Method of and apparatus for continuous analysis of samples from a continuous material stream, and method of and arrangement for mixing cement implementing or using the analysis method and apparatus, respectively

Abstract

A method (30) of continuous analysis of samples from a continuous bulk raw material stream comprises continuously diverting a fraction from the continuous bulk raw material stream of a production process to a sample processing and analysis apparatus (400; 700), and continuously processing, in the sample processing and analysis apparatus (400; 700), the diverted fraction (171) into a continuous sample raw material string or flow having predefined and constant properties. The continuous sample raw material string or flow is passed past an illumination zone or spot, which is illuminated by a light source (520) emitting infrared light. Light reflected by the continuous sample raw material string or flow at the illumination zone or spot is received in a sensor, and the properties of the reflected and / or transmitted light received at the sensor are analysed and evaluated.

Description

[0001] TITLE

[0002] METHOD OF AND APPARATUS FOR CONTINUOUS ANALYSIS OF SAMPLES FROM A CONTINUOUS MATERIAL STREAM, AND METHOD OF AND ARRANGEMENT FOR MIXING CEMENT IMPLEMENTING OR USING THE ANALYSIS METHOD AND APPARATUS, RESPECTIVELY

[0003] FIELD

[0004] This invention generally relates to closed-loop control of a process of mixing bulk materials, notably minerals for the cement industry. The invention relates in particular to analysing the composition of the bulk materials, and to monitoring and controlling the production process, e.g., in the cement industry.

[0005] BACKGROUND

[0006] Bulk materials are utilized and produced in industrial applications such as cement production, scrap material processing, and process waste handling. Bulk materials can be characterized as materials used in industrial applications that are transported in high volumes on a continuously moving means after the materials are crushed, ground or otherwise reduced in size for purposes of easier handling in downstream production. Typical bulk materials include heterogeneous masses of coarsely crushed mined or quarried bulk materials such as ores of limestone, gypsum, bauxite, copper, zinc, lead, iron, silica, phosphate rock, potash, clay, rare earths. The bulk material may be provided in different degrees of viscosity and fineness, from stones down to fine powders, from sticky to easily separable. Additives may be provided in liquid form. Other bulk materials transported similarly include scrap materials, chalk, coal and coke, alumina, marl, pyrite, fly ash, process waste, etc. Such bulk materials are utilized in process streams in which the bulk materials are fed or supplied from a source continuously, in batches, or over an extended period of time.

[0007] In some processes that utilize bulk materials, components or raw materials are transported from dispensing sources, such as bins or silos, mixed together, and processed to form a new material. Typically, bulk materials are transported through these processes in large volumes utilizing conveyor belts. A conveyor belt consists of two end pulleys, with a continuous flexible heavy-duty rubber, rubberized fabric, or metal composite belt that rotates about them in a continuous closed loop. The pulleys are powered, moving the belt and the loaded bulk material on the belt typically to another belt transfer point, or other belt system used in the specific manufacturing process forward at fixed or variable speeds. Some processes that transport high volumes of bulk materials use pneumatic tubes or air slides to transfer the bulk materials between process points.

[0008] During the transportation and processing of bulk materials, it becomes necessary to analyse the exact or average chemical or mineral content and composition of the bulk material for control purposes. Such analysis is especially necessary when the bulk materials are mixed, ground, or processed to form new materials. Notably natural and recycled minerals may heavily vary in their chemical composition and structure due to their origin or contamination from prior use. In the context of process waste, the characterization of bulk materials can be effective in diagnosing the effectiveness of a process and monitoring for contaminants. Acquiring sufficiently accurate and detailed knowledge of the physical and chemical state of a moving stream of bulk materials can be difficult and challenging.

[0009] As noted above, cement processing is characterized by the processing and formation of bulk materials. Cement can be formed by mixing and intergrinding different raw material components. An exemplary flow diagram for a cement manufacturing process 10 is depicted in Figure 1. In this typical version of the cement manufacturing process, one or more feeders 101-103 introduce crushed raw components on to a first conveyor belt, indicated by the arrow 110. The type of raw components combined to ultimately form cement depends on the type of cement being produced and the composition of the raw components being utilized. Typical raw components include calcareous materials, such as limestone, gypsum, clinker, marl, chalk, oyster shells, aragonite and the like, argillaceous materials, such as clay, shale, slate, slag, fly ash, sand, sandstone and the like, ferruginous material such as mill scale, iron ore or pyrites, alumina, such as bauxite or materials high in alumina, and certain additives that contribute to the characteristics of the cement. In some parts of the world, the limestones, marls and the like that include the calcareous component may also include sufficient proportions of the argillaceous material, such as aluminium oxide and iron oxide, so that only siliceous materials need to be added. Siliceous materials can similarly contain argillaceous material so that such siliceous material may incorporate the needed aluminium oxides. Filler materials are used in modern cement production to reduce the amount of burned clinker. Classic filler materials are pozzolan, fly ash, limestone and blast furnace slag. Each raw component can have a different mass particle size. For instance, one raw component may have a greater relative particle size while another raw component may have a much smaller average particle size. As a result, the overall admixture of these components can differ in terms of different chemistry as well as widely different particle sizes.

[0010] The raw components are typically admixed in predetermined proportions and conveyed to a mill 130. The proportions in which the raw components are admixed can be controlled by the rate in which the feeders dispense the raw components and the rate at which the conveyor belts transport the raw components. As a result, each of the raw components are admixed at different rates of quantity per unit time. Table 1 shows the relative mineral composition of a typical admixture:

[0011] Table 1

[0012] The admixed raw components are transported through a series of coarse and / or fine grinding mills (only exemplary mill 130 represented in the figure). The mills integrate the raw components into a homogeneous mixture and dispense a coarse granulation, such as between 50 and 100 mesh, or a fine granulation, such as smaller than 100 mesh, respectively. The mills can be any kind of grinding apparatus, such as an industrial roller, rotary mill, ball mill, disc mill, cage mill, muller mill, high speed mill or the like. A particle separator 150 downstream of the mill 130 rejects too coarse particles and sends them back through the so-called recirculation 190 back into the mill 130. A preferred type is the rotary particle separator because of an easy control the separation threshold. Mill 130 dispenses the resulting raw mixture stream 170 onto a second conveyor belt 113, which transports the raw mixture to a silo 210 for intermediate storage. Silo 210 serves as a buffer so that the production can be continuous. For the dispatching process 290, pre-ground or already fine filler material 220 may be added through filler stream 260, producing a final mixture 240. The dosage 280 is supervised by a second laboratory 600 analysing the final mixture 240.

[0013] One important consideration in the creation of cement is that the proportion of components must be maintained within narrow limits. Differences in the amount of components introduced in the raw mixture and differences in the composition of the components formed during processing affects the quality and grade of cement. Other factors that influence the type of cement produced include temperature, residence time, size of the particles and intimacy of contact between the particles. As a result, care must be taken in making decisions to consider both upstream conditions and predict downstream results when any adjustments are made to the mix of raw components materials in order to achieve the desired result.

