FIELD OF THE INVENTION

This invention relates to a system and process for generating concentrated seawater by tlie condensing low pressure water vapors (LPWV) in a condenser.

BACKGROUND OF THE INVENTION

In thermal power stations the exhaust steam from the steam turbine is passed through surface condensers. These condensers are heat exchangers which convert steam from its gaseous to its liquid state at a pressure below atmospheric pressure. Normally large volume of cooling water is pumped into Surface Condensers (a form of heat exchangers) to condense the low- pressure water vapors (LPWV) entering it. Huge quantity of cooling water is required to extract the latent heat present in low-pressure water vapors (LPWV) thus leading to its condensation. Normally low pressure water vapors (LPWV) under vacuum at around 40°C are condensed in 'Surface Condensers'. Cooling water from 'Cooling Towers' are circulated through the surface condensers, and returned to the Cooling Towers, and the warm water losses its heat in the cooling towers. Make-up water is added to the cooling towers, towards evaporation loses. If raw seawater is available nearby then, seawater is drawn directly from sea, circulated through the surface condenser and returned to the sea - once through. The pumping cost of circulating cooling water from cooling tower / sea and return is quite high and the energy is lost to a heat sink sea / atmosphere

OBJECT OF THE INVENTION

The object of the present invention is to provide a system for generating concentrated seawater by condensing low pressure water vapors (LPWV) in a condenser.

Further object of the present invention is to provide a system to mitigate electric power consumption during generating concentrated seawater by condensing low pressure water vapors (LPWV) in a condenser.

Yet another object of the invention is to use the latent heat present in low-pressure water vapors (LPWV) by cooling it with large volume of cooling water to enable the water vapors to condense.

Yet another object of the invention is to use the water of the sea bodies by dipping the condensers in the nearby water body, and leading the low-pressure water vapors to the submerged heat exchanger tubes for condensation.

Yet another object of the present invention is to provide a process for generating concentrated seawater by condensing low pressure water vapors (LPWV) in a condenser.

SUMMARY OF THE INVENTION

In order to achieve the objects of the present invention and to obviate the drawbacks of the prior art, the present invention provides a system for generating concentrated seawater by condensing low pressure water vapors (LPWV) in a condenser comprising:

- a seawater concentrator with heat exchanger bundle tubes (HETl) submerged in the seawater body (SWB);

- tubes bundle for passing the low-pressure water vapor (LPWV) inside of the heat exchanger (HETl) to condense releasing latent heat;

- a surface aerator either installed inside the seawater concentrator or in an adjacent surface aerator tank having another set of heat exchanger bundle tubes (HET2) immersed in surface aerator tank;

- condensed water receiver (CWR) installed outside the water body (WB) for collecting the condensed water (CW ) removed by pump (P);

- vacuum system (VP) installed outside the said water body (SWB) to evacuates the non-condensable gases that enter the heat exchanger tubes (HET) along with low pressure water vapors;

wherein the low-pressure water vapor (LPWV) passes through both HETl and HET2; wherein agitation caused by the aerator causes efficient heat transfer from the low-pressure water vapor to the seawater ensuring complete condensation of the low-pressure water vapors inside the tubes.

The tubes system of heat exchanger (HET1 ) are either fully or partially immersed inside the water body.

The low-pressure water vapors (LPWV) are lead to the submerged heat exchanger tubes through pipes / tubes, with or without fins to facilitate cooling of water vapor while said vapors are lead to the submerged heat exchanger. Further, the said tube bundle of the heat exchanger consisting of tubes and tube sheets and bonnets (HET). Further, the heat exchanger tubes can also be spiral type or over hanging type. The tubes of the heat exchanger (HET) are maintained at the requisite temperature by the water inside the water body.

The invention further provides that a continuous water inflow (WIF) and equivalent water outflow (WOF) is maintained from the water body (WB).

The heat exchanger tubes are made of either Duplex steel or Graphite or any other suitable material of construction to withstand concentrated seawater erosion and corrosion. Further the seawater concentrator, agitator in the surface aerator are made of suitable fiber re-enforced plastic (FRP) or any other suitable material of construction to withstand concentrated seawater erosion and corrosion.

