Process and apparatus for removing impurities from solid biomass feeds
Processes and apparatus are described for removing impurities from solid biomass while preserving hydrogen and carbon content. Examples are provided of processes using acidified aqueous solutions in a countercurrent extraction process that includes the pneumatic transport of slurries between process units, or a mechanical dewatering step, or both, to produce a washed biomass suitable for various upgrading and conversion processes. Compositions related to the processes are also described.
1. A counter-current washing process for washing solid biomass, comprising:
conducting two or more wash steps in a series of wash tanks fitted with agitation devices and containing wash solutions;
wherein the solid biomass is contacted with the wash solutions to form slurries;
wherein the solids are transported as a slurry from at least one wash tank to a second wash tank or other device via a pneumatic lift pump;
wherein the pneumatic lift pump operates by injecting gas near the bottom (at a point or points within 1/5 or 1/10 by volume from the tank bottom) into a tube or tubes such that biomass is forced up and out of the tank through the tube or tubes;
wherein the wash solution for at least one wash step comprises used wash solution from a later wash step; and
wherein a mass percent of organic matter in the solid biomass lost in the counter-current washing process is less than 10% of the mass of the organic matter in the solid biomass before washing.
2. The process of claim 1 wherein each of the wash tanks comprises a stirred tank and wherein the process is conducted at a temperature of from 10° C. to 95° C.
3. The process of claim 1 wherein the slurry of solids in the wash solution is from 0.1% to 30% solids by weight.
4. The process of claim 1 wherein the slurry comprises biomass feed in which at least 85% by mass, or at least 90% by mass, or at least 95% by mass of the particles pass through a 0.25 inch (0.6 cm), or 0.5 inch (1.2 cm), or 1.0 inch (2.5 cm), or 1.5 inch (3.7 cm), or 2 inch (5.0 cm) screen.
5. The process of claim 1 wherein the slurry comprises biomass feed in which at least 85% by mass, or at least 90% by mass, or at least 95% by mass of the particles have aspect ratios (ratio of particle length to particle width) of at least 2:1, or 3:1, or 5:1, or 10:1, or 40:1, or 77:1, or from 1:1 to 100:1, or from 1.5:1 to 40:1, or from 2:1 to 10:1.
6. The process of claim 1 wherein the slurry comprises from 1% to 30% solids by weight, or from 5% to 25% solids by weight, or from 10 to 20% solids by weight, or from 15% to 20% solids by weight, or at least 10% solids by weight, or at least 15% solids by weight, or at least 20% solids by weight.
7. The process of claim 1 wherein at least one wash solution has a pH that is no more than 5, or no more than 4, or no more than 3.5, or no more than 3.0 or no more than 2.5, or no more than 2.3, or no more than 2.0, or no more than 1.7, or no more than 1.5, or in the range from 1.5 to 5, or from 2.0 to 5.0, or from 2.0 to 3.5, or from 2.5 to 3.0.
8. The process of claim 1 wherein the ratio of H+ ions in a wash step to divalent cations in the biomass is at least 1.8:1, or at least 2.0:1, or at least 2.1:1, or at least 2.2:1, or at least 2.5:1, or at least 3:1, or from 1.8:1 to 3:1, or from 2.0:1 to 2.5:1, or from 2.0:1 to 2.2:1.
9. The process of claim 1 wherein the slurry specific gravity is from 0.5 to 1.5.
10. The process of claim 1 wherein the untapped bulk density of the particles in the slurry is no more than 6 lb/ft 3 (0.096 g/cc), or no more than 8 lb/ft 3 (0.128 g/cc), or no more than 10 lb/ft 3 (0.16 g/cc), or no more than 12 lb/ft 3 , (0.192 g/cc), or no more than 20 lb/ft 3 (0.32 g/cc), or no more than 50 lb/ft 3 (0.80 g/cc), or from 1 lb/ft 3 (0.016 g/cc) to 50 lb/ft 3 , (0.80 g/cc), or from 2 lb/ft 3 (0.032 g/cc) to 20 lb/ft 3 (0.32 g/cc), or from 5 lb/ft 3 (0.08 g/cc) to 15 lb/ft 3 (0.24 g/cc).
11. The process of claim 1 wherein a pneumatic lift is used to transport the biomass slurry out of at least one of the stirred tanks, wherein the pneumatic lift utilizes a sparger for which the hole size in the sparger that feeds gas to the airlift pump has a ratio of transport cross sectional area perpendicular to the lift to hole area between 144 and 3600, with a minimum hole size of 0.1 inch (2.54 mm) and a maximum of 0.5 inch (12.7 mm), wherein the holes are at least 3 hole diameters apart, and the gas used for the pneumatic pump transport is chosen from among air, nitrogen, carbon dioxide, or a cooled combustion exhaust gas, or mixtures thereof.
12. The process as in claim 1 wherein the solids are separated from the liquids by a side hill screen, a screw press, or both a side hill screen and a screw press, to produce a washed biomass.
13. The process of claim 1 wherein the washed biomass is reacted in a catalyzed pyrolysis process to produce olefins and aromatics.
14. A counter-current washing process for washing solid biomass, comprising:
conducting two or more wash steps in a series of wash tanks fitted with agitation devices and containing wash solutions;
wherein the solid biomass is contacted with the wash solutions to form slurries;
wherein the slurries are transported from at least one wash tank to a second wash tank or other device via a pneumatic lift pump;
wherein the pneumatic lift pump operates by injecting gas near the bottom (at a point or points within 1/5 or 1/10 by volume from the tank bottom) into a tube or tubes such that biomass is forced up and out of the tank through the tube or tubes;
wherein the solids are separated from the slurry out of at least one of the wash tanks in a mechanical separation step; and
wherein the wash solution for at least one wash step comprises used wash solution from a later wash step; and
wherein a mass percent of organic matter in the solid biomass lost in the counter-current washing process is less than 10% of the mass of the organic matter in the solid biomass before washing.
15. The process of claim 14 wherein at least one wash solution has a pH that is no more than 5, or no more than 4, or no more than 3.5, or no more than 3.0 or no more than 2.5, or no more than 2.3, or no more than 2.0, or no more than 1.5, or in the range from 2.0 to 5.0, or from 2.0 to 3.5, or from 2.5 to 3.0.
16. The process of claim 14 comprising: a step in which the washed solid particles are dried.
17. The washing process of claim 1 wherein the solid biomass is in contact with the wash and/or a rinse solution for less than 30 minutes, or less than 10 minutes, or less than 5 minutes, or less than 3 minutes, or from 0.1 to 30 minutes, or from 1 to 10 minutes.
18. The washing process of claim 14 wherein the solid biomass is in contact with the wash and/or a rinse solution for less than 30 minutes, or less than 10 minutes, or less than 5 minutes, or less than 3 minutes, or from 0.1 to 30 minutes, or from 1 to 10 minutes.