[0014] Thus, on its way to silo 210 the raw mixture stream 170 passes a first laboratory station 300, where a small fraction 171 of the raw mixture stream 170 is analysed. Traditionally, analysis and monitoring of either raw material components, blended materials such as the raw mixture, and processed cement has been accomplished by extracting samples from the continuous flow and transporting them either manually or via an automatic "tube post" pneumatic capsule sampling and conveying system from the sampling point to a central laboratory for analysis. The laboratory would then prepare and analyse the samples utilizing a variety of standard equipment and instruments. The result of this time-consuming analysis is used to control both the amount of the basic ingredients 101, 102, 103 added and the particle separators speed for fineness adjustment 150. This arrangement, while providing high accuracies, is deficient because the aggregate time required for sampling, splitting, transport, preparation, and analysis can vary from a minimum of 15-30 minutes to an hour or more. During this delay, the stream of components and mixtures continue to be processed such that tons of the fast-moving bulk materials represented by each sample analysed have long passed points of control and adjustment. The path followed by these materials from the feeders, along the conveyor belts, through the grinders and into the silos is a continuous flow or stream. Any adjustments subsequently made to the process will not be able to correct deficiencies in raw mixtures and processed cement that have moved beyond positions in which corrective action may be taken. These adjustments will only affect raw components, raw mixtures and processed cement that are generated subsequent to the adjustments.

[0015] Another difficulty with the above is that this method does not provide a solution to potential problems that require prompt dynamic corrective actions. For instance, the rate of admixing raw components depends not only on the type of materials being mixed but also on the composition of those components. If a feeder contains raw components that lack compositional uniformity, the sample analysis may not be representative of the current stream. Thus, any adjustments that are made after a sample analysis may not be appropriate for the current components and respective composition of those components.

[0016] For instance, U.S. Patent 4,026,717 describes a method for monitoring the production of cement in which samples are taken from the material flow stream at various points along the process. After the samples are processed by a coarse mill, a pre-kiln sampler using a bucket extracts samples every 15 seconds and deposits the samples on a second conveyor belt. The belt transports the samples to a blending mill that collects develops a composite sample over 15 minute time period. A conveyor then transports the composite sample to an x-ray analyser. These samplers are also disclosed for extracting samples from the kiln and the clinker cooling system.

[0017] Analysis of cement bulk materials can also require knowledge of the oxides or mineralogical phases (molecular polymorphs), or a standard calculated module based on the quantity of the oxides (or other desired measured properties) present, for standard quality control. Some analytical devices used may not measure either oxide or actual phases directly, but only the elemental values.

[0018] A few methods to achieve elemental, and thereby, oxide forms of the chemical constituents of the various raw or blended materials have been utilized. They are, however, limited in terms of practical application and mainly make use of atomic events based upon neutron activation via nuclear activation. These so-called Prompt Gamma Neutron Activation Analysis (PGNAA) systems require either radioactive isotopes for neutron flux, such as the isotope of Californium, Cf2S2, or a neutron generator (tube). In these cases, the introduced neutrons cause momentary and temporary disequilibrium of the nuclei of contained materials resulting in emission of gamma radiation signatures as a reaction to restore equilibrium. Neutron activation systems apply a potentially hazardous (to humans) technique which requires protective permanent careful shielding to avoid and minimize direct or indirect exposure and frequent costly isotope or generator tube replacements. The short half-life of Cf2S2 at only approximately two and a half years and the requirement for replacement of neutron tube generators, normally every one to one and a half years, represent both expensive maintenance costs as well as the need to address increasing difficulties in convincing authorities of the public safety in transport and operation of both these types of neutron sources. Further, the resultant gamma radiation from the neutron activation of bulk materials that is caused by neutron flux bombardment of the nuclei of the irradiated materials represents potential additional health and environmental hazards. Other on-line techniques that have been attempted, such as high- power X-ray tube systems, or X-ray diffraction systems, may also require strict adherence to local regulatory authorities. In some venues, the presence of certain of these various classes of all of such devices may be restricted or prohibited altogether.

[0019] What is needed is a system and method for analysing bulk materials that provides real-time analyses for rapid and real-time control. It is critical that the apparatus and method analysed the bulk materials as they pass through. It would be beneficial if such an apparatus and method analysed the bulk materials in the process stream. Additionally, such apparatus and method must not alter or touch (either physically or chemically) the streaming bulk materials. As a result, the bulk materials analysed are to pass uninterruptedly along the process flow. Another benefit would be for the apparatus and method to implement the analysis of the bulk materials as it is transported on a moving conveyor belt from one process station to the next.

[0020] US 2003 / 0123056 discloses a hyperspectral imaging instruments array for exploiting detailed multispectral, hyperspectral and ultraspectral imaging and nonimaging signature information. This is accomplished in real-time in order to identify the unique spectral characteristics of the target. The instruments array contains at least one mechanically integrated hyperspectral sensor installed on a fixed or moveable hardware frame and co-boresighted with a similarly mounted digital camera, calibrated visible light source, calibrated thermal source and calibrated fluorescence source on a small spot on the target. The target is moved across the array, allowing the array to effect collection of absolute radiometrically corrected spectral data against the target at high spatial and spectral resolutions.

[0021] US2004 / 232339 discloses a hyperspectral imaging workstation that includes both UV and VNIR sensors together in a single enclosure. Each sensor captures an image of a target or specimen, resulting in respective UV and VNIR data sets which are then merged into a single hyperspectral data set that includes a highly correlated contiguous spectral band throughout a range of from 200 to 1000 nanometres

[0022] W02006 / 054154 discloses an apparatus for and a method of identifying and sorting target particles using reflectance spectroscopy in the visible (VIS) to the near infrared (NIR) spectral range, are disclosed. In one version, a hyperspectral imaging apparatus is used to identify and sort target particles within a batch of particles, the apparatus comprising a tray for supporting the batch of particles, levelling means for levelling the batch of particles into substantially a monolayer, a hyperspectral scanning system for scanning the batch of particles, to produce a hyperspectral image of the batch of particles, a classifier for determining the pixel coordinates of target particles in the hyperspectral image, converter means for converting the pixel coordinates to world coordinates of the target particles on the tray, and target particle extraction means for picking the target particles based on the calculated world coordinates and for transferring the picked target particles to a storage arrangement.

[0023] W02004 / 106874 discloses an apparatus and a method for photo-electric measurement. The apparatus comprises a single or a plurality of photo-electric conversion devices, preferably array sensor(s) such as CCD, CMOS, CID and the like, an optical system which is modularly expandable in one axis or a plurality of axes in order to acquire electromagnetic radiation from a line or area of any desired size on an object, with any desired resolution, wherein the said optical system preferably separates the said electromagnetic radiation modularly into a plurality of smaller segments, and projects electromagnetic radiation corresponding to the said smaller segments onto said single or a plurality of individual photoelectric conversion devices and sensor electronics related to said photo-electric conversion device(s) which enable the operating mode and functionality of said photo-electric conversion device(s) to be defined and changed in real-time, whereby functions such as the readout sequence of pixels and unlimited flexibility of pixel binning in two dimensions are fully programmable, and said photo-electric conversion device(s) may operate and / or be controlled independently and / or simultaneously.

