Waste heat boiler

A waste heat boiler for cooling a hot process stream comprising a plurality of heat exchanging tubes within a cylindrical shell, each tube having an inlet end and outlet end;

• an outlet chamber for withdrawing the cooled process stream, said outlet end of each of the tubes being located in the outlet chamber;
• attached to the shell, means for introducing water into the shell side of the tubes;
• means for introducing the hot process stream into the inlet end of the tubes and passing the process stream through the tubes in indirect heat exchange with the water in the shellside of the tubes to produce steam and to cool the introduced process stream;
• means for withdrawing produced steam, and means for withdrawing the cooled process stream,
• said waste heat boiler being further equipped with an insulated by-pass tube having an outlet end in the outlet chamber for passing a hot process stream directly into the outlet chamber such that immediately upon exiting the by-pass tube, the hot process stream mixes with the cooled process stream exiting from the outlet ends of the heat exchanging tubes,
• said outlet chamber being provided with an injection nozzle for control of flow of the hot process stream through the by-pass tube by injection of a fluid into the by-pass tube outlet end,
• said injection nozzle being installed in the outlet chamber at the center line of the by-pass tube spaced apart from the by-pass tube outlet end and having an injection muzzle directed towards the outlet end of the by-pass tube.