US1830884A - Distillation of carbonaceous materials - Google Patents

Description

Nov. 10,41931. H. NleLsr-:N ETAL DISTILLATION 0F' CARBONACEOUS MATEIALS Filed N031. 21; 1927 Patented Nev. 10,1931

UNITED 4STATESI .PATENT ort-Ica HARALD N'IELSEN, VOili BROMLE'Y, AND BRYAN LAING', 0F WESTHINSTER, ENGLAND msrrfinarforr or cAnBoNAcEoUs MATERIALS Application led November 21, 1927, Serial No. 234,904, and in Great Britain December 4, 1926.

This invention relates lto the distillation,

' with by-product recovery, of carbonaceous materials, such as coal, lignite, brown coal,`

pea-t, Wood, shale and the. like.

In order to distil carbonaceous materials for the purpose of oil recovery the amount of heat. which is necessary `per unit of weight to effect the necessary thermal changes is well known and varies from to 300 kg. cal. per kg..of dry coal. If, however, this figure is analyzed or resolved it becomes apparent that the amount of heat required to penetrate in a given time from the periphery to the centre of each particle or piece of coal or through any thickness of fu-el bed so as to effect the necessary thermal changes vactually depends upon'the following mainl four factors. Since, however, the oil vapours are very susceptible to temperatures hi her than those at which they are liberated rom the carbonaceous material, it is necessary, if cracking or decomposltion of the said vapours is to be reduced or practically elimi. nated, thatthe vapours, after being liberated at the particular temperature at which they are evolved, should not pass into zones which are at higher temperatures or be brought into Contact with highly heated surfaces, as,-

, if cracking occurs to any extent, the yield of oils is reduced, while the heavy oils which result from the process are unsuitable for lubricating purposes.A In order to reduce or effected remains the same.

eliminate cracking we have found that it is necessary to modify one or more of the four aforesaid factors, but this must' be carried on in such a way that -the total thermal work For example, the surface exposed to the action of the heating gases or the heating medium may' be increased by crushing the coal ve finely so that the distancel through which t e heat has to travel from the 'centre to the periphery of each'coal particle is greatly diminished, but in such cases special precautions,.such as the provision of stirring and agitating devices, must also be taken to maintain the fuel in thin layers and prevent a dense or thick bed of material being formed. It is'not, however,

Aalways expedient to crush finely the coal which has to be distilled, especially the socall'ed non-Coking coals' which do not agglomerate, 'and in such instances the time factor might be increased. ThereV is, however, for practical reasons, only a permissible reduction ossible in the time factor, as, if

the rate o heating is substantially reduced, not only is the capacity of the apparatus diminished and the cost of the process increased, but the properties of the resultant coke are detrimentally affected. Furthermore, and when dealing with soi-called ook ing coals which agglomerate .and form large pieces during heating, it will be clear that, although they may have been admitted` into the distillation apparatus in a finely powdered form, such agglomeration will re sult in the distance from the outside to the centre ofthe mass being considerably increased.

Onefeature ofthe present invention is based upon the discovery that, if the temperature difference which exists between that whichy prevails at the centre and the outside `of a piece of coal, or an agglomeration or bed of the same, exceeds a given figure, cracking of the oil'vapours evolved at the centre of the coal particle or piece, or of the agglomeration thereof, or of a dense fuel bed, occurs when the vapours reach the hotter external surface of the coal particle, agglomeration or fuel bed. This fact we find to be the main contributing cause of excessive. cracking despite other precautions that may be taken to avoid it, and we have discovered that the chief reason why high qualit lubrieating oils have not heretofore been o tained `by coal distillation processes is due to the fact that both the time factor andthe mean temperature difference which exists between c being subjected to a preliminary pre-heating of the coal, and ma enter the retort at ap' that which prevails at the centre and that which exists at or outside the surface or periphery of a piece of coal, or else between the exterior surface and the interior portions of a fuel bed of any given thickness, have not been so controlled as to result in the production of a primary oil rich in hydrogen from which a high class lubricating oil can be obtained.

