JPS61185320A - Purification of exhaust gas - Google Patents

Abstract

PURPOSE:To facilitate the handling of a reducing agent in the storage and transport thereof, by performing selective colalytic reductive denitration by using NH4Cl as a reducing agent. CONSTITUTION:The exhaust gas 2 generated from a boiler 1 is passed through the catalyst 4 allowed to pack a denitration apparatus 3 along with NH3 generated by thermally decomposing an aqueous NH4Cl solution, which is supplied to an injection line 10 from a storage tank 8 by a quantitative pump 9 while receives the control of an injection amount, to be denitrated and the exhaust gas after denitration is heat-exchanged by an air heater 6 to be transferred to the downstream machinery. The effect of NH4Cl to denitration reaction is not different from that of NH3 and handling in storage and transport becomes easy.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is applicable to heavy oil-fired boilers, coal-fired boilers,
Exhaust gas that effectively and economically reduces nitrogen oxides (hereinafter abbreviated as NOx) contained in exhaust gas from internal combustion engines such as combustion furnaces attached to various chemical equipment, steel plants, diesel engines, and turbines. It concerns a purification method.

(Prior art) KLOZ in exhaust gas is emitted into the atmosphere and produces harmful substances, so that its emission is regulated and various methods have been proposed to prevent it from having a negative impact on the human body. There is. The method is a wet method in which it is absorbed into a solution, a method using an adsorbent, or a catalyst is used to combine harmless nitrogen and water in the presence of a reducing gas such as ammonia (hereinafter abbreviated as NH) or -carbon oxide. There are many ways to decompose it. Among these, the selective catalytic reduction method using NH3 has been industrialized as an economical and effective method, and many plants employing this method are currently in operation.

(Problems to be Solved by the Invention) In the selective catalytic reduction method for denitrification, NH, which is commonly used in the past, is stored in the form of liquid ammonia because it easily becomes liquid when pressurized even at room temperature. The gas is then returned to atmospheric pressure, gasified, and blown into the flue. As is well known, Nu is a substance that belongs to a specified chemical substance or a deleterious substance, and sufficient care must be taken when storing and handling it.

(Means for Solving the Problems) The present inventors have solved the complexity of using ammonia as described above, and at the same time made use of the excellent properties of NH as a reducing agent for the denitrification reaction. EiW 琳6L 畢化鱹Mu 11 [東()壬／l″lノロ.

(Means for Solving the Problems) That is, the present invention is an exhaust gas purification method characterized by using ammonium chloride (hereinafter abbreviated as mH4at) as a reducing agent in a selective catalytic reduction denitrification method.

When NH2Cl is heated, NH40L-+NHs + HCl...
...(1) NH3 is generated. It also has high solubility in water, easily dissolves in water, becomes an aqueous solution, and when heated, N
It has characteristics such as generating H, MH,
A method is adopted in which NH3 generated by decomposing Ol is supplied to the flue.

Next, embodiments of the present invention will be described based on the accompanying drawings.

Figure 1 shows one example when applied to a denitrification device for heavy oil-fired boilers.
Give an example. Heavy oil is burned in a boiler 1, and the generated exhaust gas 2 passes through a catalyst 4 filled in a denitrification device 3, and the denitrified exhaust gas 5 undergoes heat exchange with an air heater 6, and then moves to downstream equipment.

NHs necessary for the denitrification reaction is supplied from a tank 8 storing an aqueous solution of N H4c to the flue through an injection line 10 with the injection amount controlled by a metering pump 9.

In this embodiment, an example is shown in which an aqueous NH4Cjt solution is used, but the present invention is not limited to this. Using a heat source near 400°C in the boiler 1, NH4C4 is thermally decomposed to generate NH3, which is pressurized to produce smoke. A method of blowing into the road may also be adopted.

(Function) As described above, in the method of the present invention, the source of NH, which is the reducing agent for selective catalytic reduction denitrification, is obtained from xH4ct, which is solid at room temperature and has extremely high solubility in water. N, which does not touch various regulations.
H4O/! Compared to conventional liquid ammonium, the use of ammonium has the same effect on the denitrification reaction and has the advantage of being easier to handle, such as storage and transportation.

Next, the method of the present invention will be explained by an example on a laboratory scale.

(Example 1) Denitration catalyst for heavy oil firing (lattice catalyst, 7 ugly pitches) 50■
A horizontal reactor was filled with 14 ports of 450 x 45 mm, and exhaust gas having the composition shown in Table 1 was heated at a temperature of 350°C and a gas amount of 2 + Nm.
3, NH, which is a reducing agent for the denitrification reaction, which flowed in at 3/H, was supplied by making 40 L of NH into an aqueous solution and injecting it into the approximately 400° C. portion at the inlet of the catalyst layer using a metering pump.

Table 1 Exhaust gas composition As a result, even in a continuous test lasting 50 hours, NH,
Regarding the supply of 9 Nu, it was possible to stably supply 9 Nu without any trouble. Second test result
As shown in the figure, results equivalent to those obtained when liquid ammonium was used were obtained. In the figure, ○ indicates N H4C using an aqueous solution method, Δ
shows the results of the conventional method.

(Example 2) NH was supplied as a gas obtained by decomposing yEI4at, and about 5001 mH4ct was packed in a metal container of about 1 ton and heated from the outside with a mantle heater.

At the top of the container, an inlet for pressurized air pressure, an outlet for decomposed gas, and a thermocouple for controlling the temperature of the mantle heater were installed to control the temperature of NH40t to be constant.

The amount of NHs injected was controlled by a flow meter installed at the outlet, and a catalyst activity evaluation test was conducted under the conditions shown in Table 2.

Table 2 Activity test conditions As a result, even if mH4at was used as the NH source,
It was confirmed that stable supply of NH3 was possible over a long period of time.

The test results obtained are shown in Figure 3 in comparison with those using liquid ammonia, and it is clear that normal activity evaluation tests are possible without any difference from using normal liquid ammonium. It became clear. In the figure, ○ indicates NH4
At decomposition method, Δ indicates the results of the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an embodiment of the present invention.
H4C! This is a diagram comparing the relationship between the NH3/NOx ratio and the denitrification rate with the conventional method using liquid ammonia in a test using an aqueous solution as the 4n3 supply source. FIG. 3 is a diagram comparing the relationship between the NH3/NOx ratio and the denitrification rate with a conventional method in a test using generated NH3. Among the sub-agents: 1) Akira

Claims (1)

[Claims] A method for purifying exhaust gas characterized by using ammonium chloride as a reducing agent in a selective catalytic reduction denitrification method.