JPS6144914B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for mixing and contacting coal-based and petroleum-based heavy oils with an aqueous surfactant solution to form quinoline-insoluble fine solid impurities in the heavy oils as interfacial floating substances, and separating and removing them. It is. The refined heavy oil obtained by the method of the present invention is
It is suitable as a raw material for producing carbon materials such as graphitizable coke used for UHP electrodes and pump shaft seals, isotropic and anisotropic carbon fibers, and high-grade activated carbon. Conventionally, raw materials for producing carbon materials have been very diverse, including coal-based heavy oils, petroleum-based heavy oils, and polymer fibers, but in terms of quantity, coal-based and petroleum-based heavy oils is widely used due to its economical advantages due to its high carbonization yield despite its low raw material cost. However, the permissible range of raw material properties for these heavy oils is also strict. For example, in the case of petroleum-based heavy oils, the sulfur content is generally high, so heavy oils with low sulfur quality are selectively used. , the range of raw material selection is greatly restricted. On the other hand, coal-based heavy oils have lower sulfur concentrations and higher carbonization yields than petroleum-based heavy oils, but coal-based heavy oils cannot be used as raw materials for high-grade carbon materials such as needle coke and carbon fibers. A small amount of quinoline-insoluble solid impurities (quinoline-insoluble matter) contained in a small amount in heavy oils is considered to be undesirable because it hinders graphitization. Note that, like coal-based heavy oils, petroleum-based heavy oils also contain minute solid impurities, albeit to varying degrees. Here, the allowable concentration of the solid impurity varies depending on the method used as the carbon material, but the quinoline insoluble content determined by the analysis method described below is
The standard is 100ppm or less for carbon fibers, and 300ppm or less for other carbon materials. Therefore, if solid impurities in heavy oils, whether coal-based or petroleum-based, can be efficiently removed, it will be possible to expand the use of high-grade carbon material raw materials, which will greatly contribute to reducing carbon material costs. It turns out. The fine quinoline-insoluble solid impurities in heavy oils refer to suspended particles of 500 μm or less, which are composed of carbon, inorganic salts, etc., and are not easily separated by sedimentation. The most common way to separate this is to apply an external force such as centrifugal force to the heavy oil and separate the suspended solid particles based on the density difference between the heavy oil, but the suspended solid particles are very fine. Therefore, it is difficult to separate them simply by centrifugation. Therefore, it is necessary to agglomerate fine suspended particles into large particles as long as separation by gravity difference is to be carried out. A particular technical problem here is how to remove such minute quinoline insoluble matter, and several techniques have been proposed for this purpose. The conventional method is to heat-treat heavy oils to increase the particle size of quinoline-insoluble components and separate and remove them. Another petroleum heavy oil is added to the coal-based heavy oil, and a polymeric component (gummy component) is attached to the quinoline-insoluble content to increase the particle size, and if necessary, aliphatic or aromatic A method of mixing the solvents of the system and separating and removing the insoluble precipitate by heating and stirring or cooling the mixture (JP-A-55-104387, JP-A-55
−113606, etc.) A method of mixing heavy oils with an organic solvent to agglomerate and separate and remove minute insoluble precipitates containing quinoline insoluble matter (Japanese Unexamined Patent Publication No. 136111/1983, Patent Application No. 43171/1983, 56-49791, Japanese Patent Application No. 54-125971, Japanese Unexamined Patent Publication No. 56-59611, Japanese Patent Application No. 135454, etc.). However, although methods that fall into the above classification are superior in principle, they have advantages and disadvantages and are not necessarily effective methods for the reasons described below. In this method, the particle size of the insoluble precipitate to be separated is extremely small, so the separation speed is slow;
Separation efficiency is low due to clogging during filtration. Furthermore, in order to lower the viscosity of heavy oils, it is necessary to separate or filter them at high temperatures, resulting in high equipment and operating costs. In addition, since the formation of insoluble precipitates is slow at room temperature,
It requires heating up to 200°C, stirring for several hours, and a large amount of expensive solvent, and therefore requires equipment for solvent recovery, making it lacking in industrial efficiency and economy. The following method requires a ratio of organic solvent to heavy oil of 10 to 100 times, which results in extremely high processing costs. Similar to the above method, many of these methods require cooling after heating and stirring, and equipment for recovering and recycling expensive solvents. The present inventors have proposed that instead of the above-mentioned conventional method in which the fine solid impurities in the feedstock heavy oil are agglomerated to a large size due to the formation of gummy components, by mixing an aqueous surfactant solution with the feedstock heavy oil, the conventional centrifugal force can be applied. Within this range, the inventors have invented that by utilizing the agglomeration effect of solids of surfactants, microscopic solids in heavy oil can