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Flow in Reactors, Fluidization and Sedimentation

Main research domains

  • Theoretical and experimental investigation of formation of separable suspension by coagulation, aggregation and agglomeration of individual particles.
  • Theoretical and experimental investigation of separation of individual particles, aggregates and agglomerates.
  • Theoretical and experimental investigation of the fluidized layer reactors.
  • Theoretical and experimental investigation of the relationship between the hydrodynamics of the fluidized layer and the chemico-technological process of denitrification.
  • Hydrodynamics of agitated vessels.
  • Sedimentation of solid particles.

Most important results

  • The aggregation efficiency of the full scale reactor with the fluidized layer of the sand proposed on the base of the results of the previous research and installed in the waterworks Želivka was evaluated. The results show that the improvement of the physical properties of the aggregates formed in the fluidized layer enables prolongation of the filter runs (30 - 50%) due to the deeper penetration of the filter bed and that the volume of liquid sludges is considerably reduced.
  • The new method of separation of mineral and organic impurities from water in the fluidized layer in the form of the solid and water-free shelf surrounding the sand grains forming the fluidized layer was elaborated and in the pilot plant reactor verified. The separation efficiency was evaluated by reduction of Al content (50-60%) and by reduction of organic matter content (30-40%). The results proved the operational applicability of the method. The analysis of the cover shell shows that the content of Al2O3 corresponds to 65%, the content of organic matter to 25%. The content of free water corresponds to 2% by weight.
  • The modified Richardson-Zaki equation describing the three-phase fluidization system formed by water, sand grains and gas bubbles produced by microorganisms during the process of denitrification was derived. It was proved that the appropriate corresponding velocity for fluidization is identical with falling velocity of a single particle as measured in the same vessel in which fluidization takes place. The dependence of the exponent in Richardson-Zaki equation on the particle size and density, water temperature and particularly on the porosity of the fluidized layer was determined.
  • The pilot plant enabling the continuous denitrification in the fluidized layer, capable of long-term run of the capacity of 10 l/min was constructed. Method of regeneration of the covered layer was developed and construction of the water in- and outlet elements was proposed.
  • The long-term pilot plant tests of denitrification of the Blanice river water were realized. The results proved the high denitrification efficiency of the reactor with the fluidized layer. Rapid changes of the water temperature as well as the temperature below 8oC were found to be the limiting factors of application of biological denitrification in the treatment of surface waters.
  • Based on settling velocity equations, the theoretical calculation gave rise to a conclusion that the appropriate continual function of the bioreactor with growing biomass in the fluidized layer is composed of particles of the same size. Beneficial migration of particles with the biofilm in the layer takes place up to a certain value of biofilm density.
  • All three components of mean velocity, turbulence and kinetic energy distribution in close mechanically agitated vessel without baffles were determined.
  • The existence of macro-instabilities, their localization in the agitated space was confirmed. The characteristic frequencies of macro-instabilities in open cylindrical vessel with baffles were found to be depending on the impeller speed.
  • Mean axial velocity of liquid and of solid particles and turbulence intensity in an open agitated vessel with baffles for model suspension were determined.
  • Using the LDA method a distribution of local velocities of particles and carrier liquid, the effect of vessel inclination on velocity and concentration distribution were determined and particle/liquid slip velocities were calculated.
  • The inner structure of sedimentation, the effect of displaced liquid flow on both the particles and the liquid velocity profiles and high sensitivity of settlement process on inclination of the wall of the vessel was analyzed. Even a gentle inclination of the vessel causes asymmetrical absolute velocity distribution, transversal migration of particles and increase of local concentration near the upward-facing wall.
  • The analysis of the internal structure of settlement process showed that the relative particle/liquid velocity is nearly constant in the whole cross-section of the vessel, independently on absolute fall velocity distribution. The effect of concentration and sizes of particles on the fall velocity of individual species in mono- and bi-disperse suspension was determined.