CN103592207A - Method for identifying slagging trend of different mineral components in coal ash - Google Patents
Method for identifying slagging trend of different mineral components in coal ash Download PDFInfo
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Abstract
The invention discloses a method for identifying the slagging trend of different mineral components in coal ash by using the computer controlled scanning electron microscope (CCSEM) technology. The CCSEM is used for analyzing the type of minerals in the coal ash and raw coals, the contents of all mineral components, the sphericity of mineral particles and the number ratio of similar spherical particles; a sphericity distribution pattern of the minerals with the same chemical compositions in the coal ash and the raw coals is drawn; the possibility of fusing the mineral components is judged according to the increment of the similar spherical particle ratio of the minerals with the same chemical compositions before and after combustion; source minerals of all mineral components in the coal ash are determined to analyze the factor of changing the similar spherical particle ratio of each component to identify the fusing and slagging trend of the coal ash particles of all the mineral compositions. The fusing behavior of the coal ash particles of all the mineral compositions is clearly identified through analyzing the variation of the coal ash particle sphericity of different mineral compositions; the theoretic and technical guidance is provided for identifying the slagging trend of each mineral component in the coal ash and searching the solution from the coal mineral source for the easily slagged mineral components.
Description
Technical field
The present invention relates to coal-burning boiler safety and economic operation field, be specifically related to a kind of while utilizing coal combustion the variation of mineral grain sphericity identify the melting of each mineralogical composition and the method for ash deposition propensity in coal ash.
Background technology
In coal fired thermal power plant, ash deposition (comprising slagging scorification, contamination, corrosion etc.) problem ubiquity in the boiler causing due to the pyrolytic conversion of coal mineral, be a great problem that jeopardizes at present safe and economical boiler operation, and slagging scorification is epochmaking a kind of in ash deposition problem.Slagging scorification is that harder ash slag sintering layer is often piled up on surface by the slag softening or the ash particle collision of melting generates on the heating surface of water-cooling wall and main raying heat.In China, the coal source ature of coal of boilers of power plants that caused in short supply is changeable, because actual coal and the excessive ash erosion meeting causing of designing coal quality deviation reduce boiler output and the thermal efficiency greatly, severe patient more, also may cause stoppage in transit, maintenance, the transformation of boiler, or even blast, cause great economic loss.
Safety and economic operation for boiler, the operations staff of thermal power plant need grasp the indexs such as ash deposition propensity that use coal in advance, engineering circles adopts the chemical composition of coal ash or ash fusion point temperature to judge conventionally, the discriminant index being calculated by coal ash essential element composition, as alkali acid ratio, silica alumina ratio, iron calcium when silicon compare etc. and to evaluate the ash deposition propensity of coal, or the coal ash softening temperature that adopts classical ash cone method to measure characterizes melting characteristic and evaluation ash deposition propensity.These method of discrimination can meet the prediction of coal dust ash deposition propensity within the specific limits, but also there is larger limitation, because large quantity research both domestic and external shows: different mineralogical composition in flying dust, different from melting property because of its chemistry source, ash deposition propensity has larger difference.If the ash particle existing with quartzy and mullite form is heat-staple composition, more difficult generation melting causes slagging scorification, and silico-aluminate and Alkaline minerals Na, K, Ca etc. can cause grey slagging scorification problem in conjunction with the low melting point silico-aluminate ash particle generating.Coal ash is made to the as a whole ash deposition propensity of analyzing coal and may introduce error, only has different mineralogical composition in identification coal ash, understand different minerals and become the melting behavior after divided combustion, just may analyze clearly and quantitatively mainly cause the mineralogical composition of grey slagging scorification problem.
