Technology for the production of wood fiber boards. Name of raw materials and materials

Fiberboard is produced at many enterprises in Russia. Let's name the most famous of them and briefly introduce each one.

This article will help you navigate the product range of specialized factories and assess the level of their technical equipment, which directly affects the quality of the final product.

Bobruisk

The Bobruisk plant is located in the town of Bobruisk, Republic of Balarus. Company rich story beginning in the late 1960s. The company has gone through many upheavals and transformations. Currently (since 2011) it is owned by BusinessStroyMir LLC.

The plant is represented by three specialized workshops. They are equipped with fairly modern import lines "SCHWABEDISSEN" and "GABBIANI".

The method of manufacturing plates - wet. The plant is focused on the production of fiberboard without the use of hazardous phenol-formaldehyde resins.

The main brand is HB. T-S. Also produced are DVPO (painted boards), as well as wood-fiber circles and rings.

Knyazhpogostsky

The Knyazhpogost enterprise in the Komi Republic (Yevma) is going through quite difficult times.

Unfortunately, it has fallen into a difficult economic situation. In 2012, the former form of the company - DVP Plant JSC - went bankrupt.

To replace it, a new enterprise was created - OOO "Knyazhpogostsky DVP Plant". There is reason to hope that the successor company will continue the tradition of quality.

Previously, the shops produced wet way hard and superhard plates of grades T and T-C.

The products were environmentally friendly - a technology was used in the production process that completely dispenses with unwanted binders.

The new management is confident in the future, plans to organize the supply of products to new markets in Germany and the Baltic states.

Novovyatsky KDP

The Kirov Plant, which has been operating since 1915. It manufactures thin solid slabs of grade T in quality classes A and B, incl. with moisture resistant lacquered and dyed.

Instead of formaldehyde binders, urea-formaldehyde resins are used (standard E1). The main production method is dry pressing. The equipment is exclusively imported, German.

A significant proportion of the range is exported.

Sokolsky pulp and paper mill

Another old, but diligently developing plant with a good reputation. Operates in Sokol, Vologda Oblast. It offers consumers both hard and soft fibreboards.

They meet international standards and are successfully exported to the USA, the Netherlands, Finland and England.

Many other enterprises of the pulp and paper sector are also engaged in the production of fibreboard, in particular, the Mari and Arkhangelsk pulp and paper mills.

Fibreboard (MDF) is a sheet material obtained by pressing a mixture of wood fibers and special additives at high temperatures. Industrial production was launched in 1922 in the USA. At present, the production of products from fiberboard is widespread in many countries of the world. But, despite this, not everyone will be able to answer the question: “Fiberboard - what is it?” Let's see what this material is and where it is used.

Raw materials for the production of fibreboard

For the manufacture of fiberboard, woodworking and sawmilling waste, wood chips, plant fires, etc. are used. Wood raw materials are processed into fiber in defibrators by steaming and grinding.

Synthetic resins are added as a binder to the pressed mass. Their number depends on the ratio of softwood and hardwood fibers and varies, as a rule, in the range of 4-7%. In the case of the production of soft boards, the binder may not be introduced, since the wood fibers contain lignin, which has adhesive properties at high temperatures.

To increase moisture resistance, ceresin, paraffin or rosin are introduced into the mass. In addition, other special additives, in particular antiseptics, are used in the manufacture of plates.

Methods for the production of fiberboard boards

As a rule, fibreboards are produced by wet and dry processes.

In the process of making fiberboard with a wet method, a carpet of a board consisting of wood fiber pulp is formed in water and pressed under heat. After that, the resulting sheet is cut into sheets. The moisture content of such material is in the range from 60 to 70%.

With the dry method, the formation of the carpet occurs in air at higher temperatures and lower pressures compared to the wet method. The result of such production is the production of low-pressure boards, characterized by a looser and more porous structure and relatively low humidity (from 6 to 8%).

There are also intermediate manufacturing methods - wet-dry and semi-dry. In the first case, the carpet of the slab is formed in water, after which it is dried and only after that it is pressed. In the second, the manufacture of fiberboards is carried out according to the dry method, but the moisture content of the material changes (from 16 to 18%).

Types of fibreboard

Fiberboards, depending on the properties and purpose, are divided into several types. Let's look at their characteristics and applications.

Soft fiberboard - what is it?

The material is characterized by low strength, high porosity and low thermal conductivity. The thickness of the plate can be from 8 to 25 mm. Material densities range from 150 to 350 kg per cubic meter. meter. Depending on the density, the following brands of soft fiberboards are distinguished: M-1, M-2, M-3.

Due to their low strength, soft boards are not used as the base material. Most often they are used in construction as a sound and heat insulating material in the construction of walls, floors, roofs, etc.

Semi-hard fibreboards

This type of slab has a much higher strength and density compared to soft slabs. The average density of semi-solid fiberboard sheets is at least 850 kg per cubic meter. meter. The thickness of the fiberboard sheet is 6-12 mm. The material is widely used in the production of such furniture structures as drawers, rear walls, shelves, etc.

Solid fiberboard options

Hardboard density values ​​range from 800 to 1000 kg per cubic meter. meter ( high performance for fiberboard). The dimensions of the carpet thickness are on average from 2.5 to 6 mm. These fiberboard sheets are used to produce the back walls of furniture, panel doors and a number of other products.

Solid fiberboard sheets depending on the indicators of density, strength and type of the front side, they are divided into the following grades:

• T - plate, the front surface of which is not ennobled;
• T-C - has a front layer made of finely dispersed wood pulp;
• T-V - has an unfinished front surface and is characterized by increased water resistance;
• T-SV - the front layer of the material is made of a finely dispersed mass, the material is characterized by increased water resistance;
• T-P - the front layer of the plate is tinted;
• T-SP - has a tinted front layer of finely dispersed mass;
• NT is a material characterized by a reduced density.

Super hard plates

This material is characterized high quality performance, ease of processing and ease of installation. It has an increased density, the values ​​\u200b\u200bof which are at least 950 kg per cubic meter. meter. The material acquires high hardness due to impregnation of fiberboard sheet with pectol. What it is? Pectol is a by-product from the processing of tall oil. Superhard plates are used for construction purposes for the manufacture of doors, arches, partitions, for the production various kinds fiberboard containers. On the floor are used for the manufacture of floor coverings.

Refined wood fiber boards (DVPO)

Distinctive advantages of ennobled fiberboards are beautiful appearance, high resistance to abrasion and moisture. In production of this type plates, a technology is used that provides for the application of a multi-layer coating on the front side. After careful processing, a primer layer that creates the background part is applied to the surface. Then a pattern is printed that mimics the wood structure.

Refined boards are used to make doors, as a material for finishing ceilings and walls, etc. They are also used to make various internal furniture parts (lower and rear walls of cabinets, drawers, etc.).

Laminated fibreboard (HDF)

To date, fiberboard laminated is also produced. This is a material that is sheets on which a special composition of synthetic resins is applied. Thanks to this coating, laminated fiberboard is characterized by increased strength and moisture resistance. This makes it possible to use it for various purposes.

Fiberboard: sheet dimensions

Despite the small thickness, fiberboard sheets are quite impressive in size. So, the length of the carpet can be from 1.22 to 3 m, and the width - from 1.22 to 1.7 m. Fiberboard is also produced, the sheet dimensions of which are 6.1 × 2.14 m. This is the maximum area of ​​manufactured fiberboard . Sheet dimensions allow the use of such material for industrial purposes.

Conclusion

Now we know the answer to the question: "Fibreboard - what is it?" Awareness is an important point when choosing certain building materials. After all, the quality and financial cost of the construction or facing work performed will depend on the correct choice.

Fiberboard production is carried out by wet and dry methods.
Wet production of fibreboard includes such operations as chipping, gluing the resulting pulp, forming a carpet, pressing, impregnating the boards with oils, thermal-moisture treatment and trimming the boards.

The washed wood chips are subjected to two-stage grinding. The first grinding is carried out in defibrator mills, in which the chips are steamed and processed into large fibers. The second grinding is carried out on refiners, which make it possible to obtain thinner fibers with a thickness of 0.04 mm and a length of 1.5...2 mm. An aqueous solution of wood-fiber pulp is prepared from such fibers - pulp, which is stored in collectors or pools, stirring occasionally to maintain a certain mass concentration, preventing the fiber from settling to the bottom.

