The reader knows that boards from crushed wood of various types are currently produced, the most important of which are particle boards and fibreboards. Fiberboards are produced in several types: hard and super-hard wet, hard dry, soft. They have common operations, but there are also fundamental differences in technology, which the author will note.

As a rule, the raw material for fiberboards is wood chips, which can be produced directly in the workshop or brought from outside. Before entering production, the chips are washed to remove mineral impurities (sand, stones, clay), and magnetic separation is also performed to extract metal from it. The chips are stored in bunkers, from where they are fed into machines for grinding into fiber. Machines are known and used for the first, coarse grinding stage, the so-called defibrators, and for the second stage, where finer grinding is carried out, refiners.

If finer grinding is required, the fibrous mass directly from the defibrator or from the pool enters the refiner, which, unlike the defibrator, does not have a heating chamber. Its grinding part is approximately the same as that of a defibrator. Often, when grinding, additives are added to the fiber: paraffin to increase the water resistance of the boards, synthetic resins to obtain the required strength. The introduction of resin is practiced in the production of fiberboards using the dry method. Here you need to pay attention to the fact that the processes for producing slabs using dry and wet methods diverge.

With the wet method, low concentration fibrous mass enters the pool, where a stock of mass is created and it is sized with water-repellent substances. From the pool the mass is supplied to cast the carpet. This is the most important operation. The main function of the low tide operation is to form a carpet of uniform density. To perform this, it is necessary to supply a uniform concentration of fibrous mass to the ebb (this is done using special regulators). The amount of supplied mass per unit time must be constant. There are special pressure tanks for this purpose. In modern production of fiberboards, most enterprises use continuous casting machines (Fig. 32).

Rice. 32. Scheme of the casting machine:
I - overhead box; II - register part; III - suction part; IV - press part; V - carpet trimming; 1 - grids; 2 - saw; 3 - guide rollers; 4 - drive drums; 5 - wood fiber carpet

The final formation of the slab occurs during pressing. The press is a complex, bulky and expensive machine. In the production of fibreboards, multi-storey batch presses are usually used. The stoves are heated with hot water (temperatures up to 230°C) prepared in a battery. Its height is up to 10 m and its diameter is up to 2.5 m. Modern presses with a force of 70000-75000 kN have up to 10 plungers with a diameter of 700-800 mm each. The presses have 20-30 working spaces into which pallets with wet carpets are pushed (Fig. 33). Pressing occurs at a pressure of 3-5 MPa and a temperature of 210-230° C. The duration of the pressing cycle is 8-11 minutes (depending on the thickness of the slab, the humidity of the carpet, the presence of resin in the carpet, etc.).

Due to the fact that the productivity of the press determines the productivity of the plant, and its cost reaches 20% of the cost of all equipment, developments were carried out to sharply reduce the duration of pressing and thereby increase the productivity of the press. This is how the dry method of producing fiberboards appeared. It differs in many ways from the wet method. With the dry method, the fiber after grinding is not diluted with water, but rather, it is dried and laid dry on a mesh. It is not water that is sucked out, but air, which makes the carpet compact. Then it is pressed, trimmed, and cut into separate formats that go into the press. To improve the quality of the boards, a resin (usually phenolic) is introduced into the fiber, as well as waterproof and other additives. It is advantageous to do this here because the resin and additives are not washed out with water, and this is one of the advantages of the dry method. Due to the fact that the fiber is dry, the duration of pressing is reduced by 2-3 times, and accordingly the productivity of the plant as a whole increases. The maximum productivity of factories operating using the wet method reaches 15 million m 2 of slabs per year, and for the dry method - 25 and even 30 million m 2 per year. With the dry method, you can make slabs even 12-15 mm thick, and also change the density of the slabs. With the wet method, the density of solid slabs is 1000-1100 kg/m 3, with the dry method 900-1100 kg/m 3 and less than the specified value, and if necessary, more.

Rice. 33. General view of a hydraulic press with near-press mechanization:
1 - press; 2 - loader; 3 - unloader; 4 - conveyor for returning transport sheets with grids; S - conveyor for finished slabs; 6 - saw for cutting carpet

The reader will obviously be interested to know that the dry method can be used to make fiberboards up to 20-30 mm thick with medium density (700-800 kg/m3). This is a major achievement in woodworking technology: such fiber boards have a very good surface, high strength, are easy to process and therefore can be used to make high-quality furniture.

