US1849197A - Operation of coal distillation plants - Google Patents

Description

March 15, 1932. s. P; MILLER OPERATION OF COAL DISTILLATION PLANTS Filed April 17, 1929 2 Sheets-Sheet JHU ATTOR N EYS March 15, 1932. s. P. MILLER 1,349,197

7 OPERATION OF COAL DIS'I'ILLATION PLANTS I Filed April 17, 1929 2 Sheets -Sheet 2 [wide/15s," I 4/ g I lvsm'o WM ATTORN EY6 Patented Mar. 15, 1932 STATES PATENT OFFICE STUART PARMELEE MILLER, OF ENGLEWOOD, NEW JERSEY, ASSIGNOR TO THE BARRETT GOMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY OPERATION OF COAL DISTILLATTON PLANTS Application filed April 17,

This invention relates to the operation of coal distillation plants such as a plant of coke ovens or gas retorts. The invention comprises both the apparatus and the meth 0d of operating the same, and relates more particularly to a new and improved method of preparing creosoting compositions which are valuablesubstitutes for the ordinary coal tar solutions, s o-called.

According" to the present invention, hot coke oven gases or gas retort gases carrying suspended heavy tar and pitch constituents are subjected to a cleaning treatment and the cleaned gases are then blended with gases not subjected to the cleaning treatment, and the blended gases are cooled to produce a tarrv oil of regulated free carbon content. The cleaning treatment is preferably carried out at a sufliciently high temperature to malntain a large proportion of the oils in the form of vapors during the cleaning treatment and the temperature at which the gases are cleaned is sufficiently high to maintain in vapor form the necessary amount of clean oils of higher boiling range so that blending of the cleaned gases with the proper quantity of the uncleaned gases followed by cooling of the blended gases willgive a tarry oil of desired free carbon content and of desired boiling range which may be employed directly as a substitute for the ordinary creosoting compositions of the type known as coal tar so lution. orin special cases it may be desirable to eliminate a part or all of the lighter oils from the tarry oils or to add tar or to add distillate oils to the tarry oils beforeuse as cpeosotin-g composition.

In making ordinary coal tar solutions the greater part of the tar collected from the col e oven gases is distilled and the distillate is blended with a relatively small proportion of undist-illed tar commonly in the proportion of 80% of distillate.to 20% of tar to make the coal tar solutions of commerce. The distillation of this large amount of tar is expensive and when distilled by the usual, methods considerable decomposition of oil tal es place during the distillation with resulting loss of valuable oil and corresponding increase in pitch production.

1929. Serial No. 355,950.

The proportion. in which coal tar is blended with coal tar distillate in making coal tar solutions is governed by commercial specifications which are of such a character as to require the distillaton of a large amount of tar and the blending of only a limited amount of undistilled tar with a large amount of distillate. For example, coal tar solutions are commonly required to contain not more than two percent of so-called free carbon. The specifications also usually limit the amount of low boiling distillate, for example to not more than 5% distillate up to 210 C. and not over 25% up to 235 C., while limitations are also imposed as to the character of the residue remaining after the distillation to a specified maximum temperature, usually constituents or both gases when the blended gases are cooled and a tarry oil of desired low free carbon content is obtained. -I carry out this cleaning of the gases at-a sufiiciently high temperature to leave in vapor form a large part of the normal oil content of the gases cleaned. sothat on subsequent blending of these gases with gases not cleaned and cooling the blended gases there is directly separated from the gases a tarry oil containing only a limited amount of tarry constituents, the amount being such that the oil as a whole.

and the oil evep after limited distillation to.

remove any excess of low boilingpoint constituents will have a snfficiently low content of so-called free carbon to enable it to be di- .rectly employed without the addition of distillate for making creosoting compositions. If the content of tarry matter as evidenced by the content of so-called free carbon is not sufficient in the tarry oil recovered, additional tar may be blended therewith, but in any event the distillation of a large amount of tar to produce a large amount of distillate oils is made unnecessary.

According to this invention the gases coming from a battery of ovens or retorts may be divided and a regulated portion of the gases subjected to a cleaning treatment. in which entrained tar and pitch particles are removed from this part of the gases and the gases-are then combined and cooled to produce a tarry oil of regulated free carbon content. The gases from the battery may be collectcd in a collector main of the ordinary type and be passed into the cross-over main in the usual manner. By dividing the gases, sending a portion to cleaning apparatus and bypassing the balance around such cleaning apparatus, then recombining the gases after cleaning and cooling the recombined gases in the same condensing system, a tarry oil of low free carbon content will be separated from the gases in the condensers.

