| GB2145343A | 1985-03-27 | |||
| GB2246080A | 1992-01-22 | |||
| US4370816A | 1983-02-01 | |||
| US5765395A | 1998-06-16 | |||
| EP0541009A1 | 1993-05-12 | |||
| EP0493846A1 | 1992-07-08 |
| 1. | A plant for recovering solvents or other liquids dispersed in air, characterised in that it comprises a finned evaporator (1) inserted inside an inlet (16) for the entry of the air to be treated containing solvent vapours and a diathermic oil heater of the treated air inserted inside an outlet (17) for the exhaust of the air, the finned evaporator (1) being the evaporator of a refrigerating plant comprising a compressor and a condenser. |
| 2. | A plant as claimed in claim 1, characterised in that it comprises a drop arresting bulkhead (8) to prevent the possible transport of solvent in the form of dew towards the heated outlet. |
| 3. | A plant as claimed in claim 1, characterised in that it comprises a plate exchanger (6) inserted in the refrigerating plant and which feeds, by means of a pump (7), the finned evaporator (1). |
| 4. | A plant as claimed in claim 1, characterised in that it comprises a tank (14) for collecting the solvent in the liquid state condensed by the evaporator (1). |
| 5. | A plant for recovering solvents or other liquids dispersed in air of the type comprising a finned evaporator (1) inserted inside an inlet (16) of a tunnel (18) of the air to be treated containing solvent vapours, the finned evaporator (1) being the evaporator of a refrigerating plant, characterised in that it comprises a heat exchanger (20) which serves as a preconditioner, positioned in correspondence with the outlet (17) of a tunnel (18) fed with the cooling fluid of the refrigerating plant which, by condensing, relinquishes heat to the treated air. |
| 6. | A plant as claimed in claim 5, characterised in that the heat exchanger (20) is of the finned type and is fed, through a conduit (21), with the cooling fluid; a conduit (22) connects the outlet of the exchanger (20) with a second condenser (23) which is connected to a tank (5) for storing the cooling fluid. |
| 7. | A work centre, characterised in that it comprises a plant for recovering a cooling liquid provided with an evaporator (31) inserted between an inlet section (32) for the entry of the air to be treated containing vapours of refrigerating liquids and an outlet section (4) for the exit of the treated air, the evaporator (31) being part of a refrigerating system comprising a compressor (6), a condenser (7) and a compensating valve (10) which can be calibrated to maintain the evaporator (1) at the dew point of the cooling liquid. |
| 8. | A work centre as claimed in claim 7, characterised in that said plant for recovering refrigerating liquid comprises a bank (14) for the recovery of heat, interposed between said evaporator (1) and said outlet section (4) for the exit of the treated air. |
| 9. | A work centre as claimed in claim 7, characterised in that said plant for recovering refrigerating liquid comprises a drop arresting bulkhead (11) positioned downstream of said evaporator (31) to prevent the possible transport of refrigerating liquid in the form of dew towards the outlet section (4). |
| 10. | A work centre as claimed in claim 7, characterised in that said plant for recovering refrigerating liquid comprises a plate exchanger (9) inserted in the refrigerating system and feeding the evaporator (31). |
| 11. | A work centre as claimed in claim 7, characterised in that said plant for recovering refrigerating liquid comprises a tank for collecting the refrigerating liquid in the liquid state condensed by the evaporator. |
TECHNICAL FIELD AND BACKGROUND ART.
The present invention relates to a plant for recovering solvents dispersed in air of spaces housing serigraph printing systems or painting systems or systems for washing with solvents or in any case where solvents are used.
The invention further relates to a work centre with a plant for the recovery of liquids for cooling tools.
In the serigraphy industry, in painting plants and in plants for washing products with solvents there is an inevitable formation of vapours of the solvents employed which are easily dispersed in the air of the space in which said plants are located.
Currently, to avoid intoxicating personnel operating in said spaces and dispersing the solvents outside, systems are provided for the aspiration of the air containing solvent vapours or gases, said air then being filtrated by means of activated charcoal filters.
