scrubber or baghouse... 

Melting Zinc oxide fume, particulates, smoke good combustion controls and slag... 

Pouring Zinc oxide fume, lead oxide fume cover high-zinc-content brass use of good combustion controls, local exhaust system, and baghouse or... 

Recovery furnace HciS, mercaptans, organic sulfides, and Proper combustion controls for... 

Municipal and Single-chamber incinerators Particulates, smoke, volatiles, CO, SO, Afterburner, combustion controls... 

Combustion-Control Equipment Combustion-control equipment can be divided into three types (1) flares, (2) thermal incinerators, (3) catalytic incinerators. 

Opacity reduction is the control of fine particulate matter less than 1 ixm). It can be accomplished through the application of the systems and devices discussed for control of particulate matter and by use of combustion control systems to reduce smoke and aerosol emission. In addition, operational practices such as continuous soot blowing and computerized fuel and air systems should be considered. 

POM emissions appear to be a function of the degree of combustion control, decreasing with increasing incinerator size (larger incinerators are more thoroughly instrumented and controlled). Table 30-1 shows the measured emission rates for POM and CO from various-sized incinerators. 

The controls are important, especially if low-percentage excess air is projected. Provide enough capital in the estimate to include metering type combustion controls, as mentioned earlier, and modern 3-element feedwater makeup controls. Stack oxygen monitoring should also be included. 

Flue gas treatment (FGT) is more effective in reducing NO, emissions than are combustion controls, although at higher cost. FGT is also useful where combustion controls are not applicable. Pollution prevention measures, such as using a high-pressure process in nitric acid plants, is more cost-effective in controlling NO, emissions. FGT technologies have been primarily developed and are most widely used in Japan. The techniques can be classified as selective catalytic reduction, selective noncatalytic reduction, and adsorption. 

Applicability/Limitations Most t qjes of solid, liquid, and gaseous organic waste or a mixture of these wastes can be treated with this technology. Explosive wastes and wastes with high inorganic salt content and/or heavy metals require special evaluation. This operation can create high particulate emissions which require post-combustion control. 

Application The zirconia oxygen sensor is widely used for combustion control processes and for air/fuel ratio regulation in internal combustion engines. The closed-end portion of the electrode tube is inserted into the exhaust gas stream. In the control of industrial combustion processes, no out stack sampling system is required. 

Late cylinder injection is typically used for diesel engines. Fuel is admitted to the cylinder as the piston is nearing top center. Very high injection pressures are required for proper fuel atomization and combustion control. Pressures can exceed 20,000 psi for this type of injection. 

A boiler house enclosed eight large boilers attended by two men. Failure of the combustion air supply shut down one of the boilers. This boiler shutdown created conditions beyond the control of just two men and lack of proper combustion control equipment finally caused seven of the eight boilers to shut down. Amid the confusion caused by low instrument air... 

SEAL SYSTEM CONTROL UNIT COMBUSTION CONTROLS BASEPLATE... 

Combustion controls such as oxygen trim help to maintain optimum operating conditions, especially on gaseous fuels. Instrumentation can give continuous visual and recorded information of selected boiler and plant functions. To be effective, it must be maintained and the data assessed and any required action taken before the information is stored. 

Boiler control systems include combustion controls, superheat steam temperature controls and FW controls. Control systems are used to maintain steam pressure, boiler load, drum water levels, and fuel-air ratios. 

Air pollution from exhaust emissions NO t and particulate matter from exhaust emissions causing air pollution are -1% at present. By adoption of better combustion control technology, better quality fuels (or even fuel cell-based motor vehicles), and more efficient catalytic converters, researchers aim to mitigate this problem. 

Combustion control for domestic hot water production is another important area where modern sensor technology comes in. New developments are discussed in Chapter 3.2. 

Furthermore factors such as stoichiometric value, heat load and design of the burner as well as the combustion chamber have a significant impact on the emission of pollutant gases. Depending on the reaction of a combustion system to a changing equivalence ratio decisions can be made how to minimize the pollutant emissions by adapting the flow rate of air or gas. A combustion control system based on monitoring the CO fraction in the flue gas could thus be considered. 

The use of sensors for surveillance of industrial combustion processes is state of the art. Especially optical sensors detect the existence of a flame. With decreasing furnace performance the amount of installed sensors declines. In residential appliances there are nearly no sensors installed because the costs for both, sensors and actuators, have to be balanced with the technical profit. The efforts for setting up combustion controls are very ambitious but in many cases not successful. First a distinction has to be made between sealed boilers and those that are open towards the room in which they are installed. The resulting controls cannot be interchanged between these two groups of appliances. 

FIS Metal Oxide Lambda Sensor LS-01 for COMBUSTION CONTROLS. Technical In-... 

The aim of this chapter is to give an overview of commercially available gas sensing techniques with a focus put on sensors in the lower price range which are suitable for combustion control. 

The excellent detection ability for flames makes UV sensing a good method for remote fire alarm-monitoring. UV radiation after the outbreak of a fire reaches a sensor much faster than heat or smoke. Also, the distance between sensor and fire is less critical. Requirements for the sensor are high sensitivity and excellent selectivity. Radiation intensities at the sensor position may be even lower and the ambient light conditions less restricted than for combustion controlling. When used outside, solar-blindness is a must. These stringent requirements make UV fire alarm monitors expensive, and they are used in industrial environments such as production floors or warehouses rather than in private homes. 

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