FIELD OF INVENTION

[0001] The object of the present invention is a method of mixing a liquid with a gas, in a gas-tight multi-tube reactor, and a device for mixing a liquid with a gas. Disclosed herewith is a multi-tube reactor for mixing liquids, at least one of which is in the form of a gas or it emits gas, especially for introducing process gases into liquids being treated, whether for oxygenating water or wastewater and sewage sludge. Furthermore, the multi-tube reactor may be used in water treatment and wastewater disinfection technologies utilising ozone and/or hydrogen peroxide. The multi-tube reactor may also be used in existing waste water treatment plants, as well as for the oxygenation of water in various bodies of water (e.g. lakes, fish breeding ponds).

[0002] If the process of mixing a liquid with a process gas allows it, an injection of the liquid-gas mixture is introduced into a discharge pipeline (e.g. for drinking water or wastewater) on a bypass line, but then there arises a problem of rapid stratification of the gas from the liquid and an incomplete reaction at the liquid-gas interface. This applies in particular to liquid discharge pipelines and reactors arranged essentially horizontally with diameters being greater than 150 mm. There are two solutions that are known from patent descriptions nos. US7779864 and US9931602, especially for ozonation of water, using venturi tubes to introduce ozone into the liquid in the lateral pipeline and then injecting the liquid-ozone mixture into the transit pipeline through nozzle pairs arranged coaxially. In this type of solutions, the gas quickly separates from the liquid, and the additional mechanical treatments as disclosed in invention description no. US2014083952 are expensive to purchase and operate, and they increase energy inputs. The additional dispersing meshes used, as disclosed in patent description No. US9931602, may not be used in reactors for wastewater aeration. In another tubular reactor solution disclosed in patent description no. US9227852, a tubular reactor solution is provided in which gas (ozone and hydrogen peroxide) is injected into the pipeline at different points in the pipeline and at different locations in its bypass lines and, after each such injection, the mixed liquid and gas are passed through a static mixer. This solution, due to its high complexity and cost, can only have a practical application in the use of ozone and hydrogen peroxide. Due to the use of static mixers, this solution may not be used in sewage treatment plants and in an aerobic treatment of sludge.

