The invention relates to a method of burning a combustable substrate, incendiary compositions for use in the method and incendiary intermediates that can be used for making the compositions as well as being useable as incendiary compositions in their own right.

The method of this invention is particularly

(but not exclusively) useful for burning of pollutants for example oil spills and other substrates especially where sustained combustion is to be maintained, and is an amplification of the methods described in co-pending

Australian Applications Nos . PJ9481 and PK2006 filed by the present inventors. The present Application claims priority from said Australian Applications now assigned to ourselves and our UK Patent Application No. 902553.4.

With the advent of off-shore oil drilling and the movement of large quantities of oil by tanker, contingency plans must always remain in force for the control of major spillages of oil at sea. Control of oil spills has, in the past been restricted to physical removal of the oil, or dispersal of the oil in the water column.

Physical methods have involved the use of urethane foams to stabilize the oil such that it may be recovered manually or by means of mechanical harvesters. Alternatively, sea booms may be disposed around a spreading oil slick to prevent further spread, permitting time to recover the oil from within the boom. Disadvantages of physical methods of oil pollution control include the invariably

labour-intensiveness of the methods. Additionally, unpredictability of sea and wind conditions means that such methods may not be effective.

The use of detergent dispersants is widespread both in combination with physical methods of oil recovery and in isolation. Whilst detergent dispersants cause the break-up of oil slicks, dispersing the emulsified oil into the water column, the effects of precipitation of oil in deep water on bottom life and pelagic marine life is poorly understood. It is however, known that detergent dispersants result in a harmful residue deposited on shallow sea beds to the detriment of benthic life.

It is known that crude oil will burn. However no effective technique based on burning has yet been developed that has proved practical as a method for removal of this pollutant. Various air deployable incendiary devices were developed in the early 1980s by the Ministry of National Defence of the Government of Canada and are described inter alia in Canadian Patent

No. 1134620, British Patent No., GB-B-2092275 US Patent

No. 4,365,557 and "An incendiary device for the in situ combustion of crude oil slicks;" P Twardawa and G

Couture; Proceedings of the International Pyrotechnic Seminar; 8; p.670-692.

These known incendiary devices consist of a canister with a float that keeps the canister afloat in the oil polluted water. The canister is loaded with an incendiary composition comprising either calcium carbide

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and a metal or a metal for example aluminium or magnesium, a perchlorate oxidizing agent, a thixotropic agent and curing components typically an hydroxy polymer and an isocyanate crosslinking agent. The canister is filled with the incendiary composition and allowed to set. During the setting step, the hydroxypolymer reacts with the isocyanate to produce a polyurethane block.

These canisters are then delivered to the polluted area by aircraft and when in place, are ignited. Although these devices were developed some ten years ago and the instances of oil slick pollution have increased, the devices previously described have not come into commercial use.

We have now discovered a very simple method by which combustible substrates and in particular combustible pollutants, especially oil spillages can be burned conveniently leaving little if any residue. The method is useful for burning substrates of this type on land or on water. According to the present invention there is provided a method for burning a combustible substrate which comprises applying to the substrate an extrudible or granular incendiary composition having a temperature of combustion of at least the combustion point of the substrate, the composition comprising particulate metal, the metal being magnesium, calcium, or aluminium, and an oxidizing agent capable of supporting combustion of the metal, dispersed in an inert extrudible carrier and igniting the composition.

The method of this invention ^' is especially useful for burning crude oil including aged oil slicks where much of the volatile or light fractions have evaporated as a result of exposure to the atmosphere. The combustion temperature of the incendiary composition can be selected by appropriate formulation of the composition to be just above the combustion point of the oil slick. Experience shows that this is unlikely to be less than 150°C. In particular it is unlikely to be less than 200° or 250°C for example it can be 300° to 750°C. More particularly higher combustion temperatures that is to say temperatures in excess 1000°C ecpecially temperatures in excess of 2000°C are more effective, especially with aged oil. Suprisingly, temperatures in excess of 3000°C cause substantially complete consumption of even heavy oil slicks .

The compositions that can be used in the process of this invention are extrudible or granular so that they can be sprayed or spread upon the substrate to be burned. When the substrate to be burned is water-borne, the composition used is formulated so that it is bouyant. That is to say the composition as a whole will be less dense than water and will float on the surface of water.

