JP5194646B2 - Purification device and boiler - Google Patents

Description

The present invention relates to a purification device and a boiler capable of reducing CO while suppressing NOx in combustion gas generated from combustion equipment.

Conventionally, when combustion gas generated from combustion equipment such as a boiler is discharged or transferred to the next process, it may be necessary to set CO and NOx contained in the combustion gas to be equal to or less than predetermined numerical values (for example, regulation values). is there.
In reducing CO and NOx to a predetermined value, the combustion gas is passed through a catalyst, and CO and NOx contained in the combustion gas are oxidized and reduced to remove them.

  As described above, as a technique for reducing NOx and CO contained in the combustion gas using a catalyst, the air ratio to the fuel is controlled to be in a narrow range near 1.0 and the combustion gas is burned. Has been disclosed (see, for example, Patent Document 1).

In addition, as a technique for reducing NOx and CO contained in combustion gas using a NOx reduction catalyst that promotes NOx reduction and a CO oxidation catalyst that promotes CO oxidation, the ratio of air to fuel (stoichiometric value). Is reduced to less than 1.0 and the CO content when passing through the NOx reduction catalyst is increased to reduce the NOx amount in the combustion gas passing through the NOx reduction catalyst to a target value or less by excess CO, and thereafter A technique for adding oxygen to combustion gas and removing CO with a CO oxidation catalyst is disclosed (for example, see Patent Document 2).
International Publication No. 2007/043216 Pamphlet JP 2001-520110 A

  However, in the technique described in Patent Document 1, NOx and CO can be removed with a simple structure in which the combustion gas is passed through the catalyst. On the other hand, complicated control of the air ratio with respect to the fuel is required. When the air ratio varies to a side smaller than 1.0, there is a problem that it is difficult to sufficiently remove CO.

On the other hand, in the technique described in Patent Document 2, since the exhaust gas passing through the catalyst is high temperature, the life of the catalyst using a large amount of expensive noble metal such as Pt is short, and the control of the CO content is complicated. When the air to fuel ratio varies to 1.0 or more, NOx remains without being sufficiently reduced.
Further, the technique described in Patent Document 2 has a problem from the viewpoint of energy saving that HC due to incomplete combustion remains and the fuel is wasted because the air ratio to fuel is smaller than 1.0.

  Furthermore, in the technique described in Patent Document 2, the N intermediate produced by the reduction reaction with the NOx reduction catalyst may be oxidized again in the high temperature atmosphere after the NOx reduction catalyst or on the CO oxidation catalyst to become NOx again. In addition, there is a problem that the N intermediate produced in the combustion atmosphere may be oxidized in a high temperature atmosphere in the passage path of the combustion gas or on the CO oxidation catalyst to increase NOx.

The present invention has been made in consideration of such circumstances, and a purification device for reducing and removing CO while suppressing generation of NOx in combustion gas generated from combustion equipment such as a boiler, and It is providing the boiler using this purification apparatus .

In order to solve the above problems, the present invention proposes the following means.
The invention according to claim 1 is a purification device for reducing CO contained in combustion gas generated by combustion , wherein the combustion gas is disposed in the ventilation path, and the combustion gas is movable. Is disposed on the upstream side of the CO oxidation catalyst in the ventilation path and cools the combustion gas, and is disposed on the upstream side of the cooling means in the ventilation path, A NOx reduction catalyst that allows combustion gas to pass therethrough is provided .

According to the purification apparatus of the present invention, the cooling means is disposed upstream of the CO oxidation catalyst, and the combustion gas is cooled to lower the temperature. And oxidation on the CO oxidation catalyst is suppressed. As a result, CO can be reduced while suppressing an increase in NOx.

Further, since the NOx reduction catalyst is arranged on the upstream side of the cooling means, NOx contained in the combustion gas is reduced and reduced.
Further, since the combustion gas after the NOx reduction catalyst is cooled and the temperature is lowered, the generation of the N intermediate in the air passage after the NOx reduction catalyst is suppressed, and the N intermediate in the CO oxidation catalyst is oxidized. Generation of NOx is suppressed.

According to a second aspect of the invention, a purification device according to claim 1, wherein the cooling means is characterized by being adjustable arrangement the temperature of the combustion gases.

According to the purification device of the present invention, since the cooling means is configured to be able to adjust the temperature of the combustion gas, the temperature when the combustion gas passes through the CO oxidation catalyst, for example, the generation of NOx is suppressed. The temperature can be set within a range where CO is selectively oxidized (hereinafter referred to as CO selective oxidation reaction temperature).
As a result, it is possible to efficiently oxidize and remove CO while suppressing the generation of NOx.
In this specification, the CO selective oxidation reaction temperature is a temperature in the range indicated by symbol E in FIG. 1, and the CO and NOx concentrations corresponding to this temperature range are, for example, the regulated values and target values of CO and NOx. It is determined based on.

The invention according to claim 3 is the purifying apparatus according to claim 1 or 2 , further comprising an oxidation assisting means for introducing a gas containing oxygen into the combustion gas upstream of the CO oxidation catalyst. It is characterized by that.

