阅读说明：本技术 一种锅炉水冷壁腐蚀结焦产物的分层分析方法 (Layered analysis method for boiler water wall corrosion coking product ) 是由 段君寨 苏振勇 张文鹏 宋岩 刘斌 谢召祥 王长普 李世强 谈金军 安冬冬 于 2019-08-30 设计创作，主要内容包括：本发明属于分析技术领域,具体涉及一种锅炉水冷壁腐蚀结焦产物的分层分析方法。该方法包括以下步骤：1)获取锅炉水冷壁腐蚀结焦产物的分析样品；2)获取步骤1)得到的所述分析样品的腐蚀结焦产物分层特性,并根据所述分层特性区分腐蚀结焦产物的各层；3)获取步骤2)区分得到的腐蚀结焦产物的各层的元素组成及元素分布、腐蚀结焦产物的各层的晶相结构；4)根据步骤2)得到的腐蚀结焦产物分层特性、步骤3)得到的腐蚀结焦产物的各层的元素组成及元素分布和步骤3)得到的腐蚀结焦产物的各层的晶相结构确定锅炉水冷壁的腐蚀结焦进程。通过该方法可以分析出腐蚀结焦的进程、腐蚀结焦反应动力学和腐蚀结焦机理。(the invention belongs to the technical field of analysis, and particularly relates to a layered analysis method for a boiler water wall corrosion coking product. The method comprises the following steps: 1) obtaining an analysis sample of a boiler water wall corrosion coking product; 2) obtaining the layering characteristics of the corrosion coking product of the analysis sample obtained in the step 1), and distinguishing each layer of the corrosion coking product according to the layering characteristics; 3) obtaining the element composition and element distribution of each layer of the corrosion coking product obtained by distinguishing in the step 2) and the crystalline phase structure of each layer of the corrosion coking product; 4) determining the corrosion and coking process of the boiler water wall according to the layering characteristics of the corrosion and coking product obtained in the step 2), the element composition and the element distribution of each layer of the corrosion and coking product obtained in the step 3) and the crystalline phase structure of each layer of the corrosion and coking product obtained in the step 3). The method can analyze the progress of corrosion and coking, the reaction kinetics of corrosion and coking and the corrosion and coking mechanism.)

1. A layered analysis method for a boiler water wall corrosion coking product is characterized by comprising the following steps:

1) Obtaining analysis samples of high-temperature corrosion and corrosion coking products of a boiler water-cooled wall;

2) Obtaining the layering characteristics of the corrosion coking product of the analysis sample obtained in the step 1), and distinguishing each layer of the corrosion coking product according to the layering characteristics;

3) Obtaining the element composition and element distribution of each layer of the corrosion coking product obtained by distinguishing in the step 2);

Obtaining the crystalline phase structure of each layer of the corrosion coking product obtained by distinguishing in the step 2);

4) Determining the corrosion and coking process of the boiler water wall according to the layering characteristics of the corrosion and coking product obtained in the step 2), the element composition and the element distribution of each layer of the corrosion and coking product obtained in the step 3) and the crystalline phase structure of each layer of the corrosion and coking product obtained in the step 3).

2. the method for analyzing the layering of the boiler water wall corrosion coking products according to claim 1, wherein the step 1) comprises the following steps:

1a) Cutting the boiler water wall subjected to corrosion and coking to obtain a cut sample of a strip-shaped water wall tube, wherein each cut surface of the cut sample is vertical to the height direction of a boiler furnace;

1b) Selecting a plurality of typical areas from the cut sample obtained in the step 1a) according to the form and color of corrosion coking, and cutting each typical area into small test pieces respectively, wherein the cutting direction is vertical to the water wall tube body, and the standard of selecting the plurality of typical areas according to the form and color of the corrosion coking is as follows:

The form is that loose coke and dense coke coexist, the color is mainly white coke, divide into a typical area;

The form is that loose coke and dense coke coexist, the color is yellow green coke as the main, divide into a typical area;

1c) Respectively embedding the small test pieces obtained in the step 1b) in fixed resin, exposing the cut surface to be used as a section to be tested, and then grinding and polishing the cut surface to obtain the test pieces to be tested.

3. the method for analyzing the boiler water-cooled wall corrosion coking product in a layered manner according to claim 1, wherein in the step 2), a scanning electron microscope is adopted to extract the surface topography, the thickness of the deposition layer and the interlayer boundary of the test surface of each test piece to be tested obtained in the step 1c), and each layer of the corrosion coking product is distinguished according to the interlayer boundary.

