Hydrogen transfer in brown coal liquefaction in BCL process --

Coal Science

J.A. Pajares and J.M.D. Tasc6n (Editors) 9 1995 Elsevier Science B.V. All rights reserved.

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H y d r o g e n t r a n s f e r in b r o w n coal l i q u e f a c t i o n in B C L p r o c e s s -- Influence of catalyst and feed solvent properties on liquefaction performance and hydrogen transfer-Osamu OKUMA a, Motoharu YASUMURO b' Tetsuo MATSUMURAb and Shnichi YANAIc apolymer & Chemical Technology Laboratory, Kobe Steel, Ltd. Takatsukadai 1-5-5, Nishi-ku, Kobe 651-22, Japan bNippon Brown Coal Liquefaction Co., Ltd. (c/o Kobe Steel, Ltd., Takasago Works) Niihama 2-3-1, Arai-cho, Takasago, Hyogo 676, Japan CNew Energy and Industrial Technology Development Organization (NEDO) Higashi-Ikebukuro 3-1-1, Toshima-ku, Tokyo 170, Japan 1. INTRODUCTION A two-stage brown coal liquefaction (BCL) process has been developed for Victorian brown coal in Australia by Nippon Brown Coal Liquefaction Co.(NBCL). As shown in Fig. 1, in this process, the coal is liquefied in the primary hydrogenation (PH) section using a disposable iron/sulfur catalyst and a mixture of the solvents from both the primary and secondary (SH) hydrogenations to obtain high distillate yield under mild liquefaction conditions[ 1]. The amount of hydrogen transferred among the coal, solvent and H2 gas is a crucial factor to determine the liquefaction performance of the process. This paper discusses the relationship between hydrogen transfer and liquefaction yields of the brown coal under the conditions varied in temperature and pressure and focuses on the role of the catalyst and solvent to estimate the efficiency of the transferred hydrogen.

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1236 2. EXPERIMENTAL Morwell brown coal was used for liquefaction. It contained 10.7 wt.% moisture, 2.4 wt.% ash, and C 67.8, H 4.8, N 0.6, S 0.3 and O 26.3 (diff.) on moisture and ash free (maf-C) basis. The solvents (b.p. 180-420~ used were the recycled solvent in the PH section and the recovered solvent from the SH section. These solvents were prepared using each process development unit. Table 1 shows the properties of these solvents. The catalyst used was Fe203 and sulfur (S/Fe atomic ratio 1.2). The liquefaction was carried out using a 5L magnet-driven autoclave under the conditions shown in Table 2. Product yields were calculated for naphtha (b.p.<180 ~ solvent (b.p. 180-420~ CLB (coal liquid bottom, b.p.>420~ H20, C1-C4, CO and CO2 [2]. Hydrogen transfer was evaluated by the following method. AH2:H2 gas consumption H(t): Amount of transferred hydrogen from feed solvent and H2 gas to total liquefaction products, H(t)= AH2- H(s). H(s): Change in hydrogen content of feed solvent, H(t)= Ws.(Cp-Cf), Ws: Weight of feed solvent, Cp: hydrogen content of feed and recovered solvent, Cf: hydrogen content of recovered solvent. *Negative value of H(s) gives transferred hydrogen from feed solvent to products. H(p): Amount of hydrogen contained in produced d i s t i l l a t e (b.p.< 420~ DY/H(t): Distillate yield per unit H(t), *Efficiency of hydrogen consumption on d i s t i l l a t e production. H(p)/H(t): Amount of hydrogen in produced d i s t i l l a t e per unit H(t), *Efficiency of transferred hydrogen to distillate.

Table 1 Properties of feed solvents Solvent

Ultimate Analysis (wt%) Stractural Parameters C H N S O(diff.)H/C fa o Hau/Ca Ln P-1" 8 9 . 2 7.6 0.7 0.2 2.3 1.01 0 . 7 2 0.24 0.86 2.00 P-2" 8 8 . 3 7.7 0.6 0.2 3.2 1.04 0 . 7 2 0.27 0.90 1.90 S-1 b 8 9 . 4 9.0 0.2 <0.1 1.4 1.19 0 . 5 7 0.35 0.90 2.63 S-2 b 9 0 . 1 9.5 0.2 <0.1 0.2 1.25 0 . 5 3 0.35 0.90 2.83 a: Recycle solvent in primary hydrogenation using iron/sulfurcatalyst with PDU. b: Recovered solnent from secondary hydrogenation over Ca-Ni-Mo catalyst with PDU.

