System and method for monitoring condensate polishing mixed bed resin leakage in a power plant

Abstract

The application provides a power plant monitoring condensate polishing mixed bed resin leakage system and method. Since OH type negative resin in the mixed bed resin starts to decompose at 60 DEG C, benzyl alcohol, trimethylamine, amine ions and hydroxyl ions are generated. When the mixed bed resin leaks after the mixed bed is put into operation, the resin passes through the low-pressure heater, the working temperature of the low-pressure heater 7 is 120 DEG C, therefore the OH type negative resin has been decomposed, the hydroxyl ions in the product can increase the measurement value of the online conductivity meter, therefore according to the difference between the condensate water conductivity at the inlet of the deaerator and the condensate water conductivity after adding ammonia in the mixed bed mother pipe, it can be determined whether the mixed bed put into operation leaks resin, the operation safety of the unit is improved, and resin waste is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to a power plant condensate polishing system, in particular to a power plant monitoring condensate polishing mixed bed resin leakage system and method. BACKGROUND

[0002] High parameter, large capacity generating units, the water vapor quality puts forward more strict requirements, condensate polishing is an important measure to ensure the water vapor quality and safe and economic operation of unit, at present, the process of condensate polishing is mainly mixed bed, the condensate polishing mixed bed resin leakage into the thermal system, will threaten the safe operation of unit, especially for the water quality requirements of high parameter, supercritical unit, the consequences are particularly serious. Ion exchange resin into the thermal system, not only affect the water vapor quality, increase the water consumption and heat loss, but also will seriously corrode the thermal system, form vicious cycle. Long time low pH value operation of boiler water, will form acid corrosion, serious hydrogen embrittlement, make the boiler tube in a short time, directly affect the safe operation of the boiler. The deterioration of the quality of boiler water, increase the steam carrying further influence the quality of steam, cause the superheater, steam turbine flow part salt deposition, affect the efficiency of steam turbine, serious can cause the superheater tube burst. Acidic substances in the steam such as sulfuric acid, formic acid, acetic acid, the distribution coefficient is very small, especially to the steam turbine wet area caused by acid corrosion, such as low pressure section, baffle, low pressure cylinder inlet steam device, exhaust casing and so on are corroded by acid, lead to the surface protection film fall off, form corrosion groove, surface roughness honeycomb, make the equipment damage.

[0003] In addition, due to the leakage of resin into the thermal system can not be recovered, not only caused great economic loss, also to the operation and regeneration of high speed mixed bed caused a series of adverse effects, seriously affect the polishing operation level and reliability. Therefore, timely and accurate monitoring of mixed bed resin leakage has important significance to the safe operation of unit. At present, the mixed bed resin leakage is mainly observed by artificial, timeliness is poor. When the artificial finds mixed bed resin leakage, it shows that the mixed bed has a large amount of leakage of a large amount of resin, which has a great influence on the safe and economic operation of unit. SUMMARY

[0004] In order to find mixed bed resin leakage in time and accurately, the purpose of the present application is to provide a power plant monitoring condensate polishing mixed bed resin leakage system and method, which can effectively and accurately monitor the mixed bed resin leakage.

[0005] The present application is realized by the following technical scheme:

[0006] A method for monitoring condensate polishing mixed bed resin leakage in a power plant, comprising the following steps:

[0007] Step 1, obtaining the conductivity value of the condensate after adding ammonia in the mixed bed mother pipe before the mixed bed is put into operation, and the conductivity value of the condensate at the inlet of the deaerator, and calculating the difference between the two conductivity values before the mixed bed is put into operation;

[0008] Step 2, obtaining the conductivity value of the condensate after adding ammonia in the mixed bed mother pipe after the mixed bed is put into operation, and the conductivity value of the condensate at the inlet of the deaerator, and calculating the difference between the two conductivity values after the mixed bed is put into operation;

[0009] Step 3, determining whether the mixed bed leaks resin according to the difference between the conductivity values obtained in step 1 and the difference between the conductivity values obtained in step 2.

