Effect of Superheated Steam

A few degrees of superheat are recommended (5-15°F), but if superheated steam is to be used, its effect must be considered in the ejector design. A high degree of superheat is of no advantage because the increase in available energy is offset by the decrease in steam density [16], 

The suction pressure of an ejector is expressed in absolute units. If it is given as inches of vacuum it must be converted to absolute units by using the local or reference barometer. The suction pressure follows the ejector capacity curve, varying with the non-condensable and vapor load to the unit. 

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The effect of superheated steam may be illustrated by reference to baizaldehyde, which boils at 178° at 760 mm. It distils with steam at 97-9° (Pj = 703-5 mm. and pg = 56-5 mm.) and the distillate contains 32-1 per cent, of benzaldehyde by weight. If one employs steam superheated to 133°, the vapour pressure of benzaldehyde (extrapolated from the boUing point - pressure curve) is 220 mm. hence pj = 540 (water), Pg = 220 (benzaldehyde), and... 

Development in Palm Oil Deodorization. The main operation in the deodorizer is the stripping of volatile materials and thermal action due to the combined effects of superheated steam, high temperature, and efficient vacuum. The older deodorizers (prior to 1985) use bubble caps or sieve-tray designs to effect the... 

David, M., 1987, Exploratory study of effect of superheated steam drying on properties of paper, ME thesis, McGill University, Montreal, Quebec, Canada, 1988. 

Effect of superheated steam on the decomposition of CaCOa and MnCOa Fig. 2 shows the X-ray dififiaction patterns of the products obtained from CaCOs heated for Ih under siq)erhealed steam. The product obtained at 800 °C was identified as single phase of CaO. CaCOs was completely decomposed under superheated steam. At 750 °C, Ca(OH)2 was formed with a small amount of CaCOa under superheated steam. And under 730 °C, CaCOs was not decomposed. In addition, the decomposition of CaCOa hardly occurs in air and in Ar at 750 °C. Single phase of CaO was obtained above 800 °C in air. 

Partly filled bottles should have their caps firmly screwed on. The steam generated within the bottle will effectively sterilise the contents but changes in volume will be prevented. It is such bottles which create the hazard in autoclaves if the temperature and pressure outside the bottle is allowed to fall suddenly. This will happen if the autoclave door is opened prematurely leaving the bottle itself full of superheated steam. 

Steam enters the turbine of a power plant operating on the Rankine cycle (Fig. 8.3) at 3,500 kPa and exhausts at 20 kPa. To show the effect of superheating on the performance of the cycle, calculate the thermal efficiency of the cycle and the quality of the exhaust steam from the turbine for turbine-inlet... 

Figure 4.18. The effects of superheating the steam to higher temperatures and reducing the condenser pressure on the ideal...

Another property of superheated steam which in chemical operations should prove valuable, but which up to the present has not been utilised to the extent which it deserves, is that of yielding in proportion to its effectiveness less water on condensation than saturated steam. If, as is often the case in chemical operations, we use live steam for heating up a liquid either to its boiling point or to a point below it, the bulk of the liquid at the end of the operation will increase by the amount of steam which becomes condensed naturally this amount will be less when we use superheated than when saturated steam is employed. 

The above experimetH showed that a heat front can be created and then displaced through the oil-bearing formation alternating the injection of superheated steam and of cold water. Such a technique can be effective under specifrc and rather uncomplicated geological conditions. In this process, the point of temperature maximum should always be kept in the middle of the bed thickness. This requirement can be met by properly restricting the volume of cold water being pumped inm the injection well. 

It is impossible to generalize the effect of steam drying on product quality. Table 20.2 gives a summary of tests carried out at McGill University on batch drying of hand-sheets in a static apparatus in which the samples were dried under an impingement flow of superheated steam. Note that the effects are all positive relative to air drying or, at most, comparable. In Finland, similar tests on paper dried on a dynamic pilot-scale apparatus have yielded comparable results. 

Biofuels and peat can be dried according to different thermodynamic principles. The most common method is the use of flue gases. Another is the use of superheated steam. Finally, double-effect drying will be discussed. 

Dryer steam should be free of superheat. Although the condensate inside the dryer desuperheats the steam, a separate desuperheater is used in some cases. The effect of superheating above 100°C is controversial. 

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