US2030575A - Pitch product and method of preparing same - Google Patents

Description

Feb. 11, 1936. E. H. ELLMS PITCH PRODUCT AND METHOD OF PREPARING SAME 5 Sheets-Sheet 1 Filed June 10, 1931 INVENTOR flaw/6%....

ATTORNEYS Feb. 11, 1936. E. H. ELLMS 2,030,575

PITCH PRODUCT AND METHOD OF PREPARING SAME Filed June 10, 1931 s Sheets-Sheet 2 ATTORNEYS Feb. 11, 1936. E. H. ELLMS PITCH PRODUCT AND METHOD OF PREPARING SAME s Sheets-Sheet 3 Filed June 10, 1951' ATTORNEYS Patented Feb. 11, 1936 UNITED STATES PITCH PRODUCT AND DIETHOD OF PREPARDIG SAME Edward H. Ellms, Fairlawn, N. 3., assignor to The Barrett Company, New York, N. Y., a corporation of New Jersey Application June 10, 1931, Serial No. 543,325 11 Claims. (Cl. 202 -36) This invention relates to an improved method for preparing pitch products from coke oven tar, including high carbon pitch products suitable for use as road tar, roofing pitch, paving pitch, waterproofing pitch, etc. The invention includes both the method and the new pitch products, more particularly the new road tars.

According to this invention, coke oven tar is distilled to produce pitch of high melting point under conditions which minimize decomposition and yield a high percentage of distillate, for example, to 80% by volume, and this pitch is blended with a heavy oil distillate to produce a desirable pitch product. More particularly, the ii ivention relates to pitch products produced by blending pitch with a melting point of 325 F. or preferably 350 F. or higher, such as 375 F. or 400 F. or higher with the heavy oil distillate produced in the production of such pitches by processes which tend to minimize decomposition and yield or more of distillate in the production of such pitches. The oil yield may advantageously be as high as '70 to '75 or and will depend upon the melting point of the pitch produced, etc. The heavy oil may be produced by the fractional distillation of tar or the vapors from the distillation of tar may be fractionally condensed to produce a heavy oil fraction and one or more other oil fractions. The heavy oil fraction is blended with the high melting point pitch in such proportions that a pitch product of high free carbon content suitable for use as a road tar or roofing pitch, etc. is produced. Other oil fractions produced may be employed for creoscting purposes, the production of tar acids, etc.

This process of making pitch products afiords an outlet for heavy oil and high melting point pitch in the form of commercially valuable pitch products in addition to the creosote oil, etc. formed which are likewise commercially valuable. Furthermore, by cutting back the pitch with a fraction of the distillate resulting from the pro- R duction of the pitch, this invention provides a method of producing high carbon pitch products directly from coke oven tar without the use or gas house tar which is generally considered necessary to the production of such high carbon pitch products. By avoiding the use of gas house tar the high carbon pitch products of this invention are produced at relatively low cost. These and other advantages result from employing the process of this invention in preparing pitch products from coke oven tar. It is within the scope of this invention to treat coke oven tar fractions, such as the heavy tar from the collector main, and thelight tar or tarry oil from the coolers or similar fractions, in the way described. The relative yields of oils and pitch will vary according to the composition of the tar fraction treated and the products pro- 5 duced. The term tar as used in this application is intended to cover such tar fractions.

By road tar in this specification and in the claims, I mean a tar of high free carbon content, for example, 12% up to 20 or 25% or more, and 10 ranging in consistency from a float test at 32 C. of 60 seconds or a viscosity of around 80 seconds Engler for cc. at 10' C. up to a float test at 50 C. of 220 seconds or a melting point of around 120 F., i. e. a pitch suitable for a binder. Road 15 tars include (1) heavy surface treatment type materials having, for example, a float test at 32 C. of 60-170 seconds or a viscosity of 80-250 seconds Engler for 100 cc. at 100 C., and a free carbon content of 12-25% and (2) penetration 20 binders with, for example, a melting point of 104-109" C., or a float test at 50 C. of 70-220 seconds, and a free carbon content of about 15-25% or higher. Specifications on road tar often include a maximum percent of distillate 25 allowable on distillation to 300. C. according to A. S. T. M. method D-2030, e. g. a maximum of 20-25% for a road tar of the heavy surface treatment type and a maximum of 15-25% for a road tar of the penetration binder type. The 30 permitted maximum varies in the specifications of difierent purchasers. Materials of the two types now quite generally employed yield 14-18% and 10-14%, respectively, on distillation to 300 C. by the above test. Pitches of high free carbon 35 content are used for binders since the free carbon tends to reduce the susceptibility of the pitch to temperature changes, and its consistency remains more or less constant under changing weather conditions.

