草木灰脱除烟气CO2特性及机理研究

Global warming, thought to be associated with the emission of greenhouse gases, has attracted significant attention of the world in recent years. It is necessary to capture CO2 in large-scale all over the world. Among various CO2 capture options, using dry alkali metal-based sorbent for CO2 capture from flue gas is considered to be an emerging technology. However, as the cost of the alkali metal-based sorbent is generally high, the application and extension of this technology are directly affected. To solve the problems above, the plant ash with a low price is chosen as the sorbent for CO2 capture. In this way, we can make full use of the residual value of this rejected material. This technology can be investigated as a new way for CO2 capture. Compared with other alkali metal-based sorbents, the compositions of plant ash are very complicated, and the form of specific is very specific. As a result, the reaction principles of various compositions in plant ash with CO2 need to be studied in detail. The failure mechanism of the sorbent caused by the reaction of other compositions in plant ash with CO2 and impurity gases, including SO2, NO, and HCl, existing in the flue gas need to be under consideration in detail either. The effects of the temperature, CO2 concentration, and H2O concentration on the reactions carbonation reaction should be investigated. The regeneration behaviors of the sorbent need to be studied either. From the investigation of this paper, the reaction principle of this technology will be found, and the basic data will be obtained in detail. The theoretical basis will be developed for the technology of CO2 capture from flue gas using dry sorbents with proprietary intellectual property rights.

近年来，温室气体排放所造成的全球变暖问题成为国际社会普遍关注的焦点，进行全球性大规模CO2减排势在必行。众多CO2捕集技术中，碱金属基固体吸收剂烟气脱碳技术被认为具有广阔的应用前景。为解决吸收剂成本过高难题，选用价格低廉的草木灰，可以变废为宝，充分利用其剩余价值，为CO2减排开辟一个新的途径。相比于其他碱金属基吸收剂，草木灰的组分特别复杂，K2CO3存在形式特殊，因此本项目将重点针对草木灰中各成分与CO2的反应机理展开研究。草木灰中其他组分以及烟气中杂质气体SO2、NO2等造成吸收剂的失效机理也是研究重点之一。另外还将研究温度、CO2浓度、H2O浓度对脱碳特性的影响机制以及吸收剂再生反应特性。通过本项目的研究，可望探明草木灰与CO2的反应机理，获得系统的基础数据，为开发具有自主知识产权的烟气CO2干法脱除技术奠定坚实的理论基础。

CO2减排是解决温室气体排放造成全球变暖问题的主要关注焦点之一。本项目提出利用价格低廉的草木灰进行燃烧后烟气CO2捕集，主要研究了以下内容：一、通过多种理化分析表征，探明五种不同草木灰中组分含量及物性结构；二、利用热重系统探究样品脱碳反应机理；三、利用固定床反应器研究草木灰的脱碳能力和再生能力；四、研究反应条件对草木灰脱碳和再生特性的影响；五、建立了草木灰脱碳反应动力学模型；六、研究了烟气中杂质气氛SO2和NO2等对草木灰脱碳失效的影响机制；最后，为提高草木灰样品脱碳能力，提出利用不同胺基复合物对草木灰样品进行改性。.获得了以下主要结论：一、五种草木灰样品富含K元素，其中向日葵秸秆燃烧的草木灰K含量最高，而稻秸秆燃烧的草木灰物性结构较好；二、样品对CO2清除主要依赖于原样中K2CO3与CO2/H2O之间的碳酸化反应及载体的物理吸附作用；三、模拟烟气气氛下五种草木灰的脱碳能力为0.35-0.54 mmol CO2/g，样品在200℃可完全再生，多次循环样品保持较高的脱碳性能；四、温度是影响样品脱碳性能的重要因素， H2O浓度增加有利于提高碳酸化转化率，反应气速对脱碳性能影响不大，样品再生转化率随温度升高而增大，升温速率和反应气速对样品再生性能影响不大；五、利用失活模型获得了样品脱碳反应活化能，利用Avrami-Erofeyev动力学模型求解样品再生反应表观活化能为79.1 kJ/mol；六、在含有水汽的杂质气氛中，样品中K2CO3与SO2相互作用形成K2SO4，K2CO3与NO2相互作用形成KNO3，造成脱碳反应转化率降低；七、30%TEPA改性后的样品脱碳能力最高可达1.76 mmol CO2/g，负载量为45%时样品的脱碳能力最高为2.02 mmol CO2/g，多元胺能够有效改进草木灰样品的脱碳性能。.通过本项目研究，揭示了草木灰脱碳和再生反应机理；剖析了温度、CO2浓度、H2O浓度、再生温度和升温速率等参数对草木灰脱碳和再生的影响规律；获得了草木灰脱碳及再生动力学基础参数；揭示了样品在含杂质烟气中失效机制；并提出利用胺基改性提高脱碳量和稳定性同时抑制样品失活的有效方法。项目的研究结果可为开发具有自主知识产权的烟气CO2干法脱除技术奠定坚实的理论基础。该技术成果最终将为实现燃烧污染物控制，为节能减排提供新的途径。