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Title:
A SYSTEM FOR SATURATING LIQUIDS WITH GAS AND A METHOD FOR SATURATING LIQUIDS WITH GAS USING THIS SYSTEM
Document Type and Number:
WIPO Patent Application WO/2021/015633
Kind Code:
A1
Abstract:
The subject of the invention is a liquid with gas saturation system comprising of a liquid source (3), a gas source (5), a gas dissolution chamber (1) and a liquid receiving tank (4), where the liquid source (3) is connected by means of a pipeline (11) equipped in the pump (8) with the cavitation system (14) which is connected via a pipeline (16) to the gas dissolution chamber (1), where the end of the pipeline (16) is a set of atomizing nozzles (7) located in the gas dissolution chamber (1) to which a gas source (5) is connected via a gas pipeline (10) with a nozzle (6); and the gas dissolution chamber (1) by means of a pipeline (12) with a control valve (9) is connected to a retention chamber (2) with alternately arranged, partly open partitions (17), which via a pipeline (13) with a valve (15) is connected to the saturated liquid receiving tank (4). The method of saturating the liquid with gas using the above system, where the liquid from the liquid source (3) is pumped by means of a pump (8), raising the liquid pressure to at least 4 bar, through the pipeline (11), to the cavitation system (14) where liquid is saturated with the gas in the form of micro-nano bubbles and then through a pipeline (10) it is pumped into a set of atomizing nozzles (7) with the help of which the liquid is sprayed in the gas dissolution chamber (1), where the liquid is additionally saturated with gas coming from a gas source (5 ) fed via the gas pipeline (10) and nozzle (6), where the gas is supplied with a pressure equal to the liquid pressure, then via the pipeline (12) the liquid is pumped into the retention chamber (2) through which it flows in not less than 13 minutes and the line speed not exceeding 0.5 m/s necessary to dissolve the gas is then pumped through the pipeline (13) to the liquid receiving tank (4).

Inventors:
WIDUCH ALEKSANDER (PL)
HERMAN FILIP MARIUSZ (PL)
Application Number:
PCT/PL2020/000063
Publication Date:
January 28, 2021
Filing Date:
July 17, 2020
Export Citation:
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Assignee:
NET SPOLKA Z OGRANICZONA ODPOWIEDZIALNOSCIA WATER TECH SPOLKA KOMANDYTOWA (PL)
International Classes:
C02F1/72; B01F3/04; B01F5/02
Foreign References:
US20060027100A12006-02-09
JP2018094533A2018-06-21
DE102009032567A12011-01-13
Attorney, Agent or Firm:
PARCZEWSKI, RafaƂ (PL)
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Claims:
Claims

1. A system for saturating liquids with gas, comprising of a liquid source (3) , a gas source (5) , a gas dissolution chamber (1) and a liquid (4) receiving tank, characterized in that the liquid source (3) is connected by a pipeline (11) equipped with a pump (8) with a cavitation system (14) which is connected via a pipeline (16) with the gas dissolution chamber (1), where the end of the pipeline (16) is a set of atomizing nozzles (7) located in the gas dissolution chamber (1) to which a gas source (5) is connected via a gas pipeline (10) with a nozzle (6) ; and the gas dissolution chamber (1) by means of a pipeline (12) with a control valve (9) is connected to a retention chamber (2) with alternately arranged, partly open partitions (17) , which via a pipeline (13) with a valve (15) is connected to the saturated liquid receiving tank (4) .

2. A gas saturation system according to claim 1 characterized in that the atomizing nozzle assembly (7) is equipped with static inserts (7b) , which are preferably made of stainless material, the edges of which are bent in the inner direction at an angle of 20 to 40 degrees with respect to the plane of the insert.

