US2732332A

US2732332A - Geller

Info

Publication number: US2732332A
Authority: US
Publication date: 1956-01-24
Anticipated expiration: 1973-01-24

Description

United States Patent COKING F BITUMINOUS SUBSTANCES Julius Geller, Bad Homburg, Germany, assignor to Rutgerswerke-Aktiengesellschaft, Frankfurt am Main, Germany Application April 25, 1951, Serial No. 222,880

6 Claims. (Cl. 20217) Pitches fromcoal or lignite tar, high boiling mineral oil residues or the like are coked in furnaces of relatively great capacity at temperatures of about 1000". This entails extremely long refining times, as the fairly wide furnace chambers make a relatively low coking speed possible. Moreover the pitches contain, when being charged, over 40 volatile constituents, so that up to the start of the formation of coke great quantities of liquid have to be evaported. The charging of large quantities of. pitch or residues into the chambers entails the further disadvantage that the liquid material under treatment has a very detrimental effect on the refractory masonry of the chambers. In addition, owing to the considerable variations in temperature of the large quantities of pitch charged into the chambers the furnace masonry is subjected to considerable temperature variations which, after the furnace has been in operation for a relatively short period, cause leakages and damage to the masonry.

In order to avoid these disadvantages of the known intermittent coking process it has already been proposed toinject pitches or oils in a finely divided state into a larger coking chamber. With this method, however, the relatively limited dropping distance is insufficient for converting the pitch or oil drops into the solid state before they strike the chamber wall. Consequently, even after a relatively short operational period, caked-together pieces of coke are formed, which becomeunevenly baked and in addition can only be removed from the chamber with difiiculty.

' Now it has been found that a uniform and rapid formation of coke can be obtained if the material under treatment, which may. be preheated, is freed above its melting temperature through distillation, oxidation or polymerisation or the like from its volatile constituents until it reaches the viscous state and is then converted through the action of high temperature into the solid state. The proposed preliminary refining can be carried out in relatively simple arrangements, for instance in columns with filling material or bell-bottom columns. The residual volatile constituents still contained in the material can be driven out very rapidly, so that the material is converted in a relatively short time from the liquid to the solid state.

, The new process can, be carried out withspecial advantage, if the preliminarily refined and viscous mate- 'rial in a finely and as far as possible evenly divided state, forinstance inthe form of drops, jets or hands, be'converted into thesolid state. Through the uniform shape given to'the material a uniform heating and consequently a uniform coke formation will also be assured, so that 'with the novel mode of operation adaptation to a great variety of conditions as-regards quality becomes possible. In order that the transmission of heat to the material shall'not be'detrimentally affected, when the coking chamber is heated indirectly, according to the invention the material is conveyed in a free downward or upward posits on the walls, which would reduce the transmission of heat, are avoided. At the same time the refractory lining of the coking chamber is as far as possible preserved from injuries.

For many purposes of use the coke made from mineral oil residues or pitches should contain as few volatile constituents as possible or even practically none. According to the present invention, therefore, the residual volatile constituents of the coke are driven out by calcination with direct or indirect heating. Particularly simple conditions are obtained, when the heat required for calcining is made available by the combustion of a corresponding part of the coke. The partial combustion must, however, lead to as uniform as possible a calcining of the entire charge. Provision is therefore made in the partial combustion of the coke to cause the combustion air and the combustion products to flow in a uniformly distributed state either from the centre of the calcining chamber radially outwards or from the periphery of this chamber radially inwards, the fuel bed being, if required, kept in heaving motion.

Through the coke bed being uniformly supplied with the combustion air and the furnace gases as they form a correspondingly uniform temperature distribution within the calcining chamber will result and also a correspondingly uniform expulsion of the residual volatile constitutents.

In the partial combustion of the coke not only furnace gases, but also still combustible gases are formed. It is therefore proposed according to the invention to burn the gases drawn by suction from the calcining chamber, under certain circumstances together with other fluid or gaseous fuels and to use the hot furnace gases for the direct or indirect heating of the coking chamber and in certain circumstances of the distilling column or refiner for the bituminous substance as well. In this way the heat consumption of the whole process is reduced to a minimum. 7

Since in the case of indirect heating of coking chamber the escape of the products of combustion and generator gases out of the calcining chamber directly into the coking chamber is undesirable, according to the invention the coke is piled up in the calcining chamber so as to reach above the gas outlet at the outer periphery of this zone.