[0003] Jet devices are simple and fairly inexpensive to build, but their efficiency in drawing gas into a liquid is low and it decreases fairly rapidly as the back pressure at their outlet increases. Mass transfer in the liquid-gas system depends on the cross-sectional area of the jet propulsion nozzle of the injector and the flow velocity through this nozzle. The smaller the diameter of the propulsion nozzle and the higher the flow velocity through this nozzle are, the better the mass transfer in the liquid-gas system is. However, injector propulsion nozzles with passage diameters of, e.g., 10 mm are not acceptable for use in aerobic reactors in wastewater treatment plants, nor are they suitable for use in sludge stabilisation reactors, as they quickly become blocked by the solid particles of wastewater present in these reactors, and they require fairly high inlet pressures of propulsion fluid. Acceptable passage diameters for injector propulsion nozzles when used in, e.g., biological reactors in sewage treatment plants are ca. 20 mm and more. However, lower oxygen uptake from air (kg 02/kWh) is then achieved in the injector itself. This relationship is related to the fact that the peripheral part of the injector propulsion jet is more involved in gas dispersion in the liquid than its core. As the diameter of the propulsion jet increases, the cross-sectional area of the jet increases with the square of its diameter, and its circumference increases linearly, resulting in a smaller proportion of the kinetic energy of the propulsion jet being used to disperse the gas in the liquid. To cope with this problem, various twisting vanes are used inside the propulsion nozzles to swirl the propulsion jet, such as in the injectors presented in patent description no. US5863128, or the outlets of the propulsion and take-up nozzles are flattened, such as in the solution presented in patent application no. US2017015573. In this type of solution, there is a need to produce fine bubbles at the outlets of the injectors; hence, small nozzle passages are used, which are periodically cleaned in back flow, and if this does not help, they are cleaned manually, which requires emptying the process tank. Due to the decreasing efficiency in sucking air through the injectors with the increasing depth of their immersion, in this type of solution, as well as in the known solution from patent description no. US6719903, the injectors are supplied with blowers or compressors, which improves the efficiency of these devices. The use of the solution disclosed in patent description No. US6719903, in order to make high use of process oxygen, requires the use of high reaction chambers and, furthermore, the use of means for mechanical destruction of the foam and blanket formed in the process of thermophilic oxygen stabilization· This is shown in detail in patent description no. US6168717. [0004] In yet other solutions, as disclosed in patent description no. US4162971, obstructions are inserted behind the propulsion nozzle to disperse the core of the propulsion fluid jet in order to increase the transfer of oxygen to the propulsion jet. The aforementioned solutions are problematic as regards their use in wastewater treatment due to a possibility of the nozzles becoming blocked with solids. These injector devices alone are not sufficient to ensure an adequate gas transfer to the fluid being treated and to wastewater in particular. Injectors inject a liquid/gas mixture into reactors with a suitably selected volume depending on the process to be carried out. A reintroduction of the gas separated from the liquid into the liquid, in order to achieve a higher degree of gas utilisation in the process, requires the use of mechanical devices, as shown in US patent description no. US2014083952, and in a cascade reactor as presented in German patent application no DE2032535. In this reactor, a gas-tight ceiling is used, under which oxygen-rich gas is introduced at one end, and in order to make maximum use of the gas, it is introduced several times from under the ceiling back into the liquid using blowers, which is a costly solution, one that generates additional operating expenses. In addition, the gas introduced at one end can flow quite freely to the other end under the ceiling, where it has its outlet, which somewhat reduces the cascade effect of reintroducing the gas into the liquid for its maximum utilisation. Another solution used to oxygenate wastewater with pure oxygen is the one presented in patent description no. US9181106, which uses an upgraded Speece cone solution. This solution is characterised by a good utilisation of oxygen in the process, yet this requires large reactor volumes, as the process of intensive oxygenation based on the shock wave phenomenon takes place in a fairly small volume in relation to the volume of the reactor, and the whole process requires a fairly complicated process control system, as this process can easily be “extinguished” and re-initiated. In patent application no. DE102007034133, a certain optimisation of the wastewater treatment process in flow reactors is presented that optimises the amount of air supplied to the reactors for nitrification processes, so that an optimal dissolved oxygen concentration of 2 grams per one cubic metre is maintained throughout the reactor volume. The idea is to supply more oxygen to the first reactor chambers than to the last ones, as wastewater supplied at the beginning has a higher oxygen demand than that at the end of the reactor. However, this requires the use of rather complicated monitoring and control equipment. In addition, this solution does not completely solve the problem of high oxygen utilisation, as such reactors are relatively shallow (about 4-5 m high) and, in the process of a single passage of air through this layer of liquid, they sometimes use less than 30% of oxygen from air. [0005] In description of invention no. WO2019243571, a water ozonation installation is disclosed in the form of chambers connected in a cascade manner with fine bubble introduction of ozone. In order to retain the ozone bubbles in the water even longer, despite the cascade connection of the chambers, special transverse obstacles were introduced which make it possible to cause large vortices retaining ozone bubbles in water for a longer period of time, which is also associated with a better gas-liquid mass exchange, similar to that in the device presented in patent description No. JPS523571. In order not to use any additional devices for returning ozone to the lower parts of the successive chambers in the solution as disclosed in WO2019243571, chambers with fairly large height are used, which generates high investment and energy expenses.

[0006] Thus, there is a need to develop a solution of a reactor which is characterized by a simplicity of its execution, an uncomplicated construction, and which could be connected in a series/cascade to maximize the use of the process gas without the use of any additional mechanical devices. It should also, by cascading the individual reaction chambers and their sizes, allow the use of different process gases with various reaction times required, such as air, pure oxygen, or ozone, which reacts about 15 times faster than oxygen and has a half- life of ca. 20 minutes in liquids. In order for the new solution to be universally applicable, it should be resistant to nozzle clogging with solids from mechanically treated wastewater or sewage sludge, and it needs to enable its use at elevated temperatures. The application of the new solution e.g. in aerobic sludge stabilisation chambers should be characterised by resistance to floating particles, without the use of any additional mechanical devices.

DISCLOSURE OF THE INVENTION

[0007] The purpose of the present invention is to solve the above-mentioned inconveniences by appropriately using the phenomenon known as the hydrodynamic paradox, which is described with Bernoulli’s equation, in order to construct an innovative multi reactor.

