US2314641A - Briquette carbonizing process using modified tar or pitch binders - Google Patents

Description

Patente d Mar. 23, 1943 BRIQUETTE CARBONIZING PROCESS USING MODIFIED TAR OB. PITCHBINDERS Clayton S. Wolf, New Have", Conn, assignor, by

to American Cyanamid Company, New York, N. Y., a corporation of Maine mesne assignments,

No Drawing. Application July 2, 1940,

Serial No- 343,554

3 Claims. (01. 202-34) This invention relates to the carbonization of briquettes prepared from coking bituminous coals and more particularly relates to the use of modified tar or pitch binders in such processes.

It is well known that any coking bituminous coal can'be ground to a certain degree of fineness, say to all pass through a 28 mesh screen, and without the use of any binder the ground coal can be compressed into a briquette and this briquette can be carbonized. Depending upon the method of carbonization, that is to say whether the carbonization is carried out in a so-called byproduct coke oven or whether avertical retort oven is used in which the briquettes continuously pass through the retort counter-current to a flow of heated non-oxidizing coking gas, a maximum rate of temperature rise per minute through the plastic temperature range can be determined at which rate the briquettes will not swell. Furthermore, there can be determined the maximum superimposed headload which the briquette will withstand without slumping, or deforming when it is carbonized at the maximum non-swelling rate of temperature rise through the plastic temperature range. I

It is also known that, if coal tar pitch or coal tar is used as a binder for. making briquettes of the bituminous coals, the amount of superimposed headload which the briquette will sustain at the maximum non-swelling temperature rate will be very drastically reduced. In a practical briquette coking process it is very desirable that the briquettes can be made with a binder which will permit them to be coked at the maximum temperature rate without swelling and which at the same time will withstand appreciable headloads without undue slumping or deformation. In the past many such bituminous coals could not be compressed into briquettes, using coal tar or pitch as a binder, and subsequently carbonized with any degree of success as it was necessary that the briquettes withstand superimposed headloads.

In accordance with the present invention I have discovered a method of treatingcoai tars and/or pitches so that when used as a binder in making briquettes out of finely ground coking bituminous coal the briquettes can be coked and will sustain a higher or greater headload or weight without deformation than they would have sustained if the tars and/or pitches had not been so treated. In modifying the coal tars or.

pitches in accordance with the present invention about 8 to 15% of a moderately strong (60 Baum) sulfuric acid is added to and stirred into pitch, and the-same isthen ready for use a briquette binder. In general, heating of the tar and/or. pitch is not necessary except as the case may be to soften or make liquid in order to facilitate the mixing of the acid with it. In some -instances. however, it may be possible to use a lower percentage of acid if the mixture is subjected to elevated temperatures.- The amount of acid added to the coal tar or pitch will vary with different pitches and will also vary with the type of bituminous coal upon which the material is to be used as a binder. I have found. however, that the coal tar or pitch or a mixture oi coal tar and s5 cheapness.

percentages varying from 8 to 15% cover the best ranges. The strengthoi the acid Baum) is not narrowly confined and can be varied within certain limits without appreciably altering the final results. Likewise, other inorganic acids, such as nitric and mixtures of nitric and hydrochloric, are effective. However, sulfuric acid is preferred because of the consistent results obtained when it is used and also because of its The process of the present invention is applicable to briquettins processes using a wide variety of bituminous coals. In general, it is applicable to all classes of bituminous coals which can be economically formed into briquettes using coal tar or pitch as a binder and subsequently carbonized. Many bituminous coals have a tendency to cake and swell badly when it is attempted to carbonize them at a temperature rise of more than about 1 C. through the critical temperature range. The difllculties due to swelling-and caking of such coals can be very largely overcome by pre-oxidation processes which alter the coking characteristics of the coalsto such an extent that they do not swell and cake when subjected to carbonization at a temperature rise of even 2 0. per minute through the critical range. Several methods of pie-oxidizing coal are known to the art, one being that described in the co-pending application of William J. Kruppa Serial No. 343,518, filed July 2, 1940, in which finely ground coal is subjected to air pressure of about 50 pounds per square inch for a period of about 4 hours while being maintained at a temperature of C. The present inventionis not specifically'concerned with any method of pre-oxldizing bituminous'coals but is primarily concerned with a method of. carbonizing briquettes from such coals. using coal tar or pitch as a binder which v has been modified by acid treatment so that the headload bearing properties of the briquettes are greater than similar briquettes made by using untreated tar as a binder. Many bituminous Ditchas a binder. This coals cannot be compressed into briquettes, using a coal tar binder, and subsequently carbonized at a temperature. rise of more than a fraction of a degree centigrade per minute through the plastic temperature range without badly swelling and caking.v The Pittsburgh seam coals are of this type. They can, however, be subiectedto preoxidation treatments which reduce the swelling and caking characteristics so that briquettes can be formed using coal tar or pitch as a binder and carbonized at a somewhat increased rate of temperature rise through the plastic stage. However,

