The Tudela Factory, located in Tudela Veguín, a town in the municipal district of Oviedo, dates back to 1898, is considered the first cement factory in Spain.
In 1970 the manufacture of grey cement was substituted by that of white cement, for which one of the old kilns manufacturing grey cement was transformed. Close in time was also the start of lime production in the other two old kilns which manufactured grey cement.
From that moment onwards, the factory commenced an expansion, extension and modernisation process that continues up until now, in order to satisfy that demanded by the industrial market within our scope of production.
Any transformation process starts with the quarrying of a deposit from which the raw materials feeding later processes are extracted. In our case, the Company has a quarry of high-purity limestone, this constituting the basic raw material for the manufacture of quicklime and white cement. Approximately 80% of the reserves are limestone with high carbonate content, suitable for the manufacture of white cement and quicklime, with the remaining 20% corresponding to standard limestone valid for the production of construction aggregates.
The control and follow-up of the different production lines starts at the quarry itself, where an exhaustive control is performed on the quality of the limestone belonging to the different quarry faces (via the analysis of dust from blasting obtained at the drilling) in this way ensuring that the limestone quality is that appropriate for each process and, in turn, to perform rational quarrying. 1,500,000 t is the annual production capacity of the quarry.
Primary crushing is performed in the quarry, reducing the size of the limestone to 300 mm, to be stored in an intermediate stock and transported via conveyor belts over the Nalón river and road AS-116, to reach the Crushing Bay where the washing and secondary crushing are carried out to obtain the ideal sizes for the different production processes.
The main processes taking place in the Tudela Factory are the following:
- Production of construction aggregates.
- Manufacture of quicklime.
- Manufacture of white cement.
Production of Construction Aggregates
The limestone obtained from the quarry which cannot be used in our processes due to its chemical composition, is diverted to the aggregate plant with a 70 t/h production capacity, where a washed aggregate of the sizes demanded by the construction market is obtained: sand (0/4), fine gravel (4/12) and gravel (11/22).
Manufacture of Quicklime
The manufacture of lime is performed via two clearly differentiated technologies, each with their characteristics but resulting in a product of identical quality. Both technologies are present in our Factory and correspond to manufacturing in a horizontal rotary kiln and in a double-chamber vertical kiln.
The first of these was installed in 1974 with the start-up of the Polysius horizontal rotary kiln with Lepol grill and Recupol cooler. The rotary kiln is 91 m long and 4.4m in diameter.
The lime production capacity varies between a technical minimum of 500 t/d and a maximum of 1000 t/d, allowing for great production flexibility.
The second technology is made up by the Maerz double-chamber vertical kilns defined as parallel flow regeneration kilns. They are particular characteristic is their great operating elasticity, together with the fact that they are the BAT for lime manufacture due to their low energy consumption.
This production unit is made up by a set of 4 Maerz kilns, the first two being installed in 1990 (after dismantling the two old horizontal ones for grey cement transformed to manufacture lime) and later with the start-up of two new units in 2003. Each of these has a lime production capacity of 250 t/d.
As a whole, the production lines add up to an annual lime production capacity of 600,000 t.
The main lime market is made up by the steelworks industry, basically caused by the purity of the lime manufactured (low content of sulphur, silica, phosphorous) and its high reactivity.
It is obtained in different sizes depending on its application and to satisfy the needs demanded: lime in grains (10/40 mm), crushed lime (0/1.5 mm), micronized lime (maximum size 250 microns). To obtain this diversity of sizes there is a closed-circuit mill with a 45 t/h capacity and a micronized lime mill with dynamic separators and a capacity of 15 t/h.
With the aim of extending the market quota in the lime sector and to, in this way, cater for the demand of the industry in general for our product, a Cimprogetti Hydrator came into service in 1998 with a hydrate (calcium hydroxide) production capacity of 15 t/h. This product is essentially destined to the sectors of construction, agriculture, water treatment and public works land stabilisation.
