WO2020115675A1

WO2020115675A1 - Contact and degassing tank for equipment for ozonation treatment

Info

Publication number: WO2020115675A1
Application number: PCT/IB2019/060433
Authority: WO
Inventors: Salvatore Teti; Marco Nava
Original assignee: Biomarine Srl
Priority date: 2018-12-04
Filing date: 2019-12-04
Publication date: 2020-06-11
Also published as: IT201800010775A1

Abstract

Device (100) for the treatment and temporary storage of liquids, the device (100) comprising a tank (10), working under pressure, adapted to contain and treat fluid for the purification of ship ballast water; an inlet aperture (20) for supply of ozone, hydrogen peroxide and treatment water within the tank (10); a take-out aperture (30) for taking the fluid for purification of ballast water out from the tank (10); a tubular element (40), placed inside the tank (10) and set in fluid communication with the inlet aperture (20), the tubular element (40) being adapted to release the fluid for purification of ballast water near the bottom (101) of the tank (10). The device is characterised in that it includes at least one helical element (50, 50', 50") coaxial with the tubular element (40), the at least one helical element (50, 50', 50") being able to force the flow of fluid coming out of the tubular element (40) to rise towards the top (102) of the tank (10) following a predetermined path.

Description

DESCRIPTION OF THE INVENTION

TITLE

CONTACT AND DEGASSING TANK FOR EQUIPMENT FOR OZONATION

TREATMENT TECHNICAL FIELD

The present invention relates to a contact and degassing tank for the separation of undissolved ozone in excess from water in equipment for treating water by ozonation.

In particular, the invention refers to a contact and degassing tank suitable in particular for use in a ship ballast water treatment plant by ozonation.

STATE OF THE ART

As it is known, water purification can take place through the use of mixing plants consisting of portions of piping including differently shake elements in which the liquid to be purified and the treatment fluid are made run.

GB 2316014 A describes an oxygenator for separation of polluting substances from water including a tubular body inside which a pair of helical elements are arranged. The water is introduced from below and rises up the tubular element and is oxygenated by air bubbles introduced by a plurality of nozzles arranged at the bottom of the tubular element. The water to be treated and the air bubbles flow in the same upward direction.

WO2010/107077 A1 describes another oxygenator, or micro-bubble generator, designed to purify water from pollutants and microorganisms the construction and operation concept of which is similar to the previous one: a cylindrical body inside which the water to be treated flows upwards from the bottom and a bubble generation system in which nozzles are arranged in the lower part of the cylindrical body. The cylindrical body has an internal shape designed to optimize water treatment efficiency.

WO2017/200336 A1 describes a water purifier designed to eliminate microorganisms from water, comprising a tubular body in which water is introduced from below and follows a helical upward path while it is treated to be purified from microorganisms.

In the above mentioned devices the treatment fluid is a gas, usually air or ozone. In other cases the treatment fluid is ozone enriched water, in which ozone, thanks to its oxidizing power, is able to inactivate unwanted microorganisms, such as bacteria, viruses, fungi, and transform many non-biodegradable substances into biodegradable forms. Another example of a mixing plant is given by static mixers, in which treatment water with addition of ozone is provided. Inside the mixers, the treatment water and the liquid to be purified encounter resistance to motion caused by the shape of the ducts. These imposed resistances, in terms of variation of speed and direction of motion, improve the mixing of the fluids.

However, the treatment water that arrives at the mixing plant is usually a previously ozonated water in which ozone is either not well dissolved in it, or it is dissolved but according to an excessive stoichiometric ratio with respect to its solubility in water, so that undissolved air and ozone bubbles remain in the treatment water.

In fact, it may happen that the amount of ozone not dissolved in water goes ahead to the subsequent purification chambers which, being open air, do not prevent ozone from being released into the air, leading to ozone pollution problems and health risks for the operators who have to work in such environments.

Moreover, the low gas/liquid solubility causes very often a non-optimal treatment of the liquid to be purified, as it can occur that water and ozone do not undergo an optimal mixing process, remaining in two separate phases.

