GB2131146A

GB2131146A - Vapour condensing plant

Info

Publication number: GB2131146A
Application number: GB08329410A
Authority: GB
Inventors: Guido Galante
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-11-16
Filing date: 1983-11-03
Publication date: 1984-06-13
Also published as: ES8406705A1; IT8224269A0; IT1156338B; GB8329410D0; ES525922A0

Abstract

Plant for the condensation of hydrocarbon vapours comprises a compressor limited power refrigeration unit, an accumulator tank 2 for cold refrigerant, a primary vapour condenser 1' fed with the refrigerant liquid coming from the accumulator 2, a secondary vapour condenser 1<iv> including a first evaporator of the refrigeration unit, and a second evaporator 3' in series with condenser 1' and tank 2. <IMAGE>

Description

SPECIFICATION Condenser plant for hydrocarbon vapours This invention relates to a condenser plant for hydrocarbon vapours.

More particularly, the invention relates to a high output plant for the condensation of hydrocarbons using a low power refrigeration unit, usable in particular in the loading stations of road tankers where gas flow is discontinuous and of variable output and the.use of the plant is concentrated in a few hours each day.

There is known plant for condensation of hydrocarbon vapours through cooling of the flow of gases freed during loading of road tankers, which use exchanger-condensers fed directly by a refrigeration unit which is designed for the maximum period of use of the plant, and therefore has large installed power.

There is further known plant in which the transitional refrigeration unit is fed from an accumulator tank of cold refrigerant which is filled during the course of the day and then permits withdrawal of large quantities of refrigerant liquid at operating temperatures even during small periods of time, without it being necessary to instal a refrigerating unit of high power.

This plant with accumulators whilst solving the problem of reducing the power of the refrigeration unit which is installed, and therefore the cost of the whole plant, does guarantee complete condensation of the hydrocarbon vapours as a result of the still insufficiently low temperature which it manages to confer to the liquid, and especially to maintain a low temperature within the accumulator. In this plant in fact, the refrigerant liquid only reaches a minimum temperature of - 45" to - 50"C. Sufficient to condense only 80 to 85% of the hydrocarbon vapours present in the flow of gases, whilst the remaining percentage, which is condensable at lower temperatures, is still lost in the vapour phase.

To increase the output of this plant, it is necessary to equip it with refrigeration units of high power, cancelling therefore in part the resultant advantage of the use of accumulators of cold refrigerant.

It is an object of the present invention to obviate or mitigate the limits and inconveniences of traditional solutions set out above.

According to the present invention there is provided a condenser plant for the condensation of hydrocarbon vapours comprising a single compressor refrigeration unit of low power, an accumulator tank for cold refrigerant, a first circuit having a primary exchanger-condenser for circulation of refrigerant liquid, obtained from said tank and a second circuit having a secondary exchangercondenser fed directly by said refrigeration unit.

The refrigeration unit is constituted by a single, two-stage compressor, by a freon condenser, by two thermostatic valves, one of which feeds a tube nest evaporator for the cooling of refrigerant liquid in the primary circuit, and the other of which feeds the secondary exchanger-condenser.

Condensation of hydrocarbon vapours takes place in two successive stages: a first cooling of the gases to temperatures of - 45" to - 50"C is obtained in the primary exchangercondenser in the coil of which flows a refrigerant liquid coming from the accumulator tank; and a second cooling at temperatures of - 55" to - 60'C is obtained in the secondary exchanger-condenser, following the primary, in which there evaporates directly gaseous freon coming from the refrigeration unit.

The refrigeration unit, when the plant is not in use, feeds directly, through a suitable thermostatic valve, a tube nest evaporator where the evaporation of freon causes cooling of the refrigerant liquid of the primary circuit which flows in the coil fed by a suitable pump and which is continously taken from and sent to the accumulator tank in order to reach the operating temperature. During the operating stage of the plant the refrigeration unit, through a thermostatic valve, causes evaporation of freon to the gaseous state in the secondary exchanger-condenser, then recycling the same freon output from the secondary exchanger-condenser for cooling of the refrigerant liquid of the primary circuit.

A blower of hot gases, advantageously recovered from the output of the compressor of the refrigeration unit, effects defrosting of the exchange surfaces of the exchanger-condensers at the end of each cycle of use of the plant itself.

Further according to the present invention there is provided condenser plant for the condensation of hydrocarbon vapours comprising a single compressor refrigeration unit of low power, an accumulator-tank for cold refrigerant, a primary exchanger-condenser for circulation of refrigerant liquid, and by an activated carbon adsorption unit.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates one embodiment of a condenser plant made in accordance with the present invention and with a secondary exchanger-condenser; and Figure 2 illustrates a modified embodiment with an activated carbon adsorption unit.

