GB2375056A

GB2375056A - Apparatus and method for removing volatile contaminants from thermal oil

Info

Publication number: GB2375056A
Application number: GB0200907A
Authority: GB
Inventors: Richard Geoffrey John Franklin
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-01-25
Filing date: 2002-01-16
Publication date: 2002-11-06
Anticipated expiration: 2022-01-16
Also published as: GB0101917D0; GB0200907D0; GB2375056B

Abstract

Thermal heating oil is introduced into a cavity 4 of a vessel 3 through a pipe 10 where it is sprayed into the cavity 4. That spraying causes volatile contaminants present in the oil to be vaporised. Decontaminated oil is discharged through an egress pipe 14 to be returned to the thermal oil system. Contaminants leave through an egress pipe 24. Decontamination apparatus and methods of removing volatile contaminants from thermal oil are disclosed.

Description

Improvements relating to oil decontamination and method therefor Technical field of the Invention This invention relates to oil decontamination apparatus and a method of decontaminating oil, in particular apparatus and methods for decontaminating thermal oil.

The invention further extends to apparatus and methods for decontaminating thermal oil in situ without the need to shut down the heating system.

Background to the invention Thermal oil, otherwise known as heat transfer oil, is used in many processes whereby prolonged periods of heating are required at constant temperatures. In particular thermal oil is used in process heating such as cooking vessels, ovens and chemical processes, for instance as oil baths or in heating oil jackets for performing chemical reactions at elevated temperatures. Typically in such systems and processes the thermal oil is required to be heated to an elevated temperature and continuously pumped around a piping system at this elevated temperature.

The use of thermal oil at such elevated temperatures has certain advantages over conventional hot water or steambased systems. A particular advantage of thermal oil over hot water/steam-based systems is that thermal oil does not require the application of high pressures in order to attain elevated temperatures above 100 C. High pressure equipment is relatively expensive to purchase and the

equipment used is thermal oil heating processes is generally cheaper.

Thermal oil systems suffer from certain disadvantages over conventional water-based systems. Typical thermal oils include minerals oils distilled from crude oil and as such are flammable materials. Common mineral oil used in thermal oil-based heating systems include BP TRANSCAL N, SHELL THERMIA B and ESSOTHERM 500, which all have auto ignition temperatures of around 3500C. During prolonged heating of such mineral oils, build up of volatile materials can occur.

As volatile compounds are produced, the flashpoint of the mixture decreases, and in some cases can fall as low as around 50 C. The lower flashpoint coupled with the high operating temperatures further exacerbates the fire and/or explosion risks.

The fire and explosion risks posed by the lowering flashpoints leads to users needing to replace the entire oil content of the system periodically to minimise problems-in a typical 8000 litre heating oil system, the cost of replacing the oil can be in the order of tens of thousands of pounds per year.

Replacing the entire oil content of a system can also bring the system off-line for the length of time it takes to change the oil. The new oil must then be heated to operating temperature, which further increases the time for which the system must be off-line.

In some industrial scale chemical reaction processes, even a short period of time off-line can lead to substantial losses in revenue.

After the degraded oil has been removed there is also a problem in the environmentally acceptable disposal of the oil, in such large quantities.

It is therefore an object of the present invention to reduce at least one of the problems described above, or other problems.

Summary of the invention According to a first aspect of the present invention there is provided a thermal oil decontamination apparatus comprising a decontamination vessel having contaminated oil ingress means and decontaminated oil egress means, and wherein the apparatus further comprises means for the removal of one or more volatile contaminants of the oil from the vessel.

By volatile contaminant, we include a volatile compound having a tendency to pass into the vapour state at the operating temperatures of the apparatus. Such volatile compounds include hydrocarbons with a vapour pressure equal to or greater than 0. lmm Hg. It will be appreciated that removal of the one or more volatile contaminants of the oil includes removal of volatile contaminants which are only partly vaporised at the operating temperature of the apparatus. When the vapour portion of the contaminant is removed, the equilibrium of the volatile contaminant shifts, forming more vapour from the remaining portion of

the contaminant, which vapour can then be removed. It will be appreciated that not all of the or each contaminant may be removed.

