GB2103650A - Microspherical pitch spheres - Google Patents

Abstract

Substantially nonadhesive pitch spheres having a weight average diameter of 30-200 mu m, oil content of 55-15 wt%, fixed carbon content of 45-85 wt% and softening point of not lower than 80 DEG C and capable of maintaining the spherical shape at ordinary temperature and under compression at 1 kg/cm<2> are produced by atomizing molten pitch in an inert gas stream and rapidly cooling the atomized pitch. The pitch spheres may be converted to green coke spheres by heat-treating the pitch spheres to accelerate polymerization thereof. The spherical pitch and green coke particles are easy to handle, transport, store and use.

Description

SPECIFICATION Microspherical oil-containing carbonaceous particles and process for producing the same This invention relates to microspherical pitch and raw coke particles, and more specifically to such pitch and green coke spheres made of pitches from processes for treating petroleum, coal or the like, and from naturally occurring bitumen and asphalts, and which can be handled like fluids for convenience in transportation and storage.

Generally, from the viewpoint of composition, it is difficult to draw a clear distinction between pitch and raw coke. The same applies to this invention in that pitch and green coke spheres have fixed carbon, hydrogen/carbon ratio, and other compositional ranges partly in common. However, for the purposes of the invention, they are distinctly distinguishable because of their dissimilarities in manufacturing process (degrees of cracking and polymerization) and in physical and chemical properties. Therefore, the two are hereinafter referred to separately as pitch spheres and green coke spheres.

Pitches are available in abundance from the processes for treating and refining petroleum, coal and the like. For example, treatments of petroleum bottom (residual) oils, tar sands, and oil shales, and coal coking and liquefaction processes afford pitches. Besides, there occur bitumen and asphalts in nature. These pitches are partly in use, after appropriate treatments, for varied applications, e.g., as electrode-, steel-, and other binder pitches, solid fuels such as electrode coke, carbonaceous and other cokes, and as feedstocks for fuel gas and hydrogen gas production.

However, as is well-known with the naturally occurring bitumen and asphalts, those pitches are either viscous liquids or solids which become viscous as the temperature rises. The inherent viscosities make them difficult to handle for transportation and storage, thus limiting their fully effective utilization.

The present invention provides novel pitch and raw coke products, in the form of pitch and green coke spheres, which eliminate the disadvantages of the existing pitches and permit handling like fluids without adhesiveness. The pitch and green coke spheres, so easy to transport and store, are much helpful in settling the problems in processes for treating heavy distillates and bottoms to which increasing importance is being attached. Of the crude oils in production and on market, heavy ones have accounted for increasing percentages, while another tendency is a gradual shift in demand from heavy to light and lighter petroleum products. Consequently, there is a strong need for expanding the capacities of processes for converting and upgrading heavy or bottom oils to lighter materials. In the meantime, early development of substitute energy for petroleum is being called for.Attempts to recover oils from tar sands and oil shales and development of new coal liquefaction processes are also under way. Heavy distillates or oils from these sources are fed, too, to the heavy-to-light conversion and upgrading processes. Those processes naturally give carbonaceous residues, which present a number of handling and application problems yet to be solved with the existing installations for the heavy oil treating processes.

This will be explained, by way of example, in connection with typical processes for treating petroleum bottom oils, namely, delayed coking, Eureka process, fluid coking, and flexicoking. Delayed coking, which is a semi bath process, ptoduces residual green coke in coke drums which must be broken into lumps and taken out at regular intervals by hydraulic or mechanical means. The lumps are difficult to discharge, and the product coke is inconvenient to transport and store because of its moisture and suchlike contents. The product also involves difficulties in use as fuel. Eureka process, again for semi bath operation, yields residual pitch in a liquid form, which can be continuously taken out and cooled solid for use as binder for iron and steel. Although the residue the process gives is a pitch easy to take out, it still entails some inconvenience in transportation and storage.Moreover, in the present state of the art, there is a quantitative limit to the application of the pitch as the binder or the like. Fluid coking gives coarse coke pieces as the residue, but because relatively high temperatures are used in processing, the coke has rather poor combustibility and hence its value as fuel is low. The residual coke pieces obtained in flexicoking process are subsequently subjected to gasification. The gasified product is convenient for transportation but not for storage. In addition, the gas is low in calorific value and is limited in use as fuel.

