Economizers boiler thermal efficiency

Economizers improve boiler thermal efficiency by recovering heat from the combustion flue gases exhausted from the steam boiler section. The recovered heat is used to heat colder streams (heat sinks), before ultimate discharge of the waste gas to atmosphere. This recovered heat displaces the need to bum additional fuel to heat these same streams. 

Boiler Thermal Efficiency Traditionally, boiler thermal efficiency is calculated pour/pm, where in is the LHV (lower heating value) of the fuel. A rule of thumb for economizers is that boiler efficiency increases by 1 percent for every 22°C (40°F) drop in temperature of the dry flue gas. These two statements do not reveal the considerable quantity of additional heat, available to be recovered through condensation of the water vapor in the flue gas, which is lost to atmosphere with hot flue gas. Based on fuel HHV (higher heating value), the total latent heat loss can be substantial an additional 9.6 percent (natural gas), 8.0 percent (propane), 6.5 percent (heating ou). 

Most plants have boilers producing steam for space heating many need steam for other purposes as well. Boiler water requirements for boilers have changed radically over recent years. The old Lancashire and Economic boilers had large heating surfaces and low heat transfer rates scale deposits would do no more harm than reduce their thermal efficiency. 

One of several different types of heater used to raise the FW temperature so as to avoid boiler thermal shock and gain improved efficiency and economic benefit. 

Another boiler performance parameter is "thermal efficiency." Thermal efficiency characterizes the heat exchange effectiveness and measures the ability of the heat exchanger(s) to transfer heat from the combustion product to the water or steam in the boiler. However, thermal efficiency does not account for radiation and convection losses due to boiler body design specifics or other components, so it cannot be considered a true boiler efficiency for economic evaluations. 

Depending upon the source of the cmde oil, the refining process, and the fuel grade, varying amounts of sulfur may be present in different types of fuel oils. Combustion of the sulfur containing fuel oils produces sulfur oxides, which pollute the atmosphere and cause corrosion problems in boiler equipment. They may form sodium and vanadium complexes, and such deposits on external surfaces of superheater tubes, economizers, and air heaters cause equipment corrosion and loss of thermal efficiency. 

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