3588
Energy & Fuels 2007, 21, 3588–3592
A New Technology for Producing Hydrogen and Adjustable Ratio Syngas from Coke Oven Gas Jun Shen* and Zhi-zhong Wang Department of Chemical Engineering, Taiyuan UniVersity of Technology, Taiyuan, Shanxi 030024, P. R. China
Huai-wang Yang and Run-sheng Yao Linfen Townstar Industrial Co, Ltd. Linfen, Shanxi 041000, P. R. China ReceiVed April 26, 2007. ReVised Manuscript ReceiVed August 2, 2007
About 15 billion N m3 coke oven gas (COG) is emitted into the air in Shanxi Province in China as air pollutants. It is also a waste of precious chemical resources. In this study, COG was purified respectively by four methods including refrigeration, fiberglass, silica gel, and molecular sieve. Purified COG was separated by a prism membrane into two gas products. One consists mainly of H2 (>90 vol %) and the other is rich in CH4 (>60 vol %) with their exact compositions to vary with the membrane separation pressure and outlet gas flow ratio. The gas rich in CH4 was partially oxidized with oxygen in a high-temperature fixed-bed quartz reactor charged with coke particles of 10 mm size. At 1200–1300 °C, a CH4 conversion of >99% could be obtained. The H2/CO ratio in the synthesis product gas can be adjusted in the range 0.3–1.4, very favorable for further C1 synthesis.
1. Introduction Since 1993 China has been the largest coke producer. In 2004, the coke production in China was 209 million tons and accounted for 49% of the total in the world. While a large number of independent coking plants were built, the concomitant coke oven gas (COG) could not be utilized effectively. About 29–30 billion N m3 COG was discharged into the air annually, equivalent to 2 times the west-to-east throughput of the natural gas transportation project in China. These discharges not only pollute the environment but also waste precious fossil fuel resources heavily. There are abundant H2 and CH4 in COG, about 60 and 25 vol %, respectively. The efficient use of COG is a serious problem. At present, some plants use pressure swing adsorption (PSA) to get hydrogen from COG. However, more economical ways to recover hydrogen from COG would be required in the future.1 The use of membranes in gas separations has grown at a very rapid pace in recent times due to its inherent advantages over the more traditional methods. These include low capital and operating costs, low-energy requirements, and generally ease of operation.2–4 However, there have been no reports on the application of membrane separation COG, possibly due to the complicated nature of COG. Methane partial oxidation is an attractive route to convert methane into synthesis of liquid fuel and valuable chemicals.5 Partial oxidation of methane into syngas proceeds quite effectively on many catalysts, mostly containing a high loading * To whom correspondence should be addressed: Tel 0086-351-6014955; Fax 0086-351-6018701; e-mail
[email protected]. (1) Onozaki, M.; Watanabe, K.; Hashimoto, T.; Hitoshi, S.; Yukuo, K. Fuel 2006, 85, 143–149. (2) Wang, R.; Cao, C.; Chung, T. J. Membr. Sci. 2002, 198, 259–271. (3) Pratibha, P.; Chauhan, R. S. Prog. Polym. Sci. 2001, 26, 853–893. (4) Asad, J. Chem. Eng. J. 2005, 112, 219–226. (5) Sokolovskii, V. D.; Coville, N. J.; Parmaliana, A.; Eskendirov, I.; Makoa, M. Catal. Today 1998, 42, 191–195.
of noble metals, but only selected catalysts show more or less stable performance. In recent years, catalytic partial oxidation of methane (POM) to synthesis gas has been extensively investigated for natural gas utilization. The POM process has great promise to replace the current strongly endothermic and slow process that is for the production of synthesis gas. POM is mildly exothermic and can produce syngas of a molar ratio of H2/CO of 2/1, which can be directly used as feed for methanol synthesis or the Fischer–Tropsch synthesis. Moreover, the POM process can greatly speed up the production of syngas since it can be operated at very high space velocities of (1.0–5.0) × 105 h-1.6–8 However, the catalysts deactivation and poison are also a severe problem during the POM process. In this study, the COG was first purified and separated by prism membrane. The product gas rich in CH4 was then converted to syngas by partial oxidation at high temperature in a fixed-bed quartz reactor charged with coke particles. The coke particles can be obtained easily in coke making plant because lots of coke particles with a size 99 vol %. In the products, CO and H2 content are in the ranges 40–75 and 20–55 vol %, respectively. The H2/CO ratio is 0.3–1.4 and can be adjusted by changing reaction conditions. The (H2 + CO) percent in products can be 96 vol % with 4 vol % N2. The synthesis gas is suitable for producing precious chemicals. Acknowledgment. The authors acknowledge the financial support from Linfen Townstar Industrial Co., Ltd., China, and the collaboration with their engineers for conducting the experiments. EF700217J
