JPH02265619A - Control method for reducing agent in non-catalytic denitrification - Google Patents

Abstract

PURPOSE:To stabilize the discharging amount of a reducing agent injection pump by installing a pipe to supply clean water in a line between a drawing inlet of the reducing agent injection pump and a reducing agent storage tank. CONSTITUTION:A gas liquor is conventionally led to a gas liquor spraying in nozzle 8 from a gas liquor tank 1 through a gas liquor pipeline 7 by a gas liquor pump 2. Then, it is atomized by a compressed air in a compressed air pipeline 4 and sprayed to the inside of an incinerator. When the amount of the sprayed gas liquor become very small amount, an electromagnetic valve 9 is full opened and clean water is supplied in a gas liquor drawing pipe 10. By this method, denitration efficiency is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses a reducing agent injection pump (hereinafter referred to as the ammonium water pump) in a non-catalytic denitrification equipment for a waste incinerator that sprays ammonium water to remove nitrogen oxides. ) is related to a method of stabilizing the discharge amount of the reducing agent and controlling the reducing agent.

[Prior art] The concentration of nitrogen oxides (NO>) in the flue gas discharged from municipal waste incinerators is usually 150 ppm (0□12%
In recent years, regulations have become increasingly strict.

Therefore, removing NO from the exhaust gas from municipal waste incinerators has become a major problem.

Technologies for reducing NO in exhaust gas include methods to suppress the generation of NO by improving combustion methods, and methods to reduce NO in combustion exhaust gas.
There is a method using non-catalytic reduction denitrification that actively removes nitrification.

This non-catalytic reductive denitrification method (1) The equipment is simple and requires almost no maintenance.

(2) No operation is required during normal operation. (3) Stable denitrification efficiency can be achieved through automatic control of reducing agent and amount added.

(4) Maintenance and management costs are paper storage etc. have many advantages.

The above non-catalytic reduction denitrification method involves blowing a reducing agent such as ammonia gas or aqueous ammonia into the incinerator into the high-temperature combustion gas at 700 to 850°C, and using the following reaction formula to harmlessly remove NO in the exhaust gas. This method decomposes it into N2 and H20 and removes it.

4NH+4NO+O-4N2+6H20 Figure 2 shows a schematic diagram of the non-catalytic reduction and denitrification equipment.

As shown in FIG. 2, ammonia water (25% concentration, hereinafter referred to as ammonium water) in the ammonia tank is atomized by compressed air in a two-fluid spray nozzle and sprayed into the gas mixing chamber of the incinerator.

The relationship between the amount of reducing agent (ammonia gas) sprayed and the denitrification rate is shown in the third section.
As shown in the figure. Denitrification efficiency also improves as the amount of reducing agent spray increases.

Although it varies depending on the temperature conditions, the amount of ammonia sprayed can be adjusted to
If the H3/NOx ratio is 1.2 to 1.5 or more, unreacted ammonia and hydrogen chloride will react and produce ammonium chloride white smoke, so the NH3/NOx ratio must be kept below 1.2 to 1.5. There is.

Further, FIG. 4 shows the relationship between reaction zone temperature and denitrification rate using [N)I3/NoX ratio] as a parameter.

As shown in Figure 4, the relationship between reaction zone temperature and denitrification rate is 85
It shows maximum value near 0℃. Reaction zone temperature 750-900
By maintaining the temperature at about 0.degree. C. and operating the ammonia spray amount at a maximum NH3/NOx ratio of about 1.2, it is possible to remove about 30 to 70% of No. 2 without producing white smoke.

[Problems to be Solved by the Invention] In the above-mentioned conventional non-catalytic reduction denitrification method for removing NO from the exhaust gas of a waste incinerator, ammonium water is directly operated.

It was blown into the incinerator using a metering pump such as a hydraulic diaphragm type.

In this case, the ammonium water pump normally controls the ammonium water discharge amount by the stroke length, but as shown in Figure 5 (a),
It has been found that controllability is not sufficient below the range of 25 to 20% of the pump discharge amount.

In order to overcome this problem, there is a control method based on the number of rotations and the stroke length, but as shown in Figure 5(b), the controllability is not sufficient in the range of about 5% or less of the pump discharge amount. It has also become clear that driving on the right is not economical.

