US2971828A - Hydrazese-containing fuel oil - Google Patents

Description

Uited States Patent 9 HYDRAZINE-CONTAINING FUEL OIL COMPOSITION Arthur V. Churchill, Oakmont, and Edward Mitchell,

Valencia, Pa., assignors to Gulf Research Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Dec. 2, 1957, Ser. No. 699,911

4 Claims. (Cl. 44-64) This invention relates to improving the combustion characteristics of hydrocarbon oil fuels that normally tend to form substantial amounts of soot and smoke during combustion.

The petroleum industry has encountered a serious problem in satisfying the demand for middle distillate and heavier fuel oils that can be burned in oil burners such as those of the atomizing type and of the rotary wallfiame type with little or no accompanying formation of smoke or soot. Oils that are normally burned in oil burners of the types indicated are those of Number 2 grade or heavier, although lighter oils can be used. Although some smoke and soot formation will normally accompany combustion of any suitable oil in burners of the types indicated, especially where less than optimum combustion conditions are used, the problem is serious in the case of oils having an API gravity less than 34, as substantial smoking and soot formation will occur during combustion of such oils, even when favorable combustion conditions are employed. The poor combustion characteristics of such oils are considered attributable to the relatively high proportion of aromatic components contained therein. Fuel oils having an API gravity of less than 34 will normally contain in excess of about 20 percent aromatics, for example, 25, 40 or even 60 percent or more of aromatic components, whereas lighter fuel oils will normally contain a substantially lower proportion of aromatics, for example, 15 percent or less. In the case of distillate oils, a high aromatics content usually signifies a large proportion of cracked distillates which are relatively rich in aromatics. The proportion of catalytically cracked distillate fuel oils in commercially marketed fuel oils has increased in recent years notwithstanding the relatively inferior burning qualities of such oils, because the demand for fuel oils of comparable boiling range has exceeded the available supply of straight-run oils.

Not only do low gravity distillate oils containing large proportions of cracked distillates, that is, oils rich in aromatics, form greater quantities of soot during combustion than straight-run, high-gravity distillate oils, or similar oils low in aromatics, but also such oils form soot of different quality. Soot formed from the latter oils is a loosely deposited, low-density material having a low coefiicient of heat transfer, whereas soot from the former oils is resinous, much denser and has a higher coefiicient of heat transfer.

While the problem of clean combustion is especially serious in the case of distillate fuels, where fuel quality is of major importance, a combustion problem also exists in the case of residual fuel oils. Similarly as the middle distillate fuel oils, the residual fuels have an API gravity less than 34 (API gravity for typical No. 6 varies in the range of to 15), and they also frequently contain exceptionally large proportions, for example percent or more, of aromatic components. Residual fuels can contain relatively low-boiling aromatic components as well as higher boiling materials, as they are frequently diluted or cut-back with lower boiling cracked distillate oils in order to reduce the viscosity of the heavier oils.

Although the combustion of fuel oils having an API gravity of less than 34, and consequently a relatively large proportion of aromatics, will tend to produce soot and smoke in various atomizing burners of conventional types, that is, burners in which the fuel oil is burned in the form of a spray of liquid droplets in admixture with air, combustion of such oils in rotary wall-flame type burners constitutes an especially severe problem. In the latter instance the fuel oil is burned after vaporization of the fuel oil by impingement thereof on a hot metal surface.

Excessive smoking and soot formation during combustion of fuel oils is objectionable not only from the standpoint of cleanliness and air pollution, but also in that smoke and soot lead to stack deposits which may reduce burner draft and/or cause the stack temperature to rise to a dangerous point.

The present invention relates to improved fuel oil compositions comprising hydrocarbon fuel oils that have an API gravity less than 34, which compositions have reduced smoke and soot forming tendencies during combustion, whereby such compositions are rendered more suitable for use as fuels in oil burners of various kinds, such as domestic heating furnaces of the atomizing or rotary wall-flame type, combustion gas turbine engines, and the like. We have found that such improved fuel compositions can be obtained by incorporating in a fuel oil of the type described and that normally tends to form smoke and soot in an atomizing type burner, a small amount of hydrazine.

