AU645898B2 - Low aromatic diesel fuel - Google Patents

Description

OPI DATE 15/09/92 p AOJP DATE 29/10/92

INTERNATIC

APPLN. I9 13235 92 PCT NUMBER PCT/Allq2/00083 -ATY (PCT) (51) International Patent Classification 5 (11) International Publication Number: WO 92/14804 1/08, C10G 45/44, 7/08 Al 21/00 (43) International Publication Date: 3 September 1992 (03.09.92) (21) International Application Number: PCT/AU92/00083 (81) Designated States: AT, AT (European patent), AU, BB, BE (European patent), BF (OAPI patent), BG, BJ (OAPI (22) International Filing Date: 26 February 1992 (26.02.92) patent), BR, CA, CF (OAPI patent), CG (OAPI patent), CH, CH (European patnt), CI (OAPI patent), CM (OAPI patent), CS, DE, DE (European patent), DK, Priority data: DK (European patent), ES, ES (European patent), Fl, PK 4805 26 February 1991 (26.02.91) AU FR (European patent), GA (OAPI patent), GB, GB (European patent), GN (OAPI pateot), GR (European patent), HU, IT (European patent), JP, KP, KR, LK, LU, (71) Applicant (for all designated States except US): CENTURY LU (European patent), MC (European patent), MG, ML OILS AUSTRALIA PTY LIMITED [AU/AU]; 2 Hol- (OAPI patent), MN, MR (OAPI patent), MW, NL, NL land Street, Wickham, NSW 2293 (European patent), NO, PL, RO, RU, SD, SE, SE (European patent), SN (OAPI patent), TD (OAPI patent), TG (72) Inventor; and (OAPI patent), US.

Inventor/Applicant (for US only) LEEMING, Philip, Joseph [GB/AU]; 106 Scenic Drive, Merewether Heights, NSW 2291 Published With international search report.

(74) Agent: GORDON, Glen, Howard; Davies Collison Cave, With amended claims and statement.

Level 10, 10 Barrack Street, Sydney, NSW 200 (AU).

(54)Title: LOW AROMATIC DIESEL FUEL (57) Abstract The invention concerns an improved fuel for use in diesel engines, which comprises mainly a mixture of hydrocarbons containing not more than I by volume of aromatic type hydrocarbons. Preferably the fuel also contains less than 0.05 by weight of sulphur or sulphur compounds, and essentially no petroleum waxes. Additionally described are methods of producing this fuel, as well as the use of the fuel to reduce unwanted emissions and to improve operational performance.

64 .i 8 LOW AROMATIC DIESEL FUEL 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 a& 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: Aliphatics or open chain hydrocarbons, also known as paraffins, of the formula q,1CH 2 S: either straight or branched chain.

S

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

I)118470883:002/VMI -2- Aromatics, or the benzenoid series, examples of which are benzene, toluene, ethylbenzene, and xylene.

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 significant 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.

*e 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 S preferred that the fuel of the invention contains no, or very little, petroleum waxes. In some instances, there are advantages in using a fuel that contains reduced levels or even no naphthenes.

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osBo^Ts lO* w D118/470883:002/VMJ -3- 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 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, /470883...2 Y\ DW/8470883:002/VMJ -4resulting in cleaner combustion. This 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 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.

Another preferred feature of the invention is a diesel fuel as discussed above that has reduced levels, or very little or no naphthenes in the mixture. Such fuels contain mostly paraffinic hydrocarbons, and very little aromatic and naphthenic hydrocarbons. As shown in the example. that follow, and as summarised in Table 2, it is preferred that the fuel contains less than about 25% naphthenes (Example 3 has 23.6%) more preferably less than about 4% naphthenes (Example 1 has Diesel fuel composition can still contain normal levels of naphthenes, but lower naphthene levei fuels can provide extra advantages S. in some circumstances.

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i 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.

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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.

I: The improved fuel of the present invention can be produced in several ways such as: ;a 6 IY18/470883:002/VNM 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.

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, substantially no petroleum waxes and reduced proportions or no naphthenes, 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 removed) or are converted to naphthenes 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, petroleum waxes, or naphthenes.