The present inventors conceived the idea of continuously taking out of the system, in the form of pitch, the carbonaceous residue that consequently results from a process of heavy residual bottoms and then forming the pitch into microspherical pitch or green coke particles that can be handled like a fluid, in the belief that the product would be convenient for transportation and storage, usable directly as fuel in many cases, and be efficiently gasifiable when necessary, thus contributing greatly to the utilization of the carbonaceous residue from the bottoms treating process that offer many problems yet to be solved. Intensive investigations based on the concept have now led to the provision of pitch and green coke spheres capable of solving the problems pertaining to the bottom oil treating process.

The pitch spheres according to this invention are minute and hardened by at least a surface treatment so that they do not stick to one another. The minuteness and nonadhesiveness combine with the spherical shape to allow the mass of the spheres to behave like a fluid. Thus, ease of handling, transportation, and storage characterizes the spheres of the invention.

The pitch spheres are substantially free of moisture and, in many cases, low in ash content. They can, therefore, be fired directly as special fuel by a burner; even of a universal design through come modification of the properties. An additional advantage is that the combustibility can be controlled through adjustment of the oil (volatile matter) content of the pitch spheres.

Further, as will be described in more detail later, thermal cracking of the pitch spheres by use of a fluidized bed technique or the like will decompose part of their oil content to lighter products which are separable. The remainder is thermally polymerized to form green coke spheres having minute pores. This product can be employed directly as fuel, e.g., for kilns. It is easily gasified for use as such or as desirable feed for hydrogen gas production. The microspherical shape of the green coke particles again renders it convenient for handling, transportation, and storage.

The pitch spheres of the invention are made from material pitch having a softening point of 60-220 C and a fixed carbon content of 40-75 wt% by (1) atomizing and spherical granulation of the pitch, (2) evaporation of the oily matter from the spherical pitch surfaces if required, and (3), where necessary, slight surface oxidation and/or washing with solvent or the like treatment of the pitch spheres. The pitch spheres thus obtained are substantially nonadhesive particles having an average particle diameter (mean of 50% by weight) of 30-2001lm, oil content of 55-15 wt%, fixed carbon content (as measured in conformity with the procedure of Japanese Industrial Standards M-8812) of 45-85 wt%, and a softening point of 80"C or upwards.

For the measurement of the softening point a flow tester (Shimadzu-Koka Flow Tester (trade name) manufactured by Shimadzu Seisakusho, Ltd.) was used. In the course of the measurement it was confirmed that the particles were capable of kneeping the spherical form under compressive load of 1 kg/cm2 at ordinary temperature.

Generally, with a softening point below 80"C or a fixed carbon content of less than 45 wt%, the particles would not have adequate adhesion and strength to stand normal transportation and storage.

With regard to the composition of the pitch spheres as represented by their oil content and fixed carbon, those values are average ones. Individual particles may be either uniform throughout or have an ununiform composition, e.g., with a higher oil content (or lower fixed carbon content) in the center than in the surface layer, as if having a surface skin.

The green coke spheres according to the invention are obtained by subjecting the above pitch spheres to further thermal cracking and thereby decomposing the heavy residual oil in the pitch spheres to lighter products and recovering the same, while subjecting the remainder to polycondensation. To be more specific, they are made from material pitch having a softening point of 60-220"C and a fixed carbon content of 40-75 wt% by (1) atomizing and spherical granulation of the pitch, (2) if required evaporation of the oily matter from the spherical pitch surfaces, (3), if necessary, slight surface oxidation and/or washing with solvent or the like treatment of the pitch spheres, and (4) further thermal cracking.The resulting coke spheres are particles having an average particle diameter of 30-200 um, oil content of 25-4 wt%, fixed carbon content of 75-96 wt%, and pore volume of 0.05 cc/g.

If the fixed carbon content is less than 75 wt%, the green coke spheres will practically be unable to attain the required strength while possessing the porosity. Conversely if the value exceeds 96 wt%, the product will exhibit too poor combustibility to be used advantageously as fuel.

The green coke spheres are more or less common with the pitch spheres in respect of the composition, such as the oil and fixed carbon contents, and the average particle diameter. However, they differ distinctly from the latter in that they are in an advanced stage of coking due to further thermal cracking and polymerization, especially in that they have pores formed by the evaporation of lighter oil that resulted from the thermal decomposition.

For both the pitch and raw coke spheres the average diameter (mean of 50% by weight) is in the range of 30-200 Fm.

