Jenner & Block LLP’s international arbitration practice co-chair Lawrence S. Schaner has left the firm to form his own firm, Schaner Dispute Resolution LLC, after 29 years at the firm.Schaner, 57, is currently the sole attorney at his new practice, which officially opened its doors on Monday at 150 N. Michigan Ave. While his work will primarily consist of international arbitration work, he said he will continue to serve as counsel in some cases.He started at Jenner & Block in 1988 and went on to co-found the …