The dry method has two major disadvantages that limit its spread: increased dustiness of the environment and high fire hazard. To capture the dust generated during the production of boards, it is necessary to build expensive installations that are more complex and expensive than wastewater treatment facilities in the production of wet boards. To prevent the fiber from igniting, special complex automatic devices are required.

So, after pressing (both methods - wet and dry), solid slabs are obtained, which are cut on four sides. At the same time, it is easy to find out how the plate was made. With the dry method, both sides of the slab are smooth; with the wet method, a mesh imprint remains on one side of the slab. This is understandable, since when pressing a dry carpet there is no need for a mesh through which the water is squeezed out when pressing a wet carpet.

After cutting, solid fiberboards undergo a hardening operation. Its purpose is to complete the processes of thermochemical transformations of wood fiber components started in the press. Hardening increases the strength of the slabs and reduces water absorption. The hardening temperature is 160-170° C. The speed of the air washing the plates is 4-5 m/s, the hardening duration is up to 4 hours. Hardening is carried out in special chambers.

The slabs leave the hardening chamber with almost zero humidity. They actively absorb moisture from the air. When laid in a bag, the edges of the slabs absorb much more moisture than the middle, which leads to their warping. Therefore, a special operation is carried out to moisten the slabs in continuous or drum-type chambers. The slabs are kept in the chambers for 6-7 hours at 65°C and air humidity of 95%.

In conclusion, a few numbers. In the USSR there are factories for the production of wood fiber boards using the wet method, mainly with a capacity of 10 and 15 million m 2 boards per year, or 30 and 50 thousand tons per year. For 1 ton of slabs (approximately 300-350 m2), up to 3 m3 of wood and up to 20 tons of water are consumed. One plant employs up to 500 people of different professions. The complexity of the equipment dictates the need for highly qualified workers. There are workers servicing chipping machines, grinding equipment, casting machines, presses, hardening chambers, as well as workers for technical supervision of equipment and its repair.

Fibreboard production is carried out using wet and dry methods.
Fiberboard production using the wet method includes such operations as grinding wood chips, sizing the resulting fibrous mass, forming a carpet, pressing, impregnating slabs with oils, thermal-moisture treatment and cutting slabs.

The washed 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 in refiners, which make it possible to obtain thinner fibers with a thickness of 0.04 mm and a length of 1.5...2 mm. From such fibers an aqueous solution of wood fiber mass is prepared - pulp, which is stored in collection tanks or pools, stirring periodically to maintain a certain concentration of the mass, preventing the fiber from settling to the bottom.

The resulting wood fiber mass is then sent to a continuous sizing box, in which it is mixed with phenol-formaldehyde resin. Hydrophobic additives prepared in an emulsifier, strengthening substances and precipitants are also supplied there with a mixing pump at a temperature of no more than 60 ° C and in a volume at which the concentration of the resulting suspension for any ratio of the rock composition of the raw material fibers before casting is 0.9...1, 8%. The dosage of these components depends on the type of slabs, the composition of the fibers, the consumption of liquid, pressing modes, etc.

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

For hot pressing of fiberboard, multi-story (20 floors) hydraulic presses are used. Loading and unloading of slabs is carried out using shelves. 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 spinning. In 30 seconds, under the influence of a pressure of 4.2...5.5 MPa, water is removed from the fibrous carpet. In this case, the humidity is reduced to 45%, and the slab itself, as it warms up, becomes compacted.

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

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

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

In addition to hot pressing, soft fiberboard is 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 by 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 humidity of 2...3%.

To improve and stabilize the strength and hydrophobic properties of the slabs, they are subjected to heat treatment in batch chambers. The coolant in them is superheated water with a temperature of 190...210°C and a pressure of 1.8...2.2 MPa. Air movement speed is at least 5 m/s. The heat treatment time, taking into account the thickness of the plates, is 3...6 hours.

To give the slabs 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 kept for at least 24 hours.

