JPH083094B2 - Method and apparatus for producing high quality calcined coke - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method and apparatus for producing high quality calcined coke, and more particularly but not exclusively, calcined needle coke with a high degree of particle strength. (Calc
The present invention relates to a method and an apparatus for manufacturing an ined needle coke).

Intended for producing graphite carbon for ultra high strength electrodes in coke or arc furnaces intended for use in producing certain metals from raw materials by electrolysis of melts containing compounds of metals The coke present must be substantially free of volatiles such as hydrocarbons. Therefore, raw coke for such purposes (so-called "raw coke" in the case of petroleum-based raw coke and similar raw cokes).
Is calcined at an elevated temperature suitable to produce volatile free coke calcinated. In the case of petroleum coke obtained by coking of hydrocarbon substances of petroleum origin, calcination is carried out at temperatures of about 1300 to 1500 ° C and higher temperatures, for example 1400 ° C. Similar or different calcination temperatures can be used to exclude volatiles from coke obtained from other sources (eg coal, coal tar, lignite, etc.).

Although the present invention is described in detail below in connection with petroleum coke, it is understood that the present invention applies equally to coke derived from other sources such as coal, lignite and other carbonaceous and hydrocarbon materials. It should be.

It is preferable that the coke used for the above purpose is substantially free of volatile matter (for example, the content of residual hydrogen is preferably less than 0.01 to 0.03% by weight), high particle strength, and identification of particle size distribution. It is preferable to meet other stringent quality standards, including ranges and / or specific ranges of absolute densities. Having a high degree of particle strength is especially important for the production of black smoke electrodes with high mechanical strength, which are used under high and varying temperatures.

BACKGROUND OF THE INVENTION There are well-collected records of methods and equipment for the production of calcined coke, generally speaking in two categories: rotary kiln furnaces and rotary hearth rotary furnaces. Can be divided into

Broadly speaking, the "rotary kiln process" supplies a suitable packing material to the upper end of a downwardly sloping rotating cylinder, in which the packing material is heated to drive off volatiles. And, as a result, the product consists of recovering the low volatility coking material from the bottom end of the cylinder. By the way, the heat required to drive off the volatiles is (a) in the flame partially extending in the cylinder, or (b) heated combustion gas is introduced into the cylinder from another combustion chamber, It is provided by burning the fuel with any combustion supporting gas (usually air) in separate fuel chambers such that the coke and the heated gas flow countercurrent to each other as they pass through the cylinder. In some examples, the volatiles driven off are combusted, for example in a cylinder, to generate some of the heat required to convert the charge to calcined coke.

Then, in general terms, the "hearth rotary kiln process" consists in feeding the feedstock to the outer circumference of a flat or saucer type hearth rotating about a central vertical axis.

The hearth has a central hole through which the calcined coking material is discharged and a stationary stirrer or skim so that the packing material creates a generally spiral path from the outer circumference to the central hole.

The hearth is placed under a stationary roof and the fuel, as it passes across the hearth, has a combustion supporting gas (usually in the space between the roof and the hearth for heating the feedstock). In the air)
Burned.

Volatiles expelled from the filling material are also burned in this space, thereby increasing the heat supply. Calcined coking material is discharged from the hearth through its central hole and received in a cylindrical or downwardly tapered vessel and provides an additional period for escape of the volatilizable material. As such, it is soaking at a temperature close to the maximum temperature achieved.

The hearth may be substantially flat. Alternatively, it may be sloped downward from either the outer rim or from a location between the rim and the central hole toward the central hole. See U.S. Pat. No. 3,475,286 (Klemmerer et.al.) for a detailed description of hearth rotary furnaces. Rotary kiln calcined coke is usually of a quality that passes various purposes. However, the yield of calcined coke is lower compared to hearth rotary calcined coke.
(Typically less than 4-6% by weight). Moreover, the investment amount for the rotary kiln equipment is higher than the operation cost.

The above-mentioned disadvantages are reflected in the higher cost of rotary kiln calcined coke.

Hearth rotary calcined coke is usually accepted for many purposes. Thus, its notable drawbacks are its friability and low particle strength. Premium grade high quality calcined coke required for ultra high strength electrodes for arc furnaces must meet stringent quality standards, including quality standards for particle size distribution. Such electrode coke must contain a certain minimum proportion of coarse calcined coke with good particle strength, and it has hitherto been impossible to meet such quality standards. .

BACKGROUND OF THE INVENTION We have selected a range of feedstocks to be heated in two stages with hydrogen, without treatment, and without intermediate cooling, and not greater than a particular heating rate. Has a maximum heating rate in the first stage held as
It was also found that calcined coke with a high degree of particle strength that meets the quality specifications for premium grade high quality coke is produced substantially consistently when the temperatures in both stages are tightly controlled. . (However, the specific ratio of the volatile matter content of the raw material supply material should be eliminated in the first stage.)
Furthermore, the inventors have found that, with all the attendant advantages over rotary kilns, hearth rotary furnaces can be used to produce premium grade high quality coke.
(However, the furnace must be configured and operated in a special way as specified and described below.) SUMMARY OF THE INVENTION The present invention resides in a first aspect. And how to produce high quality calcined petroleum coke from raw coke,
And consists of the following steps: (a) 14 wt% based on dry weight of raw coke
Feeding a raw coke with a volatiles content not exceeding not more than: (b) said raw coke in the first heating stage,
Volatiles released from coke in the absence of added hydrogen and volatiles of raw coke exposed to a heating environment that is substantially retained only by combustion at a controlled rate of fuel and combustion supporting gas. 100 to 100% until 50 to 90% by weight of the content is removed and the temperature of the whole coke is in the range of 650 to 850 ℃.
Providing a coke heating rate of not more than C / min, (c) the heated coke produced by step (b) at the total temperature in the range of 650-850 ° C without intermediate treatment or cooling steps; Sending to a calcining step, (d) in the calcining step, increasing the temperature of the heated coke to an overall temperature in the range of 1350 to 1470 ° C. and averaging it for at least 10 minutes. Exposure to a heated environment maintained only by the combustion of combustibles and fuels released from the coke by combustion supporting gases so as to maintain temperature; and (e) high quality from the calcination step (d). The process of collecting coke from is done.

