HAZARDOUS MATERIALS CONTROL

Hazardous Materials Control

This invention relates to a method of combating the issue of hazardous material from a pipeline, for example during a blowout at an oil well or leakage of dangerous material from a chemical plant.

Escape of hazardous material is a major danger in many industries and can result in widespread and expensive damage being caused.

The problem is potentially worse if the hazardous material is concentrated and/or under pressure.

In general, previously-proposed methods of dealing with such escapes have been aimed at combating the hazardous material after its escape while attempting to cut off its source. Thus damage can be caused by the issuing material before the source can be isolated, as the material is treated only after its escape.

According to the present invention there is provided a method of combating the issue of hazardous material from a pipeline, comprising providing the pipeline with a secondary inlet for introduction of a fluid inert to the hazardous material flowing in the pipeline, the fluid at normal temperature and pressure being a gas, and introducing said fluid into the pipeline through the secondary inlet, the introduction being made under conditions whereby the fluid expands and undergoes a temperature increase on introduction.

Pressuring means may be provided for injecting the fluid into the pipeline. A valve may also be provided in association with the secondary inlet to allow the introduction of the fluid to be started, stopped and controlled as required.

The method of this invention operates in general terms by treating the hazardous material prior to its escape from the pipeline. The treatment constitutes dilution by the inert fluid, and lowering of the hazardous material temperature and therefore, in many cases, its flash point. When a cryogenic fluid is employed the hazardous material may even be liquefied or solidified as a result of heat exchange with the fluid, thus making it easier to deal with. When it is solidified by the cryogenic fluid the solidified ma£erial can form a frozen plug in the pipeline, thus sεalingthe pipeline against further escape until the cause of the escape can be located and dealt with.

The secondary inlet may be fed with any of a number of fluids depending on the particular hazard being presented by the issuing material. For example, if the escaping material is inflammable the fluid selected would be incapable of supporting combustion, so that its injection into the pipeline would prevent ignition of the material or would extinguish any already-burning material. This particular effect would be enhanced by the cooling effect of the fluid. Alternatively, the fluid may be selected to provide in the pipeline sufficient daikition of the escaping material to reduce its concentration to below its threshold limit value, and in this case it is of advantage to use a fluid which undergoes a change of state on introduction into the pipeline, preferably from particulate solid or liquid to gas, so as to provide rapid volume expansion within the pipeline and provide fast dilution of the material. Especially advantageous fluids to introduce into the pipeline are solid carbon dioxide, liquid nitrogen, liquid helium, liquid neon, liquid argon, liquid krypton, liquid xenon and liquid carbon dioxide, and mixtures thereof. As these fluids are cryogenic it is important. to ensure that the material of the pipeline, secondary inlet and. any valves has the capability of withstanding low temperatures without failing. Stainless steel is useful in this context, and as much existing chemical plant is manufactured of this material the method of this invention can be introduced to existing plant without major replacement of pipework.

As well as introduction of the fluid directly into the pipeline, the fluid can be passed in contact with the pipeline wall before introduction into the pipeline, thereby providing initial heat exchange between the fluid and the hazardous material through the pipeline wall. To this end an annular conduit can be provided around a portion of the pipeline and communicating with the secondary inlet, the inner wall of the conduit being formed by the pipeline wall.

A. proportion of the fluid can also be fed to a cooling unit within the pipeline for cooling purposes, and this unit may be an annular passageway which allows heat exchange through its wall without greatly impeding the normal flow of material through the pipeline.

In this specification and the accompanying claims the term "pipeline" is used to describe any conduit for passage of material. The hazardous material is material which presents a problem, whether to the environment or to health or in any other manner, on escape from the pipeline.

The invention in its aspects can be used, for example, in the following situations, with especial regard to oil wells: 1. Blow-out wild well control,

1.1 land based exploration and production oil rigs,

1.2 offshore based exploration and production platforms,

1.2.1 concrete platforms situated on the sea bed,

1.2.2 steel platforms situated on the sea bed,

1.2.3 semi-submersible platforms,

1.2.4 drill ships,

1.2.5 sub sea completions,

2. Leakages of hazardous chemicals with toxic, pyrophoric, flammable or explosive properties whilst under conditions of storage, transfer, physical processing or chemical processing,

2.1 inert fluids, 2.1.1 cryogenic liquids - for example:- neon, argon, 2.1.2 cryogenic gases - for example:- neon, argon, 2.1.3 inert liquefied gases - for example:- krypton, xenon, carbon dioxide,

2.1.4 inert gases - for example:- krypton, xenon, carbon dioxide,

2.2 non-inert materials, 2.2.1 cryogenic liquids - for example:- oxygen, hydrogen, carbon monoxide,

2.2.2 cryogenic gases - for example:- oxygen, hydrogen, carbon monoxide,

2.2.3 liquefied flammable gases, 2.2.3. 1 liquefied natural gases - for example:- methane, ethane,

