JPS60174409A - Nox-reduced burning procedure of pulverized coal - Google Patents

Abstract

PURPOSE:To remarkably suppress the emission of NOX without lowering a combustion efficiency, by using a secondary fuel with a fuel ratio lower than that of primary fuel. CONSTITUTION:To burn, a primary fuel C with a relatively large fuel ratio is first burnt with a primary air (a) as the primary combustion stage of low air ratio, and then a secondary fuel (d) with the fuel ratio lower than that of primary fuel (c) is supplied from its backward flow in a flow exceeding an amount needed to consume an oxygen remaining in a primary combustion exhaust gas. A secondary combustion zone is thus converted into a reducing atmosphere, and NOX produced in a primary combustion zone is reduced to N2 in this secondary combustion zone. Subsequently, a secondary air (b) is supplied from its backward flow to form a third combustion zone where a reducing substance is completely burnt into a pollution-free product. In this way, NOX can be effectively reduced to lower the concentration of nitrogen oxide.

Description

【発明の詳細な説明】 産業上の利用分野 本発明は微粉炭の低ＮＯｘ燃焼法に関するものである。[Detailed description of the invention] Industrial applications The present invention relates to a low NOx combustion method for pulverized coal.

従来例の構成とその問題点 微粉炭等粉砕した固体燃料を燃料に使用するボイラー、
加熱炉等の燃焼装置においては、通常固体燃料中にかな
りのＮ分が含まれ、燃焼によって発生する窒素酸化物の
濃度は非常に高く、かつ水噴射、排ガス再循環法、燃料
濃淡燃焼法、空気２段燃焼法等でその発生を効果的に抑
制することは困難であり、現在最も有効な燃焼法は３段
燃焼法である。これは１次燃料と１次空気で低空気比の
１次燃焼を行なわせ、その周辺から２次燃料のみを１次
燃焼排ガス中に残在する酸素を消費するに必要な量より
過剰に供給して２次燃焼域が還元性雰囲気となるように
なし、この領域で１次燃焼域で発生したＮＯｘをＮ、に
環元させた後、さらにその外周部又は後流から２次空気
を供給して８次燃焼域を形成し、ここでＣＯ，Ｈ２＋　
ＣｍＨｎ等の還元性物質を完全に酸化し無公害のＣ０２
，Ｈ２Ｏにする燃焼方法である。Conventional configuration and its problems Boilers that use pulverized solid fuel such as pulverized coal as fuel;
In combustion devices such as heating furnaces, the solid fuel usually contains a considerable amount of N, and the concentration of nitrogen oxides generated by combustion is extremely high. It is difficult to effectively suppress the generation using a two-stage air combustion method or the like, and the currently most effective combustion method is a three-stage combustion method. This allows primary combustion to occur at a low air ratio using primary fuel and primary air, and supplies only secondary fuel from the surrounding area in excess of the amount required to consume the oxygen remaining in the primary combustion exhaust gas. The secondary combustion zone is made to have a reducing atmosphere, and after the NOx generated in the primary combustion zone is converted to N in this zone, secondary air is further supplied from the outer periphery or downstream. to form the 8th combustion zone, where CO, H2+
Completely oxidizes reducing substances such as CmHn and produces non-polluting CO2
, H2O.

この際、２次燃料の微粉炭、特にその燃料比（固定炭素
／′揮発分）が大きい場合は、供給された２次燃料の分
解ガス化が急速に行なわれず、ＮＯｘの還元が効果的に
行なわれない。また未燃カーボンも残り易く、燃焼効率
の低下が起るなどの問題があった。At this time, if the secondary fuel is pulverized coal, especially if its fuel ratio (fixed carbon/volatile matter) is large, the supplied secondary fuel will not be decomposed and gasified rapidly, and NOx reduction will not be effective. Not done. In addition, unburned carbon tends to remain, causing problems such as a reduction in combustion efficiency.

発明の目的 本発明は上記従来の欠点を解消する微粉炭の低ＮＯｘ燃
焼法を提供することを目的とする。OBJECTS OF THE INVENTION It is an object of the present invention to provide a low NOx combustion method for pulverized coal that eliminates the above-mentioned conventional drawbacks.