In a second aspect, the present invention is a rotary hearth rotary furnace for producing high-quality petroleum coke from raw petroleum coke, which has the following configuration. That is, a circular rotary hearth that comprises a circular hole in the center, a means for mounting the hearth for rotation about its central vertical axis, and a stationary set spaced above the hearth. Roof, an annular wall to prevent hot gas from escaping from the inside of the furnace, (a) an outer periphery of the calcination zone outside the central hole, and (b) an annular wall connected by an annular wall. An annular radiation shield hanging down from the stationary roof to form the inner circumference of the preheat zone, wide enough to allow coke particles to pass from the preheat zone to the calcination zone However, a vertical gap, which is sufficiently small to substantially prevent radiation of heat from the central calcination zone to the annular preheating zone, produces a radiation shield consisting of the hearth, and a temperature in the range of 1350 to 1600 ° C. For coke due to combustion supporting gases on the hearth in the fuel and calcination zone Burner means for burning the volatiles released from the coke, the fuel and the volatiles released from the coke by the combustion-supporting gas on the hearth in the annular preheating zone, and 650-850 ℃ in the preheating zone To heat the coke to a range of temperatures, the burner means, which serves as a substantial main heat source to generate a temperature in the range of 650-900 ° C in the preheating zone, the raw material in the zone outside the hearth of the annular preheating zone Means for adding petroleum coke particles, means for rotating the hearth about a central vertical axis, central calcination from an area outside the annular preheating zone through a vertical gap between the radiation shield and the hearth. Stirring means for moving coke particles to the zone, stirring means for moving coke from the outer periphery of the central calcination zone to the central hole, and central for collecting coke from the central hole Coke recovery means, below the hole of the.

For the first aspect of the invention, it has already been proposed to calcine the petroleum coke filling feedstock in a separate stage.

British Patent Specification No. 1,603,924 (Koa Petroleum) describes a method for calcining raw coke containing combustible volatiles and water obtained by coking process, glazing in three or more stages of a furnace. And claiming. The furnaces are connected in series, in which the regulation of the atmosphere and the control of the temperature in each furnace can be carried out independently, and the method is (according to the order shown in each furnace) And (a) evaporating the water contained in the raw coke,
And preheat the coke, (b) evaporate and remove volatiles from the dried coke, and (c) heat and calcine the coke from the step (b).

In the specific example described, each of the three independent furnaces is a rotary kiln, but in the above-mentioned patent document, other types of furnaces (for example, hearth rotary kiln) are provided for each rotary kiln. It is mentioned that it can be used instead. Obviously, the drawbacks associated with rotary kilns apply to each of the above furnaces, and the investment is very large when three rotary kilns or other types of furnaces are used to carry out the method of the above patent. Furthermore, when transferring coke from one furnace to the next, the risk or fact of cooling some amount of coke and contact with molecular oxygen would be unavoidable. We need to remove in the first heating step 50% or more and 90% or less by weight of volatiles contained in the raw coke in order to produce a high quality or highest quality final calcined coke, It has been determined to be important that preferably the volatiles removal should be in the range 55 to 85% by weight, for example in the range 60 to 80% by weight. British Patent No.
The data in the table of No. 1,603,924 show that about 91% by weight of volatiles were removed in the second of the three furnaces, with raw coke at initial temperatures ranging from 1100-1300 ° C. It makes sense to expect additional amounts of volatiles to be generated in the first of the three furnaces exposed to countercurrent gas.

A proposal similar to British Patent No. 1,603,924 is described in Koa oil Company's British Patent Application No. 2,043,676, with partially volatile and third dried coke. An additional step is provided to cool the coke before passing it through the furnace.

British Patent Application No. 2,093,061 A is (a) raw petroleum coke having a sulfur content greater than 2.5% by weight and a volatile content of at least 7% by weight at a temperature in the range of 250 ° C to 450 ° C in an acidified atmosphere. Heating for less than 30 minutes, (b) adding the oxidized coke in an atmosphere containing added hydrogen such that the sulfur content of the coke is 1.5% by weight or less, so that the sulfur must be removed in the final stage. (C) the partially desulfurized coke at a temperature in the range of 1350 ° C to 1600 ° C in the absence of added hydrogen to a sulfur content of 1.5 to 2.5% by weight. Heating for a sufficient period of time to reduce to within the range of 1.5 to 2.5% by weight from the above raw petroleum coke
Describes a three-step process for producing a calcined petroleum coke with a sulfur content in the range of and a vibrated bulk density of at least 78 g / 100 cc.

For comparison, British Patent Application No. 2,093,061 A shows that 70% by weight of raw coke volatiles was obtained by performing the first step at 490-850 ° C.
A two-step calcination as described in U.S. Pat.No. 4,160,814 in which the partially volatile coke is then heated at a temperature of at least 1500 ° C for 30 to 70 minutes to calcine and desulfurize, with the following exceptions: Mention the law. Also British Patent No. 2,
For the purpose of comparison, 093,061 A shows 650 raw coke with a sulfur content of 4.4% by weight and a volatile content of 10.5% by weight.
It describes a two-step calcination process in which it is calcined at 1 ° C for 1 hour and at 1400 ° C for another hour. 1.9% by weight of final calcined product
And has a low bulk density (vibrating bulk density, VBD), indicating that the latter is a weak particle strength calcined product. We have found that high quality calcined coke, that is, calcined coke with relatively high particle strength and low friability, is calcined by a method in which the sulfur content of the main coke is not significantly lost, for example 10% by weight. The following, preferably less than 5% by weight, more preferably less than 3.5% by weight, most preferably 3.0% by weight
It has been established that the following can only be obtained if it is done so that it disappears. The reason for this is not fully understood, but the above conditions, which lead to a significant loss of sulfur, also result in micropores and fractures in the coke particles, which results in particle strength and friability. It is estimated to have an adverse effect. Factors that are believed to cause a reduction in the sulfur content of coke particles include:

(I) Transiently fast heating rate of raw coke, (ii) Transient rate of raw coke volatiles in the initial devolatilization of raw coke, and (iii) Time coke sufficient to cause significant desulfurization Be exposed to desulfurization conditions.

Factors (i) and (ii) depend on the time and temperature at which the initial devolatilization of raw coke takes place. According to the present invention, the maximum total temperature of the first stage coke is 850 ° C, the average coke heating rate is 100 ° C / min or less, and the first stage devolatilization amount is the total volatile matter in the raw coke. It is in the range of 50 to 90% by weight. With respect to factor (iii), the maximum total coke temperature during the second stage is less than 1470 ° C. Temperatures above 1470 ° C are especially important if the coke has sufficient time for loss of sulfur 1470 ° C.
It can be seen that having an overall temperature above 0 ° C. has an adverse effect on the particle size and friability of the calcined coke product.

In the practice of the method of the present invention, the overall temperature of the coke during the final calcination stage is in the range of 1350 to 1470 ° C, and generally good quality calcinated coke is the time between subjecting the coke to the final calcination stage. Is longer at the lower end of the range of 1350 to 1470 ° C. and shorter at the upper end of the range.

