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Volume 52, 1920
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Art. V.—The Distillation of Waikaia Oil-shale.

By W. Donovan, M.Sc., and G. C. Burton.

[Read before the Wellington Philosophical Society, 3rd December, 1919; received by Editor, 31st December, 1919; issued separately, 4th June, 1920.]

The following paper embodies the results of an investigation of the properties of Waikaia shale, conducted at the Dominion Laboratory during 1918, at the request of the Director of the Geological Survey.

Eight representative samples were received from various bores put down by the Waikaia Shale Company. Proximate analyses were made, and also distillation tests, to obtain the yields of oil and gas. The results were:—

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No. Fixed Carbon. Volatile Hydrocarbons Water lost at 100° C Ash. Sulphur. Crude Oil (Gallons per Ton). Gas (Cubic Feet per Ton).
1 9 60 33.42 7 78 49.20 2 30 23 5 2,000
2 17 20 43 74 10 13 28 93 2 93 37.0 3,400
3 17 25 42 67 8 63 31.45 3 40 Not distilled.
4 20 80 46.87 9.83 22.50 3 40 48 0 4,000
5 20.75 51.42 10.78 17.05 3.08 46 0 4,000
6 18 30 46 65 15 70 19.35 3.20 38 0 3,800
7 17 65 51.45 10 40 20.50 3 07 35 0 3,500
8 17 70 47.35 13 75 21.20 3 06 42 0 4,000

Note.—There was not sufficient of No. 3 for a distillation test to be made.

A composite sample, made by taking equal weights of the above eight and mixing thoroughly, was examined in greater detail, The proximate analysis was—

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Fixed carbon 17.10
Volatile hydrocarbons 43.03
Water 10.42
Ash 29.45
100.00
Total sulphur per cent. 3.05

An ultimate analysis yielded—

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Hydrogen 5.64
Carbon 39.55
Nitrogen 0.30
Sulphur 3.05
Oxygen 22.01
Ash 29.45
100.00

On distillation there was obtained—Crude, oil equivalent to 38 gallons per ton of shale; ammonium sulphate equivalent to 8 lb. per ton of shale; gas equivalent to 4,000 cubic feet per ton of shale.

The specific gravity of the crude oil was 0.96.

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The oil was redistilled into the following fractions:—

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Below 200° C. 7.0 (naphtha).
200°–250° C. 11.5 burning-oils.
250°–300° C. 14.0
300°–350° C. 18.0 lubricating-oils.
Above 350° C. 41.0
Residue 6.0
Loss 2.5
100.0

The distillate above 350° C. contained 14.2 per cent. of paraffin of melting-point 58.5° C., equivalent to 22 lb. paraffin per ton of shale.

If all the fractions were collected in the same vessel they would give once-once-run shale-oil, 91.5 per cent. (equivalent to 34.75 gallons per ton of shale).

The fuel values of this and of the crude oil were determined in the calorimeter, together with a crude oil from the Orepuki Shale-works, year 1903, and crude Taranaki petroleum, received in 1906 (No. 562). The sulphur was also estimated at the same time. The results were:—

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Walkaia Shale. Crude Orepuki Shale-oil., Crude Taranaki Petroleum.
Crude. Once run.
Calorides per gramme 9,470 10,032 10,339 10,713
British thermal units per pound 17,046 18,058 18,610 19,283
Evaporative power per pound in pounds of water at 212° F. 17 67 18 72 19 29 19 28
Total sulphur per cent. 1 80 1 76 1 79 0 21

A good fuel-oil should not contain more than 0.5 per cent. of sulphur.

The yield of ammonium sulphate, 8 lb. per ton of shale distilled, is low. It would be increased if the distillation were conducted in the presence of superheated steam, as is usual in working practice; but even if all the nitrogen were recovered in this form it would not exceed 28.3 lb. per ton.

The gas from the distillation had the following composition:—

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Carbon dioxide 18.3
Oxygen 1.0
Carbon monoxide 14.3
Methane 37.3
Hydrogen 22.3
Nitrogen 6.8
100.0

(Sulphur compounds, which were not determined, would be partly included in the carbon dioxide.)

When purified from carbon dioxide the composition would be:—

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Oxygen 1.2
Carbon monoxide (CO) 17.5
Methane (CH4) 45.7
Hydrogen 27.3
Nitrogen 8.3
100.0
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Calorific value, gross, in calories per cubic foot 1529
" net, in calories per cubic foot 1375
" gross, in British thermal units per cubic foot 6111
" net, in British thermal units per cubic foot 5456
" (Gas measured at 15.5° C. and 762 mm.)

There would be about 3,250 cubic feet of such gas per ton of shale. The calorific value is approximately the same as that of good coal-gas.

Summary.

Waikaia shale would yield on distillation the following products per ton: 38 gallons crude oil, equivalent to 34¾ gallons once-run oil; ammonium sulphate, 8 lb.; gas free from carbon dioxide, 3,250 cubic feet.

After fractional distillation and refining the oil would give the following products per ton, allowing 10 per cent. for impurities and loss: Light oil (naphtha), 2.5 gallons; burning-oil, 8.8 gallons; light lubricating-oil, 6.2 gallons; heavy lubricating-oil, 12.0 gallons; paraffin, 20 lb.

(The amount of light oil would probably be increased by scrubbing the gas evolved with a suitable medium oil, to dissolve the light hydro-carbons that escape condensation.)

The shale appears to be very similar to Orepuki shale.

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