The inventions is directed to a new design for catalyst tubes, which makes it possible to apply the concept of regenerative reforming into steam reformers having catalyst tube inlets and outlets at opposite sides of the furnace chamber. The catalyst tube comprises an inlet for process gas to enter the catalyst tube and an outlet for process gas to exit the catalyst tube, which inlet and outlet are located at opposite ends of the catalyst tube. The catalyst tube further comprises a first annular channel comprising the catalyst, a second annular channel for process gas to flow countercurrently or co-currently to the process gas flowing through the first annular channel.