Claytons superheated steam generators provide superheated steam for a variety of industrial applications as auxiliary boilers in power plants and wherever superheated steam is required. Abstract this paper presents a numerical simulation and experimental validation of a spray dryer using superheated steam instead of air as drying medium, modelized with a computational fluid dynamics cfd code. The results suggested remarkably lower moisture contents of the samples at higher superheated steam drying temperatures at. Properties of superheated steam specific volume, cubic feet per pound h g total heat of steam, btu per pound pressure lbs. Therefore the drying works without direct contact to flue gases but with superheated steam at low oxigen content, which is very product indulgent. Superheated steam drying food tech innovation portal. Applications of superheated steam for the drying of food products. Sheng li 1, bin jiang 1, yongchun shi 1, jie li 1, wenxue dong 2, jian xu 2, hong zhang 2, jun yang 3, fuxiang chen 3. Using superheated steam instead of air in a spray dryer can allow a high volumic evaporation rate 20 kg.
Industrial superheated steam drying tno deventer h. The infrared ir spectra of raw and dried samples were curvefitted to a series of bands in aliphatic hydrogen 30002800 cm 1 and carbonyl. D efforts owing to the rising demand for improved product quality and reduced operating cost as well as diminished environmental impact. When steam is more than 100% dry it is called superheated steam. The drying system is more complex with regard to feeding and discharge of products as air leaking and steam leaking out, respectively, need to be prevented. Superheated steam is not suitable for sterilization. Please read our short guide how to send a book to kindle. Steam sterilization products such as tree nuts, herbs, and teas may require sterilization or disinfection without overcooking or leaving residual moisture that could support mold growth. It is then heated further in a superheater and is then 2 able to absorb additional moisture. Environmental and energy saving drying technology treatment. In steam impingement, drying superheated steam 300c, 1. Free choice of conveying techniques due to the difference in density between air and superheated steam, a boundary stratification layer between the atmosphere of superheated steam and the ambient air is created, thus preventing infiltration of air. Cfd modeling and simulation of superheated steam fluidized. Superheated steambased process for low energy and high.
Superheated steam drying, parawood introduction over the years, the application of superheated steam for drying have been studied by a number of researchers111. This type of steam is created by adding heat above the saturated steam threshold. The ecodry drying technology of the swiss combi ecodry drum dryer is based on an indirectly heated drying process with closed steam loop superheated steam and a process integrated thermal oxidation of the dryers exhaust gas. It has the technological advantages of energy efficiency and safety inert environment required for use in drying bagasse.
It is also known as subcritical water or pressurized hot water. Due to several advantages, superheated steam drying of timber has attracted great attention. Superheated steam drying has been known for over 100 years, but its acceptance in industry has been slow. These fivevolume series provide a comprehensive overview of all important aspects of drying technology like computational tools at different scales volume 1, modern experimental and analytical techniques volume 2, product quality and formulation volume 3, energy savings volume 4 and process intensification volume 5. The objective of this study, therefore, is to explore the potential of this technology for drying western red cedar towards a subsequent fullscale study or industrial implementation. Superheated steam, steam containing excessive liquid water, and steam containing excessive boiler additives or contaminates such as rust should be avoided. Use our dry superheated steam region steam table calculator to help you plan and design your steam system. However, the technology is still restricted to some special cases, partly due to the lack of fully understanding of the drying process. Superheated steam is created by further heating wet or saturated steam beyond the saturated steam point. The steam can therefore cool lose internal energy by some amount, resulting in a lowering of its temperature without changing state i. The wet solids are fed into the flow of pressurized superheated transport steam by means of a pressure tight rotary valve, plug screw or similar. Testing of a pilotscale and mathematical model development. Steam table calculator superheated steam region spirax.
Utilizing superheated steam as the drying medium allows for the same efficiencies as a direct rotary dryer, typically heated by gas. The conditions in the dryer make it possible to provide heat treatment andor effective sterilization of products. For supply steam above 30 bar g in the dry saturated state, the throttled steam might be superheated, dry saturated, or even wet, depending on the amount of pressure drop. One of the first industrial uses of superheated steam drying was to dry brown coal. Principle of superheated steam drying ssd atmospheric. In austria the fleissner process was developed in the late 1920s to provide a dry coal from a lowgrade highmoisture content 5565% coal potter and beeby. Aug 05, 2009 we usually think of water as a substance used to put out fires. However, the steam drying process involves the simultaneous transfer mechanisms of heat, gas and liquid. Superheated steam generators 200 to 1,000 bhp clayton. Superheated steam drying identification key words superheated steam, low pressure, drying latest version 20110909 completed by ku leuven lft how does it work.