By roofing pitch, I mean pitches generally of high free carbon, for example, 15-35%. and a melting point between about 140-and 150 F. By paving pitch, I mean pitches with a melting point of about 100-125 F. or higher, and 45 a high free carbon content of about 15-35%. By waterproofing pitch, I mean pitches with a high free carbon content, for example 12% or 15% up to 35% or more and a melting point of F. or F. to F. or more.

At the present time road tars are generally prepared by distilling coke oven tar and gas house tar separately and blending the distillation residues or by distilling a mixture of coke oven tar and gas house tar. Depending upon the 05 method of distillation and type of tar distilled and the nature of the product desired some 8-20% of oil is distilled from the tar and the residue from this distillation constitutes the desired road tar. The extent of the distillation is varied depending upon the consistency of the road tar desired and the conditions under which the distillation is carried out, i. e. whether the distillation is carried out in a still in which considerable decomposition of tar and formation of carbon takes place or whether less decomposition and formation of carbon occur. The percent of gas house tar blended with the coke oven tar is also varied, depending upon the percent of free carbon desired in the product, etc. In general, 30 percent of gas house tar blended with '70 percent of coke oven tar distilled in a pipe still until the desired viscosity or melting point is reached, yields a pitch of free carbon content, distillation to 300 C. etc., suitable for use as road tar. The extent of the distillation is varied somewhat, depending upon the nature of the road tar desired.

According to this and other methods ordinarily employed for producing road tar, gas house tar is an essential raw material and but a small percentage of distillate is obtained. By distilling coke oven tar to pitch of high melting point, i. e. 300 or 325 F. to 400 F. or higher. as contemplated by the process of this invention, a high yield of distillate oil is obtained. This high melting point pitch is then blended with heavy oil of such composition and in such proportions that road tar, etc. will result. By distilling the coke oven tar to pitch of this high melting point a pitch of sufliciently high free carbon content is produced to yield a material suitable for road tar, roofing pitch, etc. when blended with heavy oil, without the addition of gas house tar. The heavy oil employed for blending may be heavy oil distillate produced by any usual process of distilling tar. The pitch employed is a pitch produced under conditions which tend to minimize decomposition. Otherpitches do not yield blended pitch products of the type contemplated by this invention.

The coke oven tar is distilled to pitch of high melting point under conditions which tend to minimize decomposition and yield a high percent of distillate and the distillation is carried to a point where suificient decomposition of the tar ingredients and formation of carbon result to yield on blending with heavy oil, in suitable proportions, a pitch with a melting point or viscosity, free carbon content, and other properties suitable for road tar, etc. Pitches of this type have not hitherto been produced by straight-rim distillation of coke oven tar to a similar melting point. Even though the distillation is carried out under conditions which decomposition, by carrying the distillation to pitch of high melting point, some decomposition, and possibly other molecular rearrangement takes place, so that even though all of the distillate produced were blended with all of the distillation residue, the

resulting product would not have the same properties as the original tar nor as a residue of the same viscosity resulting directly from a simple distillation. The heavy oil and pitch which are blended together to produce the new pitch product are not necessarily blended in the proportions in which they are obtained by the tar distillation. The heavy oil used is preferably oil produced by a distillation process which tends to decomposition, although any heavy oil distillate may be used.

The new pitch products are characterized by being derived entirely from coke oven tar, havingv a high free carbon content, 1. e. 12% or more, low distillation to 300 C. and the float test, viscosity, or melting point required for road tar, roofing pitch, paving pitch, waterproofing pitch, etc.

