A method of assembling a gasification reactor includes extending an injection device at least partially into the gasification reactor. The injection device includes a plurality of substantially concentric conduits coupled to a modular tip and at least one outer surface. The modular tip includes a plurality of cooling channels and a plurality of substantially annular nozzles defined therein. The method further includes forming at least one layer of insulation about at least a portion of the at least one outer surface to facilitate insulating at least a portion of the injection device from heat within the gasification reactor.