The identification of the ash deposition propensity in sum, different minerals in coal ash being formed is significant for the safety and economic operation of station boiler.Computer control scanning electron microscope (Computer-Controlled Scanned Electron Microscope, CCSEM) technology be at present in the world unique can be by the identification of particle the technology of a large amount of mineral physicses and chemical property, it can analyze the chemical composition of coal ash individual particle, can analyze form factor-" sphericity " that it characterizes melting behavior for individual particle again.The theoretical foundation that the sphericity analysis of employing individual particle refers to ash particle meltbility is that mineral can melting occur and tend to be converted into spherical at high-temp combustion environment.The particle radius that the particle radius that sphericity is defined as calculating through particle " girth " calculates divided by warp " area ", i.e. expression formula: [(Perimeter/2 π)/(Area/ π)
1/2], the girth of particle, area all automatically draw with sphericity data after " Particles " of the corresponding power spectrum software of CCSEM functional analysis.Perfect spherical sphericity numerical value is 1, and particle shape is more irregular, and sphericity numerical value is larger, adopts domestic and international correlative study experience, and the particle of sphericity≤1.2 is defined as to spherical particle.
The difficult point that adopts sphericity to change effective evaluation individual particle coal ash melting tendency is to need the comprehensive sphericity of analyzing ash particle, playing source mineral with raw coal mineral and the ash particle of the identical chemical composition of ash particle with emphasis.If after burning, the spherical particle ratio of certain chemical composition coal ash particle increases, and may be the melting from former mineral, or the common melting of several mineral, or even the direct conversion of the corresponding mineral of other spherical particle; And if the components of coal ash spherical particle ratio of finding certain class chemical composition reduces, may be only the conversion that comes from aspherical particle in other heat-staple mineral.Therefore, adopt sphericity to identify grey melting tendency, need combine with the Origin of ash component.Domestic scholars has utilized CCSEM technology by analyzing approximately 3000 mineral grains in people such as honest happiness, Xu Minghou, kind and the content of the main mine material that exists in coal dust and coal ash have been obtained, therefore, current prior art can realize the Origin of ash component, but the sphericity of various types of mineral grain changes to identify melting and the ash deposition propensity of different minerals composition in coal ash during for utilization burning, have no and having relevant record both at home and abroad.
Summary of the invention
Based on this, the object of the present invention is to provide the method for each mineralogical composition ash deposition propensity in a kind of CCSEM of utilization technology identification coal ash, after the method can be distinguished coal dust firing, whether various ash components cause slagging scorification harm.
For achieving the above object, the technical solution used in the present invention is as follows:
A method of utilizing each mineralogical composition ash deposition propensity in CCSEM technology identification coal ash, comprises the following steps:
(1) collect the coal ash after coal dust firing, utilize the content of computer control scanning electron microscope (CCSEM) its mineral species of technical Analysis and various mineralogical compositions; Utilize kind and the content of computer control scanning electron microscope (CCSEM) technical Analysis raw coal Minerals; Meanwhile, utilize computer control scanning electron microscope (CCSEM) technology to obtain the sphericity of all mineral grains in coal dust and coal ash, and calculate number and ratio that the shape that can characterize melting approaches the spherical particle of spheroid;
(2) utilize the analysis result of step (1), draw the sphericity distribution plan of the mineral that coal ash is identical with chemical composition in raw coal, according to the spherical particle ratio of the mineral that before and after burning, chemical composition is identical, whether increase to judge the possibility of this mineralogical composition generation melting;
(3) analyze the source mineral that comes of each mineralogical composition in coal ash, determine that this mineralogical composition is the direct conversion coming from after the mineral combustion that in raw coal, chemical composition is identical, still comes from the conversion of other mineral matter;
(4) integrating step (3) is for result that in coal ash, each mineralogical composition analysis obtains, the reason that the spherical particle ratio observing in analytical procedure (2) changes, the reason of coal ash particle generation change of shape after burning, thereby determine in coal ash the source mineral that comes of easy slagging scorification mineralogical composition, and identify melting and the ash deposition propensity of each mineral composition coal ash particle.
Beneficial effect of the present invention is: by analyzing different minerals, form the variation of coal ash particle sphericity, the clear melting behavior of identifying each mineral composition coal ash particle, and then be the identification of each mineralogical composition ash deposition propensity in coal ash, and from thing source, colliery, seek solution for easy slagging scorification mineralogical composition, theory and technological guidance are provided.