The resulting pulp is then sent to a continuous sizing box, where it is mixed with phenol-formaldehyde resin. Hydrophobic additives prepared in an emulsifier, hardening agents and precipitants are also fed there with a mixing pump at a temperature of not more than 60 ° C and such a volume at which the concentration of the resulting suspension for any ratio of the rock composition of the fibers of the raw material before casting is 0.9 ... 1, eight%. The dosage of these components depends on the type of boards, the composition of the fibers, water consumption, pressing modes, etc.

The operation of forming a wood-fiber carpet is carried out on an endless mesh in casting machines. The final humidity of the carpet for hard and superhard boards with a thickness of 3.2 mm should be (72 ± 3)%, for soft boards with a thickness of 12 mm - ((61 ... 63) ± 1)%. To form raw slabs, the pressed carpet is cut to obtain dimensions in length and width that are 30–60 mm smaller than those of the finished slab.

For hot pressing of fiberboard, multi-storey (20 floors) hydraulic presses are used. Loading and unloading of plates is carried out by whatnots. The fiberboard pressing cycle includes three phases, each of which is characterized by a certain pressure, holding time and moisture content of the boards.

The first phase is spin. Water is removed from the fibrous carpet in 30 seconds under pressure of 4.2...5.5 MPa. Humidity at the same time decreases to 45%, and the plate itself, warming up, is compacted.

The second phase is drying. The slabs are kept for 3.5...7 min at a reduced pressure (0.65...0.85 MPa), at which the humidity of the slabs reaches 8%.

The third phase is the hardening of the plates, which contributes to their compaction, increase in strength and hydrophobic properties. The plates are kept under pressure of 0.65...0.85 MPa for 2...3 minutes.

The resulting plates must have a final moisture content of 0-.5 ... 1.5% and a flexural strength of at least 35 MPa, which is ensured by observing the technological parameters of the process: the thickness of fiberboard, the width of the press plates and the rock composition of the raw material.

In addition to hot pressing, soft fiberboards are produced by drying fibrous carpets in continuous roller dryers, in which free moisture is removed. The dryer has 8-12 rows of roller conveyors heated with saturated steam at a pressure of 0.9...1.2 MPa. The air circulation speed is 5...9 m/s, drying time is 1.5...2 hours to a moisture content of 2...3%.

To improve and stabilize the strength and hydrophobic properties of the board, they are subjected to heat treatment in cells periodical action. The coolant in them is superheated water with a temperature of 190...210°C and a pressure of 1.8...2.2 MPa. The speed of air movement is not less than 5 m/s. The heat treatment time, taking into account the thickness of the plates, is 3...6 hours.

To give the plates dimensional stability after heat treatment, they are cooled and then moistened in humidifying machines or batch chambers. Wet slabs are cut to size and then aged for at least 24 hours.

Superhard plates are also subjected to the heat and moisture treatment procedure, but after they are impregnated with drying oils in an impregnating machine in order to increase strength and water resistance.

Production of fiberboard by dry method much the same wet fibreboard production . But the dry method can be used to produce boards of double-sided smoothness with a thickness of 5...12 mm and boards with special properties (fire- and bio-resistant, profiled, etc.).

The production of fiberboard by the dry method is also different in that when grinding chips, the operations of steaming it, separating the fibers for the outer and inner layers and mixing them with additives and resin are included.

The carpet is formed from dried fibers by felting and vacuum compaction, and then pressing with belt-roll and format presses. Hot pressing lasts 5...7 min and is carried out at a temperature of 200...230 °C with a single rise in pressure up to 6.5 MPa for 15...25 s and its stepwise discharge first to 0.8...1 .0 MPa, and then to zero. Profiled fiberboards are fixed on the press plates of special matrices.

At present, it successfully competes with chipboard, which is more homogeneous in structure MDF material, which is much easier to cut and process.

All slabs, regardless of the process of their preparation, after 24 hours of exposure, are cut to size on circular saws for sizing and cutting machines according to their standard sizes.

Fibreboard is produced by a dry continuous method on the line of the company "Bison"

1) Characteristics of manufactured products, raw materials and basic materials

Fibreboards of the dry continuous production method are made from hardwood and coniferous wood with the addition of binders.

The dimensions and basic physical and mechanical parameters of the boards must comply with the requirements of TU BY 600012401.003-2005 "Wood fiber boards".

Plates are tested according to TU BY 600012401.003-2005.

Raw materials and materials must comply with the requirements of the relevant standards (Table 1.1).

Table 1.13 - GOSTs or TU for raw materials and materials

Name of raw materials and materials	GOST or TU
Technological chips	GOST 15815-83
Technological chips from thin trees or branches
Urea-formaldehyde resin grades:
	TU 135747575-14-14-89
or KF-MT-15	TU 6-06-12-88
Ammonium chloride technical	GOST 2240-73
Ammonium sulfate	GOST 9097-82
Firewood for hydrolysis production and fiberboard production	OST 13-200-85
Raw wood technological	TU RB 100195503.014-2003

For the production of fiberboard by a dry continuous method, the following species composition of wood raw materials is recommended:

50% - aspen, poplar, alder

20-30% - softwood

20-30% - birch

The ratio between the types of wood raw materials is recommended as follows: technological chips - at least 70%;

technological chips from thin trees or branches - no more than 30%;

it is allowed to use sawdust from sawmilling, woodworking - no more than 10.

2)Technological process

The technological process for the production of fiberboard by a dry continuous method includes the following operations:

Acceptance and storage of raw materials and materials

Process chip preparation

Grinding technological chips into fiber

Preparation of the introduction of binder and hardener.

Drying wood pulp

Forming a wood fiber carpet

Pressing wood fiber boards

Cutting slabs into formats, stacking and packaging slabs

2.1) Acceptance of raw materials and materials.

The raw material for the production of fiberboards is purchased technological chips, technological chips from thin trees and branches from the timber industry, chips from lumpy woodworking and sawmill waste, firewood, technological chips made from firewood.

Raw materials are delivered by road and unloaded to an open storage warehouse.

Samples are taken from each batch of incoming chips according to GOST 15815-83 for analysis to determine the content of coniferous and hardwoods, bark, rot, mineral impurities and fractional composition.

Accounting for the amount of chips and methods for measuring it must comply with OST 13-74-79 or GOST 15815-83.

The transfer of the mass of crushed raw materials into volume at a known moisture content is carried out according to the formula:

where V is the volume of wood chips, cubic meters; m - mass of wood chips, t; - chip density at actual moisture content, kg/m.cub.

Urea-formaldehyde resin is delivered in railway tanks to the department for receiving and unloading railway tanks. Resin is accounted for by the level of filling of containers with a reading on calibrated scales with the conversion of volume into mass by multiplying the measured volume by the density of the resin. From each batch of incoming resin, a sample is taken for analysis according to TU 135747575-14-14-89 or TU 6-06-12-88.

Ammonium sulfate (ammonium chloride) is delivered to the workshop by transport in bags Accounting for solid, packaged chemicals is carried out by the weight of each bag indicated on the label or by weighing.

Firewood delivered to the site by road is unloaded by a tower crane KB572 and stacked according to the species composition. The diameter of the raw material is set to 800mm, length from 1 to 6m with a gradation of 1m. Defects are not allowed in raw materials:

External rotten rot;

charring;

sound rot;

Other defects and defects are allowed. Raw materials of coniferous and deciduous species are supplied with bark and debarked. Measurement and accounting of firewood with a length of up to 3m is carried out in accordance with GOST 3243-88, with a length of more than 3m - in accordance with GOST 2292-74. Raw materials with a length of less than 2 m - in bags.

2.2) Preparation and sorting of wood chips

Firewood delivered to the site by road is unloaded by a KB572 tower crane and stacked according to the species composition. The height of the stack should not exceed 1 BUT its length, but should not exceed one and a half length of the logs stacked in this stack. The height of the stack of logs when stacking by hand should be no more than 1.8 m.

Firewood is fed from the stack by a tower crane KB572 to the overpass. From the overpass, the raw material is rolled piece by piece onto the log carrier. By means of a log hauling chain conveyor, the raw material is fed into the disk chipper MPP8-50GN, where it is processed into technological chips.

