N. Deliiski, D. Angelski. Computation of the Processing Medium Temperature during Autoclave Steaming of Non-frozen Wooden Prisms

Кey Words: Wooden prisms; veneer production; autoclave steaming; 2D model; processing medium temperature; energy consumption; heat balance; loading level of autoclave; moisture content of prisms.

Abstract. A methodology for computation of the processing medium temperature and connected with it energy consumption and heat fluxes during autoclave steaming of non-frozen ooden prisms for veneer production at limited heat power of the steam generator, depending on the dimensions of the prisms cross section, wood moisture content, and loading level of the autoclave has been suggested.
The methodology is based on the use of two personal mathematical models: 2D non-linear model of the temperature distribution in subjected to steaming non-frozen prismatic wood materials and model of the non-stationary heat balance of autoclaves for steaming wood materials. The heat balance of the autoclaves consist of following components: energy used for heating of the subjected to teaming wood materials, energy used for heating of the body of the autoclave and of the situated in it metal trolleys for positioning of the wood materials, energy used for heating of the insulating layer of the autoclave, energy used for covering of the heat emission from the autoclave in the surrounding air, energy used for filling in with steam the free (unoccupied by wood materials) part of the working volume of the autoclave and energy, which is accumulated in the gathered in the lower part of the autoclave condense water. For numerical solving of the models and practical application of the suggested methodology, a software package was prepared in the calculation environment of Visual FORTRAN Professional developed by Microsoft. Using this package computations and research of the non-stationary change of the processing medium temperature in an autoclave with a diameter of 2.4 m, length of its cylindrical part of 9.0 m and loading level of 40, 50, and 60% at a limited heat power of the steam generator, equal to 500 kW during the initial part of the steaming process in it of beech prisms with cross-section dimensions of 0.3 × 0.3 m, 0.4 × 0.4 m, and 0.5 × 0.5 m, initial temperature of 0 °C, basic density of 560 kg·m-3, moisture content of 0.4, 0.6, and 0.8 kg·kg-1 have been carried out. Simultaneously with this the heat fluxes and energy consumption required for the heating of the prisms and for the whole steaming process in the autoclave have been calculated. The suggested methodology can be used for the computation and model based automatic realization of energy efficient optimized regimes for autoclave steaming of different wood materials