WO2007043216A1

WO2007043216A1 - Method of treating gas containing nitrogen oxide

Info

Publication number: WO2007043216A1
Application number: PCT/JP2006/312381
Authority: WO
Inventors: Osamu Tanaka; Yukihiro Tokunaga; Yusuke Okamoto; Kenji Yasui
Original assignee: Miura Co., Ltd.; Miura Protec., Ltd.
Priority date: 2005-10-14
Filing date: 2006-06-21
Publication date: 2007-04-19

Abstract

A method of cutting down carbon monoxide and nitrogen oxides that is capable of easy realization of low NOx lowering the emitted NOx value to below 5 ppm and simultaneously realization of low CO. Further, there is provided a method of treating a gas containing nitrogen oxides that is capable of not only realizations of ultralow NOx and low CO but also realization of energy saving. There is provided a method of treating a gas containing carbon monoxide, nitrogen oxides and oxygen and not containing HC, characterized by including the steps of regulating the respective concentrations of carbon monoxide, nitrogen oxides and oxygen in the gas so that these satisfy the formula: ([NOx]+2[O2])/[CO] ≤ 2.0 (2) (in the formula (2), [CO], [NOx] and [O2] respectively represent the concentration of carbon monoxide, the concentration of nitrogen oxides and the concentration of oxygen, provided that [O2]>0); and bringing the gas having the concentration ratios regulated into contact with a catalyst capable of reducing of nitrogen oxides.

Description

Specification

Method for treating nitrogen oxide-containing gas

Technical field

[0001] The present invention relates to a method for treating a gas containing nitrogen oxides applied to a water tube boiler, a regenerator of an absorption chiller, and the like.

Background art

[0002] In general, as a principle for suppressing NOx generation, suppression of flame (combustion gas) temperature, shortening of residence time of high-temperature combustion gas, and the like are known. There are various low NOx technologies that apply these principles. For example, the two-stage combustion method, the concentration combustion method, the exhaust gas recirculation combustion method, the hydrogenation combustion method, the steam injection combustion method, and the flame cooling combustion method using water tube groups have been proposed and put to practical use.

[0003] By the way, environmental impacts of NOx generation sources with relatively small capacities, such as water tube boilers, have been increasing with the times, and even lower NOx emissions have been demanded. At this low NOx level, reducing NOx production increases CO emissions, making it difficult to reduce NOx and CO simultaneously.

[0004] The cause is that low NOx and low CO are contradictory technical issues. In other words, if the combustion gas temperature is drastically lowered to promote low NOx and suppressed to a low V and temperature of 900 ° C or less, a large amount of CO is generated and the generated CO is not oxidized. As a result, CO emissions will increase. Conversely, if the combustion gas temperature is suppressed to a high level to reduce CO emissions, the amount of NOx produced will be insufficiently suppressed.

[0005] In order to solve this problem, the applicant suppresses the combustion gas temperature so that the amount of CO generated with low NOx emissions is reduced as much as possible and the generated CO is oxidized. The company proposes and commercializes low N Ox and low CO technologies (see Patent Document 1). However, the low NOx technology described in Patent Document 1 actually produced a NOx value of about 25 ppm.

[0006] As a solution to this problem, the applicant reduced the NOx generation step by suppressing the combustion gas temperature so that the suppression of NOx generation has priority over the reduction of the emission CO value, and reducing the generated NOx value to a predetermined value or less. After that, a low NOx combustion method is proposed in which a CO reduction step for reducing the emission CO value from the NOx reduction step to a predetermined value or less is performed (see Patent Document 2). According to the technology of Patent Document 2, it is difficult to realize a low NOx concentration of less than 5 ppm, which enables a low NOx amount of less than 10 ppm. This is due to the inevitable production of NOx over 5ppm due to the characteristics of combustion.

[0007] And, the low NOx technology described in Patent Document 2 belongs to a so-called high air ratio combustion region having an air ratio of 1.38 or more. On the other hand, in the premixed combustion region with an air ratio of 1.1 or less, the amount of carbon monoxide generated significantly exceeds the regulated value of 300 ppm, making it difficult to put it into practical use, and when the air ratio is 1 or less, This has been the subject of almost no research and development until now due to the difficulty of stable combustion control, such as fire. Here, the air ratio is defined as air ratio = 2lZ (21— [02]) when the oxygen concentration in the exhaust gas is [02] (the same applies hereinafter in this application).

[0008] On the other hand, as the background of the times, there has been a demand for boilers that require even lower NOx and low energy ratio operation that saves energy.

[0009] The inventors of this application have conducted intensive research, and as a result, almost no research has been conducted so far.

Infinitely close to 1 and in the low air ratio combustion region! Nitrogen oxide emissions can be reduced to almost zero, while carbon monoxide emissions can be reduced to an acceptable range. In pursuit of a combustion method that can realize energy saving with a low air ratio, and invented a solution for it o

The present invention can be applied to a method for treating a gas containing carbon monoxide, nitrogen oxides and oxygen without being limited to a combustion method having a low air ratio.

[0011] Patent Document 1: Japanese Patent No. 3221582

Patent Document 2: JP-A-2004-125378

Disclosure of the invention

Problems to be solved by the invention

[0012] The problem to be solved by the present invention is that, in a gas containing carbon monoxide, nitrogen oxide and oxygen, and not containing HC, the amount of NOx emission is reduced to almost zero and the amount of CO emission It is to reduce.

Means for solving the problem

[0013] The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 is characterized in that a first reaction for oxidizing a mono-acid carbon and a nitrogen oxide are converted into a mono-acid. Using a catalyst that generates a second reaction that is reduced by carbon, a gas containing oxygen, nitrogen oxides, and carbon monoxide is passed through the catalyst, and oxygen is consumed by the first reaction in the catalyst. A method for treating a nitrogen oxide-containing gas by reducing the concentration of nitrogen oxides and reducing the concentration of nitrogen oxides by the second reaction with carbon dioxide that cannot be consumed. And an adjustment step of adjusting the predetermined concentration of carbon monoxide so as to satisfy the following formula (1).