According to this feature of the present invention the process of distilling solid carbonaceous materials is carried on in such a manner that, for any given size ofparticle or piece of carbonaceous material or for given thickness of fuel bed, the period or time factor of distillation is so controlled that at any sta e in the distillation process a temperature di erence exceeding 120 C. to 150 C., but preferably of the order of 100 C. to'120o C., is not allowed to exist between the temperatures prevailing at the centre and at the periphery of any given size of particle or piece, or any given thickness of fuel bed. For example, when distilling bituminous black coal of sizes below 2 mesh or cube, we have found that, in order to maintain a range of temperature difference of approximately 100 C. between the temperatures prevailing at the inside and the outside of the coal particles, the duration of the distillation perlod must be about two hours; raw coal, after or drying treatment, being allowed to enter the retort at a temperature of 150. C. and the solid residue, after distillation, leaving the retort with a temperature of 550 C. The heating medium, which may be constituted by producer or water gas or byany heated and inert or relatively inert gas or by combustion gases, is preferably brought into d1- rect contact with the carbonaceous material, although external heating or acomblnatlon of internal and external heatlng may be used, and should be of such a volume that itl carries with it in the form of sensible heat the required heat units to eiect the thermal cha'nges in the solid material within the pre- -scribed temperature and time lm nts. In the case of internal heating the heatmg medium preferably travels in countercurrent to that proximately 650 and leave the same at approximately 100 C. to 110 C. In the case o external heating the temperature of the4 heating gases progressively increases from the point where the arbonaceous material enters the retort to the outlet thereof, and stirring or agitating devices are preferably provided by means of which the material is kept in constant motion and in thin layersfso as to promote uniform heating, and to allow of the removal, without passmg into hotter zones, of the vapours and gases at the temperatures at which they are evolved, while Aalso to prevent overheatlng of the coal particles due to prolonged contact -with the externally heated metal or brickwork of the retort. Subject to the process being carried 011 in the aforesaid manner, that is to say, in such a manner that a temperature difference exceeding 150 C. does not'exist between the centre and the periphery of any given size of coal piece or particle, or any given thickness of fuel bed, excessive and disadvantageous cracking of the oil vapours does not occur, and we have been able to produce from the so-called crude oils resulting from the distillation of bituminous coal a lubricating o il of a standard equivalent to that obtained from the iinest well oils. The determination of the length of retort to be used and thel ing or diminishing the speed of rotation ofv the stirring or agltating devices where such are employed, or varying the temperature gradient, for example by bye-passing heating gases either at hi'her or lower temperatures as required to different points in the distillation apparatus, overheating of the material can be avoided. Provisiormay also be made for withdrawing the evolved vapours at or about the temperature at which they arev evolved, or for preventing them, for example by drawing them off in uniflow with the heatlng gases and in counterurrent to the solid material, from passing into vhotter zones where cracking may occur, precautions being also taken to prevent them'from passing into cooler zones where condensation may take Another feature of the present invention relates to processes of distillingcarbonaceous materials of the kind' in whichadistilling medium, such as water, producer or combustion gas (after being superheated if necessary) is passed through an apparatus, such as a rotary retort, in direct contact with, and

in contraflowto, the solid carbonaceous may terials so that the so-called sensible heat of the distilling medium is employed to distil of the volatilizable and condensable oils containedtherein, the inert heating gas containing the volatilizable oils, being subsequently vpassed through condensers', scrub-- bers, oilwashers, etc., for the purpose of recoltering in liquid form thesaid condensable o1 According to this feature of the present invention the temperature zones throughout the length of the retort are graduated or controlled so that the said oils are distilled off at the temperatures at which they volatilize and are then withdrawn from the apparatus in unifiow with the heating medium either at one end or at different points along the length thereof vand at temperatures at which 11o excessive cracking can occur, while the I provided a sulicient quantity or volume of the inert heating gas. is employed to carry with it in the form of sensible heat the total heatrequirements for the distillation process, it is possible to obtain an increased yield of the heavier and more valuable oils, while if the aforesaid precautions to prevent overheating and to secure exact temperature regulation are observed, it is also possible to obtain an increased yield of heavier oils with a high viscosity, both lighter and heavier oils produced by this process having properties and a composition hitherto unobtainable by low temperature distillation processes. According to this feature of the present invention the volume of gas employed for distillation purposes is of such a magnitude (e; g., 35,000 up to 100,000 cubic feet per ton ofcarbonaceous material) that the vapour tension or so-called partial pressure of the heaviest oil fractions present in the carbonaceous materials is lowered sufficiently tov enable such oils lto -be liberated in vapour form from the carbonaceous materials at temperatures not exceeding 450 C. to