[0024] Standard analytics of mineral phases are X-ray powder diffraction (XRD) and X-ray fluorescence (XRF) for the elemental composition. XRF elemental analysis is also used for legal justification. Although attempts have been made to establish online devices, they lack sample frequency. So normally these methods require that material to be examined is pre-ground into powder and pressed into tablets. The production of these tablets is elaborate and time consuming with the consequence that the production process cannot be controlled in closed loop.

[0025] With optical technologies such as near infrared (NIR) spectroscopy, the requirements for samples are more relaxed and thus allow in principle for (nearly) real time measurements. SUMMARY OF THE INVENTION

[0026] It is therefore an objective of the present invention to provide a robust, consistent, real-time bulk material analysing system for identifying and quantifying the elemental, chemical, and mineralogical characteristics of a bulk material mixture.

[0027] This object is achieved by the method of analysis presented in claim 1 , the sample processing and analysis apparatus presented in claim 9, the process of mixing cement presented in claim 15, and the arrangement for mixing cement presented in claim 18. Advantageous embodiments and developments are presented in respective dependent claims.

[0028] The present invention builds on optical analysis of the material stream, more particular on optical analysis using infrared light. Infrared is commonly separated into five regions by the wavelength:

[0029] Near-infrared having wavelengths in a range of 0.78 pm - 1.4 pm Short-wavelength infrared having wavelengths in a range 1.4 pm - 3 pm Mid-wavelength infrared having wavelengths in a range of 3 pm - 8 pm Long-wavelength infrared having wavelengths in a range of 8 pm - 15 pm Far-infrared having wavelengths in a range of 15 pm - 1000 pm

[0030] Near-infrared spectroscopy (NIRS) is a spectroscopic method that uses the nearinfrared region of the electromagnetic spectrum (from 780 nm to 2500 nm). Low cost materials like quartz transmit NIR radiation and can be used for large and extensive optics. Also black body emitters peak at NIR wavelengths. Planck’s well- known law of blackbody radiation describes the higher energy levels at shorter wavelengths. It is notable that the energy levels increase with the power of 5 in intensity which, in addition to high performance photo-conductive detectors being widely available, renders NIR better suited for sensing purposes than the regions on the farther end of the infrared spectrum. Near infrared (NIR) measurements were therefore commonly established in process analysis and control due to the comparatively high signal amplitudes in the regions of interest and the resulting good signal to noise ratios, strong detector sensitivity, availability of sensors with high sampling frequency and minimal sample preparation efforts. However NIR measures mainly optical-overtones of the fundamental molecular vibrations and software is needed to relate these overtones to the fundamentals. Due to frequency-overlaps, this is not always possible, especially when no other information like material type or contained mineral phases are known. Also reference samples measured with typically one of the X-ray based standard methods are required. The resulting black box calibration model is hard to transfer to other plants and sites with slightly different materials and frequent recalibrations are required. Further SiC>2, a key oxide in earth’s crust and the main component in cement beside CaO is hardly detectable in the NIR frequency range especially when amorphous, which makes cement and other minerals analysis highly difficult.

[0031] LWIR stands for Long Wave Infrared in the range of 8 - 15 pm. Successful qualitative infrared laboratory measurements were done in laboratories in the 1970’s, long before NIR became the technology for infrared process measurements. Challenges are infrared source intensity, detector sensitivity without liquid nitrogen cooling for the given wavelength range and high demands regarding optics and sample preparation. Recent developments in technology push for a re-evaluation of this frequency region of highest information, the so called fingerprint region.

[0032] Optical online measurements in the mid to far infrared region require high sample preparation efforts in order to provide consistent and reliable results. That led to the common opinion that mid to far infrared measurement present too high obstacles to overcome for practical and frequent use in at-line, in-line and on-line process analysis, not even talking about usage for process control purposes. For good process control, the measurements should be as close as possible to the production process, with a minimum time delay, and as consistently as possible.

[0033] The inventors exploit the fact that the LWIR (8 - 15 pm) allows direct measurement of the fundamental vibrations and accordingly direct assignment of peaks to molecular chemical properties. This so-called fingerprint region may be used for qualitative measurements and also for trace identification (% weight<1).

[0034] Quantitative measurements are believed to be limited to resolutions of percentages for standard absorbing materials. Using the mid to long wave IR frequency region allows to directly assign spectral absorption features to molecular structures (qualitative analysis) leading to more robust calibrations.

[0035] Using mid to long wave infrared spectroscopy for determining chemical compositions and functional groups typically involves a directing a corresponding light-beam on the sample, and measuring either the diffuse reflectance or transmission. The sample is placed on a holder, which positions and holds the sample in place during the measurement. A sample that is uniformly distributed and well-defined in shape and thickness is critical for achieving a satisfactory infrared absorbance spectrum.

[0036] Frequently, a compartment or holder with one or more windows, e.g. an infrared transparent cell, is used for placement of the sample. These windows are slightly absorbing and may cause a shift in the spectra. Also the window might scratch over time, changing its reflective characteristic and reduce its thickness and absorbance over time. Further it might not be chemically inert.

[0037] While direct transmission measurements are applicable for gases and liquids, solids need to be molten into a thin film. Where this is not possible another technique is to disperse the sample in an infrared transparent matrix, often potassium bromide, and press it into a pellet. The mixture is also fine-ground, which increases uniformity, but adds another step onto the already elaborate process. Broken tablets or tablets with a non-even or scratched surface are common as well.

[0038] In both cases non-uniform distributed films or tablets lead to high variability of illuminated material leading to high variations in the spectrum’s absorbance peaks. While qualitative conclusions are still possible, for quantitative measurements statistical uniformity is a requirement.

[0039] As mentioned before, traditional sample preparation is a tedious, labour-intensive, multi-step and yet error-prone process. This effort is slightly reduced, when diffuse reflection techniques are used, where material compactness and dispersion as well as the optical illumination surface start to dominate the spectral errors, not to mention temperature outside of climatized laboratories.

[0040] Further, the amount of material measured is small compared to amounts processed by an industrial process. A proper selection involving homogenization has to be made. Therefore the process of obtaining a representative amount from the process should not be neglected, but often is, due to the additional work it involved when dozens of samples have to be homogenized and evaluated according to one of the traditional sample preparation processes above.

[0041] Most important, the sample temperature between the bulk raw material flow and the sample should remain identical, as, in accordance with Planck’s law, the effects of the self-emitted radiation due to the sample temperature become more pronounced in in the MIR and LWIR range, i.e., towards the long and far infrared region. Samples taken to a separate laboratory may have a significantly different temperature than the bulk raw material they are taken from, which may render the measurements inaccurate.

