CN101015925A - Method for drying yate - Google Patents

Abstract

The invention discloses a method for drying eucalyptus, which adopts the following steps: (1) board preparation: processing fresh or high-humidity low-density fast-growing eucalyptus with a basic density lower than 0.55 g/ ^cm3 into boards of various specifications; 2) Intermittent drying of wood: put the board into the drying kiln, and keep it for 1-6 hours at a temperature of 80-100°C and a humidity of 90-100% - a temperature of 15-30°C and a humidity of 90-100% The lower holding time is 1-4 hours and multiple intermittent cycles, and the wood is dried to a moisture content of 30-40% to stop the intermittent drying process; (3) Then the conventional kiln drying process is used to dry the wood to the required equilibrium moisture content. The invention not only solves the problems of eucalyptus wood quality degradation caused by defects such as serious shrinkage, cracking and drying stress, but also opens up a new approach for fast-growing eucalyptus as a high value-added solid wood product.

Description

A method for drying eucalyptus

technical field

The invention relates to a method for drying eucalyptus.

Background technique

Eucalyptus wood structure is thin and uniform, hard, high strength, beautiful pattern. Eucalyptus trees are fast growing, highly adaptable and have high wood yields. It is recognized as one of the three fast-growing and high-yielding plantation tree species in the world. Its planted area accounts for about 25% of the world's planted forest area. Eucalyptus has been introduced in southern China since the founding of the People's Republic of China, and the plantation area has reached 1.5 million hm ² at present. At present, most eucalyptus plantation wood is used to make wood chips as pulpwood, and the general price is only US$80/dry ton, while the market price of foreign eucalyptus solid wood and its products is more than 5,000 yuan/m ³ . In order to increase the added value of eucalyptus wood and obtain higher economic benefits, many wood processing production and scientific research departments at home and abroad have extensively carried out research on the properties and processing and utilization technologies of eucalyptus solid wood. Australia, South Africa and Brazil have taken the lead in obtaining many Eucalyptus solid wood processing technology. Due to the high growth stress of eucalyptus wood, high wood density, large variation in material properties, poor wood permeability, slow drying speed, severe shrinkage and cracking. It is generally believed that the drying technology of eucalyptus wood is the key to the processing and utilization of eucalyptus wood, and it has also become the most difficult technology to overcome. The research results show that the shrinkage and cracking of eucalyptus wood during the drying process are relatively serious drying defects, especially the shrinkage. The shrinkage rate of eucalyptus is as high as 95%. The shrinkage not only greatly reduces the strength of the wood, but also reduces the utilization rate of the wood. Severe shrinkage also causes internal cracks (honeycomb cracks) in the wood, and even makes the wood scrap. Shrinkage is often accompanied by internal cracking and surface cracking, which reduces the strength of the wood or even scraps it. The key to eucalyptus drying technology is to prevent or reduce wood shrinkage and cracking defects. At present, measures such as steam treatment in the early stage of drying, pre-freezing treatment, and humidity control treatment in the later stage are often adopted, or a two-stage drying process is adopted. Some of these drying processes and technical measures have been partially applied in production, and some are still in the stage of theoretical discussion and experimentation.

For this reason, the applicant of the present invention based on shrinkage is the main defect that eucalyptus wood produces when drying, and for the first time focuses on the intermittent cycle drying method that effectively avoids shrinkage. Defects such as shrinkage, cracking and drying stress lead to the degradation of wood quality, and open up new ways for fast-growing eucalyptus to be used as high value-added solid wood timber products. Therefore, the invention will produce good economic and social benefits, and has good popularization value.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for drying eucalyptus, so as to solve the problems of wood quality degradation caused by serious shrinkage, cracking and drying stress of eucalyptus.

In order to solve the problems of the technologies described above, the method for the eucalyptus drying that the present invention adopts adopts the following steps:

(1), board preparation: process fresh or high-humidity low-density fast-growing eucalyptus with a basic density lower than 0.55g/ ^cm3 into various specifications of boards;

(2) Intermittent drying of wood: put the board into the drying kiln, and keep it for 1-6 hours at a temperature of 80-100°C and a humidity of 90-100%-at a temperature of 15-30°C and a humidity of 90- The holding time at 100% is 1-4 hours for multiple intermittent cycles, and the wood is dried to a moisture content of 30-40% to stop the intermittent drying process;

(3), and then use the conventional kiln drying process to dry the wood to the required equilibrium moisture content.

