JPS6136392A - Low solid coal tar impregnating pitch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves the oxidation of selected coal tar fractions with air or oxygen at elevated temperatures to obtain a product whose end use is advantageous for low solids utilization. The present invention relates to an improved coal tar-based low solids pitch produced by.

Industrial carbon electrodes currently in use generally consist of petroleum coke particles (filler) fused to coal tar pitch (binder).
and extrude the resulting mixture to form one raw electrode (g
Reen e1θctrode)' is manufactured by K. The live electrode is then baked at approximately 1300°C. This heat treatment process reduces the carbon content of the raw electrode body to 95%.
Converts from carbon to over 99% carbon. During the heat treatment process, some of the organic substances are decomposed and distilled or evaporated, and others decompose and deposit carbon on the electrode. As the evaporated material exits the electrode body, it forms channels in the electrode wall, creating a porous structure. This inherent porosity reduces density and conductive capacity.

In manufacturing carbon electrodes, Carbon Industries uses a 28-inch diameter x 10-foot long (approximately 71 x 30
Electrodes with dimensions of 5ffi) are manufactured.

These electrodes are used, for example, in steel melt processing to conduct large amounts of current. Desirable carbon electrode features are as follows.

1. High density 2. High elastic modulus 3. High conductivity 4. High bending strength 1. Pitch for impregnation in the electrode to negate the undesirable effects of channel formation, inherent porosity, and 4. Impregnate. It must have properties that are particularly suitable for this purpose.

Coal tar pitch has been historically used as an impregnating agent because of its density and high carbon content compared to petroleum pitch. However, technical improvements in charcoal electrodes have lowered the porosity and pore size of the raw electrodes. As a result, impregnating pitches with low solids content must be used.6 Ordinary coal tar pitch does not meet this requirement. Although the market is currently dominated by petroleum pitch, this material also has certain distinct disadvantages. Furthermore, it should be understood that the solids content of one pitch is only one K, which indicates the quality of the pitch.

The ultimate measure of quality is related to the penetration rate (higher is better) and the final coke yield after rebaking.

The solids content of pitch is usually measured in weight percent of pitch and is defined by ASTM D2318-76 K or "Quinoline Solubility" (QII).

In this regard, it is important to note that the term 'pitch 1' applies to a wide variety of compositions and that there are distinct differences between pitches used for various purposes. Particularly with respect to electrode manufacturing, 'pitch 1' can be used in at least three ways.

1. Pitch is coked to form 1 pitch coke 1, which is pulverized and sized, and can be used as a filler. Currently, most coke-based fillers are produced from petroleum (as mentioned above).

It is also known to produce pitch coke 1 from pitch produced by oxidizing coal tar at high temperatures.

However, it should be noted that the pitch used as a precursor for 1-pitch coke 1 does not have the 1-low-1 minute requirement as in the case of the impregnating pinch, which is the material to which the present invention relates.

2. Pitch can be used as a binder or cement to hold the carbon electrode during shaping and baking. This application inherently requires a coal tar pitch with a high quinoline soluble (QI) content. Regarding the importance of the quinolinated content in the binder pitch, see, for example, R. Ball's 1 Effect of the type of quinolinated content on the quality of the binder coal tar pitch 1 (Carbon 16, p. 205 [1
978'))K stated. It is generally agreed that the solids content of binder pitch is measured by the "QI" test. High-temperature oxidation of carbonaceous materials (6 oils, coal tar and oils) traditionally used to produce pitches suitable for electrode manufacture is intended for the production of binder pitches and pitches for pitch coke and impregnation. It should also be noted that this product is not intended for drug pinchers. These prior art pitches typically had QI fractions on the order of 14%.

3. The pitch 1 for impregnation used in electrode manufacturing has been described, but this use clearly requires a pitch of 1 minute of low height. A discussion of the use of impregnating pinches and the physical properties of pitch for use as both a binder and an impregnating agent can be found in Quilt-Osmer's Encyclopedia of Chemical Technology, Vol. 4, 1.
68, pages 181-XS3. The main difference between binder pitch and impregnating pinch can be seen by examining the column ``Quinoline Soluble 2'' in Table 3, page 168 of this reference.

Typical coal tar binder in the production of carbon and graphite Soft Medium High Impregnation pitch Pitch Pitch Pitch QI (%) 12
12 15 5 The QI of the binder is significantly higher than that of the impregnating agent.

As shown in the table, the QI content of a common coal tar-based impregnant is 5% by weight.

Recently, the quality of electrodes has improved and the standards specifying impregnating pinches have become more stringent; impregnating pitches containing a QI of 5% are no longer satisfactory.

