CN104063585A - Boiler scaling risk assessment method - Google Patents
Boiler scaling risk assessment method Download PDFInfo
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- CN104063585A CN104063585A CN201410254340.7A CN201410254340A CN104063585A CN 104063585 A CN104063585 A CN 104063585A CN 201410254340 A CN201410254340 A CN 201410254340A CN 104063585 A CN104063585 A CN 104063585A
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Abstract
The invention provides a boiler scaling risk assessment method and belongs to the technical field of the electric power equipment monitoring. The boiler scaling risk assessment method comprises the following steps: silicon dioxide content in feedwater is acquired through average flow of short period feedwater entering a boiler and silicon dioxide concentration in the feedwater; the silicon dioxide content in steam is acquired through the average flow of the steam generated in the boiler and the silicon dioxide concentration in the steam; the silicon dioxide content in boiler water is acquired through the average flow of sewage discharged from the boiler, wherein the silicon dioxide concentration in the sewage and the silicon dioxide concentration in the boiler water are the same; the scale deposit amount in the boiler is equal to the silicon dioxide concentration in the feedwater minus the silicon dioxide concentration in the steam and further minus the silicon dioxide concentration in the boiler water; the scale deposit amount in the boiler at certain period in the future can be predicted and acquired through the accumulation of the scale deposit amount in this period. According to the boiler scale risk assessment method, chemical supervision can be conducted more effectively, the quality of moisture indicators in a thermal generator set is guaranteed and the safe, economic and stable operation of the thermal generator set is guaranteed.
Description
Technical field
The invention belongs to power equipment monitoring technical field, relate to gyp Forecasting Methodology.
Background technology
After the fuel-burning power plant water and steam quality to a large amount of is added up, find, although some Power Plant Water Vapor quality qualification rate is very high, in the time that unit maintenance checks, still find that boiler water-wall tube exists serious fouling situation.Even if water and steam quality has reached standard value requirement thus, can not avoid the risk of boiler water wall fouling.
This project conducts a research mainly for the gyp risk of sub-critical and above parameter fuel-burning power plant.The dirty composition of subcritical and above parameter heat power plant boiler water screen tube is mainly taking the oxide of silicon dioxide and iron as main, general few impurity such as calcium, magnesium that contains.Main cause is effective control of boiler feed water water quality, makes water and steam quality meet the requirement of national standard " thermal power generation unit and apparatus of steam power plants Water Vapor Quality standard " (GB/T 12145-2008).Although there is no the impact of calcium ions and magnesium ions in boiler feed water and boiler water, but in boiler During Process of Long-term Operation, due to the continuous evaporation and concentration of boiler water, silicon dioxide in stove water and the oxide of iron still can form dirt at boiler water-wall tube surface deposition, based on this, we think that the process of dirt deposition and dissolving can transform mutually to a certain extent, therefore, be just the fouling risk of the prediction boiler water-wall tube of science, the risk of gyp is assessed and become possibility.Can adopt an effective measure, blowdown in time, avoids boiler to be in operation fouling, impact heat transfer or pipe explosion accident occurs.
It is dangerous and can Operations Analyst (HAZOP) method that China's the 23rd the 8th phase of volume of special equipment 2007 " low-pressure boiler water system corrosion and fouling safety evaluation " has used, and corrodes and the reason of fouling is searched comprehensively causing, proposes corresponding measure.
Above method for just to causing the analysis of causes and the measure suggestion of boiler corrosion and fouling, all belong to the analyzing and processing occurring after defect, and actual boiler water wall fouling is to accumulate to form, fail not yet to develop into serious situation and take appropriate measures from fouling, control the development of fouling, therefore the scope of application has limitation.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of gyp methods of risk assessment, and the fouling situation in boiler future is predicted.
The scheme of technical solution problem of the present invention is based on material balance principle, boiler water wall fouling tendency to be assessed, by completing with the following step:
Step 1: by entering silica concentration in boiler short-term feedwater average discharge and feedwater, obtain dioxide-containing silica in feedwater;
Step 2: silica concentration in the steam average discharge producing by boiler and steam, obtains dioxide-containing silica in steam;
Step 3: silica concentration in the average discharge by boiler effluent sewerage and sewage, obtain dioxide-containing silica in boiler water, wherein in sewage, silica concentration is identical with silica concentration in boiler water;
Step 4: in feedwater, dioxide-containing silica cuts dioxide-containing silica in steam, then cut in boiler water dioxide-containing silica and be during this period of time dirt deposition amount in boiler;
Step 5: dirt deposition amount in the boiler of certain time of predict future, by the acquisition that adds up of dirt deposition amount in boiler during this period of time.
The wherein average discharge of step 3 effluent sewerage, average blowdown flow can take advantage of the blowdown rate of boiler to obtain by steam average discharge.