be efficiently separated and removed by taking them into the oil-water surface and coagulating them to a large size. In addition, conventional methods cause polycondensation of components in heavy oil due to heating, resulting in a significant change in the properties of the raw material heavy oil, and as the excessively polycondensed material is removed, carbonization occurs in the product. This will reduce the yield. The present invention differs from this in that it simply attempts to agglomerate minute solid impurities using a surfactant, so it does not involve any change in the essential properties of the raw material heavy oil, and it does not cause the reduction in carbonization yield in the prior art. This is a significant improvement. On the other hand, methods for separating the solid matter of the present invention by adding a reagent such as a surfactant include a flotation method in which concentrate and ore are separated from crushed minerals. This is most commonly known as the ``foam separation method,'' which involves adding a small amount of reagents (surfactants) such as foaming agents and scavengers to mechanically or, rarely, chemically. This is a method of introducing air to create bubbles, attaching specific mineral particles to the bubbles, and floating them on the liquid surface as foam to separate them. However, the method of the present invention does not form bubbles, but rather This method is different from "foam flotation," as it agglomerates minute solid impurities at the oil/water interface. Other "flotation methods" include adding oil or forming a monomolecular layer on the surface of water to separate concentrates and ores by utilizing the difference in their selective adhesion. These methods separate minerals (solid content) into concentrate and ore, and are different from the method of the present invention in which all solid content is separated from liquid. On the other hand, various surfactants have the function of separating mineral particles and paraffin crystals in the extracted crude oil from the emulsion interface and transferring them to the water layer or oil layer when separating oil and water emulsions in crude oil extraction. is used. Although the effect of these surfactants in separating oil and water is known as a technique for achieving the object of the present invention, the present inventors have investigated the effect of quinoline-insoluble fine solids in heavy oils. As a result of many experiments, we have discovered that when using commercially available surfactants to separate impurities, sufficient effects cannot be achieved unless the stirring method used during mixing is appropriate. In other words, in general, vigorous stirring is required to ensure sufficient mixing contact between the surfactant and solid impurities in heavy oil, but vigorous stirring does not have the effect of aggregating solid impurities at the oil-water interface. They discovered that the effect can only be achieved by slowing down the stirring conditions. This invention will be explained in detail below. In this invention, coal-based heavy oil refers to coal tar such as high-temperature tar and low-temperature tar that are by-produced during coal dry distillation, coal liquefaction products, etc., and petroleum-based heavy oil refers to atmospheric distillation. It refers to residual oil, vacuum distillation residue oil, naphtha cracked bottom oil, fluid contact bottom oil, solvent extraction residue oil, etc., and is a single type of oil or a combination of these oils. In the present invention, by mixing an aqueous surfactant solution with the raw material heavy oils, fine solid impurities insoluble in quinoline in the heavy oil are aggregated to a large size at the interface of both liquids, and after separating both liquids, the heavy oils are This is a method for producing raw material heavy oil for carbon molded bodies, characterized in that light oil fractionated in an oil refining process is mixed as a viscosity modifier and removed by centrifugation. Each step constituting the present invention will be explained in order below. The flow of the present invention is shown in FIG. 1 as an example. (A) As the surfactant, a water-soluble commercially available surfactant having demulsifying and defoaming properties for conventional oil-water emulsion separation is used. Commercially available surfactants having such characteristics are generally anionic, cationic, nonionic, or amphoteric ionic, and any of these can be used. Those that foam violently when mixed and stirred with raw material heavy oils,
An emulsion that becomes cloudy is not preferable because it makes subsequent separation operations difficult. Therefore, those having the properties of a general antifoaming agent or demulsifying agent for oil/water separation are suitable. For example, anionic surfactants include alkyl and/or allyl sulfates and sulfonates, and alkyl and/or allyl groups may also be modified in the form of acid or alcohol esters or ethers. The cationic surfactant is an alkylamide type, a quaternary ammonium salt type, or an imidazoline type modified with an alkyl group. As the nonionic surfactant, polyoxyethylene alkyl phenyl ether, polyoxyethylene modified alkyl allyl ether, polyethylene glycol alkyl ether, sorbitan fatty acid ester, fatty acid monoglyceride, etc. are used. In the present invention, in addition to the various effects of these commercially available surfactants on oil/water content such as demulsification breaking, antifoaming, etc., when removing quinoline-insoluble minute solid impurities from raw material heavy oil, surprisingly, It has become clear that the quality of agglomeration and subsequent separation of minute solid impurities is influenced by the stirring conditions of the mixed liquid. The above surfactant should be completely dissolved in water beforehand.
