OPTIMISING DRYING SYSTEMS IN COTTON PRODUCTION

Cotton is one of the most commonly used fabrics in the world, and its cultivation goes back almost 7,000 years. It is derived from shrubs of the Gossypium genus, part of the mallow family, and is grown in tropical and subtropical regions of the world. The plant’s seeds are surrounded by white, fluffy ‘bolls’ consisting mainly of cellulose, from which, after a long and complex process, cotton threads are produced.

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Brazil is the world’s fourth-largest cotton producer, and around seven per cent of its planted area is represented by SLC Agricola. The company is one of the country’s largest agricultural producers, and has been growing cotton on the Brazilian savannah for more than 25 years. Its mission statement puts considerable emphasis on sustainability, and it uses the latest technology to improve efficiency. For example, its cotton harvesting machines are equipped with sensors that record georeferenced productivity data, allowing crop production to be visualised on harvest maps.

Once harvested, the cotton bolls are processed in cotton mills on SLC Agricola’s farms. Samples are first subjected to fibre quality analysis in a laboratory, to ascertain their characteristics, including length and resistance. Then the bolls are stored in bales before being transported to foreign and domestic markets, where they are spun into yarn.

One key step in the process is the drying of the cotton bolls after harvest, which is essential for the quality of the final product. At SLC Agricola’s farms, there were issues around their drying technology, leading the company to call Güntner for help. Thainã Garcia, Güntner’s Sales Manager EPC line in Brazil, arranged a technical visit, where he could identify points for improvement and adjustments that could be made to increase the efficiency of the process.

“Their heat exchangers just weren’t giving them the performance they required,” explains Garcia. “One reason was that they hadn’t taken into account the amount of particles in the air, so the heat exchangers were getting blocked and the team was spending hours cleaning them every week. Also, they hadn’t properly calculated the total flow of air available throughout their ventilation systems, and so hadn’t allowed for the pressure drops the fans experienced.”

Garcia says that at one of the farms, for example, the customer had a heat exchanger that heated 16,200m³/h of air to 45°C, while in fact the requirement was for 60,000m³/h of air at 65°C.

“The customer didn’t know how to do the calculations, so I gave him my support. I verified that he needed a new heat exchanger that provided an air flow almost four times greater and that generated air that was 20°C warmer.”
THAINÃ GARCIA SALES MANAGER EPC, GÜNTNER

As well as resolving efficiency issues, Garcia also proposed a solution to solve the issue of the heat exchangers getting blocked: this was to increase the spacing between the tubes and the fins, resulting in far less need to clean the equipment.

In total, ten new Güntner Air Cooler Coils were installed across six different farms belonging to SLC Agricola. All of them were individually customised, with different dimensions and fixing points, because each farm had them installed in different ways, some horizontally, some vertically, others inside boxes. All of them were designed for maximum efficiency in the drying process. And three years later, that’s exactly what they continue to provide.

“Today, the heat exchangers are still operating perfectly and the drying process has improved significantly,” says Garcia. And the customer has been impressed by Güntner’s expertise.

“The equipment designed by Güntner has greatly improved our system. Because of its quality and performance, Güntner is the heat exchanger company we want to use for all our needs at SLC from now on.”
JOSÉ VALMIR DE SOUZA REGIONAL CO-ORDINATOR, SLC AGRICOLA