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

Dry fiberboard production much the same wet fiberboard production . But using the dry method it is possible to produce double-sided smooth slabs with a thickness of 5...12 mm and slabs 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 fibers for outer and inner layers and mixing them with additives and resin are included

The formation of a carpet is carried out from dried fibers by felting them and compacting them with a vacuum, and then pressing them with belt-roll and format presses. Hot pressing lasts 5...7 minutes and is carried out at a temperature of 200...230 °C with a single increase in pressure to 6.5 MPa for 15...25 s and a stepwise release of it first to 0.8...1 .0 MPa, and then to zero. Profiled fibreboards are secured to the press plates with special matrices.

Currently, MDF, which is more homogeneous in structure, which is much easier to cut and process, successfully competes with chipboard.

All slabs, regardless of the process of their production, after 24 hours of exposure are cut to size on circular saw format-edging machines according to their standard sizes.

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Fibreboard is produced using a dry continuous method on a Bison line.

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

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

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

Testing of slabs is carried out according to TU BY 600012401.003-2005.

Raw materials and supplies must meet the requirements of the relevant standards (Table 1.1).

Table 1.13 – GOSTs or specifications for raw materials and materials

Name of raw materials and supplies	GOST or TU
Technological chips	GOST 15815-83
Technological chips from thin trees or branches
Urea-formaldehyde resins 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
Wood technological raw materials	TU RB 100195503.014-2003

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

50% - aspen, poplar, alder

20-30% - coniferous wood

20-30% - birch

The recommended ratio between types of wood raw materials is as follows: process wood chips – at least 70%;

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

It is allowed to use sawdust from sawmilling and woodworking - no more than 10.

2)Technological process

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

Reception and storage of raw materials and supplies

Preparation of technological chips

Grinding process chips into fiber

Preparation: introduction of binder and hardener.

Wood fiber drying

Formation of wood fiber carpet

Pressing of fibreboards

Cutting slabs into formats, laying and packaging slabs

2.1) Acceptance of raw materials and materials.

The raw materials for the production of fibreboards are purchased technological chips, technological chips from thin trees and branches from the timber industry, chips from lump waste from woodworking and sawmilling, firewood, technological chips made from firewood.

Raw materials arrive by road and are unloaded into an open storage warehouse.

From each batch of incoming chips, samples are taken in accordance with GOST 15815-83 for analysis to determine the content of coniferous and deciduous species, 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 conversion of the mass of crushed raw materials into volume at a known humidity is carried out according to the formula:

where V is the volume of chips, cubic meters; m - mass of chips, t; - chip density at actual humidity, kg/m3.

Urea-formaldehyde resin is delivered in railway tanks to the reception and unloading department of railway tanks. Resin is accounted for by the level of filling of containers with readings on calibrated scales with the volume converted into mass by multiplying the measured volume by the density of the resin. A sample is taken from each batch of incoming resin 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 arriving at the site by road is unloaded by a KB572 tower crane and stacked according to its species composition. The diameter of the raw material is set to 800mm, length from 1 to 6m with gradation every 1m. Defects in raw materials are not allowed:

External rotten rot;

Charring;

Kernel rot;

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

2.2) Preparation and sorting of process chips

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

Firewood is transported from the stack using a KB572 tower crane to the trestle. From the overpass, the raw materials are rolled individually onto the log transporter. Using a chain conveyor of a log transporter, the raw material is fed into a disk chipper MPP8-50GN, where it is processed into process chips.

Technical characteristics of the MRR8-50GN disc chipper:

Volumetric productivity, cubic meters/hour 50

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

600-800mm, cubic meters/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 and group it into bundles. The size of the pack should not exceed the size of the cartridge loading window

