NL2039144A - METHOD AND GRINDING SYSTEM FOR PRODUCING A CEMENT MIXTURE - Google Patents

Abstract

METHOD AND GRINDING SYSTEM FOR MANUFACTURING A CEMENT MIXTURE EXTRACT The present invention relates to a method for manufacturing a cement mixture, in which granular raw materials such as clinker, slag, limestone, fly ash and gypsum are supplied and separated into contaminated and uncontaminated material using a metal separator. The uncontaminated material is then ground, mixed and dried in a vertical roller mill using a heated gas stream with a flow rate between 650,000 10 and 800,000 m3/h. The roller mill comprises stationary wheels and a rotating grinding table with a hardfacing layer for wear resistance. During grinding, additives such as triisobutyl phosphate (max. wt%), sodium thiocyanate (20-50 wt%), triisopropanolamine (15-30 wt%), diethanolamine (max. 5 wt%), benzisothiazolinone (max. 100 ppm), and ethanolamine (max. 10 wt%) are added to improve the properties of the cement. The mixed cement powder is separated into coarse and fine powder by a separator with a rotor rotating between 130 and 160 RPM. The fine powder, with a maximum particle size of pm, is discharged to a filter unit, while the coarse powder is ground again.

Description

METHOD AND GRINDING SYSTEM FOR THE PRODUCTION OF A

CEMENT MIXTURE

TECHNICAL DOMAIN

The invention relates to a method for producing a cement mixture.

In a second aspect, the invention also relates to a grinding system for producing a cement mixture.

In another aspect, the invention also relates to a use in the construction sector, in particular for the production of a cement mixture.

STATE OF THE ART

Typically, cement is produced using a vertical roller mill. The process of cement production using a vertical roller mill begins with the extraction of raw materials such as limestone, clay, sand, and iron ore from quarries or mines. These materials are transported to the cement plant and finely ground into a consistent powder. Typically, a vertical roller mill will finely grind the raw materials resulting in the formation of a fine cement powder.

The vertical roller mill is known for its efficiency, but suffers from high energy consumption during the grinding process. Grinding raw materials into a fine powder requires a lot of energy, which leads to high costs and increased CO: emissions, which has a negative impact on sustainability. On top of that, an unstable energy supply, especially in areas with weak energy infrastructure, can lead to inconsistency in production and lower efficiency.

The moisture content of raw materials is another problem. Damp materials require more energy to grind, which reduces the efficiency of the mill and affects the productivity of the cement plant. In addition, damp raw materials can clump in the mill, causing blockages and damaging the equipment, leading to additional maintenance costs.

Furthermore, inaccurate control of raw material ratios will lead to variability in the quality of the cement produced, which results in inefficient energy use and waste of materials. In addition, problems with filtration and inadequate air cleaning can lead to dust emissions, which not only endangers air quality and health, but also increases energy consumption.

The present invention aims to find a solution to at least some of the above-mentioned problems or disadvantages.

SUMMARY OF THE INVENTION

In a first aspect, the present invention relates to a method according to claim 1.

The method for manufacturing a cement mixture comprises supplying granular raw materials 1, wherein these granular raw materials are selected from clinker, slag, limestone, fly ash, gypsum and combinations thereof. Subsequently, the granular raw materials are separated into contaminated feed material and non-contaminated feed material by means of a metal separator 3, wherein the contaminated feed material contains metal particles. The non-contaminated material is discharged to a vertical roller mill 9, where it is ground, mixed and simultaneously dried to cement powder. The vertical roller mill 9 is provided with at least two stationary wheels that roll on the rotating grinding table on which the granular raw materials are ground. The rotating grinding table is provided with a hardfacing layer, and during the grinding a heated gas stream is blown into the vertical roller mill via an annular gas outlet opening, which is placed around the rotating grinding table. A partition is placed between each opening, and an air flow rate of at least 650,000 m3/h and a maximum of 800,000 m3/h is created.

After grinding, an aggregate is added to the vertical roller mill. This aggregate comprises triisobutyl phosphate in an amount of up to 10% by weight, thiocyanate salts, preferably sodium thiocyanate, in an amount of at least 20% by weight and up to 50% by weight, triisopropanolamine in an amount of at least 15% by weight and up to 30% by weight, diethanolamine in an amount of up to 5% by weight, benzisothiazolinone in an amount of up to 100 ppm, and ethanolamine in an amount of up to 10% by weight, relative to the total weight of the aggregate. These components are mixed with the cement powder to form a homogeneous cement powder.

Subsequently, the homogeneous cement powder is separated by a separator into coarse and fine cement powder. The coarse cement powder falls back onto the rotating grinding table to be ground again, while the fine cement powder, with a particle size of maximum 200 µm, is discharged to a filter where it is separated from the heated gas stream. The built-in separator contains a rotor that rotates at a speed of at least 130 RPM and at most 160 RPM.

Preferred embodiments of the method are set out in claims 2 to 12. The method comprises feeding, separating, grinding, drying, and mixing granular raw materials and an aggregate to obtain a homogenized cement mixture having improved performance and durability.

An essential step involves the removal of metal contaminants, which not only increases the quality of the final product, but also extends the life of the equipment and minimizes unnecessary energy waste. The parallel grinding and drying processes, performed by a vertical roller mill, result in efficient processing of moist raw materials, which saves both time and energy, while maintaining product consistency.

Not only the mechanical processes contribute to the advantages of this method, but also the optimal management of air flows, powerful heating with high-quality burners or gas generators, and the use of wear-resistant materials for equipment components enhance durability and efficiency.

The integrated separator optimizes the particle size distribution of the milled material, while temperature control of the fine cement powder improves storage stability.

The addition of a suitable aggregate within the described production process contributes significantly to the refinement of the final product, whereby specific technical advantages are achieved. The targeted incorporation of an aggregate, such as thiocyanate salts, trissopropanolamine, triisobutylphosphate, benzisothiazolinone, ethanolamine, diethanolamine or combinations thereof, introduces a range of strengthening properties into the cement mixture. Among other things, the aggregate influences the hydration reaction, which will lead to the formation of stronger cement bonds. This will significantly increase the final strength and durability of the cement. The precise regulation of the hydration and setting time, using an aggregate, offers considerable flexibility in adapting the cement mixture to specific construction requirements.

Furthermore, the antimicrobial properties of the aggregate help to inhibit microbial growth, which not only enhances the durability but also the visual appearance of the cement surface. The ability of the aggregate to act as a superplasticizer improves the workability and fluidity of the mix, enabling it to better tackle complex structures. All this, combined with the environmental benefit of reducing cement usage and CO2 emissions, contributes to a strong and durable cement mix that meets the complex needs of modern construction applications.

In a second aspect, the present invention relates to a grinding system according to claim 13. A preferred form of the grinding system is described in subclaim 14.

This grinding system has the advantage of ensuring accurate dosing of raw materials. A built-in metal separator separates contaminated materials to ensure the quality and durability of the cement. Furthermore, a vertical roller mill will be used to grind and separate materials, resulting in fine and coarse cement powder. To this end, the cement powder will be mixed with a specific aggregate in the vertical roller mill to form a homogeneous cement powder, which provides consistency and improved performance. The final cement mixture will be stored in a storage silo. The grinding system can also automatically load trucks with the cement mixture, which increases efficiency and accuracy. This advanced system provides high-quality cement with improved properties and optimizes processes while reducing waste.

In a third aspect, the present invention relates to a use according to claim 15.

This use results in a cost-effective production of a cement mixture, which contributes to a more sustainable and economically beneficial approach to building materials production.

DESCRIPTION OF THE FIGURES

Figure 1 shows a schematic representation of a cement production process according to an embodiment of the present invention.

DETAILED DESCRIPTION

Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning as commonly understood by one skilled in the technical field of the invention. For a better appreciation of the description of the invention, the following terms are explicitly explained.

