APPARATUS FOR PRODUCING AIR SATURATED WATER

Abstract: The invention refers to an apparatus for producing water saturated with air under high pressure and preferably intended for dispersion in flotation plants, which apparatus comprises a preferably standing cylindrical pressure vessel (21) which during operation to a controlled level is partly filled with pressurized water flowing through said vessel and out through an outlet in the lower part of the vessel and partly with continuously added compressed air, whereby during the passage of the water through the vessel (21) air is dissolved in the water. The supply of pressurized water to the apparatus is arranged at the upper part of the pressure vessel (21) by means of a spray-nozzle (24) or similar arrangement which splits the water flow. The spray-nozzle is so designed that at least part of the water flow sprays and essentially covers the inner walls, of the upper, during operation air filled portion, of the vessel (21) by means of a water curtain which portion is supplied with compressed air through a conduit (27) arranged in the wall of the vessel in this portion.

Description: APPARATUS FOR PRODUCING AIR SATURATED WATER TECHNICAL FIELD The present invention refers to an apparatus for producing water saturated with air under high pressure and preferably intended for dispersion in flotation plants, which appara¬ tus comprises a preferably standing cylindrical pressure vessel which during operation to a controlled level is partly filled with pressurized water flowing through said vessel and out through a bottom outlet and partly with con¬ tinuously added compressed air, whereby during the passage of the water through the vessel air is dissolved in the wa- ter. PRIOR ART When treating water, drinking water as well as sewage wa- ter, flotation plants are used to an increasing extent in order to increase the rate of flow of the water through the treatment plants and as a consequence of this also making it possible to decrease the size of the necessary basins and thereby the size of the complete treatment plants. When it comes to drinking water the requirements on the finished product are mainly uniform and the design of a treatment plant is mainly decided by the character of the source of water supply. If the source is a lake or a water course usually separation of larger particles is taking place in a filter chamber whereafter the water is subjected to a chemical and biological treatment carried out by means of the addition of precipitation- and flocculation- agents in a flocculation chamber. The particles which are precipi¬ tated are then to be separated from the water which can be done by means of sedimentation which means that the parti¬ cles through the influence from gravity sink to the bottom in a sedimentation basin. Different types of particles have different density and therefore different sinking velocity. In order to make it possible for particles having low den¬ sity, "light particles", to sediment while the water passes a sedimentation basin a long time is required which means that the surface of the sedimentation basin must be large. The time for the particle separation could be considerably reduced by means of flotation which means that microscopic air bubbles are added to the water which adhere to parti¬ cles or particle flocculations in the water and also con¬ tribute in the process of creating particle flocculations and keeping them together. Air bubbles raise fast towards the water surface bringing adhered particles and particle flocculations to the water surface where they create a sta¬ ble sludge cover which can be removed by means of scrapers or by intermittently raising the water level in the flota¬ tion basin so that the sludge cover transfers to a sludge channel arranged at one of the edges of the basin. The microscopic air bubbles which are used in the flotation procedure have a diameter of 30-80 micrometer and can not be generated for instance by means of the injection of air directly in the water. Microscopic air bubbles for flota- tion of drinking water are usually generated by means of dissolving air in clean water in a pressured vessel under overpressure whereby the biggest possible saturation level is aimed at. This water which usually is called dispersion water is fed with maintained high pressure to the inlet for the flocculated water in the flotation basin positioned at its bottom where it is added to said water via special noz¬ zles or sprayers which are designed to give an instantane¬ ous decrease in the pressure at which the air dissolved in the water is released in the form of microscopic bubbles creating a dispersion of air in the water. The pressure vessels which are used for the generation of high pressure dispersion water, saturated with air to the greatest possible extent, are usually kept half filled with water by means of a control unit including sensors and the in- and outlets for the water are positioned below the wa¬ ter surface in the pressured vessel. The addition of com¬ pressed air takes place in the space filled with air above the water surface and the vessel is rather big in order to make the contact surface between air and water large. In another known embodiment the pressure vessel which often is as tall as a man has a reduced diameter and the conse¬ quently reduced contact surface between the water and air has been compensated by the feeding of the water through a nozzle arranged in the side wall of the vessel in the air filled space through which nozzle the water is spraying against the opposite wall of the vessel where the water jet to some extent is splitted up. The flotation method has considerably decreased the time for water treatment and the decreased time of flow means that water treatment plants could be made smaller keeping the same capacity. When the space requirement of the treat¬ ment plants decreases new application fields are opened. Such a development requires that all the devices are made smaller and if possible are given improved characteristics. This also goes for the apparatus for producing dispersion water in which already treated, recirculated, water is used. An increase of the saturation