Claims
- 1. A method for concentrating process wastewater in an evaporator, wherein the process wastewater comprises at least one acid process flow and one alkaline process flow, said method comprising alternatively concentrating the acid process flow and the alkaline process flow in the same evaporator, wherein the precipitates resulting from the evaporation of the respective proceeding process flow are dissolved in the evaporator when the subsequent process flow is concentrated.
- 2. The method of claim 1 wherein further concentration is brought about by evaporation.
- 3. The method of claim 1 wherein the acid and alkaline process flows are mixed after the evaporation.
- 4. The method of claim 3 wherein solid precipitates formed during concentration are separated after mixing of the process flows.
- 5. The method of claim 1 wherein lignocellulose-containing wastewater from a bleach plant is the process stream to be concentrated.
- 6. The method of claim 1 wherein the acid process flow contains chloride-containing and/or chlorate-containing salts.
- 7. The method of claim 1 wherein the process flow is subjected to a preliminary cleaning treatment before the evaporation.
- 8. The method of claim 1 wherein the evaporation is carried out in a falling-film evaporator with recirculation.
- 9. The method of claim 1 wherein the degree of evaporation is at least about 5% by weight of dry solids.
- 10. The method of claim 1 wherein the acid process flow is evaporated in a first stage.
- 11. A method for concentrating process wastewater in an evaporator, wherein the process wastewater comprises at least one acid process flow and one alkaline process flow, said method comprising first concentrating the acid process flow and thereafter concentrating the alkaline process flow, wherein precipitates resulting from the evaporation of the acid process flow are dissolved in the evaporator by the subsequently added alkaline process flow.
- 12. A method for concentrating process wastewater in an evaporator, wherein the process wastewater comprises at least one acid process flow and one alkaline process flow, said method comprising first concentrating the alkaline process flow and thereafter concentrating the acid process flow, wherein precipitates resulting from the evaporation of the alkaline process flow are dissolved in the evaporator by the subsequently added acid process flow.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9502198 |
Jun 1995 |
SEX |
|
Parent Case Info
This Patent Application claims priority of Sweden Patent Application No. 9502198-6, filed 16 Jun. 1995 and benefit of U.S. Provisional patent application No. 60/001, filed Jun. 20,1995.
This invention concerns an improved method for concentrating process wastewater by evaporation. In the method according to the invention, one acid process flow and one alkaline process flow are evaporated alternately in one and the same evaporator.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
4800042 |
Kurumada et al. |
Jan 1989 |
|
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