JP2718120B2 - Operating method of exhaust gas denitration equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an operation method of an exhaust gas denitration apparatus which controls a temperature of an exhaust gas at an inlet of a catalyst to obtain a desired denitration rate.

The catalyst used in the denitration of (prior art) exhaust gas is deteriorated denitration performance by SO _X and soot and the like in the exhaust gas by the long-term use decreases.

Conventionally, as a countermeasure against the decrease in the denitration performance, a method of increasing the injection amount of NH ₃ with the deterioration of the catalyst, a method of spraying a vanadium solution onto the catalyst to prevent the deterioration of the catalyst, a method of washing the catalyst with water or using a soot blower. There is a method of removing soot by heating.

Japanese Patent Application Laid-Open No. 55-844 discloses a briquette stove in which the temperature of the catalyst or the inlet gas of the catalyst is raised to activate the reaction of the catalyst.

(Problems to be Solved by the Invention) In the above-mentioned conventional denitration, first, NH 4
Method of increasing the _third injection volume, although the deterioration of the catalyst is no problem in the initial stage, when it reaches to the point where there is a deterioration, the amount of NH ₃ to be injected considerably increases, the acidic ammonium sulfate Occurrence increases.

When the acidic ammonium sulfate is generated as described above, there is a problem that the denitration device, the accessory device, the duct, and the like are corroded.

As a result, the injection amount of NH ₃ is naturally limited, and even a sufficiently usable catalyst cannot be used,
There is a problem that the service life of the expensive catalyst is shortened.

Also, the method of using a vanadium solution to prevent the deterioration of the catalyst itself is high in running cost because vanadium is about 10 times as expensive as NH ₃ , and is unsuitable for use in denitration equipment such as diesel engines. It is.

Further, also dropped pay soot sootblower or washed to remove the catalyst deterioration of the catalyst itself is not improved, and the work is a problem that leads to results as directly neglect emissions Hanrawashiku NO _X is there.

The system disclosed in Japanese Patent Application Laid-Open No. 55-844 raises the temperature of the catalyst or the exhaust gas to a predetermined temperature when the briquette stove is ignited or digested, so that the control is performed independently of the deterioration of the catalyst.

Therefore, for example, there is a problem that it cannot be used as an exhaust gas denitration device for a diesel engine.

(Means for Solving the Problems) In order to solve the above problems, the present invention increases the injection amount of NH ₃ with the deterioration of the catalyst to maintain the degreasing rate of the denitration apparatus at or above a set value, When the injection amount of NH ₃ exceeds the set value, the temperature of the exhaust gas at the inlet of the catalyst is increased by the heater.
The injection amount of NH ₃ is reduced, and the injection amount of NH ₃ is increased again as the catalyst deteriorates.

In this way, when the injection amount of NH ₃ reaches the set value, the temperature of the exhaust gas at the inlet of the catalyst is increased stepwise to maintain the denitration rate within the set value.

(Operation) With this configuration, inexpensive NH ₃ is used for denitration.
Is used.

Then, by detecting that the injection amount of NH ₃ has reached the set value, deterioration of the catalyst is sensed, and the exhaust gas at the inlet of the catalyst is heated to reduce the injection amount of NH ₃ . As a result, no extra NH ₃ is injected and no ammonium sulfate is generated.

Also, by gradually increasing the exhaust gas temperature,
The minimum required thermal energy consumption associated with catalyst degradation.

(Example) Hereinafter, an example of the present invention will be described in detail. First
In the figure, an exhaust gas generated by an exhaust gas generating source, for example, a self-generated diesel engine 1 passes through a duct 10 and passes through a heater 2.
to go into. Then, the gas enters the denitration apparatus 3 through the duct 11, where the NH ₃ is sprayed from the NH ₃ sprayer 6, then denitrated while passing through the catalyst 4, and exhausted from the chimney 5 through the duct 12.

In the process of flowing the exhaust gas, the heater 2
Is output to the outlet duct 11 and the denitration apparatus 3 respectively before denitration from the outlet duct 12 NO _X meter 16 and the denitration after NO _X meter 15 NO _X is measured by denitrification rate comparator 17, the denitration rate setting signal 20 To determine whether the denitration rate has reached the set value.

This comparison signal is input to the NH ₃ injection amount calculator 18, and the NH ₃ injection amount is calculated between the comparison signal and the load signal 22 from the exhaust gas generation source 1.

Next, the calculated NH ₃ injection amount signal is output to the NH ₃ injection amount comparator 19 and compared with the set NH ₃ injection amount signal 21.

In this comparison, when the calculated NH ₃ injection amount is smaller than the set NH ₃ injection amount 21, it is determined that the catalyst 4 still has sufficient denitration performance at the exhaust gas temperature at that time. Then, the flow rate control valve 8 is controlled by a signal from the NH ₃ flow rate controller 14, and the calculated flow rate of NH ₃ is supplied from the supply source 7 and sprayed from the sprayer 6. Then, the exhaust gas temperature at the inlet of the catalyst 4 is maintained as it is.

