Numerical simulation of co-combustion of coal and refuse derived fuel in coupling with decomposition of calcium carbonate in precalciner with swirl type prechamber

doi:10.11949/j.issn.0438-1157.20170028

Abstract

Abstract:

Numerical simulation of co-combustion of pulverized coal, refuse derived fuel (RDF) and thermal decomposition of calcium carbonate was carried out aiming at an actual precalciner with swirl type prechamber. The predicted burn-off rates of pulverized coal and RDF were 99% and 100% respectively,and the predicted decomposing rate of calcium carbonate was 95%, being in accordance with engineering data actually measured. The results show that the fuel and raw meal are carried by gas stream to rise spirally. The pulverized coal stream starts to burn soon when injected into the furnace from the top of the prechamber, and then burns rapidly, being dominated by char combustion, when rising into the cone section and the column section above the prechamber, forming a violent combustion region. The RDF starts to burn soon, being dominated by volatile combustion, when blown into the furnace horizontally from the lower part of the column section of the precalciner, forming a main combustion zone, and then rises spirally intertwining with the pulverized coal stream. The calcium carbonate begins to whirl in the prechamber, being decomposed by absorbing the heat of high-temperature gas stream, when falling into the furnace from the top of the prechamber, and then is further decomposed in the main combustion zone of coal and RDF on the way up. As a result of the coupling of co-combustion and decomposition, there is a uniform and steady temperature field in the column section of the precalciner.

Key words: precalciner, RDF, coal combustion, co-combustion, calcium carbonate decomposition, chemical reaction, numerical simulation

摘要：

针对一实际尺寸的带下置涡流室的分解炉进行了数值模拟，探讨了煤、垃圾衍生燃料（RDF）两种燃料共燃与碳酸钙分解相耦合的化学反应过程。计算所得煤粉及RDF燃烬率分别为99%和100%，碳酸钙分解率为95%，与工程实际数据吻合较好。结果表明：煤粉自涡流室顶部入炉后，先向下俯冲，再在气流的携带下转而向上运动，在分解炉柱体部分螺旋上升，其燃烧时以焦炭燃烧占主导，在涡流室上方的锥体部分及锥体部分上方的下半柱体部分形成主燃区；RDF自分解炉柱体部分下部水平入炉后，先运动至中部，旋即与煤粉流交织在一起螺旋上升，其燃烧时以挥发分燃烧占主导，在分解炉下半柱体部分形成主燃区；CaCO₃自涡流室顶部入炉后，首先在涡流室及其下方的锥体部分做涡旋运动，一部分因吸收高温气流的热量而分解，剩余大部分上旋至燃料主燃烧区，因吸收燃烧所释放的热量而分解；燃料燃烧放热与CaCO₃吸热分解相耦合后，最终在分解炉柱体部分形成了均匀、稳定的温度场。

关键词: 分解炉, 垃圾衍生燃料, 煤燃烧, 共燃, 碳酸钙分解, 化学反应, 数值模拟

CLC Number:

TQ172

MEI Shuxia, XIE Junlin, CHEN Xiaolin, LI Xuemei, PEI Kepeng, HE Feng. Numerical simulation of co-combustion of coal and refuse derived fuel in coupling with decomposition of calcium carbonate in precalciner with swirl type prechamber[J]. CIESC Journal, 2017, 68(6): 2519-2525.

梅书霞, 谢峻林, 陈晓琳, 李雪梅, 裴可鹏, 何峰. 涡旋式分解炉中煤及垃圾衍生燃料共燃烧耦合CaCO₃分解的数值模拟[J]. 化工学报, 2017, 68(6): 2519-2525.

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