TECHNICAL FIELD

The present invention concerns an improved fuel for use in diesel engines, composed chiefly of a mixture characterized by being of hydrocarbons containing not more than 1% by volume of aromatic type hydrocarbons.

BACKGROUND ART

It has long been recognised that there are problems in using commercially available diesel fuels in diesel engines. Of particular concern is the operation of diesel engines in poorly ventilated areas, or areas having limited ventilation such as underground mines and tunnels. The exhaust emissions produced by these diesel engines and the odour of the fuel are unpleasant to persons working in these areas and, in confined spaces, can be a health and safety hazard.

In addition, emissions produced by diesel powered vehicles or equipment are a major source of air pollution and there are moves to limit or restrict the production of emissions in line with current global environmental concerns.

It is therefore advantageous for several reasons to find a way to significantly reduce the production of such diesel exhaust emissions.

Hydrocarbon fuels, such as diesel fuels, contain three main classes of compounds:

(1) Aliphatics or open chain hydrocarbons, also known as paraffins, of the formula H- _+2/ either straight or branched chain.

(2) Naphthenes, or cycloalkanes, some examples of which are methylcyclopentane, cyclohexane, dimethylcyclopentane and methylcyclohexane.

(3) Aromatics, or the benzenoid series, examples of which are benzene, toluene, ethylbenzene, and xylene.

STITUTE SHEET

Other components may also be present, such as sulphur or sulphur compounds and petroleum waxes. Additives may be included after the refining and blending processes to produce fuels having desirable characteristics.

Conventional diesel fuels commonly contain 15% to 30% or even higher levels of aromatic type hydrocarbons, but generally between 20% to 30% of aromatic type hydrocarbons and from 0.08% to 0.5% of sulphur together with significnt levels of petroleum waxes. By reducing the amount of aromatic type hydrocarbons present to not more than 1% by volume and optionally reducing the total sulphur content to not more than 0.05% together with significant reductions in the petroleum wax content, it has been found that a considerable reduction in unwanted diesel exhaust emissions can be achieved.

DISCLOSURE OF INVENTION

The present invention is directed to a fuel for diesel engines which is more acceptable than the currently available fuels in that in use it causes fewer operational problems, is more environmentally kind and is safer, cleaner and less hazardous from an occupational health and safety aspect.

Such a fuel is one which contains not more than 1% by volume of aromatic hydrocarbons, and preferably not more than 0.05% by weight of sulphur or sulphur compounds. It is also preferred that the fuel of the invention contains no, or very little, petroleum waxes.

When conventional diesel fuels are combusted the products of combustion are typically soot, oxides of carbon, oxides of sulphur, oxides of nitrogen and water vapour together with partially combusted fuel vapour which is likely to contain aromatic and polynuclear aromatic hydrocarbons, aldehydes, ketones and other hydrocarbons. In diesel powered equipment for use in underground applications it is necessary to

remove soot, particulates, fuel vapour, acidic gases, etc from the exhaust emissions and to cool the exhaust gases prior to discharge to the atmosphere. The method currently adopted is to pass the exhaust emissions through a water filled gas scrubbing unit. However, these scrubbing units have been found to operate inefficiently for various reasons.

The content of aromatic hydrocarbons in the fuel of the present invention is not more than 1% by volume when compared to commercial diesel fuels that contain typically about 15 to 30% by volume of aromatic hydrocarbons, some of which are of the carcinogenic polynuclear aromatic variety. The fuel of the present invention is virtually free of polynuclear aromatic hydrocarbons. This reduction in aromaticity of the new fuel gives rise to improved fuel combustion efficiency resulting in exhaust emissions that are much less carcinogenic and much less polluting than conventional diesel fuel emissions.

A further preferred feature of the invention is the elimination or significant reduction of other components of conventional diesel fuel which cause either operational difficulties and or pollution when combusted in diesel engines, e.g. petroleum waxes such as paraffin and microcrystalline waxes, sulphur and sulphur compounds.

Conventional diesel fuel contains a significant amount of petroleum waxes which gives rise to poor low temperature ignition characteristics necessitating different diesel blends for winter and summer conditions. Also, incomplete combustion of the petroleum waxes gives rise to the production of solid particulate matter/soot in the exhaust emissions. The fuel of the present invention in one preferred embodiment, contains no petroleum waxes, resulting in cleaner combustion. In addition the improved fuel exhibits acceptable low temperature ignition characteristics thus avoiding the necessity to produce different blends of diesel fuel for winter and summer use.

Sulphur and sulphur compounds, when combusted, produce gaseous acidic oxides of sulphur (e.g. sulphur dioxide), which dissolve in atmospheric moisture giving rise to the formation of acid rain. When compared to conventional diesel fuel, the fuel outlined in the invention in a preferred form contains significantly lower levels of sulphur, thus effecting a consequent reduction in acidic gas emissions.

In addition the proposed fuel is more readily biodegraded than conventional fuel and of lower toxicity to marine life by virtue of its minimal content of aromatic hydrocarbons.

Also to be noted is that when the fuel of the present invention is combusted lower levels of smoke and hydrocarbon vapour are produced, thus reducing atmospheric pollution and smog formation.

The improved fuel of the present invention can be produced in several ways such as:

Refining and/or re-refining and chemical processing of conventional diesel fuel to remove or convert the aromatic hydrocarbons present, such that they do not exceed more than 1% by volume of the fuel.

