JP2002528304A - Method and apparatus for continuous production of lignocellulose-containing plates - Google Patents

Abstract

(57) [Summary] The present invention relates to a continuous method and apparatus for producing a lignocellulose plate, in which a raw material is decomposed into particles and / or fibers and paste and dried to obtain a mat 1. The mat is squeezed in a continuous steam injection squeezing machine 2 to a plate shape 3 and then passes through a rear adjustment unit 4. Gas exhaust and steam generated in the squeezing process are captured. As the exhaust and steam mix with the escaping air from the surroundings, hot air is provided to prevent condensation of the gas exhaust and steam and to carry the steam and exhaust to a combustion plant for combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for continuously producing lignocellulosic sheets according to the preamble of claim 1 and to an apparatus for carrying out the method.

[0002] Methods for producing boards from lignocellulose-based raw materials are well known in the art and have found wide application in practice. The manufacture of such a plate includes the following main steps. Decomposition of the raw material into fibers and / or particles of suitable size, drying of the particles and / or fibers to a predetermined humidity, and bonding the raw material before or after the drying process; Forming a mat consisting of
And optionally cold pre-pressing of the mat, pre-heating of the mat, spraying of water on the mat surface, etc., and intermittent or continuous pressing of the mat while simultaneously compressing and heating the raw materials to obtain the finished board. Hot pressing.

[0003] A well-known problem with current manufacturing techniques, whether involving intermittent or continuous squeezing, is the generation of gas at high temperatures in the squeezing machine during the squeezing process. These gases consist of water vapor (steam), different volatiles dissolved wood and glue, so-called volatile organic compounds (VOC), and gaseous phenol from wood and glue. Long-term exposure to these substances gives a pungent odor and high concentrations have been shown to be harmful to health. Therefore, authorities in the majority of countries where boards are manufactured according to the methods described above have struggled to establish rules indicating acceptable exhaust concentrations in the workplace and acceptable concentrations in emissions to the atmosphere.

[0004] Since current pressing techniques involve the use of homogeneous heating plates or steel belts, in the pressing process only a portion of the gas generated during pressing emerges through the edges of the plate. However, most of these gases exit the plate as it leaves the press.
The effect of these gases on the working environment can be limited to some extent by protective casings and covers, even if room temperature air is normally used as conveying air due to the large size of the press. Thus, this volume of air typically exceeds the combustion air requirements of a factory's standard heating plant. This has required complex and expensive equipment facilities in connection with the majority of plants producing lignocellulose sheets and plates. For example, plants are usually equipped with a so-called RTO (Regener
Includes an attached Thermal Oxidizer unit and a gas scrubber for purifying compressed gas.

It is an object of the present invention to provide a method and apparatus for producing lignocellulosic plates without the emission of VOCs or formaldehyde to the workplace concerned and the surrounding environment, without having to install expensive purification equipment. To provide. The purpose is
This is achieved with the method and the device according to the invention having the features described in the claims.

Next, the present invention will be described in detail with reference to the accompanying drawings, which are schematic cross-sectional views of the device according to the present invention.

[0007] The plant shown in the figures is based on the plant disclosed in Swedish patents 502,272 and 504,638 which describe two continuous steam pressing processes. The fibrous mat 1 previously formed in the manufacturing process is squeezed by a continuous steam injection squeezing machine 2 to form a plate or sheet 3, and then the plate or sheet 3 is passed through a rear adjustment unit 4. As the fibrous mat 1 passes through the nip between the two steam injection rollers 5, steam is added to the mat via wires 6 and injected. At this time, the temperature rapidly rises to 100 ° C. or higher, usually to 120 ° C. or higher. The mat thereby becomes a solid plate 3. The pressure drops as the plate leaves the nip between the steam injection rollers 5, while the temperature drops rapidly to around 100 ° C. This is caused by extremely rapid vaporization of some of the enclosed moisture. VOC emissions and formaldehyde emissions are accompanied by the generation of steam.

[0008] Since this process takes place between the two gas-permeable wires 6, the vapor and the gas exiting with the vapor can exit the full width of the plate. Vapors and other exhaust air are trapped by a suction unit 8 provided inside the press before it can escape to the workplace or the surrounding environment. Air heated to a temperature above 100 ° C. is sent to this suction unit. The hot air is used together with air leaking from the surroundings as steam and the other exhaust carrier gas described above. The hot air, leaking air, steam and exhaust are sent to a heating plant 9 in the factory for combustion. The hot air delivery unit 11 is connected to the curing zone 10 in the press 2 and the supplied hot air then proceeds to the suction unit 8.