When “about” or “around” is used in this document with reference to a measurable quantity, a parameter, a time or moment, or the like, it is intended to mean variations of +/-20% or less, preferably +/-10% or less, more preferably +/-5% or less, even more preferably +/-1% or less, and even more preferably +/-0.1% or less than and from the quoted value, to the extent that such variations are applicable to the invention described. It is to be understood, however, that the value of the quantity for which the term “about” or “around” is used is itself specifically disclosed.

Quoting numerical intervals through the endpoints includes all integers, fractions, and/or real numbers between the endpoints, including these endpoints.

The term “cement mix” refers to a composition comprising fine cement powder. This cement mix is supplemented with water and other materials such as sand, gravel or other aggregates, which are carefully mixed in the correct proportions. This results in a uniform substance that is used for the construction of various structures, including buildings, roads, bridges and other infrastructure projects.

The term “blaine” should be understood as a measure of the specific surface area of a powdery material, especially finely ground cement, which is used to indicate the fineness of the cement. The Blaine number is a value that indicates how much surface area a cement powder has per gram, expressed in square centimeters per gram (cm2/g). Measuring the Blaine number is an important procedure in the cement industry, because it determines the fineness of the cement, which in turn affects the properties and performance of the cement during hardening and use. The Blaine number affects the strength, durability and other technical properties of the cement mixture and the final concrete or mortar produced from the cement mixture. The measurement of the Blaine number is carried out using a special device, a so-called Blaine air flow permeability meter.

The sample of finely ground cement is placed in this device, and the air flow determines the specific surface area. This value is then expressed as the number of square centimeters of surface area per gram of cement sample. The higher the Blaine value, the finer the cement powder. Finer ground cement generally has a larger surface area, which will promote the reaction with water and hydration. This will improve the strength development of the cement. The Blaine value is typically measured after adding an aggregate to the cement powder.

The term “dry flowability” also known as a flow property of powders, refers to the ability of a dry cement powder to flow or move under the influence of gravity or external forces, without external wetting. A powder with good dry flowability flows easily and evenly through equipment and processes, such as conveyors, hoppers, dosing systems and packaging machines, without sticking or stiffening.

This enables efficient and reliable production processes to be achieved.

Powders with poor dry flowability exhibit problems such as bridging, arching or channeling, which impede flow and dosability. This can lead to production stoppages, blockages or inaccurate dosing, which can negatively affect productivity.

The term “end product” should be understood as the cement mixture, which includes the fine cement powder. After the filtration process, in which the fine cement powder is separated from the heated gas stream, additives can be added to this cement mixture, among other things, to form the final cement mixture.

The term “stationary wheel mechanism” refers to the ‘arm’ or structure to which the wheel of a vertical roller mill is attached. This mechanism ensures that the wheel remains firmly in place and does not rotate or move during the grinding of the granular raw materials.

The term “homogeneous cement powder” is to be understood as the fine cement powder that is thoroughly and evenly mixed with the added aggregate so that there are no undesirable irregularities, lumps or separations in the cement powder. The result is a uniform and consistently composed powdery substance that is suitable for further processing without segregation of the components.

In a first aspect, the invention relates to a method for manufacturing a cement mixture. According to an embodiment, the invention relates to manufacturing a cement mixture comprising supplying granular raw materials 1, wherein these granular raw materials are selected from clinker, slag, limestone, fly ash, gypsum and combinations thereof. Subsequently, the granular raw materials are separated into contaminated feed material and non-contaminated feed material by means of a metal separator 3, wherein the contaminated feed material contains metal particles. The non-contaminated material is discharged to a vertical roller mill 9, where it is ground, mixed and simultaneously dried to cement powder. The vertical roller mill 9 is provided with at least two stationary wheels that roll on the rotating grinding table on which the granular raw materials are ground. The rotating grinding table is provided with a hardfacing layer, and during the grinding a heated gas stream is blown into the vertical roller mill via an annular gas outlet opening, which is placed around the rotating grinding table. A partition is placed between each opening, and an air flow rate of at least 650,000 m3/h and a maximum of 800,000 m3/h is created.

After grinding, an aggregate is added to the vertical roller mill. This aggregate comprises triisobutyl phosphate in an amount of up to 10% by weight, thiocyanate salts, preferably sodium thiocyanate, in an amount of at least 20% by weight and up to 50% by weight, triisopropanolamine in an amount of at least 15% by weight and up to 30% by weight, diethanolamine in an amount of up to 5% by weight, benzisothiazolinone in an amount of up to 100 ppm, and ethanolamine in an amount of up to 10% by weight, relative to the total weight of the aggregate. These components are mixed with the cement powder to form a homogeneous cement powder.

Subsequently, the homogeneous cement powder is separated by a separator into coarse and fine cement powder. The coarse cement powder falls back onto the rotating grinding table to be ground again, while the fine cement powder, with a particle size of up to 200 um, is discharged to a filter where it is separated from the heated gas stream. The built-in separator contains a rotor that rotates at a speed of at least 130 RPM and at most 160 RPM.

According to a preferred embodiment, in a first step of the method, the granular raw materials are supplied. Preferably, the method comprises the supply of granular raw materials, whereby the granular raw materials are selected from the list of: clinker, slag, limestone, fly ash, gypsum and combinations thereof.

In one embodiment of the method, the granular raw materials are supplied via one or more dosing hoppers, the dosing hoppers being equipped with dynamometric cells. This ensures accurate dosing of granular raw materials, which is essential for achieving the desired properties of the end product. The dynamometric cells provide real-time measurement data, allowing operators to closely monitor the process and ensuring the quality of the end product. This makes it a cost-effective approach that contributes to the consistent and high-quality production of the cement mixture.

In an alternative embodiment, dosing hoppers can be designed for volumetric dosing. In this case, the amount of raw materials is measured based on volume instead of weight. However, it is important to consider the density and consistency of the raw materials in volumetric dosing, as this can affect accuracy.

According to an alternative embodiment, other types of measuring sensors can be used to control the dosing of the raw materials, such as ultrasonic sensors, pressure sensors or optical sensors. Each of these sensors has its own advantages and disadvantages in terms of accuracy, cost and applicability. Furthermore, automated dosing systems are available that control the dosing process. These systems can use advanced algorithms and sensors to optimize and control the dosing of the raw materials.

According to a preferred embodiment, in a second step of the method, the granular raw materials are separated into contaminated feed material and non-contaminated feed material. Preferably, the granular raw materials are fed to a metal separator, where they are separated into contaminated feed material and non-contaminated feed material. The contaminated feed material comprises metal particles, which must be removed to improve the quality of the final product. Removing the metal particles has several beneficial effects. First, it improves the quality of the final product, i.e. the cement mixture, by increasing its purity and uniformity. In addition, it extends the life of the vertical roller mill, as it prevents the metal particles from causing damage to the equipment during the grinding process. Furthermore, it contributes to the efficiency of the grinding process by preventing energy waste. It also promotes the safety of the final product by reducing the risk of undesirable reactions or weakening of the cement mixture.

According to a preferred embodiment, the contaminated material is discharged to an intermediate bunker where a metal check takes place to further separate the non-contaminated material from the contaminated material. The contaminated material will be discharged to a waste storage. The non-contaminated material will be discharged to the vertical roller mill. This step of discharging contaminated material to an intermediate bunker for a second metal check is intended to further separate the non-contaminated material from the contaminated material.

This increases the purity of the uncontaminated material, resulting in a higher quality of the final product. At the same time, the process minimizes the impact on production efficiency by feeding only the uncontaminated material to the vertical roller mill and avoiding unnecessary handling of contaminated material. The result is a safer, more efficient and regulatory-compliant production process that meets the stringent requirements of the construction industry and contributes to high-quality cement for building construction and other applications.