This is why petroleum pitch has replaced coal tar pitch in this application.

The current industry standard is petroleum pitch containing 0.5% QI. The coal tar pitch of the present invention also has QI min<0,
It is 5%. Until now, no one has shown that high quality impregnating pitch can be produced by oxidizing coal tar.

An important characteristic of petroleum-based impregnating pinch is the fact that it has a lower solids content than ordinary coal tar pitch. This equates to greater productivity in that less processing time is required to perform the impregnation. However, petroleum pitch has the disadvantages of low density, high sulfur content, and low in-situ coking value. In-situ coking value means the actual yield of carbon in the electrode after quenching compared to the amount of pitch initially picked up during the impregnation process. For example, by impregnating the electrode, Using the weights of 1 before and 1 after, let's say the electrode impregnated 1 oo pounds (45.4 kli+) of impregnation pitch. This pitch is converted into carbon by the king. During baking, low-boiling substances are distilled off from the pitch, resulting in lower yields. This °Previous 1 and 1 regarding the baking process
The weight from step 1 is used to determine the amount of pitch remaining as carbon in the electrode. For example, if the electrode weight after baking is 30 Bonds (13,6 Yu) more than impregnated 1@1, the in-situ coking value is 30/100-30. %.

Generally, the specific gravity of petroleum pitch for impregnation is 1.24 at 25°C, and the specific gravity of coal tar pitch is 1.30. This difference would equate to a 1" increase of 5% for either impregnation step. The presence of sulfur poses an air pollution risk during baking and also reduces the potential for 1" thickening during graphitization. )' It should also be noted that sulfur is an undesirable pitch component, as it also results in undesirable density reduction phenomena.Thus, it features particularly low solids content, high in-situ coking values, and improved permeability and penetration rates. It seems necessary to provide an improved pitch that allows for better performance.

It is an object of the present invention to provide an improved coal tar product as a rare impregnating pitch in the production of industrial bare electrodes. This improved impregnating pinch has the following advantages over petroleum-based impregnating pitches.

(a) Increased yield (b, l) Lower sulfur content (C) Increased density As further shown by the comparisons below, this results in higher permeability (i.e. lower solid content).

The improved coal tar-based impregnation pinch is prepared by oxidizing selected coal tar distillates with air or oxygen at elevated temperatures.

This pitch can be used in end uses where low solids content is desired. 4!1. This can be advantageously used for impregnation of the backing material. Compared to the petroleum pitch currently used commercially, its main advantages when used as an impregnating pinch are high carbon yield, better product placement, and lower sulfur content. This pitch features low solids content, increased impregnation, and high coke yield.

Hitherto it has not been known to produce impregnating pitch from coal tar of suitable practical quality. More particularly, until the knowledge provided by the present invention, the importance of selecting a low-lying feedstock and processing it at a specific temperature range was not recognized. Processing temperatures below 750''F (400C) are used in the present invention to produce exceptional coal tar-based impregnants. Particularly advantageous properties of the pitch obtained in accordance with the present invention include: is included.

(a) Sulfur content not more than 0.5% by weight (b) 77″
Density of 1.2 El/cIn3 or higher at F (25°C) fcJ Cleveland open cup flash point of 200°C or higher (d) Field coking value of 32 heavy lid % (eJ Comparable to that of petroleum pitch, other calls Better impregnating rate of impregnating agent by electrode than for tar pitch Other advantages and contributions of the present invention will become apparent from the detailed description below.

The improved impregnating pinch of the present invention is comprised of a high residue, low solids content oxidation product of coal tar oil.

For manufacturing the desired pitch! +7 The oil used as a precursor during the distillation of crude coke oven tar is
Separating 1 minute gives K. The quality of the precursor oil is decisive. This quality is determined by the Pi test, and the solid content of the oil must be 0.05% or less as measured by ASTM D231B-76. This low solids heavy oil is oxidized by sparging K of air at 300-700'F to yield an intermediate having a substantially higher average molecular weight than the precursor. On the other hand, the surface temperature of the six capitals is very similar to that of the human body. It is preferably kept below 700°F (371°C) and should not exceed 800°F (427°C).

Otherwise the formation of solids cannot be controlled. The intermediate is then stripped with an inert gas (steam and nitrogen can be used) to remove unwanted low boiling components.

The end point of the oxidation period is determined by two criteria: (1) yield of intermediate and softening point as defined by (21 ASTM D-3104-77).