A portion of the gases collected in the collector main of the ordinary type. may be withdrawn thru a conduit connected with one end of the collector main. The balance of thegases may be taken oil thru the usual ed gases cooled and the Whole operation may be controlled so that creosoting composition is obtained directly or, at any rate, a tarry w oil may be obtained from which creosoting composition can be prepared without the addition of distillate oils.

The device employed for cleaning the gases may be operated intermittently. All of the gases may pass thru the cleaning device, but due to the intermittent operation only a part of the gases will be cleaned. The cleaned and uncleaned gases will be cooled in the same condenser and a tarry oil of low free carbon content will be obtained.

The gases given off from a coke oven or gas retort during the various stages of the coking of each individual charge vary in composition and the percent of entrained tar and pitch particles carried forward by the gases varies during the coking of each charge. By separately collecting the gases during different stages of the coking opera-' tion as byseparately collecting the lean gases given off during the later stages of the coking operation, or separately collecting the rich gases given off during the-earlier stages of the cokingoperation and then subjecting removal of light oils or the addition of tar or. tarry oil. By tarry oil I refer to a com position such as the tar product rich in low boiling constituents obtained in the condensers of an ordinary coke oven by-product recovery system.

Different types of cleaning apparatus may be employed according to this invention. An ordinary gas scrubber may be employed for removing entrained tar and pitch particles from the gases. In such a scrubber the gases may be passed up thru a tower and a scrubbing medium sprayed down thru the tower. A considerable proportion of the entrained impurities may be removed in an ordinary scrubber although complete'cleaning is not ordinarily obtained in such equipment. The cleaning of the gases contemplated by this invention is substantially complete cleaning or cleaning in which the pitch content of the gases is reduced to such an extent that on cooling oil would be obtained of lower free carbon content than the maximum permissible for creosoting composition. By blending with ordinary gases before cooling the free carbon content of the product will be raised.

The scrubbing contemplated by this invention may be effected in that type of apparatus commonly known as an Otto injector in which a liquid is injected into the gases and intimate contact between the liquid and the gases is obtained. Such an apparatus may be successfully employed for forcibly bringing the scrubbing medium into contact with the gases.

Still a different type of scrubbing device which may be employed comprises a scrubbing chamber in the bottom of which is located a reservoir for the scrubbing me di'um. By rapidly rotating a horizontally positioned cylindrical member such'as a horizontal roll, Within the chamber-in such a way that it dips to only a slight extent into the contents of the reservoir, the scrubbing medium will be sprayed up into the gases passing thru the chamber and the gases will be subjected to an intimate and intensive scrubbing which eliectively removes entrained material from the gases.

The medium employed for scrubbing the gases may be the tar or pitch removed from the gases during the scrubbing operation. The gases are advantageously scrubbed at a regulated high temperature. In many cases it will be desirable to regulate the cooling of the gases in the collector main in order to avoid cooling to such an extent that excessive amounts of the higher boiling oils will be condensed. With properly regulated cool ing these high boiling oils will then pass thru the scrubber in vapor form. If the gases are scrubbed with a heavy tar or pitch of the same composition as that suspended in the gases, the oil vapors in the gases will not be changed in composition within the scrubber but will leave the scrubber containing substantially the same ingredients and vapor constituents as were present in the gases when they entered the scrubber, except that entrained tar and pitch particles will be removed duringthe' scrubbing operation.

When a tar or pitch containing lower boiling oil than those present in the pitch or tar in equilibrium with the gas is employed for scrubbing the gas, the latter will, to a greater or less degree. be enriched by the lighter oils in the scrubbing medium providing the temperature of the scrubbing medium is approximately at the temperature of the gas, or

higher. With a limited amount of scrubbing medium, enrichment will be obtained even it the temperature of the scrubbing medium is below that of the gas. If the temperature of the scrubbing medium is above that of the gas. a substantial degree of distillation with attendant enrichment of the gas in oil vapors will be attained. The increase in vapor content results in a corresponding decrease in the free carbon content of the vapors contained in the gases leaving the scrubber when figured on a percentage basis. On condensing gases which have been scrubbed and enriched a condensate of relatively low free carbon content will be produced. According to this in vention these scrubbed gases of relatively low free carbon content are blended with ordinary gases and the ratio of the two gases blended is so regulated that a tarry oil is produced which may be employed directly as creosoting composition. When the free carbon content of the resulting product is low, tar or tarry oils may be blended there-- with to produce creosoting-composition of the desired character.