3. A method of saturating liquids with gas using the system according to claim 1, characterized in that the liquid from the liquid source (3) is pumped by means of a pump (8) , raising the liquid pressure to at least 4 bar, through the pipeline (11) , to the cavitation system (14) where the liquid is saturated with gas in the form of micro-nano bubbles and then through a pipeline (10) it is pumped to a set of atomizing nozzles (7) by means of which the liquid is sprayed in the gas dissolution chamber (1) , where the liquid is additionally saturated with gas coining from a gas source (5) fed through gas pipeline (10) and nozzle (6) , where the supplied gas has a pressure equal to the liquid pressure, then through the pipeline (12) the liquid is pumped into the retention chamber (2) through which it flows not less than 13 minutes and at a linear speed not exceeding 0.5 m/s necessary to dissolve the gas, then through the pipeline (13) the liquid is pumped into the liquid receiving tank (4) .

Description:
A system for saturating liquids with gas and a method for saturating liquids with gas using this system

The subject of the invention is a system for saturating liquids with gas and a method for saturating liquids with gas.

The invention belongs to the field of the water treatment and wastewater treatment technique.

In the state of art there are known devices and methods for saturating liquids with gas . Etchepare R., Oliveira H., Nicknig M., Azevedo A., Rubio J. (2017) . Nanobubbles: Generation -using a multiphase pump, properties and features in flotation. Minerals Engineering, 2017 (Volume 112), pp. 19-26. The authors in their solution used a saturating pump to produce a compressed water-air mixture, then it was expanded to obtain nano air bubbles. This solution is based on the suction of air under atmospheric pressure and mixing it with water in liquid form. The solution according to the invention ensures the introduction of gas at an absolute pressure of 4 bar and atomization of the saturated liquid, which allows the creation of a significant phase contact surface, which transfers into high process efficiency.

B. J. Vinci, B. J. Watten, M. B. Timmons, (1995) . Modeling gas transfer in a spray tower oxygen absorber. Aquacultural Engineering, Volume 16, Issues 1-2,1997. In their work they use spray nozzles to spray water in the column to which oxygen is supplied. The issue of clogging of the spraying nozzle with solid particles was not solved by the authors. In the case of using uncleaned liquid, the atomizer nozzle will easily become clogged, which will increase the device's failure rate. In the solution according to the invention the nozzles are equipped with static grinding inserts which significantly reduce the risk of clogging of the nozzles. Also, the use of an atomizer will ensure the greatest possible atomization of the supplied water.

S. Nazari, S.Z. Shafaei, B. Shahbazi, S. Chehreh Chelgani, (2018) . Study relationships between flotation variables and recovery of coarse particles in the absence and presence of nanobubble. Colloids and Surfaces A: Physicochemical and Engineering Aspects. Volume 559, 2018, pp. 284-288. In the presented solution, the authors introduce compressed air into the water, mixing takes place in the two static mixers, then the water-air mixture is directed to the venturi vent, where as a result of hydrodynamic cavitation nano-bubbles a e to be formed. The authors did not propose more effective phase mixing than static mixers, which significantly reduces the solubility of air in water, which transfers directly into the amount of air bubbles generated.

R. Etchepare, H. Oliveira, M. Nicking et al. In the publication entitled "Nanobubbles: Generation using a multiphase pump, properties and features in flotation" describe the system for generating micro- nano bubbles later used in the flotation process, to improve the efficiency of sludge separation in the flotation chamber from sewage to remove suspended matter. A system equipped with a multi-phase pump is used for this. The proposed solution differs from the solution presented in the publication in that it is used to dissolve gas in a liquid, thus it aims to completely dissolve the gas without creating bubbles, which indicate insoluble gas, while the method of the publication assumes the production of fine gas bubbles, which role is to lift solid particles up to the level of the waste water mirror so that it can be further mechanically removed.

Kim Yu Beom in application No. KR101771124 OXYGEN DISSOLUTION APPARATUS AND FARM WITH THE SAME describes a water aeration system using spray nozzles that reduce the size of liquid droplets passing through the gas atmosphere. The solution according to the invention carries out the process under high pressure and maintains the condensed water mixed with the gas molecules in an overpressure until the gas is completely dissolved in the liquid.

