When it comes to processing industrial waste in the steel industry in an environment friendly way, ZincOx is a world leader with no close second. Furthermore, it is gaining ground with the set up of its first Full Cycle plant in Vietnam. Andrew Woollett, Chief Executive, ZincOx, shares interesting insights with Steel360 about various technologies concerned with metal recoveries, the upcoming plant in Vietnam. Excerpts of the interview
What prompted you to start ZincOx? When did you first realise the opportunity?
I am a geologist and was running an enterprise in mineral exploration and development in Africa when we came across a very interesting zinc deposit in Namibia. The mineralogy was unusual and other companies were not able to extract the zinc out of it. We put together a very talented team of zinc metallurgists and later, developed a new flowsheet. Then we sold our share and it was developed as a mine and integrated refinery at the cost of USD 450 million and it became the biggest zinc mine in Africa.
My company looks at developing unconventional sources of zinc. In the first few years of ZincOx, beginning 1999 we were mostly concentrating on primary ore deposits. Later we came up with a better solution for extraction of zinc from Electric Arc Furnace Dust (EAFD) and in 2007, we realised that we had got a ground breaking technology and ever since we have been applying the new technology for extraction of zinc.
Tell us about the full cycling technology of EAF and IF dust ?
The objective of this technology was to have a process which got very high metal recoveries while generating no solid waste and remain economically viable even at low zinc prices. It is done in three-stage process.
We take the EAFD and mix it with coal and a binder make it into briquettes and gently introduce this into the furnace. It is a circular tunnel about 5 metres wide, with fixed walls and roof. It takes about 16 minutes for the full rotation during which the coal reduces the metals back to their metallic form. This is done at about 1300 degrees centigrade. At that temperature, zinc metal is a gas, which boils off and immediately reacts with the oxygen in the upper parts of the furnace forming zinc oxide particles, which are very tiny, are then cooled and filtered . That is intermediate zinc oxide concentrate, which runs about 60% zinc.
The iron, consequently, is left behind. This is about 50% iron, of which about 85% is in metallic form. This iron is essentially very low quality DRI. These two intermediate products can then be upgraded to final products. If we take the DRI, we can put it into the conventional submerged arc furnace-type smelter, where the temperature is raised to about 1550OC. The iron sinks to the bottom as pig iron, and the slag, which can be used in the cement industry floats on the surface. Any residual zinc that carries through to the melter also recovers back 95% of the zinc about to go through the iron product and so the overall recovery of the zinc is over 99%.
The biggest impurity of the intermediate zinc concentrate is salt, which we can wash out together with lead and other metals. Indeed we produce a lead concentrate, with about 80% lead. The salt goes into an effluent. We put the effluent through a sophisticated treatment plant, which removes all the metal impurities and what we’re left with meets the international standards for marine discharge.
We started with hazardous waste and after our process there are just saleable products, except for the salt, which of course goes off into the sea without causing an environmental problem.
What is the minimum and maximum capacity plant that can be set up based on this technology ?
As 90% of the revenue is zinc so, it is difficult to be precise about capacity because it depends on the grade of the dust, which can be very variable, anything from 20% to 35% zinc. But we could take it as average 28% zinc. We are trying to find regions and areas where a 100,000 tonnes of dust are being generated. Because this technology is so environmentally benign, we’d make a 100,000 tonnes minimum.
How different is it from other technologies, specially Chinese RHF technology?
There are about 64 different patented ways of treating this dust. The industry standard is a very well known and simple sort of equipment, the rotary kiln and it recovers about 95% of the zinc. The resulting iron bearing material is all oxidised and is a waste. In part, it has been possible to use this in some industries. But people have been increasingly worried about lead and cadmium in this material. And governments are getting stricter and stricter about environmental regulations. The other benefit of full cycle is that we don’t have any cost of waste to go to landfill.
Now, it would be fair to point out that we are using a more sophisticated process which is producing value added products. So the cost of our installation is over twice that of the rotary kin. But because our product is worth so much more it compensates for the extra development cost and it is much better process for the environment. And therefore, we feel there is an increasing market and interest in our technology.
The Chinese RHF technology has not been applied to dust of this type. It’s been applied to blast furnace dust, where the amount of zinc contained is extremely low. So, the RHF in China have been used to get rid of the last zinc rather than concentrating on it as the main source of revenue.
How many plants in the world have been set on this technology?
The core technology was first built in Korea. It’s been running for five years. And the first plant, which is the Full Cycle technology, is under construction in Vietnam. The upgrading of the zinc intermediate product is quite new and it uses very simple equipment but people have not applied it this way before; because they never had a feed which is of such high quality, which is uniquely from the furnace, which has been well demonstrated in Korea.
When do we expect Vietnam plant to start?
We don’t own plants anymore the plant can start in the middle of next year, may be around June 2019. We sold the Korean plant to Korea Zinc. They were so pleased with that- they armed into the pre-development work in Vietnam. ZincOx did all the designing with our technology and then, we sold our interest in the project to Korea Zinc. Now we’re moving ahead with our own plans for Europe and Japan.
Can this technology process dust bearing low Zinc %?
Well, it can, but the problem is, as most of our revenue is from zinc, if we have low zinc grade, it means that we don’t get enough revenue potentially to cover our costs. So, it is technically feasible but probably not economically viable unless the mills were prepared to pay a disposal fee. I think it’s quite interesting to talk about disposal fee because our technology does not take any sort of fee from the steel mills. Except in recent years, where the zinc price has been high, the existing traditional treatment methods has always required a subsidy from the steel industry to be viable. In fact, at high zinc prices, we will share some of that upside with the steel mills, so that we can transform the EAFD into a profit centre.
Do you see India and other scrap consuming countries as potential buyer for this technology?
The issue in India is that, in addition going to electric arc furnaces, scrap is used in conventional steel production using blast furnaces. Because India’s production of blast furnace is so high, it uses a lot of scrap and there is less left for Electric Arc Furnaces. Furthermore a lot of electric arc furnaces use DRI, and so there is no zinc feed or, therefore, in the EAFD.
However any EAF that is working on high proportion scrap, should have dust that would be interesting to us. Therefore, there could be the potential for Indian plant. But in the first instance, we would perhaps be interested in exporting EAFD from India.
How does the math work for an investor? Out of every ton of dust processed, what percentage of Zn is extracted?
Well, it all depends on the chemistry of the dust. We get 100% of the iron and 100% of the zinc. If it’s 25% zinc, then it’s 250 kilos of zinc per tonne of dust processed.
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