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A-395
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Development of an Automatized Control System for the Process of Concentration of Molybdenum Ores

Project Status: 8 Project completed

Commencement Date: 01.02.2001

Duration in months: 24 months

The technology of concentration of ores involves rather complicated physical and chemical processes, which are associated with great number of varying factors, and these processes result in releasing of ores and getting the maximum of useful component in the final product-concentrate.

Optimal control of such processes is available on the basis of adequate and rather adjusting to the varying conditions mathematical model.

The existing models, which give descriptions of ore concentration processes are stochastic, the complexity of their structure is adopted a priori and the influence of some variables on the optimal process is not quite reasonable, and it results in the loss of product quality. On the other hand optimal control when using the corresponding criterion is impossible without sufficient information concerning the state of the process and without formation and realization of necessary effects on the process. It is obvious that the effectiveness of the given technological process depends on the choice of the final aim of production provided the above mentioned analytical and technical problems are successfully solved with the help of computer technologies.

**The aim of the Project** is to improve technical and economical indices of molybdenum ore concentration on the example of concentration factory in Kajaran (Republic of Armenia) through automatization and optimization of the flotation process control.

**Preliminary Studies:** The technology of concentration of ores consists of the following consecutive stages: ore output, crushing, grinding, flotation, drying and storing of the final product.

*Extraction* of ores is carried out by excavators in the open quarries.

*Crushing* of ores is carried out with vibration jaw crushers, providing granules sized 25mm in diameter.

*Grinding*** **of ores is carried out by ball mills in two stages to get granules sized 74 mkm.

*Flotation* is a complicated technological process, which consists in releasing of the useful component into the concentrate and washing out of admixtures by means of physical-chemical methods. The flotation process lasts about 20 minutes.

*Drying* of the concentrate is carried out after filtration of water in cylinder dryers, reducing the moisture content to 3-4%.

The** ***flotation* process is the most important and complicated. The grinded ore with certain granulometric parameters is mixed with water forming the pulp of definite density, which goes into the flotation section, which consists of a great number of consecutive chambers. Reagents are added into the chambers in succession for splitting and falling out the dirt and bringing the concentrate to the surface. Then the concentrate with the foam goes into the filtration chamber.

Getting of the useful component in the concentrate depends on its content in the initial ore. Preliminary studies have shown, that the loss of the useful component and the presence of admixtures in the concentrate in most cases are caused by:

- deviations of granulometric composition of grinded ore from the standard;

- errors in the pulp density measurements;

- imprecise dosage and measurements of the reagent concentration in chambers;

- imprecise definition of the foam thickness on the flotation chamber surface.

Flotational concentration of ores is a complex of rather complicated physical and chemical processes, the mechanisms of which are not studied thoroughly. That's why stochastic methods are used to describe these processes, involving statistic observation data. Our preliminary studies have revealed that the model of these processes must be adequate, it must have predicting character and its structure must be flexible to enable taking into account the variations of input and intermediate factors. But even if we get a satisfactory mathematical model of the process, additional problems will occur due to unskilled control of the real process state, insufficient metrological guarantee while measuring the parameters and transport delay. All the above mentioned circumstances constitute the ground for not optimal regimes of the process, for decreasing of the effectiveness of the whole process and low quality of the final product.

Preliminary studies have revealed that it is necessary to solve the following main problems to attain the objectives:

1. To work out a rather flexible adequate mathematical model of optimal complexity for the flotation process of molybdenum ore concentration.

2. To create a complex of measuring equipment with corresponding metrological characteristics attended by the controlling computer.

3. To select the most available technical-economical indexes for the technological process under consideration and provides its optimization.

4. To construct an imitational model of the flotation process.

**Research Design and Methods**

*Construction of the model.* The application of the regressive analysis apparatus for description of the flotation process, which is characterized by a great number of variable factors, depends on a priori choice of the model complexity; in case of unsuccessful choice the model obtained after defining the regression parameters may be unreliable for solving optimization problems. Besides to obtain a rather adequate mathematical model we need great preliminary statistics. In the given Project the flotation process mathematical model is to be constructed by using the method of group accounting of arguments and it will allow to work out a hierarchical model of optimal complexity, the levels of which are represented by simplest models, obtained by natural selection of variables. To provide the adequateness of the model statistical selection is required. Models, constructed by the method of group accounting of arguments are rather flexible, what makes possible rapid correction of the model on the basis of current selection in case of variations of the available limits of variations of the available. To increase the effectiveness of the model it is supposed to study the influence of prediction of parameter variation range on the model reliability; it enables to decrease the volume of information concerning measured and controlled parameters, being in use.

