Projektowanie suszarek do suszenia parą przegrzaną
Ładowanie...
Data
2011
Autorzy
Tytuł czasopisma
ISSN czasopisma
Tytuł tomu
Wydawca
Wydawnictwa Politechniki Łódzkiej
Lodz University of Technology. Press
Lodz University of Technology. Press
Abstrakt
Praca ta powstała w wyniku rozpoczętych przeze mnie w 2000 r. badan nad
suszeniem para przegrzana zainicjowanych przez współprace z firma ITM Poland
z Radomia. W wyniku tej inspiracji oraz owocnej współpracy zrealizowano m.in.
projekt badawczy finansowany przez KBN na temat suszenia drewna wierzby
energetycznej pod ciśnieniem atmosferycznym. Obecnie w realizacji jest drugi,
dotyczący suszenia węgla brunatnego pod zwiększonym ciśnieniem. W toku tych
badan powstał szereg prac magisterskich oraz dwie prace doktorskie.
W pierwszej z nich dr Beata Krupińska zbadała własności sorpcyjne, kinetykę
suszenia i współczynnik oporu aerodynamicznego cząstek drewna wierzby energetycznej
nowo opracowana metoda stanu nieustalonego oraz wykonała obliczenia
suszarki pneumatycznej do suszenia para mielonych zrębków wierzby i przeprowadziła
badania w pilotowej suszarce, udostępnionej przez ITM, weryfikujące te
obliczenia.
W drugiej pracy dr Robert Adamski przebadał proces suszenia próbki
o kształcie walca z drewna wierzby energetycznej, zbudował model procesu
transportu masy i ciepła w materiale i zidentyfikował współczynniki materiałowe,
w tym dyfuzyjność efektywna, przepuszczalność Darcy i współczynnik termodyfuzji.
Udało mu się powiązać otrzymana przepuszczalność Darcy ze strukturalnymi
parametrami drewna otrzymanymi z pomiarów mikroskopowych. Pozwala to na
modelowanie procesu suszenia drewna w dowolnej skali.
Podstawowe stanowisko do badania procesu suszenia para wykorzystane
w obu pracach jest darem firmy ITM Poland dla Wydziału Inżynierii Procesowej
i Ochrony Środowiska PŁ. Obecnie dwoje młodych doktorantów pracuje nad
procesem suszenia lignitu pod normalnym i zwiększonym ciśnieniem, korzystając
ze zdobytego przez nasz zespół doświadczenia i aparatury.
Superheated steam drying (SSD) is known for almost 140 years but still not as popular as it deserves. SSD uses superheated steam as the drying agent. During contact with wet solid it picks up moisture and cools down but still remains superheated. The excess steam may be purged, the rest is reheated and recycled. The advent of SSD, on the wave of interest in sustained development, is largely due to the following facts: • Excess steam can be re-used and it’s heat recovered thus the net heat used for vaporization of 1 kg of water may be reduced down to almost ¼ of its nominal value. • The cycle is closed so no pollutants, neither odors are emitted, • No oxidation nor fire hazard exist inside the dryer because of oxygenfree atmosphere. • Since product temperature reaches boiling point thus the product leaves the dryer sterilized so it is harmless for humans and ready for storage. The last point indicates that only temperature resistant solids can be dried in this way. However, the problem can be overcome by lowering the pressure in the dryer. The list of products suitable for SSD is endless. The most common are: pulp and paper, lignite and peat, solid biofuels, agro and food industry products and waste, raw mineral materials and many others. This book presents methods of process design of selected dryers using superheated steam. It is a summary of research on various aspects of SSD, which has been carried out at Lodz TU on such materials as tobacco, wood chips of willow and now lignite. In the initial chapter it contains the description of the process including its three stages: condensation, constant drying rate and falling drying rate. The constitutive equations for the drying rate in the tree periods are defined. The problems of inversion temperature, dependence of maximum drying rate on process pressure, depth of steam penetration in granular beds and model of internal heat and mass transfer in the solid during SSD are described. The model includes diffusion, Darcy flow and thermodiffusion terms. A collection of equations to approximate the diffusivity is presented. In the next chapter thermodynamic properties of superheated steam and thermodynamic equilibrium of steam and solid are presented. Isotherms and isobars of desorption are described and a collection of equations used to describe them is presented. Ways to describe drying kinetics are shown including thin layer equations, characteristic drying curve equations and solution of a full model of the internal heat and mass transfer.
Superheated steam drying (SSD) is known for almost 140 years but still not as popular as it deserves. SSD uses superheated steam as the drying agent. During contact with wet solid it picks up moisture and cools down but still remains superheated. The excess steam may be purged, the rest is reheated and recycled. The advent of SSD, on the wave of interest in sustained development, is largely due to the following facts: • Excess steam can be re-used and it’s heat recovered thus the net heat used for vaporization of 1 kg of water may be reduced down to almost ¼ of its nominal value. • The cycle is closed so no pollutants, neither odors are emitted, • No oxidation nor fire hazard exist inside the dryer because of oxygenfree atmosphere. • Since product temperature reaches boiling point thus the product leaves the dryer sterilized so it is harmless for humans and ready for storage. The last point indicates that only temperature resistant solids can be dried in this way. However, the problem can be overcome by lowering the pressure in the dryer. The list of products suitable for SSD is endless. The most common are: pulp and paper, lignite and peat, solid biofuels, agro and food industry products and waste, raw mineral materials and many others. This book presents methods of process design of selected dryers using superheated steam. It is a summary of research on various aspects of SSD, which has been carried out at Lodz TU on such materials as tobacco, wood chips of willow and now lignite. In the initial chapter it contains the description of the process including its three stages: condensation, constant drying rate and falling drying rate. The constitutive equations for the drying rate in the tree periods are defined. The problems of inversion temperature, dependence of maximum drying rate on process pressure, depth of steam penetration in granular beds and model of internal heat and mass transfer in the solid during SSD are described. The model includes diffusion, Darcy flow and thermodiffusion terms. A collection of equations to approximate the diffusivity is presented. In the next chapter thermodynamic properties of superheated steam and thermodynamic equilibrium of steam and solid are presented. Isotherms and isobars of desorption are described and a collection of equations used to describe them is presented. Ways to describe drying kinetics are shown including thin layer equations, characteristic drying curve equations and solution of a full model of the internal heat and mass transfer.
Opis
Red. serii : Wodziński, Piotr
Słowa kluczowe
suszarki, suszarki-projektowanie i konstrukcja, para przegrzana, drying, dryers - design and construction, drying - thermodynamics, superheated steam
Cytowanie
Pakowski Z., Projektowanie suszarek do suszenia parą przegrzaną., Wydawnictwo Politechniki Łódzkiej, Łódź 2011, ISBN 978-83-7283-428-7.