such briquettes have a very poor headload bear- 1 in: strength and the carbonization cannot, be

carried out in ovens wherein the briquettes in the lower portion of the oven must bear the weight of the briquettes contained in the upper portion of the oven. The Beckley seam coals represent a second class of bituminous coals which cannot be successfully formed into briquettes-using coal tar or pitch'as 'a binder and carbonized at a reasonable rate or temperature rise through the plastic range unless the coal has first been subjected to a pro-oxidation treatment. Even after pre-oxidation these briquettes, using coal' tar or pitch as a binder, have a relatively poor headload bearing strength. when these pre-oxidized coals as described above are formed into briquettes using my modified 'or acid treated tar as the binder, they have a much greater headload bearing strength than those using an untreated tar or binder of the present invention, to produce bri- The procedure was as follows: 7

The 3.2 lbs. of tar were placed in a can which was immersed to about one-half its depth in boiling water until thetar reached a temperature of about '75? C. The diluted acidwas then stirred into the tar. The ground coal was then placed in a. horizontal paddle. mixer or iluxer and the treated tar was poured into the coal and the whole stirred or fiuxed for about ten minutes, which length of time was sufficient to thoroughly mix or flux the tar and coal. The coal and tar fiux was next placed in the feed box of a typical roll briquetting press and compressed into hard.

strong 2 ounce pillow shaped briquettes. These briquettes were then carbonized in a vertical cylindrical retort which gave a column 'depth of briquettes of about 4 feet. The carbonization was effected by passing a stream of coal" gas through the column of briquettes, said coal gas, by means of proper controls and equip ment, was made to risein temperature at a rate of 2% e. per minute. The carbonization was carried to a finishing temperature of 600 C. The carbonized briquettes were \very hard and dense and showed no deformation or slumping of those at the bottom'of'the pile. when a. straight 'raw tar, i. e., non-acid treated tar, was used as a binder, the maximum headloa'd which the briquettes wouldsustain at the rate of 2% C. per

represents the outstandminute was in the order of about Binches rather than 4 feet, without undergoing such a degree of slumping or distortion that the free void spaces between briquettes were so completely closed up that the heated carbonizi'ng gaseould not be passed through any voids and around each briquette to thereby accomplish the carboniaation.

Tests were also carried out on oxidized Beckley seam coal and on oxidized Pittsburgh seam coals.

and in all cases the briquettes using acid treated coal tar or pitch is a binder had a much greater headload bearing ability than briquettes prepared from the same coal using untreated tar or pitch as a binder. Tests were also conducted on the coals described in the test above in which.

quettes having greater headload bearing strength than briquettes. produced from the same coal usinguntreated tar or pitchas thebinder. In. two such coals mined in England and knownas Thorne" and "Alerton Main" respectively it wasfound that when these coals were ground to all 1 pass 28 mesh screen and then compressed into briquettes using about 8% of a suimric acid treated coal tar hinder, the briquettes could be carbonized at a rate 012% C. per minute rise.

through the plastic temperature range and yet sustained a superimposed headload of a 4 foot column of the briquettes, which was comparable with the same performance of these coals at the same rate wherein the briquettes were made with no binder. This is the exact opposite of results usually obtained when coal tar isused as a binder.

in which instance the coal tar bound briquettes always have a much less 40 lbs. of coal ground to'all pass a 28 mesh 3.2 lbs. of raw oven tar 0321b. or 1.84 specific gravity H2804 diluted with 0.18 lb. of water V the proportionflof sulfuric acid added to the .coal tar or pitch was about 8%, 12%, and 15% The results were, in general, comparable to those in which 10% sulfuric acid was used, and in all cases the briquettes had .a greater headload bearing strength than briquettes carbonized under the same conditions but using untreated coal tar as the binder.