As the calcining of the coke takes place at temperatures above 1000", the calcined coke must be directly or indirectly cooled before leaving the apparatus. Direct cooling can be effected with water vapour, so that water gas is still formed at the lower end of the calcining zone. The water gas can then be made use of for heating the coking chamber.

Thenew process can be carried out in a particularly simple manner, if the bituminous material be freed in a distilling column, a refiner or the like from a substantial part of its volatile constituents and thereupon be conveyed into an upright, preferably cylindrical shaft, in which the coking, calcining and cooling chambers are arranged dire ctly. one under the other.

According to the invention the distilling column may be arranged above the coking chamber, so that the pitch which is driven off will pass out of the column directly into the coking chamber. The bottom wall of the column is so constructed that the pitch enters the coking chamber in a definite form as drops, a band or a jet of definite dimensions.

If the apparatus for the preliminary driving off of the bituminous substance andvthe coking chamber be heated indirectly, according to the inventionthe two will be provided each with a jacket for conveying the heating gases, the space between the inner and outer jacket being bounded at the top and bottom in each case by a collecting channel. These collecting channels serve the purpose of supplying and conveying away the heating gases. In order, however, to ensure a uniform flow of gas within the heating space and to equalise the one-sided motion of the inflow and outflow ducts, according to the invention the free cross-section area between the heating gas space and the collecting channel becomes smaller and smaller as the distance from the connecting pipe diminishes. Through suitably dimensioning the free cross-section it becomes possible to obtain a very uniform supply of heating gases to the chamber walls.

For conveying away the furnace gases and the like from the calcining chamber the lower collecting channel of the coking chamber is connected by a narrow opening with the upper end of the calcining chamber. In this way the gaseous products of the calcining chamber can be made available for the indirect heating of the coking chamber in a very simple manner.

According to the invention the supply of the combustion air to the calcining chamber takes place through one or more pipes extending to about the middle of this chamber and provided in certain circumstances with water cooling means. It is of course also possible to convey the combustion air, the produced furnace gases and so forth inside the calcining chamber radially from the outside to the inside. In this case an annular gap for the inlet of the combustion air must be provided at the outer periphery of the calcining chamber, whilst the furnace gases and so forth are conveyed away from the middle of the calcining chamber and conveyed to the heating jacket of the coking chamber.

In the accompanying drawing a constructional example of an apparatus according to the invention is illustrated diagrammatically. Figure 1 illustrates the apparatus in vertical sectional view, while Figure 2 is a fragmentary vertical section through a modification of a part of the heating jacket. The apparatus consists substantially of the refiner 1 and the shaft furnace 2. The coal tar pitch to be coked passes through the connection 3 into the refiner 1 and flows there on sheet metal deflectors 4 downwards in a relatively thin film.

The refiner is provided with a heating jacket 5 for conveying the heating gases. These gases enter through the opening 6 into the channel 7 and flow through the narrow space 8 upwards in a uniformly distributed state. At the upper end of the heating jacket 5 is the annular channel 9, out of which the heating gases are drawn by suction through the opening 10. According to the properties and the composition of the pitch and the pressure prevailing in the refiner, the latter is heated up to a temperature of from 300 to 500. The vapours liberated from the pitch are conveyed away through the opening 11.

In order to reduce the evaporation temperature of the pitch, superheated water vapour or any other carrier gas can be conveyed to the refiner through the opening 12.

The evaporation of the more readily boiling pitch constituents is so controlled that the pitch will at the particular working temperature pass into the distributer 13 in the viscous state. In general coal tar pitch will then still contain only about 20% volatile constituents. The distributer 13 is provided with numerous bottom openings, so that the pitch will pass into the coking chamber 14 in a corresponding number of thin jets. Forming a downward continuation of this coking chamber are the calcining chamber 15 and the cooling chamber 16. The calcined and cooled pitch coke is discharged in such a manner by the worm 17 that the coke within the shaft furnace will remain piled up to the upper end of the calcining chamber 15. On the other hand, the coking chamber 14 is filled only by gases and vapours and freely falling jets of pitch.

The coking chamber 14 is surrounded by a heating jacket 18 for conveying the heating gases. These gases enter through theopening 19 into the annular channel 20 and then flow in a uniformly distributed state through the narrow space 21 upwards. At the upper end of the col:-

ing chamber 14 the heating gases collect in the annular channel 22 and are drawn ofi by suction through the opening 23. A portion of the heating gases can be conveyed into the annular channel 7 for heating the refiner 1. The other portion of the waste gases can be used for preheating the combustion air or the pitch.

