WO2019095658A1

WO2019095658A1 - Design method of chemical cleaning scheme for superheater pipe of supercritical power station boiler

Info

Publication number: WO2019095658A1
Application number: PCT/CN2018/087695
Authority: WO
Inventors: 张颖伟; 王洋
Original assignee: 东北大学
Priority date: 2017-11-15
Filing date: 2018-05-21
Publication date: 2019-05-23
Also published as: CN107844863A; CN107844863B

Abstract

The present invention provides a design method of a chemical cleaning scheme for a superheater pipe of a supercritical power station boiler. The method comprises: determining a mathematical model of oxide scale growth; performing static tests at different temperatures and concentrations to determine the time required for complete reaction between oxide scale and an acid solution, a reaction amount of the acid solution per unit time and per unit area, and chemical reaction rates of the acid solution at different temperatures and concentrations; estimating a burst probability of a superheater pipe according to an operating condition of the superheater pipe, and determining, on the basis of the burst probability of the superheater pipe, a time to start performing acid pickling on the superheater pipe; determining a theoretical time of acid pickling of oxide scale at the same chemical reaction rate; and preparing the acid solution, thereby determining a chemical cleaning scheme for a superheater pipe of a supercritical power station boiler. The present invention provides a novel idea for cleaning a superheater pipe of a power plant, selects an optimal time to start performing acid pickling on the pipe, increasing operational time of the superheater pipe, and reducing economic losses caused by burst pipes.

Description

Design method of chemical cleaning scheme for superheater pipeline of supercritical power station boiler

Technical field

The invention belongs to the technical field of process control, in particular to a design method for a chemical cleaning scheme of a superheater pipeline of a supercritical power station boiler.

Background technique

The working fluid of a thermal power plant is water. Under normal conditions, when the heating temperature reaches the saturation temperature at a given pressure, a phase change will occur, and the water will start to change from a liquid to a gaseous state. When the steam pressure reaches 22.129 MPa, the water When heated to 374.15 ° C under this pressure, it is completely vaporized. The role of the superheater in the working process of the power plant is mainly to take out the water in the saturated steam and protect the steam turbine, mainly by superheating the steam to dry. In this process, due to the high temperature and high pressure steam environment inside the superheater pipe, the inner wall of the metal will be oxidized in contact with the steam. The operating temperature of the superheater steam is 571 ° C. At this temperature, the oxygen in the air and the inner wall of the superheater metal are combined. An oxide film is formed, and the oxide film is divided into three layers over time. The metal matrix of the superheater tube is inwardly followed by FeO-Fe ₃ O ₄ -Fe ₂ O ₃ , and the outer layer of triiron tetroxide and trioxide The structure of the diiron oxide is dense, chemically stable, and the structure of the ferrous oxide in the inner layer is loose. When the temperature of the superheater pipe changes drastically, the oxide film may be broken due to the different thermal stress of the pipe matrix and the iron oxide. The oxide crack penetrates into the metal matrix and further oxidizes, impinging on the overall stability of the scale, the oxide film is easy to fall off, and accumulates in the pipeline, causing blockage of the pipeline, further causing the problem of pipeline bursting.

At present, the means of treating oxide scale in power plants is mainly to stop the pipe after the pipe burst, and to cut and replace some pipes of the pipe burst, so that the intuitive economic loss caused by the power plant boiler from the pipe bursting to the shutdown to the maintenance is immeasurable, and in fact only solves The problem of scale accumulation of the squib pipe is not taken for other pipes, but the cutting method is replaced again when the next blast occurs, and the treatment method is rough.

Summary of the invention

In view of the deficiencies of the existing scale treatment technology, the present invention proposes a design method for a chemical cleaning scheme of a superheater boiler superheater pipeline.

