US1935317A - Coking pitch - Google Patents

Description

NOV- 14, 1933 M. L. HAMLIN 1,935,317

COKING FITCH Filed nec. 28, 1929 ATTORNEYS Patented Nov. 1 4, 1933 i'iE STA 11S COKING FITCH Marston Lovell Hamlin, Lynbrook, N. Y., assigner to The Barrett Company, New York, N. Y., a corporation of New Jersey Application December 28, 1929 Serial No. 417,262

` 5 Claims.

This invention relates to a method of coking pitch and more particularly to a method of charging pitch into an oven or retort in several steps and converting it to coke.

5 The conversion of pitch tocoke is accompanied by the evolution of vapors and gases. This causes ebullition of the pitch during the coking operation. The ebullition may take place in one or more distinct stages during the coking period,

after each of Vwhich stages the foam produced by the ebullition eventually subsides. It is desirable in carrying out the coking operation to prevent ebullition or foaming of the pitch to such a degree that the charge of pitch being coked over l5 flowsthe oven or retort or enters Athe gas outlet causing partial or complete stoppage. The amount of foam produced during the conversion of a given pitch to coke'depends upon the composition of the pitch, the temperature to which the pitch is heated, the rate of heating, etc. It will vary with different types of pitch and with pitches of the same type when subjected to different coking conditions.

According to this .invention the pitch to be coked is charged to an oven or retort in steps. The pitch charged in the first step is heated until most of the gases and vapors have been given off or at least until violent ebullition has ceased and the foam producedl has somewhat subsided. The y pitchis then plastic or semi-plastic and when fresh pitch is added to this mass which has already been heated it does not readily blend therewith. The newly added pitch is heated and gases and vapors are evolved without overflowing the oven or retort or stoppage of the gas outlet. When violent ebullition has ceased, pitch may again be added to the oven or retort and by repeated additions any desired amount of pitch may be charged into the oven or retort up to its full working capacity. In general, according to this invention the amount o f pitch added in the first step is greater than that added in any additional stepL and the amount of pitch added in any one step is less than that added in any preceding step, but, if desired, the larger addition may be made later in the charging operation. The largest increment ofpitch added will be substantially greater than any other increment added, and will usually be at least twice any other increment. The object of the invention is to operate the oven at its maximum practicable capacity and this is accomplished by charging tothe oven or retort in each step an amount of pitch which, when it foams, will substantially fill the oven or retort without overflowing or plugging the gas outlets. With suitable materials and proper regulation of the ovens this will frequently amount to at least one-half the total charge. When the foaming or ebullition ceases more pitch is added to the oven or retort but since the pitch or semi-coke already present occupies a portion of the space within the oven or retort a smaller amount of pitch is added so that when it foams it will not overflow or plug the gas outlets.

`If an oven or retort becomes overheated in a previous coking operation and it becomes desirable to cool it somewhat before introducing the charge proper, this may be done, without departing from the spirit of my invention, by introducing small amounts of pitch before the main body of the charge is introduced.

In the drawing, a vertical section of a fragment of a coke oven battery operated in accordance with this invention is shown diagrammatically.

Ovens l to 6 of the battery 7 are heated byhorizontal heating lues 8. A suitable pitch supply conduit 9 is provided above the ovens and has valve controlled pitch outlets 10 for introduc- 30 ing pitch into the individual ovens. The ovens illustrated-in various stages of the charging operfation show the manner of operating a three step process for coking pitch. Oven 1 illustrates the condition of the pitch in the o ven in the first step at its condition of maximum foaming. Oven 2 shows an oven in which foaming of pitch added in the first step has subsided and the oven is ready for an addition of pitch. The oven 3 shows the condition of the charge with foaming of pitch added in the second step at its maximum. Oven 4 indicates the condition of the charge after this foaming has subsided. The pitch of the first step is now in a partially coked condition while that added in the second step is in a plastic, not foaming, state. The oven 5 shows the result of foaming in the third step of the process, while in oven 6 there is a complete charge of pitch being heatedat coking temperature to produce the coke product.

The following example further illustrates the invention. After the oven or retort has been raised to the proper temperature the oven or retort is half lled with pitch which may be pitch with a melting point of 225 F. or over. The 105 heating of the oven is continued and the pitch foams, but as the gases and vapors escape from the pitch the body of pitch eventually becomes more or less quiescent and the foam subsides somewhat. After violent ebullition has ceased a 110 plastic or semi-plastic mass of partially coked pitch remains. More pitch is then added. The rst addition of pitch to this partially coked mass will be only approximately one-half of the amount charged to the oven in the rst step, since the partially coked pitch already occupies about half of the working space of the oven or retort and only the balance of the space is available for foaming. This added pitch does not blend with the plastic or semi-plastic, partially coked pitch in the oven or retort to any great extent. It foams and the amount added is such that the foam nearly lls the oven or retort. When the ebullition of this portion of pitch has ceased, further pitch maybe added to the oven or retort in a third step. The plastic mass of semi-coke resulting from the coking of the pitch added during the rst two steps fills somewhat less than three-quarters of the working space of the oven or retort. The remaining operating space in the oven or retort is then approximately one-quarter the original volume, and the pitch added in the third step isonly about one-quarter of the amount added in the rst step. In this way, by adding less and less pitch at each succeeding step, the total charge is added to the oven in the minimum time. When the last addition of pitch has been made to the oven or retort the heating is continued until the total charge is converted to coke. The oven is then emptied and may be recharged in the manner here described.