The apparatus may include egress means from the vessel for the or each contaminant.

I Suitably the contaminated oil ingress means comprises an ingress conduit in fluid communication between the vessel and a thermal oil system. Preferably the ingress conduit is arranged to deliver thermal oil to the vessel at an elevated pressure or at an elevated temperature, for instance above ambient temperature, or both.

The apparatus preferably comprises means to adjust the flow rate of oil to the vessel. Suitably the flow rate adjustment means of the ingress means comprises a flow valve. The flow valve may, alternatively or additionally be arranged to allow complete cessation of the flow of oil into the vessel. Alternatively or additionally the ingress means may comprise a separate flow shut-off valve.

Advantageously the oil ingress means extends into the cavity defined by the vessel.

Suitably the vessel is a generally sealed vessel.

Preferably the vessel is constructed from any suitable material which can withstand elevated pressure. Preferably the vessel has a volume capacity of at least 200 litres, more preferably at least 500 litres, most preferably at least 1000 litres.

The decontaminated oil egress means may comprise an egress conduit in fluid communication between the vessel and the thermal oil system.

The egress means preferably comprises means to adjust the

flow rate of oil from the vessel. Suitably the flow rate , adjustment means of the egress means comprises a flow valve. The flow valve is preferably arranged to allow complete cessation of the flow of oil from the vessel.

Alternatively or additionally the egress means may comprise a separate flow shut-off valve.

Suitably the means for the removal of one or more contaminants from the contaminated oil comprises means for the vaporisation of at least part of the or each volatile contaminant and alternatively or additionally means for the egress of said the or each volatile contaminant from the vessel.

The apparatus may be arranged to operate such that oil ingresses into the vessel under conditions wherein the or part of this oil remains in a substantially liquid state within the vessel whereas the, or part of the or each volatile contaminant present is in a substantially gaseous state within the vessel. Preferably the oil entering the vessel is at a temperature of at least 100oC, more preferably at least 150 C, most preferably at least 2000C.

Preferably the oil entering the vessel is at a temperature of no more than 350 C, more preferably no more than 3250C and most preferably no more than 300 C.

In order to further effect conditions whereby the oil remains in a substantially liquid state within the vessel

whereas the or each volatile contaminant present remains in a gaseous state within the vessel, the oil ingress means preferably further comprises a restricted diameter aperture in fluid communication with the cavity formed by the vessel, such that oil entering the vessel may be in the form of a mist or spray.

, Suitably the volatile contaminant vaporisation means may further comprise at least one oil deflection member, such as a baffle or a flange, connected to or integral with the internal surface of the vessel. Preferably there is a plurality of oil deflection members.

Preferably the means for the egress of volatile contaminants from the vessel comprises a volatile contaminant egress conduit. Suitably the volatile contaminants egress means comprises means to adjust the flow rate of volatile contaminants from the vessel.

Preferably the volatile compound adjustment means of the volatile compound egress means comprises a flow valve.

Suitably the flow valve may, alternatively or additionally be arranged to be able to effect complete cessation of the flow of volatile compounds from the vessel. Alternatively or additionally the volatile contaminant egress means may comprise a separate volatile contaminant shut-off valve.

The volatile contaminant egress means may be connected to waste disposal means. Preferably the waste disposal means may comprise a vessel such as a waste tank. Suitably the volatile contaminant egress means is connected to a volatile contaminant liquefying means which is in turn connected to the waste disposal means. Preferably the

volatile contaminant liquefying means comprises a condenser, more preferably a water condenser.

Thus in use, volatile contaminants passing through the volatile contaminant egress means may pass through the condenser, and the volatile contaminants will be condensed from substantially gaseous form to substantially liquid form within the condenser before entering the waste tank in substantially liquid form.

Suitably the waste disposal means comprises a drainage means for draining the or each volatile contaminant, from the waste disposal means, which drainage means may be in the form of a drainage valve.

