JPS6030909A - Method of cleaning exhaust gas from gas burner - Google Patents

Abstract

PURPOSE:To reduce production of noxious component such as NOX, CO contained in exhaust gas from a Bunsen type burner and a Schwank type burner, by using a catalyst formed by a perovskite type composite oxide. CONSTITUTION:A mixture ratio of the fuel to a primary air is brought to less than an equivalent, i.e., a fuel excess state to form a fuel excess range 7 in flame. A net 2, in which catalyst powder, represented by a general formula of Sr(1+x)12La(1-x)12Co1-xMaxO2, wherein Me is a metal selected from Fe, Mn, V, and Ti, and 0<x<1, is mixed with MgO, being a carrier, and magnesia mixture to firmly adhere the mixture to the surface, is located above a burner 1. The catalyst is formed by a relatively cheap element, but has a catalyst power equal to that of a precious metal and high resistance to heat. Besides, it is stable even in reducing gas, and furthermore, if basic oxide forms a carrier, catalyst activity if further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for reducing harmful components (NOX, Go, etc.) contained in exhaust gas from a gas burner.

[Description of conventional examples and problems] Mixture burners, particularly Bunsen type burners and Schwank type burners, have been used as city gas and propane gas combustion burners.

Bunsen-type burners burn gas that has been mixed with 60 to 70% air in advance, but city gas (
When the type of gas 13A-1) is combustible gas, the exhaust gas contains approximately 120 ppm of NOX <approximately 20% of this amount.
contains about 3 oppm of aldehydes.

In addition, in the Schwunk type burner, 90% of the current m1lP
The gas mixed with the above air is combusted through a wire mesh of about 33 mesh, and about 10 pDm of NOx is produced in the exhaust gas on a platform using city gas (gas type 13A-1) as fuel.
Of this, approximately 5ppm is N02), and approximately 50ppm is CO1.
Contains about 45 ppm of aldehydes.

In the case of the Schwunk type, NOX and CO can be reduced compared to the Bunsen type, but the difference is that the Shubunk type is slightly more complicated and the gas amount adjustment range (calorie adjustment range) is narrower.

Recently, the JP regulations for exhaust gases from combustors have become stricter, and many studies have been conducted on catalysts that eliminate harmful gases. Broadly speaking, two types of catalysts are used. One of them is one in which a noble metal such as platinum or palladium is supported on a carrier such as A9203.

Another method uses oxides such as manganese, copper, cobal, and nickel. Although the latter is inexpensive, it is not effective in eliminating NOx.

The former is effective in eliminating NOx when the ratio of fuel and oxygen is close to equivalent, but when exposed to high temperatures, sintering of the catalyst metal progresses and activity is lost, and the disadvantage is that it is expensive. It also had

(However, Me is a metal selected from Fe, Mn, V, and Ti, and the catalyst is represented by the general formula of It has been discovered that it has a high heat resistance, is stable even in reducing gases, and that the catalytic activity is further improved when a basic oxide is used as a carrier. Gansho 57-196480>.

[Object of the Invention] An object of the present invention is to provide an inexpensive method for effectively purifying the exhaust gas of a single-type burner and a Schwank type burner using the catalyst body of the above-mentioned invention.

[Structure of the Invention] The present invention forms a fuel excess area in the flame by setting the mixture ratio of primary air to fuel to an equivalent amount or less, that is, in a state of excess fuel, in a mixture burner, and in this excess fuel area, General formula SryuLayuCO□-2M1xe3 (However, M
e is a metal selected from Fe, Mn, V, and Ti;
It is characterized by disposing a net in which a catalyst powder represented by Q<z<1) is mixed with a carrier MoO and a magnesia cement mixture and fixed to the surface.

The catalyst represented by the above general formula is made of a perovskite-type composite oxide that has the ability to simultaneously oxidize reducing gases and decompose and reduce oxidizing gases, and the ratio of each component element is determined as shown in the above general formula. The catalytic activity is highest at the point determined by .

The activity of this catalyst is further improved when MoO is used as a carrier, and in the present invention, magnesia cement 1 to 1 is further mixed with these and fixed on the surface of the net, and this catalyst-equipped net is placed in the fuel-excess region of the flame. to purify exhaust gas.

The catalyst represented by the above general formula is obtained by mixing oxides or salts such as carbonates and acetates of each component element to obtain a predetermined composition and calcining the mixture.

Hereinafter, the present invention will be described based on preferred embodiments shown in the accompanying drawings.

FIGS. 1a and 1b show an embodiment in which the present invention is applied to a Bunsen type burner. Figure 2a and J: and 2b
The figure shows an embodiment in which the present invention is applied to a Schwunk type burner. The difference between the two is that in the case of the Bunsen type, a long flame is formed from the gas outlet, so a net with a catalyst is placed along the inner flame circumference in the inner flame area where there is excess fuel. In contrast, in the case of the Schbank type, the flame is uniformly short and formed from the wire mesh, so the silk with the catalyst is placed along the inside of the inner flame part parallel to the gas release mesh. be. In each figure, 1 is the burner main body, 2 is a mesh with a catalyst, and 3 is a wire mesh (approximately 33 mesh 1) for discharging the waste of the Schwunk type burner. 4 is a fuel r8+ gas inlet, 4- is a mixture inlet, 5 is a primary air hole, 6 is a Bunsen type burner gas discharge hole, 7 is an inner flame part (fuel excess area), and 8 is an outer flame part.

