Coal is not the only solid transported by slurry. Some ore has been transported by slurry pipeline for quite some time. Particularly in Brazil.
Years ago, when concerned about erosion from solids in pipelines I did some research on the subject. It is well documented and there is experience supporting documentation. Erosion is not absent it is not as bad as one might think if velocities and bends and valves are managed properly. I could dig out the papers but one could Google the material faster.
Slurry pipelines in the US would have already been built and the coal trains would have been much fewer in number but rail interests in the US blocked them by denial of right-of-way. It was quite a battle 50 years ago. Never mind the problems of finding water in Wyoming and then cleaning and disposing of it in Connecticut or where ever the pipeline terminus might be. Railroads won.
By mandate coal may be ending its life cycle here. Obozo set that into motion and once a mandate is executed only another mandate can usually reverse it. The natural order of things, be they in nature or in business with market forces, once disturbed is not easily reversed. The market moves on against the new normal because reversing what has already been justified by mandate is not easily done by market forces somewhat like going across a river there comes a point of no return.
As for the export of coal, what is most fungible and cost effective will be bought and exported. It is a matter of the most cost effective delivered BTU. In the developing world there are not ZERO environmental concerns. Much of international financing is by World Bank and the like and they do impose environmental considerations.
40 years ago fuel switching from Gas to Coal was done in a panic because we were “running out of natural gas”. Chemical Engineers were darn near crying to see such a valuable feed stock burned for fuel. We’ll see that again, not in my lifetime though probably. Some of the chemicals and plastics we enjoy just can’t be made without natural gas feed stock.
I remember the fascination 40 years ago with the resurgence of trains hauling coal and calculating how far you could maybe hop one with certainty that it was going somewhere. I doubt seriously that wind, solar and batteries will fuel our future. We will burn something and I hope that we eventually wise up and burn Thorium. Meanwhile, we are still going somewhere.
“”I’d think there’d be huge amounts of wear on the inside of pipes running what is essentially rocks and water through them, at least as compared to liquids.””
There are various thing you can pump along with it to cut down abrasion, we add a variety of compounds depending on needs in the fracing business.