sewage treatment system

Abstract

A sewage treatment device (1) comprising: a sealed container (2) in which a liquid to be treated is boiled inside; a vacuum generating device (3) configured to maintain the interior of the sealed container (2) at a given pressure having a value lower than the environmental / external pressure; and a heat pump assembly (5) connected to the sealed container (2) to transfer heat to a liquid present at the bottom of the sealed container (2) to boil the liquid, and simultaneously remove heat from steam reaching the top of the sealed container (2) to condense the steam and obtain a distillate, and containing a refrigerant fluid comprising one or more gases of the hydrofluoroolefin series in a percentage greater than 3%.

Description

Technology Field

[0001] Cross-reference of related applications

[0002] This patent application claims priority from Italian patent application No. 102019000022839 filed on December 3, 2019, the disclosures of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a sewage treatment device. More specifically, the present invention relates to a vacuum evaporator for the treatment of aqueous-based liquids. In the following description, express references will be used without loss of generality. Background Technology

[0005] As is known, vacuum evaporators are machines capable of concentrating contaminants present in sewage received at an inlet through evaporation at a pressure lower than atmospheric pressure, and providing two distinct liquid flows at an outlet, one containing high-concentration contaminants and the other containing low-concentration contaminants.

[0006] A flow of liquid containing low concentrations of pollutants is substantially pollutant-free and can be reused in the production process or freely discharged into the environment.

[0007] Next, liquids containing high concentrations of pollutants are generally collected and treated at specific treatment plants.

[0008] The most widely distributed vacuum evaporators on the market are provided with a large sealed container maintained at a pressure of less than 0.9 bar, and to concentrate contaminants in the liquid fraction remaining at the bottom of the container, a heat pump circuit is used to boil the liquid present inside the container at a low temperature and condense the generated vapor. CN109701291 A, JPH0852461 A and US2012 / 055777 A1 disclose this type of vacuum evaporator.

[0009] Unfortunately, current heat pump circuits of vacuum evaporators use hydrofluorocarbons (e.g., R-134a gas) as refrigerant gases, which are non-toxic and do not contribute to the ozone hole, but nevertheless have a very high GWP (Global Warming Potential) and consequently entail environmental problems.

[0010] The object of the present invention is to provide a vacuum evaporator for treating aqueous liquids that has greater efficiency while having less environmental impact than currently known vacuum evaporators.

[0011] For this purpose, according to the present invention, a sewage treatment device as defined in claim 1 and, preferably but not necessarily, any one of its dependent claims is provided. Brief explanation of the drawing

[0012] The present invention will now be described with reference to the accompanying drawings illustrating non-limiting exemplary embodiments. ― FIG. 1 is a perspective view of a sewage treatment device implemented according to the teachings of the present invention, with parts removed for clarity. ― FIG. 2 is a schematic diagram of the sewage treatment system exemplified in FIG. 1, with parts removed for clarity. In contrast, - Fig. 3 is a schematic diagram of a modified embodiment of a sewage treatment device shown in the previous drawings. Specific details for implementing the invention

[0013] Referring to FIGS. 1 and FIGS. 2, reference number 1 generally shows a sewage treatment device that can be advantageously used for the treatment of aqueous liquids.

[0014] More specifically, the sewage treatment device (1) is configured to receive a flow (f1) of sewage to be treated at an inlet, and is particularly structured to concentrate contaminants present in the sewage at the inlet by evaporation at a pressure lower than atmospheric pressure, while simultaneously providing a flow (f2) of distillate and a flow (f3) of wastewater at an outlet.

[0015] Distillates contain virtually no or low concentrations of contaminants and can be reused in production processes or freely discharged into the environment. On the other hand, waste liquids contain high concentrations of contaminants and are suitable for collection for subsequent treatment at known types of treatment facilities.

[0016] Referring to FIGS. 1 and 2, the sewage treatment device (1) first comprises: a sealed reactor or container (2) preferably having a capacity in the range of 100 to 7000 liters—the sealed reactor or container (2) is traditionally referred to as an evaporation chamber, in which the liquid to be treated, i.e., sewage, is boiled—; and a vacuum generating device (3), preferably electrically operated, configured to maintain the internal volume of the reactor / container (2) at a given pressure having a value lower than the environmental / external pressure.