The decontamination vessel may further comprise means for the ingress of an inert gas into the cavity formed by the vessel. Suitably the inert gas ingress means comprises an inert gas ingress conduit in fluid communication between the cavity of the vessel and an inert gas storage device.

Preferably the apparatus includes means for the adjustment of the flow rate of the insert gas into the cavity of the vessel. Suitably the inert gas flow rate adjustment means comprises a flow valve. Suitably the flow valve is arranged to be able to effect complete cessation of the flow of inert gas into the vessel if required.

Alternatively or additionally the inert gas ingress means may comprise a separate inert gas flow shut-off valve.

Preferably the inert gas is at an elevated pressure.

Suitably the inert gas is nitrogen gas.

Although the applicant is not limited by any theoretical explanation, it is believed that the introduction of an inert gas helps in the removal of volatile compounds as follows.

As the oil enters the cavity of the vessel and any volatile contaminants are vaporised,'the inert gas such as nitrogen gas may be introduced into the cavity of the vessel via the inert gas ingress means. As the gas continues to fill the void space in the cavity of the vessel, the pressure in the vessel increases. The increase in pressure serves to further retain the oil in a substantially liquid state. The inert gas within the cavity helps to effect the egress of the vaporised volatile contaminants from the vessel, through the volatile contaminants egress means. It will be appreciated that the inert gas will also leave the vessel by way of the volatile contaminants egress means, either as the elemental gas or in a volatile contaminant-inert gas mixture, and be transported to the waste disposal means.

Suitably the decontamination vessel further comprises means for the emergency egress of gases and/or oil from the vessel. The emergency egress means may comprise an emergency egress conduit in conjunction with a safety valve. The safety valve may be arranged in use to move from a first position in which the egress of gases and/or oil through the emergency egress conduit is prevented, to a second position in which the emergency egress conduit is opened to allow egress of gases and/or oil. Suitably the safety valve is a pressure sensitive valve, arranged to move from the first position to the second position, when

the pressure inside the vessel attains a prescribed limit.

Alternatively the safety valve may be a temperature sensitive valve, arranged to move from the first position to the second position when the temperature inside the vessel attains a prescribed limit.

Suitably the apparatus comprises means for adjusting the temperature and/or pressure inside the vessel.

The apparatus may comprise one or more sensing means arranged to sense at least one parameter selected from temperature, pressure, vapour volume, liquid volume and fluid ingress and egress rates.

Preferably the decontamination apparatus further comprises means for sampling oil within the vessel to determine the degree of contamination of the oil. Suitably the sampling means comprises one or more oil sample egress conduits and one or more oil sample ingress conduits in fluid communication between the vessel and suitable diagnostic apparatus. The diagnostic apparatus may include flashpoint determination apparatus, auto ignition temperature determination apparatus, gas sensing apparatus and the like.

Suitably the decontaminated oil egress means comprises an oil egress conduit in fluid communication between the vessel and the thermal oil system. Preferably the oil egress conduit is connected to a pump arranged to pump oil from the vessel, through the oil egress conduit and to the thermal oil system. Thus the thermal oil may be decontaminated in the decontamination vessel and returned to the thermal oil system for use in the relevant process.

According to a second aspect of the invention there is provided a decontamination apparatus as described herein, arranged to be connected to a thermal oil system, wherein connection is effected during normal operation of the thermal oil system.

Thus connection is effected without'the need to shut down or slow down the thermal oil system, and thus the flow of the thermal oil to and from the relevant process of the system can continue unhindered.

According to a third aspect of the invention there is provided a method of removing one or more volatile contaminants from thermal oil, the method comprising exposing thermal oil to conditions in which contaminants can be separated, separating at least some of the volatile contaminants from the oil and returning the decontaminated oil to a thermal oil system.

The method may comprise determining the level of contamination of a thermal oil by monitoring the amount of contaminated and decontaminated oil. The method may comprise monitoring the amount of volatile contaminants in the oil.

The method may comprise using the conditions of a thermal oil system, such as the heat in that system, to create at least part of the conditions at which contaminants and oil can be separated.

