US3896023A - Process for producing synthetic coking coal - Google Patents

Abstract

wherein C/H represents the ratio of carbon atoms to hydrogen atoms, H Alpha /H represents the ratio of hydrogen atoms in the Alpha -position of the aliphatic hydrocarbon groups attached to the aromatic rings to the total hydrogen atom content and Ho/H represents the ratio of hydrogen atoms in the Beta -position or higher positions of the aliphatic hydrocarbon groups attached to the aromatic rings to the total hydrogen atom content, at a temperature greater than that which initiates cracking.

A synthetic coking coal or a binder pitch is prepared by coking a heavy hydrocarbon composition which has an aromaticity factor, fa value greater than 0.4, wherein the aromaticity factor, fa is derived from the equation:

Description

United States Patent [191 Ozaki et al.

[ July 22, 1975 PROCESS FOR PRODUCING SYNTHETIC COKING COAL [73] Assignee: Nippon Mining Co., Ltd., Tokyo,

Japan [22] Filed: Feb. 1, 1974 [2]] Appl. No.: 438,861

[30] Foreign Application Priority Data Feb. 3, 1973 Japan 48-13369 [52] U.S. Cl. 208/46; 208/50; 208/87 [51] Int. Cl. ..C10g 9/00 [58] Field of Search 208/46, 86, 106, l3l, 87, 208/127 [56] References Cited UNITED STATES PATENTS 2,775,549 12/1956 Shea 208/l3l 2,922,755 l/l960 Hackley 208/39 3,547,804 l2/l970 Noguchi ct al. 208/13] 3,617,481 ll/197l Voorhies et al. 208/86 Primary Examiner-Herbert Levine Attorney, Agent, or Firm-Oblon, Fisher, Spivak, McClelland & Maier [57] ABSTRACT A synthetic coking coal or a binder pitch is prepared by coking a heavy hydrocarbon composition which has an aromaticity factor, fa value greater than 0.4. wherein the aromaticity factor. fa is derived from the equation:

wherein C/H represents the ratio of carbon atoms to hydrogen atoms, Ha/l-l represents the ratio of hydrogen atoms in the a-position of the aliphatic hydrocarbon groups attached to the aromatic rings to the total hydrogen atom content and Ho/H represents the ratio of hydrogen atoms in the B-position or higher positions" of the aliphatic hydrocarbon groups attached to the aromatic rings to the total hydrogen atom Content, at a' temperature greater than that which initiates cracking.

7 Claims, NO Drawings 1 PROCESS FOR PRODUCING SYNTHETIC COKING COAL BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a synthetic coking coal from a heavy hydrocarbon source. More particularly, the invention relates to a process for producing a synthetic coking coal and/or a binder pitch which is used as a raw material for metallurgical coke by initially treating a heavy hydrocarbon such as atmospheric residual oil or vacuum residual oil.

under extraction conditions or under thermal cracking conditions to increase the aromaticity factor fa or by blending the atmospheric residual oil or vacuum residual oil with a thermally cracked tar which has a high aromaticity in order, to increase the aromaticity factor, fa and then coking the composition.

2. Description of the Prior Art Recently, shortages in the supply of coal for producing metallurgical coke such as blast furnace coke has been realized. In order to counteract these shortages. coke produced by coking a petroleum residual oil has been used to satisfy a part of the demand for the production of metallurgical coke. However, the conven-.

tional coke produced by coking a petroleum residual oil such as by delayed coking, fluid coking or the like has poor coking properties and isnot very fluid. Thus, blends of the green coke produced from petroleum sources has been limited and accordingly, this coke has been chiefly used only as a low ash content carbon source. Up to the present, no satisfactory processes are known for producing a synthetic coking coal which has good coking properties and fluidity from residual oil or thermally cracked oil which is useful as a raw material for metallurgical coke such as a blast furnace coke.

A need therefore continues to exist for a method of producing synthetic coking coals and/or binder pitches from heavy hydrocarbons such as petroleum residual oils which are used as a metallurgical coke having substantial stiffness such as blast furnace coke.

SUMMARY OF THE INVENTION ju MC/H wherein C/H represents the ratio of carbon atoms to hydrogen atoms (measured by an elemental analysis), H /H represents the ratio of hydrogen atoms in the a-position of the aliphatic hydrocarbon groups attached to the aromatic rings to the total hydrogen atom content (measured by a high resolution NMR), and l-Io/l-I represents the ratio of hydrogen atoms in the B-position or higher positions of the aliphatic hydrocarbon groups attached to the aromatic rings to the total hydrogen atom content (measured by high resolution NMR). [The method is illustrated in J. K. Brown, W. R. Ladner, Fuel 39, 87 (1960)] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the conventional process for producing metallurgical coke, the feed stock is coked with or without blending the feed stock with a recycled oil. When the coke prepared is to be used in an electrode, the heavy oil component in the cracked oil produced in the coking reaction is thermally cracked and recycled. However, the coking properties of the resulting green coke have not been improved, although the needle-like cyrstalline properties of the coke have been improved.

