Kronospan, the first board manufacturer in Spain, an example of a circular economy

Kronospan factory

KRONOSPAN is a company founded in 1897 in Lungötz (Austria). Currently, it occupies a privileged position in the board and its derivatives market. In 2002, it created its subsidiary in Spain, KRONOSPAN SPAIN, with the aim of marketing its products in our country. At the end of 2012, it acquired the assets of the INTERBON GROUP and generated the subsidiaries: KRONOSPAN, SL, KRONOSPAN MDF, SL and KRONOSPAN CHEMICALS, SL

Its business strategy has turned the province of Burgos (Castilla y León) into one of the epicenters of board production in Southern Europe, with two production centers: one located in the municipality of Burgos, specifically in the Castañares neighborhood where manufactures particle board and plywood and another in the Burgos municipality of Salas de los Infantes where it produces MDF fiber chipboard.

The Castañares factory underwent a thorough renovation in 2015, the result of which we can say has become the circular economy paradigmBecause the plant currently produces around 1.700 m3 / day of chipboard, from recycled wood, in a percentage that has been increasing to reach 80% today, with a forecast of reaching 100% in the coming years.

This change towards the use of materials from the recycling of pallets, doors, furniture, carpentry remains, etc., maintaining the quality and finish of the board, has meant providing in a special way the infrastructures of the reception area, classification, rejects and conditioning of the crushed raw material that comes mainly from large population centers such as Madrid and Barcelona.

The pre-classified material is deposited in huge storage warehouses over 20 meters high, indoors, which means minimizing the inconvenience caused by the generation of dust particles due to the handling of this type of material.

Currently, new investments continue to be made in the field of reception of recycled material, with the construction of new warehouses and the expansion of the fields.

Process of obtaining the particles to make board


From the storage sheds the material is transferred to one of the two chippers in the plant. One with a 600 kW motor that drives a rotor equipped with three blades that grinds the wood that comes from a vibrating feeding table and the other with a 400 kW motor that drives a rotor equipped with 28 hammers. The two unload the chipped material, via a traveling conveyor belt, onto covered moving bottoms. These are divided by concrete walls in several sections to be able to separate the storage of the different types of materials: recycled wood chips, clean wood chips and sawdust. The discharge conveyor belt moves along the different sections, positioning itself in the place corresponding to the material produced. One of the sides of the mobile funds is left uncovered to allow the loading of materials, which do not need to go through the chippers and which are directly unloaded from the transport trucks. The storage capacities, in the mobile bottoms, for the different types of materials are: 3.000 m3 recycled chip, 3.000 m3 clean chip and 1.000 m3 sawdust.


Chips and sawdust are transported through conveyor belts to the cleaning towers. The quantity of each material that you want to introduce in the process is set from the control post. In the towers the material is conditioned by removing everything that is not wood: ferrous metals, non-ferrous metals, plastics, cardboard, silica ...; A classification by size is made sending the large chips to be reprocessed, the good chip to the feed silo of the chippers, the good fines to the storage silo before the dryer and the superfine ones to the storage silo to use them as an energy source in the dryer burner.

Chip formation

After going through the cleaning process, the chip is transformed into shaving. The clean chip arrives at the mills through a redler, where the shaving process is carried out. Most of the mills are of blades and basically consist of a rotor provided with slats, whose purpose is to push the chips against the blades fixed to a basket that rotates in the opposite direction to that of the rotor. There is also a hammer mill that breaks the splinter by hitting.

To achieve high board quality, the chips must have high uniformity in thickness, length, width and fine content. Thus, these mills grind the wood until obtaining particles with a slenderness [length / thickness] close to 100 and dimensions between 0,1 to 0,8 mm thick, 2 to 8 mm wide and 15 to 30 mm long. .


The already conditioned material would go to the dryer, which is a huge tromel (rotary dryer) with a diameter of 8 m and a length of 30 m, capable of processing 45 tons / hour until leaving the wood with a humidity between 3-4%. Inside the drum, conditions vary, from the first sector with higher relative humidity and ambient temperature to the final sector with low relative humidity and high temperatures. Throughout the drying process, which lasts about 20 minutes, the wood loses its humidity due to the effect of circulating hot air.

This is another very important process to obtain high board qualities. Although the final moisture content of the board is around 10%, the particles must be dried at humidity levels of around 3-4% previously mentioned, since the wood absorbs the water coming from the adhesive. If the humidity in the particles is excessive, "blisters" can be generated on the board and if it is insufficient, premature setting of the adhesive can occur, which would lead to poor bonding and therefore, a board with low mechanical resistance and poor quality surfaces .

Particle screening and classification

Once dried, the particles are sieved using suitable size screens, as a result of applying alternate movements or by ventilation, and are classified into four types of chip: very thick chips, good chips, fine fine and superfine chips. The very thick shavings are forwarded to the refining mill for resizing, the superfines and dust are removed for energy use and the good shavings and fines are cleaned of silica particles before proceeding to the next gluing and pressing process. The destination of the smallest particles will be the face and back of the board and that of the largest for the soul or center of the board. This is to minimize the consumption of adhesives, maintain good mechanical resistance and improve the finish of the board.

The boiler

The heat needed both for this process and to heat the thermal oil used in the presses comes from a 50 MW KABLITZ boiler, fed with biomass from the chipping of the remains of cuttings from the poplar mills of Castilla y León and silvicultural actions of nearby mountains and pine forests. Average daily consumption would be around 75 mt, making this KRONOSPAN plant one of the main industrial consumers of residual biomass for energy use. In addition, there is an extra contribution of heat due to the recovery of superfine particles and wood dust that is generated in the cutting and sanding of the boards and which is combusted in a burner.

The boiler, installed in a structure of 500 tons of iron and which is covered with another 250 tons of refractory material, has a continuous feeding system and is equipped with a system of mobile grills, cooled by water and allows the obtaining of Combustion gases at 700ºC that will heat the 100.000 liters of thermal oil to (300ºC), which promote, among others, the pressing process and will provide heat to the dryer. The thermal energy consumption per unit of product is 175 kWh / m3.

Particle filtering system

Before leaving the chimney, the gases pass through a wet electrostatic filter (WESP). It is double, with alternative operation, while one filters the other maintenance work. This equipment is fed by the gases from the dryer and the press to reduce its concentration of particles and volatile organic compounds before its emission into the atmosphere.

Its basic principle of separation consists in passing these gases through a chamber where an established electrostatic field is created between electrodes of different charges: negative emitting or discharge electrodes and the collector or positive plate electrodes connected to ground. These gases are injected with water in order to drag part of the particles and absorb part of the polluting gases as the first separation stage and finally, they are negatively charged when passing through the emitting electrodes and are attracted by the collecting electrodes.

By spraying water, the particles adhering to the collecting plates are dragged into the collection tanks (absorbent tanks). From these tanks the contaminated water is filtered through sieves. The retained solid part is taken to a centrifuge in order to remove as much moisture as possible. The obtained sludge is treated by an authorized manager.


The water used to clean / wash the electro-filters as it contains high amounts of sediments and leachates is treated in a small pond. The larger particles are removed by decantation and the smaller particles are separated using rotary machines (centrifuges) that separate the water from the solids. Part of the water is reused and another part is removed by an environmental manager.


The ashes from the boiler are the only waste that is generated, which has been reused as fertilizer on some occasions, as inert in sealing landfills on others, or which is sent to the cement industry for its use.

Socio-economic benefits: employment

The KRONOSPAN-Castañares plant employs 180 workers and generates indirect employment for approximately 1.400 workers, mainly transporters, external maintenance and repair personnel, biomass supply companies and service companies.