Steam temperature

Different plant operating conditions (steady load, load variations, startups / shutdowns) have been encountered during the monitoring period. Electrical load, steam pressure and steam temperature values vs time have been acquired and stored during the entire period. At the same time, the RMS values of the acoustical background noise were have been continuously checked and stored, thus providing a quick check of proper instrumentation condition and a correlation between variations of plant parameters and the acoustical behaviour of the components. 

Assessments of control, operabiHty and part load performance of MHD—steam plants are discussed elsewhere (rl44 and rl45). Analyses have shown that relatively high plant efficiency can be maintained at part load, by reduction of fuel input, mass flow, and MHD combustor pressure. In order to achieve efficient part load operation the steam temperature to the turbine must be maintained. This is accompHshed by the use of flue gas recirculation in the heat recovery furnace at load conditions less than about 75% of fiiU load. 

Thermal stabihty of the foaming agent in the presence of high temperature steam is essential. Alkylaromatic sulfonates possess superior chemical stabihty at elevated temperatures (205,206). However, alpha-olefin sulfonates have sufficient chemical stabihty to justify their use at steam temperatures characteristic of most U.S. steamflood operations. Decomposition is a desulfonation process which is first order in both surfactant and acid concentrations (206). Because acid is generated in the decomposition, the process is autocatalytic. However, reservoir rock has a substantial buffering effect. 

Some indicators can determine whether a specific temperature has been achieved. Because the entrapment of large amounts of air can result in the lowering of steam temperatures, these indicators react to some critical defect in sterilization conditions. Eor each different temperature, a different indicator must be used. 

Steam can be contaminated with soHds even when carryover is not occurring. Contaminated spray attemperating water, used to control superheated steam temperature at the turbine inlet, can introduce soHds into steam. A heat exchanger coil may be placed in the boiler mud dmm to provide attemperation of the superheated steam. Because the mud dmm is at a higher pressure than superheated steam, contamination will occur if leaks develop in the cod. 

Resin Cure. Resin cure systems yield carbon—carbon cross-links and, consequendy, thermally stable materials. Butyl mbber vulcanised with resins are used as tire-curing bladders, and have a life of 300—700 curing cycles at steam temperature of 175°C at about 20 m/cycle. 

Apphcations requiring accurate temperature control are generally limited to electric tracing. For example chocolate lines cannot be exposed to steam temperatures or the product will degrade and if caustic soda is heated ove 150°F it becomes extremely corrosive to carbon steel pipes. 

The heat-transfer performance capacity of cylinder diyers is not easy to estimate without a knowledge of the sheet tenmerature, which, in turn, is difficult to predict. According to published data, steam temperature is the largest single factor affecting capacity. Overall evaporation rates based on the total surface area of the diyers cover a range of 3.4 to 23 kg water/(h m ) [0.7 to 4.8 lb water/(h fF)]. 

Screw conveyor and mdii ect rotaiy. Indirect type, continuous operation Applicable with dry-product recirculation Appbcable with dry-product recirculation Generally requires recirculation of dry product. Little dusting occurs Chief advantage is low dust loss. Web suited to most materials and capacities, particularly those requiring drying at steam temperature Low dust loss. Material must not stick or be temperature-sensitive Not applicable Not appbcable Not appbcable... 

Indirect. steam-tube dryer This is a bare metal cylinder provided with one or more rows of metal tubes installed longitudinally in the shell. It is suitable for operation up to available steam temperatures or in processes requiring water cooling of the tubes. 

For best operation, the feed rate to rotating equipment should be closely controlled and uniform in quantity ana quality. Because sohds temperatures are difficult to measure and changes slowly detected, most rotating-equipment operations are controlled by indirect means. Inlet and exit gas temperatures are measured and controlled on direct-heat units such as direct dryers and kilns, steam temperature and pressure and exit-gas temperature and humidity are controlled on steam-tube units, and direct shell temperature measurements are taken on indirect calciners. Product temperature measurements are taken for secondaiy control purposes only in most instances. 

Heat-transfer coefficients in steam-tube dryers range from 30 to 85 J/(m s K). Coefficients will increasewith increasing steam temperature because of increased heat transfer by radiation. In units carrying saturated steam at 420 to 450 K, the heat flux UAT will range from 6300 J/(m s) for difficult-to-diy and organic solids and to 1890 to 3790 J/(m s) for finely divided inorganic materials. The effect of steam pressure on heat-transfer rates up to 8.6 X 10 Pa is illustrated in Fig. 12-71. 

Satisfactory performance is obtained with tubes having helical ribs on the inside surface, which generate a swirling flow. The resulting centrifugal action forces the water droplets toward the inner tube surface and prevents the formation of a steam film. The internally rifled tube maintains nucleate boiling at much higher steam temperature and pressure and with much lower mass velocities than those needed in smooth tubes. In modern practice, the most important criterion in drum boilers is the prevention of conditions that lead to DNB. 

Economizers Economizers improve boiler efficiency by extracting heat from the discharged flue gases and transferring it to feedwater, which enters the steam generator at a temperature appreciably lower than the saturation-steam temperature. 

Increasing the steam temperature at a given steam pressure lowers the steam output of the steam turbine slightly. This occurs because of two contradictory effects first the increase in enthalpy drop, which increases the output and second the decrease in flow, which causes a loss in steam turbine output. The second effect is more predominant, which accounts for the lower steam turbine amount. Lowering the temperature of the steam also increases the moisture content. 

Applieations requiring aeeurate temperature eontrol are generally limited to eleetrie traeing. For example, ehoeolate lines eannot be exposed to steam temperatures or the produet will degrade, and if eaustie soda is heated above 150°F (66 °C), it beeomes extremely eorrosive to earbon steel pipes. 

Steam pressure available at the ejector, psig, Steam temperature at the ejector, F. ... 

As steam temperatures increase, more expensive materials must be used to manufacture the turbine. Above 750" F, the price increase will be about 5% to about 850°F. Another 5% will be added for temperatures between 850°F and 900°F, and another 5% for temperatures above 900°F Steam turbine designers have selected as a standard for single-stage turbines a limit of 600 psia and 750°F maximum inlet steam conditions. 

Steam turbine, 53, 146, 282-92, 179 back pressure, 282 blade deposits, 479 condensing, 282 efficiency, 288 extraction, 282 induction-type, 282 paitial admission, 288 rating, 290 reliability, 478 selecuon variable, 275, 285 speed, 278 stage losses, 286 steam temperatures, 284 steam velocity, 288 trip and throttle valve. 479 Step unloading system, 80 Stiffness coefficients, 385 Stodola slip, 153, 155 Stonewall, 186 Straight labyrinth. seal leakage, 532... 

The exhaust gases from a gas turbine contain substantial amounts of excess air, since the main combustion process has to be diluted to reduce the combustion temperature to well below that which could be obtained in stoichiometric combustion, because of the metallurgical limits on the gas turbine operating temperature. This excess air enables supplementary firing of the exhaust to take place and higher steam temperatures may then be obtained in the HRSG. 

With the gas temperature at turbine exit known (T ), the top temperature in the steam cycle (T ) is then obtained from (a). It is assumed that this is less than the prescribed maximum steam temperature. 

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