[NOx] + 2 [02] ≤ [CO]

However, [CO]:-carbon oxide concentration, [NOx]: nitrogen oxide concentration, [02]: oxygen concentration

[0014] The invention according to claim 2 is a method for treating a gas containing carbon monoxide, nitrogen oxide, and oxygen, but not HC, wherein the carbon monoxide contained in the gas is oxidized with nitrogen. A step of adjusting the concentration of the product and oxygen to satisfy the following formula (2), and a step of bringing the gas having the adjusted concentration ratio into contact with a catalyst capable of reducing nitrogen oxides. It is characterized.

([NOx] + 2 [02]) / [CO] ≤2. 0--(2)

(In Equation (2), [CO], [NOx] and [02] indicate the concentration of carbon monoxide, nitrogen oxide and oxygen, respectively, and satisfy the condition [O2]> 0.)

[0015] The invention according to claim 3 is a method for treating a gas containing carbon monoxide, nitrogen oxide and oxygen and not HC, wherein the carbon monoxide and nitrogen oxide contained in the gas are included. The main reaction is an adjustment process that adjusts the concentrations of substances and oxygen to a predetermined relationship, and a first reaction that oxidizes carbon monoxide with oxygen and a second reaction that reduces nitrogen oxides with carbon monoxide. And the contacting step of bringing the gas having the adjusted concentration into contact with the catalyst, wherein the adjusting step includes reducing the concentration of carbon monoxide on the primary side of the catalyst in the catalyst by the first reaction. The value is approximately equal to or higher than the value obtained by adding the carbon oxide concentration and the carbon monoxide concentration reduced in the catalyst by the second reaction. [0016] The invention according to claim 4 is a method for treating a gas containing carbon monoxide, nitrogen oxide and oxygen and not containing HC, the carbon monoxide contained in the gas, and nitrogen oxidation. Before the catalyst that performs the adjustment process for adjusting the concentrations of the product and oxygen to a predetermined relationship, the first reaction for oxidizing carbon monoxide with oxygen, and the second reaction for reducing nitrogen oxide with carbon monoxide. Contacting the gas with the concentration adjusted, and the adjusting step adjusts the carbon monoxide concentration, the nitrogen oxide concentration, and the oxygen concentration on the primary side of the catalyst to a predetermined relationship. The nitrogen oxide concentration

It is characterized in that it is qualitatively zero and the carbon monoxide concentration is reduced. The invention's effect

[0017] According to the present invention, by adjusting the carbon monoxide concentration, the nitrogen oxide concentration, and the oxygen concentration, the emission amount of nitrogen oxides which are harmful substances is substantially zero, and the CO emission amount Can be reduced.

Brief Description of Drawings

FIG. 1 is a schematic configuration diagram illustrating Example 1 of a combustion apparatus according to the present invention.

2 is a cross-sectional explanatory view taken along line II-II in FIG.

FIG. 3 is a front view showing the main configuration of the catalyst of Example 2.

FIG. 4 is an electric circuit diagram of the main part of the second embodiment.

FIG. 5 is a schematic configuration diagram illustrating Example 2 of the combustion apparatus of the present invention.

6 is a cross-sectional explanatory view taken along line VI-VI in FIG. 5 of Example 2. FIG.

FIG. 7 is a view for explaining control characteristics of the damper of the second embodiment.

FIG. 8 is a view for explaining output characteristics of the sensor of Example 2.

FIG. 9 is a view for explaining a modification of the first embodiment and the second embodiment.

Explanation of symbols

[0019] 1 catalyst

2 Gas

3 Pana

4 Water pipe (heat absorption means) BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will be described. Before describing the embodiments of the present invention, terms used in the present application will be described. The gas refers to a gas during a combustion reaction (combustion process) and includes a gas passing through a catalyst. The exhaust gas is a gas that has completed the combustion reaction.

Next, an embodiment of the present invention will be described. The present invention is particularly preferably applied to combustion equipment (also referred to as thermal equipment or combustion equipment) such as a water tube boiler such as a small once-through boiler, a water heater, or a regenerator of an absorption chiller.

(Embodiment 1 of processing method)

Embodiment 1 of this treatment method uses a catalyst that generates a first reaction that oxidizes monoxide and carbon and a second reaction that reduces nitrogen oxide by monoxide and carbon, and oxidizes oxygen and nitrogen. And a gas containing carbon monoxide is passed through the catalyst, and oxygen is consumed by the first reaction in the catalyst to reduce the concentration of carbon monoxide and carbon, which cannot be consumed. In this method, the nitrogen oxide concentration is reduced by the second reaction, and the predetermined concentrations of oxygen, nitrogen oxide, and carbon monoxide satisfy the following formula (1): It is the processing method of the nitrogen oxide containing gas characterized by including the adjustment process adjusted so that it may satisfy | fill.

[NOx] + 2 [02] ≤ [CO]

In Embodiment 1 of this treatment method, the concentration ratio of oxygen, nitrogen oxide, and carbon monoxide in the gas on the primary side of the catalyst is controlled so as to satisfy the formula (1). Thereafter, carbon monoxide is oxidized by the catalyst, and nitrogen oxides are reduced. As a result, the discharge amount of nitrogen oxides in the gas is reduced to a value close to zero of 5 ppm or less. In addition, carbon monoxide emission is reduced.