The technical scheme of the present invention is as follows:

A design method for a chemical cleaning scheme for a supercritical power plant boiler superheater pipeline, comprising:

Determining the relationship between the running time of the superheater pipe and the corresponding scale thickness of the superheater pipe under the working conditions of the rated working condition, that is, the mathematical model of the scale growth;

The static test is carried out at different temperatures and concentrations to determine the time required for the complete reaction of the scale and the acid solution, and the reaction amount of the acid solution per unit area per unit time, and determine the chemical reaction rate of the acid solution at different temperatures and concentrations;

Determining the squib probability of the superheater pipe for the operating condition of the superheater pipe, and determining the time at which the superheater pipe starts to pickle based on the squib probability of the superheater pipe;

Determine the theoretical time of the scale pickling at the same chemical reaction rate;

Based on the theoretical time of scale pickling, the acid solution was configured, and the chemical cleaning scheme for the superheater boiler superheater pipeline was determined.

The mathematical model for the growth of the scale is established as follows:

Obtain historical data of the superheater pipeline under the working conditions of the rated working condition, including the steam temperature, pressure, t-time oxide scale thickness and running time of the superheater pipeline during operation;

Regression of historical data, fitting the relationship between the running time of the superheater pipe and the corresponding scale thickness under the condition of constant steam temperature and pressure, and obtaining the mathematical model of scale growth.

The mathematical model for the growth of the scale is:

Where δ is the thickness of the t-time scale, A is the undetermined coefficient, n is taken in [1, 2], and when n=1, the growth curve of the scale is linear, and when n=2, the growth curve of the scale In the shape of a parabola, the estimation of the undetermined coefficient A is performed based on the historical data of the superheater pipe.

The determining the chemical reaction speed of hydrochloric acid at different temperatures and concentrations is as follows:

Separate acid solutions with different concentrations, set different temperatures, and cut the same scale of oxide scale for static test, and record the time required for complete reaction between oxide scale and acid solution;

According to the time required for the complete reaction of the scale and the acid solution, the reaction amount of the acid solution per unit area per unit time is determined, and the chemical reaction speed of the acid solution at different temperatures and concentrations is determined.

The predicted flooding probability of the superheater pipe for the operating condition of the superheater pipe is as follows:

Extracting historical data related to the squib failure in the historical data of the superheater pipeline;

Based on the historical data related to the blaster failure in the historical data of the superheater pipeline, the risk prediction model for training the squib probability of the superheater pipeline is trained;

After a superheater pipe is run to a state feature vector at a certain time, the value of the pipe burst probability function of the superheater pipe is calculated.

The squib probability based on the superheater pipe determines the time at which the superheater pipe starts pickling, specifically, the time at which the blasting probability function value reaches the set upper limit as the time at which the pickling is started.

The risk prediction model of the superheater pipeline burst probability is established as follows:

The risk prediction model for the probability of pipe burst in superheater pipeline is defined. The Weibull distribution is selected as the base burst risk function, and the risk prediction model of the final superheater pipe burst probability is obtained. The maximum likelihood function method is used to predict the pipe burst probability of the superheater. The parameter estimation of the risk prediction model, the historical function of the N superheater pipeline related to the blasting fault, the likelihood function of the risk prediction model for determining the burst probability of the superheater pipeline; the likelihood function is maximally based on the DFP method The solution of the value.

The method for determining the theoretical time of the scale pickling in the case where the chemical reaction rate is constant is:

Determine the chemical reaction rate of the acid solution according to the concentration of the acid solution disposed in the pickling and the temperature of the pickling environment;

Calculate the time required for the complete reaction of the single layer of scale on the unit area of the pipeline;

Calculate the time required for the complete reaction of the three layers of scale on the unit area of the pipeline;

Calculate the amount of hydrochloric acid consumed by the three oxides contained in the three-layer scale;

Calculate the consumption of hydrochloric acid per unit area of the inner wall of the pipeline;

The theoretical time of the scale pickling is determined under the condition that the chemical reaction rate is constant, that is, the sum of the amounts of hydrochloric acid consumed by the three oxides contained in the three-layer scale is divided by the consumption of hydrochloric acid per unit area of the inner wall of the pipe.