According to the purification apparatus of the present invention, the auxiliary oxidation means is provided on the upstream side of the CO oxidation catalyst, and it is possible to introduce a gas containing oxygen (including pure oxygen) into the combustion gas. It becomes possible to efficiently oxidize CO in the oxidation catalyst.

The invention according to claim 4 is a boiler, and is characterized by including the purification device according to any one of claims 1 to 3.

According to the boiler according to the present invention, CO can be efficiently reduced while suppressing generation of NOx due to oxidation of the N intermediate contained in the combustion gas.

According to the purification device and the boiler according to the present invention, it is possible to reduce CO while suppressing generation of NOx.

The first embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a graph showing the relationship between the temperature of combustion gas and the concentration of CO and NOx at the subsequent stage (downstream side) of the CO oxidation catalyst at that temperature.
In FIG. 1, symbol E is a CO selective oxidation reaction temperature, and indicates a temperature range for keeping CO below a predetermined concentration while suppressing the generation of NOx.
The upper limit temperature TH of the CO selective oxidation reaction temperature E is determined by the NOx concentration characteristic curve J representing the NOx concentration in FIG. 1 and the target value V of the NOx concentration, and the lower limit temperature TL of the CO selective oxidation reaction temperature E indicates the CO concentration. It is determined by the CO concentration characteristic curve K and the target value W of the CO concentration.

2 and 3 are views for explaining the small once-through boiler 10 according to the first embodiment. FIG. 2 is a longitudinal sectional view, and FIG. 3 is a transverse section taken along the line III-III in FIG. The figure is shown.
The boiler 10 includes a casing 11, a can 12, a burner 16, a combustion gas discharge pipe 17, and an air blowing means 18, and a discharge path (air passage) 17 </ b> A configured by the combustion gas discharge pipe 17. A purification device 30 is arranged in the case.

  The can 12 includes a water tube group 13, a lower header 14A positioned below the water tube group 13, and an upper header 14B positioned above the water tube group 13. The water tube group 13 includes a plurality of inner water tubes 13A. And a plurality of outer water pipes 13B. A combustion gas passage 12G is formed in the water pipe group 13, and the combustion gas G2 moves from the burner 16 toward the combustion gas discharge pipe 17 between the inner water pipes 13A. Yes.

As shown in FIG. 2, each of the inner water pipe 13A and the outer water pipe 13B constituting the water pipe group 13 is disposed vertically between the lower header 14A and the upper header 14B, and the lower header 14A and the upper header 13B. It is connected to the header 14B so that water can pass therethrough.
A castable (refractory) 11A is disposed on the upper portion of the lower header 14A and the lower portion of the upper header 14B.

Further, as shown in FIG. 3, the water tube group 13 has a water tube wall portion 13C that partitions the housing 11 and the combustion gas passage 12G, and the inner water tube 13A is arranged inside the water tube wall portion 13C. Has been.
The water pipe wall 13C is combusted with the outer water pipe 13B arranged from the burner 16 toward the combustion gas discharge pipe 17, the adjacent outer water pipes 13B, the inner wall of the casing on the outer water pipe 13B and the burner 16 side, and the outer water pipe 13B. The inner wall of the casing on the side of the gas exhaust pipe 17 is composed of connecting members 15 that connect to each other, and a pair of left and right sides are arranged across the combustion gas passage 12G.

The burner 16 in the first embodiment is formed in a box shape having a nozzle portion 16A on the surface on the water tube group 13 side, and a plurality of nozzle holes are arranged in a planar shape in the nozzle portion 16A and supplied by a blowing means. The premixed gas G1 is supplied to the nozzle portion 16A.
The burner 16 can control the combustion state (for example, high combustion, low combustion) based on, for example, the pressure of a steam collecting portion (not shown) detected by a pressure sensor.
2 and 3, the broken line portion shown from the nozzle portion 16 </ b> A to the water tube group 13 side conceptually represents a flame formed by the nozzle portion 16 </ b> A.

  The premixed gas G1 supplied to the nozzle portion 16A is injected and burned from the nozzle hole to become a high-temperature combustion gas G2, and the combustion gas G2 passes through the combustion gas passage 12G and heats the water in the water tube group 13 Then, it is introduced into the purification device 30 through the discharge path 17A.

  The combustion gas discharge pipe 17 constitutes a discharge path 17A for discharging the combustion gas G2 to the outside of the boiler 10 and is connected to the end of the combustion gas path 12G. The discharge path 17A guides the combustion gas G2 to the purification device 30. It has become.

The blower means 18 includes a blower 18A, an air supply passage 18B, and a damper 18C. The blower 18A transfers the combustion air A1 to the air supply passage 18B, and the fuel supplied from the combustion air A1 and the fuel supply unit 19 is supplied. The gas G0 is mixed in the supply passage 18B to become the premixed gas G1, and is supplied to the burner 16.
The blower 18A rotates the blower fan to supply the combustion air A1, and the blower 18A in this embodiment controls the number of rotations of the blower fan by an inverter corresponding to the combustion state of the burner 16 and burns it. The blast volume of the working air A1 is adjusted.
Further, the opening degree of the damper 18C can be controlled by a motor (not shown), and the amount of combustion air A1 can be adjusted together with the blower 18A or independently.