This yields steam that has a higher temperature and lower density than saturated steam at the same pressure. However there are few studies applying the superheated steam with the wood drying. Sheng li 1, bin jiang 1, yongchun shi 1, jie li 1, wenxue dong 2, jian xu 2, hong zhang 2, jun yang 3, fuxiang. Primary objective drying of food products working principle this closedsystem drying method is based on the vapourization of water in the product by contact with superheated steam. Impingement drying rates can be about twice as high for drying in superheated steam as in air. Superheated steam dryer ssdtm advantages superheated. Pdf superheated steam drying arun mujumdar academia. The knowledge and practice of drying in superheated steam has been known for over a hundred years hausbrand 1912. A superheated steam dryer ssd was used to dry the parawood. Drying kinetics and ann modeling of paneer at low pressure. The superheated steam processor ssp can be used for drying andor heat treatmentofmanyproducts. There are no air or flue gases that can oxidize or contaminate the product. The heat generation is separated from the drying process by a unique high temperature gasgas heat exchanger. Superheated steam is frequently used in the power industry, with other typical applications including foodstuffs, and solventladen minerals.
The added heat raises the steam s temperature higher than its saturation point, allowing the amount of superheat to. Superheated steam has continually provided these benefits through superior drying. Food drying with superheated steam open source ecology. For example, dry saturated steam at 60 bar g would have to be reduced to approximately 10. Superheated steam is a steam at a temperature higher than its vaporization boiling point at the absolute pressure where the temperature is measured. For these purposes, superheated steam drying can play an important role. The results suggested remarkably lower moisture contents of the samples at higher superheated steam drying temperatures at corresponding time intervals.
Superheated steam drying of foods and biomaterials modern. The unique drying conditions in the superheated steam dryertm are favorable for the drying of many products where quality is important. Superheated water is stable because of overpressure that raises the boiling point, or by heating it in a sealed vessel with a headspace, where the liquid water is. Controlled temperatures and short residence times 560 seconds make the technology suitable for drying of sensitive products. Superheated steam drying of porous clay similar concepts for wood and other media concept of inversion temperature above which steam drying is faster than air drying mhi superefficient steam dryers see. Drying technology a superheated steam fluidizedbed dryer for parboiled rice. Superheated steam vacuum drying times for thick lumber luiz c. Operations other limitations superheated steam drying needs to be performed at reduced pressure when drying heatsensitive products, as this lowers the boiling point of water and thus the thermal damage. There is no free oxygen in superheated steam, so the decomposition of easily oxidized nutrients such as vitamin c is greatly reduced. Desorption equilibrium shows that completely dry paper can be obtained at very low superheats. Due to the drying principle, a very uniform dryness of the product is achieved. If you continue without changing your cookie settings, we assume that you consent to our use of cookies on this device.
Steam drying may have additional advantages in specific applications in the food industry, for example, where sterilization of the product is an objective. We use cookies to give you the best experience on our website. Superheated steam an overview sciencedirect topics. The superheated steam dryer ssd is a closed loop pneumatic conveying type dryer.
Low pressure superheated steam drying lpssd is being explored for drying of food materials due to its numerous advantages such as less energy wastage, high heat transfer coefficient, no oxidative changes during drying, no resistance to mass transfer at the surface, higher. Using low pressured steam as heating medium will decrease the energy intake while improving the final product quality low temperature drying. Superheated steam dryer ssd cyclone screw drying loops super heater pc generated steam tc backmix dry product wet feed mixer air heater fresh air process air natural gas combustion fan exhaust clean lp steam reboiler coldhot water. Whether youve loved the book or not, if you give your honest and detailed thoughts then people will find new books that are right for them. Twostep cleaning system to remove the dustparticles from the extra steam and allow its reuse in the. Drying western red cedar with superheated steam drying. The development took 7 years starting with 2 years with fundamental research in the lab followed by 2 years of intensive work on a 10 m high pilot installation having a capability to evaporate 1 ton water per hour.