U.S. Pat.No. 4,160,814, which is a British patent application corresponding to British Patent No. 2,016,512, performs first stage calcination in a rotary kiln to heat coke to a temperature of 490 to 850 ° C. and second stage calcination. Two-stage calcination using raw coke with a high sulfur content (about 4% by weight of sulfur) as raw material, which is carried out in a rotary kiln to heat coke to a temperature over 1500 ° C to remove a majority of residual sulfur. The method is described. While the above method is intended to achieve the goal of obtaining a low sulfur (about 0.5 wt% sulfur) calcined product, the high temperature of the coke during the second calcination step results in loss of sulfur from the coke and associated particle strength. Cause a drop in.

British Patent No. 2,078,775 A includes (a) a sulfur content of at least 3.5% by weight and at least 7
Raw petroleum coke having a volatile content of wt% is heated in the absence of added hydrogen at a temperature in the range of 600 ° C to 800 ° C for a time sufficient to reduce the volatile content of the coke to a value in the range of 3 to 6% by weight. (B) The partially volatile coke is subjected to a sulfur content of 2.8 to 3.3% by weight at a temperature in the range of 600 to 800 ° C. in an atmosphere containing added hydrogen. (C) the partially desulfurized coke described above in the absence of added hydrogen at a temperature in the range of 1350 ° C. to 1600 ° C. to reduce the sulfur content of the coke to 1.8% to 2.5% by weight. Heat for a sufficient period of time to reduce to within the range, from the above petroleum coke consisting of 1.8 to 2.5% by weight
Describes a process for producing a calcined petroleum coke having a sulfur content in the range and an oscillating bulk density of at least 78 g / 100 cc.

This method is described in British Patent Application No. 2,016, except that a hydrodesulfurization step is interposed between the first and final calcination steps.
Similar to method 512A. The high loss of sulfur in the above process results in low particle strength coke calcined products. Moreover, the use of hydrogen in the additional process adds a significant operating cost to the cost of the baked coke product. For comparison, British Patent Application No. 2,078,775 A also includes, for example, 700 ° C. in the first step.
Calcination for the other stages of high sulfur coke with heating for 1 hour at 1 hour and a second stage at 1500 ° C for 25 minutes. It is not clear whether hydrogen will be used to desulfurize coke in any of several stages, but the high temperature in the second stage may be reflected in the transient loss of sulfur content (50% by weight). Undoubtedly reduces the particle strength of baked products. British Patent No. 2,078,77
5 A is also a calcined coke with a raw content of 4.8% by weight of raw coke as the starting material, a sulfur content of 1.9% by weight (sulfur loss of 60.4% by weight), low particle strength and high friability. Other two-step calcination processes are finally obtained which result in calcinated products having other properties which indicate

British Patent Specification No. 1,129,322 and corresponding US Patent No.
No. 3,448,012 is for supplying a substance to the heating chamber, the hearth installed in the chamber, the material outlet in the center of the hearth, and the hearth near the outer periphery of the hearth to form the bed of the material on the hearth. Equipment, arranged on the hearth and at regular intervals arranged to move the substance on the hearth continuously and inwardly toward the substance outlet relative to the relative movement between the hearth and the stirring rod. And describes and claims a hearth rotary furnace comprising a stirrer provided at 1, and at least one partitioning device which divides the chamber into at least one internal zone and at least one external zone. The partition device has an upper end and a lower end, the upper end of the partition device being substantially gas impermeable and joined with a wall surrounding the chamber to form a mechanically fixed seal with the chamber wall. The partitioning device has a lower end that extends downwardly toward the hearth and is positioned proximate to the top of the bed and is substantially parallel to form a substantially gas-impermeable seal at the lower end. However, the outlet for gas is provided from at least one internal area, and the conduit device is at least one such that the exhaust gas from the internal area or the gas heated by the exhaust gas passes through at least a part of the external area. An exhaust device is connected to the inlets in the two outer zones so that the material on the hearth moves substantially inwardly under the partitioning device, and thereby only between the inner and outer chambers. A small gas flow occurs between the top of the bed and the bottom of the divider.

The purpose of the partitioning device is to separate the interior of the furnace into different temperature zones and to provide a seal that prevents the passage of gas from one zone to another. In a preferred embodiment, the outer zone is heated by the hot flue gas produced by the combustion of the volatiles and fuel generated from the coke in the inner zone. British Patent No. 1,219,322 (page 2, lines 94-102) states: "The temperature within each zone is sufficient to reduce the volatiles and oxidize them within each zone at a rate sufficient to provide the desired temperature to each zone. Can be controlled by a voluntary process, or a cooling device such as a burner or cold air blower,
It can be used to control the temperature within various ranges. ", And the burners used in the internal and external areas, page 4, page 28-
Further description is given on line 30.

However, the exterior of the two chambers is merely intended to dry the raw coke at temperatures below 500 ° F (260 ° C) to avoid volatilization of the coke within it, and the subsequent steps Is carried out in the internal chamber at a temperature of 2000 ° F (1093 ° C) or higher, for example, page 4,
It is clear from lines 43-62. This means that the raw coke is dried and devolatized within the external limits within certain limits.
Furthermore, it is completely different in purpose and operation from the rotary hearth rotary furnace of the present invention which is subjected to final calcination in the internal region.
These differences are reflected in the construction of the furnace of the present invention.

Another feature of the furnace of the present invention, which is not described or suggested in GB 1,219,322, is that the bottom of the radiation shield forms a complete circle or ring with a gap therein. On the other hand, in British Patent No. 1,219,322, the partition or curtain wall 62 is formed with gaps, notches or small windows 68, or into multiple arcs with gaps between adjacent pairs of their ends. Formed, whereby substantially all of the coke is moved through the gap from the outer chamber to the inner chamber. Therefore, the arc of the gap limits the coke throughput per unit time through the furnace. In contrast, the arrangement in the furnace of the present invention allows the coke to pass through the gap between the radiant shield and the hearth from the external zone to the internal calcination zone without limiting the capacity of the furnace by the presence of the radiant shield. It is something that moves.

In one embodiment of the invention, the roof of the outer zone is inclined downward and inward with respect to the foundation of the annular radiation shield,
Finally, it borders the hot zone on the internal zone, so that substantially no radiant heat is directly received from the hot zone to the external zone during operation.

Preferably, the hot zone has a roof configured to reflect radiant heat downward toward the hearth of the interior zone so as to heat the coke on the hearth within the interior zone by at least partial radiation.

The raw volatile-containing coke contains 14% by weight or less, preferably 10% by weight or less, more preferably 8.5% by weight or less. In a preferred embodiment, the volatile content is in the range of 5-8% by weight, for example about 7% by weight.
Is.