level in the dispersion water decreases the need of recirculated water whereby the efficiency of the whole treatment plant is improved. DESCRIPTION OF THE INVENTION One object of the present invention is to propose an appa- ratus for producing dispersion water having a high degree of air saturation. Another object is to propose an appara- tus which combines high capacity with small dimensions. This is attained by means of an apparatus having the char¬ acteristics according to the appended claims. DESCRIPTION OF THE DRAWINGS One embodiment of the invention will be described more in detail with reference to the enclosed drawing on which fig¬ ure 1 in a side view and schematically shows a convention- ally equipped flotation basin in section and figure 2 shows partly in section an apparatus according to the invention for producing dispersion water. In figure 1 which schematically and in a side view shows a conventionally equipped flotation basin in section the ba¬ sin is generally designated 1. The basin has an inlet 2 to which water is fed from a flocculation chamber, not shown. By means of an inclined barrier 3 arranged in front of the inlet 2 in the basin 1 the water is caused to flow upwards in the basin 1. At the bottom of the pocket which is cre¬ ated between the wall 4 of the basin and the barrier 3 a set of tubes provided with nozzles or sprayers debouch, one tube 6 of which is shown in the figure. The tubes 6 feed air saturated water, dispersion water, to the flocculated water fed to the basin through the inlet 2 which water is given an increased movement by the dispersion water in¬ jected under pressure. The nozzles or sprayers 5 are so de¬ signed that the dispersion water is subjected to an instan¬ taneous pressure decrease which releases the air in that water in the form of microscopic bubbles which in their movement towards the water surface adhere particles and particle flocculations and relatively fast carry most of these particles to the water surface where a sludge cover is created which by means of some kind of sludge scraper 7 or in another way is transferred to the sludge channel 8 at the wall 9 of the basin. Heavy particles which the Micro bubbles are not able to lift are collected by the filter 10 which is arranged between the back side of the barrier 3 and the wall 9 of the basin and through which filter the treated water passes on its way via the outlet 11 to a clear water basin, not shown. From this basin part of the treated water is pumped, under high pressure, to the water inlet 13 of the pressure vessel 12. The vessel 12 in which the dispersion water is produced is provided with com¬ pressed air via the air inlet 14 from a compressor, not shown, and the air saturated water is fed back via the out¬ let 15 and its branchings 6 to the nozzles 5 arranged in the flotation basin 1. In figure 2 an apparatus according to the invention is shown, schematically and partly in section, for producing dispersion water. The apparatus comprises a vertical pres¬ sure vessel 21 which is implemented by means of commer¬ cially available tube parts and has the form of an enlarge¬ ment on a conduit 22, 23. The inlet tube 22 debouch into a spray-nozzle 24 which has the form of a prolongation of the inlet tube 22, closed at its free end. The envelope surface of the prolongation tube 24 is completely perforated by means of small spray holes 25 only a smaller number of which are shown in figure 2. During operation the pressure vessel 21 is halfway filled with water and two detectors arranged in the wall of the vessel deliver signals to a control unit, not shown, which if necessary decreases or increases the water flow into the vessel alternatively ad¬ justs the air pressure in the pressured vessel 21. The feeding of compressed air is carried out via the conduit 27 and is controlled by means of a magnet valve 28 arranged on said conduit. During operation water is spraying, as indi¬ cated in figure 2 with a couple of dashed arrows, from the spray-nozzle 24 against the inner wall of the pressured vessel which will be covered by a curtain of water which continuously is provided with new water whereby the air ab- sorbing ability of the curtain all the time is kept at the maximum level. Due to the considerable improvement in the air absorbing ability of the apparatus according to the invention com¬ pared to known apparatuses it has been possible to reduce its dimensions to a great extent. Thus, a conventional ap¬ paratus having a height of close to 2 meters and a diameter of 35 cm has been possible to replace with an apparatus having a height of approximately 1 meter and a diameter of 10 cm. Due to this reduction of the dimensions conventional, spe¬ cially made pressure vessels have for certain purposes been possible to replace with a 4" tube having reduction cou¬ plings as end portions and e.g. an inlet conduit of 1" and an outlet conduit of 2".

Claims: CLAIMS 1. Apparatus for producing water saturated with air under high pressure and preferably intended for dispersion in flotation plants, which apparatus comprises a preferably standing cylindrical pressure vessel (21) which during op¬ eration to a controlled level is partly filled with pres¬ surized water flowing through said vessel and out through an outlet in the lower part of the vessel and partly with continuously added compressed air, whereby during the pas¬ sage of the water through the vessel (21) air is dissolved in the water, characterised in that the supply of pressur¬ ized water is arranged at the upper part of the pressure vessel (21) by means of a spray-nozzle (24) or similar ar¬ rangement which splits the water flow and is so designed that at least part of the water flow sprays and essentially covers the inner walls, of the upper, during operation air filled portion, of the vessel (21) by means of a water cur- tain which portion is supplied with compressed air through a conduit (27) arranged in the wall of the vessel in this portion.

Inventors: ERIKSSON HANS, ISAKSSON KENT, ERIKSSON, HANS, ISAKSSON, KENT
Applicants: ERIKSSON HANS, ISAKSSON KENT, ERIKSSON, HANS, ISAKSSON, KENT
Application year: 1996
Main classification: C02F1
IPC codes: B01F3, B03D1, C02F3