| Show oil 01 1 shale and its refining Re refining finin BY ALBERT RT H LOW the refining of petroleum begins with the crude oil this oil must be taken as it comes from the ground and if it varies considerably in its nature in different localities the process of refining may be varied to meet the case in hand with shale oil however the situation is different no oil as such exists in the shale and the oil that may be produced from it by destructive distillation may be of good or poor quality according to lie he construction of the still and the skill and knowledge of the operator the refining of the oil may therefore be said to start with its production the source of the oil is an organic substance called this is disseminated throughout the shale and its decomposition by heat in the process of destructive distillation is the source of the oil destructive distillation of oil shale the main products by destructive distillation til are shale oil resembling crude petroleum ammonia eventually recovered in the shape of ammonium sulphate which is a valuable fertilizer and permanent inflammable gas which may be utilized in conducting further operations the primary consideration is the oil and the problem is to produce it in maximum amount and of the best quality this oil is a liquid mixture of hydrocarbons and these hydrocarbons taken as a whole are of two kinds saturated and unsaturated hydrocarbons saturated and unsaturated hydrocarbons the terms saturated and unsaturated refer to the molecular structure of the oily matters they constitute the saturated compounds are stable in their nature and can be recovered in the shape of colorless and odorless products of an unchanging nature suitable for storage and the market the unsaturated compounds are unstable and even if obtained in a colorless and odorless condition they may soon discolor and develop a disagreeable odor products containing them possess poor keeping qualities and they are therefore usually removed during the process of refining their removal usually means the loss of just so much oil although of course the crude 1011 n or the residual oil after a partial distillation til lation to recover gasoline may be used tor for fuel purposes crude petroleum always contains some of these unsaturated hydrocarbons and whatever amount is found must be accepted and be subject to the refining pro process groces ces 3 as the oil is a natural product shale oil on the contrary is manufactured it is produced by a process of distillation sod and this process if properly conducted will result in the formation of a minimum assor in professor es sor of chemistry colorado school of amount of unsaturated products while it if improperly conducted the percentage of 0 un saturates is materially increased this increase of un saturates is due to secondary decomposition that is the oily vapors after their initial production are decomposed and changed into other compounds with the formation of un saturates lack of knowledge concerning 11 no one seems to know as yet the exact nature of the organic matter contained in the or to what extent it consists of saturates unsaturated un we are therefore unable to judge as to the minimum amount of un saturates we might theoretically expect under ideal conditions of destructive distillation we do know however that by working along certain lines we can reduce the amount of saturates unsaturated un in the resulting oil materially I 1 therefore as before stated the refining of shale oil begins with its production it so happens that the conditions resulting in the production of the maximum amount of oil from a given shale also result in oil of the best quality that is oil containing the least amount of un saturates proper condition for distillation the proper conditions of distillation to effect these best results appear to be as follows decompose the in the shale and distil dastil the oil at the lowest possible temperature pera ture when the oily vapors are once produced remove them from the retort as quickly as possible and in such a way that they do not become additionally heated much above the temperature of their production as thi this s causes secondary decomposition and the formation of un saturates avoid any condensation of the oil in the retort as this eventually necessitates which likewise causes secondary decomposition the use of steam superheated super heated or otherwise is also advocated both to equalize the temperature and prevent overheating and to increase the yield of ammonia a matter that will be referred to later the necessity of using steam is questionable as it would appear that proper conditions might be attained without it and steam undoubtedly increases the expense and inconvenience of operating the scotch process in scotland d where shale oil has been profitably produced for many years tho the style of the retort for distilling the shalo shale has varied more or less but has clung to one general type the retort is a hollos vertical shaft enclosed in brickwork with an upper portion of iron and a lower por tion of firebrick the whole being surmounted by a hopper for holding a fresh charge the retorts are clustered in groups ot of four and a series of such clusters constitute a bench heat is derived from the combustion of the carbon still remaining in the