At 20c per share dividend they would be paying out around $166m...

At 20c per share dividend they would be paying out around $166m per annum, whereas our scenario above shows around $300m in FCF before paying dividends per annum (which I think is conservative at US$110/t). So around $140m per annum of cash building up x 10 years (without assuming any investment of that cash, which we should do) would give around $1.1bn in net cash (after deducting current net debt) or $1.30 per share for a terminal value. Without giving any value to any other assets, so lets conservatively say $1.60 TV, before discounting (however the discounting would be roughly offset with the assumption of investing the cash). That's 10 years, obviously 15 years will be higher, and I think we have around 15 years of reserves. Not sure why you went from $2 in divs over 10 years to only $2.25 in divs over 15 years (seems overly conservative to only apply 5 cps dividends for the last 5 years).

Obviously all valuations that involve so much judgement will turn out to be wrong, however I currently have a back of the envelope valuation as a minimum of $2.50, however I think a more realistic valuation if the coal market ends up looking anything like what I think it will is $3 - $4, as I think there will be some years where it generates very large amounts of cash compared to the current market cap.