Case Study: C.I. MILPA S.A., Colombia
C.I.Milpa is a Columbian extraction and processing company that has acquired several Ash Probes from Bretby Gammatech. The company carried out trials with one of its Ash Probes back in 2005, which were hugely successful and since then C.I. Milpa has bought four Ash Probes.
These are used to control the quality of the coal entering the company, as well as the inert material produced by the washing plants. The extraction of coal is carried out across an area of approximately 200 hectares, with the coal extracted from three different mines, San Miguel, Incarsa and La Limpia, where low, medium and high volatile coals are found.
The ash content percentage of the coal ranges between 6% and 25%. Also, coal is purchased from 150 local supplies, with similar volatile ash content levels.
Bretby Gammatech’s Ash Probe is used at access points of the plant for two purposes; to analyse the ash in the coals purchased and produced and secondly to analyse the ash content of the coal sent for export. At the washing plants, the equipment is used to analyse the output of ash and to control the quality of the washed product.
The Ash Probe is being used to enable separation of the coals. If the product is tested and reveals less than 10% ash content it is sent for export or is used in the coking process, greater than 10% ash content and the coal is sent to the washing plants.
Where the coal has an ash content that is greater than 10%, the product is organised in piles according to the quantity of ashes, for example from 10 to 12 in a pile, from 12 to 14 in another pile, from 14 to 16 in another pile, etc. This process is carried out in order to send coals with the same grade of ashes to the washing plant for greater speed and efficiency. Occasionally, this organisation is used to mix coals, for example a coal with a 7% ash content with one with 12, in a 1:1 proportion to obtain a coal with 9.5% ash content.
There are significant benefits that the plant gains from using the Ash Probe, in terms of time savings, as the process to obtain ash content readings in the laboratory takes an average 15 hours, compared to the 5 to 10 minutes it takes to obtain accurate ash readings with the Ash Probe.
It also means coal-loaded vehicles can be tested at the entrance to the plant, so the destination of the coal can be quickly decided upon, according to its ash content grade. This results in cost savings too, as it means clean coals do not need to be washed and it also improves product quality as it prevents ‘dirty coals’ with a high ash content being directly used in the coking or export process.
Coal processing
Coals extracted by the company C.I. MILPA S.A., as well as those purchased from suppliers are used both for export and for processing in coking plants and exported to steel mills. The low volatile coals that are exported present ashes below 10% and the coke for export presents ash content ranging between 11 and 12%.
Coal with an ash content greater than 10% are passed through the washing plants. The plant contains three plants, two of them with an average washing of 50 tons/hour and the other with an average of 150 tons/hour and an output of 75%.
MILPA supplied some of the most prominent clients in the coking coal and coke markets in Colombia, so it is essential that the coal is processed to the very highest quality levels.
