US1849198A - Method of preparing creosoting compositions and apparatus therefor - Google Patents

Description

l,849,19&

March 15, 1932.

vS. P. MILLER METHOD OF PREPARNG CREOSOTING COMPOSITIONS AND APPARATUS THERFOR Filed June 8. 1927 2 Sheets-Sheet www March 15, 19,32. 1,849,198

METHOD oF PREPARINGCREOSOTLNG- COMPOSITIoNs AND APPARATUS THEREFOR S. P. MILLER 2 Sheets-Sheet 2 Filed June 8. 1927 INVENTOB 72M- gaw; )[JM' ATTORNEYS hot coke-'oven gases may be cooled in a reg- Patented Mare 15, 1.9.32

UNITED STATES l'PATENT OFFICE STUART PARMELEE MILLER, OF TENAFLY, NEW JERSEY, ASSIGNOR TO THE BARRETT COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY METHOD OF PREPARING'CREOSOTING COMPOSITIONS AND APPARATUS THEREFOR Application led June 8, 1927. Serial No. 197,341.

This invention relates to improvements in the operation of coal-distillation plants, and more particularly coke-oven batteries, and is directed especially to the direct production of salable by-products by such operation.

In the ordinary operation of b -product coke ovens the gases produced by t ie cokmg operation pass from the individual ovens through uptake pipes and goose-necks to a collector main common to the ovens of the battery. The coke-oven gases which leave the ovens at temperatures of from 600o to 700o C.' or higher are cooled in the collector main and in condensers connected therewith to separate tar constituents therefrom. The separated coal tar is commonly shipped to tar-distillation plants where it is subjected to distillation to produce coal-tar distillates and pitches.

One of the important products produced from coal-tar is the so-called coal-tar solution consisting of a mixture of coal-tar distillate with raw tar in the proportions of about eighty per cent. of distillate to about twenty per cent. of tar. This product is used widely for'creosoting purposes. The preparation of thi-s product involves, as indicated, the distillation of large amounts oftar with the incident expense of transporting the tar to the tar-distillation plant and the cost of distillation thereof. Moreover.

' the distillation of coal tar in ordinary eX- ternally heated stills causes a considerable of an improved product at decreased expense.

In carrying out the invention the cokeoven plant may, for the most part, be operated in theusual manner, that is to say, the

ulated manner in the collector main by sprays of ammonia liquor or ammonia liquor and tar to separate from the gases some of the tarry constituents which may be withdrawn from the collector main and utilized in any desired manner, for example, by distillation to separate oil Aconstituents therefrom and to produce pitch. The resulting partially cooled gases can ,then be conducted through the usual cross-over main to the condensing system in which the gases are further cooled to separate oils therefrom. These oils contain normally too high a proportion of tarry constituents to be useful as substitutes for ordinary coal-tar solution. To reduce this proportion of tarry constituents, a part of the gases ilowingfrom the collector main to the condensing system is by-passed and subjected to cleaning to remove the tarry constituents therefrom after which the gases are passed to the condensing` system. y By thus by-passing and cleaning part ofthe gases, e. g., about one-third of the gases, the tarry constituents therein are removed and when the clean anduncleaned gases are mingled and cooled in the condensers, a composite product suitable for use as a creosoting composition can be obtained directly. The relative proportions of the clean and uncleaned gases can be regulated readily by the application of suitable valves which may be adjusted from 'time to time as may be necessary to produce a product suitable for use as a creosoting com; position.

The condensers employed may be of the usual wet type in which the gases flow upwardly and counter-current to a stream of ammonia liquor which is divided in the condenser by the provision of suitable batliing devices therein to ensure maximum contact between the gases and the solution. The condensed oil can be withdrawn from the condensers togetherv with the ammonia liquor and separated therefrom in a decanter provided for that purpose. The gases escaping from the condensers can be delivered to the usual exhauster and passed thence through'- most eiectively by the use of an electrical precipitator such, for example, as the well known Cottrell precipitator. To ensure ef- :Eective operation thetemperature of the collector main and of the precipitator should be carefully regulated. The dewpoints of the y 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 main and during recipitation, it is possible to retain the desired oil constituents in the vapor phase while the heavier tarry or pitch constituents are converted into the liquid phase in which condition they are separated readily by electrical precipitation. The temperature of the gases should, to accomplish the intended purpose, be maintained above the dew point of the gases for the most readily condensable oil constituent desired so that the greater proportion of the oils will be retained and will bey carried over with the gases from the collector main. The electrical precipitator should be operated at substantially the same temperature asthe collector main, and should be insulated if necessary to avoid the loss of heat from the gases undergoing precipitation. The temperature of the gases leaving the collector main and passing through the electrical precipitator may be, for example, around 200 C., or in some cases even higher, although in other cases it may be lower, e. g., around 160 C. or 150 C., etc. The electrical pecipitator should beconstructed so as to' capable of withstanding the `temperatures to which it is subjected in the operation as described. n The operation ofan electrical precipitator consists of passing the gas to be treated bctween electrodes whose difference in electrical potential is very great. Experience has shown that it is best to use a rectified alternating current. The alternating current (the primary) is sent through a step-up transormer 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 from the converter to the electrical precipitator at practically the potential at which it leaves the transformer.

