Online estimation of rice powder moisture in a pneumatic conveying dryer

In rice powder drying process, the online estimation and control of moisture content is necessary in order to produce the desired product efficiently and continuously. However most of the rice powder drying and processing industries equipped with the pneumatic conveying/flash dryers are still lean towards the manual control procedures for monitoring the drying conditions, which renders high variations in the final product moisture content. As because many of the online moisture sensors used in powder handling processes are indirect, costly, inaccurate and have a short life span due to harsh condition present in the dryer. In view of these problems, the present study has developed a soft sensor model of the powder moisture of a continuous pneumatic conveying dryer involves with the rice powder processing. The empirical soft sensor is based on the temperature drop model of the batch dryer with the consideration of preheated air drying and negative pressure conveying. The soft sensor model was intended to evaluate the final moisture content of the processed material in terms of the control variables such as dryer inlet preheated air temperature and air flow velocity to facilitate the drying control. The various results computed using the soft sensor model with the stringent design specifications and operating conditions of the dryer have been compared with the experimental results obtained with the conventional oven drying procedure and the comparative results were found to be consistent.