Agranonik R. J. and Pisklov G. A. in the application RU 94030202 METHOD FOR SATURATION LIQUID WITH GAS describe the method of saturation of liquid intended for the flotation process with gas. In their solution, they use a thermo-compressor to reduce energy consumption. In the invention according to application a conventional pump is used and the increase in dissolved oxygen is based on extended retention period.

Wiidley P.S. in the application WO2013017935 DEVICE AND METHOD FOR SATURATING LIQUID WITH GAS describes a method of aerating liquids using a device that crosses accelerated liquid streams in a gas atmosphere. The solution according to the invention uses the free fall of liquid particles at significant overpressure and extended retention time at a given flow rate.

Sulej anov B.A.O in the application EA030820 METHOD FOR PRODUCTION OF NANO-FLUID WITH GAS NONO-BUBBLES describes a method of producing of a gas saturated liquid by conducting a pressurized process. In the solution according to the invention, the liquid is saturated with micro-nano bubbles to increase its contact surface with oxygen and then retained in the flow reservoir so that the oxygen is completely dissolved before the liquid expanses.

Lugovkin A. N . and Kuznetsov A. D . in the application RU2236898 DEVICE FOR SATURATION OF LIQUID WITH GAS describe a device for improving the efficiency of liquid saturation with gas based on an increase in the efficiency of the process of liquid spraying in the chamber. In the solution according to the invention, the increase in efficiency is based on a combination of saturation with micro-nano bubbles and an extension of hypertensive retention time while maintaining an appropriate flow rate.

Ignatkin V.I. in the application RU2230700 METHOD OF AND DEVICE FOR SATURATION OF LIQUID WITH GAS AND DISPENSING OF LIQUID present a method to improve the efficiency of gas dissolution in a liquid using a device that uses a heat exchanger to improve solubility. In the solution according to the invention all processes take place at a constant temperature.

Agranonik R.V. and Piskolev G. A. in application EP0700873 (Al) WASTE WATER TREATMENT METHOD, SUSPENSED MATTER SEPARATION METHOD, AND METHOD FOR SATURATING A LIQUID WITH A GAS describe the method of wastewater treatment based on saturation of wastewater with gas under pressure and then, before dissolving gas in liquid, expanding it to create air bubbles that float contaminants. In the solution according to the invention, the aim is to fully and completely dissolve the gas in the liquid, which will guarantee the absence of gas bubbles after the liquid is expanded to atmospheric pressure.

In the state of the art, activated sludge chambers are aerated by means of membrane disk or tube diffusers, and by means of surface aerators. Aeration by means of diffusers arranged on the bottom of the chamber consists of injecting atmospheric air into them by means of blowers. In this process, l-2mm diameter air bubbles are formed on the surface of the membrane, which rise towards the wastewater mirror. The aeration method using surface aerators is based on the movement of the aerator blades, which suck the sewage from the bottom of the tank towards the aerator in the body of which the sewage is ejected when the direction of the sewage suddenly changes from axial to radial. During this process, the wastewater intensively mixes using atmospheric air for aeration. The oxygen transfer coefficient for membrane diffusers oscillates at level of 8% per meter of depth of the sludge chamber and depending on the manufacturer, its total value exceeding about 70% for the whole chamber cannot be obtained. This transfers into standard aeration efficiency in the range of 3-8 kgCh/kWh. For surface aerators, the standard aeration efficiency does not exceed 3 kgC kWh. The aeration methods presented here, due to their low energy efficiency, contribute to generate about 60% of the operating costs of the entire treatment plant.

In contrast to the known state of the art, in the solution according to the invention, due to the introduction of compressed oxygen into the gas dissolution chamber, where pressurized water mist is previously saturated with micro-nano bubbles, which thanks to the atomizers used has a developed surface area, it is possible to achieve a high concentration of oxygen >30 g/m 3 in aerated water. This will transfer into the possibility of obtaining an oxygen transfer coefficient > 99%, which in consequence will allow achieving standard aeration efficiency of 10-12 kgCk/kWh. Compared to high-performance air diffusers, this will lead to an average 15-fold reduction in the volume of fluid injected into the activated sludge chambers by significantly increasing the oxygen transfer coefficient depending on the exchange surface, pressure and temperature while maintaining the same oxygen concentration in the chamber, which will directly affect the applicability of much smaller blowers. The production of nanobubbles is also of a key importance when conducting flotation, where any reduction in the size of the flotation particles transfers into an increase in process efficiency, and thus a reduction in the volume of flotation devices. The purpose of the invention is to obtain in an energy e fficient manner water with a high (> 30 g/m 3 ) oxygen concentration for the purposes of the purification process.

