High temperature and pressure solids handling system

1. 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 D I and having an inlet pipe end; an outlet pipe having a second diameter D O 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/D I ratio is between the range of about 1-3.

2. The system of claim 1 , further comprising a cooling device into which the solids are discharged from the outlet pipe.

3. The system of claim 1 , further comprising an ash cooling vessel located between the ash discharge outlet of the fluidized gas reactor and the inlet pipe of the L-valve.

4. The system of claim 1 , further comprising a means for fluidizing the ash particles discharged from the bottom ash discharge outlet of the fluidized gas reactor wherein gas from the reactor is stripped from the ash particles with a stripping gas.

5. The system of claim 4 , wherein the means for fluidizing the ash particles comprises a transition region or conical region where a wider downcomer of the bottom ash discharge outlet is transitioned into a narrower inlet pipe of the L-valve.

6. The system of claim 4 , further comprising a differential pressure control means (DP-3) for measuring and controlling the pressure differential the transition region or conical region, and a point in the bottom ash discharge outlet near the point where venturi steam enters the discharge outlet, wherein operation of the stripping fluidized bed above the L-valve inlet pipe is monitored.

7. The system of claim 1 , wherein the H/D I ratio is about 1.5-2.5.

8. The system of claim 7 , wherein the H/D I ratio is about 1.5-2.

9. The system of claim 1 , wherein the aeration fluid is steam, CO 2 , or N 2 , or a suitable mixture thereof.

10. The system of claim 1 , wherein the valve angle is about 90 degree.

11. The system of claim 5 , further comprising a first differential pressure control means (DPT1) for measuring pressure differential between the aeration fluid inlet conduit and a location where the stripping gas is added in the transition region or conical region.

12. The system of claim 10 , further comprising a second differential pressure control means (DPT2) to measure the pressure drop between the aeration fluid inlet conduit and a point in the L-valve outlet pipe.

13. The system of claim 1 , further comprises a differential pressure control means to measure and control pressure across the horizontal section.

14. A method for managing bottom ash discharge rate of a fluidized bed gasification reactor, wherein the system of claim 1 is used and wherein bottom ash discharge rate is controlled by controlling the amount of aeration fluid inputted to the L-valve.

15. A method for controlling the height of the fluidized bed inside the fluidized bed reactor of the system of claim 1 , wherein when the bed height drops below a desired value, the controller sends a signal to an L-valve aeration control valve to close slightly in order to reduce the discharge rate through the L-valve; and wherein when the bed height increases above a desired bed height, the controller will send a signal to the L-valve aeration control valve to open to increase the aeration to the L-valve so that more solids will be discharged.