By the straight run fractional distillation of hydrocarbon feedstocks containing not more than 1% by volume of aromatic hydrocarbons.

Fractional distillation, refining and chemical processing of conventional hydrocarbon feedstocks by various methods to produce feedstocks or hydrocarbon fractions containing not more than 1% by volume of aromatic hydrocarbons.

By mixing and blending products from any of the above processes.

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The above steps can be used in a similar manner to provide a fuel which also contains not more than 0.05% of total sulphur and substantially no petroleum waxes, if desired.

One of the most convenient commercial methods for producing fuel of the present invention involves the processing of a refinery feedstock whereby the aromatic species are either extracted (i.e. removed) or are converted to naphthenes (e.g. by hydrogenation) , the refinery feedstock being brought within the boiling range parameters by fractional distillation before or after treatment of the aromatic species. Similar factors apply if removing the sulphur or petroleum waxes.

It is preferred to produce a fuel or fuels of the present invention which conform to the specification shown in Table 1.

TABLE 1

PROPERTY UNIT LIMITS TEST METHOD

Ash % (by mass) 0.01 (max) ASTM D482-IP4

Carbon Residue % (by mass) 0.05 (max) or ASTM D524-IP14 (on 10% residuum) 0.04 (max) ASTM D189-IP13

Cetane Index (calculated) 45 (min) ASTM D976

Cloud Point -10 (max) ASTM D2500-IP219

Cold Filter Plugging Point -10 (max) IP309

ASTM D130-IP154

ASTM D86-IP123 ASTM D86-IP123

ASTM D93-IP34

ASTM D2274

PROPERTY UNIT LIMITS TEST METHOD Sulphur % (by mass) 0.05 (max) ASTM D129-IP61? or ASTM D2622; or ASTM D2785; or IP336

Water % (by vol) 0.05 (max) ASTM D95-IP74 Sediment % (by mass) 0.01 (max) ASTM D473-IP53

OR

Water & Sediment % (by vol.) 0.05 (max) ASTM D1796-IP75 ASTM D2709

Viscosity Kinematic @ 40°C mm ² /s 1.4 to 4.0 ASTM D445-IP71

Aromatic % (by vol.) 1.0 (max) ASTM D1319 Hydrocarbons (F.I.A.); or F.T.I.R. compared to toluene

Distillation Range (I.B.P.) 180 (min) ASTM D86-IP123 (F.B.P.) 350 (max) ASTM D86-IP123

Recovery by % (by vol) 98 (min) ASTM D86-IP123 Distillation

Note: "ASTM" is the American Society for Testing and Materials "IP" is the Institute of Petroleum (U.K.)

MODES FOR CARRYING OUT THE INVENTION

We now further describe the invention with reference to certain examples, which are non-limiting on the scope of the invention. The Examples 1, 2 and 3 of the invention as described below are covered by the above specification and would exhibit the typical characteristics as shown in Table 2.

Example 1.

The fuel in this Example is derived from highly refined and chemically treated paraffinic hydrocarbon feedstock to produce a predominantly paraffinic hydrocarbon mixture containing low concentrations of naphthenic hydrocarbons and not more than 1% by volume concentration of aromatic type hydrocarbons.

Example 2 .

The fuel in this Example is derived from highly refined and chemically treated feedstocks to produce a predominantly paraffinic/naphthenic hydrocarbon mixture containing not more than 1% by volume concentration of aromatic type hydrocarbons.

Example 3.

This fuel is a mixture of Examples 1 and 2.

TABLE 2

PROPERTY EXAMPLE NUMBER 1 2

Density @ 15 ^* C (ASTM D1298) 0.772 0.792 0.782

Distillation ( ^* C) (ASTM D86)

Initial Boiling Point

10% Recovery

20% Recovery

30% Recovery

40% Recovery

50% Recovery

60% Recovery

70% Recovery

80% Recovery

90% Recovery

Final Boiling Point

Recovery by Distillation 98 98 98 (% Volume) (ASTM D86)

Flashpoint ( °C) (ASTM D93)

Ash Content (% m/m) . (ASTM D482)

Carbon Residue (on 10% Residuum) (ASTM D524)

Cetane Index (Calculated) (ASTM D976)

Cloud Point ( ^* C) (ASTM D2500) -12 -15 -13

Cold Filter Plugging Point ( ^* C) (IP309) <-15 <-18 <-16

Copper Corrosion (3h at 100 ^β C) 1A 1A 1A (ASTM D130)

SUBSTITUTE SHEET

TABLE 2 (continued)

PROPERTY

Oxidation Stability (mg/lOOml)

(ASTM D2274)

Sulphur p.p.m. (I.C.P.)

Water & Sediment (% volume) (ASTM D1796)

Kinematic Viscosity § 40°C 1.6 1.5 1.6 (mm ² /s) (ASTM D445)

Hydrocarbon Type Analysis (% vol) (Infra-Red)

Petroleum waxes content none* none* none*

Aromatic Hydrocarbons Naphthenic Hydrocarbons Paraffinic Hydrocarbons

*Note: The petroleum waxes content was determined as being undetectable by consideration of cold filter plugging point and the cloud point.

INDUSTRIAL APPLICABILITY

The invention is of use in connection with the petroleum industry, for producing fuels for diesel engines, and for operating diesel engines in various industries, such as mining, construction and transport.