JPS58120004A - Two-staged combustion - Google Patents

Abstract

PURPOSE:To further lower the concentration of NOx in exhaust gas, by feeding a specified rate of ammonia into the air to be fed into the combustion furnace on the secondary stage, or a subsequent part, in two-staged combustion. CONSTITUTION:A specified rate of ammonia is injected into the secondary air feeding line 7 from its middle part, passing through a line 8, in two-staged combustion. The more the injection rate of NH3 gas is increased, the larger the effect can be expected. But the injection rate is to be determined, considering the concentration of NOx being fed into an oxidation part 4B, which is different according to the ratio of fuel to the primary air, together with the target rate of NOx to be lowered, economy, and other. With such an arrangement, residual NOx which is not reduced in the reduction part 4A is reduced in the oxidation part 4B, so that the concentration of NOx in exhaust gas is further decreased, and the exhaust gas is discharged, passing through a line 9.

Description

【発明の詳細な説明】 本発明は二段燃焼方法に関し、さらに詳しくは、燃焼用
空気を二段またはそれ以上に分割して供給する窒素酸化
物（ＮＯ，）低減を目指した二段燃焼方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-stage combustion method, and more specifically, a two-stage combustion method aiming at reducing nitrogen oxides (NO,) in which combustion air is divided into two or more stages and supplied. Regarding.

燃焼排ガス中のＮＯ，＠［を低減させる方法は数多く提
案および実施されているが、そのうち、炉内で低減させ
る方法の主なものは次のとおりである。Many methods have been proposed and implemented to reduce NO,@[ in the combustion exhaust gas, among which the main methods for reducing NO in the furnace are as follows.

（１）燃焼用空気を分割した二段燃焼法、（２）燃焼用
空気に燃焼排ガスを混ぜた排ガス循環法、（３）高温燃
焼ガスＫ　ＮＥ（ｓを注入する無触媒還元法、（４）超
高温燃焼ガスに燃料の一部を注入する燃料注入法。(1) Two-stage combustion method in which combustion air is divided, (2) Exhaust gas circulation method in which combustion air is mixed with combustion exhaust gas, (3) Non-catalytic reduction method in which high-temperature combustion gas KNE(s) is injected, (4) ) A fuel injection method in which a portion of the fuel is injected into the ultra-high temperature combustion gas.

これらの方法は、廃棄物焼却炉、加熱炉、ｌイラ等にお
い【単独、または組合わせて採用されている。しかし一
般に流動層焼却炉などの流動炉においては、超高温部（
１１００℃以上］がないため、燃料注入法は適用するこ
とができない、またバーナ燃焼でないため、排ガス循環
法の効果は非常に少ない、無触媒還元法はＳＯＯ〜９５
０℃の燃焼ガスに微量のＮＨｓガスを注入する方法であ
るが、燃焼ガスとＮＥＩｓガスの混合が重畳であるため
、−特別の注入ノズル等を設けて工夫をこらす必要があ
る。従って、流動層燃焼炉に対しては簡便な二段燃焼法
が現在主流となっている。These methods are employed singly or in combination in waste incinerators, heating furnaces, lira, etc. However, in general, in fluidized bed incinerators and other fluidized bed incinerators, the ultra-high temperature section (
1100℃ or higher], so the fuel injection method cannot be applied.Also, since it is not burner combustion, the effect of the exhaust gas circulation method is very small.The non-catalytic reduction method is SOO ~ 95
This method involves injecting a small amount of NHs gas into the combustion gas at 0°C, but since the combustion gas and NEIs gas are mixed in a superimposed manner, it is necessary to use a special injection nozzle or the like. Therefore, the simple two-stage combustion method is currently the mainstream for fluidized bed combustion furnaces.

本発明者は先に、このような、二段燃焼法において、酸
素１１度の低い、または酸素がはとんとない一次燃焼部
でＮＯｘが充分還元されるように一次燃焼部のガス滞留
時間を充分長くとった後に二次空気を供給し、残りの未
燃分を完全燃焼させる低ＮＯ。The present inventor previously discovered that in such a two-stage combustion method, the gas residence time in the primary combustion section should be sufficient so that NOx is sufficiently reduced in the primary combustion section where the oxygen temperature is low at 11 degrees Celsius or oxygen is completely absent. Low NO that supplies secondary air after a long period of time and completely burns the remaining unburned matter.