  The fuel supply unit 19 includes a fuel supply pipe 19A and a flow rate adjustment valve 19B. By controlling the flow rate adjustment valve 19B, an amount of fuel gas G0 corresponding to the combustion state of the burner 16 is supplied to the fuel supply pipe 19A. It comes to supply.

As shown in FIG. 4, the purification device 30 includes a NOx reduction catalyst 31 that promotes NOx reduction, an air supply nozzle 34, an economizer (cooling means) 35, and a CO oxidation catalyst 39 that promotes CO oxidation. These are arranged in this order from the upstream side to the downstream side of the combustion gas G2, and NOx and CO in the combustion gas G2 introduced into the exhaust passage 17A can be reduced.
The structures of the NOx reduction catalyst 31 and the CO oxidation catalyst 39 are not particularly limited, but the NOx reduction catalyst 31 and the CO oxidation catalyst 39 in this embodiment are catalytically active on a base material having air permeability through the vent holes. It is configured to carry a substance.

  The NOx reduction catalyst 31 removes NOx by reducing NOx contained in the combustion gas G2 to N2 and has a breathable base material 32 in which a plurality of ventilation holes through which the combustion gas G2 passes are formed. It is comprised by.

As shown in FIG. 5, the base material 32 is formed by stacking a first base material 32 </ b> A made of a flat plate and a second base material 32 </ b> B made of a corrugated plate, and winding the first base material 32 </ b> A and the second base material 32 </ b> A. What is formed in a roll shape in which the base material 32B overlaps alternately is surrounded and fixed by the side plate 32C.
The base material 32 is configured such that all of the combustion gas G2 flowing into the purification device 30 passes through.
Each of the first base material 32A and the second base material 32B is made of a stainless steel plate that has been subjected to a surface treatment in order to increase the contact area with the exhaust gas, and a large number of micro unevennesses are formed on the surface. Further, for example, a catalytically active material made of platinum is supported.

For the catalytically active material, a precious metal other than platinum (Ag, Au, Rh, Ru, Pt, Pd) or a metal oxide (NiOx, CuOx, CoOx, MnOx) can be used.
Further, instead of the base material 32, for example, a NOx reduction catalyst 31 may be configured by forming a base material that can be ventilated by a metal such as stainless steel or ceramic, and supporting a catalytically active material on the surface thereof. In addition, the breathability of the combustion gas G2 may be ensured by a sponge-like porous structure instead of the vent hole.

The CO oxidation catalyst 39 removes CO by oxidizing CO contained in the combustion gas to CO _2, and is composed of a base material 32 similar to the NOx reduction catalyst 31 shown in FIG. Platinum is supported on the surface of the material 32 as a catalytically active material.
The base material 39 is configured such that all of the combustion gas G2 discharged from the purification device 30 passes through.
For the catalytically active material, a precious metal other than platinum (Ag, Au, Rh, Ru, Pt, Pd) or a metal oxide (NiOx, CuOx, CoOx, MnOx) can be used.

The air supply nozzle (oxidation auxiliary means) 34 is disposed downstream of the NOx reduction catalyst 31 and increases the oxygen concentration contained in the combustion gas G2 to promote the oxidation of CO in the CO oxidation catalyst 39. For example, air (gas containing oxygen, hereinafter referred to as “oxidation assisting air”) A2 supplied from the blower 18A is jetted from the nozzle hole and can be mixed with the combustion gas G2.
The air injected from the air supply nozzle 34 is mixed with the combustion gas G2 so that the combustion gas G2 is cooled.

  The economizer 35 is intended to save energy by heating the water supplied to the can body 12 using the waste heat of the combustion gas G2 that has passed through the water tube group 13, and heat exchange arranged in the discharge passage 17A. Water is passed through the section 36, the heat of the combustion gas G2 is exchanged in the heat exchange section 36 to heat the water in the heat exchange section 36, and the heated water is passed to the lower header 14A of the can body 12 It comes to be supplied.

  The heat exchanging part 36 is connected to the heat transfer pipe 37 and the heat transfer pipe 37 that are allowed to pass water, for example, and a plurality of heat dissipation that spreads in a direction substantially orthogonal to the heat transfer pipe 37 with an interval through which the combustion gas G2 can pass. And a fin member 38 made of a plate. Water heated and supplied from the inlet 37A of the heat transfer tube 37 is discharged from the outlet 37B, and the discharged water is guided to the lower header 14A. ing.

  In the purification device 30, a temperature sensor 35T is disposed downstream of the economizer 35 in the discharge passage 17A, and the amount of water supplied to the economizer 35 is controlled based on the temperature of the combustion gas G2 detected by the temperature sensor 35T. Thus, the temperature of the combustion gas G2 can be adjusted to the CO selective oxidation reaction temperature E.