The method may comprise causing at least part of the oil in a thermal oil system to pass through a region where contaminants are separated from the oil. The method may

comprise selectively causing the oil to pass through that region.

The method may comprise selectively attaching and detaching means to cause separation of contaminants from contaminated oil to a thermal oil system whilst the thermal oil system is operating.' Preferably the method further comprises the steps of condensing the or each gaseous volatile contaminant into a liquid state after removal from the decontamination apparatus.

Suitably the method further comprises the step of introducing an inert gas into the apparatus, before, during or after introduction of the oil to the apparatus.

The present invention includes any continuation of features or limitations as herein referred to including a method of removing contaminated compounds from thermal oil when using apparatus as herein referred to.

Brief description of the drawings For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawing, in which: Figure 1 illustrates a vertical cross-section of a preferred embodiment of the thermal oil decontamination apparatus of the invention.

Description of the preferred embodiment A preferred thermal oil decontamination apparatus comprises a decontamination vessel 2 in the form of a closed tank. The decontamination vessel comprises means to adjust the pressure of the cavity 4 within the vessel 2, by way of pressure pump 6, and also includes means to adjust the temperature of the cavity 4 within the vessel 2, by way of a thermostat 8 connected to suitable heating and/or cooling apparatus (not shown).

Thermal heating oil from a thermal oil system is introduced into the cavity 4 of the vessel 3 through a contaminated oil ingress means in the form of oil ingress pipe 10, which in use is arranged to be connected to a thermal oil system (not shown) such as a central heating system or a system for heating reaction ingredients in an industrial chemical process. The oil ingress pipe includes oil flow rate adjustment means in the form of flow valve 12. The flow valve 12 can be operated to adjust the flow rate of oil entering the vessel 2, and if necessary can be oriented to completely stop the flow of oil down the oil ingress pipe 10 into the vessel 2.

The vessel includes decontaminated oil egress means in the form of an oil egress pipe 14. The oil egress pipe 14 is arranged in use to carry decontaminated oil from the vessel 2 back to the thermal oil system which the decontamination apparatus is connected to. Included on the oil egress pipe 14 is an oil egress flow adjustment means in the form of a flow valve 16. The flow valve 16 can be operated to adjust the flow rate of decontaminated oil leaving the vessel 2 via the oil egress pipe 14, back

to the thermal oil system. The flow valve 16 can also be operated to completely stop the flow of oil from the vessel 2 down the oil egress pipe 14. Also connected to the oil egress pipe 14 is a pump 18. The pump 18 operates to draw decontaminated oil from the vessel 2 down the oil

egress pipe 14 and to the thermal oil system. The I operation of the pump 18 can be altered to increase or decrease the rate of flow of oil from the vessel 2 down the oil egress pipe 14, and this may be operated separately to or in conjunction with the flow valve 16.

Inert gas ingress means are provided on the vessel 2 in the form of an inert gas ingress pipe 20, which extends into the cavity 4 of the vessel 2. In use, an inert gas such as nitrogen gas is pumped from a gas storage facility (not shown), such as a gas tank or cannister, down the gas ingress pipe 20 into the cavity 4 of the vessel 2. The gas ingress pipe 20 includes a gas flow adjustment means by way of a flow valve 22. The flow valve 22 is operated, in use, to adjust the rate of flow of the inert gas from the gas storage facility down the gas ingress pipe 20. If necessary, the flow valve 22 can be operated to completely stop the flow of gas down the gas ingress pipe 20.

In order to remove any gaseous chemicals from the cavity 4 of the vessel 2, such as gaseous volatile contaminants removed from the oil, the inert gas, or mixtures thereof, a volatile compound egress means is provided in the form of gas egress pipe 24, connected to the vessel 2. The gas egress pipe 24 is provided with a means to adjust the rate of flow of gas from the vessel 2, in the form of flow valve 26, which can also be operated to completely stop

the flow of gas from the vessel 3 down the gas egress pipe 24.