The exact mechanism by which hydrazine functions to reduce smoking and sooting during combustion of fuel oils of the class disclosed has not been definitely determined, and accordingly, We do not intend the present invention to be limited to any particular theory of operation. It may be that the hydrazine reduces the ignition temperature of the oil, thus enabling more complete combustion and at the same time reducing the possibility of thermal cracking of the oil prior to combustion. On the other hand, it may be that the hydrazine causes the oil to burn at a higher temperature, thus facilitating more complete combustion. Regardless of the mechanism by which hydrazine functions in the present invention available experimental evidence shows that a definite reduction in smoke and soot forming tendencies is obtained by the use of small amounts of this material in fuel oils that normally tend to promote excessive soot and smoke for mation during combustion in atomizing type burners.

The use of unsubstituted hydrazine is important for the purposes of this invention since unsubstituted hydrazine imparts distinctly superior combustion characteristics to fuel oils containing this material.

The hydrazine is added to the fuel oils in a proportion sufiicient substantially to reduce the smoking tendencies of the oil. The optimum proportion will vary to some extent according to the nature of the fuel oil. The type of fuel oil burner employed can also affect the optimum proportion of agent to be added. Within the limits of these considerations, we have found that best results are obtained by addition to the fuel oils of small amounts of hydrazine. Thus, a noticeable improvement usually will be obtained by addition of as little as 0.02 weight percent of this material to the fuel oil, and a major improvement will be obtained by the addition of about 0.05 weight percent to the fuel oil. Normally, it will not be necessary to add the hydrazine in excess of the latter proportion, but in some cases it may be desirable to employ the hydrazine in proportions up to its solubility limit in the fuel oil. 4

Hydrazine may be incorporated in the fuel oil in'any suitable manner. Thus, it can be added to the fuel oil either as such or in the form of concentrated solutions in mutual solvents for oil and polar substances, for example, butanol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and the like. After addition of the hydrazine to the oil, some circulation of the oil is desirable to facilitate early formation of a homogeneous composition, but this is not absolutely essential.

use in vaporizing pot-type burners) and having the following inspections:

In order to demonstrate the extent of the improvement obtained with the test additive, test fuel A was also subjected to the test without addition of hydrazine.

In the following table there are tabulated the results obtained in the combustion tests described above.

Table A Smoke Disc Number at- Compositlon Avg.

8% 8. 5% 9% 9. 5% 10% 11% 12% Smoke 00; C01 C02 CO: CO; C0; 00; Spot 1. Test Fuel A 1. 80 1.70 1. 75 1. 85 2.05 2. 50 3. 10 2.11 2. Test Fuel A plus 0.05 Wt percent Hydrazine 1.40 1.00 0.85 0.80 0.90 1.35 2.00 1.19

In order to demonstrate the effectiveness of the combustion improvement agent disclosed'herein, hydrazine was incorporated in a No. 2 fuel oil that normally tends to form smoke and soot on combustion, and the thuscompounded fuel oil was tested for smoking tendencies by combustion in an atomizing type burner. The test was carried out in a domestic oil burner (Timken, Model OFH-60Hi-Furnace). Conventional burner controls were associated with the test apparatus in conjunction with electrical timer relays to provide a minute on-lO minute ofi cycle of burner operation. After permitting a warm-up of at least one 20 minute on phase of burner operation with maximum combustion air, smoke spot and CO readings were taken at the middle of each on phase for 7 cycles using different air gate settings to regulate the quantity of combustion air. Changes of gate setting were made during burner off phases of the cycle. Smoke spot readings were obtained by withdrawing flue gas from a sampling probe installed in the chimney pipe through a disc of No. 4 Whatman filter paper one inch in diameter for 2 minutes. A vacuum pump was used to maintain a pressure differential of 2 1, inches Hg across the disc. The smoke spot reading was then determined by means of a photocell meter which had been calibrated using a Shell smoke spot chart graduated in increasing shades of black ranging from zero (clean disc) to 9 (black disc) as the standard. The CO readings were obtained by withdrawing flue gas through a sampling probe installed in the chimney pipe (according to United States Department of Commerce Bulletin CS104-46) and by analyzing the flue gas for percent CG in an Orsattype flue gas analyzer.