Technical characteristics of the disk chipper MRR8-50GN:

Volumetric productivity, m3/hour 50

2. Volumetric productivity when cutting unfrozen wood with a diameter of 50-90

600-800mm, m3/hour

3. Dimensions of processed wood, mm:

Diameter 200-800

Length at least 1000

It is allowed to process wood with a diameter of 60-200 mm with its grouping into packs. The size of the pack should not exceed the size of the loading window of the cartridge

4. Geometric dimensions of wood chips according to GOST 15815-83

5. Chuck diameter, mm 850 2.7

6. Blade disc:

Diameter, mm 2900

Number of cutters, pcs 25

The angle of inclination of the disk to the horizon, deg. 37

Speed, rpm 152

7. Disc drive - electric motor:

Type AO3-400M-10V2

Power, kW 160

Speed, rpm 590

8. Feed drive

Power, kW 2.2

Speed, rpm 750

Quantity, pcs 2

Picture 6 - Technological scheme of storage and sorting of wood chips

Figure 7 - Scheme of cleaning wood chips at a hydrowasher

9. Overall dimensions, mm:

Length, mm 6805

Width, mm 5090

Height, mm 3265

The chip storage area (Figure 6) consists of two sections: a hardwood chip storage area and a softwood chip storage area. Technological wood chips delivered by road are transported to the concrete storage area for coniferous (12), hardwood (14) wood chips. The formation of heaps in the woodchip warehouse is carried out with the help of a bulldozer. A bulldozer feeds chips from the concreted area to the dosing station for softwood chips (4) and to the dosing station for hardwood chips (13). From the dosing station for softwood chips (4), technological chips are fed by scraper conveyors (7) for sorting SSh-120 (11). From the dosing station for hardwood chips (13), the chips are fed by scraper conveyors to the sorting of the REWiBRALL type (10) with a capacity of 700 kg/h of absolute dry chips. Sorters have two sieves and a pallet and separate the wood chips into three fractions. The top sieve has openings of 50x50 mm and 40x40 mm, the bottom 8x8mm. The coarse fraction from the upper sieve and the fine fraction from the lower sieve are fed by a belt conveyor into the chip screening bunker.

The optimal size of wood chips is 15-35mm, 4-6mm thick. The conditioned wood chips are fed by the conveyor to the hydrowasher. The scheme of woodchip cleaning at the hydrowasher is shown in Fig.7.

Through the transport device, the chips enter the heavy particle separator (1) of the washing plant, where the paddle wheel (3) is located, mixing the chips under water. Due to the flow of water, which picks up the chips from the bottom up, the chips are prevented from entering the intermediate container (4) located below and removing them through the sluice gate (7). Only mineral impurities with a high specific gravity can overcome the flow of water and sink into the intermediate container. The same flow of water brings the chips into the lower part of the dewatering screw (2), equipped with a stream with holes for draining water from the chips along the way of its transportation to the funnel (6). The openings of the tray are cleaned with water, which is fed into upper part tray. Water, together with particles, enters the intermediate tank (5) and then returns to the circulation system.

The chips transported by the dewatering auger (2) enter the chip funnel (6), from where they are directed to the steaming chamber. To heat the funnel bunker in winter, a heater (14) is installed, into which steam is supplied, and a fan (15), which blows hot air into the bunker.

To control the filling of the funnel, a measuring device with a gamma emitter is installed, which operates as follows.

The protective shell and the radiation detector are mounted opposite each other. The gamma rays emitted by the radioactive substance penetrate the walls and the empty container. The Geiger counter converts radiation into current pulses, which are transmitted over a two-wire cable and summed up in a control device (Gammapilot). The resulting current is then used to switch on the output relay. If the level of filling the container with chips exceeds the height of the passage of gamma rays, then the gamma radiation is attenuated, the output relay switches and the supply of chips stops.

Heavy particles (mineral impurities) that enter the heavy particle separator (1) and then through the intermediate tank (4) are sent to the sluice gate (7) open from the side of the tank, in which they settle. After some time, the lock on the tank side closes and a drain hole opens through which heavy particles and water are fed through pipelines to the multi-chamber stilling basin (8) of the storage tank (11), where the cleaning scraper conveyor (10) is located.

Suspended particles leaving together with wastewater from the dewatering screw (2), designed to remove water, enter the intermediate tank (5) and accumulate in the sluice gate (7), which operates similarly to the above sluice gate. The sluice gate (7) also delivers suspended particles to the multi-chamber stilling basin (8).

After the sluices have been emptied in this way (the emptying cycles can be adjusted independently), the drain holes are closed and the sluices are automatically filled with water via the self-acting shut-off valves. After that, the sluice gates are opened again from the tank side.

From the multi-chamber stilling basin (8), heavy particles (mineral impurities) contained in the waste water are fed by a scraper conveyor to the screw conveyor. By means of a pump (12), clean water from the reserve pool (9) of the storage tank (11) is directed to washing the perforated tray of the dewatering screw (2). Part of this water is returned back to the storage tank (11).

The pump (13) supplies water from the intermediate tank (5) to the heavy particle separator (1), from which the water is again directed to the dewatering screw (2) together with the wood chips. Losses of water in this circuit, due to the operation of locks, are replenished with water from cross-flushing.

2.3) Grinding technological chips into fibers

In the process of grinding technological chips, the most complete separation of wood into individual fibers should be achieved, which ensures an increase in the surface of the particles and an increase in their plasticity. The increase in plasticity facilitates the convergence of the particles during the formation of the wood fiber carpet and the pressing of the boards. To ensure the plasticity of the fibers, the chips are treated with saturated steam at a pressure of 0.7-1.2 MPa before grinding.

In the process of steaming and grinding, partial hydrolysis of wood occurs. Water-soluble products are retained in the fibers during further technological processing, participating in the formation of physico-chemical bonds between the fibers. In the process of hydrolysis, the formation of functional groups on the expanded surface of the fibers occurs. Different types of wood require different processing conditions. So, spruce, fir and pine, which contain unsaturated acids capable of polymerization in extractive substances, require minimal heat treatment. Other species, such as birch and aspen, require more stringent heat treatment conditions. The pressure of the hydraulic pressure of the grinding discs of the refiner for hardwood chips is recommended, on the contrary, less than for softwood.

Technological scheme for obtaining fiber on the refiner "PR-42" FIRM "Pallmann" is shown in Fig.8. From the washing plant, the chips are poured into the refiner funnel (1). In the same bunker-funnel pneumotransport serves cuttings from FOS. From the bunker - funnel chips and sawdust stuffed (boot) auger (2) is fed into the steam boiler (4). From the steaming boiler, the chips are fed by the unloading screw (5) into the grinding chamber (6) between the fixed and rotating disks. The resulting fiber is ejected by steam pressure through the unloading valve into the mass pipeline (8) and further into the dryer pipe.

Waterlogged fiber, formed during the start-up of the refiner, is fed through a cyclone (9) into the start-up fiber hopper.

Technical characteristics of the refiner "PR-42"

Productivity on absolutely dry fiber, kg/hour 5500

The volume of the steaming chamber, m3 2.5

Chip steaming time, min 3-6

Steam pressure, MPa 0.7-1.2

Operating temperature, С 190

Steam consumption, kg/h 5000

Grinding disc diameter, mm 1066.8

Disc rotation frequency, mm - 1 1485

Engine speed, min-1 1485

Engine power, kW 1600

Type of engine coolant water

The rotational speed of the stuffing (boot) screw depends on the productivity of the refiner and the bulk density of chips (Fig. 9). So, with a refiner productivity of 5.5 t/h and a bulk density of chips of 150 kg/m3, the rotational speed of the stuffing screw will be 62 min-1.

The duration of the steaming of chips is determined using diagrams (Fig. 10-12). The performance of the grinding plant (the number of revolutions of the unloading screw) is set according to Fig. 10, and then the duration of steaming, depending on the bulk density of chips, according to Fig. 11-12. So, for example, at a screw speed of 32 min-1, the refiner performance will be 5.0 t/h of absolutely dry fiber (with a bulk density of chips of 150 kg/m3). According to Fig. 11, it is established that for such a productivity, the duration of fiber steaming can be from 2 to 5 minutes at a height of filling the steaming boiler with wood chips from 1.6 to 4.0 m.

The gap between the discs, the hydraulic clamping pressure of the discs and the degree of opening of the unloading valve significantly affect the quality of the resulting fiber. With an increase in the productivity of the refiner, the gap must be increased. The required hydraulic pressure should be set depending on the rock composition of the chips.

