Abstract: A system for pressure letdown and flow control of high-pressure erosive fluid streams containing gas, liquid and solid particles, such as process slurries used in coal gasification and liquefaction. Throttle valves presently used for this application suffer excessive impingement erosion and corrosion damage, leading to short valve lifetime even with super-resistant valve materials. The present invention uses pairs of fixed-geometry opposing nozzles whose jets meet head-on with consequent energy dissipation and stream containment at the reduced pressure. The only erosion encountered here is scouring of internal nozzle surfaces which is minor and permits long lifetimes to be attained with conventional materials. This system provides flow control by (1) varying the number of nozzle pairs which are on-line by use of on-off shutoff valves for stepwise flow increments, and (2) low-pressure-drop operation of a conventional throttle valve in the main line for proportional control within one step increment.