Pellets wearability The mining and processing industry is committed to a zero waste approach, which includes minimizing particulate emissions. One challenge involves the shipping and handling of bulk commodities, ranging from coal and iron ore to limestone and bentonite. These types of bulk granular materials can break down and abrade during handling and discharge, producing particle fragments of a wide range of sizes. Certain particle sizes can be airborne and are undesirable for a variety of reasons. Commercial iron ore pellets are also susceptible to cracking and abrasion during shipping and handling, resulting in the formation of undesirable fines and dust. Manufacturers characterize the attrition resistance of their pellets using an abrasion index (AI) to indicate whether their products will produce acceptable or unacceptable levels of fines. Structurally weak pellets tend to produce a significant amount of fines from both impact and attrition. In pelletizing, the abrasion index is used to indicate the resistance of pellets to attrition. The abrasion index is defined according to ISO 3271 as the amount of material smaller than 0.5mm produced by the rotation of the pellets in a rotating drum. Historically, AI has been one of the main quality indicators for pellets and should therefore be as low as possible. The maximum limit for AI depends on the pellet user, but it is generally desirable that it does not exceed 5% when tested in a drum according to ISO 3271. Factors influencing pellet dustiness can range from the starting materials to agglomeration; to the solidification or heat hardening conditions; depending on the type and degree of processing – all of these can interact to some extent, influencing the final structure and properties of the granules and, ultimately, dust formation (figure). The use of binding additives and an increase in the specific surface area of the concentrate reduce the abrasion index. However, the use of organic binders leads to higher abrasion indices compared to pellets on a bentonite binder. Pellets obtained on conveyor firing machines have a higher abrasion index due to uneven firing along the height of the pellet layer. Granules from the lower layer have many fragile pellets, leading to an increase in the abrasion index compared to pellets of the middle and upper layers fired at higher temperatures with a longer time interval. For example, when the firing temperature was reduced from 1280 C in the upper part of the layer to 1200 C at the layer-bed boundary, the abrasion index increased from 3.7% to 11.9%. Insufficient firing is the main reason for the formation of fine particles and dust. Each type of batch has its own critical firing temperature required to achieve good solidification of the granules. The quality of pellets is very sensitive to temperatures below the critical temperature. The lower the firing temperature, the longer the time interval required for pellet processing. It has been found that larger pellets in the lower layer are insufficiently fired, and increasing pellet diameter requires longer firing times for complete solidification. Consequently, pellets produced in SG have a higher proportion of insufficiently fired pellets, resulting in a higher level of fines. In GK, all pellets are fired at high temperatures, so the pellets are sintered to a more uniform level. Granules are formed from powder material and easily disintegrate into individual particles and weakly bonded fragments if the solidification process and the phenomena associated with it (oxidation and recrystallization, melt formation, reduction in pore size and porosity, and grain growth) are not complete. The physical principles for the formation of the abrasion resistance index are based on two factors: shape (degree of surface roughness) and the degree of sintering of the particles located in the surface layer of the pellet. The surface condition ultimately determines the formation of fines during mutual contact of pellets. Pellets of class +5-8mm have the greatest abrasion due to a larger contact surface with each other and a greater friction force. Pellets in the class range of 11.0-12.5mm have the minimum abrasion. With an increase in the basicity modulus of granules and the addition of solid fuel to the charge, the abrasion index increases due to an increase in pellet porosity and a change in the pellet microstructure. Pellets are decomposed as a result of impacts and abrasion during their production and handling. Depending on the type (impact or abrasion) and degree of destruction, different amounts of finely dispersed material are formed. When destroyed by impact (when falling from different heights at handling units, loading and warehousing), the destroyed granules are distributed in the range of particle size class from 0.5mm to 16mm, when destroyed by abrasion (during transportation due to friction of granules between themselves), the resulting material is distributed in the range of size class 0-0.5mm and is the main source of dusting and material losses, including emissions into the environment. 0 0