*Elaboration of the measuring and executing equipment.* Like any process under control, the flotation process is characterized by input, output and outer parameters, which define the state of the process. Measuring of some parameters can be realized with the existing standard means. However, in the technology being at work a series of parameters are measured in the laboratory conditions. These parameters include: the content of molybdenum in the grinded ore, foam and the final product, the density and granulometric composition of the pulp, concentration of reagents in the pulp (xanthat, sulphide sodium (Na_{2}S), water glass, soda, quicklime etc.). It is supposed to design special means for measuring the above mentioned parameters just during the current process and to store their values in the controlling computer. The methods of direct and indirect measurements will be applied, involving gravitational electrical and electro-chemical techniques and ensuring corresponding requirements to metrological characteristics. Besides, it is supposed to design controllable dosing equipment as a control executing body.

*Optimization of the process.* The effectiveness of the concentrate production can be estimated according to technological and economical criteria. In the given Project it is supposed to give a detailed analysis of these criteria with the purpose of giving grounds and choosing the production effectiveness criterion. We assume that the problem will be reduced to nonlinear programming.

To solve the optimization problem the existing program packets can be used. However, to provide corresponding flexibility for solving the problems in the conditions of real production an attempt should be made to work out simpler algorithms and programs, built in the computer.

As a result of the solution of the optimization problem there will be defined optimal adjustment of the technological process control parameters.

*Construction of an Imitational Model.* Imitation model is necessary for carrying out research experiments and predicting the production results. To construct an imitation model we intend to use the obtained mathematical model of the flotation process, with further generation of corresponding effects, using the methods of statistical experiments.

1. Balasanyan S. Sh., Sarkisyan R. G. Stratified Model of a Complex computing system.- In: Proceeding II International Conference on Reliability and Exploitation of Computer System "RELKOMEX 81". Wrozlav, Poland, 1981, p. 80-85.

2. Balasanyan S. Sh., Abgaryan S. V., Hayrapetyan S. G. The Influence of Ore Parameters on the Molybdenum Concentrate Cost. - Inter-college Proceedings of Yerevan Polithechnic Institute, XVIII, ed. II. Yerevan, YerPI, 1978, p.32-34.

3. Balasanyan S. Sh. The Imitational Model of Real Functioning of Ore, Grinding Technological System - Informational list Arm. RINTI "Gornoye delo", series 07-10, 1979, № 6.

4. Abgaryan S. V. Technological Process Regime Optimization of Molybdenum Ore Flotation //Proceedings of NAS and SEU of RA, series TS, v. 51, 1998, № 1., pp. 67-71.

5. Kyureghyan S. G., Kyureghyan N. S. The Quest of Bordering Solving one-class problems of Non-linear Programming. // Proceedings of NAS and SEU of RA, series TS, v.51, 1998, № 3, p. 13-17.

6. Kyureghyan S. G. The Minimization of Indirect Measuring Error. // Izmeritelnaya tekhnika, 1994, № 12, p. 17-19.

7. Kyureghyan S. G. To the problem of Analytical Constructing Elements of Indirect Measuring Systems //Izmeritelnaya tekhnika, 1995, № 8, p. 17-18.

8. Mamikonyan В. М. The Device for Measuring of Capacity. RF patent on claim of № 4784899, 1994.

9. Mamikonyan В. М. The Transformator of Great Line Shifts. // Proceedings of NAS and SEU of RA, v.48, 1995, №1, р.51-55.

10. Mamikonyan В. М., Mamikonyan Kh. В., Meters of increment in resistance. RA patents: № 272, BI № 1, 1996, p. 52-53; № 409, BI №1,1998, p.53; № 549, BI №1, 1999, p.47.

11. Mamikonyan B. M. The Peculiarities of Constructing Narrow-limit Measuring Temperature meters with Use of Thermotransformator of Resistance. Reports at NAS of Armenia, 1999, №1, p. 56-63.

**The Expected Results.** The Project is meant for introduction of the results in the production of the copper-molybdenum concentration of mills in Kajaran (Republic of Armenia). Preliminary studies have shown, that if recommended optimal adjustments of the process control are observed, the expected increase of molybdenum in the concentrate will be 5-6% more and as a result we can get additional several hundred tons of pure molybdenum per year, thus decreasing the admixtures. Application of the measuring and executing equipment computer will allow to automatize the control of the concentration processes, avoiding labour-consuming procedures, to increase profitableness and to provide high quality level for the production. The Project is of great economic value for Republic of Armenia, especially when market-relations are being formed.

The results and approaches, used while solving the problems, raised in the Project, can be used in other rock-concentration mills for other analogical processes of production.

In the Project formation process Department of Electrical and Computer Engineering of the California State Politechnic University, Pomona, USA (Professor Elhami T. Ibrahim) and Institute of Communication and Computer Systems of National Technical University of Athens (Professor Nicolaos Uzunoglu) agree to take part in the capacity of collaborators, and they accepted obligations on discussion, consultant’s investigation and test of the received results.

The Project authors will welcome enlargement of specialists circle in the capacity of collaborators and they will be grateful to everybody, who will take part in discussion and test of the Project results.