EP0906548A1

EP0906548A1 - Cooling device for condensation of oil fractions during oil transport on tankers

Info

Publication number: EP0906548A1
Application number: EP97918438A
Authority: EP
Inventors: Carl Jorgen Rummelhoff; Jorund Bakke
Original assignee: Kvaerner Maritime AS
Current assignee: Moss Maritime AS
Priority date: 1996-05-06
Filing date: 1997-05-06
Publication date: 1999-04-07
Also published as: AU2654397A; WO1997042454A1; NO961825A; KR20000010938A; NO301443B1; NO961825D0; AU706988B2; JP2000509805A

Abstract

A cooling plant with a refrigerating machine (18), in which a coolant is refrigerated and supplied to a consumer thereof and subsequently returned to the refrigerating machine (18). According to the invention, the cooling plant (14) comprises a storage tank (20) for collecting coolant which has been refrigerated in the refrigerating machine (18), and a return tank (22) for collecting heated coolant from the consumer.

Description

Cooling device for condensation of oil fractions during oil transport on tankers

The invention concerns a cooling device as specified in the introduction to claim 1. In the Standard Handbook for Mechanical Engineers, Marks, 1916, 8. edition, a cooling device is described where brine is used as a cold-carrying fluid. The capacity of this unit's refrigerating machine is so great that during operation in day-time, in addition to the continuous cooling requirements of a consumer it can also effect a cooling of brine in a storage tank and accumulation of surplus cold therein. At night-time when the cooling requirement is reduced, the refrigerating machine can be stopped and the cooled brine in the storage tank is pumped to the consumer. In this known installation the refrigerating machine's capacity is at least as great as the current cooling requirement at any time. A continuous operation of the refrigerating machine is therefore not considered to be necessary or economically justifiable. The consumer, however, receives a continuous supply of the cold-carrying fluid.

An installation of this kind where the refrigerating machine has such a large capacity that it alone can effect condensation of evaporated oil during loading would not be economically justifiable in connection with condensation of oil fractions during the loading of oil in large tanks in tankers since the cooling and thereby the power requirements during the short period when the installation is in use during loading are so great that it would entail a substantial increase in the capacity of the power supply on board the vessel. In this case the refrigerating machine, which would then be the most expensive component in the installation, would have to be dimensioned for an output which is only required during approximately 1% of the installation's lifetime.

The object of the invention is to provide a device of the type mentioned in the introduction which is not encumbered by the above-mentioned disadvantages.

The characteristics of the device according to the invention are presented in the characteristic features indicated in the claim. The invention will now be described in more detail with reference to the drawing whose only figure is a schematic block diagram which illustrates a device according to the invention.

As illustrated in the figure a device for condensation of oil fractions during oil loading on a tanker comprises a pipe 2 via which, e.g., a gas containing several fractions, at least some of which have to be condensed, is passed to a first heat exchanger 4. This heat exchanger 4 may in the known manner comprise a first passage 6 which, e.g., is composed of an inner compartment in a housing 8 of the heat exchanger 4, and a second passage 10, which is composed of a pipe or the like, which extends in the inner compartment.

A coolant is supplied via a supply pipe to the second passage 10 of the heat exchanger 4 from a cooling plant 14 and passed back to the cooling plant 14 via a return pipe 16. The cooling plant 14 compπses a refrigerating machine 18. In the supply pipe 12 between the refrigerating machine 18 and the first heat exchanger 4 there is provided a storage tank 20 for refrigerated coolant, and in the return pipe 16 there is provided a return tank 22 for heated coolant, i.e. coolant which has been used for cooling in the heat exchanger 4.

Gas fractions which have been condensed in the first heat exchanger 4 are passed to a collecting tank 24 from this heat exchanger 4 via a pipe 26. Gas fractions which have not been condensed in the first heat exchanger 4 are passed via a pipe 28 to a second heat exchanger 30. Like the first heat exchanger 4, this heat exchanger 30 has a first passage 32 which is composed of an inner compartment in a housing 34, and a second passage 26 which is composed of a pipe or the like which extends in the inner compartment. The pipe 28 communicates with an inlet end of the second passage 36 of the second heat exchanger 30, and the outlet end of this passage 36 leads, e.g., into the open air via a pipe 38.