The electrical precipitator consists commonly of a group of vertical pipes with a. wire or rod in the center of each, the pipes being connected to proper headers for the intro` duction and discharge of the gases. The pipes generally constitute the positive electrodes and the wires or rods the negative electrodes.

Y The size of the pipes may vary but in general pipes of less than six inches in diameter are not used'. Electrical precipitators with pipes six inches in diameter using secondary voltages from 35,000 to 50,000 volts are satisfactory for the purpose of this invention. It is generally Ibest to operate with maximum potential di'erence (secondary current) b etween the electrodes, this maximum being just below the break-down voltage at which arcing occurs.

The eliciency of the cleaning is dependent upon several variables. Satisfactory cleaning of the gas may be accom lished if the i time of treatment is of the or er of one second although this time may be varied widely dependingupon the character of the oil-to be recovered from the gases passing through the precipitator.v In worklng with tubes nine feet long and six inches in diameter, for example, a gas substantially free from all tarry constituents has -been obtained with 'a time of treatment of from one and onehalf to two seconds, that is to say, with a as velocity of 6 to 4.5 feet per second. Tis has given an efficiency of cleaning of a proximately ninety-nine per cent. If it 1s desired to collect oils containing small amounts of tar, shorter treatment may be used, for example, a treatment of from 0.5 to one second, that is to say, a velocity of from 18 to 9 feet per second. Since the gases after cleaning are mingled with thev dirty gases and condensed therewith, it is not essential that the cleaning ofthe gases in the electrical precipitator be thorough or complete. The operation can be adjusted readily to produce the desired amount of cleaning and thus to provide upon condensation an oil product of the desired character. The tarry or pitch constituents which are separated in the electrical recipitator can be withdrawn and utilized or any de sired purpose.

The present invention is of more or less general application to the operation of coaldistillation plants and particularly to byproduct coke-oven plants. It may be utilized, for example, in connection with Semet- Solvay, Koppers and other coke ovens.A It will be further illustrated by the following more detailed description taken with the accompanying drawings which show an apparatus embodying the invention and adapted for the practice thereof. It is intended and will ybe understood that the invention is not limited to the specific details of the apparatus as illustrated in the drawings, in which a centre box 8. The collector main is profrom the gases.

vided with spray nozzles 9 supplied through a pipe 10 with ammonia liquor or ammonia liquor and vtar for the purpose of coollng the gases in the collector main. The ammonia liquor and the separated tar can be Withdrawn from the centre box through a pipe 11. The gases pass from the collector`ma1n through a cross-over main 12 to condensers 13 which, as hereinbefore indicated, may be of the ordinary or Wet type. The separated oil with the ammonia liquor used for coollng escapes through a pipe 14 to a decanter 15 Where the oil is separated from the ammonia liquor; The oil is delivered through a pipe 16 to a storage tank 17 from which it may be withdrawn as required. The ammonia liquor is withdrawn through-a pipe 18 and delivered to a storage tank 19 from which it maybe returned by a pump 20 to the pipe 10 and to the condensers 13 for further use as acoolng medium. The gases from the condensers 13 pass ,through a pipe 21 to an exhauster 22 which'maintains the pressure balance in the system and are conveyed thence through the equipment (not shown) which separates ammonia, light oils, etc.,

To accomplish the purpose of the present invention part of the gases are passed from the collector main to the condensing system through an electrical precipitator. In the apparatus illustrated, a by-pass 23 is provided in the cross-over main, preferably closely adjacent to the ycollector main, and valves 24, 25 and 26 are introduced in the cross-over main and in the by-passto permit regulation of the proportions of the gases which are diverted through the by-pass. An electrical precipitator 26 is disposed in the by-pass so that the gases passing therethrough are subjected to cleaning by electrical precipitation to remove tarry constituents therefrom, the' gases being returned thereafter to the crossover main to be mingled with the dirty gases therein and thereafter to be cooled in the condensers 13 to produce the composite product of the operation. The electrical precipitator comprlses a shell enclosing a number of tubes 27 which are supported in heads 28 and 29 Within the shell. An inlet 30 near the bottom of the shell communicates with a chamber 31 which is partially separated from the top section by a baile 32. An outlet 33 permits the escape of gases from the separator after the latter have passed through the tubes.

