GB2234448A

GB2234448A - Water purification

Info

Publication number: GB2234448A
Application number: GB8916925A
Authority: GB
Inventors: Peter Stefan Zabell
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-07-25
Filing date: 1989-07-25
Publication date: 1991-02-06
Also published as: GB8916925D0

Abstract

A process for the purification of impure water by evaporating the impure water to provide vapour and condensing the water vapour to give a purified water, in which process evaporation of the water is carried out under reduced pressure in a closed vessel 1. <IMAGE>

Description

WATER PURIFICATION This invention is concerned with improvements in and relating to the purification of impure water and, more particularly, is concerned with the purification of impure water by a distillation process.

There are, of course, a wide variety of processes available for the purification of impure or contaminated water (such as seawater) including, for example, distillation, reverse osmosis and treatment with ion-exchange resins. Distillation is a most effective process for purifying contaminated or impure water but suffers from the disadvantage that it is generally difficult to provide apparatus for use in small-scale installations, in view of the high temperatures and energy requirements of a distillation process.

It is an object of the present invention to provide an improved process for the purification of impure water by a distillation process, which process is particularly adapted for small-scale distillations such as, for example. yachts, fishing boats, life rafts and other small vessels, caravans, etc.

Basically, the present invention provides a process for the purification of impure water by evaporating the impure water to provide water vapour and condensing the water vapour to give a purified water, in which process evaporation of the water is carried out under reduced pressure in a closed vessel. Thus, in the process of the invention, evaporation or ebullition of the water to be purified can be carried out at reduced temperature as compared with a similar process operated under ambient atmospheric pressure. The evaporation is suitably carried out at a pressure of JS to atom, preferably :4: to . 'A atom.

The process of the invention will generally be carried by feeding the water to be purified to a closed vessel, maintained under reduced pressure, allowing the water fed to the vessel to evaporate and recovering water vapour from the vessel and condensing it to produce purified water. The vessel to which the water is supplied is suitably provided with water-level control means, such as a float operated valve or ball-cock so that the water is maintained at a desired level within the closed vessel, e.a. at a level at which the maximum surface area is exposed to facilitate evaporation. The closed vessel may be maintained under reduced pressure by employing a suitable form of vacuum pump which most conveniently, at the same time, serves to withdraw water vapour from the vessel for later condensation.Alternatively, the vessel may be maintained under reduced pressure by conducting vapour from the vessel to a suitable condensing system and removing condensed water from that condensing system whereby to maintain a reduced pressure throughout the distillation vessel and the condensing system and associated pipeworth.

The condenser employed may, for example, take the form of a simple air-cooled condenser e.g. a coil or pipe, but it is generally preferred, if possible, to arrange for recycling of heat energy from the condensation step to assist in the distillation of the water within the distillation vessel, either by heating the water supplied to the vessel or by heating water present in the vessel itself. Thus, the water vapour from the distillation vessel may be condensed in a suitable condenser or heat exchanger system which serves to heat incoming feed water. Alternatively, the vapour from the distillation vessel may be condensed in a suitable condenser system or heat exchange system whereby a heat-exchanger fluid is circulated between the condenser and heating means (e.g. heating coil) immersed in the water in the distillation vessel.Condensation of the vapour in a condenser or heat exchange system from which a part of the heat energy is recycled to the distillation vessel will serve only to partially conserve energy within the system and, of course, energy will have to be supplied to the system as a whole in order for it to operate. This energy may conveniently be supplied by heating the feed water to an appropriate temperature, e.g. a.. . to 7..#.0C. This heating may be effected by conventional heating means operating from an outside source of energy such as oil, gas or electricity, but it is generally preferred, in accordance with the invention, that at least part of the heat energy supplied to the feedwater is waste or other "alternative" energy such as solar energy.Thus, the water may be heated using the waste energy (from the cooling water) of an internal combustion engine or by using energy from a naturally source such as solar energy. The distillation vessel itself may be so constructed as to use solar radiation as available.

As will be appreciated, there will be a build up of impurities within water contained in the distillation vessel during the course of distillation and, accordingly, it is preferred to provide means for periodically removing or flushing at least part of the water from the vessel. This may be achieved, for example, by another vacuum pump to withdraw water, continuously or intermittently, from the vessel or, alternatively, by providing suitable vents whereby the vessel may be periodically drained during inoperative periods (i.e. while it is not under reduced pressure).

In order that the invention may be well understood reference is made to the accompanying drawing which is a schematic section through a simplified embodiment of distillation apparatus for use in accordance with the invention.

Basically, the apparatus shown in the drawing comprises a cylindrical distillation vessel 1 having conduit means 2 for supplying water to the vessel via a float operated valve 3, conduit means 4 for removing vapour from the, vessel via a vacuum pump 5 and thence to appropriate condensing means (not shown), and conduit means 6 for discharge of concentrated impure water from the vessel by means of pump 7.

Claims

CLAIMS:

1. A process for the purification of impure water by vaporating the impure water to provide water vapour and condensing the water vapour to give a purified water, in which process evaporation of the water is carried under reduced pressure in a closed vessel.

2. A process as claimed in claim 1 in which the vessel to which the water is supplied is provided with water-level control means.

3. A process as claimed in claim 1 or claim 2 in which the closed vessel is maintained under reduced pressure by means of a vacuum pump which also serves to withdraw water vapour from the vessel for later condensation.

4. A process as claimed in claim 1 or claim 2 in which the vessel is maintained under reduced pressure by conducting vapour from the vessel to a suitable condensing system and removing condensed water from that condensed system whereby to maintain reduced pressure throughout the distillation vessel and condensing system.

5. A process as claimed in any one of the preceding claims in which water vapour is condensed by means of heat exchange system and heat recovered by the condensation of the water vapour is used to heat feed water to the vessel and/or water within the vessel.

6. A process as claimed in any one of the preceding claims in which feed water is heated by means of "waste" heat from an internal combustion engine or by solar energy.

7. A process as claimed in claim l substantially as hereinbefore described with reference to the accompanying drawing.