For the method aspect of the invention, the first heating step and the subsequent calcination step are preferably performed in a single furnace. Preferably, the single furnace is a rotary hearth furnace.

Preferably, the coke recovered from the calcination step is maintained at an average temperature of at least 1275 ° C. for a period of at least 10 minutes, more preferably 15 to 30 minutes. This temperature maintenance or soaking time improves the quality of the coke product in terms of its residual hydrogen and other volatile content and in other respects.

The particle size of the raw coke feed can be nominally up to 100 mm, and actually includes a fraction of the particle size up to 150 mm (eg up to 15%). However, preferably, the particle size of the raw coke is nominally up to 50 mm, but in practice it is somewhat larger (roughly not exact, for example up to 80 mm).
Feeds with a small fraction of particles (up to mm) (eg up to 15%) are usually used.

Preferably, the temperature of most of the coke transferred from the first heating stage to the calcination process is in the range of 730-780 ° C, for example 740-760 ° C.

The average temperature of the atmosphere in the first heating stage is 800-900
C, more preferably adjusted to a range of 830 ~ 870 ° C., and the average residence time of the coke in the first stage is 0.2 to 2.0 hours, preferably 0.25 to 1.5 hours, for example
It can range from 0.3 to 1.0 hours. The most preferred residence time or residence time in the first heating stage depends on the temperature and throughput per unit time. At a temperature of about 850 ° C, the residence time is 0 at high throughputs.
It can vary from 5 hours to 1 hour with a low throughput per unit time.

The temperature and residence time in the first heating stage are 100 ° C
Per minute, more preferably up to 60 ℃ / min to heat the coke, for example in the range of 35 ~ 45 ℃ / min,
50-90% by weight of the volatiles content is selected to drive or remove from the raw coke feed in the first heating stage. Preferably, the volatiles loss in the first heating stage is
The range is 55 to 85% by weight, more preferably 60 to 80% by weight, and most preferably 65 to 75% by weight.

An important result of the process of the present invention is that the sulfur content of the calcined coke product is very different from that of the raw coke feed. Maintaining the sulfur content at a nearly constant value has been found to impart high stability and hardness to the calcined coke, thus meeting the quality standards for high, excellent quality calcined coke. While there is a loss of sulfur during the conversion of raw coke to calcined coke, the loss of sulfur is preferably not more than 8% by weight of the weight of sulfur in the raw coke, more preferably not more than 4% by weight, and Preferably 2.
The loss is 5% by weight or less. Such a beneficial low loss of raw raw coke sulfur results from the temperature and residence time in the two heating stages of the process of the invention. Most of the sulfur loss occurs in the second heating stage, so careful control of the maximum temperature to which the coke is exposed in the second heating stage is important. In the practice of this invention for the production of higher and superior quality calcined cokes useful in the production of electrodes used in steelmaking arc furnaces, the sulfur content of the raw coke is 1.33 wt% (dry coke basis). ) Or less, preferably 1.0% by weight or less, and more preferably 0.85% by weight or less. For many uses,
0.2% by weight, such as 0.5% by weight (or more) sulfur, based on the dry weight of raw coke.
It can be produced economically by the process according to the invention starting from a raw coke having a sulfur content above, for example 0.4% by weight of sulfur.

In the calcination step, the coke is a partially volatile-depleted coke from the first heating step with a very low residual content of volatiles (e.g., 0.05 wt.% Or less hydrogen, preferably 0.035 wt.%). Hydrogen below, most preferably 0.030
1350 to 1470 ° C., preferably 1400-1460, for conversion into a hard calcined coke product having less than wt.% Hydrogen).
C., more preferably to a temperature in the range 1415-1445.degree. The average residence time of the coke in the calcination stage is at least 10 minutes and can be of the order of 2 hours (depending on the temperature in the calcination stage and the treatment rate of coke per unit time), preferably 0.3-. 1.5 hours, for example 0.5
~ 1.2 hours range. In many cases, residence times of 30-60 minutes or average residence times are usually adequate for calcining coke. Careful control of the temperature of the atmosphere to which the coke is exposed during the calcination step is important to ensure that the coke is not exposed to transient high temperatures. The inventors have found that coke temperatures above 1470, for example 1490 ° C., cause sharp opposite changes in the factors leading to low particle densities and thus low particle strengths, with optimal particle properties falling within the more preferred ranges as described above. Have 1350
It is believed to be obtained in the temperature range of ~ 1470 ° C. The ambient temperature to which the coke is exposed is preferably 1380-15
It is in the range of 65 ° C, and depends on the heat transfer efficiency to the coke by radiation and conduction and the residence time. In most cases, the ambient temperature will be between 1480 ° C and 1560 ° C, more preferably 1490 ° C.
Can range from ˜1555 ° C. At high coke throughputs (eg, at or near the design throughput of the apparatus for practicing the method of the present invention), temperatures near the high end of the temperature range are preferred and low coke is preferred. At throughputs per unit time, correspondingly low temperatures will give high or superior quality calcined coke.

The calcined coke from the calcination process is collected in so-called heat-soaking pits, where the quality as high quality coke, especially the content of volatiles is very low, preferably high true. Density (e.g. 2.10-2.
18, preferably 2.12 to 2.15), and further aged at high temperature (ag to obtain a property with a particle size distribution that includes hard and relatively non-dusting, somewhat coarse particles (eg 30 to 50 mm).
e) be done. This calcined coke has 1
200 ~ 1470 ℃, preferably 1300 ~ 1450 ℃, average 10 ~ 4
Hold for 0 minutes, preferably 15-30 minutes. No heat is applied to the coke in the soaking pit except when freshly calcined coke from the calcination step is added. The aged or soaked coke is removed from the pit and then cooled in a suitable manner as known to those skilled in the manufacture of calcined coke.

With respect to the apparatus outline of the present invention, a rotary hearth furnace is equipped with burners to maintain the preheating and calcination zones at the desired temperature. The burners in each zone are preferably equipped with means for adjusting the fuel feed rate.
The burner may be provided with means responsive to the temperature of each zone or a representative temperature to regulate the rate of fuel delivery. A representative temperature can be, for example, the temperature of the fuel gas exiting each zone.

The furnace is 10-40 minutes, for example 10-30 minutes, preferably 15-30 minutes.
It is preferable to provide a container, which is a soaking pit, which acts as the coke recovery means in order to provide a residence time of 1 minute or a residence time. The soaking pit can be provided with a discharging means for discharging coke from the soaking pit at the end of the residence time. The soaking pit can be made of a steel material lined with a refractory and can be integrated with the hearth so as to rotate together with the hearth. A soaking pit integrated with the hearth of a rotary calciner is described and illustrated in British Patent Specification No. 1,219,322 and its corresponding US Pat. No. 3,448,012.

