Research primary processing of live of silk cocoons in a solar installation

. This article presents the results of research to determine the main technical and economic indicators of a new installation we have created for marinating cocoons with the help of solar radiation energy. The possibility of marinating cocoons both on sunny and cloudy days has been proven through direct and indirect use of the energy of solar radiation. The performance of the installation, the temperature inside the drying chamber and the time for complete marinating of cocoons were determined. On the basis of the data obtained, it can be said that the installation provides complete of marinating cocoons and the use of this installation contributes to 100 percent savings in energy resources spent for freezing cocoons.


Introduction
The Republic of Uzbekistan is a manufacturer and supplier of such an important strategic material as the mulberry cocoon, which has a huge export potential and the possibility of obtaining various types of products from it. To further increase the production of mulberry cocoons, improve their quality and reduce the consumption of fuel and energy resources for their soaking, along with other measures, the development and implementation of modern energy-saving technologies is required [1][2][3][4][5].
The amount of silk that can be obtained from the cocoon, that is, the maximum use of the cocoon shell, largely depends on the methods of cocoon soaking and cocoon drying. The method of pretreatment of the steps should allow preserving the natural properties of the cocoon, as well as providing valuable physical and mechanical properties of the cocoon thread.
Many scientists have dealt with the issues of harvesting and primary processing of silkworm cocoons. There are several ways to mork and dry live mulberry cocoons [6,7].
The cocoon-harvesting season in Uzbekistan coincides with the months of sunshine in the year, i.e. May and June. During these months, coconut dryers are widely used for brewing mulberry cocoons, working on the principle of convective heat and mass transfer. In all the leading silk-growing countries of the world, including in our republic, conveyor cocoon dryers are used for soaking cocoons, which process cocoons with hot air. Coconut dryers of the SK-150K type installed in our republic, 85-90 kg of diesel fuel and 70-75 kW of electric energy are consumed to lure 1 ton of live cocoons [8][9][10].
One of the ways to reduce the consumption of fuel and energy resources for brewing mulberry cocoons in the conditions of our republic is the use of solar radiation energy. Raw silk is obtained by reeling the silk cocoons. About 90% of the silk produced in India is mulberry silk. Mulberry silk is drawn from mulberry silk cocoons [1]. The present system of silk reeling operation involves cocoon drying, cooking, reeling and re-reeling. Raw cocoon has initial moisture content of 60-62% (wb). The major source of moisture (about 80%) was the pupa present inside the cocoon shell [2]. To store and extend the reeling period (more than 3-4 weeks), the raw cocoons need to be dried without in anyway interfering with the structure of silk shell around it. The recommended optimum moisture content of dried cocoon is 10-12% (wb) and optimum temperature for cocoon drying is around 60-80 C [3]. In the case of steam-heat radiation drying, if the temperature is raised too high, it is liable to cause uneven drying as radiated heat degenerates the quality of the cocoon, bringing about bad results [3]. Traditionally, freshly harvested cocoons are exposed to the hot sun for drying the cocoons. Although sun drying is simple and cheap, it is a very slow process and takes several days for drying. Moreover, due to the effect of ultra-violet rays, in open sun drying, the silk thread become tender and yellowish. Hence, the traditional process of drying is not suitable for modern reeling. Presently, hot air electrical dryers are used for drying silk cocoons. The factors involved in proper drying of cocoons that enable high percentage of reelability are: moisture content, moisture evaporation rate from cocoon, temperature inside the dying chamber and duration of drying etc. [4]. Fresh cocoons are placed inside the drying chamber preferably in thin layers. Though optimum temperature for cocoon drying is around 60-80 C, higher starting temperature schedule is followed in the electrical dryer for faster drying operations. The drying of cocoon with high temperature at initial stage requires training and skill. Reduction of drying temperature is done in a stipulated manner strictly; otherwise quality of silk gets affected. In the electrical dryers, the drying temperature starts from 95 to 100 C initially and as drying proceeds, it is gradually reduced and stabilized at 55-60 C. Drying time is usually 9-10 h. Most popularly used are cabinet type hot air electrical dyers. The cocoon drying is an energy intensive exercise. Electrical dryer consume 0.8-1.0 kW electrical energy/kg of fresh cocoons. Solar energy is an environment friendly and inexhaustible source of energy and available abundantly at most of the places in world [5]. There are limited literature available solar drying of the silk cocoons. Tawon et al. [6] used a mixed mode type forced convection solar tunnel dryer for drying silkworm pupae and found that the lipid content of the dried pupae was not affected by the solar drying. Study on cocoon drying behaviour in solar dryer and assessment of the quality of the dried cocoon would be very useful for researchers and silk cocoon processors in adoption of solar gadgets and energy saving by supplementation of the solar energy.
The territory of the Republic of Uzbekistan is located in relatively favorable climatic conditions for the use of environmentally friendly and inexhaustible solar energy. The annual value of the radiant energy of the sun falling on 1 m of the horizontal surface of the earth in Uzbekistan averages 6.0 GJ, which is equivalent to the thermal energy obtained by burning conventional fuel in the amount of 0.2 tons [11].
In this regard, the creation of a prototype of an upgraded installation for soaking a cocoon using solar energy and the development of technology for drying starved cocoons is an urgent task.
The installation for of marinating cocoons with solar energy (Fig. 1) is a common heatinsulating chamber 1, which consists of an upper drying chamber 2 and a lower 3 for additional air heating, where electric water heaters are installed. The upper part of the chamber serves as a receiver of sunlight and consists of two-layer glass 6 and 7, with an air gap of 20 mm. Loading and unloading of cocoons is carried out by cassettes 8. To maintain the light-receiving surface perpendicular to the sun's rays, a special device 9 is provided.
On sunny days, the sun's rays passing through the two-layer glass heat the air and the chrysalis inside the cocoon is marinated with the heated air. On cloudy days, air heaters are additionally turned on to increase the air temperature, which are powered by solar panels.