The gap between the discs is set using a set microscrew. One full turn of the microscrew causes an axial displacement of the disc by 0.75mm. When the microscrew is rotated “to the right”, the disks approach each other and vice versa. The gap is measured with a measuring probe with the measurement result output to a digital device with an accuracy of 0.01 mm. The point of contact of the disks is taken as the zero position of the measuring probe. To determine the point of contact of the disks, the microscrew is rotated “to the right” until a whistling sound appears, which occurs when the rotating disk comes into contact with the stationary one. Then the microscrew is rotated « to the left » before setting the required gap, the value of which is shown by a digital indicator.

The discs can only be in contact for 1-2 seconds, otherwise overheating and destruction of the segments is possible.

The refiner should be started with a gap between the discs of at least 5 mm. This prevents starting with flattened discs. If the grinding discs are at a distance of less than 5 mm from each other, then by “left” rotation of the microscrew they are still separated until the “rotor in position” lamp on the refiner control panel lights up, which indicates that the grinding discs are 5 mm apart from each other. friend.

Before feeding chips, the grinding chamber must be heated to a temperature of at least 100°C.

After the discharge of the first portions of the fiber, the gap between the disks is adjusted, taking into account the operation of the unloading valve and the hydraulic pressure of the disks to obtain a fiber of the required quality. Some time after the start of the refiner, the load on the engine begins to fall, which indicates an increase in the gap. In this case, the discs are brought together to the initial indication of the load on the engine.

With a constant gap and an ever-increasing degree of wear of the disc segments, an increase in the electric power consumed by the engine occurs. To maintain a given gap in this case, it is necessary to increase the hydraulic pressing pressure of the disks.

The unloader valve also gradually wears out, so it is necessary to periodically adjust the degree of its opening during operation.

Figures 8-11

Pictures 12 - 13

Schemes of preparation and dosing of the working solution of resin and hardener are shown in Fig.12-13.

Urea-formaldehyde resin from the warehouse is pumped by a pump (1) into a supply tank with a volume of 9000 kg, from where the resin is rolled into a measuring cup (4) with a volume of 200 liters, and from there into a container for preparing a working solution of resin (8) with a capacity of 300 liters. After dilution and vigorous stirring, the resin solution is taken for analysis.

The hardener is prepared and injected into the mass pipeline.

Ammonium sulfate (ammonium chloride) in bags is fed to the hardener preparation site and dissolved in water with stirring in a container (1) with a volume of 480 l. The water temperature should be 35-40 C. Water is dosed according to the meter (2). Prepared solution circulation pump(8) dosing containers (6) are filled one by one through the filters (7). The dosing pump (10) delivers the hardener solution to the oil pipeline. Lumps of wood fiber with resin are separated in the heavy material separator and removed from the stream. Standard wood fiber, without lumps, is fed by a fan through cyclones to the belt conveyor of the forming machine.

Figure 14 - Technological scheme of drying wood pulp

2.4) Drying the pulp

Drying of the wood fiber mass after the refiner is carried out in the RT60 dryer pipe of the Scheuch company (Scheuch), when passing through which the wood fiber mass is dried in a stream of hot gases to a moisture content of 6-12%. The drying agent is hot gases mixed with air, which are formed during combustion in the burner of a natural gas furnace. The drying process is controlled automatically by maintaining the temperature of the gas-vapor mixture leaving the dryer at a given level by changing the volume of natural gas supplied to the furnace burner. To prevent fiber ignition, the temperature of the drying agent at the inlet to the dryer should be no more than 170 C.

Technological scheme of wood fiber mass drying is shown in Fig.14.

The CK-100-G burner (1) of the furnace (2) is fed with natural gas for combustion. Hot gases generated during combustion are mixed with air and fed by a smoke exhauster (3) to the dryer pipe (5). At the same time, air (6) containing formaldehyde collected from the press umbrella is fed into the furnace for combustion. The wood fiber mass from the refiner through the mass pipeline (7) is introduced into the dryer pipe. The working solution of the binder and hardener enters the mass pipeline, where intensive mixing with the fiber occurs due to the turbulence of the flow that occurs during the transportation of the fiber. In the flow of hot gases in the dryer pipe, the wet fiber is dried to a moisture content of 6-12% for 3-4 s and fed into four cyclones (8), in which the dry fiber is separated from the drying agent, and then unloaded through the sluice gate (9). onto the conveyor belt (10).

When a fiber ignites in the dryer, the Grecon fire detection and localization system is automatically activated, the belt conveyor (10) is turned on in the opposite direction and the extinguished fiber is removed from the stream.

Dry fiber from the belt conveyor enters the separator of heavy fibrous material (11) and then to the cyclone of the forming machine.

The main technological parameters of the wood pulp drying process are given in Table 1.16

Table 1.16 - Main technological parameters

Parameter name		Parameter value
The temperature of the drying agent at the inlet to the dryer pipe
The temperature of the drying agent at the outlet of the dryer pipe
Initial fiber moisture
Final fiber moisture
Drying agent speed
Mass of fiber passing through
dryer for 1 hour

Control and regulation of the drying mode is carried out by a system of cascade regulation and temperature control at the inlet and outlet of the dryer, in the furnace.

The drying mode is set by setting a certain temperature of the drying agent at the outlet of the dryer pipe by means of a control regulator connected to the thermal resistances located at the outlet of the dryer pipe. When the set temperature value is exceeded by 5-10°C, the burner automatically switches off.

The maximum temperature of the drying agent at the inlet to the dryer pipe is set using an electronic controller connected to the thermal resistances installed at the inlet to the dryer pipe. If the set temperature value is exceeded, the supply of fiber to the dryer and fuel to the burner is automatically turned off.

If one of the units installed after the dryer fails, the supply of fiber to the dryer and fuel to the burner are automatically stopped.

The dryer must be cleaned of loose fibers at least once a week. The dryer must be cleaned only when the temperature in the dryer drops to 30°C and the motors are switched off. The fuses of all dryer drive motors must be removed.

Clogging of the dryer pipe or cyclones with pulp usually results in the inlet and outlet temperatures being exceeded and the dryer automatically shutting down. If this does not happen, immediately turn off the burner manually, stop the fiber supply to the dryer and clean it.

After a forced or special stop, the supply of fiber to the dryer should be started gradually, without a sharp increase in productivity.

In the event of a fiber fire, the fire extinguishing system is automatically activated with water supply to the dryer. After extinguishing the fire, the dryer must be thoroughly cleaned and the water removed from the fan.

2.5) Formation of the wood fiber carpet.

The purpose of the technological operation of formation is to obtain a continuous wood-fiber carpet of certain dimensions in thickness and width. The technological process of forming a wood-fiber carpet is interlocked with other areas. The formation of a wood-fiber carpet is carried out in one forming chamber (Fig. 15).

The fiber from the receiving cyclones is fed through the sluice gates to the belt conveyor (1), which transports it to the dosing bin (2) of the forming chamber. At the same time, the conveyor performs reciprocating movements, distributing the fiber across the width of the hopper-dispenser (2). From the conveyor (1), the fibrous material enters the dosing conveyor (3) of the dosing bin. If the level of the fibrous material reaches a certain height, then the excess fiber is thrown back by the leveling combs (4). Then the fiber is fed by a dosing conveyor (3), the speed of which is in direct proportion to the volume of the poured fiber, to the discharge rolls (5) and then to the opening rolls (6), which rotate in opposite directions. After passing through the opening rolls (6), the fibrous material is taken up by the air flow generated by the vacuum boxes (7) and deposited on the moving web (11). Due to the air permeability of the mesh and the strong suction under it, the fibrous carpet layer is compacted and at the same time rolled up. The thickness of the fibrous carpet depends on the speed of the tape mesh. The formed fibrous carpet is cut to a predetermined height by a scalping device (8). The scalping device consists of a toothed roller that removes excess material, which is removed by a pneumatic system and then returned again for further use. The thickness of the fiber layer is set behind the sensor of the radioisotope density meter (9) and automatically maintained at a given level by changing the speed of the grid or moving the scalping device in height. The formed carpet is pre-pressed with a belt-roller (10), as a result of which the height of the carpet is reduced by 2-2.5 times and its transportability is increased.

Figure 15 - Scheme of the formation of a wood-fiber carpet

Picture 16 - Technological scheme of pressing wood fiber boards

2.6) Pressing fibreboard

The pressing of fibreboards is carried out in a continuous calender type press "Auma-ZOR" of the company "Berstorff" (Fig. 16.)

