DESIGN DEVELOPMENT OF A CONTINUOUS INDUSTRIAL DRYING PLANT FOR DRYING POMACE OF WALNUTS, PEANUTS AND PISTACHIOS

The object of research is the drying process of the pomace of a walnut kernel, peanuts and pistachios in a fluidized bed dryer with an inert support. One of the most problematic places is the issue of recycling of secondary raw materials, which represent significant potential for the food industry. The solution to the problem that is urgent is the preservation of pomace of the walnut kernel, peanuts and pistachios for their further use in the food industry. At the same time, the advantages of dried semi-finished products:– ability to transport over long distances;– long shelf life of dried products;– use in food technology;– use as a protein supplement.Therefore, the work is devoted to the development of new and modernization of existing drying methods. One of such methods is drying in a fluidized bed of an inert support; this product has not been used before for drying because of the complexity of the process.During the study, the method of microscopic determination of the dispersed composition of the product is used, which allows measuring particles with a size of 0.3-100 microns. Test powders of different fineness are investigated using USB Digital Microscope. The mathematical processing of the results using modern computer programs is carried out. The data obtained are processed in the Mathcad environment and presented as integral and differential particle distribution functions for each analyzed sample. This is due to the fact that the analysis of the determination of the dispersed composition is a mandatory control method in all technological processes. Thanks to this, it is possible to obtain a given product size. In the course of the study, a design of a continuous industrial drying unit for drying pomace of walnut kernels, peanuts and pistachios was developed. The drying method proposed in this work has several advantages over other methods, the main of which are the reduction of energy consumption and improving the quality of the finished product.


Introduction
One of the important issues of the food industry is to increase the resources of food protein, improve the technique and technology of processing traditional and non-traditional raw materials in various sectors of the food industry and expand the range of high-grade food [1]. One way to solve the problem of increasing protein resources is to use secondary raw materials [2]. The use in Ukraine of secondary raw materials from food industry enterprises is becoming increasingly important. Large volumes of industrial processing of various raw materials of plant origin for food purposes constitute a significant potential for the agricultural sector [3]. This also applies to oil-fat production. In the production of oil from the walnut kernel, peanuts and pistachios, a large number of squeezes are formed, which are valuable raw materials containing proteins, fats, fiber, ash and vitamins [4]. Dry powders from these products are characterized by a high content of technologically constant protein (48...60 %), low fat (8...20 %) and moisture (2...9 %). Adding dry powders from squeezes into wafer products improves their quality, in particular, their biological value: it ensures the presence of essential amino acids, polysaccharides, unsaturated fatty acids, dietary fiber and other valuable components. The introduction of dry powders from pomace has a positive effect on the organoleptic characteristics of fillings (changes color, gives the finished product a pleasant taste and aroma of nuts) [5,6]. Powdered materials are used in many industries. Many properties of powders are highly dependent on dispersion. Analysis of the dispersed composition is a mandatory control method in all technological processes associated with the manufacture and processing of powdered materials [7][8][9]. There are several methods for determining the dispersed composition [10,11]: sieve analysis, sedimentation analysis, hydrodynamic methods, ISSN 2226-3780 and microscopic analysis. In this case, the microscopic method is different in that it allows to determine not only the geometric dimensions of the studied objects, but also to see the features of their shape, structure and surface structure. The microscopic method allows to measure particles with a size of 0.3-100 microns. To determine the particle size less than 1 micron, electron microscopes with a higher resolution than optical ones are used.
Thus, the object of research is the drying process of the pomace of the walnut kernel, peanuts and pistachios in a fluidized bed dryer with an inert support. The aim of research is determination of the dispersed composition of the powders from the pomace of the walnut kernel, peanuts and pistachios for further use in the food industry.

Methods of research
During the study, a microscopic method was used to determine the dispersed composition of the powders, which differs in that it allows to determine not only the geometric dimensions of the objects under study, but also to see the features of their shape, structure and surface structure.
Based on the results of laboratory studies, a pilot plant was designed for drying the pomace of the walnut kernel, peanuts and pistachios. Drying took place as follows: drying of the saw material in a direct flow with a gaseous coolant and final drying on the surface of inert materials in a state of fluidization [12][13][14].
The theoretical and experimental studies made it possible to obtain empirical relations [15,16] necessary for the engineering calculation of the design features of a dryer with a fluidized bed of an inert drying carrier. Fig. 1 shows the design of a drying chamber. Features of the installation for drying are: -in the upper part of the chamber there is a device for capturing the product, which prevents the removal of an inert carrier with the particles; -the use of fluoroplastic chips allows to intensify the drying process due to the increase in the surface of heat and mass transfer; -the use of a fan and air heater allows to get dry hot air of the required temperature, preventing darkening of the product. The initial data for the development and creation of the drying installation are given in Table 1.

Research results and discussion
Using further computer data processing, the integral distribution functions of powder particles are constructed [17,18] (Fig. 2). Let's begin the construction of the smallest particles, deferring their percentage (Q 0 ) on the ordinate. Then, for the particles of the next fraction, the ordinate is postponed, equal to the sum of the percentage of particles of the previous fraction and the fraction with a large radius and so on. They work until the last ordinate (corresponding to the maximum diameter) brought 100 %.
Further, using the following operations in the environment of the Mathcad program, let's construct differential distribution functions [19] (Fig. 3). As it is possible to see, they completely and accurately describe the experimental data and fall at the experimental maximum, which makes it possible to determine the most probable particle size for a given sample (Fig. 4).
Let's construct differential distribution functions (Fig. 5). The integral and differential particle size distribution functions of the research product for three model products of different dispersion are described quite accurately by the experimental data in Fig. 5. It is seen that, after drying, distribution curve 1 has a pronounced maximum and a smaller width, since the particles are more uniform in size, while squeezed samples from peanut kernels and pistachios (curves 2, 3, respectively) are characterized by a maximum shift. Obviously, this is due to the fact that large particles of moisture due to partial swelling increase in size, provided that it reflects a certain asymmetry of the curves themselves. So, during drying, this fact should be taken into account, it affects mass transfer, since particles with high dispersion give moisture more easily.

Conclusions
In the process of research, a design of a continuous industrial drying plant for drying pomace of walnut kernels, peanuts and pistachios is developed, for which declarative patents of Ukraine is obtained. The drying method proposed in this work has several advantages over other methods, the main of which are the reduction of energy consumption and improving the quality of the finished product.