A novel fluidized bed gasification reactor has been developed to get a product gas with a high calorific value (up to 15 MJ/Nm³) and nearly free of nitrogen. The gasification process is based on an internally circulating fluidized system and consists of a gasification zone fluidized with steam and a combustion zone fluidized with air. The circulating bed material acts as heat carrier from the combustion to the gasification zone. Gas mixing between these two zones is avoided by construction measures. Furtheron, the apparatus is characterized by a very compact design.The development of the gasification reactor has been carried out step by step. First, a cold flow model was operated to study the fluid mechanics of the fluidization system. The second step was a laboratory scale test rig to study the main features of the reactor by varying different operating and geometrical parameters. After this step a pilot plant was constructed and has been successfully operated. The results attained came fully up to the expectations.