[0008] This is a method of mixing a liquid with a gas, in a gas-tight multi-tube reactor, wherein the liquid mixed with the gas is fed, in a form of a propulsion jet, to the front part, by or towards the bottom, of the main mixing chamber of the multi-tube reactor, and the gas- saturated liquid, as the main portion of the propulsion jet, is discharged from the rear part of the main mixing chamber of the multi-tube reactor, and it is fed into at least one additional mixing chamber of the multi-tube reactor, wherein the additional mixing chamber or a set of the additional mixing chambers has a cross-sectional area that is at least two times smaller than that of the main mixing chamber of the multi-tube reactor, wherein the mixture of the gas that is not dissolved in the liquid and a portion of the liquid from the main mixing chamber is drawn, due to the kinetic energy of the main portion of the propulsion jet flowing into the additional mixing chamber, by means of a bypass connection, led from the ceiling of the main mixing chamber of the multi-tube reactor and supplied to the additional mixing chamber, according to Bernoulli’s equation, wherein at least one additional mixing chamber has, on its inlet side, an injector nozzle tapering towards the outlet side, and wherein the flow velocity, on its inlet, is at least two times smaller than the flow velocity on the outlet from the injector nozzle.

[0009] Preferably, the velocity of the flow stream at the outlet from the injector nozzle is in the range from 3 m/s to 20m/s, and the velocity of the flow through the additional mixing chamber, before the inlet to the injector nozzle, is in the range from lm/s to 5m/s.

[0010] More preferably, the velocity of the flow stream at the outlet from the injector nozzle is in the range from 6m/s to 12m/s, and the velocity of the flow stream through the additional mixing chamber before the inlet to the injector nozzle is in the range from 1.2m/s to 4m/s.

[0011] In order to induce large reverse vortices in the main mixing chamber, the mixture of the gas undissolved in the liquid and the liquid is drawn from under the ceiling of the front part of the main mixing chamber of the multi-tube reactor, and it is fed to the additional mixing chamber via a bypass connection.

[0012] In the device according to the invention for mixing a liquid with a gas, the multi tube reactor is provided with a main mixing chamber having a front part, a rear part, a bottom and a ceiling, wherein at least one propulsion injector nozzle, located at the bottom of the main mixing chamber, is introduced into the front part of the main mixing chamber, and an additional mixing chamber is led out of the rear part of the main mixing chamber, the additional mixing chamber having at least two times smaller cross-sectional area than the cross-sectional area of the main mixing chamber of the multi-tube reactor. The device according to the invention is characterised in that at the opposite end of the main mixing chamber (i.e. on the side, where the additional mixing chamber is led out), in the additional mixing chamber, a propulsion injector nozzle is installed, directed with its tapering end towards the outlet from the additional mixing chamber, and from the ceiling of the main mixing chamber, at least one bypass connection is provided, which is connected at its other end to the additional mixing chamber.

[0013] Preferably, a suction chamber is attached to the propulsion injector nozzle, with the injector nozzle leading therefrom at the other end, connected to a pump via a supply line, whereby an air hose with a blower or a compressor installed thereon is introduced from the top into the suction chamber (8).

[0014] In another embodiment, a mixing chamber is attached to the propulsion injector nozzle, with a supply line, which is equipped with a pump, introduced thereto at the other end, and an air hose is introduced from the top into the mixing chamber with a blower or a compressor installed thereon, whereas the air hose may also be connected to a gas tank.

[0015] Most preferably, in order to induce large reverse vortices by an asymmetric fluid jet in the main mixing chamber, the bypass connection is led out of the ceiling, at the front part of the main mixing chamber, and the flow rate through the bypass connection is controlled by a control diaphragm valve.

[0016] In one embodiment, the bypass connection, in a vertical plane, has corrugations to intensify mixing of the liquid and the gas and a gate valve mounted thereon. Preferably, the cascaded multi-tube reactors are connected to the discharge pipeline by means of a bypass line.

[0017] Equally preferably, the cascaded multi-tube reactors are connected to the process reactor by means of bypass lines, whereas the outlet end of the bypass line is provided with a nozzle assembly.