On the other hand, depending on the operation of the incinerator, the amount of No. generated is very small, and depending on the concentration of No. generated, the amount of ammonium water blown into the non-catalytic denitrification equipment may be small, resulting in pulsation of ammonium water, and this may cause nozzle clogging and burnout. Problems such as this arise. It is difficult to ensure a stable ammonium water pump discharge amount to prevent this, even with the conventional control method using rotation speed + stroke length.

That is, the object of the present invention is to provide a method for stabilizing the discharge amount of the -source side injection pump, controlling the reducing agent, and reducing NO in non-catalytic denitrification equipment for a waste incinerator that removes nitrogen oxides. Our goal is to provide the following.

[Means for Solving the Problems] The present invention provides a non-catalytic denitrification method in which nitrogen oxides are removed by spraying ammonium water as a reducing agent into an incinerator using an ammonium water pump. A method for controlling the reducing agent in non-catalytic denitrification, which is characterized by installing a pipe between the reducing agent storage tank and the pipe that adds fresh water so as to add fresh water when the amount of ammonium spray is small. .

[Function] In the method for controlling the reducing agent in non-catalytic denitrification of the present invention, a pipe for adding fresh water is provided in the pipe between the suction port of the reducing agent injection pump and the reducing agent storage tank. The amount of NO generated is low! Since fresh water can now be added when the amount of ammonium water sprayed is small, the amount of ammonium water can be increased, and the operating performance of the ammonium water pump can be shifted to a range with good controllability.

Next, examples of the present invention will be described.

[Example] FIG. 1 is an explanatory diagram of a method for controlling a reducing agent in non-catalytic denitrification to which the No. 2 reduction blade method is applied, which is an embodiment of the present invention.

In Figure 1, 1 is a cheap water tank, 2 is a cheap water pump, and 3
is fresh water piping, 4 is compressed air piping, 5 is a regulating valve, 6 is a flow meter, 7 is ammonium water piping, 8 is ammonium water injection nozzle, 9 is a solenoid valve,
10 is an ammonium water suction pipe.

As shown in FIG. 1, normally ammonium water (25% concentration) is guided from an ammonium tank 1 to an ammonium water injection nozzle 8 through an ammonium water piping 7 by an ammonium water pump 2, and compressed air from a compressed air piping 4 is introduced. It is atomized and sprayed into the incinerator.

Next, when a small amount of ammonium water is injected, the solenoid valve 9 is fully opened to supply clean water to the ammonium water suction pipe 10.

The opening of the regulating valve 5 is adjusted in advance and confirmed by the flow meter 6.

[Effect of the invention] According to the method for controlling the reducing agent in non-catalytic denitrification of the present invention,
The poor controllability of conventional ammonium water pumps and the pulsation of ammonium water when injecting small amounts of ammonium water can be easily improved by connecting fresh water piping to the ammonium water piping and supplying fresh water.

In addition, by diluting the ammonium water with clean water, the injection pressure increases as the amount of injection increases, and as a result, the spray particles of the ammonium water become fine and are sprayed over a wide range, allowing for better mixing with the furnace exhaust gas. This has the effect of improving the denitrification efficiency.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the system for controlling the reducing agent in non-catalytic denitrification, which is an example of an embodiment of the present invention, Figure 2 is a schematic diagram of the non-catalytic reduction and denitrification equipment, and Figure 3 is the reducing agent spray amount and denitrification rate. relationship diagram,
Figure 4 is a diagram of the relationship between reaction zone temperature and denitrification rate using [N)I3/Nox ratio] as a parameter, Figure 5 (a), (b)
2A and 2B are explanatory diagrams for explaining the control of the pumps, respectively. In the figure, 1: cheap water tank, 2: cheap water pump, 3: fresh water piping, 4: compressed air piping, 5: regulating valve, 6: flow meter,
7: Ammonium water piping, 8: Ammonium water injection nozzle, 9: Solenoid valve, 10
: Ammonium water suction pipe.

Claims (1)

[Claims] In a non-catalytic denitrification method in which nitrogen oxides are removed by spraying ammonium water as a reducing agent into an incinerator using an ammonium water pump, A method for controlling a reducing agent in non-catalytic denitrification, characterized in that a pipe for adding fresh water is provided between the pipes so that the fresh water can be added when the amount of ammonium water sprayed is small.