Mathematical Tool Based on Breakthrough Curves to Evaluate the Economic Advantages of Chemical Regeneration of Activated Carbon in Power Plants: A Comparative Study

A mathematical tool has been developed to evaluate the economic advantages of in-situ chemical regeneration of fixed-bed industrial adsorbers of granular activated carbon for cooling water treatment systems in Cuban power plants. Two scenarios of activated carbon (AC) management in a power plant were compared by applying the proposed model. The economic profit by implementing the regeneration strategy as a function of the number of regeneration cycles was determined and optimized. Breakthrough curves were obtained to assess the adsorption performance of the AC after progressive saturation–chemical regeneration cycles using synthetic water and hydrochloric acid, respectively. For the first saturation cycle, the breakthrough time was 272 min and after 10 cycles, it was reduced to 58 min, indicating a decrease of the adsorption capacity of 21%. The AC adsorption performance in terms of saturation time as a function of the number of regeneration cycles was considered one of the tool parameters. The proposed tool allows to determine the optimal number of regeneration cycles for a maximum economic profit in the regeneration strategy. It was demonstrated, using the proposed tool, that after an optimum of seven regeneration cycles, the power plant expends only 26% of the total investment. The simplicity of the tool permits a rapid way to find the most profitable number of regeneration cycles by combining economic, technical and adsorption efficiency parameters in one function, thus improving the AC management strategy at an industrial scale with corresponding environmental and economic advantages, including sustainability.

Computer prediction of technological modes of rapid cone-shaped adsorption filters with automated discharge of part of heat from separation surfaces in filtering mode

In the paper a mathematical models of technological modes of filtration with automated removal of part of heat from interface surfaces (water purification from multicomponent impurities), backwashing, chemical regeneration and direct washing of rapid cone-shaped adsorption filters with chemical regeneration of piecewise homogeneous porous loads while maintaining constant velocities of the respective modes is formulated. The proposed models in the complex allow to conduct computer experiments to investigate the change in the concentrations of components of a multicomponent impurity in the filtration stream and on the surface of the loading adsorbent, retained by both physical and chemical adsorption, filtration flow temperature, filtration coefficient, active porosity and pressure along the filter height and on their basis to predict more optimal options for the use of adsorbents of each loading layer and increase the protective time of rapid cone-shaped adsorption filters with automated heat removal from the interface surfaces in filter mode.

Chemically/Electrically-assisted Regeneration of Polyacrylonitrile-based Hydrogel Adsorbed Heavy Metals

Adsorption is an important technology for the removal of heavy metals from industrial effluents. Efficient regeneration of exhausted adsorbents is essential for improving the applicability of different adsorbents. In this work an adsorptive polyacrylonitrile-based hydrogel was characterized and investigated in terms of adsorption/regeneration using both conventional chemical and electrical-assisted regeneration techniques. The hydrogel characterization includes FTIR, XRD, SEM, EDAX, porosity, and electrical conductivity. Hydrogel performance in adsorption and conventional chemical regeneration was tested. Further, electrically-assisted regeneration using a specially designed cell was also investigated.The maximum adsorption capacities for chromium and nickel were 8.082, and 17.437 mg/g, respectively. The isotherm data fitted Freundlich, while kinetic data fitted pseudo-second-order model.Conventional chemical desorption showed regeneration efficiency of 15.58, and 27.27 % for chromium and nickel, respectively. While, the electrically-assisted regeneration showed much higher values of 51.6, and 98.3 % for chromium and nickel, respectively indicating the merit of using electrically-assisted chemical regeneration for enhancing heavy metals adsorbing hydrogel applicability.

