Claims
- 1. A method for regenerating sodium hydroxide in a wood pulping process comprising the steps of:
(a) partially autocausticizing a sodium carbonate-containing smelt by reaction with borate, thereby producing a borate-containing partially autocausticized smelt which includes a reacted portion and an unreacted portion; (b) dissolving in aqueous solution said borate-containing partially autocausticized smelt, including said reacted and unreacted portions thereof, to form a borate-containing liquor, thereby regenerating sodium hydroxide and forming dissolved sodium carbonate from said reacted and unreacted portions, respectively, in said borate-containing liquor; and (c) introducing lime into said borate-containing liquor so as to react said dissolved sodium carbonate with said lime, thereby regenerating additional sodium hydroxide from said borate-containing liquor and forming calcium carbonate.
- 2. The method according to claim 1 wherein said process includes bleaching of pulp.
- 3. The method according to claim 1 further comprising the step of separating the calcium carbonate from the borate-containing liquor.
- 4. The method according to claim 3 further comprising the step of converting the calcium carbonate to calcium oxide.
- 5. The method according to claim 3 further comprising the step of contacting the borate-containing liquor with wood pulp, thereby delignifying said pulp.
- 6. The method according to claim 1 wherein the autocausticizing reaction is carried out in a recovery boiler.
- 7. The method according to claim 1 wherein trisodium borate is formed in the autocausticizing reaction.
- 8. The method according to claim 7 wherein the trisodium borate reacts with water to form sodium hydroxide.
- 9. The method according to claim 7 wherein the autocausticizing reaction is carried out at a sodium to boron molar ratio of greater than 3:1.
Parent Case Info
[0001] This application is a divisional of copending application Ser. No. 09/238,828 filed Jan. 28, 1999, which claims the benefit of U.S. Provisional Application No. 60/087,779 filed Jun. 1, 1998. This invention relates to the use of borates in the recausticization of alkali-containing liquors such as are produced in the chemical and semi-chemical pulping of wood and in the oxidation and bleaching of wood pulp, and more particularly to the partial autocausticization of such liquors by the addition of limited amounts of borate. It also relates to a process for complete recausticization of such liquors by a combination of partial autocausticization using borate with conventional lime recausticization.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60087779 |
Jun 1998 |
US |
Divisions (1)
|
Number |
Date |
Country |
Parent |
09238828 |
Jan 1999 |
US |
Child |
09964187 |
Jan 2001 |
US |