Anti-coking property of the SiC^/S coating during light naphtha steam cracking in a pilot plant setup

摘要

On the basis of development in the laboratory, the SiO_2/S coating was prepared on the internal surface of HK40 alloy tube in a pilot plant setup. The coating sampled on the outlet of furnace tube was characterized by scanning electron microscope (SEM). The anti-coking property of the SiO_2/S coating was evaluated with light naphtha according to pressure changes. The morphologies and chemical components of cokes on the outlet of the coated and blank tubes were characterized by SEM and energy dispersive spec-troscopy (EDS), respectively. The main product yields of light naphtha steam cracking were analyzed by gas chromatography-mass spectrometry (GC-MS). The results show that the SiO_2/S coating is compact and has a thickness of 15 Jim on the outlet of furnace tube. The SiO_2/S coating reduces coke yield by 60% compared to that observed in the blank tube during 8 h cracking run. However, the coke reductions of the SiO_2/S coating are both about 40% when the cracking time is 26 h and 66h, respectively. The outlet of the coated tube has the exfoliated coke with a thickness of about 30 um. The coke on the process side has many irregular particles, and the coke on the metal side is not filamentous coke but amorphous coke particles after the exfoliated coke is taken away. The yield of C_2H4 has a slight increase in the coated tube, and the yield of C_4H_8 has a decrease. However, the SiO_2/S coating has little influence on the total yield of olefin.