JP2695654B2 - Control device for ammonia gas injection volume - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a control device for an injection amount of ammonia gas used for desulfurization of an electric dust collector (hereinafter referred to as EP) used for a boiler.

[Conventional technology]

In a device for performing desulfurization by injecting ammonia gas into the EP-side flue of an EP, as shown in FIG. 2, the ammonia gas is injected into the inlet-side flue 107 of the EP 108 through an injection pipe to perform desulfurization treatment. Purified gas is discharged through the flue 109 on the EP exit side.

A conventional control device for controlling the injection amount of ammonia gas is shown in FIGS. 2 and 3 proposed by Japanese Patent Application Publication No. 171733/1987 (Japanese Patent Application No. 12118/1986). is there.

That is, the amount of ammonia gas injected into the inlet flue 107 of the EP 108 is determined by the fuel flow rate signal 101 and the sulfur content set value signal 1 of the fuel.
20, EP output ammonia concentration setting device 113 output signal and EP1
The output signal of the arithmetic circuit 102 to which the output signal of the ammonia gas concentration meter 111 for detecting the ammonia gas concentration in the exhaust gas of the outlet flue 109 of 08 is input and the ammonia gas injection amount detector 103 set in the ammonia gas injection pipe 106 The output signal is compared with the controller 104, and the control valve 105 provided on the ammonia gas injection pipe 106 is opened and closed by the deviation signal to increase or decrease the output signal.

In the arithmetic circuit 102, a reaction ammonia gas amount is calculated by a reaction ammonia gas amount calculation circuit 112 to which the fuel flow rate signal 101 has been input, and the reaction ammonia gas amount is input to a correction circuit and the sulfur content in the fuel is calculated. The amount of ammonia gas for reaction corrected by the above is obtained. Further, the fuel flow rate signal 101 is input to a surplus ammonia gas amount calculation circuit 114 to determine the surplus ammonia gas amount, and the surplus ammonia gas amount outputs the set value of the surplus ammonia gas concentration remaining at the EP108 outlet. Is corrected by a correction circuit that inputs a signal from the excess ammonia gas concentration setter 113 to obtain the corrected amount of excess ammonia gas. The corrected excess ammonia gas amount is added to the corrected excess ammonia gas amount in the excess ammonia gas adder 117, and the set value output from the excess ammonia gas concentration setter 113 is further added to the corrected ammonia gas amount for reaction. The sample control circuit 116 corrects the surplus ammonia gas amount correction signal output from the comparator 115 based on the actual measurement value output from the ammonia gas concentration meter 111, and the ammonia gas injection amount 110 is output.

The reaction for ammonia gas, the reaction was carried out as indicated by sulfur and the following reaction scheme contained in the fuel, ammonium sulfate (NH ₄₎ generates ₂ SO _4, the ammonium sulfate (NH _{4) 2} SO ₄
Is removed by EP108.

S + O ₂ → SO ₂ 2SO ₂ + O ₂ → 2SO ₃ SO ₃ + H ₂ O → H ₂ SO ₄ NH ₃ + H ₂ SO ₄ → NH ₄ HSO ₄ NH ₄ HSO ₄ + NH ₃ → (NH ₄ ) ₂ SO _{4 For the} above reaction The amount of ammonia gas is calculated in the arithmetic circuit 102 based on the above reaction formula.

The reason for determining the injection amount of ammonia gas by adding excess ammonia gas to the above-mentioned reaction ammonia gas is that when ammonia gas is insufficient, the reaction of the following equation proceeds to the right (NH ₄ ) ₂ SO ₄ NH ₃ This is because + NH ₄ HSO ₄ generates acidic ammonium sulfate NH ₄ HSO ₄ and adversely affects EP.

[Problems to be solved by the invention]

In the conventional apparatus, the reaction rate of the ammonia gas concentration meter is slow (about 10 to 40 minutes), so that it is impossible to inject an appropriate amount of ammonia gas by ordinary proportional-integral-derivative control.

Further, the change in concentration of SO ₃ contained in the boiler exhaust gas by connexion generated in the combustion of sulfur over time gently portion (annual about 100% increase) to increase the Ya operating state or the excess air ratio of the boiler Although there are portions that change rapidly depending on the temperature and the like, the conventional apparatus cannot sufficiently cope with these.

The gradual increase in the above SO ₃ concentration increases the amount of heavy metals accumulated in the boiler with the operating time of the boiler,
This is because it acts as a catalyst for converting SO ₂ to SO ₃ .