The temperature is increased to prevent exhaust and vapor from exiting the suction system and condensing, and to take advantage of the fact that the moisture with the calculated volume of air per kilogram increases with increasing temperature. Maintained at high temperatures. This allows the total amount of air and gas to be maintained at a level that does not exceed the volume of combustion air required by a standard plant system that generates the heat and process steam needed to manufacture the board. Therefore, there is no need to install other equipment to prevent exhaust to the surroundings.

[0010] The plate manufactured by the continuous steam injection press 2 is heated to a predetermined temperature so that a plate having a desired humidity and temperature is obtained, and a predetermined volume of air containing a predetermined humidity is absorbed by the plate. Through the rear adjustment unit 4 (see Swedish Patent 504,638). The air exiting the rear conditioning unit contains VOC and formaldehyde emissions, albeit in small amounts, and most of the emissions are generated in continuous steam injection presses, as measured by experimental plants. For this purpose, a suction unit 12 is arranged in the rear adjustment unit 4. Air is drawn in at section 13, heated by heater 14,
Feed steam through 5.

The air leaving the rear conditioning unit is conveyed by a suction fan 16 to the hot air supply unit 11 of the steam injection press 2 and its curing zone 10. Supply unit 1
As one proceeds, the air is energized through the medium of the heat exchanger 17.
If the air from the rear conditioning unit 4 is excessive, the excess can be mixed with the flow from the press 2 in the closed hood 18 and passed to the heating plant 9. If there is a shortage of air to the curing zone 10, the suction fan 16 draws excess air through the sealing hood 18. The air leaving the rear conditioning unit 4 is used as hot input air for the internal suction unit 8 of the continuous steam injection press. Experiments have shown that these volumes sufficiently satisfy the transport volume required for a continuous steam injection press.

After passing through the rear adjusting unit 4, the plate 3 can optionally be passed through a surface compact press (not shown) according to Swedish Patent 502,272. This latter press also includes a special suction unit which functions to capture in the press the exhaust carried by the hot air to the factory combustion plant for the production of heat and steam.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an apparatus according to the present invention.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID , IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW (72 ) Inventor Shiedein, Kurt S-856 31 Sünsval, Hyogaritsutsugatan 34 F-term (reference) 2B260 AA10 BA01 BA07 BA18 BA19 CA02 CB01 EA05 EB02 EB05 EB06 EB21 EC18

Claims (6)

[Claims] 1. A raw material is decomposed into particles and / or fibrous or glue-like material and dried to form a mat (1). In a continuous process for the production of lignocellulosic plates, wherein the plates pass through a rear conditioning unit (4), to capture the steam and gas exhaust generated during the squeezing process and to mix said exhaust and steam with the leaking air from the surroundings In order to prevent condensation of the gas exhaust and the vapor and to prevent condensation of the leaking air from the surroundings, and to carry the exhaust to a combustion plant for combustion (9), A method characterized by supplying air. 2. A heating plant (9) wherein hot air and air leaking from the surroundings are heated.
2. The method according to claim 1, wherein the air is supplied in approximately the same amount as the required combustion air. 3. The method according to claim 1, wherein the curing zone (10) in the pressing machine (2) is supplied with air at a temperature of 100 ° C. or higher. 4. A rear adjustment unit (4) so that the temperature is 100 ° C. or higher.
A method according to any of the preceding claims, characterized in that energy is supplied to the intake air from the steam generator and air is used as carrier gas for transporting the exhaust gas from the steam injection press (2). 5. An apparatus for carrying out the method according to claim 1, comprising a continuous steam injection press (2) and a rear conditioning unit (4). 2) a suction unit (8) located in and functioning to capture gas exhaust and steam and carry said exhaust and steam to a combustion plant (9) and a unit for supplying hot air to the suction unit (8) (11) An apparatus comprising: 6. A hot air supply unit (11) is connected to a suction unit (12) in a rear adjustment unit (4) for air supply, and a heater (17) is provided between said units. 6. The device according to claim 5, wherein the device is connected to a transport conduit.