US1963589A - Fuel composition and method of producing the same - Google Patents

Description

June 19,1934. s. P. MILLER 19963589' FUEL COMPOSITION AND METHOD OF PRODUGING THE SAME Filed Jan. 5, 1928 2 Sheets-Sheet 1 S. P. MILLER June 199 1934e FUEL COMPOSITION AND METHOD OF PRODUCING THE SAME Filed. Jan. 5. 192s 2 Sheets-Sheet 2 H n n "Inun- M Il- --.n

Patented June 19, 1934 UNITED sTATlazsl PATENT OFFICE FUEL COMPOSITION AND METHOD OF PRODUCING THE SAME Application January 5,

3 Claims.

This invention relates to anew fuel composition and to an improved method for its manufacture.

The new fuel composition comprises pitch of low carbon content, produced by distillation of tar in direct Contact with hot coal distillation gases, together with petroleum oils blended therewith to form a composite fuel product.

It has heretofore been proposed to distill tar in ordinary tar stills and blend the resulting pitch with fuel oil. The pitch so produced, however, is relatively high in carbon content, particularly where the distillation is carried to a .point where a relatively high melting point pitch is produced in order to obtain a high yield of creosote oils from the tar before using the 'pitch' for blending with the fuel oil. The high carbon content of such pitch is largely due to the distillation of the tar in externally heated stills, where the heating of the still is effected by direct contact. of the flames or heating gases upon the surfaces with which the tar comes into direct' contact. During such distillation a considerable proportion of the oil content of the tar is decomposed and the decomposition products remaining in the pitch are indicated by an increased free carbon content of thel pitch. This so-called free carbonl is not necessarily elemental carbon but is a material relatively insoluble in benzol and certain other solvents. In cases where tar is exposed to extreme local overheating elemental carbon may be produced and if present in any substantial amount may actually tend to settle out'of the hot fluid pitch, this tending toward trouble due to clogging of fuel valves, furnaces, etc.

The pitch produced by my process contains free carbon but it appears to be considerably different from that present in ordinary pitch. For 4 example, in a test on one pitch the free carbon .insoluble in benzol and recovered by digesting the new pitch with benzol followed by filtration was almost completely soluble in aniline, whereas the free carbon from a corresponding pitch of the usual type is only slightly soluble in aniline. The improved fuel composition of the present invention is made by blending pitch of relatively low carbon content, produced by distillation of coal tar by direct contact with hot coal distilla- '5 tion gases and without overheating or prolonged heating of the tar undergoing distillation and of the pitch residue, with heavy petroleum oils. Pitch so produced is produced without the large amount of decomposition of oil constituents which accompanies the distillation of tar in or- 1928, serial No. 244,656

(ci. 44-s) dinary tar stills, and its free carbon content is largely of a hydrocarbon character. Its tendency to deposit carbon when blended with petroleum oils is much less than that of ordinary pitch. The difference in the pitch employed in the new composition, as compared with pitch produced by ordinary tar distillation in externally heated stills, will be appreciated from the fact that when tar is distilled, for example, in a still of 10,000 gallons capacity to produce a pitch around 300 F. melting point, the yield of oil is only around 44 per cent; while by subjecting tar to distillation by direct contact with hot coke oven gases to produce a pitch residue having a melting point around 300 F., there is obtained a yield of oil around per cent or higher. This radical increase in oil recovery from the tar is. accompanied by a corresponding decrease in pitch produced and particularly by a reduction in decomposition products of the kind produced by distilling tar in contact with heated surfaces where decomposition and carbon formation take place to an important extent.

The use of suchlow carbon pitches with fuel oils enables more fuel oil to be blended therewith, as compared with ordinary pitches of the same melting points; while with the same amounts of fuel oil added the critical temperature, above which the mixture-.or blend remains homogeneous, or in a fluid and dispersed state, is materially lower.

A new fuel composition can advantageously be produced in a continuous manner, by subjecting tar to distillation continuously in contact with hot coke oven gases and drawing olf the resulting pitch continuously and `blending it with petroleum oil. Pitch so produced is at a high temperature and thinly fluid, and is in a condition adapting it for intermixture to advantage with petroleum oil, and particularly with preheated petroleum oil 5 where the heat of the hot pitch may not be suiicient to heat the petroleum oil to the proper temperature for obtaining a homogeneous blending of the materials.

