Increasing the efficiency of drying cellulose by ultrasonic influence

Abstract

Relevance. Significant part of renewable and fossil energy resources is spent to generate heat and electricity needed to implement drying. At the same time, cellulose drying, due to the large-tonnage production, is one of the significant consumers of energy resources. One of the ways to reduce energy costs of drying is ultrasonic vibrations impact. There are practically no studies on ultrasonic exposure during cellulose drying. Therefore, it is necessary to consider possible options for non-contact ultrasonic treatment during convective drying of wood cellulose. Main aim. To identify the most rational options for placing the material to be dried, taking into account the direction of exposure to ultrasonic vibrations and the flow of warm air relative to the layers of the material to be dried at different temperatures. Objects. Non-contact ultrasonic action on wood cellulose. Methods. Mathematical modeling based on the finite element method was used to determine the distribution of oscillation amplitudes of a disk radiator. In the experimental part of the research, a material moisture content was determined by the weight method using verified technical means. Results. When ultrasonic vibrations have parallel direction relative to cellulose thin layers, a 2.5-fold reduction in drying time was shown at a sound pressure level of 162 ±3 dB and a drying agent temperature of 60 °C. The authors have found that temperature decrease of a drying agent makes it possible to increase the relative efficiency of ultrasonic treatment. An assessment of energy efficiency showed that the use of ultrasonic exposure leads to a 2.3-fold decrease in the energy spent on drying compared to only convective drying, all other things being equal. The conducted studies confirmed the effectiveness of the ultrasonic drying method for industrial use and made it possible to recommend options for the most rational placement of the material to be dried when designing the structures of drying chambers.