When distillingl materials containing a very large percentage of oil such as oil shales Sor torbanites the volume of the distilling' carrying theoil vapours may be of such av ,magnitude that the oils will not 'separate out or condense within the distillation apparatus or the dust extractor at temperatures -as `low as C. to 100 C. Generally speaking, the conditions to be observed, in the case of internal heating-by means of an inert gas, are (l) Ithe volume ofinert'heating gas, although such `as to carry with it through and from the retort the vapours evolved during the distillation period without allowing the heaviest oil fractions to reach their socalled dew point until actual condensation of'the condensable volatile products, or any desired fraction thereof, is desired, is so controlled that the vapour tension of the volatilizable oils is lowered so that the heaviest oil fractions are liberated in vapour form from the solid materials Vat temperatures not exceeding 450 C. to 500` C., and (2) thetime factor and temperature gradientare so controlled that a temperature rdifference exceedlng 150 C. is avoidedb'etween the temperature prevailing at the centre and the periphery of any glven size of material or thickness of fuel bed.`

In order to maintain the requisite temf perature gradient orto increase. the'fvolume of the heating or carrying gas at any point in the heat treatment, or to 'maintain any desired temperaturein the dust extractor or in any ofthe condensers, additional volumes of gases .at the desired temperatures may be admitted at any stage inthe process to the combined heating and retort gases or vapours, or a. heating or cooling medium may be applied as and when required at any particular stage in the process. For example, the retort used' for carrying on the distilla tion processfmay be 'of the type hereinafter described;

` We vhave also .found that, by controllingV the'temperature gradient so that the heaviest oil fractions' are liberated in vapour form from the carb'onaceous materials at temperatu'resl not exceeding 45o-500 C., coking or agglomeration of the solid materials does not take place to the same extent as occurs with any usual process or distillation. For example, when distilling Esthonian shale, which shale, when normally treated, melts -to a semi-liquid or pitch-like conglomeration,l

we haveo found that, after the oil va'ours have been evolved `and-removed, the car onaceous residue is discharged -from'theretort in a solid form, the pieces being'of a shape and size approaching that at which they were originally chargedjinto the retort, that is to say, no agglomeration'has been observed and the individual pieces vhave retained their original size and shape more or less unaltered. It would thus appear that, owing to the large volume of gas passed through the retort, the vapour tension of the various oilfractions was so lowered that the oil vapours in the example under consideration were evaporated from the' solid material without through the so-called sticky period during -the lheating process. In other words, the

the retort without excessive cracking, as not only does the present process produce an `causing the `solid material to melt lor pass 1 oils should, as aforesaid, be withdrawn from 'i possible, that is to say, at temperatures ranginglfrom 185 C. to 580 C. We have found that thesolid residue produced by the present process can be burnt in open domestic firegrates and is more readily ignitable than the ordinary semi-coke obtained by any of the usual processes of low temperature distillation and far more readily combustible than ordinary so-called gasworks coke or gas oven coke. This property of the solid ca rbonaceoiis residue obtained by the aforesaid process appears to be due to the fact that the original cell structure of the raw material -is left intact and the deposition of an inert carbon film on the residual fuel is avoided, while the thinness of the cell walls is maintained, so that a very large supercial surface is made available for attack by oxygen either combined or in a free state.

We have also found that a fusible or coking coal, which on distillation passesthrough a so-called plastic state, can be given the same degree of reactivity, etc., as a so-called non-Coking or -non-caking coal, that is to say, be made to retain its original cell structure by being subjected to a .preliminary heat treatment by gases containing sufficient oxidizing constituents, free oxygen and the like to an extent which will stop fusing and agglomeration. l

-The preliminary treatment may consist 1n drying and/.or pre-heating-the coal or carbonaceous material in a so-called coal dryer,

rotary or otherwise; During these operations the carbonaceous material is subjected.

to the action of a hot gas, such as combustion gases, for example, containing a percentage of free oxygen of the order of from 2% to 8% which will suffice to oxidize some of the ,so-called coking constituents to the desired degree and theieb5r. influence their coking power. Y A p As a -detailed description of onel method of carrying .on the present process and involving all the features Apreviously dericribed, the following exam le s-given: AA

bituminous coal was distille by' means ofa controlled volumeof an inert gaseous heating medium (i. e. superheated water gas) which was brought into direct contact with the Acoal in a rotary retort, the raw coal,

after preheating to a temperature of about 150 C., having a volatile content of 30%.-

The volume of'water gas used was of the order of 55,000 cubic feet and entered the rev with a small volume of gas and at or about 570 C. all the oil-giving or condensable hydrocarbons were removed from the material under distillation.

The quantity of products obtained per ton of raw materials at this temperature (570 C.) wasfz- Y 20 gallons of oil.l 15 gallons of ammoniacal liquor. 2,500 cubic feet of strippedA retort gas coinl bined with water gas.