If the particle diameter is less than 30 calm, the particles tend to aggregate, especially in a fluidized state. If the diameter is above 200 um, particularly where they flow together with some gas, the particles will exhibit inadequate smoothness, which is undesirable for transportation, storage, orfluidization.

Starting material for the production of pitch and green coke spheres may be any of the pitches from the petroleum thermal cracking processes and heavy bottom (residual) oil treating processes (e.g., Eureka process and SDA (standing for solvent deasphalting) process], naturally occurring bitumen and asphalts and other petroleum pitches, coal pitches produced by coal coking and liquefying processes (e.g., SRC process), and various other pitches. The pitch to be used should have a softening point in the range of 60-220"C, preferably in the range of 100-180"C, and a fixed carbon content (as measured in conformity with JIS M-8812) of 40-75 wt%.If the softening point is below 60"C or the fixed carbon content is less than 40 wt%, the material is not suited for the production of the pitch and green coke spheres of the invention, because of its adverse effect upon the softening point of the pitch spheres or upon the rigidity of the green coke spheres.

The pitch and green coke spheres of the invention can be produced in a plurality of ways. For example, in one method (1) material pitch melted at 150-400 C to a relatively low viscosity is mixed with an inert gas at a higher temperature by means of a two-fluid nozzle, high-pressure nozzle or a rotating disk and the like, thus effecting atomization and evaporation of part of heavy bottom oil in the feedstock, and then cooling the atomized pitch in an appropriate manner to obtain pitch spheres. (In this case, the heavy oil is recovered by evaporation if necessary). In another method (2) material pitch melted at 150-430 C to a relatively low viscosity is mixed with an inert gas at a lower temperature to effect atomization and cooling, and, where necessary, water spray or the like is used for added cooling effect, so as to obtain pitch spheres. Still another method (3) consists of grinding pitch, solid at ordinary temperatures, by suitable means, introducing the pulverized pitch into a gas at a temperature above the melting point of the material (i.e., higher than the latter by about 20"C), thereby melting and granulating while, at the same time, evaporating part of the heavy oil content of the feed if necessary, and then cooling the resultant in a suitable way to obtain pitch spheres.

(Here again the heavy oil is recovered by evaporation if necessary.) The term "inert gas" as used herein means a substantially inert gas not chemically reactive with pitches. Examples are fuel gases containing methane and other light hydrocarbons, cracked gases from various processes, nitrogen gas, carbon dioxide gas, steam, and combustion waste gases.

In the manufacturing methods (1), (2), and (3), it is possible to include, if necessary, in a suitable stage, e.g., in the course of atomization, treatment of the pitch spheres separated from the inert gas, or in a pretreatment of the coke spheres, an additional treatment step, e.g., (a) slightly oxidizing the particle surface with an oxidant-containing gas or the like or (b) washing the pitch spheres separated from the inert gas with a suitable solvent, e.g., naphtha or other light hydrocarbon solvent for a short period of time. Such a treatment is necessary particularly when the material pitch used in the method (2) above has a softening point below 80"C and the product pitch spheres should have a higher softening point. In the methods (1) and (2) the viscosity of the pitch melted by the application of heat is reduced to a level low enough for spraying.Where necessary, a smali amount of the oil formed by cracking or the like may be added to ensure the decrease in viscosity.

In any of the methods (1) to (3) the process pressure varies with the quantitative ratio of the inert gas to the pitch spheres, but usually ranges from the atmospheric to 10 kg/cm2. Where the pressure is to be below this range, a larger proportion of the inert gas must be consumed and accordingly a laiger equipment is required to an economical disadvantage. Any pressure beyond this range is undesirable, too, because of a greater chance of mutual impingement and adhesion among the particles during the course of formation.

In the manner described above, pitch spheres can be obtained which have a softening point of not lower than 80"C and maintain the spherical shape at ordinary temperatures and under compression of 1 kg/cm2. In addition, the particles can remain spherical without fusing together during the treatment at 400-520"C for conversion to green coke spheres.

In the methods (1), (2), and (3) above, the product pitch spheres and the gas stream may be separated by mechanical means, such as a cycle-one, bag filter, falling by gravity, etc.