In this work, experiments were conducted to dry radiata pine timber using superheated steam under vacuum and at pressure. Superheated steam drying needs to be performed at reduced pressure when drying heatsensitive products, as this lowers the boiling point of water and thus the thermal damage. Superheated steam drying identification how does it work. Superheated or dry steam has the ability to drive moisture out of solid materials much faster and more costeffectively than air drying while being gentler on the end product. Pdf drying technology a superheatedsteam fluidizedbed. Steam that has additional sensible heat added so that its. Invented in the late 70s at chalmers university of technology, gothenburg, sweden, shsd uses superheated steam as media for drying of solid materials like paper pulp, saw dust, wood waste, animal feed, peat, sludge, tea, efb empty fruit bunches, agro biomass, bagasse, sugar beet pulp, wet solid waste etc. Volume 1 modern drying technology, computational tools at different scales volume 1. As these examples show, superheated steam can be a useful technique in drying certain foods, but it is not a sure solution for every situation. A superheated steam fluidized bed drying system has been designed on an industrial scale 5, 6. Superheated steam drying ssd is an innovative drying technology, utilizing heated steam beyond its boiling point as a drying medium in a dryer to remove excess water from the material. A hybrid cycle was developed in which drying is partially by superheated steam impingement drying and partially by conventional cylinder drying.
Pressure superheated steam drying lpssd application of lpssd to improve the quality of foods and biomaterials. Drying parawood with superheated steam surachai bovornsethanan and somchai wongwises department of mechanical engineering, king mongkuts university of technology thonburi kmutt bangmod, bangkok 10160, thailand abstract. Background superheated steamnacuum ssv drying is a process in which the lumber. During drying, kinetic rate constants of shs were significantly higher than those of mha. This is one of the key reasons why separation is used to disentrain condensate from distributed steam. Using superheated steam as the drying medium, high temperature and high vapor pressure within the materials are induced during the drying process, thus promoting more intense moisture transfer throughout the materials. In that case, lowpressure superheated steam drying needs to be applied. 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. To the best knowledge of authors, up to now, there has. The drying technology swiss combi ecodry is based on a indirect heated drying process with a closed superheated steam loop and a process integrated thermal oxidation of the dryer exhaust gas.
This is a key advantage over food drying with hot air, which exposes the food to oxygen. Using superheated steam in drying and sterilization. Study of chemical structure changes of chinese lignite upon. Other readers will always be interested in your opinion of the books youve read. Mujumdar, color publications, 2004 special issues on shsd of drying technology journal, 2007. Mujumdar, crc press, usa, 2006, 1280 pp see chapter in guide to industrial drying, a. Drying materials may appear in the form of wet solid, liquid, suspension, or paste, which require drying to extend the period of storage, ease of transportation, and for downstream processing to.
From the saturated steam table mentioned above, one can see that it takes 419 kjkg 180 btulb to. Even from its early beginnings, superheated steam was being utilised for the alternative benefits it provides in addition to its abilities to act as a drying medium. Super heated steam drying of wood on industrial scale. Before industry accepts a new technology like processing in superheated steam drying, it must be proven to provide these benefits in the area of processing where drying of a product is not the primary concern. Investigation of drying characteristics in superheated. In summary, although the present utilization of superheated steam drying in food processing is limited, the potential advantages of the method in specific applications cannot be ignored. Detailed specifications of a ssfbd, however, must be fixed in accordance with a certain grade of.
Background superheated steamnacuum ssv drying is a process in which the lumber is dried under a vacuum and therefore at. Diverse model types for the drying of products and the design of drying processes shortcut methods, homogenized, pore network, and continuous thermomechanical approaches are treated, along with computational fluid dynamics, population balances, and. Fluidized bed superheated steam drying is one of the technologies successfully applied to drying pulp in the sugar beet industry. Nov 15, 2017 the moisture contents of the samples in superheated steam drying experiments at the temperatures of 120, 140, and 150 c are shown in fig. Water is heated in a boiler, generating saturated steam 1. Chemical changes of chinese lignite upon drying in superheated steam, microwave, and hot air have been studied in this paper using the fourier transform infrared ftir spectroscopy technique.
Energy consumption is an important economic factor in industrial mass production. Superheated steam drying emerged as a viable new drying technology with immense potential only in the past decade or so. Savings can be achieved by means of energy recovery, optimized process engineering or multiple use of the energy flows. Experimental investigation and practical application of. See chapter on superheated steam drying in handbook of industrial drying. Innovative drying technology, using superheated steam at low pressure, ensuring efficiency through better heat transfer and a better quality of product due to lower temperature.
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