Therefore, there is a need to improve both the dissolution of ozone with treatment water, and consequently to provide the mixing plant with better treatment water, and, above all, to prevent the gaseous ozone exceeding in the treatment water from going ahead through the plant.

Contact and degassing devices are known in the form of tanks or pipes, in which the treatment water containing ozone in excess flows from top downwards and the gaseous bubbles of ozone separate from the liquid phase by going up towards a degassing valve, that conveys them towards an ozone destructor. Some types of such devices are internally shaped in a way that facilitates the separation of the gaseous phase from the liquid phase.

However, such known devices do not prove to be efficient.

In the shipbuilding sector, ballast water, which is necessary to provide stability to vessels, is generally taken in an area close to the coast and, once the vessel reaches its destination, is discharged in the port. This water, being rich in micro-organisms, needs to be purified before being discharged. Therefore, it is essential also in the shipbuilding sector that the water be purified in an optimal manner, and anyway, the use of contact and degassing devices and ozone destructors is essential to avoid the risk of dispersing gaseous ozone into the environment where the purification plant is installed, with a high risk for the personnel working in such environments.

SUMMARY OF THE INVENTION

It is therefore the object of the present invention to provide a contact and degassing tank for ozone purification plants, that allows better ozone dissolution in the treatment water and at the same time effectively eliminates undissolved ozone from the treatment water.

It is another object of the present invention to provide a contact and degassing tank for ozone treatment plants that is both reliable and simple to implement. It is a further object of the present invention to provide a contact and degassing tank for ozone purification plants that maximizes the contact surface area of the fluids contained therein.

It is a yet further object of the present invention to provide a contact and degassing tank for ozone purification plants that can be used especially in plants for purification of ship ballast water by ozonation treatment.

These and other objects are achieved by a contact and degassing tank for ozone purification plants, the device comprising:

- a tank, working under pressure, adapted to receive treatment water intended for the purification by ozonation of water, in particular ship ballast water;

- an inlet aperture aimed at conveying said treatment water containing undissolved ozone and ozonated water into said tank;

- a take-out aperture aimed at taking said treatment water out from the tank, said take-out aperture being located near the bottom of said tank; - a vent valve situated at the top of said tank and adapted at allowing gaseous ozone to leave said tank towards an ozone destructor;

- a tubular element, placed inside the tank and set in fluid communication with the inlet aperture, the tubular element being adapted to release the fluid for purification of ballast water near the bottom of the tank;

The contact and degassing tank is characterised in that it includes, thereinside, at least one helical coaxial element set outside the tubular element, extended vertically from the bottom of the container to the proximity of its top, the at least one helical element being able to force the flow of fluid coming out of the tubular element to rise towards the top of the tank following a predetermined path before falling back downwards in the direction of said take-out aperture. In this way, by means of the present invention, the treatment water, for example water coming from the ship utilities or from the engine room, after having been enriched with ozone and possibly with oxygen, by means of a venturi injector, is introduced into the tank through the inlet aperture. This liquid continues its flow along the tubular element to the bottom wall of the tank. The helical element forces the treatment water to follow a rising path along which, thanks to the contact with the walls of the helical element, the bubbles of undissolved ozone and oxygen present in the treatment water are released from the liquid and directed towards the top of the tank to be released by the vent valve. The special helical shape increases the path covered by the gas and consequently the liquid/gas contact surface. Therefore, this particular geometry makes it possible to maximize the contact surface between the fluids inside the tank, thus facilitating dissolution of gaseous ozone in the treatment water and allowing at the same time the fraction of undissolved gas to separate from the liquid phase.

In fact, the tank is provided with water rich in ozone, but for pure economical reasons, the exact amount of ozone to be blown is not determined, so that the ozone is blown in considerable excess with respect to its solubility in water. The ozone that is undissolved in water, due to its larger quantity with respect to the solubility limit, tends to return to the gaseous state, and the presence of the vent valve allows the ozone in excess to be released towards an ozone destructor. The contact and degassing tank of the present invention is therefore a particularly efficient trap for the undissolved gaseous ozone which, going upwards, is conveyed towards the vent valve.

In particular, the inlet aperture is positioned near the top of the tank, so that falling by gravity of the liquid before it meets the bottom surface of the tank improves mixing inside the tank.