shale after it has passed from the top to the lowest portion of the retort the shale in the upper or iron section of the retort is destructively distilled and largely exhausted at a point where the temperature is comparatively low the resulting oily vapors being taken off at the top As the charge settles either by being drawn off at the bottom at intervals or by the action of an automatic movable grate it gradually arrives at the brick section where the heat is much greater steam superheated super heated or otherwise is introduced into this section and besides equalizing the temperature is supposed to react more or less with the nitrogen and carbon in the shale and increase the production of ammonia pumpherston Pump herston retort in the pumpherston Pump herston retort the upper part or cast iron portion is 15 ft in length 2 ft in diameter at the top and 2 ft 4 in in diameter at the bottom the lower or firebrick portion is 2 ft 4 in in diameter at the the top where it joins the cast iron portion and 3 ft in diameter at the bottom at the end of the firebrick portion there is a disc support or table which supports the column of shale in the retort this table is provided with a revolving arm or quadrant which removes the spent shale and maintains a movement in the shale column by revolving at regular intervals at the top of the are iron hoppers holding 4 tons 10 cwt cat each into which one ton of broken shale is charged every hour tho the iron portion is heated to a dull red heat externally and it is in this part of the retort that the destructive distillation takes place the oil vapors passing out below the hoppers in an iron main 2 ft 6 in in diameter in the lower or firebrick part of the retort the shale is subjected to a temperature pera ture sufficiently high to burn off all the carbon from the oil spent shale this is done in the presence of steam and the arn ammonia is produced by the hydrogen of the steam uniting with the nitrogen contained in the shale about 60 per cent of the total nitrogen is converted into ammonia and recovered this type of retort has a throughput of 5 or 5 tons of shale per day henderson retort the henderson retort used at broxburn brodburn Brox burn scotland is an improved modification of the pumpherston Pump herston retort the shape and dimensions are varied somewhat som but the general type is the same it has two toothed rollers at the bottom to support the shale column and to maintain the downward movement description taken from br bacon and hamor thereby regulating the speed of the discharge of spent shale into the hopper below the 1901 retort is capable of a throughput of 4 tons of shale per 24 hours four of these retorts are arranged in an oven and 16 ovens constitute a bench nature of scotch shale oil crude scotch shale oil is a dark green to a brownish color has a specific gravity of from to and a congealing point of approximately 32 degrees C F it is substantially a mixture of the paraffin and olefine series with a small amount of naph thenes ben zenes and bases it contains about 1 per cent of nitrogen the quality of the crude oil depends greatly on the temperature at which it is formed from the or bituminous matter in the shale it has been ascertained that the greater part of the decomposition and distillation in the retorts occurs below degrees C F and upon investigation it seems probable that degrees C 1029 F is the maximum temperature pera ture required in a retort as this temperature pera ture is the highest boiling point of any normal paraffin since scottish shale oil is of a paraffin base steam is necessary in the iron portion of the retorts just as it is in the firebrick part and its presence prevents decomposition the above description and remarks are arc taken from bacon and hamors treatise in the scotch process the oil and water vapors leave the retorts by an outlet pipe usually about 8 in in diameter and enter a common main generally about 30 in in diameter this main conveys the gases into a water heater a tower in which water for the steam boilers is heated in pipes and then into large upright air cooled condensers of light cast iron 4 in in diameter fitted with cast iron chests and resting on them crude oil and ammonia water the crude oil and ammonia water collected from the condensers are run into a separator where they are separated while the un gases pass into exhaust ers the gases then pass into a vertical water scrubber where the last traces of ammonia are removed and next into a naphtha scrubber where the gas is washed with mineral oil to absorb the naphtha the theoretical limit is never reached in the ammonia sc rubbers and the practical limit is reached when the gas contains not more than 05 grain of ammonia per cu f ft t for the naphtha scrubbing an intermediate oil is used of about sp gr and about 2 gal of light spirit sp gr are recovered from the scrubbing oil per ton of shale anale retorted the scrubbing oil is denuded of naphtha by steaming it in a special apparatus the denuded oil is used continuously after cooling after the retort gas is freed from all con densille den sible and absorbable matters it is caught by a fan which forces it under a few inches pressure into the main which supplies the burners at the bottom of the retort flues after the removal of ammonia water and