発明の構成 上記目的を達成するため、本発明の微粉炭の低ＮＯｘ燃
焼法は微粉炭を１次および２次燃料に分割供給し、燃焼
用空気を１次および２次空気に分割供給して８段燃焼を
行うに際し、２次燃料に１次燃料の燃料比より小さい燃
料比の燃料を使用する構成としたものであり、これによ
り、固体燃料においても液体燃料と同様に燃焼効率を低
下させることなく大巾なＮＯｘの抑制を行うことができ
るものである。Structure of the Invention In order to achieve the above object, the pulverized coal low NOx combustion method of the present invention divides and supplies pulverized coal into primary and secondary fuel, and divides and supplies combustion air into primary and secondary air. When performing eight-stage combustion, the structure uses a fuel with a fuel ratio smaller than that of the primary fuel for the secondary fuel, which reduces the combustion efficiency even for solid fuels in the same way as for liquid fuels. This makes it possible to significantly suppress NOx without causing any problems.

実施例と作用 以下、本発明の一実施例を図面に基づいて説明する。Examples and effects Hereinafter, one embodiment of the present invention will be described based on the drawings.

図において、（１）は燃焼炉、（２）は炉壁に設けられ
た１次燃料ノズル、（３）は該１次燃料ノズル（２）の
周囲から１次空気（ａ）を供給する１次空気口、（４）
は１次燃焼域に後流から２次燃料（ｄ）を供給して２次
燃焼域を形成する２次燃料ノズル、（５）は２次燃焼域
に後流から２次空気（ｂ）を供給して８次燃焼域を形成
する２次空気口である。（６）は１次燃料ホッパーで、
燃料比の比較的大きい微粉炭がブロワ−（７）を通して
１次燃料（Ｃ）として１次燃料ノズル（２）に供給され
る。（８）は燃料比の比較的小さい微粉炭が入れられた
２次燃料ポツパーで、その微粉炭がブロワ−（９）を通
して２次燃料（ｄ）として２次燃料ノズル（４）に供給
される。In the figure, (1) is a combustion furnace, (2) is a primary fuel nozzle provided on the furnace wall, and (3) is a primary fuel nozzle that supplies primary air (a) from around the primary fuel nozzle (2). Next air vent, (4)
(5) is a secondary fuel nozzle that supplies secondary fuel (d) from the wake to the primary combustion zone to form a secondary combustion zone, and (5) supplies secondary air (b) to the secondary combustion zone from the wake. This is a secondary air port that supplies air to form the eighth combustion zone. (6) is the primary fuel hopper,
Pulverized coal having a relatively large fuel ratio is supplied as primary fuel (C) to the primary fuel nozzle (2) through the blower (7). (8) is a secondary fuel popper containing pulverized coal with a relatively low fuel ratio, and the pulverized coal is supplied to the secondary fuel nozzle (4) as secondary fuel (d) through the blower (9). .

本実施例ではこのような粉炭燃料燃焼装置を用い、燃焼
条件として燃焼量を３００ｋｇ／ｈ　に維持し、１次燃
料（ｃ）として２１ｏｋｇ／ｈ　（７０％）、２次燃料
（ｄ）として９０ｋｇ／ｈ（８０％）を供給した。また
１次空気（ａ）としては、全燃料を燃焼するに必要な空
気量の０．７５倍を供給した。In this example, such a pulverized coal fuel combustion device is used, and the combustion conditions are such that the combustion amount is maintained at 300 kg/h, the primary fuel (c) is 21 ok/h (70%), and the secondary fuel (d) is 90 kg/h. /h (80%). Further, as primary air (a), 0.75 times the amount of air required to burn all the fuel was supplied.