二段燃焼法を提案したが（轡願１８５２−１４１９１８
号）、ＮＯ，低減効果については必らずしも充分ではな
かった。I proposed a two-stage combustion method (Request No. 1852-141918)
(No.), NO, the reduction effect was not necessarily sufficient.

本発明の目的は、前記二段燃焼法を改善し、さらＫＮＯ
，を抑制することができる方法を提供するととＫある。The purpose of the present invention is to improve the two-stage combustion method and further improve the KNO
, K provides a method that can suppress .

本発明は、燃倫炉Ｋｍ鉤用空気を二段またはそれ以上に
分割供給して燃焼ガス中のＮｏ、を低減させる二段燃焼
方法において、二段目またはそれ以降に供給する空気中
にアンモニアを供給することを特徴とする。The present invention provides ammonia in the air supplied to the second stage or later in a two-stage combustion method in which air for the combustion furnace Km is dividedly supplied to two or more stages to reduce NO in the combustion gas. It is characterized by supplying.

以下、本発明を図面によって詳細に説明する。Hereinafter, the present invention will be explained in detail with reference to the drawings.

第１図は、本発明の代表的な実施例を説明するための流
動炉の概略図である。図において、燃焼用空気は２段に
分けられ、それぞれ１次空気供給ライン５および２次空
気供給ライン７から流動炉１内に供給される。すなわち
、供給燃料量の理論空気量近辺の量（１次空気比＝０．
８〜１４）Ｋ和尚する空気は、１次空気供給ライン５が
ら空気箱２を介してペッドｓｓに供給され、燃料供給ラ
イン６から供給された燃料はペッドｓ３で北壁的酸素不
足の条件下で１次燃焼される０次にペッド部３から上昇
する燃焼ガスは、還元部４ムで所定の滞留時間を与えら
れた後、フリーボード部４内で２次空気供給ライン７か
ら２次空気の供給を５ける。ついで酸化５４　Ｂにおい
て燃焼ガス中和残存す−る未燃分が完全燃焼される。こ
の場合、還元部４ムで与える所定のガス滞留時間は、ペ
ッド部３から上昇する燃焼ガス中のＮＯｘが共に含有し
ている未燃分により充分還元されてＮ！になるのに必要
な時間であり、ＬＯ〜３．０秒が適当である。FIG. 1 is a schematic diagram of a fluidized bed furnace for explaining a typical embodiment of the present invention. In the figure, combustion air is divided into two stages and supplied into the fluidized bed furnace 1 from a primary air supply line 5 and a secondary air supply line 7, respectively. In other words, the amount of supplied fuel is close to the theoretical air amount (primary air ratio = 0.
8 to 14) Air for cooling is supplied from the primary air supply line 5 to the ped ss via the air box 2, and fuel supplied from the fuel supply line 6 is supplied to the ped s3 under oxygen-deficient conditions on the north wall. After being given a predetermined residence time in the reducing part 4, the combustion gas rising from the zero-order ped part 3, which is primarily combusted in Multiply the supply by 5. Then, in oxidation step 54B, the combustion gas is neutralized and the remaining unburnt components are completely combusted. In this case, the predetermined gas residence time given by the reducing section 4 is such that NOx in the combustion gas rising from the ped section 3 is sufficiently reduced by the unburned components contained together with N! This is the time required for the LO to 3.0 seconds.

本発明（おいては、上記二段燃焼における２次空気供給
ライン７の途中でライン８から所定量のアンモニア（Ｎ
Ｈｓ　）ガスを注入する。　ＮＨｓガスの注入量は多い
椙効釆が大きいが、燃料および１次空気比などＫよって
異なる酸化部４８に流入する燃焼ガス中のＮＯ，濃度、
ＮＯｘ抑制目標および経済性等を考慮し【決定される。In the present invention, a predetermined amount of ammonia (N
Hs) Inject gas. The amount of NHs gas injected is large, but the concentration of NO in the combustion gas flowing into the oxidizing section 48 varies depending on the fuel and primary air ratio.
[Determined] taking into account NOx suppression goals and economic efficiency.