The use of activated charcoal filters presents several drawbacks, such as: -solvents cannot be recovered; -problems with the disposal of said filters once they are saturated; -high operating costs for said plants.
The present invention further relates to work stations for the removal of shavings such as turning, milling or boring stations in which particular cooling liquids are employed.
In the shaving removal work process, use is made of enclosed booths in which air is aspirated and sent outside by means of a series of fans.
The use of cooling liquids on pieces and tools that reach high temperatures inevitably produces vapours containing the cooling products employed which are easily dispersed
in the air of the enclosed booth in which the machining is operation is conducted.
Currently, air is discharged outside with an evident dispersion of cooling liquids and heat, thereby generating considerable drawbacks. In the first place, it is impossible to recover the cooling liquids employed, thus polluting the external environment, in addition to the fact that continual refills are necessary, thereby considerably impacting on the operating costs of said plants.
To the above are added the problems related with disposing of vapours and hot air externally. This matter is governed by regulations that prohibit the outside emission of the vapours deriving from the cooling liquids used in the work centres.
DISCLOSURE OF INVENTION.
The main aim of the present invention is to eliminate the aforementioned drawbacks and in particular to recover the solvent present in the treated air, for its possible reuse and consequently for the elimination of all disposal problems.
A further aim is substantially to decrease the operating costs of solvent recovery plants.
Yet a further aim of the present invention is to make available a work centre with plant for the recovery of cooling liquid which allows continuously to recover the coolant present in the treated air and to reuse it, eliminating all disposal problems.
Another aim is to decrease the operating costs both of the work centre and of the plants for the recovery of the cooling liquids for the tools and for the pieces undergoing work.
Said aims are fully achieved by the plant for the recovery of solvents dispersed in air, constituting the subject of the present invention, which is characterised by the contents of the claims set out below and in particular in that it provides for cooling the air to be treated until it is brought to a dew point of the solvent which returns to the liquid state and can thus be stored in a tank.
A refrigerating system or thermodynamic condenser maintains at a constant level such a
pre-set temperature value as to allow for the rapid cooling of the air.
A work centre with cooling liquid recovery plant, also constituting the subject of the present invention, is characterised in that it comprises an evaporator operating at constant temperature through a compensating valve and inserted between a section for the entry of the air to be treated, containing vapours of the cooling liquids, and a section of the exit of the treated air, the evaporator being a part of a refrigerating system comprising a compressor and a condenser.
BEST MODE FOR CARRYING OUT THE INVENTION.
This and other characteristics shall become more readily apparent from the following description of some preferred embodiments illustrated, purely by way of non limiting example, in the accompanying drawing tables, in which: -Figure 1 shows the functional diagram of the plant with direct cooling; -Figure 2 shows the functional diagram of the plant with indirect exchange; -Figure 3 shows a front view of the way the whole plant is grouped to form an assembly readied for operation; -Figure 4 shows the functional diagram of the plant with direct cooling according to a variation; -Figure 5 shows the functional diagram of the plant with indirect cooling of the plant with secondary fluid according to a variation; -Figure 6 schematically shows a work centre whereto is applied the cooling system for the recovery of the cooling liquid of the centre itself.
With reference to Figure 1, the number 1 indicates a finned evaporator through which air containing solvent is made to pass.
The finned evaporator is directly part of a refrigerating system comprising a traditional compressor 2 which compresses the intermediate vapour in a condenser 3, with electrical
fan 4, where, shifting to the liquid state, it relinquishes heat. The plant comprises a tank 5 for the cooling liquid for instance HFC R-22. According to a possible embodiment variation illustrated in Figure 2, the finned evaporator is not fed directly from the refrigerating system, but from a plate exchanger 6 containing ethyl or monopropylene glycol, by means of a circulating pump 7.
The air containing solvent vapours, passing through the finned evaporator 1, cools rapidly until it reaches the dew point of the solvent which precipitates, liquefied, into a collecting tank 14 provided with exhaust duct exiting from the container.
