218 research outputs found
The XDEM Multi-physics and Multi-scale Simulation Technology: Review on DEM-CFD Coupling, Methodology and Engineering Applications
The XDEM multi-physics and multi-scale simulation platform roots in the Ex-
tended Discrete Element Method (XDEM) and is being developed at the In- stitute
of Computational Engineering at the University of Luxembourg. The platform is
an advanced multi- physics simulation technology that combines flexibility and
versatility to establish the next generation of multi-physics and multi-scale
simulation tools. For this purpose the simulation framework relies on coupling
various predictive tools based on both an Eulerian and Lagrangian approach.
Eulerian approaches represent the wide field of continuum models while the
Lagrange approach is perfectly suited to characterise discrete phases. Thus,
continuum models include classical simulation tools such as Computa- tional
Fluid Dynamics (CFD) or Finite Element Analysis (FEA) while an ex- tended
configuration of the classical Discrete Element Method (DEM) addresses the
discrete e.g. particulate phase. Apart from predicting the trajectories of
individual particles, XDEM extends the application to estimating the thermo-
dynamic state of each particle by advanced and optimised algorithms. The
thermodynamic state may include temperature and species distributions due to
chemical reaction and external heat sources. Hence, coupling these extended
features with either CFD or FEA opens up a wide range of applications as
diverse as pharmaceutical industry e.g. drug production, agriculture food and
processing industry, mining, construction and agricultural machinery, metals
manufacturing, energy production and systems biology
Developing a Lab-Scale Fluidized Bed Dryer System to Enhance Rough Rice Drying Process
For more than half of the world\u27s population, rice (Oryza sativa L.) is a staple meal. However, rice growers encounter difficulties supplying this demand, particularly in developing nations, where rice is susceptible to spoilage if the moisture content is not lowered to a safe level soon after harvest. As a result, traditional drying methods, such as sun drying and natural air drying, are commonly used by rice growers, particularly in underdeveloped nations. However, these procedures are time-consuming and can lead to rice spoilage. On the other hand, fluidized bed drying is a well-established technology that might give rice growers a rapid, practical, economical, and portable drying procedure. According to past research, the primary benefit of fluidized bed drying is the increased drying rate.
On the other hand, other research has expressed concerns about inferior rice quality, which is considered a significant weakness in fluidized bed drying. In the United States of America, the farmers and processors lack consensus and thus there is a mistrust to utilize fluidized bed drying for rice. As a result of the lack of agreement, an extensive study to understand the fluidized bed drying of rice is needed.
In the Mid-South region of the United States, high humidity ambient air is typical, resulting in stoppage of the in-bin rice drying process to avoid rewetting of rice. Ambient air dehumidification may be able to solve this problem and allow for a continual drying process. However, no study utilized desiccant for ambient air dehumidification for drying rice; through this study, an attempt was made to bridge the research gap and determine the benefits and practicalities of ambient air dehumidification to achieve continuous rice drying.
A lab-scale mobile batch fluidized bed dryer was constructed and used in this study. Several tests were done to improve the system that included designs, additions, and replacements of parts.
In a fluidized bed and fixed bed drying system, the effects of ambient air dehumidification, air temperature, and drying duration on rough rice quality were investigated. Energy and exergy analyses were done to determine the thermal efficiency of the drying system. Mathematical modeling was done to optimize the drying of rough rice.
Overall, it was found that fluidized bed drying technology can be utilized for drying rough rice without compromising the quality compared to the fixed bed drying. The air temperature used was between 40 to 50Ā°C, and rice was dried for no more than 60 min. In addition, the ambient air dehumidification reduced the relative humidity of drying air and did not affect rice quality but increased the rice moisture removal, ultimately increasing the drying rate.