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

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)0 I118/470883:002/VM i t &1 TABLE I Ppeqt unit Limits Test Method AAsh (by mass) 0.01 (max) ASTM D482-1P4 Carbon Residue 0.05 (max) or ASTM D524-1P14 (on 10% residuumn) (by mass) 0.04 (max) ASTM D189-IP13 Cetane Index (calculated) (min) ASTM D976 Cloud Point 0 C -10 (max) ASTM D2500-1P219 Cold Filter 0 C -10 (max) IP309 Plugging Point Copper Corrosion (3h at 100-C) lb (max) ASTM D130-1P154 Density (at 15 OC) Kg/I 0.76 to 0.83 ASTM D1298-1P160 Distillation a recovery) 325 (max) ASTM D864I23 recovery) (max) ASTM D86-IP 123 Flash Point 0 C (min) ASTM D93-1P34 Oxidation Stability mg/lOO mL, 5 (max) ASTM D2274 Sulphur (by mass) 0.05 (max) ASTM D129-1P61; or ASTM D2622; or ASTM D2785; or Water (by vol) 0.05 (max) ASTM D95-1P74 Sediment (by mass) 0.01 (max) ASTM D473-1P53

OR

Water Sediment (by vol.) 0.05 (max) IASTM D1796-1P75 I ASTM D2709 .00.

.0.

0 0 0 Viscosity Kinematic 40 OC Mm 2 /S 1.4 to 4.0 ASTM D4145-IP71I U1/47fl81OO2VM -7- TABLE 1 (continued) PROPERTY UNIT LIMITS TEST METHOD Aromatic (by vol.) 1.0 (max) ASTM D1319 Hydrocarbons or F.T.I.R. compared to toluene Distillation °C Range 180 (min) ASTM D86-IP123 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 Also, it is preferred that the fuel contains less than 25% naphthenes or preferably less than 4%.

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 fiom highly refined and chemically treated paraflinic hydrocarbon feedstock to produce a predominantly paraffinic hydrocarbon mixture containing kow concentrations of naphthenic hydrocarbons and not more than 1% by volume concentration of aromatic type hydrocarbons.

1i8/4,170883:002/VM Exmple 2 The -fuel in this Example is derived from highly refined and chemically treated feedstocks to produce a predw~nantly paraffinic/naplithenic; hydrocarbon mixture containing not more than 1% by volume concentration of aromatic type hydrocarbons.

Exampe This fuel is a mixt-re of Examples 1 and 2.

TABUE 2 PROPERTY EXAMPLE NUMBER 1 2 3 Density 15 TC (ASTM D1298) 0.772 0.792 0.782 Distillation OC) (ASTM D86) initial Boiling Point 187 188 187 10% Recovery 199 197 19()8 20% Recovery 202 200 200J Recovery 1 205 201 202 40% Recovery 209 203 205 50%/ Recovery 213 205 208 60% Recovery 218 208 212 70% Recovery 225 211 217 80% Recovery 232 217 223

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p p p p. pp p p p p p p p *pp.

p p pp pp..

p p p.

p p p p *ppp p WY814708831OO2VM -9- TABLE 2 (Continued) PROPERTY EXAMPLE NUMBE R 1 2 3 Recovery 239 222 232 Final Boiling Point 255 249 252 Recovery by Distillation C/o Volume) (ASTM D86) 98 98 98 Flashpoint OC (ASTM D93) 70 69 69 Ash Content rn/rn) (A.,STM D482) <0.01 <0.01 <0.01 Carbon Residue (on Residuum) (ASTM D524) 0.025 0.025 0.02.1 Cetane Index (Calculated) 61 50 (ASTM D976) Cloud Point C) (ASTM -12 -15 -13 D2500) Cold Filter Plugging Point (1P309) <-15 <-18 <-16 Copper Corrosion (3h at 100 OC) (ASTM D130) la la la Oxidation Stability (rng/lO0rnl) (ASTM D2274) <5.0 <5.0 0 Sulphur p.p.rn. I 1 1 I1/4170883:002/VMJ TABLE 2 (Continued) PROPERTY EXAMPLE NUMBER 1 2 3 Water Sediment volume) <0.05 <0.05 <0.05 (ASTM D1796) Kinematic Viscosity 40 °C 1,6 1.5 1.6 Hydrocarbon Type Analysis vol) (Infra-Red) Aromatic Hydrocarbons 0.1 0.7 0.4 Naphthenic Hydrocarbons 3.6 41.5 23.6 Paraffinic Hydrocarbons 96.3 57.8 76.0 petroleum waxes content none* none* none* *Note: The petroleum waxes content was determined as being consideration of cold filter plugging point and the cloud point.