[0018] Very preferably, process lines of the cascaded multi-tube reactors are connected by means of a bypass line with a recirculation pump installed thereon and connected at the inlet to feeding manifolds and gas manifolds and, at the outlet, to receiving manifolds.

[0019] The main advantage of the method according to the invention is that by using Bernoulli’s equation, in combination with numerous reaction chambers mixing the liquid with the gas, it was possible to master such a liquid-gas mixing process, which does not require any complicated mechanical devices, and which requires practically one propulsion source, namely the liquid jet. Furthermore, this method is very versatile and it can be used both for fast reacting gases like ozone and extremely slow reacting gases like air. In applications for gases such as ozone, the method according to the invention may demonstrate a fast reaction time and a high degree of their utilisation. There are practically no limitations here except for energy.

[0020] The device according to the invention is characterised by a high modularity of its construction and scalability in design processes. In thermophilic treatment processes of sewage sludge, it demonstrates a high resistance to failures and it excellently copes with the problem of spontaneous destruction of the foam and the blanket. It may also have applications in wastewater treatment, industrial wastewater treatment in particular, due to its ability to utilise pure oxygen to a high extent.

BRIEF DESCRIPTION OF FIGURES

[0021] The object of the invention is shown in greater detail in the examples of its implementation in the drawing, where Fig.l diagrammatically presents a multi-tube reactor in its longitudinal section in a cascade arrangement in the first example of implementation; Fig. 2 diagrammatically presents the multi-tube reactor in its longitudinal section in the second example of implementation connected to another reactor, and Fig. 3 diagrammatically presents a multi-tube reactor in its longitudinal section in a cascade arrangement in the second example connected via a bypass to a discharge pipeline, Fig. 4 diagrammatically presents a multi-tube reactor in longitudinal section in a cascade arrangement from the first example connected via a bypass to another process tank, while Fig. 5 diagrammatically presents the multi-tube reactor in its longitudinal section in a cascade arrangement in various implementations; Fig. 6 presents, in a perspective view, three process lines of the multi-tube reactor in a cascade arrangement for three process lines in various designs; Fig. 7 diagrammatically presents the multi-tube reactor in its longitudinal section in a cascade arrangement as in the first example of implementation but using the construction as in Fig. 2 in a cascade arrangement as shown in Fig. 6. Fig. 8 shows detail “A” of the multi-tube reactor magnified from Fig. 7, and Fig. 9 shows detail “B” of the multi tube reactor magnified from Fig. 7, while Fig. 10 diagrammatically presents the multi-tube reactor in a cascade arrangement from the first example of implementation connected via a bypass to the nitrification chamber in a sewage treatment plant.

EXAMPFES OF THE IMPFEMENT ATION OF THE INVENTION

[0022] The multi reactor according to the invention is diagrammatically presented in the drawings. Fig. 1 shows the multi-tube reactor 1 in the first example of implementation, in a cascade connection, having the main mixing chamber 2 in the form of a horizontally positioned cylindrical tank. The main mixing chamber 2 has its front part 2.1, its rear part 2.2, a bottom 2.3 and a ceiling 2.4. Into the front part 2.1, at the bottom 2.3, a propulsion injector nozzle 3 is introduced, and from the rear part 2.2 of the main mixing chamber 2, the injector nozzle 4 is led out, whose inlet is positioned on the side of the main mixing chamber 2, while on the outlet side thereof the additional mixing chamber 5 is connected.

[0023] From the additional mixing chamber 5, the bypass connection 6 is led out, which is hydraulically connected to the ceiling 2.4 of the main mixing chamber 2, close to its front part 2.1. A control diaphragm valve 7 may be mounted on the bypass connection 6. To the propulsion injector nozzle 3, which is located in the suction chamber 8, being a gas-liquid mixing chamber, at the inlet of the first multi-tube reactor 1, a liquid jet is supplied via a supply line 9 by means of a pump 10, whereby a gas jet is also supplied to the suction chamber 8 by an air hose 11 fed by a blower 12.