Technological characteristics of the press "Auma-ZOR":

Calender diameter, mm 3000

Diameter of pressing heating rolls, mm 1400

Idler and drive roll diameter, mm 1400

Working width of the calender, mm 2500

Steel tape length, mm 27900

Width of steel tape, mm 2650

Steel strip thickness, 2.1 Number of cleaning rolls, pgg

Heating of the calender and rolls thermal oil

Temperature of the calender and rolls, °С up to 200 Maximum working pressure of the hydraulic clamp, MPa:

Roll №2 20

Roll #3 15

Roll №4 28

Maximum working pressure in the hydraulic system

Steel tape tension, MPa 14

Pressing speed, m/min 3-30

After cutting the edges, the wood-fiber carpet is fed through the metal detector by a belt conveyor (18) to the input zone of the calender press, is captured by a continuous steel tape (7) and pressed against a calender (1) heated to 160-190°C. Pressing is carried out mainly by pressure rolls (2,3,4), which press with a predetermined pressure on the steel strip and the wood fiber carpet. In the area after the roll (4), the carpet is held by a steel tape in a pre-pressed state, the binder roll (5) is finally warmed up and cured, it creates tension in the steel tape, the drive of the tape is carried out from the roll (6). The resulting slab is transported along the guide rollers, passes through the thickness gauge (19) and is fed to the sizing and trimming machine.

The line provides for the possibility of applying a single-layer coating of textured steam-conducting paper on the formed wood-fiber carpet with its subsequent pressing. For these purposes, a laminating unit (22) is used, located directly in front of the calender (1) and representing a frame on which the working and spare paper rolls (with a diameter of not more than 600 mm) and three guide rolls (with a diameter of 148 mm) are attached. After the roll has been installed, it is necessary to pass the strip of paper through the three guide rolls to the entrance to the calender. Immediately after the start of the laminating operation, it is necessary to set the required amount of paper strip tension using the pressure regulator located next to the brake, the maximum speed of the coating machine is 50 m/min.

For lamination, steam-conducting paper is used, weight 1 sq.m. which is 60-150g., and the working width is 2550 mm.

2.7) Fibreboard sizing, packing and stacking After hot pressing in a calender press and automatic thickness measurement, a continuous sliver of fibreboard is fed in two rolls to a ME-02 (Shwabedissen) sizing and trimming machine.

The machine is equipped with 2 cutters and four circular saws for longitudinal cut(two milling cutters and two saws for trimming the longitudinal edges and two saws for cutting the slab along the length into two or three parts) and five cross cutting saws. Edge trimming boards are equipped with crushers. After crushing the edges with a pneumatic system, they are sent to a waste bin for subsequent combustion in the boiler furnace. Saws for transverse cutting are located in series and close to each other and, when cutting, make oscillatory movements in an arc, while the plate on 2-3s is clamped by clamping rolls and stops, forming an arc in front of the machine. After cutting the board, the saws are raised, the nip rolls are retracted, the arc of the fibreboard is straightened and the board advances the next step up to the limit switch (to the set length dimension).

Finished fiberboards are sorted and stacked in packs of 50-200 pieces. depending on the thickness of the boards. Standard boards intended for export deliveries are packed in accordance with OST 13-34-81 “Fiber boards supplied for export. Packing, marking, transportation, storage.

Packaging of a standard slab is carried out as follows (Fig. 17): the formed slab packages are fed to the driven roller tables (3). Then the plate package goes to the driven roller table (5) for packing. The second package of the plate, through the drive roller table (7), is fed to the drive roller table (8) for packing. Packaging is in progress. Packed packages are transported to roller tables (6.9) and removed by a forklift. Packing of a non-standard (large-format) plate is as follows:

The formed slab package enters the drive roller tables (3). Then the package enters the driven roller tables (4,7) for packaging. The slab is packed and transported to roller tables (6.9), after which it is removed by a loader. For packaging of fiberboard packages, fiberboard linings or stretch film are used. The formed package is tied with hard-worked packaging tape according to GOST 3560 "Steel packaging tape" or with polyester packaging tape.

The tension and fastening of the ends of the packaging tape should exclude the possibility of relaxation of the packaging during loading and unloading operations and transportation.

At the joints of the upper, lower and side facing plates, corners are placed under the packing tape to protect the plates from crushing.

Dimensions, mass of packages, number of sheets in a package, number of belt belts, dimensions of pallet parts, their number and material, as well as marking are produced, determined and performed according to OST 13-34-81.

Packed boards are transported by a loader to a dry closed warehouse, where packs of boards are stacked in piles of the same standard size. The stack must be at least 1.5 m from doors and at least 0.5 m from walls and heaters. Passages and driveways are made between the stacks, providing free access to them. The width of the passage should ensure the transportation of packages of plates of maximum length.

Fibreboards not intended for export are stored, packaged, labeled and transported in accordance with TU BY 600012401.003-2005.

Figure 17 - Scheme of organizing the trimming and packaging of fiberboard

Introduction

Varieties and brands of materials and products

Characteristics of raw materials

Description of technological processes of production

Characteristics of the main equipment

5. Control production process and product control

Conclusion

Bibliographic list

Introduction

Fibreboard - a sheet material made by hot pressing or drying a carpet of wood fibers with the introduction, if necessary, of binders and special additives. Fibreboards are used in construction for heat and sound insulation, for the manufacture of interfloor ceilings, walls, for interior decoration, etc. For the production of fiberboard used wood waste in the form of technological chips, lumpy waste and non-commercial wood. You can use only chips. The production of fibreboard is one of the most promising ways to use wood waste.

Fibreboard (Fibreboard) is widely used in the furniture industry, production of building materials and other industries, being a substitute for plywood. Fiberboard is a sheet material that is made from wood, ground to the degree of fiber. The fibers are formed into a carpet in a wet or dry way.

During wet forming, the fibers suspended in water are fed onto the mesh, the water goes down through the mesh, and a fibrous carpet remains on the mesh.

In dry forming, fibers suspended in air are fed onto the mesh. A vacuum is created under the mesh, due to which the fibers, deposited on the mesh, form a dry carpet.

After the carpet has been formed, it is pressed in a hot press, and the pressing may be wet or dry. During wet pressing, water and steam residues escaping from the carpet require a net under the carpet to escape. After pressing, one layer of the plate is smooth, the other with mesh prints.

With dry pressing, there is little moisture in the carpet and no a large number of steam that manages to escape through the edges of the plate. With this method, the grid is not required, both sides of the plate are smooth. Thus, depending on the technology used, there may be methods for the production of fiberboard: wet, dry, semi-dry, wet-dry.

1. Varieties and brands of materials and products

According to GOST 4598-74, plates of the following grades are manufactured:

soft M-4 (density up to 150 kg/m3); M-12, M-20 (up to 350 kg/m3);

semi-solid PT-100 (400-800 kg/m3);

solid T-350, T-400 (>850 kg/m3);

superhard ST-500 (>950 kg/m3). According to TU 13-444-79, boards of the following grades are produced by dry method: semi-solid PTS-220 (density > 600 kg/m3);

solid Ts-300, Ts-350 (> 800 kg/m3), Ts-400 (> 850 kg/m3); Тс-450 (> 900 kg/m3); STs-500 (> 950 kg/m3).

In all indicated brands of plates, the numbers after the dash characterize the ultimate strength of the plate in static bending (kgf / cm2). Plate dimensions: thickness 2.5-25 mm, length up to 5.5 m, width up to 1.83 m.

Fibreboard (Fibreboard) wet process:

Fiberboard: GOST 4598-86, TU 5536-024-06279163-94

DVP T gr. Ah, gr. B

Format, mm: 2745*1700, 2745*1220

Thickness, mm: 3.2; 2.5

Emission class: E1

Producer: Kotlas Pulp and Paper Mill, Sukhon Pulp and Paper Mill, Nelidovsky DOK, Arkhangelsk Pulp and Paper Mill.

Advantages: excellent sheathing material for cladding frame partitions, walls, ceilings, floors residential buildings, for the manufacture of doors, parts of built-in wardrobes, the production of furniture, laminated parquet, the production of containers.

Fibreboard (Fibreboard) dry continuous production method:

Fiberboard: TU 5536-001-49602733-2001, TSN-30, TSN-40

Format, mm: 2440*1220, 2620*1220, 2440*1830, 2440*2050

Thickness, mm: 3.2 -6.0

Emission class: E1

Producer: KDP Novaya Vyatka, Sheksninsky KDP, Kronospan, Plitspichprom, CJSC Yug.