According to a preferred embodiment, the method comprises discharging the uncontaminated material to a vertical roller mill for grinding, mixing and simultaneously drying the uncontaminated feed material into cement powder. A heated gas stream is blown into the vertical roller mill via a gas inlet ring through an annular gas outlet opening, which is placed around a rotating grinding table. An air flow rate of at least 650,000 m?/h and at most 800,000 m?/h, preferably at least 675,000 m?*/h and at most 780,000 m?/h, more preferably at least 700,000 m?/h and at most 760,000 m?/h, even more preferably at least 725,000 m?/h and at most 740,000 m3/h is created.

The inventors have found that this airflow rate enables optimum heat transfer during the grinding and drying of the granular raw materials. The efficient heat transfer ensures faster drying of the granular raw materials, which accelerates the grinding process and reduces energy consumption. If less airflow rate is created, this could lead to insufficient drying of the granular raw materials, which negatively affects the grinding efficiency and increases energy consumption. The grinding of moist granular raw materials will then become inefficient, leading to lower yields and potentially a lower quality level of the final product. On the other hand, if more airflow rate is created, this could potentially cause excessive drying of the granular raw materials. This will result in poorer grinding efficiency and an increased risk of dust formation or material loss. This optimum airflow rate provides a good balance between efficient drying and heat transfer, resulting in an energy-efficient grinding process and a high-quality final product.

The airflow rate not only plays a role in drying the granular raw materials, but it also has an important function in conveying the homogeneous cement powder to the separator in the vertical roller mill. The airflow rate creates an upward airflow in the roller mill, which helps in conveying the homogeneous cement powder upwards to the top of the mill where the separator is located. This is essential to achieve the desired separation between coarse and fine cement powder. The optimum airflow rate is therefore crucial to ensure that the homogeneous cement powder is efficiently conveyed to the separator and that the desired fine cement powder is separated from the coarse cement powder. The optimum airflow rate is carefully selected to ensure a smooth conveying process and contribute to an efficient and effective grinding process in the vertical roller mill.

A lower airflow rate will result in insufficient upward force to transport the homogeneous cement powder to the separator. This may lead to blockages or frequent material (re)circulation and thus a reduced efficiency of the grinding process. The homogeneous cement powder will not be separated properly, resulting in a suboptimal end product. On the other hand, a higher airflow rate will result in too strong an upward airflow, causing the homogeneous cement powder to be fed through the vertical roller mill at a higher speed. This may lead to excessive wear of the mill parts and the separator, resulting in a shorter life span of the equipment and higher maintenance costs. Furthermore, a higher airflow rate will negatively affect the efficiency of the separator. The upward force may cause fine particles to be carried away together with coarser particles before the separation has taken place completely. As a result, the desired fine cement powder may be lost and the end product may have a lower quality.

In one embodiment, the desired air flow is created by means of a gas inlet ring that is placed around the rotating grinding table. This gas inlet ring is provided with a series of openings or holes that extend over the entire circumference of the ring. A partition is placed between each opening. Each opening extends from the inner diameter to the outer diameter of the gas inlet ring. This gas inlet ring plays a crucial role in controlling the air flow within the vertical roller mill. Air flows into the vertical roller mill through the openings of the gas inlet ring. The combination of the openings and partitions allows the air flow to be accurately guided and controlled in the desired direction. This is essential to optimize the air flow in the grinding process and to ensure a uniform distribution of the air around the grinding table. Thanks to the series of openings in the gas inlet ring, a balanced distribution of the air over the granular raw materials to be ground is achieved. This equalizes temperature differences and reduces the risk of overheating or uneven processing of the granular raw materials. This leads to a more efficient grinding process and contributes to the production of a high-quality cement mixture with the desired properties, such as particle size, compressive strength and volumetric mass.

In a further embodiment, the portion of the gas inlet ring above which a portion of the stationary wheel mechanism is positioned will not comprise any openings. The inventors have discovered that this specific configuration of the gas inlet ring optimizes the heated gas flow and helps to achieve a uniform and efficient distribution of the heated gas flow around the rotating grinding table. This minimizes temperature differences and minimizes the risk of overheating or uneven processing of the granular raw materials to be ground.

A gas inlet ring that is provided with openings all around its circumference will possibly allow the gas or air to flow freely without resistance.

This can lead to an uncontrolled heated gas flow within the mill, with the air or gas entering the mill at random locations. Such uncontrolled gas flow can negatively affect the efficiency of the classification process, as the gas or preferably the air is not optimally directed to the correct areas within the vertical roller mill. In addition, air leaks can occur around the openings, which will lead to higher air loss and a decrease in the usable air flow used for conveying and classifying the homogeneous cement powder. For this purpose, the gas outlet ring therefore comprises sealed sections, which are provided at a strategic location, i.e. below the mechanism of a stationary wheel. This results in a more controlled heated gas flow, which is directed to specific areas in the vertical roller mill. A further notable advantage of providing this configuration of gas outlet ring is the potential energy saving. By improving the air tightness and reducing the loss of air flow and pressure, the energy consumption will be reduced while maintaining the same air flow.

Simultaneous grinding and drying in the vertical roller mill ensures that the material is dried efficiently during grinding, making it possible to process moist raw materials. The ability to process wet raw materials is very beneficial. Firstly, it increases the versatility and flexibility of the production process, as it becomes possible to use materials with higher moisture contents directly without prior drying. This saves both time and energy, as drying raw materials is normally a time-consuming and energy-intensive step in the production process. Grinding or processing wet materials can reduce the risk of overheating, which can lead to thermal degradation of the product. This is especially important when processing temperature-sensitive materials, such as gypsum and fly ash. Furthermore, the ability to process moist raw materials will contribute to energy savings. Grinding or processing wet materials requires less energy than processing dry materials, as less energy is needed to reduce the size of the material.

The specific airflow rate is essential for the successful operation of the grinding process. A correctly adjusted airflow ensures that the uncontaminated material has sufficient time to be completely ground and dried into cement powder before it is discharged to the built-in separator at the top of the vertical roller mill. This allows an optimum end product to be obtained with an efficient use of energy and raw materials.

Too low an airflow rate would not generate enough airflow to dry the uncontaminated material sufficiently. This can cause moisture problems, such as clumping of the material or incomplete drying, which will adversely affect the quality of the final product. Furthermore, the efficiency of the process will be reduced, as the milling will take longer than expected. In addition, too low an airflow can lead to blockages, as the material can build up in the roller mill.

On the other hand, if the airflow rate is too high, other problems will arise. Too high an airflow rate will lead to excessive evaporation of moisture in the uncontaminated material, making the cement powder and also the final product very dry. This can make the material brittle and fragile, especially in sensitive materials, resulting in quality deterioration and material loss. In addition, heating an excessive amount of gas requires more energy than is required to achieve the desired level of drying. This results in unnecessary energy loss, which increases the operating cost and reduces the efficiency of the drying process. Furthermore, too high an airflow rate will increase the mechanical stress on the equipment. This can lead to accelerated wear of parts in the roller mill, such as the grinding table and the gas outlet port.

Increased wear requires more frequent maintenance and can ultimately result in higher maintenance costs and a shorter equipment life.

According to a preferred embodiment, the gas flow is heated by means of at least one burner, each burner having a thermal power of maximum 10 MW, preferably maximum 9 MW, more preferably maximum 8 MW, even more preferably maximum 7 MW. The heat output of the burners ensures that the air flow can be quickly brought to the desired temperature, thereby optimising the grinding and drying process. Each burner will therefore quickly bring the gas flow, and preferably air flow, to the desired temperature, thereby minimising the heating-up time and limiting energy consumption. It also offers the ability to precisely adjust the air flow temperature to the required specifications, thereby preventing unnecessary energy consumption. This results in a more efficient use of heat and a more optimal energy consumption in the grinding and drying process.

Preferably, the gas stream is heated by a hot gas generator.

