Petkus completes modern corn seed processing plant in China

by Emily Wilson
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In the center of one of the largest maize growing areas of China, the China National Seed Group Corporation (CNSGC) recently constructed a new corn seed plant in the city of Chengde, approximately 250 kilometers northeast of Beijing. The new plant will support the growing maize production in China.

The 35,000-square-meter plant was manufactured by Petkus Wutha GmbH, Wutha-Farnroda, Germany. The corn seed plant will have an annual capacity of 20,000 tonnes of ear corn per year, and is the biggest such project in China. According to Petkus Wutha, the facility will meet the growing corn seed demands in China, which is currently producing about 15% of the global maize output and is the third largest maize exporter.

The project began in February 1999. The complete plant was delivered seven months later in modular elements in 57 containers and was assembled within four months. Test operation and training of the technical staff began in spring 2000.

The Chinese Vice Minister of Agriculture, Lio Yang, and the German Ambassador to China, Christian Ueber-schaer, attended the inauguration of the plant on Sept. 24, 2000.

THE FACILITY. The plant can intake harvested raw product via truck in either ear corn cobs, wet loose corn or dry loose corn. Usually, incoming harvested ear corn is without husk, as husking is often done by hand in the fields in China.

The Chengde plant produces treated or untreated corn seed and provides bulk loading into trucks or in various bagged sizes. The plant consists of five main sections: reception, ear corn drying, storage, seed cleaning and bagging.

The receiving section includes an intake pit, vibration feeder and sorting belt conveyors. Corn cobs are unloaded in an intake pit, where a vibration feeder with screens elevates the corn and separates the loose kernels and small waste. Ear corn cobs are then distributed on four sorting belts to a section where 16 employees remove by hand the unhusked ears. The good corn ears are elevated by a distribution belt into the drying house.

A special feature of the new seed processing plant is the ear corn dryer house. The modular dryer — 35 x 18 x 11 meters and made from galvanized steel sheets — uses warm air circulation to dry the ears, usually within two days depending on the moisture of the corn.

The dryer house works as a single-pass-reverse-system, in which each drying chamber is provided with one heat exchanger and fan. This system allows each chamber to be controlled separately and allows small quantities of ear corn to be dried while efficiently controlling energy use and costs.

The modular construction allows for cheaper shipping costs and easy assembly and erection by local companies, the company added. In addition, the modular dryer house can be extended at any time with standard elements, if required.

The dryer house constructed for CNSGC has 12 drying chambers and six can be expanded later to include a unit that produces heat by burning corn spindles.

The storage area (22 x 7 x 17m) includes an ear corn shelling section, pre-cleaning of loose corn, a silo plant and two more reception points for dry and wet loose corn, which is dried in a separate continuous flow dryer. The dried ear corn are shelled in a special 30 tph shelling machine.

Loose corn is conveyed into the pre-cleaner. With screens and air channels, the sheller rejects corn spindles and waste, which flow into a separate bin or bag. The cleaned corn seed will be conveyed into the silo plant. Dry loose corn is input directly into the pre-cleaner, while pre-cleaned wet loose corn is conveyed first into a 3-tph capacity continuous flow dryer and then into the silo.

Loose corn is temporarily stored in a 14,000-tonne capacity square profile wall silo. The self-emptying steel silo consists of two blocks, each with seven interconnected, hoppered silos equipped with aeration systems and temperature control devices. Like the dryer house, the modular-constructed silos and hoppers were erected on site.

The 8-tph capacity seed cleaning section combines fine cleaning by a Petkus Multicleaner, sorting and calibrating by five cylinder graders, cleaning by gravity separators and a chemical seed treater. Belt conveyors carry the pre-cleaned corn seed from the silo plant into the Multicleaner, which consists of six screen layers, two independent air suction channels and electronic control of each flap to optimize the cleaning process.

The cylinder graders then produce six different corn sizes that will be stored into separate buffer bins. The graded corn is then loaded into bags by a separate bulk loading station. This process allows the other five types of sized corn to be conveyed to the gravity separator later, if required. Only one size of corn is continuously loaded into the gravity separator to remove small and light corn from the good corn seed.

The seed is then conveyed to the chemical seed treater or directly to the bagging line for untreated corn seed. Designed especially for treating corn seed, the treater consists of a spraying chamber with two impeller discs and a mixing chamber. The chemical liquid treatment protects the seeds before sowing. After treatment, the corn seed is dried in a special octagonal drum dryer with an aeration device.

The bagging line consists of two bagging stations (up to 50 kilograms per bag), one for treated seed and another for untreated seed. A third bagging line for treated seed has eight bagging stations for 1-kg, 2.5-kg or 5-kg plastic bags.

Large buffer bins before the bagging line ensure continuous operation of the plant, and a 100 x 30-meter warehouse was built for storage and trade.