Method and apparatus for conveying a cellulosic feedstock
A method and apparatus for preparing a cellulosic feedstock are disclosed. Embodiments of the method comprise passing the cellulosic feedstock through an optional impregnation chamber to an outlet of the impregnation chamber, passing the cellulosic feedstock from the outlet of the impregnation chamber to a holding tank having an inlet and an outlet, and conveying the cellulosic feedstock downwardly and laterally as it travels through the holding tank. Embodiments of the apparatus comprise at least one sidewall defining a passage. The passage has an upper portion and a lower portion, and the lower portion has a greater cross-sectional area than the upper portion. At least one inlet is provided adjacent the upper portion, and at least one outlet is provided adjacent the lower portion, at an elevation below the inlet.
1. A method of preparing a cellulosic feedstock for ethanol production, comprising:
passing the cellulosic feedstock through a moisture impregnation chamber to an outlet of the impregnation chamber, wherein the moisture content of the cellulosic feedstock is raised to from about 30 wt % to about 60 wt % and the temperature is raised to between about 50° Celsius and about 75° Celsius;
passing the cellulosic feedstock from the outlet of the impregnation chamber to an inlet of a holding tank, the holding tank having an outlet, an upper portion, a lower portion and outer periphery extending between the inlet and the outlet of the holding tank, the lower portion having a greater cross-sectional area than the upper portion;
conveying the cellulosic feedstock downwardly and laterally outwardly through the holding tank; and,
withdrawing the cellulosic feedstock from the outlet of the holding tank.
2. The method of claim 1 , further comprising maintaining a temperature in the holding tank between about 50° Celsius and about 75° Celsius.
3. The method of claim 2 , wherein the cellulosic feedstock moves from the inlet to the outlet of the holding tank in about 10 to about 30 minutes.
4. The method of claim 1 , wherein the inlet of the holding tank is disposed at an elevation above the outlet of the holding tank, and the cellulosic feedstock migrates from the inlet towards the outlet of the holding tank under the force of gravity.
5. The method of claim 1 , further comprising conveying the cellulosic feedstock laterally across the outlet of the holding tank.
6. The method of claim 5 , wherein the step of conveying the cellulosic feedstock laterally across the outlet of the holding tank comprises actively withdrawing the cellulosic feedstock from essentially an entirety of the outlet.
7. The method of claim 5 , wherein the step of conveying the cellulosic feedstock laterally across the outlet of the holding tank comprises withdrawing a generally equal amount of cellulosic feedstock from each portion of the outlet.
8. The method of claim 5 , wherein the step of conveying the cellulosic feedstock laterally across the outlet of the holding tank comprises withdrawing a first portion of the cellulosic feedstock in a first lateral direction and withdrawing a second portion of the cellulosic feedstock in a second lateral direction.
9. The method of claim 1 , further comprising conveying the cellulosic feedstock from the outlet of the holding tank to a hydrolysis reactor downstream of the holding tank.