[0017] More specifically, the container (2) is preferably rectangular in shape, preferably arranged in a substantially vertical position, and preferably configured so that the liquid to be processed is only partially filled, so that the liquid to be processed accumulates only in the bottom part of the container (2) / occupies only the bottom part.

[0018] In the illustrated example, the container (2) is preferably made of a large, watertight sealing container preferably made of a metal material and preferably having a substantially cylindrical shape.

[0019] Preferably, the bottom end of the container (2), or rather the bottom end of the watertight-sealed container, is also approximately frustoconical in shape.

[0020] Meanwhile, the vacuum generating device (3) is preferably structured to continuously maintain the pressure inside the container / reactor (2) at a value of less than 0.8 bar, and optionally less than 0.6 bar.

[0021] More specifically, in the illustrated example, the pressure inside the container / reactor (2) is preferably maintained at a value in the range of 3 to 8 kPA (kilopascals).

[0022] Referring to FIGS. 1 and 2, the sewage treatment unit (1) also includes a supply line (4) for the liquid to be treated, configured to channel the liquid to be treated, i.e., sewage, into a reactor / container (2).

[0023] In other words, the supply line (4) is configured to deliver sewage flow (f1) from the inlet of the container (2).

[0024] Preferably, the supply line (4) is also structured to control / varie the flow rate of the liquid directed toward the container (2). More specifically, the supply line (4) is preferably configured to control / varie the flow rate of the liquid to be processed flowing into the container (2) so as to continuously maintain the liquid level inside the container (2) near a given value.

[0025] Referring to FIGS. 1 and 2, the sewage treatment unit (1) also includes a heat pump evaporator / condenser assembly (5) connected to / linked to a container / reactor (2) to transfer heat to a liquid present at the bottom of the container (2) so that the liquid can boil, and at the same time remove heat from the steam reaching the top of the container (2) so that the steam can be rapidly condensed and a distillate can be obtained.

[0026] Additionally, the sewage treatment unit (1) is also provided with a first drain line (6) — the first drain line (6) branches off from the bottom portion of the container (2) and is configured to transfer / transfer liquid accumulated / stagnated in the bottom portion of the container (2) to the outside of the container / reactor (2); and a second drain line (7) — the second drain line (7) branches off from the top portion of the container (2) and is configured to transfer / transfer steam formed inside the container (2) and / or distillate resulting from the condensation of said steam and / or distillate accumulated at the top of the container (2) to the outside of the container / reactor (2).

[0027] More specifically, the drainage line (6) preferably branches off / starts from the bottom of the container (2), while the drainage line (7) preferably branches off / starts from the top of the container (2).

[0028] Clearly, the liquid flowing along the drain line (6) has a high concentration of contaminants, while the condensed steam or liquid flowing along the drain line (7) has a low concentration of contaminants.

[0029] Accordingly, the flow of waste liquid (f3) is transferred / carried outside the machine (1) by the drain line (6), while the flow of distillate (f2) is transferred / carried outside the machine (1) by the drain line (7).

[0030] Referring to FIG. 1, preferably, the sewage treatment device (1) is further provided with a rigid support framework (8) preferably made of a metal material and configured to be stably placed on the ground and optionally anchored to the ground. The container (2), vacuum generator (3), supply line (4), heat pump evaporator / condenser assembly (5), and two drainage lines (6, 7) are preferably stably fixed / placed on the rigid support framework (8) to form a single block that can be easily transported.

[0031] In the illustrated example, in particular, the rigid support framework (8) preferably has a cage-like structure and / or has a shape substantially parallelepiped, and is preferably formed by metal rod butts fixed to each other.

[0032] Referring to FIG. 1, preferably the sewage treatment unit (1) finally includes an electronic control device (9) that controls various components of the container (2), and / or vacuum generating unit (3), supply line (4), and / or heat pump evaporator / condenser assembly (5), and / or two drainage lines (6, 7), and preferably is stably fixed / placed on a rigid support framework (8).