Next, green coke spheres can be produced by thermally decomposing the pitch spheres obtained in the foregoing way, at a temperature of 400-520 C and a pressure from the atmospheric to 10 kg/cm2. The oil content in the pitch spheres can be recovered by thermal cracking and conversion to lighter products, while the remainder is subjected to polycondensation and further coking to form green coke spheres having pores produced by evaporation of the lighter oil fraction. If the thermal cracking temperature to be used is below 400"C the cracking velocity will be low, and if it is above 520"C the resulting raw coke spheres will have insufficient oil content and strength and sometimes fail to retain the spherical form.Where the green coke spheres are to be formed directly without going through the pitch sphere formation, it is possible in the method (1) or (3) to adjust the atomizing and granulating conditions and/or the temperature for rapidly cooling and thereby subject the resultant while at a relatively high temperature directly to thermal cracking, thus achieving good thermal economy.

For clear understanding of the features and advantages of the pitch and raw coke spheres according to the invention, the manufacturing process (1) will now be described with reference to a flow chart in the drawing wherein the single figure is a process flow chart of an embodiment of the invention.

The process for producing the pitch spheres of the invention is, for the purposes of the invention, called the first step, and the process for producing the raw coke spheres the second step.

The first step consists of spray drying hot, liquid pitch into solid pitch spheres having a spheroidal contour and a nonadhesive, hardened surface, and if necessary, recovering part of the heavy residual oil from the material pitch.

Material pitch, heated or kept at 1 50-4000C and desirably having a viscosity of not more than 300 cps., is supplied from a constant-temperature tank 1 by a high pressure pump 2 into an atomizer 3, where it is sprayed against a gas from a heating oven 9. The gas is heated to a temperature in the range of 200-800"C, preferably in the range of 300-600"C, and is substantially inert to the pitch. The atomizer 3 is a contactor such venturi-type contactor, which injects the liquefied pitch through a plurality of pressure nozzles (for example, of the swirl type) countercurrent against a high speed stream of the inert gas whose linear velocity is desirably at least 10 m/sec locally.

The material pitch temperature is to be in the range of 150-400"C. At below 150"C the pitch generally is too viscous for smooth atomization, and above 400'the pitch quality is adversely affected by the heat. For the inert gas the temperature range of 200-800 C is desirable, because at below 200"C the gas retards the evaporation of the oily content from the pitch and requires a large volume of gas for poor economy, whereas at above 800"C it causes too rapid evaporation to produce pitch spheres of desired shape. The inert gas is used usually in an amount 0.1-1.5 times, preferably 0.5-8 times, (weight ratio) that of the pitch spheres.. The high speed of the inert gas stream is important in that it facilitates the atomization of the liquid pitch and shortens the time for contact with the atomized liquid pitch. The process pressure, as noted above, ranges from the atmospheric to 10 kg/cm2.

In this process, minute droplets of the liquid pitch are formed first, and heat is transfered from the hot gas stream to the pitch and depending on the condition, the heavy oil contained in the pitch droplet is partly evaporated.

As a consequence, the temperature of the mixed pitch-gas stream declines, in many cases down to 175-475 C in about 10 seconds. Next, this flowing mixture is rapidly cooled to solidify the pitch droplets. By separating the resulting solids from the gas stream, microspheroidal pitch particles having an average particle diameter (mean of 50% by weight) of 30-200 Fm can be obtained. Retrieval of heat from the pitch spheres and recovery of the heavy oil from gas stream are accomplished by suitable methods if necessary.

Important parameters of the atomizer operation are the temperature and rate of supply of the inert gas relative to those of the liquid pitch as feedstock, conditions of injection and/or mixing, retention time of the fluid mixture, and temperature for rapid cooling. Adjustments of these parameters dictate the fixed carbon content, average oil content, and distribution of oily matter in the pitch spheres, and also the softening point (i.e., adhesiveness) of the spheroidal particles.

Rapid cooling of the pitch spheres can be effected in a different way, e.g., by injecting water or low-temperature gas into the mixed stream, thereby cooling the latter to 70-400"C. If the mixture is cooled below 70"C, vaporized oil and steam can condense and regain entrance into the product. If cooled above 400"C, thermal cracking of the pitch spheres or secondary aggregation of the particles can take place. As a further alternative, the pitch spheres may be rapidly cooled by use of a multiple fluidized-bed column 5.After passage through a cyclone 4, e.g., for separation from the gas stream, the pitch spheres are allowed to exchange heat directly or indirectly with an inert gas being introduced into the column at a temperature in the range of ordinary to 100"C and at a velocity of usually 5-100 cm/sec, preferably 10-60 cm/sec. The spheres thus cooled are taken out of the vessel at a temperature of ordinary to 1 00'C. The multiple fluidized-bed column may be supplanted by a moving-bed one.

