The basic principle of wood drying

Wood drying refers to the heat and humidity treatment of wood with appropriate targeted drying technology and equipment under the premise of ensuring good quality of wood, which is a process of continuous removal of moisture in wood.The moisture in wood includes free water;Absorbed water;And combined water 1. Free water exists in the large capillary system of wood.(this type is easily removed in wood drying, and the content is the largest, for example, the free water content of paulownia is up to 250%.)This type of moisture is not easy to remove because it is able to suck water out of the wood by overcoming the binding force of the microcapillaries.3. The combined water exists in the chemical composition of wood and its content is about 1%, which cannot be removed by drying. Generally, it is not considered.1. Moisture content: refers to the content of moisture in wood.The ratio of moisture content in the weight of wood to the weight of absolutely dry wood is amazing to moisture content, abbreviated moisture content, expressed with W.2. Electric measurement method: a method for direct determination of moisture content in accordance with the relationship between wood electrical characteristics and moisture content.Commonly used resistive wood moisture content meter.3. Fiber saturation point of wood: the moisture content of the wood when the free water in the large capillary is completely evaporated, and the moisture content of the wood when the water is still saturated in the capillary system.(the junction between free water and absorptive water) the saturation point of wood fiber is the turning point of material variation.4. Balance moisture content of wood: after a piece of wood is in hot and humid air for a period of time, the moisture content of wood and the moisture content of air will no longer exchange and reach the balance state, which is called the balance moisture content in the air state.Three, the moisture movement in wood drying process: wood drying moisture can move along the fiber direction from plate at both ends of the ruled out, also can across the surface of the fiber direction from the board and side out, because the lumber surface area and the area is greater than the side area, so the lumber dry moisture mainly along the direction of thickness and width and discharge.When moisture content is higher than that of wood fiber saturation point is given priority to with liquid water movement, with water vapor when parts of the moisture content is lower than that of wood fiber saturation point or soda mixed mode current port price fang wood logs or plate is upside down, plate fang material inversion were: SPF and pine plate 3 #, 4 # are down 20 yuan/m3 state, Russian mongolica were flat, European Finnish pine upside down 100 yuan/m3, expected future prices will fall.The situation of the three land ports is different, with the price of natural balustrade building materials rising by 100 yuan /m3 and that of other balustrade materials rising by 30 yuan /m3, which is optimistic about the market.According to the latest customs statistics in January 2018, the import volume of changzisong was 720,000 m3, up 10.7% year-on-year.The sf1-4 grade of Russian camphor pine timber was recently quoted by foreign suppliers at 275 usd /m3, an increase of 30 usd from 245 usd /m3 in March 2017, and the supplier also reported 285 usd /m3.The market price in China (taicang) is sf1-4 grade of Russian camphor pine timber timber, and the market price in March continues to be 2,100-2,200 yuan /m3. The current quotation still has a profit space of about 50 yuan /m3. The inventory of Russian timber timber of taicang port also reaches 720,000 square meters at the same time, which is at the high level of historical inventory.Qingdao market is also not hot, shipments are basically normal, but the market is not active.Tianjin market relatively good shipments relatively large, stable prices.The selling price of Qingdao timber is 2000-2050 yuan /m3 and the selling price in tianjin is about 1950 yuan /m.According to the proportion of timber timber in taicang port area, the proportion of timber timber in Russia is 55%, European timber 30%, SPF 15% and other timber 5%.

December 13, 2023