Any suitable'type of oven or retort may be employed for coking the pitch. An ordinary coke oven may be used in which a narrow 'vertical mass of pitch is heated on both sides by combustion gases in fiues in the walls of the oven; the bottom may or may not be heated by one or more sole ues. An oven built of silica brick or other fire brick and heated from below from vthan a coke oven may alternatively be used to advantage. In an oven of this type a large surface of the pitch is exposed to the gas space, which permits ready escape of the gases and vapors from the coking mass into the vapor chamber. Cast iron retorts of suitable design'may be employed. The retorts may be heated directly .by hot combustion gases.

'Ihe gases and vapors evolved during the coking operation are advantageously collected and cooled to separate tar and pitch products which may be burned as fuel or which on distillationv will yield valuable oils and pitches. When the pitch is coked in a coke oven battery the ordinary by-product recovery system may be employed for separately recovering the tars and gases evolved, blended with the tars and gases separately recovered from the coking of coal.

When pitch is charged to an overheated oven or retort the pitch may foam to an unusual degree. When pitch is to be coked in an overheated oven or retort according to this invention the amount of pitch charged to the oven or retort in the first step may be somewhat less than that which would be charged to the oven or retort if it were not so highly heated. In general, however, it may be considered that the amount of pitch charged in the rst step is greater than that charged in any succeeding step. lIf but a small amount is charged to an overheated oven or retort in the iirst step to cool the oven or retort the amount charged in the second step may then be greater than that charged in any succeeding step.

The pitch coked according to this invention may be pitch of any desired melting point although in general it will be desirable to distill the material to be coked to pitch of a relatively high melting point, for example, 225 F. or higher in a still particularly adapted to convert tar or pitches of lower melting point to pitches of such higher melting point. Pitch produced by distilling coke oven tar, gas retort tar, water gas tar, low temperature tar or mixtures thereof,

etc., may be converted to pitch according to this process. Pitches with a. melting point of 300 orv 350 or up to 400 F. or higher may be charged to the oven.

The pitch may be charged in relatively finely divided solid form but is advantageously charged to the oven in a liquid form, and pitch which has been allowed'to cool and harden may be remelted and charged to the oven or retort. When, however, pitch of a high melting point, for example, 350 F. or4 higher'V is to be converted to coke, this pitch is advantageously maintained at a high temperature in a thin fluid state from the time it is made until it is charged to the oven or retort. J

Any suitable means may be employed for introducing the pitch into the oven or retort. It is advantageously introduced in liquid form through one or more pipes. When the pitch is coked in a coke oven, for example, it may be introduced through pipes placed in the coal charging holes; and during those periods in the coking loperation when no pitch is being' charged to the oven the pipes may be Withdrawn so as to prevent pitch which clings to them from becoming coked by the heat in the oven or retort.

The pitch is charged to the ovens or retorts according to this invention in two or more steps and preferably in three or four steps although a larger number of steps may be employed to advantage, particularly when` a large oven or retort is being charged. Where a large number of steps is employed the amount of pitch charged to the oven at each of the later steps of the series may be substantially the same in amount without avoiding the'invention. The greatest economy according to this invention is obtained when the rst charging steps are carried out as described and the invention includes those processes in which the rst steps are so carried out.

I claim:

1. The method of charging an oven or retort with pitch in at least three steps and converting the pitch to coke, which comprises charging the oven or retort partly full of pitch in the rst step, heating the charge of pitch so as to coke it and while it is being coked adding in the second vstep an additional amount of pitch, then in the third step adding more pitch when the pitch ,added in the preceding step has become partially coked, and converting all of the pitch to coke, the amount ofpitch added in the second step being less than that charged to the oven or retort in the first step and the amount of pitch added in the third step being less than that added in the second step.

2. The method of charging an oven or retort with pitch in at least three steps and converting the pitch to coke, which comprises charging the oven or retort partly full of pitch in the first step, coking this until violent ebullition has` ceased, in the second step adding more pitch to the oven or retort and coking it until violent ebullition has ceased, in the third step adding more pitch, and converting the entire charge to coke, the amount of pitch added in each of the second and Vthird steps being less than that charged to the oven or retort in the first step.

3. The method of charging pitch to an oven or retort in a plurality of steps and converting the pitch to coke, which comprises adding pitch to the oven or retort in a plurality of steps, heating the pitch charged in each step until violent ebullition ceases before adding more pitch, the amount of pitch charged to the oven or retort in each step being lessthan that charged to the oven or retort in any preceding step, and continuing the heating to convert the pitch to coke.

4. The method of charging an oven or retort with pitch in a plurality of steps and converting the pitch to coke, which comprises heating the oven or retort and charging pitch to the oven or retort in the iirst step in such an amount that when the pitch becomes heated and foams during conversion to coke, the Working space of the oven or retort will be substantially lled with the pitch and after violent foaming subsides adding additional pitch in a second step on top of the pitch charged in the rst step in such an amount that when this pitch foams on conversion to coke the working space of the oven or retort will be substantially filled, and converting the entire charge to coke.

5. The method of charging an oven or retort with pitch and converting the pitch to coke, which comprises charging the pitch to the oven or retort in a plurality of steps, heating the oven or retort so as to coke the pitch added in the several steps and heating the pitch added in each step atleast until it becomes plastic and luntil foaming of pitch substantially ceases before addp ing the' next charge of pitch, the amount of pitch added in one of the steps being about twice the largest amount added in any subsequent step.

. MARSTON HAMLIN.

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