JPH044483B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for reducing harmful components (NOx, CO, etc.) contained in exhaust gas from a gas burner. [Configuration and Problems of Conventional Examples] Conventionally, mixture burners, particularly Bunsen type burners and Schubank type burners, have been used as city gas and propane gas combustion burners. In a Bunsen type burner, 60 to 70
% of air is burned in the atmosphere,
When city gas (gas type 13A-1) is used as fuel, the exhaust gas contains approximately 120 ppm of NOx (of which approximately
It contains 20% NO ₂ ), about 90 ppm CO, and about 30 ppm aldehydes. In addition, in the bank type burner, 90
Gas mixed with more than 30% air is burned through a wire mesh of about 33 mesh, but city gas (type of gas)
13A-1) is used as fuel, approximately
10ppm NOx (of which about 5ppm is NO ₂ ), approx.
Contains 50ppm CO and about 45ppm aldehydes. The Schubank type can reduce NOx and CO than the Bunsen type, but the difference is that the structure is somewhat more complex and the gas amount adjustment range (calorie adjustment range) is narrower. Recently, combustor exhaust gas regulations have become stricter, and much research has been conducted into catalysts that eliminate harmful gases. Broadly speaking, two types of catalysts are used. One is one in which a noble metal such as platinum or palladium is supported on a support such as Al ₂ O ₃ . The other type uses oxides such as manganese, copper, cobalt, and nickel. Although the latter is inexpensive, it is not effective in eliminating NOx. In the former case, where the ratio of fuel and oxygen is close to equivalence,
Although it is effective in eliminating NOx, it also has the disadvantage that when exposed to high temperatures, the catalytic metal sinters and loses its activity, and it is also expensive. The inventors

[Formula] (Me is a metal selected from Fe, Mn, V, Ti, 0<x
Although the catalyst represented by the general formula of It was discovered that the catalytic activity was further improved when an oxide was used as a carrier, and a patent application has already been filed for this (patent application filed in 1983).
196480). [Object of the Invention] An object of the present invention is to provide an inexpensive method for effectively purifying exhaust gas from Bunsen type and Schubank type burners using the catalyst body of the above invention. [Structure of the Invention] The present invention forms an excess fuel region 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 an air-fuel mixture burner, and in this excess fuel region, the general formula

[Formula] (Me is a metal selected from Fe, Mn, V, Ti, 0<x
It is characterized by disposing a net in which the catalyst powder represented by <1) is mixed with a mixture of MgO and magnesia cement as a carrier 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 when the The activity of this catalyst is further improved when MgO is used as a carrier, and in the present invention, magnesia cement 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 emit exhaust gas. Purify. The catalyst represented by the above general formula is made of oxides or carbonates of each component element so as to have a predetermined composition.
It is obtained by mixing a salt such as acetate and firing 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. FIGS. 2a and 2b show an embodiment in which the present invention is applied to a bunk 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 inside of the periphery of the inner flame in the inner flame area, which is the fuel-excess area. On the other hand, in the case of the Shubank type, the flame is uniformly formed from a short wire mesh, so the mesh with the catalyst is arranged parallel to the gas release mesh along the inner side of the inner flame periphery. In each figure, 1 is the burner body, 2 is a mesh with a catalyst, and 3 is a gas release wire mesh (approximately 33 meshes) of the bank-type burner. 4 is the fuel gas inlet, 4' is the mixture inlet, 5 is the primary air hole, 6
1 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 examples] Experimental example 1 A 3000 kcal/h Bunsen burner with gas fully opened, ratio of primary air to equivalent air amount (Pa)
The combustion was carried out by varying the amount in the range of 40% to 85%. At the best combustion condition Pa=65%, 3, 5, 10
Sr _0.9 La _0.1 on mesh stainless steel wire mesh
A catalyst prepared by mixing Co _0.2 Fe _0.8 O ₃ , MgO, and magnesia cement in a solid weight ratio of 6:3:1 was applied to a thickness of 200 μm, and a fixed wire mesh was placed along the inner flame periphery. It was placed inside as shown in Figure 1. The distance between the top of the catalyst network and the gas release hole is 35 mm for 3 meshes, 50 mm for 5 meshes, and 50 mm for 10 meshes.
It became 70mm. Under this condition, Pa was changed and changes in the concentrations of 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 is for 3000kcal/h,
A has no catalyst wire mesh, B has 3 meshes, C has 5 meshes, and D has a 10 mesh wire mesh with a catalyst attached. The dotted line D' shows the combustion value of 1000 kcal/h for D. No matter which catalyst wire mesh is used, the harmful gas will be Pa=
It reaches its minimum at 60-70%. It is recognized that the finer the mesh of the wire mesh, the better the purification ability. Experimental Example 2 The catalyst network of Experimental Example 1 was attached to a Shubank type burner with Pa=95% as shown in Fig. 2, and combustion was carried out. The appropriate distance of the catalyst mesh from the 33-mesh wire mesh unique to the bank type burner was 1 to 2 mm. The measured values of NOx and CO were as shown in Table 1.

