The effects of solvent/coal ratio on slurry viscosity and liquefaction reaction of Victorian brown coal were investigated using a solvent derived from the primary hydrogenation of the two-stage brown coal liquefaction (BCL) process. The liquefaction reaction was carried out in the presence of iron/sulfur catalyst with an autoclave of 5 L. The amount of catalyst added was 3 wt% on moisture and ash free (maf) coal as Fe, and the S/Fe atomic ratio was 1.2. The slurry viscosity was measured under N2 pressure with a high temperature and pressure viscometer. The distillate yield (b.p.<420°C) and hydrogen efficiency increased and the C1-C4 yield decreased with a decrease in the solvent/coal (maf) ratio ranging from 3.0 to 1.7. The effects of the ratio was large at high temperature (460°C) compared to that at low temperature (430°C). The slurry viscosity increased with the decrease in the ratio and decreased monotonically as temperature increased. These results show that the solvent/coal ratio of the feed slurry in the brown coal liquefaction process should be small when the slurry can be transported by a pump for the liquefaction because it improves the efficiencies of processing, hydrogen consumption and distillate yield.
In order to clarify the influence of outlet hole of a mixing chamber on the atomization by the internal mixing twin-fluid atomizer, visualization of the flow pattern within the mixing chamber and measurement of the Sauter mean diameter were made under the condition of various outlet hole diameters, ratios of outlet hole length and diameter, positions of the outlet hole and numbers of the outlet holes. The changes of the outlet hole have an effect on the flow pattern within the mixing chamber and the Sauter mean diameter especially at the low atomizing air/water mass ratio. Since the water is mixed with the atomizing air in the mixing chamber well by using an eccentric outlet hole, the atomizer with an eccentric outlet hole produces smaller Sauter mean diameter than that of the atomizer with a center outlet hole. The ratio of outlet hole length and diameter influences the Sauter mean diameter. When the water injected into the outlet hole as a column state, the ratio of outlet hole length and diameter is required to be longer than 2 for efficient atomization.
The liquefaction of powdered rice straw, suspended in an aqueous solution of sodium carbonate or potassium carbonate as a catalyst, was examined at temperatures ranging from 250 to 376°C, and with reaction times 0, 30 and 60 min. by using a convenient small-sized tubing-bomb as a reactor. Separation procedure of the reaction mixtures is demonstrated in Fig. 1. The effect of reaction temperature on the yield of products, using sodium carbonate, is shown with different reaction times in Fig. 2. The oleaginous substance O-1 and O-2 are the major parts of the liquefaction products. The whole oily products, the sum of O-1, O-2, O-3 and O-4, increase with the rise in temperature until 350°C, ranging from 6% (250°C, 0min.) to 27% (350°C, 60min.) of the original weight of rice straw, while the case at 376°C, a super-critical temperature of water, is exceptional. Similarly, the temperature-dependence of the yield of products, using potassium carbonate, is shown in Fig. 3, with different reaction times. The yield of main oily product O -1 increases with the rise in reaction temperature. Potassium carbonate is slightly better than sodium carbonate as a catalyst.(Fig. 4) The effect of addition of organic solvent, e. g. acetone, on the yield of main oily product O-1 is shown in Fig. 5. The yields, elementary compositions and heating values of oily products O-1 and O -2, which obtained under various reaction conditions, are listed in Table 1.