Beneficial effects:

Determining the squib probability of the superheater pipe according to the operating condition of the superheater pipe, determining the time at which the superheater pipe starts pickling based on the squib probability of the superheater pipe; determining the concentration of the hydrochloric acid and the temperature of the pickling environment according to the pickling The chemical reaction rate of hydrochloric acid is determined based on the mathematical model of scale growth to determine the thickness of the scale at the beginning of the pickling, and the weight of the scale is calculated, and the theoretical time of the scale pickling is determined without changing the chemical reaction rate. Based on the theoretical time of the oxide skin pickling, the acid solution was configured to determine the chemical cleaning scheme for the supercritical power plant boiler superheater. The invention provides a new idea for the cleaning of the superheater pipeline of the power plant, selects the best time for the pipeline to start pickling, and the power plant selects the appropriate time to apply for shutdown, and performs chemical cleaning of the pipeline oxide scale. It reduces the bursting probability of the superheater, enhances the running time of the superheater pipeline, reduces the economic loss caused by the pipeline bursting, and improves the economic benefit of the power plant.

DRAWINGS

Figure 1 is a schematic diagram of pickling equipment, wherein 1 pickling tank, 2 constant temperature water bath, 3 water washing tank, 4 magnetic pump, 5 electromagnetic flowmeter, 6 to be pickled pipeline, 7 waste tank;

2 is a graph showing the chemical reaction rate of hydrochloric acid at room temperature as a function of concentration in a specific embodiment of the present invention;

Figure 3 is a graph showing the relationship between the absolute temperature and the chemical reaction rate of hydrochloric acid in a specific embodiment of the present invention.

Detailed ways

The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

In the present embodiment, for the recyclable pickling platform, the pickling device shown in FIG. 1 mainly includes: pickling tank 1, constant temperature water bath 2, washing tank 3, magnetic pump 4, electromagnetic flow meter 5, to be pickled. The pipeline 6 and the waste liquid tank 7 mainly control the flow rate by controlling the opening degree of the valve, and the constant temperature water bath 2 performs the reaction temperature setting. The acid solution used in the embodiment is hydrochloric acid, and the reaction temperature is controlled at room temperature. 30 degrees Celsius.

The embodiment provides a design method for a chemical cleaning scheme of a superheater pipeline superheater pipeline, comprising:

Step 1: Determine the relationship between the running time of the superheater pipe and the corresponding scale thickness of the superheater pipe under the working conditions of the rated working condition, that is, the mathematical model of the scale growth.

Step 1.1: Obtain the historical data of the superheater pipeline under the working conditions of the rated working condition X=[T, P, δ, t], including the steam temperature T, pressure P, t time oxide scale thickness δ when the superheater pipeline is running. , running time t.

Step 1.2: Regression processing of historical data, fitting the relationship between the running time of the superheater pipe and the corresponding scale thickness under the condition of constant steam temperature T and pressure P, and obtaining a mathematical model of scale growth.

The growth of scale in the superheater pipeline is divided into two stages: the growth curve of the oxide scale is linear in the first stage; the growth curve of the scale tends to be gentle in the second stage due to the thermal insulation of the scale, in a parabolic shape. . Therefore, the mathematical model for the growth of scale in the superheater piping under rated operating conditions is:

Where δ is the thickness of the t-time scale, A is the undetermined coefficient, n is taken in [1, 2], and when n=1, the growth curve of the scale is linear, and when n=2, the growth curve of the scale It is in the shape of a parabola. When selecting, the estimation of the undetermined coefficient A is performed according to the historical data of the superheater pipe. In the present embodiment, n=1.62 and A=136.2.

Step 2: Perform static tests at different temperatures and concentrations to determine the time required for the complete reaction of the scale and hydrochloric acid, and the amount of hydrochloric acid per unit area per unit time to determine the chemical reaction rate of hydrochloric acid at different temperatures and concentrations.

Step 2.1: Prepare different concentrations of hydrochloric acid separately, set different temperatures in a constant temperature water bath, cut the scales of the same area for static test, and record the time required for the scale to react completely with hydrochloric acid.

In the present embodiment, the dilute hydrochloric acid solutions of 10 g/L, 20 g/L, 50 g/L, 100 g/L, and 150 g/L, respectively, are set in a constant temperature water bath at a temperature ranging from 20 to 40 degrees Celsius, and the cut areas are respectively A static test was conducted for a 1 cm square scale to record the time required for the scale to react completely with hydrochloric acid.