Where complete cleaning of the gases is desired an electrical precipitator may ad- Vantageously be employed.

' In general the cleaning device is located between the collector main and the condensing system. It can be located immediately adjacent the collector main to receive the gases-at the tem erature at which they leave the collector main and the gases leaving the cleaning device may then pass thru a main similar to the ordinary cross-over ma n to the usual condensing system where thcv will be blended with ordinary gases and the blended gases will be cooled'together.

The temperature of the gases passing from lating the cooling of the gases in the collector main. The cooling in the collector main should be regulated to avoid condensation of desired higher boiling oil vapors in order to allow these desired high boiling constituents to pass over into the condenser with the uncleaned gases. Ordinarily the gases in the collector main of a coke oven plant are cooled by the circulation of tar or ammonia liquor thru the mainor by spraying ammonia liquor into the gases passing thru the main. Where such methods are employed the cooling of the gases should be regulated so as to avoid cooling to too low a temperature since it is desirable that a considerable portion of the heavier oils remain vapor form when the gases enter the condensers in order that a tarry oil of proper boiling range will be produced. The temperature of the gases can be increased by reducing the spraying of ammonia liquor into the collector main. By proper regulation of the cooling effected in the collector main the gases which are to be cleaned may be brought to and passed thru the cleaning device at a fairly high temperature, for example, at 200 C. or higher. The action of the cleaning device is to separate out from the gases suspended heavy tar and pitch particles carried in suspension therein.

If a tar or pitch of the same temperature and composition as that suspended in the gases is employed for scrubbing the gases or if uct comprising ingredients originally presentv in the gases as well as ingredients present in the scrubbing medium, and other ingredients originally present in the scrubbing medium may be volatilized by the hot gases and carried over to the condensers.

By maintaining the temperature of the gases so that they enter the condenser at a sufficiently high temperature, the oil. condensed in the condenser will contain alarge proportion of medium and heavy oi'ls so that the tarry oils thus condensed can be directly employed in making creosoting compositions, or may be'employed-directly as creosoting composition. In special cases it may be desirable to free them from lighter oils in order to meet particularspecifications. This can be done by distillation or by fractionally condensing the'desired oil direct from the gases.

The temperature of the cleaning operation can be varied. The gases may be cleaned at a temperature up to 250 C. or 300 C- or higher or they may be cleaned at a lower temperature, around 200 0r 150 C. or in some cases even lower. 'Where an electrical precipitator is employed for cleaning, temperatures which involve the separation of high melting point pitch in a non-liquid state or carbonizing of pitch should be avoided, but these temperatures will not ordinarily be necessary with gases as commonly'produced at a byproduct coke oven plant or gas retort plant.

The cooling of the gases in the collector main results in the separation of a heavy tar which is drawn oil from the collector main together with material circulated thru the main. Another product of the operation is obtained from the cleaning device. The subsequent cooling of the cleaned gases blended with uncleaned gases gives a tarry oil containing a limited amount of heavy tar or pitch constituents and therefore of relatively low free carbon content. Three products are thus produced, the heavy tar from the collector main, the heavy tar or pitch from the cleaning device, and the tarry oils from the condensers. The tar from the collector main may be employed in the cleaning device when a scrubber is used, or the tar or pitch from the scrubber may be employed for flushing the collector main. The invention will be. further described in connection with the accompanying drawings-which show in a more or less conventional and diagrammatic manner apparatus suitable for carrying out the invention.

Fig. 1 is a plan of apparatus suitable for carrying out the invention;

Figs. 2 and 3 are an elevation and section of the scrubber employed in Fig. 1;

Fig. 4 is a plan of modified apparatus; and

Fig. 5 is a plan of still another modification.

In the drawings a coke oven battery is represented at 5 with the usual uptake pipes 6 and collector main 7 thru which the gases from the individual ovens pass into the center-box 8 and thence to apparatus for the recovery of tarry oils, etc. According to this adaptation of the invention a scrubbing device 9 is located in the main leading from the center-box and the gases enter this scrubbing device at a temperature approaching that at which they leave the collector main and center-box. The scrubbing device is connected with the center-box 8 by the short main 10 andit is connected with the condensers 11 and 12 by the mains 13 and 14. An exhauster 15 of the usual type is indicated for drawing the gases thru the system.