Research methods
As methods of research for complex systems approach to solving problems based on methods of study of complex systems, cause-and-effect analysis of various factors influence on qualitative indicators of live cocoons. When conducting research using mathematical modeling techniques, statistical methods and methods of comparative analysis.

Method for obtaining experimental data
The main technical and economic indicators for marinating cocoons are the air temperature inside the chamber, the time of complete marinating of cocoons and the productivity of the installation.
The ambient temperature and humidity were measured using an Assmann aspiration psychrometer. To measure the temperature inside the chamber, thermoelectric meterschromel -kopel thermocouples TChK were used. The thermoelectric power of thermocouples was measured with a V7-21 digital universal voltmeter, and the temperature inside the chamber was determined by this method.
In three places along the length of the chamber, in the middle of the thickness of the layer of cocoons, samples of cocoons were placed in gauze bags, 100 g of live cocoons each, to analyze the condition of the pupae. The state of pupae was determined by inserting the shell of cocoons, visually. The condition of the pupae was checked every 15 min until the pupae were completely marinated.
The experiments explored the possibility of using solar energy in three ways, i.e. with direct use, indirect use (using a solar battery) and the simultaneous use of direct and indirect methods. For an objective comparison of the quality indicators of processed cocoons with indirect use of solar energy, the temperature inside the chamber was maintained at the same level as with direct use of solar energy.

Results and discussion
The capacity of the solar installation is designed for the harvest of cocoons from one box of caterpillars and it is 65 kg. The obtained data of experimental studies are given in Tables 1, 2 and 3.  1  27  69  110  0  2  30  75  110  0  3  32  76  110  0  4  34  78  110  0  5  35  76  110  0  6  36  75  110  0  7  34  70  110  0  8  32  68  110  0  9 33 79 110 0 Dried silk cocoons in the solar dryer were reeled in the reeling machine and compared with the cocoon dried in the conventional electrical oven dryer commonly used at the silk reeling centres. The tenacity test of the silk thread is an important test for its quality assessment. The tenacity indicates the load a given fibre can support before breaking [12,13]. It was measured with help of the Texture Analyser Machine (make: Stable Micro Systems). Silk thread pieces were randomly cut from a bunch of silk thread. The single silk thread was held at two ends and one end was pulled at the rate of 0.5 mm/s until it broke. Length of the silk thread between the two holding points was 50 ± 2 mm. The force at the breaking point was noted. The ambient temperature and relative humidity were also measured. Tenacity of the silk thread obtained from the solar dried cocoons was compared with the same of electrical oven dried cocoons. The uncertainties in the measured data were calculated as per the procedure suggested by Moffat [14]. The uncertainty in measurement of temperature, flow rate, tenacity, moisture content and time were ±0.5%, ±2.8%, ±1.5%, ±2.0% and ±1.0% respectively. The uncertainty in experimental efficiency of the solar collector was ±3% Dried silk cocoons in the solar dryer was reeled in the reeling machine and compared with dried cocoons in the conventional electrical oven dryer used at silk reeling centres. In the electrical dryers, air temperature reduced in the steps from 95 C to 55 C [15,16]. Drying time in the dryer was about 10 h. There was no marked difference in the physical appearance of the silk obtained from the dried cocoon cocoons in both dryers. However, the silk yield from the dried cocoon in the solar dryer was slightly better. On average, the silk yield was 0.126 kg/kg of dried cocoon in the solar dryer as compared to 0.125 kg/kg of dried cocoon in the electrical oven dryer [17].   1  29  85  110  0  2  32  88  110  0  3  32  90  110  0  4  33  93  110  0  5  31  93  110  0  6  29  83  110  0  7  32  91  110  0  8  34  93  110  0  9 29 92 110 0 Analysis of the obtained data shows that the time for complete of marinating of cocoons both in direct and indirect use of solar energy is 90 minutes, hence the productivity of live cocoons is 45 kg/h [18].
The use of solar energy in direct and indirect ways at the same time reduces the time of marinating cocoons by 30% and is 60 minutes and, accordingly, the productivity increases to 65 kg / h. The use of this installation contributes to the complete saving of energy resources, which is an urgent problem at the present time [19].

Conclusions
According to the data obtained, the temperature inside the chamber is 75-800C, which ensures complete marinating of cocoons. When marinating cocoons with direct or indirect use of solar energy, the processing time is 90 minutes, the productivity of the installation is 45kg / hour of live cocoons, and when using two methods at the same time, the processing time is 60 minutes, the productivity is 65kg / hour.
Studies have shown the efficiency of using a solar installation for freezing cocoons, and the possibility of increasing the air temperature inside the chamber, using solar energy in an indirect way, shows the possibility of increasing the productivity of the installation in further studies.