Advantages: used for cladding interior walls, making bases for parquet, linoleum, carpet.

Wood fiber boards are used in the manufacture of furniture, door panels, office partitions, exhibition stands.

Fibreboard (Fibreboard) dry process production:

MDF (Medium Density Fiberboard): TU 5536-007-44779728-03DVP (SP) - medium density (MDF)

Format, mm: 1830, 2050, 2100, 2250, 2750, 2800, 2850, 3050, 3500*1650

Thickness, mm: 6.0-24.0

Emission class: E1

Producer: Zheshart Plywood Mill, Sheksninsky KDP, Kronospan, Plitspichprom, JSC "Lesplitinvest"

Advantages: all-pressed MDF boards are used for the manufacture of decorative furniture facades, the production of wall panels, profiles, countertops, skirting boards, doors and moldings.

2. Characteristics of raw materials

Chips must meet the following basic requirements: length - 25 (10-35) mm, thickness - up to 5 mm, clean cuts without wrinkled edges, clogging with bark - up to 15%, rot - up to 5%, mineral impurities - up to 1%, relative moisture content of chips - not less than 29%. In the production of fiberboard, the use of hardwood and conifer tree.

Synthetic resins used for the preparation of waterproofing and anti-corrosion materials and compositions in construction conditions epoxy resins should be viscous liquid. In the production of fiberboard, hydrophobic (water-repellent) substances and reinforcing additives are used. Fiberboard, MDF as a wood-based sheet material have a porous structure and absorb moisture from the air or when immersed in water. Therefore, in their manufacture, hydrophobic substances are used, which make it possible to maintain dimensional stability during changes in humidity. These viscous substances (refined products), melting, close the pores on the surface of the material and prevent moisture from penetrating inside. Hydrophobic substances include paraffin, distillate slack, ceresin and its compositions, which are introduced into the wood fiber mass in the form of alkaline emulsions diluted hot water, and deposited on the fibers with aqueous solutions of sulfuric acid or aluminum sulfate.

Strengthening additives are used to ensure the strength characteristics of fiberboard when the board contains more than 30% hardwood fibers or the presence of shortened fibers in the composition. As additives, phenol-formaldehyde resin is used.

3. Description of technological processes of production

Production of fiberboard by wet method. The technology for the production of fiberboard by this method consists of the following operations: washing the wood chips; chip grinding; sizing; carpet tide; plate pressing; impregnation of boards with oil; thermal moisture treatment; plate cutting. Chips are washed to remove solid inclusions from it - sand, dirt, metal particles, which, when grinding chips into fibers, cause accelerated wear of the grinding mechanisms. The chips are washed in baths using drums with paddles, which mix the chips with water and wash them. Chips are taken from the bath by a screw conveyor, water and impurities are sucked off from the bottom of the bath and sent to settling tanks, from where the purified water enters the bath again.

Process chip grinding- the most responsible operation in the production of fiberboard. The quality of the plates depends on the quality and degree of grinding. Since binders are not used in the production of fiberboard, the strength of the boards is provided by their interfiber bonds, which should be similar to the types of bonds between the fibers of natural wood. In the process of grinding wood into fibers, a wood-fiber mass is obtained - pulp. Pulp is a suspension of fiber in water of various concentrations. The grinding of chips into fibers is carried out in two stages. After the primary grinding, the mass concentration is 33%, before the secondary grinding, the mass is diluted with water to a concentration of 3-12%, at low tide 0.9-1.8%. The average fiber thickness is 0.04 mm, length is 1.5-2 mm. At the first stage, the grinding of chips is carried out at mills - defibrators UGR-03, UGR-02. The chips first enter the steaming chamber of the defibrator, where they heat up and become more plastic, then they are fed into the grinding chamber by a screw conveyor. The grinding chamber consists of two discs - one fixed and one rotating. The distance between the discs is 0.1 mm or more. Grinding sectors with teeth are fixed on the disks, the size of which decreases in the direction from the center.

The chips are first captured by large teeth, abraded, and as they move to the edge of the disk, they are ground into small fibers.

The ground mass is fed into the outlet, where, after passing through a system of two valves that maintain a certain steam pressure in the mill, it is thrown into the collection. The performance of the defibrator UGR-03 is 25-35 tons, UGR-02 50 tons of dry fiber per day. Mixing of the mass is carried out in mills - refiners.The design of refiners is similar to that of defibrators. The distance between the discs is 0.05-0.15 mm. After the defibrator and refiner, the fiber mass is stored in collectors and tanks equipped with agitators that maintain a uniform mass concentration, preventing the fiber from settling to the bottom.

Sizing- this is the introduction of various additives into the mass: hydrophobic to increase water resistance, fire retardant, bio-resistant and gluing. Paraffin is introduced as a hydrophobic additive, which, in addition, prevents the fibers from sticking to the nets and slabs during carpet pressing and gives the slab a shine. For mixing with water, paraffin is emulsified (an emulsion is made), which is well mixed in water. To increase the strength of the plates, glue or oil is introduced into the mass and in the form of an emulsion. To precipitate fatty emulsions (paraffin, oils) from water onto fiber, precipitants are used - additives that promote precipitation. Sizing compositions are introduced before casting the mass. The ebb of the carpet is done at a concentration of wood fiber mass of 0.9-1.8% on casting machines. This operation consists of applying mass to the forming net of the machine, filtering the water through the net, suctioning the water with a vacuum, mechanically squeezing the water, trimming the side edges and cutting the endless carpet into sheets of a certain length. The overflow box pours the mass evenly onto the continuously moving mesh. The mesh is supported by rollers through which water flows freely. On the path of the carpet movement, a device for compacting (ramming) the mass and a filling box for pouring ennobling compositions onto the mass are installed. Next, the carpet comes to three rotabelt vacuum mechanisms that suck water out of it. A leveling roller is installed in front of the second rotabelt, which rolls and evens out the thickness of the carpet.

Further pressing of water and pressing of the carpet are carried out by three rollers of the press. This is followed by three pairs of press rollers that squeeze out the water and compress the pile driver with a force of 1500 N/m. The saws cut the longitudinal edges, the saw cuts the web from the endless belt, and the conveyor 12 carries away the raw web, the moisture content of which is about 60-80%.

Plate pressing- an operation in which the raw web, under the influence of temperature and pressure, is terminated into a solid fibreboard. Pressing is carried out in a 25-storey press PR-10. Loading and unloading are carried out by loading and unloading whatnots. The pressing cycle consists of three phases: I phase - water extraction; II phase - drying; III phase - hardening. The temperature of the press plates is 180-200 °C.

I phase- the pressure is gradually increased to 2-4 MPa, maintained at this pressure for 30 s; the humidity of the boards drops to 45%.

II phase- the pressure is reduced to 0.8-1 MPa and the plates are maintained at this pressure until their humidity drops to 8% (usually 3.5-7 minutes).

III phase- the pressure is increased to the previous value or to a slightly lower value. At this pressure, the plates are maintained until the humidity decreases to 0.5-1.5%. Thus, hardening of the plate takes place, i.e. raising her mechanical properties. The duration of the last phase is 2-3 minutes. The boards are impregnated with oil to increase their strength and moisture resistance. Slabs are impregnated in baths with linseed or tall oil heated to 120°C. The plates are impregnated hot from the press. The consumption of oils is 8-10% of the weight of the boards. Impregnation is subjected only to special-purpose plates.

Thermal moisture treatmentplates consists of two operations - heating and humidification. The plates are heated to 160-170°C and kept at this temperature for 3.5 hours. Heat treatment increases the physical and mechanical properties of the plates and reduces their hygroscopicity. It is performed in chambers in which hot air is circulated at a speed of 5-6 m/min. The heat treatment of the oil-impregnated boards is carried out at an initial temperature of 120° C., which is then increased by the exothermic reaction of the oil.

Humidify the plates to give them moisture corresponding to the equilibrium moisture content. If the plate is not specially moistened, then, by adsorbing vapors from the surrounding air, it can be moistened unevenly, which will lead to warping. Humidification chambers are used to moisten the plates.