As pointed out heretofore, coking bituminous coal briquettes bound with coal tars and/or pitches have been carbonized in many ways, and it is invariably true that such briquettes during the softening range of carbonization (about 800' to 500 0.) could sustain only a relatively small superimposed hesdload without undergoin deformation or slumping of the briquettes. In

using the process of this invention, the acid,

treated tars and/or pitches permitincreases in headioad bearing ability as than the no binder briquettes. The results and the method of carrying out the tests describedas much as the. prior methods. In a preferred carbonization process. in accordance with the present invention, the finely ground coking bitmninous coals compressed into briquettes using myaoidtreatedtarasabindenistheprocessin which the briquettes are carbonized in a vertical retort wherein the briquettes fiow continuously down through the retort counter-current to an ascending stream of a heated, non-oxidising gas. In this process it is obviously an advantage that the briquettes passing through the 300' to 500' 6. range have theability to sustain the maximum possible headload without deformation. This process is of real commercial importance because it permits the use of the coal tar and/or pitch, which are by-products in'coking operations, under conditions which compare favorably with more expensive binders such as sultlte liquor and under conditions which coal tar or pitches could not heretofore be successfully employed.

What I claim is:

1. A method of making briquettes having increased strength during the coking operation, from swelling bituminous coking coals capable of being compressed into briquettes, using coal tar as a binder and carbonized without undue swelling at a temperature rise through the plastic temperature range of at least 2 C. per minute which comprises forming a briquette of such coal, using from 5 to 10% of the binder comprising a mixture of sulfuric acid with a substance included in the group consisting of coal tars, coal pitches, and mixtures of coal tar and coal pitches, and subjecting said briquette to a. carbonization process in which the temperature rise is at least 2 C. per minute through the plastic temperature range, said binder containing from 8 to 15% S111- furic acid.

2. A method of making briquettes having increased strength during the coking operation, from swelling bituminous coking coals capable of being compressed into briquettes, using coal tar as a binder and carbonized without undue swelling at a temperature rise through the plastic temperature range 01 at least 2 C. per minute which comprises forming a briquette of such coal,

using from 5 to of a binder a mixture of sulfuric acid with a substance included in the group consisting of coal tars, coal pitches, and mixtures of coal tar and coal pitches, and subjecting said briquette to a carbonization proces in which the temperature rise'is at least 2 C. per minute through the plastic temperature range, said binder having from 8 to sulfuric acid.

'3. A method of carbonizing bituminous coal briquettes having increased strength during the coking operation which comprises finely grinding the coal, mixing the ground coal with from 5 to 10% of a binder comprising a mixture of sulfuric acid and a substance included in the group consisting of coal tar, coal pitches and mixtures of coal tar and coal pitches, compressing into briquettes and subjecting said briquettes to carbonization, at a temperature rise through the plastic stage of about 2 C. per minute, in a vertical retort wherein the briquettes flow continuously down through the retort counter-current to an ascending stream of heated non-oxidizing gas, said briquettes being capable of sustaining about a 4 foot column .of briquettes superimposed thereon while passing through the plastic stage without undue deformation, said binder containlng'from 8 to 15% sulfuric acid.

CLAYTON s; WOLF.

CERTIFICATE OF CORRECTION. Patent No. 2,51h,6LL1. March 2;, 151g.

CLAYTON s. woLF..

It is hereby c'erti iied that error appears in the printed specification of the above numbered patent requiring correction as follows Page 5, second column, line l before "a mixture" insert -comprising--; and that the said Letters Patent should be read with this correction therein that t Same may conform to the record of the case in the Patent Office.

Signed and sealed this hth day of May, A. D. 1914.5.

I Henry Van Arsdale, (Seal) Acting Commissioner of Patents.