The petroleum oil employed is a cheap petroleurn oil of the character commonly used for fuel, for example, mixed base fuel oils. Such oi/l can advantageously be preheated by bringing it into direct contact with some of the hot coal distillation gases to remove some of the more volatile constituents therefrom and tol give a preheated residue, preheated to a temperature which facilitates its blending with the pitch to form the new composition.

The blending of the pitch and petroleum oil can 1,10

advantageously be carried out in a continuous manner, by owing a regulated stream of the hot pitch and of the preheated fuel oil into a mixing 'chamber in regulated proportion and by subjecting the pitch and petroleum oil to intermixture, with mechanical agitators, if necessary, to form a homogeneous composition at a. high temperature. If the temperature is too low, separation may tend to take place, but with the pitch directly produced at a high temperature and employed directly for blending with preheated fuel oil, or even in some cases with petroleum oil Which has not been preheated, the pitch and petroleum oil can be blended to form a substantially homogeneous composition, which will remain homogeneous at high temperatures, and Which can advantageously be maintained in the heated state and supplied to the fuel burners in such condition.

'Ihe petroleum oil employed for blending with the pitch can also be advantageously preheated by means of hot flue gases escaping from a coke oven. By placing a pipe coil in the ue leading from the coke oven to the stack, and by pumping the fuel oil through the pipe coil at a regulated rate, it can readily be preheated to a temperature which enables it to be readily blended with the pitch and which may result in driving oi some of the more volatile components of the petroleum oil.

The present invention is of special advantage at coke oven plants adjacent tosteel mills, where tar is commonly employed as fuel, e. g., in open hearth furnaces. The distillation of tar by direct contact with hot coke oven gases results in a radical increase in oil distilled therefrom as compared with the yield obtained in ordinary externally heated tar stills; and the resulting distillate oil has a much greater value than its fuel value. The production of this increased yield of oilv suitable for use, for example, for creosoting purposes, is accompanied by a corresponding decrease in the amount of pitch pro- Iduced, so that less pitch is available for use for fuel purposes, than would be the case if tar were distilled in ordinary tar stills. This pitch, however, is of a character and composition which makes it advantageous for blending with petrleum oils Awhich supplement the fuel value of the pitch and make up for the loss of oil recovered from the tar as distillate oil of greater value. The practice' of the present invention accordingly, enables coal tar to be employed to give products of greater value, i. e., an increased yield of creosote oils, etc., with decreased yield of pitch from the tar, While the pitch can advantageously be blended with and supplemented by petroleum oils, which are much cheaper than the creosote oil, which is no longer available for fuel purposes.

'I'he present invention presents the further advantage, among others, that a minimum of added equipment is required at a coke oven plant for production of the new fuel composition and of a high yield of cresote or other oils simultaneously, and, in particular, it makes unnecessary the provision of an externally heated tar still for the distillation of tar. f

In producing the pitch which is blended with petroleum oils to make the new fuel composition, the tar, and particularly coke oven tar, such as is produced from coke oven gases in ordinary byproduct coke oven operation, is subjected to distillation by bringing it directly into contact with hot coal distillation gases at the cokeV oven plant,

. and the distillation is so carried out as to produce a hard or relatively high melting point pitch which will, nevertheless, have a much lower carbon content than the pitch produced by ordinary tar distillation methods in externally heated stills.

The gases from coke ovens or retorts leave the ovens at a high temperature, around 600 to '700 C., or higher, and are commonly cooled in the collector main of the battery by the introduction of ammonia liquor, or ammonia liquor and tar directly into the collector mainto throw down a heavy tar from the gases and by further cooling of the gases in the coolers or condensers to throw down a light tar or tarry oil therefrom. The heavy tar and light tar are commonly mixed and subjected to distillation or are burned.

'I'he tar so -produced may be employed by subjecting it to distillation by bringing it into direct contact with hot coke oven gases at a sufficiently high temperature to distill the tar to remove a large part of the oil components therefrom, and to leave a pitch residue of high melting point but of relatively low carbon content; and the resulting pitch can then be blended with petroleum oil to form the new pitch composition. The distillation of tar in direct contact with the hot coke oven gases can be carried out, for example, by'

This'di'stillation will remove from the individual particles of the tar sprayed into the gases, a large part of the vaporizable components, leaving a pitch residue which will varyv in its melting point with the extent to which the distillation is carried.