[0024] This reduction action is considered to be performed as follows. In the catalyst, as the main reaction, a first reaction for oxidizing carbon monoxide and a second reaction for reducing nitrogen oxide with carbon monoxide are generated. In the reaction in the catalyst (catalytic reaction), in the presence of oxygen, the first reaction is superior to the second reaction. Subsequently, carbon monoxide is consumed by oxygen, and after the concentration is adjusted, nitrogen oxides are reduced by the second reaction. This description is simplified. Actually, the first reaction is a competitive reaction with the second reaction, but the reaction between carbon monoxide and oxygen occurs apparently faster than the second reaction in the presence of oxygen. It is thought that carbon monoxide (first reaction) is carried out in step 1, and nitrogen oxides are reduced (second reaction) in the second stage.

In short, in the catalyst, in the presence of oxygen, oxygen is consumed by the first reaction of CO + lZ202 → C02, and the remaining CO is used for the second reaction of 2CO + 2NO → N2 + 2C02. Nitrogen oxides are reduced by two reactions to reduce the concentration of exhausted nitrogen oxides.

[0026] Here, [NOx] in the formula (1) is the total concentration of the nitric oxide concentration: [NO] and the nitrogen dioxide concentration: [N02]. In the description of the above reaction formula, NO is used without using NOx. The composition of the generated nitrogen oxide in a high temperature field is NO as the main component, and N02 is only a few percent. This is because it can be described approximately. NO 2 is thought to be reduced by CO in the same way as NO.

[0027] The value of ([NOx] + 2 [02]) Z [CO] (concentration ratio value) In the case of 1, theoretically, the oxygen concentration, nitrogen oxide concentration and The carbon oxide concentration can be made zero. However, in the experiment, it is a component that a small amount of carbon monoxide is emitted. [NOx] +2 [02]) Z [CO] = 1 is theoretically derived from the first reaction and the second reaction force based on the experimental results.

[0028] When the value of the concentration ratio is less than 1, the concentration of carbon monoxide is higher than the concentration necessary for the reduction of the nitrogen oxides, so the exhaust oxygen concentration is zero and the concentration after passing through the catalyst Carbon monoxide and carbon remain in the gas. It is preferable to further provide an acid means for acidifying the residual carbon monoxide. The oxidizing means can be configured to provide a catalyst separate from the catalyst and to add oxygen to acidify carbon monoxide. The source can be an incinerator or jet turbine.

[0029] The adjustment step is preferably performed in a generation source such as a panner that generates a gas containing oxygen, nitrogen oxides, and carbon monoxide, and the concentration ratio of oxygen, nitrogen oxides, and carbon monoxide is changed to oxygen, nitrogen. Adjust the generation process of acids and carbon monoxide However, the present invention is not limited to this, and the concentration ratio can be adjusted between the generation source and the catalyst. In the former case, there is an effect that it is not necessary to provide a means for adjusting the concentration ratio separately from the generation source.

[0030] The catalyst is a catalyst having a function of reducing the nitrogen oxide in the gas, and has a configuration in which a catalytically active substance is applied to a base material having air permeability. As the substrate, a metal such as stainless steel or a ceramic is used, and a surface treatment is performed so as to widen the contact area with the gas. Platinum is generally used as the catalytically active material, but depending on the implementation, noble metals such as white gold (Ag, Au, Rh, Ru, Pt, Pd) or metal oxides may be used. it can.

[0031] (Second Embodiment of Processing Method)

The present invention includes Embodiment 2 of the following processing method. Embodiment 2 is a method for treating a gas containing carbon monoxide, carbon oxide, nitrogen oxide, and oxygen but not HC, each of carbon monoxide, nitrogen oxide, and oxygen contained in the gas. Adjust the concentration to satisfy the following formula (2)

And a step of bringing the gas whose concentration ratio has been adjusted into contact with a catalyst capable of reducing nitrogen oxides.

([NOx] + 2 [02]) / [CO] ≤2. 0--(2)

[0032] The value 2.0 of the concentration ratio in the formula (2) in the second embodiment is considered to be an experimentally obtained value. The reaction occurring in the catalyst has not been completely elucidated, and it is considered that a side reaction has occurred in addition to the main reaction of the first reaction and the second reaction. As one of the side reactions, when the concentration of carbon monoxide and carbon is high, hydrogen is generated by the reaction between steam and monoxide and carbon, and this hydrogen reduces nitrogen oxide and oxygen. Can be considered.

[0033] In this Embodiment 2, "not containing HC" means that the gas from the source substantially contains HC that reduces nitrogen oxides (below the measurement limit). It means that. [0034] Thus, the value of the concentration ratio may be slightly changed by reactions other than the main reaction in the catalyst. Therefore, considering the main reaction that is surely occurring, Embodiments (1) and (2) can be expressed by Embodiment 3 of the following processing method.

[0035] That is, Embodiment 3 is a method for treating a gas containing carbon monoxide, nitrogen oxides and oxygen and not containing HC, wherein the carbon monoxide and nitrogen oxides contained in the gas are used. And the adjustment process for adjusting the respective concentrations of oxygen and oxygen to a predetermined relationship, and the main reaction of the first reaction for oxidizing carbon monoxide with oxygen and the second reaction for reducing nitrogen oxide with carbon monoxide. And the contacting step of contacting the gas with the adjusted concentration, wherein the adjusting step comprises reducing the carbon monoxide concentration on the primary side of the catalyst in the catalyst by the first reaction. It is characterized by being approximately equal to or higher than the value obtained by adding the carbon concentration and the carbon monoxide concentration reduced in the catalyst by the second reaction.

In the third embodiment, focusing on only the main reaction, “the carbon monoxide concentration on the primary side of the catalyst is reduced in the catalyst by the first reaction and It is approximately equal to or greater than the sum of the carbon monoxide concentration reduced in the catalyst by the second reaction. Therefore, an embodiment in which the concentration ratio in the equation (2) slightly fluctuates due to a side reaction and does not satisfy the equation (2) is also included in this embodiment 3.

[0037] Further, the treatment method of the present invention can be applied to the following combustion method. Embodiments 1 to 4 of this combustion method will be described.