The new road tars, for example, differ from ordinary road tars in several respects. They are made entirely from coke oven tar and contain no gas house tar, which is ordinarily blended with coke oven tar in producing road tars to provide the required free carbon content. Ordi nary road tars of the penetration binder type include a considerable percentage, e. g. 10-l4%,

of oils distillable from pitch up to 300 C., which are present to a much smaller extent, e. g. 4-'7% in these new road tar products. A similar relation of content of oils distillable up to 300 C. exists between road tars of the heavy surface treatment type prepared by ordinary methods and by the method of this invention. Due to the low content of these oils of lower boiling range, distillation of the new road tars to 300 C., is low. The amount of distillation to 300 0.,

will vary, depending upon the amount and the boiling range of the heavy oil blended with the high melting point pitch and on the type of road tar produced.

By heavy oil I include oils obtained by the distillation of tar, especially coke oven tar, and characterized by one or more of the following properties:

(1) The specific gravity at 25 C. lies within the range 1.09 to 1.22 (the specific gravity of ordinary creosote oil at 25C. liesin the range 1.03 to 1.09).

(2) Distillation by the A. S. T. M. Method D- 24630 gives results which lie within the following ranges:

Start to 210 C between 0 and 3% Start to 235 C between 0 and 10% Start to 315 C between 0 and 35% Start to 355 C etween 2 and 52% (3) The Engler viscosity for 100 cc. at 100 C. lies between 25 and 100 seconds.

These heavy oils do not contain the lowest boiling oils present in tar and' the so-called middle oils may be partially or even totally absent.

/ The following examples of the various heavy oils which may be employed to advantage in blending with high melting point pitch in the present process are cited as illustrations without intending to limit the scope of the invention. A

fraction may be used which'distills over after 40% of oil has been distilled from coke oven tar in a distillation process in which a total of about of oil is distilled, i. e. the heaviest fraction representing about 35% by volume figured on the tar distilled. This oil has a specific gravity of about 1.140-1.160 at 25 C. A heavier oil such as the oil which distills over ,after about 55.0r 65% of oil has been distilled from coke oven. tar in a process in which about 75% of oil is distilled, i. e. 10 or 20% by volume figured on the tar distilled, may be used. Such an oil will have a specific gravity at 25 C. of about 1.l70-l.220. A lighterheavy oil such as the oil which distills over after about 10 or 20% of oil has been distilled from coke oven tar in a process in which about 75% of oil is distilled, i. e. 55 to 65% by volume figured in the tar distilled, may be used. Such an oil will have a specific gravity at 25 C. of about 1.090 to 1.130. It should be understood that in the above examples the specific gravities given apply to oils obtained by the distillation of normal coke oven tars and that if abnormally light or heavy tars are distilled the gravities of the oil fractions will vary correspondingly.

The following example shows the application of the process to the production of a road tar. Coke oven tar was distilled to produce an oil yield of 74% by volume (based on tar) and a pitch of 390 F. melting point. The fraction of condensate representing the first condensable by regulated cooling of the total vapors, i. e. a fraction representing 20% by volume of the tar,

1. was successfully blended with the high melting point pitch produced to obtain a suitable road tar. This heavy oil had a gravity of 1.174 at C., a viscosity of seconds, Engler, for 100 cc. at 100 C., and on distillation yielded:

20 0 at 170 C. 2.3% at 235 C. 4.8% at 270 C. 8.6% -1 at 300 C.

Pitch of the high melting point required for the successful carrying out of this process was prepared by distilling coke oven tar in the form of a fine intense spray in superheated steam or other hot inert gases such as coke oven gases, etc. In producing the heavy oil described in the preceding paragraph, 100 parts of coke oven tar were distilled in hot coke oven gases. The distillation yielded 20 parts of the heavy oil, 54 parts of creosote oil, and 25 parts of pitch with a melting point of 390 F. Thirty-seven and four-tenths percent by volume of the high melting point pitch was blended with 62.6% by volume of the heavy oil. A road tar of very desirable characteristics was obtained, as shown by the following tests:

Melting point 108 F. Free carbon 18.7%. Absolute viscosity at 55 C.193 poises.

Distillation according to A. S. T. M. Method D920--28 yielded.