Such distillation can be carried out with much less increase in carbon content, due to decompositionduring the distillation than occurs when tar is distilled in the ordinary way, although some such decomposition may take place, particularly where the time of contact of the tar and the resulting pitch 'residue with the hot gases is prolonged. In any event, the pitch residue produced will be of relatively much lower carbon content,

and it will be obtained in radically lower yield than pitch residues produced by distillation in ordinary externally heated tar stills, while its carbon content will be of a diierent and more advantageous character, adapting it to be blended to advantage with petroleum oils.

Hot coke oven gases coming from the individual coke ovens have a temperature of 600 to 700 C., or higher and are capable of distilling an amount of tar many times that which is produced from the gases from a Asingle oven. Accordingly,in a coke oven plant Where the tar to be distilled is that produced at the same plant, the gases from a few only of the ovens will suice for the distillation of the tar produced from the remainder of the battery. Where, however, the tar from several batteries is to be distilled, the gases from an increased number of ovens, or from an entire battery, or from so much of a battery as is connected to a single collector main, may be employed for the distillation. By bringing the tar intimately into contact with the hot gases at substantially their maximum temperature as they leave the coke oven, the tar can be continuously distilled in a single operation to produce a. high yield of distillates and a relatively high melting point pitch residue which can be drawn oi continuously and blended continuously with petroleum oils to produce the new composition. The distillation can be carried to such an extent that pitch of moderately high melting point, is obtained, for example, pitch having a melting point up to around 300 F., although it may suflice to produce a 4pitch of lower melting point, e. g., around 200 F., or even as low as 110 F., for blending with the petroleum oil. Pitch of melting point above 160 F. is however a preferred type of pitch for this process.

The blending or mixing of the pitch with the petroleum oil can' advantageously be carried out, as abovenoted, in a continuous manner, by running streams of the hot pitch while still at a high temperature, and of petroleum oil, preheated, if necessary, into a mixing chamber or receptacle in which the streams blend and mix with each other to form a homogeneous product at a high temperature, with agitation of the mixture, if necessary, to promote inter-mixture and homogeneity.

The resulting fuel composition, produced at a high temperature, can advantageously be maintained at a high temperature until it is employed for fuel purposes. This canreadily be effected by circulating a stream of the composition through a pipe coil located in the ue leading from the coke oven to the stack and returning the mixture to the storage tank. The stack gases are at a temperature, e. g., of 300 to 400 C., and have sufficient heat so that a pipe coil located therein can be continuously heated and the mixture circulated therethrough at aregulated rate to maintain it at the proper temperature, where it will remain homogeneous and sufficiently fluid for pumping to the burners. Such circulation o1' the fuel composition from the' storage tank through a heating coil and vback to the storage tank keeps the contents of the storage tank not only at a sufficiently high temperature, but in a substantially uniform blended condition.

The proportions in which the pitch and the petroleum yoils are mixed with each other can be varied, depending upon the melting point of the pitch, the character of the fuel oil, etc. In some cases, the pitch and fuell oil can be blended in equal proportions, while in other cases, an excess of the pitch4 or fuel oil can be employed.

When coal tar is subjected to distillation by direct contact with hot coke oven gases, the gases will become materially enriched in vapors from the distillation and the gases will still be at a high temperature when pitch of high melting point is produced by the distillation. Such gases can be directly condensed to recover an oil therefrom which may contain an appreciable amount of tar or pitch constituents; but the gases can advantageously be subjected to a cleaning treatment, e. g., with an electrical precipitator at a high temperature to separate suspended pitch particles therefrom, Whileleaving oil vapors uncondensed and then by further cooling of the gases, a clean oil can be directly produced, for example, a creosote oil, or first a creosote oil and then a tar acid oil, etc. The pitch separated from the gases at a high temperature by the electrical precipitator will be largely made up of constituents contained in the gases employed for distillation, although there may be entrainment of pitch particles where the tar is mechanically atomized into the gases in a fine state, so that suspended pitch is carried in the gas into the electrical precipitator. The pitch so separated from the gas in the electrical precipitator at a high temperature may also be advantageously blended with the petroleum oil and with the pitch from the distillation.

The tar which is subjected to distillation for the production of the pitch may be the total tar, including both the heavy tar from the collector main, and the lighter tar or tarry oils from the condensers, or it may be only the heavy tar from the collector main, leaving the tarry oils from the condenserto berused for other purposes, for example, for blending with the oils recovered from the distillation to make creosoting compositions. Tar from another source can also be subjected to distillation to produce a pitch residue for blending with the petroleum oil.