2.2.3. 2 liquefied petroleum gases - for example:- propane, butane,

2.2.3. 3 other liquefied flammable gases - for example:- acetylene, ammonia, ethylene, propylene, vinyl chloride

2.2.4 flammable liquids, 2.2.4.1 petroleum spirits with flash points less than 22.8°C - for example:- motor gasoline, aviation fuel, unrefined crude oils, toluene, benzene, naphtha,

2.2.4.2 highly flammable liquids with a flash point between 22°C to 32°C - for example:- xylene, naphtha,

2.2.4.3 non-petroleum derived flammable liquids with flash points less than 22.8°C:- for example diethyl ether, ethanol, methanol, acetone,

2.2.4.4 other flammable liquids with flash points above 32°C

- for example:- kerosene, dissel, styrene,

2.2.5 liquefied toxic gases - for example:- chlorine, ammonia sulphur dioxide,

2.2.6 toxic gases - for example:- chlorine, ammonia, sulphur dioxide, hydrogen sulphide,

2.2.7 flammable gases -for example:- vapourised LNG's, LPG's HFL'S, petroleum spirits etc.,

2.2.8 hazardous chemical liquids and gases,

2.2.9 materials at or above their autoignition temperature and which may be in the liquid or gaseous phase, 2.2.10 materials contained under pressure and which may be in the liquid or gaseous phase,

2.2.11 materials being processed under unit operations,

2.2.12 materials being processed under continuous operations,

3. Leakage of the above groups of toxic/pyrophoric/flammable/ explosive materials from - for example:- petrochemical works, refineries, oil platforms, tank farms/storage depots, rail tank wagons, road tankers, marine vessels, aeroplanes, advanced gas cooled reactors, pressurised water reactors, fast breeder reactors and pipelines.

The method of the invention is especially effective when the fluid has low-boiling point and high vapour, liquid-vapour or solid-vapour expansion ratio.

The invention can be used with regard to: (a) preventing the ignition of flammable concentrations of vapours or aerosols;

(b) controlling the leakage of any hazardous material by either liquefaction and/or solidification; and

(c) diluting any gaseous or volatile hazardous material to below its respective threshold limit value or T.L.V. prior to complete dispersal to the atmosphere.

The first of these may involve the injection of an inert cryogenic liquid or liquefied inert gas into any line leaking flammable concentrations of vapour or aerosols. This requires the use of a low temperature liquid injection valve. Alternatively the injection of an inert cryogenic gas or inert gas into any line leaking flammable concentrations αf vapour or aerosol requires the use of a gas injection valve capable of operation at low temperatures.

These two types of valve would thereby permit injection of an inert cryogenic liquid, liquefied inert gas, inert cryogenic gas or inert gas directly into the leaking hazardous material prior to release, so that the vapourising inert cryogenic liquid or liquefied inert gas would both cool and inert the escaping release, through starving the hazardous material of oxygen, whilst the inert cryogenic gas or inert gas would inert the escaping release mainly by starving the fuel of oxygen, and additionally cool the escaping release should its temperature be sufficiently below the temperature of the escaping release.

Technology currently exists whereby a down-hole valve below the Christmas-Tree on an oil rig, situated between an outer annulus and the main well-pipe, will allow drill-mud to be pumped directly into a blow-out in an attempt to overcome the main pressure of the well. This type of arrangement can be adapted for the injection of fluid by the method of this invention directly below the Christmas-Tree on any oil-well, whether on a platform, a sub-sea completion or on land, so that in the event of a blow out, the possibility of an ignition is greatly reduced. Further, by the injection of an inert cryogenic liquid, liquefied inert gas, inert cryogenic gas or inert gas, a blow-out that has iynited can be safely extinguished.

Similar injection devices may be installed at selected parts of all hazardous chemical installations etc., in order to control any potentially hazardous release.

At present, technology exists for utilising liquid nitrogen to solidify the material in a pipe in order to facilitate the removal of a section of pipe from between two solidified plugs of material. This has been achieved by placiny an annulus around the pipe which will contain the liquid nitrogen and thereby allow a frozen plug of material to form on the inside of the pipe to form an effective seal.

Within the ambit of the present invention the inert fluid, for example cryogenic liquid, liquefied inert gas, inert cryogenic gas or inert gas may be pumped into an existing facility that form an integral part of the pipelinp before and/or after the fluid injection facility, in order to effect the formation of a plug of material that will form an effective seal and thereby allow appropriate measures to be taken in order to control the material, once the plug of material is allowed to melt under controlled conditions.

Where the pipeline does not require to be open, as in the case of a drill-pipe, an inner annulus may be incorporated in order to increase the surface area available for the cooling effect of these inert liquids or inert gases.