The end of the gas egress pipe 24, is connected to a gas condensing means in the form of a water-cooled condenser 28. The water-cooled condenser 28 is equipped with a water inlet pipe 30 and a water outlet pipe 32 which allow water to flow round the water-cooled condenser. The water inlet 30 and outlet 32 pipes are equipped with flow valves 34 for adjusting the rate of flow of water round the condenser 28. The condenser 28 is connected to a waste tank 36 via an intermediate pipe 38. The waste tank, in use, collects the condensed volatile contaminants and inert gas which pass out from the condenser 28 and through intermediate pipe 38.

The decontamination vessel 2 includes a number of subsidiary features for monitoring the process of decontamination within the cavity of the vessel 2. An oil sample egress outlet 40 is provided, which in use enables samples of oil, which have passed into the cavity 4 of the vessel 2, to be transported to diagnostic equipment (not shown) in order to determine the state of contamination of the oil. Suitable diagnostic equipment for determining contamination of the oil could include flashpoint determination apparatus, auto ignition temperature determination apparatus and such like. After the sample has been tested, it can be discarded or returned to the vessel 2 through a sample ingress inlet 44. Both the egress outlet 40 and ingress inlet 44 are provided with flow valves 42 and 46 respectively, which are operated to allow the required sample volume to be withdrawn from and returned to the vessel 2.

The vessel 2 also comprises outlet pipes 48 and 50, which are connected to sensing devices (not shown), in order to determine various parameters of the oil and gaseous compounds within the cavity 4 of the vessel 2. Suitable sensing devices include temperature sensors, pressure sensors, and specific chemical sensors. Outlet pipes 48 and 50 include flow valves 52 and 54 respectively which are operated to allow oil and/or gaseous compounds to be transported to the sensing devices via pipes 48 and 50.

In order to avoid a dangerous build up of gases, vaporised volatile contaminants and/or oil within the cavity 4 of the vessel 2, the vessel 2 is provided with a safety valve 56. The safety valve in use is designed to sense when a dangerous level of gases and/or oil has built up within the cavity 4 of the vessel, at which point the safety valve automatically opens to allow gas and or oil to vent back to the thermal oil system via a venting outlet 58 which in turn is connected to the thermal oil system via the oil egress pipe 14. The safety valve 56 therefore reduces the chance of any fire or explosion within the cavity 4 of the vessel 2. Once the levels of gas, volatile contaminants and/or oil returns to acceptable levels within the cavity 4, the safety valve 56 automatically closes to prevent any further venting of material back into the thermal oil system.

A typical operation of the decontamination apparatus illustrated in Figure 1 will now be described.

The decontamination apparatus can be detachably secured directly to a thermal oil system via the oil ingress pipe

19 and oil egress pipe 14. The apparatus is designed so that the thermal oil system does not need to be shut down during connection or removal of the apparatus, and during operation of the apparatus. The oil ingress pipe 10 and oil egress pipe 14 can be connected to the thermal oil system by any suitable means including to outlets and inlets already present on the thermal oil system.

After the decontamination apparatus has been connected, contaminated oil from the thermal oil system is allowed to flow through the oil ingress pipe 10, by opening the flow valve 12 on the oil ingress pipe to achieve the desired flow rate. In typical thermal oil systems the oil coming

from the system will be at a temperature of about 200oC- 300*C. The oil flows through the oil ingress pipe 10 until it reaches the distal end of the ingress pipe 10.

The distal end 11 of the oil ingress pipe 10 comprises an opening within the cavity 4 which allows oil to be sprayed into the cavity 4. The distal end 11 is formed such that oil leaving the oil ingress pipe 10 is sprayed into the cavity under elevated pressure compared to the oil running through the thermal oil system. The elevated pressure can be achieved by any suitable means such as a restricted diameter aperture in the distal end 11, or use of a spray head. As the oil is sprayed into the cavity 4 at elevated temperature and pressure volatile contaminants present in the oil become vaporised, evaporating off from the oil.

The decontaminated oil then drops to the bottom of the decontamination vessel 2. A series of baffles 60 may be placed within the decontamination vessel 2, which serve to further aid in vaporising any volatile contaminants mixed with the oil by necessitating impact of the oil on the baffles 60 as the oil falls to the bottom of the vessel 2.