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

5. Chuck diameter, mm 850 2.7

6. Cutter disc:

Diameter, mm 2900

Number of cutters, pcs. 25

Angle of inclination of the disk to the horizon, degrees. 37

Rotation speed, rpm 152

7. Disk drive – electric motor:

Type AO3-400M-10V2

Power, kW 160

Rotation speed, rpm 590

8. Feed drive

Power, kW 2.2

Rotation speed, rpm 750

Quantity, pcs 2

Figure 6 – Technological scheme for storing and sorting wood chips

Figure 7 – Scheme for cleaning wood chips using a hydro washer

9. Overall dimensions, mm:

Length, mm 6805

Width, mm 5090

Height, mm 3265

The woodchip storage area (Figure 6) consists of two sections: the hardwood chips storage area and the softwood chips storage area. Technological chips arriving by road are transported to a concrete storage area for coniferous (12) and hardwood (14) chips. The formation of piles in the wood chip warehouse is carried out using a bulldozer. A bulldozer delivers wood chips from a concrete area to the softwood chips dosing station (4) and to the hardwood chips dosing station (13). From the pine chips dosing station (4), process chips are fed by scraper conveyors (7) to sorting SShch-120 (11). From the hardwood chips dosing station (13) the chips are fed by scraper conveyors to the “REWiBRALL” type sorting station (10) with a capacity of 700 kg/hour of absolute dry chips. The sorters have two sieves and a tray and separate the wood chips into three fractions. The top sieve has holes measuring 50x50 mm and 40x40 mm, the bottom 8x8 mm. 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 chip sizes are 15-35mm, thickness 4-6mm. The conditioned wood chips are conveyed to the hydro washer by a conveyor. The scheme for cleaning wood chips using a hydro washer is shown in Fig. 7.

Through the transport device, the wood chips enter the heavy particle separator (1) of the washing unit, where there is a paddle wheel (3) that mixes the wood chips under water. Thanks to the flow of water, picking up the chips from the bottom up, it is prevented that the chips will enter the intermediate container (4) located below and be removed through the sluice valve (7). Only mineral impurities with a high specific gravity can overcome the flow of water and fall into the intermediate container. With the same flow of water, the chips are introduced into the lower part of the dewatering auger (2), equipped with a flow with holes for draining water from the chips along the way of its transportation into the funnel (6). The tray openings are cleaned with water, which is supplied to the top of the tray. Water along with particles enters the intermediate container (5) and then returns to the circulation system.

The chips transported by the dewatering auger (2) enter the chip funnel hopper (6), from where they are sent 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 forces hot air into the bunker.

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

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

Heavy particles (mineral impurities) entering the heavy particle separator (1) are then directed through an intermediate container (4) into a sluice valve (7) open on the side of the container, in which they are deposited. After some time, the gateway on the side of the tank closes and the drain hole opens, through which heavy particles and water are supplied through pipelines to the multi-chamber stilling pool (8) of the storage tank (11), where the cleaning scraper conveyor (10) is located.

Suspended particles coming out along 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-mentioned sluice gate. The sluice gate (7) also supplies suspended particles to the multi-chamber stilling pool (8).

Once the sluice gates have been emptied in this way (the emptying cycles can be adjusted independently), the drain openings are closed and the sluice gates are automatically filled with water through the automatically operating shut-off valves. After this, the sluice gates are opened again from the tank side.

From the multi-chamber stilling basin (8), heavy particles (mineral impurities) contained in the wastewater are fed by a scraper conveyor into a screw conveyor. By means of a pump (12), clean water from the reserve pool (9) of the storage tank (11) is sent to wash the perforated tray of the dewatering auger (2). Some 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 sent along with the chips to the dewatering auger (2). Water losses in this circuit due to the operation of the locks are replenished with water from cross flushing.

2.3) Grinding process chips into fibers

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

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

The technological scheme for obtaining fiber on the PR-42 refiner of the Pallmann COMPANY is presented in Fig. 8. From the washing installation, the wood chips are poured into the refiner's funnel hopper (1). The trimmings from the FOS are fed into the same funnel hopper by pneumatic transport. From the hopper - funnel, chips and sawdust are fed into the steaming boiler (4) by a stuffing (loading) auger (2). From the steaming boiler, wood chips are fed by an unloading auger (5) into the grinding chamber (6) between stationary and rotating disks. The resulting fiber is released by steam pressure through the unloading valve into the mass pipeline (8) and then into the drying pipe.

The over-moistened fiber formed during the start-up of the refiner is fed through the cyclone (9) into the starting fiber hopper.

