Stacked type falling film evaporator, zero liquid discharge system comprising the same, and zero liquid discharging method using the same

Patent metadata

Field	Value
Publication number	US-10857478-B2
Application number	US-201916565483-A
Country	US
Kind code	B2
Filing date	Sep 9, 2019
Priority date	Jan 8, 2014
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

A stacked type falling film evaporator includes a first evaporator, a second evaporator, a first vapor recovering device, a second vapor recovering device and a vapor recompressor. The first evaporator and the second evaporator respectively have evaporation tubes of a length of 5 m to 10 m, and are stacked in such a manner that wastewater passes through the first evaporator and the second evaporator in order. The first vapor recovering device collects vapor generated from the wastewater in the first evaporator and supplies the collected vapor to the second evaporator. The second vapor recovering device collects vapor generated from the wastewater in the second evaporator and supplies the collected vapor to the first evaporator. The vapor recompressor compresses the vapor collected in the second vapor recovering device before the vapor is supplied to the first evaporator.

First claim

What is claimed is:

1. A zero liquid discharging (ZLD) method using a stacked-type falling film evaporator including a first falling film evaporator stacked on a second falling film evaporator, the ZLD method comprising:
evaporating and concentrating wastewater in the stacked-type falling film evaporator;
phase-separating the concentrated wastewater to generate vapor and sludge, respectively;
concentrating the vapor generated by the phase-separating in order to recover condensate water; and
treating the sludge generated by the phase-separating in order to produce a sludge cake through centrifugation,
wherein the evaporating and concentrating the wastewater includes:
introducing the wastewater into an upstream space of the first falling film evaporator;
passing the wastewater sequentially through the first falling film evaporator, a first liquid storage tank of the first falling film evaporator, the second falling film evaporator, and a second liquid storage tank of the second falling film evaporator, to evaporate and concentrate the wastewater passing through the first and second falling film evaporators;
collecting vapor generated from the wastewater in the first liquid storage tank;
supplying the vapor collected in the first liquid storage tank to the second falling film evaporator;
collecting vapor generated from the wastewater in the second liquid storage tank;
compressing the vapor collected in the second liquid storage tank; and
supplying the compressed vapor to the first falling film evaporator.

2. The ZLD method of claim 1 , further comprising
pumping the concentrated wastewater having passed through the second falling film evaporator to the second liquid storage tank to the upstream space of the first falling film evaporator.

3. The ZLD method of claim 1 , further comprising
compressing the vapor collected in the first liquid storage tank before supplying the collected vapor to the second falling film evaporator.

4. The ZLD method of claim 3 , wherein the vapor collected in the first liquid storage tank is transferred to a first thermal vapor recompressor, and
wherein the vapor collected in the second liquid storage tank is transferred to a second thermal vapor recompressor.

5. The ZLD method of claim 1 , further comprising
pretreating the wastewater before the wastewater is introduced into the upstream space of the first falling film evaporator.

6. The ZLD method of claim 5 , wherein the pretreating includes at least one of a caustic soda treatment, an alum treatment, a polymer treatment, and a settling separation.

7. The ZLD method of claim 5 , wherein the wastewater is pretreated by passing through a sequential arrangement of a caustic soda treatment tank, an alum treatment tank, an polymer treatment tank, and a settling separation tank.

8. The ZLD method of claim 5 , further comprising
separating the pretreated wastewater in a reverse osmosis separator disposed upstream of the first falling film evaporator.

9. The ZLD method of claim 1 , wherein the wastewater passing through the first and second falling film evaporators is transferred to a forced circulation evaporator provided as a crystallizing device.

10. The ZLD method of claim 1 , wherein
the wastewater passing through the first falling film evaporator passes through a first plurality of evaporation tubes of a length of 5 m to 10 m, and
wherein the wastewater passing through the second falling film evaporator passes through a second plurality of evaporation tubes of a length of 5 m to 10 m that are stacked vertically with the first plurality of evaporation tubes.

11. A zero liquid discharging (ZLD) method comprising:
a pretreatment step of pretreating introduced wastewater through a wastewater pretreatment device;
an evaporation step of evaporating and concentrating the pretreated wastewater through a stacked-type falling film evaporator;
a crystallizing step of phase-separating the concentrated wastewater through a crystallizing device to produce vapor and sludge, respectively; and
a post-treatment step of
concentrating the vapor through a condenser so as to recover condensate water, and
treating the sludge into a discarded form through centrifugation by a sludge treatment device,

wherein the evaporation step includes:
a first evaporation step of evaporating and concentrating wastewater introduced into a first falling film evaporator of the stacked-type falling film evaporator, the first falling film evaporator including a first plurality of evaporation tubes having a vertical length;
a second evaporation step of evaporating and concentrating wastewater introduced into a second falling film evaporator of the stacked-type falling film evaporator from the first falling film evaporator, the second falling film evaporator including a second plurality of evaporation tubes having a vertical length that is stacked with the vertical length of the first plurality of evaporation tubes;
a downward supplying step of
collecting vapor generated from wastewater in the first falling film evaporator, and
supplying the collected vapor to the second falling film evaporator through a first vapor recovering device;

an upward recompressing step of
collecting vapor generated from the wastewater in the second falling film evaporator, and
transferring the collected vapor to a vapor recompressor through a second vapor recovering device; and

an upward supplying step of supplying the vapor compressed in the vapor recompressor to the first falling film evaporator.

12. The ZLD method of claim 11 , wherein
the evaporation step is achieved through a flow of wastewater and a flow of vapor and condensate water, the flow of wastewater proceeding first through the first falling film evaporator in the first evaporation step and then through the second falling film evaporator in the second evaporation step, and
wherein some of the wastewater concentrated after the second evaporation step is returned to the first falling film evaporator in a wastewater circulating step performed after the second evaporation step.

13. The ZLD method of claim 11 , wherein
the evaporation step is achieved through a flow of wastewater and a flow of vapor and condensate water, and
wherein the flow of vapor and condensate water proceeds by vapor introduced into the first falling film evaporator being concentrated through heat exchange with the wastewater inside the first plurality of evaporation tubes generating vapor from the wastewater, the generated vapor sequentially going through
the downward supplying step of collecting the vapor and supplying the collected vapor to the second evaporator,
the upward recompressing step of collecting vapor generated from the wastewater in the second evaporator and transferring the collected vapor to the vapor recompressor, and
the upward supplying step of supplying the compressed vapor generated in the vapor recompressor to a heat exchange space of first falling film evaporator.

14. The ZLD method of claim 11 , further comprising
a downward recompressing step of supplying high-pressure vapor generated by a second vapor recompressor to the second falling film evaporator after the downward supplying step.

15. A stacked type falling film evaporator for use in a zero liquid discharging (ZLD) method, the stacked type falling film evaporator comprising:
a first falling film evaporator and a second falling film evaporator stacked such that wastewater passes through the first falling film evaporator and the second falling film evaporator in sequence;
a first pipe, connected between a liquid storage tank of

Assignees

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

Inventors

• Kim Sang Moon
• Ro Youngjun
• Lee Gun Myung
• Choi Jae Seung

Classifications

• C02F11/127

  by centrifugation · CPC title

• C02F1/441

  by reverse osmosis · CPC title

• C02F2301/046

  Recirculation with an external loop · CPC title

• B01D3/007

  Energy recuperation; Heat pumps · CPC title

• C02F1/08

  Thin film evaporation · CPC title