US1650127A - Process of coking pitch - Google Patents

Description

Patented Nov. .22, 1927.

UNITED STATES 1,650,127 PATENT OFFICE.

BAY P. PERRY, OI UPPER MONTCLAIB, NEW JERSEY, ASSIGNOR TO THE BARRETT I COMPANY,

A CORPORATION OF NEW JERSEY.

PROCESS OF OOKING PITCH.

Application filed Apirl 5,

As distinguished from thecoking of coal and of certain grades of coal-tar pitch which are not or do not become thoroughly liquid in the coking process, my invention relates to the coking of coal-tar pitch and the like under conditions where or when the material is in such a condition that it is introduced in a liquid condition into the coking chamber or becomes liquefied by heat in such chamber in the course of the coking process or before 1 .the coking operation takes place.

In most types of modern equipment for coking coal, such for example as so-called by-product coke ovens or gas retorts, it is customary to supply the heat required for the coking process through the walls of the coking chamber. For example, in a byproduct coke oven the heat is supplied through the side walls of the oven, the heating flues in these side walls and the heating ases in the fiues being distributed and regu- Iated so as to produce a substantiall constant and uniform temperature over the entire side walls of the oven. This permits thorough and substantially uniform coking of the entire charge of coal in the oven, the coking rogressing from the two sides toward t e median line of the charge.

Because of the successful coking of coal in such by-product ovens, it was expected that coal-tar pitch could be satisfactorlly coked in the same ovens and in the same way, but in the attem ts to coke liquid or liquefiable coal-tar pitc serious difficulties have been encountered which render the process unsuccessful and make the coke unsatisfactory for certain purposes. The pitch, upon being heated to a certain critical temperature, ap pears to have some of its const tuents decomposed, or at least there is a very large evolution of gases and vapors resulting 1n sudden and rapid development of pressure, accompanied by expansion and foaming of the li uid mass. This critical temperature depen s upon the melting point and other characteristics of the pitch and can be easily ascertained by trial.

If a mass of liquid or liquefiable pitch is heated in a by-product coke oven in the so manner customary in coking coal, there sets up in the pitch, when it is in a liquid condition, a natural thermal circulation or convection currents by which the entire liquid mass is raised to a substantially uniform to temperature throughout, and consequently I tion of the pitch charge 1922. Serial N0. 549,664.

when a suflicient amount of heat has been supplied to reach the critical temperature mentioned above, it will be noted that the entire mass at one time may be at this temperature as distinguished from the conditions resent in coking coal. Coal being nonlique able, does not have a thermal circulation and does not reach a uniform temperature throughout, but on the contrary the heat penetrates slowly and the coal is coked slowly and progressively from the two sides towards the centerwitha consequently less violent or sudden evolution of gases.

Ihave discovered that the unsatisfactory condition and troubles arising in coking liquid or liquefiable pitch can-be minimized or avoided by, applying from the top or from the sides near the top suflicient heat for converting the top portion only of the liquid pitch into coke with the accompanying large gas evolution from that portion, while the remainder of the charge of pitch in the oven, although a considerable portion or all of it may be in liquid form, is nevertheless maintained at a temperature below that at which the heavy gas evolution takes place in changing from pitch into coke. After this top porhas passed the critical gas evolution stage, I continue the coking rogressively in a downward direct1on eit er continuously or intermittently, applying a sufiicient amount of heat for convertingonl a small portion at a time of the liquid-pitc near-the top into coke, while the balance of the charge below, although it may be liquid, is maintained at a temperature below the heavy gas evolution sta e.

The invention Wlll be-understood rom the descri tion in connection with the drawings whic illustrate an apparatus for carrying out the process. In the drawings Fig. 1 is a vertical section of an oven.

Fig. 2 is a section along the line H of Fig 1.

ig. 3 is an end section of a modified form of oven.

In the drawings reference character 1 indicates the wall of an oven which is provided with a bottom 2 and a cover 3. An outlet 4extends through the cover 3, and a pair of openings are shown at 5 through which the material may be charged.

A series of horizontal conduits or flues 6,

7 8, 9, etc., extend through the walls of the oven. klhese flues 6, 7, etc. are connected by means of the pipes 6, 7', etc. which are furnished with valves 6", 7 etc. with a feed or inlet pipe 10 for hot gases or for hot products of combustion, and the other end of these conduits or flues are connected to a common header 11, through which thehot products are discharged.