The pressure pump 6 and thermostat 8 can also be used to optimise conditions for the evaporation of volatile contaminants from the oil within the vessel 2.

At this point the vessel 2 will contain vapour in the form of gaseous volatile contaminants. These volatile contaminants may leave the vessel by'way of the gas egress pipe 24. The flow valve 26 on the gas egress pipe 24 is opened to allow any vapour within the cavity 4 of the vessel 2 to leave. In order to aid the egress of the gaseous volatile contaminants, an inert gas such as nitrogen is pumped into the cavity 4 through the inert gas ingress pipe 20. The flow valve 22 on the inert gas ingress pipe 20 is opened into the vessel 2. As the gas enters the vessel 2 it rises to the top, mixing with any vaporised volatile contaminants present, bringing those compounds to the top of the vessel 2 also. The inert gas, volatile contaminants and mixtures thereof then leave through the gas egress pipe 24.

All the gases leaving the vessel 2 through the gas egress pipe 24 travel through a water condenser 28. The water condenser 28 acts to cool down the gases and liquefy the gaseous volatile compounds passing through. The resultant liquid and any inert gas present, pass through the condenser 28, through intermediate pipe 38 and into the waste tank 36. When the waste tank 36 becomes full the waste can be drained into a suitable disposal container through drain pipe 62, via the flow valve 4 present, on the pipe.

The oil which collects at the bottom of the vessel 2 is recycled back to the thermal oil system by way of an oil

egress pipe 14, and a pump 18. The flow valve 16 on the oil egress pipe 14 is opened to allow oil from the vessel 2 to enter the oil egress pipe 14. The pump 18 is activated to provide suction which assists in the removal of oil from the vessel 2, down the oil egress pipe 14. The oil egress pipe 14 is connected at one end to the thermal oil system, and the oil moving down the oil egress pipe 14 is eventually returned to the system.

If there is a dangerous build up of gases within the cavity 4 of the vessel 2, or the oil level in the vessel rises too high, the vessel can be vented via a venting outlet 58 which is controlled by a flow valve 56. The flow valve 56 can be opened to allow material to leave the vessel 2 and travel down the venting outlet 58, which is connected to the thermal oil system via the oil egress pipe 14. Thus the oil and/or gases flowing down the venting outlet 58 is returned to the thermal oil system. Once the level of gases and/or oil has returned to acceptable levels, the flow valve 56 is closed to prevent egress of any material down the venting outlet 58.

During or prior to operation of the apparatus the decontaminated oil which collects at the bottom of the vessel 2 maybe sampled, for instance to see if it is necessary to separate out the contaminants. A sample of oil can be withdrawn through the sample egress outlet 40, using the flow valve 42 on the outlet to control the flow.

The oil can then be tested to determine any relevant characteristics such as flashpoint, auto ignition temperature, and dissolved gases, before being returned to the vessel 2, if desired, through sample ingress outlet 44, controlled by the flow valve 46 on the outlet.

The vessel 2 also includes sensing outlets 48 and 52, controlled by flow valves 50 and 54 respectively. The sensing outlets 48 and 52 are connected to suitable sensing equipment (not shown) which is used to monitor any desired parameters within the vessel 2, such as vapour temperature, vapour pressure, specific compounds present and the like.

It will be appreciated that the apparatus can be used continuously to decontaminate thermal oil within a system, or be used to clean oil then be disconnected from the system once the decontamination process is complete, to be reconnected at a later time, if desired.