The test fuel, hereafter referred to as test fuel A, was a commercial-type, API gravity No. 2 fuel oil having an aromatics content of about 45.5 percent and consisting of 34.1 volume percent straight run No. 2 fuel oil distillate and 65.9 volume percent catalytically cracked No. 2 fuel oil distillate, and that had been inhibited against sludge deposition.

Percentages given herein are by weight of the composition unless otherwise specified. The term No. 2 fuel oil is defined in ASTM Standards on Petroleum Products and Lubricants for November 1956 as a distillate oil for general purpose domestic heating for use in burners not requiring No. 1 fuel oil (an oil intended for The data presented in the foregoing table indicate that a marked improvement in burning qualities of fuel oils 'is obtained by incorporation therein of the combustion improvement agent of this invention. Thus, 0.05 percent hydrazine in test fuel A produced an average improvement of more than 43 percent in the smoke spot number.

The test fuel described in the foregoing test is illustrative only. Substitution of other fuels disclosed herein in the foregoing test compositions will produce similar benefits. Examples of other fuel compositions included by this invention are shown in the following table.

It is emphasized that the problem with which the present invention is concerned involves only fuel oils that are normally burned in fuel oil burners that utilize middle distillate and heavier oils and that normally exhibit severe smoking and soot forming tendencies in such usage. As indicated, such oils are those having an API gravity less than 34. The problem with which this invention is concerned is especially serious in the case of distillate fuel oils of the type described, because combustion quality is a primary consideration with such oils. Although a clean combustion problem also exists in the case of residual fuel oils suitable for use in atomizing type burners, the relatively low price of such fuels and the absence of a superior competitive fuel renders the problem less serious in the case of such oils.

In order to demonstrate the nature of the problem with which the present invention is concerned, a number of fuel oils having varying densities and aromatics contents were subjected to a combustion test substantially similar to that described above, but carried out in a Timken Vertical Rotary Wall Flame Burner, Model F,

installed in a Weil-McLain Type 4-8-19 steam boiler, in order to determine the burning characteristics of the oils. These tests were carried out at 11.0% CO in the flue gas, a recommended figure for the burner model in question. The results of the tests are presented in Table C below:

Table C Gravity, Percent Smoke Fuel Oil API Argmat- Disc No.

1. FCC N0. 2 Distillate 25. 8 42 4. 4 2. 50/50 by Vol. Eastern Venezuela St.

Run and FCC No. 2 Dist 28.0 29. 3 2. 8 3. Fixed Bed Cat. racked No. 2 Dist" 29.0 28. 7 3.0 4. TOO No. 2 Distillate 30. 9 24. 2. 2 5. 80/20 by Vol. E.V.S.R. and FCC N0.

2 Dist 32.1 23. 2 l. 3 6. TOG Rafinate 34. 5 16.3 0.6 7. 50/50 TOO Raffinate West Texas St. Run 35. 6 15.6 0. 6 8. Blend of Kerosene and Gas Oil 41. 8 13. 9 0.4 9. Kerosene 42. 6 14.0 0.7

From the results shown in the foregoing table, it will be seen that fuel oils having an API gravity of less than about 34 and an aromatics content of about 20 percent or more produce a relatively high smoke spot number which is a measure of the smoking and sooting tendencies of the oils. Even a small decrease in the API gravity of such lower gravity oils normally results in a disproportionate increase in the smoke spot rating. In contrast, oils having a gravity above 34 API produced a low smoke spot number and little difference in smoke spot number resulted despite substantial differences in API gravity.