undetectable by r Example 4 The advantages achievable by practice of this invention were demonstrated in a sequential series of engine tests in which a 6.234 litre MWM 916-6 diesel engine mounted to a 400 KW Test Automation eddy current type dynamometer Model FE 600 was used. The system was operated using the following Standards Australia test methods as general guides; AS 3584 1991 Diesel Engine Systems for Underground Coal Mines, Appendix C- Dynamometer Testing of Diesel Engine Systems; AS 2789.1 1985 Internal Combustion Engines Performance, Part 1 Engines for Land, Rai,- Traction and Marine Use Standard Reference Conditions and Declarations of Power, Fuel Consumption and Lubricating Oil Consumption. In these tests, the six fuels exhibiting the physical and chemical characteristics described in Table 3 were run using the conventional Standard Diesel Fuel as a baseline comparison.

D?18/470883:002/VMJ 11 In all instances the quantities of oxides of nitrogen (NOX), carbon monoxide (CO) and particulates emitted in the raw exhaust by the engine when operated at full load and at a constant rated speed of 2,500 r.p.m. (maximum engine speed 2,710 were measured and integrated. The results of these engine tests are summarised in Table 4.

The values shown herein for NOX, CO and Particulates are presented in terms of grams per kilowatt per hour. Thus the lower the value the lower the rate and amount of emissions.

e o *o f18/470883:O~C2VMJ 7 *4 *S S* S 12 TABLE 3 Standard Property Unit Diesel Fuel MEliel MF Fuiel Fuel EF4 Riel EF5 Fuel Ashi (nrn) 0.005 0.005 0.005 0.005 0.005 0.005 Carbon Residue (on 10% residuum) (rn/rn) 0.1 0.05 <0.05 0.05 0.05 0.05 Cloud Point 0 C -6 -46 -42 -50 -2 -42 Cold Filter Plugging Point "C -5 -45 -46 -35 -4 A4 Cetane Index 47 47 51 61 64 52 Copper Corrosion (3 h at 100'C) la la. la la la la.

Density (at 15-C) kg'L 0.851 0.804 9.789 0.784 0.797 0.789 Distillation (at 90% recovered) Initial Boiling Point 321 229 219 185 215 229 245 255 26.5 273 283 195 201 203 205 207 209 211 214 196 201 202 203 204 205 207 208 195 204 207 211 215 224 229

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181 200 2?09 221 233 244 256 269 219 196 201 202 203 204 205 207 208 4 a 13 TABLE 3 (Continued) Standardi Property Unit Diesel Fuel M~ Fuel EFu iel ME Fuel EF4 Fuel EF5 Fuel 70% 294 218 210 234 283 210 80% 307 222 214 239 299 2141 90% 321 229 219 244 318 219 95% 344 235 225 249 225 Final Boiling Point 352 260 253 266 338 253 Flash Point (PMCC) 0 C 70 71 69 72 70 Oxidation Stability mg/L 5 5 3 4 2 2 Sulphur Content 0.1708 0.001 0.05 0.005 0.0047 0.0001 wax content at -10'C below Cloud Point ,or at-15 0 C (MlM) 2.8 0.1 0.1 0.1 6.3 0.1 Water and Sediment 0.001 0.001 0.001 0.001 0.001 0.001 Kinematic Viscosity (at 401C) Mm 2 /S 2.95 1.54 1.49 2.31 2.39 1.49 Aromatic Hydrocarbon 24.6 14.3 0 0 7.5 0 Paraffric Hydrocarbon 40.4 34.1 38.4 0 62.5 40.2 ISO-PaafinIc Hydrocarbon 8 22.4 1 15.3 100 12.51 151 Naphthenic, Hydrocarbon (vlv) 27 -29.2 46.3 L 0 17.51 44.81 14- TABLE 4 Standard EF1 EF2 EF3 EF4 Diesel Fuel Fuel Fuel Fuel Fuel Fuel Carbon Monoxide 2.349 2.233 2.385 1.251 1.485 1.496