During the free fall of the relatively thin jets of pitch through the coking chamber 14 the residual volatile constituents are evaporated so rapidly and to such an extent under the reaction of the chamber walls which are heated to over 1000 that the pitch is converted into the solid state. The calcining chamber 15 is therefor filled with a relatively fine grain pitch granulate which still contains a few volatile constituents. As, however, the pitch coke is in general to be as free as possible from volatile constituents for the subsequent purposes of use, a suitable calcining takes place in the chamber 15.

In the present constructional example the heat required for this purpose is produced by the combustion of a portion of the coke. For this purpose air is introduced through one, two or more horizontally arranged pipes 24 into the middle of the calcining chamber. In view of the high temperature the pipes are either made of highly fireresistant material or are cooled with a suitable cooling medium, for instance water. It is also of advantage, when the air is supplied through a plurality of pipes, to arrange the latter symmetrically, in order to bring about a uniform fiow of gas within the shaft. The quantity of air conveyed in through each pipe may be regulated independently in any suitable manner.

The gaseous combustion products formed and the volatile constituents driven out of the coke fiow within the shaft from the middle upwards and to the side and pass through the slits 25 into the annular channel 20. Through the symmetrical supply of the combustion air and through it being conveyed away symmetrically a symmetrical rotary fiow of gas is formed within the shaft, so that the pitch coke is calcined uniformly.

The volatile constituents which are driven off in the calcining zone serves the purpose of heating the coking chamber 14. For this purpose the annular channel 20 is supplied through the opening 19 with a corresponding amount of combustion air. Should the volatile constituents, however, be insufficient for heating the coking chamber 14 and the refiner 1, the annular channel 20 can be supplied with additional liquid or gaseous fuel and a corresponding amount of combustion air. The com bustion air will with advantage be considerably reheated in an air preheater.

From the calcining chamber 15 the pitch coke passes into the cooling chamber 16 which is surrounded by a cooling jacket 26. Here a suitable cooling medium, for instance water, enters through the opening 27 and leaves the cooling jacket through the opening 28.

The worm 17 conveys the pitch coke continuously out of the shaft furnace. Through a suitable construction the worm can to a considerable extent seal the shaft furnace with respect to the atmosphere.

In order to heat the walls of the shaft furnace and of the refiner uniformly, provision must be made for a correspondingly uniform distribution of the heating gases. For this purpose the annular channel 22 is provided, as will be seen from Figure 2, with a throttling strip, the height of which decreases as the distance increases. For showing this more clearly, the annular channel 22 is shown in Figure 2 to a larger scale. As will be seen, the throttling strip 29 decreases its height as its distance from the connecting opening 23 increases, this being indicated by a dotted line. To a corresponding extent the free cross-section of the gap 30 for the gases increases as the distance from the opening 23 increases. In this way the shaft furnace is fed uniformly with the heating gases along its entire periphery.

According to the material to be coked the temperatures of the

chambers

14 and 15 range from 900 to 1400 preferably. The walls, more particularly at the higher temperatures, will be made of a refractory material. The wall of the cooling chamber 16, however, will preferably be made of sheet iron.

I claim:

1. A process for coking pitch from coal tar, lignite tar, and high boiling mineral oil residue, as well as similar meltable bituminous starting materials containing over 40% high boiling volatile ingredients comprising passing the starting material downwardly through a distilling zone, subjecting the material while passing through said zone to distillation eifected by heat applied extraneously to the wall of the zone to convert the material into a viscous mass containing only about 20% of volatile constituents, discharging vapors from the distillation of the starting material from the upper portion of said distilling zone, dividing the viscous mass of material as it emerges from the lower portion of the distilling zone into streams, dropping them downwardly as free falling particles through a coking zone positioned directly beneath the distilling zone, heating the particles of viscous material as they fall through the coking zone by radiant heat applied extraneously to the walls of the coking zone the path of fall being suificient to convert the viscous particles into coke particles, collecting the coke particles in a calcining zone beneath the coking zone, and heating the coke particles to a temperature of over l000 to remove remaining volatile constituents.

2. A process according to claim 1 in which the solid particles are heated by burning a portion of the coke in the lower portion of the calcining zone and passing the products of combustion upwardly through the calcining zone, removing the products of combustion and entrained volatile material from the upper portion of the calcining zone, and discharging coke from the lower portion of the calcining zone at a rate correlated with the feed of starting material, to maintain the level of solid particles extending up into the lower portion of the coking zone to reduce the tendency of the products of combustion and entrained volatile material to enter the coking zone.

3. A process according to claim 2 in which the products of combustion discharged from the upper portion of the calcining zone are passed in heat exchange relation with the exterior of the walls of the coking zone to extraneously heat said walls.