In this context "extrudible" is to be understood broadly to include low viscosity liquid compositions that are capable of being sprayed through a conventional spray jet, nozzle or rose and pastes that are extrudible

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into self supporting strips from an Achemedian screw or ram extruder.

In the context of this invention also, granular compositions consist of solid granules and particularly granules that can be fluidized. Such granules can be for example from 0.125cm 3 to 5cm3.

The metal can be magnesium, calcium, or aluminium . Preferably it is magnesium or aluminium.

Generally the metal will be in particulate form for example it can be in the form of a powder or granules . Metal powders and granules within the scope of the invention have a particle size in the range 30 to

The oxidizing agent is one that supports the combustion of the metal particularly in the absence of atmospheric oxygen and allows the high temperatures called for in the method of this invention to be sustained. In particular the oxidizing agent is one that liberates oxygen (either nascent or molecular oxygen) on thermal decomposition . Examples are Group I and Group II metal and ammonium chlorates, perchlorates and nitrates and Group I metal permanganates.

In practice the Group I metal is sodium or potassium and the Group II metal is magnesium. Examples of oxidizing agents are sodium chlorate, sodium perchlorate, ammonium perchlorate, sodium nitrate, potassium nitrate, ammonium nitrate and potassium permanganate.

Preferably the oxidizing agent is sodium,

potassium or ammonium nitrate , especially sodium nitrate .

The carrier liquid consists of an inert liquid or solid diluent in which the metal and the oxidizing agent and any other optional additive can be dispersed. By an inert carrier is meant one that does not react with the metal or oxidizing agent or other optional ingredient unless the compositions is ignited.

Examples of liquid carrier are polar petroleum products for example naphthenic acid, saturated or unsaturated branched or linear C _, _fl carboxylic acids, alcohols and esters, liquid lipids and mixtures of lipids especially including natural oils particularly nut and seed oils for example coconut oil and liquid hydrocarbons particularly hydrocarbons and mixtures thereof that occur in the gasoline or kerosene hydrocarbon fractions of petroleum.

Particular examples of liquid carriers are naphthenic acid, saturated and unsaturated, branched and linear CQ _T carboxylic acids, alcohols and esters and mixtures thereof.

As used hereinafter, the term naphthenic acid should be understood in the sense that it is used in petroleum science and means carboxylic acids obtained from petroleum. The acids can be prepared in a number of ways. One convenient way is via the action of mineral acid upon the salt, especially the sodium salt. Naphthenic acids are generally mixtures the precise nature of which depends upon the origin of the crude oil

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Generally lower boiling naphthenic acids have 5, 6 or 7 carbons. An intermediate group has from 8 to 12 carbon atoms . Generally the upper limit for naphthenic acids is 22 to 23 carbon atoms. Examples of saturated C„_, _n carboxylic acids are octanoic acid, decanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic and eicosanoic acid.

Examples of mono unsaturated C« , _n carboxylic acids are undec-10-encic acid, hexadeca-8-enoic acid and octadeca-9-enoic acid.

Examϋles of di-and tri-unsaturate C 8 _Q --.,.,0,

carboxylic acids are octadeca-9 , 12-dienoic acid and octadeca-9, 12, 15-trienoic acid.

Examples of saturated C„___ alcohols are octanoi (particularly octan-1-ol and octan-2-ol), decanol, dodecanol, hexadecanol, octadecanoi and eicosanol.

Exa cies of unsaturated C O _Q — a,_S _n U alcohols are octadec-9-en-ol and octadeca-9, 12-dien-l-ol .

By C _o -, _n carboxylic acid ester is meant that the ester molecule in total contains from 8 to 30 carbon atoms. Examples of such esters are C, ,-alkyl, C ₀ __alkanoates, alkenoates and alkadienoates especially o — 2U methyl octanoate, ethyl octanoate, methyl decanoate, ethyl decanoate, methyl hexadecanoate, ethyl hexadecanoate, methyl octadecanoate, methyl undeca-10-enoate, methyl octadeca-9-enoate, and methyl octadeca-9, 12-dienoate. Other examples of such esters are C„ -, _n alkyl, alkenvl and alkadienyl-C, _^ alkanoates, especially octyl acetate, octyl propionate, decyl

Co_ _n alkanoates, alkenoates and alkadienoates especially methyl octanoate, ethyl octanoate, methyl decanoate, ethyl decanoate, methyl hexadecanoate, ethyl hexadecanoate, methyl octadecanoate, methyl undeca-10-enoate, methyl octadeca-9-enoate, and methyl octadeca-9,12-dienoate. Other examples of such esters are C„ .. alkyl, alkenyl and alkadienyl-C-, _,al anoates, especially octyl acetate, octyl propionate, decyl acetate, hexadecyl acetate, octadecyl acetate, undeca-10-enyl acetate, octadec-9-enyl acetate and octadeca-9,12-dienyi acetate.