A lurality of electrodes 34, preferably in the orm ofA metal rods, extend through the tubes andare supported on a bus-bar 35 near the upper ends of the tubes. The bus-bar 35V extends at both ends into casingsl36 which enclose insulators 37 upon which the bus-bar is supported. The high tension current line extends into one of the casings and is connected with the bus-bar 35, thus supplying the necessary current from any suitable source of uni-directional current under high tension. The casing of the separator is groundedl or otherwise connected to the source of current to complete the circuit. The casing and tubes form the positive electrode, the electrodes connected to the bus-bar being negative. The

ionization of the solid and liquid particles causes them to separate Afrom the -gases and condensable vapors. together with the solid particles, run down the inner walls -o the tube into the chamber at the bottom of the precipitator and can be Withdrawn through a pipe 38. The gases carrying condensable vapors escape from the top of the precipitator and are delivered as hereinbefore indicated to the cross-over main 12. By adjusting the valves 24 and 25 so as to permit `approximately one-third of the gases to pass through the electrical precipitator a suiicient proportion of the tarry constituents is separated from the gases so that the composite oil when condensed is suitable for use as a creosoting rcomposition which is similar to, but an improvement upon, ordinary coal-tar solution. The exact proportion ofthe gases passing through the electrical precipitator will be Varied, of course, to meet the conditions imposed by the operation of the particular coke oven, that is to say, to permit more or less of the tarry constituents to pass with thev gases to the condensers as may be necessary to produce an oil having the desired characteristics. The valves'can be adjusted readily to meet these conditions.

The method and ap aratus as described permit the direct pro uction of creosoting compositions at a coke oven plant in a satisfactory and economical manner, utilizin existing equipment. It is particularly a vantageous in that it avoids the expense oftar distillation and the losses of oil through cracking incident to such distillation, while it gives a new and improved creosoting composition in increased yield Adirectly from the condensing system of a coke oven plant. The

new creosoting composition, while compara- The separated liquid,

stituents incapable of distillation without decomposition by ordinary distillation methods in externally heated stills.

It will be understood that the foregoing description is illustrative of 4the invention land that various changes may be made in the form and arrangement of the apparatus and in the operation thereof without departing from the invention or sacrificing any of its advantages.

I claim:

l. The method of preparing creosoting compositions, which comprises partially cooling hot fresh coal-distillation gases so as to separate tarry constituents therefrom, dividing the gases to form two substantial portions, subjecting one portion thereof to cleaning by electrical precipitation While `the gases are still hot so as to separate tarrv constituents, then combining the resulting gases' and cooling them so as to recover a composite oil product containing tar.

2. The method of preparing creosoting compositions, which comprises partially cool'- ing hot fresh coal-distillation gases so as to separate tarry constituents therefrom, dividing the gases to form two substantial portions, subjecting onaportion thereof to cleaning by electrical precipitation while the gases are still hot so as to separate tarry constituents, then combining the portion of hot cleaned gases with a portion which is not 'cleaned and cooling the combined gases so as to recover a composite oil product containing tar.

3. The method of preparing creosoting compositions, which comprises collecting hot fresh coke oven .gases from a plurality of cokel ovens in a gas collector main, subjecting them to coollng therein while they still contain oily and tarry constituents, dividing the gases to form two substantial portions, separating the tar from one portion of the gases by electrical precipitation while the gases are still hot, combining the resulting gases and cooling them so as to recover a composite oil product containing tar.

4. In a coke oven battery, the combination of a pluralit of ovens, a collector main connected there o, an electrical precipitator, a condensing system, means for passing a portion of the gases from the collector main thru the electrical precipitator at a high itemperature to remove entrained impurities While the gases retain oil vapors, means for passing the gases `from the electrical precipitator to the condensing system and means for passing the balance of the gases from the collectorl main to the condensing system without going through the electrical precipitator.

5. In a, coke oven battery, the combination of a plurality of ovens, a collector main connectedthereto, means for cooling the gases in the collector main, an electrical precipita` tor, a condensing system, means for passing a portion of the gases from the collector main Legales STUART PARMELEE MIILER.

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