Step 2.2: Determine the reaction amount of hydrochloric acid per unit area per unit time according to the time required for the complete reaction of the scale and hydrochloric acid, and then determine the chemical reaction rate of hydrochloric acid at different temperatures and concentrations. The chemical reaction rate of hydrochloric acid at room temperature is shown in Figure 2. The relationship between the absolute temperature and the chemical reaction rate of hydrochloric acid is shown in Fig. 3.

Step 3: Predict the squib probability of the superheater pipe for the operating condition of the superheater pipe, and determine the time at which the superheater pipe starts to pickle based on the squib probability of the superheater pipe.

Step 3.1: Extract the historical data related to the squib failure in the historical data of the superheater pipeline, and establish the following data set:

DataSet(i)=(t _i ,X _i ,δ _i )i=1,2,...,N;

Wherein, the operating state data of the i-th pipe X _i =(x _i,1 ,x _i,2 ...x _i,p-1 ,x _i,p ), x _i,p represents the i-th pipe of the superheater The state feature vector, p=4 in the embodiment, that is, the operating state data of the i-th pipe includes four state feature vectors of steam temperature, pipe wall temperature, running time, and temperature change rate. δ _i is an indication of random right censored data, δ=1 indicates that a squib event occurred in the superheater pipeline during the observation period, and δ=0 did not occur in the observation time, which is right censored data. squib time event _i T i-th pipeline representation occurs. N is the number of superheater pipes in the data set.

Step 3.2: Based on the historical data related to the blaster failure in the historical data of the superheater pipeline, training the risk prediction model of the squib probability of the superheater pipeline;

Step 3.2.1: Define the risk prediction model for the probability of pipe burst in the superheater:

h(t _i ,X _i )=h ₀ (t _i )exp(x _i,1 β ₁ +x _i,2 β ₂ +...+x _i,p β _p )

Where h(t _i , X _i ) is the probability that the superheater pipe with the operating state X _i will burst at the time t _i (starting at t _i =0), β ₁ , β ₂ ... β _p-1 , β _p is a parameter of the influence of different operating conditions on the tube explosion of the superheater. It is called the regression coefficient and affects the probability of the pipe burst. It is estimated by using the historical data related to the pipe burst fault in the historical data of the superheater pipe. h ₀ (t _i ) is the base burst risk function.

Step 3.2.2: Select the Weibull distribution as the base burst risk function, and obtain the risk prediction model of the final superheater pipeline burst probability;

Base blasting risk function:

Where: η>0 is a proportional parameter, γ>0 is a shape parameter, and h ₀ (t _i ) is brought into h(t _i , X _i );

Obtain a risk prediction model for the probability of tube bursting in the final superheater:

Step 3.2.3: Using the maximum likelihood function method to estimate the parameters of the risk prediction model of the superheater pipe burst probability, determine the pipe burst probability of the superheater pipe for the historical data related to the pipe burst fault of the N superheater pipes. The likelihood function of the risk prediction model is:

Where S _i (t _i , X _i ) is a reliability function derived from the cumulative distribution function:

By taking the logarithm of both sides of the reliability function at the same time, you can get:

Thus, the parameter estimation is converted into the problem that the function ln L(γ, η, β) finds the maximum value.

Step 3.2.4: Solve the maximum value of ln L(γ, η, β) based on the DFP method.

The DFP method is an optimization algorithm named after Davidon, Fletcher, and Powell.

Step 3.2.4.1: Determine the objective function f(γ, η, β) = ln L(γ, η, β), and the gradient of the objective function f(γ, η, β) is g(γ, η, β).

Step 3.2.4.2: Randomly select a set of γ, η, β as the selected initial point of the iteration I ₀ = (γ, η, β), and calculate the initial objective function f ₀ = f (I ₀ ), the initial gradient g ₀ =g(I ₀ ); set the termination limit and the maximum number of iterations n';

Step 3.2.4.3: Set the initial value of H _{o to} the unit matrix, set the initial search direction to p ₀ =-g ₀ , and the number of iterations k=0.