The scrubbing may be effected by a heavy tar or pitch of the same composition and temperature as that carried in suspension in the gases entering the scrubber. A body of the scrubbing medium is maintained within the bottom of the scrubber 9 and is sprayed up into the gases by the roll 16 which is center-box of the collector main in the usual manner and collected first in the decanter 19 (Where considerable ammonia liquor is used in the collector main) and then into the tank 19 may be employed for scrubbing. It may advantageously be admitted to the scrubbing device thru spray means 20 in the settling tower 18 and is advantageously preheated and preferably dehydrated before being brought into contact with the hot gases in-the scrubbing device. Lighter oils contained in this tar which may be volatilized by the hot gases will be carried by the gases over into the condensing system. The undistilled residuetogether with entrained matter removed from the gases in the scrubber will be drawn off thru the outlet from the scrubber which comprises the trap 21 and the levelling arm 21', and may be collected and disposed of in any suitable manner.

A by-pass 22 around the scrubber 9 is shown and valves in the main 10 and by-pass 22 are indicated at 23 and 24. By properly regulating the valves 23 and 24 so that a portion of the gases pass thru the scrubber 9 and the balance thru the by-pass 22, 'a portion of the gases will be cleaned and the cleaning may be such as to remove substantially all of the entrained matter from the gases and the proportion cleaned and the proportion not subjected to the cleaning treatment may be so regulated that a tarry oil of the desired low free carbon content will be obtained directly from the gases in the condensing means provided.

When for any reason it is desired to discontinue the use of the scrubber as for repairs, by completely closing the valve 23 and opening, the valve 24, all of the gases mav be bypassed around the scrubber.

Fractional condensers 11 and 12 are shown for separately collecting the heavier and lighter oils condensed from the gases. The boiling range of the oils collected in the condenser 11 may be regulated to meet the specifications for creosoting compositions or to produce tarry oils from which creosoting composition may be readily prepared. Lighter oils will be collected in the condenser 12.

Where the cooling in the collector main is so regulated that higl'ier boiling oils are carried over by the gases as they leave the main, 9. total condensate may be obtained which will have a boiling range satisfactory for the production of creosoting composition.

A total condensate may be collected which comprises higher as well as lower boiling oils which may thereafter be distilled to produce a tarry oil of desired boiling range, as by passing steam thru the total condensate or by distilling in a fire heated still.

Fig.4 shows a plan View of a coke oven battery, partly broken away, showing the uptake pipes 26 connected to the collector main 25 provided with the center-box 28 and the usual cross-over main 27.

An auxiliary gas main 30 leads from one end of the collector main 25 to a cleaning device 31, from which cleaned gases are delivered thru the main 32. The uncleaned gases delivered thru cross-over main 27 and cleaned gases delivered thru the main 32 are passed thru the main 34: to the condenser 29. The proportion of gases passed thru the cleaning device 31 and the cross-over main 27 is, regulated by the butterfly valves 33 and 33", which also serve to equalize the pressure drops thru the cross-over. main 27, and the auxiliary gas main 30 with its cleaning device 31 respectively. By regulation of valves and 46 the proportion of the gases passing thru mains 30.. and 27, respectively, may be governed and the character of the oils recovered from condensers 29 may be governed.

Blending of the cleaned gas and uncleaned gas takes place in the line 34 and condenser 29 and a composite oil is condensed in the condenser 29,containing a definite and limited proportion of clean oils, tarry constituents and free carbon, as determined by proportioning the volumes of gas passed through the cleaning device 31 and thru the cross-over main 27, and by operating the collector main 28, at regulated temperatures sufiiciently high to maintain desired oil constituents in vapor form.

The scrubber 31 is a scrubbing tower in which the gas is cleaned by passing upwardly against a descending spray of tar or pitch, delivered through pipe 42 and drawn of? through pipe 43. The spraying medium may be recirculated by means of pump 44. Other suitable forms of scrubber may be used such as a horizontal casing with horizontal spray roll.

In Fig. 5 two collector mains 35 and 36 are shown connecting uptake pipes 37 with the cross-over mains 38 and 39. The drawing indicatesv the usual two-main system in which each of the two collector mains is connected with each oven. The collector mains may be connected with the ovens thru uptake pipes and goose-necks of any usual type which include valve means for directing the gases to either one of the two collector mains. As an alternative arrangement individual uptake pipes may be employed leading to each of the mains and in such a. case the mains may advantageously be located on opposite sides of the blocks.