[0038] (Embodiment 1 of combustion method)

Embodiment 1 of the combustion method includes a step of supplying air to a fuel and combusting, and a catalyst capable of reducing nitrogen oxides in a gas not containing HC generated by the combustion with carbon monoxide. A step of contacting and a step of discharging the gas in contact with the catalyst, so that the concentration of carbon monoxide in the gas before contacting with the catalyst is substantially equal to or higher than the concentration of nitrogen oxides. Further, the combustion method is characterized in that the air ratio in the combustion process is adjusted to a set air ratio.

[0039] (Embodiment 2 of combustion method) In the second embodiment of the combustion method, air is supplied to the fuel and continuously burned, and the monoxide and carbon in the gas not containing HC generated by the combustion is oxidized with oxygen. A step of contacting with a catalyst for performing a first reaction to be performed and a second reaction for reducing nitrogen oxides with carbon monoxide, and a step of discharging the gas in contact with the catalyst, before contacting with the catalyst. The carbon monoxide concentration in the gas is approximately equal to a value obtained by adding the carbon monoxide concentration reduced in the catalyst by the first reaction and the carbon monoxide concentration reduced in the catalyst by the second reaction. The combustion method is characterized in that the air ratio in the combustion process is adjusted to a set air ratio so as to be equal to or greater than that.

[0040] (Third embodiment of combustion method)

Further, Embodiment 3 of the combustion method includes a step of supplying air to the fuel and continuously burning it, and a catalyst capable of reducing nitrogen oxides in the gas not containing HC generated by the combustion. And the step of discharging the gas in contact with the catalyst, the carbon monoxide concentration, the nitrogen oxide concentration, and the oxygen concentration in the gas before contacting with the catalyst are represented by the following formula (2): The combustion method is characterized in that the air ratio in the combustion process is adjusted to a set air ratio so as to satisfy the concentration ratio indicated by (2).

([NOx] + 2 [02]) / [CO] ≤2. 0--(2)

[0041] (Embodiment 4 of combustion method)

Further, Embodiment 4 of the combustion method is a combustion method characterized in that, in Embodiments 1 to 3 of the combustion method, the set air ratio is set to 1.0 to 1.0005.

[0042] Further, the processing method of the present invention can be applied to the following combustion apparatus. Embodiments 1 to 5 of this combustion apparatus will be described.

(Embodiment 1 of the combustion apparatus)

Embodiment 1 of this combustion apparatus includes a combustion section (parner) that continuously burns by supplying air to fuel, a gas discharge path for discharging gas that does not contain HC from the combustion section, and A catalyst disposed in the gas discharge path, which can contact the gas and capable of reducing nitrogen oxides by carbon monoxide, and contacts the catalyst in the gas discharge path An air ratio adjusting means for adjusting the air ratio in the combustion process to a set air ratio so that the concentration of carbon monoxide in the previous gas is substantially equal to or higher than the concentration of nitrogen oxides It is a combustion apparatus characterized by this.

(Embodiment 2 of the combustion apparatus)

Embodiment 2 of this combustion apparatus includes a combustion section that supplies air to fuel and continuously burns, a gas discharge path for discharging gas that does not contain HC of the combustion section power, and the gas discharge A catalyst disposed in a passage, which is capable of contacting the gas and that performs a first reaction for oxidizing carbon monoxide with oxygen and a second reaction for reducing nitrogen oxide with carbon monoxide; and the gas In the exhaust path, the carbon monoxide concentration in the gas before contacting the catalyst is reduced in the catalyst by the first reaction and reduced in the catalyst by the second reaction. Combustion apparatus comprising air ratio adjusting means for adjusting the air ratio in the combustion section to a set air ratio so as to be approximately equal to or greater than a value obtained by adding the acid and carbon concentration. It is.

(Embodiment 3 of the combustion apparatus)

Embodiment 3 of this combustion apparatus includes a combustion section that continuously burns by supplying air to the fuel, a gas discharge passage for discharging gas that does not contain HC of the combustion section power, and the gas discharge A catalyst disposed in the channel that is in contact with the gas and capable of reducing nitrogen oxyhydride; and the gas

In the exhaust passage, the air in the combustion section is set so that the carbon monoxide concentration, the nitrogen oxide concentration, and the oxygen concentration in the gas before contacting with the catalyst satisfy the concentration ratio represented by the following formula (2). An air ratio adjusting means for adjusting the ratio to a set air ratio.

([NOx] + 2 [02]) / [CO] ≤2. 0--(2)

[Embodiment 4 of Combustion Apparatus]

A combustion apparatus according to a fourth embodiment is a combustion apparatus characterized in that, in the first to third embodiments of the combustion apparatus, the set air ratio is set to 1.0 to 1.0005. (Embodiment 5 of the combustion apparatus)

Further, Embodiment 5 of the combustion apparatus is a combustion apparatus characterized in that in Embodiments 1 to 4 of the combustion apparatus, an endothermic body is provided between the above-mentioned partner and the catalyst.

(Embodiment 6 of the combustion apparatus)

Embodiment 6 of this combustion apparatus includes a combustion section that supplies air to fuel and continuously burns it to generate a gas that contains carbon monoxide, nitrogen oxides, and oxygen, but does not contain HC. A gas discharge path for discharging the gas from the combustion section; and the gas disposed in the gas discharge path, which is in contact with the gas, and acid-oxidizing carbon with oxygen, A catalyst for reducing waste by carbon monoxide; and an air ratio adjusting means for adjusting an air ratio in the combustion section to a set air ratio in the gas discharge path,

When the combustion ratio is adjusted to the set air ratio by the air ratio adjusting means, the concentration of nitrogen oxides, nitrogen oxides, and oxygen on the secondary side of the catalyst is substantially zero. The combustion apparatus is characterized in that a concentration ratio can be obtained.