Accompanying drawing explanation
Fig. 1 is content schematic diagram when essential mineral composition transforms to ash in coal;
Fig. 2 is that before and after burning, the particle sphericity distribution schematic diagram of each mineralogical composition (is defined as spherical particle by the mineral of sphericity≤1.2 or ash particle; Mineral or the ash particle of sphericity ﹥ 1.2 are defined as aspherical particle);
Fig. 3 is the mass distribution schematic diagram in each mineralogical composition before and after the burning of Si element;
Fig. 4 is the mass distribution schematic diagram in each mineralogical composition before and after the burning of K element;
Fig. 5 is the schematic diagram that in coal, in smalite and ash, mullite composition neutral and alkali tenor changes.
Embodiment
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.
The disclosed method of utilizing each mineralogical composition ash deposition propensity in CCSEM technology identification coal ash of the present embodiment, concrete steps are as follows:
(1) the selected raw coal of the present embodiment is datong bitumite, collects coal dust coal ash after 1300 ℃, air atmosphere burning in laboratory scale sedimentation furnace;
(2) utilize the content of each mineralogical composition in CCSEM technical Analysis raw coal and coal ash, as shown in Figure 1, the concrete grammar of analyzing is: coal dust or coal ash powder are evenly mixed by melting, cooling curing, grinding, polishing with Brazil wax, obtain backscatter images clearly in scanning electron microscope; To being shown as white mineral grain in backscatter images, carry out the inorganic elements composition that energy spectrum analysis obtains individual particles; Analyze the mineral grain in a plurality of enlargement factors, how much particle size range 0.5-211 μ m, in power spectrum " Particles " function, choose enough picture number, to guarantee the mineral grain to each 3000 left and right of sample automatic analysis; Each mineral grain is formed to the mineral that are defined as each concrete kind according to the element shown in table 1; The all granular masss that are defined as mineral of the same race are added and after divided by total mineral amount, be the content of this mineral species; By CCSEM, analyze, in discovery raw coal, the larger mineralogical composition of content is the difficulty identification mineral of smalite, pyrite, quartz, kalzit and complicated component etc., and in ash, main composition is mullite composition, K silico-aluminate, difficult identification mineralogical composition, Fe silico-aluminate, quartz etc.;
(3) the larger mineralogical composition of content in the ash providing for step (2), draw the sphericity distribution plan of coal dust and the corresponding particle of these compositions in coal ash, as shown in Figure 2, identification respectively becomes the variation of divided combustion front and back spherical particle ratio, after wherein mullite composition becomes divided combustion with Fe silico-aluminate, spherical particle ratio increases, after K silico-aluminate and quartz combustion, spherical particle ratio reduces, and in difficult identification mineral, spherical particle ratio is substantially constant;
(4) based on mineral content after burning, change and the migration of typical element in each mineral, analyze a source mineral of each composition in ash, as mullite composition comes from kaolinic direct conversion (Fig. 1) in coal, Fe silico-aluminate obviously comes from the combination of pyrite decomposition product and silico-aluminate, the conversion that K silico-aluminate comes from quartz, smalite and K in pyrite with react (Fig. 1, Fig. 3 and Fig. 4), the quartzy conversion (Fig. 1) that obviously comes from quartz in raw coal, and difficult identification mineralogical composition is also the difficulty identification mineral (Fig. 1) that directly come from coal;
(5) according to the result of step (3)-(4), analyze melting and the ash deposition propensity of each mineralogical composition in coal ash: during burning in coal smalite directly to mullite conversion, mullite constituent class spheric grain ratio increases approximately 23%, Fig. 5 characterizes is the content of two kinds of compositions alkalinous metal while directly transforming, while showing that smalite transforms to mullite, part alkalinous metal adds and has caused mullite congruent melting point to reduce, and causes slagging scorification problem.Fe silico-aluminate spherical particle ratio increases approximately 19%, is mainly because cause silico-aluminate melting point depression to cause slagging scorification a large amount of adding of alkalinous metal Fe.The mineral source of K silico-aluminate is mainly heat-staple quartz and smalite, so fusing point do not reduce, and is presented as that spherical particle ratio reduces on the contrary.Quartzy spherical particle ratio also reduces, and is mainly because quartz is heat-staple mineralogical composition, and melting does not obviously occur when in raw coal, quartz directly changes into ash.In coal, difficult identification mineral are when transforming in ash, and spherical particle ratio does not obviously increase, and therefore melting does not occur, and also can obviously not cause slagging scorification problem.Example for datong bitumite shows, the main ash component that causes slagging scorification problem is mullite composition and the Fe silico-aluminate that after burning, spherical particle ratio obviously increases, and after other mineralogical composition burning, obvious melting do not occur.
