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| 2. |
- Boman, Christoffer, et al.
(författare)
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Development of innovative small(micro)-scale biomass-based CHP technologies
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To enhance the overall efficiency of the use of biomass in the energy sector in Europe, the large electricity production potential from small-scale biomass heating systems should be utilised. So far, no technologically sound (in terms of efficiency and reliability) and economically affordable micro- and small-scale biomass CHP technologies are, however, available. Therefore, the present ERA-NET project (MiniBioCHP) aimed at the further development and test of new CHP technologies based on small-scale biomass combustion in the electric capacity range between some W and 100 kW. Within the project, an international consortium consisting of 12 partners from 4 countries, including university institutions, institutes and industry (both engineering and manufacturing), collaborated closely to perform high level R&D on three promising micro/small-scale biomass based CHP technologies which are covering a broad range of applications in the residential heating sector. The Austrian engineering company BIOS, coordinated the international project. The project was based on earlier basic research and development work related to these promising new technologies and aimed at the achievement of a technological level which allows a first (commercial) demonstration after the end of the project. The three CHP concepts included in the MiniBioCHP project were;1. Pellet stoves with a thermoelectric generator (TEG)2. Small-scale biomass boilers (10-30 kWth) with a micro-ORC process3. High temperature heat exchanger (HT-HE) for an externally fired gas turbine (EFGT)The Swedish part of the project was focused on the development of the concept of biomass based EFGT with dedicated R&D activities related to the development of the HT-HE system. The Swedish project consisted of the research partners Umeå University (project leader), Luleå University of Technology, Chalmers University of Technology and RISE Research Institutes of Sweden, together with the industrial partners Enertech AB/Osby Parca and Ecergy. The expertise of the Swedish partners regarding ash related problems, grate boiler combustion and modelling, deposit formation and high temperature corrosion, were combined with the know-how of a Polish partner regarding HT-HE design, construction, testing and optimisation.The HT-HE is the most crucial component in EFGT processes significantly influencing the investment costs, availabilities as well as the efficiencies that can be achieved. With a thermal capacity from several hundred kW up to 2-3 MWth) the CHP technology based on a biomass boiler and an EFGT is suitable for district heating systems, or process heat consumers. The electricity produced by the gas turbine (up to some 100 kWel) can be used to cover the own electricity consumption of a company and/or fed into the grid. Even though the concept of biomass based EFGT has been an interesting alternative for small-scale CHP production for some decades, and R&D activities have been undertaken, tackling both economic and technical aspects, only a few pilot-plants have been in operation and no initiative has so far reached the level of commercial implementation. Thus, the concept of EFGT fed with biomass is still considered to be in a rather early development stage and the main technical challenges are related to alkali deposit induced corrosion and thermal stress of the HT-HE material, turbine design/operation and system integration.Within the present project, a HT-HE prototype aimed for an EFGT system was therefore designed, constructed and successfully tested at flue gas temperatures up to 900°C. Thus, appropriate guidelines for a compact design of the HT-HE and recommendations have been worked out to minimize thermal stresses as well as ash related problems regarding ash deposit formation and high temperature corrosion in a biomass boiler system. Furthermore, different concepts for the overall biomass based EFGT system have been worked out and evaluated. The outcome of the project will hopefully be used in the further development work and form the basis for a first testing and demonstration plant within the coming years.
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| 3. |
- Darelius, Anders, 1977, et al.