3. Results and discussion 3.1. Influence of catalyst and solvent property (Run A series) As shown in Table 2 and Fig.2, the liquefaction reaction was accelerated and the distillate yield (DY) increased by addition of the catalyst in both feed solvents (P-I, S-l) although the effect of the catalyst on the DY was larger in P-1 than in S-1. The yields of H20, CO and CO2 were little affected by the catalyst and feed solvent properties. The S-1, a hydrogen-donor solvent, provided higher DY than the P-1 at the lower catalytic condition and/or shorter reaction time. The P-1 provided higher DY than the S-1 at the higher catalytic condition and longer reaction time. This is because the hydrogen transfer from the donor solvent (expressed by negative value of H(s) in the S-1) is fast and plays an important role in non-catalytic liquefaction, and the catalyst is more effective in the non-donor and high aromatic solvent (P-l) and plays an important role in conversion of the CLB to the solvent fraction [2]. AH2 and H(t) were markedly increased with addition of the catalyst although they were saturated above its concentration of 3 wt.% on maf-C as Fe. C1-C4 gas yield was suppressed

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Table 2 Liquefaction conditions, yields and transferred hydrogen Run A S e r i e s Conditions- Temp. 430 ~ H2 int. press. 6 MPa, Feed solv/maf-C (wt/wt) 2.5 Run Solv." Cat. b T i m e Yields(wt% on maf-C) Transferred Hydrogen (wt% on mar-C) (wt%) (min) CLB Solv. Naph.Cl-C~ DY c AH2 H(s) H(t) H(p) H(p)/H(t) RA-OI P-I 1.5 0 74.5 -3.2 5.2 2.4 2.0 2.25 0.15 2.10 0.33 0.16 RA-02 3.0 69.2 3.1 6.8 2.3 9.9 2.61 0.25 2.36 0.99 0.42 RA-03 5.0 62.9 7.2 6.5 2.3 13.7 2.83 0.50 2.33 1.26 0.54 RA-04 i0.0 58.4 12.7 7.9 1.9 20.6 2.90 0.52 2.37 1.87 0.79 RA-11 P-I 0 60 76.6 -13.1 6.6 6.5 -6.5 1.88 -0.03 1.91 -0.19 RA-12 1.5 53.7 6.0 12.7 6.7 18.7 3.44 0.32 3.11 2.02 0.65 RA-13 3.0 48.6 15.0 10.9 6.0 25.9 3.80 0.50 3.30 2.57 0.78 RA-14 5.0 44.3 18.2 10.4 6.0 28.6 4.06 0.60 3.46 2.69 0.78 RA-15 i0.0 37.5 27.4 11.7 5.4 39.1 4.07 0.60 3.47 3.54 1.02 RA-21 S-1 0 0 70.9 -2.3 9.7 2.2 7.4 0.46 -2.25 2.71 1.03 0.38 RA-22 3.0 66.0 2.4 9.8 2.3 12.2 1.78-1.68 3.46 1.38 0.39 RA-23 i0.0 59.3 9.6 9.8 2.1 19.4 2 . 1 8 - 1 . 0 8 3.25 2.09 0.64 RA-31 S-1 0 60 58.9 -3.3 11.2 6.6 7.9 0 . 9 3 - 2 . 8 8 3.81 1.14 0.30 RA-32 3.0 47.6 13.5 13.6 4.5 27.1 2.24 -1.98 4.21 3.52 0.84 RA-33 i0.0 45.5 6.5 22.9 4.5 29.4 2.69 -1.70 4.39 3.30 0.75 a- See Table i, b- Fe203, wt% on maf-C as Fe, S/Fe atomic r a t i o 1.2, c" D i s t i l l a t e yield (b.p. <420~ -- Naphtha (b.p.<180~ y i l d + Solvent (b.p. 180-420 ~ Run B S e r i e s Conditions" Reaction (hold) time 60 min, Cat.(Fe2Oa) 3 wt% on maf-C as Fe, S/Fe 1.2 Run Solv. Press d Temp. Yields(wt% on maf-C) Transferred Hydrogen Kind e Ratio' (MPa) ( ~ CLB Solv. Naph. CI-C4 DY AH2 H(s) H(t) H(p)H(p)/H(t) RB-OI P-2 250 3 430 63.5 2.0 10.6 6.3 12.6 2.53 -0.24 2.77 1.04 0.37 RB-02 S-2 54.9 7.9 13.9 5.2 21.8 1.45 -1.45 2.90 1.95 0.67 RB-11 P-2 250 3 460 62.5 -12.6 15.4 16.6 2.8 3.44 -1.04 4.48 RB-12 S-2 46.9 -1.6 22.2 13.3 20.8 2.22 -2.41 4.63 2.37 0.51 RB-21 P-2 250 6 430 53.2 14.8 9.6 5.0 24.4 3.64 0.31 3.33 2.03 0.61 RB-22 P-2/S-2 150/100 52.4 15.2 10.3 5.1 25.5 2.85 -0.64 3.49 2.30 0.65 RB-23 S-2 250 47.4 18.7 11.3 4.0 30.0 2.49 -1.08 3.57 2.31 0.64 RB-31 P-2 250 6 460 40.3 11.6 16.0 14.1 27.6 5.13 0.07 5.06 2.68 0.52 RB-32 P-2/S-2 150/100 39.5 15.7 14.7 12.2 30.4 4.14 -0.96 5.10 2.99 0.57 RB-33 S-2 250 37.3 12.9 20.9 11.7 33.8 3.40 -1.38 4.78 3.32 0.69 RB-41 P-2 250 12 430 46.4 21.1 10.5 5.8 31.6 3.83 0.89 2.94 3.01 1.02 RB-42 P-2/S-2 200/50 45.7 20.5 11.3 5.1 31.8 3.70 0.38 3.32 3.08 0.93 RB-43 S-2 250 45.5 19.6 13.0 4.0 32.6 3.21 -0.12 3.33 2.66 0.79 RB-51 P-2 250 12 460 26.5 27.2 16.8 12.9 44.0 6.18 0.77 5.41 4.17 0.77 RB-52 P-2/S-2 200/50 27.4 21.8 20.4 12.4 42.2 6.11 0.43 5.67 4.42 0.77 RB-53 S-2 250 33.2 18.8 20.9 9.7 39.7 4.82 -0.43 5.25 3.88 0.74 d" H2 i n i t i a l pressure at room temp., e: See Table 1, f- wt% on maf-C (Solv/maf-C 2.5, wt/wt)

