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Masharipov Shodlik Masharipovich, Miralieva Aziza Qayumovna, Raxmatullaev Sarvar Anvarovich, Fattoev Firuz Farhod ugli, Tashkent State Technical University named Islam Karimov E-mail: [email protected]
ANALYSIS OF THE MODERN CONDITION OF THE METHODS OF CONTROL OF HUMIDITY OF AGRICULTURAL MATERIALS
Abstract. The article discusses the main stages of controlling the humidity of raw cotton while ensuring product quality. Analyzed the role of moisture control in the reception and processing of raw cotton. Defined trends in the development of methods for measuring humidity.
Keywords: raw cotton, moisture, moisture measurement methods, the main stages of control.
In modern measuring processes in the cotton industry, monitoring and measuring devices that control humidity with high accuracy are required. One of the important tasks of technical progress in the cotton-growing and cotton-ginning industry is the creation and implementation of moisture control devices for raw cotton and other cotton materials, primarily because the moisture index affects the physical, mechanical and chemical properties of the material. The moisture content of cotton is necessary to maintain quality from the moment cotton is in the field, until the bale is processed into yarn and fabric. Moisture in cotton affects color, length and strength.
During the sowing of cotton, the quality and similarity of the seed depends on the moisture content of the seeds. During the period of harvesting and harvesting, it is necessary to determine the moisture content of raw cotton for mutual settlements with suppliers, as well as for proper storage, storage and, if necessary, pretreatment. Optimum cleaning efficiency is achieved only when the moisture content in the seeds of cotton is about 6%. In the early season of cotton, the moisture content in seed cotton is about 10-15%, which makes it difficult to clean the cotton, and also affects the efficiency of the process. Effective cotton gin can only be achieved when the moisture content of the cotton seed is about 8%.
Humidity control during the storage of raw cotton is of great importance for the cotton industry. In technological processes of cotton preprocessing, its increased humidity causes an increase in energy consumption, a decrease in the efficiency of cleaning and ginning, and an increase in the yield of lower quality fibers. In the production of cottonseed oil, the effectiveness of the use of raw materials, the quality and yield of the final product depend on the moisture content of cotton seeds.
The main stages of moisture control in the production and processing of raw cotton are shown in (Figure 1).
The moisture indicators of cotton and its products are of great importance when:
a) in cotton-growing, during sowing and harvesting, in the processes of storage and delivery;
b) in the procurement system in the processes of acceptance, storage and transportation;
c) in the industry, technological processes of the cotton-cleaning industry and in the production of cotton oil;
d) in the industry processing cotton as a raw material for the production of cotton yarn and cellulose.
The conductometric method is based on the dependence of the electrical conductivity of the sample material on its humidity. With increasing humidity, the conductivity of the material increases, which is provided by a growing number of charge-ion carriers. A large number of various moisture meters (for example, the following models, like WALCOM TK-100C, GMH 38-LW1/LW2, GMH2710, GMH 3810) of agricultural materials are based on this method. Advantages of the conductometric method - its implementation, as well as high sensitivity in the range of low moisture content. The disadvantages of this method when using it to determine the moisture content of cotton and its products include the effect on the result of measuring the density of the material, which determines its bulk resistance; temperature, which depends on the ionic conductivity inherent in moisture-containing dielectrics and semiconductors; chemical composition of the material and the humidifier, which determines the resistance; surface conductivity of the material affected by cotton seed drooping.
The problem is that, despite the development of elements and devices of measuring equipment, the thermo-gravimetric method for controlling humidity with a sufficient number of flaws remains as an exemplary (reference) method for measuring this parameter. The essence of the
Section 9. Technical sciences
thermogravimetric method is that the masses of the sample are measured before and after air-heat drying. The standard method is characterized with significant losses of energy and labor resources. The thermogravimetric method has several drawbacks: a significantly large number of certified technical means is required; it takes more time to complete the experiment; laboratory conditions are required, it is impos-
sible to measure in the mobile mode, and the method is not suitable for continuous control of the material in the stream. As is known, the essence of the method for measuring the moisture of products consists in extracting water from the material being analyzed by evaporation by heating a sample. Thermogravimetric method (TGM) is absolute and is used as an initial tool in measuring humidity.
Figure 1. Stages of moisture control in the production and processing of raw cotton
One of the non-destructive indirect and most common is the capacitive method of moisture control of cotton materials, which provides efficiency, significantly reduces energy and labor resources to perform humidity control, and also significantly expands the range of controlled materials.
