Abstract: A process gas compressor for the stepwise compression of process gases with increased percentage of hydrogen sulfide (H2S), with an H2S-uncritical area and an H2S-critical area, in the housing (5) of which impellers (3) and (2) with a direction of flow to the right (7) and, after cooling (6), impellers (2) with a direction of flow to the left (8) are arranged on a shaft (1), wherein the impellers (3) and (2) are provided with blade ends (4). The transition from the uncritical H2S area to the critical H2S area takes place after the outlet of the first or second larger impeller (3) on the shaft on the left. This is followed by another impeller (2) with a direction of flow to the right (7), which is already located in the critical H2S area. The precompressed process gas is subsequently sent to a cooler (6) before it enters the impellers (2) in the critical H2S area of the process gas compressor at the second gas inlet stage (8) and leaves it at the housing outlet (9).