Technical characteristics of the PR-42 refiner

Capacity for absolutely dry fiber, kg/hour 5500

Steaming chamber volume, m3 2.5

Duration of steaming wood chips, min 3-6

Steam pressure, MPa 0.7-1.2

Operating temperature, C 190

Steam consumption, kg/hour 5000

Diameter of grinding discs, mm 1066.8

Disc rotation speed, mm - 1 1485

Engine speed, min-1 1485

Engine power, kW 1600

Type of engine coolant: water

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

The duration of woodchip steaming is determined using diagrams (Fig. 10-12). Set the productivity of the grinding installation (the number of revolutions of the unloading auger) according to Fig. 10, and then the duration of steaming depending on the bulk mass of the chips according to Fig. 11-12. So, for example, at a screw rotation speed of 32 min-1, the refiner’s productivity will be 5.0 t/h of absolutely dry fiber (with a bulk weight of chips of 150 kg/m3). According to Fig. 11, it is established that for such 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. As refiner productivity increases, the gap must be increased. The required hydraulic clamping pressure should be set depending on the species composition of the chips.

The gap between the discs is set using a microscrew. One full turn of the microscrew causes an axial displacement of the disk by 0.75 mm. When the microscrew rotates “to the right,” the disks move closer together and vice versa. The gap is measured using a measuring probe with the measurement result displayed on 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 a stationary one. Then the microscrew is rotated « left » until the required gap is set, the value of which is shown by a digital indicator.

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

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

After the first portions of fiber are discharged, 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 fiber of the required quality. Some time after the refiner starts operating, the load on the engine begins to drop, which indicates an increase in the clearance. In this case, the disks are brought closer to the initial reading of the load on the engine.

With a constant gap and an ever-increasing degree of wear on the disc segments, the energy consumed by the engine increases. To maintain the specified gap in this case, it is necessary to increase the hydraulic clamping pressure of the disks.

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

Figures 8-11

Figures 12 - 13

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

Urea-formaldehyde resin from the warehouse is pumped by pump (1) into a supply container 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 the 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 introduced into the mass pipeline.

Ammonium sulfate (ammonium chloride) in bags is supplied 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). The prepared solution is filled one by one with a circulation pump (8) through filters (7) into dosing containers (6). The dosing pump (10) supplies the hardener solution to the oil line. Lumps of wood fiber with resin are separated in a heavy material separator and removed from the stream. Standard wood fiber, without lumps, is fed by fan through cyclones to the conveyor belt of the forming machine.

Figure 14 - Process flow diagram for drying wood fiber mass

2.4) Drying wood fiber mass

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

The technological scheme for drying wood fiber mass is shown in Fig. 14.

Natural gas is supplied to the CK-100-G burner (1) of the furnace (2) for combustion. The hot gases generated during combustion are mixed with air and supplied by a smoke exhauster (3) to the dryer pipe (5). At the same time, air (6) containing formaldehyde collected from the press hood is supplied to the furnace for combustion. The wood fiber mass from the refiner is introduced into the dryer pipe through a mass pipeline (7). 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 fiber transportation. In the flow of hot gases in the drying 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 discharged through a sluice valve (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 reverse direction and the extinguished fiber is removed from the flow.

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

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

Table 1.16 – Main technological parameters

Parameter name		Parameter value
Temperature of the drying agent at the inlet to the dryer pipe
Temperature of the drying agent at the outlet of the dryer pipe
Initial fiber moisture content
Final fiber moisture content
Drying agent speed
Mass of fiber passing through
dryer in 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 thermal resistances located at the outlet of the dryer pipe. When the set temperature value is exceeded by 5-10°C, the burner automatically turns off.

The maximum temperature of the drying agent at the inlet to the drying pipe is set using an electronic regulator connected to thermal resistances installed at the inlet to the drying pipe. When 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 is automatically stopped.

Cleaning the dryer from settled fiber should be done at least once a week. The dryer must be cleaned only when the temperature in the dryer drops to 30 C and the electric motors are turned off. The fuses for all dryer drive motors must be removed.