[Explanation of experimental example] A 3000 kcal/11 Bunsen burner on the Tomo 11 was set to full gas, and the ratio of primary air to the equivalent air amount (P
Combustion was carried out by varying a) in the range of 40 to 85%. At the best combustion condition, pa = 85%, 5r1-aO, 90
, 1 COo, 2 Fe0.803 and MU Oz magnesia cement were mixed with a solid content mm ratio of 3:3:1, and then the catalyst was applied to a thickness of 200 μm, and a fixed wire mesh was placed around the inner flame periphery. The distance between the top of the catalyst network and the gas release holes was 35 mm for 3 meshes, 50 m + n for 5 meshes, and 7011 m for 1 o mesh.In this state, By changing Pa, changes in NOX and CO in the exhaust gas were measured.

The measured values are shown in FIGS. 3 and 4, respectively. In the figure, the solid line indicates the case of 3000 kcal/h, where A is without catalyst wire mesh, B is with 3 meshes, C is with 5 meshes, and D is with catalyst attached to 10 meshes of wire mesh. Dotted line D
' indicates the combustion ratio of 1000 kcal/h for D.

No matter which catalyst wire mesh is used, harmful gases will reach pa-60 to 7.
It is minimum at 0%. It is recognized that the finer the wire mesh, the better the purification ability.

Experimental Example 2 The 8!I! net from Example 1 was placed in a Schwunk type burner with Pa = 95% as shown in Fig. 2 (d l-J T combustion was performed).

The appropriate distance of the catalyst mesh from the 33-mesh wire mesh unique to the Schwunk type burner was 1 to 2 mm.

The measurement values for NOx and CO were as shown in Table 1.

Table 1 Even in Schwunk type burners, the finer the mesh, the better the purification ability of the catalyst.

Experimental Example 3 A wire mesh of 10 meshes coated with a catalyst as in Experimental Example 1, and alumina cement coated with 1% platinum black were made, and the yield was 3000 kcal/h.

It was attached to a Bunsen burner with Pa=65% in the same manner as in Experimental Example 1, and a combustion experiment was conducted to measure changes in exhaust gas components.

Figure 5 shows the measured values. In the figure, E and E- are those of the present invention, and F and F- are those using platinum black. Solid line E
, F indicates NOX, and dotted lines E- and F- indicate measured values of CO.

Initially, the catalyst of the present invention had a slightly inferior purification ability compared to platinum black, but it showed little deterioration over time and maintained high purification ability over a long period of time.

[Effects of the Invention] As described above, the present invention does not require expensive means such as applying heat to a catalyst body, which is an inexpensive filtrate, to a highly heat-resistant wire mesh such as stainless steel or a mesh made of inorganic oxide fibers. By supporting the catalyst and distributing it inside the inner flame periphery, it does not inhibit combustion and exhibits higher purification ability over a longer period of time than those using expensive catalysts such as platinum. Even in a Bunsen-type burner with a wide width, the exhaust gas can be suppressed to the same level as a Schwunk-type burner.

[Brief explanation of drawings]

Fig. 1a is a perspective view showing a Bunsen-type burner according to the present invention (with part of the catalyst wire mesh cut away);
Figure 2a is a cross-sectional view showing the combustion state of the same embodiment, Figure 2a is a plan view showing an embodiment of the Schwunk type burner of the present invention with the catalyst wire mesh partially cut away, and Figure 2b is a plan view showing the combustion state of the same embodiment.
Figure 3 is a cross-sectional view showing the combustion state of the same example. Figure 3 is a diagram showing the degree of NOx purification in Experimental Example 1 of the present invention. Figure 4 is a diagram showing the degree of CO gamma deterioration in Experimental Example 1 of the present invention. , FIG. 5 is a diagram showing the catalyst life in comparison with the conventional example of Experimental Example 3. 1...Burner body 2...Catalyst network 3...Schbank type burner gas discharge network 4...Fuel gas inlet 4'
...Mixture mixture inlet 6...Bunsen type burner gas discharge LJ 7...Inner flame section 8...Outer flame section Patent applicant Matsushita Electric Industrial Co., Ltd. Figure 1a Book ib Figure i2a Figure 2b Figure 2a Collection a Figure 4

Claims (4)

[Claims] (1) In the mixture burner, the mixture ratio of primary air to fuel is equal to or less than the equivalent amount (fuel excess), and the MezO3 of the flame
(Me is a metal selected from Fe, Mn, V, and Ti, and catalyst powder represented by A method for purifying exhaust gas from a gas burner, characterized by arranging a net. (2) the mixture burner is a Bunsen type burner;
The exhaust gas purifying method for a gas burner according to claim (1), wherein the net is arranged inside the inner flame section along the inside of the inner flame section. (3) the mixture burner is a Schwunk type burner;
The exhaust gas purifying method for a gas burner according to claim 1, wherein the net is arranged inside the inner flame section along the inside of the inner flame section and parallel to the gas release net. (4) The method for purifying exhaust gas from a gas burner according to any one of claims (1) to (3), wherein the mesh is made of a wire mesh or an inorganic oxide 41 fiber.