The conventional kiln drying process described in the above step 3 refers to the drying process based on the kiln drying benchmark of the Baidu test method.

The eucalyptus wood drying method of the above-mentioned technical scheme adopts high temperature and high humidity-low temperature and high humidity multiple intermittent cycles to destroy the conditions for eucalyptus wood shrinkage, and the shrinkage rate of eucalyptus wood can be reduced to 2-10%. The indicators all meet the requirements of the national standard, which not only solves the problems of eucalyptus wood quality degradation caused by defects such as severe shrinkage, cracking and drying stress, but also opens up new opportunities for fast-growing eucalyptus as a high value-added solid wood product. way. Therefore, the invention will produce good economic and social benefits, and has good popularization value.

Detailed ways

The present invention will be described in further detail below in conjunction with specific embodiments.

Example 1:

(1) Plate preparation: process fresh or high-humidity low-density fast-growing eucalyptus with a basic density lower than 0.55g/ ^cm3 into various specifications of plates suitable for construction;

(2) Intermittent drying of wood: put the board into the drying kiln, and use a temperature of 80°C and a humidity of 90 to keep it for 1 hour-a temperature of 15°C and a humidity of 90% to keep it for 4 hours in multiple intermittent cycles. Dry to a moisture content of about 30% to stop the batch process;

(3), and then use the drying process based on the kiln drying standard of the Baidu test method to dry the wood to the required equilibrium moisture content, which can reduce the shrinkage rate of eucalyptus wood to less than 5%, and other physical and mechanical indicators have reached the national level. standard requirements.

Example 2:

(1) Plate preparation: process fresh or high-humidity low-density fast-growing eucalyptus with a basic density lower than 0.55g/ ^cm3 into various specifications of plates suitable for furniture;

(2), wood intermittent drying: put the board into the drying kiln, adopt a temperature of 90°C and a humidity of 90% to keep for 4 hours - a temperature of 25°C and a humidity of 95% to keep for 1 hour in multiple intermittent cycles. The wood is dried to a moisture content of about 35% to stop the batch process;

(3), and then adopt the conventional kiln drying process to dry the wood to the required equilibrium moisture content, which can reduce the shrinkage rate of the eucalyptus wood to less than 10%, and other physical and mechanical indexes all meet the requirements of the national standard.

Example 3:

(1) Plate preparation: process fresh or high-humidity low-density fast-growing eucalyptus with a basic density lower than 0.55g/ ^cm3 into various specifications of plates suitable for interior decoration;

(2) Intermittent drying of wood: put the board into a conventional drying kiln, and use a temperature of 100°C and a humidity of 100% to keep it for 6 hours-a temperature of 30°C and a humidity of 100% for 2 hours. Dry the wood until the moisture content is about 40% to stop the batch process;

(3) Then, the conventional kiln drying process is used to dry the wood to the required equilibrium moisture content, which can reduce the shrinkage rate of the eucalyptus wood to less than 4%, and other physical and mechanical indexes all meet the requirements of the national standard.

Claims (2)

1, a kind of method of drying yate is characterized in that: adopt following steps:

(1) sheet material preparation: basic density is lower than 0.55g/cm ³The living eucalyptus of low-density speed of fresh or high humidity be processed into all size sheet material;

(2) timber intermittently drying: sheet material is put into dry kiln, employing is that 80-100 ℃, humidity are to be that 1-6 hour-temperature is that 15-30 ℃, humidity are to be 1-4 hour repeatedly intermittent cyclic mode the following retention time of 90-100% the following retention time of 90-100% in temperature, and the drying of wood is stopped intermittently drying technology to moisture content 30-40%;

(3) and then adopt conventional kiln drying (kd) technology with the drying of wood to required equilibrium moisture content.

2, the method for drying yate according to claim 1 is characterized in that: the conventional kiln drying (kd) technology described in the step (3) is meant the drying process that carries out based on the kiln drying schedule of Baidu's test method(s).