The aqueous solution is used in an amount of 0.1 to 5.0 times the weight of the heavy oil, preferably 0.5 to 3.0 times the weight of the heavy oil, with a concentration of 0.1 to 5.0% by weight, preferably 0.5 to 2.5% by weight.
Generally, the concentration of surfactant in aqueous solution is several percent or less, but if it exceeds 2.5%, the removal effect of quinoline insoluble matter (QI) tends to be saturated, while keeping the QI in refined heavy oil below 100 ppm. In order to achieve this, it must be 0.5% or more. The surfactant solution was used at a ratio of 0.1 to 5.0 times, which is enough to separate the oil and water layers, but it was found that as much as 2.5 times the QI could be lowered to the target value of 50 ppm or less. The QI value of refined heavy oil can be adjusted by adjusting the concentration and usage ratio (mixing ratio) of the surfactant aqueous solution. In the subsequent oil layer and water layer separation (water separation) process, it is desirable that the liquid viscosity be 75 c.p. or less to facilitate centrifugal sedimentation, but it is particularly important to keep the viscosity of heavy oil within this range. In order to maintain the temperature, it is necessary to heat the mixture to 50℃ or higher, and in the mixing tank, the temperature of the mixed liquid must be maintained at 50℃ or higher and 80℃ or lower by appropriate heating. (B) Next, mix and stir the mixture of heavy oil and surfactant aqueous solution from (A). The surfactant dissolved in water will incorporate minute solid impurities in the heavy oil onto the surface of the oil droplets suspended in the water layer, and these oil droplets will be brought to the interface between the water layer and the oil layer by stirring in the mixing tank. levitate to,
Plays a role in coagulating solid impurities. In this case, increasing the degree of mixing contact and increasing the interfacial area per unit volume of heavy oil would increase the rate at which solid impurities are taken into the interface, which would be preferable, but as a result, vigorous stirring may be necessary. As a result, fine oil droplets with a diameter of 1 mm or less become dispersed and suspended throughout the tank, and even though solid impurities are captured at the interface between the oil droplets and the water medium, they are not separated in the next process and become heavy. It will remain in quality oil,
It was unexpectedly and surprisingly discovered that it is difficult to reduce the QI value in refined heavy oil to the target value. The slow stirring that characterizes the present invention depends on the type of surfactant used, the type of raw heavy oil, the temperature of the mixed liquid, the geometric position and structure of the stirring blade in the stirring mixing tank, and Although it cannot be determined unambiguously because it is influenced by many factors such as the rotation speed, the results of numerous experiments indicate that the long diameter of the oil droplets dispersed in the water layer is 2 to 10 mm as determined by visual observation. It is necessary to perform such stirring. The specific stirring conditions are shown below as an example from the experimental specifications, but the present invention is not limited thereto. In other words, a sliding-type torsion four-blade stirring blade is arranged horizontally on the center axis of the mixing tank, and the rotation direction is selected to give an upward flow to the liquid in the tank, and the ratio of the blade diameter to the tank diameter is 0.5 to 0.7. The position is 1/4 of the liquid depth from the bottom of the tank.
At 1/3 depth, the blade span ratio to tank diameter is 0.08 ~
0.12, using a stirring blade with a twist angle of 30 to 45 degrees with respect to the horizontal plane, and a rotational speed of 30 to 440 rpm, preferably 50 to 150 rpm for carbon fibers. The stirring time is approximately 60 minutes. Therefore, the surfactant may be dissolved more than necessary, or
It is necessary to avoid generating minute oil droplets in the water medium by stirring more strongly than necessary. (C) Next, the solid impurities collected at the oil-water interface in step (B) were coagulated into a large aqueous layer containing a surfactant by applying a centrifugal force of 30,000 to 100,000 G sec in a centrifugal sedimentation machine. Separates into a heavy oil layer containing solid impurities. The unit of centrifugal force is G・sec, which is the product of centrifugal force ratio to gravity (G) and action time (sec.)
