Online calculator with Saturated Steam Table by Pressure. Includes 53 different calculations. Equations displayed for easy reference. What is a Steam Gift? When you purchase a game on Steam, we offer the option to “gift” the item to anyone on your Steam friends list. The recipient will receive the gift as an attractive e-mail card with a personal message from you and instructions to redeem the game. Steam condensing rate is known. In the application section of this Handbook, there are several references to the use of the steam table. Total Heat of Steam (Column 6). The sum of the Heat of the Liquid (Column 4) and Latent Heat (Column 5) in Btu. It is the total heat in steam above 32°F. Specific Volume of Liquid (Column 7).
Superheated steam is steam at a temperature higher than its vaporization point at the absolute pressure where the temperature is measured.
Superheated steam can therefore cool (lose internal energy) by some amount, resulting in a lowering of its temperature without changing state (i.e., condensing) from a gas, to a mixture of saturated vapor and liquid. If unsaturated steam (a mixture which contains both water vapor and liquid water droplets) is heated at constant pressure, its temperature will also remain constant as the vapor quality (think dryness, or percent saturated vapor) increases towards 100%, and becomes dry (i.e., no saturated liquid) saturated steam. Continued heat input will then 'super' heat the dry saturated steam. This will occur if saturated steam contacts a surface with a higher temperature.
Superheated steam and liquid water cannot coexist under thermodynamic equilibrium, as any additional heat simply evaporates more water and the steam will become saturated steam. However this restriction may be violated temporarily in dynamic (non-equilibrium) situations. To produce superheated steam in a power plant or for processes (such as drying paper) the saturated steam drawn from a boiler is passed through a separate heating device (a superheater) which transfers additional heat to the steam by contact or by radiation.
Superheated steam is not suitable for sterilization.[1] This is because the superheated steam is dry. Dry steam must reach much higher temperatures and the materials exposed for a longer time period to have the same effectiveness; or equal F0 kill value. Superheated steam is also not useful for heating, but it has more energy and can do more work than saturated steam, but the heat content is much less useful. This is because superheated steam has the same heat transfer coefficient of air, making it an insulator - a poor conductor of heat. Saturated steam has a much higher wall heat transfer coefficient.[2]
Slightly superheated steam may be used for antimicrobial disinfection of biofilms on hard surfaces.[3]
Superheated steam's greatest value lies in its tremendous internal energy that can be used for kinetic reaction through mechanical expansion against turbine blades and reciprocating pistons, that produces rotary motion of a shaft. The value of superheated steam in these applications is its ability to release tremendous quantities of internal energy yet remain above the condensation temperature of water vapor; at the pressures at which reaction turbines and reciprocating piston engines operate.
Of prime importance in these applications is the fact that water vapor containing entrained liquid droplets is generally incompressible at those pressures. In a reciprocating engine or turbine, if steam doing work cools to a temperature at which liquid droplets form, then the water droplets entrained in the fluid flow will strike the mechanical parts with enough force to bend, crack or fracture them.[4] Superheating and pressure reduction through expansion ensures that the steam flow remains as a compressible gas throughout its passage through a turbine or an engine, preventing damage of the internal moving parts.
Saturated steam[edit]
Saturated steam is steam that is in equilibrium with heated water at the same pressure, i.e., it has not been heated above the boiling point for its pressure. This is in contrast to superheated steam, in which the steam (vapor) has been separated from the water droplets then additional heat has been added.
These condensation droplets are a cause of damage to steam turbine blades,[5] the reason why such turbines rely on a supply of dry, superheated steam.
Dry steam is saturated steam that has been very slightly superheated. This is not sufficient to change its energy appreciably, but is a sufficient rise in temperature to avoid condensation problems, given the average loss in temperature across the steam supply circuit. Towards the end of the 19th century, when superheating was still a less-than-certain technology, such steam-drying gave the condensation-avoiding benefits of superheating without requiring the sophisticated boiler or lubrication techniques of full superheating.[6]
By contrast, water vapor that includes water droplets is described as wet steam. If wet steam is heated further, the droplets evaporate, and at a high enough temperature (which depends on the pressure) all of the water evaporates, the system is in vapor–liquid equilibrium,[7] and it becomes saturated steam.