The radiation shield of the furnace preferably has no gaps on the circumference. Such a gap is provided in the curtain wall of British Patent No. 1,219,322 and US Patent No. 3,448,012, outside of the curtain wall, i.e. from the outer area to the inner area (eg as is apparent from Figure 3 of these patents).
Constitutes a single means of passing coke. In contrast, the furnace of the present invention moves all coke from the preheat zone to the calcination zone through the vertical gap between the bottom of the radiation shield and the hearth. As a result, coke grinding can be reduced and a large amount of processing can be performed.

A preferred vertical gap between the bottom of the radiation shield and the hearth is 50-100 cm, more preferably 60-90 cm. The gaps in the dimensions of these ranges are small enough to substantially prevent large amounts of heat from calcination zones from escaping due to direct radiation and convection in the preheating zone, but between the zones for maintenance, investigation and repair. Large enough for workers to enter and leave. However, smaller dimensions are preferred when entry and exit through the gap is not considered important. in this case,
The vertical spread of the gap can be 40-60 cm.

In a preferred embodiment, the furnace has a high temperature zone for exhausting flue gas from both the preheat zone and the high temperature zone.
It is preferred that there be three smoke outlets and that the gap between the hearth baffle and the hearth baffle is large enough to allow flue gas to pass from the preheat zone to the hot zone as well as the coke. However, instead of or in addition to them, the preheat zone may have its own flue for discharging the flue gas produced in the preheat zone. In the latter case, the vertical gap between the bottom of the radiation shield or baffle and the hearth can be 15-45 cm, for example 20-40 cm, which allows this gap to pass from the preheating zone to the central calcination zone. Allows at least some of the flue gas to pass through.

In a preferred embodiment of the furnace according to the invention, the roof of the preheating zone is inclined inwardly and downwardly with respect to the foundation of the annular baffle, which annular baffle is above the hearth of the calcination zone. It is connected to the side of the high temperature area and prevents direct radiation heat from entering the preheating area from the high temperature area. In this preferred type of embodiment, the hot zone is located above the average height of the preheat zone, where the fuel is burned and the temperature is preferably 1400 to 1600 ° C, for example 1475 to 1575 ° C ( In general, these temperature ranges are also typical temperature ranges for many other configurations of the furnace of the present invention. Heat is radiated from the burning fuel flame directly to the hearth of the calcination zone by radiation from the walls and roof of the calcination zone.

Next, the present invention will be described more specifically with reference to Examples and the drawings, but the present invention is not limited thereto. This drawing shows the features necessary for those skilled in the art to understand the present invention, without detailed description of the matters known or obvious to those skilled in the art. This drawing is not intended to be of any specific size and is intended to illustrate general characteristics of non-limiting embodiments of the invention.

The same reference numbers have been used to represent the same or similar features in all drawings.

In the embodiment of FIG. 1, the furnace 10 has a turntable or hearth 11 that slopes down toward a central hole. The lower part of the hole is a soaking pit 12, which receives the coke falling from the hearth 11 and recovers the calcined coke from there, as indicated by arrow 23. A roof member 13 fixed to the upper part of the hearth is provided. The side wall 15 extending upward from the edge of the hearth 11 is sealed (for example,
The outer edge of the roof member 13 has a side wall 14 which extends downward (by a water seal or sand seal means of a known type, as indicated by numeral 14a). Hearth 11
It is supported and rotated by other means known in the art, such as racks and pinions, which are driven by a suitable gear wheel 16 and / or an electric motor (not shown). A hole 17 is provided in the roof member 13 for discharging the flue gas from the inside of the furnace to the flue gas discharge duct 18. An annular baffle 19 extends downwardly from the roof member 13 to define the outer boundary of the central high temperature combustion chamber 20. The bottom of the baffle 19 is provided at a sufficient distance (for example, about 50 cm) from the upper part of the side of the hearth 11 so that the coke and the flue gas under the baffle 19 are distributed in the radial direction of the hearth. It allows movement from the outer area to the hole in the center of the hearth, but the radiation and hot gases from the combustion chamber 20 impede baffles.
It prevents affecting the radially outer region of 19.
If for maintenance, investigation and repair it is desirable to provide an outlet leading to the gap between the bottom of the baffle 19 and the top of the side of the hearth 11, the gap should be approximately 80 cm in size. be able to. Conduit 320 supplies feed petroleum coke (eg, from a delayed coker) to the outer area of the hearth. To produce high quality calcined coke, select raw coke with less than 14 wt% volatiles and less than 1.33 wt% sulfur (based on the dry weight of coke). In order to produce a high quality calcined product, preferably about 7 wt% volatiles and less than about 1.0 wt% sulfur (eg about 0.6 wt%) based on the dry weight of coke is selected. In order to move the coke adhering to the upper outer edge of the hearth spirally in the direction of the hole in the center of the hearth, it is preferable to provide a stirring rod 24 hanging from the roof 13. In order to expose all the coke in the coke layer to the atmosphere above the coke layer, it is preferable to provide a separate stir bar (not shown) to flash the coke layer. The average thickness of the coke layer is about 15-40 cm, preferably 20-30 c
It is preferably m, for example about 25 cm.