Temperature, 0. I Percent Melting point of residue 147 F.Penetration,

- 50 gms., 5 seconds Temperature, C. Percent assess 31.9 gallons of road tar of this composition were obtained from one hundred gallons of coke oven tar by this process and in addition there were When a heavier oil is employed, a larger percentage of the oil is blended with a smaller percentage of the pitch to obtain a road tar of the same melting point, and this lowers the free carbon content of the pitch product. But a lighter oil, which contains the heavy oil and, in addition, lower boiling constituents, may be blended with the pitch to produce road tar of the same melting point and the same or a higher free carbon content, a small proportion of the oil being employed to produce a product of the same melting point.

Pitch of higher melting point and higher free carbon content, such as roofing pitch with a melting point of F., for example, maybe produced by blending less oil than in the case of road tars. The quantity of heavy oil to be blended with a high melting point pitch to produce the pitch of given melting point depends in this case also on the character of the heavy oil used; a very heavy oil must be used in greater proportion than a moderately heavy oil of, for example, 1.140-1.160 gravity at 25 C.

Heavy oil having a specific gravity in the heavier end of the range specified is suitable for the production of higher melting point pitches such as roofing pitch, but it is not suitable for the production of road tars. The maximum gravity at 25 C. of heavy oil suitable for blending with hard pitch, without the addition of other materials, to produce road tar is 1.180 or 1.190 but for the production of roofing pitch the heavy oil may have a specific gravity at 25 C. as high as 1.220 without requiring the addition of any other material to produce satisfactory roofing pitch.

Using an oil with a specific gravity of 1.170 at 25 C., for example, roofing pitch with a melting point of 147 F'., and a free carbon content oi 21.9% was prepared by blending 68.4 parts by volume of the oil with 31.6 parts by volume of 394" F. melting point pitch. The oil was moisture free and contained 0.3% free carbon.

Distillation according to A. S. T. M. Method B- 246-30 yielded:

Temperature, C. Percent Float on residue -Soft.

Roofing pitches which yield no more than 1.5%

.distillate on distillation to 300 C. by A. S. T. M.

Distillation D20 30 Temperature, C. Percent roe-0 The foregoing are examples of pitch products made according to the method of this invention which, on distillation, yield less distillate than pitches of the same melting point made by the usual methods for use as road tars, roofing pitches, etc. The following is an example of one of the new pitch products of this invention which does not differ from road tars prepared by the usual methods in respect to the percent of distillate it yields on distillation by A. S. T. M. Method 20-- 30 to 300 C., but it, like all of the preceding examples, is made entirely from coke oven tar and has a high free carbon content. It is a new product. A road tar of the penetration binder type having a float test at 50 C. of was made by blending 38.9 parts by volume of 417 F. melting point pitch with 61.1 parts by volume of light wide boiling heavy oil. The oil used showed the following tests: Specific gravity at 25 C 1.112

Water h 1.0% Free carbon 0.16%

Distillation by D246-30 S. T. M. Method Temperature, C. Percent Float on residue-31".

This oil represents approximately the highest boiling 50-55% cut condensable by regulated cooling from the total oil vapors produced by distillation to approximately 400 F. melting point pitch. The road tar made as above showed the following tests:

Float at 50 C. (A. S. T. M. Method D- 139-27) 170" Specific gravity at 25 C 1.216

Free carbon 21.3

Melting point of residue-459 C.

When road tars of the same melting point or float test are made .by the regular methodsthey usually show 10 to 14% of distillate at 300 C. By blending a heavy oil with a high carbon pitch in suitable proportions, a high carbon tar may be prepared which is similar to gas house tar and which may be used as a substitute for gas house tar for blending with coke oven tar to prepare a tar mixture suitable for distillation to road tars by the ordinary methods.

Iniproducing pitch from tar according to the usual methods of distillation such as those which involve heating a large volume of tar in a still by the external application of heat to the still, considerable decomposition result probably as a result of over-heating, such as local over-heating at the heated surfaces of the still. Constituents of the tar which would volatilize if the tar were heated under conditions which minimize decomposition, break down into volatile oils of more stable composition and free carbon is formed. Pitches of lower melting point can be produced processes of distillation and the distillate pro- I duced contains ingredients which are decomposed by other methods. The yield of distillate is higher than by other methods and it contains constituents of high boiling point which are absent from distillate produced by ordinary methods, or are present in such distillate only in small amounts. The distillate obtained by distilling tar by ordinary methods and by methods which tend to minimize decomposition may not differ greatly when pitches of lower melting point are produced, but in producing pitches of higher melting point the distillate produced contains constituentswhich are not volatilized by the ordinary methods of distillation.

