BE1024466B1 - Mechanical water vapor desalination unit - Google Patents

Abstract

The unit comprises a vacuum sealed envelope (1), an evaporator-condenser (8) and at least one compressor (12), in which the evaporator-condenser (8) is arranged to operate at a low temperature, is in one a heat-conducting plastic material whose exchange surfaces (9) are determined such that the transfer energy (Wt) of the unit is less than or equal to twice the minimum desalination energy Wm, so that to minimize the total desalination energy W.

Description

(73) Holder (s):

INDUSTRIAL ADVANCED SERVICES FZ-LLC -, AL-JAZEERAAL-HAMRA United Arab Emirates (72) Inventor (s):

WINANDY François-Mathieu SW19 2RR LONDON United Kingdom (54) Water desalination unit by mechanical vapor compression (57) The unit includes a hermetic vacuum envelope (1), an evaporator-condenser (8) and at least a compressor (12), in which the evaporator-condenser (8) is arranged to operate at low temperature, is made of a heat-conducting plastic material and the exchange surfaces (9) of which are determined so that the transfer energy (Wt) of the unit is less than or equal to twice the minimum desalination energy Wm, in order to minimize the total desalination energy W.

fig. 1

BELGIAN INVENTION PATENT

FPS Economy, SMEs, Middle Classes & Energy

Publication number: 1024466 Deposit number: BE2017 / 5530

Intellectual Property Office International Classification: C02F 1/04 B01D 5/00 B01D 1/28 B01D 3/10

Issue date: 02/28/2018

The Minister of the Economy,

Having regard to the Paris Convention of March 20, 1883 for the Protection of Industrial Property;

Considering the law of March 28, 1984 on patents for invention, article 22, for patent applications introduced before September 22, 2014;

Given Title 1 “Patents for invention” of Book XI of the Code of Economic Law, article XI.24, for patent applications introduced from September 22, 2014;

Having regard to the Royal Decree of 2 December 1986 relating to the request, the issue and the maintenance in force of invention patents, article 28;

Given the patent application received by the Intellectual Property Office on 07/27/2017.

Whereas for patent applications falling within the scope of Title 1, Book XI of the Code of Economic Law (hereinafter CDE), in accordance with article XI. 19, §4, paragraph 2, of the CDE, if the patent application has been the subject of a search report mentioning a lack of unity of invention within the meaning of the §ler of article XI.19 cited above and in the event that the applicant does not limit or file a divisional application in accordance with the results of the search report, the granted patent will be limited to the claims for which the search report has been drawn up.

Stopped :

First article. - It is issued to

INDUSTRIAL ADVANCED SERVICES FZ-LLC, P.O. Box 31291, - AL-JAZEERAAL-HAMRA United Arab Emirates;

represented by

OFFICE KIRKPATRICK S.A., Avenue Wolfers 32, 1310, LA HULPE;

a Belgian invention patent of 20 years duration, subject to the payment of the annual fees referred to in article XI.48, §1 of the Code of Economic Law, for: Water desalination unit by mechanical compression of steam.

INVENTOR (S):

WINANDY François-Mathieu, 60, Windsor Avenue, SW19 2RR, LONDON;

PRIORITY (S):

DIVISION:

divided from the basic application: filing date of the basic application:

Article 2. - This patent is granted without prior examination of the patentability of the invention, without guarantee of the merit of the invention or of the accuracy of the description thereof and at the risk and peril of the applicant (s) ( s).

Brussels, 02/28/2018, By special delegation:

- 1 BE2017 / 5530

Water desalination unit by mechanical vapor compression

The field of the invention is the desalination of water, essentially sea water or brackish water, to produce potable or demineralized water, by the thermal distillation process by mechanical vapor compression, commonly known as "mechanical vapor compression" (CMV).

It should be noted that such a desalination process is in competition with the reverse osmosis, freezing, electrodialysis, ion exchange, etc. processes.

The minimum desalination energy, common to all the processes, to reach the production threshold of permeate (osmotic pressure reached) or distillate (ebullioscopic distance reached), being Wm, and the transfer energy, to truly produce the permeate or the distillate, being Wt, energy which is inversely proportional to the exchange surface used in the process, the total energy W of desalination is given by the formula:

Wm + Wt

CE being the total energy efficiency of the equipment used for desalination, in particular pumps or compressors and their motors.

With the reverse osmosis process, we can admit:

Wt = Wm

With the mechanical vapor compression process, Wt is in the range of 7Wm to 15Wm.