The gasoline fraction of petroleum is a mixture predominantly of C- to C, „ linear, branched and sometimes cyclic alkanes. The mixtures have boiling points of 40 to 180°C. Linear alkanes are generally less efficient fuels than branched alkanes because they tend to burn explosively whereas the latter tend to burn more smoothly and in a more controlled manner.

Kerosine consists cf C, , and C, _ alkane hydrocarbons and is used as domestic heating and jet aviation fuel. The hydrocarbons have boiling points in the range 160° to 250°C.

Preferably the liquid carriers are non-volatile and have a boiling point in excess of 100°C. Examples of solid carriers for the compositions are inorganic and organic gel-forming materials and thickening agents .

Examples of inorganic gel-forming agents and thickening agents are aluminium hydroxide gel, silica,

natural clays and synthetic clays, ^' for example bentonites.

Examples of organic gel forming materials and thickening agents are carboxymethyl cellulose, alginic acid, algenate salts and crosslinking resin systems for example isocyanate-hydroxy resins and epoxy resins.

The compositons used in the method can also comprise additives, for example phenol to modify the rheological properties of the composition by acting as a thickener and to improve the miscibilty of the composition with the oil and oxidative catalysts, for example ferric oxide, boric acid and Group I and Group II metal borates to increase the temperature at which the composition burns. Equally the composition can comprise a retardant, especialy silica that extends the duration of combustion.

The compositions for use in this invention are novel. Accordingly the invention also provides an incendiary composition that is granular or extrudible and comprises particulate metal, the metal being magnesium, calcium, or aluminium, an oxidizing agent capable of supporting combustion of the metal and an inert solid or extrudible carrier.

Examples of particular metals, oxidizing agents and carriers have been discussed above with reference to the process of this invention.

In general, the exact make-up of a composition according to the invention depends upon the temperature of combustion the rate of burn, and the period for which

it is required that the composition should burn. Such parameters can of course be set by empirical methods.

The proportion of oxidizing agent to metal is calculated based upon the molar amount of oxygen necessary to burn the metal entirley to the metal oxide.

Where atmospheric oxygen can be expected support combustion there can be a molar excess of metal over oxidizing agent, the oxidizing agent being present to support burning initially. Where the composition has to burn entirely without atmospheric oxygen, a molar equivalent or an excess of oxidizing agent will be called for.

In practice the oxidizing agent and metal mix¬ tures will be made upon a weigh proportion basis for example 25:75 or 50:50 or 75:25% by wt oxidizing agent to metal. In the preferred combinations of this inven¬ tion (viz sodium nitrate: magnesium and sodium nitrate: aluminium) the metal is present in a molar excess.

The extrudible compositions of this invention embrace within their scope low viscosity sprayable liquids at one extreme and pastes at the other.

Low viscosity compositions according to the invention have a carrier consisting of or comprising naphthenic acid or one or more C „ to C _ _n carboxylic acid and mixtures thereof.

Where the carrier is a mixture of naphthenic acid and one or more carboxylic acids, the ratio of naphthenic acid to total C _ft to -. r. carboxylic acids is from 90:10 to 10:90% by wt.

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Particular carrier compositions comprise from 30 to 80% wt naphthenic acid and from 20 to 70% wt Co to C, _n carboxylic acid.

A particular example of such a carrier composition comprises 50% wt naphthenic acid, 25% wt octadeca-9-enoic acid (oleic acid) and 25%wt dodecanoic acid (lauric acid).

The liquid compositions referred to above can also contain other additives for example up to 40% wt of phenol. So by way of example the carrier comprises from 30 to 79% wt naphthenic acid, 20 to 30% wt Cg to C _3Q

carboxylic acid and 1 to 40% wt phenol.