[0024] The operation of the multi-tube reactor 1 in the first example of implementation in the cascade arrangement as in Fig. 1 differs from the multi-tube reactor 1 from the second example of implementation as in Fig. 2 in that it possesses injector nozzles 4 to assist in sucking the gas into the additional mixing chamber 5 and into the suction chamber 8. In the multi-tube reactor 1 of the second example of implementation as in Fig. 2, there is a mixing chamber 13 in place of the suction chamber 8. Furthermore, in this particular example as in Fig. 2, the multi-tube reactor 1 is not connected to the same type of reactor, but to another process reactor 14. The operation of the multi-tube reactor 1 as in Fig. 1 consists in the fact that the liquid, due to the pressure generated by the pump 10, enters the suction chamber 8 through the injector nozzle 4. Due to the high kinetic energy of the liquid stream flowing out through the injector nozzle 4, the gas is sucked into the suction chamber 8 through the air hose 11 which, in this case, is additionally fed by the blower 12, in order to improve the efficiency of gas suction through the jet system. Then, the liquid stream mixed with the gas stream enters the injector nozzle 4 placed at the beginning of the additional mixing chamber 5, where again the propulsion jet 15 with high kinetic energy is generated which, owing to the asymmetric introduction of the propulsion jet 15 into the main mixing chamber 2, generates, apart from strong turbulences, large reverse vortices 16. To further intensify these large reverse vortices 16, in the main mixing chamber 2, the ceiling 2.4 of the main mixing chamber 2, close to its front part 2. 1, is connected with the additional mixing chamber 5 by means of the bypass connection 6. This is because according to the Bernoulli’s equation and the so-called hydrodynamic paradox, this causes the gas and part of the liquid to be sucked from under the ceiling 2. 4 of the main mixing chamber 2 to the front part of the additional mixing chamber 5, through the bypass connection 6, which causes definitely stronger large reverse vortices 16, due to the asymmetric fluid stream 17 with respect to the propulsion jet 15. In the system of successive cascade connections of the multi-tube reactors 1, these phenomena of the formation of intense large reverse vortices 16 are repeated. Returning of the liquid and the gas results in fairly strong shear forces forming at the gas-liquid interface in these vortices, which causes rapid diffusion and reaction of the liquid with the gas. Also in the bypass connection 6 itself, there occur intensive liquid-gas mass exchange phenomena. Due to these phenomena, propulsion injector nozzles 3 as well as injector nozzles 4 with larger passage cross-sections can be used, since the intensive gas-liquid diffusion takes place simultaneously in large reverse vortices 16, in the additional mixing chamber 5, as well as in the bypass connection 6, i.e. in the area of strong turbulences, which makes this technology versatile and easy to control. The intensity in the induction of large reverse vortices 16 can be controlled, for example, by means of control diaphragm valves 7 by throttling the flow through the bypass connection 6. The induction of additional large reverse vortices 16 causes a slower release of the gas, which has not reacted with the liquid, while this is done by means of only one liquid propulsion jet 15, at the beginning of the cascade system of multi-tube reactors 1. Furthermore, the additional flow of the liquid and the gas through the bypass connection 6 means that the flow through the main mixing chamber 2 can be increased and, at the same time, the gas that is not dissolved in the liquid can be reintroduced into the multi-tube reactor system 1, without the use of any additional mechanical devices.

[0025] Fig. 2 presents a single multi-tube reactor 1 in the second example of implementation where, at the inlet, instead of the suction chamber 8, the mixing chamber 13 is installed, and at the outlet from the main mixing chamber 2 to the additional mixing chamber 5, there is no injector nozzle 4 from Fig. 1. In order to introduce strong flow turbulence in the bypass connection 6, this connection is corrugated in the vertical plane of the multi-tube reactor 1. In contrast to the implementation as shown in Fig. 1, the multi-tube reactor 1 in the second example of implementation has the mixing chamber 13 with no gas suction function. The outlet of the injector nozzle 3 from the additional mixing chamber 5 is connected to the process reactor 14.

