Shunichi Yanai

Viscosity of brown coal-solvent slurry

Abstract The viscosities of coal-solvent slurries which consist of raw brown coal and coal-derived solvent from a two-stage liquefaction process were measured using a high temperature and high pressure viscometer, since viscosity strongly affects the transportation and heat transfer of the slurry. The dependence of slurry viscosity on temperature, coal concentration, and the properties of the recycling solvents was discussed, and equations to estimate and predict slurry viscosities were obtained based on the results of these measurements. The effects of the solvent properties on slurry viscosity were explained by the interaction between the coal and solvents. This interaction is closely related to the content of oxygen-containing compounds in the solvents, and correlates with the atomic ratio of oxygen to carbon of the solvent.

Effects of gas flow rate on brown coal liquefaction with a continuous reactor system. 2. Effects of temperature and vaporization of solvent fraction

Abstract The effects of stripping the solvent and lighter fraction derived from coal under liquefaction conditions were investigated in the presence of iron-sulfur catalyst at temperatures of 420–450°C using a continuous stirred tank reactor (CSTR) system. This was done to clarify the mechanism for the enhancement of brown coal liquefaction by increasing the gas flow rate in the reactors. The increase in the distillate yield was correlated to the prolonging of actual residence time ( θ RT ) of the liquid phase in the reactors due to stripping of the solvent fraction. In addition, the changes in the composition of the liquid phase and the concentration of the catalyst and heavy fraction derived from the coal were also found to influence the yields because, at the same θ RT of the reactor liquid, the increase in the ratio of the gas flow rate to solvent in the feed slurry provided a higher distillate yield than that obtained by decreasing the slurry-feeding rate. The increase in gas hold-up and gas/liquid interface by the gas flow rate did not influence the yield. Based on these results, the enhancement of the liquefaction by the increase in the gas flow rate was ascribed to the stripping of the solvent fraction from the reactor liquids; resulting simultaneously in the prolonged θ RT and the increased concentration of the catalyst used and of the heavy fraction derived from the coal.

Effects of Iron/Sulfur Catalyst and Solvent Property on Yields and Hydrogen Transfer of Victorian Brown Coal Liquefaction

Effects of the amount of iron/sulfur catalyst on yields and hydrogen transfer of Victorian brown coal were investigated using two kinds of process solvents derived from the two-stage brown coal liquefaction (BCL) process; one is a solvent recycled in primary hydrogenation (PY-S, non-hydrogen donor solvent), and the other is a solvent recovered from secondary hydrogenation over Ni-Mo catalyst (SD-S, hydrogen donor solvent). In addition, the influence of hydrogen pressure and reaction time were also investigated using these solvents in the presence of the catalyst.SD-S was effective under non-catalytic and lower hydrogen pressure conditions compared with PY-S, but distillate yield was low under these conditions. On the other hand, PY-S provided higher distillate yield and hydrogen efficiency (defined by ratio of distillate yield to amount of hydrogen transferred to all liquefaction products) than SD-S under the condition of high hydrogen pressure and high catalyst concentration. These results indicate that the effects of the catalyst on liquefaction reaction is small in hydrogen donor solvent, and non-donor solvent is effective under severe conditions. The hydrogen efficiency increased with increases in pressure and catalyst concentration, and showed a peak at the optimum reaction time, which depended on the conditions and solvent properties.

Kinetic study of primary hydrogenation reaction in brown coal liquefaction (BCL) process

Publisher Summary This chapter presents a model for the brown-coal-liquefaction reaction that is constructed using results from the 0.1t/d Process Development Unit (PDU) experiments and shows the applicability of this model to the 50t/d Pilot Plant (PP) results. The calculated yields obtained from the reaction model shows good agreement with the actual experimental yields that prove the validity of the reaction model for the brown-coal-liquefaction reaction. New Energy and Industrial Technology Development Organization (NEDO) and Nippon Brown Coal Liquefaction Co., Ltd. (NBCL) have developed a coal liquefaction process (BCL process) suitable for Australian brown coal. It is a two-stage process that is composed of new slurry-dewatering, primary hydrogenation, de-ashing, and secondary hydrogenation sections. The primary hydrogenation section is the thermal decomposition reaction that occurs mainly in the preheater, and the hydrogenation and hydrocracking reactions occur in the reactors. Many researchers conducted quantitative analysis to describe these reactions, but most are concerned with reactions using bituminous or subbituminous coal. Kinetic study on brown-coal-liquefaction reactions is also reported.