For ease of use the entire apparatus is mounted on a stage 66, which is easily transportable on a suitable vehicle.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.' The invention is not restricted to the details of the foregoing embodiment (s). The invention extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

Claims 1. A thermal oil decontamination apparatus comprising a decontamination vessel having contaminated oil ingress means and decontaminated oil egress means and wherein the apparatus further comprises means for the removal of one or more volatile contaminants of the'oil from the vessel.
2. Apparatus as claimed in claim 1 including egress means from the vessel for the or each contaminant.
3. Apparatus as claimed in any preceding claim including contaminated oil ingress means comprising an ingress conduit in fluid communication between the vessel and a thermal oil system.
4. Apparatus as claimed in any preceding claim in which the ingress means is arranged to deliver thermal oil to the vessel at an elevated pressure.
5. Apparatus as claimed in any preceding claim in which the ingress means is arranged to deliver thermal oil to the vessel at an elevated temperature.
6. Apparatus as claimed in any preceding claim comprising means to adjust the flow rate of oil to the vessel.
7. Apparatus as claimed in claim 6 in which the means to adjust the flow rate of oil to the vessel comprises a flow valve.

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8. Apparatus as claimed in claim 7 in which the flow valve is arranged to allow the complete cessation of the flow of oil into the vessel.
9. Apparatus as claimed in any preceding claim in which the ingress means comprises a separate flow shut-off valve.'
10. Apparatus as claimed in any preceding claim in which the oil ingress means extends into the cavity defined by the vessel.
11. Apparatus as claimed in any preceding claim in which the vessel is a generally sealed vessel.
12. Apparatus as claimed in any preceding claim in which the vessel has a volume capacity of at least 200 litres.
13. Apparatus as claimed in any preceding claim in which the decontaminated oil egress means comprises an egress conduit in fluid communication between the vessel and a thermal oil system.
14. Apparatus as claimed in any preceding claim in which the egress means comprises means to adjust the flow rate of oil from the vessel.
15. Apparatus as claimed in claim 14 in which the means to adjust the flow rate of the egress means comprises a flow valve.

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16. Apparatus as claimed in claim 15 in which the flow valve is arranged to allow complete cessation of the flow of oil from the vessel.
17. Apparatus as claimed in any preceding claim in which

the egress means comprises a separate flow shut-off valve. i
18. Apparatus as claimed in any preceding claim in which the means for the removal of one or more contaminants from the contaminated oil comprises means for the vaporisation of at least part of the or each volatile contaminant.
19. Apparatus as claimed in any preceding claim arranged to operate such that oil is arranged to ingress into the vessel under conditions where the or part of the oil remains in a substantially liquid state within the vessel whereas the or part of the or each volatile contaminant present is in a substantially gaseous state within the vessel.
20. Apparatus as claimed in claim 19 in which the oil entering the vessel is arranged to be at a temperature of at least 100 C.
21. Apparatus as claimed in claim 20 or 21 in which the oil entering the vessel is arranged to be at a temperature of no more than 350 C.
22. Apparatus as claimed in any preceding claim in which the oil ingress means comprises a restricted diameter aperture in a fluid communication with a cavity formed on a vessel.

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23. Apparatus as claimed in any preceding claim including volatile contaminant vaporisation means comprising at least one oil deflection member.
24. Apparatus as claimed in any preceding claim in which the means for the egress or volatile contaminants from the vessel comprises a volatile contaminant egress conduit.
25. Apparatus as claimed in claim 24 in which the volatile contaminant egress means comprises means to adjust the flow rate of volatile contaminants from the vessel.
26. Apparatus as claimed in claim 25 in which the volatile compound adjustment means of the volatile compound egress means comprises a flow valve.
27. Apparatus as claimed in claim 26 in which the flow valve is arranged to effect complete cessation of the flow of volatile compounds from the vessel.
28. Apparatus as claimed in any preceding claim including volatile contaminant egress means comprising a separate volatile contaminant shut-off valve.
29. Apparatus as claimed in any preceding claim in which the volatile contaminant egress means is connected to waste disposal means.
30. Apparatus as claimed in claim 29 in which the waste disposal means comprises a vessel.
31. Apparatus as claimed in claim 29 or 30 in which the volatile contaminant egress means is connected to a

