A process and apparatus for reducing pressure of a flue gas stream including passing a pressurized flue gas stream to a vessel and through a bed of particulates in the vessel to reduce the pressure of the flue gas stream. The flue gas passes from the vessel at a lower pressure than at which it entered. The bed of particulates is disposed in the vessel between the outlet end of the inlet conduit and the inlet end of the outlet conduit. If deposits develop in the bed of particulates, the particulates can be replaced with fresh particulates to avoid excessive pressure drop. Data may be received from a stream in fluid communication with the foregoing process and apparatus.