Stir bars for propelling coke particles along a spiral path towards the central hole in the hearth and overturning the coke in the coke bed are well known. Such a stir bar and its arrangement are described in U.S. Pat. No. 3,859,172, British Pat. No. 1,272,880 (and corresponding U.S. Pat. No. 3,652,404).
No.), British Patent No. 1,345,845 (and US Patent No. 3,47).
0,184) and British Patent 1,440,883 (and U.S. Pat. No. 3,788,800) in detail. Therefore, it will not be described in further detail here. Combustion gases and air flow from their respective manifolds 25 to the outside surface of baffle 19 and sidewalls 14,
It is supplied at a constant rate to the combustion burner 26 in the annular space 21 between the inner surface of 15 and the internal temperature is maintained at 650 to 850 ° C, preferably 700 to 800 ° C, more preferably about 750 ° C, and the raw coke is used. As it passes through space 21, it is preferably preheated at an overall heating rate of less than 100 ° / min, more preferably less than 60 ° C / min (eg most preferably about 40 ° C / min.). Coke in space 21 for 0.25-1.5 hours, preferably 0.3-1.3 hours (eg 0.4-1.25 hours)
It is capable of dwelling and passes through the bottom of the baffle 19 at an overall temperature of 600-850 ° C, preferably 700-850 ° C, for example about 750 ° C upon first exposure to the conditions of the hot combustion chamber 20.
In the preferred embodiment described herein, an annular preheating space
21 does not have a separate flue for exhausting flue gas or combustion gases from it, and the gap between the bottom of the baffle and the hearth is about 80 cm s, and the coke and flue gas are in the preheating zone. The coke in the preheat zone 21, which can be passed to the calcining zone from 21, is substantially prevented from receiving heat from the calcining zone. The chamber 20 is provided with a burner 27 extending downwardly from the roof 13, which is supplied with a properly controlled amount of air and fuel and which keeps the temperature in the chamber 20 at least 1375 ° C., preferably 14 ° C.
The temperature is maintained at 50 to 1560 ° C, for example, about 1500 to 1550 ° C. The rotation and propulsion of the stir bar 24 exposes the coke to the effects of radiation from the chamber 20 and other high temperatures, causing the coke volatile content to drop to very low levels. The coke below the combustion chamber 20 and above the hearth is about 14 due to the effects of combustion and radiation.
It is heated to 70 ° C and maintained at that temperature for calcination. about
The coke calcined at 1460-1480 ° C. (eg, about 1470 ° C.) is received in a soaking pit 12 from which the last residue of unstable volatiles can escape. The calcined coke is heated and soaked in this soaking furnace at an average temperature of about 1400 ° C for an average time of about 20 minutes. The calcined coke removed from the soaking furnace 12 through the line 23 has an extremely low amount of residual volatiles (for example, 0.01 to 0.03% by weight of hydrogen), excellent particle distribution and high particle stability. , Which meet the criteria for higher premium grade calcined coke (eg, needle coke).

Preferably, the operating conditions in the annular space 21 are 90 wt% or less of the volatile content of the raw coke raw material, but preferably at least 50 wt% (more preferably 55 to 85 wt%,
(E.g. 60-80% by weight, most preferably about 70% by weight) is removed in the first heating stage constituted by the preheating portion of the space 21, the remainder being constituted by the portion containing the hot combustion chamber 20 Under a condition that a small amount is removed in the heating and soaking process in the heating and soaking furnace 12.

As shown in FIG. 1, air may be introduced into the flue gas exiting the combustion chamber 20 through line 28 to combust the combustion materials remaining in the flue gas.

The method of construction of the hearth of FIG. 1 can take any convenient form suitable for the task. In a preferred embodiment, the hearth is as shown in any of the above cited patent documents, for example British Patent No. 1,055,857, among others:
British Patent No. 1,219,322 (and corresponding US Patent No. 3,4
It can be an insulating material supported by a steel structural member similar to the hearth of No. 48,012). In order to further increase the structural stability of the heat-resistant hearth, a thin steel sheet, for example, a steel sheet having a thickness of 2 to 4 mm, may be provided between the structural steel member and the heat-resistant hearth. This is done by engaging a pinion driven by an electric motor mounted on a rotating structural steel member of the hearth with a circular rack mounted on the underside of the hearth. Pinions, electric motors and racks are conventional in this technical field and are referred to in British Patent No. 1,
It is not shown in the drawings as it is well known to those skilled in the art, as described on page 3, lines 1 to 4, of 219,322. The manner of construction of the other parts of the hearth of the present invention can be similar to the corresponding parts, if any, in the patent documents cited herein. The heating soak furnace is preferably integrated with the hearth and is adapted to rotate with the hearth about a central vertical axis of the hearth. Alternatively, however, it may be rotatable independently of the hearth, as described and shown in, for example, British Patent 1,345,106 and corresponding US Patent 3,763,011.

The hearth slopes towards the central hole at a relatively small angle to the horizon, which angle is preferably well below the coke rest angle. This angle is 8
The angle may be between 12 ° and 12 °, for example about 10 °.

Next, FIG. 2 will be described. This FIG. 2 is almost the same as FIG. 1 except for the arrangement of the roof and the annular baffle. Items common to FIGS. 1 and 2 are given the same reference numbers. The agitator rod 24 is not shown in full form for clarity. As is clear from the figure, the fixed roof 113 has a circular shape, and the rotary hearth 11 has a soak furnace 12 with a central hole.
It slopes downwardly and inwardly toward the central opening 114 in the same manner as it slopes toward the connection point with.
The roof 113 and the hearth 11 can be tilted downward at the same angle or at slightly different angles. Preferably the angles are the same and may be between 8 ° and 12 °, for example about 10 °. An annular baffle 119 extends upwardly from the edge of the opening 114 to form a sidewall of the hot combustion chamber 120, the top of which is provided by a cap member 121 with a central hole 17 for flue gas to escape into the flue duct 18. It is closed.

Combustion gases and air are passed from respective supply lines 26 and 27 through respective burners into spaces 21 and 12
0 to the desired temperature of coke in each part of the hearth (as specifically illustrated here), for example 800-900 ° C and
Supplied at a constant rate and in an amount sufficient to maintain an appropriate range for heating to temperatures of 1380-1565 ° C. The furnace geometry of FIG. 2 is such that the coke in the preheat portion 21 is shielded from radiation from the combustion chamber 120 and other high temperature effects until the coke in the preheated portion 21 reaches the imaginary downward geometric protrusion of the baffle 119. Is.

In order to more strongly shield the coke in the preheat section 21 from radiation from the combustion chamber 120 and other high temperature effects, the gap for the coke and gas passages between the preheat section 21 and the hot section 120 is reduced. A downwardly extending annular baffle 122 (shown in phantom) that is resistant to heat resistant material may be provided. The gap between the bottom of the baffle 122 and the hearth 11 is about 80 cm when it is desirable to have access between the preheat section 21 and the hot section 120 for maintenance, inspection and / or repair. can be s. If it is not necessary to approach this way, place the baffle 122 in the hearth 11
Extend it further downward to bring it closer to the gap,
Approximately equal to the depth of coke layer in hearth 11 during operation
It may be 15 to 25 cm s. The gap shown in FIG. 2 is a gap of about 80 cm s.

The absolute and relative amounts of the volatiles removed in the preheat section 21 and the hot section are similar to those in the embodiment of FIG. 1 by means readily apparent to those skilled in the art.
Adjusted for the illustrated embodiment.

Next, FIG. 3 will be described. FIG. 3 is that of FIG. 1 except that the rotary hearth 211 of FIG. 3 is substantially flat (instead of sloping down toward the central hole as shown in FIG. 1). It turns out that they are almost the same. Rotary hearth
A stir bar 24 moves the coke in 211 from the outer portion where it enters the hearth from the supply duct 320 to the central hole above the soaking pit 12. An additional stir bar (not shown) is preferably provided to dig back the coke layer so that all coke in the coke layer is exposed to conditions in the hearth.