[0010] Preferably, the conductivity value of the condensate after adding ammonia in the mixed bed mother pipe and the conductivity value of the condensate at the inlet of the deaerator in step 1 are the average conductivity values of the condensate after adding ammonia in the mixed bed mother pipe and the average conductivity values of the condensate at the inlet of the deaerator within a set time before the mixed bed is put into operation.

[0011] Preferably, the conductivity value of the condensate after adding ammonia in the mixed bed mother pipe and the conductivity value of the condensate at the inlet of the deaerator in step 2 are the average conductivity values of the condensate after adding ammonia in the mixed bed mother pipe and the average conductivity values of the condensate at the inlet of the deaerator within a set time after the mixed bed is put into operation.

[0012] Preferably, in step 3, the difference between the two conductivity difference values is calculated according to the conductivity difference value obtained in step 2 and the conductivity difference value obtained in step 1, and when the difference value δ is greater than a set threshold value, an alarm signal of mixed bed resin leakage is output.

[0013] Preferably, before step 1, when there are multiple mixed beds, the sequence number of the mixed bed put into operation is determined according to the valve position signal of the mixed bed electric valve.

[0014] A system for monitoring condensate polishing mixed bed resin leakage in a power plant, comprising a controller and a mixed bed mother pipe conductivity meter, a deaerator inlet conductivity meter and an electric valve connected thereto;

[0015] The mixed bed mother pipe conductivity meter is arranged on the pipeline after adding ammonia in the mixed bed mother pipe, and the deaerator inlet conductivity meter is arranged on the deaerator inlet mother pipe, which is connected to the outlet of the low-pressure heater, and the inlet of the low-pressure heater is connected to the mixed bed mother pipe.

[0016] The controller is used to output an alarm signal of mixed bed resin leakage according to the detection data of the mixed bed mother pipe conductivity meter and the deaerator inlet conductivity meter.

[0017] Preferably, an electric valve is arranged on the outlet pipeline of the mixed bed, and the electric valve is connected to the controller, which is used to obtain the valve position signal of the electric valve and determine the sequence number of the mixed bed put into operation.

[0018] Preferably, an electric valve is arranged at the outlet of each mixed bed when a plurality of mixed beds are included.

[0019] Compared with the prior art, the present application has the following beneficial technical effects:

[0020] The method for monitoring resin leakage of a mixed bed in a condensate polishing system of a power plant provided by the present application can determine whether resin leakage occurs in the mixed bed in operation according to the difference between the conductivity at the inlet of a deaerator and the conductivity after ammonia is added at the total outlet of the mixed bed, thereby improving the safety of unit operation and avoiding waste of resin. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The control system schematic diagram of the present application.

[0022] Figure 2 The historical curve diagram of the conductivity at the inlet of a deaerator and the conductivity after ammonia is added at the total outlet of a mixed bed in Example 1 of the present application.

[0023] In the figure, 1 is a mixed bed mother pipe conductivity meter, 2 is a deaerator inlet conductivity meter, 3 is a first electric valve, 4 is a second electric valve, 5 is a third electric valve, 6 is a mixed bed mother pipe, 7 is a low-pressure heater, 8 is a deaerator inlet mother pipe, and 9 is a controller. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below with reference to the accompanying drawings, which are provided to explain the present application rather than to limit the present application.

[0025] Referring to Figure 1 A system for monitoring resin leakage of a mixed bed in a condensate polishing system of a power plant, which comprises a controller 9 and a mixed bed mother pipe conductivity meter 1, a deaerator inlet conductivity meter 2, a first electric valve 3, a second electric valve 4 and a third electric valve 5 connected to the controller 9.

[0026] The mixed bed mother pipe conductivity meter 1 is arranged on the pipeline after ammonia is added to the mixed bed mother pipe 6, the deaerator inlet conductivity meter 2 is arranged on the deaerator inlet mother pipe 8, the first electric valve 3 is arranged on the outlet pipeline of the mixed bed A, the second electric valve 4 is arranged on the outlet pipeline of the mixed bed B, and the third electric valve 5 is arranged on the outlet pipeline of the mixed bed C.

[0027] The deaerator inlet mother pipe 8 is connected to the outlet of the low-pressure heater 7, and the inlet of the low-pressure heater 7 is connected to the mixed bed mother pipe 6.