Step 3.2.4.4: Perform a straight line search along the initial search direction, and get k+1 iteration points I _k+1 = ls(I _k , p _k ) to obtain a new iteration initial value, and calculate f _k+ on this basis. ₁ = f(I _k+1 ), g _k+1 = g(I _k+1 ), p _k is the search direction of the kth iteration point, and I _k is k iteration points.

Step 3.2.4.5: Determine whether the current iteration satisfies the termination limit, and if it is satisfied, stop iterating and obtain the parameter estimation value corresponding to the current iteration point.

Go to step 3.3; otherwise continue to step 3.2.4.6;

Step 3.2.4.6: If k=n', then set I ₀ =I _k+1 , f ₀ =f _k+1 , g ₀ =g _k+1 , go to step 3.2.4.4 above, otherwise go to step 3.2. 4.7;

Step 3.2.4.7: Calculate the gradient difference y _k between k+1 iteration points and k iteration points, the difference between k+1 iteration points and k iteration points s _k , k+1 iteration points The inverse of the corresponding second-order Hessian matrix, H _k+1 :

y _k =g _k+1 -g _k s _k =I _k+1 -I _k

p _k+1 =-H _k+1 g _k+1

Set k=k+1 and go to step 3.2.4.4 to continue the line search.

Step 3.3: after a given superheater pipes running state at the time t _i to the feature vector X (t _i), is calculated superheater tubes squib probability function values:

In this way, based on the real-time data of the power plant for each superheater pipe, the probability of a pipe bursting at a certain moment is known.

Step 3.4: Determine the time at which the superheater pipe starts to pickle based on the squib probability of the superheater pipe: the time at which the blasting probability function value reaches the set upper limit (90%) is the time at which the pickling is started, at which time the field personnel apply for shutdown. Pickled.

Step 4: Determine the chemical reaction rate of hydrochloric acid according to the concentration of hydrochloric acid disposed in the pickling and the temperature of the pickling environment, determine the thickness of the scale at the time of starting the pickling based on the mathematical model of the scale growth, and calculate the weight of the scale. The theoretical time of the scale pickling is determined without changing the chemical reaction rate.

Step 4.1: determining the chemical reaction rate of hydrochloric acid according to the concentration of hydrochloric acid disposed in the pickling and the temperature of the pickling environment;

Taking the hydrochloric acid having a concentration of 300 g/L as an example, the chemical reaction rate of hydrochloric acid determined at room temperature is determined.

Wherein C _HCL represents the concentration of hydrochloric acid and T represents the temperature of the pickling environment.

Step 4.2: Theoretically calculate the time required for the complete reaction of the single layer of scale on the unit area of the pipeline;

Assume that a pipe with a length of one meter and a size of 55*4.5 mm is used. According to the scale growth model, the thickness of the inner wall of the pipe is 300 micrometers. Under the premise that the scale is evenly distributed, the weight of the scale inside the pipe is calculated. _FeO is:

Where ρ is the ferrous oxide density, r is the inner diameter of the pipe, δ is the thickness of the scale at t time, and l is the length of the pipe

At this time, the consumption of hydrochloric acid m _HCl is:

The reaction rate of hydrochloric acid per unit area of the inner wall of the pipe is:

Δm _HCl =k·2·π·r _n ·Δl=0.867g/s

Theoretically the time required for the complete reaction of a single layer of oxide on a unit area of the pipeline:

Step 4.3: Calculate the time required for the complete reaction of the three layers of scale on the unit area of the pipeline;

The scale is divided into three layers from the metal matrix to the outside, respectively: FeO-Fe ₃ O ₄ -Fe ₂ O ₃ , and the thickness ratio is recorded as 100:10:1, and the three layers of oxide scale are completely calculated again. Time required for the reaction:

Step 4.4: Calculate the amount of hydrochloric acid consumed by the three oxides contained in the three-layer scale;

Under the dissolution of hydrochloric acid, the amount of hydrochloric acid consumed by the three oxides contained in the three-layer scale is calculated as follows:

Step 4.5: Calculate the amount of hydrochloric acid consumed per unit area of the inner wall of the pipe:

Where k is the chemical reaction rate of hydrochloric acid and r _n is the inner diameter of the pipe.

