In this disclosure, a reactor system is described. The reaction system comprises (a) a reaction vessel having an inner wall, wherein said reaction vessel is configured to receive reactants and export products and byproducts; (b) a primary quench device (PQD) configured to receive a coolant and disperse said coolant into said reaction vessel; and (c) a secondary quench device (SQD) configured to receive a coolant and disperse said coolant into said reaction vessel; wherein said PQD comprises an array of spray nozzles fixed on the inner wall of said reaction vessel at a first axial position; and wherein said SQD comprises (1) an axially movable pipe having a coolant entry end and a nozzle end, wherein said pipe is configured to be removably fixed inside said reaction vessel; and (2) a spray nozzle that is fluidly connected to said pipe at its nozzle end via a fluid tight seal connection.