Solvent pulping of biomass

Abstract

An apparatus and process for solvent pulping of cellulose-containing biomass utilizes at least one steaming vessel, a plug screw feeder or compression screw device, at least one super-atmospheric impregnation vessel, a solvent delignification reactor capable of operating at a pressure of 350 psig or more, and a solvent containing line for introducing solvent-containing liquor at the plug screw feeder outlet or compression screw device outlet. The process and system can also include at least one series connected pressure diffuser and optionally a retention tube downstream of each pressure diffuser to provide sufficient retention time to substantially preclude re-deposition of lignin on the cellulose fibers of the biomass, a blow tank connected to the last of the pressure diffusers and retention tubes, and vessels for multistage alcohol washing. The method steams the biomass and impregnates it with solvent to produce an aqueous slurry of biomass and solvent, delignifies the particulate biomass in the slurry, removes solvent while continuing delignification of the biomass in the slurry and while substantially precluding re-deposition of lignin on the cellulose of the biomass, reduces the pressure of the slurry; and then washes the slurry.

Description

BACKGROUND AND SUMMARY OF INVENTION[0001] Solvent pulping is a well known, though heretofore economically impractical, technique for producing cellulose pulp, primarily from wood-based cellulose (although it has been known to produce cellulose pulp by solvent pulping wheat straw and reed). The term "solvent pulping" as used herein means pulping cellulose material using organic cooking chemicals, such as (but not restricted to) aliphatic alcohols (e.g., methanol, ethanol, tert-butanol, and isopropanol) with or without a small amount of a mineral or organic acid, carboxylic acids with or without hydrogen peroxide, formic acid, sulfuric acid or other mineral acids, and / or acetic acid (with the effective component of the cooking liquor peracetic acid).[0002] The economic problems associated with solvent pulping have been the inability to recover a high enough percentage of the cooking liquor effective component (e.g., alcohol), the increased COD pollution as a result of the discharge of...

AI Technical Summary

Benefits of technology

[0004] The raw material comprises cellulose-containing biomass, and desirably biomass that would typically be a waste or minor use product. The invention may use any known or subsequently developed suitable cellulose-containing biomass including (without limitation) kenaf, whole industrial hemp stalks, bamboo, agricultural residues (the byproducts of annual food and fiber production) such as the straw of various grains, cereal grasses (such as corn), flax, cotton linters, bagasse (sugar cane pulp), banana stalks, and pineapple residue. The biomass that is desirable is a chopped, crushed or shredded version--e.g., to a maximum particle dimension of about one inch. For some agricultural residues such as corn stovers, it can be advantageous to discard roots and kernels.

[0006] Using simple, but effective blow-back prevention upon upset conditions;

[0008] Using simple, highly reliable, equipment to provide pressure and temperature step-up, while performing different functions (e.g., steaming and impregnation);

Problems solved by technology

The economic problems associated with solvent pulping have been the inability to recover a high enough percentage of the cooking liquor effective component (e.g., alcohol), the increased COD pollution as a result of the discharge of the unrecovered cooking liquor effective component, the need for significant amounts of purchased power for electricity or steam, and the need to build-in high levels of safety into the process in view of the volatility of the cooking liquor effective component.

Also, technical and / or market problems with lignin or other chemical (such as furfural) recovery for sale (often necessary for there to be any chance that solvent pulping will be economical) have been common.

Images