shale dust in the separators the crude oil is pumped into charging tanks from which the oil may flow by gravity into the refinery stills observations by D E steuart the following observations relative to the scotch process are taken from an article by D E steuart in the jour soc chem ind for 1889 p to get a good quality of crude oil the temperature of distillation must be low a red heat invisible in daylight and faintly visible in the dark in general a higher temperature produces a heavier darker crude oil giving more loss in refining and less solid paraffin but a higher yield of ammonia the shale used contained the following constituents carbon hydrogen S 30 0 clo nitrogen 0 07 7 sulphur 15 0 the ammonia produced is of course formed from the nitrogen present steam is used in all the retorts it acts mechanically in protecting the ammonia and the complex hydrocarbons from decomposition at 1000 degrees C according to ramsay and young ammonia in the presence of iron is nearly completely decomposed into its elements but where steam is used in excess all the nitrogen of organic compounds is at this temperature converted into ammonia sulphur appears as hydrogen sulphide oxygen combines with the carbon while some hydrogen is left free steam at such a high temperature is a powerful chemical reagent at the comparatively ively low temperature of the henderson retort its action is very gentle but it does act on the carbon to some extent to give nascent hydrogen to help build up the ammonia and solid paraffin and the yield of these is a good deal more than in the old vertical retorts worked at the same temperature pera ture neither lime nor soda added to the charge has any appreciable effect in increasing ammonia or otherwise improving the oil the permanent gas of the distillation is also used as fuel it used to be passed among the spent shale but is now burned in the bottom of the retort oven steam superheated super heated by passing through pipes in the oven is passed to the top of the retort it introduces the right temperature throughout the mass of shale and sweeps the distillation til lation products rapidly out of the heat where they would undergo decomposition no coals are required for fuel except to make a start after a stoppage temperature of oven to 1000 F n steam as it goes into the retort y p shale inside retort 1 ft from the top 3 hours after charging y 16 hours after charging p F products of 0 distillation at the exit pipe to F the nitrogen in the shale is equal to 70 to 90 lbs ibs of sulphate of ammonia per ton of shale of this we get no more than one fourth while nearly one half remains in the spent shale mr steuart states I 1 got a sample ol of crude oil taken from a retort every two hours and tested sp gr setting point loss with oil of vitriol and loss with caustic soda I 1 found there was a gradual increase throughout in the sp gr from to and in the setting point from 78 F to 87 8 F the loss with sulphuric acid gradually increased from 5 at the beginning to 1070 10 ao in the middle and then fell to at the end the loss with caustic soda increased from 26 to 38 A general idea of the scotch method ol of producing oil from shale has now been given the products obtained and so far referred to are crude shale oil ammonal water naphtha and permanent D gas W we e will now consider the refining of the crude oil treating the crude oil the crude oil is pumped into charging tanks situated behind each bench of stills the ol 01 11 these tanks are elevated so that may flow into the stills by gravity low tanks are arranged to receive the distillates once run oil the crude oil is first once olice run naphtha is recovered at the beginning and the remaining oil in iii tile the still I 1 distilled to dryness the distillate other ow oil run than the naphtha is called once to espel eaps the stills are first heated externally all the water and then steam is gradually introduced the steam is more or less sup sul er heated it serves to prevent and to to carry the oil vapors over lower the boiling point of the oil A residue resi of coke is finally left in the stills so dis the permanent gas is produced during oil of the til lation from the decomposition it is used for fuel free broo the once run oil is first settled water and is then pumped into an acid ag cid a where it is treated with sulphuric takes from after the acid treatment which to according accor ding 15 minutes to over an hour ed is allo al the grade of the oil the mixture Is the tar to settle for about a day and the oil then drawn off from the bottom is then dumped into the soda ag agitator afar receives a caustic soda treatment eat which it is settled and then pum pumped ped to storage tank oil 1 s green oil the treated oil once ce run called green oil this is fra fractionally alad heavy y oil 01 tilled into naphtha light oil beav heavy oil and wax distill dis atlo the heavy oil of the above is again distilled and fractionated into burning oil gas oil and heavy oil the latter is added to the heavy oil and wax of the first distillation while the gas oil is cooled and pressed in the paraffin house to separate into soft paraffin and sp gr gas oil the burning oil of this distillation I 1 is given the sulphuric acid and soda treatments and is then distilled along with the light oil distillate |