  Note that the water supply amount control to the economizer 35 may correspond to the combustion state of the burner 16 (high combustion, low combustion, stop), and in that case, for example, when the burner 16 is in high combustion and low from high combustion. By increasing the flow rate until a predetermined time elapses after shifting to combustion, and decreasing the flow rate when the burner 16 shifts to low combustion and from low combustion to high combustion until a predetermined time elapses You may adjust the time lag which arises between the combustion state of the burner 16, and combustion gas G2 temperature.

Next, the operation of the boiler 10 and the purification device 30 will be described.
1) First, water is supplied to the economizer 35. The water supplied to the economizer 35 is guided to the can 12.
2) Next, the blower 18A is activated to supply combustion air A1 to the burner 16 and oxidation auxiliary air A2 to the air supply nozzle 34.
3) The flow rate adjustment valve 19B of the fuel supply unit 19 is opened, and the fuel gas G0 is supplied from the fuel supply pipe 19A.
The fuel gas G0 supplied from the fuel supply pipe 19A is mixed with the combustion air A1 in the supply passage 18B to become the premixed gas G1 and supplied to the burner 16.
4) The premixed gas G1 supplied to the burner 16 is ejected from the nozzle hole of the nozzle portion 16A and burned.
When the premixed gas G1 is burned by the burner 16, it becomes high temperature combustion gas G2.
In addition to H ₂ O and CO ₂ , the combustion gas G2 contains CO and NOx, and also appears to contain N intermediates.
Combustion of the premixed gas G1 by the burner 16 can be controlled in a plurality of stages that are set in accordance with the amount of steam used in the steam-using facility, and corresponds to the combustion state of the burner 16. The combustion air A1 of the blower 18A and the opening degree of the flow rate valve of the fuel supply unit 19 are adjusted.
5) The combustion gas G2 generated by the combustion of the burner 16 heats the water in the water tube group 13 into steam while passing through the combustion gas passage 12G, and moves toward the discharge passage 17A after passing through the water tube group 13. .
6) The combustion gas G2 that has reached the discharge passage 17A is introduced into the purification device 30 through the discharge passage 17A.
7) The combustion gas G2 introduced into the purification device 30 passes through the NOx reduction catalyst 31, whereby the NOx contained in the combustion gas G2 is reduced, and the concentration of NOx decreases.
Further, it is considered that an N intermediate is generated when NOx is reduced on the NOx reduction catalyst 31.
8) The combustion gas G2 that has passed through the NOx reduction catalyst 31 then moves toward the CO oxidation catalyst 39, and in the movement path, the oxidation auxiliary air A2 supplied from the air supply nozzle 34 is added to the combustion gas G2. As the amount of oxygen in the medium increases, the temperature of the combustion gas G2 decreases.
9) Next, the combustion gas G2 passes through the heat exchange section 36 of the economizer 35, and the combustion gas G2 comes into contact with the heat transfer pipe 37 and the fin member 38 constituting the heat exchange section 36 and is transferred by the heat of the combustion gas G2. While the water in the heat pipe 37 is heated, the temperature of the combustion gas G2 is lowered.
The amount of water supplied to the economizer 35 is adjusted based on the temperature detected by the temperature sensor 35T, and the temperature of the combustion gas G2 when passing through the economizer 35 and reaching the CO oxidation catalyst 39 is CO. The selective oxidation reaction temperature E is adjusted.
10) Next, the combustion gas G2 passes through the CO oxidation catalyst 39, the CO contained in the combustion gas G2 is oxidized, and the concentration of CO contained in the combustion gas G2 decreases.

According to the purification device 30 according to the first embodiment, when the combustion gas G2 passes through the NOx reduction catalyst 31, NOx in the combustion gas is reduced and NOx is removed.
Further, when the combustion gas G2 is cooled by the economizer 35 and the temperature is lowered, an N intermediate produced during combustion and contained in the combustion gas G2 or an N intermediate produced by being reduced by the NOx reduction catalyst 31 is produced. Since the oxidation in the exhaust passage 17A and the CO oxidation catalyst 39 is suppressed, the CO oxidation catalyst 39 can oxidize and remove CO while suppressing the generation of NOx in the combustion gas G2.

In the first embodiment, since the temperature of the combustion gas G2 passing through the CO oxidation catalyst 39 is adjusted to the CO selective oxidation reaction temperature E, NOx and CO in the combustion gas can be sufficiently reduced. Can do.
Further, since the oxidation assisting air A2 is injected from the air supply nozzle 34 to the combustion gas G2 to increase the amount of oxygen contained in the combustion gas G2, the CO oxidation catalyst 39 efficiently oxidizes and removes CO. Can do.

  According to the boiler 10 according to the first embodiment, since CO is sufficiently removed while suppressing the generation of NOx in the combustion gas G2, the concentrations of both NOx and CO contained in the combustion gas G2 are kept low. be able to.

  Further, according to the purifying device 30, the combustion gas G2 is cooled by the economizer 35 and the temperature of the combustion gas G2 passing through the CO oxidation catalyst 39 is kept low, so that the deterioration of the CO oxidation catalyst 39 is suppressed. The life of the CO oxidation catalyst 39 can be extended and the cost can be reduced.