An object of the present invention is to solve the above-described problems and to provide an apparatus capable of constantly injecting an appropriate amount of ammonia gas, minimizing the amount of excess ammonia gas, and reducing running costs.

[Means for solving the problem]

The control device of the present invention is a control device that includes an arithmetic unit that corrects a reaction ammonia gas amount signal using a sulfur content set value signal in fuel and outputs an ammonia injection amount signal.
A comparator that inputs a surplus ammonia gas concentration set value signal output by the ammonia gas concentration setter and an ammonia gas concentration signal output by the ammonia gas concentration meter, and inputs a deviation signal output by the comparator to set upper and lower limit values. A high / low signal selector for selecting a deviation signal that has exceeded the signal output by the high / low signal selector, and outputs a conversion rate correction signal proportional to the time when the deviation signal exceeds the upper and lower limit set values, and outputs the same signal. The present invention is characterized in that an integration adjuster for inputting to the arithmetic unit is provided.

[Action]

In the above description, the comparator that receives the surplus ammonia gas concentration set value signal from the ammonia gas concentration setter and the ammonia gas concentration signal from the ammonia gas concentration meter outputs the deviation signal. The high / low signal selector which has input the same deviation signal selects a deviation signal exceeding the upper limit or lower limit set value, and outputs a signal to the integration controller. The integrator receives the above signal, and outputs a conversion rate correction signal proportional to the time when the deviation signal exceeds the upper limit or lower limit set value. The conversion rate correction signal is input to the calculator. The arithmetic unit corrects the input ammonia gas amount signal for the reaction with the sulfur content set value signal and the conversion rate correction signal, and the control device outputs an appropriate ammonia gas injection amount signal. I do. By the above, apart from the control corresponding to the normal change of the SO ₃ concentration which changes relatively quickly, the conversion rate of the conversion from SO ₂ to SO ₃ with time can be gradually reduced by inputting the conversion rate correction signal to the calculator. As a result, a control device capable of minimizing the amount of excess ammonia gas and injecting ammonia gas was realized.

〔Example〕

 One embodiment of the present invention is shown in FIG.

The present embodiment is the same as the conventional device except for the part where the signal is fed back from the comparator, and therefore the description is omitted.

This embodiment shown in FIG. 1 is an ammonia gas concentration setting device.
The comparator 115 receives the surplus ammonia gas concentration set value signal 3 output by 113 and the ammonia gas concentration signal 2 output by the ammonia gas concentration meter 111 and outputs a deviation signal 4. The comparator 115 outputs the deviation signal 4 to the high / low signal selector 5. An integration controller 7 for inputting a conversion rate correction signal 8 and a reaction ammonia gas amount signal 1 output from a reaction ammonia gas amount calculation circuit 112, and further receives a sulfur set value signal 120 for fuel.
And a conversion unit 6 for inputting the conversion rate correction signal 8 and outputting a corrected ammonia gas amount signal 9, and a surplus ammonia gas amount signal 10 output from a surplus ammonia gas amount calculation circuit 114. A computing unit 11 for outputting a surplus ammonia gas amount signal 15 corrected by the surplus ammonia gas concentration set value signal 3, the corrected ammonia gas amount signal 9 and the surplus ammonia gas amount signal
An adder / subtractor 12 for inputting and adding 15 to output an ammonia amount signal 13, a correction ammonia gas amount signal 17 output from a proportional-integral controller 16 to which the deviation signal 4 is input, and a correction excess ammonia gas amount signal for inputting High / low setting device 18, which outputs 19,
Further, there is provided an adder / subtractor 14 which receives the ammonia amount signal 13 and the correction excess ammonia amount signal 19 and outputs an ammonia injection amount signal.

In the above, the excess ammonia gas set value signal 3 output from the comparator 115 and the deviation signal 4 of the ammonia gas concentration signal 2 are input to the high / low signal selector 5. The height signal selector 5 outputs a signal to the integration controller 7 when the deviation signal 4 exceeds an upper limit or an adjustment value set in the selector 5, and the controller 7 outputs the signal to the integration controller 7. The conversion rate correction signal 8 proportional to the time exceeding the lower limit is output. The conversion rate correction signal 8 is input to an arithmetic unit 6 to which the reaction ammonia gas amount signal 1 and the sulfur set value signal 120 have been input, and the arithmetic unit 6 outputs a corrected reaction ammonia gas amount signal 9. .