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volatile contaminant liquifying means which in turn is connected to the waste disposal means.
32. Apparatus as claimed in claim 31 in which the volatile contaminant liquifying means comprises a condensor.
33. Apparatus as claimed in any preceding claim in which the vessel further comprises means for the ingress of an inert gas into the vessel.
34. Apparatus as claimed in any preceding claim in which the vessel comprises means for the emergency egress of gas and/or oil from the vessel.
35. Apparatus as claimed in claim 34 including a pressure sensitive safety valve arranged to move from a closed position to an open position to permit emergency egress when the pressure inside the vessel attains the prescribed limit.
36. Apparatus as claimed in claim 35 in which the safety valve is a temperature sensitive valve arranged to move from the first to the second position when the temperature inside the vessel attains a prescribed limit.
37. Apparatus as claimed in any preceding claim including means for adjusting the temperature inside the vessel.
38. Apparatus as claimed in any preceding claim including means for adjusting the pressure inside the vessel.

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39. Apparatus as claimed in any preceding claim including means for sampling oil within the vessel to determine the degree of contamination of the oil.
40. Apparatus as claimed in any preceding claim in which the oil egress means comprises an oil egress conduit in fluid communication between the vessel and a thermal oil system.
41. Apparatus as claimed in claim 40 in which the oil egress conduit is connected to a pump arranged to pump oil from the vessel through the oil egress conduit and to the thermal oil system.
42. Thermal oil decontamination apparatus substantially as herein described with reference to, and as shown in the accompanying drawing.
43. Decontamination apparatus as referred to in any preceding claim arranged to be connected to a thermal oil system in which the connection is arranged to be effected during normal operation of the thermal oil system.
44. Decontamination apparatus when connected to a thermal oil system substantially as herein described with reference to, and as shown in the accompanying drawings.
45. A method of removing one or more volatile contaminants from thermal oil comprising supplying the thermal oil to a decontamination vessel and removing one or more volatile contaminants from the vessel.

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46. A method as claimed in claim 45 comprising returning decontaminated oil to a thermal oil system.
47. A method of removing one or more volatile contaminants from thermal oil, the method comprising exposing thermal oil to conditions in which contaminants can be separated, separating at least some of the volatile contaminants from the oil and returning the decontaminated oil to a thermal oil system.
48. A method as claimed in claim 47 when using the method as claimed in claims 45 or 46.
49. A method as claimed in any of claims 45 to 48 comprising determining the level of contamination of a thermal oil by monitoring the amount of contaminated and decontaminated oil.
50. A method as claimed in claim 49 comprising monitoring the amount of volatile contaminants in the oil.
51. A method as claimed in claim 45 to 50 comprising using the conditions of a thermal oil system to create at least part of the conditions at which contaminants and oil can be separated.
52. A method as claimed in any of claims 45 to 51 comprising causing at least part of the oil in a thermal oil system to pass through a region where contaminants are separated from the oil.
53. A method as claimed in claim 52 comprising selectively causing the oil to pass through that region.

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54. A method as claimed in any of claims 43 to 53 comprising selectively attaching and detaching means to cause separation of contaminants from contaminated oil to a thermal oil system whilst the thermal oil system is operating.

j
55. A method as claimed in any of claims 45 to 54 comprising the steps of condensing the or each gaseous volatile contaminant into a liquid state after removal from a decontamination apparatus.
56. A method as claimed in any of claims 45 to 55 comprising the step of introducing an inert gas into the region where the oil is exposed to conditions in which contaminants can be separated.
57. A method as claimed in any of claims 45 to 56 comprising oil entering a cavity in a vessel having volatile contaminants vaporised whilst introducing inert gas into the vessel.
58. A method as claimed in claim 57 comprising increasing the pressure within the vessel by introducing the inert gas into the vessel.
59. A method as claimed in claim 58 in which the increase in pressure due to the inert gas serves to assist in the retention of the oil in a substantially liquid state.
60. A method as claimed in any of claims 45 to 59 comprising sampling oil within a vessel in which

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separation is occurring to determine the degree of contamination of the oil.
61. A method of removing one or more volatile contaminants from the thermal oil substantially as herein described with reference to, and as shown in the accompanying drawing.
62. A method of removing one or more volatile contaminants from thermal oil as claimed in any of claims 45 to 61 in which the apparatus is as claimed in any of claims 1 to 44.