The invention further provides a process for generating concentrated seawater by condensing low pressure water vapors (LPWV) in a condenser comprising the steps of:

• preparing partially concentrated seawater from near 6 Bohme to near 10 Bohme in surface aerator tank, in seawater concentrator or solar evaporation pond;

• cooling and condensing the low pressure water vapor (LPWV) from the evaporation section in heat exchanger tubes (HETl) of the seawater concentrator;

• condensing said cooled low pressure water vapor (LPWV) by passing through the HETZ in seawater concentrator to the heat exchanger tubes (HET2) of the surface aerator;

• removing the non-condensable gases by vacuum pumps;

• diverting and removing condensed water outside the water body (seawater);

The heat exchanger tubes are kept immersed in seawater in the bottom section of the seawater concentrator.

DESCRIPTION OF THE DRAWINGS

Figure 1: schematic diagram of the system for generating concentrated seawater by condensing low pressure water vapors (LPWV) in a condenser.

DETAILED DESCRIPTION OF THE INVENTION

Normally, in order to extract the latent heat present in low-pressure water vapor (LPWV) and facilitate its condensation in a Surface Condenser, cooling water at ambient temperature from a near-by water body is pumped into the Surface Condenser. Instead of pumping huge quantity of cooling water from a nearby water body to condense low-pressure water vapor in a surface condenser; it has now been advocated by the applicant, to lead the low-pressure water vapor to the heat exchanger tubes submerged in the water body itself. This will save in the electric power consumption of the cooling water pumps. Electric power consumption required to pump the small quantity of condensed water will be much lower compared to the electric power consumption by the cooling water pumps.

Latent heat present in low-pressure water vapors is normally lost to the ambient when it is cooled in surface condensers wherein cooling water is circulated once through and the warm cooling water is then cooled in cooling towers before being returned to the surface condenser. The invention further provides for the effectively utilization of the latent heat of LPWV to generate concentratred seawater from near 6 Bohme to near 10 Bohme. Hot and dirty flue gas emitting from the coal fired boilers of a thermal power plant can thus be scrubbed & cleaned utilising the concentrated seawater. Increase in concentration level of the alkaline matter in the seawater will assist in enhancing the neutralisation of the acidic media present in the hot and dirty flue gas.

1. Warm raw seawater with specific gravity of (4 Bohme) can be concentratied to near (6 Bohme) in Solar Evaporation Ponds (salt pans) and / or Cooling Towers whenever warm seawater at 42° C is made available by the thermal power plant from their surface condenser.

2. Seawater is further concentrated say from (6 Bohme) to near (10 Bohme) in the unique combination of SURFACE AERATOR and COOLING TOWER.

3. Seawater is further concentrated in the flue gas scrubber unit from say (10 Bohme) to (18 Bohme) by continously re-circulating the scrubbing liquid through the scrubber and ensuring direct contact between hot and dirty flue gas and scrubbing liquid. The concentrated seawater is then being bled from the scrubber section and sent to evaporation section for recovery of sensible heat and mixing with raw seawater of 4 - 5 Bohme speccific gravity.

Cooling towers: Mechanical draft cooling towers are much more widely used. These towers utilize large fans to force air through circulated water. The water falls downward over fill surfaces that help increase the contact time between the water and the air. This helps maximize heat transfer between the two.

Surface Aerator: The fixed type aerators are mounted on a RCC or M. S. platform to the ground. The impeller is conical and the RPM of the aerator range from 45-60. Heavy duty gear box is provided. Oxygen transfer capacity of the aerator varies from 1.1 -1.2 kg o2 per H.P. per hour.

Normally low pressure water vapors (LPWV) under vacuum at around 40°C are condensed in 'Surface Condensers'. Cooling water from 'Cooling Towers' is circulated through the surface condensers, and returned to the Cooling Towers, and the warm water loses its heat in the cooling towers. Make-up water is added to the cooling towers, towards evaporation loses.

