飞灰熔融气相产物盐分布规律

Distribution Rule of Gaseous Phase Salts During Melting of Fly Ash from MSW Incineration Plant

生活垃圾焚烧飞灰(简称"飞灰")熔融技术应用过程中产生的二次飞灰问题成为掣肘,掌握飞灰熔融气相产物盐分布规律,有利于二次飞灰无害化和资源化利用技术开发,对烟气净化设备设计和生产运行具有借鉴作用。选用江苏省某生活垃圾焚烧电厂产生的飞灰,利用自主研发的等离子体飞灰熔融中试系统进行飞灰高温熔融试验。通过重量差减法、X射线荧光光谱仪、电化学法等测定飞灰熔融过程中气相产物盐及熔渣的组成和产量,获得Na、K、Ca、Mg和Fe的气相迁移率。利用热力学模型模拟1000-1600℃、不同气氛(不通气体、氮气气氛或空气气氛)、添加0-50%辅料、飞灰含水率0-12%条件下,气相产物盐的组成及分布规律。结果表明:飞灰熔融过程中气相产物盐主要以NaCl、(NaCl)_(2)、KCl、(KCl)_(2)、CaCl_(2)、KCaCl_(3)、KMgCl_(3)、FeCl_(2)等形态存在,其分布规律受熔融温度影响较大,受熔融气氛、辅料添加量、飞灰含水率影响相对较小。空气气氛条件下,飞灰熔融气相产物盐中出现新产物Na_(2)SO_(4)。对比中试试验和热力学模型模拟结果,碱金属Na和K气相迁移率的模拟值与试验值吻合较好,碱土金属Ca、Mg和Fe气相迁移率的模拟值远小于试验值。建议利用气相产物盐的分布规律开发分盐或氯盐利用技术,实现二次飞灰的综合利用,改变二次飞灰以填埋为主的现状,彻底实现飞灰的无害化和资源化。

The secondary fly ash problem in the application process of fly ash of municipal solid waste incineration(shorter form:fly ash)melting treatment technology has become a constraint.It is beneficial to the development of harmless and resource utilization technology of secondary fly ash by mastering the distribution law of salt in the gas phase product of fly ash melting,and it can be used as a reference for the design of tail gas purification equipment and operation.The fly ash released from one municipal solid wastes incineration plant in Jiangsu Province was adopted.The fly ash melting experiments were performed in a self-designed high-temperature pilot-scale plasma arc furnace system.The weight subtraction method,X–ray fluorescence spectroscopy,atomic absorption spectrometry and electrochemical process were used to analyze melting fly ash and slag during melting and to abtain gaseous phase migration rate of Na,K,Ca,Mg and Fe.The thermodynamic model was used to simulate the distribution rules of gaseous phase salts at 1000-1600℃,with 0-50%auxiliary material,at different atmosphere(without gas,nitrogen or air)and 0-12%water content of fly ash.The simulation results showed that NaCl,(NaCl)_(2),KCl,(KCl)_(2),CaCl_(2),KCaCl_(3),KMgCl_(3),FeCl_(2) etc.were main compositions of gaseous phase salts during fly ash melting.These compositions distribution was greatly effected by melting temperature and was little effected by melting atmosphere,auxiliary material amount and water content of fly ash.At atmosphere,there were new product Na_(2)SO_(4) in gaseous phase salts.The simulation values and the experimental values of gaseous phase migration ratio of Na and K fitted well,and the simulation values were largely smaller than the experimental ones of Ca,Mg and Fe.It is suggested that the distribution law of gaseous product salt should be used to develop the technology of salt separation or chloride salt utilization,so as to realize the comprehensive utilization of secondary fly ash,change the current situation that the secondary fly ash is mainly landfill,and thoroughly realize the harmless and resource utilization of fly ash.