01 Pelletizing Process – Why? Vale Read more 02 Developing a Canadian Green Steel Supplier Strategic Resources Read more 03 Pelletizing Technology CEMTEC Read more 04 DR Grade Pellet Quality, Supply and Prices Dr. Joseph J. Poveromo Read more 05 Metso Straight Grate Pelletizing Solution (VALE) Metso Read more 06 Fresh thinking iron ore pellet production at LKAB Kent Tano Read more 07 Iron ore pelletizing process Hassan Z. Harraz Read more 08 Straight Grate vs Grate Kiln Ken Oja Read more 09 KOBELCO Pelletizing System Kobe Steel, Ltd. Read more 10 Testing equipment R.B.Automazione Read more 11 Revolutionizing iron ore pelletizing: The screening process flowsheet of the future Steve Beaudin Read more 12 SNF Organic Binder Polyacrylamide binders Gilles Zakosek Read more 13 Pellets for an Evolving Global Iron and Steel Scenario Dr. Joseph J. Poveromo Read more 14 Enhancing DR Pellet Quality in Iron Ore Pelletizing using HPGR for Compact Hematite Ore Maycon Athayde Read more 15 Ni 43-101 Technical report on the feasibility study on Kemag taconite project Met-Chem Canada Inc. Read more 16 Roller screens for pellet plants Metso Read more 17 MIDREX® Plants Midrex Read more 18 Future of pellet industries D L Saralaya Read more

Influence of pellet size Green pellets loaded into the indurating machine must contain at least 95% of the 9-16mm class. In this range of values, it is advisable for blast furnace pellets to have as high a content of the 9-12.5mm class as possible; this class usually ranges from 65 to 80%; for direct reduction pellets, the content of the 9-12.5mm class is regulated by a value of 45-55%. This difference is primarily due to the different behavior of pellets in a blast furnace and in metallization furnaces. In blast furnaces, the pellet in the charge passes into the liquid phase after reduction, and in metallization furnaces, after reduction, the pellet must retain its almost original shape, preventing the formation of conglomerates and small fractions. Larger pellets are less prone to sticking together and forming lumps of material due to a decrease in the contact area of the surfaces, and larger granules have greater gas permeability, an increased yield of the good class due to the formation of a smaller number of small particles after recovery. However, there are also disadvantages of such a distribution by fractional composition - this is a decrease in the efficiency of recovery due to a decrease in heat transfer and strength of granules. If the production of raw pellets of the 9-16mm fraction in the composition of more than 50% of the 12.5-16mm class does not cause any particular difficulties when obtained both on disc and drum pelletizers, then the production of raw pellets with a content of class 9-12.5mm more than 50% is easier to organize on drum pelletizers, which are less demanding on the influence of changing characteristics of the supplied raw material and can operate with a recirculation load of up to 300%. In practice, the production of raw pellets of a given class is associated with two moments. Either we produce raw pellets with the maximum required grain size distribution by class and partially improve it on a roller screen by screening out a small amount of substandard large and small classes, or we produce an average product that does not correspond to the specified class in grain size distribution and completely improve it on a roller screen by removing large and small classes as much as possible by setting appropriate gaps between the rollers on the upper and lower decks of the roller screen. If this situation is still acceptable when using drum pelletizers, then the use of disc pelletizers with a recommended recirculation load of up to 25% will only worsen the quality characteristics of pellets, since the recirculation load will be 25-40%. Therefore, if we want to produce raw pellets with the maximum grain size of 9-12.5mm, it is necessary to minimize deviations in the quality characteristics of the feedstock materials and install modern pelletizing equipment. Some pellet manufacturers, who for one reason or another (high moisture content of the concentrate, use of dehydrating reagents) cannot obtain the optimal grain size of raw pellets after disc pelletizers and still focus on a recirculation load of up to 25%, install gaps on the upper deck of the roller screen to limit the grain size class slightly higher than 16mm, for example 17mm or 18mm. Practical results of the work show that with a decrease in the content of the 9-16mm class in raw pellets, the amount of return increases, and, as a consequence, the recirculation load. The most optimal average pellet diameter is in the range of 11.8-12.2mm. The operation of pelletizers in the range above these average values lead to a decrease in the number of suitable pellets in the required range of 9-16mm and, as a consequence, a decrease in the homogeneity of the layer on the firing trolleys, which is critically important for the subsequent stages of the technological process. Also, raw pellets of the 12.5-16mm fraction are more