As can be seen here, utilize the present invention can clear identification to cause the main ash component of boiler scaling, Origin in the coal of grey mineralogical composition also be can be and from source, seeks slagging scorification control method and provide theoretical and support.
The invention is not restricted to the restriction of embodiment, steam coal for other kinds such as stone coal, brown coal, also can identify clearly mineralogical composition and the content of their afterburnt coal ash, analyze the sphericity variation of each composition particle and carry out source mineral, finally obtain mainly causing the grey mineralogical composition of slagging scorification problem, utilize the method for this invention also to can be used for other solid fuel to carry out the analysis of each mineralogical composition ash deposition propensity in ash.
The above; be only the present invention's embodiment preferably, but the scope of protection of the invention is not limited to this, is anyly familiar with in technical scope that those skilled in the art disclose in the present invention; the variation that can expect easily or replacement, within all should being encompassed in protection scope of the present invention.
Table 1 CCSEM mineral classification and elemental composition decision rule
Claims (3)
1. a method of identifying each mineralogical composition ash deposition propensity in coal ash, comprises the following steps:
(1) collect the coal ash after coal dust firing, analyze mineral species wherein and the content of various mineralogical compositions, and analyze kind and the content of raw coal Minerals; Meanwhile, obtain the sphericity of all mineral grains in coal dust and coal ash, and calculate number and ratio that the shape that can characterize melting approaches the spherical particle of spheroid;
(2) utilize the analysis result of step (1), draw the sphericity distribution plan of the mineral that coal ash is identical with chemical composition in raw coal, according to the spherical particle ratio of the mineral that before and after burning, chemical composition is identical, whether increase to judge the possibility of this mineralogical composition generation melting;
(3) analyze the source mineral that comes of each mineralogical composition in coal ash, determine that this mineralogical composition is the direct conversion coming from after the mineral combustion that in raw coal, chemical composition is identical, still comes from the conversion of other mineral matter;
(4) integrating step (3) is for result that in coal ash, each mineralogical composition analysis obtains, the reason that the spherical particle ratio observing in analytical procedure (2) changes, the reason of coal ash particle generation change of shape after burning, thereby determine in coal ash the source mineral that comes of easy slagging scorification mineralogical composition, and identify melting and the ash deposition propensity of each mineral composition coal ash particle.
2. method according to claim 1, wherein, in described raw coal and coal ash, the method for the content of each mineralogical composition is as follows: coal dust or coal ash powder are evenly mixed by melting, cooling curing, grinding, polishing with Brazil wax, obtain backscatter images clearly in scanning electron microscope; To being shown as white mineral grain in backscatter images, carry out the inorganic elements composition that energy spectrum analysis obtains individual particles; Analyze the mineral grain in a plurality of enlargement factors, how much particle size range 0.5-211 μ m, in power spectrum " Particles " function, choose enough picture number, to guarantee the mineral grain to each 3000 left and right of sample automatic analysis; The all granular masss that are defined as mineral of the same race are added and after divided by total mineral amount, be the content of this mineral species.
3. according to the method described in claim 1 and 2, described coal is bituminous coal, stone coal or brown coal.
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| CN112557429A (en) * | 2020-12-15 | 2021-03-26 | 广东省科学院资源综合利用研究所 | Quantitative determination method for all minerals in graphite ore and sample preparation method |
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| CN112557429A (en) * | 2020-12-15 | 2021-03-26 | 广东省科学院资源综合利用研究所 | Quantitative determination method for all minerals in graphite ore and sample preparation method |
| CN112557429B (en) * | 2020-12-15 | 2023-12-01 | 广东省科学院资源综合利用研究所 | Quantitative determination method and sample preparation method for all minerals in graphite ore |
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