Optimization of desulphurization process in a flue gas obsorber by adjusting flow patterns and rotary atomizer

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.Efficiency of desulphurization process in a flue gas absorber depends strongly on flow patterns of the continuous gas phase and interaction with water slurry phase that is injected into the absorber. The main task is to ensure that undesulphurized flue gas moves optimally to where a high concentration of water slurry in the form of droplets “flies”. In the paper, a model for desulphurization process is presented. The problem was solved using commercial CFD code StarCD into which a model for desulphurization was integrated. The model distinguishes between two phases of heat and mass transfer. One called “constant rate period” where the water droplet formed by an aggregate of calcium hydroxide particles encapsulated in water evaporates by convection mechanism and sulphur dioxide is transferred by the same mechanism. In this phase the spherical reaction front recedes as calcium hydroxide is converted. In the second phase called “falling rate period” water is contained only in the free space between solid particles of calcium hydroxide and sulphur dioxide is transferred by diffusion that is modified by tortuosity reflecting torturous paths inside the structure of particles. By the same mechanism water evaporates from the aggregate of particles. A model for age of flue gas was developed that shows residing time of flue gas in individual parts of the absorber. Together with values of water content and void fraction of water phase one can suggest different design modifications of the absorber (for example different inclination of inlet vanes that guide the flue gas into the absorber).cs201

Transport and deposition of aerosols in human airways

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.A numerical model of aerosol transport in human airways is presented that contains 6 to 9 bifurcations and about 100 terminations. The model was acquired from a CT scan of a living person and contains oral/nasal cavity, thoracic and lower airways. Two breathing activities are modeled: 1) Resting conditions with a tidal volume 0,5liter, the minute ventilation 15 l/min and the period 4 sec/cycle and 2) Heavy activity (maximum exercise) with the tidal volume 3.33 liter, the minute ventilation 120 l/min and the period 1.25 sec/cycle. The inspiration/expiration cycle was modeled following the sinusoidal function. Euler-Lagrange approach was used to model aerosol transport and deposition in the airways. The total concentration of aerosol was assumed 50μg/m3 divided into three classes PM10, PM2.5 a PM 1 with appropriate fractions 25μg/m3, 9 μg/m3 and 16 μg/m3, respectively. Results of the modeling show the velocity field in several locations along the airways in different time steps of inspiration and expiration phases as well as deposition of individual aerosol sizes in the individual segments of the human airways.cs201

Liquid wall film formation in steam piping in nuclear plant

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.A numerical investigation is carried out for turbulent droplet-laden flow of saturated steam produced in a steam generator (SG) that feeds steam turbine (ST) through a long and multi-bend steam piping. The main purpose of the study is to analyze deposition of droplets that form a wall film in the piping system. Two tasks were performed: parametric study of the deposition in 90° elbows and the deposition in a more complex piping system. This system starts with outlets from the steam generator with five mouthpieces leading to a collector pipe and connecting the steam piping leading to a steam turbine. Results of the simulations show where droplets deposit and where a liquid separator should be placed to drain away the water film and to avoid droplets from entering the steam turbine. Dynamic temporal development of the film is presented showing mutual impact of gravity and entrainment by the co-flowing steam.cs201

Optimization of flue gas desulphurization absorber by means of computational fluid dynamics analysis

In the paper we present an optimization study/retrofit of the flue gas desulphurization (FGD) absorber focusing on the flow field in the desulphurization vessel and the performance of the rotary atomizer used there. The study is performed using CFD code with a well validated model for the semi-dry desulphurization. For the numerical modeling of the multiphase flow in the absorber, the Euler-Lagrange approach is used with the Eddy Interaction Model. The numerical study focuses on the optimization of the flow field inside the absorber with the aim to increase the time during which the lime slurry remains in contact with flue gases. Results of the numerical modelling are in very good agreement with operational tests.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Numerical optimization of the taper a vertically cast plate

The temperature field of the studied plate was analyzed with different angles of widening in its cross section (in the range from 0° to 4.4°). From the inclined side, the plate was either insulated or uninsulated. Plastizol was used as an insulator. An uninsulated plate has a calculated optimum angular expansion of 3°. A widening of 2° is the minimum angle at which internal defects (e.g. shrinkage voids) begin to disappear. The insulated plate has an optimum angle of 2°. Using numerical calculations, it is possible to predict that after crystallization without insulation, the plate itself with a widening of 3° will have the same internal quality as a widening of 2° with insulation. The knowledge gained from this study can lead to a reduction in the volume of liquid metal used and also to a reduction in machining costs. These research results have already been successfully applied to the design of the technology for casting nodular cast iron cylinder liners