Clogging of the dryer pipe or cyclones with fibrous material usually leads to exceeding the set inlet and outlet temperatures, and the dryer automatically turns off. If this does not happen, you must immediately turn off the burner manually, stop feeding fiber into 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 by supplying water to the dryer. After eliminating the fire, the dryer must be thoroughly cleaned and water must be removed from the fan.

2.5) Formation of 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).

Fiber from the receiving cyclones is fed through sluice gates to a belt conveyor (1), which transports it to the dosing hopper (2) of the forming chamber. At the same time, the conveyor makes reciprocating movements, distributing the fiber across the width of the dosing hopper (2). From the conveyor (1) the fibrous material enters the dosing conveyor (3) of the dosing hopper. If the level of fibrous material reaches a certain height, the excess fiber is thrown back by leveling combs (4). Then the fiber is fed by a dosing conveyor (3), the speed of which is directly dependent on the volume of fiber poured, to the discharge rollers (5) and then to the loosening rollers (6), which rotate in opposite directions. After passing through the loosening rollers (6), the fibrous material is picked up by the air flow created by the vacuum boxes (7) and deposited on the moving belt mesh (11). Due to the air permeability of the mesh and the strong suction effect underneath, the fibrous layer-carpet is compacted and at the same time curled. The thickness of the fiber carpet depends on the speed of the belt mesh. The formed fibrous carpet is cut to a given 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 radioisotope density meter sensor (9) and is automatically maintained at a given level by changing the speed of the mesh or moving the scalping device in height. The formed carpet is pressed with a belt-roller underdresser (10), as a result of which the height of the carpet is reduced by 2-2.5 times and its transportability increases.

Figure 15 – Scheme of formation of wood fiber carpet

Figure 16 – Technological diagram for pressing wood fiber boards

2.6) Pressing of fibreboards

Pressing of fiberboards is carried out in a continuous calender-type press "Auma-ZOR" from Berstorff (Fig. 16.)

Technological characteristics of the Auma-ZOR press:

Calender diameter, mm 3000

Diameter of pressure heating rollers, mm 1400

Diameter of tension and drive rolls, mm 1400

Working width of the calender, mm 2500

Length of steel tape, mm 27900

Width of steel strip, mm 2650

Thickness of steel belt, 2.1 Number of cleaning rollers, pgg

Heating of the calender and rolls thermal oil

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

Roll No. 2 20

Roll No. 3 15

Roll No. 4 28

Maximum operating 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 a metal detector by a belt conveyor (18) to the input zone of the calender press, captured by a continuous steel belt (7) and pressed against a calender (1) heated to 160-190°C. Pressing is carried out mainly by pressure rollers (2,3,4), which press with a given pressure on the steel belt and the wood-fiber carpet. In the area after the roll (4), the carpet is held by a steel belt in a pressed state, the binder is finally heated and cured; the roll (5) creates tension on the steel belt; the belt is driven by the roll (6). The resulting slab is transported along guide rollers, passes through a thickness gauge (19) and is fed to a format-edging machine.

The line provides the possibility of applying a single-layer coating of textured vapor-conducting paper to the formed wood-fiber carpet with its subsequent pressing. For these purposes, a laminating installation (22) is used, located directly in front of the calender (1) and representing a frame on which the working and spare rolls of paper (with a diameter of no more than 600 mm) and three guide rolls (with a diameter of 148 mm) are mounted. After installing the roll, you need to pull the strip of paper through the three guide rollers until it enters the calender. Immediately after starting the laminating operation, it is necessary to set the required tension value of the paper strip using the pressure regulator located next to the brake; the maximum speed of the coating installation is 50 m/min.

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

2.7) Cutting fibreboard into formats, packing and laying the boards After hot pressing in a calender press and automatic thickness measurement, a continuous strip of fibreboard is fed with two rollers to a formatting and trimming machine type ME-02 (Shwabedissen).

The machine is equipped with 2 cutters and four circular saws for longitudinal cutting (two cutters and two saws for cutting longitudinal edges and two saws for cutting the slab lengthwise into two or three parts) and five cross-cut saws. The edge trimming boards are equipped with crushers. After crushing the edges by a pneumatic system, they are sent to a waste bunker for subsequent combustion in the boiler furnace. The cross-cut saws are located sequentially and close to each other and, when cutting, make oscillatory movements in an arc, while the plate is clamped at 2-3s by the clamping rollers and stops, forming an arc in front of the machine. After cutting the slab, the saws are raised, the clamping rolls are retracted, the arc of the fiberboard is straightened and the slab is advanced to the next step to the limit switch (by a given length).