4. The method for analyzing the boiler water wall corrosion coking product layer by layer as claimed in claim 1, wherein in step 3):

analyzing the element composition and element distribution of corrosion coking products in each piece to be tested by adopting an energy dispersion X-ray spectrometer;

Analyzing the element composition of the corrosion coking product in each piece to be tested by adopting an X-ray fluorescence spectrum;

And analyzing the crystal phase structure of the corrosion coking product in each test piece to be tested by adopting X-ray diffraction.

5. The method for analyzing the boiler water wall corrosion coking product layer by layer as claimed in claim 1, characterized in that in step 4): determining the corrosion coking process of the boiler water-cooled wall according to the layering characteristics, element composition, element distribution and crystalline phase structure of each test piece, wherein the specific determination method comprises the following steps:

4a) determining the chemical composition of each layer of corrosion coking product through the element composition, the element distribution and the crystalline phase structure of each layer of corrosion coking product;

4b) analyzing the evolution rule formed by each layer of product through a basic chemical reaction theory and reaction kinetics;

4c) And (4) determining the corrosion coking process and the corrosion coking mechanism of the boiler water wall by integrating the analysis results of the sample wafers in each typical area.

Technical Field

The invention belongs to the technical field of analysis, and particularly relates to a layered analysis method for a boiler water wall corrosion coking product.

background

The high-temperature corrosion and coking are mainly influenced by factors such as coal quality, combustion parameters, flue gas composition, ash deposition on the surface of a water wall and the like, and the influence factors are complex and variable, SO that problems such as gas phase corrosion (such as SO _x oxidizing atmosphere corrosion and H ₂ S reducing atmosphere corrosion), molten salt corrosion (such as sulfate corrosion and chlorine salt corrosion), coking and slagging on the surface of the water wall and the like are caused, and the high-temperature corrosion process can be greatly accelerated by multi-factor superposition, SO that more serious damage is caused to the water wall pipe.

The problems of high-temperature corrosion and coking of the water-cooled wall are continuously researched by a plurality of scientific researchers, documents are reported very much, and the high-temperature corrosion of the water-cooled wall is generally divided into the following types according to the factors such as the occurrence reason of the high-temperature corrosion, the characteristics of an oxide layer, the composition difference of corrosion products and the like: sulfate type high temperature corrosion, sulfide type high temperature corrosion, high temperature corrosion by reducing gas, and chloride type high temperature corrosion; because the formation mechanism and the transport mechanism of the fly ash particles are different, two different processes exist in the deposition of the ash particles on the wall surface of the water-cooled wall: one is an initial deposition layer, and the other is larger ash particles which impact on the initial deposition layer of the pipe wall under the action of inertia force and are captured by the viscous initial deposition layer, so that the thickness of the slag layer is rapidly increased. The initial deposit is formed primarily by the condensation of volatile ash components on waterwalls. The deposition of the inertially transported soot on the initially deposited layer is not only dependent on the properties of the initial layer, but also on the temperature level of the impinging soot, which, when in a molten state at a high temperature, is liable to cause adhesion and thus accelerates the slagging process.

In many current researches, corrosion and coking products are generally considered as a whole in analysis, high-temperature corrosion and coking are associated processes in the actual boiler operation process, the formation process of deposits on the surface of a water wall is very complex, the dynamic evolution process of the high-temperature corrosion and coking association cannot be revealed in the corrosion and coking result description and mechanism discussion of the existing analysis method, and the corrosion and coking products are analyzed according to a single uniform whole according to a black box method, so that the analysis result of a detailed reaction process often has certain one-sidedness, contingency and uncertainty.

Disclosure of Invention

in order to solve the defects of the prior art, the invention provides a layered analysis method for a boiler water wall corrosion coking product.

The technical scheme provided by the invention is as follows:

A layered analysis method for corrosion and coking products of a boiler water wall comprises the following steps:

1) obtaining an analysis sample of a boiler water wall corrosion coking product;

2) obtaining the layering characteristics of the corrosion coking product of the analysis sample obtained in the step 1), and distinguishing each layer of the corrosion coking product according to the layering characteristics;

3) obtaining the element composition and element distribution of each layer of the corrosion coking product obtained by distinguishing in the step 2);

obtaining the crystalline phase structure of each layer of the corrosion coking product obtained by distinguishing in the step 2);

4) Determining the corrosion and coking process of the boiler water wall according to the layering characteristics of the corrosion and coking product obtained in the step 2), the element composition and the element distribution of each layer of the corrosion and coking product obtained in the step 3) and the crystalline phase structure of each layer of the corrosion and coking product obtained in the step 3).

by adopting the technical scheme, the layering characteristic, the element composition, the element distribution, the crystalline phase structure and the like of each layer of the corrosion coking product can be obtained. Through the information, the process of corrosion and coking, the reaction kinetics of corrosion and coking and the mechanism of corrosion and coking can be further analyzed, so that more dynamic evolution information of high-temperature corrosion and coking associated can be obtained compared with an analysis method of 'overall consideration' in the prior art, and the detailed process of corrosion and coking can be more accurately analyzed.