  Further, the oxidation auxiliary air A2 is injected from the air supply nozzle 34, and the amount of oxygen contained in the combustion gas G2 is increased to sufficiently oxidize the carbon monoxide CO. Therefore, carbon such as soot is converted into the CO oxidation catalyst 39. Therefore, the lifetime of the CO oxidation catalyst 39 and the cost can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 6 is a view showing a purification device 40 and a heat treatment furnace (combustion device) 100 according to the second embodiment. The heat treatment furnace 100 is, for example, a metal product stored in a heat treatment product tray when heat treating the metal product. Is a batch-type heat treatment furnace that heats up to a predetermined temperature and holds it at a predetermined temperature for a predetermined time.

  The heat treatment furnace 100 includes a housing 101, an air blowing means 103, a fuel supply unit 104, a burner 106, a support frame 108, and a discharge pipe 109, and a heat treatment product tray 111 can be placed on the support frame 108. A purifier 40 is provided in a discharge passage (venting passage) 109A formed by the discharge pipe 109.

The casing 101 includes an opening (not shown) for carrying in and out the heat-treated product tray 111, a burner 106, and a support frame 108. The case 101 is loaded through the opening and placed on the support frame 108. The metal product in the heat-treated product tray 111 is heated by the combustion gas G2 burned by the burner 106. In this embodiment, a castable 101A is disposed on the inner wall of the housing as necessary.
In addition, the heat-treated product tray 111 is three-tiered.

The blower means 103 includes a blower 103A and an air supply passage 103B. Combustion air A1 sent from the blower 103A is introduced into the air supply passage 103B, and the fuel gas G1 supplied from the fuel gas supply unit 104 and the supply air are supplied. The gas is mixed in the passage 103 </ b> B to become a premixed gas G <b> 1 and supplied to the burner 106.
The blower 103A rotates the blower fan to supply the combustion air A1, and the blower 103A in this embodiment controls the rotation speed of the blower fan by an inverter based on the valve opening of the fuel supply unit 104. Thus, the blowing amount of the combustion air A1 is adjusted.

  The fuel supply unit 104 controls the valve opening degree of a flow rate adjustment valve (not shown) according to the atmospheric temperature in the case 101 detected by a temperature sensor (not shown) arranged in the case 101. The fuel gas G0 corresponding to the opening is supplied to the supply passage 103B.

One burner 106 is arranged on the left and right sides of the heat treatment product tray 111 as viewed from the opening, and the surface of each burner 106 on the heat treatment product tray 111 side is a nozzle portion 106A. The premixed gas G1 is injected and burned from the nozzle holes to become a high-temperature combustion gas G2, and the metal product in the heat-treated product tray 111 is heated.
Thereafter, the combustion gas G2 is introduced into the purification device 40 through the discharge passage 109A and discharged.
In FIG. 6, a broken line portion shown from the nozzle portion 106A to the heat treatment tray 111 side conceptually represents a flame formed by the nozzle portion 106A.

The burner 106 is preferably a premixed burner in which the combustion air A1 sent from the blower 103A and the fuel gas G0 supplied from the fuel supply unit 104 are mixed in advance, and a plurality of nozzle holes are nozzles. It is more preferable to use a so-called planar burner arranged in a plane on the portion 106A.
By adopting such a configuration, the metal product in the heat-treated product tray 111 is heated by a small number of flame combustion gases G2, and as a result, direct contact between the metal product and the flame is suppressed and the inside of the housing 101 is also suppressed. Uniform heating is possible.

  The support base 108 is disposed on the floor at the center of the casing 101, and the heat treatment product tray 111 can be placed thereon.

  The combustion gas discharge pipe 109 is connected to the upper portion of the casing 101 to form a discharge path 109A for discharging the combustion gas G2 to the outside of the casing 101, and guides the combustion gas G2 to the purification device 40.

FIG. 7 is a diagram illustrating the purification device 40 according to the second embodiment.
The purification device 40 according to the second embodiment differs from the purification device 30 according to the first embodiment in that, instead of the economizer 35, the cooling water is circulated between the cooling towers and heat exchange with the combustion gas G2. A possible water heat exchanger (cooling means) 45 is arranged, and the same parts as those of the purification device 30 are denoted by the same reference numerals and the description thereof is omitted.

The water heat exchanger 45 allows cooling water to flow from the cooling tower disposed outside the heat treatment furnace 100 to the heat exchanging section 46 disposed in the discharge passage 109A, and heat with the combustion gas G2 in the heat exchanging section 46. The cooling water whose temperature has been increased by the exchange is returned to the cooling tower.
The heat exchanging portion 46 is made up of a heat transfer tube 47 that is made to be able to pass water, and a plurality of heat radiating plates that are connected to the heat transfer tube 47 and spread in a direction substantially orthogonal to the heat transfer tube 47 with an interval through which the combustion gas G2 can pass. The outlet 47B is connected to the reflux pipe so that the water supplied from the inlet 47A of the heat transfer tube 47 is returned to the cooling tower.

  In the purification device 40, a temperature sensor 45T is disposed downstream of the water heat exchanger 45 in the discharge passage 17A, and water is supplied to the water heat exchanger 45 based on the temperature of the combustion gas G2 detected by the temperature sensor 45T. By controlling the amount, the temperature of the combustion gas G2 can be adjusted to the CO selective oxidation reaction temperature E.