(CO)

Oxides of Nitrogen 13.404 13.346 13.173 11.387 13.404 13.039 (NOX) as NO, Total CO NOX 15.753 15.579 15.558 12.638 14.889 14.535 Emissions Particulates 1.380 0.984 0.723 0.389 0.948 0.711 p p

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p

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It can be observed from Tables 3 and 4 that the following trends in exhaust emissions occur and these appear dependent upon the fuel sulphur content, paraffin waxes content and hydrocarbon types present together with their concentration and distribution.

Fuels containing the highest levels of sulphur, paraffin waxes, aromatic type hydrocarbons and naphthenic type hydrocarbons tend to produce the highest concentrations of CO, NOX and particulates in the exhaust gases.

(ii) Fuels containing very low levels of sulphur, paraffin waxes and aromatic type hydrocarbons, but which contain up to 45% v/v naphthenic type hydrocarbons, the remainder being paraffinic type hydrocarbons, tend to produce lower levels of CO, NOX and particulates in the exhaust gases, th n the fuel types described in (iii) Fuels contaiing low levels of sulphur, aromatic type hydrocarbons and naphthenic type hydrocarbons, but which contain high levels of paraffin waxes produce lower levels of CO, similar levels of NOX, but higher levels of particulates in the exhaust gases than the fuel types described in (ii).

ID8/470883:002/VM 15 (iv) Fuels containing very low levels of sulphur, paraffin waxes, aromatic type hydrocarbons and naphthenic type hydrocarbons, which are predominantly v/v) paraffinic type hydrocarbons, produce the lowest levels of CO, NOX and particulates in the exhaust gases.

A summary of our findings with regard to diesel fuel characteristics and factors which can influence exhaust emissions for both gaseous and particulate matter is described in Table TABLE Fuel Modification CO NOX Particulates Reduce Sulphur 4 0 ,to Reduce Aromatic Hydrocarbons 4 -lo 44 Reduce Paraffin Waxes 44 44 44 Reduce Naphthenic Hydrocarbons 44 44 44

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S

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*5

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Key: 0 No effect ,tO Small decrease or no effect 44 Decrease 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.

DU18/470883:002/VMI

Claims (2)

16- The claims defining the invention are as follows: 1. A fuel for use in diesel engines characterized by containing not more than 1% by volume of aromatic hydrocarbons and not more than 0.05% by weight of sulphur and/or sulphur compounds. 2. The fuel of claim 1 which is further characterized by containing substantially no petroleum waxes. 3. A fuel for use in diesel engines having the specification shown in Table 1. 4. The fuel of claim 1 or claim 2 which is further characterized by containing less than by weight of naphthenes. The fuel of claim 4 which contains less than 4% by weight of naphthenes. 6. A method of producing a fuel for use in diesel engines which contains not more than 1% by volume of aromatic hydrocarbons and not more than 0.05% by weight of sulphur and/or sulphur compounds, by: refining or re-refining and chemical processing conventional fuel to remove or convert the aromatic hydrocarbons present until said hydrocarbons are not more than 1% of S said fuel, or straight-run fractional distillation of hydrocarbon feedstock to produce said fuel, said feedstock containing not more than 1% by volume of aromatic hydrocarbons, or fractional distillation or refining and chemical processing conventional hydrocarbon feedstocks to produce a feedstock containing not more than 1% of aromatic hydrocarbons, and then straight-run fractional distillation of said hydrocarbon feedstock to produce said fuel, or mixing or blending the products from or and, if necessary removing sulphur and/or sulphur compounds until not more than 0.05% by weight of said sulphur and/or sulphur compounds remain, b 470883 002NMJ bi 470S83 002/VMJ

