RU2333036C1 - Method of granular materials treatment - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: method of granular materials treatment is implemented in two stages. At the first stage granular material is heated for 30-90 sec by means of convection heat supply up to temperature of 105-120°C with pressure increase in chamber of up to 0.15-0.20 MPa. At the second stage granular material is heated for 10-30 sec up to temperature of 120-180°C, using electromagnet microwave filed with specific power of at least 5 kilojoule/kg·s, with simultaneous reduction of pressure in microwave chamber down to 0.01-0.02 MPa.

EFFECT: invention allows to reduce portion of the most expensive component of power inputs for process implementation.

Description

The invention relates to the processing of capillary-porous grain materials used for food and feed purposes, as well as in the chemical industry and other industries, and allows to reduce the proportion of the most expensive component of energy costs for its implementation - the energy of the microwave electromagnetic field.

A known method of processing bulk materials in an electromagnetic field of ultrahigh frequency (EMF microwave), implemented using special devices (AS USSR No. 1793838 A3, MKI A01C 1/00, F26V 23/08. - 1993; AS USSR No. 1316645, MKI А23L 3/32, Н05В 6/78. - 1987), which consists in uniform heating of the material due to the absorption of microwave energy by the electromagnetic field and the intensive removal of the intracapillary moisture released from the material, carried away by the air stream supplied to the treatment chamber. The method can significantly improve the quality and reduce the duration of the processing of materials. Its disadvantage is the high energy intensity of the process.

A known method of drying products of plant and animal origin by heating them with microwave energy to 70 ÷ 90 ° C and mixing in a sealed vacuum chamber with a residual pressure of 3 ÷ 5 Pa (AS USSR No. 2151984, MKI 7 F26V 7/00, 5 / 04, 3/347. - 2000). The method allows to significantly intensify the process of dehumidification from the product, but in comparison with the above, it is characterized by even higher energy intensity, since in addition to energy costs for generating an electromagnetic field, microwave requires additional energy costs for evacuating the material processing chamber.

There is also known a method of heat treatment of grain products by electrophysical methods (RF patent No. 2085088, MKI A23L 1/18, F26B 3/30, 3/347. - 1997), performed in two stages and adopted as a prototype. At the first stage, the product is heated for 30–90 s with thermal energy to a temperature of 95–105 ° C without a significant change in moisture content, at the second stage, the temperature is brought to 120–180 ° C for 20–60 s with a microwave electromagnetic field. The method can significantly improve the quality of grain processing. Its disadvantage is that more than half (up to 52%) of all energy costs are costs associated with the microwave electromagnetic field used to heat the material, which is relatively low (about 0.54 ÷ 0.6 versus 0.7 ÷ 0.9 at convective heating by electric energy) by the coefficient of conversion of electric energy of industrial frequency to heat due to the low coefficient of conversion of electric energy of industrial frequency to microwave energy (0.6 ÷ 0.65) by the generating devices used for this purpose.

The purpose of the invention is the reduction of specific energy costs while maintaining the required quality of the processed material.

This goal is achieved by the fact that at the first stage, the grain material is heated for 30 ÷ 90 s by convective heat supply to a temperature of 105 ÷ 120 ° C with an increase in pressure in the chamber to 0.15 ÷ 0.20 MPa to eliminate the phase transformation of intracapillary moisture of the grain and at the second stage, the grain material is heated to a temperature of 120 ÷ 180 ° C for 10–30 s using a microwave electromagnetic field with a specific power of at least 5 kJ / kg · s, while reducing the pressure in the microwave chamber to 0.01 ÷ 0.02 MPa.

The proposed method of heat treatment of grain materials is as follows.

At the first preliminary stage, the material being processed is heated for 30–90 s by convective heat supply to a temperature of 105–120 ° С. The treatment regimes adopted at the same time, as shown by the results of experimental studies, provide optimal quality indicators for the preparation of grain material by the degree of dextrinization of starch, protein denaturation and protein digestibility and contribute to a decrease in the energy intensity of the process as a whole. The possibility of phase transformation of intracapillary moisture of grain into steam, requiring 2–3 times greater energy expenditures in comparison with grain heating, is excluded by the creation of excessive (up to 0.15–0.20 MPa) pressure in the heating chamber due to the injection of pumped from the evacuated air chambers, which shifts the boiling point of water in the capillaries of grain to the region of higher temperatures (up to 105 ÷ 120 ° C).

The second stage is characterized by an abrupt increase in the temperature of the grain material to 120 ÷ 180 ° C due to heating it for 10 ÷ 30 s in the microwave electromagnetic field with a specific power of at least 5 kJ / kg · s with a simultaneous decrease in pressure in the microwave chamber to 0, 01 ÷ 0.02 MPa. Using at this stage the microwave electromagnetic field and the accepted processing modes provides intensive local heating of moisture inside the capillaries of the grains, since water has a significantly larger (80 times) dielectric loss coefficient compared to the actual dry matter of the grain, which contributes to a sharp increase in the pressure of the vapor-air mixture inside grain due to the phase transition of intracapillary moisture into a vapor state. Additional evacuation of the material, achieved by a sharp decrease in pressure in the microwave chamber, further enhances this effect by reducing the temperature of the phase transition (boiling point) of water by 15–20% and using vapor accumulated in the grain for vaporization (as a result of more economical convective heating at the first stage of processing) part of the energy.

The proposed processing method allows to reduce the share of the most expensive component of energy costs for the implementation of the process - the energy of the microwave electromagnetic field - 1.5 ÷ 2.0 times, while maintaining all the prerequisites inherent in the known method to ensure the required quality transformations of the processed grain materials. In general, in the process, taking into account the two-stage processing of the material and the additional costs of evacuating it, the total specific energy costs in comparison with the prototype, as shown by theoretical calculations and experiments, can be reduced by 10-15%.

Claims (1)

A method of processing grain materials, performed in two stages, which consists in heating materials with thermal energy and microwave electromagnetic field energy, characterized in that at the first stage the grain material is heated by convective heat supply to a temperature of 105-120 ° C for 30-90 s increasing the pressure in the chamber to 0.15-0.20 MPa to exclude the phase transformation of the intracapillary moisture of the grain, and in the second stage the grain material is heated to a temperature of 120-180 ° C for 10-30 s using a microwave electromagnetic field with specific power Strongly least 5 kJ / kg · s, with simultaneous lowering of the pressure in the microwave chamber to 0.01-0.02 MPa.