JP2538548B2 - Ammonia injection control method for supply / condensation system - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to an ammonia injection control device in a feed / condensation system, and more specifically, the amount of ammonia injected into the feed / condensation system of a thermal power plant is controlled by a deaerator. The present invention relates to a supply / condensation system ammonia injection control device that is determined according to the conductivity of a sample at an inlet.

[Prior art and its problems]

In general, the amount of ammonia injected into the feedwater condensate system of a thermal power plant is determined by constant value control of the conductivity at the inlet of the deaerator or economizer, and this ammonia is placed near the inlet or outlet of the condensate booster pump. Often injected. In this case, the distance between the ammonia injection point and the conductivity measurement point is large, and as a result, a time delay occurs in the system, the constant value control does not work smoothly, and hunting occurs in the conductivity control. is there.

An apparatus for carrying out this type of conventional ammonia injection control method is shown in FIG. That is, in FIG. 2, the conductivity μS of the sample at the inlet of the deaerator or economizer A is measured by the conductivity meter 10, and the measured value obtained here is supplied to the controller 12, where The stroke length of the chemical injection pump 16 is adjusted via a stroke length adjuster 14 (also referred to as spetol) by comparing the preset water quality target value S with an output generated according to the comparison result.
This controls the amount of ammonia injection to the injection point 18 at the inlet of the condensate booster pump CBP. It should be noted that the fluctuation of the condensate flow rate can be dealt with by changing the pump rotation speed, but since it can be easily understood by those skilled in the art, description thereof will be omitted.

According to the control method by the conventional device, the distance between the chemical solution (ammonia) injection point and the conductivity measurement point is large, resulting in a large time delay, and the effect of the chemical solution (ammonia) injection does not immediately appear. Cause As a result, excessive injection or under injection of the chemical solution may be alternately repeated, causing hunting in adjusting the conductivity value.

The applicant has previously provided a first conductivity measuring device on the upstream side of the ammonia water supply pipe connection part of the condensate flow path system as a pH control device of this type of desalted condensate, and further downstream thereof. A flow meter is provided on the side, and an arithmetic unit is provided for controlling the rotation speed or adjusting the stroke length of the ammonia water supply pump based on the detection signal obtained by the first conductivity measuring device and the flow meter. A second electric conductivity measuring device is provided on the downstream side of the ammonia water supply pipe connecting part of the condensate flow path system, and a detection signal from the second electric conductivity measuring device is fed back to the control mechanism of the pump. I proposed the device (Saikai Sho 53-95888).

However, this control device feed-forward-controls the ammonia water supply pump with respect to the electric conductivity of the condensate based on the detection signal obtained by the first electric conductivity measuring device and the flow system, and the rotation speed or The stroke length is controlled to be adjusted, and the pump is feedback-controlled with respect to the electric conductivity of the condensate based on the detection signal from the second electric conductivity measuring device, so that the stroke length or the rotation speed different from that of the control is controlled. It is used for adjustment control. Therefore, the control mechanism for the ammonia water supply pump and its control program are complicated.

Therefore, the present inventor, as a result of repeated studies to eliminate the drawbacks associated with the above-mentioned conventional method, the conductivity measurement of the deaerator or economizer inlet and the comparison of the measured value to the water quality target value and the main loop On the other hand, by conducting cascade control using the conductivity measurement at the outlet of the condensate booster pump as a sub-loop, hunting for water quality adjustment can be prevented with a relatively simple configuration, and the water quality at the deaerator inlet can be adjusted to the water quality. We have found that the target value can be controlled properly.

However, in general, the purpose of conductivity measurement is pH control in the boiler, so the measurement should be performed in the water supply system (after the deaerator is discharged), but the capacity of the deaerator is extremely low. However, the time delay until the conductivity as a result of ammonia injection is measured becomes too large. Therefore, it is essential to measure the conductivity at the inlet of the deaerator. However, also in this case, it takes about 2 to 5 minutes for the result of ammonia injection to be measured as conductivity in the above-mentioned water supply / condensation system, and there is a time delay until the sampling rack. Including it will take 10 to 20 minutes. On the other hand, it was confirmed that the time until the conductivity could be measured at the outlet of the condensate booster pump close to the connection point of the chemical injection pump was several seconds after the injection of ammonia.

[Object of the Invention]

Therefore, an object of the present invention is to prevent the hunting of water quality control by reducing the time delay between conductivity measurement and ammonia injection, and finally to properly and simply improve the water quality at the inlet of the deaerator. It is an object of the present invention to provide an ammonia injection control device for a water supply / condensation system in a thermal power plant that can control the water quality target value.