燃焼はまず燃料比の比較的大きい１次燃料（ｃ）と１次
空気（ａ）で低空気比の１次燃焼を行わせ、その後流か
ら１次燃料（ｃ）の燃料比より小さい燃料比の２次燃料
（ｄ）を１次燃焼排ガス中に残存する酸素を消費するに
必要な量より過剰な状態になるように供給して２次燃焼
域を還元性雰囲気となし、１次燃焼域で発生したＮＯｘ
をこの２次燃焼域でＮ２に還元させた。そして、この後
、その後流から２次空気（ｂ）を供給して８次燃焼域を
形成し、ここで還元性物質を完全に無公害物質に燃焼さ
せた。In combustion, primary combustion is first carried out at a low air ratio with primary fuel (c) having a relatively large fuel ratio and primary air (a), and after that, a fuel ratio smaller than that of the primary fuel (c) is carried out. The secondary fuel (d) is supplied in excess of the amount required to consume the oxygen remaining in the primary combustion exhaust gas to create a reducing atmosphere in the secondary combustion zone, and NOx generated in
was reduced to N2 in this secondary combustion zone. After that, secondary air (b) was supplied from the downstream side to form an 8th combustion zone, where the reducing substances were completely combusted into non-polluting substances.

この場合、２次燃料（微粉炭）（ｄ）の燃料比が１次燃
料（ｃ）の燃料比より小さいため、２次燃料（ｄ）の分
解ガス化が急速に行われ、ＮＯｘの還元が効果的に行わ
れた。すなわち、第１表に示すように、２次燃料に１次
燃料の燃料比より小゛さい燃料比の微粉炭を使用しなか
った場合（従来例）、ＮＯｘは１８０１！ｍ、未燃カー
ボンは６．４％であったのに対し、２次燃料に１次燃料
の燃料比より小さい燃料比の微粉炭を供給した場合（実
施例）は、ＮＯｘは１５０ｐｐｍ、未燃カーボンは４．
９％に低下し、窒素酸化物の濃度および未燃カーボン量
が小さくなった。In this case, since the fuel ratio of the secondary fuel (pulverized coal) (d) is smaller than the fuel ratio of the primary fuel (c), the secondary fuel (d) is rapidly decomposed and gasified, reducing NOx. It was done effectively. That is, as shown in Table 1, when pulverized coal with a smaller fuel ratio than the primary fuel is used as the secondary fuel (conventional example), NOx is 1801! m, unburned carbon was 6.4%, whereas when pulverized coal was supplied as secondary fuel at a fuel ratio lower than that of primary fuel (example), NOx was 150 ppm, unburned carbon was 6.4%. Carbon is 4.
The concentration of nitrogen oxides and the amount of unburned carbon decreased to 9%.

第１表 発明の効果 以上本発明によれば、供給される２次燃料の分解ガス化
が急速に行なわれ、ＮＯｘの還元が効果的に行なわれて
窒素酸化物の濃度を低減させることができるとともに、
燃焼効率も向上できる利点を有し、工業的価値は極めて
高い。Table 1 Effects of the Invention According to the present invention, the supplied secondary fuel is rapidly decomposed and gasified, NOx is effectively reduced, and the concentration of nitrogen oxides can be reduced. With,
It has the advantage of improving combustion efficiency and has extremely high industrial value.

【図面の簡単な説明】[Brief explanation of the drawing]

図面は本発明の一実施例を示す全体構成図である。 （２）・・１次燃料ノズル、（４）・・・２次燃料ノズ
ル、（Ｃ）・・１次燃料、（ｄ）・・２次燃料 代理人　森本義弘The drawing is an overall configuration diagram showing an embodiment of the present invention. (2)...Primary fuel nozzle, (4)...Secondary fuel nozzle, (C)...Primary fuel, (d)...Secondary fuel agent Yoshihiro Morimoto

Claims (1)

【特許請求の範囲】[Claims] １、　微粉炭を１次および２次燃料に分割供給し、燃焼
用空気を１次および２次空気に分割供給して８段燃焼を
行うに際し、２次燃料に１次燃料の燃料比より小さい燃
料比の燃料を使用することを特徴とする微粉炭の低ＮＯ
ｘ燃焼法。1. When carrying out 8-stage combustion by dividing pulverized coal into primary and secondary fuels and dividing combustion air into primary and secondary air, the fuel ratio of secondary fuel to primary fuel is smaller than the fuel ratio of primary fuel to secondary fuel. Low NO of pulverized coal characterized by using fuel with a fuel ratio
x combustion method.