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Abstract Using the self-developed viscosity measuring device, the viscosity variations of coal–oil slurries with temperature increasing during coal–oil co-processing were studied. The results show that the viscosity of coal–oil slurries prepared by different kinds of oil varies differently during heating. The viscosity of the coal–oil slurry prepared by the catalytic cracking slurry (FCC) generally decreases during heating. However, the viscosity of the coal–oil slurry prepared by the high-temperature coal tar (CT) will peak at 338 °C during heating. The differences in viscosity variations of coal–oil slurries are analyzed. In addition to the temperature, the properties of the solvents and coal are the main influencing factors. Because the used coal contains a large number of polar functional groups, the swelling behavior of the coal in polar solvent (CT) is stronger than that in non-polar solvent (FCC). The swelling effect of the coal can result in the appearance of the viscosity peak. Therefore, before 100 °C, the solvent molecules entering into the coal pores is the main influencing factor of coal–oil slurries viscosity variations. After 100 °C, the increasing of particle size of coal particles is the main influencing factor of coal–oil slurries viscosity variations.

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Using the self-developed viscosity measuring device, the viscosity variations of coal-oil slurries with temperature increasing during coal-oil co-processing were studied. The results show that the viscosity of coal-oil slurries prepared by different kinds of oil varies differently during heating. The viscosity of the coal-oil slurry prepared by the catalytic cracking slurry (FCC) generally decreases during heating. However, the viscosity of the coal-oil slurry prepared by the high-temperature coal tar (CT) will peak at 338 °C during heating. The differences in viscosity variations of coal-oil slurries are analyzed. In addition to the temperature, the properties of the solvents and coal are the main influencing factors. Because the used coal contains a large number of polar functional groups, the swelling behavior of the coal in polar solvent (CT) is stronger than that in non-polar solvent (FCC). The swelling effect of the coal can result in the appearance of the viscosity peak. Therefore, before 100 °C, the solvent molecules entering into the coal pores is the main influencing factor of coal-oil slurries viscosity variations. After 100 °C, the increasing of particle size of coal particles is the main influencing factor of coal-oil slurries viscosity variations. [ABSTRACT FROM AUTHOR]

To determine coal-oil slurry apparent viscosity accurately, establish unified determination method of coal-oil slurry apparent viscosity, investigate the rheological behavior of various coal liquefaction coal-oil slurry in different situations. Study the influence of shearing speed, measuring temperature, standing time of samples, start time of evaluation on apparent viscosity of coal-oil slurry. Confirm the method precision. The best condition is that, the shearing speed is 100 s-1,the measuring temperature is 60 °C. Under this condition, the apparent viscosity should be measured immediately. First, start the rotational viscometer, eleven minutes later, begin to record the value, the frequency of recording is 10 seconds, totaling thirty measurements. The results should be given in round figures. The repeatability limit r = 0.13η100s-1-4.30. Limited by instruments and time, the measuring method doesn't instruct the reproducibility. [ABSTRACT FROM AUTHOR]

Abstract: Heating coal-oil slurry (COSL) is an important step in direct coal liquefaction. Some physical and chemical properties of COSL including its viscosity will change during heating. A rotary viscometer was self-designed to measure the viscosity of COSL under high pressure and temperature. Three kinds of coal, which are Yanzhou coal (middle rank and caking), Shenhua coal (low rank and non-caking) and Shengli coal (brown coal), were mixed with anthracene oil to prepare the COSL. The COSL from Yanzhou, Shenhua and Shengli at the same experimental conditions showed different viscosity variations under high hydrogen pressure during heating. Yanzhou COSL had a higher viscosity peak, while Shenhua COSL had two small viscosity peaks and in the case of Shengli COSL, no viscosity peak was present under a high hydrogen pressure during the whole heating process. The coal nature is the important factor of viscosity variations of COSL. The higher the coal rank, the more caking coal is present, and the more obvious the viscosity variations of the COSL are. [Copyright &y& Elsevier]