[0033] Referring to FIG. 2, in the illustrated example, the supply line (4) preferably comprises: a pipe (10) connecting the inlet mouth of the machine (1) to the container (2) to deliver the liquid to be processed at the inlet of the container (2), i.e., sewage; a control valve (11) having a controllable opening and closing positioned along the pipe (10) and configured to control the flow of the liquid directed toward the container (2); and also preferably, a filter (12) positioned along the pipe (10), preferably upstream of the control valve (11), and configured to block solid particles exceeding a given size.

[0034] More specifically, the filter (12) is preferably structured to hold solid particles having a particle size greater than 800 to 1000 μm (micrometers) or even greater than 500 μm (micrometers).

[0035] Therefore, the liquid to be processed is drawn into the container (2) by negative pressure without the use of a supply pump.

[0036] Optionally, the supply line (4) further includes a manually operated shut-off valve (13) positioned upstream of the control valve (11) and / or filter (12) along the pipe (10).

[0037] Preferably, the supply line (4) additionally includes a water level sensor or switch (14), which is preferably located inside the container (2) and is configured to detect or switch when the water level of the liquid inside the container (2) reaches or exceeds a maximum given value.

[0038] Next, the control valve (11) is preferably configured to open and close based on a signal received from a water level sensor or switch (14).

[0039] More specifically, the control valve (11) is preferably controlled by an electronic control device (9) based on a signal received from a water level sensor or switch (14) and other operating parameters of the machine (1).

[0040] Instead, the drain line (6) preferably comprises: a main pipe (15) branching out / starting from the bottom of the container (2) and ending at the first outlet inlet of the machine (1); and a suction pump (16), preferably electrically operated, positioned along the pipe (15) and configured to suck liquid accumulated / stagnating at the bottom of the container (2), i.e., liquid having a high concentration of contaminants, from the container (2) and pump the same liquid toward the outlet inlet.

[0041] In the illustrated example, the suction pump (16) is preferably a centrifugal pump.

[0042] Optionally, the drain line (6) further includes a manually operated shut-off valve (17) located upstream of the circulation pump (16) along the pipe (15), i.e., between the suction pump (16) and the container (2).

[0043] The shut-off valve (17) isolates the container (2), allowing possible maintenance work on the suction pump (16) without damaging the vacuum seal of the container (2).

[0044] Preferably, the drain line (6) further comprises: a recirculation pipe (18) branched from the main pipe (15) downstream of the suction pump (16) and returning to the container (2)—the recirculation pipe (18) is preferably connected thereto at a given height from the bottom of the container (2)—and a control valve (19) having controlled opening and closing—the control valve (19) is located downstream of the branch of the recirculation pipe (18) along the main pipe (15) and is configured to control / regulate the flow of liquid along the end section of the main pipe (15).

[0045] Preferably, the suction pump (16) is additionally configured to allow the liquid to circulate continuously along the closed ring formed by the recirculation pipe (18) and the container (2).

[0046] Accordingly, by opening and closing the control valve (19), the liquid reaching from the bottom of the container (2) can be directed toward or not directed toward the first outlet inlet of the machine (1).

[0047] Preferably, the recirculation pipe is also connected to the container (2) above the free surface of the liquid accumulating / stagnating at the bottom of the container (2), that is, above the maximum liquid level reachable by the liquid inside the container (2).

[0048] Additionally, the drain line (6) is preferably electrically operated and preferably of the volumetric type, and is located along the end section of the main pipe (15), i.e., downstream of the branch of the recirculation pipe (18) and the control valve (19) (if present), and includes a delivery pump (20) configured to pump a liquid with a high concentration of contaminants arriving from the suction pump (16) toward the first outlet inlet of the machine at a given pressure.

[0049] In the illustrated example, the transfer pump (20) is preferably a diaphragm pump.

[0050] Optionally, the drain line (6) further includes one or more manually operated shut-off valves (21) positioned along the end section of the main pipe (15) and preferably interposed between the shut-off valve (19) and the transfer pump (20).

[0051] The shut-off valve(s) (21) can isolate single sections of the main pipe (15) so that possible maintenance work can be performed on the control valve (19) and / or the transfer pump (20) without damaging the vacuum seal of the container (2).

[0052] Preferably, the electronic control device (9) is configured to control the suction pump (16), the control valve (19), and the transfer pump (20), if present, based on some operating parameters of the machine (1) and / or based on signals received from one or more sensors (e.g., temperature sensors and / or water level sensors) located at the bottom of the container (2).

