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EP-4526007-B1 - VACUUM EVAPORATION UNIT

EP4526007B1EP 4526007 B1EP4526007 B1EP 4526007B1EP-4526007-B1

Inventors

  • VITALE, FRANCESCO
  • LONGO, VINCENZO

Dates

Publication Date
20260506
Application Date
20230519

Claims (8)

  1. Vacuum evaporation unit (10, 110) configured for the treatment of polluting liquid solutions (SL), comprising: - a vacuum chamber (11, 111) for the containment of a polluting liquid solution (SL) to be treated, comprising in turn a lower part (12, 112) for collecting the liquid solution (SL) and an upper part (13, 113) for a rising vapour (V) developing from said liquid solution (SL); - vacuum generation means connected to said vacuum chamber (11, 111); - heat exchange means (15, 115) configured to bring about a heat exchange between said vapour (V) of said liquid solution (SL) and said liquid solution (SL) itself, said vacuum chamber (11, 111) and said heat exchange means (15, 115) being operatively communicating so that said liquid solution (SL) present in said lower part (12, 112) of said vacuum chamber (11, 111) is brought into contact with said heat exchange means (15, 115); - a condensation chamber (14, 114) communicating with said heat exchange means (15, 115), in said condensation chamber (14, 114) the condensation of said vapour (V) generated by the boiling of said liquid solution (SL) occurring after said heat exchange with said liquid solution (SL); - first transfer means (16, 116) configured to conduct said vapour (V) from said upper part (13, 113) of said vacuum chamber (11, 111) to said heat exchange means (15, 115); - second transfer means (17) configured to conduct said liquid solution (SL) from said lower part (12) of said vacuum chamber (11) to said heat exchange means (15), said heat exchange means (15) comprising a tank (40) within which a heat exchanger (41) is arranged, said heat exchanger (41) being connected at the inlet with said second transfer means (17), and at the outlet with said upper part (13) of said vacuum chamber (11); characterised in that said first transfer means (16, 116) comprise: - a first conduit (31, 131) for said vapour (V), configured to connect a vapour outlet port (13a, 113a) defined in said upper part (13, 113) with a suction port of extraction and compression means (30, 130); - said extraction and compression means (30, 130); - a second conduit (32, 132) for said vapour (V), configured to connect the delivery port of said extraction and compression means (30, 130) with an inlet port (21) of a washing tower (20); - said washing tower (20) configured for the countercurrent treatment of said vapour (V) exiting from said vacuum chamber (11, 111) with a liquid absorption solution (SA); - a third conduit (33, 133) for the vapour (V1) treated with said washing tower (20), configured to connect an outlet port (26) of said washing tower (20) with an inlet port (15a, 115a) of said heat exchange means (15, 115), said tank (40) comprising an inlet port (42) connected to said outlet port (26) of said washing tower (20), so that said treated vapour (V1) exiting said washing tower (20) condenses in said tank (40) of said heat exchange means (15, 115) and releases energy to said liquid solution (SL) circulating inside said heat exchanger (41), and at least one discharge port (43) connected with discharge means (44) configured to extract the condensate from the bottom of said tank (40); said washing tower (20) further comprising: - a settling basin (22) for the collection and settling of said liquid absorption solution (SA); - an exchange column (23) of the filling type configured to operate a countercurrent exchange of matter between said vapour (V), ascending, and said liquid absorption solution (SA), descending, said exchange column (23) being placed above said settling basin (22); - dispensing means (24) configured to dispense said liquid absorption solution (SA) diffusely above said exchange column (23).
  2. Vacuum evaporation unit according to claim 1, characterised in that said washing tower (20) comprises a droplet separator (27) placed above said dispensing means (24).
  3. Vacuum evaporation unit according to claim 2, characterised in that said washing tower (20) comprises auxiliary dispensing means (28) configured to dispense a liquid washing and replenishing solution (SA1) diffusely above said droplet separator (27).
  4. Vacuum evaporation unit according to the preceding claim, characterised in that said exchange column (23) is filled with Raschig rings or other similar annular elements.
  5. Vacuum evaporation unit according to any one of the preceding claims, characterised in that said heat exchanger (41) is connected to an intermediate zone of said vacuum chamber (11), above said liquid solution (SL) and below said vapour outlet port (13a), by means of an outlet conduit (53).
  6. Vacuum evaporation unit according to any one of the preceding claims, characterised in that said discharge means (44) comprise a vacuum pump (45) connected to said discharge port (43) by means of a discharge conduit (46).
  7. Vacuum evaporation unit according to any one of the preceding claims, characterised in that said transfer means (17) comprise a circulation pump (50) connected to the bottom of said vacuum chamber (11) by means of a loading conduit (51) and connected to an inlet port (41a) of said heat exchanger (41) by means of a delivery conduit (52).
  8. Vacuum evaporation unit according to any one of the preceding claims, characterised in that said dispensing means (24) comprise a top-up pump (36) configured to introduce into said absorption solution (SA) substances useful for re-establishing the established pH level.

Description

The invention concerns a vacuum evaporation unit. So-called 'vacuum evaporators' are nowadays well-known and widespread in the disposal of polluting liquid waste. Document US 2018/305221 A1 gives an example of a vacuum evaporator. Vacuum evaporators are used for concentrating aqueous solutions containing pollutants by evaporating water at low temperature. By treating a wastewater to be disposed of with a vacuum evaporator, the volume of wastewater to be disposed of is significantly reduced, allowing the recovered distilled water to be reused and returned to the source users. In general, vacuum evaporators make it possible to totally recycle the water used in production processes, leading to a drastic reduction in the amount of wastewater to be sent for disposal, reducing disposal costs and saving on water supply. In some cases, such as wastewater from galvanic bath washes and recoveries, it is possible to reuse the concentrated recovery solution in the treatment baths. The distillates obtained by vacuum evaporation are often polluted by so-called 'low-boiling' species, which remain in the vapour and cause the quality of the distillate itself to deteriorate, making its use or discharge into the sewage system problematic, resulting in the need for chemical-physical or biological post-treatments that are often costly in terms of both investment and operating costs. The evaporator is a machine with mechanical vapour compression. For example, a vacuum evaporator may comprise an evaporation bowl, i.e. a tank, configured to contain a solution in the liquid state to be treated at a certain temperature and at a predefined pressure to lower its evaporation temperature. The liquid solution to be treated and the vapour of the same solution separate in the evaporation bowl and cross in a heat exchanger, thanks to the forced circulation imposed by corresponding pumping and compression means. The liquid which evaporates, which is the substance to be filtered and cleaned, is found in the evaporation bowl. The vapour from this liquid solution is sucked in via a circulation pump and pushed towards a heat exchanger, e.g. a shell-and-tube heat exchanger. The liquid solution is circulated inside the tubes of the heat exchanger, pushed by a circulation pump that draws it from the bottom of the evaporation bowl. The outside of the heat exchanger tubes are lapped by vapour from the liquid solution, sucked in by a compressor, which pushes it into the heat exchange chamber where the heat exchanger is located. The liquid solution passes through the heat exchanger and heats up, exiting the heat exchanger back into the evaporation bowl in the form of a superheated liquid. Upon entering the evaporation bowl, the superheated liquid solution releases vapour again, thus generating a so-called 'flash' evaporation, i.e. a partial evaporation of the liquid solution. In the heat exchange chamber, the vapour condenses outside the heat exchanger and releases energy to the solution circulating inside the heat exchanger. The condensate, or distillate, formed outside the heat exchanger collects at the bottom of the heat exchange chamber and is extracted from there, e.g. with a vacuum pump. The condensate, or distillate, is made available to the source users from which the liquid solution originated. Thanks to such a vacuum evaporator, for example, 100 cubic metres of a solution of an oily emulsion, e.g. a water-based release emulsion, are reduced by a factor of 10, i.e. they are reduced to 10 cubic metres, and the recovered distilled water is reused to prepare other release agents. As mentioned above, the wastewater to be treated may contain pollutants, such as nitrogen in the form of ammoniacal nitrogen. These low-boiling species distil, i.e. evaporate, together with the vapour formed in the evaporator. As mentioned, low-boiling species are gases that move together with vapour and are then found in the condensate of the same vapour. Low-boiling species are water-soluble gases. The species that are insoluble in water on the other hand, such as CO2, or Nitrogen, are degassed in the vacuum pump and are called 'non-condensables' in technical jargon. These known vacuum evaporators, although widespread and popular today, are all faced with the major problem of managing the low-boiling species. The task of the present invention is that of developing a vacuum evaporation unit able to overcome the mentioned drawbacks and limits of the prior art. In particular, an aim of the invention is to develop a vacuum evaporation unit capable of breaking down low-boiling pollutants from the vapour phase. Another aim of the invention is to develop a vacuum evaporation unit capable of recovering low-boiling species so that they are reusable. A further aim of the invention is to develop a vacuum evaporation unit that can incorporate any vacuum evaporator of the already existing type. The task as well as the aforementioned objects are achieved by a vacuum evaporation unit