Drying of parboiled paddy using profile control and detecting moisture placement

Abstract

In developing countries, post-harvest losses destroy about 1 5 - 1 6 percent of the rice crop. This figure is even as much as 40 -50 percent in countries where there are challenging natural events and climatic conditions, such as regular heavy monsoons. Some stages in the rice post-harvest system are more critical than others, particularly drying and storage. Rice millers and farmers are beginning to understand and accept the need to invest in post-harvest technologies not only because these technologies are now affordable, but also because they offer the potential to increase profits by adding quality and commercial value to the final products. Placement of moisture in the paddy seed is critical while drying. Traditionally, human experts determine the temperature and duration of drying to keep the proper moisture distribution within the paddy seed. It is known that, properly dried paddy will yield much higher output after the hulling and milling process.

The major considerations of this design are reducing the quantitative and qualitative losses which could occur during the drying of parboiled paddy rice. This study includes the design of a temperature profile controlled LSU (Louisiana State University) type dryer with details of the methodology, and design of the components to detect moisture placement in paddy seed which could in turn used to determine the temperature and duration of drying.

A reduction of two percent of milling loss is achieved by temperature profile control. It is established that the moisture placement can be determined using capacitive and resistive moisture sensors. A correlation between capacitance and resistance to moisture placement in paddy is determined by carrying out trials with human experts. Linguistic variables and the actions taken to control temperature and drying time are established in this study. As further improvements a fuzzy logic based approach is discussed to simulate the human decisions.