Research On High Frequency Heating Quarantine Treatment Technology For Wood Packaging Materials

Wood packaging phytosanitary treatments are the key sector in the international trade, which may have a direct impact on the success of the trading activities. However, with the awareness of environmental protection, methyl bromide fumigation will be prohibited gradually. It's urgent to find a new environment-friendly method to replace it. While high-frequency heating (HF) has many advantages, such as smaller deformation, faster pest control effection, less time and less pollution, etc. It is a new way of pest control, which is worth of in-depth studying.Large-size wood packing materials of China fir, Chinese white poplar, masson pine were selected as main objects for this study. Based on the different effect of moisture content(mc), thickness, electrode spacing and output power on heating process of lumber, used intermittent HF heating mode (1min heat / 1min stop) on lumber to treat cerambycidae larvae, the study showed that:(1)The effect of wood moisture content on the heating rate in center of lumber could be notability. At the some output power, there was the same heating process amang the three tree species.In a certain condition, the fastest heating rate(2 ~ 3℃/cycle) was at F.S.P. With output power increasing higher, mc matching that went higher. When lumber of mc15% ~ 45% was in 120mm electrode spacing, HF output power 11.2KW, 9.3KW, 7.5KW heated them respectively, the fastest rate in lumbers which mc was 45%, 40%, 30%.(2)The effect of samples thickness(20≤T≤100 mm)on the heating rate which was uniform in thickness orientation(40≤T≤100 mm )in lumber center could be negligible.(3)Direct cause of larvae mortality was holding time when the inside lumber temperature above 50℃~ 60℃. As a result of HF output power, mc , electrode spacing and thickness affecting the rate of heating, they were indirect cause of larvae mortality.(4)When different HF output power heated the lumber with over critical moisture content, the decrease rate of lumber mc in the center and both ends appeared a pattern that it reduced as the lumber mc at that point was higher than others. In other words , HF would heat lower mc parts first. However, while mc was below the matching mc, it would heat higher mc parts first. (5) Compared with heat treatment,it's faster to heat core temperature at the end of 1 m3 lumber ( mc 25 % to 70 %) reaching to 56℃with intermittent HF heating, which used 4 h at last. According to output power, 1 m3 Chinese white poplar lumber of mc 25 % ~ 35 % would use 12 to 30 kw.h with HF treating at ideal state. While mc 25% ~ 45% masson pine would use 19 to 35 kw.h.