As a guideline, the intermediate yield is usually 30-70% by weight. However, this is a function of the feedstock residual as defined by ASTM D246-73. The softening point of the intermediate should be about 30-120°C. At this stage start stripping and add another 1 of the initial charge.
Continue until the 0% lid is removed. At this point the pitch is characterized according to the criteria below.

1. Softening point (℃) (ASTM D3104-
77) 100-1502, Gawking value - Concito 9n (N amount %) ('ASTM D2416-
73) 45 minutes.

3 Flash point C, O, C, (1:) (ASTM D
92-72) 200 minutes.

According to the present invention, a novel coal tar-based impregnating pinch is produced by oxidation of coal tar distillate.

To obtain feedstock for the production of new and improved coal tar yarn impregnation pinches, K. distilled the crude tar to 35%
At 5° C., a heavy creon oat stock is produced which is described as having a distillation residue of 25-100% by weight.

The two criteria used to select the feedstock are:

(1) Quinoline solution (QII juice is ASTM D
-2318-76 and must be less than or equal to 0.0531 (% by weight).

(The distillation residue according to 21ASTM D246-73 is about 25% or more, preferably about 60%.

Other methods can also be used to appropriately define acceptable feedstock quality of heavy oil, for example as shown in Table A below.

Table A Filtration time, 500 &.

Whatman filter paper filter on steam heated pourer funnel Q engineering TI-fatty 4.2
0" ASTM ASTM oil (50,
8cm) Hg D-2318D-4072 Satisfactory A, 03m” Animal B 21 seconds
, 0040 36 seconds ・o5 unsatisfactory D , 45m
1st charge negative E 19. :l
, 47F 14.7 minutes
・When producing the 23-oxide col-tar component,
Referring to the drawings, the starting material creosote oil is heated in a container 10 at a temperature of about 300'F (149°C) to 75°F (
417°C), preferably about 600'F (315°C) to 7
Heat to a temperature of 25°F (385°C) while sparging a large amount of air through the liquid as shown at 12. The low boiling substances shown to be effectively removed in (a) 14 by simultaneous heating and heating are stripped, and (b)
Upon heating, the residual tar shown to be removed at 16 is oxidized. the desired temperature limit (generally about 725''F (385C), but it will be clear that steady state oxidation can be carried out at lower temperatures, perhaps up to <3006F (149C)) K When reached, at this temperature, sparging with air is continued until the desired oxidized intermediate is obtained.The non-condensable vapors are removed at 18 and the gas oil is removed at 20.

After obtaining the desired intermediate, oxidation is terminated, and stripping with an inert gas (for example, water vapor or fc is a carrier element) is started. Steam is preferred in the stripping operation because it is economical and can be easily condensed away from the steam stream. This reduces the need for an exhaust gas scrubbing device. This inert gas stripping step as a separate step can be omitted by employing a higher heat input during the oxidation step. In the stripping operation, undesirable low-boiling components are removed from the pitch, leaving behind the polymeric components.

The end point of the stripping process is a softening point of 115-150°C, a Conradson coking value of 45% or more, and a
Characterized by a flash point of 92"F (200C) or higher.

The invention is further described by the detailed examples below. However, while these Examples detail certain preferred operating conditions of the invention, they are presented primarily for purposes of illustration and are not intended to limit the broader aspects of the invention. should be understood. The displayed section is the sub-view section unless otherwise specified.

Example 1 A total of 117.6 QO pounds (5
Displaying coal tar heavy oil of 3390kl/)IQOOO
A gallon (378001) still was loaded in 2 increments. Heat the contents to 690'F (3
65℃)K, during which time an average of 200SCF'M (s6
63 J/juice) of air was removed. 61% of the precursor oil was stripped during the oxidation or stripping cycle.

74% of the supplied oxygen reacted with the coal tar oil.

zoooo#? (5952 kg) of material was stripped during the stripping period and water vapor was used as the stripping medium.

The properties of the final pitch for impregnation were as follows.

A) Softening point (ASTM D3104-77)
123.8℃BIQ, 1. (wt, %), 29 CI T, I, (wt0%')
31. ID) Ash 5) (wt9%)
, 009E) Corkinda Konrad 9son (wt%) 50.3F) Specific gravity 077°F
1.298G) Flash C, 0,
C,'l'' 450HIC-9 fraction (%) Up to 270℃ 0.0300℃
0.0360℃
The actual properties of the precursor coal tar heavy oil were not recorded for this operation, but were assumed to be as follows.