  The control of the amount of water supplied to the water heat exchanger 45 may be controlled based on the combustion state of the burner 106 (for example, the valve opening degree of the fuel supply unit 104). It is good also as a structure which can adjust the time lag produced between combustion gas G2 temperature.

Next, the operation of the heat treatment furnace 100 and the purification device 40 will be described.
1) Operate the cooling tower and supply water to the water heat exchanger 45.
2) Next, the blower 103A is activated to supply combustion air A1 to the burner 106 and oxidation assisting air A2 to the air supply nozzle 34.
3) The flow rate adjustment valve of the fuel supply unit 104 is opened, and the fuel gas G0 is supplied to the supply passage 103B.
The fuel gas G0 supplied from the fuel supply unit 104 is mixed with the combustion air A1 in the supply passage 103B to become the premixed gas G1, and is supplied to the burner 106.
4) The premixed gas G1 supplied to the burner 106 is ejected from the nozzle hole of the nozzle portion 106A and burned.
When the premixed gas G1 is combusted, a combustion gas G2 containing H ₂ O, CO ₂ , CO, NOx, and N intermediate is generated.
5) The combustion gas G2 of the premixed gas G1 in the burner 106 heats the metal product in the heat-treated product tray 111 and is introduced into the purification device 40 through the discharge path 109A.
The burner 106 is based on the atmospheric temperature in the housing 101 detected by a temperature sensor (not shown) disposed in the housing 101, and the opening of the flow rate adjustment valve of the fuel supply unit 104 and the blower well 103A. The air volume is controlled and the combustion state is adjusted.
As a result, the ambient temperature in the housing 101 is adjusted to a predetermined temperature.
6) The combustion gas G2 introduced into the purification device 40 passes through the NOx reduction catalyst 31, whereby the NOx contained in the combustion gas G2 is reduced, and the concentration of NOx decreases.
Further, it is considered that an N intermediate is generated when NOx is reduced on the NOx reduction catalyst 31.
7) The combustion gas G2 that has passed through the NOx reduction catalyst 31 then moves toward the CO oxidation catalyst 39. In the movement path, the oxidation auxiliary air A2 supplied from the air supply nozzle 34 is added to the combustion gas G2. As the amount of oxygen in the medium increases, the temperature of the combustion gas G2 decreases.
8) Next, the combustion gas G2 passes through the heat exchange part 46 of the water heat exchanger 45, and the combustion gas G2 comes into contact with the heat transfer tube 47 and the fin member 48 constituting the heat exchange part 46 and has the combustion gas G2. The water in the heat transfer tube 47 is heated by heat and the temperature of the combustion gas G2 is lowered.
The amount of water supplied to the water heat exchanger 45 is adjusted based on the temperature detected by the temperature sensor 45T, and combustion occurs when the water passes through the water heat exchanger 45 and reaches the CO oxidation catalyst 39. The temperature of the gas G2 is adjusted to the CO selective oxidation reaction temperature E.
10) Next, the combustion gas G2 passes through the CO oxidation catalyst 39, the CO contained in the combustion gas G2 is oxidized, and the concentration of CO contained in the combustion gas G2 decreases.

According to the purification device 40 according to the second embodiment, when the combustion gas G2 passes through the NOx reduction catalyst 31, NOx in the combustion gas is reduced and removed.
Further, when the combustion gas G2 is cooled by the water heat exchanger 45 and the temperature is lowered, the N intermediate produced during combustion and contained in the combustion gas G2 or the N intermediate produced by being reduced by the NOx reduction catalyst 31 is produced. Since the intermediate is suppressed from being oxidized in the exhaust passage 109A and the CO oxidation catalyst 39, the CO oxidation catalyst 39 can oxidize and remove CO while suppressing the generation of NOx in the combustion gas G2. .

In the second embodiment, since the temperature of the combustion gas G2 passing through the CO oxidation catalyst 39 is adjusted to the CO selective oxidation reaction temperature E, NOx and CO in the combustion gas can be sufficiently reduced. Can do.
Further, since the oxidation assisting air A2 is injected from the air supply nozzle 34 to the combustion gas G2 to increase the amount of oxygen contained in the combustion gas G2, the CO oxidation catalyst 39 efficiently oxidizes and removes CO. Can do.

  According to the heat treatment furnace 100 according to the second embodiment, since CO is sufficiently removed while suppressing the generation of NOx in the combustion gas G2, the concentrations of both NOx and CO contained in the combustion gas G2 are reduced. Can be suppressed.

  Further, according to the purification device 40, since the cooling water heated by the water heat exchanger 45 is cooled by the cooling tower, even in a combustion device such as a heat treatment device in which an economizer or the like cannot be used because hot water is not reused. The combustion gas G2 can be efficiently cooled.

Next, the purification device 50 according to the third embodiment will be described.
FIG. 8 is a diagram for explaining the purification device 50 according to the third embodiment. The purification device 50 differs from the purification device 30 according to the first embodiment by using cooling air instead of the economizer 35. An air-cooled heat exchanger (cooling means) 55 for heat exchange is disposed, and the same parts as those of the purification device 30 are denoted by the same reference numerals and the description thereof is omitted.