17- 7. The method of producing a fuel of claim 5, which has an additional step of removing petroleum waxes until substantially none of said waxes remain or not allowing said waxes to be present. 8. The method of claim 6 or claim 7, which has an additional step of removing naphthenes until less than 25% by weight of said naphthenes remain, or only allowing said naphthenes to be present in an amount of less than 9. A method of reducing unwanted emissions when operating diesel engines, which comprises using a fuel in said engines in accordance with any one of claims 1 to 3. A fuel substantially as herein described with reference to any one of Examples 1 to 3, or to Table 1 or Table 2. DATED this 10th day of September, 1993. CENTURY OILS AUSTRALIA PTY LTD By its Patent Attorneys i: DAVIES COLUSON CAVE 0 o 0/f8/470883:002/VM ABSTRACT The invention concerns an improved fuel for use in diesel engines, which comprises mainly a mixture of hydrocarbons containing not more than 1% by volume of aromatic type hydrocarbons. The fuel also contains less than 0.05% by weight of sulphur or sulphur compounds. Preferably the fuel contains essentially no petroleum waxes and less than by weight (more preferably less than of naphthenes. Additionally described are methods of producing this fuel, as well as the use of the fuel to reduce unwanted emissions and to improve operational performance. 4 4 QoII BoO *o S 0 0 4 *o 4 rr" I o* 0S 4 *04 00 4400 0 S 4 4 *0 0 4** •o* D(8/470883:002NVM Inter. onal Application No. PCTIAU 9200083 INTERNATIONAL SEARCH REPORT I. CLASSIFICATION OF SUBJECT MATTER (if several dlasiflcation symbols apply, indicate alil) According to International Patent classification (IPC) or to both National Classification and IPC Int. CI. 6 C10L 1/08, C10G 45/44, 7/08, 21/00 II. FIELDS SEARCHED Minimum Documentation Searched 7 Classification System Classification Symbols IPC C10L 1/08, C10G 45/44, 7/08, 21/00 Dcumentation Searched other thin Minimym Dog entation d to the uoet thsu ocuments aro ncluded in the ie ls earched s AU IPC as above III. DOCUMENTS CONSIDERED TO BE RELEVANT' Category' Citation of Document, 1' with indication, where appropriate of the relevant passages 12 Relevant to Claim No 13 X GB,A, 1306646 (GHEORGHE RADULESCU et &1 14 February 1973 (1,5,8) Y (14.02.73 See entire document (2,4,6) P,Y AU,A, 80371/91 (ETHYL PETROLEUM ADDITIVES INC) 16 January (1-2,4,6,8) 1992 (16.01.92) page 2, lines 30-31, page 3, lines 1-3, claims 1,2 Y US,A, 2366490 (GOULD H. CLOUD et al) 2 January 1945 (02.01.45) claims 1-4 A US,A, 3668112 (LEVIC PARKER et al) 6 June 1972 (06,06.72) A US,A, 3668113 (BERNARD WHITING BURBIDGE et al) 6 June 1972 (06.06.72) S Special categories of cited documents 10 Later document published after the international filing date or priority date and not in conflict Document defining the general state of the art which Is With the application but cited to understand the not considered to be of particular relevance principle or theory underlying the invention earlier document but published on or after the document of particular relevance; the claimed international filing date invention cannot be considered novel or cannot be document which may throw doubts on priority claim(s) considered to involve on inventive step or which is cited to establish the publication date of document of particular relevance; the claimed another citation or other special reason (as specified) Invention cannot be considered to Involve an document referring to an oral disclosure, use, inventive step when the document is combined exhibition or other means with one or more other such documents, such document published prior t the international filing date combination being obvious to a person skilled in but later than the priority date rcaimed the art document member of the same patent family IV. CERTIFICATION Date of the Actual Completion of the International Search Date of Mailing of this International Search Report 1 June 1992 (01.06.92) 0 Jun2 n n International Searching Authority Signature of Authorized Officer AUSTRALIAN PATENT OFFICE B. BOURKE "S "B e.a Frm PCTAPS2101 l"cod she) ljanuwy 19861