METHOD OF DECOLORIZING PAPER MILL EFFLUENT LIQUID

• US 3,833,464 A
• Filed: 02/16/1973
• Issued: 09/03/1974
• Est. Priority Date: 02/16/1973
• Status: Expired due to Term

• Current Assignee: OI Forest Products STS Incorporated (KOCH Industries Incorporated)
• Original Assignee: Ormond E. Rolfe
• Inventors: Rolfe, Ormond E.
• Primary Examiner(s): Bashore, S. Leon
• Assistant Examiner(s): Andrea, Jr., Alfred D.
• Application Number:
  US05/333,285
• Time in Patent Office: 564 Days
• Field of Search: 162/29,33,38,39,190,189 210/43,45,51,47 423/159,165,427,430
• US Class Current: 162/29
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 2103/28 from the paper or cellulose industry
• CPC Class Codes: D21C 11/0021 Introduction of various effluents, e.g. waste waters, into the pulping, recovery and regeneration cycle (closed-cycle)
• CPC Class Codes: D21C 11/04 of alkali lye
• CPC Class Codes: Y02P 40/40 Production or processing of lime, e.g. limestone regeneration of lime in pulp and sugar mills
• CPC Class Codes: Y10S 210/917 Color

Abstract

Effluent liquid normally discharged by paper mills is ecologically undesirable for return to streams, lakes or the like by reason of the presence of color-imparting substances, e.g., color bodies, desirably removed by a process which includes mixing therewith an excess of calcium carbonate, followed by a combination at a pressure above atmospheric with a fluid rich in carbon dioxide, serving to convert the calcium carbonate to soluble calcium bicarbonate which is in turn discharged to atmospheric pressure whereby the calcium bicarbonate reconverts to calcium carbonate precipitate, said precipitate attracting and sweeping said color-imparting color bodies; the precipitate and color bodies being readily separable from the color-free effluent which may be returned to the source, stream, river or lake or reintroduced as fresh water into the pulping process as needed.

Claims

2. pressurizing said liquid to greater than atmospheric in the presence of a fluid including an excess of carbon dioxide, CO2, whereby said calcium carbonate, CaCO3, is substantially converted to soluble calcium bicarbonate, CaHCO3, and

3. discharging the liquid comprising calcium bicarbonate into a settling tank at atmospheric pressure whereby said calcium bicarbonate converts to insoluble calcium carbonate as a solid precipitate which attracts and carries color bodies in agglomeration or admixture therewith,

4. A method of reducing color present in paper mill effluent liquid which comprises:

5. returning said precipitated calcium carbonate to said lime recovery.

6. A method of reducing color present in paper mill effluent liquid which comprises the following steps:

7. The method as claimed in claim 6, wherein said pressure measures about 20 to 100 pounds per square inch gauge.