Preparation of high performance electrorheological fluids with coke-like particles from FCC slurry conversion

doi:10.1016/j.fuel.2004.03.021

Fuel

Volume 84, Issue 6, April 2005, Pages 685-689

https://doi.org/10.1016/j.fuel.2004.03.021 Get rights and content

Abstract

The electrorheological fluid (ERF) with coke-like particles from thermal conversion of fluid catalytic cracking (FCC) slurry was prepared and their ER performance was investigated. The results show that an ERF containing these solids is a high performance material with high shear stress, low current density and long-term stability. Shear stress higher than 2 kPa and current density less than 60 μA/cm² was obtained in a 2 kV/mm DC field. The volume fraction of clear liquid released from the ERF was less than 5 vol% after several months of static test, indicating the ERF is stable and meets commercial application requirements. The influence of thermal conversion level and the orientation of condensed aromatics on ERF performance are discussed.

Introduction

Fluid catalytic cracking slurry (FCCS) is a by-product of petroleum refining. The processing and utilization of FCCS is difficult because it is a complex mixture of hydrocarbons (aromatics, saturates, resins, and asphaltenes), residual catalyst and coke fines. About 3–5 million tons of FCCS are produced annually in China. The oil refining industry has evaluated various means of FCCS utilization and disposal, including the conversion of this waste material into value-added products [1].

An electrorheological fluid (ERF) is a ‘smart material’ with promising market potential. The rheological properties, apparent viscosity and shear stress, can be rapidly, continuously and reversibly altered to form a liquid or solid in a controlled electric field [2]. An ERF is composed of insulating oil and suspended dielectric particles. When an electric field is applied, polarized particles form chains, through dipole–dipole interactions that induce an electrorheological effect. Novel devices such as clutches, dampers, valves, etc. can be designed and fabricated on the basis of the ERF effect [3]. The dispersed particles in an ERF are a key factors affecting the electrorheological properties. So far, a number of particles have been evaluated for their ERF effect. However, a comprehensive database of these materials is still lacking in supporting the commercialization of ERF technology. Some of the challenging issues for ERF technology development include adequate raw material supply, easy commercial-scale production, low cost, high performance and long-term stability.

An anhydrous ER fluid prepared with carbonaceous particles as the dispersed phase was reported [4], [5]. Petroleum cokes can be used as carbonaceous particles, which are derived from pitch materials composed of molecules with highly conjugated, aromatic ring structure [6]. A carbonaceous ERF with superior characteristics was obtained, including high ER effects at low current density, high temperature stability, durability and other properties [6]. Shima and Miyano [7], [8] reported that carbonaceous particles suitable for ERF applications could be prepared by thermal or catalytic conversion of coal tar and naphthalene oil to produce a mesophase pitch with 100% optical anisotropy. This mesophase pitch was then transformed into a carbon precursor through further thermal conversion. Both raw material refining and control of thermo-conversional conditions are critical parameters during the processing, which is similar to carbon fiber production. Choi and co-workers [9], [10] prepared the carbonaceous particles with different properties from a commercial mesophase pitch which was cationically polymerized with naphthalene and HF/BF₃. They found that the effect of particle crystallinity (crystallite thickness, one of XRD parameters) on ER characteristics is important. Sakurai et al. [11] investigated the effect of blending carbonaceous particles with different conductivities on the electrorheological properties. They indicated that uniformity of the electrical properties among the particles is the most important factors in achieving optimum ERF performance.

Our group conducted research on petroleum derived streams and by-products for use as ERFs for many years. The scope of this work includes the evaluation of ER properties for various residual oil components, residual oil from various crude oils and various ERF preparation techniques [12], [13], [14]. These results show that residual oil from petroleum refining is a potential raw material for producing ERFs. The preparation and performance of an ERF prepared using coke-like particles from FCCS conversion will be discussed.

Section snippets

Materials

The decant oil from Liaohe FCCS (LFCCS) was chosen as the test material and Liaohe vacuum residual oil (LVRO) as a reference material. Table 1 shows the bulk properties and composition of these two samples. Experiments indicated that filtration of the FCCS before use had no influence on overall ERF performance.