[0053] Next, referring to FIG. 2, the drain line (7) preferably comprises: a small tank (24) configured to receive distillate and / or steam reaching from the top of the container (2), preferably having a nominal capacity in the range of 1 to 500 liters; a first pipe (25) connecting the tank (24) to the top of the container / reactor (2); and a second pipe (26) connecting the tank (24) to the second outlet inlet of the machine (1).

[0054] In the illustrated example, in particular, the tank (24) is preferably a substantially sealed container.

[0055] Preferably, the drain line (7) also includes a check valve (27) and / or a non-condensing gas discharge device (28). The check valve (27) is positioned along the pipe (25) and oriented to prevent distillate and / or vapor from returning toward the container (2). The non-condensing gas discharge device (28) is preferably positioned at the top of the tank (24) and configured to exhaust / discharge non-condensing gas present in the tank (24) to the outside of the tank (24).

[0056] In the illustrated example, in particular, the non-condensing gas exhaust device (28) is structured to automatically exhaust / discharge the non-condensing gas to the outside of the tank (24).

[0057] Additionally, the drain line (7) preferably comprises: a suction pump (29), preferably electrically operated, configured to draw distillate from a tank (24) and transfer said liquid to a second outlet inlet of the machine at a given pressure along a pipe (26); and a control valve (30), preferably located downstream of the suction pump (29) and configured to control / regulate the flow of distillate toward the second outlet inlet of the machine, having a controllable opening and closing mechanism.

[0058] Therefore, the distillate is discharged outside the machine (1) which simultaneously operates the suction pump (29) and the control valve (30).

[0059] In the illustrated example, the suction pump (29) is preferably a centrifugal pump.

[0060] Optionally, the drain line (7) further includes one or more manually operated shut-off valves (31) located along the pipe (26), preferably upstream of the suction pump (29) and downstream of the control valve (30).

[0061] The shut-off valve(s) (31) can isolate the pipe (26) to allow possible maintenance work to be performed on the suction pump (29) and / or the control valve (30).

[0062] Preferably, the electronic control device (9) is configured to control the suction pump (29) and the control valve (30) based on signals received from one or more water level sensors located inside the tank (24), and / or based on one or more flow sensors located along the pipe (26), and / or based on some operating parameters of the machine (1), where present.

[0063] Referring to FIG. 2, the vacuum generating device (3) is preferably connected directly to the drain line (7) to use the distillate generated by the container (2) to maintain the container (2) at a negative pressure.

[0064] That is, the vacuum generating device (3) uses the distillate and / or steam generated by the container (2) as the working fluid.

[0065] More specifically, in the illustrated example, the vacuum generating device (3) preferably comprises: an ejector (34) located immediately upstream of the tank (24) along the pipe (25) (i.e., located between the tank (24) and the check valve (27); and a circulation pump (35) preferably electrically operated, preferably centrifugal, located along the recirculation pipe (36) which directly connects the tank (24) to the ejector (34).

[0066] The circulation pump (35) draws in distillate or steam from the tank (24) and transfers it to the ejector (34), causing the ejector (34) to draw in the distillate and / or steam present along the pipe (25) by negative pressure (venturi effect).

[0067] Optionally, the vacuum generating device (3) also includes one or more manually operated shut-off valves (37) located upstream and / or downstream of the circulation pump (35) along the recirculation pipe (36).

[0068] The shut-off valve(s) (37) allows the recirculation pipe (36) to be isolated so that possible maintenance work can be performed on the circulation pump (35).

[0069] Preferably, the electronic control device (9) is configured to issue a command to the circulation pump (35) based on a signal received from one or more water level sensors located inside the tank (24) and / or a signal received from one or more pressure sensors located inside the container (2) and / or some operating parameters of the machine (1).

