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# 164The Quality of Prebaked Carbon Anodes

Anode manufacturers should have strict QC system to guarantee the quality compliance of their final products during the whole production process because it is a mass production

process . The quali ty of prebaked carbon anodes in China has been improved greatly by the technical exchange s with international advanced partner s constantly during the past ten

years

. Chinese prebaked carbon anodes can not only be used in large amperage electrolytic cells b ut also large current density

ones . The gap of quality with the developed countries is getting

smaller and smaller. And the property variations, which was not paying much attention to in the past, has become one of the most important index to all manufactu rers.

Good quality prebaked carbon anodes can not only reduce

the carbon emissions in the downstream industry but also cut the production cost of downstream aluminium smelters. For instance,

it can save about 40 to 80 RMB per tonne of aluminium cost if

t he net consumption of carbon reduced by 10 to 20kg per ton ne of alumin i um . For a 500kt aluminium smelter, it could save 20 to 40 million RMB a year

. Considering the 13,000kt of aluminium output in 2009, it could save 520 to 1

, 040 million RMB

.

At the pre sent time, there is a certain gap of quality requirements for anodes between domestic and overseas

aluminium smelters because the domest ic smelters are not strict

about the quality of prebaked carbon anodes. For example, most

of the Chinese aluminiu m smelt ers require only one parameter,

that is electric al resistivity , while the overseas sm elters have 10 to 18 parameters need to be tested. If the anode specifications are not reasonable enough, it is very likely to increase the production

cost and decrease th e metal quality of smelters

. Cost

- wise, anode

cost is about 10% to 15% of the total aluminium cost , some even higher , so to some extent the anode property has a great impact

on aluminium cost

. More importantly, n owadays, large smelters worldwide are trying to increase the size or current density of the electrolytic cells to cut the cost, which consequently will require anodes to have even better quality to be running in these pots. So

it ’ s becoming more and more critical to improve the anode quality.

Ad vantage of large

- scale production

The large

- scale production of prebaked carbon anodes can

avoid the loss of raw materials and reduce the environment pollution during transport.

Comparison between transported raw materials and transported anodes as bel ow :

As the liquid CTP has the characters of no water and no melting, 40% of exported CTP is of liquid form in 2009. But it is very difficult to transport and store considering the

environmental issues.

Comparison between transported raw materials an d transported anodes as below :

The environmental protection treatment system costs not only the investment of the system itself, but also funds that keep put into it to keep it functioning efficiently. This would lead to

an increase to the unit cost of the anodes

. By large

- scale production, we could manage t o reduce the unit cost. For example, the RTO te chnology can settle the problem of benzoylene p ollution ultimately. But at present, the inves t ment is too high to popularize it all around the world. On ly some anode plants in Europe uses this technology . And it i s pr edicted that it will get popularized in the near future as every country will invest more to protect the environment. At present , the domestic anodes plant s can meet the environmental standar d s completely. Here take Sunstone as an example. The index is shown in Table

2.

Table 2 Polluting emissio s n from carbon plant

Workshop Pollution Emission mg/Nm 3 National

standard mg/Nm 3

Baking Fluoride 0

- 8 9

Coal tar 5

- 20 40

SO2 3

- 80 550

Dust 10

- 9 0 120

Calciner SO2 100

- 120 550

Dust 60

- 90 120

Green mill Coal tar 10 40

Dust 20 120

The large

- scale production can also make the further

investment on R&D possible and realize the recycling economy along with the changes of the abroad customers and the market.

Conclusions

We can learn that t he supply of GPC and CTP for large

- scale production in China is guaranteed . The large

- scale production can put a great dea l of investment into R&D and improve the quality of prebaked carbon anodes. T he gap of quality between the developed and developing countries can also be reduced in

order to meet the demand of the internati onal market. It can be proved by the increased export quantity of prebaked carbon



# 165anodes . Under the large

- scale production, it can be mor e economical and environmental friendly by transporting anode s instead of raw materials through the efficient transportation system. At the same time, these positive factors can promote Chinese prebaked carbon anode industry into a large

- scale production. It may become an active circle in the whole chain.

References

1. Xinjian Zhang, Shiwen Zhang

. “ The Carbon for Aluminium Industry and the production technology ” ( 2001 )

2. Robert H. Wombles

, “ Pitch Market Dynamics: impact of high growth / high Amperage Demand C urve ” ( Black China Conference, 2008 )

3. Zhenhui Huang, “ T he Chinese market of Coal Tar Pitch in

2010 ” ( T he conference of Coal Tar Pitch i ndustry

, 2010 )



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