Steam Points Glitch
Saturated steam is advantageous in heat transfer due to the high latent heat of vaporization. It is a very efficient mode of heat transfer. In layman's terms, saturated steam is at its dew point at the corresponding temperature and pressure. The typical latent heat of vaporization (or condensation) is 970 Btu/lb (2256.5 kJ/kg) for saturated steam at atmospheric pressure.[8]
Uses[edit]
Steam engine[edit]
Superheated steam was widely used in main line steam locomotives. Saturated steam has three main disadvantages in a steam engine: it contains small droplets of water which have to be periodically drained from the cylinders; being precisely at the boiling point of water for the boiler pressure in use, it inevitably condenses to some extent in the steam pipes and cylinders outside the boiler, causing a disproportionate loss of steam volume as it does so; and it places a heavy demand on the boiler.
Superheating the steam dries it effectively, raises its temperature to a point where condensation is much less likely and increases its volume significantly. Added together, these factors increase the power and economy of the locomotive. The main disadvantages are the added complexity and cost of the superheater tubing and the adverse effect that the 'dry' steam has on lubrication of moving components such as the steam valves. Shunting locomotives did not generally use superheating.
The normal arrangement involved taking steam after the regulator valve and passing it through long superheater tubes inside specially large firetubes of the boiler. The superheater tubes had a reverse ('torpedo') bend at the firebox end so that the steam had to pass the length of the boiler at least twice, picking up heat as it did so.
Processing[edit]
Other potential uses of superheated steam include: drying, cleaning, layering, reaction engineering, epoxy drying and film use where saturated to highly superheated steam is required at one atmospheric pressure or at high pressure. Ideal for steam drying, steam oxidation and chemical processing. Uses are in surface technologies, cleaning technologies, steam drying, catalysis, chemical reaction processing, surface drying technologies, curing technologies, energy systems and nanotechnologies.Superheated steam is not usually used in a heat exchanger due to low heat transfer co-efficient.[9] In refining and hydrocarbon industries superheated steam is mainly used for stripping and cleaning purposes.
Pest control[edit]
Steam has been used for soil steaming since the 1890s. Steam is induced into the soil which causes almost all organic material to deteriorate (the term 'sterilization' is used, but it is not strictly correct since all micro-organism are not necessarily killed). Soil steaming is an effective alternative to many chemicals in agriculture, and is used widely by greenhouse growers. Wet steam is primarily used in this process, but if soil temperatures above the 212 °F (100.0 °C) boiling point of water are required, superheated steam must be used.[10]
See also[edit]
References[edit]
- ^William D. Wise, 'Succeed at steam sterilization, 'Chemical processing' 27 November 2005. Retrieved 2010-10-10.
- ^'Saturated vs Superheat Steam Conditions'. nationwideboiler.com. Retrieved 5 December 2019.
- ^Song, L.; Wu, J.; Xi, C. (2012). 'Biofilms on environmental surfaces: Evaluation of the disinfection efficacy of a novel steam vapor system'. American Journal of Infection Control. 40 (10): 926–930. doi:10.1016/j.ajic.2011.11.013. PMID22418602.
- ^Leyzerovich, A. S., Wet-Steam Turbines for Nuclear Power Plants, PennWell, USA, 2005.[page needed]
- ^Roy, G.J. (1975). Steam Turbines and Gearing. Kandy Marine Engineering Series. Stanford Maritime. pp. 36–37. ISBN978-0-540-07338-2.
- ^Hills, Richard L. (1989). Power From Steam. Cambridge University Press. p. 203. ISBN978-0-521-45834-4.
- ^Singh, R Paul (2001). Introduction to Food Engineering. Academic Press. ISBN978-0-12-646384-2.[page needed]
- ^'Saturated Steam Calculator'. Spirax Sarco. Retrieved 13 September 2017.
- ^Superheated Steam : International site for Spirax Sarco. Spiraxsarco.com. Retrieved on 2012-01-25.
- ^Arthur H. Senner (1 August 1934). 'Application of Steam in the Sterilization of Soils'. United States Department of Agriculture. Retrieved 5 December 2019.
Steam distillation is a separation process that consists in distilling water together with other volatile and non-volatile components. The steam from the boiling water carries the vapor of the volatiles to a condenser; both are cooled and return to the liquid or solid state, while the non-volatile residues remain behind in the boiling container.
If the volatiles are liquids not miscible with water, they will spontaneously form a distinct phase after condensation, allowing them to be separated by decantation or with a separatory funnel. In that case, a Clevenger apparatus may be used to return the condensed water to the boiling flask, while the distillation is in progress. Alternatively, the condensed mixture can be processed with fractional distillation or some other separation technique.