[0042] The inventors identified that this poses a problem for MIR, LWIR and FIR range measurements and propose continuous flow of the sample measurement close to the manufacturing line, which suppresses or at least reduces temperature changes in the sample. Reducing the samples self-emitted radiation leads to clearer absorption features and generally less noise.

[0043] In light of the discussion above, a method of continuously analysing samples from a continuous raw material stream in accordance with a first aspect of the present invention comprises continuously diverting a fraction from the continuous raw material stream of a production process to a sample processing and analysis apparatus. The expression “raw”, in particular in connection with the analysis, is used herein to emphasize that, throughout the processes described herein, the material is not processed into its final form, i.e., in the case of cement, is not cured or otherwise transformed into a form that is no longer usable in the same way as the raw material from which the fraction is diverted. The diverted fraction is then continuously processed, e.g., in a sample conditioning unit of the sample processing and analysis apparatus, into a continuous sample raw material string or flow having predefined and constant properties. Predefined properties include, inter alia, one or more of a thickness, cross sectional dimensions, a compactness, a density, a surface roughness or finish, a temperature, a humidity, and the like. The continuous sample raw material string or flow output from the sample preparation apparatus is passed past an illumination zone or spot. The illumination spot is illuminated by a light source emitting infrared light. The light source emits light in the MIR, LWIR, or FIR range. Light reflected by the continuous sample material flow at the illumination zone or spot is received in a sensor, and the properties of the reflected light are analysed and evaluated. Analysing the properties comprises, inter alia, comparing the spectrum, a phase shift and / or a polarisation of the reflected light with corresponding reference values. The optical analysis benefits greatly from the processing of the sample raw material into a continuous sample raw material string or flow having predefined and constant properties, in particular across its illuminated surface.

[0044] In one or more embodiments of the method continuously processing the diverted fraction into a continuous sample raw material string or flow comprises extruding the diverted fraction, or producing a vertical trickle or drizzle of the sampled raw material.

[0045] Extrusion is a process used for continuously creating strings having a fixed cross- sectional profile by pushing material through a die of the desired cross-section and shape. During extrusion, malleable to viscous masses are continuously pressed out of a shaping opening, also known as a calibration, nozzle, die or mouthpiece. The extrusion of ceramic bodies is also known as extrusion moulding. The extrusion of metals is a similar process. Two main advantages of extrusion over other manufacturing processes are its ability to create very complex cross-sections, and to work materials that are brittle, because the material encounters only compressive and shear stresses. It also creates excellent surface finish, smooth surface, and gives considerable freedom of form in the design process. Further, extruding need not necessarily alter the material properties, i.e., the general properties of the extruded raw material can stay identical to the input raw material, permitting an actual analysis of the material in its raw form. Extruders typically include a screw-like arrangement that rotates in an enclosure. The enclosure tightly encloses the screw such that the rotation moves any material input at one end towards the opposite end of the screw. While moved by the screws the material is homogenized, transported and compacted by friction between the material, the screw and the enclosure. Dual screw extruders may provide an improved mixing and homogenisation of the material over single-screw extruders. The enclosure or a part thereof may be temperature controlled, giving the material and screw a desired temperature.

[0046] The vertical trickle or drizzle may be produced by a funnel-like or hourglass-like arrangement, where the illumination zone or spot is located at the neck and the flow of the material through the neck is regulated by an controllably actuated plug.

[0047] If open beam measurement is performed, the thickness of the sample raw material string or flow has to be selected such that the shape is stable, with minimal bending or breaking. On the other hand the thickness should be kept thin enough to measure as much material as possible. Thickness ranges spanning a few millimetres have been found useful.

[0048] It is noted that in the context of this specification the term continuous, notably in connection with transporting or measuring, may include temporary variations in speed or brief stops, if required for the respective process step.

[0049] In one or more embodiments the method further comprises adding excipients to the diverted fraction prior to processing it into the continuous sample raw material string or flow. Adding such excipients may be targeted to achieve a more stable extrusion output, an improved surface roughness or finish, a reduced friction, a reduced amount of airborne particles like dust, and the like. It is also possible to add a well-calibrated amount of specific materials for calibration purposes, e.g., potassium bromide. Excipients may also be added for diluting the sample, which may result in a better dispersion of the light impinging on the sample string or flow in the illumination zone or spot, and which also may enhance the spectral response of the sample. The sample raw material string or flow output by the sample processing and analysis apparatus may be supervised by the optical measuring arrangement or by other sensors configured for controlling the consistency of the sample raw material string or flow.

[0050] In one or more embodiments the method further comprises heating or cooling and / or controlling the humidity of the continuous sample raw material string or flow to attain a predetermined temperature and / or humidity while being passed the illumination zone or spot. Temperature and / or humidity control, along with the continuous movement, of the sample material string or flow through the illumination zone or spot reduces the heat-up and deviation effects and keeps blackbody radiation small and at point, minimising its effects on absorbance and reflexion properties, effectively improving the measuring accuracy.

[0051] In one or more embodiments of the method the sample raw material string or flow is output, by the sample processing and analysis apparatus, at substantially the same speed as the continuous raw material stream of the production process. This advantageously reduces the time offset between the material composition going into the production process and the time at which the fraction was diverted off of the continuous raw material stream. It is also possible to have the continuous raw material stream follow a longer path than the diverted fraction to compensate for different flow speeds. The latter may permit to adjust the composition in time with the results of the continuous analysis, e.g., through a second dispenser arrangement that adds one or more components to the continuous raw material stream to achieve a desired composition.

[0052] In one or more embodiments the method further comprises calibrating the sensor’s input at regular intervals or upon new bulk raw materials being received at the input of the production process. This may help to keep the measurements stable and comparable over time, and to compensate for wear or dirt build-up in the measurement apparatus. For baseline calibration the sample raw material string or flow may be replaced with potassium bromide once. The measurement of the potassium bromide is then compared to a part of the illumination impinging on a reference material, e.g., a gold plate, that is moved right above the sample material string into the illumination spot. This gold plate is then regularly measured during continuous operation and back-calculated as if it was potassium bromide in the original location. This permits compensating environmental effects and illumination drifts on a regular basis.

[0053] In one or more embodiments the method further comprises grinding the diverted fraction prior to processing it in the sample processing and analysis apparatus. This may be expedient when the raw material stream has a granularity that is too large for obtaining useful results through optical analysis, or for processing the diverted fraction into a continuous sample raw material string or flow having predefined and constant properties across the illuminated surface.

[0054] In one or more embodiments the method further comprises merging at least a portion of the sample raw material string or flow from the sample preparation apparatus with the continuous raw material stream of the production process after the analysis.

[0055] In accordance with a second aspect of the present invention a sample processing and analysis apparatus configured for continuously analysing samples from a continuous bulk raw material stream comprises a diverter configured for diverting a fraction from the continuous raw material stream to a retainer, a sample conditioning unit configured for producing, from the diverted fraction, a continuous sample raw material string or flow having predefined and constant properties, and an optical analyser configured for analysing the continuous sample raw material string or flow. The apparatus further comprises means for processing and evaluating signals from the optical analyser.