It is assumed that a nearby water body has a continuous in flow and out flow of water, and the water inside the water body is preferably maintained at ambient temperature. Suitably sized heat exchanger tubes (bundle) with dished end bonnets on both side and made of appropriate material of construction is placed partially / completely immersed in the water inside the water body. The low-pressure water vapors (LPWV) that enter the heat exchanger tubes will condense. The vacuum pump with sufficient capacity is installed outside the water body to evacuate the non-condensable gases that may enter the Heat Exchanger tubes. The condensed water is also collected outside the water body in a separate receiver and pumped out at regular intervals.

According to one of the embodiment of the invention the low pressure water vapor (LPWV) from the evaporation section is sent to the shell side of a Surface Condenser. Concentrated seawater as cooling water with specific gravity of around (6-10 Bohme) is continously re-circuated through the surface condenser after the cooling water is cooled in an appropriate Cooling Tower. The quantity of cooling water that would have to be re-ciculated through the surface condenser would be high leading to higher electric power consumption. Material of Construction of the heat exchanger tubes of surface condenser can be of Duplex steel or Graphite. The shell and tube sheet can be made of Carbon steel epoxy coated/rubber lined. Due to continous evaporation of water from the re-circulated cooling water in the cooling tower, specific gravity of the cooling water will gradually increase from 6 Bohme to near 15 Bohme. The cooling tower is made of suitable FRP that can withstand seawater erosion and corrosion. However, said system and process is not the recommended one aa sper the present invention.

As per the second embodiment of the present invention the low pressure water vapor (LPWV) from the evaporation section is lead to seawater concentrator/Cooling Tower. Heat exchanger tubes made of either Duplex steel or Graphite is kept immersed in seawater in the bottom section of the cooling tower. The low-pressure water vapor (LPWV) will commense to cool and condense inside the tubes, while exchanging heat with the seawater present in the seawater concentrator/Cooling Tower. The seawater in the seawater concentrator/Cooling Tower will gradually get concentrated to achieve a specific gravity of near 10 Bohme. The cooling tower will receive make-up seawater from the surface aerator tank installed beside it. The low pressure water vapor from the seawater concentrator /Cooling Tower is then lead to another set of heat exchanger tubes (made of either Duplex steel or Graphite) that are kept immersed inside a surface aerator tank situated next to the cooling tower. Partially concentrated seawater at ambient temperature from nearby solar evaporation pond shall supply the necessary make-up seawater to the surface aerator tank. The agitation caused by the aerator will ensure efficient heat transfer from the low-pressure water vapor to the seawater ensuring complete condensation of the low-pressure water vapors inside the tubes. Naturally a vacuum pump will remove the non-condensable gases.

Both the seawater concentrator /Cooling Tower as well as the surface aerator will be made out of suitable fiber re-enforced plastic (FRP). Even the blades of the blower in the seawater concentrator /Cooling Tower and the agitator in the surface aerator will be made out of FRP to withstand the erosive and corrosive nature of the seawater.

It may be noted that though we can expect some quantity of seawater evaporation from the surface aeration tank; our aim is to mainly create sufficient turbulance so that film formation on the heat exchanger tubes is totally mitigated leading to more effective and efficient heat exchange between the low-pressure water vapors and the partially concentrated seawater.

Electric power consumption by the blower and recirculation pump of seawater concentrator/Cooling Tower and the agitating blades of the surface condenser should not be very high.

The said invention is used for effectively uilizing waste heat, for the generation of concentrated seawater to be used as polution control device.

DESCRIPTION OF THE INVEN TION WITH DRAWINGS

The tube bundle of the heat exchanger consisting of tubes and tube sheets and bonnets (HETZ) are placed in a water body (SWB) either fully or partially immersed in the water inside the water body. It is preferred to maintain a continuous water inflow (WIF) and an equivalent water outflow (WOF) from the water body (SWB). The tubes of the heat exchanger (HETZ) are maintained at the requisite temperature by the water inside the water body. When (LPWV) low-pressure water vapor enters the inside of the tubes of the heat exchanger (HETZ); then it will tend to condense releasing latent heat. The heat exchanger tubes (HETZ) will transfer this heat to the water inside the water body (WB). The condensed water (ON) will be collected by condensed water receiver (G/VR); installed outside the water body (WB). With the help of a pump (P) the condensed water can be pumped out from the condensed water receiver (G/VR). The non-condensable gases that may enter the heat exchanger tubes (HETZ); along with low-pressure water vapors can be evacuated from the heat exchanger tubes (HETZ) with the help of an appropriate vacuum system (VP) installed outside the water body (WB). Low-pressure water vapors (LPWV) may be lead to the submerged heat exchanger tubes through pipes / tubes of suitable material of construction, with or without fins to facilitate cooling of water vapor while it is being lead to the submerged heat exchanger.