'Ihe invention will be further described in co'nnection with the accompanying drawings, which are of a more or less diagrammatic character, and which sho-w an arrangement of a coke oven plant and by-product recovery system with provision for distilling the tar to produce pitchv and for blending the pitch with petroleum oil.

In the accompanying drawings, Fig. 1 shows a layout of the apparatus including part of a coke oven by-product recovery system, etc.

Fig. 2 is an elevation partly in section sho-wing the short collector main in which the tar is distilled, together with an electrical precipitator.

As illustrated in Fig. 1, the coke oven plant 1, has the usual individual uptake pipes 2, leading to a collector main 3, common to a considerable number of ovens of the battery. From the center boxe, the gases pass through the collector main 5to the condensers 6 and '7, shown as direct condensers cooled by water spray 8. The gases then pass to the exhauster 9.

The tar separated in the collector main, together with the ammonia liquor, flows from the center box through line l0, to separator or decanter 11, where separation of tar and ammonia liquor takes place, the tar being collected in receiver 12, and the ammonia liquor in receiver 13. The tarry oils from the condensers 6 and 7, are drawn off through lines 16 and 17, and may be combined in decanter or separator 18, and the tarry oils then collected in receiver 19, and the ammonia liquor in receiver 20.

The tar from the collector main, which will be a relatively heavy tar, may be pumped from the tank 12, thro-ugh line 15, by means of pump 14, to the short collector main 21, for distillation, or outside tar may be introduced through the line 41.

The short collector main 21 is located at the back of the battery and is connected with a limited number of uptakelpipes 22, from individual ovens, so that the gases from as many ovens as desired can be introduced into the short collector main for distillation purposes. The tar supplied through line 1-5, isatomized or sprayed into the short collector main so that the tar will be distilled and a pitch residue produced. In the apparatus illustrated, spraynozzles 23 and rapidly rotating discs 53, driven by electric motor 54, are provided for atomizing or spraying the tar and pitch and bringing them into intimate contact with the gases. By regulating the rate at which the tar is supplied, the entire distillation may take place during a single passage through the short collector main, or the pitch so produced may be recirculated, if desired, to increase its melting point, or it can be subjected to further 5 shown with an agitator therein for promoting agitation and intermixture of the contents thereof.

The gases employed for the distillation of the tar will be enriched in vapors and may carry suspended pitchl particles resulting from the atomizing or spraying of the tar into the gases. These gases can be cooled to condense a tarry oil therefrom, which will, however, contain much less heavy tar or pitch constituents than ordinary tarry oil, or can be a vant geously subjected to a cleaning treatment a igh temperature, e. g., with an electrical precipitator to separate suspended pitch particles therefrom and to give clean Y gases carrying clean oil vapors, from which clean 26) oils can be directly condensed. For this purpose the gases may pass through the line 32 to an electrical precipitator 33, where the pitch particles will be removed therefrom, and then to condensers 34 and 35, which may be indirect condensers,

Where creosote oil and tar acid oils will be condensed, or a total creosote oil, after which the gases may pass through the exhauster 36, ton an absorber for ammonia, etc. The pitch thrown out of the gases in the electrical precipitator 33 may also be employedfor blending with fuel oil by leading in through the line 37 tothe mixing tank 25, although it can be drawn oi 'separately if desired.

In the distillation of tar, and when the resulting gases are cleaned in an electrical precipitator, the

uptake pipes and the short collector main are advantageously insulated to avoid loss of heat from the gases, so that the gases can be employed at substantially their maximum temperature for 40 distillation. The pipe leading to the electrical precipitator, and the electrical precipitator itself, may also be advantageously insulated or supplied with a suitable heating jacket to prevent loss Iof heat or to supply sulllcient heat to maintain the temperature substantially constant whilethe gases are passing through the precipitator. o By operating in this way a high enrichment of the gases in vapors is obtained and a pitch of relatively high melting point can be readily produced,

e. g., a pitch of melting point of around 200 F.,

or higher, or in some cases where desired, a pitch of melting point around 300 F.