通常、全燃焼ガス量基準でｓ　ｏ　ｏｐｐｔ以下、すな
わち全燃焼ガス量の２０００分の１より少ない注入量で
十分である。２０００分の１以上注入してもその増量効
果は余りない。このアンモニアガスの注入により、還元
部４ムで還元されなかった残存ＮＯ，が酸化部４Ｂで還
元され、ライン９から排出される排ガス中の黒濃度かさ
らに低減される。Usually, an injection amount of less than so optt based on the total amount of combustion gas, that is, less than 1/2000 of the total amount of combustion gas, is sufficient. Even if 1/2000 or more is injected, the effect of increasing the amount will not be significant. By injecting this ammonia gas, residual NO, which has not been reduced in the reducing part 4m, is reduced in the oxidizing part 4B, and the black concentration in the exhaust gas discharged from the line 9 is further reduced.

なお、第１図の破Ｉ１１？イン７ム、８ムで示す橡に、
２次空気を２分割（又は３分割）して供給する方法を本
発明者が先に提案したが（特願昭５２−１４１９１５号
）、この方法においてＮＨ，ガスを２次空気に注入する
と、ライン９から排出される排ガス中のＮＯ８＃１１度
は、前記の２次空気を分割しない方法に比してさらに低
減する。この場合、ＮＨｓガスを分割した２次空気の上
段、下段いづれに注入しても効果が岡薯度であることが
実験的に確絃された。In addition, break I11 in Figure 1? In the square indicated by in 7m and 8m,
The present inventor previously proposed a method of supplying secondary air by dividing it into two parts (or three parts) (Japanese Patent Application No. 141915/1982), but in this method, when NH and gas are injected into the secondary air, The NO8 concentration in the exhaust gas discharged from the line 9 is further reduced compared to the method described above in which the secondary air is not divided. In this case, it has been experimentally determined that the effect is the same even if the NHs gas is injected into either the upper or lower stage of the divided secondary air.

上記のように２次空気中ＫＮ）１ｍガスを注入すること
は、燃焼ガスとの混合が嵐いために残存Ｎｏ８と注入Ｎ
Ｈ，との反応が早く、また次式に示すＮＯ。As mentioned above, injecting 1 m of KN) gas in the secondary air is difficult to mix with the combustion gas, so the residual No. 8 and the injected N
The reaction with H, is fast, and NO shown in the following formula.

とＮＨｓの反応に必要な酸素も充分与えられるので効果
が大きい。The effect is great because sufficient oxygen is provided for the reaction between and NHs.

ガスの他に、ＮＨ，ガス成分を含む廃ガスでもよく、ま
たＮＨｍガスの代りＫＨＣＮガスを用いることも可能で
ある。In addition to gas, waste gas containing NH and gas components may be used, and KHCN gas may be used instead of NHm gas.

次に第２図は、第１図に示す流動炉を用い、総括空気比
を１．２３（すなわち空気過剰率２３嘔）と一定にした
条件下で１次空気供給量（すなわち１次空気比）を減少
させて燃料（石庚）の二段燃焼を行なった場合の洲、ガ
ス注入結果を示したものである。横軸の１次空気比は２
段燃焼の度合を示し、縦軸のＮＯ，濃度は燃焼ガス中の
値である。Next, Fig. 2 shows the primary air supply amount (i.e., the primary air ratio ) shows the results of gas injection when two-stage combustion of fuel (sekigen) is performed. The primary air ratio on the horizontal axis is 2
It shows the degree of staged combustion, and the NO concentration on the vertical axis is the value in the combustion gas.