[0026] The operation of the multi-tube reactor 1 from the second example of implementation differs in that it does not have a jet system at the inlet, since the suction chamber 8 is replaced by the mixing chamber 13, while the injector nozzle 4 is absent at the point of the introduction of the bypass connection 6 at the inlet to the additional mixing chamber 5. In this case, it is also possible to obtain a pressure difference capable of returning the gas and the liquid from under the ceiling 2.4 of the main mixing chamber 2 of the multi tube reactor 1 according to the Bernoulli’s equation, since the cross-sectional area of the cylindrical tank 19 is significantly larger than the cross-sectional area of the additional mixing chamber 5. Intensive mixing of the liquid with the gas in the additional mixing chamber 5 is achieved owing to the shock wave effect caused by an abrupt narrowing of the cross-section of the additional mixing chamber 5 by the injector nozzle 3. In order to further intensify the mixing of the liquid with the gas in the bypass connection 6, this connection is corrugated in the vertical plane where local mini-reactors are formed when the liquid and the gas flow through it, creating conditions for good mixing of the liquid with the gas. In order to regulate the flow or to shut it off, the gate valve 18 is provided at the bypass connection 6. The gas supply to the multi-tube reactor 1 may be carried out by means of the air hose 11 with the blower 12 or the compressor installed thereon, or it may be carried out using a gas liquefied in the tank 19, for example oxygen.

[0027] In the second example of implementation, as illustrated in Fig. 2, the multi-tube reactor 1 does not need to be cascaded with another multi-tube reactor 1 of the same type but with another process reactor 14. In the application of this multi-tube reactor 1, in the aerobic stabilization processes of sludge, it is not necessary to use any additional equipment to destroy the foam and the blanket, as the blanket and the foam are easily destroyed in the additional mixing chamber 5.

[0028] Fig. 3 presents the multi- tube reactor 1 in a cascade arrangement, as in the first example of implementation in Fig. 1, with the only difference that at the inlet it possesses the mixing chamber 13 instead of the suction chamber 8 and it does not have any injector nozzles 4. Its operation is similar, but more advantageous in terms of energy, although this is at the expense of a lower mixing intensity in the additional mixing chamber 5 and in the bypass connection 6. The multi-tube reactor 1, e.g. in a cascade arrangement, can be connected as a bypass by means of the bypass line 20 with the discharge pipeline 21 of water or wastewater, as shown in Fig. 3, in order to treat the flowing liquid by introducing air, pure oxygen, ozone or hydrogen peroxide into it.

[0029] Fig. 4 presents the multi- tube reactor 1 in a cascade arrangement, as in the first example of implementation. This cascade reactor assembly may operate, for example, at elevated pressure, so as to supersaturate the liquid with the gas and to introduce this mixture of the gas dissolved in the liquid via the bypass line 20 and the nozzle assembly 22 into the process reactor 14.

[0030] Fig. 5 illustrates the multi-tube reactor 1 in longitudinal section in the various implementations as described previously, in a cascade arrangement. This type of reactor is particularly suitable for being mounted vertically in a container. Gas from a gas source may be fed not only at the inlet of the cascade arrangement of the multi-tube reactors 1 but also to other locations. Also, the bypass connections 6 may fulfil specific process purposes and they may be introduced to different locations. Their operation is similar to that of the previously presented solutions, except that they are presented in a multivariant manner.

[0031] Fig. 6 shows in a perspective view three process lines of the multi-tube reactor 1 as in Fig. 2 in different variations. The three process lines of the multi-tube reactor 1 are supplied with incoming wastewater or water from one feed manifold 23 and one gas manifold 24, the mixture of which is partially returned through the receiving manifold 25 by means of the recirculation pump 26. Each multi-tube reactor 1 has three sets of additional mixing chambers 5 and the same number of bypass connections 6 associated with them, as illustrated in Fig. 7, whereby in different implementations, the bypass connections 6 may be joined to form common suction manifolds 27. Thus, it is possible to connect the multi-tube reactors 1 in series in a cascade and in parallel into independent process lines, with only one propulsion source, which facilitates the operation of the entire plant. This facilitates the scalability of a given project to adapt it to the quantitative needs and the qualitative tasks required considering the modularity of the construction and the repeatability of the structural elements. Those cascade connections possess another advantage, in the case of water ozonisation, for example, as the rapid transfer of unreacted gas to the subsequent reactors reduces the formation of bromates, whose presence in drinking water is undesirable.

[0032] Fig. 7 presents the multi-tube reactor 1 as in the first example of implementation, but using the structure illustrated in Fig. 2, in a cascade arrangement as illustrated in a perspective view in Fig. 6. The operation of this multi-tube reactor 1 is similar, but instead of being connected at the outlet to the process reactor 14, it is connected to another multi tube reactor 1 as, for example, illustrated in Fig. 6. No inspection holes or manholes are shown. [0033] Fig. 8 presents detail "A" of the multi-tube reactor 1 in magnification from Fig. 7, especially the assembly of the additional mixing chamber 5, showing details of the nozzles, especially the bypass nozzle 28, that intensifies turbulence at the liquid-gas interface, and the gate valve 18 that allows the flow between the multi-tube reactors to be shut off.

