South African gas and welding products company Afrox, part of the German Linde group, publicly unveiled its new R14-million high-purity hydrogen and oxygen plant at Pelindaba, west of Pretoria, at the end of last month. The new plant uses latest-generation electrolysis technology.
“We had a hydrogen plant, but we had it for some 40 years and we needed a new plant with new technology,” explained Afrox business manager: special products and chemicals Jaco Coetzee. “The new plant produces significantly higher purity gas, which we are very happy with.” The new plant provides hydrogen and oxygen with a purity of 99.999%. Previously, the company had to import high-purity oxygen.
Although hydrogen is both the oldest and most common form of conventional matter (as distinct from dark matter) in the universe, on earth, it exists only in combination with other atoms and molecules – most commonly, in water and various hydrocarbons. The electrolysis technology allows the production of hydrogen (and, of course, oxygen) from water instead of, as before, hydrocarbons (in the form of fossil fuels). Worldwide, only 4% of hydrogen is produced from water, as against 96% from fossil fuels.
Consequently, the new plant is one of the most advanced in the world and makes Afrox the only producer of high-purity oxygen in Africa. The new technology also means the new plant is much more efficient than the plant it has replaced. The new facility uses only 20% of the electricity consumed by its predecessor.
The main customers for the hydrogen and oxygen produced by the new plant are the petrochemicals industry, laboratories and universities. But the company is also optimistic about future opportunities in clean energy, both with the use of hydrogen itself as a fuel and with the production of fuel cells, to meet decentralised power requirements.
Currently, the plant is running at less than 50% capacity and so has considerable scope to meet increasing demand. As it is modular, it can easily be expanded when demand exceeds the current capacity.
Authorisation to acquire the new plant was granted in late 2012. It was then ordered from specialist Belgian company Hydrogenics. Delivered from Belgium and installed at the Afrox site at Pelindaba, it started operating in April. The plant is linked to Hydrogenics’ head office, allowing that company to monitor its performance and help diagnose any problems. This service operates 24/7 and the engineers who installed the plant at Pelindaba are always available, should there be a need to consult them
The entire plant is contained in three containers – one of 40 ft and two each of 20 ft in length. The 40 ft container incorporates a control point, a water demineraliser, four electrolysers and a hydrogen scrubber unit. One of the 20 ft containers holds an oxygen scrubber and the other a compressor. The plant is entirely automatic, and shuts down and depressurises itself should it detect any problems. However, human operators check all the plant’s parameters every three hours.
The electrolysis process uses potassium hydroxide as the electrolyte. In the process, the demineralised water is combined with the potassium hydroxide and electricity is applied. The resulting gases are removed and sent to the scrubbers to ensure the highest possible purity, while the electrolyte is retained. The plant is so designed that it only needs to be supplied with new electrolyte every five years.
The demineralised water is created by taking tap water and passing it through a 25 µm filter, a carbon filter, a 5 µm filter and then through a reverse-osmosis membrane. Then the water is passed through tanks of mixed bed resin. The end result is totally demineralised water. The plant is located on the South African Nuclear Energy Corporation (Necsa) complex at Pelindaba for reasons of safety. Necsa is not a customer for the plant.