RU2006765C1 - Method for drying timber - Google Patents

Abstract

FIELD: wood working. SUBSTANCE: timber is heated by live superheated steam with further holding with removal of separated moisture and cooling. The heating and holding are made at 110-150 C and pressure of the live superheated steam of 1-2 atm. The holding is provided for 1-2 hours, and cooling - by a compressed air up to the ambient temperature. EFFECT: improved efficiency.

Description

 The invention relates to techniques for drying wood materials using heat from superheated water vapor and can be used in the woodworking industry for accelerated drying of lumber.

 The purpose of the invention is the acceleration of drying with simultaneous hardening of wood due to the uniform melting and polymerization of resins in the wood.

Heating and aging of lumber in the drying process are carried out under a pressure of 1-2 at. hot superheated steam at a temperature of 110-150 ^about C. The method of drying lumber is carried out in autoclaves, sealed boilers and apparatuses operating on hot superheated steam at a pressure of up to 4 at.

 The dried wood is cooled in the same apparatus with compressed air to ambient temperature.

 PRI me R 1. Drying the floorboard and various blanks of joinery from coniferous species of wood.

Wood is dried, for example, in an airtight vulcanization boiler of the Lugansk Thermal Plant, with a capacity of 37.2 m ³ , an inner diameter of 2.8 m and a length of 6.0 m; pressure of acute superheated steam up to 4 atm and temperature up to 160 ^o C.

The sawn goods laid in bags are loaded into the boiler in an amount of 30 m ³ . The average moisture content of the source wood is 30%.

The sealed boiler fed acute superheated steam at a pressure of 1 atm, a temperature of 110 ^{° C} and heat content of 644 kcal / kg.

The heating of the wood and water are from 0 to 110 ^C. The heating period timber from the boiler steam condensate water drain. Hot condensate is used as a coolant for internal purposes.

 During the heating period, the steam flow rate is kept within 5-4 t / h.

 As the wood heats up and water condensate decreases, the drainage is blocked and the heating process continues.

Heated to 110 ^{° C} the wood is maintained at this temperature for 1.5-2 hours. During this period, the whole water absorbent wood is converted into steam, which is continuously removed from the boiler with superheated exhaust steam. During the heating period, volatile wood substances volatilize, wood resins soften and melt at a temperature of 60-80 ^о С (rosin, balms).

When the temperature rises to 110 ^C. The polymerization processes are resins to form high molecular weight compounds, which become thick, viscous state and make the timber more durable and more flexible due to impregnate the surface pores liquid timber, the molten resin. After their polymerization and hardening, the moisture absorption of wood decreases.

In the period of exposure of wood at 110 ^about With steam used only to maintain this temperature in the wood.

 At the end of the wood exposure, the steam supply to the boiler is stopped.

 When high-temperature drying of wood under pressure of water vapor, the wood is dried to almost 4-10% moisture content. The residual moisture content in the wood is controlled by the exposure time at the highest temperature.

 In the exhaust steam, volatile aromatic substances are fractionally captured, and the remaining heat is used for in-plant purposes.

 Theoretically, in this way, wood can be dried to 0.03-0.07% of residual moisture.

Wood is cooled in the same boiler, for which instead of steam compressed air is supplied under pressure up to 1.3 atm. at ambient temperature 18-25 ^C. Cool the timber at a speed of up to ^about 60-120 C / hr. Cooled bags with sawn products are unloaded and sent to the warehouse and the consumer.

PRI me R 2. Drying 10-15 cm boards of fir wood with a density of 0.3 g / cm ³ . For heating and wood processing, the same vulcanization boiler is used and the same heating and processing operations are carried out. Boards laid on the platform of the carts are imported on rails into the boiler in an amount of 25 m ³ . The average moisture content of the source wood is 30%. The lid closes the boiler and the boiler is supplied superheated steam at ¹²⁰ ° C and a pressure of 1.3 atm. The heating of the wood are from 0 to ¹²⁰ ° C at a flow rate of steam 5-5.5 tons / hr.

The heated timber to ¹²⁰ ° C held for 1 hour at a steam flow of 1.5 t / h. There are processes of the transition of wood water into steam, which together with the spent superheated steam is removed from the boiler through a drainage steam pipe. The process of resin melting, wood impregnation, then their thickening and hardening during cooling also goes on.

The absence of deformation (warping) of the boards can be explained by the fact that heating of wood to 100 ^° C occurs without removing water under pressure. Due to such heating aligned uneven tensions in the separate sections of the layer of boards with their transfer internal forces in the new equilibrium state, which remains practically unchanged in the conversion of water into steam timber at difference, the temperature is raised from the timber 100 to 120 ° ^C.

 After the steam supply stops, compressed air is supplied to the boiler for cooling at a pressure of 1 atm. At the same time, the wood is cooled intensively from the inside due to the condensation of the steam remaining in the pores of the evaporated water. This contributes to obtaining an amorphous hardening structure of resins (rosin), impregnated with the cell walls of wood, which makes the wood stronger and more elastic. The moisture content after drying is 8%. After unloading the chilled wood, the drying cycle continues.

PRI me R 3. Drying 50 mm of boards for cross-cutting of oak wood with a density of 0.8 g / cm ³ , average humidity 25%, the initial temperature of the boards 10 ^about C.

Boards loaded into the boiler are heated and treated with acute superheated steam at a pressure of 2 at and a steam temperature of 150 ^o C.

Heated boards up to 150 ^° C are held for 1 hour and cooled with compressed air under pressure. The residual moisture content in the wood is 7%.

 Wood treated by drying with hot superheated steam does not require antiseptic treatment. Thus, one drying cycle of sawn wood products lasts as long as five to six hours. (56) N.S. Selyugin. Wood drying. ML : Goslesbumizdat, 1949, p. 152-153.

Claims (1)

METHOD OF DRYING SAWLINGS by heating them with hot superheated steam, followed by soaking, with the removal of moisture and cooling, characterized in that the heating and soaking is carried out at 110 - 150 ^o C and a pressure of hot superheated steam 1 - 2.0 at, and the soaking is carried out for 1 to 2 hours, and cooling with compressed air to ambient temperature.