Aside from its value as a combustion improvement agent in oils of the type described, hydrazine has especial value when employed in combustion-improving proportions in mixtures of straight-run and catalytically cracked distillate fuel oils where the ratio of catalytically cracked to straight-run distillate is in the range of about 9:1 to 1:9 by volume. Such oils present an especially severe problem with regard to sludge deposition during storage. It has been found that hydrazine not only improves the combustion characteristics of such oils but also the stability thereof.

In order to demonstrate the effectiveness of hydrazine in the foregoing respect, a blended distillate fuel oil of the type indicated and normally tending to deposit sludge during storage, and containing a small amount of hydrazine, was subjected to an accelerated stability test. The accelerated test was carried out by storing a 4-ounce glass bottle of the oil in the dark for 24 hours at 210 F. At the conclusion of the test the oil sample was shaken and the quantity of sludge visually rated according to the scale: none, trace, light, medium, heavy.

The test oil, hereinafter referred to as test oil B, was a No. 2 fuel oil consisting of a mixture of 40 percent by volume doctor-sweetened, West Texas straight run No. 2 fuel oil distillate, 40 percent by volume of light, fluid catalytically cracked gas oil boiling in the No. 2 fuel oil range, and 20 percent by volume of a Thermofor catalytically cracked gas oil boiling in the No. 2 fuel oil range. The mixture had an API gravity of 321 and an aromatics content of 37.8 percent.

In order to afford a basis for comparison a sample of test oil B containing no hydrazine was also subjected to the same test.

The results of the foregoing stability test are set forth in Table D, following:

The foregoing data demonstrate the stabilizing effect of hydrazine on blended catalytically cracked and straight run distillate fuel oils.

If desired, the fuel oil compositions of this invention may contain in addition to the compounds previously discussed, oxidation inhibitors, corrosion inhibitors, antifoam agents, ignition quality improvement agents, sludge inhibitors, color stabilizers and other addition agents adapted to improve the oils in one or more respects.

Obviously, many modifications and variations of the invention as herein described may be resorted to without departing from the spirit or scope thereof. Therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A fuel oil composition comprising a major amount of a hydrocarbon heating oil that has an API gravity less than about 34, and that normally tends to form smoke and soot during combustion in a heating oil burner, and containing a small amount, suificient to reduce the smoke and soot forming tendencies of the oil, of hydrazine, said small amount being a fraction of 1 percent by weight of the composition.

2. The fuel oil composition of claim 1 where said heating oil is a No. 2 distillate fuel oil.

3. The fuel oil composition of claim 1 where said small amount is about 0.02 to about 0.05 percent by weight of the composition.

4. A fuel oil composition comprising a major amount of a 9:1 to 1:9 by volume mixture of straight run and catalytically cracked hydrocarbon distillate No. 2 heating oil that has an API gravity less than about 34, and that normally tends to form smoke and soot during combustion in a. heating oil burner, and containing a small amount, sufficient to reduce the smoke and soot forming tendencies of the oil, of hydrazine, said small amount being a fraction of 1 percent by weight of the composition.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Sci. Amen, vol. 189, No. 1, July 1953, Hydrazine, by Lessing, page 30.

The Chemistry of Hydrazine, by Andrieth et al., John Wiley and Sons Inc., New York, 1951, p. 225.

Claims (1)

1. A FUEL OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A HYDROCARBON HEATING OIL THAT HAS AN API GRAVITY LESS THAN ABOUT 34*, AND THAT NORMALLY TENDS TO FORM SMOKE AND SOOT DURING COMBUSTION IN A HEATING OIL BURNER, AND CONTAINING A SMALL AMOUNT, SUFFICIENT TO REDUCE THE SMOKE AND SOOT FORMING TENDENCIES OF THE OIL, OF HYDRAZINE, SAID SMALL AMOUNT BEING A FRACTION OF 1 PERCENT BY WEIGHT OF THE COMPOSITION.