In the high / low signal selector 5, when the deviation signal exceeds the upper limit value or the lower limit value, the signal is sent to the integration controller 7,
Since the controller 7 outputs the conversion rate correction signal 8 proportional to the time when the deviation signal exceeds the upper limit value or the lower limit value,
It does not respond to a change in the concentration of ammonia gas in normal exhaust gas, and correction is performed only when a gradual change with time exceeds a certain value.

The corrected ammonia gas amount signal for reaction 9 output from the arithmetic unit 6 is used as a surplus ammonia gas amount operation circuit.
The surplus ammonia gas amount signal 15 output by 114 and corrected by the arithmetic unit 11 is added by the adder / subtractor 12, and the adder / subtractor 12 outputs the ammonia amount signal 13 and inputs it to the adder / subtractor 14.

The deviation signal 4 output from the comparator 115 is input to a proportional-integral controller 16, and the controller 16 outputs a correction ammonia gas amount signal 17 corresponding to a change in the concentration of SO _{3 which} usually changes relatively quickly. I do. The correction ammonia gas amount signal 17 is input to the height setting device 18. The height setting device 18 is a correction excess ammonia gas amount signal obtained by adding a limit to the correction ammonia gas amount signal 17 so as not to cause an excessive excessive or insufficient ammonia injection amount due to a response delay of the ammonia concentration meter 111. Outputs 19.

The correction excess ammonia gas amount signal 19 is input to the adder / subtractor 14, which corrects the ammonia amount signal 13 with the correction excess ammonia gas amount signal 19 and outputs an ammonia injection amount signal 20. .

The above, since the control and has come to allow each corresponding to temporal changes in the concentration of early normal SO ₃ relatively change control for gradual increase in the conversion of from SO ₂ to SO _3, excess ammonia gas A control device capable of injecting ammonia gas with a minimum amount was realized.

〔The invention's effect〕

The present invention relates to a control device for outputting an ammonia injection amount signal, comprising a computing unit in which a reaction ammonia gas amount signal is corrected by a sulfur content set value signal, and receiving an excess ammonia gas concentration set value signal and an ammonia concentration signal. Yotsute that with a deviation signal from the comparator input via a high and low signal selector integral controller for outputting a conversion factor correction signal input to the calculator for, early normal SO ₃ relatively-changing since the control corresponding to the change in concentration has decreased to allow control over the separate conversion of the correction signal a gradual increase in the conversion to sO ₃ than by connexion temporal sO ₂ to be entered into the calculator, the excess ammonia A control device capable of injecting ammonia gas with a minimum amount of gas has been realized.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention, FIG. 2 is an explanatory view of an ammonia gas injection desulfurization apparatus, and FIG. 3 is an explanatory view of a conventional apparatus. 1 ... Ammonia gas amount signal for reaction, 2 ... Ammonia gas concentration signal, 3 ... Surplus ammonia gas concentration set value signal, 4 ... Deviation signal, 5 ... High / low signal selector, 6 ... Computing unit, 7 ... Integral controller, 8 ... Conversion rate correction signal, 9 ...
... Ammonia gas amount signal for reaction, 10 ... Ammonia gas amount signal for surplus, 11 ... Calculator, 12 ... Adder / subtractor, 13 ...
Ammonia amount signal, 14 ... Adder / subtracter, 15 ... Surplus ammonia gas amount signal, 16 ... Proportional integration controller, 17 ... Correction ammonia gas amount signal, 18 ... High / low setting device, 19 ... Correction Excess ammonia gas amount signal, 20 ... ammonia gas injection amount signal, 101 ... fuel flow rate signal, 111 ... ammonia gas concentration meter, 112 ... reaction ammonia gas amount signal, 113
... Ammonia gas concentration setting device, 114... Surplus ammonia gas amount calculation circuit, 115.

Claims (1)

(57) [Claims] A control device for correcting an ammonia gas amount signal for reaction by a sulfur content set value signal in a fuel and outputting an ammonia injection amount signal; A comparator that inputs a gas concentration set value signal and an ammonia gas concentration signal output by an ammonia gas concentration meter, and a deviation signal that is input by the comparator and selects a deviation signal that exceeds the upper or lower limit set value. And an integration controller for inputting a signal output by the height signal selector, outputting a conversion rate correction signal proportional to the time when the deviation signal exceeds the upper limit or lower limit set value, and inputting the signal to the arithmetic unit. A control device for an ammonia gas injection amount, comprising: