The quality characteristics of green pellets are characterized by three main parameters – fractional  composition, pellet strength on dropping and pellet strength on crushing. The moisture content is also additionally controlled. Green pellets at the outlet of the bowl pelletizer should have a uniform fractional composition. A narrow size distribution of green pellets is an important criterion for the quality of pellets, which characterizes high gas permeability of the layer during oxidative firing on a firing machine and the reduction process in blast furnaces and metallization units. 

      The size of granules is adjusted either mechanically, by changing the gaps of the roller screen, or technologically, by changing the moisture content, load, binder dosage, rotation speed, side height, plate or drum inclination angle. It is known that increasing the dosage of the binder component reduces the growth rate of raw pellets, making them smaller, while increasing the moisture content leads to the opposite effect of enlarging the granules. Stable operation of the granulator requires control of the humidity and grain size distribution of the batch components. 

        During the production of raw pellets, the granulometry composition of suitable pellets fluctuates, which requires constant monitoring of the process by process personnel. To increase the granule size at a constant load, additional moistening of the material, an increase in the rotation speed of the pelletizer and a decrease in the angle of inclination are required. To reduce the pellet size to the standard size, it is necessary to remove or reduce additional moistening of the material if possible, reduce the rotation speed of the plate and increase the angle of inclination of the pelletizer. An increase in the load leads to a decrease in the pellet size, and a decrease in the load makes the pellets larger.

       The correctness of the pelletizing process is determined by the maximum value of the 8-16mm fraction from the total mass of raw pellets coming out of the plate. The optimal value for the production of DR pellets is 50% of the 8-12.5mm class and 50% of the 12.5-16mm class. When producing BF pellets, it is advisable to shift the granulometric composition of raw pellets towards increasing the content of the 8-12.5mm class. The drop strength must be maintained for at least 4-7drops from a height of 500mm onto a flat steel plate. 

       It is considered that green pellets should have a minimum required strength, sufficient for their transfer to the conveyor belt from the pelletizer and further transportation to the firing machine. If the strength is insufficient, even green pellets that have retained their shape may have cracks, both internal and coming to the surface, which significantly reduce the strength of the roasted pellets, provided that they are not destroyed during the firing process. 

       Ideally, a high-quality green pellet should have high strength and porosity. However, in practice, as the strength of the green pellet increases, the porosity of the pellet decreases and vice versa. The strength of the green and dry pellet is necessary to prevent its destruction before placing it on the firing machine and during the firing process. Porosity is necessary for the processes of moisture removal and oxidation reactions of iron oxides to form a solid single-layer hematite structure of the pellet. In the process of pellet production, it is necessary to select the optimal values for the strength and porosity of the green pellet and ultimately focus on the quality indicators of the fired pellets (compressive strength, abrasion strength, impact strength, granulometric composition).

        The golden rule says that high-quality raw pellets are the main determinant of obtaining high-quality fired pellets. High-quality raw pellets have a huge potential to increase the quality of fired pellets and the productivity of firing units. The correct required strength value can be determined independently by calculating the number of overloads of raw pellets after the pelletizer plus one additional overload. The lower critical limit of the drop strength is 4 times (optimum 6-7 times), crushing strength is not less than 1kg/pellet (optimum 1.2-1.5kg/pellet). These values are calculated taking into account the load on the raw pellet in the pellet layer on the firing trolley. When designing a section of raw pelletizing at newly constructed pelletizing plants, these requirements for the quality of raw pellets are necessarily taken into account and, if possible, the number of reloads and the height of the pellet fall between reloads are minimized. In practice, it is not always possible to maintain these values for strength, which leads to the formation of an additional amount of raw pelletizing return, which is returned to the pelletizers and serves as a source of destabilization of the pelletizing process. Cracks and chips appear in some pellets, which are subsequently destroyed in the firing machine during drying and heating.

         Many pelletizing plants install video control systems for pellet grain size distribution to minimize significant deviations in the process of green pellet production. These systems allow for prompt determination of pellet grain size distribution by fraction. Their operation is based on contactless measurement of three main pelletizer performance indicators: the proportion of large class, average diameter, and roughness index of green pellets (size determination and analysis subsystem). Based on the received and processed data, the following subsystem, green pelletizing optimization, generates the main values of the pelletizing line control parameters (rotation speed, batch load, water consumption, bentonite consumption, plate inclination angle, and plate side height) in accordance with the developed action algorithm for each control loop. The system can also solve the problem of optimal load distribution between pelletizers in accordance with the quality characteristics of the pellets they produce. The optimal place for installing a video monitoring system is the tray chute, in this place it is possible to determine with a high degree of probability the entire fractional composition of pellets leaving the pelletizer. It is also  common practice to install video surveillance systems on the outfeed conveyors from the pelletizer, but such control does not allow to fully determine the entire fractional composition of the raw pellet, since only the upper part of the material located on the belt is controlled. Based on video monitoring systems for the granulometry composition of raw pellets, many companies have installed automatic control systems for the granulometric composition of raw pellets. The control elements of the system are the rotation speed, the angle of the tray, the height of the side, the amount of moisture, the consumption of bentonite, the load. The most difficult thing in this system was to create an algorithm for controlling the operation of the pelletizer, since it is necessary to determine the sequence of action of each factor or their combined effect on the process. Manual process control algorithms with several professional pelletizers were studied, and a comprehensive pelletizing process control algorithm was created on this basis. In general, the green pellet production control system in automatic mode is operational only with minor deviations in the quality characteristics of the batch or batch materials fed to the pelletizer or changes in the batch characteristics that change gradually without sharp fluctuations. If the moisture content, specific surface, fractional composition of the batch materials often change over time, the system cannot adequately assess the correctness of the control actions, it is necessary to transfer the system to manual control and then everything depends on the professionalism of the process personnel. Over time, when the neural network is implemented and a significant base of deviations and correct decisions is developed, the manual mode of operation will be minimized. Today, this system can only really assess the granulometry composition of green pellets by size classes in the video surveillance mode.​