Finished fiberboards are sorted and placed in packs of 50-200 pieces. depending on the thickness of the slabs. Standard boards intended for export deliveries are packaged in accordance with OST 13-34-81 “Fibreboards supplied for export. Packaging, labeling, transportation, storage.”

Packaging of a standard slab is carried out as follows (Fig. 17): the formed slab packages are delivered to drive roller conveyors (3). Then the slab package enters the drive roller conveyor (5) for packaging. The second package of the slab, through the drive roller conveyor (7), is supplied to the drive roller conveyor (8) for packaging. Packaging is in progress. The packaged packages are transported onto roller conveyors (6,9) and removed by a forklift. Packaging of non-standard (large-format) slabs occurs as follows:

The formed slab package enters the drive roller conveyors (3). Then the package enters the drive roller conveyors (4,7) for packaging. The slab is packaged and transported onto roller conveyors (6,9), after which it is removed by a loader. To pack fiberboard packages, fiberboard linings or stretch film are used. The formed package is tied with hardened packaging tape in accordance with GOST 3560 “Steel packaging tape” or polyester packaging tape.

The tension and fastening of the ends of the packaging tape should prevent the package from loosening during loading, unloading and transportation.

At the joints of the top, bottom and side facing slabs, corners are placed under the packing tape to protect the slabs from crushing.

Dimensions, weight of packages, number of sheets in a package, number of belts, dimensions of pallet parts, their quantity and material, as well as marking are produced, determined and carried out in accordance with OST 13-34-81.

The packaged slabs are transported by loader to a dry closed warehouse, where the packages of slabs are stacked in stacks of the same size. The stack must be at least 1.5 m from the doors and at least 0.5 m from the walls and heating devices. Passages and passages are made between the stacks, providing free access to them. The width of the passage must ensure the transportation of slab packages of maximum length.

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

Figure 17 – Scheme of organization of trimming and packaging of fiberboard

Some materials even become popular with consumers over time. This gives the entrepreneur every chance to launch his own profitable business, producing products whose technology has been developed for years. Pay attention to the manufacture of fiberboard. The enterprise will require significant expenses, but opening fiberboard production in Russia is profitable, since the investment pays off quite quickly.

Our business assessment:

Starting investments – from RUB 3,000,000.

Market saturation is average.

The difficulty of starting a business is 7/10.

Fiberboard (Fiberboard) is a material in the form of sheets, for the manufacture of which wood raw materials are used. It is actively used as a raw material in furniture factories and construction sites. To minimize financial risks, you can open a mini plant for the production of fiberboard, rather than a powerful processing plant. Analyze the sales market and draw up a business project to plan further actions. This direction is attractive to entrepreneurs for several reasons:

• An extensive sales market will allow you to quickly find interested customers.
• Simple technology makes it possible to understand the process in the shortest possible time.
• The raw materials used are inexpensive.
• Low competition in this area will contribute to the rapid development of a young enterprise.

Fibreboard manufacturing technology

To produce fibreboards, waste from wood processing enterprises is used. To ensure uninterrupted supply of raw materials, negotiate with several sawmills. It’s great if you find a production facility nearby - this will really reduce variable costs when starting a business. If the workshop introduces dry fiberboard production, synthetic resin will be required.

To give the final material strength and moisture resistance, additional raw materials for fiberboard are used - precipitants, oil or paraffin emulsions. They can be purchased in large quantities at once.

In general, the fiberboard production technology is carried out in several stages:

• preparation and dosing of components,
• sheet formation,
• pressing the material,
• cooling,
• cutting sheets according to specified sizes,
• sheet sanding,
• packaging and storage.

If you are going to purchase solid wood rather than wood chips, you will have to pre-process the raw materials - grind them to a certain fraction size and steam them. These are additional costs for the purchase of equipment - it will be much easier for novice entrepreneurs to bring “ready-made” sawdust to the workshop.

