US1871628A - Production of pitch and apparatus therefor - Google Patents

Description

ug 36, A932- I G. E. MocLosKEY ET AL LSUZS PRODUCTION OF FITCH AND APPARATUS THEREFOR Filed April 25. 1927 2 sheetsshee'f, 1

ATTQRNEYS Aug- 1932 G. E. MccLos'KEY ET AL LS'FLZ@ PRODUCTION OF FITCH AND APPARATUS THEREFOR 2 Sheets-Shet 2 Filed April 25, 1927 los INV

ATTORNEYS Patented Aug. 16, 1932 UNITED STATES PATENT OFFICE GREGORY ICCIDSKEY, OF ORANGE, NEW JERSEY, AND WILLIAI B. WINGEBT, OF DETROIT, HIGHIGAN, ASSIGNOBS TO THE BARRETT COMPANY, OF NEW YORK, Y., A CORPORATION OF NEW JERSEY PRODUCTION OF PITCH AND APPARATUS THEBEFOB Application led April 95, 1927. Serial N0. 186,354.

This invention relates to the o eration of' coke ovens, and particularly to t e production of pitches having varying characteristics from the gases escaping from the ovens. In the ordinary operation of b -product coke ovens the gases produced by t e coklng operation pass from the individual ovens through uptake pipes and goose-necks to a collector main common to the ovens of the m battery. The gases which leave the ovens at high temperature, e. 609 to 700 C., or higher, are cooled or inarlly as rapldly as possible by the application of sprays of ammonia liquor or ammonia liquor and tar 1n 15 the goose-necks and collector main. The rapid cooling causes the separation of tar containing the heavier oils in the collector` main. Further cooling is eiected in the cross-over main which connects the collector 20 main to the condensing system and an addltional quantity of tar carrying both heavler and lighter oils is thus separated. The collected tar is ordinarily shipped from the coke-oven plant to a tar-distillation plant for 25 distillation and separation of the oils and the production of pitches of varymg qualities.

The pitches produced by distillation of the tar as thus recovered contain ordinarily a 3g proportion of free carbon. They do not, however, contain such a proportion asv to make them available for certain uses for whi ch pitches having a high free carbon content are required. Such pitches are obtained ordinarily by the distillation of gas-retort tars, of which onlyla limited quantity 1s avallable. Similarly t e product of distillatlon of coke-oven tars contains too high a content of free carbon to permit the use thereof for certain other purposes Where the lowfree carbon content is essential. Pitches of low free carbon content are obtained ordinarily by distillation of water-gas tar. There is a considerable demand in the trade for pitches of both low and high free carbon content and the sources of supply thereof are not adequate to meet this demand. Consequently the production of both low and high ree carbon content pitches from the operation of coke ovens 5f: is desirable, and it is the object of the present invention to provide a method and ap- ,paratus whereby such pitches can be recovered in an economical manner from the gases delivered from the coke oven.

During the operation of a coke oven the gases discharged contain a greater or less proportion o hydrocarbon constituents depending upon the stage of the coking operation at which they are released. Thus, during the earlier.l part of the coking operation the gases contain a relatively larger proportion of hydrocarbon constituents and are referred to generall as rich gases. During the latter part o the coking operation the gases contain a lower proportion of hydrocarbon constituents and are generally designated lean gases. The coke ovens of a battery are operated in cycles so that all of the ovens are in different stages of the distillation operation and normally the rich and lean gases are delivered indiscriminately tothe collector main and treated in the manner hereinbefore described to separate tar and oils therefrom.

v We have discovered that by suitable treatment it. is possible to separate pitches havin different characteristics from the rich an lean gases and to recover low'carbon pitches by treating the rich gas and high carbon pitches by treating the lean gases. The treatment involves the regulated cooling of the gases separate] to the extent required for condensation o the pitch constituents therein, the temperature being maintained, how ever, at a point which will ensure the retention of the oils in the vapor phase and the separa tion of the globules of pitch and tar fog from the gases by subjecting them to electrical precipitation. In passlng through the electrical precipitator substantially all of the solid and liquid constituents of the gases are removed, leaving the oil vapors in the gases. These oil vapors can be condensed subsequently, and being free from tarry constituents the condensation yields clean oils which 95 can be utilized without further distillation or treatment for various commercial purposes. The invention involves the separation of the rich from the lean ases and this can be accomplished readily y providing sepa- 10o rate collector mains connected to all of the ovens of the battery with suitable connections to the uptake pipes'from these ovens and valves to permit the direction of the gas from the oven into one or the other of the collector mains, depending upon the stage of the coaldistillation operation in each of the ovens. Thus, during the early stages of distillation in an particular oven the gases will be directe into the rich gasmain and at a suitable time, which is determined by the character of the gases discharged, these gases will be diverted into the lean gas main.