Gas from the pipe 2 may be supplied to the first passage 32 by the second heat exchanger 30 via a pipe 40. In this pipe there is provided a shut-off valve 42 which, e.g., is electrically operated. The temperature of the fluid which flows in the pipe 38 from the second passage 36 of the second heat exchanger 30 may be established by a temperature sensor 44, which via an electrical cable 46 can emit an impulse to the shut-off valve 42 for operation thereof. If the temperature is less than a predetermined threshold temperature corresponding to the condensation temperature for one of the fractions of the gas, the valve is opened. If the temperature is greater, the valve is closed.

Condensed gas in the second heat exchanger 30 can flow to the collecting tank 24 from the first passage 32 via a pipe 48.

The device works as follows.

During, e.g., loading of oil in tanks of tankers some of the oil evaporates. If this vapour, hereinafter called gas, is permitted to flow directly out into the open air from the tank, the gas may cause pollution of the air, in addition to which valuable oil is lost.

Attempts are therefore made to condense the gas by means of the device according to the invention. For this purpose the gas is passed via the pipe 2 to the first passage 6 of the heat exchanger 4, where some fractions of the gas condense and flow to the collecting tank 24. Heat energy from the remaining fractions of the gas, however, is transferred to the coolant, thus causing it to be heated and these fractions to be cooled.

Release of these fractions into the open air, however, would entail a waste of the energy which has been used in the cooling plant.

The non-condensed fractions from the first passage 6 of the first heat exchanger are therefore supplied to the second passage 36 of the second heat exchanger 30 from which the fractions can flow out into the open air. If, however, the temperature of these non-condensed fractions is less than a threshold temperature corresponding to the condensation temperature for at least one of the gas fractions in the pipe 2, the non-condensed fractions will be capable of effecting condensation of this fraction. If the temperature thus falls below this threshold temperature, an impulse is emitted by the temperature sensor 44 for opening of the shut-off valve 42, whereupon gas can flow to the first passage 32 of the second heat exchanger via the pipe 40.

The fraction or fractions of the gas which are thereby supplied to the second heat exchanger 30 and there condensed are passed to the collecting tank 24 via the pipe 48. The use of the first coolant has thereby been optimised. Since the period for the loading of oil only constitutes a small part of the time during which the ship is in operation, a cooling plant which is only employed during loading will in the first place only be used for a short time during each voyage. If the cooling plant's refrigerating machine 18 hereby has the same output as the output which is necessary during the above- described condensation during oil loading, i.e. can remove a thermal quantity per time unit from the coolant corresponding to the thermal quantity which the coolant absorbs from the gas, in the second place the refrigerating machine 18 needs to be used only during loading, while it can be stopped during the greater part of the voyage, which is uneconomical.

The cooling plant 14 therefore comprises the storage tank 20 which has a capacity which is at least great enough to enable it to contain the amount of coolant which is necessary for condensation of the gas during loading. The return tank 22 has a similar capacity. The cooling machine 18, however, has an output which is small enough to enable it to run continuously during the entire voyage, but nevertheless great enough to enable it to have filled the storage tank 20 before loading with at least the quantity of cooling fluid which is consumed during loading.

The cooling machine 18 can therefore be very small. Thus the production, operating and maintenance costs can also be small.

Claims

PATENT CLAIM

A cooling device for condensation of oil fractions during oil transport on tankers, comprising a refrigerating machine ( 18) for refrigeration of a coolant, a storage tank (20), a heat exchanger (4) where refrigerated coolant is heated, a collecting tank (22), from which the coolant flows in consecutive order to the refrigerating machine (18), to the storage tank (20), to the heat exchanger (4), to the collecting tank (22) and from there back to the refrigerating machine (18), characterized in that the storage tank (20) is arranged to contain the amount of coolant which is necessary for condensation in the heat exchanger (4) of substantially the entire quantity of oil fractions which evaporate during loading of oil on board the ship, that the collecting tank (22) is arranged to contain the corresponding amount of heated coolant after the condensation, while the refrigerating machine's (18) cooling capacity is only sufficient, during continuous operation of the cooling machine (18) during the voyage, to effect a cooling of the amount of coolant which can be contained in the storage tank (20), to a temperature which is sufficiently low for condensation of the oil fractions.