Step 4.6: Determine the theoretical time of the oxide skin pickling at the same chemical reaction rate, that is, the sum of the amount of hydrochloric acid consumed by the three oxides contained in the three-layer scale, divided by the amount of hydrochloric acid per unit area of the inner wall of the pipe. :

Step 5: Based on the theoretical time of the scale pickling, the hydrochloric acid is configured, and the chemical cleaning scheme of the supercritical power plant boiler superheater pipeline is determined, including the timing of starting the pickling, the theoretical time of the scale pickling, and the concentration of hydrochloric acid. consumption.

According to the determined chemical cleaning scheme of the supercritical power station boiler superheater pipeline, the chemical cleaning is carried out by using 20% of 60g/L hydrochloric acid commercially available. At normal temperature, the density of 20% hydrochloric acid is 1.098g/cm ³ , when pickling To arrange 20 L of pickling solution, it is necessary to add 5.46 L of dilute hydrochloric acid of 20%, 14.56 L of fresh water, and 0.2 kg of rust inhibitor urotropine, and to obtain an acid washing solution.

20％盐酸20% hydrochloric acid	清水Clear water	乌洛托品Urotropine
5.46L5.46L	14.56L14.56L	0.2kg0.2kg

At this time, according to the temperature of the pickling environment of 30 degrees Celsius, the theoretical time of the scale pickling was calculated to be 84.48 minutes.

The pipe to be pickled is connected to the outlet of the acid solution, the temperature of the constant temperature water bath is set, the valve is opened, and the acid liquid is flushed, and 20% of the time is reserved on the basis of the theoretical time of the scale pickling, that is, Check the pickling of the pipe at 67.584 minutes. When the internal surface of the pipe is smooth and rust-free, the metallic luster is acceptable.

Check the effect of chemical cleaning:

First, water washing: clean the residual acid in the pipeline to prevent acid residue from further corroding the metal matrix;

Second, passivation: protection of the pipeline after pickling, the specific configuration of the passivation solution:

The configuration of the passivation solution is sodium nitrite and ammonia water. The configuration needs to ensure that the percentage of sodium nitrite is greater than 1, in a slightly alkaline environment, and the alkaline environment is configured with 25% ammonia water, and 0.5 kg of sodium nitrite is selected. Add 20L of clean water, stir evenly, add ammonia water on this basis, add the ammonia water, measure the PH value of the passivation solution, and adjust the pH of the passivation solution between 9-10 by adjusting the ammonia water.

亚硝酸钠Sodium nitrite	清水Clear water	氨水ammonia	PHPH
0.5kg0.5kg	20L20L	25％25%	99

Then, wash again: remove the passivation solution in the pipeline, connect to the clean water pipeline, clean the residual passivation solution, and wash for half an hour.

Specifically, after checking the acid-washing pipeline, it is connected to clean water for cleaning. Time is half an hour.

Finally, drying: After the pipeline has been subjected to a series of processes such as pickling and water-washing, it is blown dry immediately, and the gas is dried by dry compressed air.

An embodiment of the chemical cleaning using the method of the present invention is as follows:

Example 1:

A pipe sample is cut and observed, and the scale of the inner wall of the pipe is observed. The inner wall of the pipe is corroded, the surface is rough, and there are different sizes of particles. The black is dark red and the scale is evenly distributed. Acid washing is carried out with 6% hydrochloric acid solution. At this time, the theoretical pickling time is 84 minutes. In actual control, the pickling time is 60 minutes. After cleaning, the inner surface is smooth, there is no irregularly distributed particles, and the inner surface is presented. Clear metal luster, no pickling situation, just the control of hydrochloric acid time.

Example 2:

The sample of a pipe was cut and observed, and the scale of the inner wall of the pipe was observed. The inner wall was dark black, slightly corroded, no particle distribution on the surface, and the scale distribution was uniform. The pickling time was also controlled for 60 minutes. After cleaning, the inner surface was cleaned. The wall is smooth, there are no irregularly distributed particles, the inner surface shows a clear metallic luster, and there is no pickling condition.