When tar is distilled by being sprayed and resprayed into a current of hot gases a large continually changing surface of the tar is exposed to the hot gases and decomposition which results when thetar or distillate is subjected to prolonged heating is avoided, at least to large extent. The still may be heated externally to supply a portion of the heat for the distillation if the contents of the still are vigorously agitated, although according to the preferred method the entire heat for the distillation is supplied by the hot gases. Such distillation is referred to herein by the expression distillation under conditions which tend to minimize decomposition. By avoiding decomposition to the extent which accompanies the usual methods of distillation the heavier oils can be distilled and the pitches produced are fluid at high temperatures and free, or relatively free, from carbonaceous coke-like deposits present in pitches of even low melting point produced by the usual methods of distillation.

Apparatus designed for carrying out the process by distilling tar in hot coke oven gases is shown in the accompanying drawings, but it is intended and is to be understood that the invention is not limited to the process described in connection with the drawings.

Fig. 1 is a plan view;

Fig. 2 is an elevation partly in section of the apparatus of Fig. 1;

Fig. 3 is a section on the line 3-4 of Fig. 2;

of the battery with the hot gas header I2. By

the proper manipulation of valves in the uptake pipes 1 and the uptake pipes I I, gases from these selected ovens may be passed either to the collector main 6 or through the hot gas header I2 into the still "I. v

In the still is means for producing a fine intense spray of tar or semi-pitch in the gases. This comprises a roll l3 which dips slightly into remaining vapors.

the'tar and pitch in the still. This roll is adapted to be rotated by the motor I4 at a high rate of speed, 9004200 R. P. M., for example, which throws a fine intense spray of the tar and pitch into the gases and on to the walls of the still, keeps the walls free from accumulations of pitch and prevents the formation of coke thereon. The tar is distilled by the hot gases and the gases are scrubbed and substantially detarred. The pitch produced is drawn oil from the still through the coke trap 55 and the levelling arm IS. The depth to which the tar or pitch is allowed to accumulate in the still is controlled by the pos tion of the levelling arm.

A still of somewhat similar construction in which the tar is brought into contact with hot gases in the form of a fine intense spray may be employed for distilling coke oven tar in steam or other inert gases to produce pitch of high melting point and a high percentage yield of distillate. The conditions in such stills during distillation tend to minimize decomposition and pitches of high melting point and distillate oils which contain constituents of high boiling point can be readily produced.

The coke oven tar which is distilled to semipitc'h before it enters the still is further distilled in the still and a pitch of high melting point, for example, pitch with a melting point of 390 F. is produced in the still. This pitch is drawn oiT through the trough IT to the mixing tank l9 where it is blended with heavy oil to produce the road tar.

Gases and vapors from the still pass up through the hot gas saturator 20. The coke oven tar, preheated as described below, is sprayed into these gases through the nozzle 2|. The bafiiing means 22 provides a large surface of contact between the tar and the hot gases and vapors and serves to remove any entrained particles of pitch spray which may be carried over from the still. The semi-pitch produced is drawn off through the line 23 and fed to the end of the still l into which the hot gases enter from the hot gas header I2. This semi-pitch and the hot gases pass through the still in a concurrent direction, the semi-pitch is sprayed into the gases in the form of a fine intense spray, and the high melting point pitch is produced by such further distillation of this semi-pitch.

From the hot gas saturator 20, the gases and vapors pass through the heat interchanger 25 where the tar is preheated and heavy oil vapors are condensed and separated from the gases and The tar enters the heat interchanger from the line 26 through the header 21. The boiling range of the heavy oil which is separated in the heat interchanger is controlled by the amount of tar fed through each of the passages 28 into the coil 29. By proper adjustment of the valves 30 a heavy oil of desired boiling range is produced. The preheated tar is supplied to thenozzle 2|. It is distilled to semipitch by direct contact with the gases and vapors from the still in the saturator 20 and then further distilled in the still l0.

