Improving yields, efficiency and safety with new heat exchangers

Botash is the largest producer of natural sodium products in Southern Africa, yet they’re always looking for ways to improve their operations. They chose Vahterus Plate & Shell Heat Exchangers and instantly saw an increase in their production yields. Botash (Botswana Ash (Pty) Ltd.) is located in Sua Pan in the north eastern part of Botswana, about 180 kilometres from Francistown. Since starting their operations in 1991, they’ve grown to become the largest producer of natural sodium products in the Southern African region and they currently have a production capacity of 300 000 tonnes of soda ash (sodium carbonate) and 420 000 tonnes of salt (sodium chloride) per year. Botash now has offices in South Africa and Zambia, and the company’s vision is to be Africa’s supplier of choice for natural sodium products.

Intercooling is essential

At Botash, efficient intercooling and heat transfer is a crucial part of their sodium bi-carbonate production process, determining both its efficiency and the product yield. The first step of soda ash production is carbonation, in which carbon dioxide reacts with a sodium carbonate-rich brine to form bicarbonate crystals. The next step is crystallization. This involves bicarbonate super saturation followed by the crystallization and takes place in crystallizers arranged in series. It is here that intercooling is used to promote the precipitation of bicarbonate crystals. If the intercooling is not efficient, the bicarbonate rich stream is lost in the thickener overflow and this has a direct impact on the throughput of the plant.

Aim to improve from leaking Plate & Frame

While Botash had successfully expanded their production over the years, they knew that more efficient cooling would improve their yields. In addition, some of their existing plate and frame exchangers were leaking with crystals forming between the gasket and plate within the gasket groove on the hot side. In fact, the gaskets were incompatible with the high temperature of the washing water. And they were also troubled by fluctuating brine pressures on the cold side.

These problems led to additional maintenance costs because they needed to replace the gaskets regularly, and the leaks also led to corrosion of their equipment and structures. In addition, the leaks meant a loss of hot washing water, which increased their steam use, as well as a loss of product from the leaking heat exchangers.

As a result of all these issues, Botash decided to install more reliable and higher quality heat exchangers. After thorough research, and trials with different heat transfer technologies, Botash selected Vahterus Plate & Shell heat exchangers (PSHEs) as their preferred heat exchanger technology.

Great improvement and increased efficiency since the change to Plate & Shell

Botash started up their first Vahterus units in the crystallisation circuit in 2016, and since then their operations have been highly efficient and trouble free. They instantly saw an improvement in their production yields. And, because they were able to deliver more product faster, they experienced a phenomenal payback time for their new Vahterus PSHEs. The interval between hot water back-flushing was also improved compared to the old plate and frame exchangers. In addition, plant safety was improved thanks to Vahterus’ leak-proof heat exchangers, and the moral of their maintenance and operational staff improved too – added benefits of immeasurable value.

Thanks to their positive experience, Botash have since decided to replace additional units with Vahterus PSHEs.