The calculated NH ₃ injection amount is the set NH ₃ injection amount.
If it is larger than 21, it is determined that the catalyst 4 has deteriorated and has no denitration capability at the exhaust gas temperature.

In this case, a signal is output from the NH ₃ injection amount comparator 19 to the exhaust gas heater controller 13, and the amount calculated by the NH ₃ injection amount calculator 18 in the NH ₃ injection amount comparator 19 is converted into a set NH ₃ amount signal 21. The heater 2 is controlled by the exhaust gas heater controller 13 until it becomes equal to or less than the set value from.

When the calculated NH ₃ injection amount becomes equal to or less than the set value, the temperature of the exhaust gas is detected and input to the exhaust gas controller 13 as a signal 23, and the heater 2 is controlled so that the temperature is maintained.

In this way, the state of deterioration of the catalyst 4 at the current exhaust gas temperature and the denitration performance are determined based on the NH ₃ injection amount, and the exhaust gas temperature is controlled stepwise.

 FIG. 2 schematically shows this operation method.

That is, it is determined by the NH ₃ injection amount that the denitration rate curve A has reached the set denitration rate line B, and the exhaust gas temperature is controlled stepwise as indicated by the curve C.

In this operation method, as shown in FIG. 3, the denitration rate decreases as the catalyst deteriorates, so that the catalyst denitration rate curve D (new catalyst) changes from curve D (new catalyst) to curve E (deteriorated catalyst). The denitration rate curve is shifted, and the temperature of the exhaust gas is controlled in accordance with the portion having the highest denitration rate.

Therefore, by such an operation method, in the process of deterioration of the catalyst, the catalyst is used efficiently under the condition of the highest denitration rate, and the temperature of the exhaust gas is increased stepwise, so that unnecessary heat energy is There is no consumption.

Further, since the deterioration of the catalyst is determined based on the NH ₃ injection amount, the determination is made in a state that the deterioration is also included, for example, due to clogging of soot or the like. As a result, the exhaust gas is controlled in a state that includes all uncertain factors due to the deterioration of the catalyst.
_X is controlled as set, and there is no extra NH ₃ injection,
There is no generation of ammonium oxide.

Next, as shown in FIG. 4, when the catalyst is not used in the present operation method, that is, when the exhaust gas temperature is kept constant like the H line, as shown in FIG. The service life is reached at the intersection point P.

On the other hand, when the gas temperature is increased stepwise as shown in FIG. 2, the point P in FIG.
Equivalent to a point.

This shows that the service life of the catalyst is greatly extended.

(Effects of the Invention) As described in detail above, according to the present invention, the deterioration and denitration performance of the catalyst are determined based on the injection amount of NH ₃ , and the exhaust gas temperature at the inlet of the catalyst is raised stepwise, so that the soot Efficient use of the catalyst with the highest denitration performance irrespective of uncertain factors such as catalyst deterioration, greatly extending the service life of the catalyst and minimizing the consumption of heat energy to raise the temperature of exhaust gas Thus, denitration of exhaust gas can be reliably performed.

Further, since inexpensive NH ₃ is used and no extra NH ₃ is used, there is an excellent effect that running cost is reduced, there is no generation of acidic ammonium sulfate, and there is no problem of corrosion of ducts and equipment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of the operation method of the present invention, FIG. 2 is a diagram showing the relationship between the denitration rate during operation and the exhaust gas temperature with respect to the set denitration rate according to the present invention, and FIG. FIG. 4 is a diagram showing the relationship between the denitration rate curve of the catalyst and the exhaust gas temperature in the operation method according to the invention, and FIG. 4 is a diagram showing the relationship between the set denitration rate and the denitration rate during operation when the exhaust gas temperature is kept constant. . 1 ...... exhaust gas generating source, 2 ...... heaters, 3 ...... denitration unit, 4 ...... catalyst, 5 ...... chimney, 6 ...... NH ₃ spray nozzle, 13 ...... exhaust gas heater controller, 15 ...... denitration after NO _X total, 16 ...... denitration before NO _X meter, 17 ...... denitration rate comparator 18 ...... NH ₃ injection rate calculator 19 ...... NH ₃ injection rate comparator 20 ...... denitration rate setting signal, 21 ...... set NH ₃ quantity signal 22 …… Load signal.

Claims (1)

(57) [Claims] 1. The denitrification rate of a denitration apparatus is maintained at or above a set value by increasing the injection amount of NH ₃ with the deterioration of the catalyst, and when the injection amount of NH ₃ becomes equal to or higher than the set value, a heater is used. by elevating the temperature of the inlet exhaust gas temperature of the catalyst with a decrease and deterioration of the catalyst is again injected amount of NH ₃ to increase the amount of injected NH _3, NH ₃ thus
A step of raising the temperature of the exhaust gas at the inlet of the catalyst step by step when the injection amount of the catalyst reaches a set value to maintain the denitration rate within the set value.