Waste Heat Boiler Research Engineering Essay

macerate passion kettleful Research Engineering EssayIncorporates a boiler economiser, incorporates the chase away combust from the boilers hot plenty and transfers this wipe out genus Oestrus to the boilers feed water. The boiler feed water will then be hotter and therefore requires slight conflagrate vitality to boil it afterA boiler economizer is a device that reduces the boilersuit fuel requirements a boiler requires which results in reduced fuel costs as well as fewer emissions since the boiler now pursues at a some(prenominal) higher efficiency. Boiler economizers rec in all over the abscond instigate from the boilers hot stack feature from transfers this bumble stir up to the boilers feed-water. Because the boiler feed-water is now at a higher temperature that it would have been without a boiler economizer, the boiler does not need to provide as much additional heating to produce thesteam requirements of a facility or process, thereby apply slight fuel an d reducing the fuel expenses. Boiler economizers also help improve a boilers efficiency by extracting heat from the flue bumblees discharged from the final super-heater section of a radiant/reheat unit or the evaporative bank of a non-reheat boiler. alter is transferred, again, back to the boiler feed-water, which enters at a much let down temperature than saturated steam.Boiler Economizers are a series of horizontal tubular elements and can be characterized as bare tube and extended surface graphic symbols. The bare tube includes varying sizes which can be logical to form h ambiancepin or multi-loop elements. Tubing forming the heating surface is generally made from baseborn-carbon steel. Because steel is subject to wearing away in the presence of even low concentrations of oxygen, water must be practically 100 pct oxygen free. In central stations and other round plants it is common to use deaerators for oxygen removal.* Waste Heat RecoveryMany industrial processes generate large amounts of fellate get-up-and-go that simply swirl out of plant stacks and into the atmosphere or are otherwise lost. Most industrial violent heat streams are liquid, gaseous, or a combination of the two and have temperatures from slightly above ambient to over 2000 degrees F. Stack obliterate losses are inherent in all fuel-fired processes and increase with the exhaust temperature and the amount of excess air the exhaust contains. At stack gas temperatures enceinteer than 1000 degrees F, the heat going up the stack is likely to be the single biggest loss in the process. Above 1800 degrees F, stack losses will consume at least half of the total fuel input to the process. Yet, the capacity that is recovered from waste heat streams could displace part or all of the energy input necessitate for a unit operation within a plant. Therefore, waste heat recuperation offers a great opportunity to productively use this energy, reducing overall plant energy consumption and gree nhouse gas emissions.Waste heat recovery methods utilize with industrial process heating operations intercept the waste gases before they leave the process, extract some of the heat they contain, and recycle that heat back to the process.Common methods of acquire heat include direct heat recovery to the process, recuperators/regenerators, and waste heat boilers. Unfortunately, the economic benefits of waste heat recovery do not justify the cost of these systems in every application. For example, heat recovery from write down temperature waste streams (e.g., hot water or low-temperature flue gas) is thermodynamically limited. Equipment fouling, occurring during the handling of squalid waste streams, is another(prenominal) barrier to more widespread use of heat recovery systems. Innovative, affordable waste heat recovery methods that are ultra-efficient, are applicable to low-temperature streams, or are suitable for use with corrosive or dirty wastes could expand the number of via ble applications of waste heat recovery, as well as improve the surgical process of existing applications.Various Methods for Recovery of Waste HeatLow-Temperature Waste Heat Recovery Methods A large amount of energy in the form of medium- to low-temperature gases or low-temperature liquids (less than about 250 degrees F) is released from process heating equipment, and much of this energy is wasted.Conversion of Low Temperature Exhaust Waste Heat making efficient use of the low temperature waste heat generated by prime movers such as micro-turbines, IC engines, fuel cells and other electricity producing technologies. The energy content of the waste heat must be high enough to be able to operate equipment found in cogeneration and trigeneration tycoon and energy systems such as absorption chillers, refrigeration applications, heat amplifiers, dehumidifiers, heat pumps for hot water, turbine inlet air chilling and other similar devices.Conversion of Low Temperature Waste Heat int o Power -The steam-Rankine cycle is the principle method used for producing electric power from high temperature fluid streams. For the renewing of low temperature heat into power, the steam-Rankine cycle whitethorn be a possibility, along with other known power cycles, such as the organic-Rankine cycle.Small to Medium Air-Cooled Commercial Chillers All existing commercial chillers, whether using waste heat, steam or natural gas, are water-cooled (i.e., they must be connected to cooling towers which evaporate water into the atmosphere to aid in cooling). This requirement generally limits the market to large commercial-sized units (150 slews or larger), because of the maintenance requirements for the cooling towers. Additionally, such units consume water for cooling, limiting their application in desiccate regions of the U.S. No suitable small-to-medium size (15 tons to 200 tons) air-cooled absorption chillers are commercially procurable for these U.S. climates. A small number o f prototype air-cooled absorption chillers have been developed in Japan, still they use hardware technology that is not meet to the hotter temperatures experienced in most locations in the unify States. Although developed to work with natural gas firing, these prototype air-cooled absorption chillers would also be suited to use waste heat as the fuel.Recovery of Waste Heat in Cogeneration and Trigeneration Power PlantsIn most cogeneration and trigeneration power and energy systems, the exhaust gas from the electric generation equipment is ducted to a heat money changer to recover the thermal energy in the gas. These heat exchangers are air-to-water heat exchangers, where the exhaust gas flows over some form of tube and fin heat exchange surface and the heat from the exhaust gas is transferred to make hot water or steam. The hot water or steam is then used to provide hot water or steam heating and/or to operate thermally activated equipment, such as an absorption chiller for cool ing or a desiccant dehumidifer for dehumidification.Many of the waste heat recovery technologies used in building co/trigeneration systems require hot water, some at moderate pressures of 15 to 150 psig. In the cases where additional steam or pressurized hot water is needed, it may be necessary to provide supplemental heat to the exhaust gas with a duct burner.In some applications air-to-air heat exchangers can be used. In other instances, if the emissions from the generation equipment are low enough, such as is with many of the microturbine technologies, the hot exhaust gases can be mixed with make-up air and vented directly into the heating system for building heating.In the majority of installations, a flapper damper or diverter is employed to vary flow across the heat transfer surfaces of the heat exchanger to maintain a specific design temperature of the hot water or steam generation rate.Typical Waste Heat Recovery Installationhttp//www.bchp.org/images/2-3-3HeatRecovery.gifIn some co/trigeneration designs, the exhaust gases can be used to activate a thermal wheel or a desiccant dehumidifier. Thermal wheels use the exhaust gas to heat a wheel with a medium that absorbs the heat and then transfers the heat when the wheel is rotated into the ledger entry airflow.A professional engineer should be involved in designing and sizing of the waste heat recovery section. For a proper and economical operation, the design of the heat recovery section involves consideration of many related factors, such as the thermal capacity of the exhaust gases, the exhaust flow rate, the sizing and type of heat exchanger, and the desired parameters over a various range of operating conditions of the co/trigeneration system all of which need to be considered for proper and economical operation.