Specifically, the step 1) comprises the following steps:

1a) Cutting the boiler water wall with corrosion and coking to obtain a cutting sample of a strip-shaped water wall tube, wherein each cutting surface of the cutting sample is vertical to the height direction of a boiler hearth;

1b) Selecting a plurality of typical areas from the cut sample obtained in the step 1a) according to the form and color of corrosion coking, and cutting each typical area into small test pieces respectively, wherein the cutting direction is vertical to the water wall tube body, the small test pieces meet the conditions that a surface corrosion coking layer is kept intact after cutting, the size can facilitate the subsequent analysis of surface morphology and the like, and the standard of selecting the plurality of typical areas according to the form and color of the corrosion coking is as follows:

The form is that loose coke and dense coke coexist, the color is mainly white coke, divide into a typical area;

The form is that loose coke and dense coke coexist, the color is yellow green coke as the main, divide into a typical area;

1c) Respectively embedding the small test pieces obtained in the step 1b) in fixed resin, exposing the cutting surface as a test surface, and grinding and polishing the cutting surface to obtain the test pieces to be tested.

the coke pores of loose coke are large and easy to scrape; the coke structure of the compact coke is compact and is tightly combined with the water wall tube.

In the above technical scheme:

The section of the cut sample obtained in the step 1a) contains the parts of each layer of corrosion coking, so that the information can be conveniently extracted by a subsequent scanning electron microscope;

In step 1b), the typical zones are partitioned to take into account the morphology and color of the corrosive coke. Therefore, a plurality of typical areas are selected and analyzed in detail, and the analysis method can be used for presuming a plurality of possible chemical reactions occurring in the corrosion coking process and disclosing the dynamic evolution process of the chemical reactions, thereby ensuring that the final comprehensive analysis result is more objective, more comprehensive and more accurate.

Specifically, in the step 2), the surface morphology, the thickness of the deposition layer and the interlayer boundary of the test surface of each to-be-tested piece obtained in the step 1c) are extracted by using a scanning electron microscope, and each layer of the corrosion coking product is distinguished according to the interlayer boundary.

in the technical scheme, each layer of the corrosion coking has obvious color or shape difference, so that each information can be extracted through a scanning electron microscope.

Specifically, in step 3):

Analyzing the element composition and element distribution of corrosion coking products in each piece to be tested by adopting an energy dispersion X-ray spectrometer;

Analyzing the element composition of the corrosion coking product in each piece to be tested by adopting an X-ray fluorescence spectrum;

and analyzing the crystal phase structure of the corrosion coking product in each test piece to be tested by adopting X-ray diffraction.

Specifically, in the step 4): determining the corrosion coking process of the boiler water-cooled wall according to the layered characteristic element composition, element distribution and crystalline phase structure of each layer of each test piece, wherein the method for determining the corrosion coking process comprises the following steps: the method comprises the steps of firstly determining the chemical composition of each layer of corrosion coking product through the element composition, the element distribution and the crystalline phase structure of each layer of corrosion coking product, further analyzing the evolution rule formed by each layer of product through a basic chemical reaction theory and reaction kinetics, finally integrating the analysis results of a plurality of typical area sample wafers, and determining the corrosion coking process of the water-cooled wall of the boiler.

In the technical scheme, the method for determining the corrosion coking process can break through the limitation of the traditional 'integral consideration' analysis method, reveal the dynamic evolution process of high-temperature corrosion and coking associated, analyze the corrosion coking intermediate process in detail and perfect the corrosion coking mechanism.

drawings

FIG. 1 is an optical photograph of a sample of different representative areas.

Fig. 2 is an SEM image of the test surface of a small test piece of typical area 1.

Figure 3 is an EDS surface scan spectrum of a small test strip of representative area 1.

figure 4 is an XRD pattern of a small test piece of representative region 1. (a) Is a white deposit; (b) a black deposit.

Fig. 5 is an SEM image of the test surface of a small test piece of typical area 2.

Figure 6 is an EDS surface scan spectrum of a small test strip of representative region 2.

figure 7 is an XRD pattern of a small test piece of representative region 2. (a) Yellow-green deposits, (b) black deposits, and (c) innermost dense layers.

