煤粉气流着火机理及最佳煤粉浓度的分析

Ignition Mechanism of Pulverized Coal Flow and Analysis of Optimal Pulverized Coal Concentration

煤粉气流着火机理是煤粉燃烧的基础,最佳煤粉浓度是煤粉稳燃技术及燃烧器设计的重要参数.本文借鉴气体层流预混燃烧的分区着火机理,从层流煤粉燃烧火焰着火机制入手,阐明煤粉气流的着火机理.将煤粉气流燃烧过程分为一次、二次预热区和着火反应区、燃尽区等不同区域,认为煤粉着火主要受制于预热区和着火反应区;同时将不同区域的传热方式进行解耦,辨明了一次与二次预热区加热热量的不同来源.通过分区热量衡算,获得煤粉浓度对于煤粉气流着火影响的基本特性.提出以挥发分和少量焦炭燃烧热量作为着火供给热来评估煤粉气流着火状况的新思路,从而得到煤粉气流分区着火机理,并预测得到合理的最佳煤粉浓度.研究结果在氧燃料燃烧、高温空气燃烧和燃煤电站灵活性改造时的煤粉稳燃等方面,可提供高浓度煤粉燃烧技术的基础支撑.

The ignition mechanism of pulverized coal flow is the fundamental of pulverized coal combustion,and the optimal pulverized coal concentration is an important parameter for pulverized coal combustion stabilization technology and burner design.Based on the zonal ignition mechanism of gas laminar premixed combustion,this research initially investigated the ignition mechanism of laminar pulverized coal combustion flame,and then explored the ignition mechanism of pulverized coal flow.The process of pulverized coal combustion is divided into primary and secondary preheating zone,ignition reaction zone and burnout zone,and it is assumed that the ignition of pulverized coal is mainly controlled by the preheating zones and ignition reaction zone.At the same time,the heat transfer modes in different zones were decoupled,and different kinds of preheated sources in the primary and secondary preheating zones were identified.The influence of pulverized coal concentration on the ignition characteristics of pulverized coal flow was obtained through zonal heat balance.The new idea was proposed that the combustion heat of volatiles and a small amount of char was used as ignition supplying heat to evaluate the ignition status of pulverized coal flow,and then the zonal ignition mechanism of pulverized coal flow was obtained.The reasonable optimal pulverized coal concentration was predicted.The research results can provide the basic support for high concentration pulverized coal combustion technology in the aspects of oxygen fuel combustion,high tem-perature air combustion,and the stable combustion of pulverized coal during the flexible modification of coal-fired power plants.