Before purchasing equipment, consider the methods for producing fiberboard and choose the best option. In practice, 2 methods are used:

• Wet production. The slab is formed in an aqueous environment on a special lattice substrate. The “semi-finished products” are then pressed under elevated temperatures. All moisture evaporates and the material becomes dense. A fiberboard sheet produced by the wet process has one side that is corrugated.
• Dry production. The sheet is formed without exposure to moisture. Artificial resins are used to glue wood chips. The mixture is mixed and pressed at elevated temperatures under pressure. The finished product is then removed from the mold and further processed - cut and polished.

The production of fiberboard using the wet method is more popular among Russian manufacturers because it is simple. But in Europe this technique has already been left in the past, since high water consumption increases variable costs.

Workshop technical equipment

The fiberboard production line is the most impressive item of the planned investment. The quality of the manufactured products will depend on the quality of the purchased equipment. The line includes the following machines:

• dispensers,
• faucets,
• molding machines with molds,
• sheet sanding machine,
• Grinder.

This is a list of major equipment. To purchase everything you need, you will need at least 2,000,000 rubles. But in this way it will not be possible to completely automate the process - many operations will have to be done manually.

If preliminary preparation of raw materials is planned, you will need to purchase equipment for the production of fiberboard of the following type:

• chipper – from 150,000 rubles,
• steaming chamber - from 200,000 rubles.

The acquisition of conveyors, industrial fans for blowing off dust, and lifting packaging tables will significantly speed up the process. In this case, add at least another 800,000 rubles to the cost of technical equipment.

The full price of equipment for the production of fiberboard, automated and fully equipped, is quite impressive - from 3,000,000 rubles.

Production premises

You don't need a lot of space to place the production line. But free space will be required for warehouses. Raw materials should be stored in a dry, well-ventilated area - it will need to be equipped with ventilation systems. It should also be installed in workshops, since the fiberboard manufacturing technology involves the release of fine wood dust into the air.

Look for a workshop with an area of ​​at least 500 m2 outside the city. Renting premises here is much lower. In addition, it will be easier to collect a package of documents to start a business, since it will not take a long time to “convince” the sanitary services that the production does not interfere with the residents of nearby houses.

It will be impossible to set up the process without three-phase electricity, heating and water supplied to the workshops. And if in some industries a country garage would be enough, then the production of fiberboard needs to be carried out in a much larger and better equipped area.

Business development prospects

If you plan your activities correctly, the enterprise has every chance of success. Start looking for clients at the stage of developing a business plan. Buyers of finished products will be:

• furniture factories,
• private consumers,
• construction organizations.

Wholesale clients will bring much greater profit - focus on finding just such buyers. This way, the products will not sit in warehouses, and the company will work to order.

The success of the enterprise largely depends on the range of materials offered. Immediately consider the production of soft fiberboard and hard, laminated fiberboard - such material is much more expensive on the market and is more in demand. And if you skimp on equipment by not buying a grinder, you will lose part of the market.

When things go uphill and the costs begin to pay off, consider the option of launching related industries - the production of chipboard and MDF. This practice is common among entrepreneurs - the technologies are not much different, little additional equipment is required. This is a great chance to expand your range and attract more customers.

Profitability of the planned business

Capital costs and payback periods will depend on the planned capacity of the enterprise, the selected production technology, prices for equipment and the selling price of the final product.

The main cost items when organizing a mini-plant for the production of fiberboard:

• purchase of equipment – ​​from 2,000,000 rubles,
• purchase of raw materials for a month - from 300,000 rubles,
• rental of premises for the first 3 months – from 200,000 rubles,
• preparing the premises for work - from 400,000 rubles.

You can save on investments by installing used equipment in your workshop.

As practice shows, the technological scheme will pay for itself in 4-6 years. Be patient - the formation process may take a long time. To be prepared for “unexpected turns”, in your business plan, provide for all possible options for the development of affairs and ways to solve problems.

Set competitive prices for your products. The selling price of fiberboard depends on its type and processing method. For example, an untreated slab measuring 3.2*1220*1373 mm costs on the wholesale market from 115 rubles/piece. Sanded products are more expensive.