Hot gas generators can reach very high temperatures, which is beneficial for heating the gas stream in the vertical roller mill. With higher temperatures, the grinding and drying of the uncontaminated material can be carried out more efficiently, allowing moist raw materials to be processed effectively. Hot gas generators are generally more efficient in converting fuel into heat compared to conventional burners. This results in lower fuel consumption and therefore lower energy costs, which can reduce the overall production costs. Hot gas generators also often offer an even distribution of heat throughout the gas stream. This ensures consistent heating of the uncontaminated material in the vertical roller mill. Finally, hot gas generators have the potential to reduce harmful emissions compared to conventional burners. This contributes to a more environmentally friendly production of the cement mixture and supports sustainability in the cement industry.

According to a preferred embodiment, the vertical roller mill is provided with at least 2, preferably at least 4, more preferably at least 6 and even more preferably at least 8 stationary wheels that roll on the rotating grinding table on which the granular raw materials are ground. The rotating grinding table is provided with a hardfacing layer, with a thickness of at least 2 mm and at most 50 mm, preferably at least 5 mm and at most 45 mm, more preferably at least 10 mm and at most 40 mm, even more preferably at least 15 mm and at most 35 mm, and even more preferably at least 20 mm and at most 30 mm. This hardfacing layer is formed by applying a wear-resistant material by means of welding. The wear-resistant material is selected from a group of iron, tungsten carbide, chromium-cobalt alloy, nickel, stainless steel, manganese, ceramic materials or combinations thereof. By using this specific construction, where the rotating grinding table is covered with a wear-resistant hardfacing layer, the durability and wear resistance of the vertical roller mill is significantly improved. A hardfacing layer with a thickness between 2 mm and 50 mm enables the vertical roller mill to function effectively in heavy and demanding grinding applications, where considerable wear can occur.

In a further preferred embodiment, the hardfacing layer is thicker under the stationary wheels than on the other parts of the rotating grinding table in the vertical roller mill. By making the hardfacing layer thicker under the stationary wheels, additional wear resistance and durability is provided at the points where the greatest load and friction occur. The thicker hardfacing layer ensures that these critical areas are more resistant to wear and erosion, resulting in a longer life of the grinding table. Although the hardfacing layer is thinner on the other parts of the grinding table, it still provides sufficient wear resistance to ensure the long-term functioning of the roller mill. This design ensures that the other parts of the grinding table are not unnecessarily weighed down, thereby promoting the energy efficiency of the roller mill. Providing a thicker hardfacing layer under the stationary wheels and a thinner layer elsewhere on the grinding table combines the advantages of increased wear resistance and durability at critical load points with efficient use of materials on the rest of the grinding table. This enables the roller mill to perform more effectively while reducing the need for frequent repairs or replacement of the grinding table, ultimately resulting in lower maintenance costs and improved productivity.

According to one embodiment, the stationary wheels are provided with a hardfacing layer, with a thickness of at least 2 mm and at most 50 mm, preferably at least 5 mm and at most 45 mm, more preferably at least 10 mm and at most 40 mm, even more preferably at least 15 mm and at most 35 mm, and even more preferably at least 20 mm and at most 30 mm. This hardfacing layer is formed by applying a wear-resistant material by means of welding. The wear-resistant material is selected from a group of iron, tungsten carbide, chromium-cobalt alloy, nickel, stainless steel, manganese, ceramic materials and combinations thereof. First of all, this hardfacing layer increases the wear resistance of the wheels, which is essential given the abrasive nature of grinding granular raw materials. This results in a longer life of the stationary wheels and reduces the need for frequent replacement, thereby reducing maintenance costs and downtime.

In addition, the hardfacing layer increases the mechanical durability of the stationary wheels, making them more resistant to the heavy loads and vibrations that occur during the grinding of raw materials. This contributes to improved operational efficiency and reliability of the vertical roller mill, resulting in less unplanned downtime and more consistent production.

According to a further preferred embodiment of the method, during the grinding, mixing and drying of the uncontaminated feed material, an aggregate is added in the vertical roller mill. The aggregate is selected from the list of: thiocyanate salts, triisopropanolamine, triisobutyl phosphate, benzisothiazolinone, ethanolamine, diethanolamine or mixtures thereof, whereby the cement powder mixes with the aggregate to form a homogeneous cement powder. By adding an aggregate, the final cement mixture will obtain certain desired properties, such as improved strength, durability, and/or workability. The aggregate will influence the performance of the cement, depending on the intended use. The use of a specific aggregate will make it possible to use less cement without compromising performance. This can save costs and reduce the environmental impact, as cement production is a significant

CO2 emissions.

According to a further embodiment, the aggregate is injected into the vertical roller mill and ends up on the grinding table via the nozzles of a water injection system. The water/aggregate mixing ratio can be automatically controlled via the set recipe.

According to a preferred embodiment, the aggregate comprises thiocyanate salts. Thiocyanate salts are used as aggregates in cement mixtures because of their impact on the hydration reaction. The introduction of thiocyanate salts can influence the rate of cement hydration and can result in beneficial effects on the strength development, porosity and microstructure of the cement.

These salts contribute to the promotion of the formation of calcium silicate hydrate (C-S-H), an essential phase of cement hydration. This enhanced formation of C-S-H will lead to a denser cement structure, resulting in cement with increased strength and durability. In addition, the thiocyanate salts will delay the onset of the hydration reaction and regulate the setting time of the cement mixture, which is beneficial for controlling the cement production process. This addition will also have positive effects on the resistance of the cement to certain aggressive chemicals, such as chlorides and sulphates, as well as environmental influences. The use of this addition will improve the durability and resistance of the cement to external influences, which is especially crucial for applications in demanding construction environments or structures in contact with harmful substances.

According to a preferred embodiment, the additive comprises triisopropanolamine. Triisopropanolamine (TIPA) has several effects on a cement mixture. First of all, TIPA will slow down the setting time of cement, which means that the mixture remains fluid for longer and offers more time for its processing. This property is particularly advantageous for large projects where the cement mixture has to be transported over long distances or where additional time is needed for complex constructions. An additional positive effect of TIPA is the improvement of the fluidity and workability of the cement mixture.

Adding TIPA will make the cement mixture easier to pour,

spread and leveled. In addition, TIPA will improve the early strength development of the cement. This means that the cement mix can reach a certain strength more quickly, which is useful in situations where a faster setting is required, for example in certain constructions or repairs. Another advantage of TIPA is its ability to reduce the water requirement of the cement mix without compromising the final strength. This contributes to the durability of the cement and reduces the risk of cracking due to shrinkage. TIPA can also reduce the amount of air entrapment in the cement mix, which improves the density and durability of the cement. Reduced air entrapment is crucial to the overall quality of the cement. Finally, TIPA improves the bond between the cement mix and steel reinforcement, which contributes to the structural integrity and performance of reinforced cement. A strong bond between the cement and the reinforcement is essential for reinforced concrete structures.

According to a preferred embodiment, the additive comprises trisobutyl phosphate. Trisobutyl phosphate (TIBP) is used as an additive in a cement mixture because of its specific function to form air pores.

This results in a controlled network of microscopic air bubbles. TIBP will therefore improve the frost resistance of the cement, among other things. At low temperatures, water molecules in the cement or concrete can expand when freezing, which can cause cracks. The presence of air pores provides space for this expansion, which reduces the chance of damage. This is especially important in cold climates or structures that are exposed to freeze-thaw cycles. Secondly, the presence of air pores ensures increased durability of the cement. The controlled network of microscopic air bubbles reduces the vulnerability of the cement to chemical attacks, such as exposure to acids or salts. This maintains the integrity and performance of the cement, even in aggressive environments. The network of air pores also reduces direct contact between the particles in the cement, resulting in less wear under load. In addition, these air bubbles can act as insulators, giving the cement better thermal insulation. This is especially beneficial in structures where thermal efficiency is important, such as insulating walls or floors. It is essential to add TIBP to the cement mixture in the correct quantities, as excess air voids can weaken the cement and also the final concrete.

According to one embodiment, the additive comprises a maximum of 10 wt% triisobutyl phosphate, preferably a maximum of © wt%, more preferably a maximum of 8 wt%, even more preferably a maximum of 7 wt%, even more preferably a maximum of 6 wt%, even more preferably a maximum of 5 wt%, even more preferably a maximum of 4 wt%, even more preferably a maximum of 3 wt%, even more preferably a maximum of 2 wt%, even more preferably a maximum of 1 wt%. This is an optimum amount of TIBP to be added to the cement mixture in the correct quantities.

