Feedwater Heater
A feedwater heater is a device used in power plants to preheat water before it enters the boiler. This helps to improve the overall efficiency of the power plant by reducing the amount of fuel needed to produce steam. The heater typically uses steam extracted from the turbine to heat the feedwater, recovering some of the heat that would otherwise be wasted.
4 Key excerpts on "Feedwater Heater"
eBook - ePub- Babcock & Wilcox Company(Author)
- 2007(Publication Date)
- Perlego(Publisher)
...The time required for the conversion of water into steam is diminished and the steam capacity of the boiler thereby increased. Further, the feeding of cold water into a boiler has a tendency toward the setting up of temperature strains, which are diminished in proportion as the temperature of the feed approaches that of the steam. An important additional advantage of heating feed water is that in certain types of heaters a large portion of the scale forming ingredients are precipitated before entering the boiler, with a consequent saving in cleaning and losses through decreased efficiency and capacity. In general, feed water heaters may be divided into closed heaters, open heaters and economizers; the first two depend for their heat upon exhaust, or in some cases live steam, while the last class utilizes the heat of the waste flue gases to secure the same result. The question of the type of apparatus to be installed is dependent upon the conditions attached to each individual case. In closed heaters the feed water and the exhaust steam do not come into actual contact with each other. Either the steam or the water passes through tubes surrounded by the other medium, as the heater is of the steam-tube or water-tube type. A closed heater is best suited for water free from scale-forming matter, as such matter soon clogs the passages. Cleaning such heaters is costly and the efficiency drops off rapidly as scale forms. A closed heater is not advisable where the engines work intermittently, as is the case with mine hoisting engines. In this class of work the frequent coolings between operating periods and the sudden heatings when operation commences will tend to loosen the tubes or even pull them apart. For this reason, an open heater, or economizer, will give more satisfactory service with intermittently operating apparatus. Open heaters are best suited for waters containing scale-forming matter...
eBook - ePub- DENNIS A SNOW(Author)
- 2001(Publication Date)
- Butterworth-Heinemann(Publisher)
...As steam capacities increase, the feed tank becomes correspondingly larger, and it may be considered that on steam outputs in excess of 20 000 kg/h a duplex treatment plant should be installed in order to keep the feed tank to a reasonable size. In areas where the water demand of the plant may exceed the supply capacity of the local mains it will be necessary to install additional storage tanks. It is likely that if the local supply is subject to low flow rates additional storage is already available for services such as fire protection. Feedwater to the boiler should not be cold, as this can cause harmful thermal stresses to the boiler. A minimum feedwater temperature of 70–80°C should be designed into the system. This increased temperature has the added advantage that it accelerates some water-treatment reactions and also helps to remove oxygen and other gases from the feedwater. Once the system is working, this higher temperature may be achieved from the condense returns, but this condition is not effective until the plant has been running for some time. A tank heating system should therefore be installed. This is best achieved by direct steam injection into the feed tank. Steam is taken from the boiler and reduced in pressure to 1–5 bar to reduce noise in the tank. Passing through a thermostatic control valve, the steam mixes with the water in the tank through a sparge pipe or steam nozzle. With watertube boilers economizers are normally used, therefore the situation of cold feed to the boiler would not apply. However, the feed to the economizer should be treated similarly to that to a boiler to reduce thermal shock. With the feedwater being raised in temperature it is necessary to avoid cavitation at the inlet to the boiler feed pump. One method of reducing this problem is to elevate the feed tank to give an adequate positive head at the pump...
eBook - ePubEnergy Management
Conservation and Audits
- Anil Kumar, Om Prakash, Prashant Singh Chauhan, Samsher Gautam(Authors)
- 2020(Publication Date)
- CRC Press(Publisher)
...8 Thermal Energy Management 8.1 BOILER A boiler is a closed pressure vessel that supplies heat energy in order to increase water’s temperature to the point that it progresses to form steam. The pressurized steam is then used for giving heat energy in several industrial processes. The volume of steam is increased 1600 times approximately when water gets boiled which delivers power practically explosive as close as gunpowder. The high pressure inside the boiler results in an equipment which requires enormous care. A system of boiler is made of three parts: 1. Feedwater system, 2. Steam system, and 3. Fuel system. The feedwater system supplies the boiler with water and controls it consequently to take care of the demand of the steam. Different valves at different places are given for repair and maintenance. The steam system gathers and helps in controlling the steam formed in the boiler. Steam is guided through a channeling framework to the area of utilization. All through the system, the pressure of steam is controlled using valves and checked with pressure gauges at several points. The fuel system incorporates all the necessary materials needed to give fuel to produce the required heat. The machineries needed in the fuel system relies upon the kind of fuel utilized by the system. The measurement of heating surface of the boiler is generally calculated in square meters. Any component of the boiler material that influences in steam generation is the heating surface. The bigger the heating surface of the boiler, the higher will be its ability for steam generation...
- Paul N. Cheremisinoff(Author)
- 2019(Publication Date)
- Routledge(Publisher)
...14 Steam Production and Cooling Tower Water Treatment INTRODUCTION The objectives of modern boiler water treatment are to maintain the integrity and performance of steam boiler components. Although proper water treatment practices alone can not assure meeting these goals, the lack of proper water treatment will assure that they will not be obtained. There has been an increasing worldwide awareness that industrial growth and energy production from fossil fuels are accompanied by the release of potentially harmful pollutants into the environment. In addition to the obvious air pollution associated with steam generation, water pollution can take the form as a secondary pollutant by-product of, for example, an air-cleaning operation, a thermal pollution caused by condensing steam, blowdown, or fuel-handling runoff. STEAM-GENERATING SYSTEMS Before considering the specifics of boiler water treatment, it is helpful to focus briefly on the functional components of a typical steam-generating system and explain the importance of a water-treatment system on performance and maintenance requirements. Boiler feedwater, regardless of the type and extent of external treatment, may contain contaminants that can cause deposits, corrosion, and carryover. Deposits directly reduce heat transfer, causing higher fuel consumption, high metal temperatures and eventual material failures. Deposits, although most serious in the boiler, may also cause problems in the preboiler or after-boiler systems. Corrosion not only results in component failure but also produces serious levels of metal oxide contamination which may deposit elsewhere. As in most water-handling systems, the problems of deposit formation and corrosion are so closely related that both must be jointly corrected or prevented in order to achieve satisfactory results. Carryover results in superheater, turbine, and condensate system deposits and corrosion and/or erosion problems...