The viscosity and stability of coal-oil slurry (COS) with different concentrations prepared by recycle solvent and low-rank coal were investigated. The effect of light solvent naphtha preheating treatment on the viscosity-temperature characteristics of high-concentration COS and properties of pulverized coal was studied. Results show that when the concentration is higher than 48 wt%, the viscosity and swelling viscosity peak value of conventional COS increase exponentially, resulting in the significant deterioration of the stability of COS. The concentration of COS can be increased to 50 wt% by preheating with light solvent. With the increase of preheating temperature and time, the viscosity of COS decreases as a whole. The viscosity of high-concentration COS with the optimum preheating temperature of 375 °C and time of 4 h is 383 mPa·s (60 °C), which is 30% lower than that of conventional COS (543 mPa·s (60 °C)) with 50 wt%. Due to the influence of the full swelling, irreversible swelling, and primary pyrolysis of pulverized coal, the physical structure and chemical composition of pulverized coal changes, the swelling viscosity peak no longer appears, and the stability of COS is improved. • A preparation method of high-concentration coal-oil slurry is proposed. • Preheating with light solvent changes the physical structure and chemical composition of coal. • Pretreatment can increase concentration to 50 wt%, reduce viscosity to 383 mPa·s (60 °C), and eliminate swelling viscosity peak. [ABSTRACT FROM AUTHOR]

• Correlations between swelling behavior and noncovalent interactions were established. • Strength of π–π stacking ability of liquefaction solvents was quantified for first time. • 1,2–dihydronaphthalene had largest degree of π electrons delocalization. • Strength of noncovalent interactions should be taken into account in design of liquefaction solvents. Noncovalent interactions have achieved extensive attentions in thermal conversion of low rank coal, but have been little studied in direct coal liquefaction (DCL). In order to investigate strength of noncovalent interactions (hydrogen bonds and π–π stacking) between lignite and DCL solvents, experimental methods and DFT (density function theory) calculations were utilized. Aromatic components in industrial recycled solvents have been selected, including tetralin, 1,2–dihydronaphthalene (DHN), indane, 1–methylnaphthalene, naphthalene, indene and benzene. On one hand, total strength of noncovalent interactions between those aromatic components and lignite were integrally evaluated by swelling ratio determination. On the other hand, Spatial distribution and strength of noncovalent interactions were investigated by RDG (reduced density gradient) analysis, CVB (core–valence bifurcation) index and LOLIPOP (localized orbital locator integrated pi over plane) index, respectively. Overall, addition of DHN, indane and benzene resulted in significant swelling of lignite. Swelling of lignite in benzene and others (DHN and indane) was enhanced by stronger OH–π hydrogen bonds and π–π stacking, respectively. By conjoint study of swelling ratio and DFT calculations, both hydrogen bonds and π–π stacking play crucial roles in swelling of lignite. Adjustment of noncovalent interactions should be taken into account during design of DCL solvents, based on correlations between noncovalent interactions and structural characteristics of aromatic components. [ABSTRACT FROM AUTHOR]

• Preheating treatment at suitable temperatures can improve fluidity and SHR of COS. • Influence mechanism of preheating treatment was investigated. • Preheating treatment can change coal's structure by enhancing swelling effect. • Expansion of coal's structure and release of light components are key factors. The effects of preheating treatment at temperatures from 200 to 350 °C on the viscosity–temperature properties and slurry-phase hydrogenation reactivity (SHR) of a coal-oil slurry (COS) prepared from Xinjiang lignite and fluid catalytic cracking slurry were studied. Moreover, the structural changes to the coal after preheating treatment were characterized to reveal the origin of preheating treatment effects. As the preheating temperature increased, the viscosity of COS increased, and the sudden increases in the COS viscosity at 160 °C and 240 °C disappeared, improving the fluidity of COS. Moreover, as the preheating temperature was increased, the SHR of the COS increased with increasing preheating temperature up to 300 °C, but decreased when a temperature of 350 °C was used. Structural characterization of the coal showed that increasing the preheating temperature up to 300 °C enhanced coal swelling, promoting expansion of the coal structure, which in turn increased its average particle size, specific surface area, and porosity. The increased release of light components in the coal, which had relatively high and stable contents of ortho -substituted aromatic rings and methyl and methine groups, was also observed with increasing preheating temperatures of up to 300 °C. The irreversible swelling of the coal induced by preheating treatment was responsible for the improved fluidity and enhanced SHR of the COS. However, the pyrolysis of coal occurring at 350 °C decreased the specific surface area and porosity of coal, causing a reduction in contact between the coal and catalyst sites and decreasing the SHR of COS. [ABSTRACT FROM AUTHOR]