Claims

A design method for a chemical cleaning scheme for a supercritical power plant boiler superheater pipeline, characterized in that it comprises:

Determining the relationship between the running time of the superheater pipe and the corresponding scale thickness of the superheater pipe under the working conditions of the rated working condition, that is, the mathematical model of the scale growth;

Static test at different temperatures and concentrations to determine the time required for the complete reaction of the scale and the acid solution, the reaction amount of the acid per unit area per unit time, and determine the chemical reaction rate of the acid solution at different temperatures and concentrations;

Determining the squib probability of the superheater pipe for the operating condition of the superheater pipe, and determining the time at which the superheater pipe starts to pickle based on the squib probability of the superheater pipe;

Determine the theoretical time of the scale pickling at the same chemical reaction rate;

Based on the theoretical time of scale pickling, the acid solution was configured, and the chemical cleaning scheme for the superheater boiler superheater pipeline was determined.
The method of claim 1 wherein said mathematical model of scale growth is established as follows:

Obtain historical data of the superheater pipeline under the working conditions of the rated working condition, including the steam temperature, pressure, t-time oxide scale thickness and running time of the superheater pipeline during operation;

Regression of historical data, fitting the relationship between the running time of the superheater pipe and the corresponding scale thickness under the condition of constant steam temperature and pressure, and obtaining the mathematical model of scale growth.
The method according to claim 1 or 2, wherein the mathematical model of the growth of the scale is:
Where δ is the thickness of the t-time scale, A is the undetermined coefficient, n is taken in [1, 2], and when n=1, the growth curve of the scale is linear, and when n=2, the growth curve of the scale In the shape of a parabola, the estimation of the undetermined coefficient A is performed based on the historical data of the superheater pipe.
The method according to claim 1, wherein said determining a chemical reaction rate of hydrochloric acid at different temperatures and concentrations is as follows:

Separate acid solutions with different concentrations, set different temperatures, and cut the same scale of oxide scale for static test, and record the time required for complete reaction between oxide scale and acid solution;

According to the time required for the complete reaction of the scale and the acid solution, the reaction amount of the acid solution per unit area per unit time is determined, and the chemical reaction speed of the acid solution at different temperatures and concentrations is determined.
The method according to claim 1, wherein said predicting a squib probability of a superheater pipe for said superheater pipe operating condition is:

Extracting historical data related to the squib failure in the historical data of the superheater pipeline;

Based on the historical data related to the blaster failure in the historical data of the superheater pipeline, the risk prediction model for training the squib probability of the superheater pipeline is trained;

After a superheater pipe is run to a state feature vector at a certain time, the value of the pipe burst probability function of the superheater pipe is calculated.
The method according to claim 1, wherein the bursting probability based on the superheater pipe determines a time at which the superheater pipe starts pickling, specifically, the time at which the value of the blasting probability function reaches a set upper limit is used as the starting acid. The moment of washing.
The method according to claim 5, wherein the risk prediction model of the superheater pipe burst probability is established as follows:

The risk prediction model for the probability of pipe burst in superheater pipeline is defined. The Weibull distribution is selected as the base burst risk function, and the risk prediction model of the final superheater pipe burst probability is obtained. The maximum likelihood function method is used to predict the pipe burst probability of the superheater. The parameter estimation of the risk prediction model, the historical function of the N superheater pipeline related to the blasting fault, the likelihood function of the risk prediction model for determining the burst probability of the superheater pipeline; the likelihood function is maximally based on the DFP method The solution of the value.
The method according to claim 1, wherein said method for determining the theoretical time of scale pickling at a constant chemical reaction rate is:

Determine the chemical reaction rate of the acid solution according to the concentration of the acid solution disposed in the pickling and the temperature of the pickling environment;

Calculate the time required for the complete reaction of the single layer of scale on the unit area of the pipeline;

Calculate the time required for the complete reaction of the three layers of scale on the unit area of the pipeline;

Calculate the amount of hydrochloric acid consumed by the three oxides contained in the three-layer scale;

Calculate the consumption of hydrochloric acid per unit area of the inner wall of the pipeline;

The theoretical time of the scale pickling is determined under the condition that the chemical reaction rate is constant, that is, the sum of the amounts of hydrochloric acid consumed by the three oxides contained in the three-layer scale is divided by the consumption of hydrochloric acid per unit area of the inner wall of the pipe.