Method and apparatus for fine solids recycle
A fine solids recycle apparatus for a fluidized bed reactor comprises an eductor connected to a dipleg extending from a cyclone connected to the reactor, wherein the fine solids particles are removed from the dipleg, mixed with an eductor gas to form an eductor gas-fine solids particles mixture, which allows the return of the fine solids particles to the fluidized bed region, whereby the fine solids is further reacted in the fluidized region to improve reaction efficiency.
1. A fine solids recycle apparatus for a fluidized bed reactor, wherein the fluidized bed reactor comprises a fluidized bed region encased in a reaction vessel, at least one cyclone in fluid communication with the fluidized bed region for receiving a first gas-solid mixture which comprises fine solids particles, where the cyclone is connected to a dipleg through which the fine solids particles separated from the gas-solid mixture in the cyclone are collected, the apparatus comprising: an eductor connected to the dipleg, wherein the fine solids particles are removed from the dipleg, mixed with an eductor gas to form an eductor gas-fine solid particles mixture, which allows the return of the fine solids particles to the fluidized bed region;
wherein the dipleg is arranged vertically, and a horizontal leg is provided to connect the dipleg with a solids inlet of the eductor; wherein gas and solids flow from the dipleg to the eductor is regulated to prevent gas in the eductor from reverse-flowing to the cyclone.
2. The fine solids recycle apparatus according to claim 1 , wherein the horizontal leg comprising a first end that is connected to the dipleg and a second end that is away from the dipleg, wherein a vertical section is provided between the second end of the horizontal leg and the solids inlet of the eductor.
3. The fine solids recycle apparatus according to claim 1 , wherein one or more aeration nozzles are provided downstream of the eductor to facilitate return of the eductor gas-fine solid particle mixture to the fluidized bed region.
4. The fine solids recycle apparatus according to claim 1 , wherein the eductor gas is N 2 , CO 2 , air, steam, O 2 , or a mixture thereof.
5. The fine solids recycle apparatus according to claim 1 , wherein the fine particles have a size of less than about 100 microns.
6. The fine solids recycle apparatus according to claim 5 , wherein the fine particles have a mass mean diameter of about 15 to about 20 microns.
7. A fluidized bed reactor comprising a fine solids recycle apparatus of claim 1 .
8. The fluidized bed reactor according to claim 1 , wherein the fluidized bed reactor is a fluidized bed coal gasifier.
9. The fluidized bed reactor according to claim 1 , wherein the reactor comprises two or more stages of cyclones.
10. The fluidized bed reactor according to claim 8 , wherein an eductor is provided for each stage of cyclone.
11. The fluidized bed reactor according to claim 8 , wherein an eductor is provided for a second stage cyclone, or a stage subsequent to the second stage cyclone.