Our large chamber mills are hammer mills that are used when high throughput rates are required. They have a grinding chamber diameter of up to 1200 mm and achieve a throughput of up to 80 t/h depending on the recipe.
The large chamber mills are characterized by a robust design of the grinding chamber and the robust inlet flaps and impact plates ensure wear resistance. High-quality components, especially the balanced rotor design, ensure a long service life and reduce maintenance costs.
Hammer mills with a smaller food print and grinding chamber areas from 0.3 to 1.9 m² are our high speed mills.
The mills of the large-chamber series are designed for high grinding performance. Thanks to the special design, the rotors start up very quickly despite their size, and the beaters can be changed quickly and easily in just a few minutes thanks to the carrier frame. Both reduce downtime and increase throughput.
In hammer mills from Tietjen, the grinding chamber is symmetrically designed. This allows the rotor to be operated in both directions of rotation, which not only increases the service life of the beaters and screens, but also keeps the structure of the ground material constant over a longer period of time.
Depending on the design of a hammer mill from the large-chamber series, screen changes can be performed manually, semi-automatically, or fully automatically during operation (when the grinding chamber is empty). This also increases the throughput of the overall solution and the individual performance of our mills.
Tietjen has hammer mills in operation worldwide in various applications. The field of application of our hammer mills is very wide. And the number of mainly natural raw materials and biomasses that are ground increases continuously. Tietjen’s main focus in the grinding of raw materials is on:
Our hammer mills are used for the shredding of raw materials. The mills grind a wide variety of input materials until the material reaches the desired particle size. Another important quality criterion besides the particle size is the uniformity or distribution of the particle size (both factors together determine the so-called grinding spectrum).
The exterior view of a hammer mill design by Tietjen shows that the main components are the grinding chamber, a coupling and an electric motor mounted on a supported base. In addition, there is the control unit of the system.
Inside the cylindrical grinding chamber there is a rotor, which is connected to the electric motor via the coupling. At the top of the grinding chamber there is the inlet for the material to be ground. The inlet flap can be adjusted depending on the direction of rotation. To the right and left of the inlet are the impact zones and the remaining area is equipped with screens. Tietjen hammer mills have a particularly large sieve area for a high passage or throughput of the mill. At the bottom of the grinding chamber there is a collecting container for impurities, such as stones or metal parts. With the help of our AGS AD feeding system these impurities can be automatically separated and discharged.
At the beginning of the process, the material to be ground is fed into the grinding chamber with a feeding or dosing device. The feeding process needs to be as uniform as possible – in terms of quantity per unit of time and per distribution over the width of the grinding chamber. The feeding device is as well used to ensure good ventilation of the hammer mill. This aspiration is necessary for transporting the material to be ground through the hammer mill, keeping the screens free, and cooling the grinding chamber. The aspiration is to be optimally controlled based on the specifications for vacuum and volume flow.
In the grinding chamber of the hammer mill, the rotor rotates at high speed. A defined number of removable beaters are attached to the outer circumference of the rotor. These beaters are also called hammers. They are precisely balanced to avoid vibrations. In Tietjen hammer mills, these beaters can be replaced very quickly and easily.
During the process the rotating beaters grip the material to be ground as it enters the beating circle of the rotor. The impact of the beaters achieves the greatest particle size reduction effect. The beaters throw the pieces/particles at the impact plates and screens, where they are further broken by the impact. The ground material remains in the grinding chamber until it is so crushed that it can pass the screens in the grinding chamber.
The screen has the function of limiting the size. The oversize can be changed by replacing the screen. In addition to the screens, the aspiration, the beaters, and the speed have an influence on the particle size. Each of these factors can be individually adjusted to the customer’s recipe with Tietjen’s hammer mills. In general, it can simplified be saying:
the finer the end product. However, a lot of experience is required to obtain the most uniform particle size (“narrow particle band”) possible, which is matched to the customers’ recipes or the targeted pellet size and quality.
In the next process step, the ground material falls out of the grinding chamber through the discharge opening and is transported away mechanically or pneumatically for further processing.