Coke ovens and retorts equipped with two collector mains, i. e. rich and lean mains, are old in the art. It is recognized that the gases given off during the early and later stages of the coking operation have a difierent B. t. 11. value and therefore it has been customary to separately collect gases from different stages of the coking operation and to take advantage of thediiierent B. t. u. values. According to this adaptation of the invention, the gases are collected in the different mains depending not upon their B. t. u. values but upon their content of suspended tar and pitch particles. The lean gases, i. e., gases given off during the later stages of the coking operation in each of the ovens or retorts, may be collected in the main 35 and the balance of the gases may be collected in the main 36. The gases led to 35 will be those selected at the proper stage so that after cleaning and blending with gases from 36 and cooling, oil of the desired character will be obtained. The gases collected in the main 35 may be subjected to a substantially complete cleaning operation. An electrical precipitator for such cleaning operation is indicated at 4:0. The gases from the other collector main, i. e., the main 36, will pass thru the cross-over main 39 and bothgases will be combined and cooled in the condenser 41. Thegas in each main may be subjected to the degree of cooling necessary to regulate to the desired degree the character of the oil remaining in vapor form in the gases. Instead of an electrical precipitator other cleaning means may be employed. The condenser 41 may be a complete condenser or a fractional condenser. Beyond the condenser an exhauster and the usual means for the recovery of ammonia liq uor, light oils, etc., may be located.

By cleaning a regulated part of the gases and then combining the gases which have been cleaned with gases not subjected to cleaning and cooling the combined gases atarry oil of regulated free carbon content and having other desired characteristics is obtained. The boiling range of the tarry oil is controlled by regulating the degree of cooling of the gases in the collector main, etc.,

- as previously described, supplemented where desired or necessary by stripping of lighter oils from the recovered oils, and by blending of tar or tarry oil. This is in part a continuation of application Serial No. 197,341, filed June 8, 1927, and application Serial No. 202,735, filed-June 30, 19:27.

I claim:

1. The method of producing tarry oils in the by-product recovery system of a coal distillation plant in the ovens or retorts of which coal is distilled, which comprises subjecting a portion of the coal distillation gases from the gas collecting system while still hot to a cleaning operation to remove suspended impurities, combining this portion of cleaned gases while still hot with hot uncleaned gases from the coal distillation plant and then cooling the combined gases to separate therefrom a tarry oil of low free carbon content.

2. The method of producing tarry oils in the by-product recovery system of a coal distillation plant in the ovens or retorts of which coal is distilled, which comprises collecting the coal distillation gases from the ovens or retorts while hot in aplurality of collector mains, subjecting the gases leaving at least one of the mains to a cleaning treat:

ment while still hot, combining the gases so treated with gases from the remaining collector mains while still hot and cooling the combined gases to produce a tarry oil of low free carbon content. 4

3. The method of producing tarry oils in the by-product recovery system of a coal distillation plant in the ovens or retorts of which coal is distilled, which comprises collecting the coal distillation ases 'ven ofi during a selected portion of t e coking operation in all of the ovens or retorts of the plant in one collector main while hot, and collecting the balance of the coal distillation gases from all of the ovens or retorts in another collector main while hot, removing sus pended impurities from the gases leaving one of the collector mains while still hot, combining the gases so treated with the gases from the other collector main while hot and cooling the combined gases to separate therefrom a tarry oil of low free carbon content.

4. The method of producing tarry oils in the b -product' recovery system of a coal distillation plant in the ovens or retorts of which coal is distilled, which comprises removing suspended impurities from a portion of the coal distillation gases leaving the gas collecting system of the plant by scrubbing these gases while still hot, combining the resulting scrubbed gases while hot with hot coal distillation gases not so treated, and thereafter cooling the combined gases to separate therefrom a tarry oil of low free carbon content.

5. The method of producing tarry oils in the by-product recovery system of a coal distillation plant in the ovens or retorts of which coal is distilled, which comprises subjecting a portion of the coal distillation gases leaving the gas collecting system of a plant to an electrical discharge thereby removing suspended impurities while the gases are still hot, combining the resulting cleaned gases while hot with hot coal distillation gases not so treated and thereafter cooling the combined gases to separate therefrom a tarry oil at low tree carbon content.

In testimony whereof I afiix my signature. STUART PARMELEE MILLER.

fiERTIFICATE 0F CORRECTION.

Patent No. 1,849,197. i Granted March 15, 1932, to

' STUART PARMELEE MILLER.

it is hereby certified that error appears in the printed specification of the above numbered patentrequiring correction as foiiows: Page 6, tine 3, claim 1, after "uncleaned" insert the words coal distillation; and that the said Letters Patent should be read with this correction therein that the same may cenform to the record of the ease in the Patent Office.

Signed and sealed this 26th day of April, A. D. 1932.

M. J. Moore,

(s t) I v Acting Cemmissitmer of Patents.-

Images