Motoharu Yasumuro

Complete conversion of brown coal into distillate

The conditions for complete conversion of Victorian brown coal were investigated with an iron-sulfur catalyst in a continuous reactor system consisting of three stirred tank reactors in series. The coal was found to be completely converted into distillate (b.p. < 420°C) when the gas flow rate (GFR) through the reactors was increased and the slurry-feed rate was reduced at a temperature of 450°C and a pressure of 18.6 MPa. An analysis of the composition of the liquid in the reactors under liquefaction conditions confirmed that the increase in GFR markedly enhanced the stripping of the solvent fraction in the feed slurry and the lighter fraction derived from the coal, resulting in marked increases in the actual residence time (θ RT ) of the liquid consisting of the concentrated catalyst and heavy fraction. The stripping effect markedly enhanced liquefaction reactions, thus providing a higher distillate yield. However, the GFR effect was gradually saturated as the liquid remaining in the reactors (reactor liquid) became heavier with the increase in the GFR. The extension of nominal residence time (defined by the ratio of slurry-feed rate to reactor volume, θ NT ) from reduction of the slurry feed rate was found to be effective in extending the GFR effects under a high GFR condition, resulting in the complete conversion of the coal. In addition, the stripping of the solvent by the increased GFR was also found to be more enhanced at 18.6 MPa than that at 14.7 MPa although its vaporization was suppressed at a higher pressure. This is due to the heavy fraction in the reactor liquid being more hydrogenated over the concentrated catalyst at a higher hydrogen pressure. However, the dependencies of the conversion rate of the heavy fraction on θ RT were almost the same for both 14.7 and 18.6 MPa. These results suggested that a complete conversion of the coal could be achieved at 14.7 MPa by using a heavier 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.

Hydrogen transfer in brown coal liquefaction in BCL process --: Influence of catalyst and feed solvent properties on liquefaction performance and hydrogen transfer --

Publisher Summary This chapter discusses the relationship between hydrogen transfer and liquefaction yields of the brown coal under the conditions varied in temperature and pressure and the role of the catalyst and solvent to estimate the efficiency of the transferred hydrogen. The results obtained are as follows: (1) Hydrogen-donor solvent recovered from the secondary hydrogenations (SH) section is effective in the initial stage of the liquefaction and suitable for the liquefaction under mild conditions. The transferred hydrogen plays an important role in these conditions. However, it does not provide a higher distillate yield without the catalyst, (2) Nondonor solvent recycled in the primary hydrogenation (PH) is suitable for the liquefaction under severe conditions, and (3) Hydrogen transfer to the products increases with an increase in the severity of the liquefaction conditions. However, at higher temperatures, the hydrogen efficiency decreases due to an increase in C1–C4 gas yield. The hydrogen transfer and efficiency are quantitatively evaluated by the calculation of the hydrogen balance before and after the liquefaction.

EFFECTS OF QUANTITY AND QUALITY OF SOLVENT ON REACTION OF BROWN COAL LIQUEFACTION

Publisher Summary Coal concentration of the feed slurry is one of the most important factors in determining the efficiency of the liquefaction process. It should be kept as high as possible to increase the volumetric efficiency of the reactors. If the coal to solvent ratio of the slurry can be increased, the process will be largely improved from the viewpoint of cost-saving and efficiency of the process. This chapter discusses a study to examine the effects of quantity and quality of solvent on reaction of brown coal liquefaction. Yallourn coal from Victoria, Australia, was liquefied with the Process Development Unit consisting of three stirred tank reactors in series. An increase in gas-flow rate through the reactors, by recycling the gas from the gas–liquid separator, provided a very high yield of distillate.

Liquefaction of Victorian Brown Coal with Continuous Reactors. (IV). Effect of Preheating Conditions on Liquefaction Yields.

The effect of preheating conditions on the liquefaction reaction of Victorian brown coal (Yallourn) was investigated using a process development unit (PDU) with three stirred tank reactors and three preheaters connected in series. Four kinds of solvents (RS, RS +CLB, RS+HDAO and RS+CLB +HDAO) were used for liquefaction to examine the relationship between the solvent properties and the effect of the preheating conditions. RS, CLB, HDAO were the recycled solvent fraction (b. p.180-420°C), heavy liquefaction product derived from the brown coal (coal liquid bot-tom, b. p.>420°C) and coal liquid product further hydrogenated over Ni-Mo catalyst (b. p.<250°C), respectively. For all experiments, the liquefaction was carried out in the presence of iron-sulfur catalyst (Fe2O3, S/Fe atomic ratio 1.2) under the conditions of temperature 450°C and pressure 14.7 MPa.When the feed slurry was preheated up to 410°C for- 2 min. with hydrogen gas of 10 wt. % on daf coal, the distillate yield (b.p.<420°C) decreased 5-13 wt.% on daf coal for all kinds of the solvent in comparison with the case where reaction at the pre-heating stage was negligible. The decrease in the distillate yield resulted from the sup-pression of the conversion of the heavy fraction (CLB) into the solvent fraction (180-420°C). At the preheating stage, CO2 and H2O evolved and the coal of 20-30 wt % converted to preasphaltenes (benzene insoluble-pyridine solubles). The oxygen-contain-ing functional groups decomposed rapidly at more than 350°C, resulting in the formation of many radicals in the coal (Plorg.). Since the greater part of the coal remained as pyridine insolubles (Plorg.), the retrogressive reaction caused by the radicals in the Plorg. was considered to reduce the conversion of the heavy fraction into the distillate at the liquefaction stage.Based on these results, it is concluded that the usual preheating conditions of the liquefaction process decreased the liquedaction performance. This indicates that the distillate yield increases if the retrogressive reaction at the preheating stage is suppres-sed by controlling the preheating conditions and solvent quality such as hydrogen donor ability and catalyst activity.

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.