[0070] Referring to FIGS. 1 and 2, the heat pump evaporator / condenser assembly (5) comprises, on the other hand: a first heat exchanger (41), traditionally referred to as a high-pressure heat exchanger or condenser, configured to heat a liquid stagnant at the bottom of a container (2) and preferably located along the recirculation pipe (18) of a drain line (6) to rapidly heat a liquid containing high concentrations of contaminants that is recirculated into the container (2); and a second heat exchanger (42), traditionally referred to as a low-pressure heat exchanger or evaporator, configured to cool / condense steam formed inside the container (2) and preferably located along the drain line (7) or at its inlet to rapidly cool and also at least partially condense steam coming out of the container (2). It includes an expansion valve (43), preferably electronically controlled, which is interposed between the outlet of the high-pressure heat exchanger (41) and the inlet of the low-pressure heat exchanger (42), and is configured to induce rapid and irreversible expansion of the gaseous refrigerant fluid flowing from the outlet of the heat exchanger (41) toward the inlet of the heat exchanger (42), so that the refrigerant fluid flowing into the heat exchanger (42) has a detectably lower pressure and temperature than the refrigerant fluid flowing out of the heat exchanger (41).

[0071] Clearly, the expansion valve (43) can be replaced with a capillary tube or other active or passive expansion member.

[0072] The heat pump evaporator / condenser assembly (5) also includes a compressor (44), preferably electrically operated, which is interposed between the heat exchangers (41, 42) and configured to compress the refrigerant fluid flowing out of the heat exchanger (42) and into / returning to the heat exchanger (41).

[0073] More specifically, the compressor (44) is preferably a volumetric compressor and is interposed between the outlet of the low-pressure heat exchanger (42) and the inlet of the high-pressure heat exchanger (41) to increase the pressure and temperature of the refrigerant fluid directed toward the heat exchanger (41).

[0074] In the illustrated example, the low-pressure heat exchanger (42) is preferably located immediately downstream of the container (2) along the pipe (25) of the drainage line (7).

[0075] Additionally, preferably, a low-pressure heat exchanger (42) is at least partially received / inserted inside the container (2) at the top of the container (2) to form an initial section of the drainage line (7).

[0076] Preferably, the heat pump evaporator / condenser assembly (5) also includes a second low-pressure heat exchanger (45), traditionally referred to as an auxiliary evaporator, located inside the tank (24) to cool the distillate and / or steam inside the tank (24) of the drain line (7).

[0077] More specifically, the heat exchanger (45) is preferably connected in parallel with the low-pressure heat exchanger (42), and the heat pump evaporator / condenser assembly (5) preferably includes a second expansion valve (46) or other active or passive expansion member configured to cause rapid and irreversible expansion of a gaseous refrigerant fluid flowing from the outlet of the heat exchanger (41) toward the inlet of the heat exchanger (45), so that the refrigerant fluid flowing into the heat exchanger (45) has a detectably lower pressure and temperature than the refrigerant fluid flowing out of the heat exchanger (41).

[0078] Clearly, the outlet of the second low-pressure heat exchanger (45) is also connected to the suction part of the compressor (44).

[0079] Preferably, the electronic control device (9) is also configured to issue commands to the compressor (44) and optionally to the expansion valve (43) and, if present, the expansion valve (46) based on some operating parameters of the machine (1) and / or based on signals received from one or more pressure sensors located at the delivery and / or suction of the compressor (44).

[0080] Alternatively, the expansion valve (43) may be controlled by an automatic mechanical or electronic system. Additionally, the valve (46) may be an automatic thermostatic valve, if present.

[0081] Optionally, the evaporator / condenser assembly (5) also includes an auxiliary heat exchanger (47), preferably of a finned-pack type, which is located immediately downstream of the high-pressure heat exchanger (41) and configured to complete the condensation of the refrigerant fluid that transfers excess heat to the external environment.

[0082] In addition to or alternatively to the auxiliary heat exchanger (47), the evaporator / condenser assembly (5) also includes a second auxiliary heat exchanger (48) located immediately upstream of the expansion valve (43) and, if present, the expansion valve (46), and configured to further cool the gaseous refrigerant fluid directed toward the expansion valve(s) (43, 46).

[0083] More specifically, the auxiliary heat exchanger (48) is preferably connected to an external hydraulic circuit so that the refrigerant fluid coming from the heat exchanger (41) and the low-temperature heat transfer fluid coming from the external hydraulic circuit are crossed simultaneously, thereby removing heat from the refrigerant fluid directed toward the expansion valve(s) (43, 46).