prone to destruction during transportation to the firing machine with the formation of cracks and chips, which further worsens the gas permeability of the layer and during the firing process leads to an increase in small substandard fractions less than 6.3mm, which are sieved at the screening stage and reduce the yield of suitable pellets. Green pellets of class 10-12.5mm are more compacted and homogeneous, less susceptible to damage. In fired pellets, there is practically no stratification into a two-layer structure (core and shell). Diagrams show how the percentage of cracks changes in green and fired pellets of different granulometric composition. The larger the diameter of the raw pellets, the more difficult and time-consuming it is to remove water from the pellet during drying due to the increase in temperature between the core and the surface. The process of removing the final moisture shifts to the firing zone, where additional vaporization pressure is created due to the increase in temperature, at this point the rate of steam formation exceeds the rate of moisture removal in the pellet volume, which leads to a violation of the integrity of the pellet (rupture) destruction of the pellet with the formation of surface and internal cracks. An increase in the pellet size leads to the formation of various thermochemical conditions of the firing process across the pellet cross-section (temperature, partial oxygen pressure, oxidation reactions). As a result, its dual structure is formed. In the cross section, hematite is observed mainly in the outer shell, and magnetite in the inner part. During cooling, hematite and magnetite change their volume differently (due to differences in the structure of the crystal lattice), forming concentric cracks and disrupting the integrity of the pellet. In large pellets, oxidation processes do not occur to the full extent, which leads to the presence of residual magnetite across the pellet cross-section. The compressive strength of roasted pellets is determined according to ISO 4700. Numerous tests to determine the compressive strength of roasted pellets by size classes show an increase in the compressive strength of pellets of the 12.5-16mm class. This situation occurs because large pellets have a larger average diameter and the applied compression force is distributed over a larger area of the contact point of such a pellet. Diagram shows, as an example, the difference in the strength indicators of non-fluxed pellets of different fractional composition. If these values are converted to the average pellet diameter by size class and pellet surface area, the specific strength value will be higher, on the contrary, for pellets of the 10-12.5mm fraction (table). All tests according to ISO methods for determining the physical and metallurgical properties of pellets are carried out on pellet samples with a size class of 10-12.5mm. Statistics of tests carried out to determine the dynamic strength to destruction by class +6.3mm (TI +6.3mm ) according to ISO 3271 show the highest strength of fired pellets in the range of 10-12.5mm (diagram). The fracture strength of fired pellets during low-temperature reduction performed according to ISO 13930 for class +6.3mm (LTD +6.3mm ) also in the range of 10-12.5mm has the most optimal strength values (diagram). As was reflected earlier, this test characterizes the tendency of pellets to destruction in the upper part of the blast furnace and reflects the ability to destruction during the reduction of hematite to magnetite with a change in the crystal lattice from hexagonal hematite to cubic magnetite. There is a change in anisotropic dimensions and, as a consequence, the occurrence of additional stresses in the pellet structure, which leads to the occurrence of cracks at the grain boundary. In pellets there are two types of bonds that affect the strength of the pellets - bonds of iron oxides magnetite and iron oxides hematite and silicate slag bond obtained at high firing temperatures as a result of the interaction of silica with iron, calcium and magnesium oxides with the formation of a melt in a volume of 5-10% of the pellet volume with partial dissolution of various minerals in it. After pellet cooling, the melt crystallizes as complex silicates and forms a glassy phase. Hematite bonds affect the pellet strength in the cold state, but lose their function when reduced to magnetite in a blast furnace. Slag silicate bonds do not undergo structural changes and are actually the only main source of pellet strength during reduction. Therefore, a sufficient amount of liquid slag must be formed during the firing process, which must be distributed evenly throughout the pellet volume, followed by the formation of solid silicate bonds during cooling. The formation of a liquid silicate phase is especially important for unfluxed pellets produced from low-silicon concentrates with a silicon oxide content of less than 3.0% and an iron content of 70.0% or more. It is recommended to add up to 1% limestone to form a liquid melt and create a slag bond to stabilize and increase low-temperature strength when restoring LTD +6.3mm . During these tests it was found that with an increase in the size class, the number of cracked pellets increases. The main reason is the presence of a dual structure in the pellet volume - a hematite base with the inclusion of parts of unoxidized magnetite, and the larger the pellet, the more hematite-magnetite interfaces appear in the pellet volume. With a change in the pellet size, the phase composition of the pellets changes (diagram). An increase in the average pellet diameter leads to an increase in magnetite and a decrease in the amount of hematite. The larger the pellet size, the larger the unoxidized magnetite core remains due to insufficient oxygen supply to the inner part of the pellet, and local zones are also formed along the pellet cross-section, which are the result of an incomplete transformation of magnetite into hematite. Hematite predominates in the oxidized shell, and magnetite and slag in the core, due to which the inner part of the pellet sinters more densely than the outer part, which affects the heterogeneity of the pellet structure. An increase in the pellet size leads to a modification of the pore structure inside the pellet. From numerous small and round pores in pellets of the 8-12.5mm class, in larger pellets the pores become larger, there are fewer of them, and they acquire a more elongated shape. This pore shape becomes a source of additional stress concentrations on the pore walls and reduces the cold strength of the pellets. The pellet size also affects the content of divalent iron oxide FeO. The lowest value of this oxide characterizes the degree of completion of the oxidation process. It is necessary to achieve the lowest possible FeO value when implementing the technology. Diagram shows the change in this oxide by pellet size classes. Of great interest are also the results of the test (diagram) of dropping fired pellets from a height of 10 meters onto a flat metal surface (method proposed by the Corem research center). The data obtained allow us to estimate the degree of destruction of pellets and the formation of an additional amount of small fractions less than 6.3mm during transportation of pellets from the supplier to the end user, taking into account the initial quality of the pellets and additional destructive mechanical effects acting on the pellets during numerous overloads during delivery of the material. The chemical composition and basicity modulus of pellets by size classes do notchange and are within the limits of permissible deviations when determining the chemical composition of substances (table). Pellets swelling is practically independent of granule size and should not exceed 20% for blast furnace pellets (diagram). The swelling index is determined according to ISO 4698. The increase in pellet volume during reduction is mainly due to the transformation of hematite into magnetite. High swelling is associated with low mechanical strength of pellets. Determination of this indicator is necessary to assess the effect of increasing pellet volume during reduction on the gas permeability of the column of charge materials in the blast furnace. The next indicator, which depends on the size of pellets loaded into the blast furnace, is the reduction index – RI. The reduction index is determined according to ISO 7992 (Determination of reduction under load at 1050 C) and ISO 4695 (Determination of reduction by reduction rate index at 950 C). Since the reduction reaction occurs from the surface to the center of the pellet, the inner part of large pellets remains unreduced. The larger the pellet diameter, the more unreduced core remains in the pellet cross-section. The degree of reduction in smaller pellets is much greater than in large pellets (diagram). In fact, the higher the cold strength of pellets, the lower the pellet recovery. The main reason is the decrease in gas diffusion of reducing gases due to pellet compaction with a decrease in their open porosity. At temperatures from 1280 C to 1350 C, an additional amount of slag bonds are formed, which fill the voids and intergranular bonds with liquid melt. To obtain high cold strength of pellets, elevated temperatures are required in the furnace of the firing machine. On the other hand, it is necessary to have the highest possible degree of pellet recovery, which means it is necessary to look for an optimal compromise between pellet strength and recoverability. At most pelletizing plants, due to the remoteness from the end user and numerous overloads during delivery of pellets to the customer, preference is still given to the cold strength of pellets in order to reduce the formation of fines. 0 0 0 0