Specific gravity @100°F 1.
150 distillation 5) (wt%) up to 235℃ 0,0270℃
0.0315℃
2.2355℃
31.0 Remaining 5) (%+ (at 355℃)
68.9 xylene insoluble matter (ff
i amount %) 0.02 Example 2 2067 g of coal tar heavy oil was loaded into an A gallo/(1,91) reactor. The reactor was heated to 200°C, at which point the air flow rate was increased to 130 standard cIIL3/min. The contents were continuously oxidized as they were heated to 375°C. 51.7% of the initial charge was stripped during the oxidation period.

The average air flow rate was approximately 450 cIrL/min, and the softening point was 75.4°C at the end of the oxidation period.
there were. The pitch was then stripped with nitrogen until an additional 10% of the K was stripped of the original charge. The final yield was 38%, the softening point was 126°C, and the coking value was 55%.

The coal tar pitch of the present invention was compared with other pitch standards shown in Table BK of his book. This data demonstrated a correlation between 41-factor content, low solid juice, and permeation rate. The permeation rate of the impregnant, which is a leg material artifact, is important when determining the quality of the impregnant.Assuming that the pitch filtration simulates the impregnation process, this data is l
Showing significant advantages over Lepich. For example, the low solids 5+ (which is a measure of solids content) of the present invention as indicated by filtration rate is considered to be very good.

Table B 1 Low Solids Sweat Pitch vs. Prior Art Quinoline Solvents Permeation Simulation by ASTM by Filtration Rate 1) Manufactured according to Example 1
zg/15 juice petroleum pitch (31<5
50g/15 Juice Prior Art Low QI Coal Tar 7.
59/15 minute size 4) +1140 micron porous full base plate (diameter %'' x thickness'
/4' (1,9x O, 64cm), 9C8!
75 psig (5.3 kg/cm2 at 225°C)
) indicates the amount of pitch filtered at a differential pressure of

(21110°C binder pitch. Obtained from Arraibi Inc. (Detroit, Michigan).

(3) Ashland Oil A-240 pitch. Obtained from Atshuranhimale, Inc. (Ashland, Kentucky). Current industry standard specifications for pitches for impregnation.

(4115-V pitch, manually manufactured by Anito 9 Company (Detroit, Michigan). Impregnation pitch KtJ) Industrial standard before 3.

It will be obvious that modifications may be made without departing from the scope and spirit of the invention. Therefore, the certain details set forth herein by way of illustration should not be construed as limiting the invention except as such limitations are recited in the claims.

[Brief explanation of the drawing]

The drawing shows the production of pitch for low solids impregnation from coal tar oil and the symbols represent: 10: Container 12: Supply of air and steam 14: Collection of low boiling point pressure 16: Final product pitch (low solids content) 18: Non-condensables 20: Light oil by-product (5 others)

Claims (1)

[Claims] (1) (a) (1) Distillation residue (@355°C) > 30% by weight; (2) QI < 0.5% by weight; and (3) filtration rate of 4 Whatman filter paper 500g (b) heating the feedstock to a temperature of about 150-390°C; and (c) (1) having a temperature of about 90-150°C. ASTM D3104
-77 softening point; (2) a coking value of at least 45% by weight according to ASTM D2416-73; and (3) a flash point of at least 200°C according to ASTM D92-72. A method for obtaining coal tar pitch characterized by having a quinoline insoluble content (QI) of about 0.5% or less and high impregnating properties. (2) by continuing oxidation and stripping until a softening point (c) (1) of 100-130°C is obtained;
A method according to claim 1. (3) continuing oxidation and stripping until a coking value of at least 48% is achieved. 4. The process of claim 1, wherein the feedstock has a distillation residue of 50-70% at 355°C as measured by ASTM D246-73. (5) stripping and oxidizing until the product has a softening point of 110-130°C, a Conradson value of 45% or more, and a flash point of 200°C or more; Method. 6. A process according to claim 1, comprising oxidizing the feedstock from step (b) and then stripping with steam. (7) having a distillation residue of 25-100% by weight at 355°C, oxidized and stripped, and about 90-100% distillation residue;
Softening point of 150℃, Conradson coking value of 45% or more, and flash point of 200℃ or more, with AS
Quinoline insoluble content according to TM D2318-76 05. %
Coal tar pitch with low solids content and high impregnating properties, consisting of a coal tar oil middle distillate having: (8) having a distillation residue of 35 to 85% by weight at 355°C;
oxidized and stopped and approximately 120-1
A coal tar pitch of low solids and high impregnating properties consisting of a coal tar middle distillate having a softening point of 30°C, a Conlandson coking value of 45% or higher, and a flash point of 235°C or higher. (9) A carbon electrode impregnated with the pitch according to claim 7. (10) A carbon electrode impregnated with the pitch according to claim 8.