[0049] (Embodiment 7 of the combustion apparatus)

Embodiment 7 of this combustion apparatus is the combustion apparatus according to Embodiment 6 of the combustion apparatus, wherein the set air ratio is 1.0 to 1.0005.

[0050] Components in the first to seventh embodiments of the combustion apparatus will be described. The burner is preferably a premixing burner that premixes and burns gas fuel. In order for the catalyst to effectively cause the first reaction and the second reaction, concentration ratios as shown in the above formulas (1) and (2) regarding oxygen, nitrogen oxide, and carbon monoxide are important. It is. By using the pre-mixing burner as the burner, the concentration ratio can be obtained relatively easily with the set air ratio. However, if oxygen, nitrogen oxides, and carbon monoxide in the gas on the primary side of the catalyst are uniformly mixed and the respective concentrations can be controlled to the predetermined concentration, a non-premixed panner is used. be able to.

[0051] Further, the PANA is a gas generation source that contains carbon monoxide, nitrogen oxides, and oxygen, and does not contain HC, and burns so as to have a low air ratio of 1.0 to 1.0005. It is possible to make it S. With such a low air ratio, in addition to low NOx and low CO emissions that are close to zero, energy saving is realized, and a low pollution and energy saving combustion device is provided. be able to.

[0052] Further, the heat absorber is a water pipe when the combustion device is a boiler, and an absorbing liquid concentrating pipe when it is a regenerator. The endothermic body also has a function of controlling the gas temperature flowing into the catalyst close to the activation temperature of the catalyst. That is, the gas temperature effectively causes the first reaction and the second reaction, suppresses deterioration of the catalyst due to temperature, and takes into consideration durability.

Control every degree.

[0053] The air ratio adjusting means includes a flow rate adjusting means, a driving means for driving the flow rate adjusting means, and a control means for controlling the driving means. The flow rate adjusting means is a means for adjusting the air ratio of the burner by changing the ratio of both by changing one or both of the combustion air amount and fuel amount of the burner. When the flow rate adjusting means changes the amount of combustion air, it is preferably a damper (including the meaning of a valve). The structure of this damper is a rotary type that changes the opening degree of the flow path by a valve body that rotates around a rotating shaft, and a slide type that changes the opening degree of the flow path by sliding against the cross-sectional opening of the flow path. Can be.

[0054] When the flow rate adjusting means changes the amount of combustion air, it is preferably provided in the air flow path between the blower and the fuel supply means, but the blower, such as the suction port of the blower, is provided. Can be provided on the inlet side.

[0055] Preferably, the driving means is a motor capable of controlling the opening degree of the flow rate adjusting means according to the driving amount and adjusting the driving amount per unit time. “The amount of opening can be controlled in accordance with the amount of driving” means that when the amount of driving is determined, the opening of the flow rate adjusting means can be controlled to stop at a specific position. Further, “the drive amount per unit time can be adjusted” means that the responsiveness of the position control can be adjusted.

[0056] This motor is preferably a stepping motor (which can be called a step motor), but can also be a gear motor (which can be called a geared motor) or a servo motor. When the stepping motor is used, it is a driving pulse to which the driving amount is applied, and the opening position of the flow rate adjusting means is opened and closed by an amount corresponding to the number of driving pulses from the reference opening position. The target stop position can be controlled. Also, the gear model If the motor or servo motor is used, the drive amount is the opening / closing drive time, and the opening position of the flow rate adjusting means can be freely opened and closed by an amount corresponding to the reference opening position force opening / closing drive time. The target stop position can be controlled.

[0057] The driving means is controlled to be the set air ratio by a sensor that detects the air ratio of the panner. This sensor is preferably an oxygen concentration sensor that directly detects the air ratio of the panner. This oxygen concentration sensor detects oxygen and calculates the air ratio based on the detected value. The sensor may be a carbon monoxide concentration sensor that indirectly detects a different air ratio from the oxygen concentration sensor. This carbon monoxide concentration sensor detects the carbon monoxide concentration and calculates the air ratio based on the detected value. The mounting position of the sensor is preferably on the secondary side of the catalyst, but may be on the downstream side when an exhaust heat recovery device is provided on the downstream side of the catalyst.

[0058] Based on an air ratio control program stored in advance, the control means inputs the detection value of the sensor, controls the driving amount of the motor, and sets the air ratio to 1.0 to 1.0005. To control.

[0059] The air ratio control program preferably has a driving amount (driving unit) per unit time of the motor according to a difference between the detected air ratio (or detected oxygen concentration) and the set air ratio (set oxygen concentration). A first control zone for changing the output) and a second control zone for setting the driving amount per unit time to a fixed predetermined value outside the first control zone, The driving amount of the motor is configured to be controlled.

Example 1

[0060] Thus, Example 1 of a combustion apparatus that implements the method for treating a nitrogen oxide-containing gas according to the present invention will be described with reference to the drawings. Fig. 1 is an explanatory view of the vertical cross section of the steam boiler of Example 1, Fig. 2 is a cross sectional view taken along the line II-II of Fig. 1, and Fig. 3 shows the exhaust gas from the catalyst of Fig. 1. FIG. 4 is a diagram showing a main part configuration viewed from the flow direction, and FIG. 4 is a main part electric circuit diagram of the first embodiment.

[0061] The boiler of the first embodiment contains oxygen, nitrogen oxides, and carbon monoxide by combustion, and does not contain HC, and generates heat from the gas generated by the gas generator 3 and the gas generated by the gas generator 3. The inner water pipes 4, 4,... As the endothermic means and the gas 2 after passing through the endothermic means each containing oxygen, nitrogen oxide and carbon monoxide at a predetermined concentration are passed to The main part is a catalyst 1 that generates a first reaction to be oxidized and a second reaction to reduce the nitrogen oxides with monoxide and carbon. Then, oxygen is consumed by the first reaction in the catalyst 1 to reduce the concentration of carbon monoxide and carbon, and the concentration of nitrogen oxides is reduced by the second reaction by carbon monoxide that cannot be reduced. Is configured to do.

