Oxidation characteristics of soot in different entrained flow gasification processes
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摘要: 利用高分辨透射显微镜分别对煤和生物质快速热解炭黑、天然气非催化部分氧化小试装置炭黑和工业装置炭黑、商业天然气炉法炭黑和煤焦油炉法炭黑等六种样品的形貌结构进行了表征;基于常压热重分析仪非等温法(50−800 ℃)对炭黑的着火点、氧化反应速率进行了研究,获得了炭黑的氧化反应动力学参数。研究表明,不同的炭黑理化性质差异较大,煤和生物质快速热解炭黑的球形度更高,粒径较大;天然气非催化部分氧化小试装置炭黑在较低温度下形成,呈现被碳囊包裹的形态;天然气非催化部分氧化工业装置炭黑呈现中空结构,粒径较小。非催化部分氧化小试装置和工业装置炭黑的氧化反应性接近,是天然气炉法炭黑的3.1倍,是煤焦油炉法炭黑的3.2倍;非催化部分氧化炭黑的反应性是煤快速热解炭黑的9.0倍,是生物质快速热解炭黑的26.6倍。两种非催化部分氧化炭黑和两种商业炉法炭黑的活化能随温度变化呈现分段形式;两种快速热解炭黑的活化能随温度升高基本不变。Abstract: The morphological structure of six samples including the rapid pyrolysis soot of solid fuels (coal, biomass), the soot from non-catalytic partial oxidation (NCPOX) of natural gas in a laboratory pilot plant and an industrial plant, the commercial carbon black in natural gas furnace/coal tar furnace, were characterized by using a transmission electron microscope. Based on atmospheric thermogravimetric analyzer, the non-isothermal method (50–800 ℃) was adopted to study the ignition point and the oxidation reaction rate of soot, and the oxidation reaction kinetic parameters of soot was obtained. Studies showed that the physical and chemical properties of various soot were quite different. The soot from the rapid pyrolysis of coal and biomass presented a higher sphericity and a larger particle size. The Lab-NCPOX-soot was formed at a lower temperature which caused the particle being wrapped by a carbon capsule. The Ind-NCPOX-soot had a hollow structure and a small particle size. The reactivity of the Lab-NCPOX-soot is close to that of the Ind-NCPOX-soot, which is 3.1 times that of the commercial natural gas furnace carbon black and 3.2 times that of the commercial coal tar furnace carbon black; the reactivity of NCPOX-soot is 9.0 times of the rapid pyrolysis soot of coal, and 26.6 times of the rapid pyrolysis soot of biomass. The activation energy of 2 kinds of NCPOX-soot and 2 kinds of commercial carbon blacks present staged forms with increasing temperature. The activation energy of the 2 rapid pyrolysis soot was basically unchanged with increasing the temperature.
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Key words:
- soot /
- rapid pyrolysis /
- non-catalytic partial oxidation /
- structure /
- reactivity /
- kinetic
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Sample Proximate analysis wd/% Ultimate analysis wd/% V FC A C H N S O Coal 35.48 59.06 5.46 76.85 4.63 1.23 1.34 10.49 Saw dust 90.92 7.74 1.34 42.39 5.64 0.79 0.44 49.40 表 2 天然气非催化部分氧化实验的反应工况
Table 2 Reaction conditions of the NCPOX experiment of natural gas
O2/CH4 CH4 flow rate/ (L∙min−1) O2 flow rate/ (L∙min−1) CH4 velocity/ (m∙s−1) O2 velocity/ (m∙s−1) Residence time/s 0.80 18.89 15.11 123.34 142.51 0.929 表 3 炭黑的氧化反应特性参数
Table 3 Oxidation reaction characteristic parameters of soot
Sample Ti0/℃ Temperature of
wmax/℃Tf/℃ Reaction time/
minwmax/
(%·min−1)wmean/
(%·min−1)S/
(× 10−9·%2·min−2·℃−3)NG- furnace-CB 496.7 559.9 584.3 8.76 3.51 1.09 26.6 Tar-furnace-CB 488.6 548.3 588.4 9.98 3.87 0.93 25.5 Coal-RP-soot 518.6 580.7 614.5 9.59 1.70 0.88 9.1 Biomass-RP-soot 460.8 531.2 572.0 11.12 0.79 0.47 3.1 Lab-NCPOX-soot 453.7 493.7 503.3 4.96 5.18 1.63 81.5 Ind-NCPOX-soot 531.6 550.9 594.6 6.30 9.63 1.12 63.9 表 4 炭黑样品的氧化动力学参数
Table 4 Oxidation kinetic parameters of soot samples
Sample Temperature range/℃ b a E/(kJ·mol−1) A/min−1 R2 NG-furnace-CB stage 1 496.7−542.8 11.42 −21924 182 2.15 × 1010 0.9926 stage 2 542.8−577.3 71.65 −70943 590 9.53 × 1036 0.9970 stage 3 577.3−584.3 4.98 −14327 119 2.36 × 107 0.9759 Tar-furnace-CB stage 1 488.6−533.8 5.49 −16575 138 4.41 × 107 0.9851 stage 2 533.8−558.7 76.08 −73433 611 8.23 × 1038 0.9978 stage 3 558.7−588.4 10.00 −18630 155 4.49 × 109 0.9932 Coal-RP-soot 518.6−614.5 18.41 −26972 224 2.83 × 1013 0.9789 Biomass-RP-soot 460.8−572.0 1.17 −11222 93 4.14 × 105 0.9654 Lab-NCPOX-soot stage 1 453.7−483.9 −2.47 −9144 76 9.21 × 103 0.9941 stage 2 483.9−503.3 91.53 −80272 667 4.62 × 1045 0.9509 Ind-NCPOX-soot stage 1 531.6−547.6 5.37 −16459 137 3.91 × 107 0.9981 stage 2 547.6−556.3 201.19 −177362 1475 4.25 × 1093 0.9874 stage 3 556.3−594.6 16.06 −24071 200 2.44 × 1012 0.9777 -
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