THE INFLUENCE OF THE PARTICLE SIZE ON NO_x AND SO₂
RELEASING IN LOWER TEMPERATURE COMBUSTION

Li Jubin and Jiang Xiumin
(Northeast Institute of Electric Power,11000 Shenyang)
Wang Hong and Qiu Jianrong
(Key Laborotary of Coal Combustion,Huazhong University of Science
and Technology,430074 Wuhan)

　　ABSTRACT　Under the condition of lower heating rate and lower temperature combustion (300℃-550℃)，this paper studied the releasing characteristics of fuel NO_x and organic sulfur on four different size samples taken respectively from the two kind coal of Heshan and Jincheng by applying the apparatus of horizontal tube type electric heating furnace and obtained some qualitative relations about them. On the other hand,the paper analyzed the effects of CO on restraining NO_x and SO₂ releasing and the releasing characteristics of NO_x and SO₂ under micro-pulverized coal combustion.
　　KEY WORDS　pulverized coal,particle size,fuel NO_x,organic sulfur releasing

　　0　引言

　　煤粉燃燒過程中，產生NO_x的方式包括：熱力NO_x、瞬時NO_x和燃料NO_x.研究表明，燃料NO_x大約占煤燃燒中總NO_x排放量的80%左右.其中，燃料中的氮又可以分為揮發(fā)分氮和焦炭氮兩部分.^［1］在燃燒過程中，揮發(fā)分氮的主要中間產物是HCN和NH₃，最后生成NO和N₂；焦炭氮的中間產物主要是HCN.本試驗證明，在煤燃燒過程中煤粉的顆粒粒度對煤燃燒過程中燃料NO_x的生成特性有很大影響.
　　煤中硫元素有兩種存在形式，即有機硫和無機硫.研究表明，煤階越高煤中有機硫的含量也越多，通常來講，有機硫約占60%以上.^［2］在煤燃燒的過程中有機硫的析出溫度較低，通常在550℃以內即可全部以SO₂的形式析出.同時文獻［2］還指出，在煤燃燒過程中，有機硫和無機硫之間是動態(tài)的、可以轉化的.本試驗發(fā)現(xiàn)：煤粉的顆粒粒度對煤燃燒的過程中有機硫和無機硫之間的轉化有重要影響，而進一步影響煤燃燒中SO₂的生成特性.
　　超細化煤粉燃燒方式是近年來新興的一種煤燃燒方式，該項研究在日本已進入工業(yè)應用試驗階段，研究表明煤粉超細化燃燒方式可以很大程度上降低電站NO_x的排放.^［3］本文還研究了以CO為主的還原氣氛在煤燃燒過程中對固氮和固硫所產生的影響，以及煤粉超細化燃燒方式下NO_x和SO₂的生成特性.

　　1　實驗部分

　　煤樣的制備過程如下：將采集的一定量合山與晉城煤經(jīng)過洗滌、烘干、碾磨后制成分析基煤樣.
　　合山和晉城煤的工業(yè)分析與元素分析見表1.

表1　合山和晉城煤的工業(yè)分析與元素分析
　Table 1　Proximate and ultimate analysis of Heshan
and Jincheng

圖1　實驗裝置示意圖
Fig.1　Schematic diagram of experimental equipment

圖2　合山煤燃料NO_x的生成隨時間的變化關系
Fig.2　Variation of fuel NO_x releasing of Heshan coal with time

圖3　晉城煤燃料NO_x的生成隨時間的變化關系
Fig.3　Variation of fuel NO_x releasing of Jincheng coal with time

圖4　NO_x生成量與顆粒粒度的關系
Fig.4　Relationship between NO_x releasing and partical size

圖5　合山煤燃燒過程中CO生成量隨時間的變化關系
Fig.5　Variation of CO₂ releasing of Heshan coal with time in combustion

圖6　晉城煤燃燒過程中CO生成量隨時間的變化關系
Fig.6　Variation of CO releasing of Jincheng coal with time in combustion

圖7　合山煤與晉城煤CO生成量與顆粒粒度的關系
Fig.7　Relationship between CO relesing and particle
size for Heshan and Jincheng coal

圖8　合山煤燃燒過程中SO₂生成量隨時間的變化關系
Fig.8　Variation of SO₂ releasing of Heshan coal with time in combustion

圖9　合山煤與晉城煤SO₂生成量與顆粒粒度的關系
Fig.9　Relationship between SO₂ relesing and
particle size for Heshan and Jincheng coal