[0062] The overall configuration of the boiler will be described in detail. This boiler has a fully premixed (all primary air type) panner 3 having a planar combustion surface (premixed gas ejection surface) and a number of water pipes 4, 4,... For heat absorption. Body 5, a blower 6 and an air supply passage 7 that send combustion air to the panner 3, a gas fuel supply pipe 8, and an exhaust gas passage for discharging exhaust gas discharged from the can body 5 (usually “chimney” or “ It is called “the flue.”) As the above-mentioned PANA 3, a PANA having the same configuration as the one described in Patent Document 1 is used.

The can body 5 includes an upper header 10 and a lower header 11, and a plurality of the water tubes 4 are arranged between the headers 10 and 11. In FIG. 2, a pair of water pipe walls 14, 14 configured by connecting outer water pipes 12, 12,... By connecting members 13, 13,. A gas passage 15 is formed between the pipe walls 14 and 14 and the upper header 10 and the lower header 11 so that the gas from the panner 3 flows almost linearly.

[0064] Next, the connection relationship between the elements will be described. As shown in FIG. 1, the gas passage 15 is provided at one end with the PANA 3, and the gas outlet 16 at the other end is connected with an exhaust gas passage 9. The Pana 3 is connected to the air supply passage 7, and the gas fuel supply pipe 8 is connected to the air supply passage 7 so as to inject fuel into the air supply passage 7. The gas fuel supply pipe 8 is provided with a flow rate adjusting valve 17 for adjusting the fuel flow rate. The catalyst 1 is disposed in the middle of the exhaust gas passage 9 and in a temperature range of about 120 ° C. to 350 ° C.

[0065] The catalyst 1 generates a first reaction for oxidizing carbon monoxide and a second reaction for reducing nitrogen oxide with carbon monoxide. Specifically, it has a structure as shown in FIG. 3 and is formed, for example, as follows. A large number of minute irregularities are formed on the surfaces of the stainless steel flat plate 18 and the corrugated plate 19 as the base material, and a catalytically active material (not shown) is applied to the surfaces. Next, the flat plate 18 and the corrugated plate 19 having a predetermined width are connected. After being superposed, they are wound into a spiral shape to form a roll. This roll-shaped one is surrounded and fixed by a side plate 20. Platinum is used as the catalytically active substance. In FIG. 3, only a part of the flat plate 18 and the corrugated plate 19 is shown.

[0066] The catalyst 1 is detachably attached to the exhaust gas passage 9 so that it can be replaced when performance deteriorates.

[0067] Further, in Example 1, the concentration adjustment is performed so that the concentrations of oxygen, nitrogen oxide, and carbon monoxide in the gas before flowing into the catalyst 1 satisfy the following formula (1): Means 21 are provided.

([NOx] + 2 [02]) / [CO] ≤ 1

However, [CO]:-carbon oxide concentration, [NOx]: nitrogen oxide concentration, [02]: oxygen concentration [0068] Specifically, the concentration adjusting means 21 is designed to burn near an air ratio of 1. Adjust the concentration so that it is adjusted to almost [CO]: l lOOppm, [NOx]: lOOppm, [02]: 500ppm.

[0069] The concentration adjusting means 21 includes an air ratio adjusting means 22 for burning the parser 3 at a low air ratio in the vicinity of the air ratio 1 and a water pipe group including the parner 3, the water pipes 4 and the water pipes 12. And a first oxygen concentration detector 23.

As shown in FIG. 4, the air ratio adjusting means 22 receives a second oxygen concentration detection 37 provided on the downstream side of the catalyst 1 and a signal from the detector 37 to input the air blower 6. The motor 24 is mainly composed of a power for controlling the inverter 24 and a controller 25 for controlling the motor 24 by a damper (not shown).

[0071] By the concentration adjusting means 21, the oxygen, nitrogen oxide, and carbon monoxide concentrations in the gas 2 that is burned at a low air ratio in the vicinity of the air ratio 1 and flows into the catalyst 1 are [CO ]: L lOOppm, [NOx]: lOOppm, [02]: Almost controlled to 500 ppm. These concentrations have been confirmed to be realized based on data from various experiments.

[0072] This concentration relationship is possible because, in the low air ratio region, the amount of nitrogen oxides generated with respect to the air ratio change is almost constant (or little change), whereas the oxygen concentration This is based on the fact that the carbon monoxide concentration changes moderately and can be adjusted. [0073] The schematic operation of the steam boiler configured as described above is as follows. Combustion air (outside air) supplied from the blower 6 is premixed with the fuel gas supplied from the gas fuel supply pipe 8 in the supply passage 7, and this premixed gas is supplied from the banner 3 to the can. It is ejected toward the body 5. The premixed gas is ignited by an ignition means (not shown) and burned. This combustion is performed at a low air ratio as described above.

[0074] The gas generated by this combustion is cooled by intersecting with the upstream water tube group, and is heat-exchanged with the downstream water tube group to become a gas of about 120 ° C to 350 ° C. The gas 2 is treated with the catalyst 1 to reduce the nitrogen oxide concentration and the carbon monoxide concentration to substantially zero, and then is discharged from the exhaust gas passage 9 into the atmosphere. Generally, the exhaust gas passage 9 is provided with a feed water preheater (not shown) for preheating the feed water to the boiler, but the catalyst 1 has a gas 2 temperature of about 120 ° C. to 350 ° C. C is provided upstream or downstream of the feed water preheater.

[0075] The action of reducing nitrogen oxides and carbon monoxide in the catalyst 1 will be described in detail. Gas 2 with adjusted concentrations of oxygen, nitrogen oxides and carbon monoxide is passed through catalyst 1. Then, first, by the first reaction, the carbon monoxide in the gas 2 is reduced by oxygen and reduced to lOOppm so that the concentration is substantially equal to the nitrogen oxide concentration. Thereafter, in the second reaction, the nitrogen oxide is reduced by the reduced monoxide and carbon to reduce the nitrogen oxide. As a result, the concentration of nitrogen oxides and carbon monoxide in gas 2 can be reduced to almost zero.

