By Gerry Shih SAN FRANCISCO (Reuters) – Twitter Inc CEO Dick Costolo will meet Shanghai government officials, academics and students in his first visit to China, signaling Twitters interest in cracking a lucrative but thorny market with 600 million Internet users. Twitter, which has been blocked by Chinese censors since 2009, described the trip as a personal tour for Costolo, who is due to land at Shanghais Pudong International Airport on Monday and plans to spend three days in the business capital. Costolo is scheduled to meet Shanghai government officials — including representatives of the Shanghai Pilot Free Trade Zone, established in 2013 to test market liberalization measures, such as looser rules governing currency conversion and foreign direct investment.