The essence of the invention is a liquid with gas saturation system comprising a liquid source, gas source, gas dissolution chamber and liquid collection tank, where the liquid source is connected by means of a pipeline equipped with a pump with a cavitation system, which is connected via a pipeline with a gas dissolution chamber, where the end of the pipeline is a set of atomizing nozzles located in the gas dissolution chamber to which a gas source is connected via a gas pipeline with a nozzle. The gas dissolution chamber by means of a pipeline with a control valve is connected to a retention chamber with alternately arranged, partly open partitions, which, by means of a pipeline with a valve, is connected to a saturated liquid collection tank .

Preferably, the atomizing nozzle assembly is equipped with static inserts, which are preferably made of stainless material, the edges of which are bent inwardly at an angle of 20 to 40 degrees from the plane of the insert.

The essence of the invention is the method of saturating liquids with gas using the system described above, where the liquid from the source of liquid is pumped by means of a pump, raising the liquid pressure to at least 4 bar absolute pressure, through a pipeline, to the cavitation system, where the liquid is saturated with gas in the form of micro-nano bubbles, subsequently through a pipeline it is pumped to a set of atomizing nozzles by means of which the liquid is sprayed in a gas dissolution chamber, where the liquid is additionally saturated with gas coming from a gas source fed through the gas pipeline and nozzle, where the supplied gas has a pressure equal to the pressure of the liquid, then through the pipeline the liquid is pumped into the retention chamber through which it flows in a time not shorter than 13 minutes and with a linear speed not exceeding 0.5 m/s necessary to dissolve the gas, then via the pipeline the liquid is pumped into the liquid collection tank.

According to Henry's law, the number of moles of a given gas that can be dissolved in a given liquid depends on the pressure and the constant characterizing the given gas and liquid, that depends on the temperature at which the liquid is saturated. Therefore, it is unequivocally clear that any increase in pressure of the liquid saturation process will lead to an increase in gas solubility. The saturation process was decided to be carried out at a pressure of 4 bar (a) , because it is economically justified - it is a compromise between energy expenditure and obtained concentrations of dissolved gases. The application of the highest atomization level of the liquid is beneficial due to the increase in the contact surface of the gas and liquid phases, which results in an increase in process efficiency.

The application of the retention chamber in the presented solution with a retention time of not less than 10 minutes and obtaining a developed contact surface of the gas and liquid phase ensures adequate mixing and access of oxygen to the entire volume of the aerated liquid. For a mixture pressure of 4 bar absolute pressure and a flow velocity in the range of 0.4 - 0.6 m/s required, minimum retention time is 10 minutes - so the design of the retention chamber should assume a volume sufficient to store the mixture, in the same amount which flows for 600 seconds through the system. Absolute pressure 4bar is the minimum value, however it is possible to carry out the oxygenation process at a higher pressure and for each bar of increase in absolute pressure, the required retention time decreases by 15%, nevertheless the process pressure should not exceed 6 bar absolute pressure due to limitations associated with the devices for separating oxygen from air which maximum pressure after separation is 6 bar absolute pressure.

The invention is illustrated in the drawings, in which Fig. 1 presents a preferred embodiment of liquid with gas saturation system and Fig. 2 presents a preferred embodiment of the nozzle assembly.

