Drying and Storage Plant Attached to a Country Elevator (I)

Application as a Bin Dryer

Abstract

Drying and Storage plants (“In Bin” Drying System) have been developed and spread in Europe and America. Originally, Drying and Storage refers to the drying of paddy in the same bin in which it is to be stored. Drying usually can be accomplished with unheated air, but heating equipment might be available as an insurance for periods of high humidity weather. Squaral or round type of galvanised steel bins are installed at these plants.
In Japan, the squaral bin type plant which was imported in 1966 to the TOKACHI Agricultural Experiment Station in Hokkaido was the first plant and its commercial name was DRYSTORE.
Afterwards similar facilities were attached to some other Rice-center plants and they are now accepted as efficient means of storage and drying, and their use is spreading in Japan.
The drying and storage plant consists of the bottom ventilation system of stored grain for drying and conditioning and the mechanical handling system including airsweep floors for bin self-emptying. Generally, the drying and storage plant has many uses such as a dryer, a bulk storage bin, a temporary storage bin (a holding tank of undried paddy) and a tempering tank during drying process.
Since the end of 1971, the authors have been investigating on effective operation of the drying and storage plant (so called DRYSTORE) attached to the Country Elevator of MUKAWA Agricultural Cooperative Association in Hokkaido, that was built for the first time in Japan. This plant is installed with 40 squaral steel bins of about 90m³ (length: 5.14m, width: 3.13m, depth: 5.6m) or 55 tons capacity of dried paddy (Fig. 1).
This report is on a series of fundamental investigations conducted to determine the drying characteristics of paddy, using this plant as a drying facility with supplemental heated air (less than 30°C). The results obtained are as follows.
The drying rate reduced with increase of the thickness of paddy and increased with increase of airflow rate in both 1 bin and 3-4 bins drying tests. But when the airflow rate exceeded certain values, the increase of drying rate became smaller and it reached a fixed value (about 0.7%/hr) at 2m³/(sec. ton) airflow rate (Fig. 8).
From the viewpoints of uniformity of moisture contents and thermal and economical efficiency, the maximum depth recommended for bin drying of paddy was 2 meters when 1 bin was used as a dryer.
Whenever bins are available for drying, several bins should be used as a dryer for the efficient use of bins. And the paddy should not be piled over 1 meter depth in each bin.
When large difference of moisture content is observed between top and bottom layer samples, it may be advisable to move paddy from bin to move paddy from bin to another in order to eliminate thie moisture difference.