[Outline of Invention]

In order to achieve the above-mentioned object, an ammonia injection control device for a feed / condensation system according to the present invention has a first conductivity for a sample of a feed / condensation system at an inlet of a deaerator located a predetermined distance from a condensate booster pump. The rate is measured, the obtained measured value is compared with the target water quality value, and the stroke length or rotation speed of the chemical injection pump arranged on the suction side of the condensate booster pump is determined by the output generated according to this comparison result. In the feed / condensation system ammonia injection controller that controls and controls the amount of ammonia injection into the feed / condensation system, further measure the conductivity of the sample immediately after chemical injection at the outlet side of the feed / condensation system condensate booster pump. A second conductivity meter is provided, and the measured value obtained by the second conductivity meter is further compared with the output according to the comparison result between the measured value based on the first conductivity and the water quality target value. Comparison And a means for further changing the stroke length or the number of revolutions of the chemical injection pump by the output generated according to the comparison result obtained by the comparison means, and configured to cascade control the ammonia injection amount. To do.

Example of Invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached FIG. For convenience of explanation, the same components as those of the conventional apparatus shown in FIG. 2 will be described with the same reference numerals.

In FIG. 1, reference numeral A is a deaerator, 10 is a first conductivity meter, 12 is a controller, 14 is a stroke length controller (sptrol), 16 is a chemical injection pump, and 18 is a condensate booster pump CB.
Ammonia injection point at P inlet, 20 is condensate booster pump C
The BP exits are shown respectively. Therefore, in the above configuration,
First, the electrical conductivity μS at the inlet of the deaerator A is measured by the first electrical conductivity meter 10, and this measured value is compared with the preset water quality target value S in the controller 12 in advance. Configure the main loop.

And in this embodiment, the condensate booster pump CB
A sub loop for measuring the conductivity μS at the outlet 20 of P by the second conductivity meter 22 is constituted, and the measured value of this sub loop is compared with the output of the main loop. Note: The stroke length adjuster 14 of the pump 16 is used for further modification. In this way, the ammonia injection amount for the ammonia injection point 18 at the inlet of the condensate booster pump CBP is configured to be cascade controlled.

That is, in this example, the conductivity μS of the sample after the chemical injection in the water supply / condensation system, that is, the conductivity μS of the sample on the outlet 20 side of the condensate booster pump CBP was measured by the second conductivity meter 22. Then, the measured value obtained by the second conductivity meter 22 is output according to the comparison result between the measured value based on the first conductivity meter 10 and the water quality target value S, and the controller 12
The comparison means further compares the stroke length or rotation speed of the chemical injection pump 16 through the changing means according to the output generated according to the comparison result obtained by the comparison means. In this way, by performing the cascade control of the ammonia injection amount, the controller set value of the electric conductivity μS at the outlet 20 of the condensate booster pump CBP is
It will change sequentially depending on the controller output (deviation between the target water quality and the actual liquid) at the inlet of the deaerator A.

〔The invention's effect〕

As is apparent from the above-described embodiment, according to the device of the present invention, the ammonia injection amount is controlled by the first conductivity immediately after the ammonia injection, so that there is no time delay and hunting for water quality control can be prevented. it can. Further, since the setting value of the sub loop can be automatically corrected by measuring the second conductivity at the deaerator inlet, the control content based on the first conductivity is corrected based on the second conductivity. do it,
By properly and easily controlling the stroke length or rotation speed of the chemical injection pump, finally the water quality at the deaerator inlet is set to the water quality target value,
That is, the water quality can be controlled to a pH value that minimizes the amount of iron corrosion.

In addition to the time delay from the injection of ammonia to the measurement, the cause of hunting in adjusting the pH or conductivity is not only the adjustment of the injection amount due to the fluctuation of the condensate flow rate, but also the ion exchange of the desalination device. Although the conductivity may change largely temporarily due to the switching of the resin, according to the control device of the present invention, not only fluctuations inside the loop of the water supply / condensation system but also fluctuations due to factors outside the loop as described above However, it can be adjusted sufficiently.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a control device for performing ammonia injection control by cascade control of the present invention, and FIG. 2 is a system diagram of a conventional control device for performing ammonia injection control. 10 …… First conductivity meter 12 …… Controller 14 …… Stroke length adjuster 16 …… Medication pump 18 …… Ammonia injection point 20 …… Booster pump outlet 22 …… Second conductivity meter A …… Deaerator S …… Water quality target value CBP …… Condensate booster pump

Claims (1)

(57) [Claims] 1. A first conductivity of a sample of a feed / condensation system at an inlet of a deaerator located at a predetermined distance from a condensate booster pump is measured, and the obtained measured value is compared with a water quality target value. , The output generated according to this comparison result controls the stroke length or rotation speed of the chemical injection pump arranged on the suction side of the condensate booster pump to control the amount of ammonia injected into the condensate system. In the water-based ammonia injection control device, a second conductivity meter for further measuring the conductivity of the sample immediately after chemical injection is provided at the outlet side of the condensate booster pump of the water supply / condensation system, and this second conductivity meter is used. Comparison means is provided for further comparing the obtained measured value with the output according to the comparison result of the measured value based on the first conductivity and the water quality target value, and is generated according to the comparison result obtained by this comparing means. Do A supply / condensation system ammonia injection control device comprising means for further changing the stroke length or rotation speed of the chemical injection pump according to the output, and configured to perform cascade control of the ammonia injection amount.