However, the centrifugal force in this water separation step can be easily achieved in a short time using a centrifugal sedimentation machine having a normal centrifugal effect. The separated aqueous layer can be recycled and reused in the mixing tank while controlling the surfactant concentration as shown in FIG. (D) Next, add aromatic compounds such as benzene, toluene, xylene, etc., ketones such as acetone, ethers, esters, etc. to the oil layer separated in step (C) in an amount equal to the weight of the oil layer as a viscosity modifier. A low molecular weight organic solvent such as aliphatic compounds having a boiling point of 150° C. or lower is added, and the viscosity of the heavy oil solution is adjusted to 10 cp or lower by optional stirring. The various organic agents mentioned above are used as viscosity modifiers, but from an economical point of view, the light fraction (mainly benzene) obtained from the subsequent distillation separation process can be recycled and used as shown in Figure 1. . One way to lower the viscosity of the heavy oil solution is to heat it to about 50°C. (E) Next, the mixed oil obtained in step (D) is mixed in the heavy oil solution by applying centrifugal force of 3 × 10 ⁵ to 12 × 10 ⁵ G・sec by centrifugal sedimentation or filtering. Separate and remove solid impurities. The addition of the viscosity modifier in the previous step (D) is to facilitate centrifugation in this step, and the centrifugal separator in this step also has a normal centrifugal effect to maintain centrifugal force for the required time. Solid impurities can be easily removed by reacting with water. (F) The separated heavy oil solution and solid impurities are each subjected to atmospheric distillation to separate light fractions at temperatures below 200°C. The light fraction can be recycled as a viscosity modifier in step (D). The method of the present invention will be specifically explained below using Examples. The method for quantifying QI (quinoline insoluble content) in heavy oil according to the present invention meets the detection limit of JIS-K2425.
We use a highly accurate method that can measure down to several ppm from 500ppm, and it is based on the following steps. Add about 10 times the volume of quinoline to heavy oil, heat at 80℃ for 30 minutes, stir and mix, filter through glass fiber paper with a retained particle size of 0.5 μm, and then wash with quinoline and remove benzene. Perform cleaning 0.5
The solid matter remaining on μm glass fiber paper was heated to 110°C.
After drying for 30 minutes and cooling, the weight is expressed in ppm as a percentage of the weight of heavy oil. In addition, the solid impurity production rate is expressed as a percentage of the weight of the solid substance separated in the solid impurity separation step after drying at 110° C. for 30 minutes and then cooling to the weight of heavy oil. Example 1 A commercially available cationic or anionic surfactant was added to coal tar having the properties shown in Table 1 as heavy oil or petroleum cracked bottom oil as a heavy oil in a mixing tank with a stirrer as shown in FIG. 2 having a hot water bath. Alternatively, quinoline-insoluble solid impurities in heavy oil are removed using the nonionic products of the companies mentioned in the footnotes of Table 2 according to the process shown in Figure 1 and under the conditions shown in Table 2. The quinoline insoluble content was measured. In this example, it was confirmed how the quinoline insoluble content of refined heavy oil changes depending on the type of heavy oil and the type of surfactant. Therefore, the operating conditions for each of the other steps were kept the same. That is, the concentration of the surfactant aqueous solution, the mixing ratio (weight ratio) of the aqueous solution and heavy oil, the stirring rotation speed, the stirring time, the temperature of the mixed liquid,
Centrifugal force in water separation (processed for 30 seconds at a centrifugal force ratio of 2000 G using a centrifugal separator with a centrifugal sedimentation tube), separation temperature; viscosity modifier mixing ratio, stirring time (4
centrifugal force in solid impurity separation (processed for 5 minutes at a centrifugal force ratio of 2000 G using a centrifugal separator with a centrifugal sedimentation tube) and distillation separation (distillation up to 200°C with a simple atmospheric distiller) The light fraction (cut) is as shown in Table 2 except as noted above, and is fixed at a value selected from the preferred range of the present invention. As a result of this experiment, it was found that if the surfactant is a water-soluble surfactant that has demulsifying and antifoaming properties and is commercially available for "oil-water separation," the content of quinoline-insoluble solids in refined heavy oil can be reduced. We were able to reduce the content to 50 ppm or less, which is sufficient as a raw material for carbon fiber. Furthermore, in order to make carbon fibers from the refined heavy oil obtained in test numbers 1 and 3 in Table 2, the refined heavy oil was
Add 70% nitric acid to 5% of the weight of purified heavy oil, heat to 300℃ under normal pressure and hold for 2 hours, then distill under reduced pressure to collect the middle oil fraction (boiling point 200-350℃) and make hard pitcher. This was melt-spun at 230-260°C to make pitch fibers, and the temperature was raised from 110°C to 230°C at a rate of 1.4°C/hr in an oxidizing atmosphere, followed by infusibility treatment at 230°C for 0.5 hours. At this time, the moldability by spinning was good and no yarn breakage was observed. In addition, the fibers subjected to infusibility treatment were kept at 50℃ for 1 hour in an inert atmosphere, and then heated to 850℃ at a constant rate (6.7℃/h).
r) Carbonization treatment was carried out by increasing the temperature to obtain carbon fibers.