Plates on trolleys are installed in the chambers so that each sheet has free access to the wetting agent. The chamber is supplied with air at a temperature of 65°C and a humidity of 95-98%. Fans circulate air in the chamber. The duration of exposure in the chamber is 6-8 hours. Cutting is done to obtain plates of a given format. For cutting slabs, special format circular saws are used. Fibreboard contains 91% fibers, 7% moisture, 2% sizing additives. Rehearsal

Production of fiberboard by dry method.The main operations of fiberboard production are as follows: chip washing; wood chips steaming; grinding chips into fibers; mixing fiber with a binder and other additives (sizing); fiber drying; carpet formation; prepressing of canvases; pressing; moisturizing; cutting. Many operations of the technological process for the production of fiberboard by the dry method are similar to the operations of the production of fiberboard by the wet method, therefore, we will only consider distinctive features operations of the dry method for the production of fibreboard.

Parboilingwood chips are used for partial hydrolysis of wood. With the dry method, the water-soluble products that make up the wood remain in the fiber and participate in technological process. The chips are steamed in steamers-cylinders at a steam pressure of up to 1.2 MPa (190°C). Chips from one end of the cylinder move gradually to the output end with the help of a screw shaft rotating at a speed of 3-10 rpm. To maintain a given pressure in the apparatus, the inlet and outlet of the chips is carried out through lockable gates. Chip processing time 6 min.

Chip grindingproduce dry on defibrators, re-grinding - on refiners. In the dry method for the production of fibreboard, thermosetting resins are introduced into the fiber to increase the adhesion between the fibers. Paraffin is introduced in molten form.

Carpet pressingis performed to increase its transportability and the possibility of loading the carpet into the gaps of the press, since the poured carpet to obtain a plate with a thickness of 6 mm has a thickness of 200 mm. Pre-pressing is carried out on continuous belt presses, where the carpet is compacted 3-5 times between two belts, compressed by rollers at a pressure of 1800 N/cm 2. After pressing, the carpet is cut lengthwise and cut across into sheets. In the production of thick fiberboard (> 6 mm), the thickness of the web after pre-pressing on belt presses remains more than the permissible value (> 120 mm), which makes it difficult to load it into the gaps of a multi-storey press. Such webs are additionally pre-pressed in a one-story slab pre-press of periodic action at a specific pressure of 2.5 MPa. Pressing is carried out in the same presses as for the wet method of fiberboard production. The pressing time is reduced to 1 min per 1 mm of finished board thickness. Plate temperature 220-250°C, pressure 6.5-7 MPa. Fiberboard produced by dry process contains 89% fiber, 6% moisture, 2.5% resin, 2.5% paraffin. On the basis of dry fiber, it is possible to press not only plates, but also various parts and assemblies in the production of containers, furniture, and building materials.

Features of the production of fiberboard by wet-dry and semi-dry methods.With the wet-dry method for the production of fiberboard, the preparation of the fiber, its transportation, and the casting of the carpet are performed, as in the wet method for the production of fiberboard. However, binder components are not added to the mass, and good adhesion of the fibers is ensured by careful grinding of chips into fibers due to its preliminary thermochemical treatment. Before pressing, the fabrics are dried almost to a completely dry state (2-3%) in a multi-storey dryer. Plates are pressed without mesh, both sides are smooth. The temperature of the press plates is 240°C, the pressure is 6 MPa. After pressing, the plates are moistened to 6-9%. With a semi-dry method for the production of fiberboard, the raw material - wood fiber mass, to which a binder is added, is dried to a moisture content of 10 - 15%. A carpet is formed from dry fiber, compacted, cut into sheets. Cloths before pressing are moistened up to 18-25% and pressed in a multi-storey press on a pallet with a grid. Then comes the heat treatment.

The cost of fiberboard made by the dry method is about 10% less than that of fiberboard made by the wet method. However, the dry method of fiberboard production requires a large amount of adhesive materials(22-70 kg per 1 ton of plates); 10 times more air consumption (22.1 m3 instead of 2 m3). Positive is the fact of less (4.5 times) the need for water and less (almost 2 times) labor costs. It should be noted that the dry method of fiberboard production at the fiber drying site is especially dangerous in terms of fire.

fibreboard raw material technological

4. Characteristics of the main equipment

Chopping machine selection

The raw material is supplied to production in the form of conditioned wood chips. Preparation of raw materials for the production of boards, which consists in the preparation of conditioned chips, includes the following operations: cutting wood into sizes corresponding to the receiving cartridge of the chipper; cutting wood into chips; sorting chips to select the required size with regrinding of a large fraction and removal of fines; extraction of metal objects from wood chips; washing the chips to clean them from dirt and foreign matter.

For the preparation of wood chips, we use the DRB-2 drum chipper. The productivity of the device is 4 - 5 m 3/h, drum diameter 1160 mm and number of cutting knives - 4

Sorting machine selection

The resulting wood chips after chippers are sorted, as a result of which technological chips are selected that meet the requirements for it.

For sorting technological chips, we use a sorting machine of the gyratory type, model SSh-1M, the technical characteristics of which are given in Table. one.

Table 1

Technical specifications sorting machine

IndicatorsValueProductivity, bulk m 3/h60 Number of sieves 3 Inclination of sieves, deg 3 Electric motor power, kW3 Weight, t1.3

Selection of disintegrator

Hammer disintegrators are used to grind large chips. We choose a disintegrator of the DZN-1 type, the technical characteristics of which are given in Table. 2.

table 2

Technical characteristics of the disintegrator DZN-1

IndicatorsValueProductivity, bulk m3/h18Overall dimensions, mmlength2300width1620height825Weight, kg2248Electric motor power, kW11.4

Selection of consumable bins for conditioned wood chips

Conditional wood chips are sent to stock bins or service bins in the grinding department. There are two types of storage bins in terms of configuration: rectangular and round. We use rectangular bunkers, placing them in the building of the woodchip preparation department. With small stocks, wood chips can be stored in vertical bins. We use a DBO-60 type bunker, the technical characteristics of which are given in Table. 3.

Table 3

Technical characteristics of the vertical bunker DBO-60

IndicatorsValues ​​Hopper capacity, m360Number of unloading screw conveyors3Productivity of one screw conveyor, m3/h3.8-40Installed engine power, kW21.9Height of supports, m4Total height of the bunker, m11.75Total weight of the bunker, t18.5

Selection of a steaming plant

From the feeder bunker, chips are fed by a screw feeder into a drum feeder low pressure, from which it is sent to the heater, where it is heated by saturated steam at a temperature of 160°C. A nozzle is mounted in the outlet section of the heater, through which paraffin is introduced into it in a molten state, sprayed with compressed air at a pressure of 0.4 MPa. From the preheater, the chips impregnated with paraffin enter directly into the hydrodynamic treatment apparatus. Fibreboard factories use continuous machines of various systems.

We install the Bauer-418 steaming and grinding system, which has the following characteristics:

Steaming boiler horizontal, tubular type, diameter 763 mm

9.15 m long, designed for pressure up to 1 MPa

.The productivity of the steam plant is up to 5 t/h.

Selection of grinding equipment

In the production of fibreboard, defibrators and refiners are used to grind chips. To obtain high-quality boards, when grinding chips on defibrators, equipment for secondary grinding (refiners) is used. In the dry process, refiners with two counter-rotating discs are used for primary grinding.

We choose a defibrator brand RT-70, with a capacity of up to 70 tons / day, and install two machines. The technical characteristics of the apparatus are given in Table. 4.

Table 4

Technical characteristics of the defibrator brand RT-70

IndicatorsValueProductivity for dry fiber, t/day70Diameter of grinding discs, mm1000Feeder type screwPower of grinding disc drive electric motor, kW500-580Total weight without electric motors, t20

Selection of mixers for water-repellent additives

Water-repellent additives at most operating enterprises are introduced through special nozzles into steamers before grinding chips into fibers.

Paraffin is delivered to the enterprise in a railway tank, which is installed near the warehouse finished products. From the tank, paraffin flows down the pipeline into a storage tank with a capacity of 60 m 3, from where it is fed to a supply tank of paraffin, installed in the shop on a pedestal, from a special paraffin pipeline. Paraffin is drained by gravity through a measuring tank into a tank for preparing a paraffin emulsion.

For the preparation of sizing compositions are used various types equipment. The most common emulsifiers are cylindrical tanks equipped with agitators.

The finished emulsion is pumped into a special container (tank) for storage. The preparation of the working composition of the phenol-formaldehyde resin SFZh-3014 consists in its dilution at a working concentration of 25%. The dissolution of precipitants is carried out in a special tank, which is similar in design to the emulsion preparation tank.

