Method of designing a double-chamber flotation machine
with an aeration ejection system with dispersant

Summary

A double-chamber flotation machine with an ejection system with a dispersant is considered. It is demonstrated that the use of a dispersant provides for the multimodal distribution of bubble sizes characterized by several groups. The importance of the correct choice of the process time as one of the most important parameters for the flotation unit design is noted. The method of calculating a double-chamber flotation machine with an ejection system with a dispersant with due account for the specific features of the bubble size distribution and hydrodynamic situation in chambers is proposed. The method of calculating the process time is based on the use of multistage flotation model that presents the distribution of bubbles into several groups depending on the size. The hydrodynamic situation in the chambers is taken into account by the use of equations for perfect-mixing and plug-flow reactors. The calculation of a double-chamber flotation machine with an ejection system with a dispersant for the purification of carwash wastewater was carried out. The results of calculating the parameters of the aeration system, process constants, flotation time and specific geometrical parameters of the flotation machine are presented. The presented case study demonstrates the possible use of the given method for designing the proposed flotation unit.

Key words

wastewater , flotation , ejection aeration system , dispersant , flotation model , flotation time

Substantiation of using an improved pneumohydraulic disperser to obtain fine gas-liquid dispersion

Summary

In the processes of natural and wastewater treatment, as well as in various branches of industry and agriculture, often a need for obtaining fine gas dispersions (with average bubble diameter less than 1 mm) arises in order to achieve a large interphase surface. Practical methods of obtaining gas dispersions are considered, along with the gas bubble mechanism while separating from individual pores during bubbling. Possible formation of fine gas dispersions by dispersing gas with a highly turbulent liquid flow is shown. The pneumohydraulic method is the most preferable, since it does not require high energy costs for dispersion, is highly reliable owing to the lack of moving parts, and provides for obtaining gas bubbles with a diameter of less than 1 mm, which will ensure high efficiency of dissolving relatively expensive gases (oxygen, ozone, etc.). An original device for hydrodynamic dispersion of gas for obtaining a fine gas dispersion allowing effective introduction of gas into the liquid being processed is described.

Key words

aeration , dispersant , dispersion , газожидкостная дисперсия

Process concentrate treatment by flotation at CHP plants

Summary

The problem of processing oily wastewater generated at power plants is discussed. Much attention is paid to the purification of process concentrate that is characterized by higher temperature (55–70 °С). A pneumatic flotation unit used for the process concentrate treatment at the South CHP plant operated by Lenenergo OJSC is considered. The major drawback of the unit is pointed out: the changes in the rubber properties result in the changes in air bubble dimensions, and the efficiency decreases. A possible solution to the problem can be the use of an ejection aeration system with a disperser. The experiments in a laboratory unit on determining the size distribution of the bubbles generated by the ejection aeration system at 55°С were conducted. In addition, model oily wastewater was subject to purification in a unit with the pneumatic and ejection aeration systems. The average size of the finely dispersed bubbles generated by the ejection aeration system with a disperser was 60 μm, and that of the coarse bubbles was 105 μm. It is shown that the use of the ejection aeration system with a disperser provides for reducing the residual concentration of oil products from 4 to 1 mg/l or reducing the purification time from 25 to 15 minutes.

Key words

flotation , ejector , pneumatic aeration system , air bubble size , dispersant , process condensate

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