A kind of detection method of online sodium table
One, technical field
The present invention relates to the measure of supervision of steam quality in the firepower plant heating system, specifically a kind of detection method of online sodium table.
Two, background technology
Sodium ions content is the supervision steam quality, differentiates the operating mode of leakage, supervision base exchanger of condenser and the important control parameter of carrying out former water analysis etc. in the firepower plant heating system, can directly reflect the degree of the salification corrosion of heat power equipment.Therefore, for preventing the corrosion of metal parts in fouling, salification, the relieving system, the safety and economic operation of assurance system, must carry out strictness control and on-line monitoring to sodium ions content in the Power Plant Water Vapor system, generally use that the sodium table carries out on-line measurement, the task of monitoring sodium ions content when bearing really at present.
Because the potential electrode of sodium table is to H
+Response ratio to Na
+Also responsive, for eliminating H
+Influence to measuring must be suppressed (being commonly called as alkalization) with alkaline reagent, and afterwards the pH value must be than big 3 units of pNa value to make alkalization, if i.e. water sample [Na
+]=1.0 μ g/L, pNa=7.36 then, the pH value of water sample should be greater than 10.36, and the widely used alkalizing agent of the online sodium table of thermal power plant is pure diisopropylamine or strong aqua at present.Adding the alkali mode a kind of is the saturating alkali adding method of gas (ORION 1800 serial sodium tables), the another kind of alkali adding method (SWAN sodium table) of bleeding that adopts.
Generally react many fuel-burning power plant, and there is the situation inaccurate, that numerical value is less than normal in the measured value of present online sodium table.This is to find when overhaul of the equipments that the indicated numerical value of salification, fouling and the extent of corrosion of heat power equipment and the on-line measurement of sodium table is not inconsistent and the objective conclusion that obtains.This shows that present online sodium table detection method can not reflect variation of water timely and accurately, do not have the salification effect that improves steam quality and reduce turbine blade, numerical value situation less than normal particularly, this has brought hidden danger for undoubtedly the unit safety economical operation.
Three, summary of the invention
The present invention is intended to the detection method of existing online sodium table is improved, and technical matters to be solved is under the condition that guarantees the required basicity of measurement, improves online sodium table and measures authenticity, accuracy.
The applicant has carried out the analysis of system to existing online sodium table detection method, pinpoints the problems out on alkalizing agent.For this reason, adopt pure diisopropylamine and strong aqua to carry out many set condition tests respectively,, sum up and obtain technical scheme of the present invention by the statistical study of data as alkalizing agent to two kinds of sodium tables that add the alkali mode.The alkalizing agent of online sodium table measurement that Here it is is answered first-selected certain density diisopropylamine, specifically, when being added the online detection of basic sodium table thoroughly, gas makes concentration 65~75wt% (mass percent, diisopropylamine down together) is as alkalizing agent, preferred concentration 68~72wt% diisopropylamine is with concentration 70wt% diisopropylamine the best; Working concentration 45~55wt% diisopropylamine is as alkalizing agent when adding the online detection of basic sodium table to bleeding, and preferred concentration 48~52wt% diisopropylamine is with concentration 50wt% diisopropylamine the best.
The technical program not only can satisfy the requirement of sodion measurement to water sample basicity, can reduce the measuring error of instrument simultaneously again, strengthens the instrument measurement reliability.Compare the pure diisopropylamine of direct employing and do alkalizing agent, every sodium table year is saved diisopropylamine 6L.Moreover, the sodion measured value can allow the operator in time find the problem in the water and steam quality control and in time carry out the operating mode adjustment accurately, it is annual because the burn into fouling and the salification of system to reduce by every unit, the economic loss of the millions of units that bring, safety and economic operation to the generating plant has great significance, and really plays energy-saving and cost-reducing effect.
Four, embodiment
To the measurement result statistical study of known Na ion concentration, see Table 1 when 1, gas adds the basic sodium table thoroughly and adopts strong aqua and diisopropylamine to make alkalizing agent respectively.
Table 1
Because preparation sodium standard solution background water is a demineralized water, measuring error and background water sodium ions content are approaching more, and the instrument measurement accuracy is high more, and reliability is good more.Can draw from table 1: as alkalizing agent, diisopropylamine, strong aqua all can make alkalization back water sample pH value bigger by 3 than the pNa value, though can satisfy the demand of sodion measurement to water sample basicity, measuring error differs.During as alkalizing agent, the difference of measuring error and background water sodion is up to 4.83 with strong aqua, and when making alkalizing agent with diisopropylamine, the instrument measurement data are less than normal.
2, bleed when adding the basic sodium table and adopting strong aqua and diisopropylamine to make alkalizing agent respectively to the statistical study of known Na ion concentration measurement result, see Table 2.
Table 2
From table 2 as seen, the online sodium table that adds alkali for bleeder, adopt high concentration diisopropylamine, strong aqua also all can make alkalization back water sample pH value bigger by 3 than the pNa value, can satisfy the demand of sodion measurement to water sample basicity, but the difference of measuring error and background water sodium ions content is all very big, reach 4.4 when making alkalizing agent, reach 2.2 when making alkalizing agent with the high concentration diisopropylamine with strong aqua.
To the measurement result statistical study of known Na ion concentration, see Table 3 when 3, gas adds the basic sodium table thoroughly and adopts 70% diisopropylamine to make alkalizing agent.
Table 3
From table 3 as seen, the online sodium table that adds the alkali formula for gas thoroughly, adopting 70% diisopropylamine is that alkalizing agent can not only satisfy the required basicity of instrument measurement, the measuring error minimum that instrument is produced, the measuring error that above-mentioned measurement instrument produces and the difference of background water sodium ions content only are 0.39, and this detection method has improved the instrument measurement accuracy greatly.
4, bleed when adding the basic sodium table and adopting 50% diisopropylamine to make alkalizing agent to the statistical study of known Na ion concentration measurement result, see Table 4.
Table 4
From table 4 as seen, the online sodium table that adds the alkali formula for gas thoroughly, adopting 50% diisopropylamine is that alkalizing agent can not only satisfy the required basicity of instrument measurement, the measuring error minimum that the type instrument is produced, the measuring error that above-mentioned measurement instrument produces and the difference of background water sodium ions content only are 0.9, reduced 13-35% than existing detection method error, this detection method has improved the instrument measurement accuracy largely.