The air-cooled heat exchanger 55 cools the combustion gas G2 by exchanging heat with the combustion gas G2 through the cooling air through the heat exchange section 56 disposed in the discharge passages 17A and 109A.
As shown in FIG. 8A, the heat exchanging unit 56 is connected to the heat transfer tube 57 through which cooling air flows and the heat transfer tube 57, and is substantially orthogonal to the heat transfer tube 57 with an interval through which the combustion gas G2 can pass. The cooling air is supplied from the inlet 57A of the heat transfer tube 57, and the cooling air heated by heat exchange is supplied from the outlet 57B. The heated cooling air may be discharged to the atmosphere by providing a muffler muffler at the tip of the outlet 57B, for example.

  In the purification device 50, a temperature sensor 55T is disposed downstream of the air-cooled heat exchanger 55 in the discharge passages 17A and 109A, and the air-cooled heat exchanger is based on the temperature of the combustion gas G2 detected by the temperature sensor 55T. The amount of cooling air supplied to 55 is controlled by, for example, a flow control valve (not shown), so that the temperature of the combustion gas G2 can be adjusted to the CO selective oxidation reaction temperature E. .

  Note that the control of the amount of cooling air to the air-cooled heat exchanger 55 may be controlled based on the combustion state of the burners 16 and 106, and in that case, the combustion state of the burners 16 and 106 and the combustion gas G2 temperature. It is good also as a structure which can adjust the time lag which arises between.

According to the purification device 50, since no cooling water is used, there is no possibility of leakage of cooling water, the purification device 50 can have a simple configuration, and can be easily maintained. As a result, the cost can be reduced.
As shown in FIG. 8 (B), instead of the air-cooled heat exchanger 55, an air-cooled heat exchange having a heat exchange part 56A in which a nozzle 57C for injecting a part of the cooling air to the heat transfer tube 57 is formed. A configuration may be employed in which the oxidation auxiliary air A2 is injected from the nozzle 57C instead of the air supply nozzle 34 using the vessel 55A.

Next, the purification device 60 according to the fourth embodiment will be described.
FIG. 9 is a diagram for explaining the purification device 60 according to the fourth embodiment. The purification device 60 is different from the purification device 30 in that a large amount of cooling air A3 is used instead of the economizer 35 as a cooling means. An air nozzle (cooling means) 64 that cools the combustion gas G2 by injecting the cooling air A3 and the combustion gas G2 is provided between the NOx reduction catalyst 31 and the CO oxidation catalyst 39. Is the same as that of the purifying device 30, and thus the same reference numerals are given and the description thereof is omitted.
The cooling air A3 can also serve as the oxidation auxiliary air A2.

  In the purification device 60, a temperature sensor 65T is disposed downstream of the air nozzle 64 in the discharge passages 17A and 109A. Based on the temperature of the combustion gas G2 detected by the temperature sensor 65T, the cooling air A3 to the air nozzle 64 is supplied. The supply amount is controlled by, for example, a flow rate control valve (not shown), so that the temperature of the combustion gas G2 can be adjusted to the CO selective oxidation reaction temperature E.

  Note that the amount of the oxidation auxiliary air A2 supplied from the air nozzle 64 may correspond to the combustion state of the burners 16 and 106, and in that case, between the combustion state of the burners 16 and 106 and the combustion gas G2 temperature. It is good also as a structure which adjusts the time lag which arises.

In the purification device 60, the air nozzle 64 includes air nozzles 64 </ b> A, 64 </ b> B, and 64 </ b> C, and is arranged in three stages from the upstream side to the downstream side between the NOx reduction catalyst 31 and the CO oxidation catalyst 39.
With this configuration, the cooling air A3 and the combustion gas G2 are sufficiently mixed and stirred, and the combustion gas G2 can be uniformly cooled to the CO selective oxidation reaction temperature E.

  According to the purification device 60, the combustion gas G 2 is cooled using the air nozzle 64 with a simple structure and the oxidation auxiliary air A 2 is supplied to the combustion gas G 2, so that the NO oxidation in the combustion gas G 2 is generated in the CO oxidation catalyst 39. CO can be efficiently oxidized and removed while being suppressed.

Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention.
Although the case where the purification apparatus 30 is applied to the boiler 10 and the case where the purification apparatus 40 is applied to the heat treatment furnace 100 have been described in the above embodiment, the purification apparatuses 30, 40, 50, and 60 are replaced with the boiler 10 and the heat treatment furnace. Any of 100 can be selected arbitrarily.

The purifiers 30, 40, 50, 60 include a NOx reduction catalyst 31, a cooling means such as an economizer 35, nozzles 34, 57 C that inject oxidation assisting air A 2, and a CO oxidation catalyst 39. Although the configuration has been described, the purification device may be configured by a CO oxidation catalyst 39 and a cooling means.
It is also possible to form a purification device from the NOx reduction catalyst 31, the cooling means, and the CO oxidation catalyst 39.

