Gasification is a key process for the thermochemical conversion of coal for both energetic utilization and its application as a chemical feedstock. In this regard low grade coal with high-ash content gains in importance. Because of its high availability, production share is increasing. Therefore, adapted gasifiers of novel design are required to meet the demands associated with converting high-ash coals. The internal circulation (INCI) principle is a multi-stage gasification system with the ability to efficiently convert high-ash feedstock. The present paper introduces the test-scale COORVED reactor, which was designed according to the INCI principle. Particle image velocimetry (PIV) and computational fluid dynamics (CFD) simulations are conducted for ambient conditions in a cold-flow test facility to demonstrate the flow pattern according to the INCI principle. The evidence of a recirculation cell is provided by PIV experiments. CFD simulations show similar results in terms of overall flow pattern and size of the recirculation cell. After the intensive investigations of the flow pattern in the cold-flow test facility, first PIV results were obtained in the COORVED reactor. The complex accessibility of the reactor raised the necessity of the validation of the elaborate measurement setup. The reliability of the measurement results is proven by generating a laminar velocity profile at ambient conditions, whose results are comparable to analytical solutions. (C) 2014 Elsevier Ltd. All rights reserved.