An Analysis Of Catalyst Selection And Process Operation For Primary Steam Reforming

Brown process for ammonium synthesis was a advanced technology in 1990's, which was characterized by its low temperature purification system. It allows the primary steam reforming operate in a relative lower temperature and lower methane conversion degree. However, the new design of the primary reforming section requires special properties of the catalyst used. Zlll/CN-16 catalysts produced by Xinan Institute of Chemical Industry are commercial catalyst popularly used in. China. They were firstly used in a 300 kt/a Brown system of Sichuan Tianhua Company Limited, China. It was found that the pressure drop of reforming catalyst bed raised after one year industrial operation. From the appearance of the catalyst discharged, the mechanical strength failure of the catalyst was induced by carbon deposit. The aim of this work, is to find a suitable catalyst for the Brown primary reforming. According to the discussion about the reaction parameters and operation characters, Z112-1Q/2Q catalysts produced by Sichuan Chemical Plant can satisfied the special requirements for the Brown primary steam reforming operation.Both Z112-1Q and Z112-2Q catalysts are spherical catalysts, there are 7 and 3 holes opened inside them individually. The former is a larger sphere with a diameter of 16-17 and other is a small sphere with a diameter of 12-13. The fluid dynamics and reaction kinetics were discussed in this paper. Considering the special structure of the Brown primary reformer, a double layers filling method was used. The Z112-1Q catalyst was packed in the lower part of the reaction tube and the Z112-2Q was used in the upper section. By strictly controlling the filling program and the balance of tubes, the catalyst bed showed a good activity and flow patterns. Under a strict operation of reduction and oxidation, the new packing method and new catalysts are showed to be a successful selection.Through an analysis of the chemical and physical properties of the Z112-1Q/2Q, it is believed that the opened pores inside the catalyst balls enhanced the mass andheat transfer process. At the same time, the rare earth oxide contained in the catalyst is obviously helpful to ease the carbon deposit. The operation parameters of the new catalysts are water/carbon ratio 2.5, pressure = 0.7-4.0 MPa, temperature = 450-850. In the 3 years industrial operation, the new catalyst kept good catalytic activity. The spherical shape and regular packing of the new catalyst induced a good fluid behavior. The pressure drop was kept below 320 kPa after 3 years continuous operation. The results show that the selection of new catalysts and new packing method is suitable to the primary steam reforming of Brown process.