The number 8 indicates a drop arresting bulkhead to prevent the possible transport of solvent in dew form into a subsequent chamber in which the air, before being re-injected into the environment, is heated to be brought back to ambient temperature.
The drop arresting bulkhead (8) is formed by a plurality of offset angle elements to force air to travel along a tortuous path to stop the solvent drops against the angle elements.
On the finned evaporator is installed a thermostat 9 to verify that the cooling temperature remains constant at all times.
The number 10 indicates a heat exchanger fed with diathermic oil and provided with an expansion vessel 11 for the oil. A thermostat 12 measures the temperature of the air that is re-injected into the environment and acts on the heating of the oil also in combination with a thermostat 13 which measures oil temperature.
The refrigerating system is provided with valves and cocks, filters and manostats arranged according to the usual installation technique.
The direct cooling plant is advisable in case of condensation of pure solvents, i. e. not combined with other substances such as paints, whilst indirect exchange is advisable when other solvents are mixed with the solvent.
The entire plant is housed in a container 15, easily transportable, which provides an inlet
16 for the entry of the air to be treated in which is inserted the finned evaporator 1, and an outlet 17 for discharging the treated air in which the diathermic oil heater (10) is inserted.
This plant can recover all types of solvents down to a condensation temperature of-20°C and can be applied in closed loop on operating machines for serigraphic printing, painting, or washing products with solvents.
The heat exchanger 10 could also be of another type without thereby departing from the scope of protection of the claims set out below.
With reference to Figure 4, the number 1 indicates a finned evaporator through which air containing solvent, or another product dispersed in air, is made to pass.
The finned evaporator is directly part of a refrigerating system comprising a traditional compressor 2 which compresses the intermediate vapour in a condenser 23, with electrical fan 4, where it shifts to the liquid state and relinquishes heat.
The plant comprises a tank 5 for the refrigerating liquid for instance HFC R-22.
According to a possible embodiment variation shown in Figure 5, the finned evaporator is not fed directly from the refrigerating plant but from a plate exchanger 6 containing ethyl or monopropylene glycol by means of a circulating pump 7.
The air containing the solvent vapours, passing through the finned evaporator 1, cools rapidly until reaching the dew point of the solvent.
Consequently, the solvent precipitates liquefied into a collection tank 14 provided with a discharge duct which enters a collecting container.
The number 8 indicates a drop arresting bulkhead to avoid the possible transport of solvent in dew form into a subsequent chamber in which the air, before being re-injected into the environment, is heated to be brought back to ambient temperature.
The drop arresting bulkhead (8) is formed by a plurality of offset angle elements to force
air to travel along a tortuous path to stop the solvent drops against the angle elements.
On the finned evaporator 1 is installed a thermostat 9 to verify that the cooling temperature remains constant at all times.
The refrigerating system is provided with valves and cocks, filters and manostats arranged according to the usual installation technique.
The plant is housed in a container which comprises among other elements a tunnel 18 provided with an inlet 16 for the entry of the air to be treated in which is inserted the finned evaporator 1, and an outlet 17 for discharging the treated air in which a finned heat exchanger 20 is inserted.
The heat exchanger of the type with a finned bank 20 is fed by means of the conduit 21, with the refrigerating fluid that, by condensing, relinquishes heat to the air which is pushed through the finned bank. From the heat exchanger 20 which serves as a pre- conditioner, the outgoing fluid is sent through the conduit 22 to the second condenser 23 before being returned to the tank. The second condenser maintains working conditions within the values required for the proper operation of the plant.
It has been possible to verify that with the heat recovery described above, electrical power consumption is 60% lower than in the solution with heating by means of electrical resistors in diathermic oil.
With reference to Figure 6, a work centre 30 is illustrated in which the evaporator 31 is inserted between an inlet section 32 for the air to be treated containing the vapours of the liquid for cooling the tools.
The treated air is injected back into the booth 33 of the work centre.
The evaporator 31 may be fed according to one of the diagrams of the plant of Figure 1 or 2 and the treated air heater may be fed according to one of the diagrams of Figure 1,2, 4 or 5.