The volatile matter still present in the solidmaterial was reduced to 10%. l v I Microscopic research showed that practically no deposit of graphitic carbon was present. Y It was also found that, on account of the fact that cracking did not take place owing to exact temperature regu-lation, to the fact that the oil yielding Avolatilizable constituents were carried off in un-iow with the heating gases, and to the fact that the volume of'heating gas employed was controlled, a primary oil was obtained containing a large percentage of the more valuable high boiling fractions or lubricating oils rich in hydrogen. The neutral oil which was obtained after removal of the acidic and basis constituents was considerably richer in h drogen -than that obtained by other meth s of coal distillation. A large yield of lubricating bases 'of a specific gravity approaching that of water was also obtained from which a lubricating oil was extracted by the treatment hereinafter described which was of a character and quality hitherto unobtainable by any previous method of coal distillation. neutral oil produced had the following characteristic properties Hydrogen percentage by weight, 9.5% up to 11.5%. Heavy lubrieating bases having a hydrogen percentage above 9% by weight and' a specific gravity.

ranging from 0.95 up to 1.080, at 15 C. The total yield, after fractional distillation and refining, of oils having properties similar to the following derivatives from well oils and' adapted for similar purposes, was

as follows Petroleum ether-; 70- 90 Petroleum naphtha 90-A120 3.0%

Petroleum benzine 120-150 6.0%

Kerosene 15G-300 40.0%

-Lubricating oils 3D0-420 30.0%

Paraiiin wax "45- .65 4.0%

In order to produce a high grade lubricat- The ing oil that portion of the distillate, boiling over 300 C., was then subjected to further treatment. To this end the tar acids were removed by caustic soda, and the resultant 5 oil refined with sulphuric acid. The refined oil was then distilled and the first 25 per cent. yielded up during the distillation process was in this instance added to the so-callcd kerosene fraction. The remainder was `then l passed through a filter press at about 5 C.

and the paraffin wax extracted. The wax-free v oil after distillation gave lubricating oils .of a rather dark red colourand a marked green fluorescence. The yield of allgrades of lubricants by the aforesaid treatment amounted to about of the total original crude oil. The amountl of lubricating oil equivalent to so-called spindle oil was of the order of 5% ofthe original crude oil. On testing the lut0 bricating oil so obtained it was found that -at normal temperatures, namely from 12 C. to 18 C., it had a so-called static coefficient of friction of from 0.1 up to 0.185.

The residua-l solid fuel discharged from the t5 retort contained about 10% volatile matter and was exceedingly reactive and easily oxi-l dized, either by free oxygen or the combined oxygen present in metallic ores, such as iron or copper oxides and the like, or in steam.1

Consequently, the solid carbonaceous residue resulting from the present process is of greater value. for domestic use or industrial processes than the comparatively speaking nonreactive carbonmaterial hitherto produced 15 by low temperature distillation.

As the carbonaceous residue from certain coals, particularly those of a non-coking va-v riety, may be produced in a fria-ble state, it is eminently suitable for use, after crushing, as :Q powdered fuel, owing to its high degree of reactivity and free burning properties.

The accompanying drawing shows a layout of .a plant suitable for carrying on the present process. Referring to'the drawing, the apparatus illustrated comprises a long rotar retortE, which maybe composed of meta or refractory material, or metal lined or covered with refractory material containing semi-circular partitions of metal or re- 0 fractory material which extend inwardly from diametrically opposite points of. the casing of the retort at suitable distances apart along the length thereof. together, if desired, with one o'r more partitions extending di- .ametrically across the retort. The inert or relatively inert gas may be constituted by combustion gases from a combustion'chamb'er H. or preferably by producer or -water l gas, which, as lit is generated in `the'producer 0 G, is withdrawn 'therefrom/and, after, if necessary, :being superheated, in' the com-- bustion chamber H, is 'passed throughv the retort indirect vcontact with the carbonaceous materials so as to utilize'its so-called sensible L" heat for the purpose of,distilling off at low or moderate temperatures from the rawcarbonaceous materials passing through the retort the volatilizable and condensable oils contained therein, the inert heating gas'` admixed with the retort gas and containing the volatilized oils being subsequently passed through condensers, scrubbers, oil washers, etc.,'constituting a condenser system J, J, for the, purpose of condensing and recovering in liquid form the said oils. The so-called ,stripped gas consisting of the combined.

retort and producer or water gas which remains after the'v oils have been condensed therefromV is an enriched gas suitable for heating or illuminating purposes, but if desired the stripped gas may be employed,

after superheating, as .the distilling mediumwhich has undergone distillation is -dis.

charged from the retort at the point F. G

is a gas producer which supplies gas under a control to a combustion chamber H. From the combustion chamber G combustion` gases pass' through the retort E in counter-current to the solid carbonizable materials, the combined combustion gases, together with the gasesand vapors yielded up during the heatl treatment' being withdrawn from the retort into a' condensing system J, J. K is a booster provided vin the condensing system. The

' lstripped gases or a controlled volume thereof are forced by the booster K through a pipe L to the combustion'chamber H where they are burnt in conjunction with the gas from the gas producer G. The requisite air for use in the gas producer and also in the combustion chamber H is supplied by a fan M `through branch pipes N and O respectively.