[0056] In one or more embodiments the sample conditioning unit of the sample processing and analysis apparatus comprises an extruder or an hourglass-shaped retainer having an egress opening or a neck defining the constant cross section. The egress opening of the sample conditioning apparatus may be adjustable. If an extruder is used for a sample conditioning unit, the adjustment of the egress opening is effected preferably from the bottom side, permitting the top surface of the sample material string to maintain a constant distance to the light source and the sensor. Further, if an extruder is used as sample conditioning unit the sample raw material flow can be controlled by the extruder screw motor speed. If the material is sticky enough, the compactness and well defined surface allows open beam diffuse reflection infrared measurement in the illumination spot without creating too much dust. Sensitivity to vibration is also reduced by compacting.

[0057] If the sample conditioning unit comprises an hourglass-shaped retainer, vibrating elements may be used for controlling and maintaining a desired sample raw material flow. A desired compactness of the sample raw material string or stream may be maintained via filling level control of the retainer, which may comprise a controllable material feed from the material storage. Proper filling level control will keep the pressure in the neck that is asserted by the material in the retainer at a constant level.

[0058] In one or more embodiments the sample processing and analysis apparatus outputs the sample raw material string or flow into a conduit having a first window that is transparent to the wavelengths of a light source used for illuminating a first surface of the sample raw material string or flow in an illumination zone or spot. The first window is facing the light source and a first sensor of the optical analyser. The conduit may optionally have a second window in the illumination zone or spot, at a second surface of the sample raw material string or flow opposite of the first surface and facing a second sensor of the optical analyser. The second window is likewise transparent to the wavelengths of the light source. The egress opening of the conditioning unit may have a cross section whose dimensions are the same or marginally larger than the inlet opening of the conduit. Using one or more windows facilitates to maintain a strict separation of sample raw material from the environment if required, or if the pollution of the light path, e.g., from dust or other material deposits, would be too high. Using a second window opposite to the first window may be envisioned when the viscosity of the sample raw material is high and its absorbance low enough. In this case the egress opening can be set to a small thickness up to the point where transmission measurements become possible. Generally, in any embodiment described herein, the illumination and measuring may be made from the top side or the bottom side of the sample raw material stream.

[0059] If an hourglass-shaped retainer is used for a sample conditioning unit the illumination spot or zone of the sample raw material stream or string is defined by a window in the neck of the retainer. The window is cleaned by the moving material itself. Commonly known probes and spectrometer equipment may be used. The dynamic movement of the sample raw material is statistically averaging the spectra and thereby enhancing the measured surface.

[0060] In one or more embodiments the sample processing and analysis apparatus and / or the conduit provided therewith is / are heatable or coolable by means of a heating or cooling element, respectively. This permits maintaining the sample raw material string or flow at a constant temperature or within a certain temperature window throughout all measurements, improving the stability, reliability, accuracy, and comparability of the measurements.

[0061] In one or more embodiments the sample processing and analysis apparatus further comprises an element for adding one or more excipients to the diverted fraction prior to or while producing the sample raw material string or flow. Adding excipients may improve the surface quality and / or the optical quality of the sample raw material string or flow, improve or facilitate the processing of the sample raw material strong or flow from the diverted fraction, reduce wear, and the like.

[0062] In one or more embodiments the sample processing and analysis apparatus further comprises a changeover which enables feeding a reference material into the conduit in place of the sample raw material string or flow or over the sample raw material string or flow. The reference material may be used for calibration of the optical analyser. Alternatively, or in addition, the conduit or the optical analyser and optionally the light source are movable to allow illuminating and sensing a reference material. If the conduit is moved, the reference material may be moved under the light source, allowing measuring the reference material. If the optical analyser and the light source are moved, they may be moved over the reference material. In case a window is used in the sample processing and analysis apparatus the reference material is preferably likewise covered with such a window having the same properties than the window of the conduit.

[0063] In accordance with a third aspect of the present invention a closed-loop controlled process of mixing cement is provided. The process comprises disposing two or more raw materials on a conveyor. The amount of disposal per raw material is controlled in accordance with control signals provided from a first sample processing and analysis apparatus in accordance with the second aspect of the invention. The process further comprises milling the raw material mix into a predefined maximum coarseness and separating and recirculating milling output that does not match the predefined maximum coarseness. The process yet further comprises diverting a fraction of the milling output that matches the predefined maximum coarseness to the sample processing and analysis apparatus. The sample processing and analysis apparatus performs an analysis of the diverted fraction in accordance with the method in accordance with the first aspect of the invention, and provides control signals in accordance with the result of the analysis to the disposing step. Finally, the milling output is provided to a silo for intermediate storage.

[0064] In embodiments the process further comprises providing cement from the silo and adding filler material from a storage to the cement provided from the silo. The adding is controlled in accordance with control signals from a second sample processing and analysis apparatus in accordance with the second aspect of the invention arranged upstream of a transport, to which the cement is ultimately provided. The process further comprises diverting a fraction of the provided cement downstream of the adding step to the second sample processing and analysis apparatus, performing an analysis of the diverted fraction in accordance with the method in accordance with the first aspect of the invention, and providing control signals in accordance with the result of the analysis to the adding step.

[0065] In embodiments the process further comprises merging at least a portion of the respective analysed diverted fraction with the milling output and / or the combined silo output and added filler material. In accordance with a fourth aspect of the present invention an arrangement for mixing cement is provided. The arrangement comprises two or more feeders for raw material, a first conveyor receiving the raw material provided from the two or more feeders and transporting the received raw material to a mill, and a separator configured for receiving milling output and separating milling output that does not match the predefined maximum coarseness from the milling output. The separator is further configured for recirculating the milling output that does not match the predefined maximum coarseness. The arrangement further comprises a silo configured for receiving the milling output downstream of the separator, a first diverter configured for diverting a fraction of the milling output downstream of the separator that matches the predefined maximum coarseness to a first sample processing and analysis apparatus in accordance with the second aspect of the invention. The first sample processing and analysis apparatus is configured to perform an analysis of the diverted fraction using the method in accordance with the first aspect of the invention, and to provide control signals in accordance with the result of the analysis to the two or more feeders.

[0066] In embodiments the arrangement further comprises a filler storage and a mixer configured for providing filler from the filler storage to material output from the silo. The mixer is controlled in accordance with control signals from a second sample processing and analysis apparatus. The arrangement further comprises a second diverter configured for diverting a fraction of the material output from the silo and mixed with the filler added via the mixer to the second sample processing and analysis apparatus. The second sample processing and analysis apparatus is configured to perform an analysis of the diverted fraction using the method in accordance with the first aspect of the invention, and to provide control signals in accordance with the result of the analysis to the mixer.

[0067] In embodiments the arrangement further comprises a first and / or a second merging apparatus configured for merging at least a portion of the respective analysed diverted fraction with the milling output and / or the combined silo output and added filler material. The merging apparatus may comprise a simple chute or conveyor that drops at least the portion of the respective analysed diverted fraction onto a conveyor or into a conduit transporting the milling output or the combined silo output and added filler material.

