JPS60231791A - Green cake calcining process - Google Patents

Abstract

A process for calcining green coke containing combustible volatile matter in at least two stages, whereby in a first stage the green coke is heated in a furnace to a temperature of between 750 DEG C and 1000 DEG C and in a second stage in a second furnace to a temperature of between 1200 DEG C and 1600 DEG C, characterized in that the heating in the first stage is carried out with a controlled heat-up rate of less than 60 DEG C/min in the temperature range of between 600 DEG C and 800 DEG C, whereby said heating up is achieved by hot combusted volatile matter, which is obtained by withdrawing the released volatile matter from the first stage, burning said volatile matter outside the first stage and recycling the burnt volatile matter to the first stage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to raw coke (coke) containing combustible volatile substances.
green coke) is heated in a first stage to a temperature of 700°C to 1000°C in a furnace, and in a second stage to a temperature of 1200°C to 7600°C in a second furnace. The present invention relates to a method of burning said raw coke in stages.

Conventional technology Fresh coke made from a suitable hydrocarbon feedstock is
It is generally known that it can be converted into high quality needle coke for use in high performance graphite electrodes applied in electric ore furnaces, such as calcined carbon anodes in aluminium batteries, or for other purposes. . To this end, after the water has been removed at a relatively low temperature, the green coke is placed in a furnace at a temperature generally about ♂OO°C necessary to release at least a portion of the combustible volatiles. Heated (pre-combusted). In a subsequent stage, the coke is combusted in a second furnace to a temperature ranging from 1200°C to 7600°C. In principle, in each of these stages a shaft kiln, a rotary kiln or a rotary hearth furnace can be used depending on the particular circumstances. After pre-combustion, cooling of the product may optionally be performed before second stage combustion takes place. There are many methods for burning coke in the patent literature, such as British Patent Specification Letters 1. Otsu03. 2, No. 2, British Patent Application No. 2. Ori 3.0 Otsu/issue and 2,0
/ 4. t/2, German Patent Specification No. 2. 31μ
No. 7j and U.S. Pat. No. 2, o or r.

British Patent Specification Letter 1.1.03. No. 2 discloses a method of burning raw coke in three stages in series connected heating furnaces, namely, in the first stage water is evaporated from the raw coke and in the λth stage water is evaporated. The dry coke is distilled off and combusted, and the coke is combusted in a third stage. In the pre-burning stage, preheated air is introduced into the burner to burn the released volatiles. Disadvantages are the collapse of the particle size distribution during combustion, the high friability of the products obtained by such a process and the relatively low yield of products resulting from the combustion of coke.

Solution of invention A method has now been found in which the above-mentioned drawbacks can be avoided.

Solution, operation and effect The present invention heats raw coke containing combustible volatile substances in a furnace to a temperature of 730°C to 1000°C in a first stage, and heats it in a second furnace in a λ-th stage. 720 at
A method of burning the green coke in at least two stages, wherein the raw coke is heated to a temperature of 0°C to 1too°C.
The first stage heating is carried out at a controlled heating rate of less than 60 °C/min in the temperature range from ♂OO °C, and the volatile substances released are extracted from the first stage and the volatile substances are removed. The above temperature increase is achieved by means of hot combusted volatiles obtained by combusting outside the first stage and recycling the combusted volatiles into the first stage. Concerning the characteristic combustion method of raw coke. A portion of the hot combustion gas (combusted gas) may be obtained by burning additional combustible gas outside the first stage and introducing the combustion gas into the first stage.

The main advantage of the process according to the invention is that the calcined coke contains a sufficiently coarse material, which makes it particularly suitable for the production of ultrahigh performance electrodes.
That's what it means.

It is advantageous to carry out the first stage or pre-calcination in a non-oxidizing atmosphere, which means that, apart from some oxygen leaking into the kiln due to the operation at pressures below atmospheric, Free oxygen means that no more or little oxygen is present in the recycle gas. The atmosphere during the pre-calcination stage may also be described as reducing.

In principle, in the first stage any type of furnace is suitable, but a rotary kiln is preferred.

Also in the second stage, any type of furnace may be suitable. In the first and second stages, it is preferable to combine a rotary kiln and a rotary hearth furnace, respectively.