Referring to Fig. 1, a condenser plant for hydrocarbons comprises a heat exchanger and condensation unit 1 for hydrocarbon vapours, an accumulator tank for cold refrigerant 2, and a low power refrigeration unit 3.

The heat exchanger and condensation unit 1 includes an input conduit 1", a primary exchanger-condenser 1' for circulation of refrigerant liquid, a freon evaporation exchanger condenser 1 tv, an output vent 1"' for residual vapours, a blower 7 for defrosting of the exchanger-condensers 1' and 1 Iv and a pump 4 for extraction of the condensed hydrocarbons, which are reintroduced in to the operating cycle. The refrigeration unit 3 includes a two-stage compressor 3", a freon condenser 3"' and two thermostatic valves 3v and 3'V, one valve 3v feeds a tube nest evaporator 3' for the cooling of refrigerant liquid contained in the accumulator tank 2 and circulated by pump 6, and the other valve 3lv feeds the secondary exchanger-condenser 1 Iv.The plant is also provided with a three-way valve 5 for control of the flow of cooling fluid in the primary circuit.

To better understand the operation of the plant there are considered two operating situations which occur during the course of a day and specifically the periods of inactivity of loading of the road tankers and the periods of use of the plant itself during the loading of the road tankers.

During the period of non use of the plant, and that is for about two-thirds of the day, the refrigeration unit 3 effects cooling of the refrigerant liquid contained in the accumulator tank 2 in order to bring the liquid to a process temperature of - 45" to - 50'C. The refrigerant liquid in this period is drawn only from the top of the tank 2 in that the three-way valve 5 allows only this flow. By means of the pump 6 the liquid is fed to the tube nest evaporator 3' where it is cooled and then the liquid returns to the top of the tank 2 where it settles in layers as a function of its temperature. This liquid is caused to circulate until it reaches the desired process temperature.The refrigeration unit 3 in this period feeds directly, through the thermostatic valve 3v the tube nest evaporator 3' where the evaporation of freon causes cooling of the refrigerant liquid of the primary circuit which flows through the evaporator 3' fed by pump 6.

During the in-use period of the plant, that is when the road tankers are being loaded, for a period of time of about 8 to 10 hours per day, the gases rich with hydrocarbon vapours are cooled in the exchanger unit 1 and the hydrocarbons condensed are extracted by the pump 4 and reintroduced into the loading cycle.The gases rich in hydrocarbons enter the exchanger unit 1 through the input conduit 1" and are cooled in two successive phases, first of all in the primary exchangercondenser 1', in the coil of which there flows the liquid cooled to a process temperature of - 45" to - 50"C obtained from the accumulator tank 2, and then in the secondary exchanger-condenser 1'V, in the coil of which the freon from the refrigeration unit 3 evaporates directly being fed through the thermostatic valve 3tv at a temperature of about - 60"C. After this the residual gaseous flow is discharged to atmosphere through the vent 1".During this phase of condensation the refrigeration liquid of the primary circuit coming from the lowest, and therefore the coldest, layers of the accumulator tank 2 pass through the exchanger-condenser 1' under the control of the three way control valve 5. This valve in fact causes mixture of the fluid output from the primary exchanger 1', with that coming from the warmest layers of the accumulator tank 2, resulting in a constant output of pump 6, which feeds said liquid through the evaporator 3', where it cools due to the gaseous freon fed from the coil of the secondary exchanger 1'V. Once the road tankers are loaded, there is effected defrosting of the surfaces of the exchanger unit, through a blower 7 which recirculates warm gases recovering heat from the output of the refrigeration compressor 3".

With the above described condenser plant very low temperatures can therefore be maintained notwithstanding the refrigeration unit being provided with a single compressor of low power and the throughput of the gaseous flows being very high, thanks to a system wherein cooling of the gases is effected in two successive stages, and in which the greater part of the cold refrigerant necessary is previously produced by the same compressor during the periods of non-use of the plant, and then stored. Thus the compressor has to produce at the time only the cold refrigerant for condensation of the last portions of the hydrocarbon vapour.

Referring now to Fig. 2 there is shown a condenser plant for hydrocarbons using an activated carbon adsorption unit.

In the condenser plant of Fig. 2 the output gases from the main exchanger-condenser are fed through conduit 4V' to an activated carbon adsorption unit constituted by two tanks 4' and 4" containing activated carbon and hav ing a ring liquid vacuum pump 4"'; of the tanks 4' and 4" one is in use whilst the other is in regeneration and this is effected through the opening and closing of four exclusion shut-off automatic valves.

