This project trialled the Roben Jig (also known as Boner Jig) water-based process for washing metallurgical coal samples prior to coke quality assessment in a bulk-sized sample (340 kg). Information about two previous phases of this project can be found here (Geoscience BC project 2016-067) and here (Geoscience BC project 2017-013).
This phase of the project included testing samples in a larger scale coke oven to compare coke characteristics and quality from traditional washing methods.
Coal is BC’s largest export commodity. In 2019, BC metallurgical and thermal coal sales were $5.08 billion (view report). Innovative technologies help this sector maintain its international competitiveness.
Samples of metallurgical coal — used to make coke, an essential ingredient in steel production — are washed before quality testing in the laboratory. Coal from BC’s coal mines contains mineral and ash particles which must be removed to produce a clean sample for accurate coal and coke quality assessment. This is vital to accurately determine the economic value of a deposit and must therefore be reliable.
Currently, laboratories analyze coal samples using a float-and-sink method which uses organic liquids such as white spirit, perchloroethylene (PCE) and methylene bromide. These can have a negative effect on coking coal quality tests and potentially expose laboratory technicians to carcinogenic materials.
An alternative and effective water-based washing method, that could provide comparable results to that from an industrial coal washing plant, would remove the need to use organic liquids in the process and the associated health and environmental risks.
This project fits under Geoscience BC’s Strategic Objective of ‘Advancing Science and Innovative Geoscience Technologies’ and the goal to:
The project goal was to assess the complete coke characteristics and quality of Roben Jig washed coal and determine if the coal’s quality is equivalent or superior to two traditionally washing methods.
The main benefit of washing coal samples using the water-based Roben Jig is to remove the safety risks associated with the handling and use of organic liquids such as PCE. PCE is a known carcinogen and poses a safety hazard for laboratory operators who must handle the chemicals carefully to avoid exposure.
Investigations have also found that PCE can influence the properties of coal being tested, reducing the reliability of the test and perhaps leading to over- or under-valuing of a potential coal deposit.
The research team split one sample of raw coal from a single seam at a BC coal mine into three, and washed each sample using a different method: an industrial wash plant, a Roben Jig, and using organic liquids in a float-and-sink gravity separation. They sent the three washed samples to a laboratory and compared the characteristics of the coal samples.
They found that the fundamental coking characteristics of the samples washed using the three methods were similar and all produced good quality coke. Overall, the project found that the Roben Jig method is safer and produces similar quality coal, without the potential safety hazards for laboratory operators or a negative impact on the coking quality results of the coal samples.