AU695211B2 - Distillation apparatus - Google Patents

Description

r1 DISTILLATION APPARATUS This invention relates to distillation apparatus.

This invention has particular but not exclusive application to distillation apparatus for distilling fresh water from sea water or brackish water, and for illustrative purposes reference will be made to such application. However it is to be understood that this invention could be used in other applications such as distilling other liquids from solids or other liquids, or degassing liquids.

Lower temperature distillation is frequently used to purify water by applying a low grade heat source or the like to an evacuated still. Frequently, a vacuum generating device is provided to evacuate or decrease the pressure in the still and the fluid is often condensed in a condenser.

In many such arrangiments compression and/or other energy generated by and/or in the device creating vacuum may be lost. Additionally, such distillation apparatus may require outside heating sources to heat the fluid to be distilled.

The present invention aims to alleviate one or more of S 20 the above disadvantage-s and to provide distillation apparatus which will be reliable and efficient in use.

With the foregoing in view this invention in one aspect resides broadly in distillation apparatus including:liquid feedstock; distillate discharge means; a sealed evaporation vessel; a controlled liquid inlet to said vessel for maintaining a desired liquid level in said vessel from said liquid feedstock; heat exchange means for returning pumping and heat energy from a recompressed fluid to said vessel, and 2 evacuating means for pumping evaporated liquid from said vessel to said distillate discharge means as said recompressed fluid, wherein said evacuation means includes a vacuum pump adapted to generate a high velocity fluid stream from said recompressed fluid.

Preferably the heat exchange means and evacuating means are formed such that condensation occurs within the evaporation vess, such that both sensible heat of the liquid and evacuating means, and latent heat of the evaporated liquid are partially transferred directly to the liquid within the vessel, and that a substantial portion of the remaining energy is added by secondary heat exchange means to the feedstock.

r II The heat transfer within the veesel takes place in 15 condensation means, which is used to transfer energy to the evaporation vessel by change of phase of fluid from gas to liquid, whether the change of phase occurs in the condenser or upstream towards the evacuating means therefrom.

j Suitably, the secondary heat exchange means is operably 20 associated with a primary feedstock vessel whereby heat energy may be transferred to incoming feedstock.

Preferably, the condensation means is a condenser located within the evaporation vessel. For the evacuating I means, one or more vacuum pumps may be used, such as blowers, positive displacement pumps and such like. Preferably, the evacuating means includes an ejector assembly creating a vacuum on a vacuum port by receiving fluid from a pump assembly. Preferably, the pump assembly generates a high velocity fluid stream and gas evaporated in and received from the evaporation vessel mixes with the high velocity fluid.

Preferably, the condenser is used to heat the fluid in the evaporation vessel and the fluid passing through the condenser receives heat energy including compression energy

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3 generated by the pump assembly. Additionally, a booster heater may be provided to heat the fluid in the evaporation vessel. In a further preferred embodiment, fluid passing into the evaporation vessel through the inlet is preheated through a heat exchanger or such like receiving heat from a secondary condenser receiving fluid from the condenser within the evaporation vessel. Additionally, a discharge means is provided for discharging fluid from the evaporation vessel in order to remove impurities from the liquid. Suitably, the heat is recovered from the discharged fluid into the feed liquid entering into the evaporation vessel.

The vacuum pump may be provided inside or outside of the U evaporation vessel but preferably, the pump assembly is insulated against heat loss from the system.

15 In a further aspect this invention resides broadly in a method of distilling a liquid including the steps of:feeding a liquid feedstock into a distillation apparatus having distillate discharge means, a sealed evaporation vessel, a controlled liquid inlet to said vessel, evacuating 20 means, and heat exchange means; maintaining a desired liquid level in said vessel from said liquid feedstock; reducing the pressure of said liquid in the distillation p apparatus to cause evaporation of at least some of the liquid to form a gas; pumping evaporated liquid from said vessel to said distillate discharge means by use of a vacuum pump adapted to generate a high velocity fluid stream; recirculating some of said recompressed fluid to said vacuum pump for generation of said high volocity fluid, and

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4 recompressing the gas evaporated from the liquid and returning at least some of the pumping and heat energy from said recompressed fluid to the liquid in the distillation apparatus by said heat exchange means, and wherein said recompressed fluid transfers energy to said evaporation vessel by change of phase of fluid from gas to liquid.