The gas stream separated from the pitch spheres is cooled as it is led through a suitable heat exchanger8 and a cooler 10, and the oily content is recovered from the gas stream in a distillation column 12. The heat recovered in the heat exchanger 8 and the multiple fluidized-bed column 5 is utilized to heat the inert gas in the system shown for an improvement in thermal efficiency.

The pitch spheres so obtained are substantially non-adhesive and are an excellent product for use as special fuel easy to handle, transport, and store. The product can also be the feedstock for the second step of raw coke sphere production.

The recovered heavy oil is used as fuel oil after an appropriate treatment such as desulfurization.

The second step is resorted to, where necessary, to produce raw coke spheres. The step consists of recovering relatively light oil by thermal cracking from the microspheroidal pitch particles obtained by the first step, while converting the remainder or particles into raw coke spheres having minute pores.

The pitch spheres from the first step are fine particles substantially nonadhesive on surface and which contain, although dependent on the operating conditions employed, 45-85 wt% fixed carbon and 55-15 wt% oil.

The product pitch spheres obtained by the first step or the pitch spheres extracted at a suitable temperature from the first step are fed to a fluidized-bed thermal cracker 6 in which coke particles flow. In a fluidized state in the vessel the pitch spheres are thermally decomposed. The thermal cracking temperature is 400-520"C, the pressure is from the atmospheric to 10 kg/cm2, and the average retention time for thermal cracking is between 1 minute and 2 hours.

The coke particles to be used in this fluidized-bed vessel are the recycle of the product in this second step.

The thermal cracking and a polycondensation reaction that occurs concurrently in the second step convert the pitch spheres to green coke ones. The resulting coke spheres attain high strength thanks to the polycondensation reaction during the course of cracking as well as to the high fixed carbon content in the material pitch spheres. In addition, the product is porous.

The green coke spheres leaving the fluidized-bed thermal cracker 6 are still hot, and therefore they are cooled through heat recovery, e.g., by a multiple fluidized-bed column 7, and finally product raw coke spheres are obtained. In the multiple fluidized-bed columns and the like, an inert gas flow velocity of usually 5-100cm/sec, preferably 10-60cm/sec, is used. In the arrangements shown, the heat recovery from the multiple fluidized-bed column 7 is carried on through heat exchange with a low-temperature inert gas. The inert gas is then conducted to a heater 9 for enhanced thermal efficiency.

Meanwhile, the cracked gas and light oil discharged from the cracker 6 are joined with the inert gas used in the atomizer and cooled together through the heat exchanger 8 and the cooler 10. In the distillation column 12, the oily matter is recovered. The light oil separately recovered is desulfurized or otherwise treated to be a product. Although the cracked gas may be treated in the distillation column 12 together with the inert gas from the atomizer as shown, an additional distillation column may be installed to separate the light oil alone from the rest.

The green coke spheres produced by the second step are microspherical particles having an average diameter of 30-200 um and have pores, with an oil content of 25-4 wt% and a fixed carbon content of 75-96 wt%. The product in the form of porous particles is easy to handle, transport, and store and is useful as solid fuel or carbonaceous material. Since the porosity permits ready gasification, the product is also suitable as feedstock for gas fuel or hydrogen gas production.

The ratio in quantity of the pitch spheres from the first step to the raw coke spheres from the second step may be suitably varied to best meet the market requirements.

The invention will be more clearly understood with reference to the following examples; however, these examples are intended to illustrate the manufacturing process for better understanding only and not to be construed to limit the manufacturing process and use of the pitch and raw coke spheres according to the invention.

Example 1-A The material pitch used in Example 1 was one obtained by thermally cracking a vacuum residue. Its properties were as shown in Table 1.

TABLE 1 Softening point, "C 126 Oil content, wt% 53.6 Fixed carbon, wt% 46.4 Elements analyzed: (wt%) C 85.9 H 6.6 N 1.4 S 5.4 H/C (atomic ratio) 0.92 This material pitch was heated to 310"C (at which it attained a viscosity of 100 cps), and was sprayed by nozzles for drying, at a flow rate of 30 kg/hr, into a stream of nitrogen gas heated at 400 C. The flow rate of the nitrogen gas was 77 kg/hr.