Liquefaction of Victorian Brown Coal with Continuous Reactors II. Effects of Reaction Time and Solvent Properties on Liquefaction Reaction and Actual State in the Reactors.

Victorian brown coal was hydroliquefied with two kinds of solvents in the presence of iron/sulfur catalyst using a process development unit (PDU) with three stirred tank reactors in series.The effects of solvent properties on the progress of the liquefaction reaction and the actual state in the plural reactors were investigated by analysing product yields and liquid samples from each reactor. Vaporization of solvent fraction and actual residence time of the liquid phase in the reactors were also determined by using the results of these analyses.The solvents used were a creosote oil and a recycling solvent recovered from other PDU operations.Oil yield with the recycling solvent in the first reactor was higher than that with the creosote oil although the liquefaction reactions mainly took place in the first reactor with both solvents. However, oil yield through three reactors was almost the same with both solvents. These results indicate that the hydrogen donation from the solvent was effective at the early stages of liquefaction, and the hydrogen shuttling by solvent with catalyst was effective for hydroliquefaction of heavy products such as preasphaltenes derived from the coal. These conclusions were supported by analyses of the amount of transferred hydrogen to the products and liquid phase in the reactor.These results show that the vaporization and actual residence time of hydrogenated solvent were larger than that of non-hydrogenated solvent such as creosote oil.

Effects of solvent properties and reaction conditions on liquefaction of Victorian brown coal.

The effects of solvent properties on the liquefaction of Victorian brown coal were studied using an autoclave with iron oxide/sulfur catalyst under various reaction conditions (temperature: 430°C or 460°C, initial hydrogen pressure: 3, 6, or 12MPa). The solvents used were a recycling solvent (PR-S) and a further hydrogenated solvent (HD-S), a product of hydrogenation with Ni-Mo/Al2O3 catalyst. Results showed that hydrocarbon gas yield and hydrogen gas consumption were lower, and naphtha (b.p.<180°C) yield was higher using HD-S compared with PR-S. At lower hydrogen pressure, the HD-S provided a higher oil (b.p.<420°C) yield than the PR-S, but with more severe conditions (460°C and 12MPa), the PR-S provided the higher oil yield and more hydrogenated heavy products.The amount of transferred hydrogen to all products was the same in both solvents, and depended only on the reaction conditions, however, the distribution of transferred hydrogen was different. The results suggested that the PR-S worked more effectively as a hydrogen shuttler at severe conditions compared with the HD-S which contained a considerable amount of initial donatable hydrogen. Thus, we can conclude that the overall liquefaction efficiency of such solvents depends on the liquefaction conditions.

Effects of moisture content on liquefaction of victorian brown coal.

Since Victorian brown coal contains about 60wt.% moisture, it is necessary to remove the water from the coal before liquefaction. The effects of mois-ture content on liquefaction of the coal dewatered in a recycling solvent (DW-coal) were studied using an autoclave with iron oxide/sulfur catalyst under the following conditions: temperature of 430°C, initial hydrogen pressure of 6MPa and hold time of 1h.When moisture content of the coal decreased, distillate (b.p. 420°C) and naphtha (b.p.<180°C) yields decreased. Gaseous product yields and reaction pressure also de-pended on the moisture content of the coal. Specifically CO/CO2 ratio was strongly affected by the moisture content, which indicated that CO shift reaction occurred and affected the H2 gas consumption.The coal dried with a tubular dryer (TD-coal) was liquefied under the same con-ditions as the DW-coal to compare the coals in reactivity. The reactivity of the TD-coal was lower than that of the DW-coal. According to these results, it is shown that the dewatering in the solvent is profitable for brown coal liquefaction.