P is a meter for registering the volume of gas passing into the combustion. chamber H.

By means of the gas booster K and the air fan M and by adjusting the Valves V, V, inthe associated pipe lines the volume of gas supplied to the rotary retort for combustion purposes can be regulated as desired.. The

actual volume passed into the retort is asceri' tained by consulting the'meter P, and varies from 35,000 'to 100,000 cubic feet per ton of carbonizable -material undergoing distillation in the 'retort'E Q, Q, are pyrometers disposed at various points along the retort from the inlet to the exit end thereof for registering the temperature gradient -prevailing inside the retort.l

The carbonaceous materials afterv the oi iso ielding and volatilizable constituents have een drlven off at temperatures ran 'ng from 185 C. to 580 C. may be subjectedgio a high temperatuore ranging from 580o C. to 1200 C. so as to expel the permanent gases from the material and reduce its volatile content to from 1 to 4%. The process of high temperature distillation can be carried on as a continous step in the aforesaid process and the same heating medium may bel'employed both for the high temperature and the low pr moderate temperature process of distilla- According to another feature of the present invention a controlled volume of free oxygen is admixed with the inert heating gasesor with the combined retort and heatlng gases before, during or after the same 'have been p rought into .contact with the solid carbonaceous material undergoing distillation for the purpose of polymerizing o1- facilitating the pol merization of resinous bodies, prior to con ensation or during condensation and while the oils are still wholly or partially in the vapour state. l-Ve have found that, provided a quantity of oxygen is admixed with the distillation gases or with the oil vapours (e. g. approximately 3% to 7% of oxygen) the oils which are obtained,

after fractional distillation and refining of the primary yield, are more stable and retain their colour and valuable properties longer than other oils where polymerization only takes place after refining or after prolon ed standing. o claim is herein made to the oil proi duced by the process hereinbefore described,

- as the same forms the subject matter of a divisional application Serial- No. 356,599,

filed April 19, 1929.

- We claim:

the progressively increasing temperatures to which the material-is sub]ect ed during the distillation period are so controlled that a tem erature difference exceeding 150 C. is avoided between the temperature prevailing at the periphery of the pieces of material.

3. A process as claimed in claim 1, of distilling small pieces of carbonizable material in such a manner that cracking of the oil vapors yielded up during the heat treatment is prevented which consists 1n feeding small pieces of said material continuously through progressively increasing temperature zones in counter-current to and in di. rect contact with heating gases substantially vchemically inert with res ect to the carbonizable material and which lave a heat gradient diminishing from approximately 650 down to 100 C., and controlling during the heat treatment the temperature of the heating gases so that .a relative temperature diiference exceeding 150 C. is avoided at any stage in the heating operation between the relative temperatures prevailin at the center and the periphery of the pleces of carbonizable material.

4. A process of distilling carbonizable material as claimed in claim 1 wherein the solid material after the oil yielding and volatiliz- -able constituents lhave been driven off is subjected to a temperature ranging from 580 C. to 1200 C. so as to expel the permanent gases from the said carbonaceous resi-` due,

In etestimony whereof We have affixed our signatures.

vHARALD NIELSEN.

BRYAN ,LAINGn 1. A process of producing hydrocarbon oil l v from solid carbonizable material, to ether with a large volume of g'as suitable or illuminating or power purposes,'and also a solid residue substantially free from deposited graphitic carbon, which comprises' passing the carbonizable material to be distilled, 1n acontinuous manner through a retort, carbonizing said material by passing a controlled volume of gas of a temperature not less'than lapproximately 185- C., which is substantially chemically lnert with regard 4to said material in a continuous flowing stream in direct contact with, and in counter#v flow to said material, and controlling the volume of hot gas so that it is -of the magnif tude of from 35,000 up to 100,000 cubic feet per ton of 4carbonizable material.

2. A process of distillin solid carbonizable material with by-pro u'ct recovery, as

.` claimed in claim.1, wherein the size of the pieces of material which are to undergo distillation does not exceed 2 cube and wherein the duration of the heating operation and

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