Approximately how many tons of lignite would be required to produce the amount of heat generated by one ton of anthracite coal?

Answer 1

Use data on the heating value of bituminous coal and lignite that can be found here:
http://www.ket.org/Trips/Coal/AGSMM/agsmmtypes.html
as well as other places.

There is a range of heating values for both, depending upon quality. There is no single "right" number for the answer. In general, lignite has about half the heating value of "soft" coal; so it will require about twice as much for the same amount of heat.