In the process of the present invention, the residual oil is initially treated by extraction, thermal cracking, catalytic cracking or the like to increase the aromaticity factor, fa to values greater than 0.4, or it isblended with a thermally cracked tar which has a substantial aromaticity to increase the aromaticity factor, fa to values greater than 0.4. Thereafter, the composition is coked to improve the coking properties of the synthetic coking coal.

In the invention, the aromaticity factor, fa can be increased by various conventional methods such as by extraction, thermal cracking, catalytic cracking or the like. In the extraction step of the process, solvents are used which selectively extract hydrocarbons containing substantial amounts of aliphatic hydrocarbons, such as light hydrocarbons including propane, butane, pentane, hexane and the like. The raffinate obtained from the extracting step is then used as the raw material for the synthetic coking coal. On the other hand, it is also possible to use solvents in the extraction step which selectively extract hydrocarbons which contain substantial amounts of aromatic hydrocarbons such as dimethylsulfoxide, diethyleneglycol, sulfolane, methylcarbamate, or the like.

After the extraction process, the extracted material is used as the raw material for the synthetic coking coal.

The cracking step of the process of the invention is preferably performed under conditions which decrease the polycondensation reactions of the cracked oil. The bottom oil prepared by thermal cracking in the visbreaking process of petroleum vacuum residual oil or the residual oil prepared by thermal cracking for a short time in vacuum, can be used as the raw material for the synthetic coking coal of the invention. When' the initial treatment is performed, the aromaticity is increased. Preferably, the aromaticity factor, fa is increased to a value greater than 0.4.

The coking properties of the synthetic coking coal are increased by a direct dependency upon an increase in the aromaticity of the oil produced under low polycondensation reaction conditions in the initial treatment.

It is also possible to produce a synthetic coking coal which has substantial coking properties by blending a residual oil with about 10 90% of a thermally cracked tar which has high molecular weight aromatic components and an fa value of 0.5 to 1.0. The thermally cracked oil is prepared by thermally cracking a coker oil which is produced by coking heavy hydrocarbons to increase the aromaticity factor, fa of the composition, and then coking the composition.

If a raw material is used which contains substantial amounts of polycondensation aromatic rings, the initial treatment can be decreased in the preparation of the synthetic coking coal which has substantial coking properties. The aromaticity factor, fa of a thermally cracked oil which is the by-product of a naphtha cracking process (fraction having a boiling point greater than 450C) is 0.75. If a naphtha cracked tar is used. the initial treatment for increasing the aromaticity can be omitted in the preparation of the synthetic coking coal. On the other hand, the vacuum residual oil derived from Kuwait crude oil contains only small amounts of polycondensation aromatic rings and has an aromaticity factor fu of 0.3. If the oil is subjected to an initial treatment. the aromaticity factor fa can be effectively increased to values greater than 0.4.

Suitable feed stocks used in the process of the invention include heavy petroleum hydrocarbons such as atmospheric petroleum residual oil, vacuum residual oil, thermally cracked residual oil, catalytically cracked residual oil and the like. Other heavy hydrocarbons such as natural asphalt, shale oil, coal tar, tar sand and the like can also be used.

The coking reaction temperature in the invention is preferably in the range of about 410 490C. The lower limit, however, can be changed to the temperature at which cracking of the feed stocks in initiated.

The upper limit of the temperature is not critical and can be higher than 500C although at temperatures greater than 500C certain disadvantages arise in the coking operation such as coke deposition in the coking tube.

The process of the present invention provides a synthetic coking coal which has a high free-swelling index, for example, a free-swelling index of 6 (Example 2) in comparison to the conventionally prepared coals which have a relatively low free-swelling index (Reference 1). The free-swelling index of the coking coal is determined by the Japanese Industrial Standard method M8801 1972 (ASTM D-720-67).

The fluidity of the synthetic coking coal obtained by the process of the invention is very much higher than that of natural coking coal. For example. in Example 1, the softening temperature is less than 300C, the maximum fluidity is greater than 28,000 ddpm and the solidification temperature is 518C. (measured by ASTM D-1812-69). The synthetic coking coal produced by the process of the invention has certain advantages over the prior art coals as shown earlier, and the heavy oil prepared by the initial treatment can be used for the preparation of a lubricant fraction, and can also be used as a feed stock for gas oil desulfurization.

Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.