A particular example of such a composition comprises 50% wt naphthenic acid, 25% wt octadeca-9-enoic acid (oleic acid) and 25% phenol.

In any of the liquid compositions referred to above or in any of the paste compositions referred to below, the liquid carrier can comprise of consist wholly of a hydrocarbon particularly gasoline or kerosine.

Gasoline and kerosine are especially useful as the or a component of the carrier when the method is to be used on aged crude oil having substantially no volatile hydrocarbon components.

Carriers for paste compositions according to this invention can consist of any of the liquid carriers as described above to which a structuring agent is added, and in particular the structuring agent can be organic gel-forming agent for example carboxymethyl cellulose, alginic acid or an algenate salt or a inorganic gel forming agent.

The proportion of structuring agent depends upon the rigidity of compositions called for, the nature of ° the structuring agent and the nature of the liquid carrier. Usually the structuring agent will not exceed

50% wt of the total carrier. Often it will not exceed

25% or 10% wt of the total carrier. The remainder is made up of the liquid carrier. ^D In the granular compositions of this invention the carrier is one that will form a solid matrix for the metal and oxidizing agent and which can be handled as fluidizable granules. Examples of suitable carriers are alginate salts, polyurethane resins and polyepoxide resins.

The amount of carrier called for in the compositions of the invention is the amount necessary to confer the physical properties, including bouyancy, necessary to allow it to be applied effectively to the 5 substrate to be burned.

Compositions to be used for burning water-borne oil slicks are formulated particularly to be bouyant

For example the metal and oxidizing agent mixture can comprise as little as 2% wt or as much as

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50% wt of the composition.

Where a low combustion temperature is called for, the composition will contain from 2 to 15% wt of metal and oxidizing agent mixture. Where higher temperatures are necessary, amounts of 20 to 50% wt especially 25 to 40% wt, are called for.

The compositions of the invention are made by a process which comprise mixing either separately or as a pre-formed mixture, a metal and an oxidizing agent as previously defined with one or more components of the carrier either separately or as pre-formed mixtures and where necessary allowing the mixure to solidify.

For liquid and paste compositions the ingredients are mixed by standard techniques so as to form a homogeneous mass. This mixing can take place at or near the point of application or it can take place in situ on the substrate.

For granular compositions, the carrier is mixed in liquid form and allowed to solidify either as a mass that is subsequently broken up into granules or in moulds from which granules can be turned out. Where the carrier is a polyurethane the metal and oxidizing agent is preferably mixed with one component that is either the polyisocyanate or polyol from which the polyurethane will be formed and the mixture so obtained is then mixed with the second component. Where the resin is a polyepoxide, the metal and oxidizing agent mixture is mixed with the resin and a crosslinking agent is then added.

Some of the carriers referred to above are novel and not only are they useful in forming incendiary compositions in admixture with metal and oxidizing agents, but form incendiary compositions in their own right.

Accordingly the invention also provides an incendiary intermediate comprising naphthenic acid in admixure with a C„ ,» carboxylic acid and/or a structuring agent. The method of burning a substrate according to this invention is put into practice by applying the composition usually to the upper surface of the substrate and then igniting it.

A key application envisaged for the method of this invention is the burning of combustible pollutants, especially oil spillages on land or on water. A frequent cause of oil pollution on land is the depositing on coastal rocks and beaches of sea-borne oil slicks . Where the composition is a liquid it can be applied by spraying either from hoses or multi-nozzle booms .

Paste compositions can be extruded in strips or as a blanket on to the substrate. Where the composition is granular, the granules can be distributed on the surface from a hopper-type spreader or can be fluidized and dusted onto the surface.

Application of the composition to a water-borne slick can be from a boat or ship for example a fire

tender or other vessel or an aircraft particularly a helicopter.

In the case of a waterborne slick, the oil can be collected and concentrated into a limited area before being burned. This is an especially useful step to take when the oil has been dispersed for example by wind or tides so that it form only a very thin layer on top of the water. Collection can be carried out by conventional mechanical gathering systems for example a 3 M fire or combustion boom. Alternatively the oil can be absorbed into a porous material for example sheeps wool and the wool and oil absorbate can be burned. A further option is to use a porous ceramics of non-combustible fabric raft that is capable of absorbing oil from water.