[0028] The controller 9 is used to receive detection data from the mixed bed main pipe conductivity meter 1 and the deaerator inlet conductivity meter 2, as well as opening and closing signals of the first electric valve 3, the second electric valve 4 and the third electric valve 5.

[0029] The above-mentioned method for monitoring leakage of a condensate polishing mixed bed resin system in a power plant comprises the following steps:

[0030] Step 1: Determine the serial number of the mixed bed to be put into operation according to the valve position signal of the electric valve of the mixed bed;

[0031] Step 2: Obtain the average conductivity δ of the condensate after adding ammonia to the mixed bed main pipe within the set time before the mixed bed is put into operation 1前 , and the mean conductivity of the condensate at the deaerator inlet δ 2前 , and calculate the difference δ between the two 前 ;

[0032] Specifically, the conductivity meter of the mixed bed main pipe and the conductivity meter of the deaerator inlet are both measured online in real time, and the measured data are simultaneously sent to the controller for recording.

[0033] Therefore, in the set time range before the mixed bed is put into operation, the average conductivity κ of the condensate after adding ammonia in the mixed bed main pipe within the set time range can be obtained through historical measurement data. 1前 , and the mean conductivity of the condensate at the deaerator inlet κ 2前 .

[0034] Conductivity mean κ 2前 and the mean conductivity κ 1前 The difference δ 前 The calculation method is as follows:

[0035] δ 前 =κ 2前 -κ 1前

[0036] Step 3: Obtain the average conductivity κ of the condensate after adding ammonia to the mixed bed main pipe within the set time after the mixed bed is put into operation. 1后 , and the mean conductivity of the condensate at the deaerator inlet κ 2后 , and calculate the difference δ between the two 后 ;

[0037] Conductivity mean κ 2后 and the mean conductivity κ 2后 The difference δ 后 The calculation method is as follows:

[0038] δ 后 =κ 2后 -κ 1后

[0039] Step 4: Calculate the difference δ后 and the difference δ before δ, the calculation method is as follows:

[0040] δ = δ 后 - δ 前

[0041] When δ is greater than a set threshold value, then output step 1 mixed bed resin leakage alarm signal.

[0042] The working principle of the monitoring method of the present application is as follows:

[0043] The resin in the mixed bed includes: negative resin and positive resin.

[0044] The positive resin begins to decompose into sulfuric acid and sodium bisulfate at 150°C.

[0045] Most of the negative resin is OH type and Cl type.

[0046] The OH type negative resin begins to decompose into benzyl alcohol, trimethylamine, amine ion and hydroxyl ion at 60°C.

[0047] The Cl type negative resin begins to decompose into benzyl chloride, trimethylamine, benzyl alcohol and amine chloride at 160°C.

[0048] When the mixed bed is put into operation, if the mixed bed resin leaks, the resin passes through the low-pressure heater 7, because the working temperature of the low-pressure heater 7 is 120°C, only the OH type negative resin has been decomposed, and the decomposition products are: methanol, trimethylamine, amine ion and hydroxyl ion, among which the hydroxyl ion can increase the measured value of the deaerator inlet conductivity table 2. The leaked resin has not entered the low-pressure heater 7, and the working temperature is less than 60°C, neither the negative resin nor the positive resin will decompose, so the mixed bed mother pipe conductivity table 1 measured value will not change.

[0049] The controller 9 determines the mixed bed resin leakage according to the difference between the measured values of the mixed bed mother pipe conductivity table 1 and the deaerator inlet conductivity table 2 within a certain time, which is greater than a predetermined value, to realize the alarm of the condensate polishing mixed bed resin leakage.

[0050] Example 1

[0051] Taking a 600MW supercritical once-through boiler unit of a certain power plant as an example, after a mixed bed is put into operation, the historical curves of the deaerator inlet conductivity and the mixed bed total outlet conductivity after adding ammonia are as follows: Figure 1It can be seen that there is a significant difference between the deaerator inlet conductivity and the total outlet conductivity of the mixed bed after adding ammonia. Before the mixed bed is put into operation, the average value of the deaerator inlet conductivity is 5.83 μS / cm, and the average value of the total outlet conductivity of the mixed bed after adding ammonia is 5.81 μS / cm, and the conductivity does not change. After the mixed bed is put into operation, the average value of the deaerator inlet conductivity is 6.12 μS / cm, and the average value of the total outlet conductivity of the mixed bed after adding ammonia is 5.81 μS / cm, and the average value of the conductivity increases by 0.31 μS / cm. Through artificial observation, it is found that the resin leaks.