[0076] The water in each of the water pipes 4 and 12 is heated and vaporized by heat exchange with the gas.

This steam is supplied from a steam take-out means (not shown) connected to the upper header 10 to a steam using facility (not shown!).

[0077] According to the first embodiment, harmful substances such as nitrogen oxides and carbon monoxide can be made substantially zero, and combustion is performed at a low air ratio in which the air ratio is close to 1. Therefore, boiler efficiency is reduced. Is high

Can provide an energy-saving boiler.

Example 2

Next, another embodiment 2 of the combustion apparatus to which the present invention is applied will be described with reference to the drawings. Less than In the following description, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. FIG. 5 is an explanatory diagram of a longitudinal section of the steam boiler of the second embodiment, FIG. 6 is a sectional view taken along the line VI-VI of FIG. 5, and FIG. 7 is a control of the damper of the second embodiment. FIG. 8 is a graph illustrating the output characteristics of the sensor according to the second embodiment.

[0079] First, the steam boiler according to the second embodiment will be described. This steam boiler includes a catalyst 1, a burner 3, a can 5, a fuel supply means 27 for supplying gas fuel to the burner 3, a combustion air to the burner 3 and a combustion air. And a combustion air supply means 28 for premixing combustion, an oxygen concentration detector 37 for detecting the oxygen concentration downstream of the catalyst 1, and a signal from the oxygen concentration detector 37 and the like to input the fuel supply means 27 and A controller 25 for controlling the combustion air supply means 28 and the like is provided as a main part.

The exhaust gas passage 9 includes a horizontal portion 29 and a vertical portion 30, and the catalyst 1 is attached to the horizontal portion 29. A feed water preheater 31 as an exhaust heat collector is attached to the vertical portion 30 so as to be positioned downstream of the catalyst 1, and the oxygen concentration detector 37 is interposed between the catalyst 1 and the feed water preheater 31. Is arranged.

The fuel supply means 27 includes a gas fuel supply pipe 8 and a flow rate adjustment valve 17. The flow rate adjusting valve 17 has a function of controlling the fuel supply amount to a high combustion flow rate and a low combustion flow rate.

The combustion air supply means 27 includes a blower 6, an air supply passage 7, and an air flow rate adjustment means 3 that adjusts the air ratio of the burner 3 by adjusting the amount of combustion air flowing through the air supply passage 7. Consists of two.

[0083] The air flow rate adjusting means 32 includes a damper 33 for adjusting the opening degree (flow passage sectional area) of the air supply passage 7, and a damper position adjusting device 34 for adjusting the opening position of the damper 33. It is comprised including. The damper position adjusting device 34 includes a stepping motor (not shown) that drives the damper 33 and is hybridized.

[0084] Based on the detection signal from the oxygen concentration detector 37, the controller 25 uses the air ratio control program stored in advance so that the air ratio of the banner 3 becomes the set air ratio (first control condition). In the set air ratio of parentheses, the concentration ratio of the gas 1 on the primary side of the catalyst 1 satisfies the following formula (2) (second control condition), and is configured to control the motor! The

([NOx] + 2 [02]) / [CO] ≤2. 0--(2)

In Example 2, it is the first control condition that is directly controlled, and the second control condition is automatically satisfied by satisfying the first control condition. It is made.

[0086] When the first condition is not satisfied, an unburned component such as HC is generated. In this case, energy is lost and NOx reduction in the catalyst 1 is not effectively performed.

[0087] The second condition is a condition for making the exhausted nitrogen oxide concentration almost zero. In order to make the nitrogen oxide concentration and carbon monoxide concentration on the secondary side of the catalyst 1 zero, the concentration ratio represented by the above formula (2) can be obtained from the first reaction and the second reaction! This was found through experiments and theoretical considerations.

Then, in the air ratio control program, as shown in FIG. 7, the detected air ratio is calculated based on the oxygen concentration signal from the oxygen concentration detector 37, and the calculated detected air ratio and the setting are calculated. A first control zone that changes the time per unit drive amount of the motor (which can be referred to as feed speed or drive speed) according to the difference from the air ratio, and a unit drive amount outside the first control zone. A control procedure for controlling the driving amount of the motor is provided by providing second control zones A and B with the winning times as the first set value and the second set value, respectively.

[0089] As the oxygen concentration detector 37, an air ratio detector (for example, a zircoure-type AZF sensor with a good response response of 02 resolution of 50 ppm and a response time of 2 seconds or less) is used. As shown in FIG. 8, the output characteristics of the oxygen concentration detector 37 are outputs related to the oxygen concentration when the output is positive, and outputs related to the carbon monoxide concentration on the negative side.

[0090] According to the second embodiment, the stepping motor can reliably perform the rotational position control, and the feed speed is controlled to decrease as the detected air ratio approaches the set air ratio. As a result, overshooting, noching and nipping of the air ratio in the vicinity of the set air ratio can be suppressed. [0091] By such control, the air ratio of the Parner 3 is set to a low air ratio close to 1, and the concentration ratio change width of the gas 2 on the primary side of the catalyst 1 is controlled to be small. Can be met. As a result, the nitrogen oxide concentration on the secondary side of the catalyst 1 can be made substantially zero, and the carbon monoxide concentration can be reduced to a practical range.

