| Abstract | Simulation has been widely used many years ago by chemical engineers to represent several processes and operations, existing in industries of chemical engineering interest. Flow-sheeting calculations is a kind of simulation for preliminary evaluation of different processes. Flow-sheet itself is a key document for the evaluation, design and analysis of processing systems. It shows the processing units arrangement and the streams connecting them, the quantities and compositions at every point of the flow-sheet and the operating conditions (phase, temperature, pressure, enthalpy etc.).
Manual flow-sheeting calculations are tedious and time consuming, especially for large and complex flow-sheets. Special computer programs, which simulate different processing units existing in industries, are widely used in order to carry out these calculations, which are necessary for processes design. The designer engineer is possible to use these programs in order to evaluate existing processing units, to take into consideration different alternative solutions and to find out the optimum and more economic operating conditions.
The main object of the present work was the development of a new, user friendly, steady state simulation computer program, to perform mass and energy balance calculations in flow-sheets mainly for industries processing agricultural products, using the method of separate calculation subroutines (modules). This program works in Microsoft Windows environment. This work was a trial to solve a problem for the case of industries processing agricultural products where, the lack of sufficient and adequate physical properties data for almost all agricultural products – especially due to changes in compositions during processing – makes the whole problem more complicated and the necessity of computer aided calculation more imperative. So, it was necessary to develop a special data bank for the physical properties of several agricultural products and chemical compounds as well. The use of this data bank is based on a model, which considers that the majority of processed agricultural products exist either as soluble solids or insoluble solids in water, or in some cases as liquids, where no phase change takes place during processing. By this way, processes where there are changes in concentrations of soluble or suspended solids (such as evaporations, dilutions etc.), are calculated easily.
A set of selected and combined mathematical models simulating many types of unit operations in plants processing agricultural products in actual production conditions were used. Also a special data bank for the physical properties of several agricultural products and chemical compounds as well was developed, collecting or calculating data from several handbooks. The selection and formulation of the appropriate mathematical models as well as the selection or calculation of the appropriate physical properties of several agricultural products and chemical compounds were mainly the results of documentary analysis. The computer program developed using these models, was tested in actual production conditions. Most of them are cases existing in industries processing agricultural products. But also there are cases for other types of industries, which have been tested too. The obtained results in all cases are satisfactory, and they are in agreement with figures existing in actual plants or described in many references.
Program presentation is mainly concentrated in its organization, the required input data, the used techniques and the obtained results in some test applications. |
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