[0034] Fig. 9 presents detail “B” of the multi-tube reactor 1 in magnification from Fig. 7 including details of the propulsion injector nozzle 3 and the injector nozzle 4, and the gate valve 18, that allow the flow to be shut off between the multi-tube reactor 1 and the feed manifold 23 and the gas manifold 24.

[0035] Fig. 10 presents the multi-tube reactor 1 in a cascade arrangement from the first example of implementation connected via the bypass line to the process reactor 14 of the wastewater treatment plant, where KD denotes the dephosphatation chamber, KDN denotes the denitrification chamber, KN denotes the nitrification chamber and OS denotes the secondary settling tank. The process reactor 14 has an external recirculation driven by the recirculation pump 26, which returns the sludge from the secondary settling tank OS to the wastewater inflow stream and, with this, it flows through the dephosphatation chamber KD, the denitrification chamber KDN, the nitrification chamber KN, and then it flows to the secondary settling tank OS, from where sludge is recirculated again. In the denitrification chamber KDN, the pump 10 is installed, which pumps wastewater from this chamber to the multi-tube reactor 1 in a cascade arrangement, connected to the pump 10 with the bypass line 20, whereby the bypass line 20 at the outlet from the multi-tube reactor 1 ends with the nozzle assemblies 22. Such operation was described for the solution in Fig. 4, where the internal recirculation was achieved by rising wastewater level in the nitrification chamber KN, while wastewater was being pumped by the pump 10 from the denitrification chamber KDN.

[0036] The inner diameters Dn of the propulsion injector nozzles 3 and the inner diameters Ds of the injector nozzles 4 are in the range from 20 mm to 60 mm and, preferably, from 25 mm to 50 mm. The inner diameters Dr of the main mixing chambers 2 range from 150 mm to 3000 mm, and their lengths L range from 1000 mm to 6000 mm, while the inner diameters Dm of the additional mixing chambers 5 range from 50 mm to 150 mm, and their lengths L range from 100 mm to 2000 mm and, more preferably, from 200 mm to 1000 mm. The inner diameters Db of the bypass connections 6 range from 25 mm to 100 mm, whereby the bypass nozzles 28 are mounted for these larger diameters of the bypass connection 6 (over 50 mm), and their inner diameters Dbn are not less than 25 mm. [0037] The flow velocity, at the inlet of the injector nozzle, is at least three times lower than the velocity at the outlet of the injector nozzle 4.

[0038] The flow velocity at the outlet of the injector nozzle 4 is in the range from 3m/s to 20m/s and, more preferably, from 6m/s to 12m/s. The flow velocity through the additional mixing chamber 5, before the inlet to the injector nozzle 4 is in the range of lm/s to 5m/s and, more preferably, from 1.2m/s to 4m/s.

LIST OF DENOTATIONS

1. multi-tube reactor

2. main mixing chamber

2.1. front part

2.2. rear part

2.3. bottom

2.4. ceiling

3. propulsion injector nozzle

4. injector nozzle

5. additional mixing chamber

6. bypass connection

7. control diaphragm valve

8. suction chamber

9. supply line

10. pump

11. air hose

12. blower

13. mixing chamber

14. process reactor

15. propulsion jet

16. reverse vortices

17. asymmetric fluid jet

18. gate valve

19. tank

20. bypass line

21. discharge pipeline

22. nozzle assembly 23. feed manifold

24. gas collector

25. receiving manifold 26 recirculation pump 27. suction manifold

28. bypass nozzle KD - dephosphatation chamber KDN - denitrification chamber KN - nitrification chamber OS - secondary settling tank

Dn - diameter; propulsion injector nozzle 3 Ds. - diameter; injector nozzle 4 Dm - diameter; additional mixing chamber 5 Dr - diameter; main mixing chamber 2 Dbn - diameter; bypass nozzle 28

L - length of main mixing chamber 2 1 - length of additional mixing chamber 5