[0092] (Experiment 1)

The following describes the experimental results for an evaporation rate of 800 kg per unit time and a combustion rate of 45.2 m ³ N / h. When the set air ratio is 1.0005 or less, the carbon monoxide concentration, nitrogen oxide concentration, and oxygen concentration on the primary side of catalyst 1 (before passing through catalyst 1) are adjusted to 2295ppm, 94ppm, and 1655ppm, respectively. As a result, the concentrations on the secondary side of the catalyst 1 (after passing through the catalyst 1) were less than 13 ppm, 0.3 ppm, and lOO ppm on average for 10 minutes. Here, the oxygen concentration lOOppm of the secondary side of the catalyst 1 is the measurement limit of the oxygen concentration (measured using Ltd. HORIBA production plant made PG- 250.) ₀

[0093] (Experimental example 2)

When the amount of evaporation per unit time is 800 kg, the combustion amount is 45.2 m ³ N / h, and the catalyst is Pd with an inner diameter of 360 mm as the catalytic active substance, the concentration of carbon monoxide, nitrogen oxide, oxygen Table 1 shows the values at each concentration ratio. Here, since the oxygen concentration after passing through the catalyst was measured using the same oxygen concentration sensor as in Experimental Example 1, even if the value was less than lOOppm, it was expressed as lOOppm.

[0094] [Table 1]

NOx concentration CO concentration θ2 concentration Concentration ratio

(ppm) (ppm) (ppm) Before passing 88 3114 1380

0. 91

After passing 0. 4 103. 0 100 Before passing 89 2949 1450

1. 01

After passing 1. 0 66. 0 100 Before passing 89 2461 1730

1. 44

After passing 0. 0 18. 0 100 Before passing 89 2414 1920

1. 63

After passing 0. 0 9. 0 100 Before passing 89 2250 2030

1. 84

After passing 0. 8 11. 0 100 Before passing 88 2069 2210

2. 18

After passing 26. 1 1. 0 100 Before passing 88 1922 2410

Z. O 0

After passing 57. 2 1. 1 510 Before passing 87 1360 3430

5. 11

After passing 78. 9 0. 0 2220

Example 2 includes the following modification. That is, a controller for controlling the damper position adjusting device 34 exclusively (not shown) separately from the controller 25 for controlling the force boiler that controls the damper position adjusting device 34 by the single controller 25. It is also possible to perform the air ratio control by connecting the oxygen concentration detector 37 to this.

[0096] The present invention is not limited to Example 1 and Example 2. For example, the reduction device can be a modification shown in FIG. In this modified example, the difference from Example 1 is that the predetermined concentrations of oxygen, nitrogen oxide, and carbon monoxide are configured to satisfy the relationship [CO]> [NOx] +2 [02] The second catalyst 35 is configured to oxidize carbon monoxide that could not be treated with the catalyst 1. In this case, oxygen input means 36 for supplying oxygen upstream of the second catalyst 35 is provided. As the second catalyst 35, the same catalyst as the first catalyst 1 can be used. Alternatively, the first catalyst 1 and the second catalyst 35 may be formed integrally and continuously, and oxygen may be introduced by the oxygen input means 36 from a hole provided at a predetermined location.

[0097] Further, the installation position of the catalyst 1 is not limited to the exhaust gas passage 9, but can be downstream of the water pipe 4 group in the can 5 or in the middle of the water pipe 4 group. in front When the catalyst 1 is provided in the middle of the group of water tubes 4, a catalyst material can be carried on the surface of the water tube 4 and used as the catalyst 1.

Claims

The scope of the claims

[1] Using oxygen, nitrogen oxides, and carbon monoxide, using a catalyst that produces a first reaction that oxidizes carbon monoxide and a second reaction that reduces nitrogen oxides with carbon monoxide. Gas is passed through the catalyst, oxygen is consumed by the first reaction in the catalyst to reduce the carbon monoxide concentration, and nitric acid by the second reaction by carbon monoxide that cannot be consumed. A method for treating a nitrogen oxide-containing gas that reduces the concentration of a substance,

A method for treating a nitrogen oxide-containing gas, comprising an adjustment step of adjusting each predetermined concentration of oxygen, nitrogen oxide and carbon monoxide to satisfy the following formula (1).

[NOx] + 2 [02] ≤ [CO]

However, [CO]: — Carbon oxide concentration, [NOx]: Nitrogen oxide concentration, [02]: Oxygen concentration [2] Treatment of gas containing carbon monoxide, nitrogen oxides and oxygen, but not HC The method,

Adjusting each concentration of carbon monoxide, nitrogen oxide and oxygen contained in the gas to satisfy the following formula (2):

And a step of contacting the gas whose concentration ratio is adjusted with a catalyst capable of reducing nitrogen oxides.

([NOx] + 2 [02]) / [CO] ≤2. 0--(2)

[3] A method for treating a gas containing carbon monoxide, nitrogen oxides and oxygen but not HC.

An adjustment step of adjusting the concentrations of carbon monoxide, nitrogen oxide and oxygen contained in the gas to a predetermined relationship;

A contact step of contacting the gas having the adjusted concentration with a catalyst that performs a first reaction for oxidizing carbon monoxide with oxygen and a second reaction for reducing nitrogen oxide with carbon monoxide,

In the adjusting step, the concentration of carbon monoxide on the primary side of the catalyst is increased by the first reaction. The concentration of monoxide and carbon reduced in the catalyst and the value of acid and carbon reduced in the catalyst by the second reaction are approximately equal to or higher than the sum. A method for treating a nitrogen oxide-containing gas.

A method for treating a gas containing carbon monoxide, nitrogen oxides, and oxygen but not HC.

A contact step of bringing the gas having the adjusted concentration into contact with a catalyst that performs a main reaction of a first reaction for oxidizing carbon monoxide with oxygen and a second reaction for reducing nitrogen oxide with carbon monoxide. ,

In the adjusting step, the concentration of carbon monoxide on the primary side of the catalyst, the concentration of nitrogen oxides and oxygen are adjusted to a predetermined relationship so that the nitrogen oxide concentration is substantially zero.

A method for treating a nitrogen oxide-containing gas, wherein the concentration of carbon monoxide is reduced.