In a period of time boiler, dirt deposition amount can represent by following formula:
Wherein,
for dirt deposition amount (g);
for average feedwater flow (t/h), take from boiler operatiopn;
: for average steam flow (t/h), take from boiler operatiopn;
for average blowdown flow (t/h),
;
blowdownfor boiler blowdown rate;
for boiler operatiopn time (h) in the statistics phase, i.e. a period of time;
for feedwater silica concentration (μ g/L);
for steam silica concentration (μ g/kg);
for stove water silica concentration (μ g/L).N is n sample in the statistics phase; I is sample.
Above parameter is all the boiler for producing essential data that detect in service.
Research Thinking of the present invention is;
First utilize material balance theory, set up mass balance model.
Material balance refers in a Chemical Equilibria Systems, and the total concentration of a certain given goods and materials (being analytical chemistry concentration) equates with each relevant form equilibrium concentration sum.Material balance refers to that material can not produce without foundation, can not disappear without foundation, in a Chemical Equilibria Systems, the material total amount that enters system equal to go out from system material total amount with in system, retain material total amount sum.Can use following formula reduced representation.
,
Wherein,
enter to represent total amount of entering,
......
the total amount representing away,
represent to retain material total amount sum.
The calculating of instantaneous fouling ability
The state of boiler in High Temperature High Pressure, for some impurity entering in boiler provides the condition that is conducive to reaction, can be conducive to reaction carries out to the direction that generates indissoluble material, the rising of the solubility with temperature of indissoluble material and declining, can say the increase along with temperature and pressure, the condition in boiler is to be conducive to sedimentary formation.The precipitation of material and dissolving are a kind of dynamic balances, and when condition is conducive to when generating sedimentary direction and transform, will accelerate the generation of precipitation, and the direction that is conducive to dissolve to precipitation when condition is while transforming, will promote the dissolving precipitating.Be defined as for solubleness: in 20 DEG C, in 100g water, can dissolve material more than 10g, be called Yi Rong, the material of 1g-10g, is called solvablely, and the material of 0.01g-1g, is called slightly soluble, and the material below 0.01g is called indissoluble material.All there is tendency in any material, also all exist the equilibrium relation of Solution and precipitation in water, and same reason, at the accompanying dirt of boiler water wall inside surface, also exists dynamic dissolving---the equilibrium process of precipitation to a certain extent.
Therefore, we propose the hypothesis of " instantaneous fouling ability ", are used for representing the at a time tendency of interior some foreign ion precipitation formation incrustation scale of boiler water wall." instantaneous fouling ability " used
represent, instantaneous fouling ability be on the occasion of, and when larger, represent that fouling---dissolution equilibrium is larger to the tendency of fouling side shifting, instantaneous fouling ability is negative value and when larger, representing fouling---dissolution equilibrium is larger to the tendency of dissolving side shifting, and the computing formula of instantaneous fouling ability is as follows:
Wherein,
for feedwater flow (t/h),
for certain ion concentration (μ g/L) in feedwater,
for steam flow (t/h),
for the concentration (μ g/kg) of certain ion in steam,
for stove discharge (t/h),
for the concentration (μ g/L) of certain ion in stove water.
Choose the essential element of assessment boiler water wall fouling tendency
In the boiler water wall of our province 300MW and above parameter, fouling is generally taking iron, silicon dioxide, phosphorus as main, the iron that the iron that the source of iron enters with feedwater and water-cooling wall produce due to corrosion, silicon dioxide is to bring boiler into feedwater, and phosphorus is mainly boiler dosing basifier used.Therefore choose the essential element of silicon dioxide as assessment boiler water wall fouling tendency.
The inventive method is to derive the fouling risk of boiler water wall by the statistical computation of the steam index in subcritical and above parameter thermal power generation unit day-to-day operation.Between the variation of steam index and boiler water wall fouling risk, set up intuitively and contacted, thereby can more effectively carry out chemical supervision work, ensured thermal power generation unit steam qualified, ensured safety, economy, the stable operation of unit.
Embodiment
Example 1: so that certain 300MW of factory Sub-critical Parameter unit is as example inside the province, No. 1 unit of certain factory water quality testing data on May 21st, 2013 is as shown in table 1, and gyp risk is assessed.
Obtain following data from boiler operatiopn, average steam flow is 530t/h, and average feedwater flow is 535.04t/h, and boiler blowdown rate is 0.95%, and calculating average blowdown flow by average steam flow and boiler blowdown rate is 5.03t/h.
certain factory's boiler correlation parameter of table 1
certain factory of table 2 on May 9th, 2012 dirty analysis report
Inspection record is repaiied in May, 2012 boiler overhaul: right wall B8 soot blower place front wall is to the 133rd, rear wall, and 32 meters of absolute altitudes, cover one deck brownish red sediment in pipe, and sediment is more smooth soft, without bulge.After pickling, check: corrosion-free hole point, other are normal.Scaling rate: to fiery side 21.3g/m
2.a, back-fire side 29.2g/m
2.a.Average out to 25.2 g/m
2.a.