The gases in each of the collector mains are cooled independently and to a regulated extent by the application of sprays of ammonia liquor or ammonia liquor and tar thereto for the purpose of reducing the temperature to the desired extent. The dew .points of the gases for the several constituents carried therein as vapor are lower than the normal boiling points of these constituents, and by suitable regulation of the temperature of the gases in the collector mains it is possible to eiect the condensation of the desired pitch constituents, leaving the oils in the vapor phase. Thus, by sufficiently lowering the temperature of the gases in the collector mains all or any desired part of the tarry constituents can be converted into the liquid phase while the oils are still in the form 0fvapor. To accomplish the intended purpose the temperature of the gases should he maintained above the dew point of the gases for -all constituents which are to be retained in the gases and carried over thereby after the separation of the pitch therefrom.

The tarry or pltch constituents which are condensed by the cooling elect of the ammonia liquor do not separate readily from the gases but as lobules and as tar fog tend to remain in t e gas stream. This facilitates the separation of the tarry constituents in a form having the desired characteristics in the electrical precipitators. The precipitators used may be, for example, the well known Cottrell precipitators and they should be operated at temperatures such as to avoid the condensation of the oils. Consequently the electrical precipitators should be disposed preferably closely adjacent to the collector mains and the gases carrying the pitch constituents should be delivered directly thereto. The electrical precipitators may advantageously be insulated to prevent loss of heat from the gases.

This is particularly desirable if the products to be recovered are relatively heavy pitches requiring the maintenance of the gases at high temperature to avoid dilution of the pitches with oil constituents.

The operation of the electrical precipitator as commonly used consists in passing the gas to be treated between electrodes whose difference in electrical potential is very great. Ex-

perience has shown that it is best to use aA rectified alternatingcurrent. The alternating current (the primary) is .sent through a step-up transformer to produce a high potential current (the secondary) which is then rectified to an intermittent uni-directional current, for example, by means of a rotary converter. The rectified current is delivered Velectrodes and the wires or'rods the negative electrodes. The size of the pipes as commonly used varies but in general pipes of less than six inches in diameter are not employed. With large diameter tubes, for example, about twelve inches, the difliculty of insulating against leakage of the extremely high potential (approximately 75,000 to 100,000 volts) increases enormously. Electrical precipitators with tubes six inches in diameter using secondary voltages from 35,000 to 50,000 volts are satisfactory for the purposes of this invention. It is generally best to operate with maximum potential difference (secondary current) between electrodes, this maximum being .just below the break-down voltage at which arcing occurs.

The etiiciency of the cleaning is dependent upon several variables. Satisfactory cleaning of the gas may be accomplishedz if the time of treatment is of the order of one second although this time may be varied Widely, depending upon the character of the pitch to be recovered from the gases passing through the precipitator. In working with tubes nine feet long, for example, substantially all of the tarry constituents have been separated with a time of treatment of from one and one-half to two seconds or with a gas velocity of from' six feet to four and one-half feet per second. This gives an eiliciency of cleaning of approximately ninety-nine per cent. A shorter treatment of, for example, from 0.5 to one second corresponding to a gas velocity of from eighteen feet 'to nine feet per second may result in the passage of some of the tarry constituents through the precipitator.

From the electrical precipitators the gases carrying the condensable vapors can be conducted through suitable condensing apparatus including coolers, scrubbers, fractional condensers, ractionating columns, etc., designed to reduce the temperature of the gases and to cause the separation of oils therefrom. One total oil fraction may be collected if the gases are cooled in one step to the lowest dcsired temperature. Several oil fractions can -he recovered if the gases are cooled by stages or .in coolers designed for separate collection of the oils corresponding to the individual cooling steps.

