CFD Study of Particle Flow Patterns in a Rotating Cylinder Applying OpenFOAM and Fluent

A rotating cylinder (RC) is a common type of reactor used in the industry, the most typical example being a cement kiln. The particle flow pattern inside such a unit is necessary for the mass and energy transfer, and this flow pattern depends on the operational Froude number and the degree of filling. The main aim of this study is to compare the simulation results from OpenFOAM and Fluent applying a Eulerian multiphase flow modeling concept to study the behavior of dense particle gas mixtures under different operational conditions. Six different flow patterns are simulated, varying the degree of filling from 10 to 45 % and the Froude number from 0.0001 to 5. OpenFOAM is capable of producing results very close to those generated with Fluent, and both software appears to be suitable for simulating the RC dense particle flow using the Eulerian approach

Comparison of the influence of drag models in CFD simulation of particle mixing and segregation in a rotating cylinder

CFD modelling was used to simulate particle segregation in a transverse plane of a rotating cylinder under different particle-particle drag models. The Eulerian method was used to model the dense particulate phases in the system. Two types of particles, with different density and size, were used in the study. The simulations were performed under the rolling mode since this mode is believed to give good particle-particle mixing. The drag models of Schiller-Naumann, Morsi- Alexander and Syamlal-O’Brien Symmetric were applied in the modelling of particle-particle drag and results were compared with experiments. All the drag models were able to model the particle segregation. The Schiller-Naumann model and the Morsi-Alexander model showed good agreement with the experimental results while the Syamlal-O’Brien-Symmetric model had some deviations

Er elbilen et bærekraftig alternativ til fossilbilen?

De globale klimagassutslippene må reduseres til nær null i løpet av de nærmeste tre tiårene om vi skal unngå dramatiske endringer av klimaet. Transportsektoren, herunder personbilen, står for en betydelig del av klimagassutslippet. Vi sammenligner i denne artikkelen elektrisk drevne biler med dieseldrevne biler, i Norge og i EU. Hensikten er å undersøke under hvilke forutsetninger slike biler tilfredsstiller nye myndighetskrav, samt i hvilken grad de kan bidra til at våre personlige klimafotavtrykk blir oppnådd. Nettemisjonsfaktoren har en avgjørende innvirkning på elbilens klimafotavtrykk. I Norge er denne faktoren svært lav fordi strømproduksjonen er basert på fornybar energi. I mange andre land og regioner, for eksempel EU, er den mye høyere pga. mer bruk av fossil energi i kraftproduksjonen. Dette innebærer signifikante indirekte klimagassutslipp for elbilen. I tillegg oppstår betydelige klimagassutslipp under bilproduksjonen, både av selve kjøretøyet og batteriet. Økt bruk av fornybare energikilder i kraftproduksjon og mer miljøvennlig batteriproduksjon ventes likevel å gradvis redusere elbilens klimafotavtrykk, så vel under produksjon som i bruk. I dag medfører derfor produksjon og bruk av elbiler utslipp av CO2 både i Norge og i EU, og det er altså noe misvisende å hevde at dagens elbiler er nullutslippsbiler. Dette skyldes både produksjon av batterier og bruk av kraft fra strømnettet, som delvis er basert på fossile brennstoff (kull, olje, gass), og delvis ved bruk av fornybare teknologier. Både dieselbiler og elbiler har en kompleks global verdikjede. Det er krevende å identifisere klimafotavtrykket gjennom hele bilens livssyklus – spesielt med tanke på at dieselbiler representerer en moden teknologi, mens elbilene og særlig batteriutviklingen er i en tidlig fase. I denne studien har dette ledet til innsikt i hvilke parametere som er avgjørende å forstå og påvirke for at elbilen skal gi et viktig bidrag til det «grønne skiftet»

Waste heat availability in the raw meal department of a cement plant

The main aim of this study was to determine the available heat in the cement kiln exhaust gas subject to different process conditions. A Norwegian cement plant producing about 1.3 million tons of cement per year was used as a case study. A mass and energy balance was made for the raw meal department, and process data available from the plant process database as well as manually measured gas flow rates were used to calculate the available heat. The available heat can be utilized by a combination of low pressure (LP) steam generation and hot water generation. It was found that waste heat is 1.5–4.2 MW for LP steam generation and 2.2–5.8 MW for hot water generation. The variation in available heat is due to different raw meal types being produced, requiring different gas inlet temperatures to raw meal mill. In cases when no raw meal is produced (in maintenance shutdown periods), all the gas will bypass the mill, and approximately 20 MW of LP steam and 6 MW of hot water can be generated. The heat loss from the system was estimated based on measurements, and the fan power inputs were calculated. Both were found to be negligible compared to the available heat. Furthermore, the total false air coming into the system was estimated as 40–50% of the total gas flow rate going out from the raw meal department

CFD Study of Particle Flow Patterns in a Rotating Cylinder Applying OpenFOAM and Fluent

A rotating cylinder (RC) is a common type of reactor used in the industry, the most typical example being a cement kiln. The particle flow pattern inside such a unit is necessary for the mass and energy transfer, and this flow pattern depends on the operational Froude number and the degree of filling. The main aim of this study is to compare the simulation results from OpenFOAM and Fluent applying a Eulerian multiphase flow modeling concept to study the behavior of dense particle gas mixtures under different operational conditions. Six different flow patterns are simulated, varying the degree of filling from 10 to 45 % and the Froude number from 0.0001 to 5. OpenFOAM is capable of producing results very close to those generated with Fluent, and both software appears to be suitable for simulating the RC dense particle flow using the Eulerian approach

Combined Calcination and CO2 Capture in Cement Clinker Production by Use Of Electrical Energy