Preparation of ERF

Thermal conversion of LFCCS and LVRO were carried out in a 0.5 l autoclave with 2 MPa N₂ at 480, 490, 500, 510 and 520 °C, for the FCCS, and 440, 450, 460, 470 and 480 °C for the LVRO. After

Performance of ERF

Fig. 1, Fig. 2, Fig. 3 show the performance of an ERF containing 34 vol% of coke-like particles from LFCCS conversion. As shown on Fig. 1, at a constant shear rate of 98 s⁻¹, the shear stress changes from 100 Pa at zero field to 2000 Pa at 2 kV/mm. This shear stress change is almost 20 times that of the initial shear stress. The current density increased with the electric field from 0 to 60 μA/cm² at 2 kV/mm, as shown on Fig. 2. These results demonstrate that the ERF prepared with coke-like particles

Conclusions

(1)
An ERF, prepared using coke-like particles from thermal conversion of FCCS, exhibits excellent performance with a large ER effect, low current density and satisfactory long-term stability.
(2)
An optimum thermal conversion severity is required to produce particles that have a large ER effect at relatively low current density.
(3)
The orientation of thermo-converted products promotes the ER effect, however, a mesophase with a large domain texture that is 100% optically anisotropic is not necessary.
(4)
It is

Acknowledgements

The authors would like to thank SINOPEC for financial support of this work under contract no. 196162.