[0084] Preferably, the circulation of the low-temperature heat transfer fluid circulating through the auxiliary heat exchanger (48) can be controlled.

[0085] More specifically, in the illustrated example, the auxiliary heat exchanger (48) is connected to an external hydraulic circuit by a control-switching three-way valve (49), which is preferably electrically operated and optionally configured to deliver a heat transfer fluid to the inlet of the auxiliary heat exchanger (47).

[0086] Preferably, the electronic control device (9) is also configured to control valve(s) that regulate the circulation of the low-temperature heat transfer fluid inside the auxiliary heat exchanger (48), if present.

[0087] The refrigerant fluid contained within the heat pump evaporator / condenser assembly (5) (i.e., the gas that the compressor (44) circulates within the heat exchangers (41, 42) and optionally within the heat exchangers (45 and / or 47)) then comprises one or more gases of the hydrofluoroolefin series in a percentage greater than 3%.

[0088] Preferably, hydrofluoro-olefin series gas(s) are also components of the refrigerant fluid in larger amounts / percentages.

[0089] More specifically, the refrigerant fluid preferably comprises one or more gases of the hydrofluoroolefin series in a percentage of more than 30%, and optionally also more than 50%.

[0090] Optionally, the refrigerant fluid may also preferably contain one or more gases of the hydrofluorocarbon series in a percentage of less than 50%.

[0091] More specifically, in the illustrated example, the refrigerant fluid contained in the heat pump evaporator / condenser assembly (5) preferably contains one or more gases of the hydrofluoroolefin series in a percentage greater than 75%.

[0092] That is, the refrigerant fluid preferably consists mainly of one or more gases of the hydrofluoroolefin series.

[0093] Referring solely to FIG. 2, preferably the sewage treatment unit (1) comprises: a separator / demister filter (50) located below the inlet of the drain line (7) inside the container (2) and configured to prevent liquid droplets drawn upward by the steam flow from reaching the inlet of the drain line (7); and / or a resistor (51) located at the bottom of the container (2) and configured to selectively heat the liquid present inside the container (2) in addition to or alternatively to the evaporator / condenser assembly (5).

[0094] Clearly, the resistor (51) can be replaced with any other electrical device that generates heat when current flows through it.

[0095] In the illustrated example, the separator / mist removal filter (50) is preferably placed inside the container (2), directly below the heat exchanger (42).

[0096] Preferably, the electronic control device (9) is configured to issue commands to a resistor (51), etc., based on a signal received from one or more temperature signals located inside the container (2) and / or based on some operating parameters of the machine (1).

[0097] From what has been explained above, the operation of the sewage treatment device (1) can be easily inferred.

[0098] The liquid to be processed is drawn into the reactor / container (2) without the use of a supply pump by the effect of the negative pressure generated by the vacuum generating device (3).

[0099] The suction pump (16) sucks liquid from the bottom of the container (2) and transfers it to the heat exchanger (41) of the evaporator / condenser assembly (5), and the heat exchanger (41) provides the heat required for the evaporation of the liquid.

[0100] After passing through the heat exchanger (41), the liquid to be processed flows back into the container (2), where some of the liquid immediately evaporates (flash evaporation) due to the effect of pressure lower than atmospheric pressure and is directed toward the top of the container (2).

[0101] While moving upward along the container (2), the steam passes through a separator filter (50) that holds larger droplets, and then reaches a low-pressure heat exchanger (42) that causes full or partial condensation of the steam at or along the inlet of the drain line (7). The generated condensate / distillate accumulates inside the tank (24) and is transferred outside the machine upon activation of the suction pump (29) and simultaneous opening of the control valve (30).

[0102] On the other hand, non-condensable gases present inside the tank (24) are exhausted from the tank (4) by a non-condensable gas exhaust device (28).

[0103] Clearly, due to the evaporation of some of the aqueous base, the liquid remaining at the bottom of the container (2) gradually increases in the concentration of contaminants until it is discharged / transferred outside the machine (1) upon the opening of the control valve (19) and the activation of the transfer pump (20).

[0104] The advantages associated with the use of a new refrigerant fluid containing one or more gases of the hydrofluoroolefin series in a percentage of more than 3%, or more conveniently more than 30%, are significant.

