Boilers preheating boiler water

Economizers are heat transfer tube bundles that preheat MU water or FW flowing within the tubes by extracting waste heat from the flue gas during its exit path to the stack. They typically account for approximately 10% of the total boiler heat transfer surfaces, while absorbing only 7% of the total heat generated in the boiler system. 

A third option is to use circulating boiler water to preheat the air. If the steam already includes circulating pumps, the existing pump system may not need to be expanded. The last two options have the added advantage of reducing the steam make, which unloads the steam drum86. 

The heat of reaction generates 1) process steam in the reactor and 2) 5.5 bar pure steam. The process steam is used to preheat boiler feed water and nitric acid as well as operate the falling film evaporator. The pure steam is fed to the plant steam header295. 

The third HTS reactor will deliver product gas containing about 2.8% vol CO (on dry gas) to the low-temperature shift (LTS) section. Heat recovered from the LTS effluent is used to raise 90 psig steam and to preheat boiler feed water. 

Fire 1.4. Steam boiler and furnace arrangements. [Steam, Babcock and Wilcox, Barberton, OH, 1972, pp. 3.14, 12.2 (Fig. 2), and 25.7 (Fig. 5)]. (a) Natural circulation of water in a two-drum boiler. Upper drum is for steam disengagement the lower one for accumulation and eventual blowdown of sediment, (b) A two-drum boiler. Preheat tubes along the Roor and walls are cormected to heaters that feed into the upper drum, (c) Cross section of a Stirling-type steam boiler with provisions for superheating, air preheating, and flue gas economizing for maximum production of 550,000 Ib/hr of steam at 1575 psia and 900°F. 

Cold waler enters a steam generator at 20°C and leaves as saturated steam at the boiler pressure. At what pressure vill the amount of heat needed to preheat the water to saturation... 

The economizer utilizes the remaining waste heat to preheat boiler feed water water treatment chemicals... 

A conventional typical convection section often has tube bundles for fuel gas or air preheat, feed preheat, boiler feed water preheat, steam generation, and steam superheating. In the convection section, the heat transfer is mainly gas-to-gas heat transfer and the overall heat-transfer coefficients are relatively low. Finned tubes are generally used to improve heat-transfer rates. Material for the convection section tubes varies from carbon steel to a high temperature alloy. Sometimes, high-alloy tubes are positioned in the lower section... 

Any heat still remaining in the exit gases from the boiler may be used to preheat feed water by passing the gases through similarly packed tubes immersed in the water. 

For steam generation preheat boiler feed water with available low temperature process streams, maximize the use of heat transfer surfaces by optimizing sootblowing frequency and decoking of tubes, flash blowdown to produce low pressure steam if required. 

Flue gases exit from boilers at a temperature higher than saturation temperature of the steam corresponding to the working pressure of steam. Economisers are used to further recover heat from these hot flue/process gases for preheating feed water before entering the boiler. 

The conventional economiser is used to further recover heat from hot flue/process gases after they exit from boilers. The feed water is passed through the economiser for preheating and then fed in to the boiler. A large amount of hot water is frequently generated since the heat recovered is taken up as sensible heat of the water. If the existing boiler(s) are not able to evaporate the water, the excess hot water is wasted... 

Demineralization of boiler water with calcium under optimum conditions can reduce the silica level to 0.4 ppm, according to Sramik (257). This involves preheat ing the water to 80 C, adding lime, filtering, saturating with CO, but not below pH 9, and refiltering. The recovered CaCO is chemically pure. The nature of the deposits on turbine blades and effect on efficiency have been discussed by Kot and Lobanov (258). 

The release of waste heat must be adjusted to various temperature levels as required by the steam generation, so that matching amounts of heat are available for preheating boiler feed water, steam generation, and steam superheating. 

Taking the heat capacity of water to be 4.3 kJ kg K , heat duty on boiler feedwater preheating is... 

Acid cleaners based on sulfamic acid are used in a large variety of appHcations, eg, air-conditioning systems marine equipment, including salt water stills wells (water, oil, and gas) household equipment, eg, copper-ware, steam irons, humidifiers, dishwashers, toilet bowls, and brick and other masonry tartar removal of false teeth (50) dairy equipment, eg, pasteurizers, evaporators, preheaters, and storage tanks industrial boilers, condensers, heat exchangers, and preheaters food-processing equipment brewery equipment (see Beer) sugar evaporators and paper-mill equipment (see also Evaporation Metal surface treati nts Pulp). 

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