FEATURES OF TEMPERATURE REGIME IN A CONTACT TYPE UNIT WHEN DRYING SMALL SEED CROPS

When creati ng modern eff ecti ve complex technical systems that realize the processes of thermal impact on bulk agricultural materials with the required quality and at a high energy level, it is important to know the conditi ons of heat and moisture transfer. The target functi on of our research was scienti fi c substanti ati on of the main thermophysical parameters of the studied process of thermal eff ect on the drying product as a whole, as well as identi fi cati on of the eff ect of the created temperature regime of the drying unit on the temperature gradient when heati ng the treated seeds, and, ulti mately, on the effi ciency of the enti re process. In case of contact drying of small-seeded crops, both external heat and moisture exchange processes are carried out - from the surface of the treated seeds to the external environment, and internal - the migrati on of heat and moisture inside the seeds. The main quanti tati ve factor that most fully describes the mechanism of moisture transfer is the Bio criterion (Bim). This criterion establishes a relati on between such parameters of the contact drying process as the intensity of moisture exchange on the surface of the processed grain and its moisture conducti vity. The descripti on of the process is reduced to solving an internal problem for the moisture contained in the processed grain, when considering the latt er as a colloidal body, Bim = 0.16. In this case, the removal of moisture with its transformati on into steam directly depends on the energy consumpti on for the heat treatment process. The driving force of this process is the temperature gradient arising from thermal acti on. Studies have established that the kineti c coeffi cient, which most fully describes this phenomenon, is the thermal and moisture conducti vity coeffi cient or the thermal gradient coeffi cient δ. This parameter characterizes the moisture content change in the processed grain at a temperature gradient equal to one degree Celsius. In order to confi rm the above theoreti cal dependencies, experimental studies were carried out to identi fy the features of contact thermal eff ects on various small-seed crops. Based on the results of the studies, it was revealed that the following operati ng parameters have the greatest infl uence on temperature regime during grain drying in the developed contact type grain dryer: the temperature of the heati ng surface and the rotati on frequency of the transporti ng working body. In this study, the rotati on frequency of the transporti ng working body was changed from 30 min-1 to 110 min-1, and the temperature of the heati ng surface - in the range from 40 ºС to 100 ºС. It was revealed that the temperature gradient of grain heati ng in the developed installati on for grain drying at appropriate drying modes is 9 ... 12 ºС and does not signifi cantly depend on the type of processed seeds. When improving the operati ng parameters of the drying process of seeds of one crop, it is possible to operate the developed grain dryer without loss of quality during heat treatment of small seeds of other crops.

Experimental and Theoretical Study of Heat Losses in Drying Cylinders

The research purpose is to develop methods for determination of heat losses in drying cylinders. Experimental study of temperature of drying cylinders performed in the drying section of a paper machine during its steady-state operation. Medium, maximum and permissible statistical characteristics of drying cylinder temperatures were defined. The drying cylinders with increased condensation concentration were determined by the minimally permissible temperature levels and the repair of the condensation drainage system to reduce heat losses (steam consumption) was justified. The cause of uneven dryness of the paper web across the width has been determined. The condensate ring on the inner wall at the edges of the drying cylinders gets thickened due to moisture coming from the end caps from the action of centrifugal forces. The condensation is removed from the drying cylinders with a siphon on the drive side. Therefore, on the front side of the drying cylinders condensate film has a greater thickness, and the paper web dries worse. The single-sided condensate disposal and the physical effect of centrifugal condensate runoff from the end caps to the side inner surface of the drying cylinders cause a lower dryness from the front side of the paper web. The use of thermal insulation of end caps will contribute to uniform dryness across the width of the paper web. The results of experimental studies were processed by methods of mathematical statistics in order to describe the thermal losses during contact drying of the paper web on drying cylinders with and without thermal insulation of the end caps to the ambient air. The calculation of heat losses is carried out according to the refined method of researching thermal processes in contact drying of paper web. It is found, that the use of thermal insulation of the end caps of the drying cylinders provides a reduction in steam consumption for contact drying of the paper web without affecting the technological process. The research results can be used to reduce heat losses in the drying section of paper machines on cylinders that do not have thermal insulation of the end caps. For instance, for a paper machine consisting of 56 cylinders with a diameter of 1500 mm and a capacity of 7000 kg/h of absolutely dry paper, insulating their end caps saves up to 223 kg/h of steam for drying the paper web. Methods of detection of drying cylinders with increased content of condensation on permissible levels of temperature is developed and approved. A refined method for determining thermal losses during contact drying of the paper web on drying cylinders has been developed.

The Effect of Contact-Drying on Physical Properties of European Beech (Fagus sylvatica L.)

Beech wood is mainly used for furniture, plywood, decorative veneer manufacturing or packaging. Timber or lumber is traditionally dried in kilns by processes often taking several weeks. This research deals with more rapid process called contact-drying process. Drying was performed using the heating plates with a temperature of 160 °C and pressures of 1.0 MPa, 1.4 MPa and 1.8 MPa. The results were compared to conventional warm-air drying. The warm-air drying mode was divided into two phases, with and without free water and bound water in the dried wood. The density of the samples increased remarkably during the contact-drying. The effect of the pressure of the heating plates was substantial. The difference in the average density between the pressure of 1.0 MPa and 1.8 MPa was more than 22 kg·m−3. The pressure of the heating plates affected the process and the resulting change in the sample thickness. The change in the sample thickness was more considerable in the case of the tangential samples. The thickness did not increase significantly after air conditioning. During contact-drying, the hygroscopicity and absorptivity of wood reduced on average by 21.24% and 25%, respectively, compared to warm-air drying.

The effect of material mixing on heat transfer in the process of contact drying

This paper deals with the process of heat transfer in contact drying. Heat transfer during contact drying for a stagnant bed without mixing and drying with a mechanically agitated bed were theoretically and experimentally investigated for a contact paddle dryer. The effect of material mixing on the process of heat transfer was evaluated. For a theoretical description of heat transfer in a contact dryer, the penetration model was used. Experiments with green wood chips were realized on an experimental paddle dryer. In both cases, the stagnant bed and the mechanically agitated bed, the theoretical values were slightly higher compared to the experimental results. Mixing intensifies the process, it showed an increase to roughly twice in heat transfer for the tested experimental dryer.

Formulation of a Multifunctional Biopreparations for Phytoremediation of Oil-Contaminated Soils: from Laboratory to Pilot-Industrial Technology

A formulation method for biopreparations stimulating phytoremediation of oil-contaminated soils based on rhizobacteria was proposed. Technology involves the cultivation of bacterial cultures Bacillus RB15 and Pseudomonas RB43 in a liquid nutrient medium, followed by concentration the biomass by centrifugation and drying the finished product by contact drying. The optimal temperature (23–30 °C) and the duration of the process (three days) were determined at the stage of preparation of the liquid preparation (cultural liquor CL rhizobacteria). A comparative analysis of the results of the concentration of CL using various methods – vacuum evaporation, ultrafitration and centrifugation showed that the application of the method of concentrating biomass in a centrifugal field is most suitable both for technological and operational characteristics. То obtain the finished dry form of preparation, the contact drying method is recommended. The parameter of preservation of the viability of RB cells was used as the main controlled parameter at all technological stages of production. To obtain the finished commodity form of the microbial preparation, it is proposed to use a complex sorbent as a filler in the standardization of the finished product, the moisture sorbent in contact drying, and the carrier for immobilization of bacterial cells. To promote the technology of biopreparations in practice, a pilot experimental industrial production and technological scheme of production were elaborated.