(författare)
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A Volume-Based Multi-Dimensional Population Balance Approach for Modelling High Shear Granulation
- 2006
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Ingår i: Chemical Engineering Science. ; 61, s. 2482-2493
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Tidskriftsartikel (refereegranskat)abstract
- A volume-based multi-dimensional population balance model based on the approach used by Verkoeijen et al. (2002) is further developed and applied to a wet granulation process of pharmaceutically relevant material, performed in a high shear mixer. The model is improved by a generalization that accounts for initial non-uniformly distributed liquid and air among the different particle size classes. Only the wet massing period of the granulation process has been modelled and it is experimentally found that the pores in the granules are fully saturated by liquid, i.e. no air is present in the granules during this period. Hence, an alternative model formulation is used as no model for the air in the granules is needed. Particle volume distribution, liquid saturation, liquid to solid ratio and porosity of the granules can all be modelled, as these properties can all be expressed as combinations of three model parameters, i.e. the volume fraction of solid material, total liquid fraction and the liquid fraction inside the granules. The model is also improved by introducing a new coalescence kernel and by increasing the number of size classes used. The simulated results are compared to measurements from a series of five designed experiments where impeller speed and water content are varied. It is found that the evolution of the volume, liquid saturation and porosity distributions could all be explained by fitting the compaction and coalescence rate constants.
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| 5. |
- Darelius, Anders, 1977, et al.
(författare)
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Fluid dynamics simulation of the high shear mixing process
- 2010
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 164:2-3, s. 418-424
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Tidskriftsartikel (refereegranskat)abstract
- The Eulerian-Eulerian two-fluid approach for modelling multiphase flows is used to simulate the flow in a high shear mixer. The results are compared with experimental velocity profiles for the solids phase at the wall in the mixer obtained using a high speed camera (Darelius et al. Chem. Eng. Sci. 62 (2007) 2366).The governing equations are closed using relations from the Kinetic Theory of Granular Flow (KTGF) combined with a frictional stress model due to Johnson and Jackson and Schaeffer and inter-phase drag due to Wen and Yu. In addition, calculations are presented for a model with a constant particle phase viscosity (CPV). Free slip and partial slip boundary conditions for the solid phase velocity at the vessel wall and the impeller have been utilized.The results show that the bed height could be well predicted by the partial slip model, whereas the free slip model could not capture the experimentally found bed height satisfactorily. For the KTGF model, the swirling motion of the rotating torus that is formed by the moving powder bed was over-predicted and the tangential wall velocity was under-predicted, probably due to the fact that the frictional stress model needs to be further developed, e.g. to tackle cohesive particles in dense flow. The CPV model gave predictions in good agreement with the experiments for a solids viscosity of 0.1. Pa. s and a wall slip parameter of 0.005. m/Pa. s. However, for a very low or very high value of the particle phase viscosity and for a high value of the wall slip parameter the agreement with experiments was poor. Interestingly, values of the viscosity that are commonly employed for fluidized beds seem applicable also in the present case. © 2009 Elsevier B.V.
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| 6. |
- Darelius, Anders, 1977, et al.
(författare)
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High shear wet granulation modelling - a mechanistic approach using population balances
- 2005
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Ingår i: Powder Technology. ; 160, s. 209-218
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Tidskriftsartikel (refereegranskat)abstract
- A population balance approach based on splitting the coalescence kernel into two factors, the first describing the collision frequency of particles and the second describing the collision efficiency, is applied to modelling wet granulation in a high shear mixer. Four different expressions for the collision frequency are compared and discussed. The kernels are the size independent kernel, the shear kernel proposed by Smoluchowski [1] and the two kernels proposed by Hounslow [2], i.e. the EKE kernel and the less used kernel based on equipartition of fluctuating translational momentum (ETM kernel). Microcrystalline cellulose (mcc) is granulated under different process conditions and it is found that the ETM kernel best describes the granulation at higher impeller speeds, whereas the EKE kernel gives better agreement at lower impeller speeds. The collision efficiency is assumed to be a function of the liquid saturation. By using this assumption, it was possible to detect similar trends for the remaining part of the collision efficiency regardless of process conditions.
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| 7. |
- Darelius, Anders, 1977, et al.
