The Research On Microwave Deresination Technology Of Masson Pine

In this study, the mechanism and approach of microwave deresination was described in detail. Using Pinus massoniana as research object, based on the analysis about the mechanism of microwave deresination and the force conditions of fluid within rosin canal and resinosis cells, a mathematical model to predict the critical pressure and temperature conditions of microwave deresination was developed and verified by experiment. The basic law of microwave deresination and the effect of microwave deresination treatment on wood drying characteristics and permeability were investigated, and the optimal microwave deresination technique was attained. The main conclusion could be showed as the following:(1) The mechanism of microwave deresination was illustrated and the essential conditions to remove resination during microwave deresination was presented: the temperature of wood could be no lower than the melting point of resin; the pressure difference between wood inside and outside could make resin within the resin canal overflow to the wood surface; the inner pressure in wood was high enough to destroy the resinosis parenchyma cell, and make resin within it flow into the resin canal in an instant.(2) The mathematic model of microwave deresination was established firstly and the critical pressure and temperature were simulated. The results showed that the minimum critical pressure and temperature during the Pinus massoniana microwave deresination were respectively 1.17×105Pa and 104□. In order to rupture wood microscopic structure at resinosis cell level and attain the optimal effect of microwave deresination, the critical pressure difference between wood inside and outside and the temperature of wood should be controlled in the range of 0.23～0.3MPa and 135～140□respectively.(3) The basic law of microwave deresination was investigated. The whole temperature variation process of wood can be divided into two distinct periods:rapid heating-up period and constant temperature deresination period. The average raising rate of temperature increased with the increase of microwave input power and initial moisture content of wood; the moisture loss weight, moisture content change, moisture loss rate and deresination rate of wood increased significantly with the microwave radiation power; with the increase of microwave radiation time, the moisture loss weight, moisture content change and deresination rate of wood increased, but the moisture loss rate took a decreasing trend; with the increase of wood initial moisture content, the moisture loss weight, moisture content change, moisture loss rate and deresination rate of wood increased first and then decreased.(4) The effect of microwave deresination on the wood permeability was researched based on experiments and theory analysis. The results show:microwave desesination could improve the permeability of Pinus massoniana effectively. Liquid absorption of wood treated by microwave desesination increased with the increase of microwave input power and time as well as initial moisture content of wood. Compared with the untreated wood, the liquid absorption can increase up to 73.62% at normal pressure.(5) With the increase of microwave input power and time, the average drying rate of treated wood increased in the sequent conventional drying, but the effect is not very significant. Compared with the untreated wood, the drying rate for microwave deresination wood was increased no more than 6%.(6) The optimal process of microwave deresination was achieved: the microwave radiation intensity, radiation time and wood initial moisture content was 4Kw, 7min and about 80% respectively, and the corresponding deresination rate is up to 58.96%. The microwave deresination is a new technology with some advantages including in short time, high efficiency, and keeping the initial color of wood, which shows a good application prospect in the future.