Step 1: utilize material balance theory, set up mass balance model.
According to material balance theory, calculate with dioxide-containing silica, bring the silica volume that in boiler, silica volume should equal to take out of with steam into and take away foreign ion amount and be deposited on silica volume sum on boiler water-wall tube with blow-off of boiler water by feedwater, listing material balance formula.
Step 2: utilize fouling tendency judgement schematics to calculate amount of scale buildup
table 3 certain 300MW of factory unit water quality situation and gyp risk evaluation result
Average data is represented to formula (3), and result of calculation is as follows:
M=[535.04×24×4.8-（535.04-5.03）×24×3.5-5.03×24×132]÷1000
＝[61636.61-44520.84-15935.04]/1000
=1.2（g）
Calculating dirt deposition amount on the same day (taking silicon dioxide) is 1.2g, and a month statistics dirt deposition amount (taking silicon dioxide) is 36g, and the dirt deposition amount (taking silicon dioxide) then of amounting to is 432g.
As shown in Table 2, in total dirt amount, silicon dioxide accounts for 3.75%, with average scaling rate 25.2 g/m
2.a calculating, is 0.94g/m containing silicon dioxide composition in dirt
2.a.By high heat load area area 1030m
2calculating, is 968.2g containing silicon dioxide total amount in dirt.
The accordance of the calculated results and actual measured value is better, illustrates for the prediction of actual fouling situation and has certain guidance meaning.
Claims (3)
1. a gyp methods of risk assessment, is characterized in that being completed by following steps:
(1) by entering silica concentration in boiler short-term feedwater average discharge and feedwater, obtain dioxide-containing silica in feedwater;
(2) silica concentration in the steam average discharge producing by boiler and steam, obtains dioxide-containing silica in steam;
(3) silica concentration in the average discharge by boiler effluent sewerage and sewage, obtains dioxide-containing silica in boiler water, and wherein in sewage, silica concentration is identical with silica concentration in boiler water;
(4) in feedwater, dioxide-containing silica cuts dioxide-containing silica in steam, then cuts in boiler water dioxide-containing silica and be during this period of time dirt deposition amount in boiler;
(5) dirt deposition amount in the boiler of certain time of predict future, by the acquisition that adds up of dirt deposition amount in boiler during this period of time.
2. method according to claim 1, is characterized in that: the average discharge of effluent sewerage in step (3), average blowdown flow takes advantage of the blowdown rate of boiler to obtain by steam average discharge.
3. method according to claim 1, is characterized in that in a period of time boiler, dirt deposition amount represents by following formula:
Wherein,
for dirt deposition amount (g);
for average feedwater flow (t/h), take from boiler operatiopn;
: for average steam flow (t/h), take from boiler operatiopn;
for average blowdown flow (t/h),
;
blowdownfor boiler blowdown rate;
for boiler operatiopn time (h) in the statistics phase, i.e. a period of time;
for feedwater silica concentration (μ g/L);
for steam silica concentration (μ g/kg);
for stove water silica concentration (μ g/L); N is n sample in the statistics phase; I is sample.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105202522A (en) * | 2015-09-30 | 2015-12-30 | 广州特种承压设备检测研究院 | Once-through boiler corrosion and scaling risk diagnosis method |
| CN105891073A (en) * | 2016-04-05 | 2016-08-24 | 西安西热电站化学科技有限公司 | Online detection device and method for iron content in thermodynamic system start washing water |
| CN112598300A (en) * | 2020-12-25 | 2021-04-02 | 润电能源科学技术有限公司 | Method, device and system for determining salt deposition rate of steam turbine and storage medium |
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| CN102874967A (en) * | 2011-06-22 | 2013-01-16 | 通用电气公司 | Monitoring and control of unit operations for generating steam from produced water |
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| KHATIB ,Z.I.等: "油田蒸汽锅炉中二氧化硅含量对垢沉积和管壁损耗的影响", 《国外油田工程》 * |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105202522A (en) * | 2015-09-30 | 2015-12-30 | 广州特种承压设备检测研究院 | Once-through boiler corrosion and scaling risk diagnosis method |
| CN105202522B (en) * | 2015-09-30 | 2019-01-11 | 广州特种承压设备检测研究院 | A kind of diagnostic method of direct current cooker corrosion and scaling risk |
| CN105891073A (en) * | 2016-04-05 | 2016-08-24 | 西安西热电站化学科技有限公司 | Online detection device and method for iron content in thermodynamic system start washing water |
| CN112598300A (en) * | 2020-12-25 | 2021-04-02 | 润电能源科学技术有限公司 | Method, device and system for determining salt deposition rate of steam turbine and storage medium |
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