Boilers superheating steam from

Each steam generator was of single-wall tube-in-shell design. The evaporators were of the forced-circulation type, with each of the three circuits having a steam drum and a boiler circulating pump. Superheated steam from the three circuits flowed to a common header to drive a 300MW turbo-alternator. The main feed was via a 100% duty steam-driven pump with... 

The output from the turbine might be superheated or partially condensed, as is the case in Fig. 6.32. If the exhaust steam is to be used for process heating, ideally it should be close to saturated conditions. If the exhaust steam is significantly superheated, it can be desuperheated by direct injection of boiler feedwater, which vaporizes and cools the steam. However, if saturated steam is fed to a steam main, with significant potential for heat losses from the main, then it is desirable to retain some superheat rather than desuperheat the steam to saturated conditions. If saturated steam is fed to the main, then heat losses will cause excessive condensation in the main, which is not desirable. On the other hand, if the exhaust steam from the turbine is partially condensed, the condensate is separated and the steam used for heating. 

The Combined (Brayton-Rankine) Cycle The 1990s has seen the rebirth of the combined cycle, the combination of gas turbine technologies with the steam turbine. This has been a major shift for the utility industry, which was heavily steam-tnrbine-oriented with the use of the gas turbine for peaking power. In this combined cycle, the hot gases from the turbine exhaust are used in a heat recoveiy steam generator or in some cases in a snpplementaiy fired boiler to produce superheated steam. 

When restarting an installation that is still moderately hot, diffieulty is often experieneed during the initial phase due to the use of saturated steam (from the auxiliary boiler), whieh is eooler than the superheated steam raised by ammonia eombustion. Consequently, a sturdy steam turbine must be ehosen, eapable of withstanding the thermal stresses imposed. 

The boiler steam-water circulation system is designed to promote the delivery of steam from the various generating tubes to the boiler steam drum (top drum). From here the steam is separated from the BW and transferred to the steam delivery system for possible superheating and subsequent use in a turbine generator or other downstream process application. 

Ensuring superheated steam quality and purity is clearly essential where it is employed in prime movers (steam turbines) to prevent downstream units from corrosion and physical damage. For example, where coil boilers are employed to drive steam turbines, it should be noted that the steam produced at the coil exit may have between 10 and 30% wetness, and therefore the steam generally is passed through a separator and perhaps a superheater. 

To complete the broad picture of what is meant by burn-out, it is useful to consider further the particular burn-out condition which produces tolerable wall temperatures. Such a condition must occur, for example, in any practical, once-through boiler system, where a change from, for example, liquid water at inlet to superheated steam at outlet takes place in a single heated channel. Normal operation of nuclear reactors beyond burn-out has also been contemplated, and Collier et al. (C5) have described successful experiments with irradiated Zircaloy-clad rods operating continuously beyond burn-out... 

If the temperature of dry saturated steam is increased, then, in the absence of entrained moisture, the relative humidity or degree of saturation is reduced and the steam becomes superheated (Fig. 20.5). During sterilization this can arise in a number ofways, for example by overheating the steamjacket (see section 4.2.2), by using too dry a steam supply, by excessive pressure reduction during passage of steam from the boiler to the sterilizer chamber, and by evolution of heat of hydration when steaming... 

Water enters the pump at state 1 as a low-pressure saturated liquid to avoid the cavitation problem and exits at state 2 as a high-pressure compressed liquid. The heat supplied in the boiler raises the water from the compressed liquid at state 2 to saturated liquid to saturated vapor and to a much higher temperature superheated vapor at state 3. The superheated vapor at state 3 enters the turbine where it expands to state 4. The superheating moves the isentropic expansion process to the right on the T-s diagram as shown in Fig. 2.5, thus preventing a high moisture content of the steam as it exits the turbine at state 4 as a saturated mixture. The exhaust steam from the turbine enters the condenser at state 4 and is condensed at constant pressure to state 1 as saturated liquid. 

For volume production of an aerosol fog of small particle size, on a large scale (suited to indoor use), the thermal aerosol fog generators appear to be very efficient. The Science Service experiments were mostly with this type. Two principal varieties have been developed. One discharges the insecticide solution or suspension as a relatively coarse spray into a jet of superheated steam delivered by a flash boiler of the tubular coil t3rpe. The other discharges that insecticide solution or suspension as a relatively coarse spray into a blast of hot gas emerging from a combustion chamber. The temperature is regulated by the controlled admixture of cold air. 

The heat released from combustion of the fuel is transferred by radiation and convection to evaporate water and create superheated steam, which is then used to create electricity in a steam turbine. Steam temperatures in state-of-the-art coal-fired boilers are pushing close to 600°C (i.e. above the critical point of water) with net electricity production reaching 45% of the thermal energy of the burned fuel [43]. Modem subcritical boilers are closer to 39% net efficiency in electricity production, but older boilers can have efficiencies as low as 30% on a lower-heating-value basis. 

A hot exhaust gas is heating a boiler to produce superheated steam at 100 psia and 400°F. In the meantime, the exhaust gas is cooled from 2500 to 350°F. Saturated liquid water (stream 1) at 14.7 psia enters the boiler with a flow rate of 200 lb/h. Superheated steam (stream 2) is used in a turbine, and discharged as saturated steam (stream 3) at 14.7 psia. Determine ... 

In the preliminary design of a furnace for industrial boiler, methane at 25 C is burned completely with 20% excess air, also at 25°C The feed rate of methane is 450 kmol/h. The hot combustion gases leave the furnace at 300°C and are discharged to the atmosphere. The heat transferred from the furnace (Q) used to convert boiler feedwater at 25°C into superheated steam at 17 bar and 250 C. 

Water at 250 psia and 70°F enters a boiler, where it is converted to superheated steam at 250 psi absolute and 700°F. The superheated steam passes through an adiabatic turbine and emerges at a pressure of 15 psi gauge, 98% quality (i.e., 98% vapor). The exit wet steam is then condensed and subcooied to 100°F at a constant pressure of 15 psi gauge by heating air from 60°F to 200°F. 

In continuous steam distillation, an insulated conveying system with superheated steam as carrier is used for providing a countercurrent flow of steam and pulverised plant material. During transport, the oil is transferred into the vapour phase and exits the system with the steam. A cyclonic vessel separates the gas phase from the solid phase. In the last step the gas phase (steam and oil) is condensed, the oil is separated using a Florentine flask and the water recycled to the boiler [27]. 

At BASF, flammable solid, pastelike, and liquid residues are combusted in eight furnaces. Each combustion unit consists of a rotary kiln with afterburner chamber and a steam boiler. The superheated 18-bar steam from units 1 to 6 is fed into the BASF plant network. In units 7 and 8, a higher-value steam is generated with an efficiency of ca. 74 % and supplied to a back-pressure turbine, where it is expanded from 43 bar to 5 bar. To utilize the heat of the flue gases between 300 C and 180 C, a waste-heat boiler was installed to raise 5-bar steam. Electric power and 5-bar steam are fed into the respective plant systems (Fig. 113). 

Balajka, 1983, estimated the corrosion process in the oil-fired boiler in the Vojany power plant by studying the composition of deposits and the tube deposit interface from the very beginning of the oil-fired boiler operation. The steam boilers produced the (530°C-540°C) superheated steam. The burned heavy fuel oil had the following content of main inorganic substances S, 2%-3% V, 50-150 ppm and Na, 30-100 ppm. Table 3.5 represents the results of the deposit layer composition analysis, as obtained during the first period of operation. The probes obtained represent the bulk... 

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