Control of the heating rate in the first stage is adjusted by the temperature and amount of the combustion gas, which preferably flows countercurrently to the direction of flow of the green coke. In rotary kilns, the direction of raw coke flow has a small angle to the horizontal surface. The tilt of the rotary kiln is generally less than 50. Depending on the total length and rotational speed of the kiln, the holding time of the coke in the first run should preferably be such that the heating rate does not exceed 0°C per minute. It can be chosen to be smaller than ℃. Green coke is introduced at the top of the rotary kiln, and due to the rotation of the kiln and gravity, the green coke moves to the bottom of the kiln. Combustible volatiles released from the green coke in the first stage leave the top and are recycled through the burner to the first stage furnace. Air and if necessary additional combustible gas are added so that combustion occurs in the burner. The combustion gases entering the lower part of the kiln are
It has a temperature of 00°C to 1300°C. A portion of the combustible volatiles is removed from the recirculation system before entering the burner. In this way, the appropriate temperature and amount of combustion gas necessary to achieve a controlled release of combustible gases from the green coke is ensured. The amount of oxygen in the air introduced into the burner is generally completely used for combustion of the combustible gas before it is recycled to the first stage furnace. The pre-smoked coke leaving the lower part of the kiln is transferred to a hearth rotary furnace or other kiln. The first and second stage kilns may be arranged so that transport is by gravity. The inlet of the burner can be located directly below the outlet of the prefirer, and the presmoker coke is dropped directly into the coke feeder of the smoker. Transport can also be carried out by conveyor. After the raw coke is subjected to pre-baking, the obtained product is
Preferably it can be cooled to a temperature below 100°C (even to room temperature). As already mentioned above, the second
The step (sintering) can be carried out in any type of furnace, in which the presence of free oxygen can be tolerated. Hearth rotary furnaces well known in the industry are preferred.

This method uses residual oil from catalytic cracking, thermal cracking or steam cracking,
2′l of the oils listed above (before or after additional treatments such as heat treatment, solvent extraction, hydrotreating, etc.) before straight run and tar obtained from pyrolysis, or coal tar, or the oils listed above (before or after additional treatments such as heat treatment, solvent extraction, hydrogen treatment, etc.).
or more suitable formulations, may be applied to any type of green coke produced by silate coking of heavy oils of petroleum or coal sources.

Furthermore, the process according to the invention may be carried out using a single furnace for the λ different stages, namely pre-firing and firing, so that the temperature and gas composition are controlled.

Example 2 Raw coke with a moisture content of - by weight was heated in a four-tally kiln (
Length 7.2 meters, inner diameter 0. The raw coke was introduced from the top into a J″ meter and presmoked at a temperature of 126° C. The raw coke was introduced at a rate of 230 Kg/h, and the kiln was rotated at 2 rpm (revolutions per minute). The raw coke was obtained as the residue of a naphtha and gas oil steam cracking process.

The raw coke is on the 5th floor! The temperature was raised with flue gas having a temperature of θ° C., and the flue gas was flowing in a direction opposite to the direction of movement of the coke. The flue gas outlet temperature was 411O<0>C. The flue gas contained no free oxygen,
Natural gas in the burner room and 204 Kt
/h produced by stoichiometric external combustion with air at ambient temperature and quenching of the adiabatic flame temperature with recirculation of kiln exhaust gas of 730 Kl/h out of the total lO♂/KgA◎3, t 7 Kt/h of kiln exhaust gas was removed from the recycle stream. A pre-fired cosis of 2//rKp/h was obtained in the lower part of the rotary kiln.

The heating rate of the coke in the temperature range from 00°C to 00°C was 2 μ°C/min.

After cooling to 20°C, the pre-smoked coke was introduced from the top into the 20th tally kiln at a rate of 100 KiA, so the final temperature was 73°C and 0°C. This rotary kiln is 3. It was operated at a low rpm IIC and had the same length and diameter as the first kiln. Its inclination was 2.5 degrees. Coke is in an oxidizing atmosphere, inlet temperature/4LrO
The temperature was raised by 7 passes of countercurrent heat exchange with flue gas at .degree. The flue gas was obtained by combustion of natural gas with air, with additional air added to maintain an oxidizing atmosphere in the kiln.

/ Starting from 00 Kg/h of pre-smoked coke,
A burnt cosis of Rihiro Kp/h was obtained. The true density is 2
．． / 3 g/II/.

Comparative Example A comparative experiment was carried out in the same rotary kiln, and preliminary firing and final firing were carried out.

, 2 j OK41b raw coke was introduced into the rotary kiln from the top and presmoked. The kiln is
It was operated at 2 rpm.