From the heat interchanger 25 the gases pass to a creosote oil condenser 3|. This is shown as a direct condenser in which the gases are sprayed with water or ammonia liquor from the line 32. The resulting gases together with the vapors of light oil pass out through the line 33 and the exhauster 34 to means for the recovery of ammonia and light oil, etc. Instead of a single condenser at 3| fractional condensersmay' be employed where it is desired to recover a fraction high in'tar acids or other fractions. The creosote oil is drawn oil into the decanter 35 and thence to the oil storage tank 36.

Other condensing means may be employed for recovering the heavy oil from the gases, and rectifying means may be used where desirable. The heavy oil which is separated from the gases by indirect heat interchange with the incoming coke oven tar in the heat interchanger 25 is drawn off through the line to the blending tank.

The process may be so regulated, for example, that this oil fraction represents the highest boiling 20% by volume of the coke oven tar being distilled obtainable by fractional condensation when 'a total distillate of 74% is recovered. The creosote oil collected in the tank 36 then rtpresents 54% of the tar distilled.

All or a part of the heavy oil which is drawn oil through the line 40 may be blended with all or a part of the pitch produced in the still to form the pitch product of this invention. The heavy oil and pitch may, for example, be blended in the proportions of 37.4% by volume of pitch with 62.6% by volume of heavy oil. If only the heavy oil produced in the process is blended with the pitch, a portion of the pitch will be drawn off from the coke trap 15 through an additional levelling arm 4| provided for this purpose. This pitch may be collected and disposed of in any suitable manner. It may be chilled and granulated by contact with a stream of cold water from the line 42 in the trough 43 in which case the granulated pitch will be collected in the tank 44.

Where a quantity of heavy oil has been stored, enough may be added through line 45 to the heavy oil produced from the tar distillation to supply suificient heavy oil for blending with all of the heavy pitch produced during the tar distillation in the above proportions to produce a high carbon pitch product of the melting point, etc, desired. Heavy oil produced by other methods of distillation may be added through this line 45. When only a portion of the oil produced in the still is blended with the pitch, the balance may be drawn off through the line 45'.

The heavy oil out may be produced in such quantity that it will be sufiicient for blending with all of the hard pitch produced in the operation. The size of the heavy oil out necessary to accomplish this depends on the melting point of the final blended pitch product and increases as the pitch melting point decreases. A heavy oil out sufiicient to cut all the hard pitch back to road tar of 109 F. melting point will be in the lighter end of the range of heavy oils described. It may, for example, have a specific gravity oi. 1.110-1.130 at 25 C. If it is desired to produce roofing pitch of F. melting point, the necessary heavy oil out will be smaller, and it may have a specific gravity of 1.140-1.160 at 25 C. An operation of this character may be called self-contained; i. e., no excess hard pitch is produced and it is not necessary to store heavy oil in advance to use up all the hard pitch.

The heavy oil and high melting point pitch may be blended in any mixing tank adapted for the blending of a flux with such a high melting point pitch. The apparatus shown in the drawings is described indetail in theMcCloskey application, Serial No. 382,376, filed July 31, 1929. The high melting point pitch in a hot liquid condition is fed into the mixing tank through the inlet 46, It gradually blends with the mass of blended cumulation of deposits of high melting point pitch from hardening thereon. The resulting pitch product is drawn off from the tank through the line 53.

The heavy oil as it is drawn ofi from the bottom of the heat interchanger is hot and flows readily.

A heater 54 is shown for heating any heavy oil which is introduced through the line 45.

A condenser 55 is provided for condensing vapors which may be evolved during the blending operation and returning the condensate to the mixing tank or drawing it off as a separate product.

The character of the pitch products produced by the process of this invention is dependent to large extent upon the specific gravity, boiling range and amount of oil blended with the pitch, and also upon the properties of the pitch,

By varying the melting point of the high melting point pitch from 300 F. or 325 F. or preferably 350 F. to 400 F. or higher and controlling the collection of the distillate to produce a heavy oil of the proper boiling range and blending the .heavy oil and pitch in suitable proportions, a

pitch product of free carbon content, etc., suitable for road tar, roofing pitch, etc., may be produced.