Transportation, screening and stacking Some of the main components in the production of pellets are the processes: a. transporting raw pellets with uniform distribution on a roller screen; b. screening with separation of substandard classes -8mm and +16mm; c. loading in an even layer along the height and width of the trolley; One of the most important technological operations is the transportation of raw pellets from pelletizers to the firing section and their uniform loading onto the firing machine. Due to the low static strength of pellets and their susceptibility to deformation, it is necessary to ensure careful transportation, minimum height overloads and, finally, their careful and uniform stacking onto firing trolleys. Transportation of raw pellets after pelletizing to the firing machine is carried out by conveyor transport. As indicated above, when transporting raw pellets, it is necessary to minimize the number of handling units and the height of the pellet fall at each of the overloads. To evenly distribute the load on the roller screen, pendulum devices or reciprocating loading trolleys are installed. The most acceptable and effective way to distribute raw pellets on a roller screen is with reciprocating trolleys on a hydraulic or chain drive, allowing to distribute the load uniformly over a given stacking amplitude (without gaps and distortions in layer height) onto a wide intermediate conveyor and then over the entire area of the roller screen. Uniformity of pellet stacking on the firing trolleys is ensured by three interconnected control loops: the speed control loop of the collecting conveyor drum, the speed of the collecting conveyor belt, and the speed control loop of the wide intermediate conveyor. Such distribution allows to effectively use the entire area of the roller screen in order to increase the efficiency of screening by size classes, to give a rounded shape to the pellets, and to eliminate a number of minor defects (small internal cracks formed along the pellet transportation path) by rolling and strengthening. At pelletizing plants built in the 60-90s of the last century, raw pellets after disc pelletizers were fed to a single-deck roller screen, where only the fine fraction of -8 mm was screened. The large fraction of +16mm was not removed from the raw pellets and was placed together with the conditioned pellets of the fraction of 8-16mm on the incinerator. Drum pelletizers worked in tandem with three-product screens, where separation into three fractions of -8mm, +16mm and the conditioned class of 8-16mm was performed. Also, before placing on the incinerator, the fraction of -8mm was additionally removed on a single-deck roller screen. This solution allowed not to screen the fired pellets by small class, since the content of class -6.3mm in the finished product was no more than 3.0mm, which was acceptable for consumers of blast furnace pellets. When delivering products for metallization plants, screening of fired pellets was carried out, which made it possible to obtain a commercial product at the output with a content of class - 6.3mm of no more than 1.0%. Drum pelletizers in conjunction with a three-product screen were installed where there were significant fluctuations in the properties of the feedstock materials fed for pelletizing and additional requirements were required for the quality of the raw pellets fed to the firing machine or the grate-tube furnace-ring cooler system. Recirculation on drum pelletizers is allowed up to 300%. Modern or reconstructed factories are equipped with three-product screens after disc pelletizers, or they are installed directly before loading raw pellets onto the firing machine. The technology of raw pellet production is constantly being improved in two directions - one of them is a set of solutions allowing to obtain high-quality raw pellets with the maximum yield of the suitable class, the second is to more effectively screen raw pellets placed on the firing trolleys. The installation of two-deck screens using rollers with a diameter of 89mm or less allowed to increase the screening area by 30% compared to previously used designs. Industrial samples of three-deck, four product roller screens have been created, which allow sifting out small and large fractions, and divide the conditioned fraction placed on the firing machine into two fractions 8-12.5mm is placed at the bottom of the pellet layer, and the fraction 12.5-16mm in the upper part of the pellet layer. This type of laying of green pellets allows reducing the compaction of the layer and improve the firing of pellets along the layer height, due to the formation of a two-level layer of pellets with better permeability than a standard layer. During the firing process, the descending hot gas flow processes large pellets in the upper part of the layer, which are difficult to fire at low temperatures at the bottom of the layer, the gas flow with a lower temperature then fires small pellets, which are fired more easily and this does not lead to their over-firing in the upper part of the layer, as with standard loading. This segregation concept can also be used with a two-level roller stacker, if the pelletizing department already has an optimal screening system with large-class screening of +16mm. These solutions allow improving the quality of the product or increase the productivity of the firing machine, while simultaneously reducing energy costs due to better gas permeability