SALIENT FEATURES OF THE INVENTION

• The invention offers a significantly economic solution, with low electric power consumption for condensing low-pressure water vapors normally liberated under vacuum

• The invention enables mitigation / reduction of electric power consumption

• The invention enables easy, convenient and alternative method for tackling electric power scarcity in metropolitan and cosmopolitan cities.

• Further this process is environment friendly.

We claim:

1. A system for generating concentrated seawater by condensing low pressure water vapors (LPWV) in a condenser comprising:

- a seawater concentrator with heat exchanger bundle tubes (HETl) submerged in the seawater body (SWB);

- tubes bundle for passing the low-pressure water vapor (LPWV) inside of the heat exchanger (HETl) to condense releasing latent heat;

- a surface aerator either installed inside the seawater concentrator or in an adjacent surface aerator tank having another set of heat exchanger bundle tubes (HET2) immersed in surface aerator tank;

- condensed water receiver (CWR) installed outside the water body (WB) for collecting the condensed water (CW) removed by pump (P);

- vacuum system (VP) installed outside the said water body (SWB) to evacuates the non-condensable gases that enter the heat exchanger tubes (HET) along with low pressure water vapors;

wherein the low-pressure water vapor (LPWV) passes through both HETl and HET2; wherein agitation caused by the aerator causes efficient heat transfer from the low-pressure water vapor to the seawater ensuring complete condensation of the low-pressure water vapors inside the tubes.

2. The system as claimed in claim, wherein tubes system of heat exchanger (HETl) are either fully or partially immersed inside the water body.

3. The system as claimed in claim, wherein low-pressure water vapors (LPWV) are lead to the submerged heat exchanger tubes through pipes / tubes, with or without fins to facilitate cooling of water vapor while said vapors are lead to the submerged heat exchanger.

4. The system as claimed in claim 1, wherein the said tube bundle of the heat exchanger consisting of tubes and tube sheets and bonnets (HET).

5. The system as claimed in claim 1, wherein the heat exchanger tubes can also be spiral type
or over hanging type.

6. The system as claimed in claim 1, wherein a continuous water inflow (WIF) and equivalent water outflow (WOF) is maintained from the water body (WB).

7. The system as claimed in claim 1, wherein the tubes of the heat exchanger (HET) are maintained at the requisite temperature by the water inside the water body.

8. The system as claimed in claim 1, wherein the heat exchanger tubes are made of either Duplex steel or Graphite or any other suitable material of construction to withstand concentrated seawater erosion and corrosion.

9. A process for generating concentrated seawater by condensing low pressure water vapors (LPWV) in a condenser as claimed in claim 1 comprising:

• preparing partially concentrated seawater form 6 bohme to near 10 bohme in surface aerator tank, in seawater concentrator or solar evaporation pond;

• cooling and condensing the low pressure water vapor (LPWV) from the evaporation section in heat exchanger tubes (HET1 ) of the seawater concentrator;

• condensing said cooled low pressure water vapor (LPWV) by passing through the HETZ in seawater concentrator to the heat exchanger tubes (HET2) of the surface aerator;

• removing the non-condensable gases by vacuum pumps;

• diverting and removing condensed water outside the water body (seawater);
wherein said heat exchanger tubes (HET2) are immersed in the inside the surface aerator tank.

10. The process as claimed in claim 8, wherein said heat exchanger tubes is kept immersed in
seawater in the bottom section of the seawater concentrator.

11. The process as claimed in claim 1, wherein said seawater concentrator, agitator in the
surface aerator are made of suitable fiber re-enforced plastic (FRP) or any other suitable
material of construction to withstand concentrated seawater erosion and corrosion.