Effects of the Secondary Air Excess Ratio on the Self-Preheating Combustion Characteristics and NOx Emission of Semi-Coke

  • DING Hongliang ,
  • OUYANG Ziqu ,
  • CAO Xiaoyang ,
  • ZHU Shujun
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  • 1. Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China

网络出版日期: 2023-11-22

基金资助

This study was supported by Strategic Priority Research Program of the CAS (XDA29010200), CAS Project for Young Scientists in Basic Research (YSBR-028), and Youth Innovation Promotion Association of the CAS (2019148).

版权

Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2023

Effects of the Secondary Air Excess Ratio on the Self-Preheating Combustion Characteristics and NOx Emission of Semi-Coke

  • DING Hongliang ,
  • OUYANG Ziqu ,
  • CAO Xiaoyang ,
  • ZHU Shujun
Expand
  • 1. Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China

Online published: 2023-11-22

Supported by

This study was supported by Strategic Priority Research Program of the CAS (XDA29010200), CAS Project for Young Scientists in Basic Research (YSBR-028), and Youth Innovation Promotion Association of the CAS (2019148).

Copyright

Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2023

摘要

将超低挥发分碳基燃料,如热解半焦,作为高品位洁净燃料燃烧发电,是实现煤炭清洁高效梯级利用的重要组成部分。基于预热燃烧技术,本文研究了二次风当量比(λ2)对神木半焦预热燃烧特性和氮氧化物排放的影响,试验中选取的λ2均处于预热燃烧技术应用的常见范围。结果表明,预热煤气的快速着火及高速射流引起的烟气回流是导致二次风喷口附近温度较高的主要原因。增加λ2会使得燃烧室的温度降低,造成飞灰的未燃碳含量略有增加,但试验中燃烧效率仍可以保持在98%以上。与传统空气分级燃烧不同,NOx排放并未因λ2的增加而线性减少,主要原因是燃烧室中产生的大部分NOx来源于焦炭氮,该部分NOx无法通过空气分级进行有效还原,而控制NOx的关键在于调控高温预热燃料与二次风的掺混过程,以加快焦炭氮在还原区的释放速率,抑制焦炭氮向NOx的转化。在本研究中,不同λ2条件下燃烧区间均较透明,无明显火焰锋面,即λ2不是影响高温预热燃料实现无焰燃烧的决定性因素。试验中最佳二次风当量比为0.40,最低NOx 排放浓度为 71 mg/m3(@6% O2)。

本文引用格式

DING Hongliang , OUYANG Ziqu , CAO Xiaoyang , ZHU Shujun . Effects of the Secondary Air Excess Ratio on the Self-Preheating Combustion Characteristics and NOx Emission of Semi-Coke[J]. 热科学学报, 2023 , 32(3) : 1263 -1277 . DOI: 10.1007/s11630-023-1792-0

Abstract

The effects of the secondary air excess ratio (λ2) on the self-preheating combustion characteristics and NOx emission of semi-coke have been experimentally studied on a bench-scale test rig. Flameless combustion of the high-temperature preheated fuel (coal gas & coal char) has been achieved in all experimental cases. Through fire-observation windows, the combustion zone was transparent and no flame fronts were seen. Additionally, different λ2 in this study were basically within the common range of self-preheating combustion technology. The results manifested that the rapid ignition of coal gas and the recirculation of high-temperature flue gas resulted in relatively high combustion temperatures close to the secondary air nozzle exit. With the increase of λ2 , the unburned carbon content of fly ash increased slightly and combustion efficiencies of all experiments exceeded 98%. Moreover, the exit NOx emission was not reduced linearly, which was dissimilar from conventional air staging combustion. The main reason was that the volatile-N was released in the self-preheating device, and the air staging method could not effectively reduce the char-NOx. In the course of the experiments, the lowest NOx emission was 64.35 mg/m3 (@6%O2) when λ2 was 0.40.

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