In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawing which illustrates a f typical embodiment of the invention and wherein:- FIG. 1 is a schematic flow diagram representing a distillation apparatus according to the invention.

Referring to the figure, a distillation apparatus includes an evaporation tank 11 which receives liquid from a feed line 12 and in use is held under vacuum by a vacuum pump 14 which draws vapour from the evaporation tank 11 through a vapour line 13. The vapour is formed by evaporation and/or boiling of the liquid in the evaporation tank received 'through the feed line 12. The vacuum pumn 14 is provided with its pumping power by receiving fluid trom a fluid source The liquid in the evaporation tank 11 is maintained at a liquid level 16 and a series of baffles 17 prevents liquid from splashing into the vapour line 13. A booster heater may be used to heat the liquid in the evaporation tank 11.

Preferably, the liquid in the evaporation tank 11 is heated j primarily by the energy transferred from a primary condenser 21 located within the evaporation tank 11.

Tn order to recover heat energy from the condensed fluid exit-,_ the primary condenser 21, the condensed fluid therefrom is passed through a condenser line 22 to a secondary condenser 23 which transfers energy therefrom to the liquid in a feed liquid preheating tank 25. The fluid passing through the condenser line 22 may be liquid, gas, or a combination of liquid and gas.

Liquid in the preheating tank 25 is received from a raw feed line 26 which in turn receives feed liquid from a fresh feed line 27. Liquid exiting from the preheating tank 25 is pumped by a feed pump 28 through the feed line 12.

Condensate from the secondary condenser 23 is passed through a distillate line 31 into a fresh liquid condensing tank 30 from which fresh liquid is passed from the distillation apparatus 10 through a fresh liquid outlet 32.

Waste liquid from the evaporation tank 11 is pumped by a waste liquid pump 39 through a waste liquid line 33 to a waste liquid outlet 34. Heat energy from the waste liquid line 33, the waste liquid pump 39 and the fresh liquid line is transferred to the fresh feed line 27 in a heat exchanger 36.

In use, a distillation apparatus 10 of this invention may be provided for distilling water. Sea, salt or brackish water may fed into the fresh feed line 27 which feeds the 6 heat exchanger 36 where the feed water is preheated by the energy received from the fresh water outlet and waste water outlet. Thus, the energy received by the water distilled in the distillation apparatus is substantially recovered to the extent accounted for by heat loss from the distillation apparatus 10 and the temperature difference between the feed water in, fresh water out and waste water out.

The feed water then passes into a feed water preheating tank 25 wherein the feed water is heated further by a 10 secondary condenser 23 therein and the feed water is then passed through the feed pump 28 into the evaporation tank 11 through the feed line 12.

The evaporation tank 11 is held under vacuum so that the liquid therein may be evaporated at a lower temperature than 15 would be required for distillation at standard pressure.

It is believed that pumping energy received by the vacuum pump 14 is sufficient to cause evaporation of liquid in the evaporation tank 11 by substantially recovering the energy in condensation of the liquid in the primary condenser o 20 21 and the secondary condenser 23.

However, a booster heater 20 may be used to provide extra heat energy into the evaporation tank 11 and may use such energy sources as electrical power, steam or such like, s"i but may also use low grade heat such as heat pump energy, warm water, or cooling water from other processes which has been raised in temperature.

1_ 1~1_1~ 7 Feed water into the evacuated evaporation tank 11 is controlled through an input control valve 40 and a nonreturn valve 41 prevents distillate from being returned into the secondary condenser, primary condenser and vapour line 13. A discharged control valve 42 is used to control the discharge of waste water through the waste liquid line 33.

