Study on the fundamental characteristics of a filter press dryer with a featured model dryer

In order to study the fundamental characteristics of a filter press dryer (FPD) reported in our previous work which heats filtered cake through a thin diaphragm, we constructed a simple but featured model dryer (FMD) with the essential structure of the FPD. The results obtained with the FMD showed that the local water content in the cake is only a function of the local cake temperature, and that the relationship between the water content and the cake temperature is a unique characteristic for a given cake and a given drying condition. The same relationship is found to apply to the relationship between the temperature at the center of cake and the average water content of cake for the FPD. Furthermore, the average water content in the cake decreases exponentially with time when the water content is larger than 5% of the initial content, and the drying rate constant is higher for a thinner diaphragm and higher vacuum pressure. For the FPD with a large filtration area, it is shown that the nonuniformity in the drying of the cake causes fluctuations in local cake temperature.