Abstract: This invention provides improvements to processes for making granular lignin from black liquor. One of the improvements is that the use of a pre-carbonation column reduces the CO2 flow into the sparger of a carbonation column. The pre-carbonation column is used to reduce the pH of the black liquor to about 12. Another improvement is that it has been found that coalescing droplets into a bulk liquid-lignin phase can be enhanced by placing the exit of the carbonation column at or slightly beneath carbonated black liquor/liquid-lignin interface. It has also been found that operating the carbonation settler at a low pressure and pumping the liquid-lignin from the carbonation settler to the acidification reactor operating at a higher pressure allows recycling the vent gas from the acidification reactor to the pre-carbonation column. The invention also provides for a vent gas absorber.

Abstract: Treated wood, wood preservative compositions, and methods for treating wood generally include applying to the wood a wood preservative composition comprising a boron containing compound and a pH-reduced black liquor comprising soluble lignin, wherein the boron-containing compound is soluble in the pH-reduced black liquor and wherein the pH-reduced black liquor is derived from a carbonation process or an acid addition process of black liquor having phase-separated solid lignin and/or dense liquid lignin removed therefrom, and drying the wood.

Abstract: Treated wood, wood preservative compositions, and methods for treating wood generally include applying to the wood a wood preservative composition comprising a boron containing compound and a pH-reduced black liquor comprising soluble lignin, wherein the boron-containing compound is soluble in the pH-reduced black liquor and wherein the pH-reduced black liquor is derived from a carbonation process or an acid addition process of black liquor having phase-separated solid lignin and/or dense liquid lignin removed therefrom, and drying the wood.

Abstract: A process for recovery of lignin from black liquor that contains either soluble or dispersed lignin by generating a “liquid lignin” at high yield is disclosed. Soluble lignin at a high pH is precipitated by reducing the pH of the black liquor stream by countercurrent reaction with carbon dioxide, at elevated temperature and pressure, creating a heavy lignin-rich phase and a light lignin-depleted phase. The heavy lignin-rich phase is separated and washed countercurrently with a non-sulfur containing acid, such as acetic acid, to displace metal cations from the lignin, creating a low-salt lignin, which is then formed into a low-dust, high-bulk density lignin fuel pellet. If desired, an oxidation step may be used to eliminate odor for lignins having high value green chemistry applications.