Technology for producing high-quality slag as a by-product of sulfuric acid production from pyrite

The iron oxide red project at the MCC plant enables the extraction of iron elements from mineral powder to produce iron oxide red; it also improves the leaching efficiency in the subsequent leaching stages. However, this process seems to be kept secret

Experience needs to be gained in terms of co-firing.

The comprehensive utilization of slag is the goal that companies in the sulfuric acid industry are striving for. We follow this approach: first, we ensure strict quality control from the selection stage, aiming to achieve a grade for the selected fine sand of over 45, an iron content of 43, and a moisture level of less than 9. Next, we use some dry slag in the mixing process to combine it with the fine sand of grade over 45; the resulting material entering the furnace has a sulfur content of 36 to 39, an iron content of 42 to 43, and a moisture level of 8 to 10. The iron slag produced in this way has a grade of over 60, making it suitable for sale to steel mills at a favorable price.

The production of iron oxide red from high-quality slag has already been carried out on a large scale in Yunfu, Guangdong. But it’s hard to say about the economic benefits, and the manufacturing process isn’t a secret.

To improve the grade of pyrite slag, it is generally done by roasting pyrite with a high sulfur content; the higher the original grade of the pyrite, the higher the iron content in the resulting slag. Yunnan University of Science and Technology has developed a process that involves flotation of pyrite, raising its sulfur content to 48%-50% and achieving a fineness of 200 mesh. As a result, the slag obtained through this process typically has an iron content of around 65%, allowing it to be sold at a higher price.

I’m from the pyrite mines in Yunfu, Guangdong. The use of slag to produce iron oxide red has already been scaled up, but it’s not profitable~~~ We lose several million yuan every month~~

(Baking low-sulfur pyrite along with other ores with high sulfur content allows for the production of sulfuric acid, while also yielding slag with a high iron content as a by-product.) I believe this approach is difficult to adapt to the current conditions in China; it would be more feasible to use sulfuric acid slag in iron extraction, or to use the tailings for making bricks or as an additive in cement. There are many research materials available in China, as well as those related to industrial production; you can search if you’re interested.

This problem is mainly the result of years of wrong *habits. The production of acid from pyrite has, for many years, been affected by the low grade of domestic ore, which results in low-grade raw materials and consequently low-grade burn residues. It will be very difficult to find a solution later on. Therefore, fundamentally, it is necessary to start with mineral processing in the mining areas in order to increase the sulfur content of the ore. Fees for transportation, loading, and unloading will all decrease, and the furnaces used by acid production companies will also be easier to operate. But despite this call having been made for many years, no real progress has been made – there is no preferential policy in place for the industry as a whole!

Even during the planned economy era, there was a concept known as the \"high-quality ore policy,\" which involved building processing plants locally to transport high-grade ore outwards; this not only saved on transportation costs but also facilitated its further utilization. However, after entering the market economy, **industrial policy priorities did not shift in that direction, which led to this situation. The earliest use of slag was the sulfuric acid slag from Nanhua; Nansteel used chlorinated pellets, apparently by introducing production lines from Japan (due to the passage of time, I don’t want to look up relevant information). At present, Yunfu and Huangmailing are the more substantial in scale; Yunfu is ahead in terms of technology, but as mentioned above, its economic performance is not yet satisfactory. Huangmailing seems to be involved in the production of pellet ore, so the profits should be good. There are also some plants that produce high-quality iron slag; some of this slag is produced by directly processing high-quality ore, while it is obtained through slag concentration processes. In most cases, the volume of such slag is not sufficient for use in pellet production, so it is simply sold as slag.