Advantageously, the tank has two additional concentric helical elements. This solution maximizes the fluid/gas contact surface area by maximizing the effects of the helical element.

In particular, the helical elements include internally hollow cylinders, on the outer surface of which a plurality of blades extend along the longitudinal axis of the cylinders according to a helical shape.

This solution has the advantage of forcing the upflowing fluid rising from the tubular element to follow a predetermined path, increasing the gas liquid exchange surface. Moreover, by varying the diameter of the cylinders on which the blades are placed and their number, it is possible to vary the mixing level of the fluid.

Advantageously, the tank includes a discharge aperture, near the bottom wall, for the discharge of the fluid contained therein.

This solution has the advantage of emptying the tank if maintenance operations are required.

According to an embodiment of the invention, the tank is made of metallic material.

Advantageously, the tank includes feet stabilising it to the ground.

Advantageously, the helical elements include channels aimed at evacuating the fluid from the tubular element.

This allows the fluid, once it gets out of the tubular element positioned concentric and internal with respect to the circular elements, to run over the blades associated with each helical element and thus facilitate fluid mixing.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and/or advantages of the present invention will become more evident with the following description of one embodiment of the present invention, given by way of example and not limiting, with reference to the enclosed drawings, in which: - figure 1 shows a side view of a contact and degassing tank;

- figure 2 shows a section view of a contact and degassing tank according to the present invention;

- figure 3 shows a schematic lateral view of an helical element;

- figure 4 shows a schematic section view of the helical element of figure 3;

- figure 5 shows a plan view of an example of three concentric helical elements; DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to figures 1 and 2, an example contact and degassing tank 100 for ozonation plants is shown. The contact and degassing tank 100 is designed in particular to be applied in plants for ozonation of ship ballast water.

The contact and degassing tank 100 includes a tank 10, working under pressure, configured to contain treatment water for the purification of ship ballast water. Once filtered, the treatment water from the ship utilities is ozonated and pushed through the tank 10 by a booster pump 20' (not shown in the figure) through an inlet aperture 20'. In the section between the booster pump and the tank 10, an ozone injector and oxygen injection means (not shown in the figure) inject ozone and hydrogen peroxide 20' into the flow of the treatment water upstream of the inlet aperture 20 so that the ozonated treatment water, which typically contains undissolved ozone and oxygen in excess, enters the tank 10 from the inlet aperture 20.

A take-out aperture 30, situated near the bottom of the tank 10, allows the treatment water to exit and to be subsequently introduced 30' for example into a static mixer (not shown in the figure) where the ballast water to be treated flows.

A tubular element 40, inside the tank 10, is in fluid communication with the inlet aperture 20 and is configured to release the treatment water incoming from the inlet aperture 20 into the tank near the bottom wall 101. The fluid exiting the tubular element 40 rises upwards and meets three helical elements 50, 50', 50", arranged coaxial and external to the tubular element 40 to extend vertically from the bottom of the container to near the top of the container so that the treatment water rises to the top 102 of the tank 10 following a path forced by the shape of the helical blades 55, before it falls back downwards in the direction of the take-out aperture 30, thus increasing the duration of the stay of the treatment water in the tank and the contact surface and thus the liquid/gas exchange.

In particular, the outermost helical element 50" is placed on the bottom 101 of the tank, so as to close it, while the innermost helical elements 50, 50' are spaced from the bottom 101 , so as to allow the flow of the treatment water towards the annular compartments where the helical blades 55 are placed. On the upper side, all the helical elements 50, 50', 50" terminate at a distance from the top 102 of the tank so as to allow the treatment water, once the rise along the paths defined by the helical elements is completed, to go again downwards along the compartment between the outermost helical element 50" and the side wall of the tank 10 up to the take-out aperture 30.

The tank is also provided with a vent valve 70, positioned at the top of the tank and having the opening adjusted according to the amount of undissolved ozone to be intercepted and sent to the ozone destructor.

A safety cap 75 can be associated with the vent valve 70.

Stabilising feet 80 are necessary to fasten the tank 10 to the floor, in an upright position.