The study recommends using air temperatures below 50Ā°C and a drying duration of less than 60 min to achieve effective rough rice drying with fluidized bed drying technique. In addition, ambient air dehumidification can be employed for reducing ambient air relative humidity by few points. However, more research must be done at the farm and industrial scale to check the accuracy of these findings at a large scale
Multi-scale analyses of cycled industrial-scale packed-bed adsorbers
Separations processes account for 10%ā15% of the total energy consumed in process\ua0industries worldwide. In such separation processes, it is common to use activated carbon in packed-bed adsorbers, to remove undesired substances from a process stream.\ua0This is particularly useful for the removal of harmful volatile organic compounds\ua0(VOCs) in a multitude of settings and in an ever-growing, billion-dollar industry.\ua0Much research effort has been expended in understanding and improving the use\ua0of activated carbon for VOC removal. In this context, numerical modeling has\ua0become an increasingly useful tool as computers become more powerful and faster.Most of the currently used numerical models describe laboratory-scale environments,\ua0where the circumstances regarding the state and operation of the adsorbers are well-controlled. However, very little work has been done on this topic for industrial scale,\ua0with real-world operational cycles and bed states. Since there are major differences\ua0between the industrial operation of packed-bed units and laboratory-scale controlled\ua0environments, the applicability and performance of numerical models for real-world\ua0industrial settings need to be investigated.In this work, a one-dimensional (1D) numerical model is formulated for an industrial-size adsorber and compared with real-world, industrial temperature data from a\ua0biomass gasification plant operated in Gothenburg, Sweden. The end-goal of the\ua0model is an improved understanding of the requirements for a successful numerical\ua0model of real-world, industrial conditions. This is done to facilitate the design and\ua0optimization of packed-bed setups for industrial conditions before construction of\ua0the actual facilities, as well as to characterize and improve units that are already operational. The model is also used to study how best to simulate industrial conditions\ua0and how to use steam as a regeneration medium for temperature-swing adsorption\ua0(TSA) operation.To improve packed-bed adsorbers, a detailed three-dimensional (3D) numerical study\ua0is also performed on the material packing structure. Here, the flow through a bed\ua0section is studied and packings with different particle shapes are compared using the\ua0Lattice Boltzmann Method (LBM).The results show that major trends in the industrial data are captured, while some\ua0aspects of the dynamics of the real process are not well-described. This is due to the\ua0complex composition of the product gas from biomass gasification, and limitations\ua0associated with the adopted modeling for steam and water. The results also show\ua0that in order to simulate industrial cases, the cycling procedure used in industry\ua0should be incorporated into the model, so as to account for the different adsorption\ua0mechanisms that emerge during cycling. Finally, it is shown that packing the bed\ua0with spherical (rather than cylindrical) particles reduces the pressure drop across\ua0the bed
Design of superheated steam dryers
Red. serii : WodziÅski, PiotrPraca ta powstaÅa w wyniku rozpoczÄtych przeze mnie w 2000 r. badan nad
suszeniem para przegrzana zainicjowanych przez wspĆ³Åprace z firma ITM Poland
z Radomia. W wyniku tej inspiracji oraz owocnej wspĆ³Åpracy zrealizowano m.in.
projekt badawczy finansowany przez KBN na temat suszenia drewna wierzby
energetycznej pod ciÅnieniem atmosferycznym. Obecnie w realizacji jest drugi,
dotyczÄ
cy suszenia wÄgla brunatnego pod zwiÄkszonym ciÅnieniem. W toku tych
badan powstaÅ szereg prac magisterskich oraz dwie prace doktorskie.
W pierwszej z nich dr Beata KrupiÅska zbadaÅa wÅasnoÅci sorpcyjne, kinetykÄ
suszenia i wspĆ³Åczynnik oporu aerodynamicznego czÄ
stek drewna wierzby energetycznej
nowo opracowana metoda stanu nieustalonego oraz wykonaÅa obliczenia
suszarki pneumatycznej do suszenia para mielonych zrÄbkĆ³w wierzby i przeprowadziÅa
badania w pilotowej suszarce, udostÄpnionej przez ITM, weryfikujÄ
ce te
obliczenia.
W drugiej pracy dr Robert Adamski przebadaÅ proces suszenia prĆ³bki
o ksztaÅcie walca z drewna wierzby energetycznej, zbudowaÅ model procesu
transportu masy i ciepÅa w materiale i zidentyfikowaÅ wspĆ³Åczynniki materiaÅowe,
w tym dyfuzyjnoÅÄ efektywna, przepuszczalnoÅÄ Darcy i wspĆ³Åczynnik termodyfuzji.
UdaÅo mu siÄ powiÄ
zaÄ otrzymana przepuszczalnoÅÄ Darcy ze strukturalnymi
parametrami drewna otrzymanymi z pomiarĆ³w 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 WydziaÅu Inżynierii Procesowej
i Ochrony Årodowiska PÅ. Obecnie dwoje mÅodych doktorantĆ³w pracuje nad
procesem suszenia lignitu pod normalnym i zwiÄkszonym ciÅnieniem, korzystajÄ
c
ze zdobytego przez nasz zespĆ³Å doÅwiadczenia 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:
ā¢ Excess steam can be re-used and itās heat recovered thus the net heat
used for vaporization of 1 kg of water may be reduced down to almost Ā¼
of its nominal value.
