This work presents a formalized methodology for salt's separation from three component electrolytic systems. The methodology is based on the multi-variant modelling block of a generalized crystallization process, with options for simulating the boundary conditions of feasible equilibrium processes and the elements of crystallization techniques. The following techniques are considered: cooling crystallization, adiabatic evaporative-cooling crystallization, salt-out crystallization, isothermal crystallization, and a combination of the mentioned techniques. The multi-variant options of the crystallization module are based on different variable sets with assigned values for solving mathematical models of generalized crystallization processes. The first level of the methodology begins with the determination of salt crystallization paths from a hypothetical electrolytic AX-BX-H2O system, following by an examination of salt-cooling crystallization possibilities. The second level determines feasible processes by the communication of a feed-system with the environment through a stream of evaporated water, or introduced water with introduced crystallized BX salt. The third level determines the value intervals of the variables for feasible processes. The methodological logic and possibilities for the created process simulator are demonstrated on examples of sodium sulphate separation from the NaCl-Na2SO4-H2O system, using different salt concentrations within the feed system.

In this paper we address the synthesis problem of distributed wastewater networks using mathematical programming approach based on the superstructure optimization. We present a generalized superstructure and optimization model for the design of the distributed wastewater treatment networks. The superstructure includes splitters, treatment units, mixers, with all feasible interconnections including water recirculation. Based on the superstructure the optimization model is presented. The optimization model is given as a nonlinear programming (NLP) problem where the objective function can be defined to minimize the total amount of wastewater treated in treatment operations or to minimize the total treatment costs. The NLP model is extended to a mixed integer nonlinear programming (MINLP) problem where binary variables are used for the selection of the wastewater treatment technologies. The bounds for all flowrates and concentrations in the wastewater network are specified as general equations. The proposed models are solved using the global optimization solvers (BARON and LINDOGlobal). The application of the proposed models is illustrated on the two wastewater network problems of different complexity. First one is formulated as the NLP and the second one as the MINLP. For the second one the parametric and structural optimization is performed at the same time where optimal flowrates, concentrations as well as optimal technologies for the wastewater treatment are selected. Using the proposed model both problems are solved to global optimality.

The aims of this work were to develop a mathematical model for composting municipal solid waste (MSW), to verify the proposed model with independent experimental data and to determine the optimum values for the initial moisture content and airflow. Separated MSW (with the addition of poultry manure, mature compost and sawdust) was used as materials for laboratory simulation. The experiment was conducted in three laboratory reactors (35 L) with forced aeration. Experimental data from one reactor were used to estimate five kinetic parameters in the proposed model and the verification of the model was performed using experimental data from the two reactors. Kinetics is based on the decomposition rate of organic matter. The estimation of kinetic parameters was done using data for four measured dynamic variables (organic matter conversion, O2 and CO2 concentration, and substrate temperature). Mathematical model was implemented in MATLAB. The proposed kinetic model is: kT = 0.0152 ×[1.0176 - 2.8001(- 0.002 × (T-20) ] with the reaction order 1.6. Comparisons of experimental and simulation results showed good agreement, especially in the mesophilic-thermophilic phase of the process, considering a high heterogeneous system. Optimum values for the initial moisture content in the material (45%) and airflow (0.50 m3h-1kg-1OT) were estimated using numerical simulations for different initial conditions.

In this paper, a computer aided analysis and synthesis of the crystallization processes from multicomponent electrolyte systems were studied. In addition, the vacuum crystallization processes with adiabatic cooling of the system are presented. The cooling process of a multicomponent electrolyte system can be considered as a process with the concentration of the system and/or the crystallization of the solid phase from the system. Requirements for multivariant options of the process simulator are the result of practical needs in the design of new processes or the improvement of exploitation processes. According to this, there are needs for a simulation of a simple flashing of the system as well as for the vacuum cooling crystallization processes with the cyclic structure. The possibilities of the created process simulator are illustrated on three component electrolyte systems. Application of the process simulator for any other electrolyte systems requires only an update of the thermodynamic model, and physico-chemical properties related to electrolyte system.

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