Once the treatment water contained inside the tank 10 has left the tubular element 40, it can rise again running over the blades 55 associated with the helical elements 50, 50', 50", due to evacuation channels 56 provided along the lower base of the helical elements 50, 50', 50" arranged to facilitate the flow of the treatment water towards the paths defined by the helical elements 50, 50', 50".

With reference to the figures 3-5, an example of dimensioning of helical elements 50, 50', 50" is shown. In particular, three concentric hollow cylinders are shown, on the external surface of which helical blades 55 extend, so as to define helical paths that facilitate the fluid/gas mixing and the separation of the undissolved gaseous phase in excess from the liquid phase, with formation of bubbles that rise and are captured at the top 102 by the vent valve 70.

For example, in the case of cylinders with internal diameters of 88.9 mm, 273.10 mm and 508 mm respectively, helical blades can be obtained with 16 turns and pitch of 150 mm.

The above description of some specific embodiments shows the invention from the conceptual point of view so that others, using the prior art, will be able to modify and/or adapt this specific embodiment in various applications without further research and without departing from the inventive concept, and, therefore, it is intended that such adaptations and modifications will be considered as equivalent to the specific embodiment. The means and materials to realize the various described functions may be of various kinds without leaving the scope of the invention. It is understood that the used expressions or terminology are purely descriptive and therefore not restrictive.

Claims

1. Contact and degassing tank (100) for plants for ozone purification plants, said contact and degassing tank (100) comprising:

- a tank (10), working under pressure, adapted to receive treatment water intended for the purification by ozonation of water, in particular ship ballast water;

- an inlet aperture (20) aimed at conveying said treatment water containing undissolved ozone and ozonated water into said tank (10);

- a take-out aperture (30) aimed at taking said treatment water out from the tank (10), said take-out aperture (30) being situated near the bottom (101) of said tank (10);

- a vent valve (70) situated at the top (102) of said tank (10) and aimed at allowing the gaseous ozone to leave said tank (10) toward an ozone destructor;

- a tubular element (40), placed inside said tank (10) and set in fluid communication with said inlet aperture (20), said tubular element (40) being configured to release said treatment water near the bottom wall (101) of said tank (10);

said tank (10) being characterised in that it includes at least one helical element (50, 50', 50") set externally coaxial with said tubular element (40) and extended vertically from bottom (101) of the container (10) to the proximity of its top (102), said at least one helical element (50, 50', 50") being aimed at forcing the flow of treatment water coming out of said tubular element (40) to go up towards the top (102) of said tank (10) following a predetermined path before going down towards said take-out aperture (30).

2. Contact and degassing tank (100) according to claim 1 , wherein said inlet aperture

(20) is situated near the top of said tank (10).

3. Contact and degassing tank (100) according to claim 1 , wherein said tank (10) comprises a second and a third helical element (50', 50"), said helical elements (50, 50', 50") being concentric with one another.

4. Contact and degassing tank (100) according to claim 3, wherein said at least one helical element (50, 50', 50") includes an internally hollow cylinder, on the external surface of which there are fastened a plurality of blades (55), said plurality of blades (55) extending along the longitudinal axis (51) of said at least one cylinder (50, 50', 50") according to said helical shape.

5. Contact and degassing tank (100) according to the previous claim, characterised in that the outermost helical element (50") rests on the bottom (101) of the tank (10) so as to close it, while the innermost helical elements (50, 50') are spaced from the bottom (101), so as to allow a flow of treatment water towards the annular compartments in which the helical blades (55) are placed.

6. Contact and degassing tank (100) according to claim 1 , wherein said tank (10) includes a discharge aperture (60), near said bottom wall (101), for the discharge of said treatment water.

7. Contact and degassing tank (100) according to claim 1 , wherein said tank (10) is made of metallic material.

8. Contact and degassing tank (100) according to claim 2, wherein said vent valve is associated to a safety cap (75).

9. Contact and degassing tank (100) according to claim 1 , wherein said tank (10) comprises feet (80) for stabilising it onto the ground.

10. Contact and degassing tank (100) according to claim 1 , wherein said helical elements (50, 50', 50") include evacuation channels (56) for evacuation of said treatment water from said tubular element (40).