The raw coke was heated with flue gas at a temperature of 50° C., and the flue gas was flowing in the same direction as the coke moving through the kiln. The flue gas was obtained by combusting /7 KI of natural gas with 221 Kflb of ambient temperature air and quenched with 3/2 Wb of ambient temperature air. Combustion of the released combustible gas was carried out in the rotary kiln. There was no flue gas recirculation. A pre-fired cosis of 21 Kf/h was obtained.

The heating rate of coke in the temperature range 00° to 00° C. could be controlled if additional air was used.

The pre-smoked coke was roasted in Tarry Kiln No. 20 under exactly the same conditions as described in the Examples of the Invention. /
Starting from 0.00 kg/h of pre-burned coke, 1.0 kg/h of burnt coke was obtained.

The true density is 2. It was /3 tilt.

The roasted coke obtained by the process according to the example of the invention and the process according to the comparative example differed significantly in their physical properties.

The friability of these smoky cokes will be compared below.
□ Table / Table 2 In the friability test, the coke fraction of ♂ to R6m was
7 hours in a rotating drum with a baffle board inside.
Subjected to mechanical action of 24 tOO rotations (IA Orpm).

Table 3 As is clear from Table 1, the friability of the calcined coke produced by the method according to the present invention was reduced, and thus the skeleton coke was relatively difficult to friability.

The coke obtained starting from raw coke with a predetermined particle size distribution underwent almost no change in particle size distribution in the process of the invention.

As is clear from Table 2, the smoky coke obtained by the method according to the present invention has good deterioration resistance as compared to the brick coke obtained not according to the present invention.

As is clear from Table 3, when the smoked coke produced by the method according to the present invention is graphitized, the coefficient of thermal expansion of the graphitized smoked coke produced by the method according to the present invention is It also has a small coefficient of thermal expansion.

Name of Agent Kawahara1) - Continued from page 10 Inventor Ferdinand Johan Adriaan Ageiger @ Inventor Barent Alberts Or0 Inventor Roger Stewer Odo Downing Iran 2596 H.R. , The Hague, Karel Un Φbilantran 30 Country of Landa 2596 H.R., The Hague, Karel Un Φbilantran 30 Country of Landa 1031 C.M. Amsterdam, Bathoswech 3

Claims (9)

[Claims] (1) Raw coke containing flammable volatile substances is
in a furnace to a temperature of 730°C to 7000°C, and in a second stage to 7200°C in a second furnace.
A method of combusting the green coke in at least two stages of heating to a temperature between 600°C and 7600°C, the first stage heating at a controlled heating rate of less than 60°C/min in a temperature range between 600°C and 200°C. Furthermore, the volatile substances released are removed from the first stage,
This temperature increase is achieved with hot combusted volatiles obtained by combusting these volatiles outside the first stage and recycling the combusted volatiles into the first stage. A method of baking raw coke that is characterized by the following. (2) Burning additional combustible gas outside the first stage and introducing the combustible gas into the first stage may provide a portion of the hot combustible volatiles, as claimed in the present invention. Range 1
Smoking method described in section. (3) The smoldering method according to claim 1 or 2, wherein the first stage furnace is characterized by a non-oxidizing atmosphere. (4) Using a rotary kiln in the first stage,
A smoking method according to any one of claims 1 to 3. (5) The firing method according to any one of claims 1 to [mu], which uses a hearth rotary furnace in the second stage. (6) The method according to any one of claims 1 to μ, characterized in that, in the first stage, hot combusted volatile substances are produced in a direction opposite to the flow direction of the raw coke to be pre-baked. Smoking method. (7) Hot combusted volatile substances range from yoo℃ to 730℃.
(1) The firing method according to any one of claims 1 to 6 or claim 6, wherein the firing method has a temperature of 0°C. (8) Claims in which an oxygen bomb is used entirely for the combustion of combustible volatiles derived from coke and additional combustible gases before they are recycled to the rotary kiln. The combustion method according to any one of Items 1 to 6 or Claim 6 or 7. (9) The method according to claim 1 or 5, wherein the rotary kiln is also installed above the hearth rotary furnace so that the coke can be transported by gravity. Law. α0 In the first stage, heating is performed at a controlled heating rate of less than ≠θ°C/min. ■The firing method described in any one of the above. (b) The combustion method according to any one of claims 1 to 10, wherein the pre-baked coke is cooled to a temperature of less than 100° C. before being subjected to the λ-th stage of combustion.