図中、−纏ムは、二段燃焼単独の場合、−−Ｂは二段燃
焼で２次空気中に洲、を１１０ＷＩｐ注入した場合、Ｓ
ａＣは同様にＮＨｓを４６０簿注入した場合をそれぞれ
示す。二段燃焼を行なわない場合（１次および総括空気
比が共Ｋ　１．２　Ｂ　）は２７０−のＮＯ！濃度であ
ったものが、二段燃焼を行ない、１次空気比を下げるこ
とによってＮＯ，は１１０ｊＰ近くまで低下することが
分る（曲線ム）、これに対して一１ｉ１Ｂ％Ｃの場合は
、例えば１次空気比を０．９とした二段燃焼単独条件下
で１３０ｐであったＮｏ、ｌｓ１度が、金燃焼ガス量に
対して１１０−ないしく６Ｇｗｅｓ＠轟のＮＥｌ、ガス
を２次空気に注入することによって約８０〜６ｏ−まで
低下することが分る。In the figure, -M is the case of two-stage combustion alone, -B is the case of two-stage combustion and S is injected into the secondary air at 110 WIp, S
Similarly, aC shows the case where 460 NHs were injected. If two-stage combustion is not performed (primary and overall air ratios are both K 1.2 B), 270-NO! It can be seen that the NO concentration decreases to nearly 110jP by performing two-stage combustion and lowering the primary air ratio (curve m).On the other hand, in the case of -1i1B%C, For example, No.ls 1 degree, which was 130p under two-stage combustion alone with the primary air ratio of 0.9, is 110-6Gwes@Todoroki's NEL for the amount of gold combustion gas, and the gas is transferred to the secondary air. It can be seen that the temperature decreases to about 80 to 6 o- by injecting it to .

なお、ＮＨｓガスの注入位置として、２次空気以外に、
第１図で示す還元部４ムやベッド部３に損ｈガスを注入
してみたが、効果はあまりなかった。In addition to secondary air, the injection position of NHs gas is
I tried injecting loss gas into the reducing section 4m and bed section 3 shown in Figure 1, but it did not have much effect.

％にベッド部３に注入した場合は全く効果がない。%, it has no effect at all when injected into the bed portion 3.

本発明は、ｍｉｓに示した燃焼炉以外に、第３図に示す
ようなバーナ１３を用いたガス燃料、油、微粉炭、廃棄
物の燃焼炉にも適用することができる。この燃焼炉１１
は、１次燃焼室１１Ａおよび２次燃焼１！ＩＩＢとに区
分され、燃料１５が供給されるバーナ１３が貫通する空
気箱１４にはツイン１６から１次空気が供給される。ま
た２次燃焼室１１ＢＫはライン１７から２次空気が供給
され、該ライン１７にはライン１８からＮＨｓガスが注
入される。この場合、例えばライン１６から供給する１
次空気量を、ライン１５から供給する燃料量の理論空気
量近辺とし、１次燃焼１１１１ム内で比較的酸素不足の
状態で１次燃焼させ、２次燃焼室１１Ｂ内に供給する２
次空気に所定量の洲、ガスを注入することにより、２段
燃焼単独の効果以上に排ガス１９中のＮＯｘ磯度濃度減
させることができる。The present invention can be applied to a combustion furnace for gas fuel, oil, pulverized coal, or waste using a burner 13 as shown in FIG. 3, in addition to the combustion furnace shown in FIG. This combustion furnace 11
are the primary combustion chamber 11A and the secondary combustion 1! Primary air is supplied from the twin 16 to the air box 14, which is divided into IIB and IIB and is penetrated by the burner 13 to which fuel 15 is supplied. Further, secondary air is supplied to the secondary combustion chamber 11BK from a line 17, and NHs gas is injected into the line 17 from a line 18. In this case, for example, the 1
The amount of secondary air is set to be close to the theoretical amount of air of the amount of fuel supplied from the line 15, primary combustion is performed in a relatively oxygen-deficient state within the primary combustion chamber 1111, and the amount of fuel is supplied into the secondary combustion chamber 11B.
By injecting a predetermined amount of air into the secondary air, the NOx concentration in the exhaust gas 19 can be reduced more than the effect of two-stage combustion alone.