It ensures that the cement mix meets standards and specifications, while maintaining the desired properties of the cement. Higher weight percentage will result in reduced strength, durability, workability, and may affect setting time.

According to a preferred embodiment, the additive comprises benzisothiazolinone. Benzisothiazolinone (BIT) will be selected as an additive for a cement mixture because of its properties and advantages as a biocide. BIT is an antimicrobial agent capable of inhibiting or preventing the growth of microorganisms such as bacteria, fungi and algae in the cement. Microorganisms can multiply in cement in humid conditions and contribute to biofilm formation, biological attack and surface damage. By adding BIT, the potential for microbial growth is reduced, resulting in a more durable cement and less potential damage by microorganisms. BIT also contributes to maintaining the aesthetic quality of the cement surface. Microorganisms such as algae can cause undesirable discolouration and staining on cement surfaces. The use of BIT as a biocide can minimise these discolourations and maintain the aesthetic appearance of the cement. Another advantage of BIT is the improvement of hygiene, especially on cement surfaces exposed to environments where hygiene is of great importance, such as the food industry, healthcare or public sanitation.

Due to the antimicrobial effect of BIT, cement surfaces remain cleaner and there is less chance of microbial contamination. Finally, the use of BIT also contributes to a longer life of cement structures. By inhibiting microbial growth, the structural properties and performance of the cement are maintained, resulting in an extended life and lower maintenance costs in the long term.

According to a preferred embodiment, the additive comprises ethanolamine.

Ethanolamine will slow down the setting time, allowing the cement mix to remain fluid for longer and giving more time for processing. This will be beneficial for example in large projects where the cement mix has to be transported over long distances or where extra time is needed for complex constructions.

In addition, ethanolamine acts as a superplasticizer in the cement mixture.

A superplasticizer increases the fluidity and workability of the cement, making the mixture easier to pour, spread and level. This is particularly valuable when filling formwork or pouring complicated shapes. In addition, ethanolamine will also influence the hydration reaction, which affects the strength development of the final concrete. Ethanolamine can also act as a buffer in the cement mixture, regulating the pH value. An optimum pH value is essential for the hydration reaction. By regulating the pH value, the hydration reaction will proceed more efficiently, which will positively influence the final strength of the cement.

According to a preferred embodiment, the additive comprises diethanolamine. Diethanolamine (DEA) has the property of slowing down the hydration reaction of cement, resulting in a cement mixture that remains fluid for longer and offers more time for working and placing. In addition, DEA acts as a superplasticizer in cement mixtures, increasing the fluidity and workability of the mixture. Another important property of

DEA is the reduction of the surface tension of the cement mixture. This facilitates the escape of air bubbles, resulting in cement with fewer air voids and better density. This reduction of air bubbles improves the overall strength and durability of the cement. In addition, DEA influences the crystal growth of the cement, resulting in a finer microstructure in the cement. This can lead to increased strength and improved performance of the cement mixture. The use of DEA as an aggregate also has a positive effect on the workability of the cement into concrete. It slows down the setting time of the cement and reduces the water requirement without compromising the final strength. This makes the cement mixture easier to work with and allows for complex shapes to be achieved while maintaining the required performance.

According to a preferred embodiment, the aggregate comprises a maximum of 10% diethanolamine, preferably a maximum of 5% by weight diethanolamine, even more preferably a maximum of 2.5% by weight, even more preferably a maximum of 1% by weight diethanolamine. A higher concentration of diethanolamine may possibly cause undesirable chemical reactions, which may negatively affect the properties and strength of the final cement product. An excess of diethanolamine will also affect the workability of the cement mixture,

making it more difficult to process and shape the mixture in the desired manner during construction.

According to a further or alternative embodiment, the aggregate comprises thiocyanate salts, triisobutyl phosphate and diethanolamine, preferably the aggregate comprises sodium thiocyanate, triisobutyl phosphate and diethanolamine. This aggregate is distinguished by its ability to significantly increase the initial strength of the cement mixture by activating chemical reactions. This results in superior 1- and 2-day compressive strengths. Furthermore, this aggregate contributes to a better efficiency of both the grinding and separation process, resulting in faster realization of the desired granulometric target and improved grinding efficiency, thereby optimizing both process and energy consumption. Furthermore, it reduces the over-ground particle fraction, which promotes the overall quality of the final product. Finally, it contributes to improving the pourability of cement mixture, thereby minimizing the risk of clogging when emptying silos.

According to a further or alternative embodiment, the additive comprises at least 50 wt% and at most 50 wt% sodium thiocyanate, at most 10 wt% triisobutyl phosphate and at most 10 wt% diethanolamine, even more preferably the additive comprises at least 25 wt% and at most 45 wt% sodium thiocyanate, at most 5 wt% triisobutyl phosphate and at most 5 wt% diethanolamine, even more preferably the additive comprises at least 30 wt% and at most 40 wt% sodium thiocyanate, at most 2.5 wt% triisobutyl phosphate and at most 2.5 wt% diethanolamine, even more preferably the additive comprises at least 34 wt% and at most 36 wt% sodium thiocyanate, at most 1% triisobutyl phosphate and at most 1 wt% diethanolamine. The action of this additive results in the chemical activation of the hydration of the cement, which leads to a significant improvement of the initial strength of the cement. By adding the aggregate, the desired granulometric target, i.e. the desired Blaine value, is also achieved more quickly. Furthermore, the use of the aggregate makes it possible to achieve superior 1 and 2 day compressive strengths. An additional advantage of using this aggregate is the improvement of the pourability of the cement, resulting in less risk of clogging when emptying silos.

This combination of properties makes the aggregate a valuable addition to the cement mix, with positive effects on the final performance of the cement.

According to a further or alternative embodiment, the aggregate comprises triisopropanolamine and triisobutyl phosphate, preferably at least 15 wt% and at most 30 wt% triisopropanolamine and at most 10% triisobutyl phosphate. The use of a mixture of triisopropanolamine and triisobutyl phosphate in the cement mixture offers several advantages due to their unique properties and the mutual synergy between them. Triisopropanolamine ensures that the setting time of the cement is delayed and additional working time is allowed. At the same time, it can also serve as a superplasticizer, which improves the workability and fluidity of the cement mixture and facilitates the pouring and spreading of the concrete. By combining these two aggregates as an aggregate, synergy is created between the retarding function of triisopropanolamine and the air-bubble forming properties of triisobutyl phosphate.

By delaying the setting time, triisobutyl phosphate is given more time to minimize air entrapment and improve density. As a result, the cement mix can benefit from both the workability advantages of triisopropanolamine and the improved density and durability of triisobutyl phosphate.

According to a further or alternative embodiment, the additive comprises triisopropanolamine, triisobutyl phosphate, benzisothiazolinone and ethanolamine. This additive is generally used to increase the output of the vertical roller mill and to improve the quality of the cement powder (granulometry and dry flowability). This raw material is distinguished by its polar properties, which in particular significantly reduce the attractive forces between ground particles, which is the main cause of agglomeration in a vertical roller mill. This additive makes it possible to achieve the desired fineness level. In addition, the dry flowability is also improved.