ā¢ The cycle is closed so no pollutants, neither odors are emitted,
ā¢ No oxidation nor fire hazard exist inside the dryer because of oxygenfree
atmosphere.
ā¢ 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
Integrated computational fluid dynamics and 1D process modelling for superheater region in recovery boiler
Superheaters are the last heat exchangers on the steam side in recovery boilers. Their performance is accountable for proficient recovery boiler operation. The objective of this work is to obtain thorough knowledge about the superheating process and material temperature distribution for superheater platens. The study includes the effects of 3D flue gas flow field in superheater region and generated steam properties in steam cycle. The detailed analysis for flue gas side and steam side is important for improving recovery boilers' energy efficiency, cost efficiency, safety and contribution for carbon neutral energy production.
In this work, for the first time, a comprehensive 1D-process model (1D-PM) for superheated steam cycle is developed and linked with a full-scale 3D-CFD model of the superheater region flue gas flow. The developed 1D-PM is validated using reference data including mass and energy balance calculations, and measurements.
The results reveal that first; the geometrical structures of headers, connecting pipes and superheater platens affect platen-wise steam distribution. Second, the integrated solution of the 3D flue gas flow field and platen heat flux distribution with the 1D-PM substantially affect both generated superheated steam properties and material temperature distribution. It is also found that the commonly used uniform heat flux distribution approach for superheating process is not accurate because it does not consider the effect of flue gas flow field in superheater region.
This novel integration modelling approach is advantageous for trouble shooting, optimizing the performance of superheaters in recovery boiler and selecting their design margins for the future. It could also be applied for other large scale energy production units including industrial biomass fired boilers
Experimental and numerical investigation on tar production and recycling in fixed bed biomass gasifiers
Bioenergy has been utilized for domestic purposes since pre-recorded history and it catches the highlight in the recent decades because it naturally benefits the world climate and energy security. Gasification is one of the key technologies to efficiently and economically convert biomass into syngas and further into biofuels. Despite these outstanding advantages, biomass gasification suffers from the formation of unfavorable byproduct tar and the consequential tar elimination. Moreover, the collected tar is toxic and thus requires storage and strict deposit method to avoid environmental pollution.
To understand the mechanisms of biomass gasification and tar production, simulations with Aspen Plus were conducted for both downdraft and updraft gasifiers, which are presented in the Paper I and II, respectively. The kinetic models are implanted with reaction kinetics to ensure their ability to approximate the tar production, which are superior to the widely used Gibbs Energy Minimization model for predicting syngas compositions. Paper III focuses on the investigation of the impact of tar recycling on syngas compositions under various operating conditions including different reactor scales (4\u27\u27, 8\u27\u27, 12\u27\u27), different biomass feedstocks (pellets, picks, and flakes) and different equivalence ratios (0.15, 0.20, 0.25). --Abstract, page iv
Study on feasibility of coir dust as feedstock for entrained flow gasification system
Experimental investigations of the influence of equivalence ratio on gas composition, adiabatic flame temperature, calorific value and rate of gas generation were performed using coir dust as feedstock in entrained flow gasification system. Experiments were carried out on a pilot scale (2.5 m high X 0.25 m i.d.) existing entrained flow biomass gasifier installed at IMMT, Bhubaneswar. Model calculations were made to find out the composition and other properties of the gas taking coir dust as feedstock. Results were realized through comparison of output from theoretical as well as experimental value obtained with varying equivalence ratio. The outputs obtained from Entrained flow gasifier are of high quality and the process can be industrialized
Drying Technology Evolution and Global Concerns Related to Food Security and Sustainability
Undoubtedly, rapid population growth has sharply increased global food demand. Although the green revolution, accompanied by food industrialization practices, helped a lot in meeting this demand, the food gap is still huge. Regardless of COVID-19, due to that 14% of the worldās food is lost before even reaching the market, and thus the food insecurity prevalence by rate (9.7%), where the food losses are valued at $400 billion annually according to FAO. In the face of such issues related to food insecurity and food losses, drying technology since its inception has been known as the most common operation in food processing and preservation. However, the excessive use of the drying process and exposure to heat for long periods led to a severe deterioration in the physicochemical quality characteristics of these products. At the same time, growing attention on human health through monitoring the quality and safety of food to avoid chronic diseases led to increasing awareness of the consumer to obtaining products with high nutritional value. Therefore, there has been a great and rapid evolution in drying technology to preserve food with high quality. Hence, this chapter aims to shed light on the drying technology evolution in food processing and preservation as one of the most important post-harvest treatments in the agriculture field
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