Electrical precipitators of the type ein ployed for the initial separationI o pitch from the gases may be employed to separate the condensed vapors. -By passing the gases through such precipitators at predetermined temperatures the condensed constituents ca n be separated efectivelyand sharp cuts of oil can be obtained. The gases, after the successive c`ondensations accompanied by separation of the oil constituents, can be conducted through the usual equi ment provided for the purpose of cooling t e gases and recovering other valuable constituents such as ain-i monia and light oils therefrom.

It will be understood that in the practice ofthe present invention the cooling of therich and lean gases in the separate collector mains will be regulated by supplying more or less ammonia liquor or other cooling agent thereto for the purpose of determining the character of the pitches which will be separated in the electrical precipitators connected to the separate collector mains and that by such regulation the amount of the tar and oil constituents which are condensed in the collector mains and separated in the electrical precipitators may be regulated to -produce pitches having diiferent melting points and other characteristics. The pitch recovered by the treatment of the rich gas will, however, be a low free carbon pitch whereas the pitch recovered from the treatment of the lean gases will be a high free carbon pitch, and these pitches may be utilized for the various purposes for which they are adapted, the :melting point of the particular product being adjusted by regulation of the cooling in the separate collector mains as hereinbefore described. The high and low free carbon content pitches thus produced may also be subjected to further distillation if desired to produce harder pitches which retain, however, their peculiar characteristics with respect to the content of free carbon therein.

The invention may be applied to existing coke-oven plants without any considerable modification thereof except for the provision of two collector mains connected to all of the ovens of the battery. Coke-oven plants exist in which the separation of the rich and lean gases has been conducted by the use of separate collector mains for purposes other than the object of the present invention and in such plants substantially the only modification required is the introduction of the electrical precipitators.

The present invention is of more or less general application to coke-oven plants and to theV recovery of pitches and oils from the gases discharged therefrom. It will be further described with reference to the accompanying drawings which show apparatus embodying the invention and ladapted for the practice thereof, but it is intended and will' be understood that the invention-is not limited to the specific details of the apparatus as 'illustrated in the drawings, in which Fig. 2 is an enlarged elevation showing the collector mains and electrical precipitator.

Fig. 3 is a section thru the electrical pre-l cipitator shown in Fig. 2.

Referring to tlie drawings, 5 indicates the battery of ovens which are connected through uptake pipes and goose-necks 6 to valve boxes 7 which communicate with the collector mains 8 and 9. Valves 10 are arranged in the valve boxes to permitthe direction of the coke-oven gases into one or the other of the collector mains, depending upon the stage of the coal-distillation operation in the particular oven to which the valve box is connected. Thus, by operating the valves the rich and lean gases from the several ovens of the battery can be collected separately in the collector mains wherein they are cooled to the desired extent by ammonia liquor introduced through spray nozzles 11 which are supplied through a pump 12 and pipe 13 from a source of ammonia liquor such as the tank 1'5. The amount of cooling effected in the separate collector mains by the application of the ammonia liquor sprays will depend upon the extent to which the gases are to be cooled and therefore upon the character of the pitch which is to be separated therefrom.

c, From the collector mains the gases carrying oil vapors and the partially condensed tarry constituents are delivered through pipes 16 and 17 to the electrical precipitators. These comprisecasings 18 enclosing a number of tubes 19 which are supported in heads 20 and 21 within `the shell. An inlet 22 near the bottom of the shell communicates with a chamber 23 which is partially separated from the tube section by a batile 24. An outlet 25 -permits the escape of gases from the separator after the latter have tubes.

A plurality of electrodes 26 preferably in the form of metal rods extend through the tubes and are supported from a bus-bar 27 located near the upper ends of the tubes. The bus-bar 27 at the top of the separator extends at both ends into casings 28 which enclose insulators 29 upon which the bus-bar is supported. The high tension current lines extend into the casings 28 and connect with the bus-bar 27, thus supplying the necessary current from any suitable source of uni-directional. current under high tension. The casing of the separator is grounded or otherwise connected to the source of current to complete the circuit. The casing and tubes form the positive electrode, the electrodes passed through the connected to the bus-bar being negative. The form and arrangement of the conductors in the circuit can be varied; The arrangement should be such as to supply high tension uni-directional current to the electrodes,

thereby permitting a continuous silent discharge between the electrodes and the tubes )through which the gases pass.

particles causes them to separate from the gases and condensable vapors. The separated liquids, together with the solid particles, run down the inner walls of the tubes into the chambers at the bottom of the separators and can be withdrawn through pipes 30 and delivered to suitable storage receptacles 31.

