Rapid pretreatment
Disclosed herein are methods, systems, and compositions for the pretreatment of biomass within seconds with low inhibitor formation. The pretreatment process is used to convert biomass to a fuel or other useful chemicals by subjecting the feedstock to a rapid retention time under pressure and temperature and/or chemical reactant. The system includes a continuously-operating valve discharge apparatus to discharge pretreated feedstock while maintaining uniform pressure on the pretreatment system.
1. A system for industrial scale pretreatment of at least one dry ton of biomass per day, the system comprising:
(a) a barrel defining an inner chamber and comprising an inlet port for receiving the biomass near of a first end of the barrel and an end flange plate at a second end of the barrel, wherein the barrel has two or more zones, including a feeder zone and a reaction zone;
(b) one or more rotatable screws within the inner chamber of the barrel, wherein the one or more rotatable screws are configured to move the biomass through the inner chamber of the barrel;
(c) a pressure actuated discharge valve, wherein the pressure actuated discharge valve comprises a valve shaft, is movably seated within a discharge valve opening at the second end of the barrel, and regulates release of a pretreated biomass out of the barrel through the discharge valve opening;
(d) an actuator operably connected to the valve shaft of the pressure actuated discharge valve; and
(e) a back pressure control unit operably coupling the actuator and a pressure gauge that monitors pressure within the barrel,
wherein the back pressure control unit is configured to receive a pressure signal from the pressure gauge indicative of the pressure within the barrel, and thereafter is configured to act to maintain a set pressure within the barrel, by causing the actuator to open the discharge valve opening when the pressure within the barrel reaches or exceeds the set pressure, and close the discharge valve opening when the pressure within the barrel drops below the set pressure, thereby allowing for continuous production of the pretreated biomass, and wherein the set pressure is within a range of 50-1000 PSI.
2. The system of claim 1 , comprising two rotatable screws.
3. The system of claim 1 , wherein the system further comprises a hopper connected to the inlet port for feeding the biomass into the feeder zone.
4. The system of claim 1 , wherein the one or more rotatable screws are capable of conveying biomass through the reaction zone in less than about 20 seconds.
5. The system of claim 1 , wherein the barrel further comprises one or more sealable ports configured to add steam to the reaction zone to provide an elevated temperature, an elevated pressure, or a combination thereof in the reaction zone.
6. The system of claim 1 , wherein the barrel further comprises one or more sealable ports configured to add one or more chemical agents to the reaction zone.
7. The system of claim 6 , wherein the chemical agent comprises an acid, a base, or a combination thereof.
8. The system of claim 1 , wherein the pressure actuated discharge valve comprises a poppet valve.
9. The system of claim 1 , wherein the one or more rotatable screws comprise a single flight screw element with mixing grooves.
10. The system of claim 1 , wherein the one or more rotatable screws have a left hand screw profile.
11. The system of claim 1 , wherein the one or more rotatable screws comprise surface coatings to reduce wear and abrasion.
12. The system of claim 1 , wherein the set pressure is within a range of 100-750 PSI.
13. The system of claim 1 , wherein the set pressure is within a range of 200-600 PSI.
14. The system of claim 1 , wherein the set pressure is within a range of 300-500 PSI.
15. The system of claim 1 , wherein the set pressure is within a range of 300-450 PSI.