High temperature and pressure solids handling system

A fluidized bed gasification system which comprises a fluidized bed gasification reactor having a bottom ash discharge outlet below the reactor, wherein an L-valve is used to control the rate of bottom ash discharge, the system comprising:

• i. an L-valve located downstream of and connected to the bottom ash discharge outlet for controlling the solids flow rate, wherein the L-valve comprises:
• an inlet pipe having a first diameter DI and having an inlet pipe end;
• an outlet pipe having a second diameter DO that is between 50% and 75% of the first diameter, and oriented at a valve angle between 45 degrees and 135 degrees relative to the inlet pipe, where the outlet pipe has an outlet pipe end and the inlet pipe has a proximate side that is on the same side as the outlet pipe end and a distal side that is opposite the outlet pipe end, and where the outlet pipe end is aligned with the proximate side;
• and
• ii. an aeration fluid inlet conduit for carrying aeration fluid into the inlet and wherein the opening of the aeration fluid inlet conduit is located on distal side of the inlet pipe at a location that is above the center line of the outlet pipe by a distance H, wherein the H/DI ratio is between the range of about 1-3.