The gases carrying the condensable vapors escape through the outlets 25 and are dellvered by pipes 31 to the condensers 32. The condensers may be of any suitable form and in the present instance I. have shown condensers of the ordinary direct or wet typewhich are employed frequently in by-product recovery systems. The gases and vapors are cooled therein by contact with gridsurfaces wet by the sprays of ammonia liquor, for example, and the resultingcondensates are withdrawn through pipes 33 to decanters 34 wherein the) oils are separated from the ammonia liquor. The gases are withdrawn from the condensers-through pipes 35 and are delivered to an exhauster 36 which maintains the pressure balance in the system. The gases may be conducted thence through the usual equipment for the further recovery of ammonia, light oil, etc., therefrom.

The present invention permits the recovery of both high and low free carbon pitches directly from coke-oven gases and it also produces clean oil products which may be utilized directly or after further distillation for the separation of desired fractions therefrom. These and other advantages of the invention may be attained by the practice of the principles as hereinbefore set forth, it being understood that various changes may be made in the details of the operation and the apparatus as described without departing from the invention or sacrificing the advantages enumerated.

We claim 1. The method of producing pitch from hot fresh coal-distillation gases, which comprises separating the rich from the lean gases discharged at different stages of the distillation and subjecting one of the hot fresh gases separately from the other to regulated cooling sufficient to condense pitch constituents thereof and thereafter separately separating and separately collecting the pitch from the ases. g 2. The method of producing pitch and oils from hot fresh-coal-ristillation gases, which comprises separating the rich from the lean gases discharged at different stages of the distillation, subjecting one of the hot fresh gases separately from the other to regulated cooling sufficient to condense pitch constituents thereof and thereafter separately separating and separately collecting the pitch from the gases and cooling the gases after separation of the pitch therefrom to condense the vapors carried thereby.

3. The method of producing high free carbon pitch from hot fresh coke-oven gases, which comprises separating the lean from the rich gases discharged from ovens in whichcoal is being distilled and subjecting such gases separately to regulated cooling sulicient to condense pitch constituents thereof and thereafter separately separating and separately collecting the pitch from the gases.

4. The method of producing low free carbon pitch from hot fresh coke-oven gases, which comprises separating the rich from the lean gases discharged from coke ovens and subjecting the hot fresh rich gases to regulated cooling sufficient to condense pitch constituents thereof and thereafter separately separating and separately collecting pitch from the gases.

5. In an apparatus for producing pitch from hot fresh coal distillation gases, coal distillation means, means connected thereto for collecting separately the lean and rich gases from said distillation, means for separately cooling such gases, means connected to at least one of the collecting means for separately separating the pitch constituents therefrom, and means for separately collecting the pitch from said separating means.

6. The method of recovering pitch from hot fresh coke oven gases, which comprises` separately collecting the rich and lean gases produced'by a plurality of the ovens of a coke oven battery at different stages of the operation thereof, subjecting one of the gases separately from the other to regulated cooling suiiicient to condense pitch constituents therefrom and thereafter separately separating and separately collecting the pitch from the gases.

7. The method of recovering pitch from hot fresh coke oven gases, which comprises separately collecting the rich and lean gases produced by a plurality of the ovens of a coke oven battery during early and late stages of the distillation of coal therein, subjecting one of the gases separately from the other to regulated cooling suihcient to condense pitch the pitch from the gases, and cooling the gases after separation of the pitch therefrom to condense clean oils therefrom.

8. The method of producing pitch from hot fresh coke oven gases, which comprises separately collecting coal distillation gases from a like period of the carbonization of coal in a plurality of coke ovens, subjecting the hot fresh gases separately to regulated cooling suiiicient to condense pitch constituents therefrom, separately removing and separately collecting suspended pitch particles from the gases collected from like periods at an elevated temperature to produce pitch, and then cooling the treated gases to separate oils therefrom.

9. The method of producing pitch from hot fresh coke oven gases, which comprises separately collecting coal distillation gases from a like period of the carbonization of coal in a plurality of coke ovens, separately subjecting the hot fresh gases to regulated cooling suiicient to condense pitch constituents therefrom and then separately removing and separately collecting suspended pitch particles from the gases at an elevated temperature.

In testimony whereof We aiiix our signatures.

' 30 GREGORY EDWARD-MCGLOSKEY.

WILLIAM B. WINGERT.

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