Preferably, the fluid source 15 for the vacuum pump 14 is taken from the condensing tank 30 such that distillate io recycled through the vacuum pump 14, primary condenser 21, 0 secondary condenser 23 and condensing tank 30, and any heat energy transferred thereto by the pumping of the distillate through the vacuum pump 14 being substantially recovered in the primary condenser 21, the secondary condenser 23 and the heat exchanger 36.

15 It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to .".fall within the broad scope and ambit of the invention as 20 claimed in the following claims.

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Claims (6)

1. Distillation apparatus including:- a liquid feedstock; distillate discharge means; a sealed evaporation vessel; a controlled liquid inlet to said vessel for maintaining a desired liquid level in said vessel from said liquid feedstock; heat exchange means for returning pumping and heat 10 energy from a recompressed fluid to said vessel, and evacuating means for pumping evaporated liquid from said vessel to said distillate discharge means as said recompressed fluid, wherein said evacuation means includes a vacuum pump adapted to generate a high velocity fluid stream from said recompressed fluid.

2. Distillation apparatus as claimed in claim 1, wherein said evacuating means includes an ejector assembly operable Ato create a vacuum on a vacuum port by receiving said high velocity fluid stream.

3. Distillation apparatus as claimed in claim 1 or claim 2, wherein said vessel is provided with liquid extraction means for extracting excess liquid from the vessel. p .1 4 5 9

4. Distillation apparatus as claimed in any one of the preceding claims, wherein said heat exchange means and said evacuating means are formed such that condensation occurs within the evaporation vessel such that both sensible heat of the liquid and evacuating means, and latent heat of the evaporated liquid are partially transferred directly to the liquid within the vessel, and that a substantial portion of the remaining energy is added by secondary heat exchange means to the feedstock.

5. A method of distilling a liquid including the steps of:- feeding a liquid feedstock into a distillation apparatus having distillate discharge means, a sealed evaporation vessel, a controlled liquid inlet to said vessel, evacuating means, and heat exchange means; maintaining a desired liquid level in said vessel from said liquid feedstock; reducing the pressure of said liquid in the distillation apparatus to cause evaporation of at least some of the liquid 'to form a gas; pumping evaporated liquid from said vessel to said distillate discharge means by use of a vacuum pump adapted to generate a high velocity fluid stream; recirculating some of said recompressed fluid to said vacuum pump for generation of said high volocity fluid, and recompressing the gas evaporated from the liquid and r j -L 1-- -TY 1 returning at least some of the pumping and heat energy from said recompressed fluid to the liquid in the distillation apparatus by said heat exchange means, and wherein said recompressed fluid transfers energy to said evaporation vessel by change of phase of fluid from gas to liquid.

6. A method as claimed in claim 5, wherein said change of phase occurs in partially in any combination of a condenser located within said vessel or upstream therefrom towards the evacuation means. 10 10 DATED THIS TWENTY-SIXTH DAY OF MAY 1998 I Is GREGORY JOHN SELLERS BY PIZZEYS PATENT AND TRADE MARK ATTORNEYS U i c- ABSTRACT Distillation apparatus including a liquid feedstock, distillate discharge means, a sealed evaporation vessel, a controlled liquid inlet to the vessel for maintaining a desired liquid level in the vessel from the liquid feedstock, evacuating means for pumping evaporated liquid from the vessel to the distillate discharge means, and heat exchange means for returning fluid and pumping energy to the vessel. The vessel may be provided with liquid extraction means for 10 extracting excess liquid from the vessel. The heat exchange means and evacuating means may be formed such that condensation occurs within the evaporation vessel such that both sensible heat of the liquid and the evacuating means, and latent heat of the evaporated liquid are partially transferred directly to the liquid within the vessel, and that a substantial portion of the remaining energy is added by secondary heat exchange means to the feedstock. I