According to a further or alternative embodiment, the additive comprises at least 15 wt% and at most 30 wt% triisopropanolamine, at most 10 wt% triisobutyl phosphate, at most 100 ppm benzisothiazolinone and at most 50 ppm ethanolamine, preferably the additive comprises at least 17 wt% and at most 28 wt% triisopropanolamine, at most 5 wt% triisobutyl phosphate, at most 90 ppm benzisothiazolinone and at most 40 ppm ethanolamine, more preferably the additive comprises at least 19 wt% and at most 26 wt% triisopropanolamine, at most 4 wt% triisobutyl phosphate, at most 80 ppm benzisothiazolinone and at most 30 ppm ethanolamine, even more preferably the additive comprises at least 20 wt% and at most 25 wt% triisopropanolamine, at most 2.5 wt%

triisobutyl phosphate, maximum 70 ppm benzisothiazolinone and maximum 25 ppm ethanolamine, even more preferably the aggregate comprises minimum 22 wt.% and maximum 23 wt.% triisopropanolamine, maximum 1 wt.% triisobutyl phosphate, maximum 60 ppm benzisothiazolinone and maximum 20 ppm ethanolamine. This highly efficient aggregate is used to improve the quality of the cement mixture, especially with regard to granulometry and dry fluidity. The polar character of the aggregate has a particularly beneficial effect, because it reduces the attractive forces between particles, which are usually the cause of agglomeration. This helps to achieve a finer granulometry. In addition, the use of this aggregate ensures a remarkable reduction or even elimination of contraction phenomena, which makes it possible to further improve the granulometric properties. In addition, the dry fluidity of the cement mixture is significantly improved.

According to a preferred embodiment, a minimum of 100 g/ton and a maximum of 2,000 g/ton, preferably a minimum of 300 g/ton and a maximum of 1,800 g/ton, more preferably a minimum of 500 g/ton and a maximum of 1,600 g/ton, even more preferably a minimum of 700 g/ton and a maximum of 1,400 g/ton, and even more preferably a minimum of 900 g/ton and a maximum of 1,200 g/ton of aggregate is added to the vertical roller mill. By using said optimum amount of aggregate, it is ensured that the desired properties of the aggregate are achieved in order to promote the desired functions in the cement mixture. This is especially important if the aggregate plays a crucial role in optimizing specific characteristics of the cement, such as workability, strength development, retarding effects, or reducing air entrapment. On the other hand, by respecting the said maximum of the aggregate, it is prevented that excessive amounts of aggregate are added to the cement mixture. Overdosing may lead to undesirable effects such as delayed strength development, reduced durability or deterioration of other essential properties of the final concrete.

According to a preferred embodiment, in a next step of the method the homogeneous cement powder is separated into coarse and fine cement powder by a built-in separator. The fine cement powder with a particle size of maximum 200 µm is discharged to a filter to separate it from the heated gas stream. The purpose of this separation is to obtain the desired particle size distribution of the cement powder, which is of crucial importance for the quality and performance of the final cement product.

Different applications require cement with specific properties, such as strength, durability and workability. By separating the ground material into coarse and fine cement powder, the desired particle size distribution can be achieved.

The fine cement powder comprises the smaller particles which have a finer texture. Preferably, the fine cement powder has a particle size of at most 200 um, even more preferably at most 150 um, even more preferably at most 100 um, even more preferably at most 50 um, even more preferably at most 40 um, even more preferably at most 30 um, even more preferably at most 25 um, even more preferably at most 20 um, even more preferably at most 15 um, even more preferably at most 10 um. These fine particles contribute to a better surface finish, increased strength development and improved workability of the cement. Fine cement powder is useful in applications where a smooth surface and high strength are required, such as in the casting of concrete for smooth finishes or constructions with high loads.

The coarse cement powder comprises the larger particles, which have a particle size of at least 200 um, more preferably at least 300 um, even more preferably 400 um, even more preferably at least 500 um, and even more preferably at least 1 COO um. By continuously recycling and processing the coarse cement powder, the vertical roller mill can precisely control the particle size distribution depending on the application and specifications of the final product. It enables the manufacturer to achieve the optimum mix of particle sizes required to produce high quality cement that meets the requirements of various construction applications. Regrinding the coarse cement powder contributes to a more efficient production process and minimizes waste, as the particle size distribution is continuously optimized. This ensures that the final product is consistent and of high quality, which is critical to the performance and durability of the final structures in which the cement is used.

According to a preferred embodiment, the separator will rotate at a speed of at least 130 RPM and at most 180 RPM, preferably at least 135

RPM and at most 175 RPM, more preferably at least 140 RPM and at most 170

RPM, more preferably at least 145 RPM and at most 165 RPM, and even more preferably at least 150 RPM and at most 160 RPM. This carefully selected speed range has significant effects on the functioning of the vertical roller mill and the grinding process. By operating the separator at a speed within the specified range, an effective separation of the fine cement powder and the coarse cement powder is achieved. The speed of the separator has a direct influence on the grinding degree. At higher speeds the cement is ground finer, while at lower speeds a coarser result is obtained. Maintaining the rotational speed within the specified range ensures a consistent fineness of the cement mixture. In addition, the selected speed range also has an impact on the wear and durability of the vertical roller mill parts. Too high a speed will lead to excessive wear of the separator and other critical parts of the roller mill. Maintaining a suitable speed within the specified range provides an optimal balance between grinding efficiency and component durability, which extends the life of the roller mill and minimizes maintenance costs. Finally, the rotation speed affects the energy consumption of the vertical roller mill. Maintaining a suitable speed within the suggested range can help optimize energy consumption.

In a preferred embodiment, the fine cement powder from the vertical roller mill is discharged to a filter to separate the fine cement powder from the heated gas stream. This filtration procedure plays a crucial role in ensuring the quality of the final product. By separating the fine cement powder from the gas stream, the integrity of the cement is meticulously maintained. This translates into an increased and consistent quality of the cement mixture.

In a further or alternative embodiment, one or more additives are added to the fine cement powder after the filtration process to obtain a final cement mixture. The addition of additives to the fine cement powder enables manufacturers to further tailor the properties of the final cement mixture. These additives can further improve strength development, increase durability. This results in a cement product that meets the desired technical standards and performance criteria.

In addition, additives can be used to further influence the workability and rheological properties of the cement mixture, which can be crucial for various applications such as concrete production.

This allows manufacturers to develop cement mixes that are easier to work with on the construction site, which can save time and labor.

According to a preferred embodiment, the fine cement powder from the vertical roller mill is cooled by means of a cooling unit to a temperature of at least 50°C and at most 80°C, preferably at least 52°C and at most 78°C, more preferably at least 54°C and at most 76°C, even more preferably at least 56°C and at most 74°C, even more preferably at least 58°C and at most 72°C, even more preferably at least 60°C and at most 70°C, even more preferably at least 61°C and at most 68°C, even more preferably at least 62°C and at most 66°C. Cement powder that is too warm can form lumps and lose its storage stability. Cooling the cement powder prevents it from forming agglomerates and the powder remains easy to handle and stable for storage. Furthermore, cooling the fine cement powder is also necessary to further improve mixing performance. It can help to achieve an even distribution of the aggregate and promote the homogeneity of the final cement mixture. At higher temperatures, certain chemical reactions between the cement powder and the aggregate can also occur, which can negatively affect the quality of the final product. By cooling the cement powder, the risk of undesirable reactions is minimized. Finally, cooling the fine cement powder will also help to extend the shelf life of the cement mixture. Higher temperatures will cause the cement mixture to age faster and to deteriorate. Cooling can reduce this effect and improve the storage life.

According to a preferred embodiment, the fine cement powder is stored in one or more silos, each of which is positioned above a loading point.

Furthermore or alternatively, if additives are added to the fine cement powder, the final cement mixture will also be stored in the silos mentioned. Each loading point is equipped with a fully automatic weighing system. Each silo installed above a loading point has its own fully automatic weighing system that accurately measures the weight of the loaded cement mixture. This arrangement ensures a direct and immediate measurement of the weight of each loaded batch of cement mixture. The use of separate weighing systems at each loading point ensures a high precision and reliability in measuring the weight, without any transfer of the cement mixture between different weighing stations. The implementation of fully automatic weighing systems at each loading point above the silos offers a very efficient way to load trucks quickly and accurately with the desired weight of cement mixture. Each loading point can be operated independently and simultaneously, allowing multiple trucks to be loaded simultaneously without waiting times. This results in a significant increase in loading capacity and a faster throughput of the cement mixture to the customers. In addition, the use of the weighing systems minimizes the chance of human error or measurements that deviate from the desired weight.