In the modification shown in- Fig. 3 the apparatus is substantially the same as above described except that the oven 1' is made with walls which flare outwardly in an up either in the solid or liquid state. Assuming that the oven is in a hot condition from a preceding coking operation, the pitch will be melted if the same is not already in a molten condition. Heat will be supplied to the oven through the upper flues 6 by opening the valve 6" whilethe remaining part of the oven is not subjected to the increased heat. As a result of this method of heating, the pitch forming the upper'layer or upper portion of the mass will be heated to the critical temperature with a consequent evolution of gas and resulting coking of this portion. After the upper portion of the charge of pitch has been coked, heat may be applied in a lower set of flues 7 to cause the .coking of the next layer of pitch to take lace in a similar way. By then applying heat in the lower flues, the coking will progress downwardly toward the bottom.

It is possible to perform the coking op-' eration as above described in such a manner that the pitch atdistances considerably below'the portion that is being coked will not be liquefied. In this way the convection currents or circulation oi pitch may be minimized, thereby further limiting the danger of sudden evolution of gas froman exceedingly large mass of the pitch. When the coking is produced inthe oven, as indicated in Fig. 3, the molten pitch is supplied through the inlet 5 and as the cokin takes place near the top, the layer of cofie formed may be removed, thus permitting the introduction of more pitch through the inlet 5' and raising the level of the mass so that another layer at the top may be coked without at any time fully dlscharging the oven.

The coke made in accordance with this process is substantially free from sulfur and ash and possesses very high mechanical stren h so that the same can be used in a foun ry cupola. The coking of the pitch from the top downwardly appears to make the same very much stronger than the ordinary methods of coking. It will be clear 1,eEso,127

that this method of coking pitch may be carried out in a vertical gas retort or' other coking chamber such as the ordinary'type of beehive oven, the important and distinguishing feature being that the heat which is to cause the coking of the pitch should be supplied first at or near the top of the pitch undersuch conditions that there would be no objectionable thermal circulation or convection currents throughout the mass. Care should be exercised regardless of the sort of oven in which the coking is made to take place, so that the heat would not be supplied in sufficient quantities throughout the entiremass to bring the mass to the temperature at which there would be a large gas evolution stage at one time. The thermal circulation incidental to the liquid condition of the pitch seems to be of no particular disadvantage if the pitch is maintained below the large gas evolution coking stage. An advantage that is obtained by coking the pitch downwardly in a by-product coke oven, for example, is that the evolved gases can be collected and the valuable by-producta coking first to the upper ortion of the mass and then progressively ownward through thev mass, while retaining the masslwedge shaped with the narrower portion downwards. A

3. The process of cokin hydrocarbon pitch that is solid at norma temperatures which comprises coking an upper portion oi the mass while maintaining a lower por-" tion of the mass in a liquid but non-coking condition, any lower layer of said mass being narrower than a layer thereabove.

4. The process of coking amass of liquid hydrocarbon pitch,,"which comprises coking an upper portion of the. mass while maintaining a lower portion of the massin :a liquid but non-coking condition, and adding more pitch to theliquid non-coking rtion.

5. The process of coking a mass o liquid hydrocarbon pitch, which comprises coking an upper portion of the mass while maintaining a lower portion of the mass in a 6. The process of coking liquid -hydro-' carbon pitch in an oven, which consists in coking first the upper portion of the mass of pitch and then coking the balance of the mass progressively in a downward direction by successively transmitting heat 'throu h the walls of the oven to lower planes of t a mass.

7. The process which comprises applying heat to the upper portion of a mass of hydro carbon pitch, until coking of said portion takes place, and then applyin heat to a lower portion of the pitch, sai heat bein transmitted to both said portions through the walls of the container in which the pitch is being coked.

8. The process of coking a liquid hydrocarbon pitch in an oven, which consists in coking an upper portion of the mass by means of heat transmitted through the walls of the oven without coking any portion therebelow until the coking of such upper portion is substantially complete.

9. The process of cokin in an oven a mass of hydrocarbon pitch w liquefiable by heat, which comprises supplying the heat for coking first to the upper portion of the mass and then pro ressively downward through the mass, an recovering the volatile constituents driven off from the hydrocarbon pitch.

10. The process of coking in an oven a mass of hydrocarbon pitch which is liquid or iiquefiable by heat, which comprises transmitting the heat for coking through the walls of the oven first to the upper portion of the mass and then progressively downward through the mass, oven an atmosphere which will not support combustion, and recovering the volatile constituents driven ofi from the hydrocarbon pitch.

In testimony whereof I aflix my signature.

BAY P. PERRY.

maintaining in the 'ch is liquid or

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