- 2 BE2017 / 5530

Thus, with reverse osmosis, the energy to be consumed is of the order of 2.5 to 5 kWh for 1 m ³ of permeate. With the mechanical vapor compression process, to produce 1 m ³ of distillate, you must consume at least 8 kWh and even up to 18 kWh.

The process by mechanical vapor compression, as it is implemented today, therefore has the drawback of high energy consumption. But it still has advantages. It is very stable and very comfortable to use.

A conventional desalination unit by mechanical vapor compression has an overall envelope, generally under partial vacuum in order to reduce the boiling point of the water to be evaporated and condensed, in which there is a water bath, the surface of which ensures evaporation, and an exchanger immersed in the bath which ensures condensation. It is often an evaporator-condenser (EC) of the tube or plate type. The EC is made of a heat-conductive transfer material, one side of which ensures evaporation and the other side, condensation.

The unit is equipped with a steam transport and compression system and auxiliary equipment including a raw water supply system, a partial vacuum system and elimination of non-condensable gases, a system distillate extraction system and a concentrate extraction system.

While the units currently built use compressors with efficiencies less than or equal to around 70%, recent developments now allow the use of compressors with significantly higher efficiency to be considered.

Regardless of the desalination process considered, Wm is a constant in the salinity of the water. Desalination to separate a solution

- 3 BE2017 / 5530 saline (solution 0 or raw water) in two different salinity solutions, one upper (solution 1 or concentrate) and the other lower (solution 2, or distillate in the case of thermal processes, or permeate in the case of reverse osmosis), Wm represents the energy which is equivalent to the difference of the energy potentials between the two solutions 1 and 2.

From the above, we understand that Wm corresponds to the energy of a desalination system at equilibrium with zero production, a function of the difference in salinity between solutions 1 and 2, and that any addition of additional energy will generate the start of desalinated water production.

Wt is the energy, complementary to Wm, to ensure a quantity of desalinated water production. Wt is used to overcome energy losses in the different exchange systems implemented. Thus, in a reverse osmosis unit, Wt mainly corresponds to the hydraulic pressure losses of the permeate which passes through the membranes and, in a distillation unit, Wt corresponds substantially to the thermal differential necessary for the transfer of the latent energy of condensation through of the exchanger.

Wt is therefore directly proportional to the production flow required, to the resistance of the exchangers (pressure losses of the reverse osmosis membranes or thermal resistivity of the material of the evaporator), and inversely proportional to the surface area of the exchanger used.

The problem underlying the invention of the present application is therefore to reduce the electrical energy consumption of a desalination unit, or demineralization unit, of water by mechanical vapor compression and to return the unit to less as attractive as a unit implementing the reverse osmosis process.

- 4 BE2017 / 5530

To this end, the invention of the present application relates to a unit for desalinating water by thermal distillation by mechanical vapor compression comprising:

- a hermetic vacuum envelope, with, inside,

- a space for receiving water to be desalinated,

- an evaporator-condenser in said reception space having evaporation and condensation exchange surfaces,

at least one compressor with a motor and means of transport to the evaporating vapor compressor and, from the compressor, of compressed vapor to be condensed, the casing comprising a salt water supply inlet, heating means water to be desalinated and distillate, concentrate and non-condensable gas extraction outlets as well as means for evacuating the envelope, characterized in that the evaporator-condenser is designed to operate at low temperature, is made of a heat conductive plastic and its exchange surfaces are determined so that the transfer energy (Wt) of the unit is less than or equal to twice the minimum desalination energy Wm, so to minimize the total desalination energy W.

The solution of the invention was therefore born with the appearance on the market i) of compressors having excellent efficiencies, allowing low operating temperatures, as well as ii) of heat conductive polymers (comprising a certain percentage of nano- carbon) which can therefore be used due to the low temperature operation.

It is the conjunction of all these considerations which justifies the inventive activity of the invention.

Previously, given the low efficiency of the compressors available on the market, no one had dared to design a unit with largely excessive exchange surfaces, aiming to significantly reduce energy consumption. In fact, in order to significantly reduce this consumption, it would have been necessary to build units with exchange areas so excessive that the cost of these units would have been prohibitive.

Thanks to the efficiency of the compressors available today, which can exceed 80% or even 90%, the applicant dared to want to considerably increase the exchange surfaces of evaporator-condensers but, thanks to heat-conducting polymers, at a reasonable cost .

The vacuum prevailing inside the hermetic envelope is actually a partial vacuum, which aims only to decrease the boiling point of the water to be evaporated and condensed.