Referring to FIG. 4, the furnace shown in this figure has a rotary hearth 311 that is substantially flat, and in this respect the third
It can be seen that it is very similar to the furnace of FIG. 2 except that it is similar to the hearth 211 of the figure. The embodiment of FIG. 4 is also shown with an optional additional heat-resistant baffle 122 or dashed line, as described above with respect to FIG. 2, for the hot gases and radiation that can pass from the inner portion to the outer portion. In order to further reduce the amount, the gap at the connecting point of the inner and outer chambers is made smaller. As explained above, the gap between the bottom of the baffle 122 and the hearth should be suitable (as shown in FIG. 4) for inspection, maintenance and / or repair therethrough. (In this case, a gap of about 80 cm s will be provided). Alternatively, if this is not the case, this gap may be sufficient to allow coke and flue gas to move from the preheating zone 21 to the hot zone, in this case about 60 cm s or slightly less. A gap (eg 45-55 cm s) is suitable. Similar to the embodiment of FIG. 3, a stir bar 24 is provided,
It is designed to promote the movement of coke from the outer part to the central hole in the hearth. More preferably, for example, for this purpose, for example, in British Patent No. 1,272,880 and U.S. Pat. An additional stir bar of the type described (not shown) is provided to invert the coke layer and expose all coke to the conditions inside the combustion chamber, so that each coke particle is exposed to the high temperature conditions inside the combustion chamber. The heating rate of the coke is reduced by reducing the direct exposure time, and the heat transfer from the higher temperature coke particles heats the coke particles in the coke layer. All of the above makes the temperature of the coke particles in the hearth relatively uniform at each location and prevents the temperature from changing significantly as the coke particles move from one location on the hearth to another. It will be clear that the intent is to do so. As shown in the figure, the soaking mortar 312 is frusto-conical and is tapered downward, which is different from the cylindrical soaking pit shown in FIGS. 1 to 3. The roof 221 of the central high temperature combustion chamber 120 has a flue opening 217 and a flue duct 218 arranged eccentrically with respect to the vertical axis of the chamber 120, whereas in FIG. The furnace roof 121 of FIG. 2 except that it is arranged concentrically to the axis.
Is similar to.

The following is a description with reference to the embodiment shown in FIG. Fifth
The furnace shown is generally similar to that of FIG. 4 and similar to the furnace of FIG. 2 with the following exceptions. Since the hearth 411 below the downwardly sloping annular roof 113 (ie, the radially outer part of the hearth 411 in the preheating zone 12) is substantially horizontal, the roof 113 and the outer part of the hearth are The vertical distance between the annular baffles 11 extends upward from the inner edge of the roof 113 and forms the outer or lateral boundary of the high temperature combustion zone 120.
When 9 is joined to the inner side of the roof 113 in the radial direction, the number gradually decreases when passing inward in the radial direction from the outer periphery to the inner side of the roof 113 in the radial direction. From the position below the inner part of the roof 113 inward in the radial direction, the hearth 41
No. 1 is inclined downward and inward toward the central hole forming the entrance of the soaking pit 312. The angle of downward inclination of the inner part of the hearth is smaller than the repose angle of coke,
May be about 10 °, suitably about 10 °. A stir bar (not shown) places coke from the raw coke feed pipe 312 on the outer horizontal portion of the hearth 411, generally across the hearth 411 along a path that spirals inward and soaks heat. It is provided to pass to pit 312. The stir bar may be of the type already mentioned and already described in the documents cited herein. From the outer peripheral area of the hearth 411 to the center hole of the inner portion in the radial direction of the hearth at the entrance to the soaking pit 312, in addition to the stirring rod for passing coke, first the coke on the hearth 411. In order to expose the coke particles at the bottom of the bed to the heating conditions in the furnace, another stir bar (not shown) is provided to give the coke a flashing action. As a result, all coke fed to the furnace is exposed to preheat conditions in the preheat zone 21 and then to calcination conditions when passing along the hearth below the high temperature combustion zone. It is understood that a stir bar for flashing the coke in this way and thereby exposing all the coke is preferably provided in all other embodiments of the furnace of the invention.

The means for controlling the discharge of coke from the soaking pit 312 is apparent from FIG. Broadly speaking, the means includes a delivery table 350 mounted on a fixture 351 for rotation about the central axis of the furnace.
The coke exiting the discharge holes 352 of the soaking pit 312 is received on the rotary delivery table 350, delivered to the outlet conduit 353, and exhausted to a coke cooler (not shown), as represented by arrow 23. To be done. A suitable stir bar (not shown) of any type known in the art for the above purposes.
May be provided to aid in the discharge of coke from the discharge hole 352 to the outlet conduit 353.

FIG. 6 shows in plan view some of the features of the furnace, which is largely similar to the furnace of FIG. 5, with a central discharge hole for the soaking pit 312 and at a distance of about 120 °. It includes three sets of stir bars 24 arranged. Each of these sets of stir bars is generally designated by the reference numeral 124 in FIG.

FIG. 7 shows the outer horizontal portion of the hearth 411 and the roof 113 sloping downwards in a side view taken against the line AA in FIG. The roof slopes down and inward at a relatively shallow angle (eg, about 11 °) from the perimeter of the furnace, then from the locus of point 113a (ie, the circle) to locus 113b.
As well as larger angles (eg about 30 ° on average)
The locus 11 is inclined downward and inward at the point where the roof is joined to the lower end of the baffle plate 119 that is the boundary of the high temperature area 120.
It is horizontal up to 3c.

Using the features and / or items of the device shown in connection with one embodiment in combination with the features and / or items of the device shown in connection with another embodiment, in a workable and practical manner It should be understood that it is good. Also, although each of the described embodiments has a single continuous annular baffle to separate the hotter and cooler zones, the furnace is separated into more than two heating stages. As such, more than one baffle may be provided.

It is surprising that the practice of the present invention can result in a high grain strength calcined coke in an apparatus that is or can be operated to subject the coke to a relatively high heating rate.

The following comparative simulation illustrates the advantages obtained by practicing the present invention.

Test 1 A representative raw petroleum coke sample having a volatiles content of less than 14% by weight and a sulfur content of less than 1.33% by weight, based on dry raw coke, at room temperature was used in a kiln.
It was exposed to a temperature of 1000 ° C. for about 20 minutes to simulate the conditions in a normal rotary hearth furnace. After 20 minutes, the sample is about 1000 ℃
Achieved a temperature of. The sample was removed from the kiln. The calcined coke particles were found to be severely cracked and very brittle.

Test 2 Another sample of the same raw coke as Test 1 was used, but about 1100
Test 1 was repeated using a kiln temperature of ° C. The quality of the calcined coke was found to be somewhat inferior to the calcined coke product of Test 1.