[0068] The present invention proposes an apparatus and a method for continuously preparing and measuring samples from a continuous material stream that brings optical sample analysis, including mid and long-wave infrared measurements, close to a manufacturing process. The invention overcomes the disadvantages associated with conventional sample preparation, e.g., time delay, manual labour, etc., and permits a fast adjustment of the material stream’s composition in a closed-loop control fashion. This leads to a higher process stability, improved materials mix and superior performance of the product and the production process.

[0069] The methods and apparatus proposed herein significantly improve the repeatability and stability of the analysis, thus enabling and ensuring the accuracy of at-line quality control and fault detection. In addition to the cost effective structural design, the challenges of material compactness, inspected surface area geometry and flatness are addressed. Integrating temperature and humidity control is facilitated, since only a small sample must be heated or cooled, or hydrated or de-hydrated, further improving the quality of the analysis. The invention permits continuous or quasi-continuous sampling, outputting a series of fast, dynamic measurements and as such enlarges the inspected area leading to higher statistical representability of measured material through combined results. Quasi-continuous measuring may comprise stop-and-go measurements in a rapid succession, if the measuring method requires a sample that does not move during the actual measurement.

[0070] The process of, and arrangement for, mixing cement presented herein, implementing the method of continuous analysis of samples and the sample processing and analysis apparatus, respectively, permit processing and measuring large amounts of material by generating an endless continuous stream of material, or a quasi-continuous stream of material, running stop and go, passing through the illumination zone or spot for transmission or reflection measurement. This novel way of generating a stream of material for analysis advantageously permits the control of conveyor-speed, material density, surface quality, temperature and even the use of add-on excipients for improved analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The invention will be described hereafter with reference to the attached drawing, in which

[0072] Fig. 1 shows an exemplary conventional cement manufacturing process,

[0073] Fig. 2 shows the conventional analysis steps used in a laboratory station of a conventional production system,

[0074] Fig. 3 depicts a production system in accordance with the fourth aspect of the invention,

[0075] Fig. 4 depicts details of a first exemplary embodiment of the sample processing and analysis apparatus in accordance with the second aspect of the invention,

[0076] Fig. 5 shows details of a second exemplary embodiment of a sample processing and analysis apparatus, and

[0077] Fig. 6 shows a simplified exemplary flow diagram of the method in accordance with the invention.

[0078] In the figures, identical or similar elements may be referenced using the same reference designators.

[0079] DETAILED DESCRIPTION OF EMBODIMENTS

[0080] Figure 1 has been discussed in the background section and will not be discussed again.

[0081] Figure 2 shows the conventional analysis steps used in a laboratory station 300 of the conventional production system 10 discussed with reference to figure 1. In a first step 2a a portion 171 of the mixture 170 is ground by a mill 172. The milled output 173 is fed into a retainer 420. In step 2b the milled material 173 is filled into a form 181. The amount is controlled by gate valve 180 and a weighing system 182. In step 2c the material 173 is pressed by a tamper 185, resulting in uniform tablets 175. In step 2d the mixture 171 in form of a tablet 175 is analysed in spectrometer 500. The known spectrometer consists basically of a light source 520 and a detector system 540, both generally known. Steps 2a to 2d of the conventional process typically take place in three different spaces; each step, i.e. , filling, grinding, tamping and measuring, and the transport in between, takes substantial amounts of time even when performed by robots.

[0082] Figure 3 depicts a production system 20 in accordance with the fourth aspect of the invention executing a fully automated closed-loop process 50 of cement mixing in accordance with the third aspect of the invention. Different materials like clinker 101 , gypsum 102, and coarse filler material like limestone 103 are dosed on a first conveyor belt 110. Filler materials are used in modern cement production to reduce the required amount of burned clinker. This first mixture 120 is sent to a mill 130 that reduces the particle size to some micrometres and also ensures a good mixing of the different materials 101 , 102, 103. The particle separator 150 rejects particles that are too large and sends them back through the so called recirculation 190 back into the mill 130. The control signal 410 determines the rejection threshold for the particle size. The main stream 170, transported by a second conveyor belt 113 passes a diverter, where a small part 171 of the second mixture 170 is diverted to a sample processing and analysis apparatus 400 implementing the method 30 in accordance with the first aspect of the invention. The method 30 in accordance with the first aspect of the invention provides analysis results in real time or almost in real time. The analysis results are transformed in to control signals 410, 411 , 412, 413 and are fed back to the respective controlled elements of the system, for controlling the amount of ingredients 101 , 102, 103 and adjusting the particle separator’s 150 speed for fineness. The second mixture 170 is filled into a silo system 210. The silo serves as a buffer so that the cement production can be continuous. For dispatching 290, pre-ground or already fine filler material 220 may be added to a third stream of material 240 through controllable mixer 280. Mixer 280 is controlled in accordance with control signals output by a further sample processing and analysis apparatus 600 that operates in the same manner as the sample processing and analysis apparatus 400, i.e., a fraction 241 of the third stream of material 240 is diverted to the sample processing and analysis apparatus 600, and the analysis results are used to control mixer 280 via control signals 610 for adding additional filler material via a filler stream 260. Figure 4 depicts details of a first exemplary embodiment of the sample processing and analysis apparatus 400. A diverted fraction 171 of the second mixture 170 is fed into a retainer 420 allowing a constant flow of the diverted fraction 171 into an extruder. This extruder system includes a controllable motor 414 for rotating a screw auger 415. This rotation and the forward moving of the mixture caused thereby improves the homogeneity of the diverted fraction 171. In certain cases it is advantageous to add one or more additional excipients 440 to the diverted fraction 171 , e.g., for increasing the creaminess, consistency, and texture or the reflexion- or absorption rate of the diverted fraction for the subsequent analysis. The material is then pressed through the contraction choke 460 also called „die“ or „nozzle“. This process creates an excellent surface finish for the following spectrometry through optical analyser 500.

[0083] The extruder is not limited to a single screw extruder. Other forms of extruders like a double screw extruder, ram-extruder or caterpillar extruder etc. may also be used. The extruder may be equipped with a heating or cooling system 450 including temperature sensors. Maintaining a predefined temperature may reduce or even remove any temperature-dependent effects during the measurement. For certain materials it is expedient to have a vibrating element 422 mounted at the retainer 420 for easy flow of the mixture 171. The output die or nozzle 460 may be formed rectangular to create a flat sample material string 180 from the diverted fraction. In certain cases a curved surface of the sample material string 180 might be advantageous for the reflectometry. The thickness of the sample material string 180 can be influenced by actuators 470. The screw-speed and thus the pressure might be supervised by one or more pressure sensors. In some cases may be helpful to supervise the sample material string 180 by an optical system or camera 475 for making an automatic adjustment to parameters like screw-speed, excipients 440, temperature or form or dimensions of the sample material string 180. A similar adjustment could also be controlled based on the spectrometry 500. An light source 520, that may also be integrated in a spectrometer 540, is directing light to the illumination spot 530 on the sample material string 180 where part of the radiation is absorbed and the remainder is diffusely reflected. This diffuse part is collected by spectrometer 540, analysed by a computer (not shown in the figure) and prepared for further processing. After the measurement in the reflectometer 500 the material of the sample material string 180 is collected in a bin 490. For long-time quality control it may be useful to collect part of the sample material string 180 in separate boxes that are time-stamped and stored for future use. The detecting threshold of the spectroscopy is strongly dependent on the temperature of the sample material string 180 and an additional cooling and / or heating element may be added to the support 480. Some Spectrometers 500 may also have a built- in cooling.

