粉煤灰吸收剂固碳降碱工艺研究

Research on carbon fixation and alkali reduction process of fly ash absorbents

粉煤灰吸收剂固碳降碱工艺在减少二氧化碳(CO_(2))排放、资源综合利用和碱性废水处理等方面具有重要意义。以陕西榆林三道沟府谷电厂固体废弃物粉煤灰为原料,通过改性处理制备了粉煤灰CO_(2)吸收剂(简称“吸收剂”),研究了不同预处理剂(分别为乙酸(CA)、氯化钠(NaCl)和氢氧化钠(NaOH)溶液,质量分数均为85%)对吸收剂的固碳降碱性能和返碱、浸出性质的影响,并分析了温度和CO_(2)进气速率对固碳降碱工艺的影响。结果表明,NaOH能够有效破坏粉煤灰的球形玻璃体结构,释放活性组分。提高温度可以增大粉煤灰中的离子浸出速率,使反应向正向移动。增大CO_(2)进气速率能够提高CO_(2)在吸收剂中的溶解速率,但过高的CO_(2)进气速率会缩短气液接触时间,导致吸收效率降低。以NaOH溶液作预处理剂,在温度为60℃、CO_(2)进气速率为40 mL/min和吸收时间为5 h的条件下,该固碳降碱工艺的效果最佳,吸收剂的吸收效率可达27.89%,固碳性能为30.16 kg/t。

The carbon fixation and alkali reduction process of fly ash absorbent is of great significance in reducing carbon dioxide(CO_(2))emission,comprehensive utilization of resources and treatment of alkaline wastewater.Using the solid waste fly ash from Sandaogou Fugu Power Plant in Yulin,Shaanxi as raw materials,fly ash CO_(2)absorbents(“absorbent”for short)were prepared by modification treatment.The effects of different pretreatment agents(acetic acid(CA),sodium chloride(NaCl)and sodium hydroxide(NaOH)solution,respectively,all the mass fractions are 85%)on the carbon fixation and alkali reduction performance and carbonation and leaching property of absorbent were studied,and the effects of temperature and CO_(2)injection rate on the carbon fixation and alkali reduction process were analyzed.The results show that NaOH can effectively destroy the spherical vitreous structure of fly ash and release the active components.Increasing the temperature can increase the ion leaching rate in fly ash and make the reaction move forward.Increasing CO_(2)injection rate can improve the dissolution rate of CO_(2)in the absorber,but too high CO_(2)injection rate will shorten the gas-liquid contact time,resulting in lower absorption efficiency.With NaOH solution as pretreatment agent,under the conditions that temperature is 60℃,CO_(2)injection rate is 40 mL/min and absorption time is 5 h,the carbon fixation and alkali reduction process has the best effect.The absorption efficiency of the absorber can reach 27.89%,and the carbon fixation capacity is 30.16 kg/t.