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FCCS (Fluid catalytic cracking slurry) is a by-product in the catalytic cracking process (Zhang et al., 2019). Because of its high content of 2–5 ring short chain aromatics, FCCS can be processed to produce additional products for different applications, such as needle coke, carbon fiber, carbon black, industrial rubber softener, heat transfer oil, etc. (Dong et al., 2005; Eser and Wang, 2007; Lin et al., 2017a; Zhang et al., 2018). Catalyst particles reduce the quality of high value-added products produced from FCCS, so they need to be removed from the FCCS.
Catalytic cracking is the main method to lighten heavy crude oil, this process can produce high quality oil products such as gasoline and diesel, but also produces a large amount of fluid catalytic cracking slurry (FCCS). The catalyst particles in FCCS seriously restrict the secondary processing of FCCS and need to be removed, and the properties of FCCS is an important factor that affects the removal efficiency of the catalyst particles. Based on the “effective contact point” model proposed by the research group, this study further proposed the “electrostatic separation efficiency calculation” model. In this model, since FCCS has a uniform distribution of catalyst particles, the ratio of the number of catalyst particles can be expressed as the ratio of area to achieve the calculation of separation efficiency. Then the catalyst removal efficiency under different viscosity was analyzed, thus verifying the feasibility of this model. The effects of temperature and mass ratio of four components on the viscosity of FCCS were investigated respectively, then the effects of temperature and four components’ mass ratio on the electrostatic separation can be directly converted into the effect of viscosity on the electrostatic separation efficiency. All the results show the electrostatic separation efficiency decreases with increasing viscosity, and the best separation temperature is 120 °C.
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Electrostatic separation can be used to remove micron-sized catalyst particles from fluid catalytic cracking (FCC) slurry. In this study, simulations were performed with experimental parameters. The distributions of the electric field, slurry flow and particle motion were studied. According to the particle movement characteristics, an effective adsorption region was found in which the particles would be adsorbed on the surface of the fillers. The effect of the effective adsorption region on the electrostatic removal of catalyst particles from the FCC slurry was discussed. The size of the effective adsorption region was inversely proportional to the voltage and ionic carrier concentration. Under the same parameters, the size of the effective adsorption area and the motion of the particles were compared between the experiment and the simulation. The results showed that the numerical simulation results were in good agreement with the experimental results.
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The catalyst solid particles in fluid catalytic cracking slurry (FCCS) can be removed by electrostatic separation. In this study, on the basis of the “effective contact point” model proposed by the authors for the nonuniform electric field (Li et al., 2019a [1]), the corresponding “effective contact point” model was proposed when the applied original electric field was uniform. Then, the adsorption properties of particles under the action of a uniform electric field and a nonuniform electric field were simulated and compared. The results showed that the “effective contact point” model in uniform electric field was correct, and the adsorption of the particles in the nonuniform electric field was better than that in the uniform electric field. The simulation of the electric field strength at the contact point of ellipsoidal fillers showed that the adsorption capacity of ellipsoidal fillers on particles was higher than that of the sphere fillers within a certain range.
Mesophase pitch production from FCC slurry oil: Optimizing compositions and properties of the carbonization feedstock by slurry-bed hydrotreating coupled with distillation
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So, the high value-added utilization of FCC slurry oil is typically a concern. FCC slurry oil is predominantly rich in polycyclic aromatics [6], and it can be potentially used as the preferred raw material in the production of high value-added mesophase pitch, which is composed of planar disc-like aromatic compound of high molecular weight. The mesophase pitch is regarded as an excellent precursor for making a wide variety of industrial and advanced engineering carbon products [7], such as carbon foam [8,9], needle coke [10], carbon fiber [11,12], Li-ion battery anodes and many more [13].
Slurry-bed hydrotreating coupled with distillation may optimize the compositions and properties of heavy oils, including improving their hydrogen-donating ability of heavy oils. The effects of slurry-bed hydrotreating coupled with distillation on the compositions and properties of FCC slurry oil were determined by various analytical methods. ¹H NMR was used to characterize and determine the hydrogen-donating ability of FCC slurry oil, and the structure of mesophase pitches formed by carbonization of FCC slurry oil were characterized by polarizing microscope, softening point and X-ray diffraction method. The results showed that slurry-bed hydrotreating obviously prevents FCC slurry oil from coking behavior during the distillation process, and overall compositions and properties of FCC slurry oil after optimization meet the requirements for producing mesophase pitch. Most importantly, the hydrogen-donating ability of FCC slurry was drastically increased from 0.392 (mg-H/g-Oil) to 1.917 (mg-H/g-Oil). In turn, in contrast with the raw FCC slurry oil, the slurry oil after the slurry-bed hydrotreating coupled with distillation easily formed mesophase pitch with a large flow domain structure, low softening point, and ordered microcrystal structure through carbonization. Thus, the purpose of preparing high-quality mesophase pitch was achieved.
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However, it is actually a quite promising feedstock for producing a diversity of high value-added products. For instance, these high value-added products could be carbon fiber (Katoh et al., 2004), activated carbon (Goldshtejn et al., 1998), needle coke (Abrahamson et al., 2016; Wang and Eser, 2007), and electrorheological fluids (Dong et al., 2005). The practical applications of SLO are considerably complicated and hindered by the accompanying problematic suspended particles (SPs) resulted from catalyst breakage and coke deposition in the FCC processes.
Suspended particles (SPs) were separated from an FCC Slurry Oil (SLO) via centrifugation with the aid of toluene-dilution. Further solvent extraction of SPs with CS₂/toluene (50 V/V%) mixed solvent would generate solvent extraction insolubles (SEINS) and solubles (SES). They were sent for a series of chemical and structural characterizations, respectively, in the hope of providing clues to address issues from sedimentation and clarification processes. It was found that SPs were composed of catalyst fragments and organic substances wrapped around them, serving as a shield. The characterizations from TEM and XPS strongly suggested that the outer surface of SEINS was sufficient in oxygen-containing sites (organic functional groups and aluminosilicate), while the outer surface of SPs was not. High oxygen content and almost same nitrogen content of SES, comparable with that of asphaltenes, were detected through XPS characterization. This rationalized the strong adsorption of SES on SEINS in the form of a tedious solvent extraction process. A new structure of SPs has thus been described on the basis of these characterizations. Design sedimentation experiments verified the SPs’ structure. Furthermore, the experiments offered a promising way for acquiring high clarification efficiency with rather low usage of sinking agent through solvent pretreatment.
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Electrostatic separation can be used to remove solid particles from fluid catalytic cracking slurry (FCCS). In this study, the electric field distribution, particle behavior and separation efficiency were investigated. Experimental studies covered the tests with separation efficiency given a set of parameters where the voltage was 13, 15, 17, 19, and 21 kV; the filler diameter was 9 mm; and the particle diameter was 2 μm. Simulation studies were conducted with experimental data including the electric field distribution; particle behavior and separation efficiency, where the particle diameter was 2, 5, and 10 μm; the voltage was 15 kV; and the filler diameter was 3 mm. The results showed that the electric field strength at the contact point was related to its position. To predict whether contact points could adsorb particles, an effective contact point model was presented and verified. Most particles were adsorbed at contact points by observing the trajectories of particles, which was consistent with theories. With an increase in the voltage and particle radius, the separation efficiency increased by 6.59% and 28.88%, respectively. The conclusions could be used as the theoretical basis for optimizing the device structure.

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Preparation of high performance electrorheological fluids with coke-like particles from FCC slurry conversion

Abstract

Introduction

Section snippets

Materials

Preparation of ERF

Performance of ERF

Conclusions

Acknowledgements

Petroleum refining engineering

Electrorheological fluids

Sci Am

ER fluid requirements for automotive devices

J Rheol

Electrorheological properties of suspension of carbonaceous particles

J Mater Sci Lett