Low temperature should be understood, in the context of the present invention, a vapor temperature of the order of 20 to 60 ° C.

Preferably, the compressor or compressors of the unit of the invention have an efficiency greater than 78% and the exchange surfaces are determined so that the desalination transfer energy is greater than or equal to the minimum transfer energy Wtm.

The total minimum desalination energy (Wm + Wtm) is the energy that the compressor needs in order to overcome the boiling gap of the solution at its maximum salinity, namely that of the concentrate. If this low limit Wtm was not respected, the part of the evaporator-condenser, in contact with a solution whose ebullioscopic deviation is greater than the deviation which defines the Wtm limit, would not be operational and the rate of τ conversion of the unit would not be achieved. By conversion rate is meant the relationship between the distillate flow rate and the raw water flow rate, involving the concept of continuous water renewal. The process of the invention, like the reverse osmosis process, uses tanks whose water is renewed to avoid an infinite increase in the salinity of the concentrate. It will be noted that the boiling difference is the difference between the boiling temperature of pure water and the boiling temperature of a saline solution, all other conditions remaining equal. For a salt water with a salinity of 35 g / l and a pressure equal to atmospheric pressure, this difference is 0.54 ° C. The boiling deviation also varies with the boiling temperature. Thus, under a pressure of O.lbarA, that is to say a boiling temperature of pure water of approximately 46 ° C., the ebullioscopic difference with a salt water solution of salinity of 35 g / l will be approximately 0, 37 ° C.

The invention will be better understood with the aid of the following description of several CMV water desalination units and of the desalination process which is implemented there, with reference to the appended drawing in which

- Figure 1 is a schematic representation of the preferred embodiment of the unit of the invention and

- Figure 2 is an even more schematic representation of a unit of the invention with several effects.

The diagram of the unit in FIG. 1 is that of a preferred embodiment, but which should not be considered as limiting the invention. Other embodiments are perfectly conceivable and one can therefore advantageously refer to those presented in document WO 2015/014840.

With reference therefore to FIG. 1, the unit comprises a hermetic envelope 1 under partial vacuum comprising two compartments 2 and 3. The first compartment 2 comprises an enclosure 4 in which is disposed an exchange coil 5 crossed by non-condensable gases from the second compartment 3, escaping from the enclosure 4 and from the compartment 2, and heating the incoming desalting water coming from

ΒΕ2017 / 5530

-Ί from a power source 6. The water to be desalted and heated comes out of the enclosure 4 and of the compartment 2 through a tube 7.

The second compartment 3, in which the partial vacuum prevails, provides a space for receiving the water to be desalinated in which is arranged an evaporator-condenser 8 comprising here a plurality of evaporation tubes 9 and forming two by two of the conduits of condensation 10 opening into the first compartment 2. The inlet of the condenser tubes of the evaporator-condenser are extended, on the side opposite to the first compartment 2, by a nozzle 11 for receiving a compressor 12 and, in part, d 'an enclosure 13 in which are arranged the motor 14 for driving the compressor and an exchange coil 15. The coil 15, traversed by the water to be desalinated as described below, is here connected to a spraying boom 16 the water to be desalted on the evaporator-condenser 8, the sprinkling being effected by apples 17.

The two compartments 2, 3 are separated by a partition 18 traversed by the condensation conduits 10. The second compartment 3, which is the desalination compartment, comprises a partition 19 for retaining water of greater salinity, here of a concentrate 20, while the desalted water, that is to say the distillate 21 coming from the condensation conduits 10, is retained in the first compartment 2.

Not shown in the figure, since they are perfectly known to those skilled in the art, the water supply equipment to be desalinated from compartment 2 and from the enclosure 4, the distillate 21 and concentrate 20 extraction pumps , nor the means for evacuating the desalination compartment 3.

It will also be noted here that the unit of the invention could include several compressors.

- 8 BE2017 / 5530

In operation, the water to be desalted flowing through the tubing 7 first passes through two exchangers 22, 23 where it is heated by two coils 24, 25 traversed respectively by the distillate 21 and the concentrate 20, the two streams from two exchangers 22, 23 being joined to pass through a third exchanger 26 supplied with a heating liquid from a heating equipment 27.

At the outlet of this third exchanger 26, outside, like the first two 22, 23, at the enclosure, the water to be desalted, through a tube 28, enters the exchanger 13, inside the enclosure.

In the example illustrated in the figure, the water to be desalinated therefore reaches the evaporator-condenser by a film falling from the sprinklers 17 which distribute the water over the exchange surface of all the evaporation tubes. 9. The nozzle 11 is here shaped to transport the vapor evaporated from the tubes 9 to the compressor 12 and the compressed vapor to be condensed in the conduits 10.