Detailed Description

The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

In one specific embodiment, the layered analysis method for the boiler water wall corrosion coking products comprises the following steps:

1) Preparation of test pieces of samples of different representative areas

1a) cutting pipe sections with the dimensions of 10mm chord length, 10mm length and 8mm wall thickness from the typical area of the water wall pipe through wire cutting processing to obtain cut samples, wherein each cutting surface of each cut sample is vertical to the wall surface of the water wall;

1b) As shown in fig. 1, a plurality of typical areas are selected from the cut sample obtained in step 1a) according to the morphology and color of corrosion coking, and each typical area is cut into small test pieces respectively, wherein the cutting direction is perpendicular to the water wall tube body. Specifically, the typical area 1 is formed by coexisting loose coke and dense coke, and the color of the typical area is mainly white coke; the typical area 2 is formed by coexistence of loose coke and dense coke, and the color of the typical area is mainly yellow green coke; the typical area 3 is mainly composed of loose coke and dense coke in thickness and black coke in color.

1c) embedding the small test pieces obtained in the step 1b) into phenolic resin with carbon filler by a hot embedding method, exposing cut surfaces after embedding to be used as test surfaces, mechanically grinding the cut surfaces on a grinding instrument by using sand paper with the particle sizes of 200, 800, 1200 and 2000 in sequence, polishing the cut surfaces to a mirror surface by using silicon carbide powder with the particle size of 1 mu m in ethanol suspension, finally cleaning the cut surfaces by using deionized water and alcohol, and completely drying the cut surfaces for subsequent detection work.

2) Detection and analysis of small test pieces of samples with different typical areas

Detection analysis of a Small test strip of typical area 1

When a scanning electron microscope is used for extracting and analyzing a small test piece in a typical area 1, an SEM image is shown in figure 2, and it can be seen that a deposited layer on a test surface has a layering characteristic from loose to compact from an outer layer to an inner layer, and a clear boundary line exists in the section of each layer.

The test surface of a small test piece in the typical region 1 was subjected to an EDS point scan energy spectrum using an energy dispersive X-ray spectrometer (EDS), and the results are shown in table 1.

Table 1 cross-section EDS spot scan energy spectrum results

An energy dispersive X-ray spectrometer (EDS) is used to perform an EDS surface scan energy spectrum on the test surface of the small test piece in the typical region 1, and the spectrum is shown in fig. 3.

EDS surface scanning and point scanning can be used for analyzing the distribution and the composition of elements of each deposition layer on the section surface of the water wall sample piece, an EDS surface scanning energy spectrogram is shown in figure 3, the deposits on the surface of the water wall are formed by converting crystalline mineral substances in coal through a combustion process and then are attached to the surface of the water wall, the crystalline mineral substances mainly comprise elements such as Si, Al, S, Pb, O and the like, the result of EDS point scanning measurement is shown in Table 1, the corrosion products of the outer layer are mainly composed of elements such as Pb, S and O, the mass fraction of the element S is 36.54%, and the mass fraction of the element Pb is 43.18%; the inner layer is mainly composed of oxides formed by Al, Si and S elements, and the structure of the inner layer is denser than that of the outer layer.

the crystal phase structure of each test piece to be tested of the corrosion coking product is analyzed by X-ray diffraction (XRD), and the spectrogram is shown in figure 4.

The elemental composition and elemental distribution of each test piece of corrosion coking products were analyzed by X-ray fluorescence spectroscopy (XRF), and the results are shown in table 2.

table 2 corrosion coking products XRF results (wt%), a: a white deposit; b: a black deposit;

The deposits on the surface of the water wall tubes are classified by relative position, texture and color, and element and phase composition characterization is carried out by XRD and XRF, the results are shown in figure 4 and table 2, the deposits on the outer surface of the water wall tubes are white deposits, the main compositions of the deposits are FeS, PbS, SiO ₂, ZnS and Zn _x Fe _1-x S respectively, no sulfate is detected, which indicates that the high-temperature corrosion of the hearth at the position is mainly caused by reductive corrosion media, black deposits can be found on the surface of the water wall after the white deposits on the surface layer are stripped, the main phases of the deposits are FeS and SiO ₂, no heavy metal substances are detected, which indicates that the migration rate of the heavy metal sulfur-containing substances on the surface of the water wall is lower than that of the iron sulfur substances, and the XRF results show that the mass fractions of the heavy metal elements and the S elements are gradually reduced from the outside the deposits to the coating.