In the above embodiment, the case where the cooling means is disposed between the NOx reduction catalyst 31 and the CO oxidation catalyst 39 has been described. For example, a NOx reduction catalyst having a characteristic capable of reducing NOx in a low temperature range is used. If it can be used, the cooling means may be arranged upstream of the NOx reduction catalyst 31.
In the above-described embodiment, the case where the combustion gas G2 passing through the CO oxidation catalyst 39 is cooled to the CO selective oxidation reaction temperature E by the cooling means has been described. The temperature may be outside the range of the CO selective oxidation reaction temperature E.

Moreover, you may apply the purification apparatus 30,40,50,60 with respect to combustion apparatuses other than the above.
For example, in the first embodiment, the boiler 10 is a small once-through steam boiler in which the combustion gas G2 flows substantially linearly through the combustion gas passage 12G from the burner 16 side toward the discharge passage 17A. However, the boiler 10 can be applied not only to a steam boiler but also to a hot water boiler. In addition to a small once-through boiler, a multi-tube boiler in which water pipes are arranged in an annular shape, and a flue tube boiler. It can be applied to boilers of various structures such as a water heater that directly heats a heating tube with a burner.

In the above-described embodiment, the case of the batch-type heat treatment furnace 100 has been described. However, instead of the batch-type heat treatment furnace 100, the purification apparatuses 30, 40, 50, and 60 are replaced with a continuous heat treatment furnace and an endothermic refrigeration. The present invention can also be applied to various combustion devices such as a regenerator of a machine, a waste treatment apparatus for burning and treating waste, and an incinerator.
Further, the burner used for combustion in the combustion device is not limited to the premixed burner in which a plurality of nozzle holes are arranged in a planar shape.

In the above embodiment, the case where the oxidation auxiliary air A2 is introduced from the air supply nozzles 34 and 64 disposed on the upstream side of the CO oxidation catalyst 39 in the discharge passages 17A and 109A has been described. Instead of A2, for example, pure oxygen or an oxygen-containing gas obtained by mixing oxygen and another gas may be used.
In this case, even a gas whose oxygen concentration is adjusted to be lower than air (oxygen concentration of about 21%) may be any gas that increases the oxygen content of the combustion gas G2 when mixed with the combustion gas G2.

In the above embodiment, the case where the premixed gas G1 in which the fuel gas G0 and the combustion air A1 are mixed is supplied to the burners 16 and 106 has been described. Without being limited to the mixed gas G1, for example, other gaseous fuels, liquid fuels including petroleum, pulverized coal may be used, and solid combustibles in an incinerator may be used as fuel.
Further, in the above-described embodiment, the description has been given of the case where the ventilation passage is the discharge passages 17A and 109A for discharging the combustion gas G2 to the outside. However, the transfer for transferring the combustion gas G2 from the combustion device to the next process device or the like The path may be a ventilation path.

It is a figure explaining CO selective oxidation reaction temperature concerning the present invention. It is a longitudinal section showing the boiler and purification device concerning a 1st embodiment of the present invention. It is a longitudinal cross-sectional view which follows the III-III line of the boiler which concerns on the 1st Embodiment of this invention. It is a figure which shows the purification apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the catalyst of the purification apparatus which concerns on the 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the heat processing furnace which concerns on the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the purification apparatus which concerns on the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the purification apparatus which concerns on the 3rd Embodiment of this invention, (A) is an example of the structure which injects the oxidation auxiliary air from an air nozzle, (B) heats the oxidation auxiliary air The example of the structure injected from the exchange part is shown. It is a longitudinal cross-sectional view which shows the purification apparatus which concerns on the 4th Embodiment of this invention.

Explanation of symbols

G2 Combustion gas 10 Boiler 17A, 109A Discharge path (ventilation path)
30, 40, 50, 60 Purification device 31 NOx reduction catalyst 34 Air supply nozzle (oxidation auxiliary means)
35 Economizer (cooling means)
39 CO oxidation catalyst 45 Water heat exchanger (cooling means)
55 Air-cooled heat exchanger (cooling means)
55A Air-cooled heat exchanger (cooling means, oxidation auxiliary means)
57C Nozzle (Oxidation auxiliary means)
64 Air nozzle (cooling means, oxidation auxiliary means)
100 Heat treatment furnace (combustion equipment)

Claims (4)

A purification device for reducing CO contained in combustion gas generated by combustion ,
An air passage through which the combustion gas can move;
A CO oxidation catalyst disposed in the air passage and through which the combustion gas can pass;
A cooling means disposed on the upstream side of the CO oxidation catalyst in the air passage to cool the combustion gas ;
A purification apparatus comprising a NOx reduction catalyst that is disposed on the upstream side of the cooling means in the air passage and through which the combustion gas can pass. The purification device according to claim 1,
The cooling means is
A purification apparatus configured to be capable of adjusting the temperature of the combustion gas . The purification device according to claim 1 or 2 ,
A purification apparatus comprising an oxidation assisting means for introducing a gas containing oxygen into the combustion gas upstream of the CO oxidation catalyst. A boiler comprising the purification device according to any one of claims 1 to 3 .

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