COMPUTER PREDICTION OF TECHNOLOGICAL REGIMES OF RAPID CONE-SHAPED ADSORPTION FILTERS WITH CHEMICAL REGENERATION OF HOMOGENEOUS POROUS LOADS

Mathematical models for predicting technological regimes of filtration (water purification from the present impurities), backwashing, chemical regeneration and direct washing of rapid cone-shaped adsorption filters, taking into account the influence of temperature effects on the internal mass transfer kinetics at constant rates of the appropriate regimes, are formulated. Algorithms for numerical-asymptotic approximations of solutions of the corresponding nonlinear singularly perturbed boundary value problems for a model cone-shaped domain bounded by two equipotential surfaces and a flow surface are obtained. The proposed models in the complex allow computer experiments to be conducted to investigate the change of impurity concentrations in the filtration flow and on the surface of the load adsorbent, temperature of the filtration flow, filtration coefficient and active porosity along the filter height due to adsorption and desorption processes, and on their basis, to predict a good use of adsorbents and increase the protective time of rapid cone-shaped adsorption filters with chemical regeneration of homogeneous porous loads.

Performance of Layer-by-Layer-Modified Multibore® Ultrafiltration Capillary Membranes for Salt Retention and Removal of Antibiotic Resistance Genes

Polyether sulfone Multibore® ultrafiltration membranes were modified using polyelectrolyte multilayers via the layer-by-layer (LbL) technique in order to increase their rejection capabilities towards salts and antibiotic resistance genes. The modified capillary membranes were characterized to exhibit a molecular weight cut-off (at 90% rejection) of 384 Da. The zeta-potential at pH 7 was −40 mV. Laboratory tests using single-fiber modified membrane modules were performed to evaluate the removal of antibiotic resistance genes; the LbL-coated membranes were able to completely retain DNA fragments from 90 to 1500 nt in length. Furthermore, the pure water permeability and the retention of single inorganic salts, MgSO4, CaCl2 and NaCl, were measured using a mini-plant testing unit. The modified membranes had a retention of 80% toward MgSO4 and CaCl2 salts, and 23% in case of NaCl. The modified membranes were also found to be stable against mechanical backwashing (up to 80 LMH) and chemical regeneration (in acidic conditions and basic/oxidizing conditions).

Technological framework for the reversible chemical regeneration of water wells

Groundwater is mainly used for water supply of cities, rural settlements and industries in the Republic of Belarus. About 90% of water wells operate at reduced specific production rates as a consequence of biological and chemical clogging. Due to the insufficient efficiency of existing regeneration methods, the average service life of water wells rarely exceeds 18–20 years, which is significantly shorter than the estimated life. In this regard, creation of the effective and simple regeneration methods is becoming an urgent scientific and practical problem of great importance. A reversible pulse-and-chemical regeneration assembly has been designed for water wells; it consists of a compressor, hoses and a submersible device in the form of a two-chamber pneumatic displacement pump. The advantage of this assembly is the absence of a circulation pump in its configuration and the possibility of efficient treatment of a limited filter interval. A technology for the regeneration of water wells using the reversible pulse-and-chemical regeneration assembly is proposed. The installation, hoisting and other related operations should be carried out using a truck crane with a telescopic lifting boom. The reagent can be universal acid cleansing agent Deskam TU RB 37430824.001-97. One of the advantages of water well regeneration using the proposed assembly is the reverse movement of the reagent in gravel filter. Two regeneration modes were tested on a laboratory scale: the reversible flow and one-way flow of the reagent. The analysis of the laboratory research data shows that the use of the reversible mode of the reagent movement significantly reduces the cleaning time required for the removal of colmatant from the gravel filter as compared with the one-way flow of the reagent.

Equipment for pulsed gas-and-chemical regeneration of water wells

The development of new methods for the regeneration and recovery of specific flow rate of water intake wells is an urgent task. Based on many years of the experience in well operation, it has been proved that all wells eventually need to be repaired. The main reason for such work is the chemical clogging of the filter and filter zone with different chemical compounds. The average stable operation period of new wells is 2–4 years. Better cleaning of filters and filter zones in water intake wells is achieved using the combination of hydraulic, impulse and vibration attacks with subsequent or concurrent chemical treatment. At this date, none of the integrated approaches enjoys wide application due to some disadvantages. At the Belarusian National Technical University, the pulse-and-chemical regeneration equipment has been designed for water intake wells. The technology involves electrolysis-induced explosion of a hydrogen–oxygen mixture at the well mouth on ground surface, feed of the mixture to a working chamber in the well filter, filling of a chemical reagent in the filter treatment zone and explosion of the reagent medium. The equipment has successfully passed laboratory and field tests.