big luggage without the consighnment service possible??

i go from shanghai to nanjing by train. my luggage weighs about 25-30 kg. actually i don't want to use the consighnment service because i won't have time to pick it up in nanjing.. so is it possible to take my luggage with me on-board at a high-sped train???? and if yes, how much will it cost to pay extra-fee for each kilogram??