Additionally, facilities may be provided for permitting the interchange of inert cryogenic liquids, liquefied inert gases, inert cryogenic gases and inert gases in circumstances where the additional cooling properties of a lower boiling inert material whether liquid or gaseous may replace a higher boiling inert material, whether liquid or gaseous, in order to provide an effective plug of material for sealing the pipeline. There should also preferably be provision for a reverse procedure to allow controlled melting once the sealing operation has been successfully completed. These procedures can permit the reduction of operating costs through the use of the most cost effective material.

Under certain conditions of temperature and pressure, flow restriction may be necessary in order to permit an effective seal to be formed and maintained. However, installation of a correctly sized fluid injection and cooling unit should alleviate the need for substantial flow restriction, except in cases where prior operating conditions have been grossly exceeded.

The invention can also employ the large dilution effects achieved by the injection of inert cryogenic liquids, liquefied inert gases, inert cryogenic gases and inert gases into any pipeline leaking gaseous or volatile hazardous material prior to the point of release, through either a low temperature liquid injection valve or a gas injection valve, thereby effecting the dispersal of these materials to the air at concentrations below their threshold limit values. The dispersion would be effective for any material irrespective of the actual vapour density, when compared to that of air.

As a result of this invention it is possible to control leakages of all known hazardous materials, for example toxic, pyrophoric, flammable or explosive, through the use of specially designed low temperature liquid injection valves for use with either inert cryogenic liquids or liquefied inert gases, or specially designed gas injection valves for use with inert cryogenic gases or inert gases. These valves permit the injection of inert fluid directly into a leaking line prior to the point of release. Benefits which can be obtained are:-

( a ) inertion of flammable gases and liquids.

(b) Extinction of flammable gas and liquid fires.

(c) Condensation of gaseous or volatile hazardous materials.

(d) Solidification of gaseous or volatile hazardous materials.

(e) Dispersion of gaseous or volatile hazardous materials.

Also as a result of this invention leakages of hazardous material can be controlled, whether toxic, pyrophoric, flammable or explosive, through the use of combined inner and outer annulus cooling units, located before and/or after an injection unit to produce the liquefaction and/or solidification of these hazardous materials by the circulation of cryogenic fluids such as helium within the cooling unit. Where the pipeline has to be maintained with a specific orifice, as in the case of drill pipe then the cooling unit preferably consists solely of an outer annulus.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which :

Fig. 1 shows a schematic layout for a pre installed annulus valve used for well-killing by the method of this invention, located in a tubing pocket.

By using standard well-head kill-line connections, a fully developed blow-out can be killed by pumping an inert low-temperature fluid, for example liquid nitrogen as kill material down an annular passageway between an outer casing 2 and a pipeline 3 carrying the oil flow, through the pre-ins tailed annular valve 4 directly into the pipeline 3. The valve 4 is such that it can open from the annulus 1 to the pipeline 3 under a positive pressure difference, thereby allowing the inert kill material to be fed directly into the blow-out flow. The valve 4 in this embodiment is similar to conventional chemical injection valves and may be located at any predetermined level within the well, where it is thought to be most effective. Ancillary equipment can be pτovided so that the well killing operation can be initiated as soon as possible followiny the blow-out. Valves 5 are_^ provided for controlling the flow of the kill-material to the annulus 1.

The pipeline 3, outer casing 2, valves 5, annulus valve 4 and ancillary equipment are fabricated from materials capable of withstanding the range of temperatures to be encountered during this operation.

Fig. 2 shows a schematic layout for a pre installed annulus kill-valve together with dual inert liquid/inert gas cooling units for use on any other type of line leaking hazardous materials; and

Figs.3(a) and (b) are respectively a schematic side section and plan section of an inert liquid/inert gas cooling unit of Fig. 2.

In Fig. 2 the annulus valve 4 is disposed between cooling units 6, the valve 4 and units 6 being fed by pipes 7 leading from a common source of liquid helium. The cooling units are shown in more detail in Fig. 3, from which it can be seen that the liquid helium is fed through the pipe 7 into an outer annulus 8 surrounding the pipeline 3, and thence through passageways 9 to an inner annulus 10 within the pipeline 3 and spaced from its wall. Flow of the helium through the annuli 8, 10 is ensured by an exhaust pipe 11 leading to a recycling plant for recooling the helium. The flow of low-temperature helium through the annuli 8,10 cools the oil and gas in the pipeline 3 thereby slowing or stopping its passage. At the same time liquid helium is supplied directly into the pipeline 3 through the annulus valve 4 to cool and dilute the flow as the helium vaporises and expands.

As the mixture of helium, gas and oil issues from the end of the pipeline 3 the predominance of the helium prevents ignition or continued burning by isolating the combustible flow from the air.

Modifications and improvements may be made without departing from the scope of the invention.