Fuel oil or heavy petroleum oil, e. g., having an asphalt or mixed base and being of the character commonly employed'for fuel purposes, and particularly fuel oil resulting from operations in which cracking or decomposition takes place, may be supplied directly to the mixing tank 25, where the temperature of the pitch is sufcient to heat the resulting mixture; but the fuel oil can advantageously be preheated by bringing it directly into contact with hot coal distillation gases in the short collector main similar to that usedl for tar distillation or by heating the fuel oil in a pipe coil located in the flue from the coke oven to the stack or by other preheating means. In the drawings the pipe coil 31 is shown as located in the flue leading to the stack, and the oil is forced` through this coil and then through the line 26 to the mixing tank 25. The hot thinly fluid pitch entering the mixing tank directly from the short collector main 21, through the line 24, will require no added heating, and it may be sufficiently hot to supply all of the heat needed to heat the fuel 5 oil, although the fuel oil may be independently preheated when necessary or desirable. The fuel oil itself, preheated if necessary or desirable, en: ters the mixing tank to which the pitch is introduced, and both the pitch and fuel oil may be introduced simultaneously and continuously. The agitator in the tank serves to insure intimate intermixture and blending of the pitch and fuel oil. When the tank is partly filled, the continuous introduction of pitch and fuel oil in regulated amounts will result in the blending of added streams of material with thebody ofvmaterial in the mixing tank, which will be kept in circulation by means of the agitator 46.

'The mixing tank is shown with a vapor outlet pipe 48 leading to a condensing coil 49 from which the condensate collects in receiver 50 and can, be drawn off through pipe 51 or returned to the mixing tank through pipe 52.

Where a considerable body of the resulting fuel composition is contained in the mixing tank or in a storage tank, of which the mixing tank 25 may be taken as an example, the mixture can be heated readily by circulating it through the line 42, by means of the pump 43, to a pipe coil 44, located in the ue leading to-the stack and returning the composition through the line 45 to the storage tank. By regulating the mixture in this Way it can be kept at a suiciently high temperaturen to maintain it thinly fluid, so that it can be drawn off as required to the burners.

In addition to producing the fuel composition, in which the pitch residue produced at the coke oven plant is employed, the oils resulting from the distillation of the tar and condensed in the condensers 34 and 35, may be collected in receiving tanks 38 and 39 and employed as creosote oils or tar acid oils, etc.; or they can in part or in whole be blended with-the tarry oils collected in the receiver 19, to pro-duce creosoting compositions suitable for use, for example, as improved substitutes for coal tar solution. In this way the tar produced at the coke oven plant, or tar produced from other cofke oven plants, can be worked up into valuable creosote oils and other products, more valuable 'than fuel, and the tar which would otherwise be employed for fuel, replaced with petroleum oil, which is blended with the low carbon pitch residue from the distillation to form a new and advantageous fuel composition.

The following specific examples will further illustrate the invention. The pitches employed were coke oven tar pitches produced by distilling4 points specified, by the air bath meltinglpoint method.

In the following table the results obtained were with a heavy fuel oil of 15 tok 18 .B. (spec. grav. 0.92 to 0.94) from Midcontinent crude (mixed base oil). The table gives th proportions of pitch and fuel oil, the melting pointof the pitch and the critical temperature of the mixture.

Proportions Critical temp. Melting point. of pitch pitch to on of i e 'I'he following table shows the obtained results with a light fuel oil of 28-35 B. (spec. grav. 0.87) mixed with the pitch.

Proportions Critical temp. Memng point of pitch pitch to oil of mixture C. 4:1 95 1:1 125 122 170 4:1 165 1:1 zoo 'I'he following table shows the results obtained by mixing pitch of the melting points given with a mixture of parts heavy oil (l5-18 B.) and 20 partsextracted carbolic oil (i. e. carbolic oil from which the phenols had been extracted, leaving a neutral oil).

Proportions C -t. lt m Melting 01m ofpitch pimhto mi P- p mixed oils of mixture C'. 151 F 4:1 85 D0 1:1 76 D0 1:2 160 Melting point of pitch keegggn 151 F 11. 4 163 12. 7 m8 16. 5 l n 34. 2

References to pitch melting points refer to meltling points determined by the method described in Methods of analysis used in the coal tai' industry by J. M. Weiss in, the Journal of Industrial and Engineering Chemistry, vol. 10, No. 10, October, 1918, Page 81'1.

I claim: 1

1. A new fuel composition having a low critical tempera/.ure and comprising a mixture .of petroleum oil and coal tar pitch of low free carbon content and a melting`point not over about 300 F. produced by the distillation of coal tar by direct and intimate contact with hot gases without excessive heating of either the tar undergoing distillation or the pitch residue.

2. A new fuel composition having a low critical temperature and lcomprising a mixture ofy petroleum oil and coal tar pitch of low free-carbonv lation of coal tar, while in the form of spray by contact with hot gases and without excessive 'heating of leither the tar undergoing distillation STUART PARMELEE MILLER.

Images