The atomizer used was a venturi type contactor having a maximum diameter of 50 mm and a length of 2500 mm, with a constriction 15 mm in inside diameter. A bank of four 0.3-mm-dia. nozzles was installed immediately on the upstream side of the constriction. The material pitch was issued out of the nozzles countercurrent (at an angle of 45 ) to the stream of nitrogen gas. The nozzle pressure for injection of the feed-stock was about 150 kg/cm2.

The pitch injection into the nitrogen gas lowered the mixed gas temperature to about 350"C. At the exit of the contactor, water at 25"C was injected at a rate of about 15 kg/hr to rapidly cool the mixture down to about 90 C. Through a cyclone the mixture was separated into a gas stream and pitch spheres. The residence time required for the atomization (heat transfer and evaporation) was 0.2 sec.

The pitch spheres thus obtained had an average particle diameter of about 80m (90% of the product being in the 40-150 um range) and a softening point of not lower than 200"C. At ordinary temperatures the particles were capable of maintaining the spherical form under compression up to 10 kg/cm2. The properties of the pitch spheres were as given in Table 2.

The pitch spheres were taken out at a rate of about 26.4 kg/hr, and the yield based on the starting pitch was about 88 wt%.

TABLE 2 Average oil content, wt% 45.4 Average fixed carbon, " 54.6 Elements analyzed: (wt%) C 86.0 H 5.9 N 1.6 S 5.6 H/C (atomic ratio) 0.82 On the other hand, the nitrogen gas separated from the pitch spheres was cooled by the cooler and its oily content was recovered. The recovered oil was a heavy residual oil about 30% of which was fractions having boiling points of 540"C or upwards. The yield based on the material pitch was about 12 wt%.

Example 1-B Of the pitch spheres obtained in Example 1-A, 26.4kg was used as the starting material. In a fluidized-bed reactor having an inside diameter of 210 mm and an effective height of 1000 mm, the pitch spheres at 800C was preliminarily oxidized on the surface for 2 hours, using an air stream containing 3 vol% ozone and kept at about 100 C, at a flow rate of 20 m3/hr. Next, nitrogen gas at 6000C was blown in at a rate of 6 m3/hr and the temperature was gradually raised to 4500C to carry on thermal cracking. The conditions used were such that the reaction temperature was 450"C, pressure was 0.3 kg/cm2, and reaction time was 0.7 hour. The superficial velocity of nitrogen gas in the fluidized bed reactor was 0.1 3m/sec.

Following the conclusion of the reaction, the gas was replaced by nitrogen gas at 40"C to cool the resultant, and green coke spheres at 65"C were taken out as the product.

The product coke spheres were particles 80% of which was in the particle size range of 40-150ym. The properties of the product were as given in Table 3.

TABLE 3 Average oil content, wt% 15.1 Average fixed carbon, " 84.9 Elements analyzed: (wt%) C 88.6 H 3.6 N 1.5 S 6.0 H/C (atomic ratio) 0.49 Pore volume, cc/gr 0.25 Compressive strength, kgicm2 15 The green coke spheres were obtained in an amount of 19.7 kg, or in a yield of 74.6 wt% on the basis of the pitch spheres or 65.7 wt% of the original material pitch.

The cracked gases given by thermal cracking were cooled by the cooler to 40"C and separated into cracked oil and cracked gas of C5 or lower fractions. The cracked oil accounted for about 22.4 wt% of the total weight of the material pitch spheres, and the cracked gas accounted for 3.0 wt%. Table 4 shows the cracked oil properties.

TABLE 4 Specific gravity 1514"C 0.910 -235 C wt% 20 235-540"C wt% 76 540"C- wt% 4 Example 2-A The material pitch used in Example 2 was prepared by thermally cracking a vacuum residue, and its properties were as given in Table 5.

TABLE 5 Softening point 146 Oil content, wt% 48.2 Fixed carbon, wt% 51.8 Elements analyzed: (wt%) C 86.2 H 6.0 N 1.4 S 5.5 H/C (atomic ratio) 0.84 This material pitch was kept at 320"C (at which its viscosity was 200 cps), and at a flow rate of 30 kg/hr it was sprayed by nozzles into an inert gas stream heated at 600"C. The flow rate of the inert gas was 28 kg/hr and the gas composition was as shown in Table 6.

