Apparatus for evaporative concentration of water to be treated, which uses hot lime softening, and method for evaporative concentration of water using the same

Patent metadata

Field	Value
Publication number	US-10294137-B2
Application number	US-201615268985-A
Country	US
Kind code	B2
Filing date	Sep 19, 2016
Priority date	Sep 24, 2015
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

An apparatus for evaporative concentration of water, containing hardness-causing substances, to be treated using hot lime softening, includes: a first evaporator configured to form first concentrated water from the water to be treated by evaporatively concentrating the water by first heat exchange with hot steam; a hot lime softener configured to precipitate and to separate hardness-causing substances contained in the first concentrated water from at least a portion of the first concentrated water from the first evaporator by reaction with lime and configured to remove the hardness-causing substances from the first concentrated water; and a second evaporator configured to form second concentrated water by further evaporatively concentrating at least a portion of the first concentrated water that passed through the hot lime softener by second heat exchange with hot steam.

First claim

What is claimed is:

1. An apparatus for evaporative concentration of water, containing hardness-causing substances, to be treated using hot lime softening, the apparatus comprising:
a first evaporator configured to form first concentrated water from the water to be treated by evaporatively concentrating the water by first heat exchange with hot steam, wherein the first evaporator is disposed before a hot lime softener such that the first concentrated water is introduced to the hot lime softener to increase precipitation of hardness-causing substances contained in the first concentrated water without an additional heat source used for satisfying operating temperature condition of the hot lime softener;
the hot lime softener configured to precipitate and separate the hardness-causing substances from at least a portion of the first concentrated water from the first evaporator by reaction with lime and remove the hardness-causing substances from the first concentrated water; and
a second evaporator configured to form second concentrated water by further evaporatively concentrating at least a portion of the first concentrated water that passed through the hot lime softener by second heat exchange with hot steam.

2. The apparatus of claim 1 , wherein a temperature of the first concentrated water that is introduced into the hot lime softener is approximately 90° C. to 110° C.

3. The apparatus of claim 1 , wherein the first evaporator has a concentration factor of 5-10.

4. The apparatus of claim 1 , further comprising
a recycling line providing a path for at least a portion of at least one of the first concentrated water and the second concentrated water to be introduced into the first evaporator or the second evaporator so as to be concentrated again.

5. The apparatus of claim 1 , wherein at least one of the first evaporator and the second evaporator is a vertical tube falling film (VTFF) evaporator comprising a plurality of evaporation tubes therein and configured to evaporate the water to be treated by heat exchange with hot steam supplied to outer walls of the plurality of evaporation tubes while the water flows in the form of a falling film along inner walls of the evaporation tubes.

6. The apparatus of claim 1 , wherein at least one of the first evaporator and the second evaporator is a reduced pressure evaporator in which reduced pressure evaporation occurs.

7. The apparatus of claim 1 , further comprising
a gas-liquid separator configured to separate and remove water mist remaining in steam present as two phases together with concentrated water at a bottom of at least one of the first evaporator and the second evaporator,
wherein condensed water formed by heat exchange of hot steam supplied to at least one of the first evaporator and the second evaporator is sprayed into the steam so that hardness-causing substances contained in the steam are separated and removed.

8. The apparatus of claim 7 , further comprising
a compressor configured to compress the steam from which the hardness-causing substances and the water mist were removed in the gas-liquid separator and to supply the compressed steam to at least one of the first evaporator and the second evaporator.

9. The apparatus of claim 7 , wherein the gas-liquid separator comprises
a cyclone-type gas-liquid separator configured to
spray the condensed water in a tangential direction of an inner circumferential surface of the gas-liquid separator and
move the condensed water in a form of spiral flow along the inner circumferential surface of the gas-liquid separator.

10. The apparatus of claim 9 , wherein the gas-liquid separator comprises:
a chamber having an internal space, a steam outlet and a concentrate outlet, wherein steam is discharged through the steam outlet provided at a top of the chamber and the condensed water is discharged through the concentrate outlet provided at a bottom of the chamber;
an inlet unit connected to a side of the chamber in the tangential direction of the inner circumferential surface of the chamber such that the condensed water moves in the form of spiral flow along the inner circumferential surface of the chamber, the inlet unit being configured to spray the condensed water; and
a demister disposed in an upper portion of the chamber so as to divide the internal space of the chamber and configured to remove mist contained in the steam.

11. The apparatus of claim 10 , wherein the gas-liquid separator further comprises, in the chamber, at least one barrier configured to prevent the mist contained in the steam from rising.

12. The apparatus of claim 11 , wherein the at least one barrier is configured to protrude from an inner wall of the chamber so as to be inclined upward at an angle of approximately 90-180°.

13. The apparatus of claim 1 , further comprising
a heat exchanger in which condensed water formed by heat exchange of hot steam supplied to at least one of the first evaporator and the second evaporator is heat-exchanged with the water to be treated which is introduced into the first evaporator.

14. A method for evaporative concentration of water, containing hardness-causing substances, to be treated using hot lime softening, the method comprising:
introducing the water to be treated into a first evaporator in which the introduced water is evaporatively concentrated by heat exchange with hot steam, thereby forming first concentrated water, wherein the process of forming the first concentrated water is performed to increase precipitation of hardness-causing substances contained in the first concentrated water without an additional heat source used for satisfying operating temperature condition for precipitating the hardness-causing substances;
introducing at least a portion of the first concentrated water into a hot lime softener in which the hardness-causing substances are precipitated and separated by reaction with lime, thereby the hardness-causing substances being removed; and
introducing at least a portion of the first concentrated water, from which the hardness-causing substances were removed, into a second evaporator in which the at least a portion of the first concentrated water, from which the hardness-causing substances were removed, is further evaporatively concentrated by heat exchange with hot steam, thereby forming second concentrated water.

15. The method of claim 14 , wherein a temperature of the first concentrated water that is introduced into the hot lime softener is approximately 90° C. to 110° C.

16. The method of claim 14 , wherein the first evaporator is operated to have a concentration factor of 5-10.

17. The method of claim 14 , wherein at least one of the introducing the water to be treated into the first evaporator and the introducing the at least a portion of the first concentrated water, from which the hardness-causing substances were removed comprises a process in which at least a portion of the first concentrated water or the second concentrated water is introduced again into the first evaporator or the second evaporator so that it is concentrated again.

18. The method of claim 14 , wherein the evaporative concentration in at least one of the introducing the water to be treated into the first evaporator and the introducing the at least a portion of the first concentrated water, from which the hardness-causing substances were removed is performed by reduced pressure evaporation.

19. The method of claim 14 , further comprising
introducing steam present as two phases together with the concentrated water after at

Assignees

• Doosan Heavy Ind & Construction Co Ltd
• Doosan Heavy Ind Constr Co Ltd

Inventors

• Kim Sangmoon
• Lee Gunmyung
• Kang Weekwan

Classifications

• C02F5/025

  Hot-water softening devices · CPC title

• C02F1/042

  Prevention of deposits · CPC title

• B01D1/28

  with vapour compression · CPC title

• C02F2301/08

  Multistage treatments, e.g. repetition of the same process step under different conditions · CPC title

• B01D1/06 Primary

  Evaporators with vertical tubes · CPC title