The hydrocarbons still contained in the out put gases from the main condenser are treated by adsorption in the activated carbon bed of the tank in use (for example 4') and the residual air is discharged to atmosphere practically free from hydrocarbons through the vent 4V; the recovery of the hydrocarbons from the activated carbons is carried out through the creation of a vacuum in the regeneration tank (for example 4") by a liquid ring vacuum pump 4"' and then once again sent by the same pump to be condensed in the main condenser through the conduit 4'V CLAIMS

Claims

1. Condenser plant for the condensation of hydrocarbon vapours comprising a single compressor refrigeration unit of low power, an accumulator tank for cold refrigerant, a first circuit having a primary exchanger-condenser for circulation of refrigerant liquid, obtained from said tank, and a second circuit having a secondary exchanger-condenser fed directly by said refrigeration unit.

2. Condenser plant for the condensation of hydrocarbon vapours as claimed in claim 1, wherein the refrigeration unit comprises a single two-stage compressor, a freon condenser, two thermostatic valves, one valve feeding an evaporator for the cooling of the refrigerant liquid of the first circuit, and the other valve feeding the secondary exchanger-condenser.

3. Condenser plant for the condensation of hydrocarbon vapours as claimed in either preceding claim wherein condensation of hydrocarbon vapours takes place in two successive stages involving a first cooling to a temperature of - 45" to - 50'C, and a successive cooling to a temperature of - 55" to - 60"C.

4. Condenser plant for the condensation of hydrocarbon vapours as claimed in claim 3 wherein the first cooling of the gases is effected in the primary exchanger-condenser in the coil of which there flows the refrigerant liquid from the accumulator tank and the successive cooling is effected in the secondary exchanger-condenser, in the coil of which there evaporates directly freon from said refrigeration unit.

5. Condenser plant for the condensation of hydrocarbon vapours as claimed in any preceding claim wherein feed to the exchanger-condensers takes place through two separate circuits.

6. Condenser plant for the condensation of hydrocarbon vapours as claimed in any preceding claim wherein, during periods of non-use of the plant, said refrigeration unit effects cooling only of the refrigeration liquid contained in the first circuit.

7. Condenser plant for the condensation of hydrocarbon vapours as claimed in claim 6 wherein, during periods of non-use of the plant, the refrigerant liquid is taken from the warmest layers at the top of the accumulator tank by a pump fed at a constant rate by means of a control valve, and then sent to said evaporator where the liquid is cooled by means of evaporation of freon fed from the refrigeration unit through a thermostatic valve, and then returned to the accumulator tank.

8. Condenser plant for the condensation of hydrocarbon vapours as claimed in any preceding claim wherein, during use of the plant, the refrigeration unit produces at any time only the cold refrigerant for feeding the secondary exchanger-condenser, whilst the cold refrigerant necessary for feeding the primary exchanger is supplied by the accumulator.

9. Condenser plant for the condensation of hydrocarbon vapours as claimed in claim 8 wherein, during use of the plant, the refrigeration unit feeds, through said other the thermostatic valve the secondary exchanger-condenser and the freon from said exchanger is recycled in the evaporator where there falls the residual cold refrigerant from the refrigerant liquid of the primary circuit circulating in the evaporator.

10. Condenser plant for the condensation of hydrocarbon vapours as claimed in either claim 8 or 9 wherein, during use of the plant the refrigerant liquid of the primary circuit coming from the lowest layers of the accumulator tank are sent to the primary exchangercondenser, and then, on output, are mixed in a three-way control valve with fluid coming from the warmest layers from the top of the accumulator tank effecting a constant output of the supply pump which feeds said liquid to the evaporator where it is cooled by the gaseous freon output from the secondary exchanger before being re-input to the accumulator tank.

11. Condenser plant for the condensation of hydrocarbon vapours as claimed in any preceding claim wherein there is provided a blower for defrosting of the exchanger-condensers at the end of the cycle of use of the plant, which causes circulation of hot gases obtained from the heat of the output of the refrigeration-compressor.

12. Condenser plant for the condensation of hydrocarbon vapours comprising a single compressor refrigeration unit of low power, an accumulator-tank for cold refrigerant, a primary exchanger-condenser for circulation of refrigerant liquid, and by an activated carbon adsorption unit.

13. Condenser plant for the condensation of hydrocarbon vapours as claimed in claim 12 wherein said activated carbon adsorption unit includes two tanks containing carbon and a liquid ring vacuum pump, one of said tanks being in use, whilst the other is in regeneration through the opening and closing of exclusion shut-off automatic valves.

14. Condenser plant for the condensation of hydrocarbon vapours substantially as herein before described with reference to Fig. 1 of the accompanying drawings.

15. Condenser plant for the condensation of hydrocarbon vapours substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.