4. Apparatus for coking pitch from coal tar, lignite tar, and high boiling mineral oil residue, as well as similar meltable bituminous starting materials containing highboiling volatile ingredients comprising an elongated vertically extending coking chamber, a heating jacket surrounding the coking chamber, a distilling column positioned on the upper portion of the coking chamber in vertical alignment and in direct communication therewith, a heating jacket surrounding the distilling column, means for introducing starting material into the upper portion of the distilling column, said column having an outlet in its upper portion for discharge of volatile material, means at the lower portion of the distilling column for dividing viscous material resulting from distillation of the starting material and dropping it into the upper portion of the coking chamber for free falling downwardly through the coking chamber, a calcining chamber positioned beneath the coking chamber in vertical alignment and in direct communication therewith for receiving coked particles from the coking chamber, means for feeding combustion supporting air into the lower portion of the calcining chamber, the upper portion of the calcining chamber being of larger area than the lower portion of the coking chamber to provide a discharge at the upper peripheral portion of the calcining chamber for products of combustion.

5. Apparatus according to claim 4 further comprising means for controlling the discharge of coked particles from the lower portion of the calcining chamber to maintain a body of particles in the calcining chamber extending up into the lower portion of the coking chamber to close the lower portion of the coking chamber whereby gases from the calcining chamber are introduced into the jacket surrounding the coking chamber.

6. Apparatus according to claim 4 in which each heating jacket is bounded at the top and bottom by a collecting channel, the bottom collecting channels having an opening for the introduction of a heating gas and the collecting channels at the top each having an opening for the discharge of heating gas and provided with a throttling strip, the height of which decreases with the distance of the strip from the opening.

References Cited in the file of this patent UNITED STATES PATENTS 830,248 Von Orth Sept. 4, 1906 842,170 Bryant et al J an. 29, 1907 1,358,663 Wallace Nov. 9, 1920 1,490,354 Wallace et al Apr. 15, 1924 1,637,683 Clarkson Aug. 2, 1927 1,805,711 Andrews et a1 May 19, 1931 2,131,702 Berry Sept. 27, 1938 2,179,080 Alther Nov. 7, 1939 2,237,414 Day Apr. 8, 1941 2,366,057 Russell Dec. 26, 1944 2,448,223 Lantz Aug. 31, 1948

Claims

4. APPARATUS FOR COKING PITCH FROM COAL TAR, LIGNITE TAR, AND HIGH BOILING MINERAL OIL RESIDUE, AS WELL AS SIMILAR MELTABLE BITUMINOUS STARTING MATERIALS CONTAINING HIGHBOILING VOLATILE INGREDIENTS COMPRISING AN ELONGATED VERTICALLY EXTENDING COKING CHAMBER, A HEATING JACKET SURROUNDING THE COKING CHAMBER, A DISTILLING COLUMN IN TIONED ON THE UPPER PORTION OF THE COKING CHAMBER IN VERTICAL ALIGNMENT AND IN DIRECT COMMUNICATION THEREWITH, A HEATING JACKET SURROUNDING THE DISTILLING COLUMN, MEANS FOR INTRODUCING STARTING MATERIAL INTO THE UPPER PORTION OF THE DISTILLING COLUMN, SAID COLUMN HAVING AN OUTLET IN ITS UPPER PORTION FOR DISCHARGE OF VOLATILE MATERIAL, MEANS AT THE LOWER PORTION OF THE DISTILLING COLUMN FOR DIVIDING VISCOUS MATERIAL RESULTING FROM DISTILLATION OF THE STARTING MATERIAL AND DROPPING IT INTO THE UPPER PORTION OF THE COKING CHAMBER FOR FREE FALLING DOWNWARDLY THROUGH THE COKING CHAMBER, A CALCINING CHAMBER POSITIONED BENEATH THE COKING CHAMBER IN VERTICAL ALIGNMENT AND IN DIRECT COMMUNICATION THEREWITH FOR RECEIVING COKED PARTICLES FROM THE COKING CHAMBER, MEANS FOR FEEDING COMBUSTION SUPPORTING AIR INTO THE LOWER PORTION OF THE CALCINING CHAMBER, THE UPPER PORTION OF THE CALCINING CHAMBER BEING OF LARGER AREA THAN THE LOWER PORTION OF THE COKING CHAMBER TO PROVIDE A DISCHARGE AT THE UPPER PERIPHERAL PORTION OF THE CALCINING CHAMBER FOR PRODUCTS OF COMBUSTION.