The technical feasibility of electrifying the calcination process in a precalciner cement kiln system was assessed by studying different electrification concepts. Resistance-based heating was selected as it requires no CO2 recycling, has a high electricity-to-heat efficiency and has no major safety concerns. Resistance-based heating may be implemented in different types of calcination reactors. In this study, a rotary calciner was selected because the material flow can be readily controlled, it appears to be technically feasible to implement heating elements with a sufficiently high surface temperature to perform calcination, and rotary kilns are already in use in the cement industry, hence can be regarded as well-known technology. It is possible to integrate the electrified calciner with an existing cement kiln system in such a way that minimum disturbance of the production process is obtained. Hence, no negative impacts on the process, product quality or emissions are expected. The required electrical energy input for calcination in a kiln system producing 1 Mt of clinker per year, is about 85 MW. An early-phase cost estimate was conducted resulting in total annualized costs of 67 € per ton of CO2 avoided. The net avoided CO2 emission was 72 % (using a CO2 footprint of 47 g/kWh for electrical energy). The described CO2 capture concept was technically and economically compared with amine-based absorption of CO2 from the preheater exhaust gas. Two amine-based cases were calculated, one using electrical energy as the source of solvent regeneration (85 % net CO2 reduction) and another one using only available waste heat as the energy source (48 % net CO2 reduction). The annualized costs of these two cases were 75 and 40 € per ton of CO2 avoided, respectively. Hence, in cement plants where large amounts of waste heat are available, aminebased absorption appears to be the least expensive option for reduction in CO2 emissions. However, in systems with no such waste heat available, electrified calcination, for example in the form of electrified rotary calciners, may be a competitive alternative to post-combustion capture technology.publishedVersio

Combined Calcination and CO2 Capture in Cement Clinker Production by Use Of Electrical Energy

The technical feasibility of electrifying the calcination process in a precalciner cement kiln system was assessed by studying different electrification concepts. Resistance-based heating was selected as it requires no CO2 recycling, has a high electricity-to-heat efficiency and has no major safety concerns. Resistance-based heating may be implemented in different types of calcination reactors. In this study, a rotary calciner was selected because the material flow can be readily controlled, it appears to be technically feasible to implement heating elements with a sufficiently high surface temperature to perform calcination, and rotary kilns are already in use in the cement industry, hence can be regarded as well-known technology. It is possible to integrate the electrified calciner with an existing cement kiln system in such a way that minimum disturbance of the production process is obtained. Hence, no negative impacts on the process, product quality or emissions are expected. The required electrical energy input for calcination in a kiln system producing 1 Mt of clinker per year, is about 85 MW. An early-phase cost estimate was conducted resulting in total annualized costs of 67 € per ton of CO2 avoided. The net avoided CO2 emission was 72 % (using a CO2 footprint of 47 g/kWh for electrical energy). The described CO2 capture concept was technically and economically compared with amine-based absorption of CO2 from the preheater exhaust gas. Two amine-based cases were calculated, one using electrical energy as the source of solvent regeneration (85 % net CO2 reduction) and another one using only available waste heat as the energy source (48 % net CO2 reduction). The annualized costs of these two cases were 75 and 40 € per ton of CO2 avoided, respectively. Hence, in cement plants where large amounts of waste heat are available, aminebased absorption appears to be the least expensive option for reduction in CO2 emissions. However, in systems with no such waste heat available, electrified calcination, for example in the form of electrified rotary calciners, may be a competitive alternative to post-combustion capture technology

Experimental study of thermal and catalytic pyrolysis of plastic waste components

Thermal and catalytic pyrolysis of virgin low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and mixtures of LDPE/PP were carried out in a 200 mL laboratory scale batch reactor at 460 °C in a nitrogen atmosphere. Thermogravimetric analysis (TGA) was carried out to study the thermal and catalytic degradation of the polymers at a heating rate of 10 °C/min. The amount of PP was varied in the LDPE/PP mixture to explore its effect on the reaction. In thermal degradation (TGA) of LDPE/PP blends, a lower decomposition temperature was observed for LDPE/PP mixtures compared to pure LDPE, indicating interaction between the two polymer types. In the presence of a catalyst (CAT-2), the degradation temperatures for the pure polymers were reduced. The TGA results were validated in a batch reactor using PP and LDPE, respectively. The result from thermal pyrolysis showed that the oil product contained significant amounts of hydrocarbons in the ranges of C7–C12 (gasoline range) and C13–C20 (diesel range). The catalyst enhanced cracking at lower temperatures and narrowed the hydrocarbon distribution in the oil towards the lower molecular weight range (C7–C12). The result suggests that the oil produced from catalytic pyrolysis of waste plastics has a potential as an alternative fuel

Models for Predicting Average Bubble Diameter and Volumetric Bubble Flux in Deep Fluidized Beds

The average bubble diameter and volumetric bubble flux give indications about the overall bed expansion in a fluidized bed. As these properties depend on the particle properties and fluidized bed regime, their accurate predictions have been a challenge. A new set of models for predicting the average bubble properties within the bubbling and slugging regimes in a deep fluidized bed is proposed, where bubble flux is modeled by G = U − c( ) U U U a 0 mf 0 mf, bubble diameter is modeled by db̅ = 0.848G D 0.66 0.34 and transition velocity is modeled by = + φ − − − 1 2.33U ( c 1)( ) U U a h mf D 0.027 0.35 t 0.588 bs mf t 0 . he models are developed using the information obtained from an experimental setup equipped with a ualplane electrical capacitance tomography and a porous distributor plate. Although they are empirical, the proposed models are based on the two-phase theory used in describing the bubble flow in a fluidized bed. These models have been validated, and the results show that they can be used to predict the behavior in different regimes at different gas velocities