Abstract:

Carbon deposition will occur on the catalyst surface during the operation of the external reformer of solid oxide fuel cells, which will damage the internal pore structure and reduce the catalyst activity, and eventually completely block the catalyst pores, causing the reformer to fail. A three-dimensional transient multi-physical field coupled carbon deposition model was established by using finite element simulation software, and the processes of fluid flow, mass transfer, heat transfer and chemical reaction were simulated. The effects of methane concentration, feed gas flow rate, porosity of catalytic bed and hydrogen content in feed gas on carbon deposition behavior in reformer were analyzed. The results show that the change of porosity of catalytic bed has little effect on carbon deposition in catalytic bed, and the optimum porosity is 0.30—0.50. The increase of feed gas flow rate will change the carbon deposition position of catalytic bed, and the optimal gas flow rate is 0.06 m/s. Increasing methane concentration and hydrogen content in feed gas will aggravate the carbon deposition behavior of catalytic bed. The carbon atoms produced by methane pyrolysis can be rapidly consumed by reasonably adjusting the process parameters such as methane feed gas flow rate, methane concentration, hydrogen content and porosity of catalytic bed, and the carbon deposition in the reformer can be effectively reduced.

Key words: reformer, carbon deposition, porosity, fuel cells, methane, catalyst

摘要：

固体氧化物燃料电池外重整器工作过程中，催化剂表面会产生积炭，导致其内部孔道结构破坏并降低催化剂活性，最终会完全堵塞催化剂孔道，造成重整器失效。采用有限元模拟软件，建立三维瞬态多物理场耦合积炭模型，模拟流体流动、质量传递、传热和化学反应过程，分析甲烷浓度、原料气流速、催化床层孔隙率以及原料气中氢气含量对重整器内积炭行为的影响。研究结果表明，催化床层孔隙率改变对催化床积炭影响较小，最佳孔隙率为0.30~0.50；原料气流速增加会改变催化床的积炭位置，最佳气体流速为0.06 m/s；增大甲烷浓度和原料气中氢气含量都会加重催化床的积炭。可通过合理调控甲烷原料气流速、甲烷浓度、氢气含量及催化床层孔隙率等工艺参数，快速消耗甲烷热解产生的碳原子，有效降低重整器内部积炭。

关键词: 重整器, 积炭, 孔隙率, 燃料电池, 甲烷, 催化剂