[0105] In experimental tests, it was confirmed that the new refrigerant fluid increases the efficiency of the heat pump evaporator / condenser assembly (5) while simultaneously lowering the GWP index value of the machine.

[0106] Finally, however, it is evident that changes and modifications can be made to the aforementioned sewage treatment device (1) without departing from the scope of the present invention.

[0107] For example, the non-condensing gas discharge device (28) may be structured to discharge non-condensing gas outside the tank (24) according to a command. In this case, the electronic control device (9) may also issue a command to the non-condensing gas discharge device (28).

[0108] Additionally, referring to FIG. 3, in an alternative embodiment, the high-pressure heat exchanger (41) of the heat pump evaporator / condenser assembly (5) is positioned, preferably outside the container, adjacent to the bottom of the container (2), or more conveniently in contact with it, to transfer heat directly to the liquid present at the bottom of the container (2).

[0109] Next, the low-pressure heat exchanger (42) is preferably placed / accommodated entirely inside the container (2), and the top of the container (2) is preferably structured to temporarily collect condensate falling from the heat exchanger (42).

[0110] Additionally, in this embodiment, the sewage treatment unit (1) is preferably provided with a rotatable stirring member (60) positioned near the bottom of the container inside the container / reactor (2)—preferably having the ability to rotate about a given rotation axis (A) that substantially coincides with the longitudinal axis of the container (2)—and preferably an electric motor assembly (61) positioned outside the container (2) and configured to drive the stirring member (60) around the axis (A).

[0111] Preferably, the rotatable stirring member (60) is also structured to scrape the inner surface of the container (2) during rotation around the axis (A).

[0112] More specifically, the rotatable stirring member (60) is preferably provided with a series of radial blades that are angularly distributed around an axis (A) and extend to skim the inner surface of the container (2).

[0113] Preferably, the rotatable stirring member (60) also starts from the top and protrudes into the container (2) and extends cantileveredly inside the container (2) coaxially with the axis (A), and is fixed / fitted in a rigid manner to the end of a support shaft (62) which is rotatably driven by a motor assembly (61).

[0114] Next, the motor assembly (61) is basically composed of an electric gear motor that is preferably located on the top of the container (2) outside the container (2) and is mechanically coupled to the support shaft (62) to enable rotational driving of the support shaft (62) and the one integrally formed therewith around the axis (A).

[0115] Preferably, the electronic control device (9) is also configured to issue commands to the motor assembly (61) based on some operating parameters of the machine (1).

[0116] In this embodiment as well, the refrigerant fluid contained in the heat pump evaporator / condenser assembly (5) contains one or more gases of the hydrofluoroolefin series in a percentage greater than 3%, more conveniently in a percentage greater than 30%, or even in a percentage greater than 50%.

[0117] In an alternative and unillustrated embodiment, finally, the container / reactor (2) may be made of a large watertight sealed vessel that is substantially cylindrical and rectangular in shape, and preferably extends substantially horizontally.

[0118] Additionally, a rotatable stirring member may be inserted into the container / reactor (2) in a manner that allows it to rotate axially substantially coaxially or somehow parallel to the longitudinal axis of the container / reactor (2), and optionally, may be made of a screw sized to scrape the bottom of the container / reactor (2) during rotation around the longitudinal axis.

[0119] Clearly, the screw is rotated by a motor assembly, preferably electric, which is preferably located outside the container / reactor (2).