The technical characteristics of the mixing tank are given in Table. 5.

Table 5

Technical characteristics of the mixer

IndicatorsValueCapacity, m31Outer diameter, mm1206Height, mm909Overall height, mm1834Agitator diameter, mm150Electric motor power, kW1.1Total weight, kg267

Selection of dryers

The moisture content of the wood fiber before pressing the boards according to the dry method of production should be 6-8%. The choice of method for drying shredded wood is largely determined by the size and uniformity of the material. Fibreboard factories use two-stage dryers with partial recirculation of the drying agent.

The fiber after grinding is fed into the pipeline of the drying plant, where it is mixed with the air heated in the heater, the temperature of which at the entrance to the dryer is 160-190°C. The fiber temperature at the outlet of the first stage dryer is about 70°C. After the first stage, the moisture content of the pulp is reduced to approximately 65-67%. It is most effective to use the work of combined dryers: airfountain - drum.

Selection of the first stage dryer

For the first stage of drying, it is advisable to use an aerofountain dryer. In an airfountain dryer, due to the speed of the drying agent, the fiber gushes many times, then it is taken out of the drying space after it has dried to the required (specified) humidity. The drying agent is hot air, which is heated in a lamellar steam heater to 160°C.

Air and fiber are moved by a centrifugal fan. The same fan also transports the fiber sorted in the separator to the cyclone - air separator.

Technical characteristics of the dryer are given in table. 6.

Table 6

Technical characteristics of airfountain dryer

ParameterValueCapacity (in terms of evaporated moisture), kg/h1000Air temperature after the heater, °C up to 160Air temperature at the outlet of the dryer, °Cup to 70 outer pipe, m/s3 - 4Diameter inner pipe, mm400Height of the dryer, m15.2Width, m7.4Total length of pipes, m46

Selection of a drying plant for the second stage of drying

The second stage of drying takes place in drum dryers. The second stage dryer uses the principle of low temperature with a large volume of drying agent. In table. 9 shows the technical data of drum dryers.

Table 7

Specifications of drum dryer

IndicatorsValueProductivity (in terms of evaporated moisture), kg/h2886Air temperature at the inlet to the dryer, °C180 - 205Air temperature at the outlet of the dryer, °C50Pressure drop in the dryer, Pa2820Fan performance, m3/h61200Diameter of the transmission valve, m0.95Air velocity, m/s19Air volume passing through the dryer, reduced to a standard temperature of 21°С, m3/h52500 Electric motor power, kW75

Selection auxiliary equipment at the drying stage

In aerofountain dryers, air and fiber move with the help of a centrifugal fan with a capacity of 21,000 m 3/h at a pressure of 22 MPa. The amount and speed of air are regulated by a rotary device on its inlet. With the same fan, the dried and sorted fiber in the separator is transported to the cyclone - air separator.

Choosing a centrifugal fan high pressure in accordance with GOST 5976-90. Technical characteristics of the fan are given in table. eight.

Table 8

Technical characteristics of centrifugal fan

Grade Q, m3/sρgH, Pan, s-1ŋn

Cyclones are selected according to performance. The gas speed in the inlet pipe can be 12, 15 and 18 m/s, respectively, the cyclone performance can change. So for w in = 18 m/s cyclone capacity will be 6000 m 3/h, and for w in = 12 m/s - 4000 m 3/h, i.e. cyclone performance at any input speed compared to w 18can be calculated using the formula:

i =w ini /w 18 m 3/h (15)

In an airfountain dryer, air (drying agent) moves at a speed of 18 -20 m/s. Thus, the productivity of the cyclone will be 6000 m 3/h We choose a cyclone OST 26-14-1385-76 with the following technical characteristics presented in Table. nine

Technical characteristics of the cyclone

Cyclone sizeCross-sectional area of ​​the cylindrical part of the body, m2Productivity, m3/h Working volume of the bunker, m3Weight, kgTsN-15-800P0.50263250.56825

The air entering the dryer is preheated to the required temperature when it passes through the steam heaters. Single-pass steel lamellar heaters are used.

5. Production process control and product control

Requirements for the surface quality of fiberboard

Control methods

The selection and preparation of samples, the determination of the physical and mechanical properties of the plates is carried out in accordance with GOST 19592 and in accordance with the requirements of this standard.

Dimensional control is carried out according to GOST 27680.

Determination of water absorption by the front surface

After conditioning and weighing the samples intended for determining water absorption according to GOST 19592, waterproofing of their edges and non-facial surface is carried out, as well as re-weighing of the samples before soaking.

Waterproofing is carried out by immersing samples in molten paraffin according to GOST 23683 at a temperature of (85±5)°C with edges and non-front side. When applying paraffin to the edges, the sample is immersed in turn with each edge to a line 3 mm from it.

Testing of plates - according to GOST 19592. The moisture content of plates moistened in humidifying machines is determined no earlier than 24 hours after they leave production. The color tonality and the degree of grinding of the wood of the front layer are evaluated visually when compared with standard samples with dimensions of 200-300 mm.

The deviation from the straightness of the edges is determined according to GOST 27680 or using a straightedge (according to GOST 8026) with a length of 1000 mm not lower than the second accuracy class and a set of probes No. 4 according to TU 2-034-225. Measurements are carried out at least in three places along the length of two adjacent edges with an error of not more than 0.1 mm.

The deviation from the squareness of the edges is determined in accordance with GOST 27680 or using calibration squares in accordance with GOST 3749 not lower than the second accuracy class with a length of one side of 1000 mm and a set of probes No. 4 according to TU 2-034-225. The measurement is carried out at each corner of the plate with an error of not more than 0.1 mm.

The tensile strength perpendicular to the plate plate is determined according to GOST 26988.

The spot area on the surface of the board is determined to the nearest 0.25 cm2 using a 5 mm square grid applied on a transparent sheet. Deviations from the accuracy of drawing grid lines - no more than 0.5 mm. When calculating the number of cells covered by a spot, cells with an overlap of more than half of their area are considered as integers, and those with an overlap of less than half are not taken into account.

The depth of the dents and the height of the bulges are determined using a dial gauge of the ICH-10 brand according to GOST 577, fixed in a metal U-shaped bracket with cylindrical supporting surfaces with a radius of (5 ± 1) mm and a span between the supports of 60-100 mm.

The indicator scale is set to the zero position when the bracket is installed on a calibration ruler in accordance with GOST 8026 or a calibration plate in accordance with GOST 10905.

The stroke of the indicator rod in both directions from the reference plane must be at least 2 mm. The linear dimensions of defects are determined using a metal ruler according to GOST 427.

Quantity chemical substances emitted from the finished slabs, as well as the frequency of control are determined by the authorities sanitary supervision in accordance with the current guidelines approved by the Ministry of Health of the USSR.

Table 10

Permissible defects in the finished material

Name of the defect Norm for plates of grade I, grade II Recesses (protrusions) on the front surface Not allowed Not allowed with a depth (height) exceeding the maximum thickness deviations Recesses (protrusions) on a non-front surface Not allowed more than 1 pc. with an area of ​​25 cm2 per 1 m2 with a depth (height) exceeding the maximum deviations in thickness Not standardized Scratches on the front surface Not allowed per 1 m2 with a total length of more than 100 mm in an amount of more than 2 pcs. surfaces Not allowed per 1 m2 with a total area of ​​more than 5 cm2 from oil and paraffin on the front surface Not allowed more than one spot per 1 m2 with a diameter of more than 8 mm Not allowed per 1 m2 with a total area of ​​​​more than 10 cm2. are not taken into account) Not allowed per 1 m of length with a width of more than 5 mm

Conclusion

Fibreboard (Fibreboard) is a promising material. It is widely used in the manufacture of furniture and in finishing work in the form of a laminate. Fiberboard is currently widely used, and I think the demand will only grow. This is also due to its low price relative to other similar materials.

Its perspective is also explained by the fact that wood is currently very widely used. In the production of certain building materials from wood, residues remain that can also be used in the production of fiberboard. And in the future, fiberboard will be widely used in construction, since it is also an environmentally friendly material. Currently, the issue of ecology in construction and decoration is acute, and fiberboard is produced without the addition of harmful chemicals.

Bibliographic list

1. Gorchakov G.I. Bazhenov Yu.M. Construction Materials: Textbook for universities. - M: Stroyizdat, 1986.