The compressor 12 is again, here, an axial flow compressor, of an excellent efficiency, in this case, here, greater than 78%. The evaporation-condensation tubes 9 are made of a heat-conductive polymer, the unit operating at low temperature.

The total exchange surface of the tubes 9 is very large and such that the transfer energy Wt of the unit is less, possibly equal to twice the minimum desalination energy Wm and such that, in the example considered , this transfer energy Wt is between the minimum transfer energy Wtm and double 2 Wm of the minimum desalination energy.

It will be noted that the heating equipment supplying the exchanger 27 may be an electrical resistance, a heat pump or an exchanger supplied with auxiliary thermal energy by steam or water.

-9 BE2017 / 5530 hot. The heating liquid of this exchanger 27 heats the water to be desalted which will penetrate into the casing 1 through the tube 28, while in the exchangers 22, 23, the water to be desalinated is heated by recovery of the heat energy. outgoing flows of distillate and concentrate.

The unit shown in the figure has evaporation tubes. Another CMV water desalination unit could be fitted, not with tubes, but with plates, in the same material as the tubes.

The equipment for supplying the unit with water to be desalinated generally comprises tanks whose water is renewed in order to avoid an infinite increase in salinity of the concentrate. This water renewal characterizes the conversion rate τ of the unit.

At constant raw water salinity, the higher the conversion rate, the higher the average salinity of the concentrate and therefore the higher Wm. Wm therefore depends on the salinity of the raw water and the conversion rate applied to the desalination unit.

Example of calculation of the parameters of a water desalination unit by

CMV:

Or a unit operating on raw water with a salinity equal to 35 g / l, with an evaporator-condenser under partial vacuum operating at a vapor temperature of 50 ° C, a conversion rate τ of 33%, here only one compressor with a 90% efficiency and that of its motor with 95%, and a definition of the exchange surface such that Wt = 2, Wm.

Calculation of Wm τ

T °

Maximum concentrate salinity Average concentrate salinity%

50 ° C (323 ° K) 35 / (1-0.33) = 52.2g / kg 43.6g / kg

- 10 BE2017 / 5530

Vapor pressure of concentrate Pl

Salinity of the distillate

Vapor pressure of distillate P2

P2 / P1

Wm

Wtm calculation

Maximum salinity of the concentrate Vapor pressure Pc (# Pl) of the concentrate

Salinity of the distillate

Vapor pressure of distillate P2

P2 / Pc

Result # 1

Wtm

Wt calculation

Wt

THIS

W: 12,058kPa: Og / kg (theoretical approximation): 12,350kPa: 1,024: RTIn (P2 / Pl) = 17.85 10 ' ⁶ kWh / mole or 0.99kWh / m ³ (m ³ of distillate), In being the natural logarithm.

: 35 / (1-0.33) = 52.2g / kg: ll, 991kPa: Og / kg (theoretical approximation): 12.350kPa: 1.030: RTIn (P2 / Pc) = 22.05 10 ' ⁶ kWh / mole or 1.23kWh / m ³ (m ³ of distillate): Result # l-Wm = 0.24kWh / m ³ : 2.Wm = 1.98kWh / m ³ : 0.9. 0.95 = 0.855: (Wm + Wt) / CE = 3.49kWh / m ³

Calculation of the heat exchanger exchange surface

P3 is the operating pressure of the desalination unit

P3 / P1

Steam temperature before the compressor (Tin) Boiling temperature (Tevap)

Condensation temperature (Tcond) dT of the evaporator-condenser

Hec e ((Wm + Wt) / (R.T)) = 1.074

50 ° C

50.48 ° C

51.45 ° C

0.97 ° C

6kW / (m ^2. ° C)

- 11 BE2017 / 5530

Hec is the heat exchange coefficient of the evaporator-condenser, determined empirically and fixed, here, arbitrarily

Latent heat (approximation): 635kWh / Ton

Exchanger surface S: 635 / (6. 0.97) = 109, lm ^{2 /} Ton.h (Ton / h of distillate)

According to the same hypotheses as in the example above, by now varying Wt over the interval [Wtm, 2, Wm], we obtain the following results:

Wm Wt THIS W P2 / P1 P3 / P1 Tin Tevap Tcond dT HEC S ΈΓ ΈΓ where? -vs vs vs VS vs vs o vs , o vs , o s. O Q) ς 1 1 § Where o S VS VS? VS E vs £ g ——J ——J ——J ——J 0.99 0.240 0.855 1,439 1.024 1.030 50 50.48 50.60 0.12 6 878 0.99 0.495 0.855 1.737 1.024 1.036 50 50.48 50.72 0.25 6 432 0.99 0.990 0.855 2,316 1.024 1.049 50 50.48 50.97 0.49 6 217 0.99 1.485 0.855 2,895 1.024 1.062 50 50.48 51.21 0.73 6 145 0.99 1,980 0.855 3.474 1.024 1.074 50 50.48 51.45 0.97 6 109

These results demonstrate that the combination of the characteristics of the invention is necessary for the design of a CMV desalination unit which offers competitive electrical energy consumption with desalination by reverse osmosis. Indeed, the application of a usual CE efficiency, with 70% for the compressor efficiency and 95% for that of its engine, would generate either too high electrical energy consumption to compete with the reverse osmosis process, or surfaces exchanges of such magnitude that the cost of the unit would also be uncompetitive.

Finally, it should be noted that the desalination unit can have several evaporation-condensation effects 31, 32, 33. In this case, and in a manner perfectly known to those skilled in the art, the vapor 34 created on the surface 12 BE2017 / 5530 evaporation face 35 of the first effect 31 is channeled to the condensation surface 36 of the next effect 32 and so on until the last effect 33 where the vapor 37 is then transported and compressed in the compressor 38 again before being recycled at the top of the first effect 31.

The respective steam temperatures in the compartments of the three effects 31, 32, 33 are different and drop by a few degrees from one compartment to another, here, with temperatures of 50 ° C, 49 ° C and 48 ° C respectively. .

The concentrates and distillates from the three compartments 31, 32, 33 are grouped respectively by two tubes 39, 40. As for the water to be desalinated, it reaches the compartments of the three effects 31, 32, 33 by a tube 41 and three groups of watering can apples 42-44.

- 13 BE2017 / 5530

Claims (8)

1. Unit for desalinating water by thermal distillation by mechanical vapor compression comprising: - a hermetic vacuum envelope (1), with, inside, - a space (3) for receiving water to be desalinated, - an evaporator-condenser (8) in said receiving space (3) having exchange surfaces (9) for evaporation and condensation, - at least one compressor (12) with a motor (14) and means (11) for transporting the evaporating vapor to the compressor and, from the compressor, of compressed vapor to be condensed, the casing (1) comprising an inlet salt water supply (4), means (27, 4, 22, 23, 13) for heating the water to be desalinated and distillate (22), concentrate (23) extraction outlets and non-condensable gases (4) as well as means for evacuating the envelope, characterized in that the evaporator-condenser (8) is designed to operate at low temperature, is made of a heat-conducting plastic material and its exchange surfaces (9) are determined so that the transfer energy (Wt) of the unit is less than or equal to twice the minimum desalination energy Wm, in order to minimize the total desalination energy W . 2. Unit according to claim 1, in which the space for receiving water to be desalinated comprises a first compartment (2) comprising an enclosure (4) for heating the incoming water to be desalinated by non-condensable gases. 3. Unit according to one of claims 1 and 2, in which the space for receiving water to be desalinated comprises a second compartment (3) under vacuum in which the evaporator-condenser (8) is arranged, comprising conduits condensation (10) opening into the first compartment (2). - 14 BE2017 / 5530 4. Unit according to claim 3, wherein there is provided in the second compartment (3), a ramp (16) for watering desalination water. 5. Unit according to one of claims 3 and 4, wherein the outlet (22) for extracting the distillate is provided in the first compartment (2) and, the outlet (23) for extracting the concentrate, in the second compartment (3). 6. Unit according to one of claims 1 to 5, comprising several effects of evaporation-condensation (31, 32, 33). 7. Unit according to one of claims 1 to 6, in which the compressor (12) has an efficiency greater than 78%. 8. Unit according to one of claims 1 to 7, in which the exchange surfaces (9) are determined so that the transfer energy Wt is equal to or greater than the minimum transfer energy Wtm. -15BE2017 / 5530 BE2017 / 5530 Abridged Water desalination unit by mechanical vapor compression The unit comprises a hermetic vacuum envelope (1), an evaporator-condenser (8) and at least one compressor (12), in which the evaporator-condenser (8) is arranged to operate at low temperature, is in one heat conductive plastic and the exchange surfaces (9) of which are determined so that the transfer energy (Wt) of the unit is less than or equal to twice the minimum desalination energy Wm, so to minimize the total desalination energy W.