Kibo Mining has flagged up better-than-expected potential returns from a coal project in Tanzania, boosting its shares.Kibo said a report had shown that the anticipated deliverable margin per tonne and overall estimated profitability of the coal mining element of its Rukwa Coal-to-Power project were significantly ahead of the company's earlier expectations."As a result we can confidently say that the robustness and attractiveness of the coal mining element and the wider RCPP have been ratified and further enhanced with the findings of this report," the company said in an update."We are currently examining the report in detail and preparing an update for shareholders that will include an operational project summary and key financial data. We are looking to expedite this review and anticipate releasing this update very shortly."Kibo's shares rose 0.45p or 22% to 2.5p at 11:30 in London.