[0084] Figure 5 depicts details of a second exemplary embodiment of a sample processing and analysis apparatus 700. Instead of a mechanical extruder the gravity is used for moving samples under test in this vertical arrangement. Like in the sample processing and analysis apparatus 400, a diverted fraction 171 of the second mixture main stream 170 is fed into a retainer 710. The level of the material under test is supervised by one or more filling-level meters or other sensors 720. Retainer 710 has an hourglass-like shape providing a good flow of the sample material. The material from the diverted fraction 170 drizzles or trickles down and passes the neck of the hourglass-shaped retainer, which is where the spectroscopy 500 happens. The drizzling or trickling speed is controlled by valve head 730 that can be adjusted by actuator 732. For avoiding sticking of the sample material the valve head 730 is equipped with a pressure sensing and vibrating element 731 . The actuator 732 allows to adjust the gap and therefore control the drizzle or trickle based on the level information provided by filling level meter 720 or the impact force acting on the pressure sensing / vibrating element 731 for various material types. In case of blocking increasing the gap will help deblocking the system. For some mixtures another vibrating element 722 is positioned at the upper part of the retainer 710 for providing a good flow. Temperature control elements 721 and 723 allow a controlled cooling or heating of the mixture providing reliable measurements in the measuring spot or zone 530. The measurement is identical to the one described with reference to figure 4. An light source 520, that may also be integrated in spectrometer 540, is directing light to the illumination spot or zone 530, which can be round or flat shaped infrared-transparent material at the neck of retainer 710, and onto the stream 180 of material to be sampled. A part of the radiation is absorbed and the remainder is diffusely reflected. This diffuse part is collected by spectrometer 540, analysed by a computer (not shown in the figure) and prepared for further processing. After the measurement in the reflectometer 500 the sample material is collected in bin 490. Again, for long-time quality control it may be useful to collect part of the sample material stream 180 in separate boxes that are time-stamped and stored for future use.

[0085] Figure 6 shows a simplified exemplary flow diagram of the method 30 in accordance with the first aspect of the invention. In step 32 a fraction 171 from the continuous raw material stream 170 of a production process is diverted to a sample processing and analysis apparatus 400, 700. In step 34 the diverted fraction 171 is processed, in the sample preparation and analysis apparatus 400, 700, into a continuous sample raw material string or flow 180 having predefined and constant properties. In step 36 the continuous sample raw material string or flow 180 is moved past or through an illumination zone or spot. The illumination spot is illuminated by a light source 520 emitting infrared light. In step 38 light reflected by and / or transmitted through the continuous sample raw material string or flow at the illumination zone or spot 530 is received in a first and / or a second sensor. The properties of the reflected and / or transmitted light received at the first and / or second sensor 540 are analysed and evaluated in step 40.

[0086] Figure 7 shows a simplified exemplary flow diagram of the method 50 in accordance with the third aspect of the invention. In step 52 two or more raw materials 101 , 102, 103 are disposed on a conveyor 110, the amount of disposal per raw material being controlled in accordance with control signals 411 , 412, 413 provided from a first sample processing and analysis apparatus 400 in accordance with the second aspect of the invention. In step 54 the raw material mix is milled into a predefined maximum coarseness, and separated and recirculated, in step 56, if the milling output does not match the predefined maximum coarseness. In step 58 a fraction 171 of the milling output 170 that matches the predefined maximum coarseness is diverted to the sample processing and analysis apparatus (400), which performs an analysis of the diverted fraction 171 using the method 30 in accordance with the first aspect of the invention. Control signals 411 , 412, 413 are provided to the disposing step in accordance with the result of the analysis. In step 60 the milling output 170 is provided to a silo (210) for intermediate storage. LIST OF REFERENCE NUMERALS (PART OF THE DESCRIPTION)

[0087] 10 conventional production 35 260 filler stream system 280 mixer

[0088] 20 production system in 290 dispatch accordance with the invention 300 laboratory

[0089] 30 method 400 sample processing and

[0090] 32 diverting 40 analysis apparatus

[0091] 34 processing 410 particle separator control signal

[0092] 36 passing 411 clinker control signal

[0093] 38 receiving 412 gypsum control signal

[0094] 40 analysing 413 limestone control signal

[0095] 50 closed loop process 45 414 motor

[0096] 52 disposing 415 screw auger

[0097] 54 milling 420 retainer

[0098] 56 diverting 422 vibrating element

[0099] 58 providing milling output 440 excipient

[0100] 101 clinker 50 450 heating / cooling element

[0101] 102 gypsum 460 die / nozzle

[0102] 103 limestone 470 actuator

[0103] 110 first conveyor belt 475 sample material string / flow

[0104] 113 second conveyor belt supervising sensor

[0105] 120 first mixture 55 480 support

[0106] 130 mill 482 cooling / heating element

[0107] 150 particle separator 490 bin

[0108] 170 second mixture main stream 500 optical analyser

[0109] 171 diverted fraction 520 light source

[0110] 180 sample material string / flow 60 530 illumination / measuring

[0111] 190 recirculation stream zone / spot

[0112] 210 silo 540 spectrometer

[0113] 220 filler 600 sample processing and

[0114] 240 third material stream analysis apparatus

[0115] 241 diverted stream 65 610 mixer control signal 700 vertical sample processing and 723 temperature control element analysis apparatus 730 valve head

[0116] 710 retainer io 731 pressure sensing / vibrating

[0117] 720 filling level meter / sensor element 721 temperature control element 732 actuator

[0118] 722 vibrating element

Claims

CLAIMS1. Method (30) of continuous analysis of samples from a continuous bulk raw material stream comprising ingredients for cement production, the method comprising:- continuously diverting (32) a fraction (171) from the continuous raw material stream (170) of a cement production process to a sample processing and analysis apparatus (400, 700),- continuously processing (34), in the sample preparation and analysis apparatus (400, 700), the diverted fraction (171) into a continuous sample raw material string or flow (180) having predefined and constant properties,- passing (36) the continuous sample raw material string or flow (180) past or through an illumination zone or spot, the illumination spot being illuminated by a light source (520) emitting infrared light in the mid, long and far wavelength region,- receiving (38) light reflected by the continuous sample raw material string or flow at the illumination zone or spot (530) in a sensor (540), and- analysing (40) and evaluating the properties of the reflected light received at the sensor (540).