Claims

Claim 1 A sewage treatment device (1), comprising: a sealed container (2) in which a liquid to be treated is boiled; a vacuum generating device (3) configured to maintain the interior of the sealed container (2) at a given pressure having a value lower than environmental pressure or external pressure; a supply line (4) for the liquid to be treated, configured to deliver the liquid to be treated into the interior of the sealed container (2); a heat pump assembly (5) connected to the sealed container (2) to deliver heat to the liquid present at the bottom of the sealed container (2) to cause the liquid to boil, and simultaneously remove heat from the steam reaching the top of the sealed container (2) to condense the steam and obtain a distillate; and a first drainage line (6) branching or starting from the bottom portion of the sealed container (2) and configured to deliver or move the liquid accumulated or stagnant at the bottom of the sealed container (2) to the outside of the sealed container (2). and includes a second drain line (7) configured to branch or start from the top of the sealed container (2) and to transfer or move a distillate generated from at least one of the steam formed inside the sealed container (2) or the condensation of the steam to the outside of the sealed container (2); the sewage treatment device (1) includes a tank (24) configured to receive a refrigerant fluid comprising one or more gases of the hydrofluoroolefin series in a percentage greater than 3% of the heat pump assembly (5), and the second drain line (7) includes a tank (24) configured to receive at least one of the steam or distillate reaching from the sealed container (2); the heat pump assembly (5) includes a first heat exchanger (41) configured to heat a liquid stagnated at the bottom of the sealed container (2); and a second heat exchanger (42) configured to cool or condense the steam formed inside the sealed container (2);A sewage treatment device characterized by comprising: a first expansion member (43) interposed between the first heat exchanger (41) and the second heat exchanger (42) and configured to induce expansion of the refrigerant fluid directed toward the second heat exchanger (42); a third heat exchanger (45) located inside the tank (24) of the second drain line (7) and connected in parallel to the second heat exchanger (42) so as to cool at least one of the steam or distillate located inside the tank (24); and a second expansion member (46) interposed between the first heat exchanger (41) and the third heat exchanger (45) and configured to induce expansion of the refrigerant fluid directed toward the third heat exchanger (45). Claim 2 A sewage treatment device according to claim 1, wherein the refrigerant fluid comprises one or more gases of the hydrofluoroolefin series in a percentage greater than 30%. Claim 3 A sewage treatment device according to paragraph 2, wherein the refrigerant fluid comprises one or more gases of the hydrofluoroolefin series in a percentage greater than 50%. Claim 4 A sewage treatment device according to paragraph 3, wherein the refrigerant fluid comprises one or more gases of the hydrofluoroolefin series in a percentage greater than 75%. Claim 5 A sewage treatment device according to any one of claims 1 to 4, wherein the refrigerant fluid comprises one or more gases of the hydrofluorocarbon series. Claim 6 A sewage treatment device according to claim 1, wherein the vacuum generating device (3) is configured to continuously maintain the pressure inside the sealed container (2) at a value of less than 0.8 bar. Claim 7 A sewage treatment device according to claim 1, wherein the supply line (4) is configured to control or vary the flow rate of the liquid to be treated flowing into the sealed container (2) to continuously maintain the liquid level inside the sealed container (2) within a given range. Claim 8 In claim 1, the first heat exchanger (41) is a sewage treatment device located along the recirculation pipe (18) of the first drainage line (6) or adjacent to the bottom of the sealed container (2). Claim 9 In claim 1, the second heat exchanger (42) is located at least partially inside the sealed container (2) or upstream of the tank (24) along the second drain line (7), a sewage treatment device. Claim 10 A sewage treatment device according to claim 1, further comprising a rotatable stirring member (60) positioned near the bottom of the container inside the sealed container (2) - the rotatable stirring member (60) has the ability to rotate around a given rotation axis (A) - and a motor assembly (61) configured to drive the stirring member (60) to rotate around the rotation axis (A), wherein the stirring member (60) is structured to scrape the inner surface of the sealed container (2) during rotation around the rotation axis (A). Claim 11 A sewage treatment device according to claim 1, further comprising a separator or demister filter (50) positioned below the inlet of the second drain line (7) inside the sealed container (2) and configured to prevent any liquid droplets drawn upward by the flow of steam from reaching the second drain line (7). Claim 12 A sewage treatment device according to claim 1, further comprising a support framework (8) configured to be placed on the ground, wherein the sealed container (2), the vacuum generating device (3), the supply line (4), the heat pump assembly (5), the first drain line (6) and the second drain line (7) are arranged on the support framework (8) to form a single transportable block. Claim 13 A sewage treatment device according to claim 1, wherein the vacuum generating device (3) comprises: an ejector (34) located upstream of the tank (24) along a main pipe (25) connecting the tank (24) to the top of the sealed container (2); and a circulation pump (35) located along a recirculation pipe (36) directly connecting the tank (24) to the ejector (34). Claim 14 A sewage treatment device according to claim 13, characterized in that the second heat exchanger (42) is located downstream of the sealed container (2) along the main pipe (25). Claim 15 delete Claim 16 delete

Images