terra cotta lippage removal?
sorry, but you are out of luck.  terrazzo is an homogenous material, and can thus be ground.  terra cotta is heterogenous, and cannot.  if you cut a terra cotta tile in half, you will find a thin layer of glazed vitreous oxide material at the top, and then unglazed parent substrate below that.  if you grind the tiles, you will remove the glaze in a random way (terra cotta by its very nature is a very warped, uneven material, with differing surface finishes and depth of glazing).  this will result in a spotty floor that is now as porous as a sponge, and not a lot harder than brick mortar.  not a good choice for a flooring material.  

rip it up or lay new tile over it.