Sub-Saharan industrial gases company Afrox in March indicated the Bokpoort concentrated solar power (CSP) project in South Africa’s Northern Cape is now ready for commissioning.
Afrox secured the long-term contract in 2014 to supply high-purity nitrogen and liquid petroleum gas (LPG) to the Bokpoort CSP project located 125km South-East of Upington.
The $565 million CSP project will have the capacity to generate 50MW of power with nine hours of thermal storage once fully commissioned by the end of 2015.
With the country’s state-run power utility Eskom unable to keep the lights on due to technical faults and unplanned maintenance, industry stakeholders are looking to more sustainable means of power such as, CSP as a commercially viable solution.
Assisting CSP with LPG
Afrox business manager for bulk Air Separation Unit (ASU) gases, Carte Lubbe explains that the company is supplying the Bokpoort CSP plant with a turnkey solution.
“LPG will be used by the CSP plant during the start-up phase for melting of salts for the Thermal Energy Storage system, whereby the transfer medium is heated to the point that it transforms from a solid state into a molten state,” Lubbe said.
As LPG is only required during the heating phase of the project, Afrox has designed a modular supply system that can be installed, dismantled and removed from the site within days, ensuring minimal project disruption.
Lubbe added: “Following the heating period, the entire LPG supply plant will be removed from site.
“Similar projects in the past have made use of fixed installations that become redundant after the start-up phase and take up unnecessary space, while costing a fortune to maintain. Upon service completion, our modular plant can be removed by specialised vehicles in under a week.”
LPG supply agreement
Following the heating of the molten salts, a blanketing system is required in order to minimise the risks due to flammable products, as well as minimising the emissions to the atmosphere and to avoid the deterioration of process fluids.
For this reason, the plant will include a nitrogen network that will provide an inert atmosphere to the salt storage tanks, the expansion tanks and the high temperature fluid boiler.
Lubbe reveals that the company has been working together with Bokpoort CSP to develop a nitrogen supply system to meet its specific needs. “As a result of the critical need for nitrogen, special care was taken to ensure that all aspects of demand and supply had been considered. The nitrogen supply system comprises an on-site nitrogen production system, backed up by a high pressure liquid nitrogen storage and supply system.”
The on-site nitrogen generating facility is supplied by Afrox’s parent, the Linde Group Engineering division, while the cryogenic storage facility and custom designed nitrogen reticulation system is supplied by Afrox.
According to Afrox, the logistical routes in place enable the easy delivery of back-up liquid nitrogen to the CSP plant which is easily accessible by road from several of its regional operations across South Africa.