The infrared method of moisture control for agricultural and fibrous materials and products ofits processing takes a considerably widespread introduction. The physical basis for controlling the humidity of the infrared method is characterized by significantly high accuracy (± 0.5%). The infrared method of moisture control can be applied to a wide range of materials, besides it has the functionality in a wide range of moisture control%. In addition, the infrared method ofmoisture control is characterized by a long duration of moisture control (up to several hours) and it is not applicable to moisture control in a stream.
The analysis of published works and foreign practice shows that the thermogravimetric method has the most ac-
curate moisture control - up to%. The analysis of the methods for controlling the humidity of cotton materials shows that the thermogravimetric method has the best actual metrological properties. Among the methods for controlling the humidity of cotton materials (raw cotton, fiber, seeds and products of its processing), the thermogravimetric method has become popular. It is characterized by high accuracy, but requires a lot of time, and therefore not suitable for continuous monitoring of the material in the stream.
The microwave method is based on the interaction of electromagnetic waves with a frequency from 50 MHz to 30 GHz with the material under study. The principle underlying it is simple and consists in measuring the parameters of a transmitted or reflected wave, previously collected in narrow beams with the help of a transmitting and receiving antenna, after interacting with the material. The most common is the method of measuring moisture by absorbing microwave energy. It is
simple in terms of technical implementation, has a high sensitivity, a wide dynamic range, low measurement error, low cost equipment in the most common three-centimeter wavelength range. However, moisture meters based on this method have so far not found wide industrial use.
Studies have shown that the result of moisture measurement by the amplitude microwave method is mainly influenced by the temperature of the material, the degree of heterogeneity in the sample volume and the uneven distribution of moisture between the components. Depending on external influences (humidity and air temperature, intensity of sunlight) and time elapsed between the specified natural effects and the moment of measurements, the moisture content of cotton changes, and the moisture is redistributed between the fiber and the seeds and differs from the equilibrium. At the same time, the electrophysical parameters of the raw cotton sample change, which also leads to an error in measuring its humidity at the microwave.
The undoubted advantage of capacitive measuring transducers is the ability to control the investigated volume of the material over a wide range by changing the geometric parameters of a capacitive transducer and the intensity of its field. Due to the rapidity of measurements, ease of use, low cost and acceptable accuracy, the capacitive method of control has been widely used in moisture measurement of cotton materials. Currently, the capacitive method means are used in agricultural production technologies, mainly to control the moisture content of cotton materials.
After analyzing the methods, it can be said that it is advisable to use them not as separate methods to increase the
accuracy and reliability of the control, but in combination with other methods, as a necessary condition. The dielectric constant of a substance is measured at different temperatures, for example, positive and negative. The theoretical possibility of compensating for the influence of a variety of substances is present, but in practice, even with deep freezing, some of the water remains in a liquid state and the amount of unfrozen water can be determined only approximately. The process of freezing a substance, for example, moving in a continuous flow, is also difficult and not always possible. The problem is that the dielectric constant of the controlled material - the objects of control is not normalized and varies significantly even for one type of object under study. Take into account the full range of such changes is almost impossible.
The analysis revealed that the group of methods using capacitive transducers is the most promising. It is the capacitive method and transducers that should be taken as the basis for developing raw cotton transducers for moisture control.
The capacitive method of moisture control involves exposing the material under control to an electromagnetic field and an appropriate analysis of the behavior of the material in this field. Such measuring devices are widely used due to a number of incontestable advantages, the main ones of which are:
- the ability to use them to control the humidity of a wide class of materials of the agro-industrial complex
- the use of such systems is relatively simple, inexpensive, easy to use and highly reliable in the work of electronic equipment;
- lack of potential danger to attendants;
- ease of obtaining a unified output signal.
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2. Matyakubova P. M., Masharipov Sh. M. Problems of ensuring the uniformity of measurements when controlling the humidity of bulk materials // International Scientific and Technical Journal "Chemical Technology. Control and management.-Tashkent, 2015 - No. 1.-C.48-53.
3. Masharipov Sh. M. Mathematical modeling of the dielectric constant of heterogeneous wet systems // Herald of Tashkent State Technical University.- Tashkent, 2015. Special Edition.- P. 29-34.
4. Masharipov Sh. M. Analysis of modern methods and technical means of measuring the moisture of cotton materials // Journal "Instruments".- St. Petersburg, 2016.- No. 4 (190).- P. 31-37.