2. The method (30) of claim 1 , wherein continuously processing (34) the diverted fraction (171) into a continuous sample raw material string or flow (180) comprises extruding the diverted fraction (171), or producing a vertical trickle or drizzle of the sampled raw material.

3. The method (30) of claim 1 or 2, further comprising adding excipients (440) to the diverted fraction (171) prior to processing it into the continuous sample raw material string or flow (180).

4. The method (30) of one or more of claims 1 to 3, further comprising heating or cooling and / or controlling the humidity of the continuous sample raw material string or flow (180) to attain a predetermined temperature and / or humidity while being passed the illumination zone or spot (530).

5. The method (30) of one or more of claims 1 to 4, wherein the sample raw material string or flow (180) is provided, by the sample processing and analysis apparatus (400, 700), at substantially the same speed as the continuous raw material stream (170) of the production process.

6. The method (30) of one or more of claims 1 to 5, further comprising calibrating, at regular intervals or upon new bulk raw materials being received at the input of the production process, the sensor’s input.

7. The method (30) of one or more of claims 1 to 6, further comprising grinding the diverted fraction prior to processing it in the sample preparation apparatus (400, 700).

8. The method (30) of one or more of claims 1 to 7, further comprising merging at least a portion of the analysed sample raw material string or flow (180) with the continuous raw material stream (170) of the production process after analysing.

9. A sample processing and analysis apparatus (400, 600, 700) configured for continuously analysing samples from a continuous bulk raw material stream (170) of a cement production process comprising a diverter configured for diverting a fraction (171) from the continuous raw material stream (170) to a retainer (420, 710), a sample conditioning unit configured for producing, from the diverted fraction (171), a continuous sample raw material string or flow (180) having predefined and constant properties, an optical analyser (500) configured for analysing the continuous sample raw material string or flow (180), and means for processing and evaluating signals from the optical analyser (500).

10. The sample processing and analysis apparatus (400, 600, 700) of claim 9, wherein the sample conditioning unit comprises an extruder or an hourglass-shaped retainer having an egress opening or a neck defining the constant cross section.

11. The sample processing and analysis apparatus (400, 600, 700) of claim 9 or 10, wherein the sample conditioning unit outputs the sample raw material string or flow (180) into a conduit having a window in an illumination zone or spot (530), the window facing a light source (520) and a sensor of the optical analyser (500) and being transparent to the wavelengths of the light source (520) illuminating a surface of the sample material string or flow.

12. The sample processing and analysis apparatus (400, 600, 700) of claim 9, 10 or 11 , wherein the sample conditioning unit and / or the conduit is heatable or coolable by means of a heating or cooling element (450, 482), respectively.

13. The sample processing and analysis apparatus (400, 600, 700) of any one or more of claims 9 to 12, further comprising an element for adding one or more excipients to the diverted fraction (171) prior to or while producing the sample raw material string or flow (180).

14. The sample processing and analysis apparatus (400, 600, 700) of any one or more of claims 9 to 13, further comprising a changeover which enables feeding a reference material into the conduit in place of the sample raw material string or flow (180) or over the sample raw material string or flow (180), for calibration of the optical analyser (500), and / or wherein the conduit or the optical analyser (500) and optionally the light source (520) are movable to allow illuminating and sensing a reference material.

15. A closed-loop controlled process (50) of mixing cement comprising:- disposing (52) two or more raw materials (101 , 102, 103) on a conveyor (110), the amount of disposal per raw material being controlled in accordance with control signals (411 , 412, 413) provided from a first sample processing and analysis apparatus (400) in accordance with one or more of claims 9 to 14,- milling (54) the raw material mix into a predefined maximum coarseness,- separating (56) and recirculating (190) milling output that does not match the predefined maximum coarseness,- diverting (58) a fraction (171) of the milling output (170) that matches the predefined maximum coarseness to the sample processing and analysis apparatus (400), performing an analysis of the diverted fraction (171) in accordance with the method (30) of any one or more or claims 1 to 7, and providing control signals (411 , 412, 413) in accordance with the result of the analysis to the disposing step, and- providing (60) the milling output (170) to a silo (210) for intermediate storage.

16. The cement-mixing process (50) of claim 15, further comprising:- providing cement from the silo (210),- adding (280) filler material from a storage (220) to the cement provided from the silo (210), the adding (280) being controlled in accordance with control signals (610) from a second sample processing and analysis apparatus (400, 700) in accordance with one or more of claims 9 to 14 arranged upstream of a transport (290), to which the cement is ultimately provided,- diverting a fraction (241) of the provided cement downstream of the adding step (208) to the second sample processing and analysis apparatus (400, 700), performing an analysis of the diverted fraction (241) in accordance with the method (30) of any one or more or claims 1 to 8, and providing control signals (610) in accordance with the result of the analysis to the adding step (280).

17. The cement-mixing process (50) of claim 15 or 16, further comprising:- merging at least a portion of the respective analysed diverted fraction (171 , 241) with the milling output (170) and / or the combined silo output and added filler material.

18. An arrangement for mixing cement comprising two or more feeders for raw bulk material (101 , 102, 103), a first conveyor (110) receiving the raw bulk material provided from the two or more feeders and transporting the received raw bulk material to a mill (130), a separator (150) configured for receiving milling output and separating milling output that does not matchthe predefined maximum coarseness from the milling output (170), the separator further configured for recirculating (190) the milling output that does not match the predefined maximum coarseness, and a silo (210) configured for receiving the milling output downstream of the separator (150), wherein the arrangement further comprises a first diverter configured for diverting a fraction (171) of the milling output (170) downstream of the separator (150) that matches the predefined maximum coarseness to a first sample processing and analysis apparatus (400, 600, 700) in accordance with one or more of claims 9 to 14, the first sample processing and analysis apparatus (400, 600, 700) being configured to perform an analysis of the diverted fraction (171) in accordance with the method (30) of any one or more or claims 1 to 8, and to provide control signals (411 , 412, 413) in accordance with the result of the analysis to the two or more feeders.

19. The arrangement of claim 18, further comprising a filler storage (220), a mixer (280) configured for providing filler from the filler storage (220) to material output from silo (210), the mixer being controlled in accordance with control signals (610) from a second sample processing and analysis apparatus (400, 600, 700), and a second diverter configured for diverting a fraction (241) of the material output from the silo (210) and mixed with the filler added via the mixer (280) to the second sample processing and analysis apparatus (400, 600, 700), wherein the second sample processing and analysis apparatus (400, 600, 700) is configured to perform an analysis of the diverted fraction (241) in accordance with the method (30) of any one or more or claims 1 to 7, and to provide control signals (610) in accordance with the result of the analysis to the mixer (280).

20. The arrangement of claim 18 or 19, further comprising a first and / or a second merging apparatus configured for merging at least a portion of the respective analysed diverted fraction (171 , 241) with the milling output (170) and / or the combined silo output and added filler material.

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