EXAMPLE 1 A vacuum residual oil derived from Kuwait crude oil having a specific gravity of 1.0176 (at 25/25C), a softening point of 31C, a penetration value of 315 (at 25C). a Conradson carbon value of 21.1 wt%, and an fa value of 0.30 was fed to a countercurrent extractor having a length of 2,100 mm and an inner diameter of 100 mm to extract hydrocarbons containing 34 wt% aliphatic components under temperature and pressure conditions of 60C and 30 kg/cm (pressurized with nitrogen), respectively, and a ratio of butane to residual oil in the feed stock of 10. The properties of the extracted oil are shown in Table 1.

A 10 kg amount of the resulting residual oil having a specific gravity of 1.0563 (at 25/25C), a softening point of 60C, a penetration value of 15 (at 25C), a Conradson carbon content of 29.6 wt% and an fa value of 0.45, was charged into a 20 liter reactor and was coked at 430C for 3 hours under atmospheric pressure. The yield of the resulting synthetic coking coal was 46%, and the free-swelling index (Japanese Industrial Standard M 8801-1972) of the synthetic coking coal was 5V2 and the volatile matter content (Japanese Industrial Standard M 8812-1972) was 29.1%.

According to the fluidity tests of the synthetic coking coal as determined with a Gieseler plastometer, (Japanese Industrial Standard M 880l-l972) the syn-' thetic coking coal had a softening point less than 300C, a maximum fluidity above 28,000 ddpm and a solidification temperature of 518C.

In the box test (Japanese Industrial Standard M 88011972) of the synthetic coking coal, the- Drum index (Japanese Industrial Standard K 2151-1972) of the coke prepared from the standard blend was D 93.1 and the Drum index of the coke prepared by substituting a portion of the natural Japanese coking coal which contains 15 wt% in the standard blend of the synthetic coking coal (10 wt%) was D 92.9. The results are shown in Table 3.

TABLE 1 Example 1 Yield of extracted oil 34 Viscosity (cst: 989C) 47.80 Specific gravity (ZS/25C) 0.9397

EXAMPLE 2 In the reactor of Example 1, 10 kg of a vacuum residual oil derived from the Kuwait crude oil of Example 1 was charged and thermally cracked at 420C under a pressure of 50 mm Hg abs for 30 minutes in the initial treatment to obtain a residual oil having an fa value of 0.65 in a 40% yield.

The residual oil having a high fa value of 0.65 was charged into the reactor and was coked at 420C for 3 hours under atmospheric pressure. The results are shown in Table 3.

EXAMPLE 3 EXAMPLE 4 The vacuum residual oil derived from the Kuwait crude oil of Example 1 was sprayed into a fluid catalytic cracking unit containing a fluidized catalyst of silica in order to achieve high temperature cracking con- EXAMPLE 5 The vacuum residual oil derived from the Kuwait crude oil of Example 1 was coked to form a thermally cracked oil which was distilled whereby a fraction having a boiling point greater than 200C was separated. A 3 liter amount of the fraction was charged into a 5 liter autoclave made of stainless steel, and was thermally cracked at 500C for 1 hour under a pressure of 100 kg/cm". The properties of the resulting oil are shown in Table 2.

A 30 g amount of a thermally cracked tar having a boiling point greater than 350C and an fa value of 0.72 which was one of the fractions of the thermally cracked oil was blended with 70 g of a vacuum residual oil derived from Kuwait crude oil. The blend was charged into a 300 ml reactor made of stainless steel and was coked at 430C for 3 hours under atmospheric pressure. The results are shown in Table 3.

TABLE 2-Continued Properties of thermally cracked tar Fraction having a boiling point greater than 200C Specific gravit) l5/4C) 1,0310 Fraction Analysis of components saturated component aromatic component resin component REFERENCE 1 A 100 g amount of a vacuum residual oil derived from the Kuwait crude oil of Example 1 was charged into a 200 ml reactor and was coked at 430C under atmospheric pressure for 4 hours. The results are shown in Table 3.

REFERENCE 2 A cracked heavy oil derived from a by-product from naphtha cracking was distilled and a fraction having a boiling point greater than 425C and an fa value of 0.75 was collected. A 100 g amount of the fraction was charged into a 200 ml reactor and was coked at 420C for 5 hours under atmospheric pressure. The results are shown in Table 3.

TABLE 3 Coking conditions and properties of synthetic coking coal Example Example Reference 1 2 3 4 5 1 2 Type of feed stock naphtha cracked tar Initially treated composition Initial treatment butane vacuum viscatalytic None None None extraccracking breaking cracking tlon Yield (bp 450C) wt% 66 4O 71 23 100 100 fa 0.45 0.65 0.42 0.53 0.43 0.30 0.75 Coking conditions Temperature (C) 430 420 420 430 430 430 420 Pressure (mmHg) 760 760 760 760 760 760 760 Time (hr.) 3 3 5 3 3 4 5 Property of synthetic coking coal Yield 46 76 44 37 33 30 41.6 Volatile matter 29.1 25.0 27.1 30.1 24.8 20.6 38.0 Free-swelling index 5 /2 6 4 5 S 6 Fluidity test Softening temperature (C) below 320 308 below below nonbelow 300 300 300 softening 300 Maximum fluidity temp.*(C) 431 458 432 428 435 412 Maximum fluidity (ddpm) above 11,000 above above above above 28,000 28,000 28,000 28.000 28,000 solidification temp. (C) 518 503 524 521 512 524 Coke strength (D 92.9 93.3

Maximum fluidity: temperature is an estimated value. when the maximum fluidity is above 28,000.

" Coke strength: the test was run for the coke materials obtained from the box test (.115 M 8801-1972). A portion of the natural Japanese coking coal (15 wt% in a standard blend) was substituted for the synthetic coking coal 10 wt% in the test blend).

Vacuum residual oil derived from Kuwait crude oil.

""70 wt% vacuum residual oil derived from Kuwait crude oil. 30 wt% thermally cracked tar.

TABLE 2 Properties of thermally cracked tar Fraction having a boiling point greater than 200C Specific gravity /4C) 1.0310

Fraction initial boiling point (C) 181 10% (C 258 (C) 352 (C) 391 end point (C) 4001 coking a heavy hydrocarbon feedstock having an aromaticity factor fa greater than O.4,'wherein fa is defined by the equation:

C/H /2(H01/Hl V2(H0/H) C/H and wherein C/H represents the ratio of carbon atoms to hydrogen atoms, Ha/ H represents the ratio of the hydrogen atoms in the a-position of the aliphatic hydrocarbon groups attached to the aromatic rings to the total hydrogen atom content, and Ho/H represents the ratio of the hydrogen atoms in the ,B-position or higher positions of the aliphatic hydrocarbon groups attached to the aromatic rings to the total hydrogen atom content at a temperature greater than that which initiates cracking; and

recovering said synthetic coking coal or binder pitch from said coking step.

2. The process of claim 1, wherein the hydrocarbon composition having an fa value greater than 0.4 is prepared by extraction of a residual oil with a light hydrocarbon solvent to remove hydrocarbons containing substantial amounts of aliphatic hydrocarbons.

3. The process of claim 2, wherein said light hydrocarbon solvent is propane, butane, pentane or hexane.

4. The process of claim 1, wherein the hydrocarbon composition having an fa value greater than 0.4 is prepared by extraction of a residual oil with a solvent which selectively extracts hydrocarbons which contain substantial amounts of aromatic hydrocarbons.

5. The process of claim 4, wherein said solvent is dimethylsult'oxide, diethyleneglycol, sulfolane or methylcarbamate.

6. The process of claim 1, wherein the hydrocarbon composition having an fa value greater than 0.4 is prepared by thermal cracking or catalytic cracking a residual oil. v

7. The process of claim 1, wherein the hydrocarbon composition having an fa value greater than 0.4 is prepared by blending a residual oil with a thermally cracked tar having a high aromatic hydrocarbon content and an fa value of 0.5 to 1.0.

Claims (7)

1. A PROCESS FOR PREPARING A SYNTHETIC COKING COAL OR A BINDER PITCH, WHICH COMPRISES THE STEPS OF: COKING A HEAVY HYDROCARBON FEEDSTOCK HAVING AN AROMATICITY FACTOR FA GREATER THAN 0.4, WHEREIN FA IS DEFINED BY THE EQUATION:

2. The process of claim 1, wherein the hydrocarbon composition having an fa value greater than 0.4 is prepared by extraction of a residual oil with a light hydrocarbon solvent to remove hydrocarbons containing substantial amounts of aliphatic hydrocarbons.

3. The process of claim 2, wherein said light hydrocarbon solvent is propane, butane, pentane or hexane.

4. The process of claim 1, wherein the hydrocarbon composition having an fa value greater than 0.4 is prepared by extraction of a residual oil with a solvent which selectively extracts hydrocarbons which contain substantial amounts of aromatic hydrocarbons.

5. The process of claim 4, wherein said solvent is dimethylsulfoxide, diethyleneglycol, sulfolane or methylcarbamate.

6. The process of claim 1, wherein the hydrocarbon composition having an fa value greater than 0.4 is prepared by thermal cracking or catalytic cracking a residual oil.

7. The process of claim 1, wherein the hydrocarbon composition having an fa value greater than 0.4 is prepared by blending a residual oil with a thermally cracked tar having a high aromatic hydrocarbon content and an fa value of 0.5 to 1.0.