Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7606303 | Journal of Analytical and Applied Pyrolysis | 2018 | 20 Pages |
Abstract
Petroleum coke (petcoke) contains high carbon and low ash qualities, but often with an undesirably high sulfur content. High-temperature (>1000â¯K) calcination produces a coke, suitable for many industrial uses, with an acceptable S content. Here the sulfur removal behavior during high-temperature pyrolysis was evaluated by combining high-temperature thermogravimetric analysis with product gas mass spectrometry (TG-MS), and reactive molecular dynamics (ReaxFF) simulations. From the TG-MS data the pyrolysis temperature of >1000â¯K significantly affected the S rejection. Three petcokes under 1273-1773â¯K in six different particle sizes (â¤6â¯mm) were pyrolyzed to determine the desulfurization initiation temperature and desulfurization extent. A non-uniform behavior across the particle size ranges was obtained. Six Qingdao petcoke samples with cut sizes of <0.038, 0.07-0.05, 0.11-0.09, 0.25-0.15, 1.18-0.88, and 5.00-6.00â¯mm all achieved a similar desulfurization extent (â¼80%) at >1673â¯K. However, considerable variability was shown in larger particles (1.18-0.88 and 5.00-6.00â¯mm) for Qingdao, Zhenhai, and Qilu petcoke between 1473 and 1773â¯K. The products included water (presumably from coke quench, 350-410â¯K), volatiles (430-550â¯K), CO2 and H2 (>800â¯K, mainly), CO and SO2 (>1200â¯K, mainly), and trace quantities of CS2 (>1400â¯K). The stable sulfur-containing products of this petcoke during high-temperature pyrolysis were SO2 and trace amounts of CS2. However, COS and H2S pyrolysis products were absent or below the detection limits. The pyrolysis behavior was explored using ReaxFF on a macromolecular petcoke structure with the S atoms in thiophene-like functional groups. The mechanism of S loss, under the simulation conditions, involved molecular rearrangement and thermolysis into intermediate states (C2S and CNS) and COS. These were explored for 250â¯ps for 3000, 3500, and 4000â¯K with the constant volume/temperature (NVT) ensemble. The sulfur removal transformation during pyrolysis is generally followed: thiophene sulfurâ¯ââ¯COS, C2S, or CNSâ¯ââ¯HSâ¯ââ¯SO2 or CS2.
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Qifan Zhong, Qiuyun Mao, Jin Xiao, Adri van Duin, Jonathan P. Mathews,