Example of Implementation 1

The system consists of a Gas Dissolution Chamber (1) made of 316L stainless steel, with external diameter of 500mm, height 2000mm and wall thickness 3mm, sewage accumulation tank (3) , centrifugal pump (8) adapted for pumping liquids with a maximum diameter of solid particles of 1mm and liquid pumping pressure up to 4 bar (a) , pipeline ( 11) made of Polyethylene, atomizing nozzle set (7) with diameter of droplets of atomized liquid not exceeding 5 microns, made of PVDF plastic and equipped with 1mm thick static inserts made of stainless steel 316L. The nozzles (7) are connected by means of a pipeline (16) made of Polyethylene with a cavitation system (14) which is an injector made of 316L stainless steel, which draws in atmospheric air in the amount of 3 Nm 3 /h, forming air bubbles with a diameter of 100 nano -meters. The gas dissolution chamber (1) is connected to the gas source (5) in the form of an oxygen cylinder with a purity above 95%, via a gas pipeline (10) made of 316L stainless steel and a nozzle (6) made of 316L stainless steel. The gas dissolution chamber (1) through a pipeline (12) made of 316L stainless steel with a diameter of 80mm and a control knife valve (9) made of 316L stainless steel, is connected to a retention chamber (2) made of 316L steel, 2200mm in diameter, 1200mm of height and a wall thickness of 3mm, in which the semi circular (17) partitions have been placed; which is connected to the oxygen-saturated waste water collection point (4) via a pipeline (13) made of 316L stainless steel with a diameter of 80mm.

Example of Implementation 2

The method of saturating liquids with gas, whereby liquid from a liquid source (3) which is a buffer tank for municipal wastewater with a suspension content of 240mg/l and BZT5 at a level of 250mg/l in the amount of 20m 3 /h at a temperature of about 25 degrees Celsius, is pumped using centrifugal circulation pump, adapted for pumping liquids classified as municipal sewage (8) , raising the liquid pressure to at least 4 bar (a) , through a pipeline (11) made of polyethylene, to the cavitation system (14) where liquid is saturated with gas (atmospheric air) with a diameter of bubbles between 50 and 100 microns, and then through a pipeline (16) made of polyethylene, it is pumped to a set of atomizing nozzles (7) to a diameter of droplets not exceeding 5 microns, made of PVDF plastic, equipped with static inserts made of lmm thick 316L stainless steel, which task is to break aggregated suspended solid particles into smaller fractions, for the protection of the nozzles from clogging. This is accomplished thanks to the use of turbulent flow and the accompanying forces by which the liquid is sprayed in a gas dissolution chamber (1) made of 316L stainless steel 3mm thick, 2200mm diameter and 2000mm high, where the liquid is additionally saturated with gas (oxygen with concentration of 95%) originating from a gas source (5) in the form of an oxygen generator (PSA - Pressure Swing Adsorption Type) fed through a gas pipeline (10) made of 316L stainless steel and nozzle (6) , where the supplied gas has a pressure equal to the pressure of the liquid.

As a result of atomization of liquid into 5 micron diameter droplets and their injection into a volume of gas under pressure in the gas dissolution chamber (1), the liquid-gas exchange surface is developed to a value of 1200 m2, thus 1000% more than in a conventional solution, while maintained pressure of 4 bar (a) increases the gas dissolution coefficient in the liquid, being 5 times the coefficient observed in the case of surface aeration, which allows for a very dynamic and effective gas saturation process. Then, via a pipeline (12) made of 316L stainless steel, the liquid is pumped into the retention chamber (2) made of 316L steel, with diameter 2200mm, height 1200mm and wall thickness 3mm, in which semi-circular partitions (17) are placed, welded alternately to force the designed retention time in the chamber and counteract irregular residence time, which would occur if the retention chamber would be through (without partitions) . The partitions (17) are made of 316L stainless steel, 5mm thick, forcing retention time in the retention chamber (2) not shorter than 13 minutes and a linear speed not exceeding 0.5 m/s necessary to dissolve the gas. Then, through a pipeline (13) made of 316L stainless steel, the liquid is pumped into the liquid receiving tank (4), which is the next stage of the biological wastewater treatment system, i.e. flotation. By carrying out the embodiment of the present invention, its purpose has been achieved. After applying the method described above, a liquid having a very high oxygen concentration exceeding 30 g/m 3 was obtained.