of the layer and better heat exchange between the pellets and the coolant passing through the layer. The founder of this concept is the Canadian company Metal7. The efficiency of screening (sifting) depends on the following factors: Characteristics of the screen a. number of rollers – the greater the number of rollers, the higher the screening efficiency; b. roller diameter – the smaller the diameter of the rollers, the higher the screening e fficiency and removal of fine fraction; c. roller length – the greater the length of the rollers, the higher the screening efficiency; Characteristics of the state during operation a. wear of rollers – reduces screening efficiency; b. uniformity of gap opening – uniformity of space between rollers over the entire area of the screen – increases screening efficiency; c. straightness of rollers – increases screening efficiency; d. angle of inclination – set during commissioning; e. rotation speed – set during commissioning (increasing speed promotes the efficiency of removing small class, but also leads to a decrease in the efficiency of preserving granules of the conditioned class); f. transport capacity of rollers – excessive roller roughness of more than 50 microns reduces the screening efficiency due to material sticking, a smoother surface of less than 30 microns – reduces the efficiency of transporting and screening due to the creation of a "cigarette" effect with deformation of the pellet shape; g. distribution of material on the roller screen – the more uniformly the material is distributed, the higher the screening efficiency; Characteristics of the material fed to the screen a. granulometric composition – the percentage content of each range in the product exiting the pelletizers (the higher the content of the required size range, the higher the screening efficiency); After screening of raw pellets, fractions of -8mm and +16mm are removed as a recirculation load to the pelletizers. This load is especially critical for disc pelletizers, since its optimal amount should not exceed 25% of the mass of the material fed to the pelletizers. Lower humidity of the recirculation load, usually 0.25-0.35% lower than the humidity of the batch fed for pelletizing, leads to the appearance of many small conglomerates in the mixture with a humidity different from the humidity of the batch. An imbalance in moisture in the volume of the batch and uneven distribution of capillary forces between the particles occurs, which leads to the formation of small and less durable raw pellets or large substandard pellets. The greater the recirculation load, the greater its influence on the granulometry composition of the pellets. The volume of recirculation load often contains large, half-destroyed pieces of raw pellets of class +16mm, which, when entering the pelletizer, are sources of formation of large, substandard pellets of 50-100mm in size, having a layered structure. To destroy these pellets, devices of various configurations, called "hedgehogs", are used. Some of them (a conveyor roller with welded rods) are installed on cables and lowered into the zone of formation of large balls, others (a metal ball with welded rods) are thrown directly into the bowl itself in the same zone. Some Chinese companies are conducting industrial tests of robotic devices (like an arm) for removing large pellets from the pelletizer, eliminating human intervention in this process. One of the problematic issues is the destruction of the large class +16mm formed after screening on the upper deck of a two-level screen. There are many types of equipment for crushing this class with varying degrees of efficiency, one of which is installed on top of the outgoing conveyor from under the roller stacker and is based on the principle of crushing large pellets (car wheels, rollers of various configurations), the other (crusher) is installed in the transfer unit of the large-class conveyor and is based on the principle of impact load (a fast-rotating shaft with stiffening ribs). Recently, a device has found its application consisting of a rotating roller, which is installed on the upper deck of the roller screen at the end of the working rollers of the screen, in front of the largeclass conveyor and operates in automatic mode. Periodically, this roller is lowered to the main roller of the upper deck with a gap of 8mm to crush large pellets before entering the large-class conveyor. The most acceptable option, taking into account the efficiency and ease of maintenance, is the installation of a fast-rotating shaft with stiffening ribs in the transfer unit of the discharge conveyor from under the roller screen. The laying of raw pellets after the roller screen is carried out on the calcination trolleys using a sliding board or direct layer-by-layer laying. In general, the control system of the raw pelletizing section should ensure stabilization of the quality of raw pellets, their efficient transportation and uniform stacking, thereby contributing to the stabilization of the high-temperature pellet processing mode on the firing machine.