(författare)
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LDA measurements of near wall powder velocities in a high shear mixer
- 2007
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 62:21, s. 5770-5776
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a new method has been developed to measure particle velocity distributions in the near wall region of a high shear mixer by using Laser Doppler Anemometry (LDA). The velocities along the side of the granulator have been measured at different impeller speeds and it has been found that it is possible to obtain tangential and axial velocity data in the dense powder flow up to 4 mm in depth. Moreover, it has been found that the tangential velocity component increases slightly with distance from the wall in the near wall region, indicating a partial slip boundary condition for the solid phase at the vessel wall. It is also shown that the tangential velocity decreases with increased vertical distance to the impeller. The velocity fluctuations, represented by root mean square (rms) velocities, also decrease with increased vertical distance to the impeller and the tangential and axial rms components are found to be of the same order of magnitude.
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| 8. |
- Darelius, Anders, 1977, et al.
(författare)
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Measurement of the velocity field and frictional properties of wet masses in a high shear mixer
- 2007
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Ingår i: Chemical Engineering Science. ; 62, s. 2366-2374
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Tidskriftsartikel (refereegranskat)abstract
- In order to develop predictive process models and to enhance process understanding in high shear granulation, there is an ongoing search for non-intrusive methods for measuring the wet mass velocities in the mixer. In this study a high speed CCD camera is used in combination with software for Particle Image Velocimetry (PIV) calculations to obtain information about the wet mass velocities. The focus has been on obtaining good spatial and angular resolution for the velocities along the glass bowl wall. In a Jenike shear cell, both internal and wall frictional properties have been measured and together with velocity data, this information is used for prediction of the impeller torque. It has been shown that the near wall velocities are strongly dependent on the coefficient of wall friction, which decreases during liquid addition. The decrease in the coefficient of wall friction results in increased wet mass velocities close to the bowl wall. It is also found that the wet mass velocity has a strong angular dependence, resulting in a high frequency pulsing bed behaviour which cannot be detected by visual inspection. The predictive impeller torque model developed by Knight et al. (2001) has been generalized to account for cohesive materials and with frictional and velocity data, the level of the impeller torque is well predicted. However, the model is based on crude assumptions regarding the velocity distribution and hence, it cannot capture the dynamics in the measured torque curve satisfactorily.
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| 9. |
- Niklasson, Anders M. N., et al.
(författare)
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Extended Lagrangian Born-Oppenheimer molecular dynamics with dissipation
- 2009
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Ingår i: JOURNAL OF CHEMICAL PHYSICS. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:21, s. 148075-
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Tidskriftsartikel (refereegranskat)abstract
- Stability and dissipation in the propagation of the electronic degrees of freedom in time-reversible extended Lagrangian Born-Oppenheimer molecular dynamics [Niklasson , Phys. Rev. Lett. 97, 123001 (2006); Phys. Rev. Lett. 100, 123004 (2008)] are analyzed. Because of the time-reversible propagation the dynamics of the extended electronic degrees of freedom is lossless with no dissipation of numerical errors. For long simulation times under "noisy" conditions, numerical errors may therefore accumulate to large fluctuations. We solve this problem by including a dissipative external electronic force that removes noise while keeping the energy stable. The approach corresponds to a Langevin-like dynamics for the electronic degrees of freedom with internal numerical error fluctuations and external, approximately energy conserving, dissipative forces. By tuning the dissipation to balance the numerical fluctuations the external perturbation can be kept to a minimum.
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| 10. |
- Niklasson Björn, Ingela, 1960, et al.
(författare)
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Empirical to mechanistic modelling in high shear granulation
- 2005
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Ingår i: Chemical Engineering Science. ; 60, s. 3795-3803
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Tidskriftsartikel (refereegranskat)abstract
- This paper gives an overview of the different models available for granulation in high shear mixers with a focus on applicability in the pharmaceutical industry. Three examples of applications are given. The examples indicate the potential of mechanistically based models for scale-up and the importance of understanding the dynamics of the granulation process. The first two examples show how the impeller torque can be modelled and predicted in the dry and wet mixing phases of the high shear granulation process, using a solid mechanics and a hierarchical multivariate model, respectively. In the third application the particle size distribution is modelled using population balances and it is shown how different operating conditions can be included in the coalescence kernel to describe the granule growth.
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