Design of superheated steam dryers

Red. serii : Wodziński, PiotrPraca 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

Historia wsi Gniazdowej Olszoskich h. Wilczekosy

The first written record of Olszowa, a village in Brzeziny district of Łęczyca province, comes from A.D. 1379. In the early XV century the village was owned by the Bielinas of Wola Drzazgowa and it is the family seat of the Olszowski family of Prus II (Wilczekosy – Wolfscythes) coat of arms, originating from the nearby village of Gutków. The Olszowski’s were descendants of Prussian settlers, and descendants include the Primate Andrzej Olszowski. The property of the Olszowskis, in Olszowa dates from 1445 to 1824 i.e. almost 400 years. Since 1824 the ownership of Olszowa property is well documented in mortgage registers. Important people that lived in and owned Olszowa include Ludwik Szweycer and his son Wincenty – a January Uprising volunteer, Wiktoria Lewińska, a sister of Narcyza Żmichowska – a writer and feminist, and her son Ludwik Lewiński – also a January Uprising volunteer, professor Kazimierz Glinka-Janczewski, a forester, university professor and popularizer of forestry, and finally the Malcz family: Julian and his sons Bolesław – landowner and social activist, and Władysław – head of division of Warsaw firefighters and Lucjan – sublieutenant of the “Bayonnais”, who fell at the Western Front of the Great War

Pressure measurement as a tool to identify moisture transport mechanisms in convective drying of non-shrinking material

The drying process is one of the most important stages in the production of building materials. The choice of the drying method affects the chemical and physical properties of the final product. The aim of this research is to measure and analyze the dynamic changes of internal pressure in non-shrinking, porous material during convective drying. In this work the problem will be discussed with special attention to the behavior of rewetted plaster. A commercial gypsum of company PIOTROWICE II (Alpol brand), typically used in construction and decorative plastering was applied. Gypsum was mixed with water in recommended proportion of 0.6 water/gypsum and drying experiments were performed at 50°C. The changes in sample overall mass as well as pressure and material temperature on the midpoint of sample axis were monitored. On the basis of the obtained experimental data of axial pressure, it is possible to perform a more detailed analysis of mass and heat transfer mechanisms than based on the drying kinetics alone. The pressure trends in the sample allow one to determine the moment of transition from the first to the second drying period, without the need to determine the kinetics of drying. The element of novelty consists of using a direct internal pressure measurement to provide information on the variation of the actual drying rate and mass transfer mechanisms