I claim:

1. The method of producing pitch products from coke oven tar, which comprises spraying the tar into a hot gas and avoiding prolonged heating of the tar thereby distilling it with minimum decomposition to produce a high melting point pitch and a high yield of distillate including a heavy oil fraction and blending at least a portion of the high melting point pitch with at least a portion of the heavy oil fraction to produce a pitch product of high free carbon content,

2. The method of producing pitch products from coke oven tar, which comprises spraying the tar into a hot gas and avoiding prolonged heating of the tar thereby distilling it with minimum decomposition to produce a high melting point pitch and blending the pitch with coal tar distillate having a specific gravity between 1.09

and 1.22 at 25 C.

3. The method of producing a low melting point pitch product of high free carbon content from coke oven tar, which comprises spraying the tar into a hot gas and avoiding prolonged heating of the tar, thereby distilling it with minimum decomposition to produce a pitch having a melting point of at least 300 F. and a high yield of distillate including a heavy oil fraction, and blending the pitch with the heavy oil fraction in proportions to yield a pitch product with a carbon content between 12% and 35%.

4. The method of producing a low melting pitch product of high free carbon content from coke oven tar, which comprises spraying the tar into a hot gas and avoiding prolonged heating of the tar, thereby distilling it with minimum decomposition to produce a pitch having a melting point of at least 300 F., blending the resulting pitch with coal tar distillate having a specific gravity between 1.14 and 1.22 at 5 C, in P p tions to yield a pitch product having a carbon content between 12% and 25%.

5. The method of producing a road tar, which comprises spraying coke oven tar into a hot gas and avoiding prolonged heating of the tar, thereby distilling the tar with minimum decomposition to produce pitch of at least 300 F. melting point and blending the pitch with coal tar distillate having a specific gravity between 1.14 and 1.18 at 25 C. in proportions to yield a pitch product having a carbon content between 12% and 25%.

6. The method of producing a pitch product, which comprises distilling coke oven tar in the form of a fine intense spray in a hot inert gas to distill ofi at least 60% of the tar as distillate and produce a pitch with a melting point of at least 300 F. and blending the resulting pitch with a. portion of the distillate fraction having a specific gravity between 1.14 and 1.22 at 25 C. in proportions to yield a pitch productvwith a carbon content between 12% and 35%.

7. The method of producing a. road tar, which comprises spraying coke oven tar into a current of hot inert gases and avoiding prolonged heating of the tar, thereby distilling 011? from the tar with minimum decomposition at least 60% of distillate and producing a pitch with a melting point of at least 325 F., fractionally condensing the resulting vapors to obtain a fraction with a gravity between 1.14 and 1.22 at 25 C., and blending at least a portion of the pitch with at least a portion of this fraction of distillate to produce a pitch product with a free carbon content between 12% and 25%.

8. A pitch product obtainable by blending pitch of at least 300 F. melting point produced by spray distillation of coke oven tar with a heavy coke oven tar oil having a specific gravity between 1.09 and 1.22 at 25 C., said pitch product having a free carbon content. of between 12 per cent and 35 per cent and yielding on distillation to 300 C. not more than about '7 per cent distillate.

9. A road tar obtainable by blending pitch of at least 300 F. melting point produced by spray distillation of coke oven tar with a heavy coke oven tar oil having a specific gravity between 1.11 and 1.22 at 25 C., said road tar having a free carbon content of 12 per cent to 25 per cent and yielding less than 7 per cent distillate on distillation to 300 C.

10. A road tar of the penetration binder type composed of pitch with a melting point of at least 325 F., prepared by spraying coke oven tar into a hot gas and avoiding prolonged heating of the tar, blended with a heavy oil of specific gravity between 1.14 and 1.18 at 25 C., prepared by distillation of coke oven tar, said road tar having a float test between '70 and 220 seconds at 50 C. and a free carbon content between per cent and per cent, and yielding between 4 per cent and 7 per cent distillate upon distillation to 300 C.

11. A roofing pitch composed of pitch with a melting point of at least 325 F. and heavy oil having a specific gravity between 1.11 and 1.22 at 25 0., both derived from coke oven tar by spray distillation thereof, said pitch having a melting point of 140 to'150 F. and a free carbon content between 15 per cent and per cent, and yielding not over 1.5 per cent distillate upon distillation to 300 C.

EDWARD H. EILMS.

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