Trials 3 and 4 The same raw coke samples used in Trial 1 were first exposed to relatively low temperatures in the first heating stage and in a second heating stage at about 1100 ° C in a series of different testing experiments. It was cooled to room temperature (about 20 ° C) before exposure to temperature. At each heating step, the sample was exposed long enough to approximately achieve the temperature at which it was exposed. Table 1 shows the results.

Experiments 2 and 3 simulate the process of the invention, especially in the treatment of coke in what is found to be a critical period of immediate exposure of the coke to the second stage of high temperature. Previously, there were considerable problems in converting raw petroleum coke into hard, low-friability calcined coke. The method and apparatus of the present invention enable the production of hard coke with low friability in a consistent and relatively simple manner. Those skilled in the art will recognize that the low friability calcined cokes of Runs 2 and 3 do not meet the quality specifications of the higher grade coke because the final calcination temperature is too low. However, the present inventors have found that coke preheated immediately to a temperature in the range of 650 to 850 ° C. for 10 minutes to 2 at a temperature in the range of 1350 to 1470 ° C.
Calcination for hours in the range of hours yields higher grade coke with a hard crystalline structure of low friability suitable for use in the manufacture of ultra high strength electrodes for arc furnaces. I confirmed that.

[Brief description of drawings]

FIG. 1 shows a sectional front view of one type of hearth rotary coke calciner of the present invention, and FIG. 2 is a sectional front view of another type of hearth rotary coke of the present invention. . 3 and 4
FIG. 5 and FIG. 5 are also sectional front views of another rotary hearth rotary furnace of the present invention. FIG. 6 is a cross-sectional plan view of a hearth rotary furnace similar to that shown in FIG. 5, showing the hearth, stir bar arrangement and other features. FIG. 7 is a sectional front view of a portion of the furnace of FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Otto-Manfredt Kirschyubaum, Federal Republic of Germany 2104 Hamburg 92 Bergheide 68 (72) Inventor, Klaus Arnop Phuifah, Federal Republic of Germany 7517, Waltbronn 1 St. Barbara Strasse 42 (56) References 54-123101 (JP, A) JP-A-53-102901 (JP, A)

Claims (13)

[Claims] 1. (a) feeding to the first heating stage raw coke having a volatile content of not more than 14% by weight, based on the dry weight of the raw coke, (b) in the first heating stage Raw coke,
Volatiles released from coke in the absence of added hydrogen and volatiles of raw coke exposed to a heating environment that is substantially retained only by combustion at a controlled rate of fuel and combustion supporting gas. 100 to 100% until 50 to 90% by weight of the content is removed and the temperature of the whole coke is in the range of 650 to 850 ℃.
Providing a coke heating rate of not more than C / min, (c) the heated coke produced by step (b) at the total temperature in the range of 650-850 ° C without intermediate treatment or cooling steps; Sending to a calcining step, (d) in the calcining step, increasing the temperature of the heated coke to an overall temperature in the range of 1350 to 1470 ° C. and averaging it for at least 10 minutes. Exposure to a heated environment maintained only by the combustion of combustibles and fuels released from the coke by combustion supporting gases so as to maintain temperature; and (e) high quality from the calcination step (d). A method of producing high quality calcined petroleum coke from raw coke, including the steps of recovering the coke of. 2. A method according to claim 1, wherein the first heating step and the subsequent calcination step are carried out in one furnace. 3. A method according to claim 1 or 2, wherein one furnace is a rotary hearth furnace. 4. The process according to claim 1, wherein the coke recovered in step (e) is kept at a temperature of at least 1275 ° C. for at least 10 minutes. the method of. 5. The particle size of the raw coke feed in step (a) is not more than 100 mm.
The method according to any one of (4). 6. The method according to claim 1, wherein the total temperature of the coke in step (c) is in the range of 730 to 780 ° C.
The method according to any one of (5). 7. The method according to any one of claims (1) to (6), wherein in step (d), the temperature of the entire coke is raised to a temperature in the range of 1410 to 1450 ° C. and is maintained at that temperature. The method according to item 1. 8. A method according to claim 1, wherein the coke is maintained at the temperature for a time in the range of 15 to 30 minutes.
The method according to any one of (7). 9. A step of monitoring the temperature in at least one of the heated environments of steps (b) and (d) and to that environment for maintaining the temperature therein in a respective selected temperature range. The method according to any one of claims (1) to (8), which comprises the step of adjusting the fuel supply rate. 10. A circular rotary hearth comprising a central circular hole, means for mounting the hearth for rotation about its central vertical axis, spaced apart above the hearth. A fixed roof, an annular wall to prevent hot gas from escaping from the inside of the furnace to the outside, an outer periphery of the calcination zone outside the central hole and an annular preheating zone connected by the annular wall. An annular radiant shield hanging downwards from a stationary roof to form a perimeter, wide enough to allow coke particles to pass from the preheat zone to the calcination zone, but in the central calcination zone Is sufficiently small to prevent radiation of heat to the annular preheating zone substantially, the radiation shield consisting of the hearth in the vertical gap, fuel and calcination to generate temperatures in the range 1350 to 1600 ° C. Emitted from the coke in the region by combustion supporting gases on the hearth Burner means for burning volatiles, fuel and combustion of volatiles released from coke by combustion-supporting gases on the hearth in an annular preheating zone and producing a temperature in the range 650-850 ° C in the preheating zone A burner means to serve as a substantially primary heat source for the heating, a means for adding raw petroleum coke particles to the area outside the hearth in the annular preheating zone, a hearth around the central vertical axis Means for rotating, stirring means for moving coke particles from the area outside the annular preheating zone to the central calcination zone through the vertical gap between the radiation shield and the hearth, the outer to the central calcination zone Quality stones from raw petroleum coke, including stirring means for moving coke to the hole in the coke and coke recovery means under the central hole for recovering coke from the central hole A hearth rotary furnace for producing oil coke. 11. Means for monitoring the temperature in one or both of the zones, and for adjusting the rate of fuel feed into both zones to maintain the temperature in both zones within their respective temperature ranges. A furnace according to claim (10) including means. 12. The coke recovery means comprises a soaking pit to provide a residence time in the range of 10 to 30 minutes for the thermal coke received or recovered from the central hole in the calcination zone. A furnace as claimed in claim (10) or (11), which comprises a container for discharge and discharge means for discharging coke from the thermal infiltration pit at the end of the residence time. 13. The roof of the preheating zone is inwardly and downwardly inclined with respect to the foundation of the annular baffle, the annular baffle being on the side of the high temperature zone on the hearth of the calcination zone. Combined,
The furnace according to any one of claims (10) to (12), which substantially prevents the receipt of radiant heat directly from the high temperature zone in the preheating zone.