[Table] Even in bank-type burners, the finer the mesh, the better the purification ability of the catalyst. Experimental Example 3 A 10-mesh wire mesh was coated with a catalyst as in Experimental Example 1, and alumina cement was coated with platinum black at a rate of 1%, and 3000 kcal/
A combustion experiment was conducted by attaching it to a Bunsen burner with h and Pa = 65% in the same manner as in Experimental Example 1, and changes in exhaust gas components were measured. 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.
The solid lines E and F show the measured values of NOx, and the dotted lines E' and F' show the measured values of CO. Although the catalyst of the present invention initially had a slightly inferior purification ability compared to platinum black, 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 allows the catalyst body, which is an inexpensive material, to be fixed to a highly heat-resistant wire mesh such as stainless steel or a mesh made of inorganic oxide fibers without using expensive means such as applying heat. By supporting it and placing it inside the inner flame periphery, combustion is not inhibited.
It exhibits higher purification ability over a long period of time than those that use expensive catalysts such as platinum, and has the advantage of being able to suppress harmful gas emissions to the same level as a Schubank burner, even with a Bunsen burner that is inexpensive and has a wide range of heat control. has.

[Brief explanation of drawings]

Fig. 1a is a perspective view showing an embodiment of the Bunsen type burner of the present invention with a part of the catalyst wire cut away, Fig. 1b is a cross-sectional view showing the combustion state of the embodiment, and Fig. 2a is a Fig. 2b is a cross-sectional view showing the combustion state of the embodiment, and Fig. 3 is the degree of NOx purification in Experimental Example 1 of the present invention. Figure 4 shows the CO of Experimental Example 1 of the present invention.
FIG. 5 is a diagram showing the degree of purification, and 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...Shubunk type burner gas discharge network, 4...Fuel gas inlet, 4'...Mixture inlet, 6...Bunsen type burner gas discharge port, 7...Inner flame Part, 8... External inflammation part.

Claims (1)

[Claims] 1. In the air-fuel mixture burner, the mixture ratio of primary air to fuel is equal to or less than equivalent (fuel excess), and within the fuel excess region of the flame, the general formula [formula] (where Me is Fe, Mn, V, metal selected from Ti, 0<x
A method for purifying exhaust gas from a gas burner, characterized by arranging a net in which the catalyst powder represented by <1) is mixed with a carrier of MgO and a magnesia cement mixture and fixed to the surface. 2. The exhaust gas purification method for a gas burner according to claim 1, wherein the air-fuel mixture burner is a Bunsen type burner, and the net is disposed inside the inner flame portion along the inner side of the periphery of the inner flame. 3. Exhaust gas purification of a gas burner according to claim 1, wherein the air-fuel mixture burner is a sybank type burner, and the mesh is disposed inside the inner flame section along the inner side of the inner flame periphery and parallel to the gas discharge network. Method. 4. The exhaust gas purification method for 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 fiber.