Steam distillation can be used when the boiling point of the substance to be extracted is higher than that of water, and the starting material cannot be heated to that temperature because of decomposition or other unwanted reactions. It may also be useful when the amount of the desired substance is small compared to that of the non-volatile residues. It is often used to separate volatile essential oils from plant material.[1] for example, to extract limonene (boiling point 176 °C) from orange peels.
Steam distillation once was a popular laboratory method for purification of organic compounds, but it has been replaced in many such uses by vacuum distillation and supercritical fluid extraction. It is however much simpler and economical than those alternatives, and remains important in certain industrial sectors.[2]
In the simplest form, water distillation or hydrodistillation, the water is mixed with the starting material in the boiling container. In direct steam distillation, the starting material is suspended above the water in the boiling flask, supported by a metal mesh or perforated screen. In dry steam distillation, the steam from a boiler is forced to flow through the starting material in a separate container. The latter variant allows the steam to be heated above the boiling point of water (thus becoming superheated steam), for more efficient extraction.[3]
Principle[edit]
Every substance has some vapor pressure even below its boiling point, so in theory it could be distilled at any temperature by collecting and condensing its vapors. However, ordinary distillation below the boiling point is not practical because a layer of vapor-rich air would form over the liquid, and evaporation would stop as soon as the partial pressure of the vapor in that layer reached the vapor pressure. The vapor would then flow to the condenser only by diffusion, which is an extremely slow process.
Simple distillation is generally done by boiling the starting material, because, once its vapor pressure exceeds atmospheric pressure, that still vapor-rich layer of air will be disrupted, and there will be a significant and steady flow of vapor from the boiling flask to the condenser.
In steam distillation, that positive flow is provided by steam from boiling water, rather than by the boiling of the substances of interest. The steam carries with it the vapors of the latter.
The substance of interest does not need to be miscible water or soluble in it. It suffices that it has significant vapor pressure at the steam's temperature.
If the water forms an azeotrope with the substances of interest, the boiling point of the mixture may be lower than the boiling point of water. For example, bromobenzene boils at 156 °C (at normal atmospheric pressure), but a mixture with water boils at 95 °C.[4] However, the formation of an azeotrope is not necessary for steam distillation to work.
Steam Points Free
Applications[edit]
Steam distillation is often employed in the isolation of essential oils, for use in perfumes, for example. In this method, steam is passed through the plant material containing the desired oils. Eucalyptus oil, camphor oil and orange oil are obtained by this method on an industrial scale.[1]
Steam distillation is also sometimes used in chemical laboratories as one of many substance separation methods.
Steam distillation also is an important means of separating fatty acids from mixtures and for treating crude products such as tall oils to extract and separate fatty acids and other commercially valuable organic compounds.[5]
Equipment[edit]
On a lab scale, steam distillations are carried out using steam generated outside the system and piped through macerated biomass or steam generated in-situ using a Clevenger-type apparatus.[7]
See also[edit]
References[edit]
- ^ abFahlbusch, Karl-Georg; Hammerschmidt, Franz-Josef; Panten, Johannes; Pickenhagen, Wilhelm; Schatkowski, Dietmar; Bauer, Kurt; Garbe, Dorothea; Surburg, Horst (2003). 'Flavors and Fragrances'. Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a11_141. ISBN3-527-30673-0.
- ^Zeki Berk (2018): Food Process Engineering and Technology, 3rd edition. 742 pages. ISBN978-0-12-812018-7doi:10.1016/C2016-0-03186-8
- ^Manuel G. Cerpa, Rafael B. Mato, María José Cocero, Roberta Ceriani, Antonio J. A. Meirelle, Juliana M. Prado, Patrícia F. Leal, Thais M. Takeuchi, and M. Angela A. Meireles (2008): 'Steam distillation applied to the food industry'. Chapter 2 of Extracting Bioactive Compounds for Food Products: Theory and Applications, pages 9–75. ISBN9781420062397
- ^Martin's Physical Pharmacy & Pharmaceutical sciences, fifth edition, ISBN0-7817-6426-2, Lippincott williams & wilkins
- ^M.M. Chakrabarty (9 November 2003). Chemistry and Technology of Oils & Fats. Allied Publishers. pp. 12–. ISBN978-81-7764-495-1.
- ^Sadgrove & Jones, A contemporary introduction to essential oils: Chemistry, bioactivity and prospects for Australian agriculture, Agriculture 5(1), 2015, DOI: 10.3390/agriculture5010048
- ^Walton & Brown, Chemicals From Plants, Imperial College Press, 1999.
Steam Point System