According to the International Aluminium Institute (IAI), China used an average of 12,875 kilowatt hours (kWh) per tonne of aluminium produced in 2015, against a global average of 13,403 kWh. It was the only region to fall below 13,000 kWh, which it has done for the last three years.
Chinese smelters’ energy efficiency has risen as the country has replaced old smelting facilities with new plants. Rather than the efficiency improvements being a result of upgraded smelting technologies, it is the sheer size of the new facilities that affords Chinese producers such economies of scale as to bring energy usage per tonne of metal produced to world-beating lows.
“China is scaling up the pot lines and the pots. The smelters are significantly bigger, and it’s helping to lower energy consumption dramatically,” Citi analyst David Wilson said.
Dr Mark Dorreen, director of the Light Metals Research Centre at the University of Auckland, told Metal Bulletin that the efficiency gains made by China in recent years are mostly a result of bigger pots. And these advances are happening faster in China than anywhere else.
“Technology development is happening much faster in China, driven by the demand for new smelting capacity, than in the west and Middle East,” Dorreen said. “It took 25 years for western pot technology to go from 300 kilo-amperes (kA) to over 500kA, while in China they have gone from 300, 400, 500 and over 600 to now 640kA in only ten years.”
Although the Chinese plants are using a higher amperage in the pots, the physical size of the pots means that average energy consumption per tonne of metal produced is lower than in western smelters.
“When compared with western technology of similar amperages, the Chinese pots are physically even larger again,” Doreen explained. “This means that the current density [electric current per unit area] is actually lower. This is the main factor behind China’s lower energy consumption per tonne of aluminium produced.”
Demand for new facilities drives tech improvements
The speed of improvement in China is driven by demand for new facilities to produce more and more metal. These drivers are not present on other regions, where production growth has slowed far more than in China.
“In the west and in the Middle East they are not building many new smelters, so there isn’t much demand for new tech,” Dorreen said. “But in China, there is still demand for new smelters.”
So big are the new Chinese smelters becoming that there are efficiency gains to be had not just in the pot rooms, but all over the facilities. Though the overwhelming majority of the power used in an aluminium smelter is used in the cells, the power used in the rest of the plants is not altogether insignificant and is providing another efficiency avenue for the Chinese facilities.
And these efficiency gains are all being made despite little prompting from the government.
“China wants to make more metal. We’re not seeing regulations as a significant factor, or we would have seen a larger impact on existing smelters,” Dorreen said. “We were expecting a significant ramp-up in environmental regulations and enforcement, but we’ve not seen a lot of that yet. It is coming, slowly, however there is a lot of improvement left to go.”
Dorreen added a caveat to China’s impressive efficiency statistics, however. Numbers reported in China tend to be taken from very early in a new smelter’s lifetime, when it is operating at its optimal rate.
“Pot technology in China is capable of achieving very low energy consumption, however in practice the numbers claimed in most cases are not sustained over the entire lifetime of the pots,” he said, but added that the disparity would not be enough to stop China being the most efficient producer.
Efficiency improvements elsewhere
Other producers in other regions are making similar strides in efficiency improvements, such as at Norsk Hydro’s Karmøy pilot plant in Norway, which is targeting a similar efficiency to the most efficient new Chinese facilities, and Rusal, which recently launched the first RA-550 pot of a new generation running at over 550 kA at the Sayanogorsk aluminium smelter in Russia as part of a $28 million project.
“Hydro has ambitious energy consumption targets for its Karmøy pilot plant, apparently without any revolutionary breakthroughs,” Dorreen said. “Other western pot technology developers such as Rusal, EGA and Rio Tinto are also on a similar pathway to lower energy consumption. The playing field is not so uneven as the numbers suggest.”
But China is leading the way, and is also attempting to export its technology around the world. New-build smelters will exclusively be large facilities, to take advantage of energy. And China is trying to become the supplier of efficient aluminium smelter infrastructure and technology to the rest of the world. It has even been willing to provide financing for the new facilities.
“They’ve been trying to do that for some time, and had success in India, Iran, Malaysia and Vietnam,” Dorreen said. “This success is often linked to Chinese financial backing for the new smelters, however it hasn’t translated into newer western smelters picking up the Chinese technology yet.”
Western smelters may not have picked up China’s technology, but they aren’t building many smelters in the west any more.