REGULATING THE MOISTURE OF OILSEED MATERIAL IN A TOASTER FOR VEGETABLE OILS EXTRACTION
The influence of the moisture in the process of thermal moisture treatment of oilseed material has been determined. The behaviour of the electronic system for adjustment of oilseed moisture has been investigated. For this purpose, experimental data on the current moisture values have been obtained in treatment period via grain sample method. The obtained experimental data have been statistically compared with the simulation results from a model, which describes the thermal moisture process. REZIuME Opredeleno e vliianieto na vlazhnostta na z'rneniia material v protsesa na dobivane na rastitelno maslo. Izsledvano e povedenieto na elektronna sistema za regulirane vlazhnostta na z'rneniia material. Za tselta sa polucheni eksperimentalni danni za momentnata stoinost na vlazhnostta v perioda na obrabotka chrez z'rnena proba. Tezi danni sa statisticheski s'postaveni s's simulatsionni rezultati ot predvaritelno razraboten model, opisvashch vlagotoplinniia protses. INTRODUCTION The first operation after harvesting the oilseeds involves grinding, and then heat and moisture treatment. Decortication or shelling separates the oil bearing portion of the raw material and eliminates the parts that have little or no nutritional value. Small scale mechanical shellers are available for kernels and nuts although manual cracking is still prevalent. Most oil seeds and nuts are heat treated by roasting to liquify the oil in the plant cells and facilitate its release during extraction. To increase the surface area and maximize oil yield, the oil bearing part of groundnuts, sunflower, sesame, coconut, palm kernel and shea nuts is reduced in size. Mechanical disc attrition mills are commonly used in rural operations (Kabutey et al, 2011; Kadirova S. Manukova A. 2009b; Manukova A. Kadirova S. 2009; Sigalingging R. et al, 2014) Moreover, mechanical pressing is most popular method in the world to separate oil from vegetable seeds crops. Thus, the impact of several variables on oil recovery, oil quality, rupture force of seeds, deformation, and energy cost for pressing is essential for an adequate design of equipment for pressing seeds crops (Sigalingging R. et al, 2014) Heat treatment before extrusion is necessary for improvement of the amount of recovered oil. Pre treatment has a significant impact on the efficiency of pressing (Sayyar S. et al 2009; Willems P. et al, 2008; Kadirova S. 2008; Kadirova S. Manukova A. 2009a; Kadirova S. Manukova A. 2009b; Sigalingging R et al, 2014; Herak D. et al 2013; Kabutey A. et al, 2012) The main point of thermal moisture processing of meal is accomplished in the simultaneous action of water vapour and heat to the cells of the milled mass. Oleaginous cells consist of two main parts a hydrophilic, which is associated with the water (carbohydrates, proteins and other nitrogen containing substances) and hydrophobic, which is not associated with the water (oil and other substances dissolved therein) During the heating of the meal, the water contained in the cells, is associated with the hydrophilic portion that swells and intersects coagulate. It is thus a sharp demarcation between hydrophilic and hydrophobic phase. To suppress the hydrophilic phase it is necessary a precisely defined amount of water. If naturally the water content of meal is insufficient, then it has to be additionally moistened by water or by wet steam (Sigalingging R et al, 2014; Herak D. et al, 2013; Kabutey A. et al, 2012) The dynamics of variation of meal moisture and temperature as a function of time depends on many interdependent factors. The main parameters are the temperature values of the heating fluid and the incoming meal, the initial moisture content of meal, the relative weight of dry basis, thermal conductivity, heat Vol. 50, No. 3 2016 100 exchange etc. The recognition of their influence during the thermal moisture processing of the meal is possible based on the simulation model (Kadirova S. 2008; Herak D. et al 2013; Kabutey A. et al, 2012) The moisture content of the meal is necessary to be controlled in each stage of the process. It significantly affects the quality of the treatment, which is necessary for the next operation, for extrusion. This requires control of meal moisture variation in all stages of the process (Herak D. et al, 2013, Kadirova S. 2008) The aim of the publication is to investigate the efficiency of the developed electronic system for control of moisture content in the thermal moisture treatment of meal the preliminary substantiated control points of the treatment process. MATERIAL AND METHOD Object of investigation The structure of the investigated system is presented in Fig. 1. In the current research the parameters of corn germ meal are investigated. Starting of the system begins with entering of initial conditions kind of oilseed material and kind of treatment depending on the next stage of the technological process for oil extraction. The initial moisture and specific density of incoming meal are determined by grain sample method, as there is a possibility for process interruption to enter data and to change the treatment parameters. The opportunity for simulation of the process for two main technological operations is provided in the developed software. They respectively are thermal moisture treatment of meal for full pressing, and treatment for pre pressing and next chemical extraction (Manukova A. Kadirova S. 2009a) Because of the continuous character of the process the meal in the toaster passes through the sections for exact duration, which depends on the current values of temperature and moisture content of the treated meal. The heating of the material is done indirectly by energy exchange between the meal and heating fluid through the metal wall of the toaster. The surface of the toaster is heated by the fluid circulating in the heating chamber. The meal is processed as it contacts with the heated surface of the section and receives its heating energy via heat exchange. Fig.1 Structure of the electronic system for control of thermal moisture processing of oilseeds in a toaster for extraction of vegetable oils The temperature and humidity of the ambient air are important input data for the environment parameters and they influence the processes' control. The steam saturated air from the section is exhausted by external vent pipe with exhaust fan, as at the output of each section are installed control valves. The initial moisture content of treated oilseeds is determined by grain sample method before it enters into the toaster. The current moisture content of meal is calculated by the proposed model at each stage of the processing. In case of not corresponding to moisture requirements, proposed in the criteria, the electronic system controls the operating mechanisms (Kadirova S. A. Manukova, 2009a) Vol. 50, No. 3 2016 101 Toaster's sections are closed vessels containing free airspace intended to absorb the moisture evaporated from meal during heating. This provides a better moisture exchange between the air and the processed material, which helps to intensive the evaporation process of the material and leading away the humid air from the toaster. The movement of meal from one section of the toaster to the other one is realized by cross valves, connected to a mechanical system. It provides constant and uniform passing of meal in the toaster by an exact preliminary defined step in time as well as the quantity of treated meal. In each section are placed temperature sensors for control of the meal temperature in real time. The amount of the discharging meal is controlled by a sliding valve, placed in section No4. The sliding valve is controlled by the electronic system based on the results obtained from process simulation via the developed model compared with the measured values of parameters at the current time. The position device helps to position the operating mechanism of a sliding valve to a desired position. Thereby, the treated material is being discharged from the toaster at the exact time which leads to a significant increase in system efficiency by reducing the material's duration of stay in the toaster and reduces the energy consumption.