In a second aspect, the invention relates to a grinding system for producing a cement mixture.

According to a preferred embodiment, the grinding system comprises means for dosing granular raw materials, the granular raw materials being selected from the list of: clinker, slag, limestone, fly ash, gypsum and combinations thereof.

An example of means for dosing granular raw materials are automatic dosing hoppers with dynamometric cells. These dosing hoppers are equipped with sensors that can accurately measure the mass or weight of the granular raw materials during the dosing process. The granular raw materials selected from the list, such as clinker, slag, limestone, fly ash, gypsum and combinations thereof, are dosed in a controlled and optimized way in the production process.

The dynamometric cells in the dosing hoppers continuously record the load on the hopper as the raw materials are added. This allows the system to determine the exact amount of raw materials being dosed, ensuring accurate and consistent composition of the cement mixture. These automated dosing devices contribute to the quality and uniformity of the final product, optimize the production process and reduce waste of raw materials.

In addition to the use of dynamometric cell controlled dosing hoppers for accurate dosing of granular raw materials, there are several alternatives available for dosing these raw materials into a grinding system.

Volumetric dosing systems with known internal capacity, belt weighers with integrated load cells, screw dosing systems, pneumatic dosing systems and vibratory feeders.

According to a preferred embodiment, the milling system comprises a metal separator for separating the granular raw materials into contaminated feed material and non-contaminated feed material,

wherein the contaminated feed material comprises metal particles. Integrating a metal separator into the grinding system, as described in the preferred embodiment, is critical for several reasons. First, it helps separate contaminated feed material, which contains metal particles, from uncontaminated feed material. This is essential to ensure the quality and durability of the final cement mixture. Metal particles can have negative effects on the properties of the concrete, such as strength and durability, and can lead to wear and tear on the processing equipment. In addition, the presence of a metal separator helps to extend the life of the processing equipment. Removing potentially harmful metal particles prevents damage to the grinder, mixers and other equipment, which in turn reduces maintenance and replacement costs. Overall, the metal separator helps to maintain the purity of the raw materials and optimize the final product quality, resulting in high-quality cement with improved performance and durability.

According to a preferred embodiment, the grinding system comprises a vertical roller mill for grinding, drying and separating the uncontaminated feed material, which vertical roller mill is provided with means for adding an aggregate to a vertical roller mill 9, the aggregate selected from the list of: thiocyanate salts, triisopropanolamine, triisobutyl phosphate, benzisothiazolinone, ethanolamine, diethanolamine or mixtures thereof, thereby obtaining fine cement powder and coarse cement powder, the fine cement powder having a particle size of maximum 200 µm;

According to a preferred embodiment, the grinding system comprises one or more storage silos in which the fine cement powder or cement mixture is stored.

Preferably, the grinding system is configured to perform the method according to the first aspect of the invention. The same advantages can be repeated, and the same features can be included.

According to a further or alternative embodiment, the grinding system further comprises an automated transport and loading system provided with identification means, adapted to fill trucks with the homogenized cement mixture from the storage silos based on preset weighing parameters. This automated system offers a range of advantages that are of great value to both the production process and the logistics in the construction industry. Firstly, the automated transport and loading system significantly promotes the efficiency of the loading process. By eliminating manual intervention, the time required to fill trucks with the cement mixture is significantly reduced. This increased efficiency results in an improved production capacity and a faster throughput of the cement mixture to various construction sites.

Another important advantage is the accuracy provided by the use of pre-set weighing parameters. The automated system precisely doses the correct amount of cement mix into each truck. This ensures accurate and consistent loading, which is crucial for maintaining the desired concrete quality and minimizing material waste.

In addition, the use of identification means contributes to careful quality control. The system can identify the specific composition of the cement mixture in each silo and then accurately load it into the truck. This approach guarantees a uniform and reliable quality of the concrete, which in turn leads to improved consistency and performance of the concrete structures. An additional advantage is the time saving that the automated system brings. Reducing the loading time of trucks contributes to a streamlined delivery process of the cement mixture to construction sites. This helps to keep construction projects on schedule and minimizes any delays. In addition, the implementation of this automated system contributes to an increased level of safety on the work floor. It reduces the physical interaction of workers when loading the cement mixture, thus reducing the risk of accidents and injuries.

In a third aspect, the invention relates to a use of the method according to the first aspect of the invention or the grinding system according to the second aspect of the invention in the construction sector, in particular for the production of a cement mixture.

First of all, the application of the method results in a significant improvement of the cement quality due to the homogenization of the cement powder with the aggregate. This leads to a better mixing and consistency of the cement, which in turn results in stronger and more durable concrete structures.

A person of ordinary skill in the art will appreciate that the method according to the first aspect of the present invention will be carried out on a milling system according to the second aspect of the present invention. To that end, each feature may relate to each of the aspects, even when the feature is described in conjunction with a particular aspect of the present invention.

In the following, the invention is described by means of non-limiting examples or figures which illustrate the invention, and which are not intended or should be interpreted as limiting the scope of the invention.

FIGURE DESCRIPTION

1= Bunker with granular raw materials 2= Dosing funnel 3= Metal separator 4= Metal detector 5= 2-way changeover 6= Intermediate bunker 7= Waste container 8= Dosing lock

S= Vertical roller mill 10= Separator 11= Water injection system 12= Hot air supply 13= Cooling unit 14= Filter 15= Mixer 16= Additive silos 17= Storage silos 18= Truck

Figure 1 shows a schematic representation of a cement production process according to an embodiment of the present invention. It represents a simplified scheme of cement production.

The granular raw materials 1 are supplied via seven dosing hoppers 2 or loading hoppers 2 which are filled from the bunker with granular raw materials 1.

The granular raw materials 1 include clinker, gypsum, blast furnace slag, fly ash and limestone. A recipe management system enables predetermined optimum compositions of raw materials to be sent to the vertical roller mill 9.

The granular raw materials 1 are weighed from the dosing funnels 2 onto weighing belts. The granular raw materials 1 then fall onto a conveyor belt. Optionally, an additional tank with an additive, for example a chromium VI reducing agent, can be located above this conveyor belt. If necessary, this additive is added to the granular raw materials 1. A metal separator 3 is also placed above the conveyor belt to remove metal particles from the granular raw materials 1. The granular raw materials 1 are then conveyed to a metal detector 4 via a bucket elevator, for example. If the metal detector 4 detects metal, the granular raw materials 1 are separated into contaminated feed material and non-contaminated feed material via a 2-way diverter 5.

Contaminated supply material

The contaminated feed material, i.e. the granular raw materials 1 containing metal, are transported to an intermediate bunker 6. From the intermediate bunker 6, the contaminated feed material is pulled off by means of a slow-moving conveyor belt. A metal detector 4 is located above this conveyor belt. If metal is detected, a 2-way switch 5 is activated. The granular raw materials 1 that still contain metal are discharged to a waste container 7. The uncontaminated part of the feed material re-enters the grinding process via, for example, a bucket elevator.

Uncontaminated feed material

Uncontaminated feed material, i.e. the granular raw materials 1 which do not contain metal, are fed to the vertical roller mill 9 through a dosing lock 8. The vertical roller mill 9 grinds the uncontaminated feed material into cement powder with a desired final fineness. This roller mill is equipped with four stationary wheels which roll over a rotating grinding table. The uncontaminated feed material is fed between the rotating grinding table and the wheels, and the grinding is done by pressure and shear forces. The pressure force is adjusted by a hydraulic system. The uncontaminated feed material which is crushed into cement powder between the rotating grinding table and the wheels is guided to the edge of the grinding table by the rotating movement.

In the vertical roller mill 9, a water injection system 11 will inject water and an aggregate between the stationary wheels and the grinding table to improve the stability of the vertical roller mill. The aggregate is selected from the list of: thiocyanate salts, triisopropanolamine, triisobutylphosphate, benzisothiazolinone, ethanolamine, diethanolamine or mixtures thereof. The aggregate mixes with the cement powder to a homogeneous cement powder.