さらに第４図は、バーナ回りから供給する燃焼用空気を
分割した通常の二段燃焼法に本発明を適用した例を示す
。炉壁ＩＫ挿入されたバーナ１３０回り忙は１次空気箱
１４Ａと２次空気箱１４Ｂが設けられ、ライン１６およ
び１７からそれぞれ１次空気および２次空気が供給され
、２次空気にはライン１８から所定量のＮ１（ｓガスが
供給される。Furthermore, FIG. 4 shows an example in which the present invention is applied to a normal two-stage combustion method in which combustion air supplied from around the burner is divided. A primary air box 14A and a secondary air box 14B are provided around the burner 130 inserted into the furnace wall, and primary air and secondary air are supplied from lines 16 and 17, respectively, and the secondary air is supplied from line 18. A predetermined amount of N1(s gas is supplied from

なお、図中、２０は火炎、２１は’ＮＨｓガスを含む２
次空気を示す、上記のような炉構成においても、２次空
気にライン１８から麗、ガスを注入することにより、単
なる二段燃焼以上に排ガス中のＮＯ。In addition, in the figure, 20 is a flame, and 21 is 2 containing 'NHs gas.
Even in the above-mentioned furnace configuration in which the secondary air is injected into the secondary air from the line 18, NO in the exhaust gas can be reduced more than just two-stage combustion.

濃度を低減させることができる。concentration can be reduced.

本発明の効果を列挙すれば下肥のようである。If the effects of the present invention are enumerated, they are similar to manure.

（１）２段燃焼の度合をやわらげることができる。すな
わち、２段燃焼Ｉ）度合を強める（１次空気比を下げる
）Ｋ従つｃＮｏ、ａ度は低下するが、わずかな量の洲、
ガスを２次空気に注入するととによって、緩慢な二段燃
焼条件下（例えば、１次空気比＝　１．１５　）　Ｋ、
おいても、度合の強い二段燃焼条件下（例えば１次空気
比＝０．＊）と同稠度のＮＯ８濃ｉ！を達成することが
できる。(1) The degree of second-stage combustion can be reduced. In other words, the two-stage combustion I) increases the degree (lowers the primary air ratio), so the cNo, a degree decreases, but only by a small amount,
By injecting the gas into the secondary air under slow two-stage combustion conditions (e.g. primary air ratio = 1.15) K,
Even if the NO8 concentration is the same as under strong two-stage combustion conditions (for example, primary air ratio = 0.*)! can be achieved.

（２）上記α）Ｋより高い燃焼効率を得ることができる
。(2) Higher combustion efficiency than α)K above can be obtained.

一般に１次空気比の低下に伴なって炉外に排出する未燃
分が増加するので、１次空気比を高くできることは高燃
焼効率につながる。Generally, as the primary air ratio decreases, the amount of unburned matter discharged outside the furnace increases, so being able to increase the primary air ratio leads to high combustion efficiency.

（３）上記（１）により１次空気比が高くなると、ベッ
ド部で燃える割合が増加し、フリーボード部で燃える後
燃焼の割合が減少するため、炉容積を小さくすることが
できる。これは流動層焼却炉や流動層ボイラ勢の大型炉
において有利である。また流動層ボイラの場合、１次空
気比が高くなると、伝熱係数の大きいベッド部での燃焼
割合が増加するので伝熱面積を減少させることかできる
。また流動（倫 層焼却の場合には、ベッド部での燃焼割合が増加するの
で、補助燃料を削減することができる。(3) When the primary air ratio increases due to (1) above, the proportion of combustion in the bed section increases and the proportion of post-combustion burning in the freeboard section decreases, so the furnace volume can be reduced. This is advantageous in large-scale furnaces such as fluidized bed incinerators and fluidized bed boilers. Furthermore, in the case of a fluidized bed boiler, when the primary air ratio increases, the combustion rate in the bed portion where the heat transfer coefficient is large increases, so the heat transfer area can be reduced. In addition, in the case of fluidized bed incineration, the combustion rate in the bed increases, so the amount of auxiliary fuel can be reduced.