TABLE 6 Analytical values, vol% H2 5 CH4 45 C2 25 C3 20 C4+ 5 The atomizer was a venturi-type contactor having a maximum diameter of 50 mm and a length of 1500 mm, with a constriction of 15 mm in inside diameter. It was equipped with four 0.3-mm-dia. nozzles installed immediately upstream of the constriction. The pitch was sprayed from the nozzles in a flow countercurrent (at an angle of 45 ) against the inert gas stream.The nozzle pressure for spraying the material pitch was 300 kg/cm2 Due to the pitch injection into the inert gas the temperature of the mixed gas stream dropped to about 450"C. With a further spray of water at 25"C and at a rate of 11 kg/hr, the mixture was rapidly cooled down to about 300"C. The residence time required for the atomization (heat transfer and evaporation) was about 0.15 sec.

The mixed stream was separated by a cyclone separator into pitch spheres and gaseous matter. The pitch spheres were then routed to a multiple fluidized-bed cooler, where the pitch was cooled through contact with an inert gas at 40"C introduced at the bottom of the fluidized-bed vessel, and a product at 650C was obtained.

The product pitch spheres had an average particle diameter of about 100 um (the particles in the 50-150 um range accounting for 90% of the total) and a softening point of not lower than 300"C. The particles at ordinary temperatures retained the spherical form under compression up to 10 kg/cm2. Table 7 gives the properties of the product.

TABLE 7 Average oil content, wt% 34.9 Average fixed carbon, wt% 65.1 Elements analyzed: (wt%) C 86.6 H 5.4 N 1.4 S 5.8 H/C (atomic ratio) 0.78 The pitch spheres were taken out at a rate of 25.5 kg/hr, and the yield on the basis of the material pitch was 8.5 wt%.

On the other hand, the pitch spheres and a cyclonically separated gas stream were cooled by a heat exchanger and a cooler, and separated by a distillation column into recovered oil, condensed water, and off-gas. The off-gas recycled as a inert gas through a heater for atomization. Part of the recycle was utilized as coolant for a multiple fluidized-bed cooler.

The recovered oil separated by the distillation column was a heavy oil containing about 50% of fractions having boiling points of 540"C or above. The yield was about 15 wt%.

As a modification of this example, the same process was repeated using the same starting pitch except that the atomizer in this example was so modified that it had a length of 3,000 mm, the wall downstream of the constriction diverged downwardly to form a dome terminating in a maximum diameter of 700 mm and the pitch injection nozzles were mounted on the dome portion immediately downstream of the constriction at right angle with respect to the axis of the atomizer. The result was similar to that of this example.

Example 2-B Using the same starting material and in the same manner as described in Example 2-A, pitch spheres were produced and separated from the gas stream by the cyclone. Next, from the second stage of the multiple fluidized-bed cooler, the pitch spheres were extracted (at 119"C) and were thermally cracked by a single-stage, fluidized-bed thermal cracker having an inside diameter of 210 mm and an effective height of 1000 mm, at a rate of 25.5 kg/hr. The thermal cracking temperature was 450"C, pressure was 0.3 kg/cm2, and average reaction time was 0.5 hour. For the fluidized bed formation the same inert gas as used for the atomization was utilized, at 600"C. The gas composition was as shown in Table 6 for Example 2-A and the superficial velocity of the gas in the cracker was 0.15 m/sec.The raw coke spheres obtained by the thermal cracking were cooled by contact with an inert gas at 40"C introduced at the bottom of the multiple fluidized-bed cooler. The cooled spheres as the product were taken out at 650C.

The product was microspheroidal raw coke particles 85% of which was in the particle size range of 50-150 um. Its properties were as shown in Table 8.

The green coke spheres were obtained at a rate of 21.0 kg/hr, and the yield was 82.4 wt% based on the pitch spheres and about 70% of the original pitch material.

Meanwhile, the cracked gas discharge from the fluidized-bed thermal cracker was cooled by the heat exchanger and the cooler, independently of the inert gas that left the atomizer.

TABLE 8 Average oil content,wt% 13.4 Average fixed carbon, wt% 86.5 Elements analyzed: (wt%) C 88.9 H 3.5 N 1.4 S 6.1 H/C (atomic ratio) 0.47 Pore volume, cc/g 0.30 Compressive strength, kg/cm2 Over 15 and separated cyclonically from the pitch spheres. In the distillation column, it was separated into cracked oil, condensed water, and overhead gas. The overhead gas was recycled as an inert gas through the heating oven for reuse as the atomizing gas or coolant for the multi-stage, fluidized-bed cooler.

The cracked gas separated in the distillation column accounted for about 2.0 wt% of the starting pitch spheres, and the cracked oil amounted to about 15.6 wt%, with properties as given in Table 9.

