化学链燃烧中载氧体磨损和产生积碳的机制及抑制方法

Mechanisms and suppression methods for attrition and carbon deposition of oxygen carriers in chemical looping combustion

磨损和积碳的产生都严重干扰化学链燃烧(CLC)的正常运行,磨损可造成载氧体的损耗,积碳可导致载氧体与燃料不能充分接触。载氧体的循环燃烧效率与CLC技术成本密切相关,是其进入商业化的关键。本工作针对载氧体的磨损和积碳抑制这两大主要问题进行了分析总结。阐述了CLC过程发生的详细反应及形成炭黑型积碳前驱物多环芳烃机制,总结了应对的可行方法,其中联合水蒸气和CO2喷射具有很好的前景。并在此基础上讨论了该领域的潜在研究需求。要点:(1)载氧体的磨损和积碳是CLC工艺目前急需解决的问题。(2)针对载氧体OC的磨损分析提出了一种选择耐磨OC材料的方法。(3)积碳形成的主要反应是热解和Boudouard反应。(4)联合传统的水蒸气喷射和新型的CO2回流喷射为一体的新方法有望成为解决载氧体积碳问题的有效方法。

The formation of carbon deposition causes the oxygen carrier(OC)to not fully contact with the fuel,and the attrition causes the loss of oxygen carriers,which seriously disturb the normal operation of chemical looping combustion(CLC).Cyclic combustion efficiency of oxygen carriers is closely related to the cost of CLC technology,and it is an important part of its near commercialization.The basic concepts,devices,reaction conditions,fuel composition and reaction process of CLC were introduced in this work.Two major problems in current CLC research were analyzed and summarized.The main contents included that:(1)prolonging the cycle life cycle of oxygen carriers providing combustion oxygen demand,(2)under the optimum reaction conditions,the mechanism of carbon deposition and the measures to solve the oxygen loss caused by carbon deposition were analyzed.Firstly,the oxygen carrier's selection,preparation methods and characteristics briefly were introduced.Different oxygen carriers had their own advantages and disadvantages,it should select suitable oxygen carriers for different fuels.The attrition analysis of oxygen carriers point was carried out.Analysts believed that with industrial significance a way to select qualified oxygen carriers materials based on attrition resistance.Secondly,the reaction mechanism of polycyclic aromatic hydrocarbons(PAHs)and the precursor of carbon black deposit were analyzed in detail by analyzing the detailed reaction in the whole process of CLC.It was concluded that the carbon deposit was mainly caused by the reaction of hydrocarbons pyrolyzed by fuel with oxygen carriers and Boudouard reaction.The corresponding solutions for different types of carbon deposit were proposed.Among them,the combination of steam injection and carbon dioxide reflux injection was promising.On this basis,the potential research needs in this field were also discussed.To improve the cycle period of oxygen carriers and restrain carbon deposition,future research should focus on the characterization and reactivity of carbon deposition on the surface of oxygen carriers,the cyclic growth model of oxygen carriers under optimal combustion conditions and the reaction mechanism of particles,as well as the exploration of new technologies for coupling removal of carbon deposition.Key learning points:(1)Abrasion and carbon deposition of oxygen carriers were urgent problems to be solved in CLC process.(2)According to the analysis of attrition OC method for selecting OC attrition resistant materials was proposed.(3)The main reactions of carbon deposition were pyrolysis and Boudouard reaction.(4)A new method combining traditional steam injection with new CO2 reflux injection was expected to be an effective way to solve the problem of oxygen-carrying volume carbon.