Method and apparatus for mixing a lignocellulosic material with enzymes

A method of liquefaction comprising:

• performing a steam explosion reaction on a lignocellulosic material to produce a slurry comprising the lignocellulosic material after the steam explosion reaction;
• mixing the slurry with an alkali-based material in a first screw conveyor until an average pH of the slurry is in a range of about 4.5 to 6.5, an average temperature of the slurry is in a range of about 45 to 55 degrees C., and the slurry has a consistency in a range of about 10 to 35 wt % wherein the wt % is of insoluble particles as compared to total weight of the slurry;
• transferring the slurry to a second screw conveyor;
• adding a first portion of an enzyme solution to the slurry in the second screw conveyer, wherein the enzyme is added to the second conveyer at more than one location in the second screw conveyor;
• transferring the slurry from the second screw conveyor to a mixer via a positive displacement pump;
• mixing the slurry in the mixer at a speed in a range of about 400 to 4,000 rpm, for a period in a range of about 0.05 to 200 seconds, wherein a second portion of the enzyme solution is added to the slurry during said mixing;
• transferring the slurry from the mixer to a first reactor section to transition the material from a higher viscosity to a lower viscosity to create a substantially liquid material, wherein the first reactor section includes a frustoconical outer wall, a cross-sectional area that expands in a downward direction and a rotating mixer with arms extending radially from a vertically oriented axial shaft and the arms become successively longer as the diameter of the frustoconical outer wall expands, and
• transferring the substantially liquid material to a second reactor section for further liquefaction and enzymatic hydrolysis, wherein the temperature of the slurry is kept at a temperature in a range of about 45 to 55 degrees C. from just prior to the addition of the first portion of the enzyme solution and throughout the duration of the process.

A system to liquefy a lignocellulosic material comprising:

• a steam explosion reactor receiving the lignocellulosic material saturated with water, subjecting the material to a rapid pressure release to cause a steam explosion reaction and discharging a slurry comprising the lignocellulosic material after the steam explosion reaction;
• a first screw conveyor in fluid communication with a discharge of the steam explosion reactor, the first screw conveyor including a rotating screw through which passes the slurry discharged from the steam explosion reactor, and an inlet through which an alkali-based material is injected into the slurry passing through the first screw conveyor;
• a second screw conveyor in fluid communication with a discharge of the slurry from the first screw conveyor, wherein the second screw conveyor includes a rotating screw through which passes the slurry from the first screw conveyor and a plurality of inlets for an enzyme to be injected into the slurry in the second screw conveyer;
• a mixer in fluid communication with a discharge of the second screw conveyor, wherein the mixer includes a mixing device rotating at a speed of about 400 to 4,000 rpm, and the mixer retains the slurry from the second screw conveyor for about 0.05 to 200 seconds, and the mixing includes an inlet through which a second portion of the enzyme is added to the slurry during mixing;
• a first reactor section to transition the slurry with the enzyme added from a higher viscosity to a lower viscosity to create a substantially liquid material, wherein the first reactor section includes a frustoconical outer wall, a cross-sectional area expanding in a downward direction, and a mixing device with rotating radial arms which are progressively longer in a downward direction through the upper section.