Graphite Rounding New, Efficient Process for the Rounding of Graphite
Due to its use as a material for anodes in lithium-ion-batteries, graphite is of great importance in the context of electro-mobility. In order to obtain the high purity required for battery applications, the finely-distributed, so-called flake graphite which occurs naturally in stone must be processed in various steps.
Spherical graphite (SPG) is ideal for use as a raw material for anodes. Its smooth, small surface prevents flaking and ensures low irreversible capacity loss and long service life. Due to its high tap density, high charging is achieved and consequently energy density is higher. The Netzsch business unit Grinding & Dispersing and Dorfner Anzaplan have joined forces to find a more efficient solution for graphite rounding to overcome the disadvantages of the previously widespread used process requiring more than 20 classifier mills installed in rows: In a first step, the flock graphite is pre-ground to the optimum initial particle size for spheroidisation in a classifier mill or fluidised bed jet mill.
The actual particle rounding process takes place directly downstream in the newly designed Netzsch Gyrho Rounding Unit which is available in various construction sizes and can be specially designed to suit the necessary output quantity. For larger throughput volumes two (or more) machines can be operated simultaneously and can replace the train of 20 machines or more as mentioned above.
The increase in efficiency and the advantages which the new process-optimised system offers compared to the previous standard-plant train are impressive: Plant availability has been increased by 30 % in comparison to previously used processes as the number of machines and consequently the probability of breakdown is reduced drastically.
For this reason, maintenance costs are reduced by almost 90 % and the compact setup means the plant can be installed in a 60 % smaller space, states the firm. In addition to this, the Netzsch/Dorfner Anzaplan system requires only half the installed power of a plant train while achieving the same production capacity and using 60 % less energy due to its optimised mode of operation.
Product yield is a decisive improvement in the process. By optimising the design of the grinding chamber and reducing the number of components, it was possible to increase yields of 30 to 40 % achieved by the standard system to 60 to 65 %, adds the company. At the same time, using specific settings, it is possible to achieve the maximum yield of final product with the desired quality.
Quality criteria such as distribution width, tap density and particle size can be influenced by varying the process parameters. In this way, using the newly developed system, all qualities required by the market, such as spherical graphite with a tap density of more than 960 g/l and a d50 value of 16.8 μm (yield based on a raw material volume of > 60 %) are achievable, according to the company.
Thus, using this process developed by the companies, not only a higher plant availability and raw material efficiency are achieved at the same production capacity but also a significantly higher product quality. The mentioned improvements result in an approximate 35 % reduction of operational costs, demonstrating the technical superiority of this newly developed system solution which has decisively improved the economic efficiency of graphite rounding, mentions the firm.
In Netzsch´s well-appointed application laboratory in Hanau, Germany, which forms part of the comprehensive service offer, graphite-rounding tests can be carried out on a laboratory scale and up to a production scale. Material samples are processed under production conditions and their behaviour analyzed to achieve the best result at the highest efficiency.