A fire boom as described above or raft can be towed behind a ship and the composition can be applied to the gathered or absorbed oil and ignited such that the oil so gathered or absorbed burns continuously at the rate at which it is collected.

In this particular application of the method of this invention the composition is sprayed, spread or otherwise distributed continuously onto the oil with the boom or onto the raft. The composition can be ignited by standard methods either after the substrate has had sufficient quantity of the composition applied to it or as the composition is being applied.

The composition of this invention can be applied

to the oil slick in an amount of 0.5 to 10% volume or

0.5 to 10% wt of the slick depending on the thickness of the slick and the nature of the composition.

Ignition of the composition can be achieved by manual torching or by incendiary projectile for example flares. In particular the composition can be ignited with a Hellitorch or other products for example gelled petroleum or proprietary materials such as Surefire gelling mix. Where the composition is sprayed or extruded and ignited during application, ignition can be caused by an electric spark or a pilot flame.

The following Examples illustrate the inventions . Example 1. The example illustrates the preparation of an incendiary intermediate.

An incendiary intermediate was made by blending the following components homogeneously :

Octadeca-9-enoic acid (oleic acid) 25% wt

Phenol 30% wt

Naphthenic acid 45% wt

The mixture can be used as a liquid carrier for metal and oxidizing agents or as an incendiary composition in its own right. The composition burns at a combustion temperature estimated at 500°F (260°C) ÷ 100°F ( +_ 55.6°C) and maintains combustion on a waterborn film of medium grade crude oil.

Example 2 .

(a) Incendiary Intermediate

The following example illustrates the , preparation of an incendiary intermediate.

An incendiary intermediate was made by blending together homogeneously the following ingredients:

Octadeca-9-enoic acid (oleic acid) 25% wt Dodecanoic acid (lauric acid) 25% wt

Naphthenic acid 50% wt

The incendiary intermediate is highly viscous and is capable of maintaining combustion at a temperture estimated at 500°F (260°C) + 100°F (+ 55.6°C) on a waterborn film of medium grade crude oil. (b) Incendiary Compositions

The incendiary intermediate referred to in Example 2 (a) above was blended with 4% wt of powdered magnesium and 4% of sodium nitrate.

The incendiary composition has a combustion temperature estimated at 1050°F (571.1°C) + 100 F (+

55.6°C) and maintains combustion on a medium heavy oil slick having an ignition point in the range estimated at 650 to 1150°F (343.3 to 626.7°C).

Example 3.

(a) Incendiary intermediate

An incendiary intermediate was made by blending

the following ingredients together homogeneously:

Octadeca-9-enoic acid (oleic acid) 25% Hexadecanoic acid (palmitic acid) 25% Naphthenic acid 50%

(b) Incendiary Composition

An incendiary composition was made by adding to the incendiary intermediate described in Example 3(a) above 12% wt powdered magnesium and 12% wt sodium nitrate. The composition so produced is a viscous slurry that has a combustion temperature estimated at

1700°F (926.7°C) + 100°F (+55.6 °C).

Example 4 (a) Incendiary intermediate

An incendiary intermediate was prepared by blending:

Octadeca-9-enoic acid (oleic acid) 25% wt Phenol 25% wt

Naphthenic acid 50% wt

(b) Incendiary Composition

An incendiary composition was prepared by adding to the indendiary intermediate described in Example 4(a) above 4% wt of powdered magnesium and 4% wt of sodium nitrate.

The composition so obtained has a combustion temperature estimated at 1050°F (571.1°C) + 100°F (+ 55.6°C). The composition has a high viscosity and is

capable of maintaining combustion on medium heavy crude oils having an ignition point between 65° and 1150° F

(343.3 to 626.7°C) .

_c Example 5

(a) Incendiary intermediate

.An incendiary intermediate was prepared by blending the following ingredients together to produce a homogeneous mixture: 0

Octadeca-9-enoic acid (oleic acid) 25% Phenol 25%

Naphthenic acid 50%

(b) Incendiary Composition An incendiary composition was prepared from the incendiary intermediate by mixing with it 12% by wt powdered magnesium and 12% by wt sodium nitrate. The composition so obtained is a viscous liquid slurry with a combustion temperature estimated at 1700°F (926.7°C) + 100°F (+55.6°C) and supports combustion on heavy oil slicks having an ignition point from 1150 to 1800°F (621.1 to 982.2°C) .