（４）上記（１）　Ｋより、流動層ボイ２の場合、炉内
で高度のＮＯ，抑制と石灰石による脱硫を同時に達成す
ることができる。１次空気比を低くすると炉内脱硫率が
悪くなるので、炉内脱硫率の高い１次空気比の高い条件
下（緩慢な２段燃焼条件）で運転し、１次空気比の増加
に伴なうＮＯ□抑制効果の低下を、２次空気への洲、ガ
ス注入で補なうことができるので、高度のＮｏＸ抑制と
高度の炉内脱硫を同時に達成することができ、また脱硫
剤を節約することができる。(4) From (1) K above, in the case of fluidized bed boiler 2, a high degree of NO suppression and desulfurization using limestone can be simultaneously achieved in the furnace. If the primary air ratio is lowered, the in-furnace desulfurization rate will deteriorate, so operate under conditions with a high primary air ratio (slow two-stage combustion conditions) where the in-furnace desulfurization rate is high, and as the primary air ratio increases, Since the decrease in the NO□ suppression effect can be compensated for by injecting gas into the secondary air, it is possible to achieve a high degree of NoX suppression and a high degree of in-furnace desulfurization at the same time. You can save money.

（５）非常に簡便な方法である。すなわち、２次空気が
炉内に入る前にＮＨｓガスを注入するだけで喪く、また
２次空気と共に炉内に注入するので、燃焼ガスとの混合
性が非常に良く、無触還元法のように特別な注入ノズル
等を設ける必要がない。(5) It is a very simple method. In other words, the NHs gas is simply injected into the furnace before the secondary air enters the furnace, and since it is injected into the furnace together with the secondary air, it mixes very well with the combustion gas, making it ideal for non-catalytic reduction. There is no need to provide a special injection nozzle or the like.

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

第１図は、本発明が適用されると燃焼炉の概略を示す断
面図、第２図は、本発明の燃焼方法の効（１Ｇ） 果を説明する図、第３１ａおよび第４図は、本発明が適
用される他の燃焼炉のアンモニア注入方法を示す図であ
る。 １・・・炉、３−ベッド部、４・−・クリ−ボード部、
４Ａ・・・還元部、４Ｂ・・・酸化部、７・・・２次空
気供給ライン、８・・・損０ガス注入ライン。 代理人　弁理士　　川　北　武　長 筒１図 第２図 第３図 手続補正書 昭和ｉ７年４月７日 特許庁長官　島田春樹殿 １、事件の表示 昭和ｓ７年　　　轡許願第１７フＯ号 ２、発明の１称　　二段燃情方法 ３　補正をする者 事件との関係　　善許出原人 ４　代　　理　　人　　〒ｌＨＩ ３″′　（マ５ｉｓ）弁理士　用北武長５、　補正命令
の日付　　　　　　　自発６、　補正により増加する発
明の数 ７、補正の対象 に改める。 （乃＠綱書嬉５頁第１３行の「上段、下段」を「上段（
７ム）、下段（η」に改める。 （３）図面第２図および第４図をそれぞれ別紙のよ５に
改める。 以上FIG. 1 is a sectional view schematically showing a combustion furnace to which the present invention is applied, FIG. 2 is a diagram illustrating the effect (1G) of the combustion method of the present invention, and FIGS. 31a and 4 are It is a figure which shows the ammonia injection method of another combustion furnace to which this invention is applied. 1...furnace, 3-bed section, 4--creeboard section,
4A... Reduction section, 4B... Oxidation section, 7... Secondary air supply line, 8... Zero loss gas injection line. Attorney Takeshi Kawakita Nagatsutsu 1 Figure 2 Figure 3 Procedural amendments April 7, 1937 Commissioner of the Japan Patent Office Haruki Shimada 1, Indication of the case 1939, Request for Permission No. 17, No. 2, First name of the invention Two-step passion method 3 Relationship with the case of the person making the amendment 4 Proxy attorney 〒lHI 3″' (Ma5 is) Patent attorney Yokita Takecho 5 Date of amendment order Voluntary 6 , The number of inventions will increase by the amendment to 7, and the subject of the amendment will be changed.
(3) Figures 2 and 4 of the drawings are respectively revised to Attachment 5.

Claims (1)

【特許請求の範囲】[Claims] （１）燃焼炉に燃焼用空気を二段またはそれ以上に分割
供給して燃焼ガス中のＮＯ，を低減させる二段燃焼方法
において、二段目またはそれ以降に供給する空気中にア
ンモニアを供給することを特徴とする二段燃焼方法。(1) In a two-stage combustion method in which combustion air is dividedly supplied to a combustion furnace in two or more stages to reduce NO in the combustion gas, ammonia is supplied to the air supplied in the second stage or later. A two-stage combustion method characterized by: