Briquetting of UBC by double roll press part I: The application and limitations of the Johanson model

The development of the double roll briquetting technology for UBC (Upgraded Brown Coal) powder is introduced. After reviewing existing mathematical models, an attempt was made to establish a scale-up logic based on the Johanson model, which is the most classic logic in this field, suited for sensitivity analysis. As preparation, the concept of relative strength was introduced in place of compressive strength to enable comparison of briquettes of different shapes and sizes; and the internal friction data of the powder and the relationship between pressure and density were studied. The relationship between relative strength of briquettes of different shapes and sizes and the pressure estimated by the Johanson model was examined to establish the scale-up logic. A limitation of the model was found at the calculation of the pressure distribution. Some modification to the model seems to be needed. On the other hand, the estimated nip angle was not far from actual value. The study is to be continued and the result will be reported in Part II.