Furthermore, a heated gas stream is blown into the vertical roller mill 9 to guide the homogeneous cement powder to a separator 10. For this purpose, a gas burner with a thermal power of maximum 10 MW is used to heat the gas stream, which makes it possible to simultaneously dry and grind wet granular raw materials 1. This hot gas stream is supplied via a hot air supply system 12 at the bottom of the vertical roller mill 9. In the separator 10, coarse and fine cement powder are separated. The coarse cement powder falls back onto the grinding table. The fine cement powder, coming from the separator 10, is cooled to a temperature between 50°C and 80°C by means of a cooling unit 13. After this cooling process, the fine cement powder is separated from the heated gas stream by a filter 14. After this, it is transported to a mixer 15 via a dosing lock 8. In this mixer 15 an additive is added to the fine cement powder. This additive is transported from a silo 16 via a dosing lock 8 to the mixer 15. In this mixer 15 the fine cement powder and the additive are mixed. The resulting cement mixture is led to a storage silo 17. For the storage of this end product there are currently 12 storage silos 17 available, with capacities varying from 1,800 to 2,400 tonnes.

These storage silos 17 provide the loading points, which are equipped with a fully automatic weighing system to load a truck 18.

Claims (15)

CONCLUSIONS 1. A method for producing a cement mixture comprising: a. the supply of granular raw materials 1, whereby the granular raw materials 1 are selected from the list of: clinker, slag, limestone, fly ash, gypsum and combinations thereof; b. separating the granular raw materials 1 into contaminated feed material and non-contaminated feed material by means of a metal separator 3, the contaminated feed material comprising metal particles; c. discharging the uncontaminated material to a vertical roller mill 9 for grinding, mixing and simultaneously drying the uncontaminated feed material into cement powder, the vertical roller mill 9 being provided with at least 2 stationary wheels which roll on the rotating grinding table on which the granular raw materials 1 are ground, the rotating grinding table being provided with a hardfacing layer, a heated gas stream being blown into the vertical roller mill 9 during grinding through an annular gas outlet opening, which gas outlet opening is placed around a rotating grinding table, a partition being placed between each opening, which gas outlet opening is placed around a rotating table, whereby an air flow rate of at least 650,000 m3/h and at most 800,000 m3/h is created, d. adding an additive in the vertical roller mill. The aggregate comprises: triisobutyl phosphate in a quantity of up to 10% by weight of triisobutyl phosphate relative to the total weight of the aggregate, thiocyanate salts, preferably sodium thiocyanate, more specifically in a quantity of at least 20% by weight and up to 50% by weight of sodium thiocyanate relative to the total weight of the aggregate, triisopropanclamine in a quantity of at least 15% by weight and up to 30% by weight of trissopropanolamine relative to the total weight of the aggregate, diethanolamine in a quantity of up to 5% by weight of diethanolamine relative to the total weight of the aggregate, benzisothiazolinone in a quantity of up to 100 ppm benzisothiazolinone relative to the total weight of the aggregate, ethanolamine in a quantity of up to 10% by weight of ethanolamine relative to the total weight of the aggregate, these components are mixed with the cement powder to form a homogeneous cement powder; e. separating the homogeneous cement powder by means of a built-in separator, wherein the homogeneous cement powder is separated into coarse cement powder and fine cement powder, wherein the fine cement powder has a particle size of maximum 200 um, wherein the coarse cement powder falls back onto the rotating grinding table for regrinding, wherein the built-in separator comprises a rotor, wherein the rotor rotates at a speed of at least 130 RPM and at most 180 RPM. 2. Method according to claim 1, characterised in that at least 100 g/ton and at most 2 000 g/ton of aggregate is added in the vertical roller mill 9. 3. Method according to any one of the preceding claims 1 to 2, characterised in that the fine cement powder is discharged to a filter 14, where the fine cement powder is separated from the heated gas stream. 4. Method according to any one of the preceding claims 1 to 3, characterised in that the contaminated material is discharged to an intermediate bunker where a metal check takes place to further separate the non-contaminated material from the contaminated material, the contaminated material being discharged to a waste storage facility, the non-contaminated material being discharged to the vertical roller mill 9. 5. Method according to any one of the preceding claims 1 to 4, characterised in that the fine cement powder from the vertical roller mill 9 is cooled by means of a cooling unit 13 to a temperature of at least 50°C and at most 80°C. 6. Method according to any one of the preceding claims 1 to 5, characterised in that the granular raw materials 1 are supplied via dosing funnels, the dosing funnels being provided with dynamometric cells. 7. Method according to any one of the preceding claims 1 to 6, characterised in that the hardfacing layer has a thickness of at least 2 mm and at most 50 mm, formed by applying a wear-resistant material by means of welding, the wear-resistant material being selected from a group of: iron, tungsten carbide, chromium-cobalt alloy, nickel, stainless steel, manganese, ceramic materials and combinations thereof. 8. Method according to any one of the preceding claims 1 to 7, characterised in that the gas stream is heated by means of at least one burner, each burner having a thermal power of maximum 10 MW. 9. Method according to any one of the preceding claims 1 to 8, characterised in that the fine cement powder is stored in one or more silos, each of which is positioned above a loading point, which loading point is equipped with a fully automatic weighing system. 10. A method according to any one of the preceding claims 1 to 9, characterized in that the vertical roller mill is provided with a water injection system, the water injection system comprising sprayers and being suitable for adding the aggregate to the grinding table. 11. Method according to any one of the preceding claims 1 to 10, characterised in that the portion of the gas inlet ring above which a part of the mechanism of the stationary wheels is located does not comprise any openings. 12. Method according to any one of the preceding claims 1 to 11, characterised in that the stationary wheels are provided with a hardfacing layer with a thickness of at least 2 mm and at most 50 mm, the hardfacing layer is formed by applying a wear-resistant material by means of welding. The wear-resistant material is selected from a group of iron, tungsten carbide, chromium-cobalt alloy, nickel, stainless steel, manganese, ceramic materials and combinations thereof. 13. A grinding system for producing a cement mixture, comprising: — means for metering granular raw materials 1, the granular raw materials 1 being selected from the list of: clinker, slag, limestone, fly ash, gypsum and combinations thereof; — a metal separator 3 for separating the granular raw materials 1 into contaminated feed material and non-contaminated feed material, the contaminated feed material comprising metal particles; — a vertical roller mill 9 for grinding, drying and separating the uncontaminated feed material, which vertical roller mill is provided with means for adding an aggregate to the vertical roller mill 9, the aggregate comprising triisobutyl phosphate in a quantity of up to 10% by weight of triisobutyl phosphate relative to the total weight of the aggregate, thiocyanate salts, preferably sodium thiocyanate, more specifically in a quantity of at least 20% by weight and up to 50% by weight of sodium thiocyanate relative to the total weight of the aggregate, triisopropanolamine in a quantity of at least 15% by weight and up to 30% by weight of triisopropanolamine relative to the total weight of the aggregate, diethanolamine in a quantity of up to 5% by weight of diethanolamine relative to the total weight of the aggregate, benzisothiazolinone in a quantity of up to 100 ppm benzisothiazolinone relative to the total weight of the aggregate, ethanolamine in a quantity of maximum 10% by weight of ethanolamine relative to the total weight of the aggregate, thereby obtaining fine cement powder and coarse cement powder, the fine cement powder having a particle size of maximum 200 um; — one or more storage silos 17 in which the cement mixture is stored. 14. A grinding system according to claim 12, characterized in that the grinding system comprises an automated transport and loading system provided with identification means, suitable for filling a truck 18 with the cement mixture from the storage silos 17 on the basis of preset weighing parameters. 15. Use of the method according to any one of claims 1 to 12 or the grinding system according to any one of claims 13 to 14 in the construction sector, in particular for the production of a cement mixture.