by the catalyst and hydrogen-donor solvent (S-l), and every/kH2 in the S-1 was smaller than that in the P-1. However, H(t) in the S-1 was larger than that in the P-1, and hydrogen efficiencies (DY/I-I(t), H(p)/H(t)) were smaller in the S-1 than in the P-1 as shown in Fig. 2 and Table 2. This is because the S-1 provided higher naphtha yield and the liquid products (CLB, solvent and naphtha) of higher hydrogen content compared with the P-1. 3.2 Influence of temperature and hydrogen pressure (Run B series) Table 2 and Fig. 3 shows the results of the liquefaction under the conditions varied in

1238 temperature and hydrogen pressure in the presence of the catalyst of 3 wt.% on maf-C as Fe. In both hydrogen-donor (S-2) and non-donor (P-2) solvents, the DY increased with an increase in the hydrogen pressure. However, the effect of the hydrogen pressure on the DY was larger in P-2 than in S-2. The S-2 provided higher DY than the P-1 at lower temperature and lower hydrogen pressure. The P-2 provided higher DY than the S-1 at higher temperature and higher hydrogen pressure. The effect of the solvent properties on the hydrogen transfer ( A H2, H(t), H(s)) was similar to that mentioned above. The S-2 gave higher DY/H(t) and H(p)/H(t) at lower hydrogen pressure, and the P-2 gave them at higher hydrogen pressure. In both solvents, a lower temperature (430~ gave higher hydrogen efficiency because C ]-Ca gas yield increased markedly at a higher temperature (460~ The mixture solvent of the P-2 and S-2 which are used in the PH section of BCL process gave the results between those of the P-1 and S-1 as shown in Table 2. 12

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4. CONCLUSION This study made clear the influence of the important liquefaction factors such as the catalyst, hydrogen-donor ability of the solvent and conditions (temperature, hydrogen pressure and reaction time) on the performance and hydrogen transfer of the brown coal liquefaction in BCL process. The results obtained are as follows; (1) Hydrogen-donor solvent recovered from the SH section is effective in the initial stage of the liquefaction and suitable for the liquefaction under mild conditions. This is because 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 PH section is suitable for the liquefaction under severe conditions. (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 calculation of the hydrogen balance before and after the liquefaction. REFERENCES 1. O.Okuma, et al., Fuel Processing Technology, 14 (1986) 23-37 2. O.Okuma, et al., Nenryo-kyokai-shi (J. Fuel Society, Japan), 69 (1989), 46-55