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Pelletizing of the charge The main component of the pellet production process is the production of green pellets in the disc or drum pelletizer itself. Drum pelletizers operate in a closed cycle with roller screens for screening of large (+16mm) and small fractions (-8mm). Disc pelletizers can operate both independently and in pairs with roller screens for screening only large class (+16mm) or screening of large (+16mm) and small fractions (-8mm). The main factors influencing the production of green pellets are: a. physical and chemical properties of concentrate; b. physical and chemical properties of additives; c. amount of added substances; d. humidity of batch; e. speed of rotation of tray (drum); f. angle of inclination of tray (drum); g. change in height of tray side; h. number and location of bottom and side scrapers in tray; i. place of loading of batch into tray; j. location of water supply; k. amount of water supplied; Points a, b, c, d were discussed above. The charge must be fed to the pelletizer with a moisture content below the optimum value so that the plant's process personnel have the opportunity to bring the charge moisture to the optimum value by feeding water to the pelletizer. In general, feeding water to the pelletizer is one of the important elements of controlling the rolling of raw pellets, which allows adding moisture to the pelletizer with a dry charge, and reducing the water feed to the pelletizer when the moisture content increases above the optimum. The process of obtaining raw pellets is conventionally divided into stages. The first begins with the formation of pellet embryos, and water serves as the center of their formation. Embryos are dense, over-moistened lumps of the charge onto which the pellet shell rolls. The charge almost always contains areas of material with increased humidity and density, which are formed after filtration, transportation and loading into the pelletizer. If their number is sufficient for pelletizing the charge with optimal humidity, then additional moistening of the charge is not performed. If the humidity of the charge is less than optimal by 0.3-1.5%, then the formation of embryos is formed by drip irrigation in the charge feed zone, which moves along a descending trajectory of the working space of the plate. The formation of the embryo also occurs after the destruction of fragile pellets. At the second and third stages of obtaining raw pellets, there is a rapid growth of the embryo and formation of lumps of the batch, which, under the action of dynamic forces when rolling along the inclined surface of the plate and impact effects between themselves and the wall of the pelletizer, gradually form the structure of the final pellet. The average static indicators of the content of the mass of fractions in the pelletizer batch are as follows: 15-20% of the conditioned class, 10-15% of embryos, 65-70% of the intermediate class. In practice, it often happens that the moisture in the batch is the optimal value or even slightly higher than the optimal value and water is not supplied to the pelletizer. If the moisture of the batch increases above the optimal value, it is necessary to take prompt measures to stabilize it. For this purpose, the consumption of bentonite or crushed return in the batch is increased and the moisture of the concentrate is stabilized by adjusting the filtration mode or changing the concentrate batching (feed from the warehouse/direct feed from the process). Diagrams show some aspects of the influence of concentrate moisture on the performance of the pelletizing process and the operation of the firing machine. The main control lever for the pelletizing process, along with changing the amount of moisture and bentonite consumption (return), is changing the rotation speed of the pelletizer. Changing the pelletizer speed to a smaller or larger value allows for the production of larger or smaller pellets. The pelletizer speed can be adjusted from 0 to 8rpm. The next element of pelletizing process control is changing the pelletizer tilt angle. For disc pelletizers, the working range of tilt angle is from 46 to 50. Adjusting the pelletizer tilt angle is used last, when all other control methods have failed to achieve the desired result. In practice, a control method is often used by decreasing or increasing the load on the pelletizer with simultaneous redistribution of the load on other pelletizers, however, this method is associated with the need to adjust the pelletizing process on all pelletizers with a redistributed feed load of the batch. Recently, some manufacturers of pelletizing equipment (Haver & Boecker Niagara) have added another element of pelletizing process control – a variable height of the pelletizing plate side. This technology works on an industrial scale, but requires further development and a clear control algorithm. Bottom and side scrapers are installed permanently during commissioning of the pelletizer according to the recommendations of the equipment supplier and during operation during operational control of the pelletizing process, their position in the pelletizer is not changed manually, Industrial samples of intelligent scrapers have been developed, which are equipped with drives and allow their position in the pelletizer plate to be quickly adjusted during operation. All criteria for the formation of high-quality green pellets must be optimally selected for each type of unit and production conditions, i.e. there is a certain relationship depending on the type and characteristics of the concentrate used, which must be determined by testing between speed, angle of inclination, side height (for a disc pelletizer), degree of filling and residence time. The green pellet production process is a multifactorial process with many changing variables. The more parameters change, the more often this happens and the greater the range of deviations from the set values, the more difficult it is to regulate the pelletizing process. 0