Table 3 shows the properties of the hard pitch and carbon fibers obtained. These properties are equivalent to or better than those of pitch and carbon fiber obtained from refined heavy oil by conventional solvent methods. In this example, the softening point and the method for determining the solvent-insoluble content excluding the quinoline-insoluble content are based on JIS-K2425. Comparative Example 1 When no surfactant is used in Example 1,
Refined heavy oil was obtained under the same conditions as in Example 1, except for the aqueous solution mixing and water separation steps, and the steps after viscosity adjustment by benzene addition. As shown in the rightmost column of Table 2, the removal of insoluble quinoline content was insufficient, and when testing carbon fiber production, thread breakage occurred frequently during spinning from pitch, and the formability of the thread was poor. The physical properties after firing are also poor, which is extremely inconvenient. Example 2 Using the coal tar shown in Table 1 as a raw material and using the stirring mixing device shown in Figure 2, the rotational speed of the stirring blade was set to 50, 500,
When changing to 900 rpm and keeping other conditions the same,
QI in refined heavy oil was measured. This result is the third
Shown in dotted form in the figure. From Figure 3, QI along with rotation speed
It can be seen that increases. In addition, in order to keep the production rate of solid impurities low and the QI to 100ppm or less, the rotation speed must be increased.
Below 300rpm, especially to keep QI below 50ppm
200rpm or less is desirable. Other conditions in this experiment were as follows. Surfactant used: Toho Chemical Ex-3 Surfactant concentration: 3wt% Mixing ratio (aqueous solution/heavy oil) 2.5; Stirring time: 60 minutes Temperature (mixing, water separation, solid matter separation): 50°C Centrifugal force Water separation: 6×10 ⁴ G・sec Solid separation 6×10 ⁵ G・sec Mixing ratio (benzene/separated oil) 1 Distillation separation Cutting temperature 200℃ Example 3 Using cationic Ex-3 manufactured by Toho Chemical Industry Co., Ltd. as a surfactant The concentration of the aqueous solution is 1, 2
and 3% by weight, the coal tar shown in Table 1 was purified using the apparatus shown in FIG. 2 with other process operating conditions being the same, and the influence of the concentration of the surfactant aqueous solution was investigated. The results are shown in Table 4. From the data in Table 4, it can be seen that as the concentration of the active agent increases, the QI decreases, but the effect becomes saturated. An increase in concentration means an increase in the amount of heavy oil used, and an increase in the mixing ratio also indicates that, as in the case of concentration, there is a limit to the reduction of QI.

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【table】 [Brief explanation of the drawing]

FIG. 1 is a simple flow sheet of the present invention.
FIG. 2a is a schematic cross-sectional view of a mixing vessel equipped with an agitator. FIG. 2b is a sectional view of a stirring blade provided in the stirrer shown in FIG. 2a. FIG. 3 shows the QI ppm and solid impurity production rate in refined heavy oil when the horizontal axis is the stirring rotation speed. 1... Raw material heavy oil, 2... Surfactant aqueous solution,
3...Mixing tank, 4...Water separation, 5...Solvent, 6...
...Mixing tank, 7...Separation of solid impurities, 8...Distillation separation, 9..., 10...Refined heavy oil, 11...Solid-containing tar, a...70 mm, b...116 mm, c...
100mm, d...140mm, e...10mm, θ...30°.

Claims (1)

[Claims] 1. A method of adding a surfactant to coal-based and petroleum-based heavy oils to form fine solid impurities in the heavy oils as interfacial suspended matter and separating and removing the particles (A) As a surfactant, 0.1 to 5.0 of a surfactant that has demulsifying and antifoaming properties for oil-water mixtures.
Add and mix 0.1 to 5.0 parts by weight of the weight percent aqueous solution to 1 part by weight of raw material heavy oil (B) Gently stir and mix so that the major diameter of the oil droplets dispersed in the water layer is 2 to 10 mm (C ) The mixed solution is centrifuged into a water layer and an oil layer. Reduce the viscosity to 10 cp or less (E) Centrifuge the solid impurities in the oil solution (F) Distill the separated oil solution and the solid impurities, separate and remove the light fraction, and use the light fraction as a viscosity modifier. A method for producing heavy oil as a raw material for producing carbon materials, characterized in that it is recycled as a raw material.