[0052] The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A method of monitoring condensate polishing mixed bed resin leakage in a power plant, characterized by, The method comprises the following steps: Step 1, obtaining the conductivity value of the condensate water after ammonia is added to the mixed bed mother pipe before the mixed bed is put into operation, and the conductivity value of the condensate water at the inlet of the deaerator, and calculating the difference between the two conductivity values before the mixed bed is put into operation; The conductivity value of the condensate water after ammonia is added to the mixed bed mother pipe and the conductivity value of the condensate water at the inlet of the deaerator are both the average conductivity value of the condensate water after ammonia is added to the mixed bed mother pipe and the average conductivity value of the condensate water at the inlet of the deaerator within a set time before the mixed bed is put into operation; Step 2, obtaining the conductivity value of the condensate water after ammonia is added to the mixed bed mother pipe after the mixed bed is put into operation, and the conductivity value of the condensate water at the inlet of the deaerator, and calculating the difference between the two conductivity values after the mixed bed is put into operation; The conductivity value of the condensate water after ammonia is added to the mixed bed mother pipe and the conductivity value of the condensate water at the inlet of the deaerator are both the average conductivity value of the condensate water after ammonia is added to the mixed bed mother pipe and the average conductivity value of the condensate water at the inlet of the deaerator within a set time after the mixed bed is put into operation; Step 3, determining whether the mixed bed leaks resin according to the difference between the conductivity values obtained in step 1 and the difference between the conductivity values obtained in step 2; According to the difference between the conductivity values obtained in step 2 and the difference between the conductivity values obtained in step 1, the difference between the two conductivity differences is calculated, and when the difference is greater than a set threshold, an alarm signal of the mixed bed resin is output; When the mixed bed leaks resin after the mixed bed is put into operation, the working temperature of the low-pressure heater is 120 DEG C, so only the OH type negative resin begins to decompose, and the decomposition products are: methanol, trimethylamine, amine ions and hydroxyl ions, among which the hydroxyl ions increase the measurement value of the conductivity meter at the inlet of the deaerator; when the resin does not enter the low-pressure heater and the working temperature is less than 60 DEG C, neither the negative resin nor the positive resin decomposes, that is, the measurement value of the conductivity meter of the mixed bed mother pipe does not change.

2. The method for monitoring the leakage of the resin in the condensate polishing mixed bed of the power plant according to claim 1, characterized in that, Before step 1, when there are multiple mixed beds, the sequence number of the mixed bed put into operation is determined according to the valve position signal of the mixed bed electric valve.

3. A system for monitoring the leakage of the resin of the condensate polishing mixed bed in a power plant according to the method of any one of claims 1-2, characterized in that, The controller (9) is connected with the mixed bed mother pipe conductivity meter (1) and the deaerator inlet conductivity meter (2) and the electric valve; The mixed bed mother pipe conductivity meter (1) is arranged on the pipeline after ammonia is added to the mixed bed mother pipe (6), the deaerator inlet conductivity meter (2) is arranged on the deaerator inlet mother pipe (8), the deaerator inlet mother pipe (8) is connected with the outlet of the low-pressure heater (7), and the inlet of the low-pressure heater (7) is connected with the mixed bed mother pipe (6); The controller (9) is used for outputting an alarm signal of the mixed bed resin leakage according to the detection data of the mixed bed mother pipe conductivity meter (1) and the deaerator inlet conductivity meter (2); The outlet pipeline of the mixed bed is provided with an electric valve, the electric valve is connected with the controller, and the controller is used for obtaining the valve position signal of the electric valve and determining the sequence number of the mixed bed put into operation; When there are multiple mixed beds, an electric valve is arranged at the outlet of each mixed bed.

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