TABLE 9 Specific gravity 15/4"C 0.913 -235 C wt% 22 235-540 C wt% 75 540"C- wt% 3

Claims (21)

1. Substantially non adhesive pitch spheres having an average diameter (mean of 50% by weight) in the range of 30-200 um, oil content of 55-15 wt%, fixed carbon content of 45-85 wt%, and softening point of not lower than 80"C, said spheres being able to maintain the spherical shape at ordinary temperature and under compression at 1 kg/cm2.

2. Pitch spheres according to claim 1 wherein said pitch spheres are capable of maintaining the spherical shape at ordinary temperature and under compression at 10 kg/cm2.

3. Green coke spheres having an average diameter (mean of 50% by weight) in the range of 30-200 um, oil content of 25-4 wt%, and fixed carbon content of 75-96 wt%, said spheres being of a porous structure.

4. Coke spheres according to claim 3 wherein said spheres have a pore volume of at least 0.05 cc/g.

5. Coke spheres according to claim 3 or 4 wherein said coke spheres are obtained by heat treating pitch spheres having an average diameter (50% by weight diameter) in the range of 30-200 um, oil content of 55-15 wt%, fixed carbon content of 45-85 wt% and softening point of not lower than 80"C.

6. A process for producing pitch spheres having an average diameter in the range of 30-200 um, which comprises atomizing a pitch selected from a petroleum pitch, and coal pitch having a softening point in the range of 60-220"C, a fixed carbon content of 40-75 wt%, heated to a temperature of 1 50-400"C, in a gas stream substantially inert to the pitch, at a pressure of the atmospheric to 10 kg/cm2, at a gas temperature of 200-800"C, rapidly cooling the mixture flow to 70-400"C, and then recovering the resulting microspherical pitch particles.

7. A process for producing pitch spheres according to claim 6, wherein said atomization of the pitch is effected by injecting it into said inert gas stream having a linear stream of at least 10 m/sec.

8. A process for producing pitch spheres according to claim 6, wherein said atomization of said molten pitch is effected by spraying said pitch into said inert gas stream.

9. A process for producing pitch spheres according to claim 6, 7 or 8, wherein oil content of said pitch spheres is partly vaporized from at least the surfaces thereof in said inert gas stream.

10. A process for producing pitch spheres according to claim 6,7 or 8, wherein the cooled pitch spheres are partly surface-treated with oxidant or solvent before they are recovered.

11. A process according to claim 6,7,8,9 or 10, wherein said cooling is effected by water.

12. A process for producing green coke spheres having an average particle diameter in the range of 30-200 um, which comprises a first step of atomizing a pitch selected from a petroleum pitch and coal pitch having a softening point of 60-220"C and a fixed carbon content of 40-75 wt%, while maintaining the pitch temperature at 1 50-400"C, in a gas stream substantially inert to the pitch, at a gas pressure of the atmospheric to 10 kg/cm2 and at a temperature of 200-800"C, rapidly cooling the mixture flow to 70-4000C, and then recovering the resulting microspherical pitch particles, and a second step of thermally cracking and polycondensating said pitch spheres from the first step by use of a fluidized bed at a temperature of 400-520"C and a pressure of the atmospheric to 10 kg/cm2 over an average residence time of 1 minute to 2 hours, and recovering microspherical green coke particles.

13. A process for producing pitch spheres according to claim 12, wherein said atomization of the molten pitch is effected by injecting into said inert gas stream having a linear stream of at least 10 m/sec.

14. A process for producing pitch spheres according to claim 12, wherein said atomization of said molten pitch is effected by spraying said pitch into said inert gas stream.

15. A process for producing pitch spheres according to claim 12, 13 or 14, wherein oil content of said pitch spheres is partly vaporized from at least the surfaces thereof in said inert gas stream.

16. A process for producing pitch spheres according to claim 12, 13 or 14 wherein the cooled pitch spheres are partly surface-treated with oxidant or solvent before they are recovered.

17. A process according to claim 12, 13, 14, 15 or 16 wherein said cooling is effected by water.

18. Non-adhesive pitch spheres substantially as hereinbefore described with reference to the accompanying drawing.

19. Green coke spheres substantially as hereinbefore described with reference to the accompanying drawing.

20. A process for producing pitch spheres substantially as hereinbefore described with reference to the accompanying drawing.

21. A process for producing green coke spheres substantially as hereinbefore described with reference to the accompanying drawing.