Manufacture of White Cement
The old wet-process white cement manufacturing line was characterised by very high energy costs and low production capacity (170 t/d clinker), justifying its substitution in the year 2000 for a new dry-process white cement line with a production capacity of 400 t/d, extendable to 550 t/d of clinker (annual production 120,000 t de clinker) with the aim of increasing the profitability of the installation by raising production and reducing energy costs.
The basic raw materials used to manufacture white cement are limestone, white clay and silica sand, which provide the essential components making up the flour to form the raw material which feeds the process. It is very important that these three basic materials contain very low percentages of those elements defined as chromophores (iron, chrome and manganese) as their presence during the manufacturing process would damage the whiteness of the clinker obtained.
The three components, dosed correctly to obtain the appropriate chemical composition, are crushed in a Polysius type RM 27/13 vertical roller mill with 55 t/h production capacity and later stored in a flour silo with capacity for 3,500m3. As the raw materials used are very homogeneous, the system does not require a previous pre-homogenization bay, the flour being stored directly on a silo defined as a homogenization silo whose aim is to achieve the highest degree of homogenization of the flour.
The correctly dosed flour is fed into the upper area of the thermal interchange tower called the Dopol tower and made up of 6 stages. The flour descends via the cyclones and guides of the tower and in the opposite direction to the flow of the hot gases coming from the kiln. This contact of the gases with the flour starts the first transformations that take place in the process and which basically constitute dehydration before and decarbonation afterwards. It is under these conditions that the flour enters the kiln and the clinkering process occurs.
The clinkering process takes place in a Polysius kiln that is 51 m long, has three supports and a diameter of 3.4 m.
The clinker leaving the kiln at an approximate temperature of 1,400 ºC is subjected to a two-stage cooling system. In the first stage it is subjected to sudden cooling by means of water injection in a rotary drum, which lowers its temperature to 600 ºC, and the second cooling stage is through air on a vibrating grill.
It is very important to work in a reducing atmosphere inside the kiln and most of all at its exit, to avoid the oxidation of the chromophore elements and, in consequence, damaging the whiteness of the clinker. The first stage of clinker cooling is just as important, this also occurring in a reducing atmosphere which, together with the sudden cooling through water injection, reduces the oxidation state of the aforementioned chromophore elements.
The clinker obtained in these conditions is transported to silos along metal conveyor belts and an elevator, with 8,500 t storage capacity for clinker.
Cement milling is performed with a Polysius tubular double-chamber mill with 35 t/h production capacity, in a closed circuit and with a high-performance dynamic separator. The storage capacity for cement is 13,000 t.
The issuance of the cement can be made in bulk by road or train. It can also be issued in sacks, on pallets and packaged with plastic.
The sacking machine is a Haver-Boecker and that for palletizing and plastic-packaging is by Metral. Finally, it is also possible to issue the cement in big-bags, the installation being by the firm Pyper, S.A.
The Factory has the following certifications and quality seals
– Quality Management Certificate in accordance with UNE-EN ISO 9001
– Environmental Management Certificate in accordance with UNE-EN ISO 14001
– Energy management certificate according to UNE-EN ISO 50001
– Cement: CE Marking in accordance with UNE-EN 197-1 and voluntary N Mark of AENOR.
Sand 0/4: CE Marking in accordance with UNE-EN 13139 (Aggregates for mortar) and UNE-EN 12620 (Aggregates for concrete).
Fine Gravel 4/12: CE Marking in accordance with UNE-EN 12620 (Aggregates for concrete).
Gravel 11/22: CE Marking in accordance with UNE-EN 12620 (Aggregates for concrete).
– Construction lime (Quicklime CL 90-Q and Hydrated Lime CL 90-S): CE Marking in accordance with UNE-EN 459-1.
The IEA (Integrated Environmental Authorisation) was obtained in 2008, proving the responsible commitment to the environment of the Tudela Factory.
Since it started its activities and up until now, the Tudela factory has permanently sought to overcome the challenges it faces day after day, together with continuously adapting both its production processes and its human resources to the new needs and demands of the market, always in compliance with the increasingly stringent autonomic, state and European regulations (Quality, environment and energy policy).